Abstract
A series of hybrid cadmium salt/cationic surfactant layered nanocomposites containing different concentrations of cadmium sulphide was prepared by exchanging chloride by sulphide ions in the layered precursor CdXx(OH)y(CnTA)z in a solid phase/gas reaction, resulting in a series of layered species exhibiting stoichiometries corresponding to CdSvXx(OH)y(CnTA)z, constituted by two-dimensional CdCl2/CdS ultra-thin sheets sandwiched between two self-assembled surfactant layers. The electronic structure of CdS in the nanocomposite is similar to that of bulk, but showing the expected features of two-dimensional confinement of the semiconductor. The nanocomposite band gap is found to depend in a non-linear manner on both the length of the hydrocarbon chain of the surfactant and the concentration of the sulphide in the inorganic sheet. The products show photocatalytic activity at least similar and usually better than that of "bulk" CdS in a factor of two.
Highlights
During the last years, much effort has been invested on the development of strategies to assemble inorganic nanoparticles in well-defined arrays
In this work we describe the synthesis of a series of layered single phases in which different amounts of CdS are confined in a CdCl2 matrix
Results described in this paper show that by using adequate synthesis procedures, it is possible to obtain hybrid semiconducting cadmium sulphide nanocomposites in which CdS forms part of two-dimensional ultrathin inorganic sheets sandwiched between two selfassembled surfactant layers
Summary
Much effort has been invested on the development of strategies to assemble inorganic nanoparticles in well-defined arrays. Optical measurements Diffuse reflectance UV-visible (UV-vis) spectra were recorded using a Shimadzu UV-vis spectrophotometer, double beam model 2450 PC, equipped with an integrating sphere The photoluminescence (PL) spectra were recorded at room temperature using a PerkinElmer spectrofluorometer, LS 55 model (PerkinElmer Inc., California, USA). This spectrometer is equipped with a 150-W Xenon lamp source, emission and excitation monochromator configurations and a photomultiplier tube (R-106). Photocatalytic properties The photocatalytic activity of CdS-surfactant nanocomposites was tested using, as reaction model, the photodegradation of methylene blue. Experiments were performed typically using 50 ml of a 2 × 10-5 M aqueous solution of the dye and photocatalyst loadings in the range of 0.5 to 0.6 g/L This solution was irradiated with a UV-visible light source emitting in the 270 to 310 nm range. The change in the concentration of methylene blue in the solution while irradiating was monitored by measuring the absorbance at regular intervals between 30 and 240 min using the UV-visible spectrometer mentioned in “Optical measurements”
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