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Herein, an oxidation‐controlled SnS2 gas sensor is reported. Different oxidation levels of SnS2 are constructed by adjusting the dosage ratio of reagents. The sensing response of oxidized SnS2 to NH3 is studied, and the working mechanism is explored. Results demonstrate that the different oxidation levels of SnS2 exhibit significantly improved gas‐sensing properties. In particular, oxidation‐controlled SnS2 (SnS2‐2 sample) shows a high response to NH3 (92 000%) with a fast response recovery time (17/2 s). The novelty of this work lies in the simple synthesis of SnS2 with oxidation regulation and its application as a high‐sensitivity NH3 gas sensor at room temperature. [ABSTRACT FROM AUTHOR]

Inspired by the structure of eggshell membranes, bacterial cellulose carbon nanofiber/AgO composite (BCCF-AgO) with a fibrous network was prepared by a one-step hydrothermal reaction. Material characterization showed that AgNO3 was an important catalyst for reducing the carbonization temperature to 120°C and spheric AgO nanoparticles came into being on the surface of carbon nanofibers. Thanks to successful formation of heterojunctions between the BCCF and AgO, the BCCF-AgO showed excellent sensitivity, good selectivity, fast response–recovery, good long-term stability (30 days), and a low detection limit (53.2 ppb) to hydrogen peroxide vapor at room temperature, providing a green, simple, and cheap strategy for a hydrogen peroxide gas sensor. [ABSTRACT FROM AUTHOR]

Waste human hair was carbonized into carbon sheets by a simple carbonization method, which was studied as gas sensing materials for the first time. The effect of carbonization temperature on the structure and gas sensing properties of hair-based carbon sheet was studied by scanning electron microscope, X-ray diffraction, infrared spectrum, Raman spectrum, and gas-sensitive tester. The results showed that the carbonization temperature had a significant effect on the structure and gas sensing performance of carbon sheets, which were doped with K, N, P, and S elements during carbonization. However, the sensor of the carbon sheet does not show good selectivity among six target gases. Fortunately, the carbon sheets prepared at different temperatures have different responses to the target gases. The sensor array constructed by the carbon sheets prepared at different temperatures can realize the discriminative detection of a variety of target gases. For the optimized carbon sheet, the theoretical limit of detection of hydrogen peroxide is 0.83 ppm. This work provides a reference for the resource utilization of waste protein and the development of gas sensors. [ABSTRACT FROM AUTHOR]

Carbon quantum dots (CQDs) co-doped with N, P and S derived from expired milk was prepared by a simple hydrothermal method. By dipping pure cotton face towel (PCFT) into CQDs ink, a flexible all-biomass CQDs/PCFT sensor was prepared for the first time. Due to the heteroatom doping, extremely small particle size of CQDs and excellent permeability of CQDs/PCFT film, the flexible CQDs/PCFT sensor showed the high sensitivity and bending stability. In the range of 0–60° bending states, the responses of CQDs/PCFT sensor to four target analytes changed by less 5.0%. After 3000 bending of 60°, the maximum change of the response to the target analytes was only 6.4%. Interestingly, due to the abundant functional groups and defects of CQDs, the flexible CQDs/PCFT sensor displayed sensing curves of different shapes for different target analytes. In this way, by establishing a database of sensing curves of target analytes, multiple analytes can be detected discriminatively by relying only on single sensor with the help of image recognition. This work provided a reference for the development of cotton fiber based all biomass flexible gas sensor. [ABSTRACT FROM AUTHOR]

Inspired by the structural similarity between the dog turbinate and bamboo, disposable bamboo chopsticks were carbonized into ordered tubular carbon materials. By optimizing the carbonization temperature, the biomimetic sensor of the ordered tubular carbon materials realizes the highly sensitive and selective detection of NH 3 at room temperature. This biomimetic sensor has been successfully used to monitor the freshness of meat in the actual environment. [Display omitted] • The biomimetic sensor derived from disposable bamboo chopsticks were created. • The structure–activity relation of biomimetic sensor was studied systematically. • Highly selective and sensitive detection of NH 3 was realized at room temperature. • Monitoring the freshness of mutton is achieved by the biomimetic sensor. Tens of billions of pairs of waste disposable bamboo chopsticks (DBC) are produced every year, and it is extremely important to utilize this resource effectively. Inspired by the structural similarity between the dog turbinate and bamboo, DBC were successfully carbonized into carbon materials with a similar structure to that of dog turbinate at different temperatures. The carbon materials derived from DBC were used gas sensors for the first time and the effect of carbonization temperature on the structures, carbon yield and gas sensing performance was studied. By optimizing the carbonization temperature, the biomimetic sensor realized the detection of ammonia (NH 3) with high sensitivity and selectivity, exhibited the high response (71.82 k%) to 500 ppm NH 3 at room temperature, and had a theoretical detection limit of 0.12 ppm. Furthermore, the biomimetic sensor showed excellent immunity to formaldehyde, acetone, relative humidity (RH) and other interference factors, and its response to 95% RH was less than one thousandth of that to 500 ppm NH 3. Compared with the fresh sensor, after 50 days the fluctuation of the sensor's response to NH 3 was less than 4.2%, and it still had excellent recovery capability in 10 consecutive response-recovery cycles. What's more, the biomimetic sensor has been successfully used to monitor the freshness of mutton in the actual environment. This study provides a reference for the development of low-cost and high-performance gas sensors and the effective utilization of biomass waste. [ABSTRACT FROM AUTHOR]

Herein, an oxidation‐controlled SnS2 gas sensor is reported. Different oxidation levels of SnS2 are constructed by adjusting the dosage ratio of reagents. The sensing response of oxidized SnS2 to NH3 is studied, and the working mechanism is explored. Results demonstrate that the different oxidation levels of SnS2 exhibit significantly improved gas‐sensing properties. In particular, oxidation‐controlled SnS2 (SnS2‐2 sample) shows a high response to NH3 (92 000%) with a fast response recovery time (17/2 s). The novelty of this work lies in the simple synthesis of SnS2 with oxidation regulation and its application as a high‐sensitivity NH3 gas sensor at room temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • N-doped porous carbon (NCOP) was prepared by simple carbonization of orange peel and applied for the first time in the field of gas sensors. • The enhancement of N doping on the gas sensitivity of NCOP was analyzed by first-principles calculations. • The gas sensitivity of the NCOP/RGO composite was further enhanced by p-n junctions between NCOP and RGO. In order to realize the resource utilization of waste orange peel, N-doped porous carbon derived from orange peel (NCOP) was prepared by simple carbonization and first used in the field of gas sensors. Compared with the reduced graphene oxide (RGO) and multi walled carbon nanotubes (MWCNTs), the responses of NCOP to five analytes were improved by 3.32 ∼ 66.72 times and the effect of N doping on the gas sensitivity of NCOP was analyzed by First-principles calculations. Furthermore, the NCOP/RGO composite with p-n junctions was prepared to improve the gas sensing properties. The theoretical limit of detection of NCOP and NCOP/RGO composites to formaldehyde vapor was determined to be 16.7 and 7.7 ppb, respectively. The response time and recovery time of NCOP and NCOP/RGO to all five analytes were no more than 15.9, 5.4 s and 14.4, 5.0 s, respectively. More importantly, the sensor array based on RGO, MWCNTs, NCOP and NCOP/RGO can discriminatively and quickly detect multiple analytes at room temperature. The study showed that both self-doping and heterojunction can effectively improve the gas sensitivity of biomass carbon materials, which provided a useful reference for the resource utilization of biomass waste and the development of gas sensors. [ABSTRACT FROM AUTHOR]

The uniform dispersion of multi-wall carbon nanotubes (MWNTs) in waterborne polyurethane (WPU) matrix was achieved by in-situ polymerization and latex particles assisted dispersion, endowing the MWNT/WPU composite film with the enhanced tensile strength, elongation at break and thermal stability. Compared with pure WPU, the breaking strength, elongation at break and initial decomposition temperature of the MWNT/WPU composite were increased by 69.6%, 16.4% and 130 °C, respectively. The decomposition amount at 400 °C of MWNT/WPU composite is only about half that of pure WPU. The latex particles assisted dispersion also effectively improved the exposure rate of MWNTs, making it easier for MWNTs to contact the target gas molecules. Increased exposure rate and uniform dispersion of MWNTs, and rich functional groups of WPU improved the gas sensing performance, making the response of the flexible MWNT/WPU to O 3 be 4.1 times of the responses of pure MWNTs. The limit of detection for O 3 reached 38.4 ppb. The enhanced mechanical properties endowed the flexible MWNT/WPU composite with the high bending stability and long-term stability. After one month, the response of the MWNT/WPU was changed by 3% and the responses decreased by no more than 10% after bending 5000 times. [Display omitted] • The uniform dispersion of MWNTs in WPU matrix was achieved by in-situ polymerization and latex particles assisted dispersion. • The evenly dispersed MWNTs endowed the MWNT/WPU composite with the enhanced mechanical and thermal properties. • Increased exposure rate of MWNTs and rich functional groups of WPU improved the gas sensing performance of flexible MWNT/WPU sensor. • The response of flexible MWNT/WPU was changed by 3% after one month and the responses decreased by no more than 10% after bending 5000 times. [ABSTRACT FROM AUTHOR]

For the first time, composite material with heterojunction structure prepared from covalent organic framework and biocarbon and used for aniline gas detection. The n-n heterojunction formed between iCOF and CMTs results in improved sensing performance for all gases, compared to CMTs. The iCOF-CMTs sensor is about 10 times more sensitive to aniline compared to iCOF and CMTs. This research provides a promising approach for producing composites of COFs and biocarbon. It also highlights the potential of using gas sensors for practical detection of aniline. [Display omitted] • For the first time, composite material with heterojunction structure prepared from covalent organic framework and biocarbon and used for aniline gas detection. • One response cycle for aniline was controlled at 26 s and the theoretical limit of detection for aniline was 10.26 ppb (below the OSHA limit of 5 ppm). • Compared to pure COFs, the composite of COFs with biocarbon provides excellent moisture resistance. • This study provides ideas for the detection of aniline at room temperature. Development of sensors for detecting aniline for environment, food quality, and medical diagnostics is highly anticipated. However, the high operating temperatures of current aniline sensors hinder their practical use. In this work, the carbon material with micron tube structure (CMTs) derived from lavender straw was used as a template, and the imine covalent organic frameworks (iCOF) was synthesized on the CMTs template at room temperature, forming the iCOF-CMTs with a heterojunction structure. This pioneering study combines COFs materials with biocarbon materials for the first time, allowing us to compare the gas sensing properties of iCOF, CMTs and iCOF-CMTs composites. Due to the presence of heterojunction, the iCOF-CMTs composites exhibited the good gas-sensitive properties among the three materials, especially for aniline vapor. The iCOF-CMTs sensors were tested at room temperature to eight different gases, with the highest response of 2155.75 % for aniline. For the iCOF-CMTs sensor to aniline, the sum of response and recovery times does not exceed 26 s in a response-recovery cycle, and the limit of detection reached 10.26 ppb. This study demonstrated that the special heterojunction structure greatly improved the sensing performance of iCOF and CMTs, providing ideas for further development of COFs-based gas sensors. [ABSTRACT FROM AUTHOR]