Photocatalytic Preparation of Encapsulated Gold Nanoparticles by Jingle-bell-shaped Cadmium Sulfide–silica Nanoparticles

Gold (Au) nanoparticles were deposited inside silica: (SiO₂) shells containing cadmium sulfide (CdS) nanoparticles through photocatalytic reduction of potassium dicyanogold(I) by CdS. Photocatalytic Au deposition occurred only when core-shell nanoparticles having a void space between the core and shell, i.e., a jingle-bell-shaped structure, were used. These core-shell nanoparticles were prepared by size-selective photoetching of SiO₂ -covered CdS nanoparticles. The size of Au nanoparticles could be controlled by adjustment of the void space in SiO₂-covered CdS. Dissolution of CdS by acid treatment from the Au-deposited jingle-bell nanoparticles did not have any effect on the surface-plasmon absorption by Au. These facts indicate that Au nanoparticles of adjustable size can be prepared in an SiO₂ shell that prevents mutual coalescence of Au nanoparticles but allows permeation of molecules and ions.     

Synthesis of metal–cadmium sulfide nanocomposites using jingle-bell-shaped core-shell photocatalyst particles

Photocatalytic deposition of gold (Au) and silver (Ag) nanoparticles was investigated using jingle-bell-shaped silica (SiO₂)-coated cadmium sulfide (CdS) nanoparticles (SiO₂/CdS), which each had a void space between the CdS core and SiO₂ shell, as a photocatalyst. A size-selective photoetching technique was used to prepare the jingle bell nanostructure of SiO₂/CdS. Nanoparticles of Au and Ag were deposited by irradiation of the photoetched SiO₂/CdS in the presence of the corresponding metal complexes under deaerated conditions. Chemical etching of Au-deposited particles enabled the selective removal of CdS without any influence on the surface-plasmon absorption of Au. TEM analyses of the resulting particles suggested that some particles were encapsulated in hollow SiO₂ particles, while other Au particles were deposited on the outer surface of the SiO₂ shell. Emission spectra of the photoetched SiO₂/CdS showed that the metal deposition developed a broad emission with a peak around 650 nm originating from surface defect sites, the degree being dependent on the kind of metal nanoparticles and their amount of deposition. This fact can be explained by the formation of metal–CdS binary nanoparticles having defect sites at the interface between metal and CdS.     

Supramolecular Chromatographic Separation of C60 and C70 Fullerenes: Flash Column Chromatography vs. High Pressure Liquid Chromatography

A silica-bound C-butylpyrogallol[4]arene chromatographic stationary phase was prepared and characterised by thermogravimetric analysis, scanning electron microscopy, NMR and mass spectrometry. The chromatographic performance was investigated by using C₆₀ and C₇₀ fullerenes in reverse phase mode via flash column and high-pressure liquid chromatography (HPLC). The resulting new stationary phase was observed to demonstrate size-selective molecular recognition as postulated from our in-silico studies. The silica-bound C-butylpyrogallol[4]arene flash and HPLC stationary phases were able to separate a C₆₀- and C₇₀-fullerene mixture more effectively than an RP-C₁₈ stationary phase. The presence of toluene in the mobile phase plays a significant role in achieving symmetrical peaks in flash column chromatography.     

P25@SiO2核壳材料的制备及其选择性光催化性能的研究

目的构筑具有尺寸选择性光催化功能的复合纳米结构,在维持二氧化钛材料光催化性能的同时,减少其对有机大分子材料及有机基底材料的腐蚀行为,拓宽光催化材料的使用范围。方法采用一锅法,通过TEOS围绕P25为核进行水解,制备了多孔SiO_2包覆TiO_2(P25)复合核壳结构(P25@SiO_2)纳米颗粒。结果 TEM、XRD、BET表征显示,这种复合核壳纳米结构具有较好的分散性和很高的比表面积(约528 m2/g)。光催化性能实验证实,这种复合核壳结构具有尺寸选择性光催化效应,即小分子氮氧化物气体(NOx)能通过壳层SiO_2孔道进入核层并降解90%以上,被氧化成硝酸盐固定下来;小分子有机物亚甲基蓝能穿过壳层孔道进入复合结构的核层部分,被氧化分解;大分子有机物胭脂红被壳层有效隔离而不被分解。老化试验显示,涂覆有这种核壳结构材料的有机基材(PET膜)被氧化老化的现象受到抑制。相反,与裸露的有机基材(PET膜)相比,由于壳层的保护作用,涂覆有核壳纳米结构的有机基材具有更好的抗紫外线性能。结论开发的这种具有尺寸选择性光催化的复合核壳结构材料,可以涂覆在各种有机基材的表面,赋予其一定的光催化功能,同时由于壳层的隔离保护作用,对基材的腐蚀作用受到抑制。这种复合核壳纳米结构也可以作为功能添加材料添加到各种涂料材料中,并赋予涂料一定的光催化性能,同时对涂料中的有机物不会产生强烈的分解作用,因此具有很好的应用前景。