A universal and scalable transformation of bulk metals into single-atom catalysts in ionic liquids.

Single-atom catalysts (SACs) with maximized metal atom utilization and intriguing properties are of utmost importance for energy conversion and catalysis science. However, the lack of a straightforward and scalable synthesis strategy of SACs on diverse support materials remains the bottleneck for their large-scale industrial applications. Herein, we report a general approach to directly transform bulk metals into single atoms through the precise control of the electrodissolution-electrodeposition kinetics in ionic liquids and demonstrate the successful applicability of up to twenty different monometallic SACs and one multimetallic SAC with five distinct elements. As a case study, the atomically dispersed Pt was electrodeposited onto Ni3N/Ni-Co-graphene oxide heterostructures in varied scales (up to 5 cm × 5 cm) as bifunctional catalysts with the electronic metal-support interaction, which exhibits low overpotentials at 10 mA cm-2 for hydrogen evolution reaction (HER, 30 mV) and oxygen evolution reaction (OER, 263 mV) with a relatively low Pt loading (0.98 wt%). This work provides a simple and practical route for large-scale synthesis of various SACs with favorable catalytic properties on diversified supports using alternative ionic liquids and inspires the methodology on precise synthesis of multimetallic single-atom materials with tunable compositions.

Metal-insulator-semiconductor photoelectrodes for enhanced photoelectrochemical water splitting.

Photoelectrochemical (PEC) water splitting provides a scalable and integrated platform to harness renewable solar energy for green hydrogen production. The practical implementation of PEC systems hinges on addressing three critical challenges: enhancing energy conversion efficiency, ensuring long-term stability, and achieving economic viability. Metal-insulator-semiconductor (MIS) heterojunction photoelectrodes have gained significant attention over the last decade for their ability to efficiently segregate photogenerated carriers and mitigate corrosion-induced semiconductor degradation. This review discusses the structural composition and interfacial intricacies of MIS photoelectrodes tailored for PEC water splitting. The application of MIS heterostructures across various semiconductor light-absorbing layers, including traditional photovoltaic-grade semiconductors, metal oxides, and emerging materials, is presented first. Subsequently, this review elucidates the reaction mechanisms and respective merits of vacuum and non-vacuum deposition techniques in the fabrication of the insulator layers. In the context of the metal layers, this review extends beyond the conventional scope, not only by introducing metal-based cocatalysts, but also by exploring the latest advancements in molecular and single-atom catalysts integrated within MIS photoelectrodes. Furthermore, a systematic summary of carrier transfer mechanisms and interface design principles of MIS photoelectrodes is presented, which are pivotal for optimizing energy band alignment and enhancing solar-to-chemical conversion efficiency within the PEC system. Finally, this review explores innovative derivative configurations of MIS photoelectrodes, including back-illuminated MIS photoelectrodes, inverted MIS photoelectrodes, tandem MIS photoelectrodes, and monolithically integrated wireless MIS photoelectrodes. These novel architectures address the limitations of traditional MIS structures by effectively coupling different functional modules, minimizing optical and ohmic losses, and mitigating recombination losses.

Cyclo[2]pyridine[8]pyrrole: An Expanded Porphyrinoid with Three Closed-Shell Oxidation States.

We report here an expanded porphyrinoid, cyclo[2]pyridine[8]pyrrole, 1, that can exist at three closed-shell oxidation levels. Macrocycle 1 was synthesized via the oxidative coupling of two open chain precursors and fully characterized by means of NMR and UV-vis spectroscopies, MS, and X-ray crystallography. Reduction of the fully oxidized form (1, blue) with NaBH4 produced either the half-oxidized (2, teal) or fully reduced forms (3, pale yellow), depending on the amount of reducing agent used and the presence or absence of air. Reduced products 2 or 3 can be oxidized to 1 by various oxidants (quinones, FeCl3, and AgPF6). Macrocycle 1 also undergoes proton-coupled reductions with I-, Br-, Cl-, SO32-, or S2O32- in the presence of an acid. Certain thiol-containing compounds likewise reduce 1 to 2 or 3. This conversion is accompanied by a readily discernible color change, making cyclo[2]pyridine[8]pyrrole 1 able to differentiate biothiols, such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH).

Mixed-Halide Perovskites with Halogen Bond Induced Interlayer Locking Structure for Stable Pure-Red PeLEDs.

Mixed-halide perovskites enable precise spectral tuning across the entire spectral range through composition engineering. However, mixed halide perovskites are susceptible to ion migration under continuous illumination or electric field, which significantly impedes the actual application of perovskite light-emitting diodes (PeLEDs). Here, we demonstrate a novel approach to introduce strong and homogeneous halogen bonds within the quasi-two-dimensional perovskite lattices by means of an interlayer locking structure, which effectively suppresses ion migration by increasing the corresponding activation energy. Various characterizations confirmed that intralattice halogen bonds enhance the stability of quasi-2D mixed-halide perovskite films. Here, we report that the PeLEDs exhibit an impressive 18.3% EQE with pure red emission with CIE color coordinate of (0.67, 0.33) matching Rec. 2100 standards and demonstrate an operational half-life of ∼540 min at an initial luminance of 100 cd m-2, representing one of the most stable mixed-halide pure red PeLEDs reported to date.

Tailoring Oxygen-Depleted and Unitary Ti3C2T x Surface Terminals by Molten Salt Electrochemical Etching Enables Dendrite-Free Stable Zn Metal Anode.

Two-dimensional Ti3C2Tx MXene materials, with metal-like conductivities and versatile terminals, have been considered to be promising surface modification materials for Zn-metal-based aqueous batteries (ZABs). However, the oxygen-rich and hybridized terminations caused by conventional methods limit their advantages in inhibiting zinc dendrite growth and reducing corrosion-related side reactions. Herein, -O-depleted, -Cl-terminated Ti3C2Tx was precisely fabricated by the molten salt electrochemical etching of Ti3AlC2, and controlled in-situ terminal replacement from -Cl to unitary -S or -Se was achieved. The as-prepared -O-depleted and unitary-terminal Ti3C2Tx as Zn anode coatings provided excellent hydrophobicity and enriched zinc-ionophilic sites, facilitating Zn2+ horizontal transport for homogeneous deposition and effectively suppressing water-induced side reactions. The as-assembled Ti3C2Sx@Zn symmetric cell achieved a cycle life of up to 4200 h at a current density and areal capacity of 2 mA cm-2 and 1 mAh cm-2, respectively, with an impressive cumulative capacity of up to 7.25 Ah cm-2 at 5 mA cm-2 // 2 mAh cm-2. These findings provide an effective electrochemical strategy for tailoring -O-depleted and unitary Ti3C2Tx surface terminals and advancing the understanding of the role of specific Ti3C2Tx surface chemistry in regulating the plating/stripping behaviors of metal ions.

Ligand-Engineered HgTe Colloidal Quantum Dot Solids for Infrared Photodetectors.

HgTe colloidal quantum dots (CQDs) are promising absorber systems for infrared detection due to their widely tunable photoresponse in all infrared regions. Up to now, the best-performing HgTe CQD photodetectors have relied on using aggregated CQDs, limiting the device design, uniformity and performance. Herein, we report a ligand-engineered approach that produces well-separated HgTe CQDs. The present strategy first employs strong-binding alkyl thioalcohol ligands to enable the synthesis of well-dispersed HgTe cores, followed by a second growth process and a final postligand modification step enhancing their colloidal stability. We demonstrate highly monodisperse HgTe CQDs in a wide size range, from 4.2 to 15.0 nm with sharp excitonic absorption fully covering short- and midwave infrared regions, together with a record electron mobility of up to 18.4 cm2 V-1 s-1. The photodetectors show a room-temperature detectivity of 3.9 × 1011 jones at a 1.7 µm cutoff absorption edge.

Manipulating Local Lattice Distortion for Spectrally Stable and Efficient Mixed-halide Blue Perovskite LEDs.

Mixed-halide perovskites are considered the most straightforward candidate to realize blue perovskite light-emitting diodes (PeLEDs). However, they suffer severe halide migration, leading to spectral instability, which is particularly exaggerated in high chloride alloying perovskites. Here, we demonstrate energy barrier of halide migration can be tuned by manipulating the degree of local lattice distortion (LLD). Enlarging the LLD degree to a suitable level can increase the halide migration energy barrier. We herein report an "A-site" cation engineering to tune the LLD degree to an optimal level. DFT simulation and experimental data confirm that LLD manipulation suppresses the halide migration in perovskites. Conclusively, mixed-halide blue PeLEDs with a champion EQE of 14.2 % at 475 nm have been achieved. Moreover, the devices exhibit excellent operational spectral stability (T50 of 72 min), representing one of the most efficient and stable pure-blue PeLEDs reported yet.

Matching Charge Extraction Contact for Infrared PbS Colloidal Quantum Dot Solar Cells.

Infrared solar cells (IRSCs) can supplement silicon or perovskite SCs to broaden the utilization of the solar spectrum. As an ideal infrared photovoltaic material, PbS colloidal quantum dots (CQDs) with tunable bandgaps can make good use of solar energy, especially the infrared region. However, as the QD size increases, the energy level shrinking and surface facet evolution makes us reconsider the matching charge extraction contacts and the QD passivation strategy. Herein, different to the traditional sol-gel ZnO layer, energy-level aligned ZnO thin film from a magnetron sputtering method is adopted for electron extraction. In addition, a modified hybrid ligand recipe is developed for the facet passivation of large size QDs. As a result, the champion IRSC delivers an open circuit voltage of 0.49 V and a power conversion efficiency (PCE) of 10.47% under AM1.5 full-spectrum illumination, and the certified PCE is over 10%. Especially the 1100 nm filtered efficiency achieves 1.23%. The obtained devices also show high storage stability. The present matched electron extraction and QD passivation strategies are expected to highly booster the IR conversion yield and promote the fast development of new conception QD optoelectronics.

Photo-assisted microbial fuel cell systems: critical review of scientific rationale and recent advances in system development.

Bioelectrochemical systems such as microbial fuel cells (MFCs) have gained extensive attention due to their abilities to simultaneously treat wastewater and generate renewable energy resources. Recently, to boost the system performance, the photoelectrode has been incorporated into MFCs for effectively exploiting the synergistic interaction between light and microorganisms, and the resultant device is known as photo-assisted microbial fuel cells (photo-MFCs). Combined with the metabolic reaction of organic compounds by microorganisms, photo-MFCs are capable of simultaneously converting both chemical energy and light energy into electricity. This article aims to systematically review the recent advances in photo-MFCs, including the introduction of specific photosynthetic microorganisms used in photo-MFCs followed by the discussion of the fundamentals and configurations of photo-MFCs. Moreover, the materials used for photoelectrodes and their fabrication approaches are also explored. This review has shown that the innovative strategy of utilizing photoelectrodes in photo-MFCs is promising and further studies are warranted to strengthen the system stability under long-term operation for advancing practical application.

Applications of atmospheric cold plasma in agricultural, medical, and bioprocessing industries.

Atmospheric cold plasma (ACP) is a nonthermal technology that is extensively used in several industries. Within the scopes of engineering and biotechnology, some notable applications of ACP include waste management, material modification, medicine, and agriculture. Notwithstanding numerous applications, ACP still encounters a number of challenges such as diverse types of plasma generators and sizes, causing standardization challenges. This review focuses on the uses of ACP in engineering and biotechnology sectors in which the innovation can positively impact the operation process, enhance safety, and reduce cost. Additionally, its limitations are examined. Since ACP is still in its nascent stage, the review will also propose potential research opportunities that can help scientists gain more insights on the technology. KEY POINTS: • ACP technology has been used in agriculture, medical, and bioprocessing industries. • Chemical study on the reactive species is crucial to produce function-specific ACP. • Different ACP devices and conditions still pose standardization problems.

Enhancing Bioactive Saponin Content of Raphanus sativus Extract by Thermal Processing at Various Conditions.

Pickled radish (Raphanus sativus) is a traditional Asian ingredient, but the traditional method takes decades to make this product. To optimize such a process, this study compared the saponin content of pickled radishes with different thermal processing and traditional processes (production time of 7 days, 10 years, and 20 years) and evaluated the effects of different thermal processes on the formation of radish saponin through kinetics study and mass spectrometry. The results showed that increasing the pickling time enhanced the formation of saponin in commercial pickled radishes (25 °C, 7 days, 6.50 ± 1.46 mg g-1; 3650 days, 23.11 ± 1.22 mg g-1), but these increases were lower than those induced by thermal processing (70 °C 30 days 24.24 ± 1.01 mg g-1). However, it was found that the pickling time of more than 10 years and the processing temperature of more than 80 °C reduce the saponin content. Liquid chromatography-mass spectrometry (LC-MS) analysis showed that the major saponin in untreated radish was Tupistroside G, whereas treated samples contained Asparagoside A and Timosaponin A1. Moreover, this study elucidated the chemical structure of saponins in TPR. The findings indicated that thermal treatment could induce functional saponin conversion in plants, and such a mechanism can also be used to improve the health efficacy of plant-based crops.

Surface-Defect-Induced and Synergetic-Effect-Enhanced NIR-II Electrochemiluminescence of Au-Ag Bimetallic Nanoclusters and Its Spectral Sensing.

Aqueous electrochemiluminescence (ECL) in the second near-infrared biowindow (NIR-II, 900-1700 nm) was anticipated for ECL evolution and spectral multiplexing. Herein, aqueous and monochromatic ECL with a single emission peak beyond 900 nm was achieved by employing methionine (Met)-capped Au-Ag bimetallic nanoclusters (BNCs) as luminophores and triethanolamine (TEOA) as a coreactant. The Met-capped Au-Ag BNCs with surface-defect-induced PL around 756 nm were water-soluble and synthesized via doping Met-capped Au NCs with Ag in a doping-in-growth way. By extensively exploiting the red-shifting nature of surface-defect-induced ECL to PL and the synergetic-effect-enhanced ECL of BNCs, physically surface-confined Au-Ag BNCs exhibited efficient NIR-II ECL around 906 nm in aqueous medium. A spectrum-based NIR-II ECL immunoassay around 915 nm was also achieved by immobilizing the Au-Ag BNCs onto an electrode surface via forming a sandwich immunocomplex, which could selectively determine CA125 from 5 × 10-4 to 1 U/mL with a detection limit of 5 × 10-5 U/mL (S/N = 3). The combined strategy of surface-defect-induced ECL and synergetic-effect-enhanced ECL would enable promising biorelated application of NIR-II ECL.

Use of Triangular Silver Nanoplates as Low Potential Redox Mediators for Electrochemical Sensing.

Redox mediators can facilitate the electrochemical communication between targets and electrodes for material characterization and investigation. To provide an alternative to the chemical-based redox mediators, herein, we present a nanoparticle-based redox mediator, i.e., the trisodium citrates (TSC)-capped triangular silver nanoplates (Tri-Ag-NPTSC), which demonstrates an efficient oxidative process at around 0.13 V (vs Ag/AgCl) with acceptable redox reversibility by exploiting the interaction between the carbonyl group of TSC and the Ag element of Tri-Ag-NPTSC. The TSC of Tri-Ag-NPs can be selectively replaced by thiols and enable the obtained Tri-Ag-NPTSC-thiol with changed electrochemical redox response, which could be utilized to determine various thiols at 0.13 V, a much lowered oxidative potential than traditional redox mediators, with a similar linear response range, response slope, and limit of detection (LOD). This work proposes a surface-engineering approach to design and develop electrochemical redox probes using Ag nanoparticles with particular morphology, indicating that the interaction between the carbonyl group and Ag nanoparticles might be extended to sensing application beyond the surface-enhanced Raman scattering.

Enhanced Near-Infrared Electrochemiluminescence from Trinary Ag-In-S to Multinary Ag-Ga-In-S Nanocrystals via Doping-in-Growth and Its Immunosensing Applications.

Screening toxic-element-free and biocompatible electrochemiluminophores was crucial for electrochemiluminescence (ECL) evolution. Herein, l-glutathione (GSH)-capped Ag-Ga-In-S (AGIS) nanocrystals (NCs) were prepared by doping Ag-In-S (AIS) NCs in a doping-in-growth way and utilized as a model for both ECL modulating and developing multinary NC-based electrochemiluminophores with enhanced ECL performance than trinary NCs. AGIS NCs not only primarily preserved the morphology, size, phase structure, and water monodisperse characteristics of AIS NCs with broadened band gap but also demonstrated obviously enhanced oxidative-reduction ECL than AIS NCs. Importantly, ECL of AGIS NCs was located at the near-infrared region with a maximum emission wavelength of 744 nm and could be utilized for an ECL immunoassay with human prostate-specific antigen (PSA) as a model, which exhibited a linearity range from 0.05 pg/mL to 1.0 ng/mL and a low limit of detection of 0.01 pg/mL (S/N = 3). This work provided a promising alternative to the traditional binary NCs for developing toxic-element-free and biocompatible electrochemiluminophores with efficient near-infrared ECL.

Bio-inspired and Eco-friendly Synthesis of 3D Spongy Meso-Microporous Carbons from CO2 for Supercapacitors.

Inspired by the spongy bone structures, three-dimensional (3D) sponge-like carbons with meso-microporous structures are synthesized through one-step electro-reduction of CO2 in molten carbonate Li2 CO3 -Na2 CO3 -K2 CO3 at 580 °C. SPC4-0.5 (spongy porous carbon obtained by electrolysis of CO2 at 4 A for 0.5 h) is synthesized with the current efficiency of 96.9 %. SPC4-0.5 possesses large electrolyte ion accessible surface area, excellent wettability and electronical conductivity, ensuring the fast and effective mass and charge transfer, which make it an advcanced supercapacitor electrode material. SPC4-0.5 exhibits a specific capacitance as high as 373.7 F g-1 at 0.5 A g-1 , excellent cycling stability (retaining 95.9 % of the initial capacitance after 10000 cycles at 10 A g-1 ), as well as high energy density. The applications of SPC4-0.5 in quasi-solid-state symmetric supercapacitor and all-solid-state flexible devices for energy storage and wearable piezoelectric sensor are investigated. Both devices show considerable capacitive performances. This work not only presents a controllable and facile synthetic route for the porous carbons but also provides a promising way for effective carbon reduction and green energy production.

High-Performance Photodetectors Based on Solution-Processed Epitaxial Grown Hybrid Halide Perovskites.

Hybrid organic-inorganic halide perovskites (HOIPs) have recently attracted tremendous attention because of their excellent semiconducting and optoelectronic properties, which exist despite their morphology and crystallinity being far inferior to those of more mature semiconductors, such as silicon and III-V compound semiconductors. Heteroepitaxy can provide a route to achieving high-performance HOIP devices when high crystalline quality and smooth morphology are required, but work on heteroepitaxial HOIPs has not previously been reported. Here, we demonstrate epitaxial growth of methylammonium lead iodide (MAPbI3) on single crystal KCl substrates with smooth morphology and the highest carrier recombination lifetime (∼213 ns) yet reported for nonsingle crystalline MAPbI3. Experimental Raman spectra agree well with theoretical calculations, presenting in particular a sharp peak at 290 cm-1 for the torsional mode of the organic cations, a marker of orientational order and typically lacking in previous reports. Photodetectors were fabricated showing excellent performance, confirming the high quality of the epitaxial MAPbI3 thin films. This work provides a new strategy to enhance the performance of all HOIPs-based devices.

Localized dielectric breakdown and antireflection coating in metal-oxide-semiconductor photoelectrodes.

Silicon-based photoelectrodes for solar fuel production have attracted great interest over the past decade, with the major challenge being silicon's vulnerability to corrosion. A metal-insulator-semiconductor architecture, in which an insulator film serves as a protection layer, can prevent corrosion but must also allow low-resistance carrier transport, generally leading to a trade-off between stability and efficiency. In this work, we propose and demonstrate a general method to decouple the two roles of the insulator by employing localized dielectric breakdown. This approach allows the insulator to be thick, which enhances stability, while enabling low-resistance carrier transport as required for efficiency. This method can be applied to various oxides, such as SiO2 and Al2O3. In addition, it is suitable for silicon, III-V compounds, and other optical absorbers for both photocathodes and photoanodes. Finally, the thick metal-oxide layer can serve as a thin-film antireflection coating, which increases light absorption efficiency.

A Liquid Junction Photoelectrochemical Solar Cell Based on p-Type MeNH3PbI3 Perovskite with 1.05 V Open-Circuit Photovoltage.

A liquid junction photoelectrochemical (PEC) solar cell based on p-type methylammonium lead iodide (p-MeNH3PbI3) perovskite with a large open-circuit voltage is developed. MeNH3PbI3 perovskite is readily soluble or decomposed in many common solvents. However, the solvent dichloromethane (CH2Cl2) can be employed to form stable liquid junctions. These were characterized with photoelectrochemical cells with several redox couples, including I3(-)/I(-), Fc/Fc(+), DMFc/DMFc(+), and BQ/BQ(•-) (where Fc is ferrocene, DMFc is decamethylferrocene, BQ is benzoquinone) in CH2Cl2. The solution-processed MeNH3PbI3 shows cathodic photocurrents and hence p-type behavior. The difference between the photocurrent onset potential and the standard potential for BQ/BQ(•-) is 1.25 V, which is especially large for a semiconductor with a band gap of 1.55 eV. A PEC photovoltaic cell, with a configuration of p-MeNH3PbI3/CH2Cl2, BQ (2 mM), BQ(•-) (2 mM)/carbon, shows an open-circuit photovoltage of 1.05 V and a short-circuit current density of 7.8 mA/cm(2) under 100 mW/cm(2) irradiation. The overall optical-to-electrical energy conversion efficiency is 6.1%. The PEC solar cell shows good stability for 5 h under irradiation.

Linking atomic to mesoscopic scales in multilevel structural tailoring of single-atom catalysts for peroxide activation.

A key challenge in designing single-atom catalysts (SACs) with multiple and synergistic functions is to optimize their structure across different scales, as each scale determines specific material properties. We advance the concept of a comprehensive optimization of SACs across different levels of scale, from atomic, microscopic to mesoscopic scales, based on interfacial kinetics control on the coupled metal-dissolution/polymer-growth process in SAC synthesis. This approach enables us to manipulate the multilevel interior morphologies of SACs, such as highly porous, hollow, and double-shelled structures, as well as the exterior morphologies inherited from the metal oxide precursors. The atomic environment around the metal centers can be flexibly adjusted during the dynamic metal-oxide consumption and metal-polymer formation. We show the versatility of this approach using mono- or bi-metallic oxides to access SACs with rich microporosity, tunable mesoscopic structures and atomic coordinating compositions of oxygen and nitrogen in the first coordination-shell. The structures at each level collectively optimize the electronic and geometric structure of the exposed single-atom sites and lower the surface *O formation barriers for efficient and selective peroxidase-type reaction. The unique spatial geometric configuration of the edge-hosted active centers further improves substrate accessibility and substrate-to-catalyst hydrogen overflow due to tunable structural heterogeneity at mesoscopic scales. This strategy opens up new possibilities for engineering more multilevel structures and offers a unique and comprehensive perspective on the design principles of SACs.

Production of bacterial cellulose (BC)/nisin composite with enhanced antibacterial and mechanical properties through co-cultivation of Komagataeibacter xylinum and Lactococcus lactis subsp. lactis.

By employing co-cultivation technique on Komagataeibacter xylinum and Lactococcus lactis subsp. lactis, bacterial cellulose (BC)/nisin films with improved antibacterial activity and mechanical properties were successfully produced. The findings demonstrated that increased nisin production is associated with an upregulation of gene expression. Furthermore, results from Scanning electronic microscopy (SEM), Fourier transform infrared (FTIR), X-ray diffraction (XRD), and Thermogravimetric analysis (TG) confirmed the integration of nisin within BC. While being biocompatible with human cells, the BC/nisin composites exhibited antimicrobial activity. Moreover, mechanical property analyses showed a noticeable improvement in Young's modulus, tensile strength, and elongation at break by 161, 271, and 195 %, respectively. Additionally, the nisin content in fermentation broth was improved by 170 % after co-culture, accompanied by an 8 % increase in pH as well as 10 % decrease in lactate concentration. Real-time reverse transcription PCR analysis revealed an upregulation of 11 nisin-related genes after co-cultivation, with the highest increase in nisA (5.76-fold). To our knowledge, this is the first study which demonstrates that an increase in secondary metabolites after co-culturing is modulated by gene expression. This research offers a cost-effective approach for BC composite production and presents a technique to enhance metabolite concentration through the regulation of relevant genes.