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A thorough understanding of the antimicrobial mechanisms of graphene materials (GMs) is critical to the manipulation of highly efficient antimicrobial nanomaterials for future biomedical applications. Here we review the most recent studies of GM-mediated antimicrobial properties. This review covers the physicochemical properties of GMs, experimental surroundings, and selected microorganisms as well as the interaction between GMs and selected microorganisms to explore controversial antimicrobial activities. Finally, we rationally analyze the strengths and weaknesses of the proposed mechanisms and provide new insights into the remaining challenges and perspectives for future studies. [ABSTRACT FROM AUTHOR]

Small molecules or metal ions can be employed as catalysts to accelerate metalloporphyrin formation. Herein, we for the first time report the coordination reaction between cadmium(II) and 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin can be accelerated by nitrogen-doped graphene quantum dots (NGQDs). This catalytic reaction results in the change of the absorption of porphyrins and the fluorescence of NGQDs as a result of the inner filter effect (IFE) of the porphyrins on the assembled NGQDs. Both signals can be used for rapid and sensitive determination of metal ions. The present work promises a novel strategy for constructing sensors for metal ions. [ABSTRACT FROM AUTHOR]

A simple and sensitive photoluminescence (PL) assay for the activity of a protein kinase based on the selective aggregation of phosphorylated peptide-graphene quantum dot (GQD) conjugates triggered by Zr4+ ion coordination has been established. With more sophisticated design of the peptide substrate sequences, detecting other enzymes could also be possible. Under optimal conditions, a linear relationship between the decreased PL intensity of peptide-GQD conjugates and the concentration of casein kinase II (CK2) in the range from 0.1 to 1.0 unit mL-1 with a detection limit of 0.03 unit mL-1 (3σ) was obtained. The EC50 value (i.e., the enzyme concentration producing 50% substrate conversion) for CK2 was evaluated to be 0.34 unit mL-1. The proposed method showed potential applications in kinase inhibitor screening. To demonstrate the potential of this GQD-based platform for screening of kinase inhibitors in real biological systems, the inhibition of CK2 phosphorylation activity by four different inhibitors (ellagic acid, 5,6-dichlorobenzimidazole-l-β-D-ribofuranoside, emodin, and quercetin) was tested in human serum by comparing signals from samples incubated with the inhibitors against that without any inhibitor. As expected, in the presence of inhibitors, the PL intensity increased with increasing inhibitor efficiency. The IC50 value (inhibitor concentration producing 50% inhibition) for ellagic acid was estimated to be 0.041 μM. The developed protocol provides a new and promising tool for the analysis of both the enzyme and its inhibitors with low cost and excellent performance. [ABSTRACT FROM AUTHOR]

We report on the spontaneous formation of superhydrophobic poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP)/graphene composite microspheres with uniform size via gelation. When the suspension of PVDF-HFP/graphene (0.25 wt. % with respect to PVDF-HFP) in DMF adsorbs water vapor, it changes to a hybrid gel. A dried porous gel is obtained after solvent exchange and freeze drying. Morphology characterization shows that this hybrid gel is composed of PVDF-HFP/graphene microspheres with a diameter of 8–10 μm. In contrast, PVDF-HFP solution gives rise to a cellular microstructure following the same experimental procedures. We further elucidate the formation mechanism on the basis of the characterization by freeze fracture transmission electron microscopy, X-ray diffraction, and differential scanning calorimetry characterizations. Furthermore, contact angle measurements of water on PVDF-HFP/graphene indicates that the hydrophobic nature of PVDF-HFP combined with the micro/nanoscale hierarchical texture creates a superhydrophobic surface. Such superhydrophobic microspheres may have potential applications as water-repellent catalyst-supporting materials. [ABSTRACT FROM AUTHOR]

We demonstrate a general approach to the preparation of layered graphene oxide structures with sandwiched conducting polymers of different morphologies. The approach is conceptualized on the basis of the electrostatic interactions between negatively charged graphene oxide sheets and positively charged surfactant micelles. A graphene oxide−polypyrrole composite prepared from this approach exhibited an excellent electrocapacitive performance with a high specific capacitance over 500 F g−1. Good rate performance and cycle ability were realized by the composite electrode. The simple method described here opens up a generalized route to making a wide range of graphene oxide-based and graphene-based composite materials for applications beyond electrochemical energy storage. [ABSTRACT FROM AUTHOR]

As a two-dimensional material with high charge carrier mobility, graphene may offer ultrahigh sensitivity in biosensing. To realize this, the first step is to functionalize the graphene. This is commonly done by using 1-pyrenebutyric acid (PBA) as a linker for biomolecules. However, the adsorption of PBA on graphene remains poorly understood despite reports of successful biosensors functionalized via this route. Here, the PBA adsorption on graphene is characterized through a combination of Raman spectroscopy, ab initio calculations, and spectroscopic ellipsometry. The PBA molecules are found to form a self-assembled monolayer on graphene, the formation of which is self-limiting and Langmuirian. Intriguingly, in concentrated solutions, the PBA molecules are found to stand up and stack horizontally with their edges contacting the graphene surface. This morphology could facilitate a surface densely populated with carboxylic functional groups. Spectroscopic analyses show that the monolayer saturates at 5.3 PBA molecules per nm2 and measures 0.7 nm in thickness. The morphology study of this PBA monolayer sheds light on the π-π stacking of small-molecule systems on graphene and provides an excellent base for optimizing functionalization procedures. [ABSTRACT FROM AUTHOR]