Organometallic clusters as precursors of metallic nanoparticles 1

Acknowledgements I express my gratitude to my research supervisor, A/P Prof Leong Weng Kee for his encouragement, patience, understanding and invaluable guidance, throughout the project with me and reading through the drafts of the thesis that you are reading Next, I would like to thank my co-supervisor at ICES, Dr Zhong Ziyi, for his guidance and help during my postgraduate studies I would like to thank Dr Goh Lai Yoong, Dr Loh Kian Ping and Dr Fan Wai Yip for their help I would like to thank the following who have given me assistance in various ways during my postgraduate studies: Garvin Mak, Chan Kiat Hwa, Chan Pekke, Leonard Pereira, Gao Lu, Alaric Koh Chun Wai, Venugopal Shanmugham Sridevi, Moawia Omer Elhag Ahmed, Kuan Seah Ling, Woo Chang Hong, Tan Hua, Li Shuping, Wong Lin Kai, Ouyang Ti and Chew Kiajia Benny I would like to thank the following laboratory staff: Mdm Han Yanhui and Ms Peggy Ler from NMR lab; Mdm Wong Lai Kwai and Mdm Lai Huiyi from MS lab; Miss Soong Foong Yee, Joanne, Mdm Leng Lee Eng, Miss Tan Tsze Yin from Elemental Analysis Lab and Thermal analytical lab; Mr Goh Ah Bah and Mr Conrado Wu Yu Ching from the glass blowing workshop; Ms Doreen Lai Mei Ying, Zhang Zhen from IMRE The Research Scholarship from the National University of Singapore over the last four years is gratefully acknowledged Last but not least, I would like to thank my parents, husband, and friends for their encouragement and moral support i Table of Contents Acknowledgements i Table of Contents ii Summary vii Molecule Numbering Scheme xi Abbreviations and Conventions xxi List of Tables xxiv List of Figures xxvi List of Schemes xxxv Chapter Organometallic complexes and nanomaterials/surfaces 1.1 Synthesis of nanomaterials from organometallic complexes 1.1.1 Organometallic complexes supported on porous materials 1.1.2 Decomposition of organometallic complexes in a hot solution 1.1.3 Surface modification 1.2 Self-assembly of organometallic clusters on the surface 11 1.2.1 Synthesis 12 1.2.2 Characterization techniques 14 1.2.3 Synthesis of molecular models 17 1.3 Objectives 20 Reference 20 ii Chapter Deposition of osmium clusters onto inorganic oxide surfaces 27 2.1 Synthesis of triosmium and ruthenium clusters with ligands containing two functional groups 28 2.2 Deposition of osmium clusters on silica 37 2.3 Deposition of clusters on ZnO and In2O3 surfaces 43 2.3.1 Deposition of Os3(CO)10(μ-H)(μ-OH) or Os3(CO)10(μ-H)2 on ZnO or In2O3 43 2.3.2 Deposition of osmium clusters containing a free functional group 46 2.4 Synthesis of molecular models for silica-supported triosmium clusters 51 2.5 Conclusion 54 2.6 Experimental 55 2.6.1 Synthesis of clusters 2.6.1.1 General procedure 55 55 2.6.1.2 Synthesis of osmium and ruthenium clusters with a ligand containing bifunctional groups 57 2.6.1.3 Synthesis of osmium-siloxane clusters 65 2.6.1.3.1 Synthesis of [Os3(CO)10(μ-H)(μ-O)][Si7O10{(CH2)5CH (CH3)2}7] (28) 65 2.6.1.3.2 Synthesis of [Os3(CO)10(μ-H)][μ-S(CH2)3Si8O12(i-butyl)7] (29) 65 2.6.1.3.3 Synthesis of [Os3(CO)10(μ-H)][μ-O(CH2)3Si8O12(i-butyl)7] (30) 66 2.6.1.3.4 Synthesis of [Os3(CO)11][P(C6H5)2(CH2)2Si8O12(C5H10)7] (32a) and [Os3(CO)10][P(C6H5)2(CH2)2Si8O12(C5H10)7]2 (32b) 66 iii 2.6.2 Deposition of osmium clusters on ZnO, In2O3 or silica surfaces Reference 67 68 Chapter Interaction of osmium clusters with metallic nanoparticles 72 and surfaces 3.1 Anchoring of osmium clusters onto silver or gold 73 3.1.1 Interaction of osmium clusters with silver or gold nanoparticles 74 3.1.2 Deposition of osmium clusters onto silver or gold surfaces 85 3.2 Anchoring of osmium clusters onto silver or gold nanoparticles via a hydrocarbon linker 89 3.2.1 Anchoring of Os3(CO)10(μ-H)(μ-S ͡ SH) 89 3.2.1.1 Interaction of osmium clusters with silver or gold nanoparticles 91 3.2.1.2 Deposition of osmium clusters onto silver or gold substrates 98 3.2.2 Anchoring of Os3(CO)10(μ-H)(μ-S ͡ OH) on silver 100 3.2.3 Anchoring of Os3(CO)10(μ-H)(μ-S ͡ COOH) on silver 105 3.2.4 Anchoring of crown-SH and Os3(CO)10(μ-H)(μ-S͡ crown) onto silver 111 3.3 Conclusion 116 3.4 Experimental 116 3.4.1 Synthesis of osmium clusters 116 3.4.1.1 General procedure 116 3.4.1.2 Synthesis of Os3Au2(CO)9(µ3-S)(PPh3)2, 34 117 3.4.1.3 Synthesis of Os3 (CO)10(μ-H)[(6-mercaptohexyloxy)methyl-15crown-5], 37 118 iv 3.4.2 Characterization 120 3.4.3 Synthesis of nanoparticles protected with osmium clusters 120 3.4.3.1 Silver nanoparticles 120 3.4.3.2 Gold nanoparticles 121 3.4.4 Deposition of osmium clusters onto substrates 121 3.5 Crystal data for 34 122 Reference 123 Chapter Organometallic clusters as precursors for metallic nanoparticles and thin films 4.1 The pyrolysis of organometallic clusters to nanoparticles 128 129 4.1.1 Effect of nuclearity and shape of the cluster core 129 4.1.2 Effect of support and temperature of pyrolysis 134 4.1.3 Effect of ligand set 140 4.1.4 Use of mixed-metal clusters 143 4.2 The preparation of surfactant stabilized metallic nanoparticles from organometallic cluster precursors 4.3 Metallic osmium and ruthenium nanoparticles for CO oxidation 146 152 4.4 Deposition of osmium and ruthenium thin films using organometallic cluster precursors 161 4.4.1 Preparation of an Os-Ru alloy thin film using a single-source CVD precursor 4.4.2 Deposition of osmium thin films using 29, 41 and 52 as CVD source 162 165 v 4.5 Conclusion 169 4.6 Experimental 170 4.6.1 Preparation of organometallic clusters 170 4.6.2 General procedure for pyrolysis of organometallic clusters 173 4.6.3 Preparation of ruthenium nanostructures on porous aluminum oxide 173 4.6.4 Synthesis of osmium and ruthenium NPs stabilized by TOPO 173 4.6.5 Preparation of RuCl3/SiO2 catalyst 174 4.6.6 Deposition of metallic thin films 174 4.6.7 Characterization of metallic particles and surfaces 175 4.6.8 Catalytic studies 176 References Chapter Conclusion 177 184 Appendices CD: X-ray data, IR, NMR, MS spectra, TEM images, EDX, XRD, ToF-SIMS, UV, TGA-DTA spectra vi Summary This thesis describes the employment of osmium and ruthenium carbonyl clusters as precursors for the preparation of metallic nanoparticles Towards this endeavor, we have synthesized clusters containing a free functional group and examined the following aspects: (i) The influence of the nature of the precursor, ligand set, pyrolysis temperature, and/or surfactant on the shape and size of the nanoparticles obtained, (ii) the interaction of these clusters with silica, In2O3, ZnO, silver and gold surfaces, and (iii) molecular models for these interactions The current knowledge on the above, especially with regard to the use of organometallic clusters as precursors, is surveyed in chapter In chapter 2, we discuss the preparation of clusters containing a free functional group linked to the cluster via a linker group, from the reaction of Os3(CO)10(μ-H)(μ-OH) or Os3(CO)10(NCCH3)2 with the bifunctional ligands HL͡ L’H, and the reaction of Ru3(CO)12 with mercaptocarboxylic acids In the case of the reaction of osmium clusters, the major products were those with the general formula Os3(CO)10(μ-H)(μ-L͡ L’H) When the ligand contains an aromatic ring or a long methylene chain spacer, the formation of clusters containing two triosmium moieties linked by the ligand, viz., [Os3(CO)10(μ-H)]2(μ-L͡ L’), increased In the case of ruthenium clusters, only the products Ru3(CO)10(μ-H)(μ-L͡ COOH) were obtained vii The interaction of these osmium clusters with oxide surfaces, including silica, ZnO and In2O3, was investigated and was found to depend on the ligands on the cluster and the nature of the surface With the clusters Os3(CO)10(μ-H)(μ-OH) and Os3(CO)10(μ-H)2, the interaction with the surface was via an oxygen, Zn or In atom, respectively When the cluster contains a ligand carrying a free –SH or –COOH group, the interaction was via a –S- or –COO- linkage In the case of a free –OH group, interaction was via a –O- linkage with ZnO or SiO2, while interaction of In2O3 was directly with the osmium core Molecular models of the deposition of osmium clusters on the silica surface via a functionalized ligand have also been synthesized from the reaction of Os3(CO)10(μ-H)(μ-OH) or Os3(CO)10(NCCH3)2 with -SH, -OH and -PPh2 derivatized silsesquioxanes These silsesquioxanes were bonded with osmium clusters via –S-, -Oor -PPh2 linkages In chapter 3, we discuss the interaction of osmium clusters with silver/gold NPs and substrates, to examine the possibility of employing cluster-NP entities as models for the study of cluster-surface interactions The mode of interaction of the clusters with the surface was found to depend on the nature of the linking group present For Os3(CO)10(μ-H)(μ-OH) and Os3(CO)10(μ-H)2, the interaction was via a μ-Ag/Au mode, i.e direct interaction with the osmium core For clusters linked to a free –SH and -OH group, the interaction was via the –S- or –O- linkage The situation for a free –COOH group was more complex; with Ag NPs, the interaction was via the osmium core and –COO- linkage while on the Ag substrates, the interaction was via the viii –COO- linkage for Os3(CO)10(μ-H)(μ-SRCOOH) (R = C6H4, C10H20), or the osmium core for Os3(CO)10(μ-H)[μ-S(CH)2COOH] In the case of a cluster containing a crown ether moiety, the interaction with Ag NPs was via the osmium core In chapter 4, we discuss the fabrication of NPs and thin films derived from organometallic complex precursors and the catalytic application of NPs in CO oxidation Silica or alumina supported osmium and ruthenium complexes Os3(CO)12, Os4(CO)12(μ-H)4, Os6(CO)18, Os2(CO)6(μ-I)2, [Os(CO)2I2]n, Os3(CO)11(PPh3), Os3(CO)11(SbPh3), Os3(CO)10(AsPh3)2, Os3(CO)10(SbPh3)2, RuOs3(CO)11(μ-H)2(PPh3), RuOs3(CO)13(μ-H)2 or [Ru(CO)4]n were pyrolyzed under vacuum to afford metallic NPs The shape of NPs obtained was found to be influenced by the molecular structure of precursor (especially the metal-metal bonds in the compound), the nature of the support, and the pyrolysis temperature The size of the osmium cluster core and the presence of certain ligands affected the size of the osmium NPs obtained The crystal shape of the precursor did not exhibit the same influence The organometallic complexes were also decomposed to metallic NPs in the presence of TOPO, and the shape and size of these NPs were determined by the surfactant rather than the nature of the precursor The osmium and ruthenium NPs so obtained were examined for their catalytic activity in CO oxidation, and it was found that ruthenium catalysts prepared from organometallic precursors exhibited better catalytic activity than that prepared from RuCl3 Ruthenium showed better catalytic activity than osmium, and the addition of ix osmium to ruthenium decreased the activity It was also found that the catalysts supported on TiO2 exhibited a higher catalytic activity than SiO2 Thin films of Os-Ru binary alloy were fabricated from RuOs3(CO)13(μ-H)2 and the ratio of osmium to ruthenium was found to vary with the deposition temperature At higher temperatures, the deposited surface was smoother and flatter Osmium thin films were also obtained with [Os3(CO)10(μ-H)][μ-S(CH2)3Si8O12(i-butyl)7], Os2(CO)6I2 and Os3(CO)12Br2 as precursors, at deposition temperatures of 400 oC and 500 oC The osmium thin films formed have a preferred (002) orientation, with the exception of that from [Os3(CO)10(μ-H)][μ-S(CH2)3Si8O12(i-butyl)7 at 500 oC, and the morphology was also found to be affected by the deposition temperature and the identity of the precursor x TLC: thin-layer chromatography NPs: nanoparticles DOE: dioctyl ether TOPO: trioctyl phosphine oxide Os: osmium Ru: ruthenium Ag: silver Au: Gold PVP: polyvinylpyrrolidone DCM: dichloromethane Cy: C6H11 coe: C8H14 Infrared (IR) Spectroscopy vCO stretching frequency in the carbonyl region (1700 – 2200 cm-1) vCH2 stretching frequency of the methylene group vC=O stretching frequency of the organic carbonyl vw very weak w weak m medium ms medium strong s strong xxii vs very strong sh shoulder br broad Nuclear Magnetic Resonance (NMR) Spectroscopy δ chemical shift s singlet d doublet dd doublet of doublet t triplet q quartet m multiplet xxiii List of Tables No Table caption 2.1 Supported osmium clusters with well-defined structures on functionlized silica surface 2.2 Page 28 Selected bond lengths (Å) and bond angles (o) for 5a, 5b, 9a, 13a, 14a and 15a 33 2.3 vCO data for supported osmium clusters 41 2.4 Reactions of with bifunctionalized ligands 57 2.5 Reactions of with bifunctionalized ligands 58 2.6 Reactions of with bifunctionalized ligands 58 2.7 Characterization data of osmium clusters 59 2.8 Characterization data of osmium clusters 61 2.9 Characterization data of ruthenium clusters 62 2.10 Crystal data for 5a, 5b, and 9a 63 2.11 Crystal data for 13a, 14b, 15a and 15b 64 2.12 Solid state IR data for 5a, 7a, 13a and 23a, and the corresponding resultant adlayer of the same compound on ZnO or In2O3 3.1 Solid-state IR spectral data for cluster-modified Ag NPs and the corresponding cluster precursors 3.2 67 95 Quantity of osmium clusters used and the yield of 33 from different starting materials 117 xxiv 4.1 Textural properties and TEM data of catalysts 154 4.2 XPS data for the supported catalysts 157 4.3 Characterization data of compounds 171 xxv List of Figures No Figure caption 1.1 Page Structural model of Os5C clusters supported on partially dehydroxylated MgO at a defect site determined on the basis of EXAFS spectra and DFT calculations (Adapted from reference 9) 1.2 Anchoring of cobalt clusters on mesoporous silica matrix 1.3 SEM image showing the hollow cores of the RuO2 nanotubes (Adapted from reference 14) 1.4 Co NPs protected by TOPO 1.5 Capped Ni NPs 1.6 Au NPs capped by ruthenium dicarbonyl carboxylate oligomers (Adapted form reference 32) 11 1.7 Adsorption of [Fe3(CO)9(μ3-Se)]- on gold surface 14 1.8 Adsorption of osmium cluster on ITO 14 1.9 Proposed surface osmium species and molecular structure of the analogue 1.10 Ruthenium or osmium cluster substituted silsesquioxanes 15 18 1.11 Representation of surface silanol and siloxane groups in SiO2 (top) and in the corresponding molecular analogues, polyhedral oligosilsesquioxanes (bottom) R represents ligands, such as cyclopentyl, t-Bu, Ph 2.1 19 Solution IR spectrum of 17a in the carbonyl region 31 xxvi 2.2 ORTEP diagram for 5a; thermal ellipsoids were drawn at the 50% probability level and aromatic hydrides have been omitted 2.3 34 ORTEP diagram for 5b; thermal ellipsoids were drawn at the 50% probability level 2.4 34 ORTEP diagram for 15b, with thermal ellipsoids drawn at the 50% probability level Selected bond lengths (Å) and bond angles (o) for 15: Os(1)-Os(2) 2.8708(7), Os(2)-Os(3) 2.8746(8), Os(3)-Os(1) 2.8450(7), Os(4)-Os(5) 2.9244(10), Os(5)-Os(6) 2.8659(7), Os(6)-Os(4) 2.8758(8), Os(1)-S(1) 2.418(3), Os(2)-S(1) 2.426(3), Os(4)-O(71) 2.131(7), Os(5)-O(72) 2.150(7), S(1)-C(1) 1.807(10), Os(1)-S(1)-Os(2) 72.69(8) 2.5 35 ORTEP diagram and selected bond lengths (Å) and angles (o) for (thermal ellipsoids were drawn at the 50% probability level): Os(1)-Os(2) 2.8067(10), Os(2)-Os(3) 2.8318(10), Os(3)-Os(1) 2.8083(10), Os(4)-Os(5) 2.8464(9), Os(5)-Os(6) 2.8413(9), Os(6)-Os(4) 2.8503(10), Os(1)-S(1) 2.426(5), Os(2)-S(1) Os(5)-S(2) 2.417(2), S(1)-C(1) 2.453(4), Os(4)-S(2) 2.413(4), 1.733(17), S(2)-C(2) 1.791(17), Os(1)-S(1)-Os(2) 70.23(12), Os(4)-S(2)-Os(5) 72.11(11) 2.6 ToF-SIMS spectra (positive ion mode) of (a) Os3(μ-H)(CO)10(μ-OSi≡), (b) silicon wafer modified by 22 2.7 36 38 ToF-SIMS spectra of a silicon wafer soaked in a dichloromethane solution of 20a in the mass range of (a) 600-900 (negative ion mode), (b) 40-80 (positive ion mode) 39 xxvii 2.8 IR spectrum for 12a functionalized silica gel in the carbonyl region 2.9 ToF-SIMS spectra (negative ion mode) of silicon wafer soaked in a dichloromethane solution of (a) 12a, (b) 18a and (c) 5a 2.10 ToF-SIMS spectrum (positive ion mode) of anchored onto ZnO 41 42 44 2.11 Solid state FTIR spectra (vCO region) for (a) 22, (b) 22 on In2O3, (c) 22 on ZnO, (d) 1, (e) on In2O3 and (f) on ZnO 46 2.12 ToF-SIMS spectra (negative ion mode) of (a) 7a anchored to ZnO, (b) 5a anchored on In2O3 and (c) 23a anchored onto ZnO 48 2.13 ToF-SIMS spectrum (negative ion mode) of 10a anchored to ZnO 49 2.14 Solid state FTIR spectra for (a) 10a, (b) 10a on ZnO, (c) 10a on In2O3 50 2.15 Schematic representation of silsesquioxanes 24, 25, 26 and 27 52 3.1 Absorption spectra of (a) 1-modified Ag NPs, (b) 22-modified Ag NPs, (c) 33-modified Ag NPs and (d-f) the corresponding precursor clusters 3.2 75 TEM images of (a) 1-modified Ag NPs (Inset: Enlarged image of elongated Ag NPs.), (b) 22-modified Ag NPs (Inset: Enlarged image of an irregularly shaped Ag NPs.), (c) 33-modified Ag NPs 76 3.3 EDX for Ag NPs protected by 77 3.4 ToF-SIMS spectra (negative ion mode) of Ag NPs modified with (a) and 22 (b) 3.5 ToF-SIMS spectrum (negative ion mode) of Ag NPs modified with 33 Inset shows the cluster of ion at m/z 192 3.6 79 80 Solid-state IR spectra of (a) 1, (b) 1-modified Ag NPs, (c) 22, (d) xxviii 22-modified Ag NPs, (e) 33, and (f) 33-modified Ag NPs 3.7 81 Absorbance spectra of 1-modified Au NPs: (a) Au NPs in ethanol, (b) in ethanol, (c-e) added to Au NPs in increments of 0.1 equivalent 82 3.8 Absorbance spectra of (a) Au NPs and (b) 22-modified Au NPs in ethanol 83 3.9 TEM images of (a) 1-modified Au NPs, (b) 22-modified Au NPs 84 3.10 EDX for 22-modified Au NPs 84 3.11 FTIR spectra for (a) 1-modified Au NPs and (b) 22-modified Au NPs 85 3.12 ToF-SIMS spectrum (negative ion mode) of 1-modified Ag substrate 86 3.13 ToF-SIMS spectrum (negative ion mode) of 22-modified Au substrate 87 3.14 IR spectra of (a) 1-modified Ag surface, (b) 22-modified Ag surface, (c) 33-modified Ag surface, (d) 1-modified Au surfaces and (e) 22-modified Au surfaces 88 3.15 ORTEP diagram and selected bond lengths (Å) and angles (o) for 34 Thermal ellipsoids are drawn at the 50% probability level and hydrogen atoms have been omitted Selected bond lengths (Å) for 34: Au(1)-P(1) 2.290(2), Au(2)-P(2) 2.287(2), Au(1)-Os(3) 2.7925(5), Au(1)-Os(4) 2.8262(5), Au(1)-Au(2) 2.9744(5), Au(2)-Os(5) 2.8048(5), Au(2)-Os(4) 2.8601(5), Au(2)-Os(3) 2.8608(5), Os(3)-S(1) 2.372(2), Os(4)-S(1) 2.379(2), Os(5)-S(1) 2.367(3), Os(3)-Os(5) 2.8898(6), Os(3)-Os(4) 3.0118(5), Os(4)-Os(5) 2.8858(5) 91 3.16 UV absorption spectra of (a) 23a, (b) 5a, (c) 7a in toluene, and (d-f) their corresponding modified Ag NPs 92 xxix 3.17 TEM images of (a) 23a-modified Ag NPs (Inset: Enlarged image of an irregular shaped Ag NPs), (b) 5a-modified Ag NPs (Inset: Image of an aggregate) and (c) 7a-modified Ag NPs 3.18 ToF-SIMS spectrum (negative ion mode) of 23a-modified Ag NPs 93 94 3.19 Scheme of the methylene groups position in the case of (a) normal alkyl chain and (b) alkyl chain having a gauche defect 95 3.20 UV absorption spectra as 23a was titrated against Au NPs in ethanol (Each time, 0.0002 mol of 23 was titrated to x 10-5 M Au NPs in 20 ml ethanol) 3.21 FTIR spectra of (a) 23a-, (b) 5a- and (c) 7a-modified Au NPs 97 98 3.22 ToF-SIMS spectra of (a) 23a-modified Ag substrate in the positive ion mode (Inset: a fragment in the negative ion mode), (b) 23a-modified Au substrate in the negative ion mode 99 3.23 TEM image of 12a-modified Ag NPs Left: spherical particles (Inset: TEM image for irregular shaped nanoparticles surrounding by one layer of amorphous materials) Right: particles with multilayer planar structures 101 3.24 UV absorption spectra (toluene) of (a) 12a, (b) 20a, (c) 12a-modified Ag NPs and (d) 20a-modified Ag NPs 102 3.25 TEM image of 20a-modified Ag NPs 103 3.26 ToF-SIMS spectrum (negative ion mode) of 12a-modified Ag substrate 104 3.27 UV absorption spectra (toluene) of (a) 14a-modified Ag NPs, (b) 15a xxx -modified Ag NPs and (c) 16a-modified Ag NPs 105 3.28 TEM images of 14a-modified Ag NPs: (a) network-like Ag structures (Inset: Enlarged image of modified Ag NPs surrounding by one layer of amorphous materials), (b) enlarged image of network-like structures, (c) rod shaped 14a-modified Ag structure 107 3.29 FTIR spectra for (a) 15a-modified Ag NPs, (b) 16a-modified Ag NPs, (c) 15a and (d) 16a 108 3.30 ToF-SIMS spectrum (negative ion mode) of 14a-modified Ag substrate Inset: proposed structure of the surface species 109 3.31 ToF-SIMS spectrum (negative ion mode) of 15a-modified Ag substrate Inset: proposed structure of the surface species 3.32 TEM and HR-TEM micrographs of dried Ag NPs capped with 36 110 113 3.33 UV–VIS spectra of silver nanoparticles capped with 36: (a) in toluene, (b) after reflux with aqueous sodium nitrate, (c) after reflux with aqueous potassium nitrate, and (d) after reflux with aqueous silver nitrate 114 3.34 Emission spectra of Ag NPs capped with 36: (a) in toluene, and (b) after reflux with aqueous silver nitrate 3.35 TEM micrographs of Ag NPs capped with 37 114 115 3.36 Absorption spectra of (a) 37, (b) 37-modified Ag NPs and (c) emission spectrum of 37-modified Ag NPs 115 4.1 Metal cluster 128 4.2 Diagrammatic representation of the metal core geometry of the clusters 130 xxxi 4.3 Thermogravimetric analysis data for clusters 3(Os), 38 and 39 130 4.4 X-ray diffraction patterns of the Os NPs from 3(Os), 38 and 39 131 4.5 TEM images of NPs from 3(Os): (a) pyrolysis at 200 oC, (b) pyrolysis at 400 oC, (c) after H2 reduction 132 4.6 TEM images of NPs obtained from (a) 40, (b) 41 and (c) 42 133 4.7 Diagrammatic representation of the metal core geometry of the clusters 40, 41 and 42 4.8 133 (a) SEM image of 42, (b) TEM images of Os NPs obtained from (inset: rod-shaped crystal precursor) 4.9 134 XRD pattern of Ru NPs (a) 170 °C; (b) 280 °C; (c) 380 °C 136 4.10 TEM image of Ru nanofibres on silica after treatment at (left) 170 °C, (middle) 280 °C and (right) 380 °C Inset show the corresponding high resolution images 4.11 SEM image of 42 on AAO before pyrolysis 137 138 4.12 (a) TEM image of Ru NPs on AAO after treatment at 170 °C (Insert: SEM image), (b) TEM image of Ru NPs after treatment at 280 °C (Insert: SEM image), (c) SEM image of Ru NPs after treatment at 380 °C 139 4.13 Diagrammatic representation of Os clusters 1, 5a and 22 140 4.14 X-ray diffraction patterns of the Os NPs from 1, 5a and 22 140 4.15 TEM images and size distribution of osmium NPs from 141 4.16 Diagrammatic representation of the geometry of Os clusters 142 4.17 TEM images NPs from 43 (left) and 46 (right) 143 xxxii 4.18 Diagrammatic representation of clusters 48 (left) and X-ray diffraction pattern of the NPs from 48 (right) 144 4.19 XPS spectrum of NPs from 48 145 4.20 TEM image of NPs from 48 145 4.21 IR spectra of the thermolysis of 39 in DOE: (a) pure 39, (b) immediately after injection of 39, (c) after min, (d) after 10 min, (e) after 30 min, (f) after 35 min, (g) after 50 147 4.22 IR spectra of the thermolysis of 49 in DOE: (a) pure 49, (b) after min, (c) after min, (d) after 12 min, (e) after 16 min, (f) after 20 148 4.23 UV-vis adsorption spectra of (a) 39, (b) osmium NPs and (c) ruthenium NPs 4.24 XRD patterns of (a) Os NPs and (b) Ru NPs 149 150 4.25 TEM images of osmium NPs from 39 at different magnifications: (a) 150 osmium aggregates, (b) HRTEM image of osmium aggregates, (c) isolated osmium NPs 4.26 TEM images of ruthenium NPs 151 4.27 TPR profiles of catalysts 156 4.28 XPS spectra of osmium of catalysts containing osmium 158 4.29 CO oxidation on supported ruthenium and osmium containing catalysts 159 4.30 EDX spectra of the Os-Ru film deposited on silica wafer at (a) 400 oC and (b) 500 oC 163 4.31 SEM images of the Os-Ru films deposited on silica wafer at (a) 400 oC xxxiii and (b) 500 oC 163 4.32 XRD patterns of the Os-Ru thin films deposited on silica wafer 165 4.33 TGA data of complexes 41, 52, 29 166 4.34 SEM images of the Os films deposited on silicon wafer (a) Os3Br2-400, (b) Os3Br2-500, (c) Os3Si-400, (d) Os3Si-500, (e) Os2I2-400 and (f)Os2I2-500 168 4.35 XRD patterns of the Os thin films deposited on silica wafer 169 4.36 Diagram of chemical vapor deposition apparatus 175 5.1 Bonding types of or 22 on silica, ZnO or In2O3 surfaces 184 5.2 Major bonding types of or 22 on Ag/Au NPs or substrates 185 xxxiv List of Schemes No Page 1.1 ………………………………………………………………………… 1.2 ………………………………………………………………………… 10 1.3 ………………………………………………………………………… 13 2.1 ………………………………………………………………………… 30 2.2 ………………………………………………………………………… 30 2.3 ………………………………………………………………………… 32 2.4 ………………………………………………………………………… 43 2.5 ………………………………………………………………………… 50 2.6 ………………………………………………………………………… 51 2.7 ………………………………………………………………………… 52 2.8 ………………………………………………………………………… 53 2.9 ………………………………………………………………………… 54 3.1 ………………………………………………………………………… 87 3.2 ………………………………………………………………………… 88 3.3 ………………………………………………………………………… 100 3.4 ………………………………………………………………………… 104 3.5 ………………………………………………………………………… 107 3.6 ………………………………………………………………………… 112 3.7 ………………………………………………………………………… 112 xxxv 3.8 ………………………………………………………………………… 116 4.1 ………………………………………………………………………… 138 4.2 ………………………………………………………………………… 151 xxxvi ... 34 12 2 Reference 12 3 Chapter Organometallic clusters as precursors for metallic nanoparticles and thin films 4 .1 The pyrolysis of organometallic clusters to nanoparticles 12 8 12 9 4 .1. 1 Effect of. .. Synthesis of osmium clusters 11 6 3.4 .1. 1 General procedure 11 6 3.4 .1. 2 Synthesis of Os3Au2(CO)9(µ3-S)(PPh3)2, 34 11 7 3.4 .1. 3 Synthesis of Os3 (CO )10 (μ-H)[(6-mercaptohexyloxy)methyl -15 crown-5], 37 11 8... Decomposition of organometallic complexes in a hot solution 1. 1.3 Surface modification 1. 2 Self-assembly of organometallic clusters on the surface 11 1. 2 .1 Synthesis 12 1. 2.2 Characterization techniques 14