Two in One Gram Negative Antibacterial Agent and Organic Dye Photocatalyst from Green Synthesized Ocimum Sanctum‐Based N and O Co‐Doped Carbon Dot Silver Nanocomposite

This study reports, successful synthesis of Oxygen(O) and Nitrogen(N) co-doped Ocimum Sanctum plant-based or tulsi carbon dots-silver nanoparticle nanocomposites (TCD-AgNP) for the development of an efficient, highly active, low-cost fingerprint antibacterial agent against gram-negative organisms and a highly efficient photocatalyst for the degradation of methylene blue (MB). Green synthesized, high quantum yield (47 %), intensely blue fluorescent, highly stable N and O co-doped TCDs from carbonization technique of tulsi leaves is achieved without any chemical treatment or surface fascination which could act as an efficient green reducing agent for the development green TCD-AgNP nanocomposites. The novelty and advantage of this study is the development of highly stable, blue fluorescent, high quantum yield (40 %) environmental -friendly TCD-AgNP nanocomposite through reduction method by using green TCDs. TCD-AgNP nanocomposites were synthesized by varying the concentrations of AgNO₃ into a fixed amount of green TCDs. Spectrochemical characteristics of synthesized TCDs and TCD-AgNP nanocomposites were investigated through UV-Vis absorbance, Photoluminescence (PL) spectroscopy, Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS) and Zeta potential measurements confirming excellent fluorescence, unique stability and effective O and N doping. High-resolution transmission electron microscopy (HR-TEM) images confirms that the synthesized TCDs and TCD-AgNP nanocomposites were spherical in shape with an average size of 6.3 nm and 11.5 nm respectively. The antibacterial studies proved that TCD-AgNP nanocomposites ware highly effective against Gram-negative (Serratia marcescens, E. coli, and Pseudomonas aeruginosa) microbial organisms and showed zones of inhibition 12, 9 and 18 mm as compared to streptomycin sulphate. Besides, TCD-AgNP nanocomposite was used as a photocatalyst for the degradation of MB (10 ppm) under sunlight irradiation for regular intervals of time at room temperature with a photodegradation efficiency of 95.63 % and a photocatalytic rate constant of 0.0195 min^-1.