Photoselective excited state dynamics in ZnO–Au nanocomposites and their implications in photocatalysis and dye-sensitized solar cells

Improving the performance of photoactive solid-state devices begins with systematic studies of the metal–semiconductor nanocomposites (NCs) upon which such devices are based. Here, we report the photo-dependent excitonic mechanism and the charge migration kinetics in a colloidal ZnO–Au NC system. By using a picosecond-resolved Förster resonance energy transfer (FRET) technique, we have demonstrated that excited ZnO nanoparticles (NPs) resonantly transfer visible optical radiation to the Au NPs, and the quenching of defect-mediated visible emission depends solely on the excitation level of the semiconductor. The role of the gold layer in promoting photolytic charge transfer, the activity of which is dependent upon the degree of excitation, was probed using methylene blue (MB) reduction at the semiconductor interface. Incident photon-to-current efficiency measurements show improved charge injection from a sensitizing dye to a semiconductor electrode in the presence of gold in the visible region. Furthermore, the short-circuit current density and the energy conversion efficiency of the ZnO–Au NP based dye-sensitized solar cell (DSSC) are much higher than those of a DSSC comprised of only ZnO NP. Our results represent a new paradigm for understanding the mechanism of defect-state passivation and photolytic activity of the metal component in metal–semiconductor nanocomposite systems

Comparative Investigation of Structure and Operating Parameters on the Performance and Reaction Dynamic of CO Conversion on Silica Aerogel and Fumed-Silica-Supported Pd Catalysts

The catalyst morphology, metal-support interaction, and reaction conditions greatly influence the catalytic performance and reaction dynamics. Similarly, the dispersion of the metal within the support plays a crucial role in the thermal stability and sintering of the catalyst. Furthermore, temperature-dependent conversion hysteresis is well-known to occur during ignition and extinction of exothermic CO oxidation over supported Pd catalysts due to the variation of CO adsorption on the surface or bulk oxidation of Pd and the ability of the catalyst to regenerate the active sites. Herein, the catalytic performance and the hysteresis behavior of mesoporous silica aerogel supported Pd (Pd/a-SiO2), and commercial fumed silica-supported Pd (Pd/f-SiO2) were investigated and compared using CO oxidation as a probe reaction under different reaction conditions and operating parameters (i.e., catalyst weight, ramp rate, and flow rate). Surface and morphologic examination using XPS, FTIR, and TEM of Pd/a-SiO2 and Pd/f-SiO2 reveal a strong correlation between the catalyst surface and structure and its catalytic performance and stability under different reaction parameters. Moreover, this study presents the effect of surface area, particle size, and size distribution on diffusion and mass transport of reactants (CO, O2) and products (CO2) and active sites accessibility. This study showed that Pd/f-SiO2 had better efficiency under high (turbulence) flow. Moreover, intrinsic apparent activation energy (Ea) and the number of active sites were calculated from the Kinetics of CO oxidation fitted using Arrhenius plots indicate that the ramp rate has less effect on Pd/f-SiO2 catalytic behavior. Even though, Pd/f-SiO2 had higher relative active sites than Pd/a-SiO2, (Ea) was lower. Cyclic stability and long-term stabilities showed that both catalysts are stable and can regenerate the active sites. The current study contributes to understanding the catalysts\u27 surface, structural and morphological properties on the catalysts\u27 performance toward CO oxidation and other reactions under dynamic conditions

Clinical Effectiveness of Facility and Accuracy of Accommodation in Diagnosis of Non Strabismic Binocular Vision Anomalies in Young Adults: A Prospective Cross-sectional Observational Study

Introduction: Orthoptic evaluation is highly recommended in children and young adults to diagnose binocular dysfunctions. Binocular vision dysfunctions may hamper academic performance in children. Accommodative facility and accommodative accuracy are two orthoptic tests to evaluate accommodative flexibility and accommodative status of eye. Aim: To investigate the effectiveness of facility and accuracy of accommodation in diagnosis of Non Strabismic Binocular Vision Anomalies (NSBVA) in young adults. Materials and Methods: This prospective, cross-sectional observational study was conducted at Optsight Eye Care in association with Amity Medical School, Gurugram, Haryana, India, from August 2020 to August 2021. A total of 175 subjects (both symptomatic and asymptomatic) with normal anterior and posterior segment findings, and aged between 18-25 years were evaluated for accommodative facility test with the help of accommodative lens flipper ±2D and for accommodative status test with the help of monocular estimation method (dynamic retinoscopy). Both the tests were done over their best corrected visual acuity after refractive error correction and the Pearson correlation test was applied to find out the correlation. Further, complete orthoptic examination was performed for all the subjects to correlate the abnormal findings from the two tests and conventional orthoptic tests. Independent sample t-test was applied to compare the accommodative facility between refractive groups. Results: Out of 175 subjects, 84 (48%) of the subjects were found to have NSBVA which included 26 (14.86%) convergence insufficiency, 30 (17.14%) with accommodative insufficiency, 25 (14.29%) with convergence insufficiency secondary to accommodative insufficiency and 3 (1.71%) with accommodative infacility. A positive correlation between binocular accommodative facility and status of accommodation was found with a p-value <0.001 (r=0.51). Conclusion: Status of accommodation and facility test can help to differentiate the accommodative and vergence problems making examination less time consuming. Both of these procedures should be a part of general routine eye examination protocol in the young adult group, so that detection of these anomalies become less time consuming and patient gets benefitted from early intervention

Sub-dimensional Mardia measures of multivariate skewness and kurtosis

The Mardia measures of multivariate skewness and kurtosis summarize the respective characteristics of a multivariate distribution with two numbers. However, these measures do not reflect the sub-dimensional features of the distribution. Consequently, testing procedures based on these measures may fail to detect skewness or kurtosis present in a sub-dimension of the multivariate distribution. We introduce sub-dimensional Mardia measures of multivariate skewness and kurtosis, and investigate the information they convey about all sub-dimensional distributions of some symmetric and skewed families of multivariate distributions. The maxima of the sub-dimensional Mardia measures of multivariate skewness and kurtosis are considered, as these reflect the maximum skewness and kurtosis present in the distribution, and also allow us to identify the sub-dimension bearing the highest skewness and kurtosis. Asymptotic distributions of the vectors of sub-dimensional Mardia measures of multivariate skewness and kurtosis are derived, based on which testing procedures for the presence of skewness and of deviation from Gaussian kurtosis are developed. The performances of these tests are compared with some existing tests in the literature on simulated and real datasets