Surfactant-mediated variation of band-edge emission in CdS nanocomposites

The optical–structural characteristics of the direct optical band-gap semiconducting series of surfactant template-mediated laminar (CdS)x(CdCl2)y(CnH2n+4N)z nanocomposites are reported. X-ray diffraction measurements of the nanocomposites exhibited interlaminar distances in the range 2.9–3.6 nm with observations of eighth order {00l} diffraction planes indicative of a high degree of laminarity and crystallographic order. Diffuse reflectance measurements have determined that the profile of their emission spectrum is that of a direct band-gap with absorption edges in the range 2.11–2.40 eV, depending on the CdS mole fraction in the nanocomposite. Photoluminescence (PL) excitation and time-resolved PL spectroscopies give an estimate of the maximum relative absorbance of the nanocomposites at ∼∼420 nm while the minimum was observed at ∼∼560 nm. The main emission was observed at ∼∼700 nm with emission from doubly ionized sulphur vacancies observed at ∼∼615 nm at room temperature. The CdS-containing nanocomposite is thus a surfactant-mediated modular system with variable band-gap energy emission.