Cost effective photocatalytic and humidity sensing performance of green tea mediated copper oxide nanoparticles

Abstract

The presentwork describes the photocatalytic degradation activity of methylene blue dyeand humidity sensing activity usinggreen synthesized copper oxide nanoparticles (CuO NPs) withgreen tea extract as fuel. TheCuO NPs werecharacterized usingXRD, FTIR, UV–visible, SEM, EDX and TEM techniques. The XRD structure confirms the crystalline nature of the CuO NPs with monoclinic phase. The FTIR spectrum manifest the appearance of the Cu-O bonding. The UV spectrum depicted the band gap of 3.84 eV. The spherical shaped morphology has been determined by SEM and TEM studies. Using image-J software the particle size has been calculated and is found to be 64.5 nm. The % degradation ofmethylene blue dye is 99% under UV light and 91% under sunlight within the short duration of 180 min. Thus, the result predicts that the CuO NPs can be used an efficient photocatalyst for pollutant water treatment. The mechanism for photocatalytic degradation was thoroughly discussed. The humidity sensing studies are performed for the CuO NPs, the variation in the resistance is drastic and the CuO NPs have achieved a best sensing response of 99% (7–97% RH) with the response time of 22 s and recovery time of 31 s. The CuO NPs shown least hysteresis and good stability over a period of two months. The sensing mechanism was discussed deliberately.