Rapid and One-Pot Synthesis of Self-Assembled CdSe Quantum Dots Functionalized with β-Cyclodextrin: Reduced Cytotoxicity and Band Gap Engineering.

We report a simple, rapid and one step method for the synthesis and in situ functionalization of CdSe quantum dots (QDs) with β-cyclodextrin (β-CD) in aqueous solution via electron beam (EB) irradiation technique. A probable mechanism has been elucidated for the formation of the QDs using pulse radiolysis technique. The average size of the QDs was found to be in the range of 2-3 nm with a size distribution of -14%. XPS measurements indicate that the -OH groups of the β-CD molecules binds predominantly with the Cd atoms present on the surface of the QDs. These QDs displayed broad photoluminescence (PL) with two emission peaks at 525 nm and 600 nm, which could be tuned by varying the experimental parameters. The broad PL spectrum has been attributed to the polydispersity in the density and the distribution of trap/defects states. Time resolved PL decay measurements further substantiated the domination of surface state originated carrier relaxation processes in the overall PL decay dynamics of QDs synthesized at higher doses and dose rates. The present study reveals that β-CD passivate the QDs by a non-inclusion complex, induces the self-assembling process into a networking architecture and simultaneously reduces their cytotoxicity as compared to the bare nanoparticles. The methodology described in this article may provide unique and interesting aspects to regulate and fine tune the formation of superstructures of nanomaterials vis-à-vis their optoelectronic properties.