Controlled Growth of the Ordered Cadmium Sulfide Particulate Films and the Photoacoustics Investigation

Abstract

Two kinds of cadmium sulfide (CdS) particulate films have been generated in situ by exposing stearic acid (SA) Langmuir monolayer at the air−aqueous CdCl2 interface to hydrogen sulfide (H2S) gas: particulate films composed of oriented rodlike nanocrystals (A-type particulate films), and those of dotlike nanocrystals which formed a stripelike domain with straight edges aligned with 6-fold symmetry (B-type particulate films). The SA- coated CdS particulate films were transferred to a solid substrate and examined by transmission electron microscopy (TEM) and photoacoustic spectroscopy (PAS). The dark field image and the transmission electron diffraction of the TEM were used to study the morphology and growth mechanisms of the CdS particulate films in detail. The PAS of the CdS particulate films composed of the oriented rodlike nanocrystals shows a new peak at 417.5 nm. This peak implies some new physical phenomena corresponding to the ordered alignment of the semiconductor nanocrystals, which exists in the ordered nanosystems. The novel synthesis method described here leads to the fabrication of the highly oriented semiconductor quantum wires and provides a new method to investigate the structure of the Langmuir monolayer at the air−water interface.

Origin of surface trap states in CdS quantum dots: relationship between size dependent photoluminescence and sulfur vacancy trap states

“…This pattern also matched with that of CdS zinc blende crystal structure. 43,44 The zinc blende structure was also obtained by others employing similar noninjection synthesis methods 39 or the injection method. 45 TEM measurements were also conducted for samples with different sizes.…”

One Pot Hemimicellar Synthesis of Amphiphilic Janus Gold Nanoclusters for Novel Electronic Attributes

“…Zhong and co-workers have assembled gold nanostructures in organized molecular films of a series of gemini amphiphiles; hybrid nanocomposite films were fabricated by adsorption of gold nanoparticles on polymeric LB films. , Swami et al have demonstrated the formation of various anisotropic gold nanostructures by in situ reduction of chloroaurate ions, stabilized by surfactants at the air−water interface . In another approach, Ag, Au, CdS, PbS, and CdSe nanoparticles, etc., have been organized at the air−water interface exploiting electrostatic interaction between the precursor ions in the subphase and the oppositively charged Langmuir monolayers, followed by external chemical/photochemical reduction of the precursor compound. − In a slightly different approach, Langmuir monolayers of alkyl amines and vitamin E have acted as reducing agents to synthesize nanoparticles and few reports explain modified reductant subphases. , Due to its unique two-dimensional reaction system in which the interfacial formation of nanostructures is carried out, the method opens new possibilities for morphological control mechanisms of organic−inorganic nanomaterials in novel interfacial reaction systems. , Therefore, a single step in situ surface pressure induced controlled synthesis and fabrication of hybrid nanostructures in which the precursor amphiphile acts as an efficient templating agent warrants attention.…”

One-Step Synthesis and Assembly of Two-Dimensional Arrays of Mercury Sulfide Nanocrystal Aggregates at the Air/Water Interface

“…These nanoparticulate films and nanoparticles were formed at the air/water interface through interfacial reactions between metal ions in the subphases and H 2 S in the gaseous phase under the direction of liquid-condensed or solid monolayers of long-chain fatty acids. This technique has been developed to be a useful tool to synthesize metal sulfide nanoparticles at the air/water interface. − On the other hand, quantum dots (QDs) of metal sulfides, including CdS, − PbS, , ZnS, and HgS , embedded in layered structures, were synthesized successfully by treating the deposited LB multilayers of metal alkanoates or metal alkanoates/thioalkanoates with dry H 2 S gas. It should be noted that the Langmuir monolayers used in these studies are liquid-condensed or solid ones that enrich metal ions from the subphases and/or direct the formation of nanoparticles during the reaction process.…”