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Antibiotic residues cause increasing concern in environmental ecology and public health, which needs efficient analysis strategy for monitoring and control. In this study, a fast, specific, and ultrasensitive sensor based on field-effect transistor (FET) has been proposed for the detection of ampicillin (AMP). The sensor involves monolayer tungsten disulfide (WS

Silver (Ag) is a widely used heavy metal, and its oxidation state (Ag+) causes serious harm to organisms after bioaccumulation and biomagnification, posing urgent demand for the rapid, efficient, and simply operated Ag+ detection techniques. In this work, a fast, portable, and label-free Ag+ detection sensor based on a Ti3C2Tx MXene field-effect transistor (FET) is reported. The Ti3C2Tx MXene works as the sensing element in the FET sensor, which shows excellent sensing performance, i.e., fast response (few seconds) and good sensitivity and selectivity to Ag+ without any detection label or probe. Utilizing the visual photograph, transmission electron microscopy image, and Ag elemental mapping analysis, the sensing mechanism of the label-free Ti3C2Tx MXene FET sensor is demonstrated to be the in situ reduction of Ag+ and the formation of Ag nanoparticles (AgNPs). Moreover, Ag+ detection in real samples shows that the proposed FET devices have satisfactory sensing capability for Ag+ in tap water and river water. This study puts forward a novel FET strategy for Ag+ detection in aqueous systems, which is of essential and inspiring meaning for motivating the potential applications of MXene-based sensor devices in analytical applications and the realization of on-site environmental monitoring.

Novel hypercross-linked β-cyclodextrin nanospheres are rapidly synthesized with 4-amino-6-hydroxy-2-mercaptopyrimidine as a cross-linker within 5 min at a low temperature of 60 °C in the open water phase, thereby radically simplifying and accelerating the conventional time-consuming and environmentally harsh synthesis of cyclodextrin-containing polymers. The nanospheres demonstrate excellent and controllable performance as alkali-responsive nanocarriers and selective adsorbents for antibiotics.

Field-effect transistors (FETs) receive growing attention for gas detection owing to their superior sensing performance over traditional techniques. The sensitivity and selectivity of FET sensors can be enhanced by tuning the structure of channel materials via doping, surface functionalization, hybridization, etc. However, the intrinsic semiconductor characteristics of the channel material and its gas adsorption capacity largely determine the sensing performance. In this work, we compared the room-temperature sensing performance of FET sensors with few-layer graphene, black phosphorous (BP), and MoS2 with mixed polymorphic phases (metallic 1T phase and semiconducting 2H phase), and 2H-MoS2 as a channel material for formaldehyde. The sensing results indicate that 1T/2H-MoS2 exhibits the best sensitivity, response time as well as selectivity for formaldehyde detection. The theoretical calculation demonstrates that 1T/2H-MoS2 yields the optimum semiconducting properties and gas adsorption capability for formaldehyde over other 2D channels. Moreover, by investigating the sensing performance under humid conditions, it was discovered that high humidity enhances the sensing response. This study demonstrates that the regulation of the intrinsic electronic structures of the 2D semiconducting channel directly affects the gas detection performance.

Monolayer MoS2 (ML-MoS2) with various polymorphic phases attracts growing interests for device applications in recent years. Herein, a field-effect transistor (FET) gas sensor is developed on the basis of monolayer MoS2 with a heterophase of a 1T metallic phase and a 2H semiconducting phase. Lithium-exfoliated MoS2 nanosheets own a monolayer structure with rich active sites for gas adsorption. With thermal annealing from 50 to 300 °C, the initial lithium-exfoliated 1T-phase MoS2 gradually transforms into the 2H phase, during which the 1T and 2H heterophases can be modulated. The 1T/2H heterophase MoS2 shows p-type semiconducting properties and prominent adsorption capability for NO2 molecules. The highest response is observed for 100 °C annealed MoS2 of a 40% 1T phase and a 60% 2H phase, which shows a sensitivity up to 25% toward 2 ppm NO2 at room temperature in a very short time (10 s) and a lower limit of detection down to 25 ppb. This study demonstrates that the gas detection capability of ML-MoS2 could be boosted with the heterophase construction, which brings new insights into transition-metal dichalcogenide gas sensors.

MXenes, a group of emerging two-dimensional (2D) transition metal carbides or nitrides, have attracted wide interest due to their unique structures and properties. Their stability and applicability in different media especially in an alkaline environment are directly associated with their potential applications and are not yet explored. Herein, a field-effect transistor (FET) is fabricated with single/double-layer Ti3C2Tx MXene. The Ti3C2Tx FET indicator shows a fast (∼1 s), sensitive, and selective response to alkali. Moreover, the device can work even in a high-salinity (2 M NaCl) environment, suggesting its high anti-interference ability for alkali in a high-ionic-strength environment. Using an in situ morphological image evolution study, it is demonstrated that the response signal results from alkali-induced denaturation of Ti3C2Tx nanosheets. The Ti3C2Tx-based alkali FET indicator and systematic evaluation on alkali-induced structure evolution of Ti3C2Tx provide essential insights into MXene-based FETs and future applications of MXene in alkaline environments.

Despite the critical need to monitor H

Mercury ions (Hg2+) are the dominant mercury species in water, and have severe toxic effects on human health and the ecosystem. Due to the limitations of traditional analytical methods for mercury determination, e.g., complex pretreatment, costly instruments, and being unsuitable for low-level online sensing, numerous efforts have been made to develop rapid, low-cost, and portable sensors for Hg2+ determination. The excellent characteristics of graphene, i.e., a unique two-dimensional structure, large surface area, high conductivity and carrier mobility, and good optical and electrochemical properties, lead to intense studies on graphene-based Hg2+ sensors with desirable performance and broad application prospects. The scope of this review is recent advances in graphene Hg2+ sensors with a special focus on optical, electrochemical, and electronic sensors. The working principles and advantages of representative graphene Hg2+ sensors are introduced and compared with traditional methods. Moreover, challenges as well as potential solutions and research directions of mercury sensors are discussed, which will guide future research of Hg2+ sensors in biomedical and environmental monitoring applications.

Silver (Ag) is a widely used heavy metal, and its oxidation state (Ag

Mercury is one of the leading chemicals of concern and receives much attention in environmental safety. It is of great necessity to develop advanced Hg

MXenes, a group of emerging two-dimensional (2D) transition metal carbides or nitrides, have attracted wide interest due to their unique structures and properties. Their stability and applicability in different media especially in an alkaline environment are directly associated with their potential applications and are not yet explored. Herein, a field-effect transistor (FET) is fabricated with single/double-layer Ti

Despite the critical need to monitor H2S, a hazardous gas, in environmental and medical settings, there are currently no reliable methods for rapid and sufficiently discriminative H2S detection in real-world humid environments. Herein, targeted hybridizing of Ti3C2Tx MXene with Ag nanoparticles on a field-effect transistor (FET) platform has led to a step change in MXene sensing performance down to ppb levels, and enabled the very high selectivity and fast response/recovery time under room temperature for H2S detection in humid conditions. For the first time, we present a novel relative humidity (RH) self-calibration strategy for the accurate detection of H2S. This strategy can eliminate the influence of humidity and enables the accurate quantitative detection of gas in the total RH range. We further elucidate that the superior H2S sensing performance is attributed to the electron and chemical sensitization effects. This study opens new avenues for the development of high-performance MXene-based sensors and offers a viable approach for addressing real-world humidity effect for gas sensors generally.

Mercury is one of the leading chemicals of concern and receives much attention in environmental safety. It is of great necessity to develop advanced Hg2+ analysis method for rapid detection and monitoring. Field-effect transistor (FET) sensor, an emerging electronic sensor, has received great attention in environmental analysis since it has unique advantages in achieving rapid analysis of chemicals. Herein, an FET sensor is constructed with Ti3C2Tx MXene as the channel material to detect Hg2+ in water. The sensor displays rapid and selective response to Hg2+. Moreover, the sensor achieves satisfactory performance in Hg2+ detection in high salinity environment (1 M NaCl), which benefits its applications in real water analysis. Based on the investigation of sensing mechanism, the strong response of Ti3C2Tx MXene FET sensor to Hg2+ is due to the adsorption and reduction of Hg2+ to Hg+ on the Ti3C2Tx surface. This reported label-free Ti3C2Tx MXene platform can detect Hg2+ in high salinity environment with high specificity, which has significant application potential for on-site monitoring and risk assessment of Hg2+ in aqueous systems.

Although aptamer has been demonstrated as an important probe for antibiotic determination, the selective sensing of different antibiotics is still a challenge due to their structure similarities and wide folding degrees of aptamer. Herein, a field-effect transistor using MoS

Although aptamer has been demonstrated as an important probe for antibiotic determination, the selective sensing of different antibiotics is still a challenge due to their structure similarities and wide folding degrees of aptamer. Herein, a field-effect transistor using MoS2 nanosheet as the channel and an aptamer DNA (APT) with its configuration shaped by a complementary strand DNA (CS) is employed for kanamycin (KAN) determination. This probe structure contributes to an enhanced selectivity and reliability with reduced device-to-device variations. This MoS2/APT/CS sensor shows time-dependent performance in antibiotic sensing. Prolonged detection time (20 s–300 s) leads to an enhanced sensitivity (1.85–4.43 M-1) and a lower limit of detection (1.06–0.66 nM), while a shorter detection time leads to a broader linear working range. A new sensing mechanism relying on charge release from probe is proposed, which is based on the “replacement reaction” between KAN and APT-CS. This sensor exhibits an extremely high selectivity (selectivity coefficient of 12.8) to kanamycin over other antibiotics including streptomycin, tobramycin, amoxicillin, ciprofloxacin and chloramphenicol. This work demonstrates the merits of probe engineering in label-free antibiotic detection with FET sensor, which presents significant promises in sensitive and selective chemical and biological sensing.