Polymer Modification of Surface Electronic Properties of Electrocatalysts.

Finding alternative ways to tailor the electronic properties of a catalyst to actively and selectively drive reactions of interest has been a growing research topic in the field of electrochemistry. In this Letter, we investigate the tuning of the surface electronic properties of electrocatalysts via polymer modification. We show that when a nickel oxide water oxidation catalyst is coated with polytetrafluoroethylene, stable Ni-CF x bonds are introduced at the nickel oxide/polymer interface, resulting in shifting of the reaction selectivity away from the oxygen evolution reaction and toward hydrogen peroxide formation. It is shown that the electron-withdrawing character of the surface fluorocarbon molecule leaves a slight positive charge on the water oxidation intermediates at the adjacent active nickel sites, making their bonds weaker. The concept of modifying the surface electronic properties of an electrocatalyst via stable polymer modification offers an additional route to tune multipathway reactions in polymer/electrocatalyst environments, like with ionomer-modified catalysts or with membrane electrode assemblies.

Operando Infrared Spectroscopy Reveals the Dynamic Nature of Semiconductor-Electrolyte Interface in Multinary Metal Oxide Photoelectrodes.

Detailed knowledge about the semiconductor/electrolyte interface in photoelectrochemical (PEC) systems has been lacking because of the inherent difficulty of studying such interfaces, especially during operation. Current understandings of these interfaces are mostly from the extrapolation of ex situ data or from modeling approaches. Hence, there is a need for operando techniques to study such interfaces to develop a better understanding of PEC systems. Here, we use operando photoelectrochemical attenuated total reflection Fourier transform infrared (PEC-ATR-FTIR) spectroscopy to study the metal oxide/electrolyte interface, choosing BiVO4 as a model photoanode. We demonstrate that preferential dissolution of vanadium occurs from the BiVO4/water interface, upon illumination in open-circuit conditions, while both bismuth and vanadium dissolution occurs when an anodic potential is applied under illumination. This dynamic dissolution alters the surface Bi:V ratio over time, which subsequently alters the band bending in the space charge region. This further impacts the overall PEC performance of the photoelectrode, at a time scale very relevant for most lab-scale studies, and therefore has serious implications on the performance analysis and fundamental studies performed on this and other similar photoelectrodes.

Surgical Notes: To Play or Not to Play.

INTRODUCTION: Music is any sound that is perceived as pleasingly harmonious. The link between music and healthcare can be traced long back in the history of mankind. Thus, our study aimed at assessing the impact of different genre of music on the cognition functioning, memory and attention levels of the surgeons. MATERIALS AND METHODS: It was a single-arm interventional trial assessing 45 surgeons from different specialities. Each participant was expected to do 5 sets of tasks, one set each for the 5 music tracks played. Each task set further contained 5 different types of tasks, namely trail marking, jigsaw puzzle, backward counting, comprehension and memory game using cards. The 5 music tracks included ambient OR noise, music of personal preference, western classical, heavy metal and pop music. Scores were assigned for each task and compared. RESULTS: The total score for music of personal choice was much less (19.68) when compared to the other genre and that for pop was the highest (25.03). Memory card tests and backward counting (tests of short-term memory) were comparatively better with music of personal choice. However, trail marking (test of speed) and jigsaw puzzle and comprehension tests (tests of complex neurological functions) were least performed when music of personal choice was played. CONCLUSION: Music of choice may help in short-term memory recall, but an over-familiarity with the music played can serve as a distractor thus affecting the speed and accuracy.

Light induced formation of a surface heterojunction in photocharged CuWO4 photoanodes.

Photocharging has recently shown the ability to significantly improve the performance of several metal oxide photoanodes, similar to the enhancements achieved with co-catalysts and passivation overlayers. Herein, we demonstrate the effect of photocharging on CuWO4 photoanodes for the first time, with prolonged AM 1.5 illumination under open-circuit conditions. The photocharging treatment on CuWO4 samples doubled the photocurrent obtained at 1.23 VRHE. This enhancement is attributed to the light induced formation of a surface bound copper complex with the solution anion species in the electrolyte. This thin semiconducting copper borate layer forms a heterojunction with the CuWO4, improving the charge separation near the surface and thus suppressing the recombination of charge carriers in the space charge region. The striking similarities in photocharging of different metal oxide semiconductors highlights that the metal oxide semiconductor-electrolyte interface is more complex than previously understood. The formation of this time-dependent light induced surface layer should therefore be considered in all experimental studies on photo-electrochemistry with metal oxide semiconductor photoanodes.

Hot Carrier Generation and Extraction of Plasmonic Alloy Nanoparticles.

The conversion of light to electrical and chemical energy has the potential to provide meaningful advances to many aspects of daily life, including the production of energy, water purification, and optical sensing. Recently, plasmonic nanoparticles (PNPs) have been increasingly used in artificial photosynthesis (e.g., water splitting) devices in order to extend the visible light utilization of semiconductors to light energies below their band gap. These nanoparticles absorb light and produce hot electrons and holes that can drive artificial photosynthesis reactions. For n-type semiconductor photoanodes decorated with PNPs, hot charge carriers are separated by a process called hot electron injection (HEI), where hot electrons with sufficient energy are transferred to the conduction band of the semiconductor. An important parameter that affects the HEI efficiency is the nanoparticle composition, since the hot electron energy is sensitive to the electronic band structure of the metal. Alloy PNPs are of particular importance for semiconductor/PNPs composites, because by changing the alloy composition their absorption spectra can be tuned to accurately extend the light absorption of the semiconductor. This work experimentally compares the HEI efficiency from Ag, Au, and Ag/Au alloy nanoparticles to TiO2 photoanodes for the photoproduction of hydrogen. Alloy PNPs not only exhibit tunable absorption but can also improve the stability and electronic and catalytic properties of the pure metal PNPs. In this work, we find that the Ag/Au alloy PNPs extend the stability of Ag in water to larger applied potentials while, at the same time, increasing the interband threshold energy of Au. This increasing of the interband energy of Au suppresses the visible-light-induced interband excitations, favoring intraband excitations that result in higher hot electron energies and HEI efficiencies.

Retroperitoneal para-aortic paraganglioma.

Paragangliomas or chemodectomas are neoplasms that arise from neural crest cells and histologically resemble their adrenal counterpart, the pheochromocytoma. Seventy-one percent of the extra-adrenal paragangliomas are located in the superior or inferior para-aortic area. This tumor usually presents as an abdominal mass producing back pain. Tumor localization has improved remarkably through the use of computed tomography and I131MIBG (metaiodobenzylguanidine) scintigraphy, particularly when tumors are hormonally active. Surgical excision remains the mainstay of treatment, although vascularity can at times make excision difficult.

Retroperitoneal para-aortic paraganglioma.

Paragangliomas or chemodectomas are neoplasms that arise from neural crest cells and histologically resemble their adrenal counterpart, the pheochromocytoma. Seventy-one percent of the extra-adrenal paragangliomas are located in the superior or inferior paraaortic area. This tumor usually presents as an abdominal mass producing back pain. Tumor localization has improved remarkably through the use of computed tomography and I131 metaiodobenzyl-guanidine scintigraphy, particularly when tumors are hormonally active. Surgical excision remains the mainstay of treatment, although vascularity can at times make excision difficult.