University of Wollongong Research Online University of Wollongong Thesis Collection University of Wollongong Thesis Collections 2001 The seu of conducting polymer sensors for environmental monitoring Roderick L. Shepherd University of Wollongong Recommended Citation Shepherd, Roderick L., The use of conducting polymer sensors for environmental monitoring, Doctor of Philosophy thesis, Department of Chemistry, University of Wollongong, 2001. http://ro.uow.edu.au/theses/1209 Research Online is the open access institutional repository for the University of Wollongong. For further information contact the UOW Library: [email protected] THE USE OF CONDUCTING POLYMER SENSORS FOR ENVIRONMENTAL MONITORING A thesis submitted in fulfilment of the requirements for the award of the degree DOCTOR OF PHILOSOPHY from UNIVERSITY OF WOLLONGONG by Roderick L. Shepherd BEnvSc(Hons) Department of Chemistry 2001 DECLARATION I, Roderick L. Shepherd, declare that this thesis, submitted in fulfilment of the requirements for the award of Doctor of Philosophy, in the Department of Chemistry, University of Wollongong, is wholly my own work unless otherwise referenced or acknowledged. The document has not been submitted for qualifications at any other academic institution. Roderick L. Shepherd 15 October 2001 II PUBLICATIONS Shepherd, R.L., Barisci, J.N., Collier, W.A., Hart, A.L., Partridge, A.C., and Wallace, G.G., Development of Conducting Polymer Coated Screen-Printed Sensors for Measurement of Volatile Compounds, Electroanalysis (In Press). Ill ACKNOWLEDGEMENTS First and foremost I must thank Professor Gordon Wallace for making this PhD an experience I will never forget, and one that I will reminisce over for the rest of my life. Through good times and bad, he was always there to help, and treated me more like a friend than a supervisor. It really made all the difference. Thanks mate, for everything, it is greatly appreciated. It has been a privilege to work under your guidance and I am sure we will continue to 'work' together in the coming years. I would also like to thank Dr Norman Barisci, for his much needed advice and assistance throughout the project. Again, I really appreciated your friendship during my time at IPRI, and for me your sense of humour in the lab always helped to keep things in perspective. Dr Ashton Partridge. The word 'Legend' springs to mind. I cannot thank you enough for the time you spent helping me out in NZ. I learned so much from you in such a short period. I think that without my trips over to Lower Hutt I would have been lost. I would also like to thank all those at Industrial Research Limited who helped make my time in NZ so enjoyable. I would also like to thank Dr Alan Hart and Wendy Collier of AgResearch, Palmerston North, NZ, for their help and advice with screen-printing. Your hospitality during my visits, and subsequent supply of electrodes is greatly appreciated. IV Thanks go to Megan Ash of Tecra Diagnostics, Sydney, for her assistance with the PMAS Listeria work and for supply of cultures over the course of the project. A wealth of much needed advice and supervision in the areas of robotics and odour plume tracking has been provided by Assoc. Prof. Andy Russell, of the Intelligent Robotics Research Centre, Monash University, Melbourne. Please accept my sincere thanks for all the time and effort you have invested in someone with little background knowledge of the area. I have thoroughly enjoyed this aspect of the work and as a consequence continue to conduct research in this area. To all at and associated with the Intelligent Polymer Research Institute, University of Wollongong, I had a fantastic time both working and socialising with you. The experience would have been much less rich without the amazing group of people at IPRI, which is more like a family than a research team. I have to take this opportunity to thank Prof. Leon Kane-Maguire, who through his incredible passion for science and life in general continues to inspire all of those around him. To my parents, Linette, and Peter, thankyou both for all your support over the years, and in particular during my PhD. I couldn't have done this without you. Finally, I have to thank my kelpie, Buster, for keeping things in focus during the last few months in the lab. V DEDICATION This thesis is dedicated to my mother, Linette, whose determination and optimism in times of incredible personal hardship inspired me to keep going. VI TABLE OF CONTENTS Chapter 1 Properties of Conducting Polymers and Application to Environmental Monitoring 1 1.1 Conducting Polymers (CPs) 2 1.2 Preparation of CPs 4 1.3 Factors Influencing CP Formation 5 1.3.1 Chemical Polymerisation 5 1.3.2 Electrochemical Polymerisation 6 1.4 CPs for Chemical Sensing 6 1.4.1 General CP Properties 7 1.4.1.1 Ion Exchange 7 1.4.1.2 Incorporation of Biological Components 8 1.4.1.3 Flexible Substrate Range 9 1.4.2 General Application Areas 9 1.5 Environmental Monitoring with CPs 10 1.5.1 Solution Based Sensors 11 1.5.1.1 Amperometric Sensors 12 1.5.1.2 Potentiometric Sensors 13 1.5.1.3 Voltammetric Sensors 18 1.5.1.4 Resistometric Sensors 19 1.5.1.5 Optical Sensors 20 1.5.1.6 Other Applications 22 1.5.1.7 Water Soluble CPs 23 1.5.2 Gas Sensors 24 1.5.2.1 Detection Mechanism 24 1.5.2.2 Resistometric Gas Sensors 28 1.5.2.3 CP Mass Sensors 35 1.5.2.4 Optical Sensors 37 1.5.2.5 CP Electronic Noses 38 1.6 Thesis Outline 42 Chapter 2 Development of Conducting Polymer Coated Screen-Printed Sensors for Measurement of Volatiles 44 2.1 INTRODUCTION 45 2.1.1 Aims and Approach 46 2.2 EXPERIMENTAL 48 2.2.1 Chemicals and Materials 48 2.2.2 Instruments 48 2.2.3 Screen-printing 49 2.2.4 Polymer Deposition 50 2.2.4.1 Direct Growth on Screen-printed Polymer Substrates 50 2.2.4.2 PPy/Cl Coated Melinex 50 2.2.4.3 Silicon Sensor Fabrication 51 2.2.5 Vapour Generation 51 VII 2.2.6 Resistance Measurement 52 2.3 RESULTS AND DISCUSSION 53 2.3.1 Polypyrrole Deposition 53 2.3.1.1 Melinex 53 2.3.1.2 Effect of Current Density 57 2.3.1.3 Other Polymer Substrates 57 2.3.1.4 PPy/Cl Modified Melinex 60 2.3.1.5 Optimisation of PPy/Tiron Growth Time 63 2.3.1.6 Silicon Sensors 69 2.3.1.7 Estimate of Film Thickness 71 2.3.2 Characterisation 73 2.3.2.1 Scanning Electron Microscopy 73 2.3.2.2 Atomic Force Microscopy 74 2.3.2.3 Cyclic Voltammetry 79 2.3.3 Sensor Responses 81 2.3.3.1 Responses to Methanol 81 2.3.3.2 Linearity of Response and Limit of Detection 85 2.3.3.3 Discrimination of Vapours 92 2.4 CONCLUSIONS 95 Chapter 3 Anion Exchange Modification of PPy/Cl Vapour Deposited Gas Sensors 97 3.1 INTRODUCTION 98 3.1.1 Aims and Approach 102 3.2 EXPERIMENTAL 102 3.2.1 Preparation of PPy/Cl sensors 102 3.2.2 Cyclic Voltammetry 102 3.2.3 Soaking 103 3.2.4 Chronoamperometry 103 3.2.5 Potentiometry 103 3.2.6 Pulsed Potential 104 3.2.7 X-ray Photoelectron Spectroscopy 104 3.2.8 Responses to Vapours 104 3.3 RESULTS AND DISCUSSION 105 3.3.1 Ion Exchange by Soaking 105 3.3.1.1 Potentiometry 106 3.3.1.2 Effect on PPy/Cl Gas Responses 108 3.3.2 Cyclic Voltammetry 111 3.3.3 Chronoamperometry 116 3.3.4 Pulse Potential Anion Exchange 118 3.3.4.1 Effect on Sensor Resistance 118 3.3.4.2 Effect of Electrolyte Concentration 120 3.3.4.3 Effect on Methanol Vapour Responses 120 3.3.4.4 Effect on Vapour Discrimination 123 3.3.5 X-ray Photoelectron Spectroscopy 126 3.4 CONCLUSIONS 129 VIII Chapter 4 Approaches to Reducing the Humidity Response of PPy Gas Sensors 131 4.1 INTRODUCTION 132 4.1.1 Aims and Approach 134 4.2 EXPERIMENTAL 136 4.2.1 Chemicals and Materials 136 4.2.2 Vapour Diffusion 137 4.2.3 Fabrication of PPy/Cl Tube Sensors 137 4.2.4 Response of PPy/Cl Tube sensors 138 4.3 RESULTS AND DISCUSSION 139 4.3.1 Silicone Coating 139 4.3.2 Diffusion Tube Sampling 145 4.3.3 Estimating Methanol Concentration 151 4.3.4 Solvent Discrimination in Solution 152 4.3.5 PPy/Cl Tube Sensor 154 4.3.5.1 Sensor Fabrication 155 4.3.5.2 Methanol Responses 156 4.3.6 T.I.T. Sensor 159 4.4 CONCLUSIONS 162 Chapter 5 Preliminary Investigations into the use of Vapour Deposited PPy Gas Sensors for Autonomous Robotic Plume Tracking 164 5.1 INTRODUCTION 165 5.1.1 Aims and Approach 166 5.2 EXPERIMENTAL 166 5.3 RESULTS AND DISCUSSION 168 5.3.1 Static Responses 168 5.3.1.1 Wind Velocity 169 5.3.1.2 Ammonia Concentration 170 5.3.2 Ammonia Plume Tracking 171 5.4 CONCLUSIONS " 174 Chapter 6 Factors Influencing the Electrochemistry of Polymethoxyaniline sulfonate (PMAS) and the Effect on Listeria Detection 176 6.1 INTRODUCTION 177 6.1.1 Aims and Approach 178 6.2 EXPERIMENTAL 179 6.2.1 Chemicals and Materials 179 6.2.2 Instruments and Apparatus 179 6.2.3 Post-GPC Processing 180 6.3 RESULTS AND DISCUSSION 180 6.3.1 PMAS Electrochemical Stability 181 6.3.2 GPC Characterisation of PMAS 184 6.3.3 Characterisation of Fractions 187 IX " 6.33.1 GPC 187 6.3.3.2 UV-visible Spectroscopy 189 6.3.3.3 Estimation of Fraction Concentration 195 6.3.3.4 Cyclic Voltammetry 196 6.3.3.5 Differential Pulse Voltammetry 199 6.3.4 Electrochemical Properties of the Monomer 203 6.3.5 Effect of MAS on PMAS Response 205 6.3.6 Dialysis of PMAS 207 6.3.6.1 Effect of Monomer on PMAS Response Stability 208 6.3.6.2 Stability of Dialysed PMAS over Time 211 6.3.7 Listeria Detection 213 6.3.7.1 MAS 213 6.3.7.2 Dialysed PMAS 215 6.3.7.3 PMAS Fractions 217 6.3.8 Effect of KC1 Concentration on Dialysed PMAS Response 221 6.3.8.1 Listeria Detection at Elevated KC1 Concentrations 224 6.4 CONCLUSIONS 225 Chapter 7 Conclusions and Future Work 228 7.1 General Conclusions 229 7.2 Chapter 2 229 7.3 Chapter 3 231 7.4 Chapter 4 233