Graphene, as a steady two dimensional (2D) carbon material, possesses intriguing physical and chemical properties, which arouses great interests of scientists for its applications in enormous fields. In particular, graphene and graphene oxide have been widely used for drug delivery and DNA detection based on π-π stacking and hydrophobic interactions. Besides, graphene with fluorescent molecules or nanoparticles and graphene quantum dots have also been frequently applied as fluorescent probe. In this article, advances of graphene and graphene oxide on biomedical applications will be highlighted from the perspective of biomolecular interaction, cell imaging, drug delivery, and toxicity.
A high efficient dye-sensitized solar cell (DSC) was fabricated using nitrogen-doped nanocrystalline titania(TiO2) photoanode. X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), X-ray powder diffraction (XRD), zeta potentials, nitrogen adsorption-desorption and elemental analysis experiments were employed to characterize the nitrogen-doped nanocrystalline TiO2 photoanode. An obvious enhancement of the optical absorption in the range of 380-550 nm was observed for nitrogen-doped TiO2, which was attributed to both the substitutional N and the chemisorbed N2 molecules. A conversion efficiency of 9.04% was obtained on the DSC based on nitrogen-doped TiO2 photoanode annealed in a flow of NH3 at 550 degrees C, with an increase of 15.6% improvement in comparison with pure TiO2 (7.82%). The mechanism for the enhanced photovoltaic performance was discussed.
We analyze 214 freshly laid eggs belonging to 16 species across three orders of Class Reptilia. Using mechanical compression tests, we measure each egg’s absolute stiffness (K, unit: N m−1) and relative stiffness (C number). The effective Young’s modulus, E, was obtained by combining experimental and numerical methods. The mineral (CaCO3) content was measured by acid–base titration, the microstructures by scanning electron microscopy (SEM), and the crystallography by electron backscatter diffraction (EBSD). We find that the C number of reptilian eggs is, on average, higher than that of bird eggs, indicating that reptilian eggs are stiffer with respect to the egg mass than birds. However, Young’s moduli of the reptilian eggshells (32.85 ± 3.48 GPa) are similar to those of avian eggshells (32.07 ± 5.95 GPa), even though those eggshells have different crystal forms, microstructures, and crystallography. Titration measurement shows that the reptilian eggshells are highly mineralized (>89% for nine Testudines species and 96% for Caiman crocodilus). Comparing the species with aragonite and calcite crystals, we find that calcite shells, including those of the Kwangsi gecko (inner part) and spectacled caiman (outer part), generally have larger grains than the aragonite ones. However, the grain size is not correlated to the effective Young’s modulus. Also, as measured by the C number, the aragonite shells are, on average, stiffer than the calcite ones (except for the Kwangsi gecko), primarily due to their thicker shells.
The microspheres/nanosheets of the ZnSe were prepared by solvothermal route. The morphological, structural, optical, as well as photocatalytic properties of the ZnSe products were studied. SEM and TEM results showed that morphologies of the products were sensitive to the presence of water or not, and a mechanism was proposed. The products shows a weak blue emission band centered at 476 nm, which is attributed to the near-bandedge emission of the products, and the strong and broad peak at 520 nm is attributed to a defect-related emission. The PL and XRD results indicate that ZnSe microspheres have high crystalline and few defects compared with ZnSe nanosheets, the degradation for Rhodamine 6G shows that the photoactivity of ZnSe nanosheets is nearly twice that of ZnSe microspheres. Therefore, the decrease of defects implies the decrease of photocatalytic activity, and nanosheets is more suitable for the degradation of Rhodamine 6G.
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