Electron Transfer Rate Research Articles

Superexchange Electron Transfer and Protein Matrix in the Charge-Separation Process of Photosynthetic Reaction Centers.

In type-II reaction centers, such as photosystem II (PSII) and reaction centers from purple bacteria (PbRC), light-induced charge separation involves electron transfer from pheophytin (PheoD1) to quinone (QA), occurring near a conserved tryptophan residue (D2-Trp253 in PSII and Trp-M252 in PbRC). This study investigates the route of the PheoD1-to-QA electron transfer, focusing on the superexchange coupling (|HPheoD1···QA|) in the PSII protein environment. |HPheoD1···QA| is significantly larger for the PheoD1-to-QA electron transfer via the unoccupied molecular orbitals of D2-Trp253 ([Trp]•--like intermediate state, 0.73 meV) compared to direct electron transfer (0.13 meV), suggesting that superexchange is the dominant mechanism in the PSII protein environment. While the overall impact of the protein environment is limited, local interactions, particularly H-bonds, enhance superexchange electron transfer by directly affecting the delocalization of molecular orbitals. The D2-W253F mutation significantly decreases the electron transfer rate. The conservation of D2-Trp253/D1-Phe255 (Trp-M252/Phe-L216 in PbRC) in the two branches appears to differentiate superexchange coupling, contributing to the branches being either active or inactive in electron transfer.

Fast Reaction of the Prussian Blue Based Nanozyme "Artificial Peroxidase" with the Substrates: Pre-Steady-State Kinetic Approach.

This letter introduces the pre-steady-state kinetic approach, which is traditional for evaluation of elementary constants in molecular (enzyme) catalysis, for nanozymes. Apparently, the most active peroxidase-mimicking nanozyme based on catalytically synthesized Prussian Blue nanoparticles has been chosen. The elementary constants (k1) for the nanozymes' reduction by an electron-donor substrate (being the fastest stage according to steady-state kinetic data) have been determined by means of stopped-flow spectroscopy. These constants have been found to be dependent on both the size of the nanozyme and the reducing substrate redox potential. For the smallest nanozymes (32 nm in diameter), log(k1) linearly decays with an increase of the substrate redox potential (cotangent value ≈125 mV). On the contrary, for the largest nanozymes with a diameter above 150 nm, k1 is almost independent of it. Moreover, for the substrate with the lowest redox potential (K4[Fe(CN)6]), the rate constant under discussion (k1) is almost independent of the nanozymes' size. Perhaps, the rate of the intrananozyme electron transfer causing bleaching becomes comparative or even lower than that of the nanoparticle interaction with the fastest substrate. Anyway, the elementary constant of nanozyme reduction with potassium ferrocyanide (k1) reaches the value of 1 × 1010 M-1 s-1, which is 3-4 orders of magnitude faster than for enzymes peroxidases. The obtained results obviously demonstrate that the pre-steady-state kinetic approach is able to discover novel advantages of nanozymes from both fundamental and practical points of view.

Enhancing Photoreduction of Cr(VI) through a Multivalent Manganese(II)-Organic Framework Incorporating Anthracene Moieties.

Exploiting a photocatalyst with high stability and excellent activity for Cr(VI) reduction under mild conditions is crucial yet challenging. Herein, the rigid aromatic multicarboxylate ligand with chromophore anthracene was selected to coordinate with multivalent metal ion manganese and to obtain a stable two-dimensional (2D) Mn-based metal-organic framework (MOF), LCUH-120, which can efficiently and quickly convert Cr(VI) into Cr(III) under light without the need for any additional photosensitizer. The efficient photosensitive anthracene group serves as a photosensitizer center and multivalent Mn(II) ion as a photocatalyst center in LCUH-120, and the conversion of Cr(VI) to Cr(III) can be realized completely in just 40 min. Specifically, the rate constant (k) and reduction rate of the Cr(VI) photocatalytic reaction can be high up to 0.134 min-1 and 2.50 mgCr(VI) g-1cata min-1 in an acidic environment (pH = 2), respectively. Compared to our previously reported three-dimensional (3D) Sm-MOF, LCUH-120 exhibits a significantly higher catalytic reaction rate, which might be ascribed to the fact that the photocatalyst center Mn node can improve the rate of electron transfer and promote the separation of holes and photogenerated electrons. In an acidic environment, the reaction mechanism can be verified through various contrast experiments and theoretical simulations.

Fluorescent/colorimetric probe for the detection of Cr(Ⅵ) based on MIL-101(Fe)–NH2 with peroxidase-like activity

In the present research, Fe-based metal-organic frameworks (MIL-101(Fe)–NH2) nanoparticles were synthesized by simple solvothermal methods and used to assay Cr(Ⅵ). The MIL-101(Fe)–NH2 performs dual functions: the 2-aminoterephthalic acid (NH2-BDC) ligand endows a strong fluorescence emission, and the Fe metal nodes are able to facilitate the oxidation of 3,3′,5,5′- tetramethylbenzidine (TMB) directly, resulting in the generation of oxidized-TMB (ox-TMB). Our research results showed that reducing agents such as ascorbic acid (AA) can collapse the structures of MIL-101(Fe)–NH2 because of the reduction of Fe3+ by AA, resulting in release of NH2-BDC. In the presence of Cr(Ⅵ), the fluorescence intensity of the MIL-101(Fe)–NH2 + AA system will be decreased due to the competitive reduction of Fe3+ and Cr(Ⅵ). Nevertheless, Cr(Ⅵ) can significantly accelerate the oxidation of TMB by MIL-101(Fe)–NH2 as it boosts the electron transfer rate between Fe3+ and Fe2+. Therefore, a fluorescent/colorimetric dual-mode platform was developed for the detection of Cr(Ⅵ) with an extensive linear range (7.5–750 μg/L and 13.3–1000 μg/L) as well as a remarkably low detection limit (0.99 μg/L and 1.98 μg/L). This MOF with the ability to release ligands not only provides inspiration for the design of new luminescent materials, but also offers a novel and reliable solution for the detection of Cr(Ⅵ).

Growth of WO3 nanostructure deposited on TiO2 nanotube arrays for electrochemical enzyme-free glucose sensor

In this study, a novel WO3-TiO2 hybrid nanostructure-based electrochemical non-enzymatic glucose biosensor has been developed. The anodization method was utilized to successfully produce TiO2 nanotubes on Ti6Al4V alloy functioning as substrates and WO3 nanomaterial decorate on the surface of TiO2 nanotubes (TNTs) deposited through electrochemical technique. The incorporation of WO3 on TNTs has resulted in a high electroactive surface and more degradation resistance in comparison to pure TNTs, resulting in enhanced electron transfer rate and electrode stability. High-resolution transmission electron microscopy (HR-TEM), field emission scanning electron microscopy (FE-SEM), and X-ray diffraction were used to investigate the crystalline structure and morphology of the WO3-TiO2 nanostructure. The electrochemical properties of the hybrid electrodes were investigated employing amperometry, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The hybrid electrode had a promising sensitivity (1228.12 μA/mM/cm2), low detection limit (0.19 mM), wide linear range (1.0–6.5 mM), and short response time (2-s). The sensors also demonstrated superior levels of reproducibility, repeatability, and stability.

Riboflavin derivatives as a novel electron transfer mediator for enhancing Cr(VI) removal by Shewanella oneidensis MR-1

Bioremediation has garnered considerable interest due to its advantages of economy and no secondary pollution. However, the direct electron transfer rate between microorganisms and Cr(VI) is low. The bioreduction of Cr(VI) by Shewanella oneidensis MR-1 (S. oneidensis) in the presence of formylmethylflavin (FMF) was conducted to understand how FMF mediated the extracellular electron transfer process to improve Cr(VI) removal. In this study, FMF was firstly synthesized by modifing RF to increase its solubility and redox activity. The findings indicate that S. oneidensis/FMF exhibited better Cr(VI) removal performance compared to that of S. oneidensis. Under optimum conditions, 40 mg/L Cr(VI) could be completely removed by S. oneidensis/FMF within 120 h, while only 48.6% of Cr(VI) was removed by S. oneidensis, and the first order rate constant (k) for the Cr(VI) elimination by S. oneidensis/FMF (0.033 h−1) was about 4.1-fold greater than that of S. oneidensis (0.008 h−1). Moreover, the removal of Cr(VI) by S. oneidensis/FMF were dominated by reduction, and supplemented by adsorption and complexation. FMF enhance the extracellular electron transfer rate (EETR) was confirmed by electrochemical cyclic voltammetry (CV) and linear scanning voltammetry (LSV) experiments. This study emphasizes the potential important role of FMF in environmental bioremediation.

2D sheet structure of zinc molybdate decorated on MXene for highly selective and sensitive electrochemical detection of the arsenic drug Roxarsone in water samples

Water contamination is a serious environmental issue posing a significant global challenge. Roxarsone (ROX), a widely used anticoccidial drug is excreted in urine and feces, potentially disrupting natural habitats. Therefore, rapid and cost-effective ROX detection is essential. In this study, we developed a 2D sheet structure of zinc molybdate decorated on MXene (ZnMoO4/MXene) for detecting ROX using electrochemical methods. The materials were characterized using appropriate spectrophotometric and voltammetric techniques. The ZnMoO4/MXene hybrid exhibited excellent electrocatalytic performance due to its rapid electron transfer rate and higher electrical conductivity. The ZnMoO4/MXene-modified GCE (ZnMoO4/MXene/GCE) showed a broad linear range with high sensitivity (10.413 μA μМ−1 cm−2) and appreciable limit of detection (LOD) as low as 0.0081 μM. It also demonstrated significant anti-interference capabilities, excellent storage stability, and remarkable reproducibility. Furthermore, the feasibility of utilizing ZnMoO4/MXene/GCE for monitoring ROX in water samples was confirmed, achieving satisfactory recoveries.

Vacancy engineering-induced spin polarization in heterogeneous phosphides by simple iron salt infiltration for efficient overall water splitting

Optimizing electronic structure and facilitating electron transfer modulation in electrocatalyst is the key to enhancing overall water splitting (OWS) performance. In this work, the heterogeneous transition metal phosphide Fe-CoPv/Ni2P@NF, consisting of cobalt phosphide and nickel phosphide, is obtained by simple iron salt infiltration and high-temperature phosphatisation. Due to the doping of iron-atom and the formation of phosphorus vacancies, the activity of metal atoms with higher valence states and spins is induced, and then highly active Fe/Co-O-Ni channels are generated in the dynamic water-splitting process, thereby increasing the exposure of reaction center and total electron transfer rate. The catalytic mechanism is attributed to reducing the potential barrier of phase remodeling and optimizing the intermediate binding strength, thus thoroughly stimulating OER and HER activities. The Fe-CoPv/Ni2P@NF shows superior performance, requiring only total voltages of 1.626 V (OWS) to reach 100 mA·cm−2 and maintaining ultra-high stability for 500 h, suggesting promising industrial applications.

Novel Self-Powered Biosensor Based on Au Nanoparticles @ Pd Nanorings and Catalytic Hairpin Assembly for Ultrasensitive miRNA-21 Assay.

An ultrasensitive self-powered biosensor is constructed for miRNA-21 detection based on Au nanoparticles @ Pd nanorings (Au NPs@Pd NRs) and catalytic hairpin assembly (CHA). The Au NPs@Pd NRs possess excellent electrical conductivity to improve the electron transfer rate and show good elimination of byproduct H2O2 to assist glucose oxidase (GOD) to catalyze glucose; CHA is used as an amplification strategy to effectively enhance the sensitivity of the biosensor. To further amplify the output signal, a capacitor is integrated into the self-powered biosensor. With multiple signal amplification strategies, the self-powered biosensor possesses a linear range of 0.1-10-4 fM and a lower limit of detection (LOD) of 0.032 fM (S/N = 3). In addition, the as-prepared self-powered biosensor displays potential applicability in the assay toward miRNA-21 in human serum samples.

Unusual electrochemical properties of boron and silicon Co-doped diamond electrodes

Boron-doped diamond (BDD) films exhibit exceptional physicochemical properties and have been utilized in numerous fields. As a common impurity in diamond, silicon is inevitably introduced into the diamond lattice during certain growth process. However, there are limited reports on the impact of silicon co-doping on the electrochemical properties of BDD electrodes. In this paper, we prepared a series of BDD electrodes with various silicon contents and made a systematic evaluation of these electrodes in terms of physicochemical properties. The results indicated that silicon and boron co-doped diamond (SiBDD) electrodes displayed a broader potential window and lower background current compared to the pure BDD electrode. Additionally, we observed that the electron transfer rate of the electrodes in the inner ([Fe(CN)6]3−/4−) redox systems exhibited a rising trend with increasing silicon content, whereas the electron transfer rate of the outer ([Ru(NH3)6]3+/2+) redox systems displayed contrasting trend. Surface analyses and electrochemical measurements results suggested that the unusual phenomena might stem from the alterations in surface functional groups and carrier density of the electrode inducing by silicon co-doping. In general, our results demonstrate, for the first time, that Si co-doping can influence the surface functional groups and carrier behavior of BDD electrodes, thereby altering the electrode's electrochemical performance. This provides new insights for the design of high-performance diamond electrodes.

Co3O4 coated carbon fiber activates PMS to degrade phenolic pollutants via 1O2 dominated non-radical pathway: Role of dual reaction center

Carbon fiber (CF) with a regular fiber skeleton structure was used to prepare the Co3O4@CF catalyst. The as-prepared catalyst was then applied to activate peroxymonosulfate (PMS) for the degradation of phenolic pollutants. Furthermore, the catalytic performance and degradation mechanisms are investigated in this study. The uniform dispersion of Co3O4 on the surface of the CF, as well as the presence of Co–O–R in the Co3O4@CF structure, was confirmed. Notably, 50 mg L−1 of bisphenol A (BPA) was completely degraded in the Co3O4@CF/PMS system within 20 min, under initial conditions of catalyst mass concentration at 0.2 g L−1, the PMS concentration at 10 mmol L−1, and a pH of 6.6. The total organic carbon removal rate reached 72.33 % over 90 min, indicating that the Co3O4@CF/PMS system exhibited strong mineralization capability for BPA. Furthermore, the catalyst demonstrated high efficiency in treating various types of refractory organic pollutants, showing promise for purifying coking wastewater from 3D-EEM. X-ray photoelectron spectroscopy and solid-state electron paramagnetic resonance revealed the formation of electron-poor and electron-rich centers in the Co3O4@CF structure. Density functional theory calculations further indicated that the charge density around the CF decreased, while the charge density around Co3O4 increased, resulting in the formation of these electron-poor and electron-rich centers. Electrochemical characterization using cyclic voltammetry and electrochemical impedance spectroscopy confirmed the excellent electron transfer rate of Co3O4@CF. Additionally, the reactive oxygen species dominated in the Co3O4@CF/PMS system were 1O2 and •O2−, with possible mechanisms for the 1O2 and •O2− generation during BPA degradation elucidated. Moreover, liquid chromatography-mass spectrometry results identified degradation intermediates of BPA, proposing three possible degradation pathways.

Truncations and in silico docking to enhance the analytical response of aptamer-based biosensors

Aptamers are short oligonucleotides capable of binding specifically to various targets (i.e., small molecules, proteins, and whole cells) which have been introduced in biosensors such as in the electrochemical aptamer-based (E-AB) sensing platform. E-AB sensors are comprised of a redox-reporter-modified aptamer attached to an electrode that undergoes, upon target addition, a binding-induced change in electron transfer rates. To date, E-AB sensors have faced a limitation in the translatability of aptamers into the sensing platform presumably because sequences obtained from Systematic Evolution of Ligands by Exponential Enrichment (SELEX) are typically long (>80 nucleotides) and that obtaining structural information remains time and resource consuming. In response, we explore the utility of aptamer base truncations and in silico docking to improve their translatability into E-AB sensors. Here, we first apply this to the glucose aptamer, which we characterize in solution using NMR methods to guide design and translate truncated variants in E-AB biosensors. We further investigated the applicability of the truncation and computational approaches to four other aptamer systems (vancomycin, cocaine, methotrexate and theophylline) from which we derived functional E-AB sensors. We foresee that our strategy will increase the success rate of translating aptamers into sensing platforms to afford low-cost measurements of molecules directly in undiluted complex matrices.

Enhancing early warning: A DNA biosensor with polyaniline/graphene nanocomposite for label-free voltammetric detection of saxitoxin-producing harmful algae

Yearly reports of detrimental effects resulting from harmful algal blooms (HAB) are still received in Malaysia and other countries, particularly concerning fish mortality and seafood contamination, both of which bear consequences for the fisheries industry. The underlying reason is the absence of a dependable early warning system. Hence, this research aims to develop a single DNA biosensor that can detect a group of HAB species known for producing saxitoxin (SXT), which is commonly found in Malaysian waters. The screen-printed carbon electrode (SPCE)-based DNA biosensor was fabricated by covalent grafting of the 3’ aminated DNA probe of the sxtA4 conserved domain in SXT-producing dinoflagellates on the reverse-phase polymerized polyaniline/graphene (PGN) nanocomposite electrode via carbodiimide linkage. The introduction of a carboxyphenyl layer to the PGN nanotransducing element was essential to augment the carboxylic groups on the graphene (RGO), facilitating attachment with the aminated DNA. The synergistic effect of the asynthesized nanocomposite of PANI and RGO, tremendously enhanced the electron transfer rate of the ferri/ferrocyanide redox probe at the SPCE transducer surface, allowing for the label-free bioanalytical assay of complementary DNA targets. The developed DNA biosensor featuring the capacity to detect a broad range of Alexandrium minutum (A. minutum) cell concentrations, ranging from 10 to 10,000,000 cells L-1. The quantification of A. minutum cells from pure algal culture by the electrochemical DNA biosensor has been well-validated with traditional microscopic techniques. Furthermore, Alexandrium tamiyavanichii, another toxigenic HAB species, exhibited a similar electrochemical characteristic signal to those observed with A. minutum, whilst the biosensor yielded appreciably distinctive results when subjected to a non-toxigenic microalgae species as a negative control, i.e. Isochrysis galbana. A compendium DNA biosensor design and electrochemical detection strategy at laboratory scale serves as a precursor to the potential development of portable device for on-site detection, thus expanding the utility and scope of biosensor technology.

Engineering Shewanella oneidensis-Carbon Felt Biohybrid Electrode Decorated with Bacterial Cellulose Aerogel-Electropolymerized Anthraquinone to Boost Energy and Chemicals Production.

Interfacial electron transfer between electroactive microorganisms (EAMs) and electrodes underlies a wide range of bio-electrochemical systems with diverse applications. However, the electron transfer rate at the biotic-electrode interface remains low due to high transmembrane and cell-electrode interfacial electron transfer resistance. Herein, a modular engineering strategy is adopted to construct a Shewanella oneidensis-carbon felt biohybrid electrode decorated with bacterial cellulose aerogel-electropolymerized anthraquinone to boost cell-electrode interfacial electron transfer. First, a heterologous riboflavin synthesis and secretion pathway is constructed to increase flavin-mediated transmembrane electron transfer. Second, outer membrane c-Cyts OmcF is screened and optimized via protein engineering strategy to accelerate contacted-based transmembrane electron transfer. Third, a S. oneidensis-carbon felt biohybrid electrode decorated with bacterial cellulose aerogel and electropolymerized anthraquinone is constructed to boost the interfacial electron transfer. As a result, the internal resistance decreased to 42 Ω, 480.8-fold lower than that of the wild-type (WT) S. oneidensis MR-1. The maximum power density reached 4286.6 ± 202.1mWm-2, 72.8-fold higher than that of WT. Lastly, the engineered biohybrid electrode exhibited superior abilities for bioelectricity harvest, Cr6+ reduction, and CO2 reduction. This study showed that enhancing transmembrane and cell-electrode interfacial electron transfer is a promising way to increase the extracellular electron transfer of EAMs.

Enhanced denitrification performance and extracellular electron transfer for eletrotrophic bio-cathode mediated by anthraquinone-2, 6-disulfonate (AQDS) at low temperature

The slow electron transfer rate and low temperature are the bottleneck in biological denitrification process, and quinone electron shuttle (e.g. AQDS) has been confirmed as a viable approach to improve the efficiency of biological denitrification by accelerating electron transport. In this study, we employed the eletrotrophic bio-cathode with cold-tolerant to explore the mechanisms of extracellular electron transfer (EET) mediated by AQDS in simultaneous nitrification and denitrification (SND) for the first time. The results indicated that adding 0.5 mmol/L AQDS increased NH4+-N removal rate and SND efficiency by 18.1% and 17.9%, respectively, and the optimal hydraulic retention time (HRT) was shortened from 5 d to 3 d. The potential mechanism was that AQDS resulted in a 1.47-fold increase in the relative abundance of cathodic electroactive microorganisms, and the relative abundance of functional genes such as cytochrome c, flavin, cold acclimation and translocator increased by about 1.15–300.42%, which accelerated the transfer of extracellular electron and significantly improved the energy metabolism efficiency. In addition, AQDS may act as an electron shuttle to accelerate the electronic transition in long-distance electron transfer. In summary, this study expands our understanding of the role of AQDS in the SND process by bio-cathode under low temperature and provides an insight into the EET of eletrotrophic microorganisms with cold-tolerant.

Numerical modelling of interspecies electron transfer in anaerobic digestion using multiple electron donors for methane production

Direct interspecies electron transfer (DIET) is an efficient approach to enhance methane production in syntrophic metabolism during anaerobic digestion; yet a quantitative understanding of DIET mechanisms between exoelectrogens and electrotrophic methanogens is still lacking. This study presents a novel diffusion–reaction multi-physics model to simulate interspecies electron transfer between rod-shaped exoelectrogens and spherical electrotrophic methanogens for the first time. The numerical results indicate that the electron transfer rate in DIET are 5.6 to 8.8 times higher than that in interspecies hydrogen transfer (IHT). The increase of substrate concentration (0.001 − 0.1 mol/L), nanowire conductivity (0.1 − 50 Ω⋅m), nanowire number (1 − 1.0 × 104) and redox cofactor number (10 − 1.0 × 104) significantly enhance electron transfer of DIET in syntrophic metabolism. Furthermore, the presence of conductive material can increase the electron transfer rates of DIET by up to 56.6–85.1 times compared to the control group. This study provides new insights into the optimization of DIET in the anaerobic digestion of organic wastes, offering a quantitative basis for improving methane production through targeted manipulation of system parameters.

Engineering ion diffusion and electron transfer dual pathways within porous spherical H1.6Mn1.6O4 for highly efficient Li+ separation

Efficient and selective electrochemical lithium adsorption from liquid resources is crucial for sustainable lithium extraction and purification. However, the sluggish Li+ diffusion kinetics often lag behind electron transfer rates, hindering the overall adsorption efficiency in capacity and kinetics. This work addresses this challenge by introducing a tunable porous spherical architecture in H1.6Mn1.6O4 adsorbent particles. The Li+ diffusion coefficient (DLi+) enhanced from 1.32 × 10-12 cm2/s to 3.61 × 10-12 cm2/s, the solution resistance (Rs) decreased from 28.88 ohm to 25.30 ohm, the charge transfer resistance (Rct) decreased from 31.04 ohm to 30.40 ohm, and the desolvation activation energy (Ea) reduced from 10.81 kJ/mol to 9.81 kJ/mol. Consequently, the optimized porous spherical H1.6Mn1.6O4 demonstrates superior adsorption capacity and adsorption kinetics, exceeding 24.23 mg/g at 180 min, which is 1.26 times that of the dense spherical counterpart (19.28 mg/g). The simulation calculations of Li+ diffusion highlight the pivotal role of the porous structure in accelerating internal Li+ diffusion, thereby significantly contributing to the enhanced overall adsorption efficiency of H1.6Mn1.6O4. This work emphasizes the significance of synergistically optimizing ion diffusion channels and electron transfer paths for enhancing electrochemical processes and provides a path for constructing similar pore structures in various ion–electron-related applications.

Potassium single-atoms anchoring on three-dimensional porous N-doped carbon material as sensing material for boosting electrochemical sensing of hydrogen peroxide.

For thefirst time potassium single-atoms (K SA) are explored as the sensing material to boost electrochemical sensing of hydrogen peroxide (H2O2). The N-doped carbon material with a three-dimensional porous structure (3D NG) was prepared using NaCl as the template, and K SA were anchored to the surface of 3D NG through high-temperature pyrolysis. The structure of K SA/3D NG was characterized by TEM, HAADF-STEM, XPS, and XRD. The results of electrochemical studies indicate that K SA play a crucial role in promoting the electrocatalytic reduction of H2O2, which not only optimized the adsorption strength for H2O2 but also improved the electron transfer rate, therefore improving the sensitivity for detecting H2O2. This study demonstrates the excellent electrocatalytic activity of K SA, which provides a promising sensing material for the detection of H2O2 andlays the foundation for the application of alkali metal single-atoms in the field of electrochemical sensing.

Integrated Effects of Soil Moisture on Wheat Hydraulic Properties and Stomatal Regulation.

The development of water-saving management relies on understanding the physiological response of crops to soil drought. The coordinated regulation of hydraulics and stomatal conductance in plant water relations has steadily received attention. However, research focusing on grain crops, such as winter wheat, remains limited. In this study, three soil water supply treatments, including high (H), moderate (M), and low (L) soil water contents, were conducted with potted winter wheat. Leaf water potential (Ψleaf), leaf hydraulic conductance (Kleaf), and stomatal conductance (gs), as well as leaf biochemical parameters and stomatal traits were measured. Results showed that, compared to H, predawn leaf water potential (ΨPD) significantly reduced by 48.10% and 47.91%, midday leaf water potential (ΨMD) reduced by 40.71% and 43.20%, Kleaf reduced by 64.80% and 65.61%, and gs reduced by 21.20% and 43.41%, respectively, under M and L conditions. Although gs showed a significant difference between M and L, Ψleaf and Kleaf did not show significant differences between these treatments. The maximum carboxylation rate (Vcmax) and maximum electron transfer rate (Jmax) under L significantly decreased by 23.11% and 28.10%, stomatal density (SD) and stomatal pore area index (SPI) under L on the abaxial side increased by 59.80% and 52.30%, respectively, compared to H. The leaf water potential at 50% hydraulic conduction loss (P50) under L was not significantly reduced. The gs was positively correlated with ΨMD and Kleaf, but it was negatively correlated with abscisic acid (ABA) and SD. A threshold relationship between gs and Kleaf was observed, with rapid and linear reduction in gs occurring only when Kleaf fell below 8.70 mmol m-2 s-1 MPa-1. Our findings demonstrate that wheat leaves adapt stomatal regulation strategies from anisohydric to isohydric in response to reduced soil water content. These results enrich the theory of trade-offs between the carbon assimilation and hydraulic safety in crops and also provide a theoretical basis for water management practices based on stomatal regulation strategies under varying soil water conditions.

Cu,Ce-containing phosphotungstates as laccase-like nanozyme for colorimetric detection of Cr(VI) and Fe(Ⅲ)

Herein, a nanocomposite of Cu,Ce-containing phosphotungstates (Cu,Ce-PTs) with outstanding laccase-like activity was fabricated via a one-pot microwave-assisted hydrothermal method. Notably, it was discovered that both Fe3+ and Cr6+ could significantly enhance the electron transfer rates of Ce3+ and Ce4+, along with generous Cu2+ with high catalytic activity, thereby promoting the laccase-like activity of Cu,Ce-PTs. The proposed system can be used for the detection of Fe3+ and Cr6+ in a range of 0.667–333.33 μg/mL and 0.033–33.33 μg/mL with a low detection limit of 0.135 μg/mL and 0.0288 μg/mL, respectively. The proposed assay exhibits excellent reusability and selectivity and can be used in traditional Chinese medicine samples analysis.