Eosin Y, a well‐known economical alternative to metal catalysts in visible‐light‐driven single‐electron transfer‐based organic transformations, can behave as an effective direct hydrogen‐atom ...transfer catalyst for C−H activation. Using the alkylation of C−H bonds with electron‐deficient alkenes as a model study revealed an extremely broad substrate scope, enabling easy access to a variety of important synthons. This eosin Y‐based photocatalytic hydrogen‐atom transfer strategy is promising for diverse functionalization of a wide range of native C−H bonds in a green and sustainable manner.
Neutral eosin Y has been employed as an effective direct hydrogen‐atom transfer photocatalyst to activate a wide range of native C−H bonds in a green and sustainable fashion. This transformation is distinguished by its operational simplicity and amenability to large‐scale synthesis using continuous‐flow technology (EWG=aldehyde, ketone, ester, amide, imide, cyanide, sulfone, nitro, pyridine).
Photo/electrocatalytic ammonia synthesis has recently developed fast while the ammonia yields over state‐of‐the‐art photo/electrocatalysts are still very moderate. Such low concentration of ...synthesized NH3 brings about a challenge to the reliable quantification of the product in photo/electrocatalysis. Notably, we found that the quantitative detection of ammonia concentration below 0.2 ppm is error‐prone, which is likely the case happening in the majority of photo/electrocatalytic NH3 synthesis, thus arising concerns about the rationality and accuracy for low‐concentration ammonia quantification in these processes. Herein, we discuss the methodology used and analyze the reliability of various detection methods for the detection of trace ammonia in aqueous media. The challenges facing the detection of low concentration of ammonia in photo/electrocatalysis can be overcome by integration with multiple detection methods. According to the data presented, we also propose an effective criterion for precise quantification of ammonia, avoiding the unreasonable comparisons in photo/electrocatalytic ammonia synthesis.
The analytical methods for the detection of ammonia concentration below 0.2 ppm in photo/electrocatalytic N2 fixation are evaluated rigorously, reliably, and insightfully. The low‐concentration ammonia quantification minefield was indicated and a rigorous ammonia detection flowchart as well as another reference standard to achieve a more accurate and responsible ammonia detection in photo/electrocatalysis was concluded.
Photocatalytic hydrogen evolution is a promising technique for the direct conversion of solar energy into chemical fuels. Colloidal quantum dots with tunable band gap and versatile surface properties ...remain among the most prominent targets in photocatalysis despite their frequent toxicity, which is detrimental for environmentally friendly technological implementations. In the present work, all-inorganic sulfide-capped InP and InP/ZnS quantum dots are introduced as competitive and far less toxic alternatives for photocatalytic hydrogen evolution in aqueous solution, reaching turnover numbers up to 128,000 based on quantum dots with a maximum internal quantum yield of 31%. In addition to the favorable band gap of InP quantum dots, in-depth studies show that the high efficiency also arises from successful ligand engineering with sulfide ions. Due to their small size and outstanding hole capture properties, sulfide ions effectively extract holes from quantum dots for exciton separation and decrease the physical and electrical barriers for charge transfer.
Semiconducting quantum dots (QDs) have recently triggered a huge interest in constructing efficient hydrogen production systems. It is well established that a large fraction of surface atoms of QDs ...need ligands to stabilize and avoid them from aggregating. However, the influence of the surface property of QDs on photocatalysis is rather elusive. Here, the surface regulation of CdSe QDs is investigated by surface sulfide ions (S2−) for photocatalytic hydrogen evolution. Structural and spectroscopic study shows that with gradual addition of S2−, S2− first grows into the lattice and later works as ligands on the surface of CdSe QDs. In‐depth transient spectroscopy reveals that the initial lattice S2− accelerates electron transfer from QDs to cocatalyst, and the following ligand S2− mainly facilitates hole transfer from QDs to the sacrificial agent. As a result, a turnover frequency (TOF) of 7950 h−1 can be achieved by the S2− modified CdSe QDs, fourfold higher than that of original mercaptopropionic acid (MPA) capped CdSe QDs. Clearly, the simple surface S2− modification of QDs greatly increases the photocatalytic efficiency, which provides subtle methods to design new QD material for advanced photocatalysis.
To unravel how surface sulfide ions (S2−)regulate photocatalytic hydrogen evolution of CdSe quantum dots (QDs), the different roles of introduced S2− on QDs are revealed. The results show that S2− at an earlier stage grows into the lattice and accelerates electron transfer, while afterward the S2− works as ligands and promotes hole transfer, and thus greatly improves the photocatalytic hydrogen evolution efficiency.
Photocatalysts based on g-C3N4 by loading cocatalysts or constructing heterojunctions have shown great potential in solar-driven water oxidation. However, the intrinsic drawbacks of g-C3N4, such as ...poor mass diffusion and charge separation efficiency, remain as the bottleneck to achieve highly efficient water oxidation. Here we report a simple protonation method to improve the activity of g-C3N4. Studies using valence band X-ray photoelectron spectra and steady-state and time-resolved spectroscopy reveal that the promotion of catalytic ability originates from the higher thermodynamical driving force and longer-lived charge separation state, which may provide guidance in designing efficient polymeric semiconductor photocatalysts with desirable kinetics for water oxidation.
PurposeThe purpose of this paper is to report the findings of a study that examines the influence of leader–member exchange (LMX) on employees' turnover intention and presenteeism with the mediating ...role of perceived organizational support in the context of the semiconductor industry.Design/methodology/approachAn empirical study based on a sample of 124 department managers and 241 team members in five high-tech companies in Taiwan. Structural equation modelling analysis was used for hypothesis testing.FindingsThe results reveal that perceived organization support significantly relates to employees' turnover intention and mediates the relationship between LMX and turnover intention. Additionally, employees' presenteeism is influenced by perceived LMX.Practical implicationsThe results of the study are of high importance for high-tech companies, which continuously strive for innovation efficiency and sustainability. Managers and practitioners could benefit from better understanding regarding the importance of perceived organization support and LMX in affecting employee behaviours and company performance.Originality/valueThe present study finds a significant positive relationship between LMX and presenteeism, which is contrary to the previous research.
The catalytic nature of semiconducting quantum dots (QDs) for photocatalytic hydrogen (H2) evolution can be thoroughly aroused, not because of coupling with external cocatalysts, but through ...partially covering controlled amount of ZnS shell on the surface. Specifically, CdSe QDs, with an optimal coverage of ZnS (≈46%), can produce H2 gas with a constant rate of ≈306.3 ± 21.1 µmol mg−1 h−1 during 40 h, thereby giving a turnover number of ≈(4.4 ± 0.3) × 105, which is ≈110‐fold to that of unmodified CdSe QDs under identical conditions. The performance of H2 evolution is comparable to or even better than the commonly used external cocatalysts, e.g., metal complexes, noble metals assisted photosystems. Mechanistic insights indicate that the dramatically enhanced activity and stability of bare QDs for photocatalytic H2 production are derived from (i) inhibiting exciton annihilation at trap states, (ii) preventing the photo‐oxidation of core frameworks, and (iii) retaining tunneling efficiencies of photogenerated electrons and holes to reactive sites with partial ZnS coverage.
The self‐catalytic nature of semiconducting quantum dots (QDs) for photocatalytic H2
evolution can be thoroughly aroused by a simple surface engineering method, which not only eliminates the reliance on external cocatalysts in designing artificial photocatalysts, but also provides privileges in making QD‐based devices practically viable.
Contact angle, a quantitative measure of macroscopic surface wettability, plays an important role in understanding liquid-vapor heterogeneous phase change phenomena, e.g., boiling heat transfer. The ...contact angles of water at elevated temperatures are of particular interest for understanding of wettability-regulated boiling heat transfer in steam-based power generation. From a more theoretical perspective, the temperature dependence of contact angle of water is also essential to estimation of several key surface thermodynamic properties, such as the solid surface tension, the surface entropy, and the heats of immersion and adsorption. Here, a comprehensive review of historical efforts in measuring the contact angles of water over a wide temperature range on a variety of solids, not limited to metallic surfaces, is presented. As suggested by the literature data, the temperature dependence of contact angle of water may be classified into three regimes: (a) low temperatures below the saturation point (i.e., 100 °C at atmospheric pressure), (b) medium temperatures up to ~170 °C, and (c) high temperatures up to 300 °C at pressurized conditions. A slightly-decreasing or nearly-invariant trend of the contact angles of water on both non-metallic and metallic surfaces was reported for the low-temperature regime. In contrast, a steeper linear decline in water contact angle was demonstrated at temperatures above 100 °C. The few experimental data available on several metallic surfaces showed that the contact angle of water either again becomes nearly temperature-independent or further decreases with temperature above 210 °C. A theoretical understanding of the temperature dependence is given based on surface thermodynamic analysis, although the exact molecular mechanisms underlying these experimental observations remain unclear. Consequently, the theoretical model for predicting the variation of the contact angle of water with temperature is not well-developed. As the critical point of water (374 °C and 22.1 MPa) is approached, the surface tension, and hence the contact angle, should become vanishingly small. However, this theoretical expectation has not yet been verified due to the lack of experimental data at such high temperatures/pressures. Finally, future research directions are identified, including a systematic exploration of the contact angle at near-critical temperatures, the effects of surface oxidation, corrosion, and deposition on contact angle during operation of boilers and reactors, and the particular effect of irradiation on contact angle in nuclear reactor applications.
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•Studies on temperature dependence of the contact angle of water are reviewed.•Rise in temperature increases hydrophilicity of solid surfaces to a large extent.•Discussions on the effects of temperature are made based on thermodynamics.•Implications for understanding and prediction of boiling heat transfer are given.•Current research gaps and future outlooks for this area are also highlighted.
The enzyme nitrogenase inspires the development of novel photocatalytic and electrocatalytic systems that can drive nitrogen reduction with water under similar low-temperature and low-pressure ...conditions. While photocatalytic and electrocatalytic N
fixation are emerging as hot new areas of fundamental and applied research, serious concerns exist regarding the accuracy of current methods used for ammonia detection and quantification. In most studies, the ammonia yields are low and little consideration is given to the effect of interferants on NH
quantification. As a result, NH
yields reported in many works may be exaggerated and erroneous. Herein, the advantages and limitations of the various methods commonly used for NH
quantification in solution (Nessler's reagent method, indophenol blue method, and ion chromatography method) are systematically explored, placing particular emphasis on the effect of interferants on each quantification method. Based on the data presented, guidelines are suggested for responsible quantification of ammonia in photocatalysis and electrocatalysis.
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