UNIVERSITI PUTRA MALAYSIA IMPREGNATION OF IN-HOUSE SYNTHESIZED CARBON NANOTUBES INBACTERIAL CELLULOSE SHARMEEN BINTI ADNAN FK 2011 123
IMPREGNATION OF IN-HOUSE SYNTHESIZED CARBON NANOTUBES IN BACTERIAL CELLULOSE By SHARMEEN BINTI ADNAN Thesis Submitted to the School of Graduated Studies, Universiti Putra Malaysia, in Fulfillment of the Requirement for the Degree of Master of Science August 2011
Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfillment of the requirement for the degree of Master of Science. IMPREGNATION OF IN-HOUSE SYNTHESIZED CARBON NANOTUBES IN BACTERIAL CELLULOSE Chair: Dayang Radiah Bt. Awang Biak, PhD Faculty: Faculty of Engineering By SHARMEEN BINTI ADNAN August 2011 Bacterial cellulose (BC) synthesized by Acetobacter xylinum has been discovered as a potential matrix for impregnating carbon nanotubes (CNT). The main objective of this study is to produce bacterial cellulose/carbon nanotube (BC/CNT) with improved hydrophobic surface. CNT addition is by mean to improve the electrical property of BC to be a conductive membrane. Hydrophobic membrane is more practical in device development since it can adhere with other hydrophobic material, which is achieved in this study by acetylation process. In this work, the membranes were produced using date extract (DE) culture medium. Three CNT impregnation techniques were tested, i.e. immersion, dispersion and spraying, whilst the acetylation conducted were homogeneous and heterogeneous processes. ii
In this study, morphological characteristic is an important property for sample selection to be characterized further. BC/CNT nanocomposite produced via spraying technique has uniform CNT dispersion and has the most dielectric conductivity value i.e. ~4.66 x 10-1 S/cm than the other techniques. Therefore, spraying was used to prepare BC/CNT acetate nanocomposite. Since the morphology of BC/CNT acetate obtained from heterogeneous process proves that the acetylation only occurred on the surface and the inner core structures of the BC are still intact, this process was used further. The most significant characteristic of BC/CNT acetate is the existence of C=O, CH 3 and C-O functional groups of acetyl and higher water contact angle (~77 ) than that of BC/CNT (~45 ). When tested, decomposition and glass transition temperatures of BC/CNT acetate have reduced by 203 C and 35 C respectively, compared to that BC/CNT. The reduction is occurred mainly because the swollen BC structure of BC/CNT acetate is easily degraded by heat treatment. The acetylated BC/CNT on the other hand, has higher crystal BC fraction, i.e. 51% compared to that of BC/CNT (49%). These findings indicate that the CNT hinders the degradation of nanocomposite and protects the BC crystals. Thus when acetylated, both elasticity and crystallite size of BC/CNT has only reduced by 9%, i.e., from 34 to 31 GPa and from 27.3 to 24.9 nm, respectively. The bigger pore size of the acetate nanocomposite (~22 Å) than that of BC/CNT (~-103 Å) might allows further functionalization process introduced to the membrane. As a conclusion, the CNT impregnation by spraying technique during the growing fermentation of BC coupled with heterogeneous acetylation treatment resulted in a more water resistant, iii
increased dielectric conductivity and increased crystal BC fraction. While, the sheet elasticity, crystallite size, surface area, decomposition and glass transition temperatures became lower. These characteristics makes acetylated BC/CNT sheet a potential as a biomaterial membrane in device development. iv
Abstrak tesis yang dikemukan kepada Senat Universiti Putra Malaysia sebagai memenuhi keperluan untuk Ijazah Master Sains. IMPREGNASI NANOTIUB KARBON YANG DISINTESIS SECARA DALAMAN KE DALAM SELULOSA BAKTERIA Oleh SHARMEEN BINTI ADNAN Ogos 2011 Pengerusi: Dayang Radiah Bt. Awang Biak, PhD Fakulti: Fakulti Kejuruteraan Selulosa bakteria (BC) yang disintesis oleh Acetobacter xylinum telah dikenalpasti sebagai matriks yang berpotensi tinggi untuk diisi dengan nanotiub karbon (CNT). Objektif utama penyelidikan ini adalah untuk menghasilkan nano-komposit selulosa bakteria/nanotiub karbon (BC/CNT) dengan permukaan hidrofobik. CNT ditambahkan bagi memperbaiki ciri elektrikal BC seterusnya menghasilkan membran yang konduktif. Membran yang hidrofobik pula lebih praktikal dalam penghasilan peralatan kerana ia lebih sesuai untuk digunakan bersama bahan hidrofobik yang lain. Dalam penyelidikan ini, membran dihasilkan menggunakan media kultur daripada ekstrak kurma. Tiga teknik impregnasi CNT yang dijalankan adalah rendaman, v
serakan dan semburan manakala proses asetilasi pula adalah proses asitilasi penuh dan asitilasi separa. Dalam kajian ini, morfologi adalah ciri penting dalam pemilihan sampel yang akan dianalisa sepenuhnya. Nano-komposit BC/CNT yang dihasilkan melalui teknik semburan menunjukkan keseragaman penyebaran CNT serta mempunyai nilai konduktiviti di-elektrik yang paling baik iaitu ~4.66x 10-1 S/cm berbanding nilai yang ditunjukkan oleh BC/CNT yang dihasilkan melalui teknik-teknik yang lain. Maka, teknik semburan telah digunakan untuk menghasilkan nanokomposit BC/CNT asetat. Disebabkan morfologi BC/CNT asetat yang disediakan melalui proses asitilasi separa menunjukkan degradasi hanya berlaku di permukaan sahaja sementara struktur teras dalam BC tidak terjejas, maka proses ini digunakan untuk penghasilan sampel seterusnya. Ciri BC/CNT asetat dikenalpasti melalui kewujudan ikatan-ikatan yang mewakili kumpulan berfungsi asetil iaitu C=O, CH 3 dan C-O dan juga nilai sudut antara air dan BC/CNT asetat yang lebih tinggi (~77 ) berbanding BC/CNT (~45 ). Apabila kedua-duanya dikaji, suhu penguraian dan peralihan kaca bagi BC/CNT asetat menurun kepada 203 C dan 35 C, masingmasing. Penurunan ini berlaku kerana struktur BC dalam BC/CNT asetat yang membengkak memudahkannya diuraikan dengan rawatan suhu. vi
Namun begitu, BC/CNT asetat mempunyai kandungan hablur BC yang lebih tinggi, iaitu 51% berbanding BC/CNT (49%). Ini menunjukkan CNT telah menghalang proses penguraian nanokomposit seterusnya melindungi hablur BC. Disebabkan itu, kedua-dua keupayaan elastik dan saiz hablur BC/CNT hanya menurun sebanyak 9% sahaja, iaitu daripada 34 ke 31 GPa dan daripada 27.3 ke 24.9 nm, masing-masing. Tambahan pula, liang nano-komposit asetat yang lebih besar (~22 Å) berbanding BC/CNT (~-103 Å) mungkin membolehkan proses penambahbaikan fungsi dilakukan ke atas membran tersebut. Kesimpulannya, impregnasi CNT melalui teknik semburan semasa fermentasi BC berlaku disamping rawatan asetilasi separa telah menghasilkan membran yang rintang kepada air, tinggi nilai konduktiviti dielektrik dan tinggi kandungan hablur BCnya. Namun, keupayaan elastik, saiz hablur, suhu penguraian dan suhu peralihan kaca telah menurun. Ciri-ciri ini menjadikan membran BC/CNT asetat berpotensi sebagai biomaterial membran dalam pembuatan peralatan. vii
ACKNOWLEDGEMENT In the name of Allah S.W.T., the most Benevolent and Merciful. All gratification is referred to Allah S.W.T. Firstly, I would like to take this opportunity to thank the chairperson of my supervisory committee, Dr. Dayang Radiah Bt. Awang Biak, whose expert guidance and support has helped me to complete the research. Her kindness, affection, encouragement and moral support gave me the courage and ability to overcome all the problems I have faced from time to time during the course of my work. I would like to extend my appreciation to her for the invaluable advice and continuous comment and support, which brighten my future through the experiences that I have gained from her. I am also very grateful to Mrs. Faizah Bt. Md. Yasin, whose expert guidance and support has helped me to overcome problems that I have encountered during the course of my study. I am also indebted to and wish express my appreciation to Mrs. Suryani Bt. Kamaruddin for her interest and invaluable suggestion that had enable me to carry on with my project successfully. viii
I would like to thank Universiti Putra Malaysia for providing me a scholarship (Graduate Research Fellowship) which has enables me to continue my research as well as my life a student. The list of thanks also goes to all my friends and the people who have known me for the joy, laughter and memories that we have shared together during my study at Universiti Putra Malaysia. Lastly, I would like to express my most sincere and warmest gratitude to my mother (Siti Hafsah Bt. Dahalan) and my father (Adnan B. Rajikan) and all my family members for their payers, love, generosity and moral supports that they have during the course of my study. ix
I certify that a Thesis Examination Committee has met on 25 August 2011 to conduct the final examination of Sharmeen Binti Adnan on her thesis entitled "Impregnation of In-House Synthesized Carbon Nanotubes in Bacterial Cellulose" in accordance with the Universities and University Colleges Act 1971 and the Constitution of the Universiti Putra Malaysia [P.U.(A) 106] 15 March 1998. The Committee recommends that the student be awarded the degree of Master of Science. Members of the Thesis Examination Committee were as follows: Fakhru l-razi Ahmadun, PhD Professor Dr. Faculty of Engineering Universiti Putra Malaysia (Chairman) Robiah Yunus, PhD Professor Dr. Faculty of Engineering Universiti Putra Malaysia (Internal Examiner) Suraya Abdul Rashid, PhD Dr. Faculty of Engineering Universiti Putra Malaysia (Internal Examiner) Fadzilah Adibah Abdul Majid, PhD Associate Professor Dr. Department of Bioprocess Engineering, Faculty of Chemical Engineering Universiti Teknologi Malaysia Malaysia (External Examiner) SEOW HENG FONG, PhD Professor and Deputy Dean School of Graduate Studies Universiti Putra Malaysia Date: 20 December 2011 x
This thesis was submitted to the Senate of Universiti Putra Malaysia and has been accepted as fulfillment of the requirement for the degree of Master of Science. The members of the Supervisory Committee were as follows: Dayang Radiah Bt. Awang Biak, PhD Senior Lecturer Faculty of Engineering Universiti Putra Malaysia. (Chairman) Faizah Bt. Md. Yasin Lecturer Faculty of Engineering Universiti Putra Malaysia. (Member) BUJANG BIN KIM HUAT, PhD Professor and Dean School of Graduate Studies Universiti Putra Malaysia Date: xi
DECLARATION I declare that the thesis is my original work except for quotations and citations which have been duly acknowledged. I also declare that it has not been previously, and is not concurrently, submitted for any other degree at Universiti Putra Malaysia or at any other institution. SHARMEEN BINTI ADNAN Date: 25 August 2011 xii
TABLE OF CONTENTS ABSTRACT ABSTRAK ACKNOWLEDGEMENT APPROVAL DECLARATION LIST OF TABLES LIST OF FIGURES LIST OF ABBREVIATIONS CHAPTER 1. INTRODUCTION 1 2. LITERATURE REVIEW 6 2.0 Introduction 6 2.1 Bacterial cellulose (BC) 6 2.1.1 Growth associate product of BC 7 2.1.2 Carbon source as crucial nutrient 9 2.1.3 Oxygen dependent of BC production 13 2.1.4 Crystal structure of BC microfibrils 13 2.1.5 BC nanocomposites 17 2.2 Carbon nanotubes (CNT) and bacterial cellulose/ 20 carbon nanotubes (BC/CNT) nanocomposites 2.2.1 Previous researches on BC/CNT nanocomposites 22 2.2.2 Dielectric properties of BC/CNT nanocomposites 23 2.3 Acetylation of BC and BC/CNT membranes 26 2.3.1 Mechanism of acetylation 27 2.3.2 Methodology of acetylation 27 2.4 Characterization of BC and BC/CNT membranes 29 2.4.1 Morphological analysis 29 Page ii v viii x xii xvii xviii xxi xiii
2.4.2 Spectroscopic identification 30 2.4.3 Thermal characteristic 31 2.4.4 Mechanical characteristic 32 2.4.5 Surface analysis 33 2.4.5.1 Wettability 33 2.4.5.2 Surface area and porosity 34 2.5 Conclusion 34 3. METHODOLOGY 35 3.0 Introduction 35 3.1 Preparation of date extract (DE) 37 3.2 Culture medium preparation from DE 37 3.3 Production of BC membrane 38 3.4 Recovery process of BC membrane 39 3.5 Sample preparation for characterization 39 3.6 Experiment for carbon source selection 40 3.7 Production of BC/CNT membrane 40 3.7.1 (A) Immersing BC membrane in CNT 41 dispersed solution 3.7.2 (B) Dispersing CNT in DE culture medium 42 3.7.3 (C) Spraying CNT dispersed solution onto growing BC 42 (a) Preparation of DE culture medium and 42 CNT dispersed solution (b) Spraying procedure of CNT dispersed solution 43 3.8 Dielectric conductivity calculation of BC/CNT membranes 44 3.9 Preparation of BC/CNT acetate nanocomposite 45 3.9.1 Homogeneous acetylation 45 3.9.2 Heterogeneous acetylation 46 3.10 Characterization of BC and nanocomposite membranes 47 3.10.1 Morphological observation 47 3.10.2 Spectroscopic identification 47 xiv
3.10.3 Crystallinity analysis 48 3.10.4 Thermal analysis 49 3.10.5 Mechanical analysis 49 3.10.6 Surface wettability analysis 50 3.10.7 Surface area and porosity analysis 50 3.11 Conclusion 51 4. RESULTS AND DISCUSSION 52 4.0 Introduction 52 4.1 Comparison of the BC produced from HS and DE media 53 4.2 Production of BC/CNT nanocomposites 58 4.2.1 CNT dispersion behavior within BC membrane 58 (A) Immersing BC membrane in CNT 59 dispersed solution (B) Dispersing CNT in BC culture medium 60 (C) Spraying CNT dispersed solution 62 onto growing BC 4.2.2 Physical characteristic of BC/CNT nanocomposites 64 4.2.3 Dielectric conductivity of the produced BC/CNT 66 4.3 Production of BC/CNT acetate nanocomposite 69 4.3.1 Physical changes of BC and BC/CNT due to acetylation 70 (A) Homogeneous acetylation 71 (B) Heterogeneous acetylation 73 4.4 Morphological observation 74 4.4.1 Character of BC produced using DE culture medium 74 4.4.2 Character of BC/CNT nanocomposites 75 (A) Immersing BC membrane in CNT 75 dispersed solution (B) Dispersing CNT in DE culture medium 76 (C) Spraying CNT dispersed solution onto growing BC 78 4.4.3 Morphological changes of BC and BC/CNT acetates 79 xv
4.5 Spectroscopic identification 82 4.5.1 The significant functional groups of the membranes 83 4.5.2 Determination of cellulose crystals via FTIR analysis 87 4.6 Crystallinity analysis 89 4.6.1 Crystalline peaks of the membranes 90 4.6.2 Determination of crystallite size 92 4.6.3 Determination of crystallinity index (CrI) 94 4.7 Thermal analysis 96 4.7.1 Weight loss percentage of the membranes 97 4.7.2 Determination of decomposition temperature 98 4.8 Mechanical analysis 100 4.8.1 Elasticity of the membranes 101 4.8.2 Viscous dissipation of the membranes 102 4.8.3 Determination of glass transition temperature (T g ) 103 4.9 Surface wettability analysis 104 4.10 Surface area and porosity analysis 106 4.10.1 Pore size investigation 107 4.10.2 Determination of surface area 109 4.11 Conclusion 111 5. SUMMARY, CONCLUSION AND 113 RECOMMENDATIONS FOR FUTURE RESEARCH REFERENCES 117 APPENDICES 130 BIODATA OF STUDENT 136 xvi