Photooxidation of Isoprene by Titanium Oxide Cluster Anions with Dimensions up to a Nanosize.

Titania (TiO2) nanoparticles are active photocatalysts, and isoprene (C5H8) is a biogenic volatile organic compound that contributes crucially to global particulate matter generation. Herein, the direct photooxidation of isoprene by titanium oxide cluster anions with dimensions up to a nanosize by both ultraviolet (UV) and visible (Vis) light excitations has been successfully identified through mass spectrometric experiments combined with quantum chemistry calculations. The potential role of "dry" titania in atmospheric isoprene oxidation has been revealed, and a clear picture of the photooxidation mechanism on titanium oxide nanoparticles has been provided explicitly at the molecular level. The adsorption of isoprene on the atomic oxygen radicals (O•-) of titanium oxide clusters leads to the formation of the crucial interfacial state (IS) within the band gap of titanium oxides. This IS is demonstrated to be the significant factor in delivering the electron from the π orbital of C5H8 to the Ti3d orbital in the photooxidation process (C5H8 + Ti4+-O•- → C5H8O + Ti3+) and creating photoactivity in the Vis region. It is revealed that after the photogeneration of the O•- radicals by UV excitation on the TiO2 particle surface, the subsequent reactions can be induced by Vis excitation through the IS. This multicolor strategy in both the UV and Vis regions can enhance the efficiency of solar energy harvesting and improve the product yield of the photocatalysis on TiO2 nanoparticles. New insights have been provided into both the atmospheric chemistry of isoprene and the photochemistry of TiO2 nanoparticles.

Oxidation of isoprene by titanium oxide cluster cations in the gas phase.

The heterogeneous oxidation of isoprene (C5H8) by metal-oxide particles, such as the typical mineral aerosols TiO2, plays an important role in the isoprene atmospheric chemistry. However, the underlying mechanism of C5H8 oxidation remains elusive owing to the complexities of aerosol surfaces and reaction channels. Herein, we report the gas-phase reactions of TixOy+ (x = 1-7, y = 1-14) cations with isoprene by using mass spectrometry and density functional theory (DFT) calculations. Five types of reaction channels were observed: association, hydrogen atom transfer (HAT), C-C bond cleavage, combined oxygen atom transfer (OAT) and HAT and combined OAT and C-C bond cleavage. It is noteworthy that formaldehyde is known as the major oxidation product of isoprene/hydroxyl radicals in the atmosphere. In addition, CO has not been observed in the reactions of isoprene with gas-phase ions. Therefore, the reaction mechanisms of CH2O and CO generation observed in Ti2O5+/C5H8 and Ti4O8+/C5H8 systems were further investigated by DFT calculations, and the calculated results are in agreement with the experimental observations. In these two reactions, both Ti and O atoms can be the adsorption sites for C5H8. The reaction channels and mechanistic information gained in these gas-phase model reactions may offer fundamental insights relevant to the corresponding oxidation processes over titanium oxide aerosols in the atmosphere.

Impact of comprehensive psychological training on mental health of recruits in Xinjiang.

OBJECTIVE: To examine the effect of comprehensive psychological training on the mental health of recruits and to provide basis for promoting mental health among recruits in Xinjiang. METHODS: From September to December, 2013, a convenience sampling was used to select 613 recruits from Xinjiang. These recruits were assigned to the training group (n=306) and the control group (n=307). The Simplified Coping Style Questionnaire,the Questionnaire of Armymen's Emotion Regulation Types and the Chinese Military Personnel Social Support Scale were used to evaluate the levels of mental health at the baseline and at the end of comprehensive psychological training. RESULTS: After comprehensive psychological training, the negative coping style score of the training group were significantly lower than the control group (P=0.000), and there were difference in cognitive focus (P=0.000) and behavior restrain (P=0.005); also, there was significant difference in social support scale (P<0.05). The coping style showed positive correlation with emotion regulation and all factors (P<0.05). Social support and all factors was positively correlated with positive coping style (P<0.05) and negatively correlated with negative coping style (P<0.05). Social support and all factors showed positive correlation with affective appeal and self comfort (P<0.05) and negative correlation with congnitive focus and behavior restrain (P<0.05). As shown by stepwise regression analysis,the positive and negative coping styles had statistically significant impacts on cognitive focus, affective appeal, behavior restrain, and self comfort (all P<0.05). CONCLUSION: Comprehensive psychological training is useful in improving the mental health of recruits.