Photoluminescence-based measurements of the energy gap and diffusion length of Zn_3P_2

The steady-state photoluminescence spectra of zinc phosphide (Zn_3P_2) wafers have revealed a fundamental indirect band gap at 1.38 eV, in close proximity to the direct band gap at 1.50 eV. These values are consistent with the values for the indirect and direct band gaps obtained from analysis of the complex dielectric function deduced from spectroscopic ellipsometric measurements. Bulk minority carrier lifetimes of 20 ns were observed by time-resolved photoluminescence decay measurements, implying minority-carrier diffusion lengths of ≥ 7 µm

Ultrafast reaction dynamics of polyatomic molecules probed by ionization

In the present work, the ultrafast dynamics of the photoinitiated electrocyclic ring-opening reactions of 1,3,5-cyclooctatriene and 7-dehydrocholesterol are investigated in a fs pump-probe experiment using ionization as the probe step. Concerning the 1,3,5-cyclooctatriene photoreaction, there are strong arguments for the participation of two different reaction channels (involving a 3-center and a 4-center substructure) which lead to three products. Studying the ring-opening reaction of 7-dehydrocholesterol, which is a substituted cyclic polyene, answers the crucial question to what extent an ultrafast reaction can be slowed down by the influence of a steric factor

Mixed-Metal Tungsten Oxide Photoanode Materials Made by Pulsed-Laser in Liquids Synthesis

Globally scalable sunlight-driven devices that convert solar energy into storable fuels will require efficient light absorbers that are made of non-precious elements. Suitable photoanode materials are yet to be discovered. Here we utilised the timesaving nature of pulsed-laser in liquids synthesis and prepared a series of neat and mixed-metal tungsten oxide photoanode materials to investigate the effect of ad-metals on optical and photocurrent generation properties. We obtained sub-μm-sized materials with different colours from W, Al, Ta, or first-row transition metal targets in water or aqueous ammonium metatungstate solutions. We observed metastable polymorphs of WO3 and tungsten oxides with varying degrees of oxygen deficiency. Pulsed-laser in liquids synthesis of Ni in ammonium metatungstate solutions produced hollow spheres (with ≤ 6% Ni with respect to W). Photocurrent generation in strong aqueous acid was highest in mixed-metal tungsten oxide photoanode materials with around 5% of iron or nickel

Impulsive Behaviors in Patients With Pathological Buying

Aim To investigate impulsive behaviors in pathological buying (PB). Methods The study included three groups matched for age and gender: treatment seeking outpatients with PB (PB+), treatment seeking psychiatric inpatients without PB (PB−), and a healthy control group (HC). PB was assessed by means of the Compulsive Buying Scale and by the impulse control disorder (ICD) module of the research version of the Structured Clinical Interview for DSM-IV (SCID-ICD). All participants answered questionnaires concerning symptoms of borderline personality disorder, self-harming behaviors, binge eating and symptoms of attention deficit and hyperactivity disorder (ADHD). In addition, comorbid ICDs were assessed using the SCID-ICD. Results The PB+ and PB− groups did not differ with regard to borderline personality disorder or ADHD symptoms, but both groups reported significantly more symptoms than the HC group. Frequencies of self-harming behaviors did not differ between the three groups. Patients with PB were more often diagnosed with any current ICD (excluding PB) compared to those without PB and the HC group (38.7% vs. 12.9% vs. 12.9%, respectively, p=.017). Discussion Our findings confirm prior research suggesting more impulsive behaviors in patients with and without PB compared to healthy controls. The results of the questionnaire-based assessment indicate that outpatients with PB perceive themselves equally impulsive and self-harm as frequently as inpatients without PB; but they seem to suffer more often from an ICD as assessed by means of an interview

A Randomized Study of Food Pictures-Influenced Decision-Making Under Ambiguity in Individuals With Morbid Obesity

Background and Aims In addition to craving responses to salient food cues, the anticipation of short-term rewarding consumption of palatable food may overrun the anticipation of long-term negative consequences of obesity. The present investigation addressed the potential interplay of food cravings and decision-making abilities in individuals with obesity. Method Study 1 included 107 bariatric surgery candidates with class 2/3 obesity (OB-group) and study 2 included 54 individuals with normal weight/pre-obesity (nonOB-group). In both studies, standardized questionnaires concerning food cravings, food addiction, and psychopathology were administered. A cue-reactivity paradigm was used to measure craving responses toward semi-individualized images of highly palatable, processed food/fruit (appetitive food cues) compared to images of raw vegetables (non-appetitive food cues). Decision-making was measured with a modified computerized version of the Iowa Gambling Task (IGT) with food pictures. Both groups were divided into two subgroups that were randomized to different IGT conditions. In one IGT condition the advantageous IGT card decks were covered by pictures of palatable, processed food or fruit and the disadvantageous decks by images of raw vegetables (= congruent condition), and in the other IGT conditionvice versa. Results Participants in the OB-group admitted on average higher craving responses toward palatable, processed food or fruit cues compared to pictures of raw vegetables. This was not the case in the nonOB-group. Contrary to our hypothesis, decision-making performance in both groups was worse when pictures of palatable, processed food or fruit were associated with advantageous IGT card decks compared to performance when those pictures were linked to the disadvantageous decks. The interference effect of food pictures processing on advantageous decision-making has been observed particularly in those individuals of the OB-group who exhibited high craving responses toward palatable, processed food cues or high levels of food addiction. Discussion The results indicate that food pictures processing interferes with decision-making, regardless of weight status. Opposed to the hypothesis, stronger tendencies to avoid than to approach pictures presenting processed, tasty food were observed. Further research should examine how cognitive avoidance tendencies toward processed, high energy food and approach tendencies toward healthy food can be transferred to real life situations

Theory of Strain-Induced Magnetic Order and Splitting of TcT_c and TTRSBT_{\rm TRSB} in Sr2_2RuO4_4

The internal structure of the superconducting state in Sr$_2$RuO$_4$ remains elusive at present, and exhibits evidence for time-reversal symmetry breaking. Recent muon spin relaxation measurements under uniaxial strain have revealed an increasing splitting between the superconducting critical temperature $T_c$ and the onset of time-reversal symmetry breaking $T_{\rm TRSB}$ with applied strain [Grinenko et al., arXiv:2001.08152]. In addition, static magnetic order is induced by the uniaxial strain beyond $\sim$1 GPa, indicating that unstrained Sr$_2$RuO$_4$ is close to a magnetic quantum critical point. Here, we perform a theoretical study of the magnetic susceptibility and the associated pairing structure as a function of uniaxial strain. It is found that the recent muon relaxation data can be qualitatively explained from the perspective of spin-fluctuation mediated pairing and the associated strain-dependence of accidentally degenerate pair states in unstrained Sr$_2$RuO$_4$. In addition, while unstrained Sr$_2$RuO$_4$ features mainly $(2\pi/3,2\pi/3)$ magnetic fluctuations, uniaxial strain promotes $(\pi,\pm\pi/2)$ magnetism.Comment: 8 pages, 4 figure

Leaping and Landing in Brave Spaces

Vapor-fed electrolysis of water has been performed using membrane-electrode assemblies (MEAs) incorporating earth-abundant catalysts and bipolar membranes (BPMs). Catalyst films containing CoP nanoparticles, carbon black, and Nafion were synthesized, characterized, and integrated into cathodes of MEAs. The CoP-containing MEAs exhibited stable (>16 h) vapor-fed electrolysis of water at room temperature at a current density of 10 mA cm⁻² with 350 mV of additional overvoltage relative to MEA's formed from Pt/C cathodic electrocatalysts due to slower hydrogen-evolution reaction kinetics under vapor-fed conditions and fewer available triple-phase boundaries in the catalyst film. Additionally, catalyst films containing a [NiFe]-layered double hydroxide ([NiFe]-LDH) as well as a hydroxide ion conductor, hexamethyl-p-terphenyl poly(benzimidazolium) (HMT-PMBI), were synthesized, characterized, and integrated into the anodes of the MEAs. The [NiFe]-LDH-containing MEAs exhibited overvoltages at 10 mA cm⁻² that were similar to those of IrO_x-containing MEAs for vapor-fed electrolysis of water at room temperature. A BPM was formed by pairing Nafion with HMT-PMBI, resulting in a locally alkaline environment of HMT-PMBI to stabilize the [NiFe]-LDH and a locally acidic environment to stabilize the CoP. BPM-based MEAs were stable (>16 h) for vapor-fed electrolysis of water at room temperature at a current density of 10 mA cm⁻², with a change in the pH gradient of 1 unit over 16 h of electrolysis for IrOx-containing MEAs. The stability of [NiFe]-LDH-based MEAs under vapor-fed conditions was dependent on the catalyst film morphology and resulting BPM interface, with stable operation at 10 mA cm⁻² achieved for 16 h. All MEAs exhibited a drift in the operating voltage over time associated with dehydration. These results demonstrate that earth-abundant catalysts and BPMs can be incorporated into stable, room-temperature, vapor-fed water-splitting cells operated at 10 mA cm⁻²

Passivation of Zn_3P_2 substrates by aqueous chemical etching and air oxidation

Surface recombination velocities measured by time-resolved photoluminescence and compositions of Zn_(3)P_2 surfaces measured by x-ray photoelectron spectroscopy (XPS) have been correlated for a series of wet chemical etches of Zn_(3)P_2 substrates. Zn_(3)P_2 substrates that were etched with Br_2 in methanol exhibited surface recombination velocity values of 2.8 × 10^4 cm s^(−1), whereas substrates that were further treated by aqueous HF–H_(2)O_2 exhibited surface recombination velocity values of 1.0 × 10^4 cm s^(−1). Zn_(3)P_2 substrates that were etched with Br_2 in methanol and exposed to air for 1 week exhibited surface recombination velocity values of 1.8 × 10^3 cm s^(−1), as well as improved ideality in metal/insulator/semiconductor devices

Mixed-Metal Tungsten Oxide Photoanode Materials Made by Pulsed-Laser in Liquids Synthesis

Globally scalable sunlight-driven devices that convert solar energy into storable fuels will require efficient light absorbers that are made of non-precious elements. Suitable photoanode materials are yet to be discovered. Here we utilised the timesaving nature of pulsed-laser in liquids synthesis and prepared a series of neat and mixed-metal tungsten oxide photoanode materials to investigate the effect of ad-metals on optical and photocurrent generation properties. We obtained sub-μm-sized materials with different colours from W, Al, Ta, or first-row transition metal targets in water or aqueous ammonium metatungstate solutions. We observed metastable polymorphs of WO3 and tungsten oxides with varying degrees of oxygen deficiency. Pulsed-laser in liquids synthesis of Ni in ammonium metatungstate solutions produced hollow spheres (with ≤ 6% Ni with respect to W). Photocurrent generation in strong aqueous acid was highest in mixed-metal tungsten oxide photoanode materials with around 5% of iron or nickel

Mechanism of Laser-Induced Bulk and Surface Defect Generation in ZnO and TiO_2 Nanoparticles: Effect on Photoelectrochemical Performance

Laser processing of neat and gold-nanoparticle-functionalized ZnO and TiO_2 nanoparticles by nanosecond–355 nm or picosecond–532 nm light enabled control of photocurrent generation under simulated sunlight irradiation in neutral aqueous electrolytes. We obtained more than 2-fold enhanced photoelectrochemical performance of TiO2 nanoparticles upon irradiation by picosecond–532 nm pulses that healed defects. Laser processing and gold nanoparticle functionalization of ZnO and TiO_2 nanomaterials resulted in color changes that did not originate from optical bandgaps or crystal structures. Two-dimensional photoluminescence data allowed us to differentiate and quantify surface and bulk defects that play a critical yet oft-underappreciated role for photoelectrochemical performance as sites for detrimental carrier recombination. We developed a detailed mechanistic model of how surface and bulk defects were generated as a function of laser processing parameters and obtained key insights on how these defects affected photocurrent production. The controlled healing of defects by pulsed-laser processing may be useful in the design of solar fuels materials