published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Chemistry / Master / Master of Philosophy

Surface enhanced Raman scattering (SERS) is a powerful means for obtaining vibrational data from the metal/electrolyte or metal/gas interfacial environment. However, SERS is only observed for a limited number of metal surfaces under certain experimental conditions. Before this method can become a universal tool, the enhancement mechanism(s) must be understood. The results reported in this dissertation assess both electronic and chemical contributions to the SERS mechanism. The electronic properties of the metal are altered by systematic deposition of Pb or Cu onto a substrate that supports intense SERS, Ag. The chemical nature of the interface is altered with different probe molecules. The effect of Pb deposition on the SERS enhancing ability of Ag electrodes has previously been investigated with strongly adsorbed probe molecules. The behavior of cyanide species in the presence of Pb⁺² is complicated by the necessity of maintaining low solution pH to prevent Pb(OH)₂ precipitation; thus, the predominant solution species is HCN. Although previous reports state that no SERS can be detected from cyanide-containing solutions below pH 6, intense SERS signals can be obtained at pH 2 if sufficiently positive electrode potentials are maintained. The two unresolved SERS bands observed in acidic solutions are attributed to HCN which interacts with the Ag surface in end-on and side-on configurations. The predominant effect of Pb deposition on HCN SERS is HCN displacement. Enhancement due to charge transfer processes is not significant, while electromagnetic effects dictate the residual SERS intensity remaining after the initial HCN displacement. The supporting electrolyte anion affects the rate of change of the potential dependent C≡N stretch in basic CN⁻ media. A correlation between the rate of frequency change and anion charge/radius ratio was observed at potentials near and slightly negative of the Ag potential of zero charge in basic CN⁻ media. These results demonstrate the extraordinary sensitivity of SERS to interfacial conditions. The contributions from chemical and electromagnetic enhancement are further assessed by following excitation wavelength dependence of the SERS intensity of pyridine and Cl⁻ as a function of Cu coverage. Contributions from both are observed, but chemical enhancement is less evident for Cu than for Pb deposition. This is related to the smaller change in work function that occurs as a consequence of Cu versus Pb deposition on Ag surfaces.

No description available.

by Yip Sung-tat. / Bibliography: leaves 120-123 / Thesis (M.Ph.)--Chinese University of Hong Kong, 1984

by Tong Ka Wing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves 60-62). / by Tong Ka Wing. / Abstract --- p.1 / Chapter Chapter 1 --- Introduction --- p.2 / Chapter Chapter 2 --- Scattering Intensities and Depolarization Ratios --- p.9 / Chapter Chapter 3 --- Raman Microprobe Experimental Set-up --- p.11 / Chapter 3.1 --- Optical Design of the Raman Microprobe --- p.11 / Chapter 3.1.1 --- Construction of the Olympus BHSM-313U Microscope --- p.11 / Chapter 3.1.2 --- Numerical Aperture of Objectives --- p.13 / Chapter 3.1.3 --- Design of the Raman Microprobe --- p.13 / Chapter 3.1.3.1 --- Design of Signal Collection Optics --- p.16 / Chapter 3.1.3.2 --- Design of Epi-illuminator --- p.17 / Chapter 3.2 --- Performance of the Raman Microprobe --- p.19 / Chapter 3.2.1 --- Collection Efficiencies of Objectives --- p.19 / Chapter 3.2.2 --- Spatial Resolution of the Raman Microprobe --- p.20 / Chapter 3.2.3 --- Rejection of Rayleigh Scattering Light --- p.20 / Chapter 3.2.4 --- Polarization Effect of the Raman Microprobe --- p.22 / Chapter Chapter 4 --- "Sample Preparation, Morphology and Measurements of Spectra" --- p.23 / Chapter Chapter 5 --- Results and Discussion --- p.31 / Chapter 5.1 --- Micro-Photoluminescence of Diamond Films --- p.31 / Chapter 5.2 --- Curve Fitting of Micro-Raman Spectra --- p.34 / Chapter 5.3 --- Part I Micro-Raman of Unoriented Diamond Crystallites --- p.41 / Chapter 5.3.1 --- Diamond Peaks --- p.41 / Chapter 5.3.2 --- D- and G- Peaks --- p.43 / Chapter 5.4 --- Part II Micro-Raman of Oriented Diamond Crystallites --- p.43 / Chapter 5.4.1 --- Diamond Peaks --- p.45 / Chapter 5.4.1.1 --- Depolarization Ratios --- p.45 / Chapter 5.4.1.2 --- Peak Shifts --- p.47 / Chapter 5.4.1.3 --- Peak Widths --- p.48 / Chapter 5.4.2 --- D- and G- Peaks --- p.48 / Chapter 5.4.2.1 --- Depolarization Ratios --- p.48 / Chapter 5.4.2.2 --- Peak Shifts and Widths --- p.48 / Chapter 5.4.3 --- Relation Between Line Width of Diamond Peaks and Intensity Ratios of Diamond Peak to G-Peak --- p.50 / Chapter 5.4.4 --- Internal Stress due to Substrate and Other Growth Defects --- p.52 / Chapter Chapter 6 --- Conclusions --- p.54 / Appendix A --- p.56 / Chapter A.1 --- Scattering Intensities of Diamond --- p.56 / Chapter A.2 --- Scattering Intensities of Graphite --- p.58 / Appendix B --- p.59 / References --- p.60

No description available.

by Wong Chun Wing = 銀膠媒介內結晶紫的表面增強共振拉曼散射研究 / 黃振榮. / Thesis submitted in: December 2004. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 74-79). / Text in English; abstracts in English and Chinese. / by Wong Chun Wing = Yin jiao mei jie nei jie jing zi de biao mian zeng qiang gong zhen la man san she yan jiu / Huang Zhenrong. / Abstract --- p.1 / Chapter Chapter 1 --- Introduction --- p.2 / Chapter Chapter 2 --- Experimental Setup --- p.7 / Chapter 2.1 --- Raman probe --- p.7 / Chapter 2.2 --- Spectrophotometer for absorption spectra --- p.7 / Chapter 2.3 --- TEM and AFM --- p.8 / Chapter Chapter 3 --- Sample Preparation --- p.9 / Chapter 3.1 --- Chemicals --- p.9 / Chapter 3.2 --- Silver Colloid --- p.9 / Chapter 3.3 --- Slide Coated with Silver Colloid --- p.10 / Chapter 3.4 --- Sampling Probe --- p.10 / Chapter Chapter 4 --- Results and Discussion --- p.12 / Chapter 4.1 --- Dependence of SERRS on CV Concentration --- p.12 / Chapter 4.1.1 --- Resonant Raman spectra of CV --- p.12 / Chapter 4.1.2 --- TEM Images of Ag Colloid --- p.17 / Chapter 4.1.3 --- SERRS at different CV Concentrations in Solution --- p.20 / Chapter 4.2 --- Dependence of CV SERRS on Ag Concentration --- p.36 / Chapter 4.3 --- Dependence of CV SERRS on NaCl Concentration --- p.42 / Chapter 4.3.1 --- UV-VIR Absorption Spectra of NaCl added Ag Colloid --- p.42 / Chapter 4.3.2 --- Dependence on NaCl Concentration --- p.49 / Chapter Chapter 5 --- Conclusions --- p.64 / Appendix A / Chapter A.1(part A) --- Estimation of the Number Density of Colloidal Ag Particles --- p.66 / Chapter A.1(part B) --- Estimation of CV Concentration needed for Monolayer Coverage on Ag colloids --- p.67 / Chapter A.2 --- Assignments of Crystal Violet (CV) Vibrational Modes --- p.69 / Appendix B Estimation of the Probed Volume of the Microscope Objective --- p.70 / Appendix C Estimation of the Effective Molar Absorption Coefficient (α) of CV --- p.71 / References --- p.74

During the last decade, Raman microscopy is experiencing rapid development and increasingly applied in biological and medical systems. Especially, stimulated Raman scattering (SRS) microscopy, which significantly improves the sensitivity of Raman scattering through stimulated emission, has allowed direct visualization of many species that are previously challenging with conventional fluorescence imaging. Compared to fluorescence, SRS imaging requires no label or small label on the target molecule, thus with minimal perturbation to the molecule of interest. Moreover, Raman scattering is free from complicated photophysical and photochemical processes such as photobleaching, and has intrinsically narrower linewidth than fluorescence emission. This allows multiplexed Raman imaging with minimal spectral crosstalk and excellent photo-stability. To achieve the full potential of Raman microscopy, vibrational probes have been developed for Raman imaging. Multiple Raman probes with a few atoms in size are applied in Raman imaging with high sensitivity and specificity. An overview of both fluorescence and Raman microscopy and their imaging probes is given in Chapter 1 with a brief discussion on the SRS theory. Built on the current progress of Raman microscopy and vibrational probes, I write on my research in the development of carbon-deuterium, alkyne and nitrile probes for visualizing choline metabolism (Chapter 2), glucose uptake activity (Chapter 3), complex brain metabolism (Chapter 4) and polymeric nanoparticles (Chapter 5) in live cells and tissues, as well as the development of polyyne-based vibrational probes for super-multiplexed imaging, barcoding and analysis (Chapter 6).