Gas Sensors Research Articles

Porphyrinoid-Functionalized ZnO Nanoflowers for Visible Light-Enhanced and Selective Benzylamine Detection at Room Temperature.

Functionalization of hybrid organic molecules as layers on ZnO nanoflowers (NFs) gives an excellent combination of sensing toward visible light and vapors of various volatile organic compounds (VOCs). In this work, hybrid organic molecules functionalized ZnO NFs were utilized for the photoinduced detection of benzylamine at room temperature. The ZnO NFs were synthesized via a facile solution route and functionalized with four different porphyrin-conjugated molecules namely (i) pyrene-porphyrin (PP), (ii) pyrene- porphyrinato zinc (ZnPP), (iii) triphenylamine- porphyrin (TP) and (iv) triphenylamine- porphyrinato zinc (ZnTP). The diameter of the flower-like structure was found to be ∼3.2 μm with the thickness of petals being ∼24.1 nm. The gas adsorption performance of the functionalized ZnO NFs on light activation at room temperature was studied by using a scanning Kelvin probe (SKP) system. The improved adsorption properties of the samples can be attributed to the heterojunctions and light activation. In particular, an enhanced response of ZnTP functionalized ZnO (ZnTPZ) toward benzylamine was observed. Further, static gas sensing experiments using ZnTPZ under various concentrations (1, 3, 5, 10, 15, and 25 ppm) of benzylamine vapors both in dark and visible light conditions have exhibited a linear increase in the response. The selectively enhanced response of ZnTPZ compared to that of pristine ZnO was thus confirmed at 1 ppm of benzylamine. The sensitivity and limit of detection of the ZnTPZ sensor were calculated to be 0.0292 ppm-1 and 197 ppb, respectively. The coordination metal (Zn) has helped in effective charge transfer between benzylamine and ZnTPZ by providing additional active sites for interactions. Also, density functional theory calculations demonstrated the role of the hybrid organic molecules on the sensor surface in improving gas adsorption. Further, fresh cabbage was utilized for real sample analysis with the proposed sensor under visible light illumination conditions, and a linear response was obtained for low ppm evaluation at room temperature. Overall, the obtained results suggest the development of novel ZnTPZ-based light-activated gas sensors for low ppm benzylamine detection at room temperature. These kinds of sensors can be used to track the freshness of vegetables as they are transported from farms to commercial outlets.

Ultrasensitive detection of hazardous gas at room temperature enabled by MOF@MXene 0D-2D heterostructure

Achieving high sensitivity in detecting trace concentrations of toxic gases, particularly under room temperature (RT) conditions, remains a significant challenge. Herein, a 0D-2D heterostructure that can detect ppb-level H2S at RT is proposed by self-assembling cobalt-based metal–organic framework (Co-MOF) on Ti3C2Tx MXene. Co-MOFs with high specific surface areas can capture and concentrate target gas molecules, enhancing host-guest interactions and thereby boosting the selectivity and sensitivity. MXene nanosheets with high conductivity enable rapid electron transport at heterointerface, hence efficiently accelerating the reaction kinetics. Thereby, the as-prepared chemiresistive gas sensor based on Co-MOF@MXene 0D–2D heterostructure possessed excellent sensitivity against interfering gases and delivered an excellent response value of 11.1 to 400 ppb H2S at RT. The judicious design of MOF@MXene heterostructure may spur advanced hybrid material systems for superior sensing applications.

Room temperature gas sensors for NH3 detection based on the heterojunction of 2D Ti3C2Tx MXenes and Bi2S3.

Bi2S3/Ti3C2Tx nanomaterials were successfully prepared through a simple hydrothermal method. Various methods were used for their characterization, including XRD, XPS, SEM, EDS, and BET, along with testing their gas-sensing properties. The results showed that the response value to 100ppm ammonia at room temperature reached 107%, which was 14.1 times higher than that of pure few-layer MXene. After undergoing anti-humidity interference testing, we observed that Bi2S3/Ti3C2Tx exhibited a higher response value in real-time monitoring of ammonia as humidity increased. Specifically, under 90% humidity conditions, its response value reached 1.32 times that of normal humidity conditions. This exceptional moisture resistance ensures that the sensor can maintain stability, and even exhibit superior performance, in harsh environments. Therefore, it possesses excellent selectivity, high-moisture-resistance, and long-term stability, making it significant in the field of medical and health monitoring.

Gas-sensitive synergistic effect of Au-decorated ZnO nano-structured materials for rapid ethanol detection based on simulated sunlight activation

Local surface plasmon resonance (LSPR) and noble metal modification/doping are classical methods for improving the performance of metal-oxide-semiconductor (MOS)-based gas sensors. However, relatively less attention is paid to their synergies. In particular, research on synergistic gas-sensing technology that combines sunlight activation with other methods is significant for using friendly energy. In this study, Au-decorated ZnO (Au/ZnO) nano-structured materials (NMs) are successfully synthesised using a cost-effective nano-seed-assisted chemical bath and UV irradiation growth methods. The sensor based on this material exhibits superior performance in ethanol vapour under simulated sunlight, maintaining high sensitivity and repeatability at a low optimal working temperature. In particular, the sensitivity to 100 ppm of ethanol is 7.5 times better and the response time is 20 times shorter (tres < 1 s) in simulated sunlight than in the dark environment. The limit of detection (LOD) of ethanol is as low as 97 ppb, which is much lower than the concentration in exhaled breath of driving under the influence of alcohol according to Chinese law (20–80 ppm). This study provides a reliable and ultra-fast ethanol detection method, with potential applications in environmental monitoring and traffic safety. A possible gas-sensitive mechanism of the Au/ZnO ethanol vapour sensor is proposed based on the synergistic effect between simulated sunlight activation (LSPR, humidity resistance and thermal activation) and noble metal modification (electron sensitisation and chemical sensitisation). It provides a promising method for exploring the utilisation of sunlight for rapid gas detection.

A review of electrical and piezoelectric properties of nanocellulose biocomposites

Abstract The increasing request for lightweight, environmentally sustainable materials with versatile functionality and strong mechanical properties is driving renewed interest in nanocellulose for electrical applications. Nanocellulose, a biologically derived polymeric nanomaterial, has seen significant growth in the global market due to advancements in nanotechnology and the increasing need for sustainable materials. This has accelerated research into the development of cellulose-based nanomaterials. However, nanocellulose on its own does not inherently possess the ability to function as a conductive material. To address this limitation, researchers have explored various modifications, such as combining nanocellulose with conductive materials or applying specific chemical treatments. These approaches have been shown to enhance the electrical conductivity of nanocellulose, making it suitable for use in electrically conductive composites. Over the past few decades, nanocellulose composites have been extensively studied for their applications in energy, electronics, biomedicine, health, and environmental sectors. Nanocellulose possesses a unique combination of exceptional properties, including biodegradability, renewability, and a distinctive fibrous structure, proving that it is the best choice for these uses. The superior electrical properties of nanocellulose-based composites, coupled with their flexibility, ease of production, and biocompatibility, make them highly desirable for various advanced technological applications. Significant advancements have been achieved by researchers in fabricating various types of nanocellulose materials and exploring their potential in nanogenerators, humidity sensors, gas sensors, and supercapacitors. The ability to modify the surface of nanocellulose and its robust properties offer numerous opportunities for creating hybrid materials within the electrical domain.

High-performance PANI sensor on silicon nanowire arrays for sub-ppb NH3 detection

For industrial production and disease diagnosis, real-time detection of low concentrations of NH3 is crucial, necessitating a gas-sensitive sensor compatible with integrated processes and exhibiting excellent performance. Herein, we employed wet etching and rapid in-situ polymerization on silicon nanowire substrates to grow polyaniline fibers, thereby fabricating NH3 gas sensors with p-p heterojunction and three-dimensional network structures. Characterization and gas sensing performance testing were conducted. The results demonstrate the outstanding NH3 detection capabilities of the sensor, providing stable responses down to concentrations as low as 1 ppb, which indicates its LOD is one to two orders of magnitude lower than current similar products. It also exhibits verified selectivity and long-term reliability. The excellent sensing performance is attributed to the high surface area from the silicon nanowire structure and efficient synergy of p-p heterojunction. Additionally, the influence of doping types of the substrates and annealing process were explored. This work serves as a reference for the design of silicon-based gas sensors with high sensitivity, low detection limits, and extended operational lifetimes, suitable for deployment in commercial integrated monitoring systems.

Chemoresistive H2S sensor based on PANI/TiO2/CuCl2 nanocomposite impregnated conductive fabric using TOPSIS and Taguchi method

Abstract Conductive polymer/metal oxide nanocomposites have been widely used for chmoresistive gas sensors. PANI/TiO2/CuCl2 nanocomposite(PTCN) impregnated conductive fabric was prepared by in-situ synthesis method. To improve the performance of PTCN impregnated fabric for detecting H2S gas, Taguchi orthogonal array(TOA) is used to experimental design, and best values of factors affecting to the sensing performance are determined using Technique for order preference by similarity to ideal solution (TOPSIS) and Taguchi optimization method. PTCNs were charactierized by SEM, XRD, FTIR. The sensing performances of the proposed sensor such as linear detection range, sensitivity, repeatability and effect of humidity for hydrogen sulfide gas were evaluated.&amp;#xD;

Semi-supervised comparative learning compensation method for chemical gas sensor drift.

The gradual and unpredictable variation in chemo-sensory signal responses when exposed to the same analyte under identical conditions, commonly referred to as sensor drift, has long been recognized as one of the most serious challenges faced by chemical sensors. The traditional drift compensation method is both labor-intensive and expensive, as it requires frequent collection and labeling of gas samples for recalibration. Introducing a small number of meaningful drift calibration samples can be an attractive strategy to reduce the computational load and improve the performance of the updated classifier. However, under the influence of drift, new challenges arise due to the difference in the distribution of source and target domain data. This paper proposes a novel algorithm framework called semi-supervised contrastive learning drift compensation (SSCLDC). The framework automatically extracts high-level abstract features based on a multilayer perceptron to better represent the structure of the source data. In addition, to address the issue of data distribution differences caused by drift between the source and target domains. We add a small number of reference sample pairs into the training for semi-supervised learning. Combining a contrastive loss function that can represent the matching degree of paired samples effectively overcomes the problem of sensor drift. The Kennard-Stone sequential algorithm is used to select the representative reference sample from the set of candidate reference samples. Experiments conducted on a widely used long-term chemical gas sensor drift dataset demonstrate that the proposed method outperforms several classic drift compensation techniques, highlighting its effectiveness and practical applicability.

Ultra-compact dual-channel integrated CO2 infrared gas sensor

Expiratory CO2 concentrations can directly reflect human physiological conditions, and their detection is highly important in the treatment and rehabilitation of critically ill patients. Existing respiratory gas analyzers suffer from large sizes and high power consumption due to the limitations of the internal CO2 sensors, which prevent them from being wearable to track active people. The internal and external interference and sensitivity limitations must be overcome to realize wearable respiratory monitoring applications for CO2 sensors. In this work, an ultra-compact CO2 sensor was developed by integrating a microelectromechanical system emitter and thermopile detectors with an optical gas chamber; the power consumption of the light source and ambient temperature of the thermally sensitive devices were reduced by heat transfer control; the time to reach stabilization of the sensor was shortened; the humidity resistance of the sensor was improved by a dual-channel design; the light loss of the sensor was compensated by improving the optical coupling efficiency, which was combined with the amplitude trimming network to equivalently improve the sensitivity of the sensor. The minimum size of the developed sensor was 12 mm × 6 mm × 4 mm, and the reading error was <4% of the reading from −20 °C to 50 °C. The minimum power consumption of the sensor was ~33 mW, and the response time and recovery time were 10 s (@1 Hz), and the sensor had good humidity resistance, stability, and repeatability. These results indicate that the CO2 sensor developed using this strategy has great potential for wearable respiratory monitoring applications.

Synthesis of ZnO NWs via Thermal Evaporation Technique

Zinc oxide nanowires ZnONWs were successfully synthesized on glass slides. The synthesis was conducted firstly by the deposition of 12 µm a thin film of Zn metal by thermal evaporation. Secondly,the coated film was annealed at a temperature of 600 ºC in air for four hours to grow the ZnO nanowires. It have been observed that the produced nanowires were grown in a vertical orientation and having a high density, very long, and a minimal aspect ratio. The crystal structure and morphology of ZnO nanowires were investigated with X-ray diffraction (XRD) and scanning electron microscopy (SEM). The UV-visible spectrophotometer was also used to calculate the optical parameters from the absorption spectrum and show a band gap energy around 3.25 eV. The crystal structure of the material was revealed to be polycrystalline with a preferred orientation in the direction of [101]. Small average crystallite size was calculated about 17nm The wires can be measured to have a length of around 10 µm with diameters ranging from 50 to 100 nm. This could be used for gas sensor applications. In addition, this ZnONWs structure has a maximum transmittance (100%) which can be a good candidate for many optoelectronic apllications.

Rational design of ZnO-SnO2 Janus nanofibers for highly sensitive triethylamine detection

Herein, ZnO-SnO2 Janus nanofibers (NFs) were synthesized by a parallel electrospinning method and its sensing performances were tested. Considering the compositions of the two metal oxide semiconductors in Janus structure, different ratios of ZnO and SnO2 were designed and controlled. The optimum ratios of ZnO and SnO2 was 1:2 by analyzing their sensing performances to triethylamine (TEA) gas. Gas sensors based on ZS-12 Janus NFs exhibited a high response to TEA (45.2) and an excellent sensing response/recovery reproducibility. In order to investigate the sensing mechanism of Janus structure, ZnO NFs and SnO2 NFs were synthesized and used as controlled experiment. The results indicated that the heterostructures in Janus NFs is the key factor for the enhanced TEA sensing performances. The electrons flowed in the ZnO-SnO2 Janus structure leading to the variation of ionic oxygen species and electron depletion layer. These phenomena improved the reaction of TEA gas molecules with ionic oxygen species so that the TEA sensing performances were enhanced. Based on the Janus structures, a satisfactory gas sensor for detecting TEA gas were developed. Significantly, this work investigated the sensing mechanism of Janus structures and provided an efficient strategy for the gas sensing materials.

A Portable Electronic Nose Coupled with Deep Learning for Enhanced Detection and Differentiation of Local Thai Craft Spirits

In this study, our primary focus is the biomimetic design and rigorous evaluation of an economically viable and portable ‘e-nose’ system, tailored for the precise detection of a broad range of volatile organic compounds (VOCs) in local Thai craft spirits. This e-nose system is innovatively equipped with cost-efficient metal oxide gas sensors and a temperature/humidity sensor, ensuring comprehensive and accurate sensing. A custom-designed real-time data acquisition system is integrated, featuring gas flow control, humidity filters, dual sensing/reference chambers, an analog-to-digital converter, and seamless data integration with a laptop. Deep learning, utilizing a multilayer perceptron (MLP), is employed to achieve highly effective classification of local Thai craft spirits, demonstrated by a perfect classification accuracy of 100% in experimental studies. This work underscores the significant potential of biomimetic principles in advancing cost-effective, portable, and analytically precise e-nose systems, offering valuable insights into future applications of advanced gas sensor technology in food, biomedical, and environmental monitoring and safety.

In-Depth Study of Ambipolar Charge-Transport Regime through External Triggers and Gas Sensing.

Ambipolar devices are a hot topic in research tables due to their unique advantage in reducing the size of the electrical system and enhancing its efficiency. Here, we report a bilayer heterojunction device constructed using octafluoro-vanadyl-phthalocyanine (VOF8Pc) and lutetium bisphthalocyanine (LuPc2), which exhibits both p- and n-type behaviors under oxidizing (NO2 and O3) and reducing gas (NH3) species depending on the humidity level and temperature variations. The initial polarity of the device is identified as n-type by measuring a current decrease under oxygen exposure. Most interestingly, we were capable of observing the zero state (no response) where both opposite charge carriers fight for the majority to dominate the electrical properties of the device when it goes from n- to p-type or vice versa. The inversion in the nature of the majority charge carriers in this ambipolar device was achieved by optimizing the external trigger. The unique property of controllable polarity inversion in a VOF8Pc/LuPc2-based bilayer heterojunction device makes it the most effective ambipolar device for real-world applications.

Novel oxygen vacancies-rich 3D porous ZnO for highly sensitive 3-hydroxy-2-butanone biomarker gas sensors

Listeriosis can cause human death via infection by Listeria monocytogenes (LMs) with a high fatality rate of 20–30 %. Detection of 3-hydroxy-2-butanone (3H-2B) biomarker of LMs can achieve estimation of LMs content, which is of great significance for human health. Exploring porous metal oxide semiconductors (MOSs) with rich vacancies towards 3H-2B sensing is quite promising for achieving this goal. Herein, we report a highly sensitive 3H-2B sensor based on novel 3D porous ZnO with rich oxygen vacancies which was facilely obtained by sacrificing Zn foam in oxalic acid and subsequent thermal decomposition. The ZnO sensor displays ultrahigh sensor response of Ra/Rg = 328@5 ppm, super-low detection limit of 0.001 ppm, excellent cycling stability and selectivity and good linear response at 120 °C, showing great potential for precise detection of 3H-2B biomarker. The porous structure and increased oxygen vacancies contribute greatly to the adsorption of active oxygen species therefore the sensing reactions on ZnO surface, which accounts for the high sensing performance. Our work provides an ingenious strategy to produce novel 3D ZnO with rich oxygen vacancies as well as new insights for boosting the detection of LMs.

Single walled carbon nanotubes/ZnO nanowires heterostructure array for NO2 gas sensing at low ppm levels

A layer-by-layer ZnO nanowire (NW)-Single Walled Carbon Nanotube (CNT) hybrid gas sensor has been proposed for effective detection of NO2 gas under a low exposure limit of 5 ppm. The fabricated hybrid sensor displayed good sensor response (S %), good selectivity and fast response time towards the target gas. S % value of 36.4 % under 5 ppm NO2 level at 250 °C and good selectivity response towards different interfering gases like SO2, CO and H2 have been observed. Meanwhile, fast response time values of 44.08 s (response) and 62.11 s (recovery) were observed at 300 °C under 5 ppm NO2 level. The sensor baseline resistance of the hybrid heterostructure (HS) was also found to be lower when compared to that of a bare ZnO NW sensor. In addition, the presence of Single Walled CNT in the HS was also shown to reduce the operational temperature of the sensor. Temperature played a significant role by controlling the adsorption and desorption kinetics of gas molecules on the surface. Moreover, the formation of p-n interface between Single Walled CNT (p-type) and ZnO NW (n-type) might have modulated the potential charge barrier on interacting with the adsorbed gases which inturn might have impacted the response of the hybrid sensor. In addition, the large surface areas offered by both NWs and nanotubes might have improved the gas adsorption capability thereby enhancing the overall hybrid sensor’s response.

Inkjet-Printed Localized Surface Plasmon Resonance Subpixel Gas Sensor Array for Enhanced Identification and Visualization of Gas Spatial Distributions from Multiple Odor Sources

The visualization of the spatial distributions of gases from various sources is essential to understanding the composition, localization, and behavior of these gases. In this study, an inkjet-printed localized surface plasmon resonance (LSPR) subpixel gas sensor array was developed to visualize the spatial distributions of gases and to differentiate between acetic acid, geraniol, pentadecane, and cis-jasmone. The sensor array, which integrates gold nanoparticles (AuNPs), silver nanoparticles (AgNPs), and fluorescent pigments, was positioned 3 cm above the gas source. Hyperspectral imaging was used to capture the LSPR spectra across the sensor array, and these spectra were then used to construct gas information matrices. Principal component analysis (PCA) enabled effective classification of the gases and localization of their sources based on observed spectral differences. Heat maps that visualized the gas concentrations were generated using the mean squared error (MSE) between the sensor responses and reference spectra. The array identified and visualized the four gas sources successfully, thus demonstrating its potential for gas localization and detection applications. The study highlights a straightforward, cost-effective approach to gas sensing and visualization, and in future work, we intend to refine the sensor fabrication process and enhance the detection of complex gas mixtures.

Enhanced sensitivity and selectivity of ZnSe/PANI nanocomposite for Low-ppm NO2 detection at room temperature gas sensor application

The utilization of n-p composite-based gas sensors has garnered substantial interest within the field of gas sensing. This heightened attention can be attributed to the remarkable band alignment of the constituent materials which results in superior charge transfer rate, increased gas interaction sites and reduced optimum operating temperature. In this work, n-ZnSe/p-PANI composites were prepared by simple hydrothermal technique. The obtained X-ray diffraction pattern confirms the phase formation ZnSe, PANI and ZnSe/PANI composites. The pure ZnSe exhibits a sensing performance at a higher operating temperature of 100 °C, whereas ZnSe/PANI composite sample demonstrates an improved sensing response at 30 °C. Notably, the 20 wt.% composite sample (ZnSe–P2) achieved a maximum sensing response of 77 % towards 20 ppm of NO2 gas molecule. Additionally, the sensor exhibits the response time (Tres) of 112 s and recovery time (Trec) of 648 s, at an operating temperature of 30 °C. It also shows better stability, reproducibility and specific selectivity towards NO2 gas molecule. The superior sensing behavior of the ZnSe-P2 sensor can be ascribed to the development of a depletion region in the interface of ZnSe/PANI composites, which improved the charge transfer rate and increased the number of reactive sites. Therefore, the formation of n-p inorganic-organic composite strategy offers an effective approach for detecting NO2 gas molecules at lower temperature of 30 °C.

Emerging Horizons in Gas Sensing: Exploring the Potential of MXenes and MBenes.

This review article is focused on the development and application of two types of emerging two-dimensional (2D) materials, namely MXenes and MBenes, in the field of gas detection. Owing to its excellent electrical conductivity, specific surface area, and tunable surface functionality, MXenes have demonstrated high sensitivity and rapid response in detecting a variety of gases, such as volatile organic compounds (VOCs), nitrogen dioxide (NO2), and ammonia (NH3). MBenes are relatively newly discovered materials with excellent electronic stability and gas adsorption capabilities. Both of these materials demonstrate significant potential in improving sensor selectivity and stability through surface functionalization and heterostructure designs. However, despite the impressive gas detection performance of these materials, challenges remain in achieving long-term stability, cost-effectiveness, and commercialization. We summarize the prominent research insights on these materials and offer an outlook on future research directions and potential applications. With ongoing research and technological advancements, MXenes and MBenes are anticipated to have a substantial impact in critical areas such as environmental monitoring and industrial safety.

Low temperature ammonia sensor with giant sensitivity and selectivity based on W@WO2.92 internal ohmic contact core-shell nanostructures

Ammonia (NH3) detection is crucial for both harnessing hydrogen energy and safeguarding public health. However, the NH3 sensors based on semiconductors is currently constrained by their necessity to operate at elevated temperatures and their limited ability to distinguish NH3 from other gases. In this study, the high oxygen vacancy W@WO2.92 core-shell nanostructures have been synthesized by pulsed laser ablation in water. The gas sensors based on W@WO2.92 nanoparticles response to NH3 with high sensitivity (|Ra-Rg|/Ra=72.6 %@100 ppm, Ra and Rg represent the resistance of the material when exposed to air and the test gas, respectively.) at room temperature with detection limit of 730 ppb. Additionally, the response to NH3 can achieve 55 % even at 5℃, which plays a great role in timely detection of NH3 during low temperature transportation. Furthermore, the sensors reveal outstanding selectivity toward NH3 in the presence of 11 other potential interfering gases. This research presents a groundbreaking strategy, holding significant potential for the development of high-performance NH3 sensors that operate efficiently at low temperatures.

Biofunctionalized magnetic nanoparticles incorporated MoS2 nanocomposite for enhanced n-butanol sensing at room temperature

N-butanol is well known to be a flammable and harmful liquid that is a potential threat to human health and property. Therefore, it is important to monitor the concentration of n-butanol in the surroundings. The need for highly efficient toxic gas detection is urgent and has been driving the research on gas sensors for practical applications. Molybdenum disulfide (MoS2) has been attracting significant interest for gas detection at room temperature. Herein, we report biofunctionalized magnetic nanoparticles incorporated MoS2 for sensing n-butanol. The biosynthesized magnetite nanoparticles (CT-Fe3O4) were synthesized by the addition of Cinnamomum Tamala (CT) leaf extract, and subsequently, the nanocomposite was synthesized using a hydrothermal method. Highly sensitive sensors based on MoS2-CT-Fe3O4 were fabricated and tested for sensing different concentrations of n-butanol. The nanocomposites showed a good sensing performance (Δ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta$$\\end{document} R/Rair %) of 72% towards 20 ppm of n-butanol, indicating the potential use of MoS2-CT-Fe3O4 nanocomposite for sensing n-butanol at room temperature.