Development of self assembly templating methods for architecture of porous core shell nanocomposites

DEVELOPMENT OF SELF-ASSEMBLY TEMPLATING METHODS FOR ARCHITECTURE OF POROUS CORE-SHELL NANOCOMPOSITES WANG DANPING NATIONAL UNIVERSITY OF SINGAPORE 2010 DEVELOPMENT OF SELF-ASSEMBLY TEMPLATING METHODS FOR ARCHITECTURE OF POROUS CORE-SHELL NANOCOMPOSITES WANG DANPING (B.Sc, Xi’an Jiaotong University, China) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CHEMICAL AND BIOMOLECULAR ENGINEERING NATIONAL UNIVERISTY OF SINGAPORE 2010 ACKNOWLEDGEMENTS On publication of this thesis, I would like to express my heart-felt thanks to a number of people. Without their help, this thesis would never have been possible. First of all, I would like to express my deepest appreciation and sincerest gratitude to my supervisor, Prof. Zeng Hua Chun for his guidance and support throughout the thesis project. It has been a truly memorable and educative experience of conducting Ph.D study in his group. His high integrity and dedication in scientific research has a profound influence in me. His broad knowledge and innovative ideas are of great value for my research. His incredible patience and unconditional encouragement have provided me with a free and vivid research environment to try out new things. I am also very grateful for his generous help during my difficult moments. I also have had the great luck of working with a number of diligent and knowledgeable colleagues in our group. I would like to express my warm thanks to Dr. Chang Yu, Dr. Li Jing, Dr. Zhang Yu Xin, Dr. Yao Ke Xin, Dr. Pang Mao Lin, Dr. Xiong Sheng Lin, Dou Jian, Liu Ming Hui, Li Cheng Chao, Li Xuan Qi, Li Zheng, Yec Christopher Cheung and Wentalia Widjajanti for their useful discussions, assistance and encouragement in my research work. Sincere thanks also go to all the staff in the General Office, especially Ms. Khoh Leng Khim, Sandy for her kind help in lab administration and BET analysis. For technical i support, I would like to thank Mr. Chia Phai Ann, Dr. Yuan Ze Liang, Mr. Mao Ning, Mr. Liu Zhi Cheng, Ms. Sam Fam Hwee Koong and Ms. Lee Chai Keng. I highly acknowledge the generosity of National University of Singapore for providing the research scholarship and rich resources throughout my Ph.D candidature. Special thanks to my family especially my parents for their unconditional love, support, encouragement and understanding during the past 27 years. I also owe my deep thanks to my friends both in Singapore and China for their selfless support and suggestion. ii CONTENT ACKNOWLEDGEMENTS……………………………………………………. i CONTENT…………………………………………………………………… . iii SUMMARY……………………………………………………………………. vii PUBLICATION RELATED TO THE THESIS……………………………… . ix SYMBOLS AND ABBREVIATIONS………………………………………… x LIST OF TABLES…………………………………………………………… . xii LIST OF FIGURES……………………………………………………………. xiii CHAPTER INTRODUCTION………………………………………………. 1.1 Overview………………………………………………………………… 1.2 Objectives and Scope………………………………………………………. 1.3 Organization of the Thesis…………………………………………………. 1.4 References…………………………………………………………………. 1 CHAPTER LITERATURE REVIEW…………………………………………… 2.1 Overview of Nanomaterial, Nanostructure and Nanocomposites…………. 2.2 Synthesis and Organization of Core-shell Nanostructures………………… 2.2.1 Direct Coating………………………………………………………… 2.2.2 Self-assembly in Core-shell Structure Fabrication……………………. 2.3 Ostwald Ripening and Hydrothermal/Solvothermal Reaction…………… 2.3.1 Ostwald Ripening…………………………………………………… . 2.3.2 Hydrothermal/Solvothermal Reaction………………………………… 2.4 Brief Introduction to Each Component Material………………………… . 2.4.1 TiO2 and Photocatalysis……………………………………………… 2.4.2 Polyaniline (PAN)…………………………………………………… . 2.4.3 SiO2-based Materials………………………………………………… 2.4.4 Au and Its Catalytic Applications…………………………………… . 2.5 References………………………………………………………………… 7 9 14 24 24 26 27 28 30 35 39 42 CHAPTER CHARACTERIZATION METHODS……………………… . 68 iii 3.1 Powder X-ray Diffraction (XRD) and Small-angle X-ray Scattering (SAXS)………………………………………… . 3.2 Transmission Electron Microscopy (TEM)……………………………… . 3.3 Field Emission-/ Scanning Electron Microscopy (FE-SEM) and Energy-dispersive X-ray Spectroscopy (EDX)……………………………. 3.4 X-ray Photoelectron Spectroscopy (XPS)…………………………………. 3.5 Fourier Transform Infrared Spectroscopy (FTIR)…………………………. 3.6 Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) Methods………………………………………………………… 3.7 Ultraviolet Visible Light Spectroscopy (UV-Vis)………………………… 3.8 Thermogravimetric Analysis………………………………………………. 3.9 References………………………………………………………………… CHAPTER NANOCOMPOSITES OF ANATASE-POLYANILINE PREPARED VIA SELF-ASSEMBLY……………………………………… . 4.1 Introduction………………………………………………………………… 4.2 Experimental Section……………………………………………………… 4.2.1 Synthesis of TiO2 Nanoparticle Suspension………………………… . 4.2.2 Preparation of Network-like Assemblages of TiO2 Nanoparticles……. 4.2.3 Synthesis of Network-like TiO2-in-Polyaniline……………………… 4.2.4 Effect of Self-assembled TiO2 Nanoparticles on Morphology of Polyaniline……………………………………………………… . 4.2.5 Effect of Amount of TiO2 on the Morphology of TiO2-in-polyaniline . 4.2.6 Solvent Effect on the TiO2 Distribution in the Polyaniline Phase…… 4.2.7 Synthesis of Interconnected Spherelike TiO2-at-polyaniline…………. 4.2.8 Surfactant Effect on the Morphology of TiO2-in-polyaniline………… 4.2.9 Materials Characterization…………………………………………… 4.3 Results and Discussion………………………………………………… 4.4 Conclusions………………………………………………………………… 4.5 References……………………………………………………………… CHAPTER MULTIFUNCTIONAL ROLES OF TiO2 NANOPARTICLES FOR ARCHITECTURE OF COMPLEX CORE-SHELLS AND HOLLOW SPHERES OF SiO2-TiO2-POLYANILINE SYSTEM…………………………… 5.1 Introduction………………………………………………………………… 5.2 Experimental Section………………………………………………………. 5.2.1 Synthesis of SiO2 Mesospheres……………………………………… 5.2.2 Synthesis of TiO2 Nanoparticles………………………………………. 5.2.3 Synthesis of SiO2/TiO2 via Self-assembly…………………………… 68 69 69 70 71 71 72 73 73 74 74 76 76 77 77 77 78 78 79 79 80 81 98 99 103 103 107 107 107 108 iv 5.2.4 Synthesis of SiO2/TiO2/PAN………………………………………… . 5.2.5 Synthesis of SiO2/TiO2/PAN/TiO2 5.2.6 Preparation of Hollow TiO2/PAN…………………………………… . 5.2.7 Preparation of Hollow TiO2/PAN/TiO2……………………………… 5.2.8 Preparation of Hollow TiO2 /TiO2…………………………………… 5.2.9 Photocatalytic Reactivity……………………………………………… 5.2.10 Materials Characterization…………………………………………… 5.3 Results and Discussion…………………………………………………… 5.4 Conclusions………………………………………………………………… 5.5 References………………………………………………………………… CHAPTER CREATION OF INTERIOR SPACE, ARCHITECTURE OF SHELL STRUCTURE AND ENCAPSULATION OF FUNCTIONAL MATERIALS FOR MESOPOROUS SiO2 SPHERES………………………. 6.1 Introduction………………………………………………………………… 6.2 Experimental Section………………………………………………………. 6.2.1 Hollowing mesoporous SiO2 spheres via Ostwald Ripening…………. 6.2.2 Hollowing Mesoporous SiO2 Spheres via Soft Templating………… . 6.2.3 Formation of Double-shelled Mesoporous SiO2 Spheres…………… 6.2.4 Encapsulation of Functional Materials in Mesoporous SiO2 Spheres . 6.2.5 Calcination of Samples……………………………………………… . 6.2.6 Photocatalytic Reactions with Nanoreactors………………………… 6.2.7 Materials Characterization…………………………………………… 6.3 Results and Discussion…………………………………………………… 6.3.1 Creation of Interior Space via Ostwald Ripening…………………… . 6.3.2 Preparation of Smooth Inner Wall via Soft-templating……………… 6.3.3 Architecture of Shell Structures……………………………………… 6.3.4 Encapsulation of Nanoparticles and Applications…………………… 6.4 Conclusions………………………………………………………………… 6.5 References………………………………………………………………… CHAPTER DESIGN OF A HIGHLY EFFICIENT MESOPOROUS CORE-SHELL NANOREACTOR WITH ENHANCED CATALYST LOADING…………………………………………………………………… 7.1 Introduction………………………………………………………………… 7.2 Experimental Section………………………………………………………. 7.2.1 Synthesis of AuNPs…………………………………….…………… . 7.2.2 Synthesis of 3-D Network with Double-shelled Au/SiO2 Nano ‘Bean-pod’ Branches…………………………………………… 109 109 110 110 111 112 112 113 133 134 143 143 146 146 147 147 148 149 150 151 152 152 166 174 182 190 191 198 198 201 201 201 v 7.2.3 Addition of a Second Functional Species…………………………… . 7.2.4 Preparation of 3-D Nanoreactor with Bean-pod-like Au@SiO2 Branches………………………………………………… . 7.2.5 Catalytic Reactivity of Evaluation of Au/SiO2 Nanoreactors by 4-nitrophenol Reduction………………………………………………. 7.2.6 Materials Characterization…………………………………………… 7.3 Results and Discussion…………………………………………………… 7.4 Conclusion…………………………………………………………………. 7.5 References…………………………………………………………………. 202 CHAPTER CONCLUSIONS AND RECOMMENDATIONS……………… 8.1 Conclusions………………………………………………………………… 8.2 Recommendations………………………………………………………… 8.3 References………………………………………………………………… 230 230 232 236 202 203 203 204 222 224 vi SUMMARY In recent years, there have been tremendous efforts in the synthesis of nanomaterials for their unique properties and applications different from their bulk counterparts. To incorporate multiple functionalities into one individual nanostructure is a challenging and interesting field in nanomaterial synthesis. Though various chemical routes have been developed to prepare core-shell nanocomposites, it is still believed that explorations of novel synthetic methodology and further engineering on shell structures will contribute new properties and applications to this field. This thesis focuses on the study of core-shell nanocomposites, aiming for producing complex nanostructures with process facility and feature application performance. Self-assembly templating is the main approach throughout this thesis, though hard-templating method is involved in some part the study. Four kinds of nanocomposites have been obtained: TiO2-polyaniline (PAN) core-shell nanomaterials, mesoporous Au-SiO2 core-shell nanocomposite, hierarchically designed SiO2-TiO2-PAN nanostructures, and mesoporous SiO2 spheres with hexagonally packed vertical channels and encapsulation of nanoparticles (Au, PAN, etc.). Material information of phase, composition, valence, and morphology are acquired from instrumental analysis to help us to further understand formation mechanisms. In order to evaluate the applicability, some of these nanocomposites are used as photocatalysts or nanoreactors. Firstly, TiO2/PAN nanocomposites have been synthesized by using vii oleate-surfactant-protected anatase TiO2 nanoparticles self-assembled aggregations as templates for aniline polymerization. By tuning the polarity of reaction system, three-dimensional core-shell network or uniform TiO2-PAN nanocomposites are acquired. Secondly, using the same rationale but different materials, Au nanoparticles enclosed in hollow mesoporous SiO2 shell is produced from self-assembly-templated TEOS hydrolysis on the surface of Au nanoparticle aggregations. With additional heat treatment, bean-pod-like Au-SiO2 nanoreactor is obtained. It has been examined to be an excellent nanoreactor in catalytic reduction of 4-nitrophenol. Thirdly, we have planted the oleate-surfactant-protected anatase TiO2 nanoparticles onto SiO2 beads via self-assembly to fabricate complex SiO2-TiO2-PAN nanostructures, in which the TiO2 nanoparticles play as seeds for the growth of different shells in the construction of highly intricate nanostructures. The method allows one to prepare core-shell, double-shell and multi-shell nanostructures by programmed coating and selective shell etching. Lastly, we have further engineered SiO2 shell structures by using non-/soft-templating methods to complete all the synthetic methodologies for core-shell/hollow structures. Assisted by the self-assembly of micelles, mesoporous SiO2 spheres with hexagonally packed vertical channels and their core-shell composites are prepared via three one-pot solvothermal routes. In addition to the synthesis of the phase-pure SiO2 spheres, we have also introduced functional materials into the central cavities of SiO2 spheres. Moreover, communicable 1D-channels of the SiO2 shells and workability of the enclosed nanomaterials have also be verified with the photocatalytic degradation of organic dyes (e.g., methyl orange). viii Chapter Design of a Highly Efficient Mesoporous Core-Shell Nanoreactor with Enhanced Catalyst Loading formation mechanism. Our time-controlled experiments indicate that Au nanoclusters made of AuNPs expand with the growth of SiO2 shell, forming Au hollow spheres (AuHSs) in the center. Bigger, elongated and interconnected AuHSs are obtained without the SiO2 septum when the reaction temperature is increased. Moreover, from our comparison experiments, it is concluded that AuNPs, TEOS and CTAB work coordinately on the final product’s morphology. Specifically speaking, AuNPs suspension provides the template for SiO2 layer formation; CTAB connects both Au nanoclusters and TEOS to guarantee the final core-shell structure; and TEOS-CTAB pairs control the size of Au nanoclusters. Last but not least, CTAB also serves as the porogen for mesoporous SiO2 shell. By using the same method, second functional component such as Fe3O4 or TiO2NPs is successfully incorporated into SiO2 chambers with AuNPs. Meanwhile, their elementary ratio can be tuned by controlling the volumes of each material’s suspension. Network of long-bean-like Au@mesoporous SiO2 nanoreactors are produced from the as-prepared Au/SiO2double-shelled bean-pod by calcinations at different temperatures. Au hollow spheres break down to bigger AuNPs due to the removal of DDT and other surfactants. Mesoporous SiO2 shell is generated at mild calcination temperatures (around 400oC). Catalytic reactivity of 4-nitrophenol reduction is examined for each nanoreactor, and AuNPs@mesoporous SiO2 made at 350oC had the highest apparent kinetic constant, kapp. FTIR and UV-Vis spectra indicate that capping agent has a higher influence on the reactivity of nanoreactors than the size of AuNPs, though both of them are the key factors to kapp values. 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J.Phys. Chem. C 2008, 112 (30), 11265-11271. 67. Zhang, Y. X.; Zeng, H. C., Gold(I)-Alkanethiolate Nanotubes. Adv. Mater. 2009, 21 (48), 4962-4965. 68. Panigrahi, S.; Basu, S.; Praharaj, S.; Pande, S.; Jana, S.; Pal, A.; Ghosh, S. K.; Pal, T., Synthesis and Size-Selective Catalysis by Supported Gold Nanoparticles: Study on Heterogeneous and Homogeneous Catalytic Process. J. Phys. Chem.C 2007, 111 (12), 4596-4605.   229 Chapter Conclusions and Recommendations CHAPTER CONCLUSIONS AND RECOMMENDATIONS 8.1 Conclusions This thesis work has developed several novel preparation approaches for the synthesis of various hollow or core-shell micro-/nanostructures. The process mechanisms, formation of nanostructures, and their properties have been investigated systematically. The most important conclusions of the research work are discussed in the following aspects: A) Self-assembly of presynthesized monodisperse TiO2 nanoparticles are adopted as soft-templates for solution-based synthesis of anatase-polyaniline nanocomposites. By tuning the polarity of mixed solvents, different aggregative forms of TiO2 nanoparticles can self-assemble into three-dimensional network-like aggregates. The self-assembled TiO2 aggregates then serve as soft templates for deposition of polyanline, and core-shell structures of anatase-polyaniline nanocomposites can thus be prepared. This preparation approach also offers a method for preparation of complex core-shell nanocomposites with higher process flexibilities. B) A nanoparticle-mediated approach is devised for preparation of complex core-shell and hollow sphere nanostructures, in which oleate-surfactant-protected anatase TiO2 230 Chapter Conclusions and Recommendations nanoparticles play multifunctional roles in the construction of highly complex nanostructures. A total of six types of composite structures have been fabricated, namely, core-shells of SiO2/TiO2, SiO2/TiO2/PAN, and SiO2/TiO2/PAN/TiO2, and complex hollow spheres of TiO2/PAN, TiO2/PAN/TiO2, and TiO2/TiO2. Our preliminary experimental results also show the applicability of these nanostructures in real photocatalytic applications, especially for the separation of used catalysts after reaction owing to their relatively large external diameters. C) Ostwald ripening and soft-tempating are employed in solvothermal process to prepare mesoporous SiO2 hollow or double-shelled spheres with hexagonally aligned 1D-channels toward the center of sphere, in which CTAB micelles play an important role on the vertical pores formation. In addition to the synthesis of the phase-pure SiO2 spheres, functional materials are introduced to the hollow SiO2 center by two solution-based methods, pre-installation and on-site synthesis. Moreover, communicable 1D-channels of the SiO2 shells and workability of the enclosed nanomaterials have also been verified, and it has been unambiguously proven that both inorganic ions and organic molecular species can penetrate through the 1D-channels and react within the interior spaces of SiO2 spheres. In view of their working flexibility, we believe that the synthetic approaches and general concepts developed should also be applicable to the preparation of other advanced composite materials, in addition to those reported in the current work. D) Self-assembly of Au nanoparticles is utilized as soft-template for TEOS hydrolysis 231 Chapter Conclusions and Recommendations so as to produce bean-pod-like Au-SiO2 core-shell nanocomposites. Mesooporous SiO2 is generated after heat treatment, and Au nanoparticles are stored in SiO2 interconnected chambers, which can considered as an ideal nanoreactor. Concerning the application, the Au@mesoporous SiO2 nanoreactor works efficiently for 4-nitrophenol catalytic reduction. In view of synthetic flexibility of our method, second core component such as Fe3O4 or TiO2 nanoparticles are successfully incorporated into SiO2 chambers by pre-mixing their suspensions with Au nanoparticles. Elementary ratio between core components can be fine-tuned by controlling the volumes of each material’s suspension. We believe that this self-assembly templating method can be generalized to design more nanoreactors by altering core materials, or addition of tertiary or even quaternary core component to fabricate multi-functional nanoreactors. Furthermore, the porous SiO2 shell can be replaced by other materials such as TiO2 or carbon. 8.2 Recommendations Based on the results obtained so far, we hereby recommend some consecutive research directions for the future work. A) In Chapter and Chapter 7, we have developed nanoparticle self-assembly templating method to fabricate TiO2/polyaniline and Au/SiO2 network-like core-shell nanocomposites. However, uniform self-assembled building blocks of TiO2 or Au nanoparticles were not achieved which might be responsible for the interconnected 232 Chapter Conclusions and Recommendations polymer or SiO2 coating. This might limit the applicability of our nanocomposites. Therefore, future work needs to be carried out on tuning experimental parameters such as polarity of solvent, surfactant concentration, and reaction temperature to achieve colloidal dispersions of nanoparticle assemblages and core-shell nanocomposites.1, The advantages of monodispersed colloidal nanocomposites lie in areas of improved dispersion in solvent, better thermal and chemical stabilities and better optical properties, etc.1, B) In Chapter and Chapter 5, we have prepared different types of TiO2/polyaniline nanocomposites. The different contacts between TiO2 nanoparticles and polyaniline may generate different properties of these nanocomposites. Polyaniline is a p-type conductive polymer while TiO2 is n-type semiconductor. The resistance of the p-n heterojunctions combining with the bulk resistance of polyaniline can function as electric current switches for NH3, when gas molecules adsorb onto polyaniline.4 Moreover, polyaniline/TiO2 nanocomposites can significantly enhance the optical contrast and coloration efficiency for pure polyaniline. Furthermore, when covalently bonded to polyanline, TiO2 nanodomains can act as electron acceptors, reducing the oxidation potential and band gap of polyaniline. This will help improve the long-term elctrochromic stability of the composites.5 C) Mesoporous SiO2 and its nanocomposites have been obtained in Chapter and Chapter 7. However, many applications (such as adsorption, ion exchange, etc) require the materials to have specific properties such as binding sites, stereochemical 233 Chapter Conclusions and Recommendations configuration, etc.6 Furthermore, modification of the internal and external surfaces of SiO2 with organic ligands is also important for the stabilization of mesostructure, to create hydrophobic surface to reduce water adsorption.7 Figure 8-1 Schematic drawing of functionalized monolayers on mesoporous supports (FMMS). One end group of the functionalized monolayers is covalently bonded to the silica surface and the other end group can be used to bind heavy metals or other functional molecules.8 Figure 8-2 Schematic conformations of functionalized monlayers on the surface under different conditions. (A) Disordered molecules at 25% surface coverage. (B) Closed-packed at 75% surface coverage. (C) Containing mercury at 75% surface coverage.8 234 Chapter Conclusions and Recommendations A lot of research work has been carried out on the covalent coupling of organic moieties onto SiO2 walls, which includes post-synthetic grafting,8,9 or surfactant-mediated co-condensation reactions of organosilane with TEOS.10-12 For instance, people introduced thiol groups to the pore surface of mesoporous SiO2 via post-synthetic grafting in Figure 8-1, by mixing tris(methoxy)mercaptopropylsilane (TMMPS) with mesoporous silica in an appropriate solvent. The organosiloxane groups were eventually covalently attached to the SiO2 after hydrolysis. This organic layer could efficiently remove mercury and other heavy metals from polluted aqueous solutions (see Figure 8-2).8, 13 Figure 8-3 TEM images of the organic-inorganic hybrid MNPs synthesized by co-condensation method. The periodicity was well maintained.14 Secondly, co-precipitation of organosiliane with TEOS has also been used recently.14, 15 235 Chapter Conclusions and Recommendations Mesoporous silica-surfactant composite nanoparticles (SSNs) were prepared from a mixture of TEOS, 3-aminopropyltriethoxysilane (APTES), CTAB, water, ethylene glycol (EG) by stirring at 50oC for h. It was reported that a high doping ratio up to 32 wt% of APTES to TEOS was achieved, and a long-range periodicity was still maintained (see Figure 8-3).14 Apart from the surface modification of the micro-SiO2, its large surface area and tunable hollow center is actually a very good hard template to fabricate other organic or inorganic materials with special structures.16-18 Lastly, some efforts are worth to be put on scaling up the fabrication of mesoporous SiO2 spheres. 8.3 References 1. Kim, J.; Lee, J. E.; Lee, J.; Yu, J. H.; Kim, B. C.; An, K.; Hwang, Y.; Shin, C. H.; Park, J. G.; Hyeon, T., Magnetic fluorescent delivery vehicle using uniform mesoporous silica spheres embedded with monodisperse magnetic and semiconductor nanocrystals. J. Am. Chem. Soc. 2006, 128 (3), 688-689. 2. Bai, F.; Wang, D. S.; Huo, Z. Y.; Chen, W.; Liu, L. P.; Liang, X.; Chen, C.; Wang, X.; Peng, Q.; Li, Y. D., A versatile bottom-up assembly approach to colloidal spheres from nanocrystals. Angew. Chem.-Int. Edit. 2007, 46 (35), 6650-6653. 3. Joo, S. H.; Park, J. Y.; Tsung, C. K.; Yamada, Y.; Yang, P. D.; Somorjai, G. A., Thermally stable Pt/mesoporous silica core-shell nanocatalysts for high-temperature reactions. Nat. Mater. 2009, (2), 126-131. 4. Gong, J.; Li, Y. H.; Hu, Z. S.; Zhou, Z. Z.; Deng, Y. L., Ultrasensitive NH3 gas sensor from polyaniline nanograin enchased TiO2 fibers. J. Phys. Chem. C 2010, 114 (21), 9970-9974. 5. Xiong, S. X.; Phua, S. L.; Dunn, B. S.; Ma, J.; Lu, X. H., Covalently bonded polyaniline-TiO2 hybrids: A facile approach to highly stable anodic electrochromic materials with low oxidation potentials. Chem. Mater. 2010, 22 (1), 255-260. 236 Chapter Conclusions and Recommendations 6. Schierbaum, K. D.; Weiss, T.; Vanvelzen, E. U. T.; Engbersen, J. F. J.; Reinhoudt, D. N.; Gopel, W., Molecular recognition by self-assembled monolayers of cavitand receptors. Science 1994, 265 (5177), 1413-1415. 7. Baskaran, S.; Liu, J.; Domansky, K.; Kohler, N.; Li, X. H.; Coyle, C.; Fryxell, G. E.; Thevuthasan, S.; Williford, R. E., Low dielectric constant mesoporous silica films through molecularly templated synthesis. Adv. Mater. 2000, 12 (4), 291-294. 8. Feng, X.; Fryxell, G. E.; Wang, L. Q.; Kim, A. Y.; Liu, J.; Kemner, K. M., Functionalized monolayers on ordered mesoporous supports. Science 1997, 276 (5314), 923-926. 9. Clark, J. H.; Macquarrie, D. J., Catalysis of liquid phase organic reactions using chemically modified mesoporous inorganic solids. Chem. Commun. 1998, (8), 853-860. 10. Sadasivan, S.; Khushalani, D.; Mann, S., Synthesis and shape modification of organo-functionalised silica nanoparticles with ordered mesostructured interiors. J. Mater. Chem. 2003, 13 (5), 1023-1029. 11. Huo, Q. S.; Margolese, D. I.; Stucky, G. D., Surfactant control of phases in the synthesis of mesoporous silica-based materials. Chem. Mat. 1996, (5), 1147-1160. 12. Lim, M. H.; Blanford, C. F.; Stein, A., Synthesis and characterization of a reactive vinyl-functionalized MCM-41: Probing the internal pore structure by a bromination reaction. J. Am. Chem. Soc. 1997, 119 (17), 4090-4091. 13. Kosuge, K.; Murakami, T.; Kikukawa, N.; Takemori, M., Direct synthesis of porous pure and thiol-functional silica spheres through the S+X-I+ assembly pathway. Chem. Mater. 2003, 15 (16), 3184-3189. 14. Gu, J.; Fan, W.; Shimojima, A.; Okubo, T., Organic-inorganic mesoporous nanocarriers, integrated with biogenic ligands. Small 2007, (10), 1740-1744. 15. Hoshikawa, Y.; Yabe, H.; Nomura, A.; Yamaki, T.; Shimojima, A.; Okubo, T., Mesoporous silica nanoparticles with remarkable stability and dispersibility for antireflective coatings. Chem. Mater. 2010, 22 (1), 12-14. 16. Kruk, M.; Dufour, B.; Celer, E. B.; Kowalewski, T.; Jaroniec, M.; Matyjaszewski, K., Grafting monodisperse polymer chains from concave surfaces of ordered mesoporous silicas. Macromolecules 2008, 41 (22), 8584-8591. 17. Wu, C. G.; Bein, T., Conducting polyaniline filaments in a mesoporous channel host. Science 1994, 264 (5166), 1757-1759. 237 Chapter Conclusions and Recommendations 18. Nakamura, T.; Mizutani, M.; Nozaki, H.; Suzuki, N.; Yano, K., Formation mechanism for monodispersed mesoporous silica spheres and its application to the synthesis of core/shell particles. J. Phys. Chem. C 2007, 111 (3), 1093-1100. 238 [...]... illustrations for formation processes of different interior spaces and shell structures of mesoporous SiO2 spheres (refer to Figure 1): (a) route (i)  formation of solid SiO2-CTAB hybrid (1), CTAB rod-like assemblies become more parallel upon aging (2), and evacuation of central SiO2-CTAB due to stress (3); (b) route (iii)  formation of micelle (1), deposition of SiO2-CTAB (2), and removal of soft templating. .. at 120oC for 4 h, (d-f) with 0.2 g of CTAB + 0.15 mL of DDT at 120oC for 3 h, (g-i) with 0.05 g of CTAB + 0.37 mL of DDT at 120oC for 3 h, and (j-l) with 0.1 g of sodium citrate + 0.2 g of CTAB + 0.05 mL of DDT at 120oC for 3 h………………………………………………………………….166 Figure 6-9 Characterization of mesoporous SiO2 spheres prepared according to route (iii) of Figure 1: (a) Representative FTIR spectra of the as-prepared... catalysts for their special structure and the combination of multifunctional component.7-10 In this thesis, a total of four kinds of core- shell nanocomposites are discussed: TiO2-polyaniline nanocomposite, complex core- shell or hollow sphere structures comprising of SiO2, TiO2, and polyaniline, microporous SiO2 hollow spheres and their organic or inorganic nanocomposites, and mesoporous Au-SiO2 core- shell. .. solvents of 20.0 mL of 2-propanol + 4.0 mL of DI water + 0.1 g of CTAB + 0.5 mL of 32% ammonia solution; magnetic stirring for 6 h at room temperature; B) Atomic Ratio of [Au]/[Ti] = 0.45 Experimental Conditions: 0.5 mL of AuNPs toluene suspension + 1.0 mL of TiO2NPs toluene suspension + 60 μL TEOS was added into mixed solvents of 20.0 mL of 2-propanol + 4.0 mL of DI water + 0.5g of CTAB + 0.5 mL of 32%... Experimental conditions : (a-b) 25.0 mL of EG + 0.2 g of CTAB + 60 L of TEOS + 2.5 mL of 6.4 wt% ammonia solution, solvothermal reaction was carried out at 120oC for 1 h., (c-d) 125.0 mL of EG + 0.2 g of CTAB + 60 L of TEOS + 2.5 mL of 6.4 wt% ammonia solution, solvothermal reaction was carried out at 120oC for 3 h, (e-f) 25.0 mL of EG + 0.2 g of CTAB + 60 L of TEOS + 2.5 mL of 6.4 wt% ammonia solution, solvothermal... route (v)  formation of SiO2-CTAB core sphere (1), deposition of less ordered SiO2-CTAB shell (2), and creation of spaces in the central core and interfacial region (3) Light green lines represent for CTAB rod-shaped assemblies imbedded in the silica matrices……164 Figure 6-8 TEM images of mesoporous SiO2 spheres prepared according to route (iii) of Figure 1: (a-c) with 0.2 g of CTAB + 0.37 mL of DDT at... Ping Wang and Hua Chun Zeng*, (Article) Nanocomposites of Anatase-Polyaniline Prepared via Self- Assembly, Journal of Physical Chemistry C, Vol 113 (2009), pp 8097-8106 2 Dan Ping Wang and Hua Chun Zeng*, (Article) Multifunctional Roles of TiO2 Nanoparticles for Architecture of Complex Core- Shells and Hollow Spheres of SiO2-TiO2-Polyaniline System, Chemistry of Materials Vol 21 (2009) pp.4811-4823 3... was carried out at 120oC for 12 h……………………………………………………………………… 158 Figure 6-5 Synthesis of mesoporous SiO2 spheres via route (i) of Figure 1 at different temperatures (a): 25.0 mL of EG + 0.2 g of CTAB + 60 L of TEOS + 2.5 mL of 6.4 wt% ammonia solution The solvothermal reaction was carried out at 120oC for 4 h (b): 25.0 mL of EG + 0.2 g of xviii CTAB + 60 L of TEOS + 2.5 mL of 6.4 wt% ammonia solution... views) of various nanoparticle-mediated synthetic schemes: (i) as-synthesized SiO2 sphere, (ii) self- assembly of TiO2 nanoparticle seeds (tiny white dots) on SiO2 sphere, (iii) polymerization and formation of polyaniline (PAN, green layer) shell on SiO2/TiO2 sphere, (iv) addition of TiO2 nanoparticles on the PAN shell, (v) growth of TiO2 on both inner and outer surfaces of TiO2/PAN shell, (vi) removal of. .. Chapter 2 Literature Review we only cover methodologies of core- shell nanocomposite synthesis Fabrication of hollow particles will also be introduced along with core- shell nanocomposites, for they are closely related to each other in a lot of cases 2.2 Synthesis and Organization of Core- shell Nanostructures Particles with core- shell structures often exhibit improved physical and chemical properties, and . DEVELOPMENT OF SELF- ASSEMBLY TEMPLATING METHODS FOR ARCHITECTURE OF POROUS CORE- SHELL NANOCOMPOSITES WANG DANPING NATIONAL UNIVERSITY OF SINGAPORE 2010 DEVELOPMENT. DEVELOPMENT OF SELF- ASSEMBLY TEMPLATING METHODS FOR ARCHITECTURE OF POROUS CORE- SHELL NANOCOMPOSITES WANG DANPING (B.Sc, Xi’an Jiaotong University, China) A THESIS SUBMITTED FOR THE. focuses on the study of core- shell nanocomposites, aiming for producing complex nanostructures with process facility and feature application performance. Self- assembly templating is the main