Orange-red luminescence from Cu doped CdS nanophosphor prepared using mixed Langmuir-Blodgett multilayers

Cu doped CdS nanophosphors were fabricated through Langmuir-Blodgett route for the first time. Precursors mixed Langmuir-Blodgett multilayers of cadmium arachidate-copper arachidate were used to grow doped sulfide nanoparticles within the organic matrix through postdeposition treatment with H2S gas. Changes in composition and layered structure of precursor multilayers were studied using Fourier transform infrared and x-ray reflection. Uptake of Cu in the multilayers was analyzed by inductively coupled plasma atomic emission spectroscopy measurements. Unannealed H2S exposed multilayers containing CdS nanoparticles show strong surface state emission centeredat similar to 570 nm, whereas Cu doped CdS nanoparticles show orange-red luminescence. Photoluminescence (PL) spectra of annealed-Cu doped CdS nanoparticles show distinct Cu-related emission compared to annealed-undoped CdS nanoparticles. Power dependent PL measurements of annealed samples show that an efficient carrier recombination takes place at T-2 level of Cu++. The carrier relaxation from the excitonic states to T-2 level results in the strong orange-red luminescence.