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Ag-TiO2 catalysts with different Ag contents were prepared via a sol-gel method in the absence of light. Based on the characterizations of XRD, photoluminescence (PL), surface photovoltage spectroscopy (SPS), field-induced surface photovoltage spectroscopy (FISPS), and XPS as well as the evaluation of the photocatalytic activity for degrading rhodamine B(RhB) solutions, it was found that the Ag dopant promoted the phase transformation as well as had an inhibition effect on the growth of anatase crystallite. The PL and SPS intensities were decreased with increasing Ag content, indicating that the Ag dopant could effectively inhibit the recombination of the photoinduced electrons and holes. However, the active sites capturing the photoinduced electrons reduced, while the Ag content exceeded 5 mol %. At rather low Ag dopant concentrations, the migration and diffusion of Ag+ ions were predominant, while at rather high Ag dopant concentrations, the migration, diffusion, and reduction of Ag ions simultaneously occurred. The Ag-TiO2 photocatalysts with appropriate content of Ag (Ag species concentration is from about 3 to 5 mol %) possessed abundant electron traps so as to be favorable for the separation of the photoinduced electron-hole pairs, which could greatly enhance the activity of the photocatalysts. From the results of FISPS measurements, it could be found that the impurity bands and abundant surface states were introduced into the interfacial layer of TiO2 because of Ag simultaneously doping and depositing, which could improve the absorption capability for visible light of the photocatalysts.

In this paper, TiO(2) nanoparticles doped with different amounts of Zn were prepared by a sol-gel method and were mainly characterized by means of X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and surface photovoltage spectrum (SPS). The effects of surface oxygen vacancies (SOVs) of Zn-doped TiO(2) nanoparticles on photophysical and photocatalytic processes were investigated along with their inherent relationships. The results show that the SOVs easily bind photoinduced electrons to further give rise to PL signals. The SOVs can result in an interesting sub-band SPS response near the band edge in the TiO(2) sample consisting of much anatase and little rutile, except for an obvious band-to-band SPS response. Moreover, the intensities of PL and SPS signals of TiO(2), as well as the photocatalytic activity for degrading phenol solution, can be enhanced by doping an appropriate amount of Zn. These improvements are mainly attributed to the increase in the SOV amount. It can be suggested that the SOVs should play an important role during the processes of PL, surface photovoltage, and photocatalytic reactions, and, for the as-prepared TiO(2) samples doped with different amounts of Zn by thermal treatment at 550 degrees C, the larger the SOV amount, the stronger the PL and SPS signal, and the higher the photocatalytic activity.

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Graphene oxide (GO) has attracted enormous interests due to its extraordinary properties. Recent studies have confirmed the cytotoxicity of GO, we further investigate its mutagenic potential in this study. The results showed that GO interfered with DNA replication and induced mutagenesis at molecular level. GO treatments at concentrations of 10 and 100 mg/mL altered gene expression patterns at cellular level, and 101 differentially expressed genes mediated DNA-damage control, cell apoptosis, cell cycle, and metabolism. Intravenous injection of GO at 4 mg/kg for 5 consecutive days clearly induced formation of micronucleated polychromic erythrocytes in mice, and its mutagenesis potential appeared to be comparable to cyclophosphamide, a classic mutagen. In conclusion, GO can induce mutagenesis both in vitro and in vivo, thus extra consideration is required for its biomedical applications. G raphene, firstly isolated from graphite in 2004 1 , is a flat monolayer of carbon atoms tightly packed into a two-dimensional (2D) honeycomb lattice. Due to the unique physicochemical properties, high surface area, excellent thermal conductivity, electric conductivity, and strong mechanical strength, graphene and graphene oxide (GO) have shown great promise in many applications, such as electronics, energy storage and conversion, mechanics, and biotechnologies [2][3][4][5][6] . Recently, many studies reported that GO has outstanding potentials in the field of biomedicine. GO and PEGylated GO exhibit certain advantages in vitro and in vivo drug delivery, such as high drug loading efficiency, controlled drug release, tumor-targeting drug delivery, and reversal effect against cancer drug resistance [7][8][9][10] . In addition, GO has strong optical absorbance in the near-infrared (NIR) region, thus is suitable for the photothermal therapy [11][12][13] . Now, it is possible to manufacture high-quality GO in large scale quantities 14,15 , and its industry production is increasing exponentially. Together with its potential applications in the biomedical field, the biosafety of GO is of critical importance. Many investigations have paid attentions to its biocompatibilty [16][17][18][19] . At a concentration approximate to 50 mg/mL or higher, GO begins to show the toxicity against erythrocytes, fibroblasts, and PC12 cells. It can induce cell apoptosis, hemolysis, and oxidative stress 16,18,19 . Surface chemical modification, such as PEGylation, is likely to improve the biocompatibility of GO 20,21 . However, the chemical bonds linking GO with modified polymer can be broken down in vivo, thus surface-modified GO can also induce in vivo toxicity.Several investigations have reported that treatments with carbon nanomaterials, such as nanodiamonds and multiwalled carbon nanotubes, can elevate the expression of p53, MOGG-1, and Rad51, which reflect the chromosomal DNA damage 22,23 . However, it is not clear whether this DNA damage induced by carbon nanomaterials can cause mutagenesis. GO, due to its unique nanosheet structure, can interact wi...