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Researchers at the Indian Institute of Science Education and Research (IISER), Thiruvananthapuram and IIT Indore developed an artificial light-harvesting device that captures light efficiently for power conversion. It mimics photosynthesis, which is how plants absorb sunlight and make sugars.

Chemical Science, a journal published annually by the Royal Chemical Society, published the results. The paper has been co-authored by Sukhendu Mandal, Associate Professor, Department of Chemistry, IISER Thiruvananthapuram, along with his research scholars Sourav Biswas and Anish Kumar Das; and Biswarup Pathak, Department of Chemistry, IIT Indore; along with research scholar Surya Sekhar Manna.

Researchers said that scientists around the world were focusing on reproducing photosynthesis’ light-harvesting stage in engineered systems. These systems could be used in solar cells or artificial leaves. The light-harvesting cells in plants and other photosynthetic organisms are called chromophores. These molecules absorb visible light and then pass it on to other parts that use the energy for chemical reactions. The sun’s energy is absorbed by the topmost chromophores. The chromophores can be arranged in an array and the energised, chromophore transfers the energy to the adjacent chromophore. The energy is rapidly accumulated until it reaches its destination.

The authors state that there have been numerous attempts to replicate the molecular or atomic structure of light-harvesting in laboratory. To mimic photosynthesis, polymeric structures, detergent-type molecules and vesicles have all been used. These molecules face the most serious problem of light extinction due to aggregation, or bunching together of the molecules. This causes poor light capture and conversion efficiency.

Scientists from IISER Thiruvananthapuram, IIT Indore and IIT Indore discovered a way to solve the problems with artificial light absorbers or transmitters. The scientists have used silver clusters that measure only a nanometer in size, which is a hundred thousand times smaller then the width of a human hair. These nanoclusters exhibit fascinating structures and unique photophysical properties. These nanoclusters were stabilized with bulky ligands by the researchers. The entire ensemble was then trapped inside a large molecule called Cyclodextrin.

This fundamental research into energy transfer systems that are highly efficient will allow them to design new light-harvesting materials. They also believe this will help reduce energy loss and improve the efficiency of solar cells. This is crucial as India wants to reduce its carbon footprint by 2070, and get 50% of its electricity from renewable sources by 2030.