Hydrogenation of ZnFe2O4 Flat Films: Effects of the Pre-Annealing Temperature on the Photoanodes Efficiency for Water Oxidation

The effects induced by post-synthesis hydrogenation on ZnFe2O4 flat films in terms of photoelectrochemical (PEC) performance of photoanodes for water oxidation have been deeply investigated as a function of the pre-annealing temperature of the materials. The structure and morphology of the films greatly affect the efficacy of the post synthesis treatment. In fact, highly compact films are obtained upon pre-annealing at high temperatures, and this limits the exposure of the material bulk to the reductive H2 atmosphere, making the treatment largely ineffective. On the other hand, a mild hydrogen treatment greatly enhances the separation of photoproduced charges in films pre-annealed at lower temperatures, as a result of the introduction of oxygen vacancies with n-type character. A comparison between present results and those obtained with ZnFe2O4 nanorods clearly demonstrates that specific structural and/or surface properties, together with the initial film morphology, differently affect the overall contribution of post-synthesis hydrogenation on the efficiency of zinc ferrite-based photoanodes

Measuring Student Engagement and Commitment on Private Academic Institutions Using Fuzzy Logic Expert System Metrics Applications

Even though academic knowledge is provided to academic institutions under very specific academic standards in teaching and research, the instruction’s management can impact significantly the student engagement and commitment on receiving and utilizing such knowledge. To analyse this challenge, a Fuzzy Logic, expert system-based software application has been developed and applied on a private academic institution. In this research the institution participated with 40 undergraduate students, from 24 different countries from two different semesters on the same course. The technology measures the student engagement and commitment via the co-evolute methodology for knowledge elicitation. By utilizing this approach, the management of academic institutions can make development analysis based on concrete bottom-up results. The collective analysis of the test results clearly identifies where students see the needs for greatest development and how they view their current state of engagement

Phronetic leadership style evaluation with a fuzzy logic application

The purpose of leadership style assessments is to determine the basic features and characteristics of leadership behaviours and to reveal the leader’s personality traits and abilities and to increase their self-awareness. The style can be, for example, democratic, autocratic, bureaucratic, laissez-faire, strategic, visionary, transformational, or transactional. However, ordinary assessments do not help leaders analyze their knowledge and wisdom behind their behaviours. The Wisdom Cube seeks to explain wisdom through the four dimensions of wisdom and provides a practical way of understanding the knowledge and wisdom in leadership. By utilising the dimensions and planes of the Wisdom Cube, we can find the way from data handling, information processing, and knowledge creation to wisdom generation. The aim of this research is, therefore, to reveal the ontology of the phronetic leader and to create a practical evaluation tool for leaders. The content of the article covers the elements of the Wisdom Cube, presents related efforts to measure and analyze phronetic leadership characteristics, and shows the practical results of the first test runs with the fuzzy logic-based application. The personal deep understanding of the leadership traits may then help the leaders to turn their current leadership styles more phronetic

Hybrid heterojunctions of solution-processed semiconducting 2d transition metal dichalcogenides

Exfoliated transition metal dichalcogenides (2D-TMDs) are attractive light-harvesting materials for large-area and inexpensive solar energy conversion given their ability to form highly tolerant heterojunctions. However, the preparation of large-area heterojunctions with these materials remains a challenge toward practical devices, and the details of photogenerated charge carrier harvesting are not well established. In this work, we use all solution-based methods to prepare large-area hybrid heterojunction films consisting of exfoliated semiconducting 2H-MoS2 flakes and a perylene-diimide (PDI) derivative. Hybrid photoelectrodes exhibited a 6-fold improvement in photocurrent compared to that of bare MoS2 or PDI films. Kelvin probe force microscopy, X-ray photoelectron spectroscopy, and transient absorption measurements of the hybrid films indicate the formation of an interfacial dipole at the MoS2/organic interface and suggest that the photogenerated holes transfer from MoS2 to the PDI. Moreover, performing the same analysis on MoSe2-based hybrid devices confirms the importance of proper valence band alignment for efficient charge transfer and photogenerated carrier collection in TMD/organic semiconductor hybrid heterojunctions

Benchmark performance of low-cost Sb2Se3 photocathodes for unassisted solar overall water splitting

Determining cost-effective semiconductors exhibiting desirable properties for commercial photoelectrochemical water splitting remains a challenge. Herein, we report a Sb2Se3 semiconductor that satisfies most requirements for an ideal high-performance photoelectrode, including a small band gap and favourable cost, optoelectronic properties, processability, and photocorrosion stability. Strong anisotropy, a major issue for Sb2Se3, is resolved by suppressing growth kinetics via close space sublimation to obtain high-quality compact thin films with favourable crystallographic orientation. The Sb2Se3 photocathode exhibits a high photocurrent density of almost 30mAcm(-2) at 0V against the reversible hydrogen electrode, the highest value so far. We demonstrate unassisted solar overall water splitting by combining the optimised Sb2Se3 photocathode with a BiVO4 photoanode, achieving a solar-to-hydrogen efficiency of 1.5% with stability over 10h under simulated 1 sun conditions employing a broad range of solar fluxes. Low-cost Sb2Se3 can thus be an attractive breakthrough material for commercial solar fuel production. While photoelectrochemical water splitting offers an integrated means to convert sunlight to a renewable fuel, cost-effective light-absorbers are rare. Here, authors report Sb2Se3 photocathodes for high-performance photoelectrochemical water splitting devices

A System for Performing High Throughput Assays of Synaptic Function

Unbiased, high-throughput screening has proven invaluable for dissecting complex biological processes. Application of this general approach to synaptic function would have a major impact on neuroscience research and drug discovery. However, existing techniques for studying synaptic physiology are labor intensive and low-throughput. Here, we describe a new high-throughput technology for performing assays of synaptic function in primary neurons cultured in microtiter plates. We show that this system can perform 96 synaptic vesicle cycling assays in parallel with high sensitivity, precision, uniformity, and reproducibility and can detect modulators of presynaptic function. By screening libraries of pharmacologically defined compounds on rat forebrain cultures, we have used this system to identify novel effects of compounds on specific aspects of presynaptic function. As a system for unbiased compound as well as genomic screening, this technology has significant applications for basic neuroscience research and for the discovery of novel, mechanism-based treatments for central nervous system disorders

Morphology stabilization strategies for small-molecule bulk heterojunction photovoltaics

The greater crystallinity of solution-processed small-molecule organic semiconductors, compared to their polymer counterparts, renders the bulk heterojunction (BHJ) more susceptible to phase separation under thermal stress, decreasing device performance. Here we demonstrate and compare strategies to stabilize the donor: acceptor BHJ in DPP(TBFu)(2):PC61BM solar cells using molecular additives designed to either afford compatiblization (CP) of the bulk heterojunction, or to in situ link (ISL) the components using a functional azide group. Both additives were found to stop phase segregation of the BHJ under thermal stress. At 5 wt% loading the ISL additive prevents phase segregation, while altering the azide reaction mechanism by using UV-induced linking versus thermal induced linking was found to significantly affect the device performance. Including 5 wt% of the CP additive slowed phase segregation and devices retained 80% of their optimum performance after 3000 min of thermal treatment at 110 degrees C (compared to 50% with the control). The CP additive at 10 wt% changed drastically the kinetics of phase segregation leading to devices with no decrease in performance over 3000 min thermal treatment. Thin film morphology characterization together with photoluminescence and impedance spectroscopy give further insight into the performance differences between the additives. These results reinforce the conclusion that the compatiblization method is the most promising strategy to engineer highly-efficient thermally-stable organic photovoltaics based on solution-processed small molecules

Single-crystalline, wormlike hematite photoanodes for efficient solar water splitting

A hematite photoanode showing a stable, record-breaking performance of 4.32 mA/cm(2) photoelectrochemical water oxidation current at 1.23 V vs. RHE under simulated 1-sun (100 mW/cm(2)) irradiation is reported. This photocurrent corresponds to ca. 34% of the maximum theoretical limit expected for hematite with a band gap of 2.1 V. The photoanode produced stoichiometric hydrogen and oxygen gases in amounts close to the expected values from the photocurrent. The hematitle has a unique single-crystalline "wormlike" morphology produced by in-situ two-step annealing at 550 degrees C and 800 degrees C of beta-FeOOH nanorods grown directly on a transparent conducting oxide glass via an all-solution method. In addition, it is modified by platinum doping to improve the charge transfer characteristics of hematite and an oxygen-evolving co-catalyst on the surface.open2

Engineering the self-assembly of diketopyrrolopyrrole-based molecular semiconductors via an aliphatic linker strategy

The solid-state self-assembly of molecular semiconductors is a key aspect for controlling the optoelectronic properties of organic electronic materials. Herein, we investigate the use of a flexible linker strategy to control the self-assembly of a solution-processable diketopyrrolopyrrole semiconductor coded as DPP(TBFu)(2). Two distinct dimers-prepared with varied linker position relative to the orientation of the conjugated core-reveal the effect of connectivity on the solid-state self-assembly and optoelectronic properties-favoring either Hor J-type aggregation. The dimer with a "vertical"linker orientation exhibits a poor crystallinity in neat films, but improves hole mobility in OFETs 10-fold, reaching 3.0 x 10(-3) cm(2) V-1 s(-1) when used as an additive with DPP(TBFu)(2). Distinctively, the dimer with a "horizontal" linking orientation does not enhance charge carrier transport, but is found to affect the thermal stability of donor : acceptor blends in OPVs with PCBM. Devices retain 90% of their initial conversion efficiency after 5 hours of thermal stress, compared to only 45% for control devices. Thermodynamic and kinetic rationales further suggest that this flexible linker strategy represents a powerful tool to control supramolecular assembly in molecular semiconductors without altering the nature of the core conjugated segment