Zinc nanoparticles for antibacterial activity of smart-phone panels

The prevention of microbial surface contamination has become most crucial in today’s health care system, and in food and pharmaceutical production. Human beings are often infected by microorganisms such as bacteria, viruses, and molds that often infect living environments. Silver nanoparticles or silver ions have been known to have strong inhibitory and bactericidal effects. Metallic nanoparticles are most promising as they show good antibacterial properties due to their large surface area to volume ratio, which is coming up as the current interest in the researchers due to the growing microbial resistance against metal ions, antibiotics and the development of resistant strains. However, although the silver NPs showed a good antibacterial effect, they exhibited a strong toxicity to humans and a high cost for mass-production. Recently, transparent electronic devices were widely used as the electronic devices were integrated onto the glass panels. All of electronic devices were required to be applied for the antibacterial function, keeping a high transparency comparable to the glass panels. In addition, the mechanical durability of the glass panels with an antibacterial effect is required for long-term applications. In the present study, zinc NPs instead of silver were chosen for antibacterial function and their influence on the transmittance was investigated using samples deposited by optimum conditions. Most of the reported results were mainly focused on the zinc oxide nanoparticles for antibacterial effect. However, zinc oxide nanoparticles were mainly prepared by solution technique, which resulted in an inhomogeneous antibacterial effect due to the severe agglomeration of the nanoparticles. Zinc oxide nanoparticles are very difficult to establish the comparable transmittance to the glass substrate. To the best of our knowledge, the study to enhance both the transmittance and the antibacterial property using pure zinc NPs has not been reported. For enhanced mechanical endurance of the zinc NPs on glass substrate, the Ti NPs were used as an adhesion layer between zinc NPs and glass. The reason that the Ti NPs deposited via a physical vapor deposition (PVD) process exhibited such a strong adhesion with the glass substrates was intensively investigated in the present study. Morphology, transmittance, antibacterial effect, and mechanical endurance of the zinc NP/glass was investigated for different structures such as Zn NPs/glass, Zn NPs/SiO2/glass, and Zn NPs/Ti NPs/glass. Homogeneously distributed zinc nanoparticles (NPs) on the glass substrate were investigated for the transmittance, mechanical durability, and antibacterial effect. The buffered Ti NPs between Zn studied for an enhancement of the transmittance and mechanical endurance. The Ti NPs buffered Zn NPs showed a high transmittance of approximately 91.5% (at a wavelength of 550nm) and a strong antibacterial activity for Staphylococcus aureus and Escherichia coli bacteria. The buffered Ti NPs are attractive for an excellent mechanical endurance of the Zn NPs. The Zn NPs did not require the protection layer to prevent the degradation of the performance for both the antibacterial effect and the transmittance.