Sensing, Antimicrobial and Photothermal Activity of Ultra-Stable Colloidal Copper Nanoparticles

Metal nanoparticles are becoming the best choice of materials in a variety of research fields due to their unique physical, chemical and optical properties. Compared to noble metals like gold and silver, copper is highly economic. The copper nanoparticles (CuNPs) possess extraordinary features like surface plasmon resonance in the visible range, antimicrobial and anticancer activities and good adsorptive efficiency which are less investigated. Therefore, in this work, colloidal copper nanoparticles (CCuNPs) were synthesised in a simple chemical reduction method, and their plasmonic behaviour was found to be optimum at precursor: surfactant molar ratio of 1:40 and reaction temperature of 50 °C. The CuNPs exhibited ultra-high stability of more than 234 days. The CCuNPs are efficient for the detection of mancozeb (MCZ) fungicide with a sensitivity of 42 nm/mM within the range of detection of 27–432 µg/mL. The antimicrobial activity of CCuNPs was evaluated, and the zone of inhibition for the bacteria Escherichia coli (20 ± 0.2 mm), Pseudomonas aeruginosa (20 ± 0.2 mm), Bacillus subtilis (19 ± 0.2 mm), Staphylococcus aureus (20 ± 0.2 mm) and the fungus Candida albicans (23 ± 0.2 mm) was obtained. The photothermal studies show a rise in temperature of 2 °C upon illumination with an LED lamp, an efficiency of 16.6% and the stability up to five cycles. This work reveals the promising scope of CCuNPs in the most relevant fields like sensing, antimicrobial and photothermal applications.