Post on 14-Aug-2019
transcript
INTERDIGITATED ELECTRODE (IDE) SENSOR OF
POLYANILINE (PANI) NANOPARTICLES THIN FILM
FOR DETECTION OF METHANOL VAPOUR
ZULKHAIRI BIN ZAKARIA
UNIVERSITI MALAYSIA PERLIS
2012
© This item is protected by original copyright
INTERDIGITATED ELECTRODE (IDE) SENSOR OF
POLYANILINE (PANI) NANOPARTICLES THIN
FILM FOR DETECTION OF METHANOL VAPOUR
by
Zulkhairi Bin Zakaria
(0930410413)
A thesis submitted
in fulfillment of the requirements for the degree of
Master of Science (Material Engineering)
School of Materials Engineering
UNIVERSITI MALAYSIA PERLIS
2012
© This item is protected by original copyright
i
UNIVERSITI MALAYSIA PERLIS
NOTES: * If the thesis is CONFIDENTIAL or RESTRICTED, please attach with the letter from the
organization with period and reasons for confidentially or restriction.
DECLARATION OF THESIS Author’s full name : ZULKHAIRI BIN ZAKARIA Date of birth : 04 JANUARY 1985 Title : INTERDIGITATED ELECTRODE (IDE) SENSOR OF POLYANILINE (PANI) NANOPARTICLES THIN FILM FOR DETECTION OF METHANOL VAPOUR Academic Session : 2010/2011 I hereby declare that the thesis becomes the property of Universiti Malaysia Perlis (UniMAP) and to be placed at the library of UniMAP. This thesis is classified as : CONFIDENTIAL (Contains confidential information under the Official Secret Act 1972)* RESTRICTED (Contains restricted information as specified by the organization where
research was done)* OPEN ACCESS I agree that my thesis is to be made immediately available as hard copy or on-line open access (full text) I, the author, give permission to the UniMAP to reproduce this thesis in whole or in part for the purpose of research or academic exchange only (except during a period of ____ years, if so requested above). Certified by:
_________________________ ________________________
SIGNATURE SIGNATURE OF SUPERVISOR
850104-03-5007 PROF DR. MOHD NOOR AHMAD __________________________ ________________________________
(NEW IC NO. / PASSPORT NO.) NAME OF SUPERVISOR
Date: 2/4/2012 Date: 2/4/2012
© This item is protected by original copyright
ii
APPROVAL AND DECLARATION SHEET
This thesis titled Interdigitated Electrode (IDE) Sensor of Polyaniline (PANI) Nanoparticles
Thin Film for Detection of Methanol Vapour was prepared and submitted by Zulkhairi Bin
Zakaria (Matrix Number: 0930410413) and has been found satisfactory in terms of scope,
quality and presentation as fulfillment of the requirement for the award of degree of Master
of Science (Material Engineering) in University Malaysia Perlis (UniMAP). The members
of the Supervisory committee are as follows:
DR. MOHD NOOR AHMAD
Professor
School of Materials Engineering
University Malaysia Perlis
(Supervisor)
DR. SUPRI ABD. GHANI
Lecturer
School of Materials Engineering
University Malaysia Perlis
(Co-Supervisor)
Check and Approved by
………………………………………………….
(PROF DR. MOHD NOOR AHMAD)
Supervisor
School of Materials Engineering
University Malaysia Perlis
(Date: …………………….)
© This item is protected by original copyright
iii
ACKNOWLEDGEMENTS
In the name of Allah The Most Gracious and The Most Merciful.
Thank to Allah for his love, blessings and enlightenment that allowed for the
successful completion of this thesis as part of my Master of Science (Material Engineering)
at University Malaysia Perlis. I wish to express sincere gratitude to my supervisor, Prof Dr.
Mohd Noor Ahmad through whom that I have learned a lot and for his unfailing patience
and guidance with regards to this master research. I am also extremely thankful my co-
supervisor Dr. Supri Abd Ghani for giving a lot of advice and encouragements for my
academic and research efforts.
It would have been impossible for me to complete my master without the help from
sensor technology and application group member and lecturers from School of material
especially Prof Dr. Ali yeon Md Syakaff, En Ammar Zakaria, Abu Hassan, Abd Hallis, Dr
Irwana and En. Tulus Ikhsan who have continuously aided in the successful completion of
this Research.
I thank my fellow colleagues of seniors and juniors at the sensor technology and
application group and at the School of Materials Engineering for sharing their time,
expertise and humour with me. They are particularly Pak Iqmal, Fathi, Seskya, Mohd
Nasha ‘Ain, Faroq and Azharudin.
Lastly, a very big thank you to my beloved family for their support, love and
constant encouragement the have bestowed upon me. Without their support, I would never
have gotten so far.
© This item is protected by original copyright
iv
TABLE OF CONTENTS
DECLARATION OF THESIS i
APPROVAL AND DECLARATION SHEET ii
ACKNOWLEDGEMENTS iii
TABLE OF CONTENTS iv
LIST OF TABLES viii
LIST OF FIGURES viii
LIST OF ABBREVIATIONS xi
LIST OF SYMBOLS xiii
ABSTRAK xiv
ABSTRACT xv
CHAPTER 1: INTRODUCTION
1.1 Introduction 1
1.2 Problem statements 4
1.3 Objective of studies 5
1.4 Scope of works 5
CHAPTER 2: LITERATURE REVIEW
2.1 Introduction 7
2.2 Conducting polymers 7
2.2.1 Synthesis of conducting polymers 9
2.2.2 Deposition method of conducting polymers 9
© This item is protected by original copyright
v
2.3 Polyaniline (PANI) 12
2.3.1 Synthesis of Polyaniline (PANI) 15
2.3.2 Mechanism of detection 19
2.4 Inkjet printing method 21
2.4.1 Inkjet printing method in sensor fabrication 22
2.4.2 Effect of deposition thickness 23
2.5 Configuration of interdigitated electrode (IDE) 24
2.6 Gas sensor 26
2.6.1 Classification of gas sensor 27
2.6.2 Characteristic of gas sensor 28
2.6.3 Conducting polymers (PANI) as gas sensor 29
CHAPTER 3: METHODOLOGY
3.1 Introduction 31
3.2 Materials, instrumentation and software 31
3.3 Fabrication of interdigitated electrode (IDE) sensor 32
3.4 Synthesis of polyaniline (PANI) nanoparticles 33
3.5 Deposition polyaniline (PANI) nanoparticles by inkjet printer 36
3.6 Resistance measurement 38
3.7 Particles size analysis 38
3.8 Fourier transform infrared spectroscopy (FTIR) analysis 39
3.9 UV-VIS spectroscopy analysis 39
3.10 Optical microscopy 40
© This item is protected by original copyright
vi
3.11 Scanning electron microscopy (SEM) 40
3.12 Experimental setup for IDE sensor response 41
CHAPTER 4: RESULTS AND DISCUSSION
4.1 Introduction 43
4.2 Characterizations of polyaniline (PANI) nanoparticles 44
4.2.1 Particles size analysis 44
4.2.2 Fourier transform infrared spectroscopy (FTIR) analysis 46
4.2.3 UV-VIS spectroscopy analysis 48
4.2.4 Resistance measurement 49
4.2.5 Optical microscopy 51
4.2.6 Scanning electron microscope (SEM) 53
4.3 Effect of deposition thickness of IDE sensor for methanol vapour 54
4.4 Characteristics of IDE sensor for methanol vapour 55
4.4.1 Response and recovery time 55
4.4.2 Repeatability and reproducibility 56
4.4.3 Sensitivity 59
4.4.4 Selectivity 60
4.4.5 Shelf life of sensor 62
CHAPTER 5: CONCLUSIONS
5.1 Conclusions 64
© This item is protected by original copyright
vii
REFERENCES 68
APPENDICES
A Particles size analysis 76
B FTIR characteristic 77
C Energy-dispersive X-ray spectroscopy (EDX) for aluminum 78
© This item is protected by original copyright
viii
LIST OF TABLES
Table 4.1 Peaks of polyaniline (PANI) nanoparticles 47
Table 4.2 Response, response time (t1), and recovery time (t2) 56
of IDE sensor
Table 4.3 Repeatability of IDE sensor upon exposure to 10 % v/v 57
methanol vapour
Table 4.4 Reproducibility of IDE sensor upon exposure to 10 % v/v 58
methanol vapour
LIST OF FIGURES
Figure 2.1 Some common conducting polymers 8
Figure 2.2 (a) Base structure of PANI, (b) for y = 1 the oxidation 14
state is leucoemeraldine (completely reduced material),
(c) for y = 0 the polymer is in the pernigraniline oxidation state
(completely oxidized form) and (d) for y = 0.5 the polymer is
in the emeraldine oxidation state (half oxidized state)
Figure 2.3 Mechanism for the polymerization of aniline to PANI in the 15
doped-ES state, where (A-) represents a charge balancing
counter-ion.
Figure 2.4 Redox transitions in PANI are showed in the vertical reaction 16
sequence: (a) pernigraniline (PB), (b) emeraldine base (EB),
and (c) Leucoemeraldine (LB). The horizontal reaction reflects
proton doping of EB to (d) emeraldine salt (ES), where (A-)
represents charge-balancing counter-ions.
Figure 2.5 Schematic representation of the polymerization in DBSA 17
reversed micelle
Figure 2.6 Schematic illustration of the synthesis of pure PANI nanofibers 18
Figure 2.7 PANI undergoes dedoping by deprotonation when expose to 20
ammonia gas
Figure 2.8 Reaction of nanocomposite of Pd/PANI toward methanol vapour 20
© This item is protected by original copyright
ix
Figure 2.9 Configuration of IDE 25
Figure 2.10 IDE with the gray pattern on PET substrate 25
Figure 2.11 Schematic layout of a gas sensor 26
Figure 3.1 (a) Stainless steel mask, and (b) IDE pattern 32
Figure 3.2 Configuration of the IDE design 33
Figure 3.3 PANI nanoparticles ink after synthesis 34
Figure 3.4 Flow chart synthesis of PANI nanoparticles 35
Figure 3.5 Epson Stylus T10 printer and compatible Epson print ink 36
cartridges
Figure 3.6 Printing setup of PANI nanoparticles ink by 37
Epson stylus T10 printer
Figure 3.7 Deposition PANI nanoparticles ink (green colour) on the IDE 37
sensor [S1 (7 prints), S2 (14 prints), S3 (21 prints), &
S4 (28 prints)]
Figure 3.8 IDE sensor held by PCB holder 38
Figure 3.9 Schematic circuit diagram for resistance measurement 38
Figure 3.10 Experimental setup for IDE sensor response 41
Figure 3.11 Schematic circuit diagram for IDE sensor response 42
Figure 4.1 Particle size distributions of PANI nanoparticles 44
Figure 4.2 TEM image of PANI nanoparticles were imaged on a carbon 45
sheet
Figure 4.3 FTIR results of PANI nanoparticles after synthesis 46
Figure 4.4 Chemical structure of PANI nanoparticles doped by DBSA 47
Figure 4.5 UV-Vis spectra of PANI nanoparticles 48
Figure 4.6 Resistance measurements of inkjet-printed PANI nanoparticles 49
films over number of prints
Figure 4.7 Optical images of PANI nanoparticles film for different deposition 51
© This item is protected by original copyright
x
layer at 5x magnification: (a) 1print (b) 7 prints, (c) 14 prints,
(d) 21 prints (e) 28 prints and (f) interface between substrate and
PANI nanoparticles film
Figure 4.8 SEM images of PANI nanoparticles film before (a) and after 53
(b) expose to 10 % v/v methanol vapour. (7 prints)
Figure 4.9 Effect of deposition thickness of IDE sensor upon 54
exposure to 10 % v/v methanol vapour at exposure time of 180s
Figure 4.10 Repeatability of IDE sensor upon exposure to 10 % v/v 57
methanol vapour at exposure time of 180s
Figure 4.11 Reproducibility of IDE sensor upon exposure to 10 % v/v 58
methanol vapour at exposure time of 120s
Figure 4.12 Sensitivity of IDE sensor upon exposure to six different 59
concentrations of methanol vapor and saturated water vapour
at exposure time of 180s
Figure 4.13 Selectivity of IDE sensor upon exposure to 10 % v/v of 61
different alcohols at exposure time of 180s
Figure 4.14 Shelf life of IDE sensor upon exposure to 10 % v/v 62
methanol vapour at exposure time 180s for 42 days
Figure 4.15 Shelf life of IDE sensor until 28 days 63
Figure 4.16 Shelf life of IDE sensor until 42 days 63
© This item is protected by original copyright
xi
LIST OF ABBREVIATIONS
Al aluminum
APS ammonium persulfate
B benzenoid
CERHR center for the evaluation of risks to human reproduction
CHEMFET chemically sensitized field effect transistor
CP conducting polymer
CV coefficient of variability
C=C carbon double bond
DAQ data acquisition
DBSA dodecylbenzenesulfonic acid
EB emeraldine base
ES emeraldine salt
FTIR fourier transform infrared spectroscopy
HCl hydrochloric acid
HCSA camphorsulfonic acid
IDE interdigitated electrode
LB leucoemeraldine
LB langmuir-blodgett
LbL layer-by-layer
N nitrogen-containing
NanoPANI polyaniline nanoparticles
NH4+
ammonium
OM optical microscopy
PA polyacetylene
PANI polyaniline
PANI-ES polyaniline – emeraldine salt
PB pernigraniline
Pd/PANI palladium/polyaniline
PEDOT poly (3,4-ethylene-dioxythiophene)
© This item is protected by original copyright
xii
PEDOT/PSS poly (3, 4-ethylenedioxythiophene)/poly (styrenesulfonate)
PET polyethylene terephtalate
PPE poly (phenylene ethynylene)
PPV poly (phenyl vinlene)
PPY polypyrrole
PTH polythiophene
PVC polyvinyl chloride
Q quinoid
QCM quartz crystal microbalance
RMS root mean square
SAW surface acoustic wave
SDS sodium dodecyl sulfate
SEM scanning electron microscopy
SO3–
sulphite ion
VOC volatile organic compound
© This item is protected by original copyright
xiii
LIST OF SYMBOLS
A
- charge balancing counter-ions
ppm parts per million
rpm revolutions per minute
S1 7 prints
S2 14 prints
S3 21 prints
S4 28 prints
V1 valve 1
V2 valve 2
V3 valve 3
V4 valve 4
v/v volume per volume
cP centipoise
dy/cm dyne per centimetre
© This item is protected by original copyright
xiv
SENSOR INTERDIGIT (IDE) DARI FILEM NIPIS NANOPARTIKEL
POLIANILINA (PANI) UNTUK PENGESANAN WAP METANOL
ABSTRAK
Metanol dilepaskan ke persekitaran melalui penggunaan industri atau secara semulajadi
daripada gunung berapi, tumbuh-tumbuhan dan mikrob. Pendedahannya boleh berlaku dari
udara persekitaran dan semasa penggunaan pelarut. Ia mempunyai ketoksikan yang tinggi
kepada manusia. Jika terminum, sebagai contohnya 10ml metanol tulen boleh
menyebabkan kebutaan kekal dan 30ml boleh membawa maut. Tesis ini melaporkan satu
kajian pada sensor interdigit (IDE) dari filem nipis nanopartikel PANI untuk pengesanan
wap methanol. Penyelidikan ini meliputi pembangunan sensor, kaedah pencirian
nanopartikel PANI dan rekabentuk satu sistem pengesanan IDE. IDE telah difabrikasikan
menggunakan teknik penyejatan pada substrat polietilena tereftalat (PET) dengan
aluminum dijadikan sebagai elektrod. Lebar dan jurang sensor ini adalah 0.25 mm dan 0.51
mm. Nanopartikel PANI telah disintesis menggunakan kaedah pempolimeran emulsi.
Kaedah semburan dakwat bercetak telah digunakan untuk menambahkan nanopartikel
PANI pada IDE. Didapati saiz nanopartikel PANI adalah 152 nm. Analisis FTIR spektrum
memperlihatkan kehadiran garam emeraldin polianilina (PANI-ES) dengan kewujudan
puncak-puncak pada 3321, 1637, 1204 dan 1037 cm-1
. UV-Vis spektrum bagi nanopartikel
pANI menunjukkan kehadiran tiga peralihan jalur pada 340, 420 dan 790-800 nm.
Kerintangan semburan dakwat bercetak bagi lapisan nanopartikel PANI ke atas bilangan
cetakan menunjukkan penurunan dari 8.34 kepada 3.24 MΩ. Permukaan semburan dakwat
bercetak lapisan nanopartikel PANI akan menjadi lebih licin dan seragam dengan
peningkatan jumlah cetak dan kehomogenan yang baik dapat diperhatikan pada cetakan ke
21 dan 28. Morfologi lapisan berliang dengan taburan liang tidak seragam telah dilihat
melalui SEM. Didapati saiz taburan liang menjadi semakin besar selepas pendedahan
kepada wap metanol menunjukkan berlakunya resapan gas. Peningkatan bilangan cetakan
menunjukkan masa tindak balas meningkat dan keluaran voltan menurun tetapi masa
pemulihan tidak berubah. Tujuh cetakan menunjukkan sensor yang optimum dengan masa
tidak balas adalah 10s. Kebolehulangan dan kebolehasilan yang baik dapat dilihat dengan
hasil respons yang tetap. Analisis kepekaan menunjukkan pengurangan kepekatan wap
metahol akan mengurangkan keluaran voltan. Had pengesanan sensor ini adalah 20 ppm.
Analisis pemilihan menunjukkan peningkatan rangkaian karbon bagi alkohol akan
mengurangkan keluaran voltan. Jangka hayat simpanan bagi sensor ini adalah 28 hari.
© This item is protected by original copyright
xv
INTERDIGITATED ELECTRODE (IDE) SENSOR OF POLYANILINE (PANI)
NANOPARTICLES THIN FILM FOR DETECTION OF METHANOL VAPOUR
ABSTRACT
Methanol is released to the environment during industrial uses or naturally from volcanic
gases, vegetation, and microbes. Exposure may occur from ambient air and during the use
of solvents. Methanol has a high toxicity to humans. If ingested, for example, as little as
10 ml of pure methanol can cause permanent blindness, and 30 ml is potentially fatal. This
thesis reports a study on interdigitated electrode (IDE) sensor of PANI nanoparticles thin
film for detection of methanol vapour. The research covers the sensor development,
characterization method of PANI nanoparticles and setting up a IDE detection system. IDE
was fabricated by evaporation technique on polyethylene terephthalathe (PET) substrate
using aluminum as electrode material. The digit width and gap of the sensor were 0.25 mm
and 0.51 mm. PANI nanoparticles was synthesized by emulsion polymerization method.
Inkjet printing method was used to deposit the PANI nanoparticles onto IDE. The size of
PANI nanoparticles was 152 nm. FTIR spectra analysis correspond to well-doped PANI-ES
with the existence of peaks at 3321, 1637, 1204 and 1037 cm-1
. UV-Vis spectra of the PANI
nanoparticles shown the three band transitions appear at 340, 420 and 790-800 nm.
Resistance of inkjet-printed PANI nanoparticles films was decreased over number of prints
from 8.34 to 3.24 MΩ. The surface of the inkjet-printed PANI nanoparticles films became
smoother and more uniform with increasing number of prints and good homogeneity could
be observed at 21 and 28 prints. Porous film morphology with non-uniform pores
distribution was observed by SEM. The size of pores distribution to be bigger after
exposure to methanol vapour indicated that diffusion gas molecule had occurred. Increasing
the number of prints shown that the response time increase and output voltage was
decreased but recovery time not changing. Seven print shown the optimum sensor with
response time 10s. Good repeatability and reproducibility was observed by constant
response. Sensitivity analysis shown that decreasing the concentration of methanol vapour
would decrease the output voltage. The limit detection of the sensor was 20 ppm.
Selectivity analysis express that an increasing the carbon chain of alcohols will be decrease
the output voltage. The shelf life of this sensor was 28 days.
© This item is protected by original copyright
1
CHAPTER 1
INTRODUCTION
1.1 Introduction
The exposed of volatile organic compounds (VOC) in human life is worrying
because it may adversely affect human health. As we know that, VOC are emitted from
certain solids or liquids. VOC include a variety of chemicals, some of which may have
short and long term adverse health effects such as eye, nose, throat irritation, headaches,
loss of coordination, nausea, damage to liver, and kidney (Kampa & Castanas, 2008). These
organic compounds tend to release by a wide array of products such as cleaning supplies,
pesticides, building materials and furnishings, office equipment, craft materials,
photographic solutions and household products like paints, varnishes and wax. Fuels also
are made up of organic chemicals. All of these products can release organic compounds
while using them, and to some degree, when they are stored.
Alcohols are a class of organic compounds formed from hydrocarbons by the
substitution of one or more hydroxyl groups for an equal number of hydrogen atoms. Some
common alcohols are methanol, ethanol, 2-propanol (isopropyl alcohol), phenol and
ethylene glycol. Ethanol is commonly known because it has countless applications as a
solvent for organic chemical. Besides, this alcohol is the only least toxic of the straight-
chain alcohols and our bodies can metabolize by produce an enzyme (Chang, 2005). The
© This item is protected by original copyright
2
most dangerous alcohol is methanol because it is highly toxic and ingestion of only a few
milliliters can cause nausea and blindness. In June 1998, methanol was identified for
evaluation by the Center for the Evaluation of Risks to Human Reproduction (CERHR)
based on high production volume, extent of human exposure, and published evidence of
reproductive or developmental toxicity (Shelby et al., 2004). The effect of methanol to
human life can be exposed through environmental sources such as air, water and contact
with methanol containing consumer products.
Due to the high levels of toxicity and adverse effects in humans, then a detection
and analysis system should be developed to detect methanol vapour. Gas sensor is an
effective tool to detect toxic substances and has a great potential for developed. A gas
sensor can be described as a device, which upon exposure to a gaseous chemical
compounds, alters one or more of its physical or chemical properties in a way that can be
measured and quantified directly or indirectly (Joshi & Singh, 2010). Actually gas sensors,
chemosensors, chemical gas sensors, or biosensors can be classified according to their
operating principle and each class having different characteristics. Gas sensors usually
utilize an electrical or optical response by adsorption of gas molecules on surface of an
active sensing layer. This makes them commonly used for industrial, commercial and
residential applications.
Conducting polymer (CP)-based gas sensors have received considerable interest in
recent years because of their sensing ability, high sensitivities, short response times, easily
synthesized and operate at room temperature (Bai et al., 2007). Trojanowicz (2003)
described CP as polymers with spatially extended π-bonding systems obtained by
electrochemical polymerization or chemical oxidation of their monomer. The common
© This item is protected by original copyright
3
feature of CP materials is the presence of a conjugated π-electron system which extends
over the whole polymer. Wilson & Baietto (2009) said that CP gas sensors operate based on
changes in electrical resistance caused by chemical reaction or adsorption of gases onto the
sensor surface. It consist of a substrate, such as silicon, glossy paper (Arenaa et al., 2010)
or polyethylene terephthalate (PET) (Cattanach et al., 2006), a pair of gold-plated
electrodes (interdigitated electrode, IDE) and a conducting organic polymer coating as the
active sensing layer (Schaller et al., 1998).
There are several CP used as the active sensing layers of gas sensor such as
Polyacetylene (PA), Polyaniline (PANI), Polypyrrole (PPY), Polythiophene (PTH),
Poly(3,4-ethylene-dioxythiophene) (PEDOT) and Poly(phenyl vinlene) (PPV) (Bai & Shi,
2007). PANI is most common used in gas sensor because of its good stability and
outstanding properties compared to other CP (Bhadra et al., 2009). It is one of the so-called
doped polymers, in which conductivity results from a process of partial oxidation or
reduction. Bhadra et al. (2009) has provided different methods for the synthesis of PANI
such as chemical, electrochemical, template, enzymatic, plasma and photo. Basically,
chemical polymerization is divided into heterophase, solution, interfacial, seeding,
metathesis, self-assembling, and sonochemical polymerizations. In this research,
heterophase polymerization has been used to synthesis PANI into nanoparticles. This
polymerization as called nanodispersion method.
In deposition of PANI films, different methods exist to deposit PANI onto a
substrate including electrochemical deposition, dip-coating, drop-coating, spin coating, and
Langmuir-Blodgett (LB) (Nicolas-Debarnot & Poncin-Epaillard, 2003). However, these
methods present a number of limitations such as thickness control and industrial
© This item is protected by original copyright
4
productivity. Inkjet printing is very interesting method to deposit PANI because it familiar
as a method for printing on paper (Mabrook et al., 2006a). The advantages of this method
compared to other methods are that it is non-contact, high speed, and can form very thin
films or build thick layers (Calvert et al., 2004). Mabrook et al. (2006a) used a commercial
HP thermal printer to print polypyrrole film for alcohol vapour detection at room
temperature. They found that the conductivity was increased when the films is exposed to
the vapours of simple alcohols.
1.2 Problem Statements
Conducting polymers (CP) are an attractive subject of research because of the
interesting properties and many application possibilities. Among the available CP, PANI is
found to be the most promising because of its ease of synthesis, low cost monomer, tunable
properties, and good stability compared to other CP. However, the main problem associated
with the effective utilization of all CP including PANI is inherent in their lower level of
conductivity, their infusibility, hygroscopic and poor solubility in all available solvents
(Rao et al., 2003; Cho et al., 2005).
According to Bhadra et al., (2006; 2008), the solubility and processability of some
CP can be improved through doping with a suitable dopant or modifying the starting
monomer. However, the selection of dopant should be based on synthesis methods, films
deposition and applications to be used. Besides that, by using the inkjet printer, PANI
should conform to quality printer ink in terms of viscosity and surface tension so that the
ink does not drop out from the printer heads. Likewise, particles size of PANI should be
smaller than the size of the nozzle printer heads to prevent the nozzle from clogging.
© This item is protected by original copyright
5
Therefore, studies in the synthesis of PANI with nanodimentional control have been
managed to overcome this issues.
1.3 Objective of Studies
The objectives of research are:
i. To investigate the physical properties of inkjet-printed thin film PANI
nanoparticles.
ii. To investigate the effect of number of printed layers (film thickness) on
the sensing performance of the sensor.
iii. To investigate sensing properties of the inkjet-printed PANI
nanoparticles thin film towards methanol vapour using IDE gas sensor.
1.4 Scope of Works
This research was focused on the study of interdigitated electrode (IDE) sensor of
PANI nanoparticles thin film for detection of methanol vapour. Firstly, an IDE sensor was
fabricated by thermal vacuum evaporation. Aluminum (Al) was used as an electrode
material. The sensing substrates upon which the PANI nanoparticles films was deposited
consisted of an Al electrodes 0.25 mm wide with 0.51 mm gap each 10 mm long on a
polyethylene terephthalate (PET) substrate. Then, PANI nanoparticles was deposit by inkjet
printing method onto the Al tracks of the sensing substrate. PANI nanoparticles was
synthesized by chemical polymerization dispersion of corresponding monomers as an
active sensing layer. Dodecylbenzenesulfonic acid (DBSA) was used as a dopant material,
© This item is protected by original copyright
6
ammonium peroxydisulfate (APS) as an oxidant material and sodium dodecyl sulfate (SDS)
as surfactants compounds.
Particles size of PANI nanoparticles was measured by Mastersizer 2000, while the
UV-Visible spectra analysis of the synthesized PANI nanoparticles was analyzed by UV-
vis spectroscopy. Optical microscopy and Scanning Electron Microscopy (SEM) was used
to investigate the morphology of PANI nanoparticles thin film. Fourier Transform Infrared
Spectroscopy (FTIR) analysis was carried out for identifying chemicals compounds that are
either organic or inorganic. IDE sensor for methanol vapour was analyzed to determine the
effect of thickness, response time, recovery time, repeatability, sensitivity, selectivity,
reproducibility and shelf life (lifetime) of sensor as sensor characteristics.
© This item is protected by original copyright
7
CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
This chapter explains the background study in this research. Chapter 2.2 reviews the
general conducting polymer (CP) include synthesis and deposition method of CP. Chapter
2.3 describes about polyaniline, route to synthesis PANI conventionally or in
nanoparticles, and mechanism of detection. In chapter 2.4 the inkjet printing method and
effect of deposition thickness is explained. The configuration of IDE is explained in chapter
2.5. Chapter 2.6 includes the classification, characteristics, and an utilization of CP as gas
sensor.
2.2 Conducting Polymers
Conducting polymers (CP) are a group of conjugated polymers that exhibit
excellent electrical conductivity. It is belong to a novel class of materials that are being
evaluated for application in charge storage devices (batteries or capacitors),
electromagnetic screens, sensors, membranes and corrosion protective coatings (Jude,
2002). Most of the commercially available sensors are made from metal oxides and it
operate at higher temperature. In comparison with that the sensor made from CP has many
improved characteristics such as higher sensitivity, short response time, and operate at
© This item is protected by original copyright