Tailoring optical properties of thermally stable Cd_1−xZn_xS:Cu, Mn quantum dots

Copper and manganese co-doped Cd_1−xZn_xS (x ≤ 1) quantum dots have been synthesized successfully using chemical co-precipitation method. XRD results confirm that Cu and Mn co-doped Cd_1−xZn_xS nanocrystallites with size 2–3 nm exhibit wurtzite structure. AFM images indicate about smoothness of the surface. The roughness height and root mean square roughness values are estimated for quantum dots nanomaterial. AFM observations found in close agreement with TEM and XRD results. Particle size determined by UV–visible method has also supported quantum dots formation. The UV–visible spectra have band edge absorption in the wavelength range 350–450 nm while the sharp peaks appeared at 240 nm and 298 nm correspond to defects levels and unreacted nuclei. The optical band gap increases for Cd_1−xZn_xS from x = 0 to x = 0.7. The band-gap is also analyzed by first order absorbance derivative spectroscopy. The photoluminescence investigation reveals broad and asymmetric emission spectra mainly in the blue-green region which may be due to the recombination of defects states. A broad hump at 565 nm probably designated by ⁴T₁ and ⁶A₁ energy levels of Mn²⁺ ions. Thermal properties show that the prepared nanomaterials are found thermally stable. Hence optical properties of the thermally stable Cd_1−xZn_xS:Cu, Mn (x < 1) quantum dots are tailored successfully for technological use.