Adrienne Borchardt

Overview

What are quantum dots? Applications Metal salt study pH adjustment study

S OH

O

S

OHO

S

OHO

SHO

OS

HO

O

SHO

O

S

OHO

S

HO

O

S OH

O

S

HO

O

S

OHOS

HO

O

S

HO

O

S

OHO

S

OHO

S

OH

O

S

HO

O

S

OHO

S

OH

O

CdSe

Quantum Dots (QDs)

Sources: http://www.tnw.tudelft.nl/live/pagina.jsp?id=5550e07d-ec54-4f77-bcf0-5736863ef4b8&lang=en; http://www.aist.go.jp/aist_e/aist_today/2006_21/hot_line/hot_line_22.html

Applications

Light-Emitting Diodes (LEDs) Photovoltaic Devices Biological Sensors Quantum Computation Dyes Display Technology

Sources: http://www.phbeta.com/samsung/samsung-electronics-created-the-first-full-color-display-with-quantum-dots/; http://www.instructables.com/id/LED-Throwies/; http://www.sciencemag.org/content/307/5709/538/F4.large.jpg; http://inhabitat.com/colored-solar-panels-dont-need-direct-sunlight/green-sun-colored-solar-panels-4/

Metal Salt Study Synthesis

Reaction Mixture• Metal salts:

• Cd(ClO4)2·H2O • CdSO4

• CdCl2• CdCl2·2 ½ H2O

• Thiol: MSA• Ligand-to-metal ratio is 2.4:1.

Metal Salt Study Synthesis

Procedure• The pH is adjusted to ≥ 11 using 1 M

NaOH while stirring. • Mixture was deaerated for ~30 minutes

with N2.• NaHSe solution is added to reaction

mixture. • Mixture was allowed to reflux over a

period of time.• Aliquots were collected based on visible

change in color.

Metal Salt Study

0 20 40 60 80 100 120 140 160550

560

570

580

590

600

610

Perchlorate Sulfate Chloride (anhydrous)Chloride (purified)

Time (min)Flu

ore

scen

ce

MA

X (

nm

)

CdSe Core

(CdSe)33 and (CdSe)34 core

Most stable

A. Kasuya et al. Nature Mater. 2004, 3, 99-102.c

Charge Deconvolution Mass Spectrometry

Sources: http://sydney.edu.au/science/molecular_bioscience/facilities/mass.php

MS of MSA-CdSe QDs

m/z ~ 44

Water-Soluble Thiols

HS OH

O

HS OH

OH

O

HS

HS

OH

OH

HO

OH

O

O

SH

NH

OH

SH

O

O

HOHN

NH

OH

O

NH2

O

HS

O

O

glutathione (GLU)tiopronin (TIO)

3-mercaptopropionic acid (MPA)

mercaptosuccinic acid (MSA)

3-mercapto-1-propanol (MPL)

thioglycolic acid (TGA)

thioglycerol (TGL)

HS

NH2

OH

O

cysteine (CYS)

4.60

4.34

3.64

3.30

3.51

pH Study Synthesis

Reaction Mixture• Metal perchlorate: Cd(ClO4)2·H2O in Type 1

water.• Thiol: MPA, TGA, TIO• Ligand-to-metal ratio is 2.4:1.

Procedure• The same initial procedure was performed. • Prior to reflux, seven aliquots of the mixture

were removed and pH was adjusted to a range starting at 1 pH unit below pka.

pH Effects on Fluorescence

Aggregation

3.5 4 4.5 5 5.5 6560

565

570

575

580

585

590

595

600

pH

Flu

ore

scen

ce

MA

X

(nm

)

MS of MPA-CdSe QDs

Time 2

pH 5.271

Future Work

Establishing proper protocol/conditions to obtain mass spectrum of QDs

Actually seeing a definitive mass spectrum of the QDs

Studying other aspects (stability, pH effects) of the QDs using the different metal salts

Acknowledgements

NSF CHE-095940 Dr. Deon Miles The Sewanee Chemistry Department