Fabrication of jingle-bell-shaped core-shell nanoparticulate films and molecular-size-responsive photoluminescence quenching of cadmium sulfide cores
Fabrication of jingle-bell-shaped core-shell nanoparticulate films and molecular-size-responsive photoluminescence quenching of cadmium sulfide cores
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DOI：
10.1002/smll.200500512
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发表时间：
2006-07-01
期刊：
影响因子：
13.3
通讯作者：
Ohtani, Bunsho
中科院分区：
文献类型：
--
作者：
Iwasaki, Kentaro;Torimoto, Tsukasa;Ohtani, Bunsho
使用半导体纳米颗粒作为功能元件的化学传感器的设计和制备已经引起了人们的极大兴趣。[1-10]这类传感器中经常使用的化学物质的检测涉及测量纳米颗粒的结构和浓度依赖的光致发光强度，这是基于纳米颗粒表面吸附的化学物种。纳米颗粒具有相对较大的比表面积来吸附化学物质，因此对器件具有优势。然而，众所周知，这种纳米粒子是不稳定的，除非稳定剂(如硫醇化合物[3-8，12，13]或三烷基氧膦[9-11])被强烈吸附在粒子上，否则会因为它们的高表面能而聚集成更大的粒子。然而，对于基于半导体纳米颗粒光致发光性质的化学传感，以及其他利用颗粒表面作为化学反应场所的器件，表面吸附的有机稳定剂层的存在是不利的，因为它们可能会阻碍目标分子从溶液相扩散到纳米颗粒表面。我们最近报道了利用尺寸选择光刻技术制备铃铛形二氧化硅(SiO_2)包裹的硫化镉(CDS)纳米颗粒(SiO_2/CDS)。[14]光刻的CDS核心表面裸露，其周围的SiO_2壳层足够多孔，可以容纳小离子物种，如镉和羟基，但不能让大分子(如甲基紫精)通过。尽管目前还没有关于SiO_2壳层孔径的详细信息，但这些事实使我们能够基于叮当状的SiO_2/CDS的光致发光特性来构建一种新型的尺寸选择分子检测系统，其中SiO_2壳层不仅作为简单的屏障防止粒子聚集，而且作为筛子来选择目标分子，而裸露的CDS核心作为检测位置。要在固体器件中利用这些粒子，必须将它们固定在固体衬底上。在本研究中，利用朗缪尔-布洛杰特技术大规模地制备了均匀的纳米颗粒薄膜。[15]在空气-水界面制备了单层二氧化硅/硫化镉薄膜，并在玻璃衬底上进行了沉积。对所得薄膜进行尺寸选择光刻蚀以修饰SiO_2/CDS纳米结构，然后以不同种类的三烷基胺为模型衬底，研究了SiO_2/CDS薄膜的光致发光猝灭行为。
Much interest has been shown in the design and preparation of chemical sensors using semiconductor nanoparticles as functional components.[1–10] The detection of chemicals often employed in such sensors involves measurement of the structure-and concentration-dependent intensity of photoluminescence of the nanoparticles, which is based on adsorbing chemical species on their surfaces. Nanoparticles are advantageous for devices since they have relatively large specific surface areas to adsorb chemical species. However, it is also well known that such nanoparticles are unstable and tend to coalesce into larger particles because of their high surface energy, unless stabilizing agents (such as thiol compounds [3–8, 12, 13] or a trialkylphosphine oxide [9–11]) are strongly adsorbed onto the particles. However, for chemical sensing based on the photoluminescence properties of semiconductor nanoparticles, as well as for other devices utilizing the particle surface as a chemical reaction site, the presence of organic layers of stabilizing agents adsorbed on the surface is unfavorable because they may act as a barrier for the diffusion of target molecules from the solution phase to the surface of nanoparticles. We have recently reported the preparation of jingle-bellshaped silica (SiO2)-coated cadmium sulfide (CdS) nanoparticles (SiO2/CdS) using the size-selective photoetching technique.[14] The photoetched CdS cores had bare surfaces, and their surrounding SiO2 shells were porous enough for small ionic species such as Cd2+ and OHÀ, but not for larger molecules (such as methyl viologen), to pass through. Although detailed information on the pore size in a SiO2 shell has not yet been obtained, these facts enable us to fabricate a novel type of size-selective molecular detection system based on the photoluminescence properties of jingle-bell-shaped SiO2/CdS, where the SiO2 shell layer acts not only as a simple barrier to prevent particle coalescence but also as a sieve to select target molecules, while the bare CdS core serves as a detection site.To utilize these particles in solid devices, it is necessary to immobilize them onto solid substrates. In this study, the Langmuir–Blodgett technique was employed to make uniform nanoparticulate films on a large scale.[15] A monoparticulate layer of SiO2/CdS was prepared at an air–water interface and accumulated on glass substrates. The obtained films were subjected to size-selective photoetching to modify the nanostructure of SiO2/CdS, and then the photoluminescence quenching behavior of the SiO2/CdS films was investigated by using various kinds of trialkylamines as model substrates.