The Langmuir-Blodgett (LB) technique was used to immobilize flat graphene oxide (GO) sheets on a PET substrate to ascertain as to whether the edges of GO play an integral part in its antimicrobial mechanism. The observed antibacterial activity suggests that contact with the edges is not a fundamental part of the mechanism.

Surfaces of commercially available membrane filters were modified by the dispersion of poly(N-vinylcarbazole) (PVK), graphene (G), poly(N-vinylcarbazole)-graphene (PVK-G), graphene oxide (GO), and poly(Nvinylcarbazole)-graphene oxide (PVK-GO) in order to impart antibacterial properties. The successful coatings of the membranes were demonstrated through scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. Investigations carried out on the surface-modified membrane filters using Escherichia coli and Bacillus subtilis showed that the presence of graphene-based nanomaterials significantly improved the antibacterial properties of the membrane filters. One of the mechanisms for this improved antimicrobial property of the filter was attributed to the production of reactive oxygen species by the nanomaterials. Among the nanomaterials used in this study, the PVK-GO-modified membrane filter exhibited the best removal of B. subtilis and E. coli with 4 and 3 log removals, respectively. The different levels of E. coli and B. subtilis removals were attributed to the differences in their cell structures and composition. This study has demonstrated that the use of graphene-based nanomaterials to modify the surfaces of membrane filters is an effective method of imparting antibacterial properties that can find useful application in water and wastewater treatment.

It is critical to develop highly effective antimicrobial agents that are not harmful to humans and do not present adverse effects on the environment. Although antimicrobial studies of graphene-based nanomaterials are still quite limited, some researchers have paid particular attention to such nanocomposites as promising candidates for the next generation of antimicrobial agents. The polyvinyl-N-carbazole (PVK)-graphene oxide (GO) nanocomposite (PVK-GO), which contains only 3 wt% of GO well-dispersed in a 97 wt% PVK matrix, presents excellent antibacterial properties without significant cytotoxicity to mammalian cells. The high polymer content in this nanocomposite makes future large-scale material manufacturing possible in a high-yield process of adiabatic bulk polymerization. In this study, the toxicity of PVK-GO was assessed with planktonic microbial cells, biofilms, and NIH 3T3 fibroblast cells. The antibacterial effects were evaluated against two Gram-negative bacteria: Escherichia coli and Cupriavidus metallidurans; and two Gram-positive bacteria: Bacillus subtilis and Rhodococcus opacus. The results show that the PVK-GO nanocomposite presents higher antimicrobial effects than the pristine GO. The effectiveness of the PVK-GO in solution was demonstrated as the nanocomposite "encapsulated" the bacterial cells, which led to reduced microbial metabolic activity and cell death. The fact that the PVK-GO did not present significant cytotoxicity to fibroblast cells offers a great opportunity for potential applications in important biomedical and industrial fields.

Biofunctionalization of silicon substrates is important to the development of silicon-based biosensors and devices. Compared to conventional organosiloxane films on silicon oxide intermediate layers, organic monolayers directly bound to the non-oxidized silicon substrates via Si-C bonds enhance the sensitivity of detection and the stability against hydrolytic cleavage. Such monolayers presenting a high density of terminal alkynyl groups for bioconjugation via coppercatalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC, a "click" reaction) were reported. However, yields of the CuAAC reactions on these monolayer platforms were low. Also, the nonspecific adsorption of proteins on the resultant surfaces remained a major obstacle for many potential biological applications. Herein, we report a new type of "clickable" monolayers grown by selective, photo-activated surface hydrosilylation of α,ω-alkenynes, where the alkynyl terminal is protected with a trimethylgermanyl (TMG) group, on hydrogen-terminated silicon substrates. The TMG groups on the film are readily removed in aqueous solutions in the presence of Cu(I). Significantly, the degermanylation and the subsequent CuAAC reaction with various azides could be combined into a single step in good yields. Thus, oligo(ethylene glycol) (OEG) with an azidotag was attached to the TMG-alkyne surfaces, leading to OEG-terminated surfaces that reduced the non-specific adsorption of protein (fibrinogen) by >98%. The CuAAC reaction could be performed in microarray format to generate arrays of mannose and biotin with varied densities on the protein-resistant OEG background. We also demonstrated that the monolayer platform could be functionalized with mannose for highly specific capturing of living targets (Escherichia coli expressing fimbriae) onto the silicon substrates.