Indium-doped melanin efficient photocatalyst for water purification from organic pollutants

In this work, undoped and indium-doped eumelanin powdered samples were prepared and experienced as photocatalysts for organic water pollutants. The X-ray diffraction (XRD) analysis shows that the eumelanin samples are completely amorphous, while the indium eumelanin samples have indium crystalline peaks mixed in with the amorphous material. The scanning electron microscopy (SEM) demonstrated the particle size and perimeter decreasing while porosity increasing with indium doping. Fourier-transform infrared (FT-IR) spectroscopy manifests O-H, N-H, and C=O functional groups existence in the samples. The optical investigation has shown that the energy gap values reduced from 2.41 eV for undoped eumelanin to 2.07 eV for indium-doped eumelanin. The photocatalytic performance was optimized through the impacts of UV & visible irradiations, pH values, indium doping, and ultrasonic wave assistance. The highly efficient catalyst of 97.3% ± 0.8% efficiency in 10 sec has been attained by indium-doped eumelanin catalyst upon visible irradiation)100 mW/cm²( and pH (~7 – 8) assisted by ultrasonic waves (40 kHz) with reusability and long-term stability.