Biological synthesis of novel carbon quantum dots using Halimeda opuntia green algae with improved optical properties and electrochemical performance for possible energy storage applications

Carbon quantum dots, known to be nanomaterials with zero dimension have recently emerged as excellent materials for versatile technological applications in optoelectronics, energy storage and conversions. They possess simple and low-cost synthesis methods with outstanding optical properties, low toxicity, high bio-compatibility with favourable charge transfer and electronic conductivity. Recently, much attention has been paid towards the eco-friendly synthesis of carbon dots from sources such as biomass as the precursors which provides solution to global challenges of waste management. Carbon quantum dots (CQDs) have attracted greater attention as energy storage materials because of their unique electrical properties and ability to host various functional groups on the electrode surface. Recently CQDs have been utilized as electrode materials towards enhancing the energy density of supercapacitors. Herein we report the biological synthesis of CQDs using biomass such as green algae of Halimeda opuntia. The obtained CQDs were characterized by High Resolution Transmission electron microscopy (HR-TEM), X-ray Diffraction (XRD), Fourier Transform-Infra Red (FT-IR) spectroscopy, UV-Vis Spectroscopy. The fluorescence properties were analysed through emission spectra. The electrochemical performance of CQDs as a supercapacitor were studied using modified Glassy Carbon Electrode (GCE). The CQDs synthesized from Halimeda opuntia green algae exhibits a specific capacitance of 311 F g-1. Due to excellent optical properties and electrochemical performances, these CQDs synthesized using Halimeda opuntia could potentially be used in energy storage and conversion applications.