Abstract:
Fundamental photophysical studies in eco-friendly as well as biocompatible quantum
dots (QDs) are essential to realize the unique size dependent optoelectronic properties
of QDs in practical applications. In this regard, the current thesis focuses on
investigating the light harvesting properties in Copper Indium Sulphide (CuInS2) QDs.
A precise surface engineering helped in imparting aqueous stability and tuning of
surface charge of CuInS2/ZnS (CIS) QDs, with ~60% retention of its
photoluminescence quantum yield. Further, the ability of CIS QDs to participate in light
harvesting processes in aqueous medium is investigated. A light induced electron
transfer in the Near Infrared (NIR) region is successfully demonstrated with CIS QDs
as the donor and Indocyanine green (ICG) dye as the acceptor. The process of
electron transfer was confirmed by carrying out quenching experiments under (i) Ar
atmosphere, (ii) varying temperature and (iii) different solvent polarity. The efficiency of
electron transfer was estimated to be as high as 85 % in aqueous medium, which is
attributed to the strong electrostatic attraction between cationic CIS QD and anionic
ICG dye. The use of CIS QDs as an efficient electron donor was extended towards
methylene blue acceptor dye as well. Our studies help in expanding the scope of ecofriendly CuInS2 QDs beyond organic solvents, thereby enabling its future potential use
in both optoelectronic and biomedical applications.
