title: Effect of reduced graphene oxide-hybridized ZnO thin films on the photoinactivation of Staphylococcus aureus and Salmonella enterica serovar Typhi.
abstract: The immobilization of photocatalyst nanoparticles on a solid substrate is an important aspect for improved post-treatment separation and photocatalyst reactor design. In this study, we report the simple preparation of reduced graphene oxide (rGO)-hybridized zinc oxide (ZnO) thin films using a one-step electrochemical deposition, and investigated the effect of rGO-hybridization on the photoinactivation efficiency of ZnO thin films towards Staphylococcus aureus (S. aureus) and Salmonella enterica serovar Typhi (S. Typhi) as target bacterial pathogens. Field-emission scanning electron microscopy (FESEM) revealed the formation of geometric, hexagonal flakes of ZnO on the ITO glass substrate, as well as the incorporation of rGO with ZnO in the rGO/ZnO thin film. Raman spectroscopy indicated the successful incorporation of rGO with ZnO during the electrodeposition process. Photoluminescence (PL) spectroscopy indicates that rGO hybridization with ZnO increases the amount of oxygen vacancies, evidenced by the shift of visible PL peak at 650 to 500nm. The photoinactivation experiments showed that the thin films were able to reduce the bacterial cell density of Staph. aureus and S. Typhi from an initial concentration of approximately 10(8) to 10(3)CFU/mL within 15min. The rGO/ZnO thin film increased the photoinactivation rate for S. aureus (log[N/No]) from -5.1 (ZnO) to -5.9. In contrast, the application of rGO/ZnO thin film towards the photoinactivation of S. Typhi did not improve its photoinactivation rate, compared to the ZnO thin film. We may summarise that (1) rGO/ZnO was effective to accelerate the photoinactivation of S. aureus but showed no difference to improve the photoinactivation of S. Typhi, in comparison to the performance of ZnO thin films, and (2) the photoinactivation in the presence of ZnO and rGO/ZnO was by ROS damage to the extracellular wall.
authors.affiliation: Nanotechnology and Catalysis Research Centre, Institute of Graduate Studies, University of Malaya, Malaysia.
authors.forename: Swe Jyan
authors.initials: SJ
authors.lastname: Teh
authors.affiliation: Institute of Biological Sciences, Faculty of Science, University of Malaya, Malaysia.
authors.forename: Soo Ling
authors.initials: SL
authors.lastname: Yeoh
authors.affiliation: Nanotechnology and Catalysis Research Centre, Institute of Graduate Studies, University of Malaya, Malaysia.
authors.forename: Kian Mun
authors.initials: KM
authors.lastname: Lee
authors.affiliation: Nanotechnology and Catalysis Research Centre, Institute of Graduate Studies, University of Malaya, Malaysia.
authors.forename: Chin Wei
authors.initials: CW
authors.lastname: Lai
authors.affiliation: Nanotechnology and Catalysis Research Centre, Institute of Graduate Studies, University of Malaya, Malaysia. Electronic address: sharifahbee@um.edu.my.
authors.forename: Sharifah Bee
authors.initials: SB
authors.lastname: Abdul Hamid
authors.affiliation: Institute of Biological Sciences, Faculty of Science, University of Malaya, Malaysia. Electronic address: thongkl@um.edu.my.
authors.forename: Kwai Lin
authors.initials: KL
authors.lastname: Thong
mesh_terms: D006108:Graphite / Q000737:chemistry*; D008027:Light; D008855:Microscopy, Electron, Scanning; D049329:Nanostructures / Q000737:chemistry / Q000633:toxicity*; D010087:Oxides / Q000737:chemistry; D017382:Reactive Oxygen Species / Q000378:metabolism; D012485:Salmonella typhi / Q000187:drug effects* / Q000528:radiation effects; D013059:Spectrum Analysis, Raman; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000528:radiation effects; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D010087:Oxides; D017382:Reactive Oxygen Species; D006108:Graphite; D015034:Zinc Oxide
keywords: Photoinactivation; Reduced graphene oxide; Salmonella enterica serovar Typhi; Staphylococcus aureus; ZnO thin films