Reusable Sensor Research Articles

Adsorption behavior of toxic nitrogen-containing gas molecules on GeC monolayer for the sensitive and reusable gas sensors: first-principles calculations

Abstract Using the first-principles calculations, the gas sensing properties of GeC monolayer are analyzed to explore the possibilities in the toxic nitrogen-containing molecular sensors to detect NH3, NO2 and NO molecules. The adsorption behavior is computed under different stable adsorption configurations. NH3 is physically adsorbed on GeC monolayer with modest adsorption energies (Eads = −0.487 eV). NO2 is chemisorbed on GeC monolayer with Eads of −0.770 eV. NO is either physisorbed or chemisorbed on GeC monolayer with Eads of −0.437 eV or −0.605 eV depending on the stable adsorption configurations. NO2 and NO molecule dramatically change the electronic properties of GeC monolayer, while NH3 molecule barely modifies those of GeC monolayer. Because of the change in the electric conductivity, the descending order of the sensitivity is NO2 > NO > NH3. Finally, the quick recovery times are found for all molecules which determine the worth of reusability of a sensing material.

Facile Construction of Soft Plasmonic Sensors with Exceptional Optical Activity for Quantitative Chiral Detection.

The facile construction of transmissive films with ultrabroad optical activity, spanning from deep-ultraviolet to short-wave infrared and offering convenient tunability across a wide range, is highly desirable for applications in sensing, imaging, and communication. However, achieving this remains challenging. Here, an easily applied wet-stretching method is introduced that simultaneously orients polymeric substrates and surface-coated plasmonic nanorods. Stacking two such hybrid films at an angle produces ultrastrong (ellipticity≈104 mdeg, gabs≈1) and broadband (200-2500 nm) circular dichroism (CD). The polymer's excellent strength and flexibility allow for broad-range tuning of the CD spectra by applying external force. The optical activity is sensitive to intervening medium, facilitating chiral detection of various inserted analytes in the forms of films, salt pellets, or solutions. This cost-effective and scalable fabrication strategy not only pioneers an expandable method for inducing chirality across diverse materials, but also offers a universal approach for constructing precise, non-destructive, non-contact, and reusable chiral sensors.

Theoretical Investigation of Rhodium-Decorated Gallium Nitride Nanotubes for Sulfur Hexafluoride Decomposition Products Sensing and Scavenging Applications.

Gas-insulated switchgear (GIS) plays an important role as a modern power distribution device in power plants and power stations, which is commonly filled with SF6 insulating gas. During the equipment operation, the inevitable partial discharge causes SF6 to be broken down into gas (SF4, SOF2, SO2, and H2S), which degrades the insulation performance of the GIS. This paper is devoted to the detection of partial discharge and the removal of SF4 and SOF2, which are not conducive to insulation, by exploring new gas-sensing materials for characteristic gas detection. Based on first-principles calculation, on the one hand, the most stable adsorption configurations of rhodium-decorated gallium nitride nanotubes (Rh-GaNNTs) and gas adsorption systems were obtained. On the other hand, the doping and adsorption mechanisms were analyzed by band structure, density of states, deformation charge density, and molecular orbital theory. Subsequently, the gas-sensitive performance of Rh-GaNNTs for these four impurity gases was evaluated by analyzing the sensing response and recovery time. The adsorption stability and recovery time of Rh-GaNNTs to these gases are ranked as SF4 > SOF2 > SO2 > H2S; the order of influence of gas adsorption on sensitivity response is H2S > SO2 > SF4 ≈ SOF2. Calculation results show the potential of Rh-doped surfaces as reusable H2S and SO2 sensors and suggest their use as gas scavengers to remove SF4 and SOF2, especially SOF2.

First-principles study of WS2 monolayer decorated with noble metals (Pt, Rh, Ir) as the promising candidates to detect nitrogenous poisonous gases

Rapid identification of nitrogenous toxic gases (NPGs, including NO, NO2, NH3, and HCN) emitted from industrial processes is essential for environmental preservation. In this research, the first-principles calculations have been employed to systematically investigate the adsorption behavior and sensing characteristics of Pt, Rh, Ir-modified WS₂ monolayers (Pt-WS2, Rh-WS2, and Ir-WS2) towards these NPGs, with the aim of assessing the potential of WS2-based gas sensors for NPG detection. The results show that Pt, Rh, and Ir atoms can be stably anchored on the WS2 surface, enhancing its chemical stability and the quantity of active sites. Additionally, the strong orbital hybridization between these noble metal atoms and gas molecules enhances the adsorption capacity of WS₂, markedly boosting the adsorption potency of these modified substances towards NPGs (Eads≥−0.69 eV) while maintaining high selectivity toward NPGs in the presence of interfering gases (H2O, N2, CO2). Analysis of the density of states, charge density distribution, and electron localization function indicates weak chemical adsorption of HCN on Pt-WS2, Rh-WS2, and Ir-WS2, while strong chemical adsorption is observed for NO, NO2, and NH3. Furthermore, the adsorption of NO and NO₂ leads to significant band gap changes (∆Eg > 30 %) of Pt-WS2, Rh-WS2, and Ir-WS2, and the response of work function to NH₃ and HCN adsorption is similarly pronounced (∆Φ > 15 %). Finally, analysis of recovery time indicates that Pt-WS2 and Rh-WS2 can serve as work function gas sensors for HCN and as adsorbents for NO, NO2, and NH3 at room temperature, whereas Ir-WS2 can function as a reusable gas sensor for the effective detection of HCN at high temperature. This investigation establishes a robust theoretical framework for the development and manufacture of high-performance WS₂-based gas sensors.

Coencapsulating TMB Probes and Bimetallic MOF Nanozymes in a Hydrogel Patch for Fabricating Reusable Visual VC Sensors.

As a typical chromogenic probe, 3,3',5,5'-tetramethylbenzidine (TMB) has been widely applied in the field of visual detection due to its low toxicity and highly sensitive response. Due to the hydrophobic nature of TMB, encapsulating it into a hydrogel, which serves as an ideal matrix for wearable sensors, presents significant challenges that complicate the fabrication of visual wearable devices. Herein, the TMB probe and bimetallic MOF nanozymes are coencapsulated in a hydrogel patch for the fabrication of reusable visual sensors. Hydrophobic TMB is oxidized to hydrophilic ox-TMB by a bimetallic MOF (CuFe-MOF), allowing its diffusion into a hydrophilic agarose hydrogel patch, where it is reduced back to TMB. This process allows the coimmobilization and coencapsulation of CuFe-MOF and TMB within the hydrogel patch. Leveraging the color change between TMB and ox-TMB, as a proof-of-concept application, a reusable visual "On-Off-On" sensor is simply constructed and successfully applied to detect vitamin C in human sweat. Color changes can be quickly read by the naked eye or by smart devices without the need for external equipment. Meanwhile, based on the reversible conversion relationship between TMB and ox-TMB, a reusable sensor construction strategy is proposed. This approach not only facilitates the use of a TMB probe in hydrogel applications but also offers inspiration for the development of point-of-care testing equipment, demonstrating significant application potential.

Reusable gallium-based electrochemical sensor for efficient glucose detection

Among wearable sensing devices, electrochemical sensors are overwhelming in biochemical detection due to their simple design but high sensitivity. Most electrochemical sensors are disposable, which significantly impairs the service life. Here we present a reusable gallium (Ga)-based multilayer electrochemical glucose biosensor to extend noninvasive monitoring of glucose in the interstitial fluid. This multilayer sensor includes Ga as a conductive interconnector, poly(3,4-ethylenedioxythiophene) as an electrode layer to prevent oxidation and metal leakage, a nano-Pt layer to enhance the electrochemical properties, and a nano-Prussian blue layer for reducing the hydrogen peroxide reduction potential. The biosensor can be renewed without causing damage to its overall structure by automatically eliminating the modified nanocomposites via the electrolysis-induced bubbles. The biosensor showed high sensitivity (24.6 μA mM−1 cm−2), wide linear range (0.01–26 mM), excellent stability (i.e., pH, long-term use) and superior selectivity, that is comparable to those of the current electrochemical tools for glucose detection. More importantly, incorporated with the reverse iontophoresis, the Ga-based hybrid sensor was applied as a skin patch on rat for the in vivo noninvasive and continuous monitoring of interstitial fluid glucose. The results showed a good correlation with that measured by blood glucometer. As a whole, this Ga-based electrochemical biosensor should endow new functions like biochemical analysis in biofluids for Ga-based bioelectronic sensing devices, in which almost are physical sensors. We believe that the reusability of electrochemically controllable processes may further inspire the development of more integrated and long-term stable Ga-based biosensing devices.

Atomic-level insights into sensing performance of toxic gases on the InSe monolayer decorated with Pd and Pt under humid environment

The timely detection and monitoring of toxic gases are crucial for preserving the ecological environment and preventing their adverse effects on human health. In this study, we investigate the adsorption characteristics and sensitivity performance of Pd- and Pt-decorated InSe monolayers, referred to as Pd-InSe and Pt-InSe, towards five toxic gases (CO, NO, NH3, H2S, and SO2) using first-principle calculations. The results show that the doping of Pd and Pt atoms significantly improves the conductivity, adsorption capabilities, and sensing properties of InSe monolayer to these toxic gases. Both Pd-InSe and Pt-InSe monolayers exhibit chemical adsorption of CO, NO, NH3, and H2S, with adsorption energies ranging from –0.56 eV to –1.04 eV, leading to noticeable changes in the bandgap (8.84 % ∼ 31.03 %). Furthermore, the CO/Pd-InSe and H2S/Pt-InSe systems demonstrate excellent sensitivity, with high sensing response values of 1.54×104 and 66.20, respectively, and their sensitivity remains unaffected under humid environments. Importantly, Pt-InSe exhibits a fast recovery time of 0.05 s at 298 K, making it highly promising for the recyclable detection of H2S at room temperature. In contrast, Pd-InSe can be utilized as a reusable gas sensor for CO at 448 K with a good recovery time of 0.5 s. This work can provides theoretical guidance for the design and fabrication of InSe-based gas sensors for the detection of toxic gases.

Reusable gasochromic gas sensor with enhanced selectivity for acidic gases via surface-engineered all-inorganic perovskite nanocrystals

The use of strong acids is crucial for the fabrication of highly integrated semiconductor devices. To effectively detect and alert against the potential hazards of acid gas leakage, considerable advancements have been made to enhance gas sensor sensitivity. However, most available gas sensors only detect cations (H+), making it challenging to precisely identify the specific types of acids present. Cesium lead halide perovskite nanocrystals, renowned for their exceptional optical properties, have emerged as promising candidates for gas-sensing applications. Nonetheless, concerns regarding reuse stability persist. In this study, surface engineering via solution-phase ligand exchange is conducted to address halide vacancies and prevent acid-induced structural degradation. The resulting surface-modified perovskites exhibit remarkable gasochromic sensitivity and selectivity towards HCl and HNO3. Furthermore, the vivid emission properties of these perovskites enable the visual detection of danger without the need for additional warning equipment. Finally, the reusability of the gas sensors is evaluated, and the perovskite-based sensors are recyclable.

Effect of NH3 preadsorption on SO2 adsorption on Hf2CO2 MXene

Preadsorbing suitable gas molecule on the substrate can effectively improve the adsorption strength of the system. The adsorption properties of preadsorping NH3 on SO2-adsorbed Hf2CO2 monolayer are explored by first-principles calculation. All possible adsorption sites are considered. SO2 molecule cannot be adsorbed by Hf2CO2 monolayer, while preadsorbing NH3 can increase the adsorption strength of SO2-adsorbed Hf2CO2 monolayer. The adsorption system has the direct semiconductor character and is the reusable SO2 gas sensor because of short recovery time and the appropriate adsorption strength. Preadsorbing NH3 can decrease the carrier mobility in conduction band, but has little impact on the carrier mobility in valence band. The charge transfer of the co-adsorption system is also investigated.

Ultrasoft Long-Lasting Reusable Hydrogel-Based Sensor Patch for Biosignal Recording.

Here, we report an ultrasoft extra long-lasting, reusable hydrogel-based sensor that enables high-quality electrophysiological recording with low-motion artifacts. The developed sensor can be used and stored in an ambient environment for months before being reused. The developed sensor is made of a self-adhesive electrical-conductivity-enhanced ultrasoft hydrogel mounted in an Ecoflex-based frame. The hydrogel's conductivity was enhanced by incorporating polypyrrole (PPy), resulting in a conductivity of 0.25 S m-1. Young's modulus of the sensor is only 12.9 kPa, and it is stretchable up to 190%. The sensor was successfully used for electrocardiography (ECG) and electromyography (EMG). Our results indicate that using the developed hydrogel-based sensor, the signal-to-noise ratio of recorded electrophysiological signals was improved in comparison to that when medical-grade silver/silver chloride (Ag/AgCl) wet gel electrodes were used (33.55 dB in comparison to 22.16 dB). Due to the ultra-softness, high stretchability, and self-adhesion of the developed sensor, it can conform to the skin and, therefore, shows low susceptibility to motion. In addition, the sensor shows no sign of irritation or allergic reaction, which usually occurs after long-term wearing of medical-grade Ag/AgCl wet gel electrodes on the skin. Further, the sensor is fabricated using a low-cost and scalable fabrication process.

Alkali metal-doped C20 fullerene sensors for COVID-19 biomarker detection: DFT insights into naked-eye and infrared techniques

Prompt diagnosis and prevention from coronavirus disease (COVID-19), a highly contagious infection, are critically required. While PCR testing is effective, it is costly, painful, and time-consuming. Alternatively, breath analysis for detecting COVID-19 provides a cost-effective and instant diagnostic approach. COVID-19 infected patients exhale ethyl butyrate (EB) as a biomarker of the infection. This study explores the doping of C20 fullerene with alkali metals to enhance its ability to detect ethyl butyrate. EB was weakly adsorbed onto C20 and strong adsorbed on doped fullerenes (M@C20) with maximum adsorption energies of −27.66 kcal/mol for Li@C20. QTAIM and IRI analyses confirmed Van der Waals interactions between EB and M@C20. NBO and MEP analyses provided evidence of charge transfer from the biomarker towards the M@C20. This charge transfer decreased the carbonyl bond stretching frequency from 1838 cm−1 to 1772, 1782, and 1788 cm−1 in three complexes (EB−Li@C20, EB−Na@C20, and EB−K@C20), respectively. This IR analysis supports the potential application of doped fullerenes in infrared-based detectors. Absorption maxima (λmax) were calculated as 534 nm (green), 594 nm (yellowish orange), and 587 nm (yellow) for three complexes. These shifts indicate potential application of M@C20 in naked-eye detectors. The shortest recovery time was 2.9 × 10−11 s for K@C20, suggesting it a suitable reusable sensor. These findings enable the development of fullerene-based sensors for both naked-eye and infrared-based detection of COVID-19.

Development of a reusable polymeric fluorescence sensor based on acryloyl β-cyclodextrin for the determination of aflatoxin B1 in grain products

AFB1 is a harmful substance that can be found in agricultural products and can seriously affect human health, even in trace amounts. Therefore, monitoring AFB1 levels to ensure food safety and protect public health is crucial. New, highly reliable, selective, and rapid detection methods are needed to achieve this goal. Our work involves the development of a polymeric membrane sensor using radical polymerization that can accurately detect AFB1. Various spectroscopic techniques (Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM)) were used to obtain information about the structural and morphological properties of the prepared sensor. The sensor displayed fluorescence selectively responsive to AFB1 at the excitation wavelength of 376 nm and emission wavelength of 423 nm. The polymeric fluorescence sensor showed good sensitivity and a wide linear range from 9.61 × 10−10 and 9.61 × 10−9 mol/L for AFB1quantification. The limit of detection (LOD) is as low as 3.84 × 10−10 mol/L for AFB1. Other mycotoxins, such as aflatoxin B2 and aflatoxin G1, did not interfere with the sensor’s high selectivity towards AFB1. To test the sensor’s effectiveness in detecting AFB1 in real samples, three different grain samples – peanuts, hazelnut butter, and peanuts with a sauce known to contain AFB1 – were utilized. The results were satisfactory and demonstrated that the sensor can be successfully employed in real samples, with an error range of 0.43 % to 12.10 %.

Reusable Cyclodextrin-Mediated Electrochemical Sensor in Automated Flow Cell for Cortisol Detection

Our focus is on using beta cyclodextrin (βCD) to electrochemically detect cortisol; cortisol is a hydrophobic molecule that is a vital hormone, and cortisol is involved in the immune system, metabolism, heart health, and overall body balance. Cyclodextrins, characterized by a hydrophobic inner cavity and a hydrophilic outer surface, emerge as promising molecular receptors for detecting hydrophobic molecules. Notably, βCD and cortisol can form host/guest inclusion complexes. Building on our success in detecting cortisol with βCD in previous static cell experiments [1], herein we introduce innovations to further improve our methodology by employing an automated flow cell system. The transition to automation offers advantages such as repeated runs for obtaining more reproducible data and the elimination of human interactions and considerations, leading to an increased number of experiments. Our efforts, including the utilization of a ten-way multi-position valve and a pump for solution transfer, were crucial for enhancing the accuracy, stability, and reproducibility of cyclodextrin-mediated biosensors in automated flow cell systems. The automation process did encounter challenges, particularly with pump control, necessitating manual pauses before electrochemical measurements. Additionally, issues related to bubbles arose, prompting the search for the optimal flow rate and the utilization of a degasser. The ultimate goal is to optimize sensor stability, sensitivity, and reproducibility, contributing to the advancement of cortisol detection with the automated cyclodextrin-mediated biosensors.Research supported by New Hampshire- INBRE through an Institutional Development Award (IDeA), P20GM103506, from the National Institute of General Medical Sciences of the NIH. Support was also provided by a National Science Foundation EPSCoR award (#2119237), BIO-SENS.[1] Z. Panahi, T. Ren, and J. M. Halpern, “Nanostructured Cyclodextrin-Mediated Surface for Capacitive Determination of Cortisol in Multiple Biofluids,” ACS Appl. Mater. Interfaces, vol. 14, no. 37, pp. 42374–42387, Sep. 2022, doi: 10.1021/acsami.2c07701.

A drug-mediated organic electrochemical transistor for robustly reusable biosensors.

Reusable point-of-care biosensors offer a cost-effective solution for serial biomarker monitoring, addressing the critical demand for tumour treatments and recurrence diagnosis. However, their realization has been limited by the contradictory requirements of robust reusability and high sensing capability to multiple interactions among transducer surface, sensing probes and target analytes. Here we propose a drug-mediated organic electrochemical transistor as a robust, reusable epidermal growth factor receptor sensor with striking sensitivity and selectivity. By electrostatically adsorbing protonated gefitinib onto poly(3,4-ethylenedioxythiophene):polystyrene sulfonate and leveraging its strong binding to the epidermal growth factor receptor target, the device operates with a unique refresh-in-sensing mechanism. It not only yields an ultralow limit-of-detection concentration down to 5.74 fg ml-1 for epidermal growth factor receptor but, more importantly, also produces an unprecedented regeneration cycle exceeding 200. We further validate the potential of our devices for easy-to-use biomedical applications by creating an 8 × 12 diagnostic drug-mediated organic electrochemical transistor array with excellent uniformity to clinical blood samples.

Flexible/Regenerative Nanosensor with Automatic Sweat Collection for Cytokine Storm Biomarker Detection.

The real-time monitoring of low-concentration cytokines such as TNF-α in sweat can aid clinical physicians in assessing the severity of inflammation. The challenges associated with the collection and the presence of impurities can significantly impede the detection of proteins in sweat. This issue is addressed by incorporating a nanosphere array designed for automatic sweat transportation, coupled with a reusable sensor that employs a Nafion/aptamer-modified MoS2 field-effect transistor. The nanosphere array with stepwise wettability enables automatic collection of sweat and blocks impurities from contaminating the detection zone. This device enables direct detection of TNF-α proteins in undiluted sweat, within a detection range of 10 fM to 1 nM. The use of an ultrathin, ultraflexible substrate ensures stable electrical performance, even after up to 30 extreme deformations. The findings indicate that in clinical scenarios, this device could potentially provide real-time evaluation and management of patients' immune status via sweat testing.

Reusable free-standing hydrogel electronic tattoo sensors with superior performance

Recently electronic tattoo sensors have attracted immense interest for health monitoring mainly due to their higher sensing performance than conventional dry sensors, owing to the ultra-low thickness which results in their conformability to the skin. However, their performance is worse than wet sensors. Further, these electronic tattoo sensors are not durable and reusable when free-standing because of their low thickness and being too delicate. Here, we report a remarkably high-performance freestanding, reusable, ultrathin and ultra-soft electronic tattoo sensor made of parylene-hydrogel double layer system with high water retention over extended periods that can be used for the extended period of 6 months. The hydrogel electronic tattoo (HET) sensors consist of electrically conductive self-adhesive hydrogel with a thickness of 20 µm and Young’s modulus of only 31 kPa at 37 °C, allowing for ultra-conformal contact to the skin microscopic features. Our HET sensors are fabricated using a scalable cost-effective method on ordinary tattoo papers and are laminated on the skin like temporary tattoos and were used for electrophysiological signals recording such as electrocardiography (ECG), electromyography (EMG), and skin hydration, temperature sensing. The HET sensors, for the first time, show 234% lower sensor-skin interface impedance (SSII) and significantly lower susceptibility to motion than gold standard medical grade silver/silver chloride wet gel electrodes which are known to have the lowest SSII and susceptibility to motion. Further, the low HET-skin interface impedance leads to a considerably larger signal amplitude and signal-to-noise ratio (SNR) of the electrophysiological signals recorded using HET sensors in comparison with those obtained using gold standard medical grade silver/silver chloride wet gel electrodes. The SNR of some types of electrophysiological signals such as EMG recorded using HET is up to 19 dB higher than gold standard medical grade electrodes due to higher signal amplitude, significantly lower susceptibility of HET to motion and lower motion artifacts. Also, the HET sensor is the first free-standing ultrathin tattoo sensor that can be transferred from the skin to tattoo paper and vice versa many times and the electrophysiological sensing quality remained high during repeated use for over 6 months.

GeC monolayer: A promising 2D material for reusable SO2 and NO2 gas sensor with high sensitivity

Gas sensors are crucial in various fields such as environmental monitoring, industrial production, and healthcare due to their ability to detect harmful gases in real-time. This study investigates GeC monolayer as a potential material for gas sensors targeting sulfur-containing toxic gases (SO2, H2S, SF4) and nitrogen-containing toxic gases (NO, NH3, NO2). The electronic and adsorption properties of GeC monolayer were explored using density functional theory (DFT) calculations. The adsorption of SO2 and nitrogen dioxide significantly affects the band structure and work function of GeC monolayer, indicating that compared to other toxic gases, GeC monolayers exhibit higher sensitivity and selectivity towards SO2 and NO2. The electron localization function analysis indicates that the adsorption process is characterized by physical adsorption. In addition, GeC monolayer exhibits good desorption behavior towards SO2 and NO2 at room temperature. These findings suggest that GeC monolayer is a promising material for developing efficient gas sensors for detecting SO2 and NO2.

A rational design of metal doped C20 fullerene based sensor for the selective detection of ethyl butyrate as COVID-19 biomarker

The detection of ethyl butyrate as a COVID-19 biomarker in exhaled breath could be a novel, rapid, less expensive, painless and non-invasive technique compared to a costly, painful and time-consuming PCR test. The potential of alkaline earth metals doped C20 fullerenes (M@C20) was explored as sensing materials to detect ethyl butyrate selectively. The ethyl butyrate (EB) exhibited the physisorption on pristine C20 fullerene with adsorption energy of -4.16 kcal/mol, while chemisorption was observed with M@C20 fullerenes. The frontier molecular orbital analysis demonstrates enhanced stability of complexes, attributed to widened Eg gaps during EB adsorption onto M@C20 fullerenes. The notable shift in λmax values in the visible region suggests using M@C20 fullerenes as UV–visible-based naked-eye sensors. The infrared analysis showed a red shift in the carbonyl bond stretching frequency of ethyl butyrate upon adsorption onto M@C20 fullerenes. The red shift resulted from charge transfer from ethyl butyrate to M@C20. These findings establish the foundation for utilizing M@C20 fullerenes in IR-based handheld sensing devices. The minimum recovery time (6.8 s) demonstrates Ca@C20 fullerene as a promising, reusable sensor for detecting ethyl butyrate at human body temperature. Our results pave the way to design rapid, reusable sensors for detecting ethyl butyrate.

Theoretical insights into gas-sensitive properties of B, Ga and In doped WS2 monolayer towards oxygen-containing toxic gases

Oxygen-containing toxic gases such as CO and NOx (x = 1, 2) have presented significant challenges to both the atmospheric environment and human well-being, thus prompting the development of efficient gas sensors for their detection at room temperature. In this work, we investigated the feasibility of B, Ga, In-doped WS2 (B-WS2, Ga-WS2 and In-WS2) monolayers as potential gas-sensitive materials for monitoring CO and NOx based on first-principles calculations, with a specific focus on analyzing the adsorption energy, electronic properties and recovery time. The results show that the doping of B, Ga, In atoms enhances the conductivity of WS2 monolayer and significantly improves the adsorption properties of WS2 towards CO and NOx. With the exception of the CO@In-WS2 system, all the systems exhibit chemisorption with adsorption energies ranging from −0.56 eV to −3.18 eV. Interestingly, the presence of H2O, CO and N2 in the atmosphere does not affect the capturing ability of B-WS2, Ga-WS2 and In-WS2 towards the target gases. Moreover, with the exception of the CO@In-WS2 system, the critical desorption temperatures of CO and NOx all exceed 300 K, highlighting the potential of the B/Ga/In-WS2 as effective adsorbents for NO and NO2 at room temperature and standard atmospheric pressure. Finally, the sensitivity and recovery time of CO and NOx on doped WS2 are evaluated. The findings confirm that Ga-WS2 exhibits a well-balanced combination of sensitivity and response speed, making it suitable as a reusable gas sensor for the detection of CO and NO, while In-WS2 is suitable for detecting NO and NO2. This study offers valuable theoretical insights into the design of innovative gas nanosensors for the detection of oxygen-containing toxic gases.

DFT-based adsorption studies of CNCl, HCN, and NH3 on metal-doped diamane

Density functional theory was used to comprehensively investigate the adsorption of cyanogen chloride (CNCl), hydrogen cyanide (HCN), and ammonia (NH3) by metal-doped diamanes. Because the weak gas adsorption ability of pure diamane renders it unsuitable for use as a gas sensor, the adsorption performance thereof was enhanced by doping with alkaline earth and transition metals. The adsorption capacities of monometallic-doped diamanes improved significantly for CNCl, HCN, and NH3. Notably, Be-doped diamane (BeD) delivered the highest adsorption performance for CNCl and HCN, whereas the addition of Au, Ag, and Cu, respectively, to diamane as dopants (AuD, AgD, and CuD) demonstrated enhanced adsorption effects for NH3. The adsorption capacities of the bimetallic co-doped diamanes for CNCl, HCN, and NH3 were significantly enhanced. In particular, diamane co-doped with Cu and Ag (Cu-AgD) exhibited superior adsorption for HCN and NH3, whereas Au and Cu co-doped diamane (Au-CuD) and Au and Ag co-doped diamane (Au-AgD) demonstrated improved adsorption effectiveness for NH3. The charge transfer, band gap, density of states, and charge density differences of these adsorption systems were investigated. Finally, recovery time analysis identified AuD, AgD, CuD, Au-CuD, Au-AgD, and Cu-AgD as potential candidates for reusable sensors.