Ng Ching Man = 在不同氣體中一的維硒化鋅鈉米結構的發光研究 / 吳靜雯. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 67-69). / Text in English; abstracts in English and Chinese. / Ng Ching Man = Zai bu tong qi ti zhong yi de wei xi hua xin na mi jie gou de fa guang yan jiu / Wu Jingwen. / Contents / Acknowledgements --- p.ii / Abstract --- p.iii / Chapter Chapter 1- --- Introduction --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.2 --- Motivation --- p.3 / Chapter 1.3 --- Our Work --- p.4 / Chapter Chapter 2 - --- Experiment --- p.5 / Chapter 2.1 --- MOCVD System --- p.5 / Chapter 2.2 --- Metalorganic Sources --- p.5 / Chapter 2.3 --- Substrates --- p.7 / Chapter 2.4 --- Growth of ZnSe Nanowires --- p.7 / Chapter 2.5 --- Sample Passivation --- p.8 / Chapter 2.6 --- PL measurements --- p.8 / Chapter 2.7 --- Ambient Gases --- p.9 / Chapter 2.8 --- Gases Handling Apparatus --- p.9 / Chapter 2.9 --- Ambient Gases and Laser Power Control in PL Measurements --- p.11 / Chapter Chapter 3 - --- Characterization --- p.13 / Chapter 3.1 --- Photoluminescence --- p.13 / Chapter 3.2 --- Secondary Electron Microscopy --- p.14 / Chapter 3.3 --- X-Ray diffraction --- p.15 / Chapter Chapter 4 - --- Results --- p.16 / Chapter 4.1 --- ZnSe Nanowires Grown on Si(100) --- p.16 / Chapter 4.1.1 --- Morphology and Structure of the As Synthesized Sample --- p.16 / Chapter 4.1.2 --- Morphology and Structure of the Sample after Passivation --- p.17 / Chapter 4.2 --- Effect of Ambient Condition on Photoluminescence --- p.19 / Chapter 4.2.1 --- PL in Vacuum Ambient --- p.20 / Chapter 4.2.2 --- PL Spectra in different Ambient Gases --- p.21 / Chapter 4.2.3 --- PL Reversibility --- p.23 / Chapter 4.3 --- "Effect of Pressure, Concentration and Power of Excitation on the Photoluminescence of Nanowires" --- p.26 / Chapter 4.3.1 --- Ambient Pressure --- p.27 / Chapter 4.3.1.1 --- H2S --- p.27 / Chapter 4.3.1.2 --- H2 --- p.30 / Chapter 4.3.1.3 --- CO --- p.32 / Chapter 4.3.2 --- Ambient Concentration --- p.33 / Chapter 4.3.2.1 --- H2S --- p.33 / Chapter 4.3.2.2 --- H2 --- p.36 / Chapter 4.3.3 --- Excitation Power --- p.38 / Chapter 4.3.3.1 --- H2S --- p.38 / Chapter 4.3.3.2 --- H2 --- p.40 / Chapter 4.3.3.3 --- CO --- p.41 / Chapter Chapter 5 - --- Discussions --- p.42 / Chapter 5.1 --- Quality of nanowires --- p.42 / Chapter 5.2 --- Surface Reaction --- p.43 / Chapter 5.2.1 --- Surface States --- p.43 / Chapter 5.2.2 --- Gas-surface interaction --- p.46 / Chapter 5.2.2.1 --- Physiosorption --- p.46 / Chapter 5.2.2.2 --- Chemisorption --- p.47 / Chapter 5.3 --- (NH4)2S passivation --- p.48 / Chapter 5.3.1 --- Etching --- p.48 / Chapter 5.3.2 --- (NH4)2S passivation --- p.48 / Chapter 5.4 --- PL increase in Vacuum --- p.50 / Chapter 5.5 --- Effects of different Gases --- p.50 / Chapter 5.5.1 --- H2S --- p.50 / Chapter 5.5.2 --- H2 --- p.53 / Chapter 5.5.3 --- CO --- p.54 / Chapter 5.5.4 --- Other explanations --- p.54 / Chapter 5.6 --- The amount of Intensity Change --- p.56 / Chapter 5.7 --- Rates of Adsorption and Desorption --- p.56 / Chapter Chapter 6 - --- Conclusions --- p.58 / Appendices --- p.60 / Chapter I - --- Fitted parameter of the adsorption and desorption of H2S and CO --- p.60 / Chapter II - --- Calculation of gas and photon fluxes --- p.65 / References --- p.67

Titanium dioxide (TiO2) photocatalysis, which can oxidise or reduce organic and inorganic pollutants, is a developing technology for water and wastewater treatment. The current work investigates the photocatalytic reduction of cadmium and selenium species as the presence of these elements in water are of environmental concern. Although TiO2 has been widely used for the photocatalytic process, its light absorption is limited to the UV region of the solar spectrum. Hence, the current project also explores the possibility to deposit cadmium selenide (CdSe) onto TiO2 to extend the photoresponse to the visible region. This study demonstrated that cadmium (Cd(II)) could be reduced to its metallic form by photocatalysis. The choice of hole scavengers and reaction pH are of importance in determining whether the photocatalytic reduction reaction will occur. It is also essential that both Cd(II) and organic additives are adsorbed on the surface of TiO2. A mechanism for cadmium photoreduction in the presence of formate as the hole scavenger was proposed. The current investigation elucidated the mechanism for the photoreduction of selenite (Se(IV)). Selenite was found to be photoreduced to its elemental form (Se(0)) as films, by direct photoreduction of Se(IV), and as discrete particles, by the reaction between Se(IV) and selenide (Se(2-)) ions. The Se(2-) ions are believed to have been generated from the 6 electron photoreduction of Se(IV) and/or the further photoreduction of the Se(0) deposits. Photocatalytic reduction reactions of Se(IV) and selenate (Se(VI)) using different commercial TiO2 materials was also studied. The current work also successfully deposited CdSe by photocatalysis using Se-TiO2 obtained from the photoreduction of Se(IV) and Se(VI). The mechanism for CdSe deposition was clarified and attributed to the reaction of Cd(II) present in the system and the Se(2-) released from the reduction of Se(0) upon further illumination. The Se??TiO2 photocatalysts obtained from the photoreduction of different selenium precursors (Se(IV) and Se(VI)) resulted in the dominance of different morphologies of the CdSe particles. This suggests a new approach to manipulate the properties of CdSe during its formation, and hence control over electrical and optical properties of this semiconductor.

Titanium dioxide (TiO2) photocatalysis, which can oxidise or reduce organic and inorganic pollutants, is a developing technology for water and wastewater treatment. The current work investigates the photocatalytic reduction of cadmium and selenium species as the presence of these elements in water are of environmental concern. Although TiO2 has been widely used for the photocatalytic process, its light absorption is limited to the UV region of the solar spectrum. Hence, the current project also explores the possibility to deposit cadmium selenide (CdSe) onto TiO2 to extend the photoresponse to the visible region. This study demonstrated that cadmium (Cd(II)) could be reduced to its metallic form by photocatalysis. The choice of hole scavengers and reaction pH are of importance in determining whether the photocatalytic reduction reaction will occur. It is also essential that both Cd(II) and organic additives are adsorbed on the surface of TiO2. A mechanism for cadmium photoreduction in the presence of formate as the hole scavenger was proposed. The current investigation elucidated the mechanism for the photoreduction of selenite (Se(IV)). Selenite was found to be photoreduced to its elemental form (Se(0)) as films, by direct photoreduction of Se(IV), and as discrete particles, by the reaction between Se(IV) and selenide (Se(2-)) ions. The Se(2-) ions are believed to have been generated from the 6 electron photoreduction of Se(IV) and/or the further photoreduction of the Se(0) deposits. Photocatalytic reduction reactions of Se(IV) and selenate (Se(VI)) using different commercial TiO2 materials was also studied. The current work also successfully deposited CdSe by photocatalysis using Se-TiO2 obtained from the photoreduction of Se(IV) and Se(VI). The mechanism for CdSe deposition was clarified and attributed to the reaction of Cd(II) present in the system and the Se(2-) released from the reduction of Se(0) upon further illumination. The Se??TiO2 photocatalysts obtained from the photoreduction of different selenium precursors (Se(IV) and Se(VI)) resulted in the dominance of different morphologies of the CdSe particles. This suggests a new approach to manipulate the properties of CdSe during its formation, and hence control over electrical and optical properties of this semiconductor.

Thesis (Ph. D.)--University of Oregon, 2007. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 81-84). Also available online in Scholars' Bank; and in ProQuest, free to University of Oregon users.

Zugl.: Regensburg, Univ., Diss., 2007

Zugl.: Regensburg, Universiẗat, Diss., 2007.

>Magister Scientiae - MSc / A novel 3-mercaptopropionic acid capped iridium selenide quantum dots based label free impedimetric immunosensor was successfully constructed. The 3-mercaptopropionic acid capped iridium selenide quantum dots synthesized were studied using HRTEM, revealing the formation of very small sizes, of about 3 nm. The optical Uv-Vis absorption wavelength of the quantum dots is blue-shifted, a phenomenon explained by the effective mass approximation (EMA) for semiconducting materials with sizes below 10 nm. Using cyclic voltammetry it is noted that the quantum dots have interesting electro-catalytical properties. The immunosensor proved to be sensitive towards nodularin, with a very low detection limit of 0.009 ng/mL and is significantly lower than the recent anti-nodularin ELISA kit developed by (Zhou et al., 2011) which has a detection limit of 0.16 ng/mL.Also the dection limit of the immunosensor is below the South African guideline value for microcystin-LR (0-0.8) μg/L (DWAF; 1996). The calibration curve of the 3MPA-GaSe nanocrystal based biosensor was successfully constructed, which exhibited a trend described by Michaelis-Menten, a typical behaviour of enzymatic biosensors. The detection limit of the biosensor is 0.004 nM and is significantly lower than the action limit of 17beta-estradiol, (1.47 x 10-10 M).

No description available.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2009. / Title from PDF title page (viewed Feb. 3, 2010). Additional advisors: Renato Camata, Derrick Dean, Chris M. Lawson, Andrei Stanishevsky, Sergey Vyazovkin. Includes bibliographical references (p. 133-140).

Nonradiative decay of excitons is a competing process to Multi-Exciton Generation (MEG) in nanoparticles. Nonradiative decay of single excitons with sufficient energy to generate bi-excitons in Cd₂₀ Se₁₉ and Cd₈₃ Se₈₁ nanoparticles was studied using Tully's Molecular Dynamics with Quantum Transitions (MDQT) method and a CdSe pseudopo- tential. Exciton decay rates increase with increases in nanoparticle temperature and density of lower-lying excitonic states. There did not appear a significant effect of size on energy decay rates. The decay dynamics generally follow a gradual decay with transitions between nearby states. This is punctuated by periodic, short-lived periods of rapid downhill tran- sitions that result in a large proportion of excess exciton energy being transferred to the vibrational motion of the nanoparticle. The time for relaxation to below the 2.0E[subscript g] cutoff was on the order of 1ps. / text