Facet-Specific Photocatalytic Activity Enhancement of Cu2O Polyhedra Functionalized with 4-Ethynylanaline Resulting from Band Structure Tuning.

Cu2O rhombic dodecahedra, octahedra, and cubes were densely modified with conjugated 4-ethynylaniline (4-EA) for facet-dependent photocatalytic activity examination. Infrared spectroscopy affirms bonding of the acetylenic group of 4-EA onto the surface copper atoms. The photocatalytically inactive Cu2O cubes showed surprisingly high activity toward methyl orange photodegradation after 4-EA modification, while the already active Cu2O rhombic dodecahedra and octahedra exhibited a photocatalytic activity enhancement. Electron, hole, and radical scavenger experiments prove that the photocatalytic charge transport processes have occurred in the functionalized Cu2O cubes. Electrochemical impedance spectroscopy also indicates reduced charge transfer resistance of the functionalized Cu2O crystals. A band diagram constructed from UV-vis spectral and Mott-Schottky measurements reveals significant band energy shifts in all Cu2O samples after decorating with 4-EA. From density functional theory (DFT) calculations, a new band has emerged slightly above the valence band maximum within the band gap of Cu2O, which has been found to originate from 4-EA through band-decomposed charge density analysis. The increased charge density localized on the 4-EA molecule and the smallest electron transition energy to reach the 4-EA-generated band are factors making {100}-bound Cu2O cubes photocatalytically active. Proper molecular decoration represents a powerful approach to improving the photocatalytic efficiency of semiconductors.

[A case control study on the relationship between trace elements and human neural tube defects].

OBJECTIVE: To explore the relationship between multi-trace elements levels in hair and human neural tube defects as well as other risk factors. METHODS: Using 88 paired cases and controls, an 1:1 matched case control study was carried out. The study subjects were collected from the China-U. S. Collaborative Project on Neural Tube Defects Prevention and Birth Defects Surveillance System. Risk factors were obtained by field investigation with standardized questionnaires and hair trace elements levels were determined by AAS and ICP-MS methods. Microwave digestion was used to digest hair samples. The detected elements would include three groups, namely nutritional elements: Cr, Mn, Cu, Zn, Co, Mo; toxic elements: Pb, As, Cd, Hg; and Lanthanons: Y, La, Pr, Nd. Cox Proportional Hazard Regression Model was used to perform risk factors analysis. RESULTS: Pregnancy fever appeared to be a risk factor of neural tube defects (OR = 6.525, P = 0.034) while hair zinc level (OR = 0.541 microg/100 g, P = 0.02) and times of prenatal physical examination (OR = 0.634, P < 0.001) served as two protective factors appeared in the last model. CONCLUSION: Zinc deficiency might serve as a risk factor for human neural tube defects, suggesting that the avoidance of pregnancy infection together with more periodical prenatal physical examination might reduce the incidence of neural tube defects.