Detection Of Xylene Research Articles

Trace detection of benzene, toluene and xylene (BTX) by chemiresistive metal oxide-based gas sensors: Recent advances in heterojunction materials design

Trace detection of benzene, toluene and xylene (BTX) by chemiresistive metal oxide-based gas sensors: Recent advances in heterojunction materials design

Synthesis and characterization of spray deposited ZnO–CuO nano composite thin films for the detection of xylene

Synthesis and characterization of spray deposited ZnO–CuO nano composite thin films for the detection of xylene

Flower-like SnO2 nanorod aggregates modified with Co3O4 nanoparticles grown on reduced graphene oxide(rGO) sheets for xylene sensing

In this paper, the ternary composite of flower-like SnO2 nanorod aggregates modified with Co3O4 nanoparticles grown on rGO sheets were synthesized by a two-step process of water heating and water bath, and characterized by SEM, TEM, XRD, EDS, and XPS. The gas-sensitive performance test results revealed that the 15-rGO/SnO2/Co3O4 sensor exhibited a higher response value (I0/Ia=24.46) to 100 ppm xylene at the optimal working temperature of 175℃. In addition, the sensor could detect 10 ppb xylene, with a low detection limit. The gas-sensitive properties of 15-rGO/SnO2/Co3O4 were significantly improved due to the large specific surface area of rGO flakes and SnO2 slender nanorods, the catalytic action of p-type semiconductor Co3O4 and the existence of p-n-p double heterojunction. Due to the special nanostructure and synergistic effect of SnO2, rGO and Co3O4, the 15-rGO/SnO2/Co3O4 sensor enabled the efficient and selective detection of xylene.

Synthesis and characterization of fluorescent poly(α-cyclodextrin)/carbon quantum dots composite for efficient removal and detection of toluene and xylene from aqueous media

This study reports the synthesis and characterization of a supramolecular composite comprised of carbon dots (CDots) embedded within net-poly[(α-cyclodextrin)-ν-(citric acid)] (α-CD/CA/CDots) for the removal and detection of toluene and xylene from aqueous media. The remarkable stability of CDots within the composite enables the preservation of photoluminescence properties for prolonged storage and extended UV-light irradiation. As demonstrated, following the adsorption of both organic compounds, the composite detected them in the aqueous medium due to a fluorescence quenching mechanism. Spectroscopic analyses reveal that the accessible Stern–Volmer quenching constants for toluene and xylene are KSVa = 15.4 M−1 and KSVa = 10.3 M−1, respectively. As a result, the α-CD/CA/CDots composite were sensitive to the tested volatile organic compounds (LODtoluene = 3.7 mg/L and LODxylene = 4.9 mg/L). Optimal conditions for toluene and xylene adsorption were found, allowing to achieve noticeable adsorption capabilities (qe(toluene) = 68.9 and qe(xylene) = 48.2 mg/g) and removal efficiencies exceeding 70%. Different characterization techniques confirmed the successful synthesis of the composite and elucidated the interaction mechanisms between the adsorbent and the tested compounds. In summary, the multifunctionality demonstrated by the α-CD/CA/CDots composite ranks it as an efficient and promising adsorbent and detection probe for this class of water contaminants.

Varying annealing temperature to enhance xylene vapor sensing performance of CuFe2O4 nanoparticles prepared by solvothermal method

In this work, CuFe2O4 nanoparticles (NPs) were synthesized through solvothermal method and then annealed at different temperatures. The tetragonal phase structure and chemical composition of the samples were measured by x-ray diffraction (XRD), the morphological features of the samples presenting nanoparticles were obtained by scanning electron microscopy (SEM), the details of the nanostructures about the resulting samples were determined by transmission electron microscopy (TEM), and the compositions and elemental chemical states of the samples were analyzed by x-ray photoelectron spectroscopy (XPS). The discussion systematically covers the influence of various annealing temperatures on the crystal morphology and topography of the resulting samples. The experimental results show that the CuFe2O4 NPs annealed at 500 °C have superior gas-sensitive properties towards xylene with high response, excellent selectivity, and therefore have some potential to develop a new, budget sensor for xylene detection. At last, the xylene sensing mechanism of CuFe2O4 NPs was discussed.

Xylene detection performances of core-shelled MnWO4 @C composites synthesized by functionalizing carbon microsphere template

As a ternary metal oxide with a suitable band gap and double catalytic center, MnWO4 has a broad application prospect in the fields of electrochemistry, catalysis, and gas detection. In this study, MnWO4 @C composite was synthesized by a one-step hydrothermal method and its sensitivity property to xylene was investigated. The carbon microspheres with favorable ion adsorption ability effectively inhibit the agglomeration of the reaction ions, thus producing uniformly dispersed nanoscale MnWO4 particles with large specific surface area, which could expose more reaction sites for the high valence W6+ with good redox ability as well as Mn2+ catalytic activation center with d-orbit. The MnWO4 @C composite material possesses enhanced gas adsorption and high catalytic activity. The response of the MnWO4 @C composite (53.4, 100 ppm) is 25 times larger than that of MnWO4 to xylene, and the modified material shows properties of lower detection limit (2 ppm), good operating temperature (157 ℃) and significant selectivity to xylene. This work provides an effective strategy to improve the sensitive activity of MnWO4.

Branched ZnFe2O4 nanorods grown via chemical spray pyrolysis technique for chemiresistive xylene gas sensor

In this work, we used a chemical spray pyrolysis technique to deposit zinc ferrite (ZF) thin films at different substrate temperatures to study xylene (C8H10) gas sensing properties. The focus is on the detection of xylene, a volatile organic compound (VOC) that is harmful to human health. It was found that the concentration of hazardous xylene gas was below the exposure limit. The substrate temperature has a notable impact on the sensor's performance, and ZF exhibits promise for discerning xylene selectively at 200 °C operating temperature. The results indicate that the ZF film deposited at 225 °C (ZF-B) exhibited a significant response (S = 47.4%) to a 50-ppm xylene concentration. Further analysis illustrates that the film substrate temperature deposited at 225 °C can have a unique morphology including thin branched rods, small nanorods with high surface area and roughness. These features contribute to enhanced sensing response by creating more active centers for gas molecule interactions. The stability test over 125 days indicates that the ZF-B film acts effectively as a xylene gas sensor, emphasizing the effectiveness of ZF thin films in detecting xylene in an air environment.

Building adsorption-segregated sites of gas molecules for sensitive xylene detection

Reasonably engineering the adsorption and excitation sites of oxygen and target gas molecules for expected sensing properties of semiconductor metal oxides (SMO) is still challenging. Here, we proposed a gas-segregated strategy involving spatially-separated Ir and W5+-Vo sites to respectively provide specific adsorption and excitation zones of oxygen and target gas molecules for sensitive xylene detection. We find that the introduced Ir sites can induce O2 adsorption and enhance the reactive oxygen species formation through spillover effects, while W5+-Vo sites tend to drive the target xylene molecules aggregation along the supported WO3 surface, and thus synergistically promote the sensing property. This process can be experimentally confirmed by NAP-XPS, ex situ XPS, in situ Raman and theoretical calculations results. The final Ir-c-WO3 sensor exhibits high response ability towards xylene (1–100 ppm) at 180 °C operating temperature, fast response/recovery speed (2.9 s/18 s @ 15 ppm) and excellent selectivity. Our study thus provides a valid method for xylene detection and opens up a new perspective for the construction of macromolecular active gas sensing materials.

Highly solvent-dependent naphthalene diimide-based fluorescent polymer sensors for detecting p-xylene

P-xylene (PX), as one of xylenes, is a kind of very important chemical raw material. It is generally fabricated using methanol (MeOH) and toluene (TOL), and serves as a useful intermediary. However, it is difficult to use a simple and convenient tool to distinguish it from TOL and MeOH. Herein, we reported a simple naphthalene diimide-based polycaprolactone polymer (NDI-PCL) as a high-sensitive fluorescent sensor for xylene detection from MeOH and TOL. NDI-PCL was synthesized via ring-opening polymerization (ROP) of ε-caprolactone. NDI-PCL showed a remarkable fluorescence change from blue to green and yellow because of the formation of charge transfer (CT) interaction between naphthalene diimide (NDI) and aromatic solvents. NDI-PCL was successfully applied as the high-sensitive sensor for discriminating binary solvent mixtures such as PX in TOL, MeOH in PX, and MeOH in TOL, and their limit of detection (LOD) were as low as 19 ppm, 16 ppm and 9 ppm. These excellent fluorescence properties ensured that NDI-PCL indicated great potential application in detecting aromatic solvents.

A MoS2 quantum dot functionalized TiO2 nanotube array for selective detection of xylene at low temperature

Electrochemically synthesized TiO2 nanotube array was functionalized with MoS2 quantum dots and transformed into metal–insulator–metal type sensor which exhibited xylene selectivity with high response magnitude at low operating temperature.

Facile synthesis of high surface area of p-n Co3O4-In2O3 heterostructure-based sensor for improved xylene detection at low temperature

This study reports on the gas sensing properties of Co3O4 – n-type semiconducting metal oxides (Co-nSMOs) heterostructures, i.e., Co3O4-In2O3 (Co-In), Co3O4-CeO2 (Co-Ce), Co3O4-SnO2 (Co-Sn) and Co3O4-ZrO2 (Co-Zr) synthesized by microwave-assisted hydrothermal synthesis. Structural studies confirmed the formation of Co-nSMO heterostructures. Electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) showed that the Co-In possesses higher surface defects compared to its counterparts. The Co-nSMOs sensors were evaluated towards benzene, toluene, ethylbenzene, and xylene (BTEX) compounds, acetone, and NO2. Amongst the tested sensors, the Co-In heterostructure showed superior selectivity and a response of 36.6 to 100 ppm xylene at an optimum effective temperature of 150 °C. The sensor further showed good sensitivity and a low limit of detection of 0.2 ppm. Moreover, the Co-In-based sensor stored for 5 months, demonstrated excellent long-term stability toward xylene vapour in dry air and under 40 % relative humidity environment. The improved performance was due to the enriched facilitation of surface oxygen adsorption, which resulted in the enhanced catalytic influence of Co3O4 for oxidizing xylene vapour. Additionally, the performance was also associated with the higher surface area, mesoporous behaviour, and biggest pore volume which offered plentiful energetic sites for redox reactions, and synergistic combination of Co3O4 and In2O3 at the nanoscale p-n heterojunction. The xylene sensing mechanisms associated with improved performance were deliberated in detail. These results demonstrated that the Co-In could be utilized to monitor xylene with trivial interference from RH.

Oxygen-functionalized MoSe2 nanoflowers for selective detection of xylene at room temperature

The selective detection of xylene among its chemically similar counter VOCs is very crucial, and challenging and has great implications in breath analysis. At this point, we are introducing MoSe2 nanoflowers, which are synthesized by a one-step hydrothermal method. Later on, the surface functionality of the as-grown MoSe2 was effectively modulated by purging different oxygen concentrations (0.25 to 20 % O2) at 200 °C. Microscopic and spectroscopic characterizations were used to identify the changes in nanostructures after oxygen functionalization. The MoSe2 sensor treated with 2.5 % O2 showed an enhanced response towards xylene (73 % at 100 ppm) that was 14 times higher than the pristine MoSe2 at room temperature. Notably, the 2.5 % O2-treated MoSe2 sensor exhibited an 8 % response in 100 ppb of xylene with a lower detection limit (LOD) of 83 ppb. The cross-sensitivity of the sensor towards xylene as compared to the chemically identical VOCs like benzene and toluene was found to be very high. The selective detection of xylene was attributed to the improved surface reaction sites and catalytic behavior of MoSe2 after oxygen functionalization. The study confirms that the introduction of sufficient oxide or oxidants in 2D selenides like MoSe2 is favorable to accomplishing superior gas sensing characteristics.

Highly sensitive and selective detection of benzene, toluene, xylene, and formaldehyde using Au-coated SnO2 nanorod arrays for indoor air quality monitoring

We report the high performance of Au-coated SnO2 nanorod gas sensors for the detection of hazardous indoor volatile organic compounds (VOCs), such as benzene, toluene, xylene, and formaldehyde (BTXF) gases. Densely ordered SnO2 nanorod arrays were prepared via glancing angle deposition with an electron beam evaporator. The Au layer coating was used as a heterogeneous catalyst to promote the oxidation of VOCs, such as hydrocarbons. After optimizing the Au thickness, the sensor exhibited an excellent sensing response and a rapid response time of < 2.5 s for 10 ppm of BTXF gases. The maximum response was ∼662 for formaldehyde at 400 °C, ∼328 for toluene at 450 °C, ∼170 for xylene at 400 °C, and ∼139 for benzene at 500 °C, which are significantly higher than those of previously reported metal-oxide-semiconductor-based sensors. Each gas was selectively detected by integrating the sensor into a miniaturized gas chromatography (GC) system. The sensors detected ppb-level gas concentrations. Significantly, GC analysis revealed that four types of gases could be separately detected in a mixed gas within 5 min. Our study shows that Au-coated SnO2 nanorod gas sensors integrated with GC can be used as a facile indoor pollutant monitoring system.

Detection of xylene from C/Co3O4 nanocomposites synthesized from double-template using g-C3N4/ZIF-67

Gas sensors based on MOS materials have the advantages of high sensitivity, adjustable components, low cost and easy integration. MOF-derived MOS materials possess high porosity, which has the potential to detect VOC gases. And the introduction of carbon materials is an effective means to improve the gas-sensing performance due to the adsorption and activation effects. In this paper, C/Co3O4 nanocomposites were synthesized from double-template using g-C3N4/ZIF-67 precursor and applied to xylene sensors. The characterization results show that graphitized carbon species/dots were successfully introduced into the surface of Co3O4 nanoparticles, and XPS results confirmed the increase of chemisorbed oxygen. The density functional theory calculations also show that the existence of carbon species could enhance the adsorption of xylene and oxygen, as well as the obvious activation of oxygen (increased O-O bond length). The effects of adsorption and activation, structural advantages and surface electronic structure modulation lead to a significant improvement in the xylene-sensing properties of the composites. The response of C/Co3O4 to 100 ppm xylene is 17.62, which is 3.2 times higher than that of pure Co3O4. Meanwhile, the sensor has a low detection limit (1 ppm), short response time (7 s) and good stability. This work provides a feasible method to improve the performance of xylene sensor and has reference value for the effect of carbon materials on gas-sensing behavior.

One-dimensional In2O3 nanofibers patterned onto functionalized catalytic electrodes: A novel approach for selective xylene detection

Remarkable efforts have been devoted for enhancing gas selectivity of chemiresistors via tuning the sensing materials. However, the selective detection of low reactive gases remains challenging. Herein, we report a new strategy for selective detection of low reactive gases by patterning nanofibers and tuning the catalytic property of electrode. In this approach, straight single In2O3 nanofibers are patterned onto Au, Pt, and ITO interdigitated electrodes (IDEs) via direct-write near-field electrospinning; the resulting low coverage of the sensing materials (∼0.12%) exposes the electrode to analyte gases. The gas sensing characteristics of the sensors are determined by the catalytic activity of each electrode. Furthermore, the functionalization of Pt IDE with Au nanoparticles could achieve extremely high selectivity and response toward xylene. The sensing properties and mechanisms of the nanopatterned sensors are investigated regarding electrode composition, degree of electrode exposure, and catalyst location on the electrode and/or sensing materials. The key strategies for achieving high selectivity are the conversion of low reactive xylene gas into more reactive intermediate species while highly reactive interference gases are completely oxidized at open catalytic electrodes. Catalyst functionalization and exposure of electrodes can provide new guidelines for designing high performance gas sensors for new applications.

Comparison study on ZnO and CuO gas sensing characteristics: Temperature modulated-dual selectivity towards benzene and xylene vapours

The selective detection of gaseous benzene, toluene, ethylbenzene, and xylene (BTEX) is challenging due to their similar molecular structures. In addition, BTEX vapours are extremely hazardous and carcinogenic. Thus, in the current study, n-type ZnO and p-type CuO nanostructures were synthesized utilizing various bases by a simple hydrothermal method. Among the tested sensors, the ZnO–NaOH-based sensor displayed a temperature dual-mode selectivity toward benzene with responses (Ra/Rg) of 2.5 and 24 at 5 and 100 ppm, respectively at 75 °C, and Ra/Rg ≈ 142 toward xylene vapour at 100 ppm at an operating temperature of 150 °C. While the CuO-based sensors showed poor response, sensitivity and selectivity towards tested analytes. Moreover, the ZnO–NaOH based sensor revealed enormous sensitivity of 1.21 ppm−1 and low limit of detection (LoD) of 0.018 ppm (i.e., 18 ppb) toward xylene. The ultra-sensitivity, selectivity, low LoD of ZnO–NaOH based sensor toward benzene and xylene are associated with the improved VO observed in the in-situ photoluminescence and electron paramagnetic resonance studies, and as well as the x-ray photoelectron spectroscopy analyses. The ZnO–NaOH-based sensor, which was stored for roughly 18 months (547 days), demonstrated a reliable repeatability and long-time operation stability for 22 h exposure to xylene. The superior sensitivity, stability, and selectivity indicate openly that the strategy of using various bases is a striking method for fabricating a temperature dual-mode selectivity for the detection of benzene and xylene vapours.

Detection of Xylene as a Detrimental Chemical Compound by Employing a Photonic Crystal Based on Porous Silicon

Detection of Xylene as a Detrimental Chemical Compound by Employing a Photonic Crystal Based on Porous Silicon

Construction of SnO2 nanofibers @ MoS2 nanosheets core-shell nanocomposites for high efficiency xylene detection

As a typical pollution gas, xylene poses a particularly serious threat to human health. The xylene sensors with low operating temperature, fast response speed, sufficient detection limit and satisfactory selectivity are required for safety protection. Herein, a novel xylene sensitive material (SnO2@MoS2) was constructed by self-assembling MoS2 nanosheets array on SnO2 nanofibers. The response of SnO2@MoS2 sensor was 23.5–100 ppm xylene vapor, which was much higher than that of single-component sensors. Additionally, the response/recovery times were 21.5/60.4 s with a limit of detection (LOD) as low as 0.5 ppm. The good sensitive was ascribed to the unique resistance characteristics of the hierarchical structure, the regulation of electronic property by heterojunctions, and the increase of adsorption sites caused by large specific surface areas and surface defects. This work enlightens a novel strategy on the construction of MoS2 based core-shell hierarchical nanomaterials and future development of high efficiency xylene sensor.

Tuning the sensing selectivity of mesoporous hierarchical Ti-doped Co3O4 to toluene and xylene via controlling the oxygen defects

Vast efforts have been made to develop high-performance gas sensing materials for the detection of harmful volatile organic compounds (VOCs) like toluene and xylene. However, it is challenging to selectively detect toluene and xylene simultaneously. Herein, the hierarchical Ti-doped cobalt layered hydroxides miscrospheres were synthesized first and sintered at high temperature consequently to prepare hierarchical Ti-doped Co3O4 miscrospheres. The incorporation of Ti into the lattice of Co3O4 decreased the crystal sizes and crystallinity, resulting in higher specific surface area and more oxygen defects. Interestingly, the 3 at.% Ti-doped Co3O4 miscrospheres sintered at 450 °C exhibited the highest response of 64.9 to 50 ppm of xylene at 210 °C, while the 1 at.% Ti-doped Co3O4 miscrospheres calcined at 500 °C displayed the highest response of 57.2 to 50 ppm of toluene at 240 °C, which were about 11.8 and 7.8 times higher in comparison with pristine Co3O4. The different selectivity of Ti-doped Co3O4 to toluene and xylene arises from the different amounts of oxygen vacancies and defect oxygen ions. The obtained Ti-doped Co3O4 microspheres also showed the merits of good selectivity, repeatability and long-term stability, indicating the promising applications of Ti-doped Co3O4 miscrospheres in the detection of toluene and xylene.

Facile Synthesis of Pure and Cr-Doped WO3 Thin Films for the Detection of Xylene at Room Temperature.

This paper focused on the preparation of pure and Cr-doped tungsten trioxide (WO3) thin films using the spray pyrolysis method. Different techniques were adopted to analyze these films' structural and morphological properties. The X-ray detection analysis showed that the average crystallite size of the WO3-nanostructured thin films increased as the Cr doping concentration increased. The atomic force microscopy results showed that the root-mean-square roughness of the films increased with Cr doping concentration up to 3 wt % and then decreased. The increased roughness is favorable for gas-sensing applications. Surface morphology and elemental analysis of the films were studied by field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy measurements. The 3 wt % Cr-WO3 has a large nanoflake-like structure with high surface roughness and porous morphology. Gas-sensing characteristics of undoped and Cr-doped WO3 thin films were investigated with various gases at room temperature. The results showed that 3 wt % Cr-doped WO3 film performed the maximum response toward 50 ppm of xylene with excellent selectivity at room temperature. We believe that increased lattice defects, surface morphology, and roughness due to Cr doping in the WO3 crystal matrix might be responsible for increased xylene sensitivity.