original - DSPACEdspace.unimap.edu.my/dspace/bitstream/123456789/31917/1/Page 1-24.pdfDate of birth...

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


2012


i


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


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


University Malaysia Perlis

(Supervisor)

DR. SUPRI ABD. GHANI

Lecturer



(Co-Supervisor)

Check and Approved by

………………………………………………….

(PROF DR. MOHD NOOR AHMAD)

Supervisor



(Date: …………………….)


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.


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


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


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


vii

REFERENCES 68

APPENDICES

A Particles size analysis 76

B FTIR characteristic 77

C Energy-dispersive X-ray spectroscopy (EDX) for aluminum 78


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


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


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


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)


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


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


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.


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.


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


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


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


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.


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,


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.


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


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