CuO Sensor Research Articles

Selective discrimination and accurate quantification of five target vapors among multiple vapors using 2D CuO and Co3O4 sensors

Selective and sensitive detection of volatile organic compounds (VOCs) are critically needed for various applications like environmental sustainability, industrial safety, healthcare, etc Metal oxides are one of the most explored chemiresistive sensing materials because of their high sensitivity, but they lack selectivity. This work reports synthesis of two metal oxides - CuO and Co3O4 using surfactant assisted hydrothermal method. The 2D morphologies of both the metal oxides were ensured through fielded emission scanning electron microscope. The polycrystalline nature of the materials was studied using X-ray diffractometer and bandgaps were found to be 1.72 eV (CuO) and 1.9 and 2.89 eV (Co3O4) through the Kubelka Munk plot. The two metal oxides were employed to detect four different concentrations (6–50 ppm) of five targeted VOCs (lung cancer biomarkers) - acetone, acetonitrile, isopropanol, methanol, and toluene. In addition, response of the sensors for 6–50 ppm of ethyl acetate, hexanal, ammonia, and NO2 were also recorded as these VOCs are naturally produced in the body as a result of metabolic processes. The responses were recorded for 10 min for all the gases with CuO and Co3O4. Despite the intrinsic metal oxides lacking selectivity towards a specific VOC, careful feature selection achieved a classification accuracy of 95% using random forest (RF) algorithm. Subsequent application of RF model on validation dataset yielded a 91% accuracy in identifying target VOCs. Multilinear regression (MLR) algorithm was then employed to quantify the concentrations of the VOCs and low mean absolute error (MAE) values were obtained.

Effect of doping level on the photoconduction and chemiresistive ethanol gas sensing of lanthanum-doped CuO films

Undoped and lanthanum (La)-doped copper oxide (CuO) thin films were prepared by the nebulizer spray pyrolysis technique. The X-ray diffraction analysis revealed that the effective doping of lanthanum does not alter the monoclinic crystalline structure of copper oxide thin films. Raman spectra confirmed the crystalline quality of undoped and La-incorporated CuO films. From, scanning electron micrograph images, the La-doped CuO films exhibit spherical particles. Energy dispersive X-ray analysis confirmed the existence of copper, lanthanum and oxygen elements. The doping of La-substituted CuO films showed a minimum bandgap when compared to undoped CuO film. The oxidation states of Cu 2p, La 3d and O 1s elements were observed. The electrical resistivity of the films was considerably decreased due to the doping of La ions in CuO matrix. The photoluminescence spectra show that the doping of La ions increases the defect states and shows increased intensity. The time resolved photoluminescence analysis revealed that an extended carrier lifetime was observed for the La-doped films. The La-doped CuO sensors achieved a superior gas sensing performance at room temperature and exhibited quick response and recovery times, suggesting that the sensor has the potential for the detection of harmful volatile gases in real-world applications. The photoconductive investigation revealed that the La-doped CuO films exhibited higher charge-transporting properties and increased light-harvesting ability. This study sheds light on designing gas sensors working under ambient conditions and photosensors for optoelectronic devices.

Comparative Study of Polymer-Modified Copper Oxide Electrochemical Sensors: Stability and Performance Analysis.

The effectiveness of copper oxide-modified electrochemical sensors using different polymers is being studied. The commercial powder was sonicated in an isopropyl alcohol solution and distilled water with 5 wt% polymers (chitosan, Nafion, PVP, HPC, α-terpineol). It was observed that the chitosan and Nafion caused degradation of CuO, but Nafion formed a stable mixture when diluted. The modified electrodes were drop-casted and analyzed using cyclic voltammetry in 0.1 M KCl + 3 mM [Fe(CN)6]3-/4- solution to determine the electrochemically active surface area (EASA). The results showed that α-terpineol formed agglomerates, while HPC created uneven distributions, resulting in poor stability. On the other hand, Nafion and PVP formed homogeneous layers, with PVP showing the highest EASA of 0.317 cm2. In phosphate-buffered saline (PBS), HPC and PVP demonstrated stable signals. Nafion remained the most stable in various electrolytes, making it suitable for sensing applications. Testing in 0.1 M NaOH revealed HPC instability, partial dissolution of PVP, and Cu ion reduction. The type of polymer used significantly impacts the performance of CuO sensors. Nafion and PVP show the most promise due to their stability and effective dispersion of CuO. Further optimization of polymer-CuO combinations is necessary for enhanced sensor functionality.

Vacuum-solvent thermal synthesis of nickel foam-supported CuO-based sensor electrode for good electrochemical detection of nitrite

Given the bad effect of superfluous nitrites on biology/environment, engineering the fast, sensitive, and real-time quantification of nitrites matters to safeguard both the eco-system and human public health. Here, a CuO nanocatalyst self-supported on nickel foam (CuO@NF) was crafted via facilely fusing a vacuum solvent recipe with ambient thermal annealing. Various characterizations show that hollow sea urchin-like CuO structures were arrayed on substrate to feature a 3D porous motif and large specific surface area. Such traits promise the effective local wetting and enrichment of nitrite to augment the nitrate capture/contact capacity, underlying a highly sensitive electrochemical determination of nitrite. Specifically, a wide linear detection range can span 0.5 to 4250 μM, with a stable current response at a concentration as low as 0.5 μM nitrite. The detection limit or sensitivity is approximately 0.0287 mM or 2.402 mAmM−1 cm−2, respectively. This electrode was also successfully applied to detect the nitrite in complex samples like pickled vegetables with satisfactory recovery rates. Our study shows that the self-supported CuO sensor provides an ingenious tactic to build high-efficiency binderless electrodes for the electrochemical sensing applications.

Highly Selective and Reversible Detection of Simulated Breath Hydrogen Sulfide Using Fe-Doped CuO Hollow Spheres: Enhanced Surface Redox Reaction by Multi-Valent Catalysts.

The precise and reversible detection of hydrogen sulfide (H2S) at high humidity condition, a malodorous and harmful volatile sulfur compound, is essential for the self-assessment of oral diseases, halitosis, and asthma. However, the selective and reversible detection of trace concentrations of H2S (≈0.1ppm) in high humidity conditions (exhaled breath) is challenging because of irreversible H2S adsorption/desorption at the surface of chemiresistors. The study reports the synthesis of Fe-doped CuO hollow spheres as H2S gas-sensing materials via spray pyrolysis. 4 at.% of Fe-doped CuO hollow spheres exhibit high selectivity (response ratio ≥ 34.4) over interference gas (ethanol, 1ppm) and reversible sensing characteristics (100% recovery) to 0.1ppm of H2S under high humidity (relative humidity 80%) at 175 °C. The effect of multi-valent transition metal ion doping into CuO on sensor reversibility is confirmed through the enhancement of recovery kinetics by doping 4 at.% of Ti- or Nb ions into CuO sensors. Mechanistic detailsof these excellent H2S sensing characteristics are also investigated by analyzing the redox reactions and the catalytic activity change of the Fe-doped CuO sensing materials. The selective and reversible detection of H2S using the Fe-doped CuO sensor suggested in this work opens a new possibility for halitosis self-monitoring.

Fabrication and characterization of chemiresistive CuO sensors sensitized by Ca-doping for detection of sweat electrolyte concentration

Intense electrolyte loss as a result of excessive sweating can disrupt the electrolyte balance in the body and cause damage to many organs, as well as potentially fatal disturbances in even brain functions. There are commercial sensors developed to monitor users' physical activity, however, few of them can provide information on users' health status through sweat analysis. Herein we report a chemiresistive sensor to monitor the sweat electrolyte concentration level. Metal oxide semiconducting CuO films were deposited on Au electrodes as sensing layers. Ca2+ ions were doped into the CuO lattice as sensitizer. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and UV–Vis spectroscopy were used to characterize the films. Sensors produced with pure and Ca-doped CuO films were tested against different concentrations of artificial sweat. The sensors responded well to sweat electrolyte concentration with a linear detection range of 20–80 mM. Detection limits between 6.64 and 9.86 mM were estimated using standard deviation methods. Average sensor response times were found to be 12 s.

Improved Structural Stability of CuO Via Bi Doping for Glucose Sensing

Glucose sensing is of great importance in fields such as medical diagnostics, food industry, and environmental monitoring. Copper oxide (CuO) has shown promising results as an electrochemical sensor for glucose detection due to its high sensitivity and selectivity towards glucose molecules[1]. However, one of the key challenges is to maintain the morphology and crystal structure of CuO during long-term glucose electrooxidation. CuO is prone to phase transformation, which can lead to changes in its crystal structure and affect its electrochemical performance. Moreover, the stability of CuO can be affected by external factors such as applied potential and pH, which can induce corrosion and degradation of the CuO layer over time.In this contribution, we propose a novel approach to improve the structural stability of CuO via surface bismuth doping. The Bi-doped CuO was prepared via an ultrasonic method, generating homogenously distributed Bi atoms on the surface of CuO thin flakes. At Bi doping level between 5% to 10%, the structure of CuO retains, indicating the replacement of Cu by Bi atoms other than phase separation. The long-term electrochemical test showed <1% current loss with the 10% Bi-doped CuO while >30% current loss with the CuO (Figure 1), suggesting that Bi atoms can act as the structural stabilizer for CuO electrocatalyst. Moreover, no significant sensitivity loss (~650 mA mM−1 cm−2) was observed after Bi doping.Our results demonstrate significant improvements in the CuO sensor's stability and accuracy, which can pave the way for its practical applications in various fields. Figure 1 Amperometric response of CuO and Bi-doped CuO (percentage shows the Bi/Cu ratio) during long-term glucose electrolysis. Reference: W. Zheng, Y. Li, L. Hu, L.Y.S. Lee, Sensors & Actuators: B. Chemical 2019, 282, 187-196 Figure 1

UV-activated CuO nanospheres modified with rGO nanosheets for ppb-level detection of NO2 gas at room temperature

Monitoring and reducing NO2 pollution at room temperature is indispensable for human survival. Thus, we propose a light-activated route (UV light, 100 mW/cm2) to realize a high-performance NO2 detection based on CuO/rGO gas sensor. The CuO/rGO sensor under UV light illumination exhibits a high response of 22.18–100 ppm NO2 at 23 ℃, which is approximately 1.36 times of the CuO/rGO sensor and 2.31 times of the CuO sensor under dark, respectively. Meanwhile, under UV light illumination, the CuO/rGO sensor has a fast response/recovery speed of 10.9/30.9 s to 20 ppm NO2 at 23 ℃, which is obviously better than that under dark. Moreover, the light-activated CuO/rGO sensor has excellent repeatability, selectivity, ultra-low detection limit (50 ppb) and long-term stability. The significantly appealing gas-sensing performance of CuO/rGO sensor is mainly ascribed to the mesoporous structure, high specific surface area and plentiful oxygen vacancy of CuO/rGO nanocomposites. More attractively, the photo-generated carriers and formed heterojunction also greatly improve the carrier migration in the context of the NO2/CuO/rGO interaction, enhancing the gas-sensing performance of gas sensor. Our work will provide insight in utilizing light illumination to realize ultrasensitive and room-temperature detection of ppb-level NO2 gas.

Effect of Cu or Ni addition to ZnO nanostructures on their n-butanol sensing performance

ZnO nanostructures with two shapes were routinely synthesised using a direct-current heating technique. These structures were coated with metals such as Cu and Ni to enhance the sensor response to n-butanol vapour. The surface modification approach associated with semiconductor materials used in gas sensor applications is essential for improving sensing performance, including the sensor response, selectivity, and stability for specific gases. Previously investigated surface modification approaches mostly involved the addition of noble metals, such as Pd, Pt, and Au. However, these metals are expensive for commercial applications. Herein, surface modification by the addition of non-noble metals is presented as a p–n junction for sensor fabrication. Cu and Ni sputter-coated onto ZnO nanostructures were transformed into CuO and NiO, respectively. The results of the gas-sensing characteristics show that the p–n junction formation of the ZnO–CuO and ZnO–NiO sensors remarkably enhanced the sensor response toward n-butanol. The sensor response of the ZnO–NiO sensor upon exposure to n-butanol at a concentration of 1000 ppm was 1400.0 at a working temperature of 450 °C, whereas that of the ZnO–CuO sensor was 775.9 at the optimum working temperature of 400 °C and an n-butanol concentration of 1000 ppm. Furthermore, these sensors exhibited excellent selectivity toward n-butanol compared to other gases. The sensing mechanism is explained by the large depletion layer width at the boundary of the p–n junction, which improves the sensor response. These results demonstrate a viable approach for manufacturing n-butanol sensors and possibly for constructing a functional active layer in e-nose applications.

Insights on the host precursor role play in the chemiresistive gas sensing properties of nebulizer spray-coated CuO films

Copper oxide (CuO) gas sensors have been designed via nebulizer spray pyrolysis onto the glass substrate using different cationic precursors. XRD analysis confirmed that the prepared CuO films with monoclinic structure and the porous morphology was observed for copper acetate precursor solution from SEM analysis. EDAX and XPS analysis revealed a near stoichiometric ratio of copper and oxygen in the films. The temperature-dependent resistivity measurements were measured using the four-probe technique. The optical band gap was calculated from 1.5 eV to 1.9 eV and the photoluminescence emission peak was recorded at 628 nm. From the TRPL analysis, the A: CuO film attained a maximum average lifetime (τavg) of 0.495 ns. The porous structure of the A: CuO sensor operating at room temperature exhibits high sensitivity, fast response and recovery speed for acetone, ethanol and toluene gas detection (16 s/47 s, 9 s/12 s and 6 s/38 s).

A Strategy to Enhance Humidity Robustness of p‐Type CuO Sensors for Breath Acetone Quantification

Low‐cost metal oxide sensors are highly attractive for emerging applications such as breath analysis. Particularly promising are p‐type sensors that can operate at low temperatures, a key requirement for compact and low‐power devices. To date, however, these sensors lack sufficient sensitivity, selectivity, and humidity robustness to fulfil stringent requirements faced in real applications. Herein, a flame‐made and low‐power sensor (operated at 150 °C) that consists of CeO2‐decorated CuO nanoparticles is introduced, as determined by X‐ray diffraction and X‐ray photoelectron spectroscopy analysis. Most remarkably, this sensor features excellent robustness to 10–90% relative humidity. This is attributed to the presence of CeO2 nanoclusters, which may act by scavenging OH− and allow the readsorption of oxygen onto the CuO surface. To demonstrate its immediate impact, this sensor is investigated for the detection of acetone, a biomarker for fat burning. It detects acetone with high sensitivity (i.e., 50 ppb) and features excellent acetone selectivity (&gt;9.8) toward key inorganic interferants (i.e., NH3, H2, and CO). Most importantly, the CeO2–CuO sensor accurately quantifies acetone concentrations in the exhaled breath of 16 volunteers (bias and precision of 90 and 457 ppb). As a result, it is attractive for low‐power and humidity robust detection of volatiles in breath analysis.

Designing one-dimensional hierarchical Cu@Cu2O/CuO core-shell heterostructure for highly sensitive detection of NO2 at room temperature

Developing high-performance room temperature (RT) gas sensors based on conventional metal oxides with simple method is attractive and significant. Herein, we reported a one-pot wet-etching self-assembly strategy to synthesize one-dimensional (1D) hierarchical Cu@Cu2O/CuO nanocomposites with low-temperature and applied it for highly sensitive detection of NO2 gas. Intriguingly, the core-shell heterostructure was longitudinally synchronously formed via in-situ self-assembly of Cu2O/CuO nanosheets and wrapped Cu nanowires (NWs). The as-prepared sensor showed high response to 10 ppm NO2 gas of ∼62.1 within 30 s, excellent selectivity and fast response speed at RT (25 °C). As a vital external factor, humidity has been systematically investigated for its influence on the performance of the Cu@Cu2O/CuO sensor. Notably, the results showed that the moisture air can enhance the sensor’s response and accelerate the recovery process. The response value has been boosted ∼70 times and the recovery time was reduced from 552 s to 14 s by introducing moisture air at the specific sensing stage. These findings provided important reference for the development and application of RT gas sensors. Specially, the facile synthesis strategy showed a good idea for the preparation of high efficiency, low cost and heterostructured sensing materials.

Hydrothermal synthesis of CuO/rGO nanosheets for enhanced gas sensing properties of ethanol

In this work, CuO nanosheets and CuO/rGO nanocomposites are synthesized by one-step hydrothermal method and characterized accordingly. Next, these samples are tested for gas sensing performance. The test data show that the CuO/rGO sensors have significantly improved gas sensing performance for ethanol compared to the pure CuO sensor. It should be noted that the CuO/rGO-10 sensor has the most outstanding gas sensing performance among the four sensors prepared, with an optimum working temperature 25 lower than that before doping, and its response value for 100 ppm ethanol at 175 °C is 10.54, which is 3.75 times higher than that before rGO doping. Also, the CuO/rGO-10 sensor has remarkable selectivity and reproducibility for ethanol. Most importantly, its limit of detection for ethanol is 100 ppb. At last, the gas sensing mechanism of the composites for ethanol is explained. Enhanced gas sensing performance of CuO/rGO sensors for ethanol is attributed to the lamellar structure and the synergistic effect between CuO and rGO.

Gold Nanoparticles Decorated Copper Oxide Nanosheets Sensor for Hydrogen Sulfide Gas Sensing at Room Temperature

This study exhibits a highly H2S-selective gas sensor based on copper oxide nanosheets (CuO-NSs) material. CuO-NSs are fabricated by a simple and economical method. CuO-NSs are decorated by gold nanoparticles (AuNPs) and used to detect H2S at room temperature. The AuNPs decorated CuO sensor has responses of 36.55% to 69.67% at 0.1 to 0.5 ppm of H2S while the pure sensor has responses from 4.77% to 13.37%. It can be seen that AuNPs can enhance H2S sensing responses five to nine times higher than pure one. The sensor also shows high H2S selectivity against NH3, SO2 and volatile organic compounds (VOCs). The beneficial effect of AuNPs allow the H2S detection of CuO material down to ppb and even lower level, which make it possible to be applied in environmental applications and portable devices.

A CuO thin film type sensor via inkjet printing technology with high reproducibility for ppb-level formaldehyde detection

High-performance gas sensors have huge application prospects and consumer demands in environmental monitoring, public security and other fields. Nevertheless, the conductive type metal oxide gas sensors prepared by traditional coating or dropping technology encounter challenges in low detection limit and excellent replication, hardly meeting the actual needs of trace harmful gas detection and mass production. Here, a uniform and high-quality CuO sensing film is formed quickly and efficiently by inkjet printing technology, which is expected to realize mass preparation of high-performance formaldehyde sensors. The CuO sensor can reach as low as 50 ppb formaldehyde detection limit, satisfying the monitor needs of the World Health Organization’s specified value 80 ppb. In addition, the gas sensors in each batch exhibit outstanding repeatability and stability with small deviation, and the relative mean deviations toward formaldehyde in the aspect of response, response and recovery times are all about only 5% between batches. The controllable micro-nano-level film thickness and uniform surface achieved by inkjet printing technology are the compelling reasons for low detection limit and superb reproducibility of gas sensors. Our work can offer a theoretical and experimental basis for large-scaled production of high-performance gas sensors from research to practical application.

Glucose determination using amperometric non-enzymatic sensor based on electroactive poly(caffeic acid)@MWCNT decorated with CuO nanoparticles.

A novel non-enzymatic glucose sensor based on poly(caffeic acid)@multi-walled carbon nanotubes decorated with CuO nanoparticles (PCA@MWCNT-CuO) was developed. The described approach involves the complexation/accumulation of Cu(II) on PCA@MWCNT followed by electrochemical CuO deposition in analkaline electrolyte. The morphology and surface characteristics of the nanomaterial were determined by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), Raman spectroscopy, and inductively coupled plasma mass spectrometry (ICP-MS). A hybrid-support sensor device was then developed to assess the glucose concentration in different solutions. The sensitivity of the electrode is 2412 μA mM-1cm-2. The electrode exhibited a broad linear range of 2µM to 9mM and a low limit of detection (LOD) of 0.43µM (relative standard deviation, RSD = 2.3%) at + 0.45Vvs Ag/AgCl. The excellent properties obtained for glucose detection were most likely due to the synergistic effect of the combination of individual components: poly(caffeic acid), MWCNTs, and CuO. Good accuracy and high precision were demonstrated for quantifying glucose concentrations in human serum and blood samples (the recovery ranged from 95.0 to 99.5%). The GC/PCA@MWCNT-CuO sensor represents a novel, simple, and low-cost approach to the fabrication of devices for amperometric sensing of glucose.

Hierarchical CuO nanostructured materials for acetaldehyde sensor application

A nanocrystalline CuO with mixed morphologies (nanorods, nanoplates and nanoparticles) were prepared using simple room temperature wet chemical synthesis route. The nanostructured CuO material was characterized using FESEM, TEM, EDS, elemental mapping, UV–visible spectroscopy, and BET surface area techniques for various physicochemical characteristics. The gas sensor device was fabricated using CuO nano-powder and its acetaldehyde gas sensing properties was investigated. The CuO sensor showed excellent sensing response towards 20–100 ppm acetaldehyde. The acetaldehyde response of the CuO sensor was recorded at various operating temperatures as well as concentrations. The responses of 418% and 115% were noted for 100 ppm and 20 ppm acetaldehyde concentration at 180 °C respectively. The higher selectivity of the CuO sensor was observed towards acetaldehyde among various gases. The transient response of the sensor was observed to be consistent with concentrations. The dynamic repetitive response of the sensor was tested at 100 ppm acetaldehyde that revealed to be same. The sensor's stability was tested and observed to be quite stable. A brief acetaldehyde sensing mechanism for CuO sensor was elucidated. The easy and large-scale formation of CuO nanostructures without growth controlling surfactants, and the good selectivity of the high response acetaldehyde sensor at relatively low operating temperatures may pave pathway for future gas sensor technology.

Green and ultrafast preparation of layered CuO nanoparticles and its ultrahigh-performance ethanol sensing application

Accurately controlling and rapidly fabricating ultra-sensitive micro/nano-scale CuO sensors without the assistance of any assembly template or organic solvent was a major challenge recently. In this work, a flower-like Cu3(PO4)2 precursor was prepared within 10 s by an ultrasonic spray method, and then the precursor was soaked in 80 °C NaOH solutions to rapidly prepare CuO material with different microscopic morphologies. Through testing the sensing performance of CuO products for 400 ppm ethanol, it was found that the highest sensitivity of CuO nanoparticles prepared by this method reached 135 (response/recovery time was 173 s/118 s respectively), which was much higher than CuO nanorods and CuO nanosheets, and the sensitivity for 10 ppm ethanol reached 19.9, indicating that the product had an ultra-high sensitivity and an ultra-low detecting limit. At the same time, the optimal detecting temperature has been reduced to 225 °C, while still retaining excellent selectivity, reproducibility, and stability. Furthermore, the whole process only took several minutes, instead of several-day reacting process in the previous work. It provided a way for the rapid fabrication of ultra-sensitive CuO sensor in a green strategy.

A simple approach for sensing and accurate prediction of multiple organic vapors by sensors based on CuO nanowires

• CuO nanowires have been synthesized using a facile solution phase method. • The room-temperature operability of CuO sensors were developed for methanol, acetone and acetonitrile and might aid in reducing the power requirements of the sensors. • A simple algorithm was developed in this research that could predict the vapors fairly accurately. • The prediction accuracy of the algorithm was improved when high-temperature data was included with room temperature data. • This work includes integration and application of knowledge of different domains to aid in prototype and product development. Development of sensors that can sense volatile organic compounds (VOCs) efficiently is imperative for different real-life applications. This paper reports synthesis of CuO nanowires using a facile solution-phase technique. The samples were found to have monoclinic polycrystalline structure when characterized using an X-ray diffractometer (XRD). The morphology was confirmed to be nanowires with diameter of approximately 10 nm when studied using field emission scanning electron microscope (FESEM), and the bandgap of the CuO nanowires was found to be 1.9 eV when characterized using UV–vis spectroscopy. The CuO nanowires based sensors were tested for five different concentrations (500–7000 ppm) of methanol, acetone, and acetonitrile at room temperature (25 °C) and four different concentrations (500–5000 ppm) of the three vapors at 200 °C. At room temperature, the response of the sensor ranged between 4.3 % and 29.9 %, 0.83 % and 14.7 %, and 1 % and 7 % for 500–7000 ppm methanol, acetonitrile, and acetone respectively. The response of the sensor was observed to be ranging between 13 % and 70 %, 150 % and 700 %, and 610 % and 2300 % for 500–5000 ppm of methanol, acetonitrile, and acetone respectively when tested at 200 °C. A novel and simple algorithm was developed that considered the initial 60 s responses of CuO nanowires exhibited for methanol, acetone, and acetonitrile at room temperature and at 200 °C and could predict the vapors along with their concentrations accurately.

Urchin like CuO hollow microspheres for selective high response ethanol sensor application: Experimental and theoretical studies

Herein, the synthesis, characterizations and gas sensor application of nano-textured urchin like CuO hollow microspheres (HM) were reported. The detailed characterizations confirmed the uniform growth and nanocrystalline monoclinic structure of urchin like CuO HM. The synthesized urchins like CuO HM were utilized to fabricate resistive sensor devices which exhibited elevated response towards ethanol with high selectivity. The optimization of operating temperature was carried out for the highest ethanol response and the effect of different concentrations were also recorded. The sensor device showed 1241% response at an operating temperature of 225 °C for 100 ppm ethanol concentration. The lowest ethanol was detected at 25 ppm having the response of 49% by the fabricated CuO sensor device. Transient responses as well as stability of the sensor were analyzed. The selectivity of CuO sensor device was studied for NO2, CO2, CH4 and H2 gases and remarkably it was seen that the developed gas sensor devices demonstrated outstanding selectivity towards ethanol gas. Finally, the density functional theory (DFT) computational quantum modelling was utilized in order to understand the adsorption phenomenon of ethanol and oxygen molecules in the sensing application. An ethanol sensing mechanism using CuO sensor was also elucidated.