Superior Gas Sensor Research Articles

Defective Diamane: A Superior Sensor for Toxic Gases Capture and Detection with Excellent Selectivity, Sensitivity, and Reversibility at Room Temperature.

The toxic gases emitted from industrial production have caused significant damage to the environment and human health, necessitating efficient gas sensors for their detection and removal. In this work, first-principles calculations are employed to investigate the potential application of diamanes for high-performance toxic gas sensors. The results show that nine gas molecules (CO, CO2, NO, NO2, NH3, SO2, N2, O2, and H2O) are physisorbed on pristine diamane by weak van der Waals interactions. After introducing H/F defects, diamane can effectively capture specific toxic gases (CO, NO, NO2, and SO2) in the presence of interfering gases (N2, O2, and H2O), suggesting excellent selectivity and anti-interference ability. Orbital hybridization and significant charge redistribution between gas molecules and defective diamane dominate the enhanced adsorbate-substrate interactions. More importantly, the high sensitivity and good reversibility of defective diamane for detecting CO, NO, and SO2 molecules enable its reuse as a superior resistance-type gas sensor. Our calculations provide valuable insights into the potential of defective diamane for detecting toxic gases and shed light on the practical application of novel carbon-based materials in the gas-sensing field.

Non-trivial designs and fabrication of chemiresistive gas sensors towards superior ammonia sensing performance

Implementation of high-end fabrication techniques e.g. e-beam lithography, photolithography etc. hinders realization of cost effective chemiresistive gas sensors. Here, for the first time, we have fabricated four different non-trivial designs of SnS2 based chemiresistive sensors namely scratched fluorine doped tin oxide (FTO) based sensor, aluminium rod based sensor, spiral copper wire based sensor and FTO/porous nickel foil based sensor towards NH3 detection at room temperature using easy and affordable processes. The new strategies of designing different sensor structures are to increase the exposed junction region (P) between sensing layer & electrode and decrease the resistance (R) of the sensor. Scratched FTO based sensor with no exposed region exhibits poor sensing performance whereas the other three sensors exhibit progressively enhanced performance (in terms of response, response time and limit of detection) with the increase of P/R ratio. Aluminium rod based sensor (P/R= 1.07 ×10−6 cm/Ω) offers response of 6.46 (at 225 ppm), 71 s of response time, 45 ppm of limit of detection whereas FTO/porous nickel foil based sensor (P/R= 13.93 ×10−6 cm/Ω) exhibits highest response of 49.5, response time of 49.2 s and limit of detection down to 10 ppm. This novel approach towards realizing a cost effective and superior gas sensor may be useful for the application in sensor technology.

CdS/TiO2 nano hybrid heterostructured materials for superior hydrogen production and gas sensor applications

In efforts to minimize environmental pollution and carbon-based gas emissions, photocatalytic hydrogen production and sensing applications at ambient temperature are important. This research reports on the development of new 0D/1D materials based on TiO2 nanoparticles grown onto CdS hetersturctured nanorods via two-stage facile synthesis. The titanate nanoparticles when loaded onto CdS surfaces at an optimized concentration (20 mM), exhibited superior photocatalytic hydrogen production (21.4 mmol/h/gcat). The optimized nanohybrid was recycled for 6 cycles up to 4 h, indicating its excellent stabity for a prolonged period. Also, the photoelectrochemical water oxidation in alkaline medium was investigated to offer the optimized CRT-2 composite with 1.91 mA/cm2@0.8 V vs. RHE (0 V vs. Ag/AgCl) that was used for effective room-temperature NO2 gas detection exhibiting a higher response (69.16%) to NO2 (100 ppm) at room temperature at the lowest detection limit of ∼118 ppb than the pristine counterparts. Further, NO2 gas sensing performance of CRT-2 sensor was increased using UV light (365 nm) activation energy. Under the UV light, the sensor exhibited a remarkable gas sensing response quick response/recovery times (68/74), excellent long-term cycling stability, and significant selectivity to NO2 gas. Due to high porosity and surface area values of CdS (5.3), TiO2 (35.5), and CRT-2 (71.5 m2/g), excellent photocatalytic H2 production and gas sensing of CRT-2 is ascribed to morphology, synergistic effect, improved charge generation, and separation. Overall, 1D/0D CdS@TiO2 is proved to be an efficient material for hydrogen production and gas detection.

Electrical and Gas Sensor Properties of Nb(V) Doped Nanocrystalline β-Ga2O3.

A flame spray pyrolysis (FSP) technique was applied to obtain pure and Nb(V)-doped nanocrystalline β-Ga2O3, which were further studied as gas sensor materials. The obtained samples were characterized with XRD, XPS, TEM, Raman spectroscopy and BET method. Formation of GaNbO4 phase is observed at high annealing temperatures. Transition of Ga(III) into Ga(I) state during Nb(V) doping prevents donor charge carriers generation and hinders considerable improvement of electrical and gas sensor properties of β-Ga2O3. Superior gas sensor performance of obtained ultrafine materials at lower operating temperatures compared to previously reported thin film Ga2O3 materials is shown.

Ni-doped boron nitride nanotubes as promising gas sensing material for dissolved gases in transformer oil

This paper reports that the transition metals (TM), including Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn, are substituted in a perfect zigzag (8, 0) boron nitride nanotubes (BNNTs) at B-site and N-site to improve the adsorption performance of intrinsic BNNTs towards oil-dissolved gases (H 2 , CH 4 , and C 2 H 2 ), particularly C 2 H 2 . In this regard, the quantum chemical calculations are performed based on the density functional theory (DFT). The results show that the C 2 H 2 gas adsorption characteristic of BNNTs is selectively enhanced due to the intervention of the TM atom. The Co B , Ni B, Cu B, Zn B, and Zn N are preliminarily selected as potential gas sensors for C 2 H 2 gas based on their suitable range of adsorption energy. The sensitivity, selectivity, and recovery time of the above five structures are compared. It is found that Ni B is a superior sensing material with exceptionally high sensitivity and selectivity. Moreover, the Ni B presented preferable desorption properties for C 2 H 2 gas at room temperature, making it promising for a chemical resistance-type gas sensing device. The analysis of charge transfer and density of states illustrates that the Ni B donates electrons to C 2 H 2 , proving its superiority over the adsorption properties for C 2 H 2 gas over H 2 and CH 4 . The suitable recovery time (2.3 s), extremely high gas response value (494383%), and stable chemisorption demonstrate that the Ni-doped BNNTs at B-site can be a superior chemical gas sensor for C 2 H 2 gas at room temperature.

ZIF-X (8, 67) based nanostructures for gas-sensing applications

Abstract ZIF-8 and ZIF-67 are the most investigated zeolitic imidazolate frameworks (ZIFs) materials that have aroused enormous scientific interests in numerous areas of application including electrochemistry, gas storage, separation, and sensors by reason of their fascinating structural properties. Recently, there is a rapidly growing demand for chemical gas sensors for the detection of various analytes in widespread applications including environmental pollution monitoring, clinical analysis, wastewater analysis, industrial applications, food quality, consumer products, and automobiles. In general, the key to the development of superior gas sensors is exploring innovative sensing materials. ZIF-X (8, 67) based nanostructures have demonstrated great potential as ideal sensing materials for high-performance sensing applications. In this review, the general properties and applications of ZIF-X (8, 67) including gas storage and gas adsorption are first summarized, and then the recent progress of ZIF-X (8, 67) based nanostructures for gas-sensing applications and the structure-property correlations are summarized and analyzed.

Novel green phosphorene as a superior gas sensor for dissolved gas analysis in oil transformers: using DFT method

ABSTRACT Regarding recent attempts for monitoring dissolved gases in oil transformers, in this paper, novel green phosphorene (GP), a new type of two-dimensional gas sensitive material was modified by transition metal decoration. We applied first-principles calculations based on Density functional theory and investigated the structures and electronic properties of H2, CH4, and C2H2 (dissolved gases) molecules adsorbed on the pristine, and metal decorated (Pt, and Pd) GP monolayer to understand its performance as a sensor. This analysis indicated that Pt-GP could be a satisfying material for C2H2 sensing at specific conditions, while it is unsuitable for detection of CH4, and H2 due to the weak interaction and short recovery time. The adsorption energy (Ead) of C2H2 on Pd-, Pt-GP systems is −1.18, and −1.84 eV, respectively, and 4, and 2 times more electrons were transferred from the C2H2 molecule to the systems, respectively in comparison with the pristine GP. Moreover, Pd-GP has a recovery time of 9.68 s under visible light at 350 K indicating that it is suitable for reusability, and it has a good sensitivity of 65.9% toward C2H2 molecule. Our results showed that the metal-decorated GP sensors are excellent candidates for analyzing dissolved gases in oil-based transformers.

Enhanced isoprene gas sensing performance based on p-CaFe2O4/n-ZnFe2O4 heterojunction composites

Isoprene, a toxic volatile organic compound, is harmful to the human body. It is of great application value to develop gas sensing materials for the effective detection of isoprene. In this work, the CaFe2O4, ZnFe2O4 and CaFe2O4/ZnFe2O4 composites are successfully synthesized by hydrothermal approach. Especially, the CaFe2O4/ZnFe2O4-50% presents porous walnut-like structure and exhibits the superior gas sensing properties to isoprene, including a high response to 30 ppm isoprene (S=19.50), low working temperature (200 °C) and fast response-recovery time (~72–35 s). Moreover, the CaFe2O4/ZnFe2O4-50% based sensor also achieves good selectivity, excellent humidity resistance, long-term stability and LOD as low as 0.12 ppb. Further analysis demonstrates that the outstanding gas sensing properties of CaFe2O4/ZnFe2O4-50% can be attributed to the improvement of electron-hole (e--h+) separation rate, the decrease of charge transfer resistance, the high content of OV, large BET surface area, the narrowed band gap and the formation of CaFe2O4/ZnFe2O4 p-n heterojunctions. These results indicate that appropriate CaFe2O4 coupled with ZnFe2O4 to form CaFe2O4/ZnFe2O4 is a promising strategy to achieve a superior isoprene gas sensor.

Bimetallic–organic framework-derived Co3O4–ZnO heterojunction nanofibers: A new kind of emerging porous nanomaterial for enhanced ethanol sensing

Design of appropriate heterojunction oxides with unique nanostructures and abundant porosities is important to develop superior gas sensors. In this study, a new kind of bimetal–organic framework (BMOF)-derived porous Co3O4–ZnO heterojunction nanofibers (NFs) was constructed using a combination of BMOF and an electrospinning technique. This emerging heterojunction NFs integrated two kinds of porous materials (BMOFs and NFs), thereby showing abundant wormhole-like pores on each nanofiber. Sensing results indicated that the BMOF-derived 1% Co3O4–ZnO NFs exhibited higher ethanol sensing properties compared to metal–organic framework-derived ZnO nanocages (NCs) and ZnO NFs, and BMOF-derived 1% Co3O4–ZnO NCs. In addition to excellent ethanol sensing response (Ra/Rg = 101.5–100 ppm at 275 °C), the BMOF-derived 1% Co3O4–ZnO NFs displayed good selectivity and stability. High ethanol sensing properties were attributed to the formation of Co3O4–ZnO p–n heterojunctions, and the unique BMOF-derived nanofiber structure with abundant pores, high surface area and anti-aggregation property. This study provides a new strategy for constructing various porous metal oxide heterojunction nanofiber network structure derived from BMOFs, that can be used for high-performance gas-sensing application.

Efficient detection of hazardous H2S gas using multifaceted Co3O4/ZnO hollow nanostructures

The rapid increases in environmental hazardous gases have laid dangerous effects on human health. The detection of such pollutants gases is mandatory using various optimal techniques. In this paper, porous multifaceted Co3O4/ZnO nanostructures are synthesized by pyrolyzing sacrificial template of core-shell double zeolitic imidazolate frameworks (ZIFs) for gas sensing applications. The fabricated exhibit superior gas sensor response, high selectivity, fast response/recovery times, and remarkable stability and sensitivity to H2S gas. In particular, the multifaceted Co3O4/ZnO nanostructures show a maximum response of 147 at 100 ppm of H2S under optimum conditions. The remarkable gas sensing performances are mainly ascribed to high porosity, wide surface area multifaceted nanostructures, presence of heterojunctions and catalytic activity of ZnO and Co3O4, which are beneficial for H2S gas sensors industry.

Nanosheet-assembled In2O3 for sensitive and selective ozone detection at low temperature

To monitor ozone (O3) concentration in the environment, it is urgent to develop highly sensitive O3 gas sensors with low limit of detection (LOD) and relatively low working temperature. Herein, a series of nanosheet-assembled In2O3 with different chemisorbed oxygen components were prepared successfully. The hierarchical In2O3 sensing materials possessed the loose and porous structure. The O3 sensing results indicated that the adjustment on the amount of chemisorbed oxygen finely enhanced the response of the sensor. As an efficient O3 detector, the sensor exhibited an outstanding response of 16.7 to low concentration of O3 (100 ppb). And the LOD was measured as low as 30 ppb at a relatively low operating temperature (80 °C). In addition, it is observed that the O3 sensing behaviors were interfered by oxygen (O2) at the background. The response of the sensor was lower at the background of pure O2 than that at the background of air. Competitive adsorption between O3 and O2 molecules might exist and was investigated. Taken together, this work expands a new perspective to design highly superior O3 gas sensors.

Ultrasensitive ethanol sensor based on nano-Ag&ZIF-8 co-modified SiNWs with enhanced moisture resistance

Silicon nanowires (SiNWs) is considered as one of the most promising candidates for gas sensing application due to its capability of operating at room temperature (20 °C) and compatibility with modern semiconductor process. However, there still remains a challenge that SiNWs is poorly sensitive to volatile organic compounds (VOCs). In this study, we reveal that the co-decoration of zeolite imidazole frameworks-8 (ZIF-8) and Ag nanoparticles can improve the gas-sensing response to ethanol and enhance the humidity resistance at 20 °C. Due to the inversion modulation introduced by nano-Ag modificaiton and the enhanced gas adsorption provided by ZIF-8 modification, the resultant co-decorated sensor of ZIF-8&[email protected] shows obviously enhanced response upon exposure to ethanol with wide concentration range. It meanwhile exhibits a practical capability to sense rarefied ethanol vapor low to 125 ppb at 20 °C and relative humidity of 25 %. Especially, the sensor exhibits a low limit of detection of 5.45 ppb of ethanol vapor. When working at high humidity of 85 %, the developed ZIF-8&[email protected] sensor still remain a significant response. The superior moisture resistance performance is clarified by first-principles caculations to be highly related to the hydrophobicity characteristic of the modified ZIF-8 and the hygroscopic center formed by Ag nanoparticles. A resistance model was proposed to demonstrate the enhanced sensing response of the ZIF-8&[email protected] Further, a two-level moisture resistance mechanism is demonstrated based on the first-principles caculations and the unique microstructure of ZIF-8&[email protected] The beneficial effect of ZIF-8&nano-Ag co-modification demonstrated in present work suggest an effective strategy for developing superior gas sensors capable of sensitive detection of VOCs with strong stability in humditiy ambient.

Effects of external electric field on adsorption behavior of organic molecules on stanene: Highly sensitive sensor devices

Motivated by the recent advances in stanene based devices for potential application such as superior gas sensors and electronic devices, we systematically investigated the structural configurations, adsorption energies and charge transfer of organic molecules (OM) on stanene sensors using first-principles calculations. The results show that aniline (C6H7N) and chlorobenzene (C6H5Cl) act as charge acceptors and are chemisorbed on stanene with sizable adsorption energies for the most stable OM/stanene systems. In particular, C6H7N/stanene and C6H5Cl/stanene systems can open the band gaps with 114.3 and 5.0 meV, respectively. Moreover, adsorption energies, charge transfer and band gaps of OM/stanene systems under external electric field can change dramatically, which indicates that external factors on stanene are highly preferred. Our results provide a theoretical basis for the application of stanene in highly sensitive sensor devices.

Enhanced Blocking Effect: A New Strategy to Improve the NO2 Sensing Performance of Ti3C2Tx by γ-Poly(l-glutamic acid) Modification.

Titanium carbide (Ti3C2Tx) with a distinctive structure, abundant surface chemical groups, and good electrical conductivity has shown great potential in fabricating superior gas sensors, but several challenges, such as low response kinetics, poor reversibility, and serious baseline drift, still remain. In this work, γ-poly(l-glutamic acid) (γ-PGA) with a blocking effect is exploited to modify Ti3C2Tx, thereby stimulating the positive response behavior of Ti3C2Tx and improving its gas sensing performance. On account of the unique synergetic interaction between Ti3C2Tx and γ-PGA, the response of the flexible Ti3C2Tx/γ-PGA gas sensor to 50 ppm NO2has been improved to a large extent (average 1127.3%), which is 85 times that of Ti3C2Tx (only 13.2%). Moreover, the as-fabricated Ti3C2Tx/γ-PGA sensor not only exhibits a shorter response/recovery time (average 43.4/3 s) compared with the Ti3C2Tx-based sensor (∼18.5/18.3 min) but also shows good reversibility and repeatability (relative standard deviation (RSD) <1%) at room temperature within 50% relative humidity (RH). The improved gas sensing properties of the Ti3C2Tx/γ-PGA sensor can be attributed to the enhancement of effective adsorption and the blocking effect assisted by water molecules. Furthermore, the gas sensing response of the Ti3C2Tx/γ-PGA sensor is studied at different RHs, and humidity compensation of the sensor is carried out using the multiple regression method. This work demonstrates a novel strategy to enhance the gas sensing properties of Ti3C2Tx by γ-PGA modification and provides a new way to realize highly responsive gas detection at room temperature.

Room temperature monitoring of SF6 decomposition byproduct SO2F2 based on TiO2/NiSO4 composite nanofibers

Sulfuryl fluoride (SO2F2) is one of the ideal decomposition components of sulfur hexafluoride (SF6), which is widely used as an insulating and arc extinguishing medium in gas-insulated switchgear. To detect the decomposition component of SF6 at room temperature, the use of SO2F2 is still a challenge. In this work, we have successfully fabricated TiO2 nanofibers and nickel sulfate (NiSO4 NPs) via simple electrospun and hydrothermal methods, followed by calcination process to improve the sensing performance. Metal oxide semiconductor materials (MOSs) are widely used in gas sensing applications due to their superior performance and fast recovery speed. Although the performance of our TiO2/NiSO4 composite nanofiber sensor decreases at higher temperatures, it shows an excellent response to target gasses at room temperature. Ni-decoration on the outer surface of the nanofibers could maximize the sensing response of 100 ppm SO2F2 by up to 189% at room temperature, showing that the TiO2/NiSO4 composite nanofibers are 2.5 times superior to the pure TiO2 nanofiber sensors. Thus, the approach for this novel composite nanofiber-based material is promising for the fabrication of superior gas sensors for decomposition of SF6.

Formaldehyde gas sensing properties of transition metal-doped graphene: a first-principles study

The formaldehyde gas sensing properties of transition metal-doped graphene have been systematically investigated by first-principles calculations. The optimized geometries of transition metal-doped graphene with and without HCHO adsorption, adsorption energies, charge transfers and magnetic moments are obtained for various doped graphene systems. The calculated results show that Co-, Ni-, Cu-, Zn-, Pd- and Ag-doped systems have moderate adsorption energies, implying their potential applications as HCHO sensors. The two-probe sensor devices consisting of the central scattering region and pristine graphene electrodes with the armchair or zigzag transport directions are built, and the spin-polarized current–voltage curves are calculated by the non-equilibrium Green’s function method within the framework of density functional theory. For the Cu-, Zn- and Ag-doped systems, the average sensor response is over 80%, 40% and 290%, respectively. In particular, the Cu- and Ag-doped graphene devices have the highest value of response over 200% and 900% at low voltages, indicating a short response time and high sensitivity of these devices. The present study provides a theoretical basis for exploring practical applications of the transition metal-functionalized graphene as superior HCHO gas sensors.

Development of high-performance sensor based on NiO/SnO2 heterostructures to study sensing properties towards various reducing gases

In this work, we report the spontaneous formation of NiO nanoparticles-decorated onto smooth SnO2 nanofibers, which is an inexpensive and scalable method for yielding a high composite surface area via a simple two-step synthesis process based on electrospinning and the hydrothermal method. A Nickel Oxide proton-conducting electrolyte is deposited homogeneously over a large surface area in a transparent solution, mixed and decorated onto Tin dioxide nanofibers, as evidenced by cross sectional imaging of the electrospun nanofibers. The composite based on nanoparticle-decorated fibers enlarges the surface area of the exposed electrolyte, which fundamentally improves the overall gas sensing performance. The crystal structure, morphology, and physio-chemical surface state of the NiO/SnO2-based specimen are comprehensively examined using XRD, SEM, TEM, HRTEM, EDX, and photoelectron (XPS) spectroscopy. The composite based on NiO/SnO2 nanoparticle-decorated fibers exhibits an optimistic mesoporous nature with a huge specific area, which is key for superior gas sensors. The result reveals that NiO/SnO2 nanoparticle-decorated fibers with an average size of 180–260 nm in diameter, where the average length of fibers was about 1.5 μm. The composite-based heterojunction of NiO/SnO2 nanoparticle-decorated fibers enhances the adsorption of oxygen molecules, which show fast response, good selectivity and quick recovery speed against ethanol gas at an optimal temperature of about 160 °C. The maximum sensitivity response of the sensor-based composite NiO/SnO2 nanoparticle-decorated fibers was 23.87 in respect of 100 ppm ethanol gas at a low temperature of 160 °C; this is approximately about 7.2 times superior to that of pure SnO2 nanofibers. The superior gas sensing capabilities of a composite based on NiO/SnO2 nanoparticle-decorated fibers may be attributable to the enhanced catalytic effect of the small sized NiO nanoparticles on smooth SnO2 nanofibers, together with the p/n heterojunction effects between NiO and SnO2 heterostructures.

Optimization of gate-bias stability and gas-sensing properties of triethylsilylethynyl anthradithiophene micro-strip field-effect transistors by incorporating insulating polymer

Abstract The control of the microstructure and patterning of 5,11-bis(triethylsilylethynyl)anthradithiophene (TES-ADT) film is essential for high-performance TES-ADT field-effect transistors (FETs) as a NO2 gas sensor. In this study, a binary blend film based on TES-ADT and insulating polymer was annealed by solvent vapor with patterned PDMS molds. The solvent-containing PDMS mold led to the TES-ADT crystallization under the phase-separation between TES-ADT and PMMA. This resulted in highly crystalline micro-strip films where TES-ADT and the insulating polymer were phase-separated on top and bottom, respectively. The micro-strip structures can have superior gas sensor performance because they have additional gas diffusion paths compared to non-patterned structures. Initial investigations to clarify morphology and microstructure of the films revealed that lateral phase separation got dominant with increasing the portion of the insulating polymer. The blended films were then used as the active layer in the FET-based gas sensors. The use of blended films instead of non-blended TES-ADT film in FETs is advantageous in reducing both the threshold voltage and subthreshold slope while compromising the field-effect mobility. The sensing response as the gas sensors is slightly lower in the blended TES-ADT FET than in the non-blended TES-ADT FET. However, the utilization of blended films significantly enhanced the bias-stress stability. Accordingly, a uniform baseline of the sensor performance was achieved in TES-ADT: insulating polymer blended FETs. This trend was in contrast to an abrupt decrease in the sensing signals of the non-blended TES-ADT FETs. The enhanced bias stability of the blended FETs was exhibited as a result of covering the silanol groups in SiO2 with a phase-separated insulating polymer. Our results provide a route for to the optimization of bias stability and response in TES-ADT micro-strip gas sensors through the application of a one-step blend technology.

Single ultrathin WO3 nanowire as a superior gas sensor for SO2 and H2S: Selective adsorption and distinct I-V response

In order to take insight into the gas sensing performance of single ultrathin WO3 nanowire, we performed first principles calculation to investigate the gas adsorption properties and used non-equilibrium Green function (NEGF) to investigate the electron transport properties of WO3 nanowires with gas adsorption. Our investigation indicated that the WO3 nanowires with/without oxygen vacancies are both sensitive to H2S due to the large adsorption energies and distinct charge transfer. Besides, we found that the WO3 nanowire with Oa type oxygen vacancies is highly selective to SO2. We supposed that the high chemical activity and the small molecular volume of H2S and SO2 are the main reasons of the selectivity. Finally, the negative differential resistance (NDR) effect of single ultrathin WO3 nanowire and the gate voltage were proposed to benefit the application of WO3 nanowires gas sensors. We also supposed two ways to take advantage of the NDR effect of single ultrathin WO3 nanowire in gas sensing applications. It should be noted that this is the first theoretical investigation of WO3 nanowires gas sensors considering the electron transport properties. Our work highlighted the possibility to use the single ultrathin WO3 nanowire as superior gas sensors for SO2 and H2S.

Penta-Graphene as a Potential Gas Sensor for NOx Detection

Two-dimensional (2D) penta-graphene (PG) with unique properties that can even outperform graphene is attracting extensive attention because of its promising application in nanoelectronics. Herein, we investigate the electronic and transport properties of monolayer PG with typical small gas molecules, such as CO, CO2, NH3, NO and NO2, to explore the sensing capabilities of this monolayer by using first-principles and non-equilibrium Green’s function (NEGF) calculations. The optimal position and mode of adsorbed molecules are determined, and the important role of charge transfer in adsorption stability and the influence of chemical bond formation on the electronic structure of the adsorption system are explored. It is demonstrated that monolayer PG is most preferred for the NOx (x = 1, 2) molecules with suitable adsorption strength and apparent charge transfer. Moreover, the current−voltage (I−V) curves of PG display a tremendous reduction of 88% (90%) in current after NO2 (NO) adsorption. The superior sensing performance of PG rivals or even surpasses that of other 2D materials such as graphene and phosphorene. Such ultrahigh sensitivity and selectivity to nitrogen oxides make PG a superior gas sensor that promises wide-ranging applications.