Silver nanoparticle enhanced metal-organic matrix with interface-engineering for efficient photocatalytic hydrogen evolution

Black Ultrathin Single-Crystalline Flakes of CuVP2S6 and CuCrP2S6 for Near-Infrared-Driven Photocatalytic Hydrogen Evolution

The development of new near-infrared-responsive photocatalysts is a fascinating and challenging approach to acquire high photocatalytic hydrogen evolution (PHE) performance. Herein, near-infrared-responsive black CuVP2S6 and CuCrP2S6 flakes, as well as CuInP2S6 flakes, are designed and constructed for PHE. Atom-resolved scanning transmission electron microscopy images and X-ray absorption fine structure evidence the formation of ultrathin single-crystalline sheet-like structure of CuVP2S6 and CuCrP2S6. The synthetic CuVP2S6 and CuCrP2S6, with a narrow bandgap of ≈1.0 eV, shows the high light-absorption edge exceeding 1100 nm. Moreover, through the femtosecond-resolved transient absorption spectroscopy, CuCrP2S6 displays the efficient charge transfer and long charge lifetime (18318.1 ps), which is nearly 3 and 29 times longer than that of CuVP2S6 and CuInP2S6, respectively. In addition, CuCrP2S6, with the appropriate d-band and p-band, is thermodynamically favorable for the H+ adsorption and H2 desorption by contrast with CuVP2S6 and CuInP2S6. As a result, CuCrP2S6 exhibits high PHE rates of 9.12 and 0.66 mmol h-1 g-1 under simulated sunlight and near-infrared light irradiation, respectively, far exceeding other layered metal phospho-sulfides. This work offers a distinctive perspective for the development of new near-infrared-responsive photocatalysts.

Photo-Excited High-Spin State Ni (III) Species in Mo-Doped Ni3S2 for Efficient Urea Oxidation Reaction

Designing robust catalysts for increasing the sluggish kinetics of the urea oxidation reaction (UOR) is challenging. Herein, the regulation of spin states for metal active sites by photoexcitation to facilitate the adsorption of urea and intermediates is demonstrated. Mo-doped nickel sulfide nanoribbon arrays (Mo-Ni3S2@NMF) with excellent light-trapping capacity are successfully prepared. Under AM 1.5G illumination, the activity of the Mo-Ni3S2@NMF exhibits a 50% improvement in the UOR current. Compared with those under dark conditions, Mo-Ni3S2@NMF achieve 10 mA cm-2 at 1.315 VRHE for UOR and 1.32 Vcell for urea electrolysis, which are decreases of 15 and 80 mV, respectively. The electron spin resonance, in situ Fourier transform infrared spectroscopy analysis and density functional theory calculations reveal that illumination led to the formation of Ni3+ active sites in a high-spin state, which strengthens the d-p orbital hybridization of Ni-N, hence facilitating the adsorption of urea. C─N cleavage of the *CONN intermediate is further inhibited, which promotes the oxidation of urea molecules via the active N2 pathway, thereby accelerating the UOR rate.

Coupling photocatalytic CO2 reduction and CH3OH oxidation for selective dimethoxymethane production

Currently, conventional dimethoxymethane synthesis methods are environmentally unfriendly. Here, we report a photo-redox catalysis system to generate dimethoxymethane using a silver and tungsten co-modified blue titanium dioxide catalyst (Ag.W-BTO) by coupling CO2 reduction and CH3OH oxidation under mild conditions. The Ag.W-BTO structure and its electron and hole transfer are comprehensively investigated by combining advanced characterizations and theoretical studies. Strikingly, Ag.W-BTO achieve a record photocatalytic activity of 5702.49 µmol g-1 with 92.08% dimethoxymethane selectivity in 9 h of ultraviolet-visible irradiation without sacrificial agents. Systematic isotope labeling experiments, in-situ diffuse reflectance infrared Fourier-transform analysis, and theoretical calculations reveal that the Ag and W species respectively catalyze CO2 conversion to *CH2O and CH3OH oxidation to *CH3O. Subsequently, an asymmetric carbon-oxygen coupling process between these two crucial intermediates produces dimethoxymethane. This work presents a CO2 photocatalytic reduction system for multi-carbon production to meet the objectives of sustainable economic development and carbon neutrality.

Iron Active Center Coordination Reconstruction in Iron Carbide Modified on Porous Carbon for Superior Overall Water Splitting

In this work, a novel liquid nitrogen quenching strategy is engineered to fulfill iron active center coordination reconstruction within iron carbide (Fe3C) modified on biomass-derived nitrogen-doped porous carbon (NC) for initiating rapid hydrogen and oxygen evolution, where the chrysanthemum tea (elm seeds, corn leaves, and shaddock peel, etc.) is treated as biomass carbon source within Fe3C and NC. Moreover, the original thermodynamic stability is changed through the corresponding force generated by liquid nitrogen quenching and the phase transformation is induced with rich carbon vacancies with the increasing instantaneous temperature drop amplitude. Noteworthy, the optimizing intermediate absorption/desorption is achieved by new phases, Fe coordination, and carbon vacancies. The Fe3C/NC-550 (550 refers to quenching temperature) demonstrates outstanding overpotential for hydrogen evolution reaction (26.3 mV at -10 mA cm-2) and oxygen evolution reaction (281.4 mV at 10 mA cm-2), favorable overall water splitting activity (1.57 V at 10 mA cm-2). Density functional theory (DFT) calculations further confirm that liquid nitrogen quenching treatment can enhance the intrinsic electrocatalytic activity efficiently by optimizing the adsorption free energy of reaction intermediates. Overall, the above results authenticate that liquid nitrogen quenching strategy open up new possibilities for obtaining highly active electrocatalysts for the new generation of green energy conversion systems.

Enhanced Photocatalytic Hydrogen Evolution of In2S3 by Decorating In2O3 with Rich Oxygen Vacancies

The hydrogen (H2) evolution rates of photocatalysts suffer from weak oxidation and reduction ability and low photogenerated charge carrier separation efficiency. Herein, by combining band-gap structure optimization and vacancy modulation through a one-step hydrothermal method, In2O3 containing oxygen vacancy (Ov/In2O3) is simply introduced into In2S3 to promote photocatalytic hydrogen evolution. Specifically, the change in the sulfur source ratio can induce the coexistence of Ov/In2O3 and In2S3 in a high-temperature hydrothermal process. Under light irradiation, In2S3@Ov/In2O3-0.1 nanosheets hold a remarkable average H2 evolution rate up to 4.04 mmol g-1 h-1, which is 32.14, 11.91, and 2.25-fold better than those of pristine In2S3, In2S3@Ov/In2O3-0.02, and In2S3@Ov/In2O3-0.25 nanosheets, respectively. The ultraviolet-visible (UV-vis) diffuse reflectance and photoluminescence (PL) spectra reveal that the formation of Ov/In2O3 in In2S3 optimizes the band-gap structure and accelerates the migration of the photogenerated charge carrier of In2S3@Ov/In2O3-x nanosheets, respectively. Both the enhancement of oxidation and reduction ability and photogenerated charge carrier separation ability are responsible for the remarkable improvement in photocatalytic H2 evolution performance. This work provides a new strategy to prepare a composite of metal sulfide and metal oxide through a one-step hydrothermal method.

Deciphering silver nanoparticles perturbation effects and risks for soil enzymes worldwide: Insights from machine learning and soil property integration

Globally extensive research into how silver nanoparticles (AgNPs) affect enzyme activity in soils with differing properties has been limited by cost-prohibitive sampling. In this study, customized machine learning (ML) was used to extract data patterns from complex research, with a hit rate of Random Forest > Multiple Imputation by Chained Equations > Decision Tree > K-Nearest Neighbors. Results showed that soil properties played a pivotal role in determining AgNPs' effect on soil enzymes, with the order being pH > organic matter (OM) > soil texture ≈ cation exchange capacity (CEC). Notably, soil enzyme activity was more sensitive to AgNPs in acidic soil (pH < 5.5), while elevated OM content (>1.9 %) attenuated AgNPs toxicity. Compared to soil acidification, reducing soil OM content is more detrimental in exacerbating AgNPs' toxicity and it emerged that clay particles were deemed effective in curbing their toxicity. Meanwhile sand particles played a very different role, and a sandy soil sample at > 40 % of the water holding capacity (WHC), amplified the toxicity of AgNPs. Perturbation mapping of how soil texture alters enzyme activity under AgNPs exposure was generated, where soils with sand (45-65 %), silt (< 22 %), and clay (35-55 %) exhibited even higher probability of positive effects of AgNPs. The average calculation results indicate the sandy clay loam (75.6 %), clay (74.8 %), silt clay (65.8 %), and sandy clay (55.9 %) texture soil demonstrate less AgNPs inhibition effect. The results herein advance the prediction of the effect of AgNPs on soil enzymes globally and determine the soil types that are more sensitive to AgNPs worldwide.

Obtaining Ligand-Free Aqueous Au-Nanoparticles Using Reversible CsPbBr3 ↔ Au@CsPbBr3 Nanocrystal Transformation

Water-hexane interfacial preparation of photostable Au@CsPbBr3 (Au@CPB) hybrid nanocrystals (NCs) from pure CsPbBr3 (CPB) NCs is reported, with the coexistence of exciton and localized surface plasmon resonance with equal dominance. This enables strong exciton-plasmon coupling in these plasmonic perovskite NCs where not only the photoluminescence is quenched intrinsically due to ultrafast charge separation, but also the light absorption property increases significantly, covering the entire visible region. Using a controlled interfacial strategy, a reversible chemical transformation between CPB and Au@CPB NCs is shown, with the simultaneous eruption of larger-size ligand-free aqueous Au nanoparticles (NPs). An adsorption-desorption mechanism is proposed for the reversible transformation, while the overgrowth reaction of the Au NPs passes through the Au aggregation intermediate. This study further shows that the plasmonic Au@CPB hybrid NCs as well as ligand-free Au NPs exhibit clear surface enhanced Raman scattering (SERS) effect of a commercially available probe molecule. Overall, the beautiful interfacial chemistry delivers two independent plasmonic materials, i.e., Au@CPB NCs and ligand-free aqueous Au NPs, which may find important implications in photocatalytic and biomedical applications.

Visible light photocatalytic NOx removal with suppressed poisonous NO2 byproduct generation over simply synthesized triangular silver nanoparticles coupled with tin dioxide

The treatment or conversion of air pollutants with a low generation of secondary toxic substances has become a hot topic in indoor air pollution abatement. Herein, we used triangle-shaped Ag nanoparticles coupled with SnO2 for efficient photocatalytic NO removal. Ag triangular nanoparticles (TNPs) were synthesized by the photoreduction method and SnO2 was coupled by a simple chemical impregnation process. The photocatalytic NO removal activity results show that the modification with Ag TNPs significantly boosted the removal performance up to 3.4 times higher than pristine SnO2. The underlying roles of Ag TNPs in NO removal activity improvement are due to some advantages of Ag TNPs. Moreover, the Ag TNPs contributed photogenerated holes as the main active species toward enhancing the NO oxidation reaction. In particular, the selectivity toward green products significantly improved from 52.78% (SnO2) to 86.99% (Ag TNPs/SnO2). The formation of reactive radicals under light irradiation was also verified by DMPO spin-trapping experiments. This work provides a potential candidate for visible-light photocatalytic NO removal with low toxic byproduct generation.

Silver Nanoparticles In Situ Enhanced Electrochemiluminescence of the Porphyrin Organic Matrix for Highly Sensitive and Rapid Monitoring of Tetracycline Residues

Accurate monitoring of tetracycline (TC) residues in the environment is crucial for avoiding contaminant risk. Herein, a novel TC biosensor was facilely designed by integrating silver nanoparticles (Ag NPs) into the porphyrin metal-organic matrix (Ag@AgPOM) as a bifunctional electrochemiluminescence (ECL) probe. Different from the step-by-step synthesis of the co-reaction accelerator and ECL emitter, the co-reaction accelerators Ag NPs were in situ-grown on the surface of 5,10,15,20-tetrakis (4-carboxyphenyl) porphyrin (TCPP) via a simple one-pot approach. Symbiotic Ag NPs on Ag@AgPOM formed an intimate interface and increased the collision efficiency of the ECL reaction, achieving the ECL enhancement of TCPP. Under the optimized conditions, the ternary ECL biosensor showed a wide linear detection range toward TC with a low detection limit of 0.14 fmol L-1. Compared with the traditional HPLC and ELISA methods, satisfied analytical adaptability made this sensing strategy feasible to monitor TC in complex environmental samples.

Enhanced photocatalysis of metal/covalent organic frameworks by plasmonic nanoparticles and homo/hetero-junctions

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have garnered attention in photocatalysis due to their unique features including extensive surface area, adjustable pores, and the ability to incorporate various functional groups. However, challenges such as limited visible light absorption and rapid electron-hole recombination often hinder their photocatalytic efficiency. Recent developments have introduced plasmonic nanoparticles (NPs) and junctions to enhance the photocatalytic performance of MOFs/COFs. This paper provides a comprehensive review of recent advancements in MOF/COF-based photocatalysts improved by integration of plasmonic NPs and junctions. We begin by examining the utilization of plasmonic NPs, known for absorbing longer-wavelength light compared to typical MOFs/COFs. These NPs exhibit localized surface plasmon resonance (LSPR) when excited, effectively enhancing the photocatalytic performance of MOFs/COFs. Moreover, we discuss the role of homo/hetero-junctions in facilitating charge separation, further boosting the photocatalytic performance of MOFs/COFs. The mechanisms behind the improved photocatalytic performance of these composites are discussed, along with an assessment of challenges and opportunities in the field, guiding future research directions.

Computational understanding of the coalescence of metallic nanoparticles: a mini review

Metallic nanoparticles exhibit extraordinary properties that differ from those of bulk materials due to their large surface area to volume ratios. Coalescence of metallic nanoparticles has a huge impact on their properties. Remarkable progress has been made by using computational methods for understanding nanoparticle coalescence. This work aims to provide a mini review on the state-of-the-art modelling and simulation of nanoparticle coalescence. First, we will discuss the outstanding performances and coalescence behaviors of metallic nanoparticles, and list some challenges in the coalescence of metallic nanoparticles. Next, we will introduce the applications of molecular dynamics and the Monte Carlo method in nanoparticle coalescence. Furthermore, we will discuss the coalescence kinetics and mechanisms of metal nanoparticles with the same element and different elements, alloy nanoparticles and metal oxide nanoparticles. Finally, we will present our perspective and conclusion.

Performance and Solution Structures of Side-Chain-Bridged Oligo (Ethylene Glycol) Polymer Photocatalysts for Enhanced Hydrogen Evolution under Natural Light Illumination

Converting solar energy into hydrogen energy using conjugated polymers (CP) is a promising solution to the energy crisis. Improving water solubility plays one of the critical factors in enhancing the hydrogen evolution rate (HER) of CP photocatalysts. In this study, a novel concept of incorporating hydrophilic side chains to connect the backbones of CPs to improve their HER is proposed. This concept is realized through the polymerization of carbazole units bridged with octane, ethylene glycol, and penta-(ethylene glycol) to form three new side-chain-braided (SCB) CPs: PCz2S-OCt, PCz2S-EG, and PCz2S-PEG. Verified through transient absorption spectra, the enhanced capability of PCz2S-PEG for ultrafast electron transfer and reduced recombination effects has been demonstrated. Small- and wide-angle X-ray scattering (SAXS/WAXS) analyses reveal that these three SCB-CPs form cross-linking networks with different mass fractal dimensions (f) in aqueous solution. With the lowest f value of 2.64 and improved water/polymer interfaces, PCz2S-PEG demonstrates the best HER, reaching up to 126.9 µmol h-1 in pure water-based photocatalytic solution. Moreover, PCz2S-PEG exhibits comparable performance in seawater-based photocatalytic solution under natural sunlight. In situ SAXS analysis further reveals nucleation-dominated generation of hydrogen nanoclusters with a size of ≈1.5 nm in the HER of PCz2S-PEG under light illumination.

Peeking into the Femtosecond Hot-Carrier Dynamics Reveals Unexpected Mechanisms in Plasmonic Photocatalysis

Plasmonic-driven photocatalysis may lead to reaction selectivity that cannot be otherwise achieved. A fundamental role is played by hot carriers, i.e., electrons and holes generated upon plasmonic decay within the metal nanostructure interacting with molecular species. Understanding the elusive microscopic mechanism behind such selectivity is a key step in the rational design of hot-carrier reactions. To accomplish that, we present state-of-the-art multiscale simulations, going beyond density functional theory, of hot-carrier injections for the rate-determining step of a photocatalytic reaction. We focus on carbon dioxide reduction, for which it was experimentally shown that the presence of a rhodium nanocube under illumination leads to the selective production of methane against carbon monoxide. We show that selectivity is due to a (predominantly) direct hole injection from rhodium to the reaction intermediate CHO. Unexpectedly, such an injection does not promote the selective reaction path by favoring proper bond breaking but rather by promoting bonding of the proper molecular fragment to the surface.

Enhanced Photoinduced Carrier Separation in Fe-MOF-525/CdS for Photocatalytic Hydrogen Evolution: Improved Catalytic Dynamics with Specific Active Sites

Single-atom metal-anchored porphyrin-based metal-organic frameworks (MOFs) have shown excellent light absorption, catalytic sites, and high stability during photocatalytic reactions, while there are still challenges for facile assembly with quantum dots to enhance catalytic dynamics. Herein, a kind of Fe single atom-doped MOF material (Fe-MOF-525) was ball milled with CdS in a proper ratio through Fe-N4 and Fe-N-C bonding, which showed the enhanced photoinduced carrier separation ability. As a result, extended light absorption ranges of CdS/Fe-MOF-5252.3 induced the promotion of the photocatalytic hydrogen (H2) value (3638.6 μmol g-1 h-1), which was 7.2 and 2.3 times higher than those of Fe-MOF-525 and CdS. In this work, the facile synthetic technique, specific active sites, and enhanced catalytic dynamics in the composite highlight the future research on MOF-based heterojunctions and their potential photocatalysis applications..

A retinomorphic neuron for artificial vision and iris accommodation

The iris of an eye automatically optimizes the amount of light that strikes the retina by accommodating the intensity of ambient light. Here, we describe a retinomorphic neuron using neuromorphic photoreceptors for artificial vision and iris accommodation that mimics the biological structure and processing functions of retinal neurons for light sensing and signal transduction. The system consists of a neuromorphic photoreceptor, an electrochromic device as a light filter, and a spike-generation unit. In particular, the Au nanoparticle (NP) decorated ITO fiber photoreceptor with a well-aligned array structure is able to rely on its own light-tunable synaptic plasticity and the plasmon-enhanced light absorption. Therefore, it allows real-time feedback about light intensity, emits a higher-frequency electrical stimulus to stronger light, flash, or prolonged light illumination time, and drives the electrochromic filter to work, allowing mild light to pass through. Compared with traditional artificial irises or artificial photoreceptors, our design introduces neural pathways and neuromorphic devices, which are closer to biological functions in simulation. To our knowledge, this is the first time that a retinal neuron with neuromorphic photoreceptors has been used for artificial iris vision. Furthermore, we demonstrate direct and consensual pupillary light reflexes. The design of artificial iris vision has potential applications in biomimetic engineering, smart interaction, and visual prostheses.

Cr2S3-Cr2O3/Poly-2-aminobenzene-1-thiol as a Highly Photocatalytic Material for Green Hydrogen Generation from Sewage Water

This study highlights the utilization of the Cr2S3-Cr2O3/P2ABT nanocomposite photoelectrode for efficient and highly sensitive photon absorption, enabling the generation of green hydrogen through the production of hot electrons upon illumination. The nanocomposite is synthesized via a one-pot reaction using K2Cr2O7 and 2-aminobenzene-1-thiol monomer, and the presence of Cr2S3-Cr2O3 is confirmed by XRD and XPS analysis within the composite. The optical properties of the Cr2S3-Cr2O3/poly-2-aminobenzene-1-thiol composite exhibit wide spectral coverage from UV to IR, with a bandgap of 1.6 eV. The diverse morphological behavior observed in the composite correlates with its optical properties, with the cleft spherical particles of the pure polymer transforming into rod-like structures embedded within the polymer matrix. The generated hydrogen gas demonstrates an impressive efficiency of 40.5 mole/10.cm2.h through electrochemical testing. The current density (Jph) values are evaluated under different light frequencies using optical filters ranging from 730 to 340 nm, resulting in Jph values of 0.012 and 0.014 mA.cm-2, respectively. These findings present a promising avenue as green hydrogen for industrial applications, leveraging the potential of the Cr2S3-Cr2O3/P2ABT nanocomposite photoelectrode.

High-Crystallinity BiOCl Nanosheets as Efficient Photocatalysts for Norfloxacin Antibiotic Degradation

Semiconductor photocatalysts are essential materials in the field of environmental remediation. Various photocatalysts have been developed to solve the contamination problem of norfloxacin in water pollution. Among them, a crucial ternary photocatalyst, BiOCl, has attracted extensive attention due to its unique layered structure. In this work, high-crystallinity BiOCl nanosheets were prepared using a one-step hydrothermal method. The obtained BiOCl nanosheets showed good photocatalytic degradation performance, and the degradation rate of highly toxic norfloxacin using BiOCl reached 84% within 180 min. The internal structure and surface chemical state of BiOCl were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman, Fourier transform infrared spectroscopy (FTIR), UV-visible diffuse reflectance (UV-vis), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectra (XPS), and photoelectric techniques. The higher crystallinity of BiOCl closely aligned molecules with each other, which improved the separation efficiency of photogenerated charges and showed high degradation efficiency for norfloxacin antibiotics. Furthermore, the obtained BiOCl nanosheets possess decent photocatalytic stability and recyclability.