Insight on Photocatalytic and Photoinduced Antimicrobial Properties of ZnO Thin Films Deposited by HiPIMS through Thermal Oxidation

Abstract

Zinc oxide thin films have been developed through thermal oxidation of Zinc thin films grown by high impulse power magnetron sputtering (HiPIMS). The influence of various sputtering power on thin film structural, morphological, photocatalytic, and antimicrobial properties was investigated. X-ray diffraction (XRD) analysis confirmed that the crystalline phase of ZnO thin films consists of a hexagonal wurtzite structure. Increasing the sputtering power will lead to intrinsic stress on thin films that promote whisker formation. In this study, whiskers were successfully developed on the thin films without precursors/catalysts and not thermally treated over the Zn melting point. This finding showed that the film phase structure and morphology are significantly affected by sputtering power. It was found that ZnO thin films exhibit high photocatalytic performance under UV irradiation (89.91%) of methylene blue after 300 min of irradiation. The antimicrobial activity on ZnO thin films showed significant inhibition activity (p < 0.05) against E. coli, S. aureus, and C. albicans. However, the whisker formation on ZnO thin films is not accessible to enhance photocatalytic and antimicrobial activity. This study demonstrates that the HiPIMS method through the thermal oxidation process can promote a good performance of ZnO thin films as photocatalyst and antimicrobial agents.

Analysis of Antibacterial and Antiviral Properties of ZnO and Cu Coatings Deposited by Magnetron Sputtering: Evaluation of Cell Viability and ROS Production

“…Moreover, different factors affect antimicrobial efficiency, including the initial amount of bacteria or virus applied on the tested sample, incubation time, temperature, and quantification method. For example, in a previous study, a ZnO deposited sample demonstrated significant inhibition of E. coli and S. aureus, up to 100% [62]. However, the number of bacteria applied on the ZnO samples was 4 × 10 3 CFU/per sample, which is extremely low compared to those used in our study (3.0 × 10 6 CFU/per sample), which made it possible to demonstrate up to a 6 log reduction rate.…”

Influence of Fluorine and Nitrogen Co-Doping on the Structural and Morphological Properties of Sol-Gel ZnO Films

“…The crystallite size effect can also be considered, as it was determined that ZnO:N:F films (Sol 2) have the smallest crystallites (see Table 1). The obtained optical band gaps of sol-gel ZnO and doped ZnO films are in the range of the reported values [8,15,16,19,35,57].…”

“…On the other hand, ZnO:N:F films (Sol 2) possess the lowest E g values except for the value of 300 • C annealed samples. It was previously reported that F doping induces the widening of the optical band gap of the sol-gel ZnO films [35,56]. The increase of the energy gap values of ZnO films with the increase of the fluorine concentration can be attributed to the well-known Burstein-Möss effect.…”

“…The weaker diffractions at 38.3 • , 44.5 • and 53.2 • are detected for ZnO:N:F films and for ZnO (the two lower angle lines). They can be probably attributed to ZnO 2 phase [34] or to Zn [35]. No secondary phases corresponding to F or N are detected.…”

Various Applications of ZnO Thin Films Obtained by Chemical Routes in the Last Decade

“…In the last decade, the development of nanostructures with various morphologies [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ] such as: nanowires, nanorods (NR), nanoflowers, nanosheets, nanobelts, nanoneedles, nanoplates, has gained tremendous attention, being used in biological applications [ 8 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ]: bioimaging, biosensing, antibacterial and drug delivery agents. In particular, ZnO thin films have optical (photoluminescence) [ 33 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ], electrical (thermoelectric [ 43 , 44 , 45 , 46 ], piezoelectric [ 47 , 48 , 49 , 50 , 51 , 52 , 53 ]) and biological (antimicrobial [ 54 , 55 , 56 ], antibacterial [ 57 , 58 , 59 ]) characteristics, which make them excellent candidates for the development of optoelectronic [ 60 , 61 , 62 , 63 , 64 , 65 ], piezoelectric [ …”