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COSMOS CLUSTER 2

Shaowei Chen, ProfessorDepartment of Chemistry and Biochemistry

University of CaliforniaSanta Cruz, CA 95064

shaowei@ucsc.eduhttp://chen.chemistry.ucsc.edu

Overview In this cluster, the focus is to introduce the fundamentals

of nanomaterials chemistry to the students and to highlight some of the important implication in energy and electronic sciences. Specifically the lectures will cover the general properties of nanomaterials, the leading technologies in the preparation of functional nanomaterials, typical experimental tools that are important in the investigation, and potential applications in energy and electronic sciences.

Prerequisite: students must have completed one year of high school algebra and chemistry and demonstrated maturity in laboratory safety.

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Syllabus 1 Overview of nanoscale materials

Metals: surface/volume ratios, coloration, surface defects, Semiconductors: introduction of bandgap and optical properties Metal oxides and polymers Carbon nanomaterials: nanoparticles, nanotubes, graphene

nanosheets Nanocomposites: synergistic effects of the constituents Demos with nanoparticle examples, as compared to bulk forms

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Syllabus 2 Nanomaterials Chemistry

Top-down synthesis: laser ablation, lithography, chemical vapor deposition,

Bottom-up synthesis : colloidal synthesis, surface protection Laboratory experiments in nanoparticle synthesis

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Syllabus 3 Electrochemistry and Nanomaterials

Electrochemistry: basic concepts of electron transfer Capacitive nature of nanomaterials Catalytic activity Demos and experiments in electrochemistry research laboratory

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Syllabus 4 Electronic and Energy Science

Fundamentals of fuel cell electrochemistry: anodic and cathodic reactions, electrocatalysts, membrane designs, fuel selection

Electronic implication: nanoelectronic transistors Demos and electrochemical measurements of model nanoparticle

systems

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Other Activities Four labs

July 13: Gold and silver colloids July 18: Quantum dots July 20: Magnetic fluids July 25: ZnO solar cell July 27: water splitting

Three field trips July 14: IBM Almaden July 21: Google July 28: SLAC August 1: UCSC Lab tour

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Nanoscale Materials Nanomaterials refer to a class of materials with at least

one dimension of the order of nanomater (109 m). They represent an intermediate structure between their

constituent atoms and the bulk forms. Accordingly, their chemical and physical properties show

drastic deviations from those of their atomic or bulk forms as well.

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How big is a nanometer?

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Significance of Nanoscale

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Nanoscale Materials 0-D

Fullerenes Nanoparticles Quantum Dots

1-D Nanorods Nanowires Nanotubes

2-D Graphene

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CARBON-BASEDNanoparticles

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6C: 1s22s22p213

Bucky FulleroRichard Buckminster Bucky Fuller

(July 12, 1895 July 1, 1983) was an American engineer, systems theorist, author, designer, inventor, and futurist.

oFuller published more than 30 books, inventing and popularizing terms such as "Spaceship Earth", ephemeralization, and synergetics.

oHe also developed numerous inventions, mainly architectural designs, the best known of which is the geodesic dome.

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Spaceship Earth at Epcot, Walt Disney World, a geodesic sphere

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Fullerenes (C60, C70, ) Fullerene is any molecule composed entirely of carbon, in the form of

a hollow sphere, ellipsoid, or tube. Spherical fullerenes are also called buckyballs. Cylindrical ones are called carbon nanotubes or buckytubes.

The first fullerene to be discovered, and the family's namesake, buckminsterfullerene (C60), was prepared in 1985 by Richard Smalley, Robert Curl, James Heath, Sean O'Brien, and Harold Kroto at Rice University. They won the Nobel Prize in Chemistry in 1996.

The name was an homage to Buckminster Fuller, whose geodesic domes it resembles.

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Fullerene Production

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Nature 1985, 318, 162

Graphite evaporation

Atomic rearrangement

Sample collection

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Fullerene FactsC60 and other fullerenes were later noticed occurring outside

the laboratory (e.g., in normal candle soot). Minute quantities of the fullerenes, in the form of C60, C70, C76,

and C84 molecules, are produced in nature, hidden in soot and formed by lightning discharges in the atmosphere. In 1992, fullerenes were found in a family of minerals known as Shungites in Karelia, Russia.In 2010, fullerenes (C60) were discovered in a cloud of cosmic

dust surrounding a distant star 6500 light years away. Using NASA's Spitzer infrared telescope the scientists spotted the molecules' unmistakable infrared signature. C60 is one of the largest objects that exhibits wave-particle

duality.

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Functionalization

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Controlled Assembly

oA single atom of dysprosium (66Dy) is encapsulated within C82 fullerenes, which line up in a chain when inserted into the carbon nanotubes.

oOver a short period of time the fullerene cages fuse as the carbon-carbon bonds break in the presence of 66Dy

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Functionalization and Engineering

The mean polarizability of (C60)n nonlinearly depends on the number of fullerene cores in their molecules, i.e. it violates the additivity.

This effect is a result of the interaction of the -electronic systems of fullerene cores in (C60)n and increases with their maximal remoteness.

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RSC Adv., 2013, 3, 19430-19439

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Buckybowls

significant enhancement of the second order nonlinearoptical response from molecules to ordered aggregates

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Phys. Chem. Chem. Phys., 2013, 15, 1810-1814

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Myths about C60 It is unclear whether C60 benefits or protects the brain.

A Russian laboratory has found that hydrated C60 can protect against the buildup of -amyloid proteins, which are associated with Alzheimers disease.

Another study reports C60 affects the brains neurotransmitter levels after it is injected into brain ventricles of mice. The second study concluded that C60 does not cross the blood-brain-barrier, suggesting that oral treatment would not affect the brain.

However, there have also been several rodent studies that suggest that hydrated C60 derivatives are neuroprotectiveand may enter into the brain through the bloodstream.

All of these studies were done in rodents, so even without these discrepancies the effects of C60 in humans remain untested.

Similarly, the safety of C60 and its derivatives have never been tested in humans.

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C60 is a good electron acceptor Synergistic agent in tumor-inhibitory doxorubicin (Dox)

treatment Dox is one of the most potent anticancer drugs, but its successful

use is hampered by high toxicity caused mainly by generation of reactive oxygen species (ROS). One approach to protect against Dox-dependent chemical insult is combined use of the cytostatic drug with antioxidants. C60 fullerene has a nanostructure with both antioxidant and antitumor potential and may be useful in modulating cell responses to Dox.

Organic solar cells

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Drugs R D. 2014 Dec; 14(4): 333340.

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Carbon Nanoparticles

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Laser ablation of carbon targets Hydrothermal reduction of sugars Combustion soot

Carbon Nanoparticles Carbon (C) nanoparticles or nanodots are black spherical high surface area

graphitic carbon . Nanoscale carbon particles are typically 10 - 45 nanometers (nm) with a specific surface area in the 30 - 50 m2/g range and also available with an average particle size of 75 - 100 nm range with a specific surface area of approximately 2 - 10 m2/g.

Gold nanoparticles and carbon nanoparticles have found novel applications in cancer treatment using radio waves to heat and destroy a tumor, lymphoma, or metastasized cancer. Recent discoveries confirm the feasibility of this technology in humans.

Surface functionalized nanoparticles allow for the particles to be preferentially adsorbed at the surface using chemically bound polymers. Development research is underway in Nano Electronics and Photonics materials, such as MEMS and NEMS, Bio Nano Materials, such as Biomarkers, Bio Diagnostics & Bio Sensors, and Related Nano Materials, for use in Polymers, Textiles, Fuel Cell Layers, Composites and Solar Energy materials.

Research into applications for carbon nanocrystals has focused on use as active materials in field emitter arrays for flat panel screen displays, in biological sensors and medical imaging devices, in solar energy cells, and in high-surface area electrodes for use in bio-science. Carbon nanoparticles are generally immediately available in most volumes.

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Laser Ablation

Fluorescent carbon nanoparticles were synthesized by laser irradiation of a suspension of carbon powders in an organic solvent. The surface modification on the CNPs was fulfilled simultaneously with the formation of the CNPs, and tunable light emission could be generated by selecting appropriate solvents.

The origin of the luminescence was attributed to carboxylate ligands on the surface of the CNPs.

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JMC 2009, 19, 484

Hydrothermal Synthesis

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Colloids and Surfaces B: Biointerfaces, Volume 87, Issue 2, 15 October 2011, Pages 326332

ex = 365 nm ex = 455 nm ex = 545 nm

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Combustion Soot

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What is Fluorescence?

An early observation of fluorescence was described in 1560 by Bernardino de Sahagn and in 1565 by Nicols Monardesin the infusion known as lignum nephriticum(Latin for "kidney wood").

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Matlaline

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Origin of Photoluminescence Here, a common origin of green luminescence in C-dots is

unraveled by ultrafast spectroscopy. According to the change of surface functional groups during surface chemical reduction experiments, which are also accompanied by obvious emission-type transform, these common green luminescence emission centers are unambiguously assigned to special edge states consisting of several carbon atoms on the edge of carbon backbone and functional groups with CO (carbonyl and carboxyl groups). This suggests that the competition among various emission centers (bright edge states) and traps dominates the optical properties of these fluorescent carbon nanomaterials.

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ACS Nano, 2014, 8 (3), pp 25412547

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Confocal PL images of LLC-PK1 cells after CD incubation

Digital image of gram scale solid fluorescent carbon nanodot (FCN) samples, digital images of their solutions under appropriate excitations and their absorption (), excitation (..) and emission (color lines) spectra. Emission spectra have been measured by exciting at 370nm for FCNblue, by exciting at 400nm for FCNgreen, by exciting at 425nm for FCNyellow and by exciting at 385nm for FCNred. All excitation spectra are recorded in respective emission maxima.

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Biomedical Applications

Schematic illustration of the preparation of carbon nanodots (CD) from -cyclodextrinand targeted photodynamic therapy with folic acid functionalized carbon nanodotsloaded with zinc phthalocyanine (CD-PEG-FA/ZnPc).

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METAL-BASEDNanoparticles

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Metal Nanoparticles

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Metallic Bonding Metallic bonding occurs as a result of

electromagnetism and describes the electrostatic attractive force that occurs between conduction electrons (in the form of an electron cloud of delocalized electrons) and positively charged metal ions.

It may be described as the sharing of freeelectrons among a lattice of positively charged ions (cations).

Metallic bonding accounts for many physical properties of metals, such as strength, ductility, thermal and electrical resistivity and conductivity, opacity, and luster

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Gold Colloids (Au [Xe] 4f14 5d10 6s1) The Chinese were the first to prepare

and use red colloidal gold as the alchemical drug of longevity.

The word alchemy derives from two Chinese words: Kim (gold) and Yeh(juice). Kimyeh (gold juice) entered the Arabic language as kimiya, and with the definite article, al, the arabic word for the red colloidal gold was alkimiya, which in the Western world, gave the word alchemy.

The procedure for the preparation of red colloidal gold is still in use today in India, prescribed by Ayurvedicphysicians for rejuvenation and revitalization in old age.

Gold And Its Relationship To Neurological/Glandular Conditions, International Journal of Neuroscience

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Nanomaterials in Ancient TimesThe Lycurgus Cup (British Museum; AD 4th

century) is a Roman cup showing thetriumph of Dionysus over Lycurgus. He isseen being dragged into the underworld bythe Greek nymph Ambrosia, who isdisguised as a vine.The glass of the cup is dichroicin direct

light it resembles jade with an opaquegreenish-yellow tone (reflection), but whenlight shines through the glass it turns to atranslucent ruby colour (transmission).

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X-ray analysis has shown nanoparticles of silver-gold alloy, with a ratio of silver to gold of about 7:3, containing in addition about 10% copper. These nanoparticles are responsible for the differential behavior of the glass when the light shines from different directions.

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Colloidal Goldo Known since ancient times, the synthesis of colloidal gold was originally

used as a method of staining glass. Modern scientific evaluation of colloidal gold did not begin until Michael Faraday's work of the 1850s.

o A so-called Elixir of Life, a potion made from gold, was discussed, if not actually manufactured, in ancient times. Colloidal gold has been used since Ancient Roman times to color glass intense shades of yellow, red, or mauve, depending on the concentration of gold, and in Hindu Chemistry, for various potions.

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Gold Colloids In the 16th century, the alchemist Paracelsus claimed to have created

a potion called Aurum Potabile (Latin: potable gold). He believed it cured all manner of physical, mental, and spiritual

ailments. "Gold receives its influence from the Sun," he wrote, "which is, as it were, the Heart of the world and by communicating these influences to the human heart it serves to fortify and cleanse it from all impurities."

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Gold Colloids In the 17th century the glass-coloring process was refined by Andreus

Cassius and Johann Kunckel.

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Gold Colloids In 1842, Sir John Herschel invented a

photographic process called Chrysotype(from the Greek word for gold) that used colloidal gold to record images on paper.

Herschel's system involved coating paper with ferric citrate, exposing it to the sun in contact with an etching used as mask, then developing the print with a chloroaurate solution. This did not provide continuous-tone photographs.

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Michael Faraday Paracelsuss work is known to have inspired Michael Faraday to

prepare the first pure sample of colloidal gold, which he called 'activated gold', in 1857. He used phosphorus (P) to reduce a solution of gold chloride (AuCl3).

o For a long time the composition of the Cassius ruby-gold was unclear. Several chemists suspected it to be a gold tin compound, due to its preparation. Faraday was the first to recognize that the color was due to the

minute size of the gold particles. In 1898 Richard Adolf Zsigmondy prepared the first colloidal gold in

diluted solution.

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Slide that Faraday used in his lecture on gold sols, in 1858

Michael Faradayo Michael Faraday, FRS (22 September 1791 25 August 1867) was an English

chemist and physicist who contributed to the fields of electromagnetism and electrochemistry.

o As a chemist, Faraday discovered benzene, investigated the clathrate hydrate of chlorine, invented an early form of the bunsen burner and the system of oxidation numbers, and popularized terminology such as anode, cathode, electrode, and ion.

o The SI unit of capacitance, the farad, is named after him, as is the Faraday constant, the charge on a mole of electrons (about 96,485 coulombs). Faraday's law of induction states that a magnetic field changing in time creates a proportional electromotive force.

Work.Finish.Publish.

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Colloidal Silver (Ag [Kr]4d105s1) Colloidal silver is a natural antibiotic which has been used throughout the

world for centuries as a means to destroy microbes of all kinds and to correct many health problems.

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Colloidal Silver (Ag [Kr]4d105s1)It was removed from public use in the United

States in the 1920's and 1930's by the medical profession in their move to purge natural health remedies from the marketplace. As late as August, 1998 the FDA ordered all colloidal silver removed from all U.S. Health Stores, but due to public outcry, that order has been temporarily relaxed. Today, the use of colloidal silver is spreading

rapidly throughout the medical community in the healing of burn victims. Medical doctors have never denied the merits of silver in the form of silver nitrate as a bactericide. Silver nitrate is routinely used in drops put into a baby's eyes at birth to prevent blindness from venereal disease.

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Surface Structures

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Surface Defects

Gold Nanoparticles

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Copper Nanoparticles (Cu [Ar]3d104s1) Printed electronics is a set of printing methods used to create electrical

devices on various substrates. Flexible electronics

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Copper Nanoparticles

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50 nm

100 nm 33 nm

As-prepared

Low-temperature annealing

Cu2+ Cu0 Cun

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Copper Nanoparticles

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Copper Nanoparticles

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Synthesis of Gold Nanoparticleso Generally, gold nanoparticles are produced in a liquid

("liquid chemical methods") by reduction of chloroauric acid (H[AuCl4]), although more advanced and precise methods do exist. After dissolving H[AuCl4], the solution is rapidly stirred while a reducing agent is added. This causes Au3+ ions to be reduced to neutral gold atoms. As more and more of these gold atoms form, the solution becomes supersaturated, and gold gradually starts to precipitate in the form of sub-nanometer particles. The rest of the gold atoms that form stick to the existing particles, and, if the solution is stirred vigorously enough, the particles will be fairly uniform in size.

o To prevent the particles from aggregating, some sort of stabilizing agent that sticks to the nanoparticle surface is usually added. They can be functionalized with various organic ligands to create organic-inorganic hybrids with advanced functionality. It can also be synthesised by laser ablation.

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Turkevich methodo The method pioneered by J. Turkevich et al. in 1951 and refined by G.

Frens in 1970s, is the simplest one available. Generally, it is used toproduce modestly monodisperse spherical gold nanoparticles suspendedin water of around 1020 nm in diameter. Larger particles can beproduced, but this comes at the cost of monodispersity and shape. Itinvolves the reaction of small amounts of hot chlorauric acid with smallamounts of sodium citrate solution. The colloidal gold will form becausethe citrate ions act as both a reducing agent, and a capping agent.

o Recently, the evolution of the spherical gold nanoparticles in theTurkevich reaction has been elucidated. Interestingly, extensive networksof gold nanowires are formed as a transient intermediate. These goldnanowires are responsible for the dark appearance of the reactionsolution before it turns ruby-red.

o To produce larger particles, less sodium citrate should be added(possibly down to 0.05%, after which there simply would not be enoughto reduce all the gold). The reduction in the amount of sodium citrate willreduce the amount of the citrate ions available for stabilizing theparticles, and this will cause the small particles to aggregate into biggerones (until the total surface area of all particles becomes small enough tobe covered by the existing citrate ions).

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Brust methodo This method was discovered by Brust and Schiffrin in early 1990s,

and can be used to produce gold nanoparticles in organic liquids that are normally not miscible with water (like toluene). It involves the reaction of a chlorauric acid solution with tetraoctylammonium bromide (TOAB) solution in toluene and sodium borohydride as an anti-coagulant and a reducing agent, respectively.

o Here, the gold nanoparticles will be 2 to 6 nm in diameter. NaBH4 is the reducing agent, and TOAB is both the phase transfer catalyst and the stabilizing agent.

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Martin Method (I)o This method, discovered by the Eah group in 2010, generates

naked gold nanoparticles in water by reducing HAuCl4 with NaBH4. Even without any other stabilizer like citrate, gold nanoparticles are stably dispersed. The size distribution is nearly monodisperse and the diameter can be precisely and reproducibly tunable from 3.2 to 5.2 nm. The key is to stabilize HAuCl4 and NaBH4 in the aqueous stock solutions with HCl and NaOH for >3 months and >3 hours respectively. In addition, the ratio of NaBH4-NaOH ions to HAuCl4-HCl ions must be precisely controlled in the sweet zone.

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Martin Method (II)o Naked gold nanoparticles are coated with a monolayer of 1-

dodecanethiol and then phase-transferred to hexane simply by shaking a mixture of water, acetone, and hexane for 30 seconds. Since all the reaction byproducts remain in the water-acetone phase, no post-synthesis cleaning is needed for gold nanoparticles in the hexane phase. The amount of 1-dodecanethiol is only 10 % of gold atoms in number. All these synthesis procedures take just

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Sonolysis o In one such process based on ultrasound, the

reaction of an aqueous solution of HAuCl4 with glucose, the reducing agents are hydroxyl radicals and sugar pyrolysis radicals (forming at the interfacial region between the collapsing cavities and the bulk water) and the morphology obtained is that of nanoribbons with width 30-50 nm and length of several micrometers. These ribbons are very flexible and can bend with angles larger than 90.

o When glucose is replaced by cyclodextrin (a glucose oligomer) only spherical gold particles are obtained suggesting that glucose is essential in directing the morphology towards a ribbon.

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Crystal Facets

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cuboid

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Nanocubes, Nanoprisms,

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(Smaller) Silver Nanocubes The success of this new method relies on the substitution of ethylene

glycol (EG)the solvent most commonly used in a polyol synthesiswith diethylene glycol (DEG).

Owing to the increase in hydrocarbon chain length, DEG possesses a higher viscosity and a lower reducing power relative to EG. As a result, we were able to achieve a nucleation burst in the early stage to generate a large number of seeds and a relatively slow growth rate thereafter; both factors were critical to the formation of Ag nanocubeswith small sizes and in high purity (>95%).

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J. Am. Chem. Soc., 2013, 135 (5), pp 19411951

Polyvinylpyrrolidone (PVP)

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(Larger) Silver Nanocubes Ag nanocubes of 30 to 70 nm

in edge length with the use of CF3COOAg as a precursor to elemental silver.

By adding a trace amount of NaSH and HCl to the polyol synthesis, Ag nanocubes were obtained with good quality, high reproducibility, and on a scale up to 0.19 g per batch for the 70 nm Ag nanocubes.

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TEM images of Ag nanocubes at different reaction times for a standard synthesis: A) 15, B) 30, C) 60, and D) 90min. The nanocubes have an edge length of A) 30, B) 42, C) 50, and D) 70nm

Chem Eur J 2010, 16, 10234

Palladium Nanocubes

0.1mL of 0.1M CTAB, 4.4mL of deionized water and 0.5mL of 10mM K2PdCl4 were mixed in a 10mL bottle, into which was added 0.15mL of 0.1M AA. The solution was shifted in a 35~40C water bath under magnetic stirring

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Scientific Reports 5, Article number: 8515 (2015)

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Palladium Nanocubes Palladium octahedra with

controlled edge lengthswere obtained from Pdcubes of a single size. Thesuccess of this synthesisrelies on a transformationinvolving oxidative etchingand regrowth.

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J. Am. Chem. Soc., 2013, 135 (32), pp 1175211755

(a) Schematic illustration of the five majorsteps involved in the oxidative etching andregrowth process. Because all of the sidefaces of the Pd cube are capped by Br ions,Pd atoms are mainly etched from the cornersite(s), and the resultant Pd2+ ions can besubsequently reduced and deposited onto theside faces. (b) Schematic illustrations showingthe formation of Pd octahedra with different butcontrollable edge lengths (l) by maneuveringthe rates of oxidative etching and regrowth forPd cubes with an edge length of l0 HCl atdifferent concentrations from high (H) to low(L).

Metal Nanoframes

Initial single-crystalline Ni3Pt nanoparticles are etched to form hollow nanoframes of the same geometry. When the nanoframes are heated the composition of the nanoframeschanges to Pt3Ni and a platinum-rich skin forms on the surfaces of all edges.

The open structure facilitates easy molecular access to all surfaces, leading to a much higher catalytic activity than that of conventional platinum-carbon catalysts.

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Science 21 Mar 2014:Vol. 343, Issue 6177, pp. 1339-1343

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Gold Nanostars

Highly symmetric Au nanostars grown from icosahedral Au seeds in a dimethylformamide (DMF) solution containing polyvinylpyrrolidone (PVP), chloroauric acid, dimethylamine (DMA), and hydrochloric acid

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J. Am. Chem. Soc., 2015, 137 (33), pp 1046010463

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Photoinduced conversion of Ag nanospheres to nanoprisms

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TEM images (reverse print) mapping the morphology changes (A) before irradiation and after (B) 40, (C) 55, and (D) 70 hours of irradiation.

R Jin et al. Science 2001;294:1901-1903

Published by AAAS

Photoinduced conversion of Ag nanospheres to nanoprisms

Rayleigh light-scattering of particles deposited on a microscope glass slide.

R Jin et al. Science 2001;294:1901-1903

Published by AAAS

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Electromagnetic Waves

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Scattering and Absorption Scattering is a general physical process

where some forms of radiation, such as light, sound, or moving particles, are forced to deviate from a straight trajectory by one or more paths due to localized non-uniformities in the medium through which they pass

Absorption of electromagnetic radiation is the way in which the energy of a photon is taken up by matter, typically the electrons of an atom.

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Scattering of LightsSunlight reaches Earth's atmosphere and isscattered in all directions by all the gases andparticles in the air. Blue is scattered more thanother colors because it travels as shorter,smaller waves. This is why we see a blue skymost of the time

As the Sun gets/rises lower in the sky, its lightis passing through more of the atmosphere toreach you. Even more of the blue light isscattered, allowing the reds and yellows topass straight through to your eyes.

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Question: if you were out in space, what color would you see?

Surface Plasmon The charge motion in a surface plasmon always creates electromagnetic fields outside (as well

as inside) the metal. The total excitation, including both the charge motion and associated electromagnetic field, is called either a surface plasmon polariton at a planar interface, or a localized surface plasmon for the closed surface of a small particle.

The existence of surface plasmons was first predicted in 1957 by Rufus Ritchie (ORNL)

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Schematic representation of an electron density wave propagating along a metal dielectric interface. The charge density oscillations and associated electromagnetic fields are called surface plasmon-polariton waves. The exponential dependence of the electromagnetic field intensity on the distance away from the interface is shown on the right. These waves can be excited very efficiently with light in the visible range of the electromagnetic spectrum.

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Surface Plasmon Resonance The simplest way to approach the problem is to treat each material as

a homogeneous continuum, described by a frequency-dependent relative permittivity between the external medium and the surface.

This quantity, hereafter referred to as the materials' "dielectric constant ()," is complex-valued () = '() + i"(). It is an expression of the extent to which a material concentrates electric

flux The real part of the dielectric constant of the metal must be negative and

its magnitude must be greater than that of the dielectric. This condition is met in the IR-visible wavelength region for air/metal and

water/metal interfaces (where the real dielectric constant of a metal is negative and that of air or water is positive).

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Mie Theory Gustav Adolf Feodor Wilhelm Ludwig Mie (29

September 1869 13 February 1957) was a German physicist.

For a spherical nanoparticle that is much smaller than the wavelength of the incident light, its response to the oscillating electric field can be described by the so-called dipole approximation of Mie theory.

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Mie Theory: Surface Plasmon Resonance

The wavelength-dependent extinction cross section of a single particle, Cext(), which defines the energy losses in the direction of propagation of the incident light due to both scattering and absorption by the particle, is described in terms of the dielectric function of the metal, () = '() + i"(), and the dielectric constant of the medium, m.

For gold nanoparticles smaller than 60 nm the scattering cross section is negligible when compared to the absorption cross section. (Hodak, J. H.; Henglein, A.; Hartland, G. V. J. Phys. Chem. B 2000, 104, 9954-9965)

where is wavelength of the incident light and R is the particle radius

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Surface Plasmon Resonance Surface plasmons are surface electromagnetic waves that propagate in a

direction parallel to the metal/dielectric (or metal/vacuum) interface. Since the wave is on the boundary of the metal and the external medium (air or water for example), these oscillations are very sensitive to any change of this boundary, such as the adsorption of molecules to the metal surface.

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Nanomaterials Enhanced SPR Sensors

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Surface Plasmon Resonance SPR is a prominent spectroscopic feature of noble metal nanoparticles

(NPs), which gives rise to a sharp and intense absorption band in the visible range. The physical origin of the absorption is a collective resonant oscillation of the free electrons of the conduction band of the metal.

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Schematic of surface plasmonoscillations induced by an oscillatingelectric field in a metal sphere. Thedisplacement of the conductionelectrons (green color) relative to thenuclei (gray color) is shown. Thefrequency of the surface plasmonresonance is denoted p.

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UV-Visible Absorption Spectroscopy

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Electronic Transition

Metal Nanoparticles

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UV-Vis absorption spectra acquired for toluene solutions of oleylamine-coated gold (Au) nanoparticles with different diameters. The spectra were normalized at 450 nm

Extinction (scattering + absorption) spectra of silver (Ag) nanoparticles with diameters ranging from 10-100 nm at mass concentrations of 0.02 mg/mL.

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Metal Nanoshells

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Gold nanoshells on a 120-nm core

Anisotropic Structures

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Surface Plasmon Resonance Localized surface plasmon polaritons (LSPRs) exhibit enhanced near-field

amplitude at the resonance wavelength. This field is highly localized at the nanoparticle and decays rapidly away from the nanoparticle/ dieletric interface into the dielectric background, though far-field scattering by the particle is also enhanced by the resonance.

Light intensity enhancement is a very important aspect of LSPRs and localization means the LSPR has very high spatial resolution (subwavelength), limited only by the size of nanoparticles. Because of the enhanced field amplitude, effects that depend on the amplitude such as magneto-optical effect are also enhanced by LSPRs.

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Photothermal Therapy

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Photolithography

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Other Applications Photothermal lithography Enhanced spectroscopy (Raman, Infrared, etc)

Single-molecule detection

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Nano in Daily Life The Most Unique and Best Hydro Nano Water

in the World For Hydration & Detoxification http://hydronanowater.com/

Hydro Nano Water is the smallest molecular particle size, most are micron and angstrom size which come from your tapThe water is Hydrating, and Ionized. After you drink this nanowater, you can fill the water bottle back up with the purest water you have, you can use your tap water if that is all you have at the time, then let it set for six hours, it will remanufacture nano water for you.

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Nano in Daily Life NANO 153 Silver Soap Cleanser - 20g Normal to Oily

www.amazon.com Product Features

If you have acnes, any types of skin inflammation, age spots, bacteria-caused dryness and cosmetic-poisoned spots, NANO 153 Cleanser can repair the damages extraordinarily.

NANO 153 Cleanser helps remove bacteria-caused body odors. NANO 153 Cleanser helps make your skin look brighter and whiter.

Natural ingredients help revitalize your damaged skin.

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Nano in Daily Life Samsung's Silver Nano Washer Ads Reportedly

ExaggeratedNov 21, 2005 http://www.appliancemagazine.com

SILVER WASH uses nano technology to electrolyze pure silver during wash and rinse cycles. Over 400 billion silver ions are released and penetrate deep into fabric for effective sanitization.

A laboratory test result showed Samsung Electronics Silver Nano washing machines are exaggerated.

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SEMICONDUCTOR-BASEDNanoparticles

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Basics of Semiconductors A semiconductor is a material with electrical conductivity

due to electron flow (as opposed to ionic conductivity) intermediate in magnitude between that of a conductor and an insulator.

This means a conductivity roughly in the range of 103 to 108 siemens per centimeter (S/cm).

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Semiconductor Energy Bands

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Band Gap In solid state physics, a band gap, also called an energy

gap or bandgap, is an energy range in a solid where no electron states can exist.

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Material BG (eV) Material BG (eV) Material BG (eV)

Si 1.11 GaN 3.4 CdS 2.42

Se 1.74 InSb 0.17 CdSe 1.73

Ge 0.67 InN 0.7 CdTe 1.49

SiC 2.86 ZnO 3.37 PbS 0.37

GaP 2.26 ZnS 3.6 PbSe 0.27

Near-Infrared Infrared

4.0

Human eyes

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Semiconductor Quantum Dots

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Particle in a Box a particle free to move in a small

space surrounded by impenetrable barriers

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8

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Quantum Confinement In an unconfined (bulk) semiconductor, an electron-hole

pair is typically bound within a characteristic length, called the exciton Bohr radius.

An exciton is a bound state of an electron and hole which are attracted to each other by the electrostatic Coulomb force.

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+

Semiconductor Quantum DotsCdSe

exciton Bohr radius(4.9 nm CdSe)

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Quantum Dotso A quantum dot is a portion of matter (e.g. semiconductor) whose

excitons are confined in all three spatial dimensions. They range in diameter from 2-10 nm. Consequently, such materials have electronic properties intermediate between those of bulk semiconductors and those of discrete molecules.

o Quantum dots are made from semiconducting materials where elements from two different families are combined. For example, families 2-4, 3-5,4-6 can be combined together to give semiconducting materials.

o They were discovered at the beginning of the 1980s by Alexei Ekimovin a glass matrix and by Louis E. Brus in colloidal solutions. The term "quantum dot" was coined by Mark Reed.

o The band gap and energy levels of electrons can be altered. As semiconductors with changable band gaps and energy levels they are very useful in other applications. Semiconductors will only conduct electrical charge if acted upon by an external source and quantum dots can be suspended in liquid solutions. This makes them useful in areas including biomedical imaging and sercurity applications.

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Facts about Quantum DotsoTypical dots are made of binary alloys such as cadmium

selenide (CdSe), cadmium sulfide (CdS), indium arsenide (InAs), and indium phosphide (InP). Although, dots may also be made from ternary alloys such as cadmium selenide sulfide (CdSexS1-x).

oThese quantum dots can contain as few as 100 to 100,000 atoms within the quantum dot volume, with a diameter of 10 to 50 atoms. This corresponds to about 2 to 10 nanometers, and at 10 nm in diameter, nearly 3 million quantum dots could be lined up end to end and fit within the width of a human thumb.

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Colloidal Synthesis

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Experimental ParametersoThe temperature during the growth process is one of the

critical factors in determining optimal conditions for the nanocrystal growth. It must be high enough to allow for rearrangement and annealing of atoms during the synthesis process while being low enough to promote crystal growth.

oAnother critical factor that has to be stringently controlled during nanocrystal growth is the monomer (precursor) concentration.

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Focusing and Defocusingo At high monomer concentrations (early

stage), the critical size (the size where nanocrystals neither grow nor shrink) is relatively small, resulting in growth of nearly all particles. In this regime, smaller particles grow faster than large ones (since larger crystals need more atoms to grow than small crystals) resulting in focusing of the size distribution to yield nearly monodisperse particles. The size focusing is optimal when the monomer concentration is kept such that the average nanocrystal size present is always slightly larger than the critical size.

o When the monomer concentration is depleted during growth (later stage), the critical size becomes larger than the average size present, and the distribution defocuses as a result of Ostwald ripening.

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Wilhelm Ostwald Friedrich Wilhelm Ostwald (2

September 1853 4 April 1932) was a Baltic German chemist. He received the Nobel Prize in Chemistry in 1909 for his work on catalysis, chemical equilibria and reaction velocities.

Ostwald, Jacobus Henricus van 't Hoff, and Svante Arrhenius are usually credited with being the modern founders of the field of physical chemistry.

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Ostwald ripening Ostwald ripening is an observed phenomenon in

solid solutions or liquid sols that describes the change of an inhomogeneous structure over time, i.e., small crystals or sol particles dissolve, and redeposit onto larger crystals or sol particles

This thermodynamically-driven spontaneous process occurs because larger particles are more energetically favored than smaller particles. This stems from the fact that molecules on the surface of a particle are energetically less stable than the ones in the interior.

An everyday example of Ostwald ripening is the re-crystallization of water within ice cream which gives old ice cream a gritty, crunchy texture. Larger ice crystals grow at the expense of smaller ones within the ice cream, creating a coarser texture.

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Polarized light microscopy images of NaClO3 crystals

in equilibrium with a saturated solution showing

the process of Ostwald ripening, in which large

crystals grow at the cost of smaller ones.

Synthesis of CdSe QDs (I)oAdd 30 mg of Se and 5 mL octadecene to a 10 mL round

bottom flask over a stirrer hot plate. Warning: Se is an inhalation hazard and this operation should be done in a fume hood.

oMeasure by syringe 0.4 mL trioctylphosphine from its Sure-Seal bottle and add to the flask

oAdd a magnetic stir bar. Stir and warm the solution as necessary to completely dissolve the selenium. Cool to room temperature. This stock solution may be prepared ahead of time, has enough Se precursor for five preparations, and can be stored in a sealed container for at least several months.

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http://mrsec.wisc.edu/Edetc/nanolab/CdSe/index.html

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Synthesis of CdSe QDs (II)oAdd 13 mg of CdO to a 25 mL round bottom flask

clamped in a heating mantle. Warning: CdO is an inhalation hazard and this operation should be done in a fume hood. Avoid plastic containers to reduce static problems.

To the same flask, add by pipet 0.6 mL oleic acid and 10 mL octadecene. Swirl the flask to mix the liquids. Insert a thermometer capable of measuring 225 C.

oHeat the cadmium solution. (For a thermowell on high this takes about 20 minutes.) When the temperature reaches 225 C, use a clean and dry pipet to quickly transfer 1 mL of the room temperature selenium solution to the 225 C cadmium solution and start timing.

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Synthesis of CdSe QDs (III)o Remove approximately 1 mL samples at frequent intervals

using a 9 inch glass Pasteur pipet as the CdSe particles grow in size. Have a partner record the times for each withdrawal, starting from the time the selenium was added. In the video the first five samples were removed at 10 second intervals.

o Continue removing samples at longer intervals so there is a noticeable color change. In the video ten samples are removed within 3 minutes of the initial injection.

o Record the absorbance spectra of the solutions to find the maximum wavelength peak. (Particle sizes can be estimated using the x-intercept and the calculation method shown below.)Graph the absorbance wavelength as a function of growth time.

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Synthesis of CdSe QDs (IV)oRecord the emission spectra of the solutions to find the

maximum wavelength peak. In the movie, sequential samples are placed in a beam of 400 nm wavelength light. What is the evidence for band gap excitation rather than molecular absorbance?

oOption: Samples show narrower peaks in the absorption spectrum when they are quenched more quickly. Instead of collecting in test tubes, they can be collected in flasks containing liquid nitrogen.

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METAL OXIDE-BASEDNanoparticles

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Metal Oxides (MOx) Metal oxides are crystalline solids that contain a metal

cation and an oxide anion. They typically react with water to form bases or with acids to form salts.

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Transition-Metal Oxides Transition metal oxides comprise a class

of materials that contain transition metal elements and oxygen.

They include insulators as well as (poor) metals. Often the same material may display both types of transport properties, hence a Metal-Insulator Transition, obtained by varying either temperature or pressure.

A number of transition metal oxides are also superconductors (e.g., yttrium barium copper oxide, YBa2Cu3O7-x).

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Conducting Glass Indium tin oxide (ITO, or tin-doped indium oxide) is a

solid solution of indium(III) oxide (In2O3) and tin(IV) oxide (SnO2), typically 90% In2O3, 10% SnO2 by weight.

It is transparent and colorless in thin layers while in bulk form it is yellowish to grey. In the infrared region of the spectrum it is a metal-like mirror.

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Conducting Glass ITO is mainly used to make transparent conductive

coatings for liquid crystal displays, flat panel displays, plasma displays, touch panels, electronic ink applications, organic light-emitting diodes, solar cells, antistatic coatings and EMI shieldings.

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Superconductivity Superconductivity is a phenomenon of exactly zero

electrical resistance occurring in certain materials below a characteristic temperature (typically, LN2). It was discovered by Heike Kamerlingh Onnes on April 8, 1911 in Leiden, the Netherlands.

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Meissner Effect Like ferromagnetism and atomic

spectral lines, superconductivity is a quantum mechanical phenomenon, characterized by the Meissner effect, the complete ejection of magnetic field lines from the interior of the superconductor as it transitions into the superconducting state.

The occurrence of the Meissner effect indicates that superconductivity cannot be understood simply as the idealization of perfect conductivity in classical physics.

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Maglev Train

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Maglev train coming out of the PudongInternational Airport in Shanghai

Transrapid 09 at the Emslandtest facility in Germany

Surface Properties Transition metal oxides are commonly utilized for their

catalytic activity and semiconductive properties. Transition metal oxides are also frequently used as pigments in paints and plastics, most notably titanium dioxide (TiO2).

Transition metal oxides have a wide variety of surface structures which affect the surface energy of these compounds and influence their chemical properties. The relative acidity and basicity of the atoms present on the surface of metal oxides is also affected by the coordination of the metal cation (Mn+) and oxygen anion (O2-), which alter the catalytic properties of these compounds. For this reason, structural defects in transition metal oxides greatly influence their catalytic properties.

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Surface Properties The acidic and basic sites on the surface of metal oxides

are commonly characterized via infrared (IR) spectroscopy, calorimetry among other techniques.

Transition metal oxides are also able to undergo photo-assisted adsorption and desorption to control their semiconductivity. One of the more researched properties of these compounds is their response to electromagnetic radiation, which makes them useful catalysts for redox reactions, isotope exchange, specialized surfaces and a variety of other uses currently being studied.

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Surface Properties There is very little known

about the surface structures of transition metal oxides, but their bulk crystal structures are well researched. The approach to determine the surface structure is to assume the oxides are ideal crystal, where the bulk atomic arrangement is maintained up to and including the surface plane.

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NiO rock salt crystal showing cation and oxygen vacancies.

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Surface Reconstruction The surfaces will be generated by cleavages along the planes of the

bulk crystal structure. However, when a crystal is cleaved along a particular plane, the position of surface ions will differ from the bulk structure. Newly created surfaces will tend to minimize the surface Gibbs energy, through reconstruction, to obtain the most thermodynamically stable surface. The stability of these surface structures are evaluated by surface polarity, the degree of coordinative unsaturation and defect sites.

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Electronic Band Structure The bulk electronic band structure of transition metal oxides consists

of overlapping 2p orbitals from oxygen atoms, forming the lower energy, highly populated valence band, while the sparsely populated, higher energy conduction band consists of overlapping d orbitals of the transition metal cation.

In contrast to metals, having a continuous band of electronic states, semiconductors have a band gap that prevents the recombination of electron/hole pairs that have been separated into the conduction band/valence band. The nanosecond scale life times of these electron/hole separations allows for charge transfer to occur with an adsorbed species on the semiconductor surface.

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Band Bending Near the surface of a semi-conducting metal oxide, the valence and

conduction bands are of higher energy, causing the upward bending of the band energy, such that promotion of an electron from the valence band to the conduction band by light of energy greater than the band gap results in migration of the electron towards the bulk of the solid or to a counter electrode, while the hole left in the valence band moves towards the surface.

The increased concentration of holes near the surface facilitates electron transfer to the solid. In the absence of any mechanism to remove electrons from the bulk of the solid, irradiation continues to excite electrons to the conduction band producing holes in the valence band. This leads to the reduction of the upward bending of the band energies near the surface, and the subsequent increase in excited electron availability for reduction reactions.

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Sol Gelo The sol-gel process is a wet-chemical technique used for the

fabrication of both glassy and ceramic materials. In this process, the sol (or solution) evolves gradually towards the formation of a gel-like network containing both a liquid phase and a solid phase.

o Typical precursors are metal alkoxides and metal chlorides, which undergo hydrolysis and polycondensation reactions to form a colloid. The basic structure or morphology of the solid phase can range anywhere from discrete colloidal particles to continuous chain-like polymer networks.

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Base-Catalyzed Sol Gelo In base-catalyzed sols, the particles may grow to

sufficient size to become colloids, which are affected both by sedimentation and forces of gravity. Stabilized suspensions of such sub-micrometre spherical particles may eventually result in their self-assemblyyielding highly ordered microstructures reminiscent of the prototype colloidal crystal: precious opal.

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Photonic Crystals

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Acid-Catalyzed Sols In acid-catalyzed sols, the

interparticle forces have sufficient strength to cause considerable aggregation and/or flocculation prior to their growth. The formation of a more open continuous network of low density polymers exhibits certain advantages with regard to physical properties in the formation of high performance glass and glass/ceramic components in 2 and 3 dimensions.

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Sol Gelo In either case (discrete particles or continuous

polymer network) the sol evolves then towards the formation of an inorganic network containing a liquid phase (gel). Formation of a metal oxide involves connecting the metal centers with oxo (M-O-M) or hydroxo (M-OH-M) bridges, therefore generating metal-oxo or metal-hydroxo polymers in solution.

o In both cases (discrete particles or continuous polymer network), the drying process serves to remove the liquid phase from the gel, yielding a micro-porous amorphous glass or micro-crystalline ceramic. Subsequent thermal treatment (firing) may be performed in order to favor further polycondensation and enhance mechanical properties.

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MnO2

TiO2

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Titanium Dioxide (TiO2) Titanium dioxide, also known as titanium(IV) oxide or

titania, is the naturally occurring oxide of titanium, chemical formula TiO2. When used as a pigment, it is called titanium white, Pigment

White 6, or CI 77891. It has a wide range of applications, from paint to sunscreen to food

colouring. When used as a food colouring, it is coded as E171.

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Titanium Dioxide (TiO2) Titanium dioxide occurs in nature as well-known minerals rutile,

anatase and brookite. The most common form is rutile, which is also the equilibrium

phase at all temperatures. The metastable anatase and brookite phases both convert to rutile upon heating. Rutile, anatase and brookite all contain six coordinated titanium.

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Titanium Dioxide (TiO2) Pigments, coating Sunscreen and UV absorber Photocatalysts and solar cells

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Photocatalysis Photocatalysis is the acceleration of a photoreaction in the presence

of a catalyst. In catalysed photolysis, light is absorbed by an adsorbed substrate. In photogenerated catalysis, the photocatalytic activity (PCA) depends on the

ability of the catalyst to create electronhole pairs, which generate free radicals (hydroxyl radicals: OH) able to undergo secondary reactions.

Its comprehension has been made possible ever since the discovery of water electrolysis by means of the titanium dioxide.

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Waste Water Treatment

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Photocatalysis Methylene blue

C16H18N3SCl + 51/2O2 HCl + H2SO4 + 3HNO3 + 16CO2 + 6H2O

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Nano TiO2

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Kinetics of Chemical Reactions Overview of chemical reactions

A B

vf = kfCA; vb = kbCB vnet =vf vb = kfCA kbCB At equilibrium, vnet = 0, so

kf

kb

b

f

A

BEQ k

kCC

K

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Transition-State Theory The theory was first developed by R. Marcelin in 1915,

then continued by Henry Eyring and Michael Polanyi (Eyring equation) in 1931, with their construction of a potential energy surface for a chemical reaction, and later, in 1935, by H. Pelzer and Eugene Wigner.

Meredith Evans, working in coordination with Polanyi, also contributed significantly to this theory.

Transition-State Theory Transition state theory is also known as activated-complex theory or

theory of absolute reaction rates. In chemistry, transition state theory is a conception of chemical

reactions or other processes involving rearrangement of matter as proceeding through a continuous change or "transition state" in the relative positions and potential energies of the constituent atoms and molecules.

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Svante August ArrheniusSvante August Arrhenius (19 February

1859 2 October 1927) was a Swedish scientist, originally a physicist, but often referred to as a chemist, and one of the founders of the science of physical chemistry.

The Arrhenius equation, lunar crater Arrhenius and the Arrhenius Labs at Stockholm University are named after him.

Arrhenius EquationWave function overlap RTAEAek

RT

G

Aek

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Transition-State Theory At equilibrium

kfCA = fABkCTS; kbCB = fBAkCTS fAB = fAB = /2

A

B

TS

RT

G

f

f

ekk '2

RT

G

b

b

ekk '2

Water Bonding Energy HO-H bond of a water molecule (H-O-H) has 493.4 kJ/mol

of bond-dissociation energy, and 424.4 kJ/mol is needed to cleave the remaining O-H bond

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H2 + O2

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Water Splitting Photocatalysts used in water splitting have several strict requirements. The redox potential needed to drive the reduction of hydrogen from

water is 0.0 eV Vs. Normal Hydrogen Electrode (NHE) at pH=0, and oxidation of oxygen from water is 1.23 eV vs. NHE (oxidation reaction) at pH=0. Therefore the minimum potential difference (voltage) needed to split water 1.23 eV at pH=0.

2H+ + 2e H2 @ 0.0 eV vs. NHE

2H2O 4H+ + O2 + 4e @ 1.23 eV vs. NHE

The minimum band gap for successful water splitting at pH=0 is 1.23 eV, corresponding to light of 1008 nm (in the near-infrared region).

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Why TiO2 is unique? Theoretically, infrared light has enough energy to split

water into hydrogen and oxygen; however, this reaction is kinetically very slow because the wavelength is greater 380 nm.

A sample semiconductor with the proper band structure is TiO2.

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Photocatalysis When TiO2 is subjected to photoirradiation exceeding the material's

band gap, electron-hole pairs, known as excitons, are generated so that additional electrons enter the conduction band, while holes remain in the valence band. These photo-generated electron-hole pairs facilitate redox reactions through the formation of adsorbed radicals on TiO2 surfaces. The photocatalytic activity of TiO2 depends on the relative rates of generation and recombination of electron-hole pairs as well as the levels of adsorbed radical-forming species on TiO2 surfaces.

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Water SplittingPhotocatalytic water splitting is the

production of hydrogen (H2) and oxygen (O2) from water by directly utilizing the energy from light. Hydrogen can be used in a hydrogen fuel cell. Water splitting holds particular interest

since it utilizes the inexpensive natural resource of water. Photocatalytic water splitting has the simplicity of using a powder in solution and sunlight to produce H2 and O2 from water and can provide a clean, renewable energy source, without producing greenhouse gases or having many adverse effects on the atmosphere. Theoretically, only solar energy (photons), water and a catalyst are needed.

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Photodegradationo Photodegradation is degradation of a photodegradable molecule

caused by the absorption of photons, particularly those wavelengths found in sunlight, such as infrared radiation, visible light, and ultraviolet light. However, other forms of electromagnetic radiation can cause photodegradation.

o Photodegradation includes photodissociation, the breakup of molecules into smaller pieces by photons. It also includes the change of a molecule's shape to make it irreversibly altered, such as the denaturing of proteins, and the addition of other atoms or molecules.

o A common photodegradation reaction is oxidation. This type of photodegradation is used by some drinking water and wastewater facilities to destroy pollutants.

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Disinfection of Drinking Water Disinfection is accomplished both by filtering out harmful

microbes and also by adding disinfectant chemicals in the last step in purifying drinking water. Water is disinfected to kill any pathogens which pass through the filters.Following the introduction of any chemical disinfecting agent, the water is usually held in temporary storage often called a contact tank or clear well to allow the disinfecting action to complete.

Chlorine disinfection Ozone disinfection Ultraviolet disinfection Hydrogen peroxide disinfection Solar water disinfection

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Solar water disinfection

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SODIS application in Indonesia

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Waste Water Treatment The average American uses over 100 gallons of water daily,

contributing to the 35 billion gallons of sewage that are produced in the United States each day. Thousands of sewer districts across the nation are unable to treat this huge volume of wastewater to suitable standards, resulting in the pollution of natural waters through the release of poorly treated effluent.

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Waste Water Treatment Primary treatment consists of temporarily holding the sewage in a quiescent basin

where heavy solids can settle to the bottom while oil, grease and lighter solids float to the surface.

Secondary treatment removes dissolved and suspended biological matter. Secondary treatment is typically performed by indigenous, water-borne micro-organisms in a managed habitat.

Tertiary treatment is sometimes defined as anything more than primary and secondary treatment in order to allow rejection into a highly sensitive or fragile ecosystem (estuaries, low-flow rivers, coral reefs,...).

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Waste Water Treatment The use of titanium dioxide (Ti02) in municipal sewage treatment

represents a low-cost alternative to the billion-dollar secondary treatment process. In the presence of sunlight, TiO2 has been shown to accelerate the natural decomposition of low-level organic compounds in aqueous solutions to carbon dioxide and water. The purpose of secondary treatment is the same -- to remove organic compounds.

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Waste Water Treatment In contrast to conventional treatment which relies on the use

of potentially dangerous E. coli and chemical disinfectant with sodium hypochlorite and chlorine, titanium dioxide is safe to the point of being edible. It is a commonly used food additive. If TiO2 were to be used in municipal wastewater treatment, secondary treatment could be eliminated, resulting in billions of dollars of savings and improved effluent quality.

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Responses to Oil Spillso Leave the oil alone so that it breaks down by natural means.o Contain the spill with booms and collect it from the water surface using

skimmer equipment.o Use dispersants to break up the oil and speed its natural degradation.o Introduce biological agents to the spill to hasten biodegradation. Most

of the components of oil washed up along a shoreline can be broken down by bacteria and other microorganisms into harmless substances such as fatty acids and carbon dioxide.

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1-D NANOMATERIALS

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Carbon Nanotubes

160

Armchair (n,n) Zigzag (n,0) Chiral (n,m)

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Carbon Nanotubes Most single-walled nanotubes (SWNT) have a diameter of

close to 1 nanometer, with a tube length that can be many millions of times longer.

The structure of a SWNT can be conceptualized by wrapping a one-atom-thick layer of graphite called graphene into a seamless cylinder. The way the graphene sheet is wrapped is represented by a pair of indices (n,m) called the chiral vector.

The diameter of an ideal nanotube can be calculated from its (n,m) indices as follows

with a = 0.246 nm

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Electrical Conductivity Because of the symmetry and

unique electronic structure of graphene, the structure of a nanotube strongly affects its electrical properties. For a given (n,m) nanotube, if n = m, the

nanotube is metallic; If n m is a multiple of 3, then the

nanotube is semiconducting with a very small band gap, otherwise the nanotube is a moderate semiconductor.

Thus all armchair (n = m) nanotubes are metallic, and nanotubes (6,4), (9,1), etc. are semiconducting

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Band structures computed using tightbinding approximation for (6,0) CNT (zigzag,metallic) (10,2) CNT (semiconducting) and(10,10) CNT (armchair, metallic).

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Mechanical Properties Carbon nanotubes are the strongest and stiffest materials

yet discovered in terms of tensile strength and elastic modulus respectively. This strength results from the covalent sp2 bonds formed between the individual carbon atoms.

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Material Young's modulus (TPa)Tensile strength(GPa)

Elongation at break (%)

SWNT ~1 (from 1 to 5) 1353 16Armchair SWNT 0.94 126.2 23.1Zigzag SWNT 0.94 94.5 15.617.5Chiral SWNT 0.92

MWNT 0.20.95 11150

Stainless steel 0.1860.214 0.381.55 1550Kevlar29&149 0.060.18 3.63.8 ~2

Thermal Properties All nanotubes are expected to be very good thermal conductors

along the tube, exhibiting a property known as "ballistic conduction", but good insulators laterally to the tube axis. Measurements show that a SWNT has a room-temperature thermal

conductivity along its axis of about 3500 Wm1K1; compare this to copper (Cu), a metal well-known for its good thermal conductivity, which transmits 385 Wm1K1.

A SWNT has a room-temperature thermal conductivity across its axis (in the radial direction) of about 1.52 Wm1K1, which is about as thermally conductive as soil.

The temperature stability of carbon nanotubes is estimated to be up to 2800 C in vacuum and about 750 C in air.

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Remarkably enhanced thermal transport based on a flexible horizontally-aligned carbon nanotube array film

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Scientific Reports 6, Article number: 21014 (2016)

Toxicity The toxicity of carbon nanotubes has been an important

question in nanotechnology. Such research has just begun. The data are still fragmentary and subject to criticism.

Preliminary results highlight the difficulties in evaluating the toxicity of this heterogeneous material. Parameters such as structure, size distribution, surface area, surface chemistry, surface charge, and agglomeration state as well as purity of the samples, have considerable impact on the reactivity of carbon nanotubes.

However, available data clearly show that, under some conditions, nanotubes can cross membrane barriers, which suggests that if raw materials reach the organs they can induce harmful effects such as inflammatory and fibrotic reactions.

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Arc Discharge Nanotubes were observed in 1991 in the carbon soot of graphite electrodes

during an arc discharge, by using a current of 100 A, that was intended to produce fullerenes. However the first macroscopic production of carbon nanotubes was made in 1992 by two researchers at NEC's Fundamental Research Laboratory.The method used was the same as in 1991. During this process, the carbon contained in the negative electrode sublimates because of the high discharge temperatures. Because nanotubes were initially discovered using this technique, it has been the most widely-used method of nanotube synthesis.

The yield for this method is up to 30% by weight and it produces both single-and multi-walled nanotubes with lengths of up to 50 micrometers with few structural defects

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Laser Ablation In the laser ablation process, a pulsed laser vaporizes a graphite

target in a high-temperature reactor while an inert gas is bled into the chamber. Nanotubes develop on the cooler surfaces of the reactor as the vaporized carbon condenses. A water-cooled surface may be included in the system to collect the nanotubes. This process was developed by Richard Smalley et al. at Rice University.

The laser ablation method yields around 70% and produces primarily single-walled carbon nanotubes with a controllable diameter determined by the reaction temperature. However, it is more expensive than either arc discharge or chemical vapor deposition.

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Chemical Vapor Deposition

169

o During CVD, a substrate is prepared with a layer of metal catalyst particles, most commonly nickel, cobalt, iron, or a combination. The diameters of the nanotubes that are to be grown are related to the size of the metal particles. This can be controlled by patterned (or masked) deposition of the metal, annealing, or by plasma etching of a metal layer. The substrate is heated to approximately 700C.

o To initiate the growth of nanotubes, two gases are bled into the reactor: a process gas (such as ammonia, nitrogen or hydrogen) and a carbon-containing gas (such as acetylene, ethylene, ethanol or methane). Nanotubes grow at the sites of the metal catalyst; the carbon-containing gas is broken apart at the surface of the catalyst particle, and the carbon is transported to the edges of the particle, where it forms the nanotubes.

Natural, incidental, and controlled flame environments Fullerenes and carbon nanotubes are not necessarily products

of high-tech laboratories; they are commonly formed in such mundane places as ordinary flames, produced by burning methane, ethylene, and benzene, and they have been found in soot from both indoor and outdoor air.

However, these naturally occurring varieties can be highly irregular in size and quality because the environment in which they are produced is often highly uncontrolled. Thus, although they can be used in some applications, they can lack in the high degree of uniformity necessary to satisfy the many needs of both research and industry. Recent efforts have focused on producing more uniform carbon nanotubes in controlled flame environments. Such methods have promise for large-scale, low-cost nanotube synthesis, though they must compete with rapidly developing large scale CVD production.

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Separation and PurificationoBundles as productsoSeparation between metallic and semiconducting

nanotubes DNA Capillary electrophoresis Chemical functionalization

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Gold NanorodsA) Seed preparation: In 20 mL vial:

1. 9 mL 0.1M CTAB (in 35 C water bath)2. 250 uL 4mM HAuCl43. Add stir bar and stir on hot plate (29 C water bath, plate set at 50 C)4. Add 600 uL ICE COLD 0.01M NaBH45. Stir for 2 hours (29 C water bath) (actual: 3 hours)

B) GNR Synthesis: In 50 mL Falcon tube:

35 mL 0.1 M CTAB (pour) 5 mL 4mM HAuCl4 400 uL mM AgNO3 Invert tube gently to mix (~3x) Add 280 uL 0.08 M ascorbic acid. Color changes from orange to clear Add stir bar in 50 mL tube, place in water bath (28 C) Add 100 uL seed solution Stir for 12 hours at 28 C (actual: 19 hours) Centrifuge 2X at 8500 rpm for 30 min and discard supernatant (check with UV-VIS to ensure you

are not discarding rods)

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Gold Nanorods Centrifuged 50 mL tube at 6000 rpm for 28 min. Gold rods detected by UV-

VIS in supernatant. Peaks at 5xx nm and 7xx nm. We resuspended the pellet in the 50 mL tube and distributed 1.5 mL seed solution into eight 1.5 mL-tubes and centrifuged at 8500 rpm for 5 min. There was a small pellet, but supernatant still pink-ish hue so we spun again at 8500 rpm for 10 min. Gold rods still detected by UV-VIS in supernatant. Centrifuged at 10,000 rpm for 10 min.

Re-disperse in solution for functionalization (thiols, etc.)

Reagent prep: 4 mM HAuCl4 (31.48 mg salt in 20 mL H2O) 0.1M CTAB (9.1 g CTAB in 250 mL H2O) 0.01 M NaBH4 (18.9 mg NaBH4 in 50 mL H2O) 8 mM AgNO3 (13.5 mg AgNO3 in 10 mL H2O) 0.08 M ascorbic acid (141 mg acscorbic acid in 10 mL H2O)

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Gold Nanorods Optical absorption

extended to the near-infrared region

Detection and therapy of cancers

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Nanobarcodes

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TiO2 Nanotubes

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ZnO Nanowires and Nanobelts177

A general view of as grown ZnOnanowire arrays at 5 mM, growing 24 h at 70 C: (a) top view; (b) enlarged top view; (c) with a 60tilt. (d) Density varied with concentration: plot of ZnOnanowire density in a 100 m2area (red line) and plot of area percentage covered by ZnOnanowires (blue line). Each data point was obtained from 4 different areas. Inset is a typical image of ZnO nanowires grown at 5 mM.

ZnO Nanowires and Nanobelts178

(a) SEM image of aligned ZnOnanowires grown on sapphire substrate using a thin layer of gold as catalyst. (b) SEM images of gold catalyst patterns using PS sphere monolayer as mask. (c) SEM image of aligned ZnO nanorods grown with a honeycomb pattern.

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Nanobelts and Pieozoelectrics179

(a) SEM image of single-crystal seamless nanoring of ZnO. (b) Low magnification TEM image of the ZnO rings and ZnO nanobelts. The nanobelts have uniform shape and their widths are 15 nm, which is about the same as the thickness of the ring shell, as measured from the tilted image inserted in the figure. The thickness of the nanobelt composing the ring is measured to be 10 nm. (ce) Proposed growth model showing the initiation and formation of the single-crystal nanoring via self-coiling of a polar nanobelt. The nanoring is initiated by folding a nanobelt into a loop with overlapped ends due to long-range electrostatic interaction among the polar charges; the short-range chemical bonding stabilizes the coiled ring structure; and the spontaneous self-coiling of the nanobelt is driven by minimizing the energy contributed by polar charges, surface area and elastic deformation.

Piezoelectricity Piezoelectricity is the electric charge that

accumulates in certain solid materials (such as crystals, certain ceramics, and biological matter such as bone, DNA and various proteins) in response to applied mechanical stress.

The piezoelectric effect is a reversible process in that materials exhibiting the direct piezoelectric effect (the internal generation of electrical charge resulting from an applied mechanical force) also exhibit the reverse piezoelectric effect (the internal generation of a mechanical strain resulting from an applied electrical field)

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Nanogenerators of Power

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Nanobelt-Based FETs182

The physical principle of the piezoelectric-field effect transistor. (a) Schematics of a conventional field effect transistors using a single nanowire/nanobelt, with gate, source and drain. (b) The principle of the piezoelectric-field effect transistor, in which the piezoelectric potential across the nanowire created by the bending force fy replaces the gate as in conventional FET. The contacts at the both ends are Ohmic. (c) SEM images with the same magnification showing the five typical consecutive bending cases of a ZnO wire; the scale bar represents 10 m. (d) Corresponding IV characteristics of the ZnOnanowire for the five different bending cases.

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2D NANOMATERIALS

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Graphite

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Graphene Graphene is one-atom-thick

planar sheets of sp2-bonded carbon atoms that are densely packed in a honeycomb crystal lattice. The term graphene was coined as a combination of graphite and the suffix -ene by Hanns-Peter Boehm, who described single-layer carbon foils in 1962.

Graphene is most easily visualized as an atomic-scale chicken wire made of carbon atoms and their bonds. The crystalline or "flake" form of graphite consists of many graphene sheets stacked together.

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Graphene The carbon-carbon bond length in graphene is about

0.142 nm. Graphene sheets stack to form graphite with an interplanar spacing of 0.335 nm, which means that a stack of three million sheets would be only one millimeter thick.

Graphene is the basic structural element of some carbon allotropes including graphite, charcoal, carbon nanotubes and fullerenes. It can also be considered as an indefinitely large aromatic molecule, the limiting case of the family of flat polycyclic aromatic hydrocarbons.

The Nobel Prize in Physics for 2010 was awarded to Andre Geim and Konstantin Novoselov "for groundbreaking experiments regarding the two-dimensional material graphene".

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Graphene Production Drawing method: mechanical exfoliation of graphite Epitaxial growth on SiC or metal surfaces Reduction of graphite oxide Cutting of carbon nanotubes From sugar: Sucrose among other substances such as

Plexiglas have been turned quickly and easily into graphene via application to a copper or nickel substrate and being subjected to 800 C under low pressure with exposure to argon and hydrogen gas

Sonication of graphite

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Why is graphene interesting? GNR band structure for zig-zag orientation. Tightbinding

calculations show that zigzag orientation is always metallic.

GNR band structure for arm-chair orientation. Tightbindingcalculations show that armchair orientation can be semiconducting or metallic depending on width (chirality).

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Applications Graphene nanoribbons

Zigzag: metallic Armchair: semiconducting or metallic

Graphene transistors Ballastic transistors

Integrated circuits

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Graphene Touch Screens

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Transparent Flexible Robust Conductive

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Energy Conversion

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Heteroatom-Doping of Graphene

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Chem. Soc. Rev., 2014, 43, 7067-7098