EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

The amount of fresh water in the globe is just around 1% and part of it is trapped in snowfields/glaciers. The lack of hygienic water in mid to low-income countries has created several health concerns like cholera outbreaks in disaster zones. This project focuses on the methodology of capturing solar radiation for heating water so that in combination with a filtration system, pathogen-and toxin-free water can be made available for drinking. Although there are lots of solar harvesting-related techniques, two problems still exist, producing boiling water (economically) that destroys pathogens and then cooling such water for potability.

Crystalline semiconductor quantum dots (Q-dots) with a size in a similar order to the exciton Bohr radius exhibit discrete energy levels. Depending on their size, these Q-dots can be tuned in the glass matrix to control the absorption and emission of electromagnetic radiation. In our scientific approach, we are exploring the engineering of Q-dots in glass media for efficient solar radiation harvesting and converting the radiation into thermal energy. The Q-dots of rare-earth (RE) and transition-metal (TM) ions will be used to engineer blackbody hotspots as such materials have enhanced absorption properties across a large part of the terrestrial solar radiation spectrum.

In this research, we have been investigating the structural and spectroscopic properties of RE and TM-ion doping of CdS and RE3+-CdS Q-dots in a silicate glass in which the size distribution of the Q-dots was controlled by selecting the TM/RE-ion, melting and post-melting heat treatment of silicate glasses.

The mechanism of captured radiation transferred as thermal energy through the glass interface into the water is analysed using a heat transfer model and radiation absorption spectroscopy. The photothermal heating and Newtonian cooling rates are analysed and compared with the standard Pyrex glass for designing an efficient heat exchanger system for boiling water.