InP/ZnS Quantum Dots for High-Sensitivity Temperature Sensors

In this work, we report the synthesis of high-quality, nontoxic InP/ZnS core-shell quantum dots (QDs). The temperature-dependent optical properties such as photoluminescence (PL), absorption, and PL decay with time have been investigated. Based on the temperature dependence of optical properties of QDs, three different configurations of temperature sensors using PMMA as the QD host material were fabricated. The temperature sensor configurations are planar thin-film (InP/ZnS QD)/PMMA deposited on a Si wafer (sensor 1), (InP/ZnS QD)/PMMA-filled borosilicate fibers (sensor 2), and InP/ZnS QD-doped electrospun PMMA nanofibers deposited on a Si wafer (sensor 3). After fabrication, the performance of the temperature sensors have been thoroughly investigated through photoluminescence reversibility tests in consecutive heating-cooling cycles, and the sensitivity of the sensors has been calculated. The three sensors have shown different critical reversible temperatures above which they go through irreversible structural damage and lose their reversibility. The highest critical reversible temperature of 95 °C and the highest sensitivity of 2.1% °C^-1 have been achieved, which are comparable to Cd- and dye-based temperature sensors reported to date. The sensors were found to be highly stable, which demonstrated negligible degradation even after 30 days of exposure to ambient conditions. The InP/ZnS QD-based optical temperature sensors can be considered to be a potential replacement for toxic heavy-metal QD-based optical temperature sensors.