Search Results (951)

We present the results of a study of europium-grafted detonation nanodiamond using X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), and photoluminescence techniques. The material was prepared by mixing an aqueous solution of europium(III) nitrate hexahydrate, Eu(NO₃)₃·6H₂O, with a nanodiamond suspension, resulting in ion exchange between Eu³⁺ ions and protons of surface carboxyl groups and direct grafting of the nanodiamond surface with Eu³⁺ ions. However, after two years of storage under ambient conditions, the compound exhibits the reduction of ~13% of Eu³⁺ ions to the paramagnetic Eu²⁺ state. This unusual finding is discussed in the context of our XPS, EPR, NMR, and photoluminescence data. We propose that this effect can be associated with surface defects and sp²-hybridized graphene-like fragments that act as electron donors to Eu³⁺ ions. The observed spontaneous partial reduction of Eu³⁺ to Eu²⁺ during long-term storage demonstrates that the oxidation state of surface-grafted europium is not completely stable under ambient conditions. This finding is important because even a partial change in the Eu valence may modify the optical and magnetic properties of Eu-grafted nanodiamonds intended for luminescent, sensing, and quantum applications. Full article

In this study, ZnO/Co₃O₄ composite thin-film room-temperature hydrogen (H₂) sensors were prepared via the hydrothermal method and self-assembly techniques. The test results show that the composite sensor with a layer assembly ratio of 1:1 has good sensing performance for H₂. The ZnO/Co₃O₄ composite sensor can detect a wide range of H₂ concentrations from 100 to 50,000 ppm, and the response toward 300 ppm H₂ is more than six-times that of a single nanomaterial. In addition, it has a faster response recovery speed, better repeatability, selectivity and long-term stability. The improvement in composite sensor performance results from the synergistic effect between ZnO and Co₃O₄ materials and the formation of heterostructures. The prepared ZnO/Co₃O₄ composite thin-film sensor was successfully applied to detect the H₂ production concentration and behavior of an electrolytic cell for hydrogen production by water electrolysis. Full article

The simultaneous and accurate detection of multiple pesticide residues remains a critical challenge in electrochemical sensing. Herein, a strategy is proposed for the in situ growth of interconnected Zn₃(OH)₂V₂O₇·2H₂O (ZVO) nanosheets on carbon cloth (CC), forming ZVO/CC electrodes for the simultaneous detection of thiophanate-methyl and diuron. A negative-potential pre-reduction treatment is employed to regulate the interfacial electronic structure and activate sensing sites of ZVO/CC electrodes. During pre-reduction, partial V⁵⁺ is reduced to V⁴⁺, accompanied by the formation of oxygen vacancies, which reconstruct local electronic states and decrease charge-transfer resistance. Meanwhile, the chemically integrated Zn–O–V framework exhibits a performance synergy, resulting in significantly enhanced and well-distinguished electrochemical responses toward the target pesticides. The ZVO/CC electrode achieves linear detection ranges of 0.1–25 μM for thiophanate-methyl and 0.1–40 μM for diuron, with low detection limits of 12.4 nM and 28.5 nM, respectively. Furthermore, machine learning algorithms are introduced to resolve partial overlapping signals, enabling simultaneous pesticide classification and concentration prediction. The integration of interfacial engineering with machine learning provides an effective strategy for achieving simultaneous multi-pesticide detection at the nanomolar level. Full article

In this work, amino-functionalized Al-based MOF Al-GM was fabricated via a mild room-temperature aqueous route, which was applied as a ratiometric fluorescent probe for the specific detection of Cr₂O₇²⁻ in water. Characterizations including XRD, FT-IR, SEM, and BET verify that Al-GM synthesized in pure water exhibits high crystallinity and abundant mesoporous channels, with fully exposed amino recognition sites on the framework, delivering dual fluorescence emission signals. Sensing performance experiments demonstrate outstanding selectivity toward Cr₂O₇²⁻ with negligible interference from coexisting metal ions. Fluorescence titration reveals a wide linear detection range and an ultralow limit of detection, which is far lower than the discharge standard of Cr(VI) for industrial wastewater. pH-dependent tests confirm the stable sensing performance of the probe in water at a pH range of 5–9. XRD and FTIR spectra before and after Cr₂O₇²⁻ adsorption confirm intact crystal and organic coordination frameworks during ion recognition. Cr₂O₇²⁻ anions are selectively captured by the synergy of electrostatic attraction and intermolecular hydrogen bonds with amino sites. This study proposes a mild, organic-solvent-free synthetic strategy for MOFs, and the prepared Al-GM displays promising application potential for trace Cr(VI) monitoring in aquatic environments. Full article

Drought and salinity are major abiotic stresses that severely constrain plant growth and agricultural productivity. Histidine kinases (HKs), as key components of the plant two-component system (TCS), play crucial roles in environmental signal perception and adaptive responses. In this study, we functionally characterized a sweet potato (Ipomoea batatas L.) HK gene, IbHK1a, and investigated its role in drought and salt stress tolerance. Expression analysis revealed that IbHK1a is predominantly expressed in root tissues, particularly in storage and fibrous roots, indicating its potential involvement in stress sensing and adaptation. Subcellular localization demonstrated that the IbHK1a protein is localized to the plasma membrane, suggesting a role in external signal perception. To elucidate its biological function, IbHK1a was heterologously overexpressed in Arabidopsis thaliana. Transgenic plants exhibited significantly enhanced tolerance to drought and salt stress, as evidenced by higher seed germination rates, improved primary root growth, reduced leaf wilting, and increased survival rates compared with wild-type (WT) plants. Physiological analyses showed that IbHK1a overexpression led to increased activities of antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), accompanied by reduced accumulation of reactive oxygen species (ROS) such as hydrogen peroxide (H₂O₂) and malondialdehyde (MDA). Consistently, leaf histochemical staining confirmed lower ROS accumulation in transgenic plants under stress conditions. In sweet potato, overexpression of IbHK1a in transgenic hairy roots enhanced tolerance to drought and salinity, whereas RNA interference lines displayed increased sensitivity, further confirming its positive regulatory role. Additionally, protein interaction analysis indicated that IbHK1a interacts with Arabidopsis histidine phosphotransferase proteins (AHPs), suggesting its involvement in conserved TCS-mediated phosphorelay signaling pathways. Functional complementation analysis demonstrated that IbHK1a partially rescues the stress-sensitive phenotype of the AHK1 mutant, indicating functional conservation with Arabidopsis AHK1. Collectively, these findings demonstrate that IbHK1a positively regulates drought and salt stress tolerance by enhancing antioxidant defense and ROS homeostasis. Its interaction with AHPs and partial complementation of the ahk1 mutant further support its involvement in the conserved TCS phosphorelay pathway. These results establish IbHK1a as an important component of abiotic stress responses and a potential genetic target for improving drought and salinity tolerance in sweet potato. Full article

Hydrogen (H₂) detection under practical operating conditions requires sensing materials that simultaneously provide accessible reaction sites, efficient gas diffusion pathways, and fast interfacial charge transfer. Here, a hierarchical star-sphere ZnCo₂O₄ (ZC) architecture was integrated with graphene oxide (GO) and Pt supported on graphitized carbon (Pt/C) to develop hybrid chemiresistive sensing layers for low-temperature hydrogen detection. The synthesized ZC-based material exhibited a hierarchical morphology consisting of porous microspheres and star-shaped assemblies, providing a multiscale framework for gas access and surface reactions. By varying the GO content from 0.1 to 1 wt% at a fixed Pt/C loading, the ZC-0.5G composite achieved the most balanced structure, with well-distributed GO sheets, preserved star–sphere morphology, the highest specific surface area (53.6 m²/g), and the largest pore volume (0.09 cm³/g). The optimized sensor gave responses of 12.96%, 19.20%, 22.87%, and 26.43% for 500, 4000, 8000 and 10,000 ppm H₂ concentrations, respectively, with measurable response down to 50 ppm. The highest sensing performance was achieved at 50 °C and 60% relative humidity (RH), where the hierarchical oxide framework, GO-assisted interfacial pathways, and Pt catalytic sites acted in concert. The sensor also showed repeatable cyclic behavior and preferential response to H₂ compared to methanol, isopropanol, ethanol, acetone, and dimethylformamide. The improved sensing performance is attributed to the synergistic combination of the hierarchical ZC framework, GO-assisted interfacial pathways, and Pt-assisted catalytic activation, which together facilitate gas diffusion, surface reactions, and resistance modulation. Full article

Strict monitoring of methane (CH₄) during underground coal mining is necessary, as the lower explosive limit (LEL) is 5 vol% in air. A conventional tin oxide (SnO₂)-based metal–oxide semiconductor (MOS) sensor has an operating temperature of 200–400 °C, which requires a prohibitive power demand and entails the risk of ignition within an intrinsically safe environment. The decoration of SnO₂ nanoarchitectures with palladium has been demonstrated to achieve room temperature (RT) detection of CH₄ due to the chemical sensitisation spillover mechanism and electronic sensitisation by Schottky barrier modulation. Moreover, palladisation of SnO₂ nanowires (NWs) is likely to be an effective route for achieving a more efficient detection of CH₄ aerosol at RT or near RT. The purpose of this mini-review is to provide a critical synthesis of advances that have been reported between 2020 and 2026. Because no published study to date has directly demonstrated room-temperature CH₄ detection using pure Pd-decorated SnO₂ nanowires, performance data from mechanistically analogous systems—namely H₂-sensing Pd–SnO₂ nanowires and CH₄-sensing non-nanowire Pd–SnO₂ nanostructures—are included in this review and are explicitly labelled as such throughout. This absence of direct RT CH₄ NW data constitutes the primary research gap motivating this review. The performance of Pd-containing SnO₂ nanostructures reported in the literature spans response values of 17.6 (300 ppm CH₄, 2.5 mol% Pd–SnO₂ nanoporous, 340 °C) to 21.3 (3000 ppm CH₄, bimetallic Pt–Pd–SnO₂ mesoporous, 400 °C), representing a 3–10× improvement over bare SnO₂ (response: 2–10 in the same concentration range). These benchmarks were obtained at elevated temperatures (340–400 °C); no equivalent room-temperature CH₄ detection data for Pd–SnO₂ nanowires currently exists in the published literature. Reported response times range from 3 to 9 s at elevated temperature (340–400 °C) to 74–78 s for room-temperature visible-light-activated systems, where photocatalytic oxygen activation is the rate-limiting step. The 30 s MSHA alarm threshold is met by elevated-temperature systems but remains a challenge for RT configurations. The LODs were 175.9 ppb (bimetallic PdxPt/SnO₂ mesoporous system). Two hybrid composites containing rGO exhibited an extended capability for RT operation. Bimetallic PdPt decoration and ML-augmented sensor arrays are identified as the most promising near-term pathways to bridge the selectivity and stability gaps for certified mining deployment. Full article

Integrated and tunable light sources are critical for advancing quantum nanophotonic chips in quantum computing, communications, and sensing. However, efficient and tunable emission amplification post-fabrication poses major challenges. Hybrid metasurfaces combining niobium pentoxide (Nb₂O₅), copper indium sulfide (CIS) quantum dots or hexagonal boron nitride (hBN), and antimony trisulfide (Sb₂S₃) as a low-loss phase-change material offer a compelling solution for dynamic control and amplification of photoluminescence and quantum light emission. In this work, an active hybrid metasurface supporting tunable bound states in the continuum (BIC) resonances in the visible regime is demonstrated, achieving experimental Q-factors up to 206 at an amorphous state and strong amplification of CIS QDs photoluminescence, as well as quantum light emission of hBN single-photon emitters. The metasurface enables BIC resonance shifts of 33.5 nm in the visible spectrum via phase transition of Sb₂S₃, and 17 nm through dimensional parametric tuning. The experiment demonstrates a highly directional photoluminescence amplification up to 33-fold, alongside broad tunable amplified PL emission upon Sb₂S₃ phase modulation. Furthermore, amplified, tunable, and on-demand strong coupling of hBN single-photon emitters is proposed with the tunable BIC metasurface for next-generation broadband quantum nanophotonic chips. This work sets a new benchmark in reconfigurable nanophotonic platforms for efficient quantum light sources in integrated photonic systems. Full article

Accurate and non-invasive monitoring of glucose levels remains a critical challenge in diabetes management, motivating the development of highly sensitive optical biosensors. In this work, a surface plasmon resonance-based biosensor operating in the Kretschmann configuration is proposed and numerically investigated for glucose detection. The sensor architecture consists of a BK7 prism/TiO₂/Ag/graphene multilayer, and the effect of incorporating a hexagonal boron nitride (h-BN) interlayer with varying thicknesses is systematically analyzed to enhance sensing performance. Electromagnetic simulations were performed using the finite-difference time-domain method in Lumerical FDTD Solutions at a wavelength of 633 nm. Key performance parameters, including angular sensitivity, full width at half maximum, detection accuracy, figure of merit, signal-to-noise ratio, and limit of detection, were evaluated for glucose concentrations corresponding to refractive indices ranging from 1.3282 to 1.3767 RIU. The conventional BK7/TiO₂/Ag/TiO₂/Graphene/Sensing Medium (SM) configuration achieved a sensitivity of 167.48 deg/RIU. By introducing an h-BN layer, significant performance enhancement was observed. The optimized structure with an 8 nm h-BN layer exhibited a maximum angular sensitivity of 205.35 deg/RIU, representing an improvement of approximately 22.6% over the reference design, while maintaining a low detection limit of 2.43 × 10⁻⁴ RIU. The results further reveal that h-BN thickness plays a crucial role in balancing sensitivity and resonance quality, where excessive thickness broadens the resonance curve and degrades detection accuracy. The proposed graphene-h-BN-assisted SPR platform demonstrates high potential for high-performance, non-invasive glucose monitoring and provides practical design guidelines for next-generation plasmonic biosensors. Full article

Quorum sensing (QS) is critically involved in mediating microbial interactions and serves as a central regulatory mechanism in bacterial pathogenesis. As an emerging countermeasure, quorum quenching (QQ) suppresses QS-regulated virulence through enzymatic or chemical disruption of signal systems. N-acyl homoserine lactone (AHL), an evolutionarily conserved QS signal, coordinates the pathogenicity of multiple plant pathogens, particularly Dickeya zeae, which causes soft rot disease in various crops and leads to substantial agricultural losses. In this study, the QQ strain Acinetobacter schindleri XJ-10 was evaluated for its capacity to degrade AHL and attenuate the pathogenicity of D. zeae EC1 in host plants. Notably, strain XJ-10 exhibited efficient AHL degradation at 0.2 mmol/L within 24 h, achieving a degradation efficiency of 98.80%. Subsequently, gas chromatography–mass spectrometry (GC-MS) analysis identified N-hexanoyl-L-homoserine lactone and propanamide as key intermediates during AHL degradation, confirming complete mineralization to CO₂ and H₂O. Based on the structural characterization of AHL and its intermediates, the metabolic pathway within strain XJ-10 was proposed. The degradation pathway initiates with the hydrolysis of the ester ring of N-hexanoyl-L-homoserine lactone, generating N-hexanoyl-L-homoserine. Subsequent carbon–nitrogen bond scission is predicted to yield N-cyclohexyl-propanamide, which is further catabolized to produce hexanamide and propanamide. Furthermore, strain XJ-10 exhibited biocontrol activity against soft rot disease affecting potato (Solanum tuberosum), radish (Raphanus sativus), and Chinese cabbage (Brassica rapa subsp. pekinensis), as its crude enzyme extract effectively reduced disease incidence and severity in planta. While strain XJ-10 showed no detectable acylase activity, it exhibited significant degradation activity against AHL, suggesting a distinct QQ mechanism. Collectively, these findings broaden the scope of QQ-based biocontrol strategies and enhance mechanistic insights into managing bacterial diseases through QS modulation. Full article

The hydrogen temperature-programmed reduction (H₂-TPR) method was used to analyze the sensing properties of nanostructured indium oxide for hydrogen detection. Commercial and mechanically activated In₂O₃ samples were selected for investigation. Mechanical activation leads to the generation of surface defects and an increase in specific surface area, which enhances sensitivity to H₂ and lowers the sensor operating temperature. An approach is proposed that allows a qualitative and quantitative relationship to be established between the H₂-TPR profiles of the oxides and the sensor response. This relationship is based on a model of electron transfer across a potential barrier at grain boundaries, formed with the participation of adsorbed oxygen. The temperature dependence of the sensor response is found to be determined by the concentration of negatively charged oxygen on the surface of the nanoparticles, which, in turn, depends on temperature. Using the sensor sensitive layer based on indium oxide as an example, a correlation is established between the parameters of the TPR profiles and the sensor response. Full article

Despite the growing preference for solid-state pH sensors due to their advantages over glass pH electrodes, their practical application is still limited by challenges, particularly in metal-oxide based systems. The main issue is their susceptibility to redox-active species such as dissolved oxygen, ascorbic acid, sulfides, and transition-metal ions. In this work, the effects of representative redox interferents, with particular emphasis on ascorbic acid, together with dissolved oxygen and potassium permanganate, were investigated and mitigated through the application of Ta₂O₅/Nafion overlayers. The solid-state metal-oxide pH-sensitive electrodes were fabricated with laser micro-etching of radio-frequency (RF) sputtered RuO₂ thin films deposited on ceramic Al₂O₃ substrates. The resulting RuO₂ electrodes exhibited excellent potentiometric pH sensing characteristics, including near-Nernstian sensitivity (58.8 mV pH⁻¹ at 25 °C), highly linear response over a wide pH range (pH 2–12, R² > 0.9999), minimal hysteresis (1.3 mV), low potential drift (2.9 mV h⁻¹), and fast response times (<30 s). Following on from our previous work, which demonstrated that the Ta₂O₅/Nafion solid-state sensor could measure beverage pH accurately, here we explain why that architecture works by systematically investigating the role of Ta₂O₅ and Nafion in suppressing redox interference and improving measurement stability in complex sample matrices. The results demonstrate that RuO₂ electrodes modified with combined Ta₂O₅/Nafion thin films exhibit significantly enhanced measurement stability compared to unmodified RuO₂ electrodes, owing to effective suppression of potential fluctuations induced by dissolved oxygen and representative redox couples, particularly those associated with ascorbic acid interference. These findings could give a promising strategy for improving the robustness and reliability of solid-state RuO₂-based pH sensors in complex electrochemical environments. Full article

This study investigates the electrochemical properties of polymer-based microelectrode arrays (pMEAs) and their performance in measuring oxygen (O₂) and hydrogen peroxide (H₂O₂). Morphological characterization by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) revealed a uniform, fine-grained platinum surface with nanoscale roughness, consistent with the Ti/Pt/Au/Pt multilayer stack architecture. The electrochemical behavior of the pMEAs was assessed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), which demonstrated favorable responses for both O₂ reduction and H₂O₂ oxidation, together with low impedance (41.1 kΩ at 1 kHz). For O₂ detection, amperometric measurements at −0.6 V vs. Ag/AgCl indicated a sensitivity of −0.25 ± 0.04 nA μM⁻¹ and a detection limit of 5.4 ± 1.4 nM. For H₂O₂ detection, application of +0.7 V vs. Ag/AgCl resulted in a sensitivity of 88.13 ± 7.61 nA mM⁻¹ and a detection limit of 41.9 ± 5.6 nM. Selectivity evaluation showed effective interferent exclusion following m-phenylenediamine electrodeposition, without compromising analytical performance. Overall, these findings indicate the suitability of pMEAs for real-time, in vivo monitoring of O₂ and H₂O₂ in brain tissue with high spatial and temporal resolution, supporting applications in oxidative stress research and neurometabolic sensing. Full article

The unique contributions of 2D Ti₃C₂ MXenes surface, electrical, and chemical features play a crucial role in determining toxic and flammable gas-sensing behavior. Specifically, its high electrical conductivity (metallic nature), layered nanosheet structure (nanosheets), and surface termination groups (–O, –F, and –OH) collectively contribute to excellent hydrogen (H₂) and ammonia (NH₃) gas-sensing behavior. This review systematically explores the impact of pristine and modified Ti₃C₂ MXene, including its interfaces with various metals and metal oxides for enhancing H₂ and NH₃ detection. Furthermore, the significance of room temperature operation and flexible gas sensing mechanisms is explored. Notably, integration of Ti₃C₂ MXene and sulfur nanosheets demonstrates rapid response and recovery times with detection limits at ppt level. Ti₃C₂ MXene-based interfaces also exhibit excellent long-term stability under various relative humidity conditions. The selective surface termination groups (–OH and –O) facilitate the formation of hydrogen bonds with NH₃ molecules for enhancing gas adsorption and sensing selectivity. In addition, the expansion of the interlayer spacing plays a vital role in improving the gas-sensing performance. Partial oxidation of Ti₃C₂ MXene into TiO₂ increases the interlayer distance, promoting faster diffusion of gas molecules and quicker sensor response. Overall, the intrinsic properties of Ti₃C₂ MXene and its composites significantly achieve high-performance room-temperature H₂ and NH₃ gas-sensing performance. Full article

Escherichia coli O157:H7 represents a major food safety concern, with cattle serving as the primary reservoir host. A better understanding of the interactions between O157 and the potential physiochemical indicators to which it is exposed to in the cattle hindgut would lend insight into the O157 colonization process and aid in the development of effective preharvest interventions to control O157 in its reservoir host. Bovine bile and oxygen are two universal cues that O157 is exposed to upon entry into the cattle hindgut and that vary between different segments of the gastrointestinal tract. Here, we exposed E. coli O157:H7 strain EDL933 to whole bovine bile powder and oxygen, both individually and in combination, and assessed the transcriptomic and phenotypic responses. Under aerobic conditions, EDL933 increased the expression of adiC, and increased biofilm production in vitro, while anaerobic conditions increased the expression of fimbrial genes, including ydeR and fimA. Bovine bile induced the expression of pathways responsible for quorum sensing and the utilization of mucus-derived sugars. These findings suggest that bovine bile and oxygen impact the transcriptomic and phenotypic characteristics of EDL933 in vitro. Full article