THE EVALUATION OF GOLD NANOPARTICLES EMBEDDED ON

POLYVINYL ALCOHOL MATRIX AS OXIDATION CATALYST

AND BIOSENSOR

SASHA MD. NASIR

UNIVERSITI TEKNOLOGI MALAYSIA

THE EVALUATION OF GOLD NANOPARTICLES EMBEDDED ON POLYVINYL

ALCOHOL MATRIX AS OXIDATION CATALYST AND BIOSENSOR

SASHA MD. NASIR

A thesis submitted in fulfillment of the

requirements for the award of the degree of

Master of Science (Chemistry)

Faculty of Science

Universiti Teknologi Malaysia

MAY 2010

iii

For my family, but especially for my mom –

thank you for your unconditional love and continuous support

and to Ed and Debo

iv

ACKNOWLEDGEMENTS

First and foremost I would like to extend my thanks to my supervisor, Assoc.

Prof. Dr. Hadi Nur, whose help, stimulating suggestions and encouragement helped me

during the time of my research and writing of this thesis.

Additionally, I would like to express my gratitude and complements to all the

lecturers, laboratory officers and research officers from the Department of Chemistry

and Ibnu Sina Institute for Fundamental Science Studies, Universiti Teknologi Malaysia

for their assistance, supervision and wonderful cooperation.

I would also like to thank the Ministry of Science, Technology and Innovation

(MOSTI) for its financial support through Project No. 03-01-06-SF0326 (Vot. 79126).

My sincere appreciation is also extended to all my friends for their understanding

and continual support and also to my fellow lab mates for their valuable experience and

opinions along this study.

Last but not least, I would like to express my deepest gratitude to my beloved

parents, my sister and my brother for without their love, patience, understanding,

continuous motivation and support, this thesis would not have been possible

.

v

PREFACE

This thesis is the result of my work carried out in the Department of Chemistry,

Universiti Teknologi Malaysia, between July 2007 to June 2009 under supervision of

Assoc. Prof. Dr. Hadi Nur. Parts of my work described in this thesis have been reported

in the following publications or presentations:

1. Nur, H., Nasir, S.M. (2008). Gold Nanoparticles Embedded on the Surface of

Polyvinyl Alcohol Layer. Journal of Fundamental Sciences. 4. 245-252.

2. Nur, H., Nasir, S.M. Gold Nanoparticles Embedded on the Surface of Polymeric

Layer as a Biological Sensor. Oral presentation in the Regional Annual

Fundamental Science Seminar 2008 (RAFSS’08). Ibnu Sina Institute for

Fundamental Science Studies, Universiti Teknologi Malaysia, Skudai, Johor.

27th - 29th

May, 2008.

3. Nur, H., Nasir, S.M. Gold Nanoparticles Embedded on the Surface of Polymeric

Layer as a Biological Sensor. Poster presentation in the Minggu Penyelidikan

Sains dan Matematik 2007. Fakulti Sains, Universiti Teknologi Malaysia, Skudai,

Johor. 31st December, 2007 – 3rd

January, 2008.

vi

ABSTRACT

In this study, a method for synthesizing polyvinyl alcohol (PVA) embedded gold film is presented. This approach takes advantage of the high affinity of thiol molecules towards gold. Gold particles, in the size range of 20 to 180 nm, were first prepared by the conventional Turkevitch method by the reduction of tetrachloroauric acid (HAuCl4

) with sodium citrate in water. The Ultraviolet-Visible (UV-Vis) absorption spectra and dark-field microscopy confirmed the presence of a surface plasmon resonance (SPR), attributed to the nanosized gold particles. The resultant gold particles of sizes as low as 27 nm with nearly spherical in shape were achieved as determined by Transmission Electron Microscopy (TEM) and Field Emission Scanning Electron Microscopy (FESEM). In the preparation of PVA embedded gold (PVA-Gold) film, PVA was functionalized with (3-mercaptopropyl) trimethoxysilane (MPTMS) which produced a thiol functionality on the surface. Then, gold particles were chemisorbed onto the surface of partially dried thiol functionalized PVA to produce PVA-Gold composite. The composite materials were characterized using Fourier transform infrared spectroscopy (FTIR), FESEM, TEM and UV-Vis diffuse reflectance (DRUV) spectroscopy. The TEM results showed that the gold particles embedded on the surface of PVA were polydispersed with the average particle size from 30 nm to 150 nm. The catalytic potential of PVA-Gold for oxidation reaction has been investigated in the liquid phase oxidation of styrene with aqueous tert-butyl hydroperoxide and the results were analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). PVA-Gold were found to be highly active catalyst (95% conversion of styrene) and selective towards the oxidation of styrene to give benzaldehyde (73%) as the main product. Moreover, PVA-Gold also showed a very good regenerability in the repeated oxidation of styrene. The unique optical properties of PVA-Gold were also exploited in the interactions with several amino acids such as L-Arginine (Arg), L-Proline (Pro), L-Tryptophan (Trp) and L-Tyrosine (Tyr). The DRUV demonstrated that the surface plasmon resonance peaks for the amino acid – PVA-Gold conjugates were relatively shifted towards longer wavelength as evidence of a successful functionalization of gold with the amine groups of amino acid. The above findings suggest that PVA-Gold have potential application as heterogeneous oxidation catalyst and can be explored as probes for biosensing application.

vii

ABSTRAK

Dalam kajian ini, suatu kaedah bagi mensintesis filem polivinil alkohol (PVA) terpahat emas dilaporkan. Kaedah ini, mempergunakan sifat saling tarik molekul tiol yang kuat terhadap emas. Partikel emas, bersaiz dalam julat 20 nm – 180 nm, pertamanya disediakan menurut kaedah konvensional Turkevitch secara penurunan asid tetrakloroaurik (HAuCl4

) dengan natrium sitrat di dalam air. Spektrum serapan ultralembayung-nampak (UV-Vis) dan mikroskopi medan gelap menunjukkan terdapat bukti plasmon resonans permukaan (SPR) yang disebabkan oleh partikel emas bersaiz nano. Partikel emas yang diperolehi bersaiz paling kecil 27 nm dan hampir berbentuk sfera seperti yang diperlihatkan oleh mikroskopi elektron pancaran (TEM) dan mikroskopi elektron pengimbasan pancaran medan (FESEM). Dalam penyediaan filem PVA bertatahkan emas (PVA-Emas), PVA telah difungsikan dengan (3-merkaptopropil) trimetoksisilana (MPTMS) bagi melekatkan kumpulan berfungsi tiol pada permukaannya. Kemudian, partikel emas dijerap kimia pada permukaan separa kering PVA berfungsikan tiol untuk seterusnya menghasilkan komposit PVA-Emas. Bahan komposit tersebut telah dicirikan dengan spektroskopi inframerah transformasi Fourier (FTIR), FESEM, TEM dan spektroskopi pemantulan difusi ultralembayung-nampak (DRUV). Keputusan daripada TEM menunjukkan partikel emas terpahat pada permukaan PVA secara berserakan dengan purata saiz partikel di antara 30 nm hingga 150 nm. Keupayaan emas sebagai mangkin bagi tindak balas pengoksidaan dikaji dalam pengoksidaan stirena dengan tert-butil hidroperoksida (TBHP) dalam fasa cecair dan hasil tindak balas tersebut telah dianalisis menggunakan kromatografi gas (GC) dan kromatografi gas-spektrometri jisim (GC-MS). PVA-Emas didapati mangkin yang sangat aktif (95% penukaran stirena) dan selektif terhadap pengoksidaan stirena kepada benzaldehid (73%), sebagai hasil utama. Tambahan lagi, PVA-Emas memperlihatkan kebolehulangan yang sangat baik bagi pengoksidaan stirena. Sifat optik emas yang unik telah dieksploitasikan dalam interaksinya dengan beberapa amino asid seperti L-Arginine (Arg), L-Proline (Pro), L-Tryptophan (Trp) dan L-Tyrosine (Tyr). Spektrum DRUV menunjukkan puncak plasmon resonans permukaan bagi konjugat amino asid-PVA Emas telah beranjak kepada nombor gelombang yang lebih tinggi secara relatif menjadi bukti bahawa emas telah difungsikan dengan kumpulan amina dalam amino asid dengan jayanya. Keputusan kajian menunjukkan bahawa PVA-Emas berpotensi diaplikasikan sebagai mangkin pengoksidaan heterogen dan berguna sebagai prob dalam aplikasi biosensor.

viii

TABLE OF CONTENTS

CHAPTER TITLE PAGE

TITLE

STATEMENT

DEDICATION

ACKNOWLEDGEMENTS

PREFACE

ASTRACT

ABSTRAK

TABLE OF CONTENTS

LIST OF TABLES

LIST OF FIGURES

LIST OF ABBREVIATIONS

LIST OF APPENDICES

i

ii

iii

iv

v

vi

vii

viii

xi

xii

xiv

xvi

1 INTRODUCTION

1.1 Research Background 1

1.2 Problem Statement 4

1.3 Research Objectives 7

1.4 Scope of Study 8

2 LITERATURE REVIEW

2.1 Historic Introduction of Gold Nanoparticles 9

2.2 Wet Chemical Synthesis of Gold Nanoparticles 11

2.2.1 Turkevitch Method 12

ix

2.2.2 Brust-Schiffrin Method 13

2.2.3 Seed Mediated Growth Method 14

2.3 Important Properties of Gold Nanoparticles 14

2.3.1 Absorption Properties 14

2.3.2 Scattering Properties 16

2.4 Polymers as Support 18

2.4.1 PVA Composite using Sol-Gel Process 18

2.4.2 Polymers as Support for Gold 20

2.5 Gold Catalysis 22

2.6 Gold Nanoparticles in Biosensors 23

3 EXPERIMENTAL

3.1 Chemicals 25

3.2 Synthesis of Gold Nanoparticles in Different 25

Sizes and Shapes

3.2.1 Synthesis of 20 nm Gold Nanoparticles 26

3.2.2 Synthesis of 30 nm to 180 nm 27

Gold Nanoparticles

3.3 Preparation of PVA Embedded Gold Film 28

(PVA-Gold)

3.4 Catalytic Oxidation Reactions 29

3.4.1 Catalytic Activity of PVA-Gold Film 29

3.4.2 Reusability of the Catalyst 29

3.5 Interactions of PVA-Gold Film with Amino Acids 30

3.6 Characterization Techniques 30

3.6.1 Ultraviolet-Visible Spectroscopy (UV-Vis) 31

3.6.2 Optical Imaging of Gold Nanoparticles 32

3.6.3 Field Emission Scanning 33

Electron Microscopy (FESEM)

x

3.6.4 Transmission Electron Microscopy (TEM) 34

3.6.5 Fourier Transform Infrared - Attenuated Total 35

Reflectance (FTIR-ATR)

3.6.6 Ultraviolet-Visible Diffuse Reflectance 36

Spectroscopy (DRUV)

3.6.7 Gas Chromatography (GC) 37

3.6.8 Gas Chromatography-Mass Spectrometry 38

(GC-MS)

4 RESULTS AND DISCUSSION

4.1 Optical Properties of Gold Nanoparticles 39

4.2 Surface Morphology of Gold Nanoparticles 44

4.3 PVA-Gold Film Characterization 46

4.3.1 FTIR Spectra of PVA-Gold Film 46

4.3.2 DRUV of PVA-Gold Film 49

4.3.3 FESEM of PVA-Gold Film 50

4.3.4 TEM of PVA-Gold Film 52

4.4 Catalytic Activity of PVA-Gold Film 53

4.5 Interaction of PVA-Gold Film with 56

Amino Acids

5 CONCLUSIONS AND RECOMMENDATIONS

5.1 Conclusions 59

5.2 Future Work 61

REFERENCES 62

APPENDICES 74

xi

LIST OF TABLES

TABLE NO. TITLE PAGE

3.1 Approximate amount of citrate and the corresponding sizes of nanoparticles for samples S2 – S6.

28

4.1 The catalytic activity of PVA-Gold film during the catalyst reuse in the oxidation of styrene.

55

xii

LIST OF FIGURES

FIGURE NO. TITLE PAGE

1.1 Schematic representation of the proposed gold nanoparticles embedded in the surface of polymer: (a) gold nanoparticles attached on the surface of the polymer layer by chemisorption, (b) gold nanoparticles embedded in the polymer layer by attachment of nanoparticles on the surface of partially dried functionalized polymeric layer.

6

2.1 The Lycurgus Cup (4th 10 Century B.C.) is ruby red in transmitted light and green in reflected light, due to the presence of gold colloids.

2.2 Chemical structure of sodium citrate.

12

2.3 Formation of gold nanoparticles coated with organic shells by reduction of Au(III) compounds in the presence of thiols.

13

2.4 Formation of surface charges on a metal particle by the electric field of light.

15

2.5 Strong absorption band around 520 nm in the spectrum is the origin of the observed colour of the nanoparticle solution.

16

2.6 Under a microscope with white light illumination, (a) 58 and (b) 78 nm gold particles have the appearance of highly fluorescent green and yellowish particles, respectively.

17

2.7 Chemical structure of PVA.

22

3.1 Synthesis of 20 nm gold nanoparticles.

26

xiii

3.2 Synthesis of gold nanoparticles of different sizes.

27

4.1 Reaction scheme for the synthesis of gold nanoparticles by Turkevitch method.

40

4.2(a) Absorption spectra of gold nanoparticle solutions for samples S1-S6.

41

4.2(b) Photographs of colloidal dispersions of gold nanoparticles with increasing size for samples S1-S6.

42

4.3 Representative photograph of gold nanoparticles viewed under optical microscope. The different colours corresponds to different shape of the particles.

43

4.4 FESEM images of gold nanoparticles prepared from different concentration of citrate. Images (a) – (f) correspond to samples S1 – S6. The inset in images (a) – (f) shows the TEM images of gold nanoparticles.

45

4.5 FTIR spectra of (a) control PVA film, (b) PVA-MPTMS film prepared under acid condition and (c) PVA-Gold film.

47

4.6 DRUV spectra of (a) PVA-MPTMS film prepared under acid condition and (b) PVA-Gold film.

49

4.7 FESEM micrograph of (a) PVA film, (b) PVA-MPTMS film, and (c) PVA-Gold film.

51

4.8 TEM micrograph of PVA-Gold film.

52

4.9 Schematic representation of the oxidation of styrene.

53

4.10 The conversion and product selectivity of the oxidation of styrene with tert-butyl hydroperoxide using PVA-MPTMS and PVA-Gold as catalyst.

54

4.11 Chemical structure of various amino acids.

56

4.12 DRUV spectra of PVA-Gold film before (a) and after interaction with amino acids; (b) Pro, (c) Trp (d) Tyr and (e) Arg.

58

xiv

LIST OF ABBREVIATIONS

% - Percentage

wt %. - Percentage of weight

° - Degree

°C - Degree Celsius

λmax wavelength of maximum

atm - atmospheric pressure

absorbance

Au - Aurum (gold)

CCD -

cm - centimeter

Charge coupled device

cm2

DNA - Deoxyribonucleic acid

- centimeter squared

E° Electrode potential

FESEM - Field emission scanning electron microscopy

FTIR - Fourier transform infrared

FTIR-ATR - Fourier transform infrared – attenuated total reflectance

g - Gram

GC - Gas chromatography

GC-MS - Gas chromatography with mass spectrometry

HAuCl4 -

HCl - Hydrochloric acid

Hydrogen tetrachloroaurate

HNO3 -

L - Liter

Nitric Acid

M - Molar

mL - milliliter

xv

μL - microliter

μm - micrometer

mm - millimeter

MPTMS - (3-mercaptopropyl) trimethoxysilane

nm - Nanometer

NA -

SO

Numerical Aperture

2

SPR - Surface plasmon resonance

- Sulfur dioxide

TBHP - tert-butyl hydroperoxide

UV - Ultraviolet

UV-Vis - Ultraviolet-visible

UV-Vis DR - Ultraviolet-visible diffuse reflectance spectroscopy

xvi

LIST OF APPENDICES

APPENDIX TITLE PAGE

A Chemical reagents for synthesis of gold nanoparticles and chemical reagents for synthesis of PVA-Gold.

74

B Chemical reagents for catalytic testing and chemical reagents for interactions with amino acids.

75

C Calculation of % Conversion and % Selectivity. 76

D GC chromatogram of oxidation of styrene with TBHP at 70º C for 3 hours.

77

E GC chromatogram of oxidation of styrene with TBHP at 70º C for more than 24 hours.

78

CHAPTER 1

INTRODUCTION

1.1 Research Background

Nanoparticles can be defined as particles with at least one of their three-

dimensional sizes in the range of 1 – 100 nm. Recent intense interest in nanoparticles

stems from the fact that nanoparticles exhibit unique properties compared to their bulk

counterparts. Many of these properties including physical, chemical, optical, electrical

and magnetic can be controlled by relatively simple tuning of their sizes, shapes,

compositions, protecting ligands and interparticle distance. To date, the most widely

studied nanoparticles have been those of metals, semiconductors and magnetic materials

due to the potential applications of these materials in optoelectronics, catalysis,

reprography, and other areas [1]. However, among these metallic particles, gold

nanoparticles stand out in particular due to their associated strong surface plasmon

resonance (SPR). Surface plasmon was found to be dependent not only on the size of the

gold nanoparticles but on their shape as well [2]. The SPR absorption and other unique

properties resulting from the small gold particle size can be exploited in a wide range of

2

sensing applications such as bioimaging [3-5], chemical and biological sensing [6, 7]

and colorimetric assays for DNA detection [8, 9].

It was demonstrated that gold nanoparticles could readily bind thiol, amine,

cyanide and diphenylphosphine functional groups [10-13]. Amino acids, which is a

constituent of proteins, are considered as suitable agents in the biofunctionalization of

gold nanoparticles due to the presence of different functional groups, such as –SH and

–NH2

, with affinity for gold. Generally, amino acids can be adsorbed on the gold

particle surface during the formation of particles, using amino acid itself as a reducing

agent [14-16], or in the latter stage, by ligand exchange reactions or binding on the

former adsorbed stabilizing molecules [17]. Most applications of gold nanoparticles as

sensors are based on detecting the shifts in the SPR peak, due to either the change in the

local dielectric constant of the nanoparticles resulting from adsorbed biomolecules or

due to biomolecule induced agglomeration of the nanoparticles [18].

Gold in the bulk is chemically inert and has often been regarded to be poorly

active as a catalyst. However, when the dimension of gold is reduced below ~10 nm, it

turns out to be surprisingly active for many reactions such as CO oxidation, especially at

low temperatures as first discovered by Haruta [19]. The catalytic activity of both

heterogeneous and homogeneous gold based catalyst is now well established in different

processes: selective or complete oxidation, hydrochlorination, and hydrogenation

reactions [20]. All of these applications show the special reactivity of gold compared

with platinum group metals and this may be explained in terms of the electronic states

(+1, +3) and the high electrode potential of gold (Eº = +1.69 V).

Nanoparticles have a tendency to aggregate and are difficult to recover from

reactions due to their small size. Therefore, in order to overcome these difficulties, it is

necessary to immobilize the gold nanoparticles onto a matrix material such as polymers

because the immobilized nanoparticles are more stable. The principle advantages of the

method are that the resulting materials are easily prepared in a single-step procedure and

the possibility to control the thickness of the polymeric layer. These materials also

3

possess the processing and handling advantages of bulk materials. Other benefits of

immobilizing nanoparticles in polymeric matrices include increased stability, improved

processability, recyclability, and solubility in a variety of organic solvents. Among

polymers, polyvinyl alcohol (PVA) is a commercially important water soluble polymer

which is known to be a good stabilizer of noble metal particles. PVA is also the most

important material for the dehydration of organic mixtures owing to its good chemical

stability, film forming ability and high hydrophilicity [21]. Other polymers commonly

used for the stabilization of gold nanoparticles are poly(1-vinylpyrrolidone) and

poly(ethylene glycol) [22]. In the case of heterogeneous catalysis, the catalytic

properties of gold were shown to depend strongly on the support, the preparation

method, and particularly the size of the gold particles [23, 24].

4

1.2 Problem Statement

Gold nanoparticles hold a particular interest to those in the biological sciences

because they are on the same size scale as biological macromolecules, proteins and

nucleic acids. The interactions between biomolecules and nanomaterials have formed the

basis for a number of applications including detection, biosensing, cellular and in-situ

hybridisation labelling, cell tagging and sorting, point-of-care diagnostics, kinetic and

binding studies, imaging enhancers, and even as potential therapeutic agents.

Recently, it has been reported that the scattering property of gold nanoparticle

could be harnessed in a living cell to make cancer detection easier [25, 26]. What makes

the approach so promising is that the method was simple, employing only inexpensive

microscope and white light. However, the method used was not practical because in the

above method, the gold nanoparticles were in solution form such that it could not be

recovered and reused. In this research, we investigated the feasibility of immobilizing

gold nanoparticles (and also their conjugates) in polymer film without degradation of

their SPR properties.

The catalysis by metal nanoparticles is one of the most important and attractive

research owing to an increase in exposed surface area and to a possibility of finding

novel properties generated by quantum size effect [27]. The use of homogeneous gold

catalyst could be unfavourable in practical applications as the separation and reuse of the

catalyst after reaction would be problematic. Most studies on gold catalysts have been

focused on gold oxide supports as these catalytic systems are mostly used for gas-phase

oxidation. However, as recently reported, gold catalysts also represent a useful

alternative to platinum group metals systems for liquid phase oxidation [28]. In this case,

the presence of a solvent such as water dramatically affects the interaction between the

reagent and the catalytically active materials. In particular, gold on polymer shows

superior selectivity and is much less affected by poisoning, when compared with

classical palladium and platinum catalysts. As poisoning represents one of the major

5

drawbacks limiting industrial application in liquid phase oxidation involving oxygen as

the oxidant, the advantage of using a gold catalyst may not be of only academic interest

but could also have industrial potential. As a consequence, there is a growing need for a

general procedure to prepare gold catalysts with high dispersion, regardless of the

polymer support used.

Despite a large number of methods reported to immobilize gold nanoparticle in

polymer film, it is still desirous to develop a simple and effective synthesis of such

nanoparticles with better size control and uniform particle distribution. Nevertheless, the

difficult handling of these extremely fine particles has posed a strong limitation to their

use. Most metal nanoparticles are very unstable. They can aggregate because of the high

surface free energy and readily oxidized-contaminated by air, moisture, sulfur dioxide

(SO2

) and so on. Therefore, the embedding of gold nanoparticles in a polymer surface

represents a valid solution to the manipulation and stabilization problems. Furthermore,

polymer embedding represents a straightforward but effective way to use the mesoscopic

properties of metal nanoparticles.

Previous studies reported that the immobilization of gold nanoparticles on

polymeric surfaces or substrates involved the immersion of the functionalized surface

such as thiol functionalized polymer in gold solutions [20] followed by drying.

However, this method is not practical as the gold nanoparticles attached to the surface

may be easily detached since they are only linked to the functionalized polymeric

surface via chemisorption so that the particle-to-surface contact area is too small to

allow a strong attachment. Our approach is different compared to the previous study as

the gold nanoparticles are annealed on the surface of partially dried functionalized

(3-mercaptopropyl) trimethoxysilane (MPTMS) polymeric layer. Thus, the gold

nanoparticles are not only linked to the functional groups on the polymer surface but are

actually embedded in the polymer layer which enhanced the particle-to-surface contact

area between gold nanoparticles and PVA film, making it more difficult for the

detachment of the gold nanoparticles as presented schematically in Figure 1.1.

6

Figure 1.1: Schematic representation of the proposed gold nanoparticles embedded in

the surface of polymer: (a) gold nanoparticles attached on the surface of the polymer layer by chemisorption, (b) gold nanoparticles embedded in the polymer layer by attachment of nanoparticles on the surface of partially dried functionalized polymeric layer.

7

1.3 Research Objectives

The objectives of the study are:

(1) To synthesize gold nanoparticles using the Turkevitch method via the reduction

of HAuCl4

with sodium citrate in water.

(2) To incorporate gold nanoparticles on the surface of functionalized PVA.

(3) To investigate the catalytic activity of the gold nanoparticles embedded on PVA

for liquid phase oxidation of styrene.

(4) To investigate the structural and morphological properties of the gold

nanoparticles embedded on PVA in the interactions with amino acids.

8

1.4 Scope of Study

In this research, the gold nanoparticles will be synthesized by the reduction of Au

(III) ions with citrate in water, a process pioneered by Turkevitch [30] in 1951 and later

refined by Frens [31]. In this method, citrate serves as both reducing agent and an

anionic stabilizer. It yields uniform and almost spherical particles with diameters

ranging from a few to approximately 150 nm. The size of the resulting colloidal gold

nanoparticles, whose surfaces are negatively charged with citrate, is controlled by the

molar ratio of HAuCl4

/ sodium citrate (the lower the ratio, the smaller the particle size).

The produced gold nanoparticles will be studied on its surface morphology and physical

properties especially related to its SPR absorption and scattering properties.

Then, the stable incorporation of gold nanoparticles on the surface of polymeric

layer, such as PVA, will be achieved by using MPTMS as a linker molecule which has

the ability to react with the functional groups of the polymeric layer [32]. The catalytic

activity of gold nanoparticles embedded on PVA (PVA-Gold) was investigated for the

oxidation of styrene and the biosensing capability of PVA-Gold were studied on the

interactions with various amino acids.