Size Separation and Photochemical Properties of Quantized Semiconductor Microcrystals

量子化半导体微晶的尺寸分离和光化学性质

• 批准号: 04650733
• 负责人: UCHIDA Hiroyuki
• 金额: $ 1.09万
• 依托单位: Yamanashi University (1993)Osaka University (1992)
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1992
• 资助国家: 日本
• 起止时间: 1992 至 1993
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04650733/
• 关键词: Semiconductor Microcrystals; Quantum-size Effect; Cadmium Sulfide; Photoinduced Electron Transfer; Size-Separation; Electrophoresis

Photochemical and photophysical properties of semiconductor microcrystals depend greatly on their size due to the quantum size effects. Bisides the size effect, properties of microcrystals must be greatly influenced by their surface conditions, i.e.nonstoichiometry in the surface composition and kinds of stabilizers. Therefore, in order to clarify their size-dependent properties, it is desirable to employ microcrystals having almost identical surface conditions except their particle size. A fractionation of CdS microcrystals with the use of gel electrophoresis is one of the promising techniques to allow such conditions. In the present research, effective methods for size-separation of quantized semiconductor microcrystals were developed and photoinduced electron transfer on size-separated CdS microcrystals were examined. Major achievements are as follows ;1. Efficient size-separation of quantized CdS by means of improved electrophoresis.First, the gel electrophoresis of quantized CdS ( … More Q-CdS, stabilized with HMP, diameter=3-9nm)) was carried out employing a polyacrylamide gel column with application of 100V.A thermal diffusion of CdS particles in the gel was inhibited by cooling of the elctrophoresis cell with ice bath. The resulting CdS-gel layr of 6cm length was cut into 6 slices. It was found that the second electrophoresis of each gel slice resulted in very efficient and prompt extraction of CdS particles from the slice of the gel. With the size-separation, the absorption spectrum of Q-CdS blue-shifted and became steep, the degree being more marked with an increase in the fraction number. It was confirmed by TEM observation that the size-separation gave narrow size distribution and particles of 5.02 nm and 3.58 nm average diameter were present in the fraction 1 and 6, respectively.2. Photoinduced electron transfer on size-separated CdS microcrystals.The rate of reduction of methylviologen on CdS microcrystals prepared by fractionation with the use of gel electrophoresis increased with decreasing the particle size. The observed results were successfully analyzed in terms of shifts in the conduction bandedge due to the size-quantization. The potential of the conduction bandedge of the microcrystals of various sizes relative to that of crystalline bulk CdS is derived based on the flat band potential of the bulk CdS and the shifts of the conduction band expected by the size-quantization. By assuming that the potential difference between the derived potential of the conduction bandedge and the redox potential of methylviologen is the overvoltage for the reduction reaction, Tafel relation with the transfer coefficient of ca. 0.3 was observed between the reduction rate and the overvoltage. Less

由于量子尺寸效应，半导体微晶的光化学和光物理性质与其尺寸密切相关。除了尺寸效应外，微晶的表面条件，即表面组成的非化学计量比和稳定剂的种类对微晶的性能也有很大的影响。因此，为了阐明它们的尺寸依赖性，希望使用除了它们的颗粒尺寸之外具有几乎相同的表面条件的微晶。使用凝胶电泳的CdS微晶的分级分离是允许这样的条件的有前途的技术之一。在本研究中，量子化半导体微晶的尺寸分离的有效方法的发展和光诱导电子转移的尺寸分离的CdS微晶进行了检查。主要成果如下：1.用改进的电泳法对量子化CdS进行了有效的尺寸分离。首先，量子化CdS的凝胶电泳（ ...更多信息 Q-CdS，HMP稳定，粒径3- 9 nm）），采用聚丙烯酰胺凝胶柱，外加电压100 V，通过冰浴冷却电泳池来抑制CdS颗粒在凝胶中的热扩散。将得到的6cm长的CdS-凝胶层切成6片。发现每个凝胶切片的第二次电泳导致从凝胶切片中非常有效和迅速地提取CdS颗粒。随着粒径的分离，Q-CdS的吸收光谱发生蓝移，光谱变得陡峭，且随着粒径分数的增加，蓝移的程度更加明显。通过TEM观察证实，粒度分离得到窄的粒度分布，并且在级分1和级分6中分别存在平均直径为5.02 nm和3.58 nm的颗粒.粒径分离的CdS微晶体上的光诱导电子转移：通过使用凝胶电泳分级制备的CdS微晶体上甲基紫精的还原速率随着粒径的减小而增加。成功地分析了所观察到的结果在由于尺寸量子化的传导带边的移位。各种尺寸的微晶的导带边相对于结晶块状CdS的电位是基于块状CdS的平带电位和尺寸量子化所预期的导带位移而导出的。通过假定导带边电位与甲基紫精氧化还原电位之间的电位差为还原反应的过电压，导出了Ca. 0.3在还原速率和过电压之间观察到。少

项目成果

米山 宏: "量子化半導体超微粒子の合成と応用" ファインケミカル. 21. 17-23 (1992)

米山浩：“量子化半导体超细粒子的合成与应用”《精细化学》21. 17-23 (1992)。

H.Yoneyama and H.Uchida: "Synthesis and Applications of size-quantized semiconductor microcrystals." Fine Chemical. 21(No.15). 17-23 (1992)

H.Yoneyama 和 H.Uchida：“尺寸量子化半导体微晶的合成和应用”。

米山 宏: "ナノメートルサイズ半導体超微粒子の特性と応用" The INTER. 143-143 (1993)

Hiroshi Yoneyama：“纳米级半导体超细颗粒的特性和应用”The INTER 143-143 (1993)。

H.Yoneyama and H.Uchida: "Properties of Semiconductor Nanocrystals and Their Applications." The INTER. 143-143 (1993)

H.Yoneyama 和 H.Uchida：“半导体纳米晶体的特性及其应用”。