Boosting room-temperature NO2 detection via in-situ interfacial engineering on Ag2S/SnS2 heterostructures

Enhancing peroxymonosulfate activation via silver nanoparticle-decorated bismuth oxybromide/silver sulfide S-scheme heterojunction with surface plasmon resonance for tetracycline degradation: Mechanisms and pathways

Catalysts with S-scheme semiconductor junctions offers an enhanced redox capacity. Herein, BiOBr/Ag/Ag2S composites with a three-dimensional structure were prepared by hydrothermal reaction. The growth of Ag2S nanoparticles on the surface of BiOBr nanoflowers was successfully achieved, leading to strong light absorption and surface plasmon resonance (SPR) effect, together with improved rates of light-induced carriers. In the presence of peroxymonosulfate (PMS), the BiOBr/Ag/Ag2S composite removed 90.1 % of tetracycline (TC), outperforming BiOBr or Ag/Ag2S, owing to its superior redox capability and reduced carrier recombination efficiency. Additionally, BiOBr/Ag/Ag2S demonstrated excellent recovery performance and stability. Liquid chromatography-mass spectrometry (LC-MS) was employed to investigate the possible intermediate products and reaction pathways. The reaction mechanism of the S-scheme semiconductor heterojunction was further elucidated through density functional theory (DFT) calculations. In conclusion, the research provides a novel approach to activate PMS using an S-scheme semiconductor heterojunction with high redox capacity for practical use in wastewater treatment.

Self-powered photoelectrochemical sensor based on molecularly imprinted polymer-coupled CBFO photocathode and Ag2S/SnS2 photoanode for ultrasensitive dimethoate sensing

Dimethoate (DIM) is one of the most extensively applied organophosphorus pesticides (OPs), which is used to boost farm productivity due to its high insecticidal efficacy. However, the excessive use of DIM can result in the extensive contamination of soil, groundwater and food. Monitoring of DIM in environmental and food samples is crucial in view of its potential health risks and environmental hazards from excessive residues. The expensive equipment and complex operations for current detection methods greatly limit their practical applications. Herein, a self-powered photoelectrochemical (PEC) sensing platform based on Ag2S/SnS2 photoanode, iron-doped cobalt borate (CBFO) photocathode, and molecularly imprinted polymers (MIPs) was proposed for the detection of DIM. The molecularly imprinted polymers at CBFO photocathode endow the self-powered PEC sensor with high selectivity. The Ag2S/SnS2 photoanode enhances the efficient of electron transfer between the photoanode and photocathode, contributing to the high sensitivity of PEC sensor. The self-powered molecularly imprinted PEC sensor exhibits outstanding sensitivity and selectivity for DIM at concentrations from 1 × 10-2 to 1 × 105 nM with a detection limit of 5.9 pM. Excellent recoveries (95.4 ± 2.6 %, 98.4 ± 2.3 %, 106.3 ± 3.3 %) were achieved in spiked crown pear samples, indicating that the molecularly imprinted PEC sensor is capable of detecting DIM in real samples. This research provides a novel simple, fast, highly selective and sensitive self-powered molecularly imprinted photoelectrochemical sensing platform for detection of DIM. The fabricated PEC sensor offers a promising candidate for the detection method of organophosphorus pesticides residues, which is of great significance for the fields of food safety and environmental protection.

Recent Advances in Engineering of 2D Layered Metal Chalcogenides for Resistive-Type Gas Sensor

2D nanomaterials have triggered widespread attention in sensing applications. Especially for 2D layered metal chalcogenides (LMCs), the unique semiconducting properties and high surface area endow them with great potential for gas sensors. The assembly of 2D LMCs with guest species is an effective functionalization method to produce the synergistic effects of hybridization for greatly enhancing the gas-sensing properties. This review starts with the synthetic techniques, sensing properties, and principles, and then comprehensively compiles the advanced achievements of the pristine 2D LMCs gas sensors. Key advances in the development of the functionalization of 2D LMCs for enhancing gas-sensing properties are categorized according to the spatial architectures. It is systematically discussed in three aspects: surface, lattice, and interlayer, to comprehend the benefits of the functionalized 2D LMCs from surface chemical effect, electronic properties, and structure features. The challenges and outlooks for developing high-performance 2D LMCs-based gas sensors are also proposed.

Advancements in MXene Composite Materials for Wearable Sensors: A Review

In recent years, advancements in the Internet of Things (IoT), manufacturing processes, and material synthesis technologies have positioned flexible sensors as critical components in wearable devices. These developments are propelling wearable technologies based on flexible sensors towards higher intelligence, convenience, superior performance, and biocompatibility. Recently, two-dimensional nanomaterials known as MXenes have garnered extensive attention due to their excellent mechanical properties, outstanding electrical conductivity, large specific surface area, and abundant surface functional groups. These notable attributes confer significant potential on MXenes for applications in strain sensing, pressure measurement, gas detection, etc. Furthermore, polymer substrates such as polydimethylsiloxane (PDMS), polyurethane (PU), and thermoplastic polyurethane (TPU) are extensively utilized as support materials for MXene and its composites due to their light weight, flexibility, and ease of processing, thereby enhancing the overall performance and wearability of the sensors. This paper reviews the latest advancements in MXene and its composites within the domains of strain sensors, pressure sensors, and gas sensors. We present numerous recent case studies of MXene composite material-based wearable sensors and discuss the optimization of materials and structures for MXene composite material-based wearable sensors, offering strategies and methods to enhance the development of MXene composite material-based wearable sensors. Finally, we summarize the current progress of MXene wearable sensors and project future trends and analyses.

Synergy of Active Sites and Charge Transfer in Branched WO3/W18O49 Heterostructures for Enhanced NO2 Sensing

Achieving reliable detection of trace levels of NO2 gas is essential for environmental monitoring and protection of human health protection. Herein, a thin-film gas sensor based on branched WO3/W18O49 heterostructures was fabricated. The optimized WO3/W18O49 sensor exhibited outstanding NO2 sensing properties with an ultrahigh response value (1038) and low detection limit (10 ppb) at 50 °C. Such excellent sensing performance could be ascribed to the synergistic effect of accelerated charge transfer and increased active sites, which is confirmed by electrochemical impedance spectroscopy and temperature-programmed desorption characterization. The sensor exhibited an excellent detection ability to NO2 under different air quality conditions. This work provides an effective strategy for constructing WO3/W18O49 heterostructures for developing NO2 gas sensors with an excellent sensing performance.

Ag2S-Decorated One-Dimensional CdS Nanorods for Rapid Detection and Effective Discrimination of n-Butanol

N-butanol (C4H9OH) is a volatile organic compound (VOC) that is susceptible to industrial explosions. It has become imperative to develop n-butanol sensors with high selectivity and fast response and recovery kinetics. CdS/Ag2S composite nanomaterials were designed and prepared by the solvothermal method. The incorporation of Ag2S engendered a notable augmentation in specific surface area and a consequential narrow band gap. The CdS/Ag2S-based sensor with 3% molar ratio of Ag2S, operating at 200 °C, demonstrated a remarkably elevated response (S = Ra/Rg = 24.5) when exposed to 100 ppm n-butanol, surpassing the pristine CdS by a factor of approximately four. Furthermore, this sensor exhibited notably shortened response and recovery times, at a mere 4 s and 1 s, respectively. These improvements were ascribed to the one-dimensional single-crystal nanorod structure of CdS, which provided an effective path for expedited electron transport along its axial dimension. Additionally, the electron and chemical sensitization effects resulting from the modification with precious metal sulfides Ag2S were the primary reasons for enhancing the sensor response. This work can contribute to mitigating the safety risks associated with the use of n-butanol in industrial processes.

Adsorption of NO2, NO, NH3, and CO on Noble Metal (Rh, Pd, Ag, Ir, Pt, Au)-Modified Hexagonal Boron Nitride Monolayers: A First-Principles Study

To investigate the application of modified hexagonal boron nitride (h-BN) in the detection and monitoring of harmful gases (NO2, NO, NH3, and CO), first-principles calculations are applied to study the geometric structure and electronic behavior of the adsorption system. In this paper, the four adsorption sites, namely, B, N, bridge, and hollow sites, are considered to explore the stable adsorption structure of metals (M = Rh, Pd, Ag, Ir, Pt, and Au) on the BN surface. The calculation results demonstrate that the geometric structures of metal at the N-site are relatively stable. Subsequently, the different adsorption structures of NO2, NO, NH3, and CO on M-BN are researched. The electron transfer, charge difference density, and work function of the stable adsorption structure are calculated. The results show that NO2, NO, and CO have the strongest adsorption capacity in the Ir-BN system, with adsorption energies of -2.705, -5.064, and -3.757 eV, respectively. The Pt-BN system has an excellent adsorption performance (-2.251 eV) for NH3. Compared with the M-BN system, the work function of the adsorption system increases after adsorbing NO2, while it decreases after adsorbing NH3. This work shows that h-BN with metal modification is a potential material for online monitoring of harmful gases.

Ultrasensitive Room-Temperature NO2 Detection Using SnS2/MWCNT Composites and Accelerated Recovery Kinetics by UV Activation

High performance with lower power consumption is one among the essential features of a sensing device. Minute traces of hazardous gases such as NO₂ are difficult to detect. Tin disulfide (SnS₂) nanosheets have emerged as a promising NO₂ sensor. However, their poor room-temperature conductivity gives rise to inferior sensitivity and sluggish recovery rates, thereby hindering their applications. To mitigate this problem, we present a low-cost ultrasensitive NO₂ gas sensor with tin disulfide/multiwalled carbon nanotube (SnS₂/MWCNT) nanocomposites, prepared using a single-step hydrothermal method, as sensing elements. Relative to pure SnS₂, the conductivity of nanocomposites improved significantly. The sensor displayed a decrease in resistance when exposed to NO₂, an oxidizing gas, and exhibited p-type conduction, also confirmed in separate Mott-Schottky measurements. At a temperature of 20 °C, the sensor device has a relative response of about ≈5% (3%) for 25 ppb (1 ppb) of NO₂ with complete recovery in air (10 min) and excellent recovery rates with UV activation (0.3 min). A theoretical lower limit of detection (LOD) of 7 ppt implies greater sensitivity than all previously reported SnS₂-based gas sensors, to the best of our knowledge. The improved sensing characteristics were attributed to the formation of nano p-n heterojunctions, which enhances the charge transport and gives rise to faster response. The composite sensor also demonstrated good NO₂ selectivity against a variety of oxidizing and reducing gases, as well as excellent stability and long-term durability. This work will provide a fresh perspective on SnS₂-based composite materials for practical gas sensors.