Janus hydrogel loaded with a CO2-generating chemical reaction system: Construction, characterization, and application in fruit and vegetable preservation.

In this study, we inserted a dynamic chemical reaction system that can generate CO2 into Janus hydrogel (JH) to develop a multidimensional preservation platform that integrates hygroscopicity, antibacterial activity, and modified atmospheric capacity. The double gel system developed using sodium alginate/trehalose at a 1:1 ratio effectively encapsulated 90% of citric acid. Furthermore, CO2 loss was avoided by separately embedding NaHCO3/cinnamon essential oil and citric acid microcapsules into a gelatin pad to develop JH. Freeze-dried JH exhibited a porous and asymmetric structure, very strongly absorbing moisture, conducting water, and rapidly releasing CO2 and essential oils. Furthermore, when preserving various fruits and vegetables in practical settings, JH provided several preservation effects, including color protection, microbial inhibition, and antioxidant properties. Our study findings broaden the application of JH technology for developing chemical reaction systems, with the resulting JH holding substantial promise for cold chain logistics.

Insights into Chitin-Degradation Potential of Shewanella khirikhana JW44 with Emphasis on Characterization and Function of a Chitinase Gene SkChi65.

Chitin, a polymer of ß-1,4-linked N-acetylglucosamine (GlcNAc), can be degraded into valuable oligosaccharides by various chitinases. In this study, the genome of Shewanella khirikhana JW44, displaying remarkable chitinolytic activity, was investigated to understand its chitin-degradation potential. A chitinase gene SkChi65 from this strain was then cloned, expressed, and purified to characterize its enzymatic properties and substrate hydrolysis. Genome analysis showed that, of the 14 genes related to chitin utilization in JW44, six belonged to glycoside hydrolase (GH) families because of their functional domains for chitin binding and catalysis. The recombinant chitinase SkChi65, consisting of 1129 amino acids, was identified as a member of the GH18 family and possessed two chitin-binding domains with a typical motif of [A/N]KWWT[N/S/Q] and one catalytic domain with motifs of DxxDxDxE, SxGG, YxR, and [E/D]xx[V/I]. SkChi65 was heterologously expressed as an active protein of 139.95 kDa best at 37 °C with 1.0 mM isopropyl-ß-d-thiogalactopyranoside induction for 6 h. Purified SkChi65 displayed high stability over the ranges of 30-50 °C and pH 5.5-8.0 with optima at 40 °C and pH 7.0. The kinetic parameters Km, Vmax, and kcat of SkChi65 towards colloidal chitin were 27.2 µM, 299.2 µMs-1, and 10,203 s-1, respectively. In addition to colloidal chitin, SkChi65 showed high activity towards glycol chitosan and crystalline chitin. After analysis by thin-layer chromatography, the main products were N,N'-diacetylchitobiose, and GlcNAc with (GlcNAc)2-6 used as substrates. Collectively, SkChi65 could exhibit both exo- and endochitinase activities towards diverse substrates, and strain JW44 has a high potential for industrial application with an excellent capacity for chitin bioconversion.

Pathway of Room-Temperature Formation of CdSeS Magic-Size Clusters from Mixtures of CdSe and CdS Samples.

The synthetic application of prenucleation-stage samples of colloidal semiconductor quantum dots (QDs) is in its infancy. It is shown that when two prenucleation-stage samples of binary CdSe and CdS are mixed, ternary CdSeS magic-size clusters (MSCs) grow at room temperature in dispersion. As the amount of the CdS sample increases, the optical absorption of the CdSeS MSCs blueshifts from ≈380 to ≈360 nm. It is proposed that the cluster in the CdSe sample reacts with the CdS monomer from the CdS sample. The monomer substitution reaction of CdSe by CdS can proceed continuously; thus, CdSeS MSCs with tunable compositions are obtained. The present study provides compelling evidence that clusters formed in the prenucleation stage of QDs. The clusters are precursor compounds (PCs) of MSCs, transforming at room temperature with the thermoneutrality principle of isodesmic reactions. The nucleation and growth of QDs follows a multi-step non-classical instead of one-step classical nucleation model.

Charge Trapping in Semiconductor Photocatalysts: A Time- and Space-Domain Perspective.

Harnessing solar energy to produce value-added fuels and chemicals through photocatalysis techniques holds promise for establishing a sustainable and environmentally friendly energy economy. The intricate dynamics of photogenerated charge carriers lies at the core of the photocatalysis. The balance between charge trapping and band-edge recombination has a crucial influence on the activity of semiconductor photocatalysts. Consequently, the regulation of traps in photocatalysts becomes the key to optimizing their activities. Nevertheless, our comprehension of charge trapping, compared to that of well-studied charge recombination, remains somewhat limited. This limitation stems from the inherently heterogeneous nature of traps at both temporal and spatial scales, which renders the characterization of charge trapping a formidable challenge. Fortunately, recent advancements in both time-resolved spectroscopy and space-resolved microscopy have paved the way for considerable progress in the investigation and manipulation of charge trapping. In this Perspective, we focus on charge trapping in photocatalysts with the aim of establishing a direct link to their photocatalytic activities. To achieve this, we begin by elucidating the principles of advanced time-resolved spectroscopic techniques such as femtosecond time-resolved transient absorption spectroscopy and space-resolved microscopic methods, such as single-molecule fluorescence microscopy and surface photovoltage microscopy. Additionally, we provide an overview of noteworthy research endeavors dedicated to probing charge trapping using time- and space-resolved techniques. Our attention is then directed toward recent achievements in the manipulation of charge trapping in photocatalysts through defect engineering. Finally, we summarize this Perspective and discuss the future challenges and opportunities that lie ahead in the field.

Promoting Photocatalytic H2 Evolution through Retarded Charge Trapping and Recombination by Continuously Distributed Defects in Methylammonium Lead Iodide Perovskite.

Inspired by its great success in the photovoltaic field, methylammonium lead iodide perovskite (MAPbI3 ) has recently been actively explored as photocatalysts in H2 evolution reactions. However, the practical application of MAPbI3 photocatalysts remains hampered by the intrinsically fast trapping and recombination of photogenerated charges. Herein, we propose a novel strategy of regulating the distribution of defective areas to promote charge-transfer dynamics of MAPbI3 photocatalysts. By deliberately designing and synthesizing the MAPbI3 photocatalysts featuring a unique continuation of defective areas, we demonstrate that such a feature enables retardation of charge trapping and recombination via lengthening the charge-transfer distance. As an outcome, such MAPbI3 photocatalysts turn out to achieve an impressive photocatalytic H2 evolution rate as high as 0.64 mmol ⋅ g-1 ⋅ h-1 , one order of magnitude higher than that of the conventional MAPbI3 photocatalysts. This work establishes a new paradigm for controlling charge-transfer dynamics in photocatalysis.

Remote Synergy between Heterogeneous Single Atoms and Clusters for Enhanced Oxygen Evolution.

Integrating single atoms and clusters into one system is a novel strategy to achieve desired catalytic performances. Compared with homogeneous single-atom cluster catalysts, heterogeneous ones combine the merits of different species and therefore show greater potential. However, it is still challenging to construct single-atom cluster systems of heterogeneous species, and the underlying mechanism for activity improvement remains unclear. In this work, we developed a heterogeneous single-atom cluster catalyst (ConIr1/N-C) for efficient oxygen evolution. The Ir single atoms worked in synergy with the Co clusters at a distance of about 8 Å, which optimized the configuration of the key intermediates. Consequently, the oxygen evolution activity was significantly improved on ConIr1/N-C relative to the Co cluster catalyst (Con/N-C), exhibiting an overpotential lower by 107 mV than that of Con/N-C at 10 mA cm-2 and a turnover frequency 50.9 times as much as that of Con/N-C at an overpotential of 300 mV.

Efficient Exciton Dissociation through the Edge Interfacial State in Metal Halide Perovskite-Based Photocatalysts.

Metal halide perovskites (MHPs) with superior optoelectronic properties have recently been actively pursued as catalysts in heterogeneous photocatalysis. Dissociating excitons into charge carriers holds the key to enhancing the photocatalytic performance of MHP-based photocatalysts, especially for those with strong quantum-confinement effects. However, attaining efficient exciton dissociation has been rather challenging. Herein, we propose a novel concept that the edge interfacial state can trigger anisotropic electron transfer to promote exciton dissociation. By taking Cs4PbBr6/TiO2 mesocrystal heterojunction as a proof-of-concept, we demonstrate that the unique interfacial state at the edge of the system is generated by the defect-mediated chemical interaction and acts as a trap state, which brings on a directionally favored electron transfer from the center to edge regions, thereby significantly enhancing the desired exciton dissociation. Consequently, such a system achieves an excellent performance in photocatalytic CO2 reduction. This paradigmatic work sheds light on the excitonic aspects for rational design of advanced photocatalysts toward high performance.

Myotonic dystrophy type 1 presenting with dyspnea: A case report.

BACKGROUND: Myotonic dystrophy type 1 (DM1) is a genetic neuromuscular disease involving multiple systems, especially the cardiopulmonary system. The clinical phenotype of DM1 patients is highly variable, which limits early diagnosis and treatment. In the present study, we reported a 35-year-old female DM1 patient with dyspnea as the primary onset clinical manifestation, analyzed her family's medical history, and reviewed related literature. CASE SUMMARY: A 35-year-old woman was admitted to the hospital with dyspnea of 1 mo duration, and sleep apnea for 3 d. Her respiratory pattern and effort were normal, but limb muscle tension was low. Investigation into the patient's medical history revealed that she might have hereditary neuromuscular disease. Electromyography showed that her myotonia potentials were visible in the resting state of the examined muscles, with decreased motor unit potential time limit and amplitude. Genetic testing for DM1 revealed that the cytosine-thymine-guanine (CTG) repeat number of the DMPK gene exceeded 50, while cytosine-CTG expansion in intron 1 of ZNF9 gene was < 30 repeats. The patient was diagnosed with DM1. CONCLUSION: DM1 is a genetic neuromuscular disease involving multiple systems, and the clinical phenotype in DM1 is extremely variable. Some patients with DM1 may be presented at the respiratory department because of dyspnea, which should be cautioned by the pulmonologists. There may be no obvious or specific symptoms in the early stage of disease, and clinicians should improve their understanding of DM1 and make an early diagnosis, which will improve patients' quality of life.

Unpaired Electron Engineering Enables Efficient and Selective Photocatalytic CO2 Reduction to CH4.

The photocatalytic CO2 reduction to CH4 reaction is a long process of proton-coupled charge transfer accompanied by various reaction intermediates. Achieving high CH4 selectivity with satisfactory conversion efficiency therefore remains rather challenging. Herein, we propose a novel strategy of unpaired electron engineering to break through such a demanding bottleneck. By taking TiO2 as a photocatalyst prototype, we prove that unpaired electrons stabilize the key intermediate of CH4 production, i.e., CHO*, via chemical bonding, which converts the endothermic step of CHO* formation to an exothermic process, thereby altering the reaction pathway to selectively produce CH4. Meanwhile, these unpaired electrons generate midgap states to restrict charge recombination by trapping free electrons. As an outcome, such an unpaired electron-engineered TiO2 achieves an electron-consumption rate as high as 28.3 µmol·g-1·h-1 (15.7-fold with respect to normal TiO2) with a 97% CH4 selectivity. This work demonstrates that electron regulation holds great promise in attaining efficient and selective heterogeneous photocatalytic conversion.

Comparative Genomic Analysis of Seven Vibrio alginolyticus Strains Isolated From Shrimp Larviculture Water With Emphasis on Chitin Utilization.

The opportunistic pathogen Vibrio alginolyticus is gaining attention because of its disease-causing risks to aquatic animals and humans. In this study, seven Vibrio strains isolated from different shrimp hatcheries in Southeast China were subjected to genome sequencing and subsequent comparative analysis to explore their intricate relationships with shrimp aquaculture. The seven isolates had an average nucleotide identity of ≥ 98.3% with other known V. alginolyticus strains. The species V. alginolyticus had an open pan-genome, with the addition of ≥ 161 novel genes following each new genome for seven isolates and 14 publicly available V. alginolyticus strains. The percentages of core genes of the seven strains were up to 83.1-87.5%, indicating highly conserved functions, such as chitin utilization. Further, a total of 14 core genes involved in the chitin degradation pathway were detected on the seven genomes with a single copy, 12 of which had undergone significant purifying selection (dN/dS < 1). Moreover, the seven strains could utilize chitin as the sole carbon-nitrogen source. In contrast, mobile genetic elements (MGEs) were identified in seven strains, including plasmids, prophages, and genomic islands, which mainly encoded accessory genes annotated as hypothetical proteins. The infection experiment showed that four of the seven strains might be pathogenic because the survival rates of Litopenaeus vannamei postlarvae were significantly reduced (P < 0.05) when compared to the control. However, no obvious correlation was noted between the number of putative virulence factors and toxic effects of the seven strains. Collectively, the persistence of V. alginolyticus in various aquatic environments may be attributed to its high genomic plasticity via the acquisition of novel genes by various MGEs. In view of the strong capability of chitin utilization by diverse vibrios, the timely removal of massive chitin-rich materials thoroughly in shrimp culture systems may be a key strategy to inhibit proliferation of vibrios and subsequent infection of shrimp. In addition, transcontinental transfer of potentially pathogenic V. alginolyticus strains should receive great attention to avoid vibriosis.

Defect-mediated electron transfer in photocatalysts.

Photocatalysis holds great potential in alleviating the growing energy crisis and environmental issues. Defect engineering has been demonstrated as an effective method to modulate the electronic structure of semiconductor photocatalysts for enhanced visible light absorption. However, the effect of defects on photocatalytic activity is still under debate because of the elusive charge transfer process mediated by defects. In this feature article, we summarize our recent progress in unraveling the defect-mediated electron transfer of the widely studied TiO2 and polymeric carbon nitride photocatalysts by combining ultrafast time-resolved spectroscopy and theoretical simulations. We find that the photogenerated electron transfer is greatly dependent on the type and concentration of defects. The location and occupation of defect states, and the dispersion degree of the energy band should be carefully tuned to maximize the advantages of defects for photocatalytic reactions.

Establishing a new hot electrons transfer channel by ion doping in a plasmonic metal/semiconductor photocatalyst.

A straightforward strategy is developed to improve the injection efficiency of hot electrons in a Ag/TiO2 plasmonic photocatalyst by introducing Fe as a dopant. The Fe dopant energy level formed within the bandgap of TiO2 provides an extra electron transfer channel for transferring the hot electrons induced by plasmonic Ag nanoparticles.

Shallow trap state-enhanced photocatalytic hydrogen evolution over thermal-decomposed polymeric carbon nitride.

We investigate the photogenerated electron kinetics of a thermal-decomposed polymeric carbon nitride (TCN) synthesized in air using femtosecond time-resolved diffuse reflectance spectroscopy. We find that the oxygen functional groups in TCN contribute to the formation of reactive shallow trap states for photogenerated electrons, leading to an enhanced activity for photocatalytic hydrogen evolution.

Near Bandgap Excitation Inhibits the Interfacial Electron Transfer of Semiconductor/Cocatalyst.

Understanding the ultrafast interfacial electron transfer (IET) process is essential for establishing the structure-property relationship of the semiconductor/cocatalyst system for photocatalytic H2 evolution. However, the IET kinetics for the near bandgap excitation has not been reported. Herein, we investigate the IET kinetics of g-C3N4/Pt as a semiconductor/cocatalyst prototype by femtosecond time-resolved diffuse reflectance spectroscopy. We find that the near bandgap excitation of g-C3N4 inhibits the IET of g-C3N4/Pt due to electron deep trapping, resulting in a markedly decreased apparent quantum efficiency for photocatalytic H2 evolution. This work complements the kinetic understanding for the photocatalytic mechanism of the semiconductor/cocatalyst system in its whole light absorption range.

Shallow Trap State-Induced Efficient Electron Transfer at the Interface of Heterojunction Photocatalysts: The Crucial Role of Vacancy Defects.

Constructing vacancies has been demonstrated to be an effective way to modulate charge flow in semiconductor photocatalysts. However, the role of vacancies in the interfacial electron transfer (IET) of heterojunction photocatalysts remains poorly understood, which hinders the general design of heterojunction photocatalysts. Herein, by taking g-C3N4/MoS2 as a heterojunction photocatalyst prototype, we unravel that vacancies play a critical role in the IET of heterojunction photocatalysts. Theoretical simulations, combined with femtosecond time-resolved diffuse reflectance spectroscopy, give a clear physical picture that N vacancy states act as shallow trap states (STSs) for photogenerated electrons and thereby facilitate the IET process due to a large energy difference between STSs and charge separation states. Moreover, the excess electrons left by the loss of N atoms (producing N vacancies) could partially transfer to MoS2 to generate STSs in the forbidden band of MoS2, where the transferred photogenerated electrons could be further trapped to efficiently drive H2 evolution. This work suggests a promising strategy to tune IET of heterojunction photocatalysts for achieving highly efficient photocatalytic reactions.

Ultrafast spectroscopic study of plasmon-induced hot electron transfer under NIR excitation in Au triangular nanoprism/g-C3N4 for photocatalytic H2 production.

Au TNP/g-C3N4 as a plasmonic photocatalyst for H2 production under NIR light irradiation was investigated by finite-difference time-domain (FDTD) simulations and time-resolved transient absorption measurements, revealing enhanced H2 production owing to a stronger electromagnetic field in Au TNP/g-C3N4 and plasmon-induced hot electron transfer from Au TNPs to g-C3N4.

The role of nitrogen defects in graphitic carbon nitride for visible-light-driven hydrogen evolution.

The introduction of nitrogen (N) defects (N vacancies labeled as Vns and cyano groups) has been demonstrated as one of the promising strategies to extend the light absorption range of graphitic carbon nitride (CN), thus improving the photocatalytic activity for hydrogen (H2) evolution. However, the photocatalysis mechanism of such N-deficient CN (DCN) has not been fully understood. In this study, N defects are introduced into CN by a KOH-assisted thermal polymerization method. On the basis of experimental investigations and density functional theory (DFT) calculations, it is found that the extension of the absorption range of DCN is attributed to both the valence band (VB) tailing induced by Vns and bandgap narrowing induced by cyano groups. Moreover, the conduction band (CB) is lowered by the N defects, indicating a reduced driving force for H2 evolution. Transient absorption (TA) spectroscopy reveals that when the electrons in the intrinsic VB of DCN are excited to the CB, the separation efficiency of these electrons and as-generated holes is seriously restricted by their low mobility. While when the electrons in VB tail states (Vn states) are excited to the CB, the separation efficiency of these electrons and as-generated holes could be almost maintained thanks to the improved mobility of the holes. As a result, DCN shows a limited enhancement of the H2 evolution rate compared with CN under visible light irradiation. This work points out that extending the light absorption range of a given photocatalyst by doping (or self-doping) may be accompanied by some negative factors, which restrict the overall photocatalytic activity.

Defect state-induced efficient hot electron transfer in Au nanoparticles/reduced TiO2 mesocrystal photocatalysts.

We investigated Au/TiO2 mesocrystals as plasmonic photocatalyst prototypes using single-particle photoluminescence (PL) spectroscopy combined with finite-difference time-domain (FDTD) simulations, and found that introduction of defect states builds up a channel for hot electrons with energies lower than the Schottky barrier height to transfer to the semiconductor.

Statistical study of ductility-dip cracking induced plastic deformation in polycrystalline laser 3D printed Ni-based superalloy.

Ductility-dip cracking in Ni-based superalloy, resulting from heat treatment, is known to cause disastrous failure, but its mechanism is still not completely clear. A statistical study of the cracking behavior as a function of crystal orientation in a laser 3D-printed DL125L Ni-based superalloy polycrystal is investigated here using the synchrotron X-ray microdiffraction. The dislocation slip system in each of the forty crystal grains adjacent to the 300 µm long crack has been analyzed through Laue diffraction peak shapes. In all these grains, edge-type geometrically necessary dislocations (GNDs) dominate, and their dislocation line directions are almost parallel to the crack plane. Based on Schmid's law, the equivalent uniaxial tensile force direction is revealed normal to the trace of the crack. A qualitative mechanism is thus proposed. Thermal tensile stress perpendicular to the laser scanning direction is elevated due to a significant temperature gradient, and thus locations in the materials where the thermal stress exceeds the yield stress undergo plastic deformation mediated by GND activations. As the dislocations slip inside the crystal grains and pile up at the grain boundaries, local strain/stress keeps increasing, until the materials in these regions fail to sustain further deformation, leading to voids formation and cracks propagation.

Cobalt-Nickel Layered Double Hydroxides Modified on TiO2 Nanotube Arrays for Highly Efficient and Stable PEC Water Splitting.

TiO2 -based photoanodes have attracted extensive attention worldwide for photoelectrochemical (PEC) water splitting, but these materials still suffer from poor electron-hole separation and low photoconversion efficiency. Here, the high PEC water splitting activity and long-term stability against photocorrosion of well-aligned hierarchical TiO2 @CoNi-layered double hydroxides nanotube arrays (TiO2 @CoNi-LDHs NTAs) are reported. The typical TiO2 @CoNi-LDHs NTAs exhibits enhancing photocurrent density of 4.4 mA cm-2 at a potential of 1.23 V (vs reversible hydrogen electrode) under AM 1.5G simulated sunlight (100 mW cm-2 ), 3.3 times higher than that of the pristine TiO2 sample. Moreover, this hierarchical electrode displays excellent stability against photocorrosion with initial activity loss no more than 1.0% even after 10 h irradiation in Na2 SO4 electrolyte solution (pH 6.8), much competitive to those reported TiO2 -based photoelectrodes. This work may offer a combinatorial synthesis strategy for the preparation of hierarchical architectures with high PEC performances.