Effect of size and shell: Enhanced optical and surface properties of CdS, ZnS and CdS/ZnS quantum dots

•Systematic study on size tunable and highly stable wurtzite CdS, ZnS and CdS/ZnS quantum dots have been attained.•Consequence of size and shell thickness was analysed.•Size dependent blue shift in absorbance has been discussed with theoretical models.•Enhanced luminescence and superior monochomaticity on CdS/ZnS formation.•Existence of OH, CH2 and C‐O functional groups and hence attachable to biomolecules.

This study reports systematic structural, optical and surface studies on wurtzite CdS, ZnS and CdS/ZnS quantum dots where the effects of size and shell thickness were analysed. Size tunable, stable and luminescent quantum dots (QDs) and their core/shell structures were synthesized by wet chemical growth method at low temperature using 2-mercaptoethanol as a stabilizer. Formation of non-agglomerated wurtzite QDs with reduced particle sizes have been confirmed from x-ray diffraction and transmission electron microscopy studies. Size dependent blue shifts have been observed by absorbance spectroscopy and discussed on the basis of various theoretical models. Significantly enhanced luminescence and monochromaticity have been observed in QDs due to particle size reduction and on core/shell structure formation. Fourier transform infrared spectroscopy indicates that OH, CH2 and C‐O functional groups are present on the QDs surfaces and for this reason these QDs can be used in various biological applications.

Graphical abstractConsequence of size/shell thickness attained in wurtzite CdS/ZnS quantum dots (QDs); analysed for excellent luminescence with brilliant monochromaticity and bioconjugatable functional groups on QDs surface.Figure optionsDownload full-size imageDownload as PowerPoint slide