Preparation and characterization of water-soluble jingle-bell-shaped silica-coated cadmium sulfide nanoparticles
Preparation and characterization of water-soluble jingle-bell-shaped silica-coated cadmium sulfide nanoparticles
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DOI：
10.1021/jp049814i
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发表时间：
2004-08-12
影响因子：
3.3
通讯作者：
Ohtani, B
中科院分区：
文献类型：
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作者：
Iwasaki, K;Torimoto, T;Ohtani, B
处理表面硅烷醇基团与亲水性化合物使二氧化硅包覆的硫化镉（SiO2/CdS）纳米粒子的核壳形态溶解在水/甲醇混合物。通过用458 nm的单色光照射来进行颗粒的尺寸选择性光刻，由于CdS的尺寸减小，导致其吸收起始的蓝移。TEM分析表明，SiO2壳结构不会因光刻而收缩，并且空隙空间（约1000 nm）也不会因光刻而收缩。2.3 nm）之间形成的US核和SiO2壳，得到一个叮当声结构。当加入镉离子（Cd 2+）并将pH调节至10时，光蚀刻颗粒的发射光谱显示出带隙发射的发展，而原始颗粒的相同处理没有给出归属于带隙发射的峰，这表明SiO2壳对于小离子物种如Cd 2+是充分多孔的以穿透壳，并且结合在SiO2壳中的光刻US核具有裸露的表面，该裸露的表面被氢氧化镉层覆盖。随着壳层厚度的增加，CdS的光刻速率降低的结果，在美国的光生电子的清除率下降的电子受体，如O-2和甲基紫精（MV 2+）在溶液中。通过用3-巯基丙酸（MPA）和3-巯基丙基三甲氧基硅烷（MPTS）对US进行表面改性，然后水解其三甲氧基甲硅烷基，从而改变SiO2层的结构。FT-IR光谱表明，MPA分子，但不是MPTS分子，附着在美国核心表面被消除的颗粒的光刻，导致在SiO2壳窗口的形成。US发射猝灭的行为表明，MV 2+通过窗口传输到SiO2壳内的空隙空间，到达US核心。
Treatment of surface silanol groups with hydrophilic compounds enabled silica-coated cadmium sulfide (SiO2/CdS) nanoparticles of core-shell morphologies to be dissolved in a water/methanol mixture. Size-selective photoetching of the particles was performed by irradiation with monochromatic light at 458 nm, resulting in a blue shift of its absorption onset because of the decreasing size of the CdS. TEM analyses revealed that the SiO2 shell structure was not shrunken by photoetching and that a void space (ca. 2.3 nm) was formed between the US core and the SiO2 shell to give a jingle-bell structure. The emission spectra of photoetched particles showed the development of band-gap emission when cadmium ion (Cd2+) was added and the pH was adjusted to 10, whereas the same treatment of original particles gave no peaks assigned to band-gap emission, indicating that the SiO2 shell was sufficiently porous for small ionic species such as Cd2+ to penetrate through the shell and that the photoetched US core incorporated in the SiO2 shell had a bare surface to be covered with a cadmium hydroxide layer. With increasing shell thickness, the rate of CdS photoetching was reduced as a result of decrease in the rate of scavenging of the photogenerated electrons in US by electron acceptors such as O-2 and methyl viologen (MV2+) in solution. The structure of the SiO2 layer was varied by surface modification of the US with both 3-mercaptopropionic acid (MPA) and 3-mercaptopropyltrimethoxysilane (MPTS) followed by hydrolysis of its trimethoxysilyl group. FT-IR spectra showed that MPA molecules, but not MPTS molecules, attached to the US core surface were eliminated by photoetching of the particles, resulting in the formation of windows in the SiO2 shell. The behavior of US emission quenching suggested that MV2+ is transported through the windows to the void space inside the SiO2 shell to reach the US core.