Remote epitaxy via graphene has recently attracted significant attention, since it provides the possibility to lift-off the grown epitaxial layer, reuse the substrate, and produce flexible devices. However, extensive research is still necessary to fully understand the III-nitride formation on the van der Waals surface of a two-dimensional material and utilize remote epitaxy to its full potential. In this work, the growth of a GaN epilayer using a GaN/sapphire template covered with monolayer graphene is presented. Metalorganic vapor phase epitaxy is chosen to fabricate both the template and the nitride epilayer on top as a cost-effective approach toward GaN homoepitaxy. One-step and multi-step growth temperature protocols are demonstrated while paying particular attention to the graphene interface. GaN seed formation on graphene is analyzed to identify remote epitaxy. Crystalline quality improvement of the epilayer by adjusting the growth parameters is further discussed to provide useful insights into GaN growth on a GaN/sapphire template via monolayer graphene.

Acinetobacter baumannii is a dangerous hospital pathogen primarily due to its ability to form biofilms on different abiotic and biotic surfaces. The present study investigated the effect of riboflavin- and chlorophyllin-based antimicrobial photodynamic therapy, performed with near-ultraviolet or blue light on the viability of bacterial cells in biofilms and their structural stability, also determining the extent of photoinduced generation of intracellular reactive oxygen species as well as the ability of A. baumannii to form biofilms after the treatment. The efficacy of antimicrobial photodynamic therapy was compared with that of light alone and the role of the photosensitizer type on the photosensitization mechanism was demonstrated. We found that the antibacterial effect of riboflavin-based antimicrobial photodynamic therapy depends on the ability of photoactivated riboflavin to generate intracellular reactive oxygen species but does not depend on the concentration of riboflavin and pre-incubation time before irradiation. Moreover, our results suggest a clear interconnection between the inactivation efficiency of chlorophyllin-based antimicrobial photodynamic therapy and the sensitivity of A. baumannii biofilms to used light. In summary, all the analyzed results suggest that riboflavin-based antimicrobial photodynamic therapy and chlorophyllin-based antimicrobial photodynamic therapy have the potential to be applied as an antibacterial treatment against A. baumannii biofilms or as a preventive measure against biofilm formation.

The remote epitaxy of GaN epilayers on GaN/sapphire templates was studied by using different graphene interlayer types. Monolayer, bilayer, double-stack of monolayer, and triple-stack of monolayer graphenes were transferred onto GaN/sapphire templates using a wet transfer technique. The quality of the graphene interlayers was examined by Raman spectroscopy. The impact of the interlayer type on GaN nucleation was analyzed by scanning electron microscopy. The graphene interface and structural quality of GaN epilayers were studied by transmission electron microscopy and X-ray diffraction, respectively. The influence of the graphene interlayer type is discussed in terms of the differences between remote epitaxy and van der Waals epitaxy. The successful exfoliation of GaN membrane is demonstrated.