Quantum Dots as Optical Materials: Small Wonders and Endless Frontiers

The contemporary lifestyle has embraced optics and photonics technologies in various ways spanning from communication, computation, energy sector, and medical science, to entertainment. Materials are playing a progressively important role in such technologies. In the last 20 years, low-dimensional materials such as quantum dots (QDs) and core–shell QDs (CSQD) comprising of compounds from II to VI group (CdSe, CdTe, etc.), have attracted attention owing to their cherished characteristics both for fundamental research and practical applications. They provide tunable emission through modifications in their sizes and shapes, and flourish in many areas such as photovoltaics, photo-electronics, light-emitting diode, nonlinear optics, and laser development. In this article, the prevalent synthetic methods are mentioned which employ rigorous conditions of temperature, pressure, passive atmosphere, toxic reducing agents, etc. Thereafter, a one-step efficient synthesis method is developed using an electron beam (EB). CdSe quantum dot (QD) is synthesized in homogeneous (aqueous) as well as in microheterogeneous systems (water-in-oil microemulsions, and ionic liquids) and characterized by recognized instrumental techniques. The radiolytic synthesis yields CdSe nanoparticles known to proceed through hydrated electrons (eaq−). Elegant pulse radiolysis technique is used to investigate the formation dynamics of these nanoparticles. Further, it is shown that the CSQD architecture has been effectively developed isolating the core QDs from the surrounding environment and in effect subdued the formation of defects/traps on the surface. By appropriately selecting first the materials for core and shell and then their size/shape and chemical composition, the band structure of these CSQDs can be modified. This overview focuses on the tailored optoelectronic properties and devices including solar cells, light-emitting diodes, optical switch/limiter, QD laser, and biological/chemical applications. These successes have maintained the momentum of this subject area for a wide-ranging group of scientists and technologists to work for future prospective applications.