Assembly of g-C3N4-based type II and Z-scheme heterojunction anodes with improved charge separation for photoelectrojunction water oxidation.

Graphitic carbon nitride (g-C3N4) has been widely studied as a metal-free photocatalyst, leading to some excellent results; however, the rapid recombination of photogenerated charge carriers substantially limits its performance. Here, we establish two types of g-C3N4-based heterojunction (type II and nonmediator assisted Z-scheme) photoanodes on a transparent conducting substrate via coupling with rod-like and nanoparticulate WO3, respectively. In these composites, g-C3N4 film grown by electrophoretic deposition of exfoliated g-C3N4 serves as the host or guest material. The optimized type II WO3/g-C3N4 composite exhibits an enhanced photocurrent of 0.82 mA cm-2 at 1.23 V vs. RHE and an incident photo-to-current conversion efficiency (IPCE) of 33% as compared with pure WO3 nanorods (0.22 mA cm-2 for photocurrent and 15% for IPCE). Relative to pure g-C3N4 film (with a photocurrent of several microampere and an IPCE of 2%), a largely improved photocurrent of 0.22 mA cm-2 and an IPCE of 20% were acquired for the Z-scheme g-C3N4/WO3 composite. The enhancement can be attributed to accelerated charge separation in the heterointerface because of the suitably aligned band gap between WO3 and g-C3N4, as confirmed by optical spectroscopy and ultraviolet photoelectron spectroscopy (UPS) analysis. The photocatalytic process and mechanism of the g-C3N4-based heterojunctions are proposed herein, which potentially explain the origin of the enhanced photoelectrochemical performance. This achievement and the fundamental information supplied here indicate the importance of rationally designing heterojunction photoelectrodes to improve the performance of semiconductors. This is particularly important for materials such as pure g-C3N4 and WO3, as their photoactivities are strongly restricted by high recombination rates.

Fe2 PO5 -Encapsulated Reverse Energetic ZnO/Fe2 O3 Heterojunction Nanowire for Enhanced Photoelectrochemical Oxidation of Water.

Zinc oxide is regarded as a promising candidate for application in photoelectrochemical water oxidation due to its higher electron mobility. However, its instability under alkaline conditions limits its application in a practical setting. Herein, we demonstrate an easily achieved wet-chemical route to chemically stabilize ZnO nanowires (NWs) by protecting them with a thin layer Fe2 O3 shell. This shell, in which the thickness can be tuned by varying reaction times, forms an intact interface with ZnO NWs, thus protecting ZnO from corrosion in a basic solution. The reverse energetic heterojunction nanowires are subsequently activated by introducing an amorphous iron phosphate, which substantially suppressed surface recombination as a passivation layer and improved photoelectrochemical performance as a potential catalyst. Compared with pure ZnO NWs (0.4 mA cm-2 ), a maximal photocurrent of 1.0 mA cm-2 is achieved with ZnO/Fe2 O3 core-shell NWs and 2.3 mA cm-2 was achieved for the PH3 -treated NWs at 1.23 V versus RHE. The PH3 low-temperature treatment creates a dual function, passivation and catalyst layer (Fe2 PO5 ), examined by X-ray photoelectron spectroscopy, TEM, photoelectrochemical characterization, and impedance measurements. Such a nano-composition design offers great promise to improve the overall performance of the photoanode material.

Prevalence and genotype distribution of human papillomavirus among Hakka women in China.

BACKGROUND: Human papillomavirus (HPV) infection is the primary risk factor for cervical cancer. HPV genotypes are associated with varying degrees of pathogenicity. To better formulate strategies for cervical cancer prevention, we investigated the population-specific distribution of HPV genotypes, including those with high carcinogenicity. METHODS: From January to December 2012, a cervical cancer-screening program for HPV infection in Hakka women of Heyuan City Guangdong province was conducted. Of 736,000 women residents, 8,284 volunteers were recruited. The cytology specimens of 107 women were not adequate and excluded. Thus, 8,177 women submitted to polymerase chain reaction (PCR) sequencing of 16 HPV genotypes via MassARRAY spectrometry. RESULTS: Risk stratification based on genotypes indicated that the prevalence of overall, high-risk, and low-risk HPV infections was 12.27%, 14.20%, and 0.79%, respectively. Of the 1,003 women positively infected, 82.75% were infected with a single HPV type; 17.25% were infected with ≥2 types. Analysis revealed a U-shaped curve in HPV prevalence that correlated with age group, with peaks at ages 18-24 y (22.03%) and 60-65 y (25%). The most frequently detected HPV genotype was HPV-52 (26.81%), and then HPV-16 (17.54%), HPV-58 (14.25%), HPV-18 (10.16%), HPV-68 (8.27%), HPV-39 (5.68%), and HPV-51 (5.38%). CONCLUSIONS: HPV-52 is the most prevalent genotype infecting Hakka women. Therefore, vaccination against HPV-52 is imperative. The prevalence of HPV infection is highest in the younger (18-24 y) and older (60-65 y) age groups, indicating that screening for HPV in Hakka women should be performed early and maintained in the elderly.

A nanostructured hematite film prepared by a facile "top down" method for application in photoelectrochemistry.

To overcome tough conditions currently used for the preparation of nanostructured hematite films on a conducting substrate, a rational and easy method of chemical etching involving Fe3+ release and material growth in the presence of OH- has been developed. By carefully tuning the parameters influencing the morphologies of hematite, including the synthetic procedure, the concentration of etching solution, temperature, etching time and the morphology controlling surfactant, hematite films grown on iron foil with various morphologies (e.g. nanorod, nanowire, ultrathin nanoflake and cauliflower-like shape) have been achieved. In particular, it is found that F- is an effective surfactant to control the morphology as well as the crystallization process of hematite. Ultrathin nanoflakes having a minimized feature size exhibit the best photocurrent of 0.5 mA cm-2 (1.23 V vs. RHE, RHE is reversible hydrogen electrode) among the samples tested as a result of facilitated hole diffusion to the electrolyte and thus lowered carrier recombination. Compared with pristine hematite, a nearly tripled photocurrent is observed when H2O2 is added in the electrolyte as a hole scavenger, suggesting the presence of a charge injection barrier in the surface of samples. According to this, the strategy of Co2+ treatment is utilized and the improved photocurrent is seen, likely due to the improved water oxidation kinetics and surface state passivation. We believe that this convenient and economical method can be extended to the synthesis of other alkaline metal oxide nanomaterials as long as the redox potential of S2O82-/SO42- is higher than Mn+/M (M refers to metal).