Luận văn electrochemical synthesis of polypyrrole nanowires and application of biosensor

Application of Biosensors, ...ccesesseseuesstininieaenatninaniateee 1.3.1, General Introduction ta DNA sensor 1.3.2, Immobilization of probe DNA on polymer based electrode essences 1

TIANO! TINTVERSITY OF SCIENCE AND TECHINOLOGY

INTERNATIONAL TRAINING INSTITUTE FOR MATERIALS SCIENCE

BUI DAI NHAN

ELECTROCHEMICAL SYNTHESIS OF POLYPYRROLE NANOWIRES AND APPLICATION

Bui Dai Nhan | 2011

Master Thesis

ACKNOWLEDGMENTS

T would like to express ty appreciation to my supervisor, Dr Mai Anh Tuần for his guidance paticuce, advive and support during the course al International Training Institute for Materials Sence (ITIMS)

T would like to express iy sincere gratitude lo Prof, Tran Trung, Hung Yen University of Education and Technology for giving me a chance to attend master course in ITIMS and providing me the necessary facilrties for my master thesis

My very special thanks goes to my co-supervisor M.Sc Luu Manh Quynh, Institute off Materials Science, Hanoi University of Science, for his endless guidance

Without his advice and technical support, this thesis would never been written

I wish fo thank to my fiend Tran Thi Trang for her friendship and cooperation, thank to Eng, Phuong Trung Dung who has helped me in doing measurements

1 am indebted to the teaching ITIMS for their motivation and support, particularly the fiiendly and helpful manner of ITIMS statis will remain in my mind, especially the members of Biosensor group in ITIMS for sharing fiiendly research environment

Many thanks to my friends who have encouraged me during the time of study

Above all, I am gratetil to my beloved family, especially my tather who always be with me wath endless encouragement, inspiration and love

ITMS, Hanci, November 2011

I hereby declare that all the result in this document has been obtained and presented in accordance with academuc rules and ethical conduct, | also declare that, as required by these rules and conduct, I have fully cited and referenced all material and results that are not original to this work

‘The author of this thesis

Bui Dai Nhan

Bui Dai Nhan | 2011

Master Thesis

LIST OF FIGURE

Figure 1.1 Conductivity of conducting polymer compared with otter materials

Figure 1.2 Three typical types of conducting polymer

Figure 1.3 Bund theory and deping-induced structural wansttions of polypyrrole

Figure 14 Three steps of polymerization process of Polypyrrole

Figure 1.5 Aromatic and Quinoid structrure of PPy

Figure 1.6 Three electrade setup for electrochemical synthesis composed of working electrode (WE), counter electrode (CH} and Reference electrode (RE)

Figure 1.7 Cyclic voltammogram of PPy nanowires and cauliflewer-like in KC}

solution at scan rate of 25 mV/s

Figure 1.5, Potentiostat curve of the synthesis of PPy on Nikel electrode and ITO electrode

Figure 1.9 A wpical structure unit of gelatin polypeptide

Figure 1.10 The schematic of a biosensor

Figure 1.11 General DNA sensor design based on CPs

Figure 1.12, The principle of DNA sensor

Figure 1.13 The total biosensors market showing the world revenue forecast for

2009-2016

Figure 1.14, Four base bypes of DNA

Figure 1.15 Hydrogen honds hetween the A-T and O-C bases of the two trands of BNA

Figure 2.1 Schematic of electrochemical synthesis system of polypyrrate

Figure 2.2 Cavalent immobilization hetween PPy fils and phosphate DNA on Pt micro-elecirade using EDC, MIA catalysts

Figure 2.3, Differential measurement using Lock-in Amplifier

Figure 2.4, The wave form of the Luck-in Anpplifier SR830

Figure 2.5 Equivalent electrical circuit of differential system

7

DNA Deoxyribonucleic Acid

PCR Polymerase Chains Reaction

EDC 1-Ethy-3-(3-dimethyi-ammopropyl)-carbodiimide

PBS Phosphate Butter Solution

SEM Scanning Electron Microscopy

TT-IR Eouier Transform Infrared Spectroscopy

SERS Surface Enhanced Raman Spectroscopy

Bui Dai Nhan | 2011

1.12, Historical back ground of the development of conducting polymere

1.13 Mechanism of electrical conduction in CPs

1.1.4, Current synthesis of conducting polymers

1.2 Polypyrrole (PPy) and Electrochemical polymerization of PPy

1.2.1 Properties of Polypyrrole

1.2.2, Electrochemical synthosis of Polypyttole «usecase

1.2.3 Effect of Synthesis conditions on Electrochemical Polymerization

1.3 Application of Biosensors, .ccesesseseuesstininieaenatninaniateee

1.3.1, General Introduction ta DNA sensor

1.3.2, Immobilization of probe DNA on polymer based electrode essences

1.4 Aim of the Study

1.12, Historical back ground of the development of conducting polymere

1.13 Mechanism of electrical conduction in CPs

1.1.4, Current synthesis of conducting polymers

1.2 Polypyrrole (PPy) and Electrochemical polymerization of PPy

1.2.1 Properties of Polypyrrole

1.2.2, Electrochemical synthosis of Polypyttole «usecase

1.2.3 Effect of Synthesis conditions on Electrochemical Polymerization

1.3 Application of Biosensors, .ccesesseseuesstininieaenatninaniateee

1.3.1, General Introduction ta DNA sensor

1.3.2, Immobilization of probe DNA on polymer based electrode essences

1.4 Aim of the Study

Bui Dai Nhan | 2011

1.12, Historical back ground of the development of conducting polymere

1.13 Mechanism of electrical conduction in CPs

1.1.4, Current synthesis of conducting polymers

1.2 Polypyrrole (PPy) and Electrochemical polymerization of PPy

1.2.1 Properties of Polypyrrole

1.2.2, Electrochemical synthosis of Polypyttole «usecase

1.2.3 Effect of Synthesis conditions on Electrochemical Polymerization

1.3 Application of Biosensors, .ccesesseseuesstininieaenatninaniateee

1.3.1, General Introduction ta DNA sensor

1.3.2, Immobilization of probe DNA on polymer based electrode essences

1.4 Aim of the Study

LIST OF FIGURE

Figure 1.1 Conductivity of conducting polymer compared with otter materials

Figure 1.2 Three typical types of conducting polymer

Figure 1.3 Bund theory and deping-induced structural wansttions of polypyrrole

Figure 14 Three steps of polymerization process of Polypyrrole

Figure 1.5 Aromatic and Quinoid structrure of PPy

Figure 1.6 Three electrade setup for electrochemical synthesis composed of working electrode (WE), counter electrode (CH} and Reference electrode (RE)

Figure 1.7 Cyclic voltammogram of PPy nanowires and cauliflewer-like in KC}

solution at scan rate of 25 mV/s

Figure 1.5, Potentiostat curve of the synthesis of PPy on Nikel electrode and ITO electrode

Figure 1.9 A wpical structure unit of gelatin polypeptide

Figure 1.10 The schematic of a biosensor

Figure 1.11 General DNA sensor design based on CPs

Figure 1.12, The principle of DNA sensor

Figure 1.13 The total biosensors market showing the world revenue forecast for

2009-2016

Figure 1.14, Four base bypes of DNA

Figure 1.15 Hydrogen honds hetween the A-T and O-C bases of the two trands of BNA

Figure 2.1 Schematic of electrochemical synthesis system of polypyrrate

Figure 2.2 Cavalent immobilization hetween PPy fils and phosphate DNA on Pt micro-elecirade using EDC, MIA catalysts

Figure 2.3, Differential measurement using Lock-in Amplifier

Figure 2.4, The wave form of the Luck-in Anpplifier SR830

Figure 2.5 Equivalent electrical circuit of differential system

7

Bui Dai Nhan | 2011

Master Thesis LIST OF ABBREVATION

DNA Deoxyribonucleic Acid

PCR Polymerase Chains Reaction

EDC 1-Ethy-3-(3-dimethyi-ammopropyl)-carbodiimide

PBS Phosphate Butter Solution

SEM Scanning Electron Microscopy

TT-IR Eouier Transform Infrared Spectroscopy

SERS Surface Enhanced Raman Spectroscopy

1.12, Historical back ground of the development of conducting polymere

1.13 Mechanism of electrical conduction in CPs

1.1.4, Current synthesis of conducting polymers

1.2 Polypyrrole (PPy) and Electrochemical polymerization of PPy

1.2.1 Properties of Polypyrrole

1.2.2, Electrochemical synthosis of Polypyttole «usecase

1.2.3 Effect of Synthesis conditions on Electrochemical Polymerization

1.3 Application of Biosensors, .ccesesseseuesstininieaenatninaniateee

1.3.1, General Introduction ta DNA sensor

1.3.2, Immobilization of probe DNA on polymer based electrode essences

1.4 Aim of the Study

Bui Dai Nhan | 2011

Master Thesis LIST OF ABBREVATION

DNA Deoxyribonucleic Acid

PCR Polymerase Chains Reaction

EDC 1-Ethy-3-(3-dimethyi-ammopropyl)-carbodiimide

PBS Phosphate Butter Solution

SEM Scanning Electron Microscopy

TT-IR Eouier Transform Infrared Spectroscopy

SERS Surface Enhanced Raman Spectroscopy

PREFACES

Recently, Polypyrole (Py) is one of the most extensively used conducting polymers in biosensor designs due to its good biocompatibility and polymerization at uculral pH [30]

‘The electronic structure of PPy is highly sensitive to change in polymeric chain environment and other perturbations in the chain conformation caused by, for example, a biological recognition event such as DNA hybridization 30] The changes

in the delocalized electronic structure can provide a signal for the presence of a target analyte molecule These advantages of conducting PPy make them suitable for biosensors and chemical sensors which play important role in public health and environment [18]

The drawback of DNA sensor based PPy weribrane inchudos limited scnsitivity aud reproducibilily dus to the low conductivity of PPy in Gln and caulilowerlike fom, presented in previous work '® In this thesis, we aim at the synthesis of PPy nanowires using electrochemical technique with the desire of obtaining better charactetistics of DNA sensor for Ecoli bacteria DNA detection,

‘The synthesis of PPy nanowires was obtained by using potentiostat method at

0.75V, in LiC]040.1M (PBS, pH —7) electrolyte containing 0.5 mL pyrrole monomer

and 0.08%wt gelatin It should be noted that gelatin is used as a ‘soft template’ to orientate the growth of PPy nanowires

‘The PPy nanowires 50 nm of diameter provide large and fine surface Especially,

N-IT group of PPy nanowires was origntated upward from the surfice which takes

advantage for DNA mobe immobilivation, As the result, the DNA based PPy

manawires has good charsetcristics for Feoh DNA detection, including a short

response time ¢-10 seconds), smal] detection limit (0.1 nM) as well as good reproducibility

PD, Tam etal, / Materials Science and Engineering C 30 (3016) 1141-1150

9

Bui Dai Nhan | 2011

3.1.2, Efftcts off parameters on electrochemical polymerization of polypymole Š1 3.1.3 Chemical composition and functional groups of obtained PPy nanowires «0 3.3 DNA sensors characlcrislics 70 3.3.1 Charaeteristios of DNA sensor is a function of time 70 3.2.2, Hybridization detection nsing DNAA scBsor no 71 3.3.3 The reprodueibillty o£ DNA sensoz 73

CONCLUSION 76

RECOMMENDATIONS Error! Bookmark not defined

REFERENCES 78

Figure 3.6 The current density recorded vs different concentration of gelatin

Figure 3.7 SEM images of Ppy structures potentiostatically synthesized at different of gelatin concentration

Figure 3.8 The current density recorded vs different sweeping (reaction time)

Figure 3.9, SEM images of Ppy structures potentiostatically synthesized at different

reaction time

Fig 3.10 Morphologies of PPy nanowires prepared at optimized condition

Figure 3.11 FT-IR spectra of obtained Ppy nanowires

Fig 3.12 Path of the stylus over the sample in the measurement of Pt thickness

Figure 3.13 The thickness of Phatimun film

Fig 3.14, Distribution of PPy nanowires over Pt surface electrode,

Figure 3.15 Surface Enhanced Raman Spectroscope of polypyrrole film deposited on Platinum surface

Figure 3.16 Response time and Reaction time of the DNA sensor

Figure 3.17 The curve of DNA sequence hybridization, Conayame 0.054, T 300°K, Figure 3.18 The reproducibility of DN: sensor

Bui Dai Nhan | 2011

Master Thesis

LIST OF FIGURE

Figure 1.1 Conductivity of conducting polymer compared with otter materials

Figure 1.2 Three typical types of conducting polymer

Figure 1.3 Bund theory and deping-induced structural wansttions of polypyrrole

Figure 14 Three steps of polymerization process of Polypyrrole

Figure 1.5 Aromatic and Quinoid structrure of PPy

Figure 1.6 Three electrade setup for electrochemical synthesis composed of working electrode (WE), counter electrode (CH} and Reference electrode (RE)

Figure 1.7 Cyclic voltammogram of PPy nanowires and cauliflewer-like in KC}

solution at scan rate of 25 mV/s

Figure 1.5, Potentiostat curve of the synthesis of PPy on Nikel electrode and ITO electrode

Figure 1.9 A wpical structure unit of gelatin polypeptide

Figure 1.10 The schematic of a biosensor

Figure 1.11 General DNA sensor design based on CPs

Figure 1.12, The principle of DNA sensor

Figure 1.13 The total biosensors market showing the world revenue forecast for

2009-2016

Figure 1.14, Four base bypes of DNA

Figure 1.15 Hydrogen honds hetween the A-T and O-C bases of the two trands of BNA

Figure 2.1 Schematic of electrochemical synthesis system of polypyrrate

Figure 2.2 Cavalent immobilization hetween PPy fils and phosphate DNA on Pt micro-elecirade using EDC, MIA catalysts

Figure 2.3, Differential measurement using Lock-in Amplifier

Figure 2.4, The wave form of the Luck-in Anpplifier SR830

Figure 2.5 Equivalent electrical circuit of differential system

7

1.12, Historical back ground of the development of conducting polymere

1.13 Mechanism of electrical conduction in CPs

1.1.4, Current synthesis of conducting polymers

1.2 Polypyrrole (PPy) and Electrochemical polymerization of PPy

1.2.1 Properties of Polypyrrole

1.2.2, Electrochemical synthosis of Polypyttole «usecase

1.2.3 Effect of Synthesis conditions on Electrochemical Polymerization

1.3 Application of Biosensors, .ccesesseseuesstininieaenatninaniateee

1.3.1, General Introduction ta DNA sensor

1.3.2, Immobilization of probe DNA on polymer based electrode essences

1.4 Aim of the Study

Bui Dai Nhan | 2011

Master Thesis

LIST OF FIGURE

Figure 1.1 Conductivity of conducting polymer compared with otter materials

Figure 1.2 Three typical types of conducting polymer

Figure 1.3 Bund theory and deping-induced structural wansttions of polypyrrole

Figure 14 Three steps of polymerization process of Polypyrrole

Figure 1.5 Aromatic and Quinoid structrure of PPy

Figure 1.6 Three electrade setup for electrochemical synthesis composed of working electrode (WE), counter electrode (CH} and Reference electrode (RE)

Figure 1.7 Cyclic voltammogram of PPy nanowires and cauliflewer-like in KC}

solution at scan rate of 25 mV/s

Figure 1.5, Potentiostat curve of the synthesis of PPy on Nikel electrode and ITO electrode

Figure 1.9 A wpical structure unit of gelatin polypeptide

Figure 1.10 The schematic of a biosensor

Figure 1.11 General DNA sensor design based on CPs

Figure 1.12, The principle of DNA sensor

Figure 1.13 The total biosensors market showing the world revenue forecast for

2009-2016

Figure 1.14, Four base bypes of DNA

Figure 1.15 Hydrogen honds hetween the A-T and O-C bases of the two trands of BNA

Figure 2.1 Schematic of electrochemical synthesis system of polypyrrate

Figure 2.2 Cavalent immobilization hetween PPy fils and phosphate DNA on Pt micro-elecirade using EDC, MIA catalysts

Figure 2.3, Differential measurement using Lock-in Amplifier

Figure 2.4, The wave form of the Luck-in Anpplifier SR830

Figure 2.5 Equivalent electrical circuit of differential system

7

1.12, Historical back ground of the development of conducting polymere

1.13 Mechanism of electrical conduction in CPs

1.1.4, Current synthesis of conducting polymers

1.2 Polypyrrole (PPy) and Electrochemical polymerization of PPy

1.2.1 Properties of Polypyrrole

1.2.2, Electrochemical synthosis of Polypyttole «usecase

1.2.3 Effect of Synthesis conditions on Electrochemical Polymerization

1.3 Application of Biosensors, .ccesesseseuesstininieaenatninaniateee

1.3.1, General Introduction ta DNA sensor

1.3.2, Immobilization of probe DNA on polymer based electrode essences

1.4 Aim of the Study

Bui Dai Nhan | 2011

1.12, Historical back ground of the development of conducting polymere

1.13 Mechanism of electrical conduction in CPs

1.1.4, Current synthesis of conducting polymers

1.2 Polypyrrole (PPy) and Electrochemical polymerization of PPy

1.2.1 Properties of Polypyrrole

1.2.2, Electrochemical synthosis of Polypyttole «usecase

1.2.3 Effect of Synthesis conditions on Electrochemical Polymerization

1.3 Application of Biosensors, .ccesesseseuesstininieaenatninaniateee

1.3.1, General Introduction ta DNA sensor

1.3.2, Immobilization of probe DNA on polymer based electrode essences

1.4 Aim of the Study

LIST OF TABLE

Table 1.1 The chronology of the development of some important conducting polymers Table 1.2 Advantages and disadvantages of chemical and electrochemical synthesis of conducting polymers

Table 1.3 Advamages and Disadvantages of Chemical and Llectrachemical synthesis

of PPy,

Table 1.4 History of biosensor development

Table 2.1 DNA sequence used mn this work

Table 3.1 Current density (mA/em*) vs added volume of pyrrole monomer (ml)

Table 3.2 Current density (mA‘en?) vs different concentration of gelatin (%4y1)

Table 3.3 Current density (wA/em) vs Reaction time (second)

Table 3.4 Absoption peaks in FT-IR spectrum

Table 3.5 Comparison between SERS peaks in this work and and those in literature.

Bui Dai Nhan | 2011

Master Thesis

PREFACES

Recently, Polypyrole (Py) is one of the most extensively used conducting polymers in biosensor designs due to its good biocompatibility and polymerization at uculral pH [30]

‘The electronic structure of PPy is highly sensitive to change in polymeric chain environment and other perturbations in the chain conformation caused by, for example, a biological recognition event such as DNA hybridization 30] The changes

in the delocalized electronic structure can provide a signal for the presence of a target analyte molecule These advantages of conducting PPy make them suitable for biosensors and chemical sensors which play important role in public health and environment [18]

The drawback of DNA sensor based PPy weribrane inchudos limited scnsitivity aud reproducibilily dus to the low conductivity of PPy in Gln and caulilowerlike fom, presented in previous work '® In this thesis, we aim at the synthesis of PPy nanowires using electrochemical technique with the desire of obtaining better charactetistics of DNA sensor for Ecoli bacteria DNA detection,

‘The synthesis of PPy nanowires was obtained by using potentiostat method at

0.75V, in LiC]040.1M (PBS, pH —7) electrolyte containing 0.5 mL pyrrole monomer

and 0.08%wt gelatin It should be noted that gelatin is used as a ‘soft template’ to orientate the growth of PPy nanowires

‘The PPy nanowires 50 nm of diameter provide large and fine surface Especially,

N-IT group of PPy nanowires was origntated upward from the surfice which takes

advantage for DNA mobe immobilivation, As the result, the DNA based PPy

manawires has good charsetcristics for Feoh DNA detection, including a short

response time ¢-10 seconds), smal] detection limit (0.1 nM) as well as good reproducibility

PD, Tam etal, / Materials Science and Engineering C 30 (3016) 1141-1150

9

PREFACES

Recently, Polypyrole (Py) is one of the most extensively used conducting polymers in biosensor designs due to its good biocompatibility and polymerization at uculral pH [30]

‘The electronic structure of PPy is highly sensitive to change in polymeric chain environment and other perturbations in the chain conformation caused by, for example, a biological recognition event such as DNA hybridization 30] The changes

in the delocalized electronic structure can provide a signal for the presence of a target analyte molecule These advantages of conducting PPy make them suitable for biosensors and chemical sensors which play important role in public health and environment [18]

The drawback of DNA sensor based PPy weribrane inchudos limited scnsitivity aud reproducibilily dus to the low conductivity of PPy in Gln and caulilowerlike fom, presented in previous work '® In this thesis, we aim at the synthesis of PPy nanowires using electrochemical technique with the desire of obtaining better charactetistics of DNA sensor for Ecoli bacteria DNA detection,

‘The synthesis of PPy nanowires was obtained by using potentiostat method at

0.75V, in LiC]040.1M (PBS, pH —7) electrolyte containing 0.5 mL pyrrole monomer

and 0.08%wt gelatin It should be noted that gelatin is used as a ‘soft template’ to orientate the growth of PPy nanowires

‘The PPy nanowires 50 nm of diameter provide large and fine surface Especially,

N-IT group of PPy nanowires was origntated upward from the surfice which takes

advantage for DNA mobe immobilivation, As the result, the DNA based PPy

manawires has good charsetcristics for Feoh DNA detection, including a short

response time ¢-10 seconds), smal] detection limit (0.1 nM) as well as good reproducibility

PD, Tam etal, / Materials Science and Engineering C 30 (3016) 1141-1150

9

Bui Dai Nhan | 2011

1.12, Historical back ground of the development of conducting polymere

1.13 Mechanism of electrical conduction in CPs

1.1.4, Current synthesis of conducting polymers

1.2 Polypyrrole (PPy) and Electrochemical polymerization of PPy

1.2.1 Properties of Polypyrrole

1.2.2, Electrochemical synthosis of Polypyttole «usecase

1.2.3 Effect of Synthesis conditions on Electrochemical Polymerization

1.3 Application of Biosensors, .ccesesseseuesstininieaenatninaniateee

1.3.1, General Introduction ta DNA sensor

1.3.2, Immobilization of probe DNA on polymer based electrode essences

1.4 Aim of the Study

DNA Deoxyribonucleic Acid

PCR Polymerase Chains Reaction

EDC 1-Ethy-3-(3-dimethyi-ammopropyl)-carbodiimide

PBS Phosphate Butter Solution

SEM Scanning Electron Microscopy

TT-IR Eouier Transform Infrared Spectroscopy

SERS Surface Enhanced Raman Spectroscopy

Bui Dai Nhan | 2011

1.12, Historical back ground of the development of conducting polymere

1.13 Mechanism of electrical conduction in CPs

1.1.4, Current synthesis of conducting polymers

1.2 Polypyrrole (PPy) and Electrochemical polymerization of PPy

1.2.1 Properties of Polypyrrole

1.2.2, Electrochemical synthosis of Polypyttole «usecase

1.2.3 Effect of Synthesis conditions on Electrochemical Polymerization

1.3 Application of Biosensors, .ccesesseseuesstininieaenatninaniateee

1.3.1, General Introduction ta DNA sensor

1.3.2, Immobilization of probe DNA on polymer based electrode essences

1.4 Aim of the Study

Figure 3.6 The current density recorded vs different concentration of gelatin

Figure 3.7 SEM images of Ppy structures potentiostatically synthesized at different of gelatin concentration

Figure 3.8 The current density recorded vs different sweeping (reaction time)

Figure 3.9, SEM images of Ppy structures potentiostatically synthesized at different

reaction time

Fig 3.10 Morphologies of PPy nanowires prepared at optimized condition

Figure 3.11 FT-IR spectra of obtained Ppy nanowires

Fig 3.12 Path of the stylus over the sample in the measurement of Pt thickness

Figure 3.13 The thickness of Phatimun film

Fig 3.14, Distribution of PPy nanowires over Pt surface electrode,

Figure 3.15 Surface Enhanced Raman Spectroscope of polypyrrole film deposited on Platinum surface

Figure 3.16 Response time and Reaction time of the DNA sensor

Figure 3.17 The curve of DNA sequence hybridization, Conayame 0.054, T 300°K, Figure 3.18 The reproducibility of DN: sensor

Figure 3.6 The current density recorded vs different concentration of gelatin

Figure 3.7 SEM images of Ppy structures potentiostatically synthesized at different of gelatin concentration

Figure 3.8 The current density recorded vs different sweeping (reaction time)

Figure 3.9, SEM images of Ppy structures potentiostatically synthesized at different

reaction time

Fig 3.10 Morphologies of PPy nanowires prepared at optimized condition

Figure 3.11 FT-IR spectra of obtained Ppy nanowires

Fig 3.12 Path of the stylus over the sample in the measurement of Pt thickness

Figure 3.13 The thickness of Phatimun film

Fig 3.14, Distribution of PPy nanowires over Pt surface electrode,

Figure 3.15 Surface Enhanced Raman Spectroscope of polypyrrole film deposited on Platinum surface

Figure 3.16 Response time and Reaction time of the DNA sensor

Figure 3.17 The curve of DNA sequence hybridization, Conayame 0.054, T 300°K, Figure 3.18 The reproducibility of DN: sensor

LIST OF TABLE

Table 1.1 The chronology of the development of some important conducting polymers Table 1.2 Advantages and disadvantages of chemical and electrochemical synthesis of conducting polymers

Table 1.3 Advamages and Disadvantages of Chemical and Llectrachemical synthesis

of PPy,

Table 1.4 History of biosensor development

Table 2.1 DNA sequence used mn this work

Table 3.1 Current density (mA/em*) vs added volume of pyrrole monomer (ml)

Table 3.2 Current density (mA‘en?) vs different concentration of gelatin (%4y1)

Table 3.3 Current density (wA/em) vs Reaction time (second)

Table 3.4 Absoption peaks in FT-IR spectrum

Table 3.5 Comparison between SERS peaks in this work and and those in literature.

Bui Dai Nhan | 2011

3.1.2, Efftcts off parameters on electrochemical polymerization of polypymole Š1 3.1.3 Chemical composition and functional groups of obtained PPy nanowires «0 3.3 DNA sensors characlcrislics 70 3.3.1 Charaeteristios of DNA sensor is a function of time 70 3.2.2, Hybridization detection nsing DNAA scBsor no 71 3.3.3 The reprodueibillty o£ DNA sensoz 73

CONCLUSION 76

RECOMMENDATIONS Error! Bookmark not defined

REFERENCES 78

Figure 3.6 The current density recorded vs different concentration of gelatin

Figure 3.7 SEM images of Ppy structures potentiostatically synthesized at different of gelatin concentration

Figure 3.8 The current density recorded vs different sweeping (reaction time)

Figure 3.9, SEM images of Ppy structures potentiostatically synthesized at different

reaction time

Fig 3.10 Morphologies of PPy nanowires prepared at optimized condition

Figure 3.11 FT-IR spectra of obtained Ppy nanowires

Fig 3.12 Path of the stylus over the sample in the measurement of Pt thickness

Figure 3.13 The thickness of Phatimun film

Fig 3.14, Distribution of PPy nanowires over Pt surface electrode,

Figure 3.15 Surface Enhanced Raman Spectroscope of polypyrrole film deposited on Platinum surface

Figure 3.16 Response time and Reaction time of the DNA sensor

Figure 3.17 The curve of DNA sequence hybridization, Conayame 0.054, T 300°K, Figure 3.18 The reproducibility of DN: sensor

Bui Dai Nhan | 2011

Master Thesis

PREFACES

Recently, Polypyrole (Py) is one of the most extensively used conducting polymers in biosensor designs due to its good biocompatibility and polymerization at uculral pH [30]

‘The electronic structure of PPy is highly sensitive to change in polymeric chain environment and other perturbations in the chain conformation caused by, for example, a biological recognition event such as DNA hybridization 30] The changes

in the delocalized electronic structure can provide a signal for the presence of a target analyte molecule These advantages of conducting PPy make them suitable for biosensors and chemical sensors which play important role in public health and environment [18]

The drawback of DNA sensor based PPy weribrane inchudos limited scnsitivity aud reproducibilily dus to the low conductivity of PPy in Gln and caulilowerlike fom, presented in previous work '® In this thesis, we aim at the synthesis of PPy nanowires using electrochemical technique with the desire of obtaining better charactetistics of DNA sensor for Ecoli bacteria DNA detection,

‘The synthesis of PPy nanowires was obtained by using potentiostat method at

0.75V, in LiC]040.1M (PBS, pH —7) electrolyte containing 0.5 mL pyrrole monomer

and 0.08%wt gelatin It should be noted that gelatin is used as a ‘soft template’ to orientate the growth of PPy nanowires

‘The PPy nanowires 50 nm of diameter provide large and fine surface Especially,

N-IT group of PPy nanowires was origntated upward from the surfice which takes

advantage for DNA mobe immobilivation, As the result, the DNA based PPy

manawires has good charsetcristics for Feoh DNA detection, including a short

response time ¢-10 seconds), smal] detection limit (0.1 nM) as well as good reproducibility

PD, Tam etal, / Materials Science and Engineering C 30 (3016) 1141-1150

9

LIST OF TABLE

Table 1.1 The chronology of the development of some important conducting polymers Table 1.2 Advantages and disadvantages of chemical and electrochemical synthesis of conducting polymers

Table 1.3 Advamages and Disadvantages of Chemical and Llectrachemical synthesis

of PPy,

Table 1.4 History of biosensor development

Table 2.1 DNA sequence used mn this work

Table 3.1 Current density (mA/em*) vs added volume of pyrrole monomer (ml)

Table 3.2 Current density (mA‘en?) vs different concentration of gelatin (%4y1)

Table 3.3 Current density (wA/em) vs Reaction time (second)

Table 3.4 Absoption peaks in FT-IR spectrum

Table 3.5 Comparison between SERS peaks in this work and and those in literature.

Bui Dai Nhan | 2011

3.1.2, Efftcts off parameters on electrochemical polymerization of polypymole Š1 3.1.3 Chemical composition and functional groups of obtained PPy nanowires «0 3.3 DNA sensors characlcrislics 70 3.3.1 Charaeteristios of DNA sensor is a function of time 70 3.2.2, Hybridization detection nsing DNAA scBsor no 71 3.3.3 The reprodueibillty o£ DNA sensoz 73

CONCLUSION 76

RECOMMENDATIONS Error! Bookmark not defined

REFERENCES 78

PREFACES

Recently, Polypyrole (Py) is one of the most extensively used conducting polymers in biosensor designs due to its good biocompatibility and polymerization at uculral pH [30]

‘The electronic structure of PPy is highly sensitive to change in polymeric chain environment and other perturbations in the chain conformation caused by, for example, a biological recognition event such as DNA hybridization 30] The changes

in the delocalized electronic structure can provide a signal for the presence of a target analyte molecule These advantages of conducting PPy make them suitable for biosensors and chemical sensors which play important role in public health and environment [18]

The drawback of DNA sensor based PPy weribrane inchudos limited scnsitivity aud reproducibilily dus to the low conductivity of PPy in Gln and caulilowerlike fom, presented in previous work '® In this thesis, we aim at the synthesis of PPy nanowires using electrochemical technique with the desire of obtaining better charactetistics of DNA sensor for Ecoli bacteria DNA detection,

‘The synthesis of PPy nanowires was obtained by using potentiostat method at

0.75V, in LiC]040.1M (PBS, pH —7) electrolyte containing 0.5 mL pyrrole monomer

and 0.08%wt gelatin It should be noted that gelatin is used as a ‘soft template’ to orientate the growth of PPy nanowires

‘The PPy nanowires 50 nm of diameter provide large and fine surface Especially,

N-IT group of PPy nanowires was origntated upward from the surfice which takes

advantage for DNA mobe immobilivation, As the result, the DNA based PPy

manawires has good charsetcristics for Feoh DNA detection, including a short

response time ¢-10 seconds), smal] detection limit (0.1 nM) as well as good reproducibility

PD, Tam etal, / Materials Science and Engineering C 30 (3016) 1141-1150

9

Bui Dai Nhan | 2011

Master Thesis LIST OF ABBREVATION

DNA Deoxyribonucleic Acid

PCR Polymerase Chains Reaction

EDC 1-Ethy-3-(3-dimethyi-ammopropyl)-carbodiimide

PBS Phosphate Butter Solution

SEM Scanning Electron Microscopy

TT-IR Eouier Transform Infrared Spectroscopy

SERS Surface Enhanced Raman Spectroscopy

Figure 3.6 The current density recorded vs different concentration of gelatin

Figure 3.7 SEM images of Ppy structures potentiostatically synthesized at different of gelatin concentration

Figure 3.8 The current density recorded vs different sweeping (reaction time)

Figure 3.9, SEM images of Ppy structures potentiostatically synthesized at different

reaction time

Fig 3.10 Morphologies of PPy nanowires prepared at optimized condition

Figure 3.11 FT-IR spectra of obtained Ppy nanowires

Fig 3.12 Path of the stylus over the sample in the measurement of Pt thickness

Figure 3.13 The thickness of Phatimun film

Fig 3.14, Distribution of PPy nanowires over Pt surface electrode,

Figure 3.15 Surface Enhanced Raman Spectroscope of polypyrrole film deposited on Platinum surface

Figure 3.16 Response time and Reaction time of the DNA sensor

Figure 3.17 The curve of DNA sequence hybridization, Conayame 0.054, T 300°K, Figure 3.18 The reproducibility of DN: sensor