國
立
交
通
大
學
應用化學所
博
博
博
博
士
士
士
士
論
論
論
論
文
文
文
文
多面體聚矽氧烷為建構單元的嵌段式共聚物
奈米複合材料及金屬晶粒複合奈米粒子
Diblock Copolymer anocomposites and Metal
anocrystal Hybrid anoparticles Incorporating
Polyhedral Oligomeric Silsesquioxane Building Blocks
研究生：呂居樺
指導教授：張豐志 教授
多面體聚矽氧烷為建構單元的嵌段式共聚物
奈米複合材料及金屬晶粒複合奈米粒子
Diblock Copolymer Nanocomposites and Metal Nanocrystal Hybrid Nanoparticles Incorporating Polyhedral Oligomeric Silsesquioxane Building Blocks
研 究 生：呂居樺 Student：Chu-Hua Lu
指導教授：張豐志 Advisor：Feng-Chih Chang
國 立 交 通 大 學
應 用 化 學 所
博 士 論 文
A DissertationSubmitted to Department of Applied of Chemistry College of Science
National Chiao Tung University in Partial Fulfillment of the Requirements
for the Degree of Doctor of Philosophy
in
Applied Chemistry
February 2009
Hsinchu, Taiwan, Republic of China
誌謝
學生在中興大學學習，很早就發現對化學有很高的興趣，雖然是主修化學 工程，課餘去修許多化學系的主修課程，博聞強記之下，對化學基本學問有充份 的了解；大學專題也和化學相關的教授學習，在何榮銘老師實驗室，讓學生了解 高分子材料，在鄭文桐老師實驗室，學習高分子在光阻劑的應用，幾年來對高分 子有基本的了解，特別在大四較空閒的那一年，和戴憲弘老師學習學生最感興趣 的高分子化學-異氰酸塩；學生能累積在高分子這方面的知識，十分感謝，中興 化工系的培養，尤其三位老師對學生的教育。 碩士學程，有機會進入交通大學應用化學系，跟張豐志老師更深入研究高 分子科學，這幾年來，學生很佩服張老師帶實驗室的遠見，讓郭紹偉及黃智峯學 長帶領實驗室，博士班學生自由發揮，張老師為學生找計劃，支持學生們的學術 研究及論文發表；因此，學生在進實驗室不久就有想攻讀博士班，碩士班一年後 如期直升博士班，想法很單純，只要我肯用時間、用心做，研究成果及論文發表 不難取得，過兩年後庸庸碌碌，表現平凡，實驗做得多，沒能有效的整理發表， 面臨四年博士班畢業期限將致的壓力，否定自己做研究的能力，甚致懷疑自己自 身難保，怎還有閒時去幫助其它同學和學弟妹在學業研究和管理實驗室，長達半 年時間，認真思考自己博士論文，實實在在去完成預定的目標-四篇研究論文； 張老師給時間讓學生自己調適，針對這一點讓學生感激萬分，此事讓學生了解做 研究，不僅只是在”做”而”寫”和”發表”同樣重要，欠一就顯得不足；雖然， 學生很早就發現自己對做研究有天份，但對語言的天份就差多了，張老師沒多說 什麼，多次幫學生修改論文，後來了解”參考”文獻對論文寫作的重要，論文寫 作就順利多了，張老師對學生的不離不棄，學生感激在心；今年順利畢業，學生 會決定留下來做博士後研究的最主要原因想回報老師的幫忙，其次完成幾篇尚未 完成的研究論文；此外，學生很感謝工研院沈永清及蘇一哲學長提供學生長達四 年的工讀，讓學生得以順利取得博士學位。四年半來，除了張老師，學生還要感謝我的直屬學長-黃智峯學長和郭紹偉 學長，雖然有時候會被學長凹，但兩位學長對我還是不錯，給我很多幫忙和指導， 尤其黃智峯學長常常聽我發牢騷，學長去了美國做博士後進修才發現學長人不 錯，沒有學長在實驗室還真得有點不習慣；郭紹偉學長人也不錯，和黃智峯學長 不同，郭學長讓我看到做研究的積極，這點是學生要跟郭學長學習的；同樣很感 謝實驗室學長姐、同學和學弟妹的幫忙；學生家境並不富裕，只算小康，家裡無 條件支持，讓學生能無憂無慮，專心研讀博士班，感謝多年來家裡媽媽、姐姐和 弟弟的支持；尤其姐姐，在多年前爸爸過世後，日夜兼差負責家計，讓學生在無 憂無慮的環境中成長順利完成學業，在此並祝幫助與關心學生的人能永遠平安快 樂。 居樺(didi) 2009年2月
Outline of Contents
PagesOutline of Contents I
List of Tables VI
List of Schemes VII
List of Figures VIII
Abstract (in Chinese) XXI
Abstract (in English) XXV
Chapter 1 Introduction
1-1 Nanomaterials 1
1-2 Nanocrystals 2
1-2.1 Metal Nanocrystals 3
1-2.2 Ionic Nanocrystals 31
1-2.2.1 Metal Oxide Nanocrystals 31
1-2.2.2 Semiconductor Nanocrystals 39
1-3 Nanoparticles 46
1-3.1 Inorganic Nanoparticles 46
1-3.2 Organic Nanoparticles 57
1-3.3 Inorganic/Organic Hybrid Nanoparticles 74
1-4 Block Copolymers 79
1-4.1 Character of Diblock Copolymers 79
1-4.2 Synthesis of Diblock Copolymers 82
Chapter 2 Synthesis and Characterization of Poly(ε-caprolactone-b-4-vinyl pyridine): Initiation, Polymerization, Solution Morphology, and Gold Metalation
Abstract 96
2-1 Introduction 97
2-2 Experiential Section 103
2-2.1 Materials 103
2-2.2 Measurement 104
2-2.3 UV–Vis Calibration of TEMPO Concentration 105
2-2.4 Syntheses of -Alkoxyamines 107
2-2.5 Synthesis of Hydroxyl--alkoxyamines 108 2-2.6 Synthesis of -Alkoxyamine Functionalized Poly(ε-caprolactone) 109 2-2.7 Synthesis of Poly(ε-caprolactone)-block-poly(4-vinylpyridine)
Copolymers
110
2-2.8 Preparation of Micelle Solutions 110
2-2.9 Synthesis of PCL-b-P4VP Copolymer-Mediated Au NPs 110
2-3 Results and Discussion 111
2-3.1 -Alkoxyamines 111
2-3.2 Nitroxide-Induced Alcohol Oxidation 113
2-3.3 Temperature Effect 115 2-3.4 PCL Macroinitiators 117 2-3.5 PCL-b-P4VP Copolymer 120 2-3.6 PCL-b-P4VP Copolymer-Protected Au NPs 126 2-4 Conclusions 130 2-5 References 131
Chapter 3 Syntheses and Characterizations of Star Polymers and Star Block Copolymers from Polyhedral Oligomeric Silesesquioxane Core through
+itroxide-mediated Radical Polymerization
Abstract 135
3-1 Introduction 136
3-2 Experimental Session 138
3-2.1 Materials 138
3-2.3 Synthesis of octa--alkoxyamine-functionalized POSS initiator (OT-POSS) 140 3-2.2 Synthesis of 1-(2-(allyloxy)-1-phenylethoxy)-2,2,6,6-tetramethylpiperidine (allyl-TEMPO) 141
3-2.4 Synthesis of eight-arm star polystyrene from a POSS core [POSS-(PS)8]
142
3-2.5 Synthesis of eight-arm stra-block
polystyrene-block-poly(4-vinylpyridine) and polystyrene-block-poly(4-acetoxystyrene) from a POSS core [POSS-(PS-b-P4VP)8 and POSS-(PS-b-PAS)8]
142
3-2.6 Hydrolysis of POSS-(PS)8 using HF 142
3-2.7 Hydrazinolysis of POSS-(PS-b-PAS)8 to give POSS-(PS-b-PVPh)8 142
3-3 Results and Discussion 143
3-3.1 Octa--alkoxyamine functionalized POSS (OT-POSS) 143 3-3.2 Synthesis of eight-arm star polystyrene from a POSS core
[POSS-(PS)8]
3-3.3 Synthesis of eight-arm stra-block polystyrene-block-poly(4-vinylpyridine) and polystyrene-block-poly(4-acetoxystyrene) from a POSS core [POSS-(PS-b-P4VP)8 and POSS-(PS-b-PAS)8]
147
3-3.4 Hydrolysis of POSS-(PS)8 and Hydrazinolysis of POSS-(PS-b-PAS)8 149
3-4 Conclusions 151
3-5 References 151
Chapter 4 Self-Assembled Fernlike Microstructures of POSS/Gold +anoparticle Hybrids Abstract 153 4-1 Introduction 154 4-2 Experimental Section 156 4-2.1 Materials 156 4-2.2 Preparation of Au NPs 156 4-2.3 Analytical Procedures 157 4-2.4 Measurements 157
4-3 Results and Discussion 158
4-3.1 POSS Crystals on Au NPs 158
4-3.2 Character of POSS–Au Hybrids 161
4-3.3 TEM and AFM Analyses of POSS–Au Micro- and Nanostructures 167 4-3.4 Thermal Sintering of POSS–Au Micro- and Nanostructures 171 4-3.5 Mechanism of Formation of POSS–Au Hybrids 174
4-4 Conclusions 174
Chapter 5 Supramolecular Catalysts by Encapsulating Palladium +anocrystals within POSS Colloids Abstract 179 5-1 Introduction 180 5-2 Experimental Section 182 5-2.1 Materials 182 5-2.2 Syntheses of POSS-Pd or C12-Pd 182
5-2.3 Conditions of Heck coupling 182
5-2.4 Measurements 182
5-3 Results and Discussion 183
5-3.1 Synthesis of POSS-Pd and C12-Pd 183
5-3.2 Character of POSS-Pd and C12-Pd 185
5-3.3 Heck coupling using POSS-Pd and C12-Pd 186
5-4 Conclusions 189
5-5 References 189
Chapter 6 Conclusions and Future Outlook 192
List of Publications 196
List of Tables
Pages Table 1-1. Representative reactions catalyzed by polymer-supported Au NPs 10 Table 1-2. Product yields for Suzuki couplings catalyzed by dendrimer-Pd NCs(1.5 mol% of metal) in 40% EtOH under reflux for 24 h
21
Table 1-3. Comparison of the catalytic activities of various supported Pd catalysts in the Heck reaction of iodobenzene with methyl acrylate
22
Table 1-4. Solution compositions for selected Pt NCs 28 Table 2-1. Oxidation Conversion of Alcohols to Ketones or Aldehydes,
Determined From Integral Area Ratio of Their Characteristic Peaks in 1H NMR Spectra
116
Table 2-2. Compositions, molecular mass distributions, and thermal properties of PCL-macroinitiator PCL and PCL-b-P4VP diblock copolymers BC1–3 and Au-BC1-3
122
Table 4-1. Crystal parameters of SH-POSS powders 159 Table 4-2. Compositions and element analysis results of thiol-protected gold
nanoparticles
List of Schemes
Pages Scheme 2-1. Synthetic route toward NMRP through BPO-TEMPO bimolecularinitiation: (a) -alkoxyamine initiator formation; (b) styrene monomer insertion
101
Scheme 2-2. Low-temperature reaction mechanism: (a) redox-induced decomposition of BPO; (b) radical addition; (c) alcohol oxidation; (d) ring-opening rearrangement
115
Scheme 2-3. Synthetic route toward PCL-b-P4VP block copolymer-mediate Au NPs: (a) redox-induced decomposition of BPO; (b) radical addition and alcohol oxidation; (c) synthesis of PCL-b-P4VP; (d) incorporation of Au NPs
119
Scheme 2-4. Diethyl aluminum alkoxide-induced ROP of ε-CL in the presence of AlEt3
119
Scheme 3-1. (a) synthesis of OT-POSS initiator (b) synthesis of (PS)8-POSS,
(PS-b-P4VP)8-POSS, and (PS-b-PVPh)8-POSS (c) synthesis of linear
PS.
137
Scheme 3-2. (a) low-temperature reaction between BPO and TEMPO; (b) synthesis of the Ester-TEMPO and HO-TEMPO
140
List of Figures
Pages Figure 1-1. Dendritic distribution of Nanomaterials 2 Figure 1-2. Preparation of Au NCs through chemical reduction with NaBH4 at 25°C and solvothermal reduction with citric acid at 100 °C. The 1.35-nm-diameter Au NCs result from the aggregation of 83 Au atoms (diameter: 0.27 nm)
7
Figure 1-3. TEM images and DLS analyses of Au and Ag NC samples. (A) 21-nm-diameter Au NCs from toluene, (B) 9-nm-diameter Ag NCs from toluene, (C) 12-nm-diameter Ag NP nanocrystals from hexane, and (D) 32-nm-diameter Ag NCs from 1,2-dichlorobenzene. Scale bars: 100 nm
8
Figure 1-4. HRTEM images of 1-dodecanthiol-protected Au NCs. The thickness (0.24 nm) indicates the layer-to-layer distance of FCC Au NCs
8
Figure 1-5. (a) Optical extinction spectra of Ag NCs (yellow), solid Au NCs (red), and hollow Au nanoshells (blue). The optical densities of the three differently colored samples have been matched to 1.8. (b) Photograph of aqueous dispersions of metal NP colloids, the SPR bands of which were tuned in terms of wavelength and intensity multiplexing
9
Figure 1-6. Evolution of the dispersion F as a function of n for cubic clusters up to n = 100 ( = 106). The structures of the first four clusters are displayed
9
Figure 1-7. Cartoon representations of four polymer-stabilized Au NCs: (a) grafted with water-soluble polymers, (b) loaded in the pores of a functionalized resin, (c) covered with polymer particles, and (d)
deposited on a polymer surface
Figure 1-8. TEM images of a 2D superlattice containing 4.18-nm-diameter Ag NCs, (left insert) a histogram of the Au NCs, and (right insert) a 2D Fourier power spectrum of the TEM images
14
Figure 1-9. Evolution of the mean particle size (circle) and 410-nm-absorbance peak (square) during the formation of 21-nm-diameter monodisperse Ag colloids (400 mg AgNO3; 10 g PVP; 75 mL EG;
1 °C/min from 25 to 120 °C, followed by isotherm)
14
Figure 1-10. TEM images of a colloidal Ag dispersions: (a) t = 0.25 h and T = 40 °C, (b) t = 0.75 h and T = 70 °C, (c) t = 1.00 h and T = 85 °C, and (d) t = 2.60 h and T = 120 °C
15
Figure 1-11. Schematic representation of the DPN procedure used to pattern a Ag NC ink on a glass substrate. This procedure is common to other substrates
15
Figure 1-12. 2D AFM images and cross-sectional analysis of linewidths: (a) 10 µm, (b) 5 µm, (c) 2 µm, and (d) 760 nm
16
FiFigure 1-13. Single-phase preparation of Ag NCs and analytical results: (a) TEM image of Ag NCs having diameters of ca. 10 nm; (b) SEM image of Ag films after treatment at 140 °C for 30 s; (c) drain current (ID)
versus source-drain voltage (VD) plotted as a function of the gate
voltage (VG) for a thin film transistor (TFT) with printed
source/drain electrodes (channel length: 90 µm; channel width: 2250 µm); (d) ID and (–ID)1/2 plotted versus VG at a constant value
of VD (–40 V), used for calculation of the mobility and current
on/off ratio
Figure 1-14. (a) SPR absorption of untreated and oxidized Ag NCs, (b) BSA-mediated shift of the SPR absorption, and (c) bacterial activity of untreated Ag NCs, oxidized Ag NCs, BSA-treated oxidized Ag NCs, and BSA
17
Figure 1-15. Photographs and statistical analyses of (a) S. aureus and (b) S. epidemidis on various substrates: Ti, HA, and Ag-HA
17
Figure 1-16. Cytotoxicity tests with human embryonic palatal mesenchyme (HEPM) cells on various surfaces after incubation for 24 h
18
Figure 1-17. (a) Mechanism of thermal decomposition of metal complexes into Pd NCs and (b) TEM image of 5-nm-diameter monodisperse Pd NPs. Inset: HRTEM image of a single NC
20
Figure 1-18. (a) Reaction scheme of the first published Suzuki coupling, the Pd-catalyzed cross-coupling between organoboronic acids and halides. (b) Reaction mechanism of the Pd NC-catalyzed Suzuki coupling of a NaOH-activated boronic acid
21
Figure 1-19. (a) Reaction scheme of Heck coupling, the Pd-catalyzed
cross-coupling between acrylates and halides. (b) Reaction mechanism of the Pd NC-catalyzed Heck coupling with based-activation
22
Figure 1-20. (A) Absorption and desorption of H2 on Pd NCs. (B) XRD lattice
constant of Pd NCs during absorption (filled) and desorption (opened) at 373 K (triangle) and 303 K (circle). (C) Solid state 2H NMR spectra of (a) 2H2 gas and (b, c) a sample of Pd NPs (b) under
86.7 kPa of 2H2 gas and (c) after evacuating the 2H2 gas at 303 K
Figure 1-21. (a) Time-dependent UV–Vis spectra of a mixture of 3 mM PtCl42–
and 0.05 mM G4-OH. (b) UV–Vis spectra of G4-OH(Pt12),
G4-OH(Pt40), and G4-OH(Pt60). (c) HRTEM image of
G4-OH(Pt60). (d) XPS spectra of G4-OH(Pt2+60) and G4-OH(Pt60)
28
Figure 1-22. (a) TEM image and (b) histogram analysis of Pt 98 NCs 29 Figure 1-23. (a) Compositions and sizes of catalysts I–IV. (b) XPS and (c) CV
spectra of Catalyst II
29
Figure 1-24. Schematic illustrations of the synthesis of Pt/CNTs nanocomposites 30 Figure 1-25. (a) TEM image of a Pt/CNT composite (24.0 wt%) after thermal
treatment at 400 °C for 1 h. (b) EDS spectrum and (c) HRTEM image of the Pt/CNT composite in (a)
30
Figure 1-26. Schematic representation of the working principle of a fuel cell 31 Figure 1-27. (a) Thermal decomposition of Fe cupferron into γ-Fe2O3 NCs. (b)
TEM image of a monolayer of individual γ-Fe2O3 NCs (10.0 ± 1.5
nm) covering an area larger than 2 µm2. Top left: HRTEM image of one of the NCs in this sample. The indicated lattice plane distances correspond to the (113) and (201) lattice planes of tetragonal γ-Fe2O3 with an ordered superlattice of the cation vacancies. Top
right: FFT of the HRTEM image looking down the [512h] zone-axis.
34
Figure 1-28. (a) Reaction scheme for the sonochemical reaction leading to Fe2O3
NCs. (b) XRD spectra of the as-synthesized Fe2O3 NCs. (c, d)
Typical sensing curves for n-butane at concentrations ranging from 250 to 1000 ppm
35
XRD spectrum, and (d) HRTEM images and Fourier transform of ZnO NCs
Figure 1-30. (a) Materials for a dye-sensitive solar cell. (b, c) UV–Vis spectra of (b) ZnO NCs and (c) ZnO/MDMO-PPV membranes. (d) PL spectrum of ZnO/MDMO-PPV membranes
37
Figure 1-31. (a) Reaction scheme for the preparation of TiO networks. (b) XRD patterns, (c) TEM images, and (d) HRTEM images and FTIR spectra of anatase TiO2 NCs having a diameter of 7.3 nm.
39
Figure 1-32. Reaction mechanism of TiO2-indcued photocatalysts 39 Figure 1-33. (a) Reaction scheme, (b) UV-vis spectra, and (c) XRD analyses of
CdS, CdSe, and CdTe NCs
44
Figure 1-34. (a) Reaction scheme for the preparation of CdSe NCs. (b) PL spectra and photographs taken during the crystal growth for CdSe NCs. (c) TEM images, DLS analysis, and XRD spectrum of 7.5-nm-diameter CdSe NCs.
45
Figure 1-35. CdSe QDs (diameters: 5–10 nm) as markers for GlyR localization in neurons. (A) QD-GlyRs (red) detected over the somatodendritic compartment identified by microtubule-associated protein-2. (B, C) Relationship between the locations of QD-GlyRs (red) and inhibitory synaptic boutons labeled for a vesicular inhibitory amino acid transporter.
45
Figure 1-36. (a) Comparison of the shapes of C60 and a soccer ball. (b) Closed
packing of hard spheres, including HCP and FCC. (c) Hexagonal needle featuring the HCP of C60 molecules.
49
attack. (b) Cyclopropane bridge formed from the reaction of C60
with a diazoalkanes. (c) Pyrrolidine bridge formed from the reaction of C60 with -methylglycine.
Figure 1-38. (a) Chemical structure of a CdSe-nC60 nanocomposite. (b) UV–Vis
spectra, (c) PL spectra, and (d) the photocurrent response of electrodes to the ON-OFF cycles of illumination of C60, CdSe, and
CdSe-nC60. (e) Photocurrent generation at CdSe-nC60 composite
clusters.
51
Figure 1-39. (a) Chemical structure of Montmorillonite clay. (b) synthesis of hectorite clay-PMEA. (c) Photograph of a transparent film containing 23 wt% clay. (d) TEM images of 11 wt% clay/PMEA nanocomposites.
53
Figure 1-40. (a) Sol–gel preparation of SiO2 inorganic NPs. (b) relationship
between UV absorbance (wavelength) and complementary color and (c) formation of SiO2 photonic crystals. (d) UV absorbance and
optical color and (e) SEM images of SiO2 photonic crystals.
57
Figure 1-41. (a) Chemical structures and properties of α-, β-, and γ-CD. (b) Top and side views of α-CD, highlighting the strong intramolecular hydrogen bond between C2-OH and C3-OH. (c) Common synthetic
paths to amphiphilic β-CD.
61
Figure 1-42. (a) Supramolecular complex formed from photosensitive β-CD and RhB and their photoreversible fluorescence modulation. (b) PL spectra (λex = 546 nm) of complex under (I) visible light for 10 min
and (II) UV light (λ = 365 nm) for 5 min, and the recycling test.
62
cone-shaped dendron.
Figure 1-44. (a) Schematic representation of the preparation of dendrimer-derived supported Pt NCs catalysts. (b) Performance of CO oxidation catalysts after oxidation at 300 °C (20% O2/He, 4 h)
and reduction at 300 °C (20% H2/He, 2 h).
65
Figure 1-45. Various self-assembled morphologies depending on the critical packing parameter (p) of the amphiphilic small molecule: (a) spherical micelles (p < 0.33), (b) cylindrical micelles (0.33 < p < 0.5), (c) spherical vesicles (0.5 < p < 1), (d) planar bilayers (p = ca. 1), and (e) reversed micelles (p > 1).
68
Figure 1-46. (a) SEM images of an alumina oxide (AAO) membrane (white height). (b) TEM images of porous SiO2 in the AAO membrane
(white cave), (c) Mass transport of bovine serum albumin, rhodamine B, vitamin B12, and myoglobin through the AAO and porous SiO2/AOO composite membranes.
69
Figure 1-47. (a) Polymerization of a homopolymer PA and a block copolymer PA-b-PB. (b, c) Self-assembly of the block copolymer (b) in solution and (c) in the condensed phase.
72
Figure 1-48. Multiple morphologies of the crew-cut aggregates formed in water from PSn-b-PAAm block copolymers (n > m) featuring PAA block
lengths (m) of (a) 21, (b) 15, (c) 8, and (d) 4.
72
Figure 1-49. (a) Chemical structure and aggregate model of HMDI-linked PLLA-b-PEO. (b) Reversible sol–gel transitions at temperatures higher and lower than 45 °C. (c) Results of a drug delivery test using an FITC-labeled dextran.
Figure 1-50. Preparation and chemical structures of silsesquioxanes (RSiO1.5)n:
(a) random networks, (b) ladder chains, and (c) the cage NPs T8 (n = 8), T10 (n = 10), T12 (n = 12), and T7 (n = 7).
76
Figure 1-51. (a) Preparation of 3-mercaptopropyl cyclopentyl-POSS via hydrosilylation and sol–gel reactions. (b) Crystallization of POSS colloids during the removal of solvent. (c) XRD spectrum of norbornyl cyclopentyl-POSS.
77
Figure 1-52. Preparation of a crosslinked POSS-based polyimide: (a) sol–gel reaction, (b) nitration with HNO3, (c) reduction with HCO2H, and
(d) imidization with dicarboxylic anhydride.
77
Figure 1-53. (a) Preparation, (b) MALDI-TOF mass spectra, and (c) DSC thermograms of OS-POSS, OA-POSS, and OP-POSS.
78
Figure 1-54. (a) Preparation of PEO-b-PCL-TE micelles for the incorporation of Au NCs and (b) TEM images of Au NCs-incorporated PEO-b-PCL-TE micelles.
79
Figure 1-55. (a) Deformation of polymer chains and (b) depictions and descriptions of the miscible and immiscible modes of small molecules and macromolecules, respectively.
81
Figure 1-56. elf-assembling morphologies of block copolymers (a) in solution (spherical micelles, cylindrical micelles, and bilayer vesicles) and (b) in condensed phases [spherical separation (FCC and BCC), hexagonal cylinder arrays (Hex), bicontinuous gyroid phases (F and P surface), and lamellar alternate bilayers (normal, modulated, and perforated)].
82
(a) the condensation polymerization of polyimide and (b) the radical polymerization of polystyrene.
Figure 1-58. Reaction mechanisms of (a) the NMRP of PS and (b) the ATRP of PMMA. (c, d) Linear correlations, for both NMRP and ATRP, between (c) the molecular weight and the conversion and (d) the value of ln([M]0/[M]) and the time.
86
Figure 2-1. UV–Vis spectra of TEMPO in THF at various concentrations 106 Figure 2-2. TEMPO calibration curve, correlating the absorbance at 469.5 nm to
the concentration in THF
106
Figure 2-3. (a) 1H and (b) 13C NMR spectra of the -alkoxyamine A and the 4-oxo--alkoxyamine OA formed from the reaction between BPO and TEMPO or 4-OH-TEMPO in styrene at temperatures below 25 °C
107
Figure 2-4. FTIR spectra of (a) the -alkoxyamine A and (b) the 4-oxo--alkoxyamine OA
108
Figure 2-5. (a) 1H and (b) 13C NMR spectra of HA and HOA 109 Figure 2-6. FTIR spectra of (a) hydroxyl the -alkoxyamine HA and (b)
hydroxyl the 4-oxo--alkoxyamine HOA
109
Figure 2-7. (a) UV–Vis spectra and (b) TEMPO conversion of the reaction mixture containing BPO, TEMPO, and styrene at various time intervals during ambient warming from 0 to 25 °C (A: UV–Vis absorbance; C0: initial concentration of TEMPO in solution;
UV-Vis quantification at 469.5 nm)
112
Figure 2-8. Structural identification of a mixture of -hydroxy-4-oxo-2,2,6,6-tetramethylpiperidine and
2,6-dimethyl-6-nitrosohept-2-en-4-one using (a) 1H NMR and (b) FTIR spectroscopy and (c) mass spectrometry
Figure 2-9. 1H NMR monitoring the alcohol conversion in the reaction mixture: (a) cyclopentanol, (b) cyclohexanol, (c) cycloheptanol, (d) 1-pentanol, and (e) 2-octanol
117
Figure 2-10. Aluminum alkoxide-initiated ROP of ε-CL leading to PCL (5g, 20,000 g/mol): (a) GPC traces, (b) 1H NMR spectra, and (c) molecular mass comparison of polymerization (r = 1.5; v = 30 mL); (d) monomer conversions at values of r of 0.6 or 1.2 and values of v of 30 or 60 mL
120
Figure 2-11. (a) GPC traces (RI and UV dual detection) of the PCL and the BC1–3 and (b) DSC thermograms of the BC1–3: PCL melting transition (left) and P4VP glass transition (right)
122
Figure 2-12. TEM images and inserted DLS graphs of PCL-b-P4VP diblock copolymer micelles (1 mg/mL) in a solvent of 10% DCM and 90% toluene (v/v) under stirring for 1h: (a) BC1, (b) BC2, and (c) BC3
125
Figure 2-13. Schematic self-assembly mode of PCL-b-P4VP copolymers in toluene/DCM (90/10 v/v)
125
Figure 2-14. TEM images of BC3 micelles (1 mg/mL) in toluene/DCM (90/10 v/v) under stirring for (a) 1hr and (b) 24 hr
126
Figure 2-15. Schematic route toward the preparation of PCL-b-P4VP-protected Au NPs (Au-BC1–3): (a to b) two-phase extraction of HAuCl4 via
ion pairs NH+···AuCl4–; (b to c) reduction with aqueous NaBH4
solution; and (c to d) stabilization of Au NPs in the micellar cores upon the addition of excess toluene
Figure 2-16. UV–Vis spectra of Au NPs located in the micellar cores of three PCL-b-P4VP copolymers (Au-BC1–3)
128
Figure 2-17. TEM images and inserted DLS graphs of Au NPs located in the micellar cores of three PCL-b-P4VP copolymers: (a) Au-BC1, (b) Au-BC2, and (c) Au-BC3
128
Figure 2-18. TGA thermograms of PCL, BC1-3, and Au-BC1-3 129 Figure 3-1. (a) FTIR monitoring of hydrosilylation and (b) 1H NMR spectra of
purified OT-POSS
144
Figure 3-2. (a) Comparative conversion of linear and star-like polystyrene using
1
H NMR spectra and (b) SEC trace of polymerization for linear and star-like polystyrene
146
Figure 3-3. (a) 1H NMR spectra and (b) SEC trace of star－block (PS)8-POSS,
(PS-b-P4VP)8-POSS and (PS-b-PAS)8-POSS
148
Figure 3-4. (a) SEC traces and (b) FTIR spectra of HF treatment of (PS)8-POSS
and N2H4 treatment of (PS-b-PAS)8-POSS
150
Figure 4-1. (a) Chemical structure and 3D model of SH-POSS; (b) WAXS spectrum and cartoon representation of the molecular packing in a SH-POSS crystal
159
Figure 4-2. Calculated layer-to-layer thicknesses dz for (a) ABA two-repeating
HCP system and (b) SH-POSS system for only z-directional close packing
160
Figure 4-3. (a) TEM images (×200k, top), (b) schematic particle distributions, and (c) probability size distributions of dilute C12-Au, POSS-Au1, and POSS-Au2
163
POSS-Au1 in N2 and (e) SH-POSS air and (f) POSS-Au1 air in air
Figure 4-5. FTIR spectra of (a) TOAB, (b) SH-C12, (c) C12-Au, (d) SH-POSS, (e) POSS-Au1, and (f) POSS-Au2
166
Figure 4-6. (a) cartoon representation of the molecular packing in the SH-POSS bilayer-protected POSS–Au1, with the center-to-center distance between two Au cores highlighted; (b) SAXS and WAXS spectra of POSS–Au1 powders. The insert photograph is a crystal powder of POSS–Au1
166
Figure 4-7. DLS analyses of (a) C12-Au, (b) POSS-Au1, and (c) SH-POSS 167
Figure 4-8. TEM images of C12-Au aggregations 167
Figure 4-9. Schematic bilayer structure of 1.3-nm-diameter SH-POSS surrounding on a 1.84-nm-diameter Au NPs
169
Figure 4-10. TEM images (various) magnifications and AFM sectional analyses of the (a, b) SH-POSS and (c, d) POSS–Au1 fernlike microstructures
170
Figure 4-11. (a) HRTEM image, (b) energy dispersive X-ray spectra, and (c) electron diffraction patterns of the POSS–Au1 aggregate. Regions A and B are rich and poor in the Au component, respectively
171
Figure 4-12. (a, b) OM images (× 500) of POSS–Au1 and POSS–Au2 (a) before and (b) after thermal fusion at 350 °C for 1 h. (c) AFM 2D images of heat-fused POSS–Au1 viewed at scales of 50 × 50 µm2; 10 × 10 µm2; (d) AFM sectional analysis of heat-fused POSS–Au1 viewed at a scale of 2 × 2 µm2
173
Figure 4-13. Schematic representation of the formation of fernlike POSS–Au1 microstructures
Figure 5-1. Direct synthesis of C12-Pd and POSS-Pd 181
Figure 5-2. (A) UV-vis, (B) FTIR, (C) TGA, (D) XRD results of C12-Pd, and
POSS-Pd. Additional informations such as FTIR and UV-vis spectra of Pd(OAc)2, Pd(OAc)2+SH-C12, Pd(OAc)2+SH-POSS,
TGA analyses of SH-C12, SH-POSS, and XRD patterns of
Pd(OAc)2, SH-POSS
184
Figure 5-3. TEM images, electron diffraction pattern, and atomic lattice frigne of (a) C12-Pd and (b) POSS-Pd
185
Figure 5-4. (a) Reaction scheme of Heck Coupling, which is the palladium-catalysed cross coupling between acrylate and halides and (b) reaction mechanism of Pd NCs-catalyzed Heck coupling with based-activation.13 Herein, we proposed the favorable pathway (dash line) without phase transfer toward products
187
Figure 5-5. (A) 1H NMR spectra of reaction mixture, (B) time-conversion and time-ln([M]0/[M]) profiles of Heck reactions using catalysts of
POSS-Pd and C12-Pd. Reaction conditions: 75 °C, catalysts 0.1 g POSS-Pd or 0.035 g C12-Pd (including 0.128 mmol Pd), NMP 30 mL, iodobenzene and methyl acrylate 5 mmol each, tributylamine 7.5 mmol
多面體聚矽氧烷為建構單元的嵌段式共聚
物奈米複合材料及金屬晶粒複合奈米粒子
學生：呂居樺
指導教授：張豐志
國立交通大學應用化學研究所 博士班
摘 要
奈米材料(nanomaterials)泛指一維空間尺度在1到100奈米的材料，我們可以 發現很多的零維奈米粒子(nanoparticles, NPs)可以有很多不同的組成及功能；在 第一章檢閱目前的文獻，我們將奈米晶粒(nanocrystals, NCs)從奈米粒子(NPs)分 類出來，因為它們的奈米結構是由原子或離子有序堆積組成。奈米晶粒(NCs)根 據組成可再細分為金屬奈米晶粒(metal NCs)及離子奈米晶粒(ionic NCs)；同理， 其它奈米粒子(NPs)可細分為無機(inorganic NPs)、有機(organic NPs)及無機有機 混成(inorganic/organic hybrid NPs)的奈米粒子。有些奈米粒子(NPs)有特定單一的 化學結構可在歸類為分子型奈米粒子(molecular NPs)，相較於其它的，凝聚或叢 集型奈米粒子(aggregative or cluster NPs)。此研究的無機有機混成的奈米複合粒 子(inorganic/organic hybrid NPs)包括：嵌段式共聚物微胞保護的奈米金晶粒 (PCL-b-P4VP-protected Au NPs) 、 嵌 段 式 共 聚 物 接 枝 的 多 面 體 聚 矽 氧 烷 [POSS-(PS)8, POSS-(PS-b-P4VP)8, POSS-(PS-b-P4VP)8]、多面體聚矽氧烷(POSS)保護奈米金晶粒(POSS-Au hybrid NPs)及鈀晶粒(POSS-Pd hybrid NPs)。
有很多有趣的研究討論雙親性嵌段式共聚物可自組裝成很多有序奈米結構 做為奈米反應器或儲存器，對聚七環ε-型己內酯及聚對位乙烯吡啶的嵌段式共聚
物[poly(ε-caprolactone)-block-poly(4-vinylpyridine)，命名為PCL-b-P4VP]，二個互 不相溶的長鏈高分子致使他們的混合焓(∆H> 0)為正混合熵(∆S~0)接近零，在熱 力學上這兩鏈段會自組裝成明顯相分離的微結構，因為它們的混合自由能為正值 [∆G= ∆H-T∆S)> 0]。聚對位乙烯吡啶的吡啶單元可做為高分子型金屬螯合劑做為 奈米儲存器用來穩定金屬離子或金屬奈米粒子，此研究的第二章，我們開發一種 較 簡 易 的 方 法 用 來 製 備 雙 官 能 基 起 始 劑 包 含 醇 基 (hydroxyl) 及 烷 氧 胺 基 (-alkoxyamine)的基團用來活性開環聚合對聚七環ε-型己內酯及可控制氮氧化物 為媒介自由基聚合對位乙烯吡啶。 多面體聚矽氧烷(POSS)有特定單一的化學結構(RSiO1.5)8包含八個有機基團 (R)共價性鍵結在矽烷氧的笼狀立方體的八個端點(SiO1.5)8，這樣的結構可歸類為
分子型無機有機混成奈米粒子(molecular inorganic and organic hybrid NPs)；與小 分子相似，POSS的膠體(溶劑溶解的有機殼層包覆不可溶的無機核心)也能有序堆 積成固態膠體結晶。可惜的是，用零價鈀催化的矽氫加成修飾的八官能基有不同 構型的異構物分別為分枝的α型(-Si-CH(CH3)-R)和線狀的β型(-Si-CH2CH2-R)，這 樣的異構物會抑制POSS的有序堆積(膠體結晶)，讓八官能基的POSS產物呈現非 晶型的液體或玻璃狀的固體。然而，含八個有機基團在1奈米大小的POSS膠體的 八個方位，這樣的化合物可預期良好的反應特性(較少的立體阻礙)用來製備POSS 為 主 的 奈 米 複 合 材 料 。 此 研 究 的 第 三 章 ， 我 們 共 價 接 枝 八 個 烷 氧 胺 基 團 (-alkoxyamine)到矽烷氧的笼狀立方體的八個端點(SiO1.5)8，做為八官能基起始 劑製備星狀的聚苯乙烯[POSS-(PS)8]，聚苯乙烯及聚對位乙烯吡啶的嵌段式共聚 物 [POSS-(PS-b-P4VP)8] 和 聚 苯 乙 烯 及 聚 對 位 乙 烯 酚 的 嵌 段 式 共 聚 物 [POSS-(PS-b-PVPh)8]。和線性聚苯乙烯比較，動力學分析星狀的聚苯乙烯有相似 的趨勢，指出從較少立體阻礙多官能起始的POSS可得到良好星狀高分子聚合的 特性。 在此研究的第二章，雙親性的嵌段式共聚物(PCL-b-P4VP)可以從水相把 HAuCl4的 離 子 化 合 物 轉 移 到 有 機 相 (dichloromethane) 利 用 離 子 間 作 用 力 如
[NH(AuCl)4]；借由NaBH4的環原及大量選擇性溶劑(insoluble P4VP blocks in toluene)，可經由嵌段式共聚物微胞穩定分散金奈米晶粒在有機溶劑中。然而， 用嵌段式共聚物微胞包覆的金奈米晶粒會降低表面反應活性；因此使用較大體積 的保護基團，可利用基團間的空隙讓反應物分子進入與產物分子出去，如此可維 持奈米晶粒表面原子的高反應性。就已報導的POSS膠體晶體，POSS膠體先堆積 而後再脫附溶劑分子造成，晶格常數a略大於POSS膠體的尺寸，意即POSS膠體 的 堆 積 的 晶 體 固 體 會 有 空 隙 。 在 此 研 究 的 第 四 章 ， 我 們 利 用 硫 醇 基 POSS(SH-POSS) 製 備 POSS 和 金 奈 米 晶 粒 複 合 的 奈 米 粒 子 (POSS-Au hybrid NPs)；當1.3奈米大小的硫醇基POSS吸附在約2奈米的金奈米晶粒表面，可預期 會抑制硫醇基POSS的結晶，造成非結晶性的複合奈米粒子(POSS-Au hybrid NPs)。加入過量的硫醇基POSS，可利用硫醇基POSS的結晶做為模板將複合奈米 粒子(POSS-Au hybrid NPs)組裝在模板的表面，構成很特別的蕨葉狀微結構。此 研究，可發現POSS是很好的保護劑可以將金奈米晶粒分散在固態或溶液中。 鈀的奈米晶粒(Pd NCs)常用來做為碳碳鍵隅合的觸媒像Suzuik或Heck的反 應，因此，我們所製備POSS和鈀奈米晶粒複合的奈米粒子(POSS-Pd hybrid NPs)，針對第二章的發現，硫醇基POSS晶體間的空隙可預期會有很好的觸媒活 性。在此研究的第五章，我們發現一種不用化學環原劑的方法製備POSS和鈀奈 米晶粒複合的奈米粒子(POSS-Pd hybrid NPs)，製備方法是把醋酸鈀和硫醇基 POSS或十二烷基硫醇在甲苯溶劑中共沸，可以觀察到溶液從紅色的鈀離子錯合 物轉變到黑色的鈀奈米晶粒。在此研究的第一章回顧金、銀、鈀和鉑奈米晶粒的 製 備 方 法 ， 可 分 為 化 學 環 原 法 (chemical reduction) 和 熱 溶 劑 法 (solvothermal reduction)；所製備的鈀奈米晶粒(Pd NCs)可用做Heck碳碳鍵隅合丙烯酸甲酯 (methyl acryalte)和碘 基苯(iodobenzene)，與 十二烷基硫醇保護的 鈀奈米晶粒 (C12-Pd hybrid NPs)比較，POSS和鈀奈米晶粒複合的奈米粒子(POSS-Pd hybrid NPs)有較好的化學反應特性。
(-alkoxyamine)化合物做為氮氧化物為媒介自由基聚合；(ii) 活性自由基聚合星 狀聚苯乙烯(star polystyrene)和其星狀-嵌段式共聚物；(iii) POSS結晶模板可用來 自組裝POSS和金奈米晶粒複合的奈米粒子(POSS-Au hybrid NPs)，構成形狀特殊 的蕨葉狀微結構和(iv) 低溫熱溶劑法環原製備POSS和鈀奈米晶粒複合的奈米粒 子(POSS-Pd hybrid NPs)做為良好觸媒用在Heck隅合丙烯酸甲酯和碘基苯。
Diblock Copolymer +anocomposites and Metal
+anocrystal Hybrid +anoparticles Incorporating
Polyhedral Oligomeric Silsesquioxane Building Blocks
Student：Chu-Hua Lu
Advisors：Dr. Feng-Chih Chang
Institute of Applied Chemistry
National Chiao Tung University
ABSTRACT
Nanomaterials are defined as materials having at least one dimension ranging in size from 1 to 100 nm. One-dimensional NPs (NPs) have been prepared with many different compositions and functions. In our review of the literature in Chapter 1 of this Thesis, we separate NPs from nanocrystals (NCs) that exhibit ordered packing of their compositional atoms or ions in confined nanodomains. Nanocrystals can be further divided, according to their compositions, into metal NCs and ionic NCs. Similarly, NPs can be further divided into inorganic, organic, and inorganic/organic hybrid NPs. In addition to aggregate or cluster NPs, some well-defined chemical structures can be regarded as molecular NPs. In this thesis, gold and palladium NCs (Au, Pd NCs) are classified as metal NCs and polyhedral oligomeric silsesquioxane (POSS) derivatives are classified as molecular inorganic/organic hybrid NPs; in addition, pure micelles of block copolymers and their metal NC-incorporated congeners are considered to be aggregate organic NPs and aggregate inorganic/organic hybrid NPs, respectively. Chemical and solvothermal reductions are
discussed in a reviewing of the methods of preparation of Au, Ag, Pd, and Pt NCs. Amphiphilic block copolymers are the focus of a great deal of research because of their ability to self-assemble into well-defined nanostructures that have the potential to function as nanosized reactors or storage vessels. The two immiscible high-molecular-mass blocks of poly(ε-caprolactone)-block-poly(4-vinylpyridine) (PCL-b-P4VP) have a positive mixing enthalpy (∆H) and nearly-zero mixing entropy (∆S); as a result, PCL-b-P4VP can thermodynamically self-assemble into microstructures featuring regions of distinct phase separation [positive mixing free energy (∆G = ∆H – T∆S)]. The pyridine units of the P4VP block can function as a polymeric metal ligand for the stabilization of metal ions and for the nanoscale storage of metal NPs. Chapter 2 describes the development of a simple difunctional initiator containing hydroxyl and -alkoxyamine groups for the living ring-opening polymerization of ε-CL and the controllable nitroxide-mediated polymerization of 4-VP.
POSS derivatives have a well-defined chemical structure (RSiO1.5)8 of eight alkyl
or aryl chains (R) presented at the corners of a cubic siloxane cage (Si8O12). Similar to
organic molecules, POSS colloids, with their insoluble siloxane cubes, can crystallize from organic solvents into ordered structures. Unfortunately, Pt(0)-mediated hydrosilylation of octakis-functionalized POSS derivatives yields products possessing both α- and β-isomeric linkages, which suppress the crystallization of POSS colloids, resulting in amorphous liquids and glasses. Nevertheless, such compound feature eight functional groups dispersed in eight directions from the corners of the 1-nm-diameter POSS core, providing POSS-based nanocomposites exhibiting high degree of chemical modification and low steric hindrance. Chapter 3 describes the incorporation of eight -alkoxyamine groups onto a POSS cage and its use in the preparation of eight-arm star polystyrene [POSS-(PS)8] and star-block
polystyrene-block-poly(4-vinylpyridine) [POSS-(PS-b-P4VP)8] and
polystyrene-block-poly(4-vinylphenol) [POSS-(PS-b-PVPh)8] derivatives. The
kinetics of the polymerization of POSS-(PS)8 were similar to that of linear PS,
indicating the ability to form excellent-quality star polymers from this low-steric-hindrance POSS-based multi-initiator.
Chapter 2 describes amphiphilic PCL-b-P4VP copolymers that are capable of transferring HAuCl4 from water to dichloromethane in ionic form [NH(AuCl4)].
Subsequent reduction with NaBH4 and micellization with excess toluene (a selective
solvent for the P4VP blocks) provided micelle-protected gold NCs (Au NCs) that could be dispersed well in organic solvents. Because the organically encapsulated Au NCs exhibited decreased activity for their surface reactions, we employed bulky protective groups with relatively large interparticlar distances to improve the reactivity of the surface atoms of the NCs. In the reported structures of POSS crystal, the lattice constant a is usually larger than the diameter of the POSS molecule, suggesting that desolvation occurs after packing of the POSS colloids. Chapter 4 describes POSS-Au hybrid NPs prepared from a thiol-monofunctionalized isobutyl-POSS (SH-POSS). As expected, the absorption of 1.3-nm-diameter SH-POSS colloids onto the surface of ca. 2-nm-diameter Au NPs through dynamic Au–S bonds suppressed the crystallization of the SH-POSS colloids, resulting in amorphous POSS-Au hybrid NPs. Excess SH-POSS colloids formed a crystalline POSS template for the surface self-assembly of POSS-Au hybrid NPs, resulting in novel fernlike microstructures. The use of such a POSS derivative as a protective agent provides an excellent dispersion of Au NCs in the condensed phase or in organic solvents.
Palladium NCs (Pd NCs) are well-known catalysts for many carbon–carbon bond-forming reactions, including Suzuki and Heck couplings. Thus, POSS-Pd hybrid
NPs are expected to be a highly reactive catalysts because of the large interstices between the absorbed SH-POSS colloids on the surfaces of the Pd NCs. Chapter 5 describes a reductant-free method for preparing POSS-Pd hybrid NPs by refluxing a toluene solution containing palladium acetate and thiol compounds, namely SH-POSS and 1-dodecanthiol (SH-C12). The Heck couplings of methyl acrylate with iodobenzene using the POSS-Pd and C12-Pd hybrid NPs as catalysts revealed the better activity of the former hybrid NPs.
Chapter 6 presents a summary of the four major accomplishments described in this thesis: (i) the low-temperature preparation of -alkoxyamine adducts for nitroxide-mediated radical polymerization, (ii) the living polymerization of a well-defined star PS and related star-block copolymers, (iii) a crystalline template of POSS colloids that incorporate POSS-Au hybrid NPs to give novel fernlike microstructures, and (iv) the low-temperature solvothermal reduction of POSS-Pd hybrid NPs that function as excellent catalysts for the Heck coupling of methyl acrylate and iodobenzene.
Chapter 1
Introduction
1-1 anomaterials
The ISI Web Knowledge, an academic search engine, lists 491 review papers that were published concerning the topic of “nanomaterials” from 1995 to 2008. Nanomaterials are defined by as materials having at least one dimensions in the range from 1 100 nm. Despite the fact that there is no consensus for the minimum and maximum sizes of nanomaterials, with some authors restricting their sizes to less than 30 nm, a logical definition would situate the nanoscale between the microscale (ca. 0.1 µm) and the atomic/molecular scale (ca. 0.2 nm). The properties of such materials are strongly dependant on their sizes and shapes. Nanomaterials include zero-dimensional NPs (NPs), one-dimensional nanowires and nanotubes, and two-dimensional nanofilms and nanowalls. In this Chapter, we focus on the zero-dimensional NPs because of their more interesting surface compositions in comparison with the bulk volume of nanomaterials. Herein, NCs (NCs), with their ordered packing of atoms or ions, are classified separately from NPs because they exhibit unique properties, such as optical absorbance and catalytic activity (Fig. 1-1). X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) analyses are very useful for displaying the ordered packing of atoms and ions within NCs. According to the composition of the nanomaterials, NCs can be further classified into metal NCs and ionic NCs. In addition, there are three classes of NPs: inorganic, organic, and inorganic/organic hybrids. These materials are all essential components of nanoscience and nanotechnology. Although nanomaterials can be generated through physical methods, such as laser ablation, arc-discharging, and evaporation, chemical methods have proved to be more effective because they
provide better control over size, shape, and functionalization. The chemical synthesis of nanomaterials has been reviewed by several authors,1–7 with improved methods being reported continually over the last few years. A large selection of reagents and strategies are available, in addition to a wide spectrum of reaction conditions, for the synthesis and manipulation of nanomaterials. In view of the intense research activity related to nanomaterials synthesis, this Chapter presents recent developments and new directions in this area. In doing so, we will deal with all classes of inorganic nanomaterials. Because it is impossible to do justice to the vast number of valuable contributions that have appeared in the literature in last three years, through necessity we will restrict ourselves to highlighting mostly recent results.
Figure 1-1. Dendritic distribution of Nanomaterials.
1-2 anocrystals (Cs)
Fahlman defined an NC as any nanomaterial having at least one dimension of 100 nm or less and having a single crystalline morphology regularly packed with ions, atoms, or molecules.8 More properly, any material having a dimension of less than 1 µm, i.e., 1000 nm, should be referred to as an NP, not an NC. For example,
any particle that exhibits regions of crystallinity should be termed an NP or nanocluster based on its dimensions. These materials are of huge technological interest because many of their electrical and thermodynamic properties display strong size dependence and can, therefore, be controlled through careful manufacturing. Crystalline NPs (NCs) are also of interest because they often provide single-domain crystalline systems that can be studied to provide information explaining the behavior of macroscopic samples of similar materials, without the complicating presence of grain boundaries and other defects. Semiconductor NCs, such as CdSe, CdTe, ZnO, and ZnS, in the sub-10-nm size range are often referred to as quantum dots (QDs). Depending on their composition, NCs can be classified as metal, metal salt, and nonmetal NCs.
1-2.1 Metal anocrystals (Metal Cs)
There are many difficulties to overcome when preparing monodisperse metal NCs. To data, only a few metal NCs, including Au, Ag, Pd, Pt, Fe, Cu, and Co NCs, have been prepared in the laboratory and not all of them can be obtained easily in monodisperse form. Thus, it remains a challenge to control the shape and the size of metal NCs. In general, it is easy to obtain monodisperse metal NCs having diameters less than 10 nm, but it is difficult to obtain them with diameters greater than 30 nm. The similar procedures of solvothermal and chemical reduction of metal salts with different protective groups are available for the preparation of Ag, Ag, Pd, and Pt NCs. The main difference between solvothermal and chemical reduction is that the weak reductant in the former needs a higher temperature to activate the reduction process.
Gold anocrystals (Au Cs).
tetrachloroauric acid (HAuCl4) and can be stabilized in the confined domain by
surrounding protective groups. Free Au atoms have a high interface free energy and are very unstable; therefore, they tend to pack into thermodynamically stable crystals. Because of absorption of a protective group on the surface, protective group/Au NC hybrid micelles having sizes of 1–100 nm can be stabilized in solution. Figure 1-2, for example, reveals that (i) HAuCl4 salts can be reduced into Au atoms
through solvothermal reduction with sodium citrate [HOC(CH2COO–Na+)3] at 100
°C or through chemical reduction with sodium borohydride (NaBH4) at 25 °C and (ii)
83 Au atoms having a diameter of 0.27 nm can be crystallized into 1.35-nm-diameter Au NCs. Hydrothermal reduction using sodium citrate was developed by Faraday in 18579 and later refined by Frens;10 the two-phase method of chemical reduction using NaBH4 was originally described by Wilcoxon et al.11
and later modified by Brust et al.12 NaBH4 is a salt comprising a sodium cation (Na+)
and a borohydride anion (BH4–); the B–H bond of BH4– anion effectively serves as a
reductant source of a hydride ion (:H–). When using a water/toluene biphasic mixture, a phase transfer agent, such as tetraoctylammonium bromide (TOAB), is employed to transfer the hydrophilic HAuCl4 and NaBH4 species into the toluene
phase in the presence of hydrophobic thiol compounds. Amphiphilic TOAB can form a hydrophilic nanosized reactor in toluene; the sizes of Au NPs are, therefore, limited by confinement in the nanoreactors to give small-size Au NCs. The thiol compound (RSH) plays an important role in stabilizing the Au NCs in toluene to form close-packed monolayers—stabilized by Au-S bonds—on their surfaces. In contrast, the hydrothermal reduction produces nearly monodisperse Au NPs in the size range from 2 to 100 nm.13 Problems associated with the hydrothermal reduction originate from the fact that a low-concentration solution [<0.01 M (ca. 4 mg/mL) for Au NCs with the equimolar 1-dodecanethiol] is needed to stabilize the colloidal Au
NCs in water.14 In addition, the charge-stabilized NPs readily undergo irreversible aggregation upon addition of electrolytes and nonpolar surfactants. Chemical reduction, on the other hand, allows the introduction of hydrophobic thiols as surfactants, but it suffers from (i) the limitation to small particle sizes (<10 nm) with greater polydispersity and (ii) difficult separation of the amphiphilic phase transfer agents. Similar to hydrothermal reduction with the hydroxyl groups of sodium citrate in water, Hiramastu et al. developed a novel solvothermal reduction method to prepare monodisperse 6–21-nm-diameter Au NCs and 8–32-nm-diameter Ag NCs through the refluxing of solvents such as toluene, hexane, and 1,2-dichlorobenzene containing HAuCl4, AgOAc, and oleylamine (Fig. 1-3).14 The reducing equivalents
in the reaction are provided by the amino group (CH2NH2), which undergo metal
ion-induced oxidation to form nitriles (-C≡N).15,16 From high-resolution TEM images, Brust et al.12 observed atomic packing of the Au NCs, with a layer-to-layer distance of 0.24 nm similar to the 0.27-nm-diameter of a Au atom (Fig. 1-4).
The size effect of NCs plays an important role in determining their physical and chemical properties. For example, bulk Au (>1 µm) is a shiny, yellow noble metal that does not tarnish, has a face-centered-cubic crystal structure composed of 0.27-nm-diameter atoms, is non-magnetic and melts at 1336 K (1063 °C). The properties of very small gold particles are, however, quite different: 10-nm-diameter particles absorb green light (λ = ca. 530 nm) and, thus, appear red. Meanwhile, the melting temperature decreases dramatically to 473K (200 °C) as the size decreases. Moreover, Au ceases to be noble at such small dimensions; for example, 2–3-nm-diameter NPs are excellent catalysts that also exhibit considerable magnetism. At this size they remain metallic, but smaller NPs are insulators. The ions or atoms on the surface of nanosized crystals are quite different from those of bulk materials because they cannot pack into a smooth surface and, therefore, leave
active defects. Thus, an atom at the surface of a bulk material is different from an atom of the same element within that material. Moreover, an atom at the smooth surface of a sizable single crystal is different from an atom at the surface of a small cluster of the same element. Furthermore, the properties of a surface atom of a small metal cluster depend on the type of support on which it sits or whether the cluster is doped with one or a few atoms of a different element. A solution of Au NCs is usually either an intense red color (diameters < 100 nm) or a dirty yellowish color (for larger particles). The excitation of surface plasmons by light results in a surface plasmon resonance (SPR) for planar surfaces and a localized surface plasmon resonance (LSPR) for nanometer-sized metallic structures. This phenomenon is the basis of many standard tools (e.g., color-based biosensors and lab-on-a-chip sensors) for measuring the adsorption of materials onto planar metal (typically Au and Ag) surfaces and the surfaces of metal NPs. For example, Lim et al. demonstrated (Fig. 1-5) the color-tuning of a colloidal solution containing red Au NCs (520 nm), yellow Ag NCs (410 nm), and blue hollow Au (650 nm).17 By necessity, there are proportionally more atoms on the surfaces of NCs that have smaller diameters than there are within them.18 Mathematically, the surface of a sphere scales with the square of its radius (r), but its volume scales with r3. The total number of atoms () in this sphere scales linearly with volume. The fraction of atoms at the surface is called the dispersion (F); it scales with the surface area divided by volume, i.e., with the inverse radius or diameter (1/r), and thus also with –1/3. As indicated in Fig. 1-6, the fraction F of atoms on the surface of NCs rapidly increases upon decreasing their size. In comparison with atoms in the internal region, the atoms on the surface facing the environment can serve as novel reactive sites for catalyzing reactions, even for inert metal NCs such as treasure gold.19 Nanocatalysts made from small particles of metals such as Au, Ag, Pd, and Pt are used widely in the chemical and
refining industries, as well as in catalytic converters in automobile tailpipes.
Over the last decade, after the pioneering work of Prati, Rossi, et al.,20,21 much attention has been paid also to the activity of Au catalysts in the liquid phase In most cases, Au catalysts display higher catalytic activity and much higher selectivity at lower temperatures and better stability than do Pd and Pt catalysts. Ishida and Haruta et al. reviewed the field, highlighting the role of polymer-supported Au NCs as nanocatalysts.19 Four examples of polymer-supported Au NCs are those stabilized by (a) grafting water-soluble polymers, (b) loading in the pores of a functionalized resin, (c) covering with a polymer particle, and (d) depositing on polymer surfaces (Fig. 1-7). Table 1-1 lists the results obtained for several Au NC-catalyzed reactions.23-26 These the ideal “green” processes are performed at atmospheric pressure and room temperature, in aqueous media or under solvent-free conditions, and using air as the oxidant or molecular hydrogen as the reductant. Gold NPs supported on activated carbon or metal oxides are active for some liquid-phase reactions, such as the selective oxidation (with O2 in aqueous media) of alcohols into
corresponding aldehydes, ketones, and carboxylic acid and the selective reduction (with H2) of nitroarenes into amino arenes.22
Figure 1-2. Preparation of Au NCs through chemical reduction with NaBH4 at 25 °C
and solvothermal reduction with citric acid at 100 °C. The 1.35-nm-diameter Au NCs result from the aggregation of 83 Au atoms (diameter: 0.27 nm).
Figure 1-3. TEM images and DLS analyses of Au and Ag NC samples. (A) 21-nm-diameter Au NCs from toluene, (B) 9-nm-diameter Ag NCs from toluene, (C) 12-nm-diameter Ag NP nanocrystals from hexane, and (D) 32-nm-diameter Ag NCs from 1,2-dichlorobenzene. Scale bars: 100 nm.14
Figure 1-4. HRTEM images of 1-dodecanthiol-protected Au NCs. The thickness (0.24 nm) indicates the layer-to-layer distance of FCC Au NCs.12
Figure 1-5. (a) Optical extinction spectra of Ag NCs (yellow), solid Au NCs (red), and hollow Au nanoshells (blue). The optical densities of the three differently colored samples have been matched to 1.8. (b) Photograph of aqueous dispersions of metal NP colloids, the SPR bands of which were tuned in terms of wavelength and intensity multiplexing.17
Figure 1-6. Evolution of the dispersion F as a function of n for cubic clusters up to n = 100 ( = 106). The structures of the first four clusters are displayed.18
Figure 1-7. Cartoon representations of four polymer-stabilized Au NCs: (a) grafted with water-soluble polymers, (b) loaded in the pores of a functionalized resin, (c) covered with polymer particles, and (d) deposited on a polymer surface.19
Table 1-1. Representative reactions catalyzed by polymer-supported Au NPs.19
Silver anocrystals (Ag Cs).
Similar to Au NCs, Ag NCs can be also prepared through both solvothermal and chemical reduction. For example of chemical reduction, He et al. prepared monodisperse Ag NCs having an average diameter of 4.18 nm through a two-phase
method, using AgNO3, NaBH4, TOAB, and 1-nonanethiol (C9H19SH) in water and
dichloromethane (Fig. 1-8).12,27 In addition, solvothermal reductions with ethanol or ethylene glycol are well established for the preparation of high quantities of Ag NC products.28,29 During the past decade, Toshima’s group developed and optimized an effective technique for the preparation of Ag NC colloidal dispersions through reduction with alcohols under reflux in the presence of a protecting agent of polymeric nature.30-35 Poly(vinylpyrrolidone) (PVP), a useful stabilizing agent with polar cyclic amide groups, forms complexes with the surface atoms of Ag NCs. In an investigation of ethylene glycol-induced solvothermal reduction, Silvert et al. obtained a plot of the variation of the mean particle size by dynamic light scattering (DLS) and the concentration in solution (UV absorbance at 410 nm) as a function of time (Fig. 1-9);29 it consists of three regions: Region 1 (up to 55 °C), Region 2 (up to 120 °C), and Region 3 (isotherm at 120 °C). In Region 1, the nucleation of 8% Ag salts predominates to produce small-size Ag colloids [95% of diameters < 10 nm; 5% diameters = ca. 20 nm (Fig. 1-10a)]. In Region 2, the growth of Ag salts becomes significant to produce a broad distribution with large and small Ag colloids [24% of diameters = ca. 20 nm (Fig. 1-10b); 92% of diameters = 20 nm (Fig. 1-10c)]. In Region 3, almost all of the Ag salt has been reduced into monodisperse Ag NCs having an average diameter of ca. 20 nm (Fig. 1-10d); therefore, in this region, stable-sized 20-nm-diameter-Au NCs are available when prepared using PVP protecting polymers.
Low-cost colloids of Ag NCs can function as precursors of conductive nanowires to fabricate patterns with at least one lateral dimension having a size between that of an individual atom and ca. 100 nm; this process is called nanolithography. For example, Wang et al. used atom force microscopy (AFM) to write Ag nanowires with a colloid ink followed by thermal sintering at 300 °C (Fig.
1-11).36 Figure 1-12 displays an AFM image and cross-sectional analysis of such well-defined nanowires having a width of 5 µm. Hydrazine (NH2NH2) is the best
established reductant for the chemical reductions used to prepare Ag NCs. Li et al. developed a facile method for the synthesis of Ag NCs used in the fabrication of high-conductivity elements for printed electronics.37 The acetate anions of AgOAc can be replaced with alkylamines to give silver complexes that are soluble in toluene (Fig. 1-13); monodisperse 5-nm-diameter Ag NCs can then be obtained through subsequent reduction with hydrazine hydrate (Fig. 1-13a). A continuous phase of sintered Ag NCs can be observed through scanning electron microscopy (SEM) (Fig. 1-13b) after heat treatment at 140 °C for 30 s. The conductivity of the sintered Ag NCs can be detected (Fig. 1-13c) after the deposition of Ag NCs colloids on a chip and subsequent thermal treatment. The electrical conductivity of the resulting Ag film was in the range from 2–4 × 104 S cm–1, which is on the same order as that of a vapor-deposited Ag thin film of similar thickness (4–6 × 104 S cm–1). This high level of conductivity is more than sufficient for applications in electronic devices. In addition, the alkylamine-stabilized Ag NPs prepared using this procedure exhibit good shelf life, both in both powder form and in solution—a feature of critical importance in electronic circuit manufacturing.
Ag NCs also exhibit antibacterial (antimicrobial) activity, allowing their use in the surface modification of biomedical materials.38 This antibacterial property has been known for thousands of years, with the ancient Greeks cooking from silver pots. Indeed, the old adage, “born with a silver spoon in his mouth,” refers to more than just wealth—eating with a silver spoon is also more hygienic. Lok et al. revealed that Ag+ cations in AgNO3 solutions can inhibit the growth of bacteria.38 For
nanosized Ag NCs, the fraction of Ag atoms on the surface of NCs increases rapidly upon decreasing the size (Fig. 1-6).18 These surface Ag atoms present a free surface
to contact the surroundings, showing high chemical reactivity to give Ag+ ions in the oxidative form (Ag2O). Thus, the antibacterial activities of Ag NPs are dependent on
the presence of chemisorbed Ag+, which is readily formed owing to extreme sensitivity to O2. In addition, Lok et al. applied SPR techniques to quantitatively
detect the level of chemisorbed Ag+ on the surface of Ag NCs; it correlated well with the observed antibacterial activities (Fig. 1-14). The SPR spectra of Ag NCs indicate a shift in the absorbance from 375 nm for the Ag NCs to 398 nm for the Ag+ ions (Fig. 1-14a). From a comparison of the reactions of untreated and oxidized Ag NCs with bovine serum albumin (BSA), it was found that BSA can convert oxidized Ag NCs into Ag+, which significantly prohibits the growth of bacteria (Fig. 1-14b,c). BSA has a high affinity for fatty acids, hematin, and bilirubin and has a broad affinity for small negatively charged aromatic compounds. It forms covalent adducts with pyridoxyl phosphate, cysteine, glutathione, and various metal ions, such as Cu(II), Ni(II), Hg(II), Ag(II), and Au(I). Thus, highly active oxidized Ag ions on the surface could be release to form stable complexes with BSA. In addition, Chen et al. prepared an antibacterial and biocompatible substrate through sputter coating with a Ag NC-containing hydroxyapatite (Ag-HA).39 Figure 1-15 displays the significant improvement in the antibacterial properties of the Ag-HA in comparison with those of different substrates (e.g., Ti) and hydroxyapatite (HA). Moreover, Although Ag has a broad antibacterial effect, high concentrations of Ag are cytotoxic (maximum toxic concentration for human cells: 10 mg/L).40 The toxicity of Ag ions affects the basic metabolic cellular functions common to all specialized mammalian cells. A concentration- and time-dependent depletion of intracellular ATP content has been attributed to the presence of Ag ions, thereby compromising the cell energy charge, which precedes cell death.41 Therefore, it is prudent to incorporate only a minimum amount of Ag on implant surfaces to
adequately reduce bacterial adhesion as well as minimize tissue cytotoxicity. Indeed, anti-bactericidal properties were observed without osteoblast-precursor cell cytotoxicity for co-sputtered Ag-HA coatings having a concentration of 2.05 ± 0.55 wt% Ag.
Figure 1-8. TEM images of a 2D superlattice containing 4.18-nm-diameter Ag NCs, (left insert) a histogram of the Au NCs, and (right insert) a 2D Fourier power spectrum of the TEM images.27
Figure 1-9. Evolution of the mean particle size (circle) and 410-nm-absorbance peak (square) during the formation of 21-nm-diameter monodisperse Ag colloids (400 mg AgNO3; 10 g PVP; 75 mL EG; 1 °C/min from 25 to 120 °C, followed by
Figure 1-10. TEM images of a colloidal Ag dispersions: (a) t = 0.25 h and T = 40 °C, (b) t = 0.75 h and T = 70 °C, (c) t = 1.00 h and T = 85 °C, and (d) t = 2.60 h and T = 120 °C.29
Figure 1-11. Schematic representation of the DPN procedure used to pattern a Ag NC ink on a glass substrate. This procedure is common to other substrates.36
Figure 1-12. 2D AFM images and cross-sectional analysis of linewidths: (a) 10 µm, (b) 5 µm, (c) 2 µm, and (d) 760 nm.36
Figure 1-13. Single-phase preparation of Ag NCs and analytical results: (a) TEM image of Ag NCs having diameters of ca. 10 nm; (b) SEM image of Ag films after treatment at 140 °C for 30 s; (c) drain current (ID) versus source-drain voltage (VD)
plotted as a function of the gate voltage (VG) for a thin film transistor (TFT) with
printed source/drain electrodes (channel length: 90 µm; channel width: 2250 µm); (d) ID and (–ID)1/2 plotted versus VG at a constant value of VD (–40 V), used for
Figure 1-14. (a) SPR absorption of untreated and oxidized Ag NCs, (b) BSA-mediated shift of the SPR absorption, and (c) bacterial activity of untreated Ag NCs, oxidized Ag NCs, BSA-treated oxidized Ag NCs, and BSA.38
Figure 1-15. Photographs and statistical analyses of (a) S. aureus and (b) S. epidemidis on various substrates: Ti, HA, and Ag-HA.39
