有机-有机界面效应的原位及非原位研究

有机-有机异质结构已被广泛应用于各种有机电子器件,包括有机发光二极管(OLEDs)、有机场效应晶体管(OFETs)和有机太阳能电池等。全面理解有机-有机异质结构的界面效应,对于器件的设计和性能优化具有重要意义。然而由于有机半导体具有多样的化学特性以及分子间较弱的范德华力,界面电荷传输特性与有机-有机电子结构、环境气氛等密切相关。在此,我们报道了随着顶层半导体并五苯(pentacene)的沉积,并五苯/酞菁氧钒(VOPc)异质结构的原位实时电学性能监测。结果显示,异质结构晶体管的p型迁移率从0.4 cm2∙V−1∙s^(−1)下降至0.2 cm2∙V−1∙s^(−1),而n型迁移率从0.01 cm2∙V−1∙s^(−1)迅速增加至约0.9 cm2∙V−1∙s^(−1)。这种n型输运行为的增强归因于pentacene向VOPc的界面电子转移效应以及由此导致的VOPc层中陷阱态的填充。此外,非原位实验对比表明,当晶体管制备过程暴露于大气时会明显抑制这种界面电荷转移效应,导致沉积pentacene后n型输运几乎没有得到改善。薄膜形态、开尔文探针力显微镜(KPFM)和X射线光电子能谱(XPS)的结果表明,界面处存在从pentacene到VOPc的电子转移。进一步的密度泛函理论(DFT)计算表明,由于pentacene/VOPc之间较强的相互作用,pentacene往VOPc的电荷转移量约为0.15 e。此外,O_(2)/H2O的存在会抑制这种界面电荷转移效应,这与我们的实验结果一致。本研究通过原位电学表征对有机-有机界面之间的电荷转移效应给出了深入解释,有利于进一步的器件性能优化及界面效应分析。

Heat rate variability and dyssomnia and their correlations to neurological defects in cerebral infarction patients complicated by insomnia A concurrent non-randomized case-control study

BACKGROUND： Heart rate variability refers to the beat-to-beat alteration in heart rate. It is usually a slight periodic variation of R-R intervals. Much information of autonomic nerve system balance can be obtained by measuring the heart rate variability of patients. It remains to be shown whether heart rate variability can be used as an index for determining the severity of insomnia and cerebral infarction. OBJECTIVE： This study aimed to analyze the correlation for each frequency spectrum parameter of heart rate variability with an insomnia index, as well as the degree of neurological defects in patients with simple cerebral infarction and cerebral infarction complicated by insomnia. The goal was to verify the feasibility of frequency spectrum parameters for heart rate variability as a marker for insomnia and cerebral infarction. DESIGN： A case-control observation. SETTING： Department of Neurology, First Hospital Affiliated to China Medical University. PARTICIPANTS： Sixty inpatients, and/or outpatients, with cerebral infarction were admitted to the 202 Hospital of Chinese PLA between December 2005 and October 2006, confirmed by CT, and recruited to the study. According to the insomnia condition （insomnia is defined by a Pittsburgh Sleep Quality Index score 〉 7）, the patients were assigned to a simple cerebral infarction group and a cerebral infarction complicated by insomnia group, with 30 subjects in each group. Thirty additional subjects, who concurrently received examinations and were confirmed to not suffer from cerebral infarction and insomnia, were recruited into the control group. Written informed consent was obtained from each subject for laboratory specimens. The protocol was approved by the Hospital＇s Ethics Committee. METHODS： Following admission, each subject＇s neurological impairment was assessed with the National Institutes of Health Stroke Scale and Pittsburgh Sleep Quality Index. Heart rate variability of each subject was measured with an autonomic nerve analyzer （Weijin Science and Technology Co., Ltd., Taiwan）. Each frequency spectrum parameter of heart rate variability was obtained, including very low frequency, low frequency, high frequency, total power, R-R interval, and its mean square. In addition, percentage of low frequency, high frequency, and ratio of low frequency to high frequency were calculated. For each heart rate frequency spectrum parameter, the difference between groups was analyzed. Moreover, correlations of each frequency spectrum parameter with insomnia and disease condition were analyzed. Data from each index, which were not normally distributed, were processed by logarithmic transformation. The t-test was used for the comparison of intergroup differences. Single-factor linear regression analysis and t-test were used for the analysis of factor-factor correlation and coefficient of correlation, respectively. MAIN OUTCOME MEASURES： （1） Differences of scores in the National Institutes of Health Stroke Scale and Pittsburgh Sleep Quality Index between the simple cerebral infarction group and the cerebral infarction complicated by insomnia group. （2） Differences of heart rate variability parameters between the simple cerebral infarction group and the control group. （3） Correlation of heart rate variability parameters, the Pittsburgh Sleep Quality Index score, and the neurological impairment score. RESULTS： Sixty patients and thirty healthy controls were included in the final analysis. （1） The scores of the Pittsburgh Sleep Quality Index and the neurological impairment were significantly higher in the cerebral infarction complicated by insomnia group compared to the simple cerebral infarction group （P 〈 0.05-0.01）. （2） R-R interval was significantly longer in the simple cerebral infarction group than in the control group, while R-R interval variance and high-frequency band were significantly lower in the simple cerebral infarction group compared to the control group （P 〈 0.05）. （3） For cerebral infarction patients with insomnia, the Pittsburgh Sleep Quality Index score was significantly positively correlated with neurological impairment （r = 0.54, P 〈 0.01）. The low-frequency band, very low-frequency band, high-frequency band, R-R interval variance, total power, R-R interval, and the percentage of high-frequency were significantly negatively correlated with the National Institutes of Health Stroke Scale score （r =4）.45 to 4）.90, P 〈 0.054）.01） and with the Pittsburgh Sleep Quality Index scores （r = 4）.56 to 4）.36, P 〈 0.054）.01）. CONCLUSION： Each heart rate variability parameter can be used as an index for assessing dyssomnia and neurologic impairment （r =4）.56 to 4）.36, P 〈 0.054）.01）.

The triggering of catalysis via structural engineering at atomic level: Direct propane dehydrogenation on Fe-N_(3)P-C

The on-purpose direct propane dehydrogenation(PDH) has received extensive attention to meet the everincreasing demand of propylene.In this work,by means of density functional theory(DFT) calculations,we systematically studied the intrinsic coordinating effect of Fe single-atom catalysts in PDH.Interestingly,the N and P dual-coordinated single Fe(Fe-N_(3)P-C) significantly outperform the Fe-N_(4-)C site in catalysis and exhibit desired activity and selectivity at industrial PDH temperatures.The mechanistic origin of different performance on Fe-N_(3)P-C and Fe-N_(4-)C has been ascribed to the geometric effect.To be specific,the in-plane configuration of Fe-N_(4) site exhibits low H affinity,which results in poor activity in C-H bond activations.By contrast,the out-of-plane structure of Fe-N_(3)P-C site exhibits moderate H affinity,which not only promote the C-H bond scission but also offer a platform for obtaining appropriate H diffusion rate which ensures the high selectivity of propylene and the regeneration of catalysts.This work demonstrates promising applications of dual-coordinated single-atom catalysts for highly selective propane dehydrogenation.