This study investigates the strong photoluminescence (PL) and X-ray excited optical luminescence observed in nitrogen-functionalized 2D graphene nanoflakes (GNFs:N), which arise from the significantly enhanced density of states in the region of π states and the gap between π and π* states. The increase in the number of the sp 2 clusters in the form of pyridine-like N−C, graphite-N-like, and the CO bonding and the resonant energy transfer from the N and O atoms to the sp 2 clusters were found to be responsible for the blue shift and the enhancement of the main PL emission feature. The enhanced PL is strongly related to the induced changes of the electronic structures and bonding properties, which were revealed by the X-ray absorption near-edge structure, X-ray emission spectroscopy, and resonance inelastic X-ray scattering. The study demonstrates that PL emission can be tailored through appropriate tuning of the nitrogen and oxygen contents in GNFs and pave the way for new optoelectronic devices.

Leukocytes are a central cellular element of innate-immune defense in mammals. In addition to the generation of toxic oxygen radicals and nitric oxide, leukocytes express and secrete a broad array of antimicrobial proteins and peptides. In the study, an antimicrobial polypeptide was isolated and purified from human peripheral blood mononuclear leukocytes in the presence of interleukin (IL)-2. Microsequencing provided that its N-terminal amino sequence was PKRKAEGDAK, which was identical to high mobility group nucleosomal-binding domain 2 (HMGN2). Mass spectrometric value and Western blot also indicated its individual character of HMGN2. The antimicrobial assays showed that the Escherichia coli-based production of HMGN2 had a potent antimicrobial activity against E. coli ML-35p, Pseudomonas aeruginosa ATCC 27853, and to some extent, against Candida albicans ATCC 10231. The HMGN2 alpha-helical domain had the same antimicrobial activity as HMGN2. The immunocytochemistry staining, enzyme-linked immunosorbent assay, and Western blot revealed that HMGN2 was present in the cytoplasm of mononuclear leukocytes and released to the extracellular environment when stimulated with IL-2. These results suggest that HMGN2 would be a novel antimicrobial effector molecule of human mononuclear leukocyte.

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These results suggest that the expression of HMG N2 and SLPI in the healthy female cervical mucus may be relevant to their immune surveillance and defense against potential pathogens in human reproductive system.

The interaction of chemical vapor deposition (CVD)-grown graphene films with water was studied by means of in situ angle-dependent X-ray absorption spectroscopy (XAS). We found that when the graphene layer is in contact with water there is a reduction in the π* peak intensity in the carbon K-edge absorption spectra, accompanied by an extension of the σ* peak to lower energies, which are indicative of chemical modifications of the graphene and a reduction in the number of unsaturated carbon bonds due to the covalent attachment of contaminant species. In addition to the chemical changes a decrease in the dichroic ratio measured by polarized XAS measurements was observed, which indicates an increase on the nanometer scale corrugation. These changes can strongly influence the electronic properties, mechanical robustness, and resistance to sloughing, as well as graphene reactivity.