Developing efficient non-enzymatic glucose sensors remains challenging due to the limited electrical conductivity and restricted catalytic accessibility of conventional transition-metal oxide electrodes. Here, we report a photoelectrochemical sensing platform based on a 2D/2D NiO nanosheet-MXene heterostructure engineered to enhance interfacial charge transport and catalytic redox activity. The heterostructure is synthesized through a pressure-assisted hydrothermal strategy that enables controlled nucleation of Ni(OH)(2) on surface-functionalized MXene sheets, followed by annealing-induced phase conversion to ultrathin NiO nanosheets. This architecture maximizes electrochemically accessible Ni redox sites while simultaneously establishing highly conductive electron transport pathways through the MXene framework. Under UV illumination, photogenerated carriers accelerate Ni2+/Ni3+ redox cycling and promote the formation of reactive hydroxyl intermediates that facilitate glucose oxidation. As a result, the NiO@MXene electrode exhibits markedly enhanced photoelectrochemical sensing performance, delivering a high sensitivity of 2474 mu A mM(-1) cm(-2), a wide linear detection range of 0.5-6 mM, and a rapid response time of similar to 11 s, together with excellent selectivity against common interfering species. Mechanistic analysis reveals that the enhanced sensing performance originates the synergistic interaction between ultrathin NiO nanosheets and conductive MXene layers, which improves charge separation, accelerates electron transport, and promotes efficient Ni2+/Ni3+ redox catalysis. These results demonstrate the importance of engineered ceramic-MXene heterointerfaces for improving catalytic charge transport and provide an effective strategy for developing advanced photoelectrochemical sensing materials.

Achieving reliable chemiresistive gas sensing under breath-like, high-humidity conditions remains a critical challenge due to water-induced charge screening and disrupted surface redox reactions. In this work, we report a 0D/2D Ti3C2Tx quantum dot–decorated V2CTx MXene hybrid synthesized via a single-step, HF-free in-situ method that simultaneously delaminates the MAX phase and constructs robust Ti–O–V chemical bonds at the interface, which regulate both charge transport and molecular recognition. These engineered linkages provide abundant active sites for H2S adsorption while enabling efficient charge transport across the heterojunction. Quantum-confined Ti3C2Tx QDs act as photocarrier generators, and the metallic V2CTx sheets serve as high-mobility electron channels, enabling fast and sensitive signal transduction under low-power UV light (365 nm). Crucially, Ti–O–V interfacial motifs and surface –OH terminations create high-affinity adsorption sites that enable proton-assisted H₂S transport through hydration layers, conferring strong selectivity over common interferents (NO2, SO2, NH3, acetone, ethanol) even at high relative humidity. The sensor exhibits linear H₂S responses from 50 ppb to 90 ppm, a low detection limit of 31 ppb, and rapid response/recovery times (8 and 9 s, respectively), while maintaining stable operation at 90

This paper introduces a streamlined three-step synthesis method for crafting porous Fe2O3/ZnO nanofibers (NFs). Initially, Fe2O3 nanoparticles (NPs) were synthesized using the hydrothermal method. Subsequently, PVP NFs laden with Fe2O3 NPs and zinc salt were synthesized via an electrospinning method. Finally, porous Fe2O3/ZnO NFs were fabricated through calcination, resulting in an average diameter of approximately 100 nm. Gas-sensing experiments illuminate that the porous Fe2O3/ZnO NFs exhibit outstanding sensitivity, selectivity, and robust long-term stability. Although the response magnitude decreased under high relative humidity (RH) due to competitive adsorption, the sensor maintained distinct detectable responses towards NO2 vapor at an optimum temperature of 225 °C. Particularly noteworthy is the substantial enhancement in NO2 sensing properties observed in the Fe2O3/ZnO composite compared to pure ZnO NFs. This enhancement can be ascribed to the distinctive microstructure and heterojunction formed between Fe2O3 and ZnO.

Ammonia (NH3) detection at room temperature remains challenging because of trade-offs among sensitivity, reversibility, and stability. Here we report a ternary MXene/NiO/Fe2O3 nanocomposite in which p-type NiO serves as the primary sensing phase, while Fe2O3 and Ti3C2Tx MXene provide interfacial and transport synergy. The MXene/NiO/Fe2O3 sensor achieves sub-ppm detection and a high response of 77 at 40 ppm, while maintaining fast response, excellent cycling reproducibility over 20 cycles, and <= 5 % drift over 60 days. Selectivity tests show a markedly higher response to NH3 than to ethanol or acetone. Humidity studies (0-80 % RH), followed by concurrent decreases in baseline resistance and response at >= 40 % RH with increased noise attributable to adsorbed water layers. The enhanced performance arises from a work-function-guided cascade band-bending network that forms two Schottky-type contacts (MXene/oxide) and a NiO/Fe2O3 p-n junction, small NH3induced barrier modulations are parallel-amplified into large macroscopic resistance changes, while MXene provides a percolating conductive network and abundant anchoring sites. These results establish MXene/NiO/ Fe2O3 as a robust, room-temperature NH3 sensing platform that combines high gain, sub-ppm responsiveness, and long-term stability.

Metal oxide semiconductor (MOS) gas sensors are widely studied for their low cost, simple fabrication, and high sensitivity to a broad range of analytes. Despite decades of progress, their broader deployment remains constrained by poor selectivity, environmental variability, signal drift, and poor inter device reproducibility. Artificial intelligence (AI) has recently emerged as a promising strategy to overcome these limitations by extracting meaningful information from complex sensor responses and enabling predictive and adaptive behavior. This review highlights the convergence of MOS gas sensing with AI. We first revisit the fundamental operating principles of MOS sensors and explain why conventional approaches often underperform in real world settings. We then summarize key AI methods, including classical machine learning, deep learning, and more recent technologies, while analyzing their respective strengths and limitations for gas sensing tasks. Particular emphasis is placed on integration strategies such as single sensor enhancement, sensor array fusion, drift correction, AI guided materials and device design, and lightweight on device deployment. We further examine application domains where AI-enhanced MOS sensors demonstrate clear advantages, including environmental monitoring, healthcare diagnostics, food safety, industrial safety, and Internet of Things (IoT) systems. Finally, we discuss ongoing challenges related to data scarcity, model generalization, interpretability, and scalability, and we outline future directions for developing intelligent, reliable, and large-scale MOS sensing ecosystems.

Choosing appropriate host materials to enhance the stability and catalytic performance of colloidal gold nanoparticles (AuNPs) is crucial for diverse chemical reactions. In this study, a series of poly(N-isopropylacrylamide)-co-polyacrylamide (PNIPAM-co-PAAM) particles are prepared to incorporate guest AuNPs via in situ reduction of gold ions under light irradiation. The formation of AuNPs in the presence of these copolymer particles is thoroughly monitored at room temperature to understand how the polymer network affects the structural features and loading efficiency of the guest AuNPs as a function of PAAM content. The resulting composite particles are also tested as colloidal catalysts in homocoupling reactions to assess the influence of the copolymer matrix. Notably, the formation kinetics of the AuNPs is greatly impacted by the interfacial interactions induced by the copolymer contents containing primary amide groups. However, increasing the number of AAM units in the main PNIPAM network leads to a detectable decrease in both loading efficiency and catalytic performance of the AuNPs, presumably due to a slightly dense and disordered structure of the copolymer network compared to homopolymer particles. Understanding the formation, loading efficiency, and catalytic activity of the guest AuNPs across the host polymer particles provides valuable insights into the structural features of the copolymer matrix and their interfacial interactions. This study experimentally explains the important role of the copolymer network in the in situ formation of metal NPs and their catalytic properties in the development of novel and effective chemical reaction systems.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have emerged as promising materials for gas sensing due to their atomic thickness, high surface to volume ratio, and tunable electronic structure. This review surveys recent advances in TMD based gas sensors, with emphasis on synthesis routes such as chemical vapor deposition, liquid phase exfoliation, mechanical exfoliation, and plasma assisted functionalization, and explains how these processes control defect density and distribution, drive phase transformations, and tailor surface chemistry. We evaluate the sensing performance of key TMDs such as MoS2, WS2, MoSe2, WSe2 and metallicphase/Janus variants, analyzing mechanisms such as charge-transfer, defect-mediated adsorption, and photoactivation. We focus on engineering strategies that raise sensitivity to ppb levels and sharpen selectivity. We also prioritize faster response and recovery and reliable operation at ambient temperature. The review also discusses scalable integration approaches, including thin-film and heterostructured sensor architectures, as well as implementation in flow-through reactors, wearable platforms, and IoT systems. This review integrates material design, performance metrics, and system-level engineering to outline a roadmap toward commercially viable, high performance TMD gas sensors.

Mechanical stress that reconfigures interfacial band profiles to generate voltage without bias-so-called stress-gated piezotronics-remains challenging to achieve in flexible, lead-free ceramics. We report a rationally engineered Eu3+/Ta5+- -doped ZnO shell coherently integrated with a ferroelectric BaTiO3 core (Eu-/Ta-ZZ@BTO), forming a true core-shell ceramic that enables dual-mode polarization by coupling shell defect dipoles with core ferroelectric strain. In the shell, Eu-Zn-V-O d defect dipoles break local symmetry and enhance d(33), while Ta5+ modulates donor density (N-D) and suppresses oxygen-vacancy screening, thereby sustaining a high g(33) with low tan delta. Under pressure, BaTiO3 and interfacial bound charges modulate the Eu/Ta-ZnO shell, reduce ZnO band bending and depletion width, and increase the open-circuit voltage-yielding a stress-gated piezotronic response consistent with XPS, Mott-Schottky, and Tauc band analyses. The optimized core-shell delivers d(33) = 195 pC/N, g(33) = 0.13 V m/N, epsilon(r) = 168, tan delta (similar to 0.0040), sensitivity of 4.14 V/kPa, and a detection limit of 1.72 kPa. Uniaxial tensile tests confirm improved stiffness and toughness through interfacial load transfer and radial interlocking, while on-body experiments (wrist, elbow, finger, fist, knee, plantar pressure, jumping, push-ups, squats, sit-ups) produce stable, bipolar waveforms that scale with local compressive stress. These findings establish a microstructure-controlled and mechanics-driven strategy for bias-free pressure transduction in lead-free oxides by uniting defect chemistry, ferroelectric domain mechanics, and interfacial band engineering.

A flower-like ZnO was successfully synthesized via a simple chemical precipitation method at room temperature (RT) in distilled water, without the use of any catalysts or substrates. The sample’s structure was analyzed using various techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (FETEM), and X-ray photoelectron spectroscopy (XPS), which confirmed its hexagonal structure. UV–visible optical absorption measurements also revealed the presence of UV absorption at 365 nm. A reasonable growth mechanism for the formation of flower-like ZnO was proposed based on these analyses. The response of the sample to low concentrations of NO2 (1 ppm) was evaluated at different calcination temperatures, and the results showed that the best response was achieved when the sample was calcined at 600 °C. The flower-like ZnO sample labeled as 6ZnO showed the highest response of 54.18 when exposed to 1 ppm of NO2 gas at RT. Additionally, 6ZnO exhibited good response and recovery properties of 11 s and 93 s, respectively, at low concentrations of NO2 at 1 ppm. The gas sensing mechanism and the mechanism of the enhanced gas response of the flower-like ZnO are discussed.

Synthesis of TiO 2 /In 2 O 3 composite and application for NO 2 gas detection at room temperature.

Multiwalled carbon nanotube (MWCNT) forests have extremely large surface areas and high catalytic activity. To use them as alternative materials for Pt/fluorine-doped tin oxide (FTO) conventional counter electrodes (CEs) in dye-sensitized solar cells (DSSCs), a unique Ru metal layer, prepared with 600-cycle atomic layer deposition, was employed. The best Ru-coated MWCNT forest (Ru/MWCNT) CE performance was achieved by examining the experimental conditions for the MWCNT forests, including deposition processes, catalyst thicknesses and synthesis time. The results revealed that 20μm-thick MWCNT forests with numerous defects/disordered sites exhibit excellent CE performance. In practice, Ru/MWCNT CEs prepared under optimal synthesis conditions show low charge transfer resistance (Rct of approximately 2.5 ohm) and series resistance (Rs of approximately 14 ohm) that are even better than those for Pt/FTO CEs (Rct=6.36 ohm and Rs=16.4 ohm). Owing to these excellent Rct and Rs values, dye-sensitized solar cells with optimized Ru/MWCNT CEs showed better performance than those containing Pt/FTO CEs. Finally, post-heat treatment of Ru/MWCNT CEs increased the cell efficiency of the DSSCs.

Introducing a groundbreaking solution, a room-temperature (RT, 25 degrees C) gas sensor addresses complexities in conventional sensors, promising enhanced performance. Synthesized through hydrothermal and thermal calcination processes, SnO2 hollow nanospheres (HNs) are integrated with In2O3 components to bolster sensing capabilities. The sensor detects triethylamine (TEA) gas upon UV light irradiation, owing to its unique surface properties and SnO2-SnO2 and SnO2-In2O3 homo-and heterojunctions. This results in unparalleled sensitivity to TEA gas (Ra/Rg 1/4 34-100 ppm) and an exceptional limit of detection (3.98 ppt), attributed to photo-ionized O2-ions' heightened reactivity. The study proposes superior sensors backed by comprehensive analyses, demonstrating their performance improvements and underlying mechanisms. The optimized sensor design, based on In2O3-appended SnO2 HNs, presents exceptional selectivity, pattern recognition for low TEA gas concentrations, humidity resistance, and reliability under UV irradiation.(c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Pd and Fe2O3 nanoparticles (NPs)-embedded porous NiO nanofibers (NFs) with high specific surface area were prepared using a facile electrospinning method. Adjusting the amount of Fe2O3 NPs in the precursor solution of electrospinning regulates the morphological evolution and crystallization of oxide heterostructures at elevated temperatures and significantly contribute to the enhanced gas sensing performance for hydrogen (H-2) gas testing. Synthesized composites present the highest response of 199.24 at the optimum operating temperature of 250 degrees C toward 1000 ppm H-2 gas, which is 65 times higher than that of only Pd-decorated NiO NFs. The response/recovery times of the sensors decreased significantly from 39/323 s for the pure sample to 11/105 s, along with good selectivity and long-term stability toward H-2. The excellent gas sensing properties of the sensors is mainly attributed to the flourishing porous one-dimensional (1D) microstructure containing closely connected p-n heterojunctions of NiO and Fe2O3, which provide large specific surface areas with many active sites to promote the reaction between H-2 molecules and O ion on the surface and the catalytic effect of Pd. The results demonstrate the potential of the method to fabricate gas sensors for H-2 detection at ppm levels at 250 degrees C environment.

In this study, the synthesis of Co3O4 nanoparticles (NPs) decorated onto SnO2 nanowires (NWs) was achieved through a meticulous vapor-liquid-solid (VLS) process coupled with a hydrothermal approach. The paramount objective was to amplify the gas sensing efficacy and refine the detection threshold of the acetone gas sensor. This endeavor encompassed a twofold enhancement strategy: the optimization of Co3O4 NP dimensions and their uniform dispersion across the SnO2 NW surface. This orchestrated approach yielded a remarkable 17-fold augmentation in the sensor's responsiveness towards 50 ppm acetone gas, as compared to sensors employing solely synthesized pure SnO2 NWs. Moreover, discernible sensor responses were adeptly elicited even at a minute concentration of 0.1 ppm acetone gas. A discernible advancement was discerned in contrast to antecedent research, reflecting substantial refinement in both response characteristics and the sensor's capacity to detect trace acetone gas levels. This heightened sensing proficiency can be attributed to the aptly tailored dimensions of Co3O4 NPs, harmoniously dispersed onto the SnO2 NW surface. This precise distribution engenders a pivotal p-n heterojunction, thereby eliciting the observed enhancement in sensing performance.

A series of porous Au nanoparticles (NPs) decorated with In2O3 nanoparticles (NPs) was embedded in ZnO nanofibers (NFs) using a facile electrospinning method, followed by calcination treatment at 400 degrees C. The crystal phase structure, morphology, elemental composition, and specific surface area were characterized using FESEM, XRD, FETEM, XPS, and BET analysis. The gas-sensing properties of the resulting Au-In2O3-ZnO NFs-based gas sensors were systematically assessed. The results showed that a small amount of In2O3 dopant improved the gassensing response properties. In particular, the sensor fabricated with a mixture containing 0.03 g In(NO3)3 (S2) exhibited excellent stability, selectivity, and a response of 95.15 towards 5 ppm of NO2 gas at room temperature (RT, 25 celcius) under ultraviolet (UV) irradiation. The S2 sensor also showed a high response of 90-5 ppm of NO2 at 80% relative humidity (RH). The high response sensing performance at low operating temperature (RT) of the fabricated Au-In2O3-ZnO sensors may be due to a synergistic effect between ZnO and In2O3, as well as the excellent catalytic effect of Au.

Toluene gas is hazardous but plays a vital role in several industries. Hence, the detection of toluene gas is important for human health and the environment. In this study, porous In2O3–ZnO nanofibers were prepared via a facile electrospinning method to fabricate a toluene gas sensor. Illumination by ultraviolet light (365 nm) was used to realize the room temperature (RT) operation of the fabricated sensor. The structural properties of the sensor were studied using various characterization techniques. The prepared nanofibers consisted of many sub-nanograins, particularly ZnO and In2O3, and contained numerous pores in-between the nanograins. Consequently, these nanofibers had a large surface area, increasing the probability of contact between the gas and sensor. The prepared sensors were functional at RT under UV illumination and showed excellent toluene-sensing properties. The porous In2O3-appended ZnO-nanofiber-based sensors showed more stable and sensitive response curves than those of the pure ZnO nanofiber–based sensor. Moreover, In2O3-appended ZnO nanofiber sensors could only faintly detect other gases, such as NO2, acetone, ethanol, H2S, and CO gases, indicating that the sensor exhibits highly selective toluene sensing.

Pd nanoparticle-decorated SnO2 nanotubes (Pd/SnO2 NTs) are synthesized in this study by electrospinning (using a coaxial spinneret) for application as a hydrogen gas sensor. The inner and outer diameters of the porous, polycrystalline Pd/SnO2 NTs are 80 nm and 120 nm, respectively, and the Pd nanoparticles decorating the Pd/SnO2 NTs are comparatively small with an average diameter of 5 nm. The catalytic effect of the Pd nanoparticles and the large effective surface area of the Pd/SnO2 NTs enhance the performance of resulting sensor. Furthermore, owing to the hollow, porous, polycrystalline structures of the SnO2 nano tubes, Pd nanoparticles decorate with high loading and uniform distribution of each constituent grain, maximizing their catalytic effect. As a result, the sensing response of a Pd/SnO2 NT sensor to 10 ppm hydrogen gas of 54.43 is 4.3 times higher than that of a SnO2 NT sensor of 12.69. (C) 2022 Elsevier B.V. All rights reserved.

Porous-structured Pd-decorated In2O3 nanoparticle-embedded SnO2 nanofibers are synthesized by electrospinning and a thermal calcination process using hydrothermally synthesized In2O3 nanoparticles. From this process, porous nanofibers can be obtained without any ZnIn2O4 components, and the sensing performance of the nanofibers can be maximized owing to the numerous pores and grain boundaries in their body. Additionally, as Pd nanoparticles form Schottky barriers with a nanofiber body and generate a catalytic effect, the hydrogen-sensing performance of these nanofibers can be increased. However, to significantly enhance the sensing performance of low-concentration hydrogen gas, sensors with more effective structures should be proposed. Hence, the Pd-decorated In2O3 nanoparticle-embedded SnO2 porous nanofibers are synthesized in this study for improved sensing performance. The response of this heterostructured nanofiber is 1291 for 100 ppm hydrogen gas, and the nanofiber exhibits a remarkable sensing performance, which is enhanced by 24 times, compared with the Pd-decorated SnO2 nanofibers. This study provides optimum In2O3 nanoparticles with the best hydrogen sensing performance and sensing mechanisms.

We report synthesis and characterization of Co3O4-decorated porous TiO2 nanofibers obtained through a facile electrospinning followed by a hydrothermal process. A morphological characterization confirmed that the diameter of the nanofiber was 250-300 nm. It was composed of subgrains, while its surface was decorated with Co3O4 nanoparticles with a diameter of 30-50 nm. The nanofiber had a porous body structure, which was conducive to the adsorption of acetone gas. The synthesized Co3O4-decorated porous TiO2 nanofibers were used as sensing materials to fabricate acetone gas sensors. Their response and recovery times were systematically analyzed with respect to the operation temperature and acetone gas concentration. The observed gas response, response time, and recovery time of the nanofiber-based gas sensor were 71.88, 122 s, and 351 s, respectively, for 10 0-ppm acetone gas at an optimized temperature of 250 ?. Therefore, the Co3O4-decorated porous TiO2 nanofibers could be a promising candidate for the fabrication of high selectivity acetone gas sensors. (c) 2022 Elsevier B.V. All rights reserved.

Tin oxide (SnO 2 ) nanowires (NWs) and indium oxide (In 2 O 3 ) nanoparticles (NPs) were synthesized using thermal evaporation and sol–gel methods, respectively. The NWs were decorated with the NPs by ultraviolet light irradiation and furnace annealing. The sensing properties of the NP-decorated NWs were compared with those of SnO 2 –In 2 O 3 core–shell nanobelts (NBs). Very few nanomaterial sensors show both strong response (response time + recovery time) and short sensing time. In contrast, the In 2 O 3 -decorated SnO 2 NW sensor fabricated in this study showed both strong response to NO 2 and fast sensing speed or short sensing time. The In 2 O 3 NP-decorated SnO 2 NWs showed stronger and faster response to NO 2 than their pristine SnO 2 counterpart and the SnO 2 –In 2 O 3 core–shell nanobelts. The experimental results also confirmed the importance of heterostructure formation and operating temperature optimization of the sensing variables, such as temperature, gas concentration, and the type of gas on the sensor response. The sensor response was strongly dependent on the type of gas. The gas sensing mechanism of the nanostructures for each sensing variable was discussed in detail. In addition, repeated sensing measurement highlighted the reversibility and reproducibility of the response of the In 2 O 3 NP-decorated SnO 2 NWs to nitrous oxide (NO 2 ).