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Recent years have witnessed the growing interest in Zinc oxide (ZnO) in nanoscale size on antimicrobial and nanomedicine applications. Two main antimicrobial mechanisms of ZnO, photo-catalysis, and Zn2+, ion release has left some possibilities for some improvement, including producing hybrid metal-ZnO nanoparticles and introducing dopant material into ZnO structure. Silver (Ag) is applied to the ZnO structure to improve the antimicrobial properties of ZnO by modifying the optical and structural properties of ZnO such that the photo-catalysis mechanism can work under normal ambient room light conditions. Ag+ ion release is expected to work in synergy with the photo-catalysis mechanism of ZnO. Pulsed laser ablation in liquid (PLAL) technique is a very promising technique to produce nanoparticles as an antibacterial agent which requires high purity and clean surface of the nanoparticle. In this work, PLAL has been performed in pure water as the solution to produce ZnO and ZnO-Ag nanoparticles, by varying Ag ablation time 1, 3, and 5 minutes expecting various concentrations of Ag in the sample. All samples were tested to inactivate Staphylococcus aureus (S. aureus) growth for 12 hours' incubation time, which shows a very prominent result. The number of living bacteria was found to be 4.42 log CFU/mL after 12 hours in contact with pure ZnO nanoparticle and it reduced significantly down to 1.48, 1.00 and 2.83 log CFU/mL respectively after contact with ZnO-Ag nanoparticle sample by varying Ag ablation time of 1, 3 and 5 minutes. [ABSTRACT FROM AUTHOR]

We successfully developed a method utilizing colloidal CdSe nanocrystalline quantum dot for anticounterfeiting label on a piece of glossy paper. We deposited numbers and lines patterns of toluene soluble CdSe quantum dot using rubber stamper on a glossy paper. The width of line pattern was about 1-2 mm with 1-2 mm separation between lines. It required less than one minute for deposited CdSe quantum dot on glossy paper to dry and become invisible by naked eyes. However, patterned quantum dot become visible using long-pass filter glasses upon excitation of UV lamp or blue laser. We characterized photoluminescence of line patterns of quantum dot, and we found that emission boundaries of line patterns were clearly observed. The error of line size and shape were mainly due to defect of the original stamper. The emission peak wavelength of CdSe quantum dot was 629 nm. The emission spectrum of deposited quantum dot has full width at half maximum (FWHM) of 30-40 nm. The spectra similarity between deposited quantum dot and the original quantum dot in solution proved that our stamping method can be simply applied on glossy paper without changing basic optical property of the quantum dot. Further development of this technique is potential for anti-counterfeiting label on very important documents or objects. [ABSTRACT FROM AUTHOR]