Sabatier phenomenon in chemoselective gas-sensing reactions induced by Ag cluster coordination.

The Sabatier principle in heterogeneous catalysis provides guidance for designing optimal catalysts with the highest activity. We report a new Sabatier phenomenon induced by nanoclusters on different atomic scales in gas-sensitive reactions. We prepared a series of Ag nanocluster catalysts with coordination structures ranging from Ag0 to Ag13 through a surface coordination strategy. When used as catalysts for gas-sensitive reactions, a volcano-type relationship between the coordination number of Ag nanoclusters and gas-sensitive activity emerges, with a summit at a moderate coordination of Ag5. Mechanistic studies show that the efficient adsorption of activated *C2H6O on electron-rich Ag5 clusters is a key factor for the Sabatier phenomenon (adsorption energy from -0.322 eV to -0.663 eV), which leads to highly selective sensing. We found that the catalyst electron-rich surface layer induced by Ag5 clusters serves as a descriptor to explain the structure-activity relationship. Furthermore, due to the well-defined geometric and electronic structures in the Ag5 clusters, the optimized catalyst achieves both maximum activity and selectivity in chemoselective sensing reactions. This study reveals the Sabatier principle and provides insightful guidance for the rational design of more efficient and practical nanocluster catalysts for heterogeneous catalysis.

Surface segregation of rigid polyarylene ether amidoxime on polyurethane nanofiber into hierarchical membranes as substrate of flexible SERS nanosensor for sulfamethoxazole detection.

Electrospun polymeric nanofibrous membranes are emerging as the promising substrates for preparation of flexible SERS nanosensors due to their intrinsic nanoscale surface roughness, easy scalability as well as rich surface reactivity. Although the nanofiber membranes prepared from high performance thermoplastics exhibit good mechanical stability, the SERS nanosensors based on these substrates normally have lower signal-to-noise ratio because of the interference from background Raman signals of aromatic moieties. Herein, we synthesized an optically transparent polyurethane (PU) and rigid polyarylene ether amidoxime (PEA), which were electrospun into core-shell nanofibers membranes with a "beads-on-web" morphology. Furthermore, the PU-PEA membranes were coated with ultra-thin silver layer and thermally annealed to prepare the flexible SERS nanosensor without any background noises. In addition, the Raman enhancement of SERS nanosensor can be readily improved by tuning of PU-PEA composition, silver thickness as well as thermal annealing temperature. Finally, the optimized SERS nanosensor enables label-free detection of sulfamethoxazole as low as 0.1 nM with a good reproducibility and detection performance in real water sample. Meanwhile, the optimized SERS nanosensor shows long term anti-biofouling capacity. Thanks to its facile fabrication, competitive analytical performance and resistance to biofouling, the current work basically open new way for design of flexible SERS nanosensors for biomedical applications.

Childhood trauma, peer victimization, and non-suicidal self-injury among Chinese adolescents: a latent variable mediation analysis.

BACKGROUND: Childhood and peer experiences can influence adolescents' perceptions of interpersonal relationships, which can, in turn, influence their emotional states and behavior patterns. Non-suicidal self-injury (NSSI) is now a common problem behavior among adolescents. The present study examined the role of childhood trauma and peer victimization in adolescents' NSSI. METHODS: A cross-sectional survey was conducted among 1783 adolescents (1464 girls and 318 boys) in the psychiatric outpatient clinics or wards of 14 psychiatric hospitals or general hospitals in nine provinces in China. Data were collected using the Multidimensional Peer Victimization Scale (MPVS), Short-form Childhood Trauma Questionnaire(CTQ-SF), and Functional Assessment of Self-Mutilation (FASM). Structural equation modeling (SEM) with latent variables was used to demonstrate the mediating role of peer victimization in the association between childhoodtrauma and NSSI. RESULTS: The SEM analysis demonstrated that peer victimization plays a partial mediating role in the relationship between childhood trauma and NSSI. In addition, several covariates (such as age, gender, education level, and place of residence) effectively regulated the relationship between peer victimization and NSSI. CONCLUSION: In future studies of NSSI among Chinese adolescents, attention should be paid to the roles of childhood trauma and peer bullying; there is a temporal sequence between these two variables and, to some extent, childhood trauma can have an impact on bullying during adolescence which, in turn, influences NSSI behavior.

Scalable fabrication of silver covered polyurethane nanofibers as flexible SERS nanosensors for aflatoxin detection.

Flexible surface enhanced Raman spectroscopy (SERS) nanosensors, constructed by integration of plasmonic nanostructures with polymeric substrates, have received increasing research interests for recent decades. When compared to abundant works on optimization of the plasmonic nanostructures, the research involving the influence of polymeric substrates on analytical performance of resultant flexible SESR nanosensors is unexpectedly limited. Herein, the ultra-thin silver layer has been deposited on the electrospun polyurethane (ePU) nanofibrous membranes via vacuum evaporation to prepare the flexible SRES nanosensors. Interestingly, we find that the molecular weight and polydispersion index of synthesized PU play important roles in regulating the fine morphology of electrospun nanofibers, which in turns determine the Raman enhancement of resultant flexible SERS nanosensors. Specifically, the optimized SERS nanosensor, obtained by evaporating 10 nm silver layer on top of nanofibers derived from electrospinning of PU with a weight-average molecular weight of 140,354 and polydispersion index of 1.26, enables label-free detection of the carcinogen of aflatoxin down to 0.1 nM. Thanks to its scalable fabrication and good sensitivity, the current work opens new way for design of cost-effective flexible SERS nanosensors for environmental monitoring and food security applications.

A method for visualization of biomolecules labeled by a single quantum dot in living cells by a combination of total internal reflection fluorescence microscopy and intracellular fluorescence microscopy.

We developed a simple fluorescence microscopy for acquisition of high-resolution images of single quantum dots (QDs) labeled to biomolecules on apical plasma membrane, in cell interior and on basal plasma membrane of living cells. The method was a combination of total internal reflection fluorescence microscopy (TIRFM) at apical cell surface and intracellular microscopy coupled with focusing objective. Insulin conjugated to single QD (insulin-QD) was chosen as the model system. In order to bind insulin-QDs to insulin receptors on the plasma membrane through the interaction between insulin and its receptor, as well as internalize them, the cells attached on a coverslip were incubated with biotinylated insulin and QD-streptavidin conjugate at 37 degrees C. Next, fluorescent molecules in the cells were photobleached by illuminating the cells using a 100-W mercury lamp with the wavelengths from 460 to 490nm. Then, the incident angle of a laser beam was adjusted to produce total internal reflection at the apical surface of a single cell. In this case, the insulin-QDs in the whole cell were excited, and the fluorescent molecules outside the cell were not illuminated. Finally, the images of single insulin-QDs on the apical plasma membrane, in the cell interior and on the basal plasma membrane of the cell were taken by focusing the objective to different positions, respectively. The resolution and contrast of the fluorescent spots in the images were much higher than those obtained by using epi-fluorescence microscopy and comparable to those obtained by using the conventional TIRFM. The method improved the image acquisition speed for the images on the apical and basal plasma membrane using the conventional TIRFM, and could acquire the high-resolution images in the cell interior quickly.