Structural and optical studies of Zn1−xCdxS quantum dots synthesized by in situ technique in PVA matrix

• In situ synthesis of PVA capped Zn1−xCdxS (x = 0.1, … 0.9) quantum dots.
• UV–Visible absorption edges shifting and band gap tuning effect were observed.
• XRD peak shifted to higher θ with increase in Cd:Zn ratio.
• Quenching of PL intensity is observed with increase in Cd:Zn ratio.
• 3PA nonlinear optical response and limiting properties were studied.

Zn1−xCdxS (x = 0.1, 0.2, 0.3, 0.4, 0.5 … 0.9) quantum dots were synthesized successfully using novel in situ technique in polyvinyl alcohol (PVA) matrix. The PVA acted as a capping agent as well as a reducing agent. The structural and optical properties of the samples were studied by X-ray diffraction (XRD), TEM analysis, UV–Visible absorption and photoluminescence spectroscopy (PL). X-ray diffraction patterns revealed cubic zinc blende phase of the samples with lattice parameter in the range 5.47–5.75 Å. Optical band gap values were calculated from the absorption spectra and observed a decreasing band gap with increasing Cd:Zn ratio. The Raman spectra were recorded using conventional Micro Raman technique. Photoluminescence spectra showed asymmetric broad emission with multiple maxima. The concentration dependent quenching of PL intensity with increasing Cd:Zn ratio was observed along with a red shift. The nonlinear optical (NLO) and limiting properties were studied using Z-scan technique.