Executive Summary : | Recent advancements in crystal studies have highlighted lattice strain as a crucial factor in understanding structure-function relationships in various functional materials. Lattice strain engineering has become a fundamental approach to enhance and optimize the performance of various crystalline materials, such as perovskites, quantum dots, and photocatalytic nanocrystals. This research aims to conduct lattice engineering of infra-red (NIR)-upconverting core-shell nanocrystals (CS-UCNCs), which can convert higher energy 808 nm photon excitation into lower energy visible photons. CS-UCNCs have been used in NIR photon-induced non-invasive therapy and diagnostics. However, the weaker intensity of visible photoluminescence (PL) emission due to the parity forbidden photon-upconversion (UC) process is a major obstacle for effective clinical application.
The proposed study aims to perturb local symmetry around the activator (Ln3+) ions to facilitate the Laporte forbidden transition by creating atomic level disorder. The optimum atomic level disorder for maximum emission intensity in CS-UCNC can be achieved through optimization of the concerned lattice strain. The study will synthesize and spectroscopically analyze a series of CS-UCNC with varying amounts of Li+ dopant, acting as a symmetry perturbing agent and lattice strain modulator. The structural analysis will be carried out using high energy synchrotron X-ray probing technique and neutron diffraction technique, which can decode how lattice strain engineering can be rationally carried out by imparting disorder at the atomic scale to create CS-UCNC with the most intense photoluminescence property. |