Size quantization effect in water-dispersible LEEH capped ZnSe nanocrystals

Abstract

Herein we report the synthesis of LEEH capped water-dispersible ZnSe (Zinc Selenide) nanocrystals using a low temp (80 °C) solution processable chemical route. The reaction parameters such as reaction time, temperature, concentrations of reactants and capping agent were tuned to achieve water dispersible ZnSe nanocrystals of average size, 2 nm with improved photophysical properties. The structure, size and optical properties of the nanocrystals are evaluated from XRD, HRTEM, optical absorption and photoluminescence studies. Both HRTEM and XRD analysis indicate polycrystalline cubic phase of ZnSe with size in the range of 2.0 nm. A strong excitonic absorption peak appearing at 385 nm in the absorption spectrum suggests the size quantization effect in ZnSe nanocrystals marked by a large blue shift from its bulk band gap. Photoluminescence of ZnSe nanocrystals at 300 K exhibit multiband spectral feature appearing with a low intensity peak at 414 nm leading to a large nonresonant stokes shift by 29 nm.