Light-Excited Ag-Doped TiO2−CoFe2O4 Heterojunction Applied to Toluene Gas Detection

(1) Background: Toluene gas is widely used in indoor decoration and industrial production, and it not only pollutes the environment but also poses serious health risks. (2) Methods: In this work, TiO2−CoFe2O4−Ag quaternary composite gas-sensing material was prepared using a hydrothermal method to detect toluene. (3) Results: The recombination of electron–hole pairs was suppressed, and the light absorption range was expanded after constructing a heterojunction and doping with Ag, according to ultraviolet–visible (UV–vis) diffuse reflectance spectra and photoluminescence spectroscopy. Moreover, in the detection range of toluene gas (3 ppm–50 ppm), the response value of TiO2−CoFe2O4−Ag increased from 2 to 15, which was much higher than that of TiO2−Ag (1.7) and CoFe2O4−Ag (1.7). In addition, the working temperature was reduced from 360 °C to 263 °C. Furthermore, its response/recovery time was 40 s/51 s, its limit of detection was as low as 10 ppb, and its response value to toluene gas was 3–7 times greater than that of other interfering gases under the same test conditions. In addition, the response value to 5 ppm toluene was increased from 3 to 5.5 with the UV wavelength of 395 nm–405 nm. (4) Conclusions: This is primarily due to charge flow caused by heterojunction construction, as well as metal sensitization and chemical sensitization of novel metal doping. This work is a good starting point for improving gas-sensing capabilities for the detection of toluene gas.

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Gas-sensing properties and in-situ diffuse-reflectance Fourier-transform infrared spectroscopy study of diethyl ether adsorption and reactions on SnO2 film

Materials Science-Poland ◽

10.1515/msp-2017-0037 ◽

2017 ◽

Vol 35 (2) ◽

pp. 265-274

Author(s):

Ning Wang ◽

Kaijin Huang ◽

Jian Song

Keyword(s):

Fourier Transform ◽

Infrared Spectroscopy ◽

Fourier Transform Infrared Spectroscopy ◽

Diethyl Ether ◽

Diffuse Reflectance ◽

Gas Sensing ◽

Fourier Transform Infrared ◽

Sensing Material ◽

Different Temperatures

Abstract Diethyl ether is a common industrial reagent and medical anesthetic. It is necessary to carry out real-time monitoring of this molecule due to its harmful effects on human health. In this paper, a highly sensitive diethyl ether SnO2 gas-sensing material has been prepared by a sol-gel method. The gas sensitivity was tested by a home-made gas-sensing equipment. The surface adsorption and reaction processes between the SnO2 gas-sensing film and the diethyl ether have been studied by in situ diffuse-reflectance Fourier-transform infrared spectroscopy (DRFT-IR) at different temperatures. The results show that the SnO2 gas-sensing material has high sensitivity to diethyl ether, and the lowest detection limit can reach 1 ppm. Furthermore, ethyl (CH3CH2●), oxoethyl (CH3CH2O●), ethanol (CH3CH2OH), formaldehyde (HCHO), acetaldehyde (CH3CHO), ethylene (C2H4), H2O and CO2 surface species are formed during diethyl ether adsorption at different temperatures. A possible mechanism of the reaction process is discussed.

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Berlin Green Framework-Based Gas Sensor for Room-Temperature and High-Selectivity Detection of Ammonia

Nano-Micro Letters ◽

10.1007/s40820-020-00586-z ◽

2021 ◽

Vol 13 (1) ◽

Author(s):

Tingqiang Yang ◽

Lingfeng Gao ◽

Wenxuan Wang ◽

Jianlong Kang ◽

Guanghui Zhao ◽

...

Keyword(s):

High Resistance ◽

Active Sites ◽

Density Functional ◽

Room Temperature ◽

High Selectivity ◽

Gas Sensing ◽

Response Recovery ◽

Sensing Material ◽

Agriculture Industry ◽

Ammonia Detection

AbstractAmmonia detection possesses great potential in atmosphere environmental protection, agriculture, industry, and rapid medical diagnosis. However, it still remains a great challenge to balance the sensitivity, selectivity, working temperature, and response/recovery speed. In this work, Berlin green (BG) framework is demonstrated as a highly promising sensing material for ammonia detection by both density functional theory simulation and experimental gas sensing investigation. Vacancy in BG framework offers abundant active sites for ammonia absorption, and the absorbed ammonia transfers sufficient electron to BG, arousing remarkable enhancement of resistance. Pristine BG framework shows remarkable response to ammonia at 50–110 °C with the highest response at 80 °C, which is jointly influenced by ammonia's absorption onto BG surface and insertion into BG lattice. The sensing performance of BG can hardly be achieved at room temperature due to its high resistance. Introduction of conductive Ti3CN MXene overcomes the high resistance of pure BG framework, and the simply prepared BG/Ti3CN mixture shows high selectivity to ammonia at room temperature with satisfying response/recovery speed.

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Fast Response Isopropanol Sensing Properties with Sintered BiFeO3 Nanocrystals

Materials ◽

10.3390/ma13173829 ◽

2020 ◽

Vol 13 (17) ◽

pp. 3829 ◽

Cited By ~ 1

Author(s):

Hongxiang Xu ◽

Junhua Xu ◽

Junlin Wei ◽

Yamei Zhang

Keyword(s):

Gas Sensing ◽

Fast Response ◽

Gas Detection ◽

Detection Range ◽

Sensing Properties ◽

Working Temperature ◽

Sensing Material ◽

Gas Sensing Properties ◽

Response And Recovery ◽

Optimum Working

BiFeO3 nanocrystals were applied as the sensing material to isopropanol. The isopropanol sensor based on BiFeO3 nanocrystals shows excellent gas-sensing properties at the optimum working temperature of 240 °C. The sensitivity of as-prepared sensor to 100 ppm isopropanol is 31 and its response and recovery time is as fast as 6 and 17 s. The logarithmic curves of the sensitivity and concentration of BiFeO3 sensors are a very good linear in the low detection range of 2–100 ppm. In addition, the gas sensing mechanism is also discussed. The results suggest that the BiFeO3 nanomaterial can be potentially applied in isopropanol gas detection.

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Hydrogen Gas Sensing Using Palladium-Graphene Nanocomposite Material Based on Surface Acoustic Wave

Journal of Nanomaterials ◽

10.1155/2017/9057250 ◽

2017 ◽

Vol 2017 ◽

pp. 1-6 ◽

Cited By ~ 8

Author(s):

Nguyen Hai Ha ◽

Nguyen Hoang Nam ◽

Dang Duc Dung ◽

Nguyen Huy Phuong ◽

Phan Duy Thach ◽

...

Keyword(s):

Acoustic Wave ◽

Surface Acoustic Wave ◽

Gas Sensing ◽

Specific Interaction ◽

High Sensitivity ◽

Fast Response ◽

Hydrogen Gas ◽

Chemical Route ◽

Response Recovery ◽

Sensing Material

We report the fabrication and characterization of surface acoustic wave (SAW) hydrogen sensors using palladium-graphene (Pd-Gr) nanocomposite as sensing material. The Pd-Gr nanocomposite as sensing layer was deposited onto SAW delay line sensor-based interdigitated electrodes (IDTs)/aluminum nitride (AlN)/silicon (Si) structure. The Pd-Gr nanocomposite was synthesized by a chemical route and deposited onto SAW sensors by air-brush spraying. The SAW H2 sensor using Pd-Gr nanocomposite as a sensing layer shows a frequency shift of 25 kHz in 0.5% H2 concentration at room temperature with good repeatability and stability. Moreover, the sensor showed good linearity and fast response/recovery within ten seconds with various H2 concentrations from 0.25 to 1%. The specific interaction between graphene and SAW transfer inside AlN/Si structures yields a high sensitivity and fast response/recovery of SAW H2 sensor based on Pd-Gr/AlN/Si structure.

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Multiformity of Photoelectron Storages in Functionalized Carbon Nitrides Enabling Reversible and Adaptable Colorimetric Sensing

10.26434/chemrxiv-2021-bwqxn ◽

2021 ◽

Author(s):

Dan Han ◽

Hong Yang ◽

Zhixin Zhou ◽

Kaiqing Wu ◽

Jin Ma ◽

...

Keyword(s):

Limit Of Detection ◽

Raw Materials ◽

High Sensitivity ◽

Terminal Group ◽

Blue Color ◽

Colorimetric Sensing ◽

Electron Hole ◽

Detection Range ◽

Linear Detection ◽

Easy Operation

Colorimetric sensing has been widely used for centuries across diverse fields, thanks to easy operation with no electricity and uncompromised high sensitivity. However, the limited number of chromogenic systems hampers its broader applications. Here, we reported that carbon nitride (CN), the raw materials-abundant and cheap semiconductors with photoelectron storage capability, can be developed as a new chromogenic platform for colorimetric sensing. Beyond most photoelectron storage materials that only demonstrated blue color in the excited state, CN could also exhibit brown color by terminal group functionalization. The experiments and DFT theoretical calculation revealed the origin of the unusual two types of color switches. Cyano and carbonyl terminal groups in CN elongated the centroids distance of electron/hole and stabilized the excited states through a physical and electrochemical pathway, respectively; meanwhile, the counter cations strengthened these processes. As a result, the CN-derived colorimetric O2 sensors demonstrated excellent reversibility in recycling hundreds of times for detection, and exhibited adaptable limit of detection and linear detection range, which was superior to commercial O2 sensors, especially for complex systems with broad variable concentrations.

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Hydrothermal Synthesis of Hierarchical SnO2 Nanostructures for Improved Formaldehyde Gas Sensing

Nanomaterials ◽

10.3390/nano12020228 ◽

2022 ◽

Vol 12 (2) ◽

pp. 228

Author(s):

Pengyu Ren ◽

Lingling Qi ◽

Kairui You ◽

Qingwei Shi

Keyword(s):

Gas Sensors ◽

Indoor Environment ◽

Gas Sensing ◽

Structural Difference ◽

Sno2 Nanostructures ◽

One Dimensional ◽

Response Recovery ◽

Sensing Material ◽

Gas Sensing Properties ◽

Volatile Organic

The indoor environment of buildings affects people’s daily life. Indoor harmful gases include volatile organic gas and greenhouse gas. Therefore, the detection of harmful gas by gas sensors is a key method for developing green buildings. The reasonable design of SnO2-sensing materials with excellent structures is an ideal choice for gas sensors. In this study, three types of hierarchical SnO2 microspheres assembled with one-dimensional nanorods, including urchin-like microspheres (SN-1), flower-like microspheres (SN-2), and hydrangea-like microspheres (SN-3), are prepared by a simple hydrothermal method and further applied as gas-sensing materials for an indoor formaldehyde (HCHO) gas-sensing test. The SN-1 sample-based gas sensor demonstrates improved HCHO gas-sensing performance, especially demonstrating greater sensor responses and faster response/recovery speeds than SN-2- and SN-3-based gas sensors. The improved HCHO gas-sensing properties could be mainly attributed to the structural difference of smaller nanorods. These results further indicate the uniqueness of the structure of the SN-1 sample and its suitability as HCHO- sensing material.

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Optimization of a Low-Power Chemoresistive Gas Sensor: Predictive Thermal Modelling and Mechanical Failure Analysis

Sensors ◽

10.3390/s21030783 ◽

2021 ◽

Vol 21 (3) ◽

pp. 783 ◽

Cited By ~ 1

Author(s):

Andrea Gaiardo ◽

David Novel ◽

Elia Scattolo ◽

Michele Crivellari ◽

Antonino Picciotto ◽

...

Keyword(s):

Low Power ◽

Failure Analysis ◽

Gas Sensors ◽

High Performance ◽

Gas Sensing ◽

Mechanical Failure ◽

Sensing Applications ◽

Theoretical Approaches ◽

Sensing Material ◽

Silicon Bulk

The substrate plays a key role in chemoresistive gas sensors. It acts as mechanical support for the sensing material, hosts the heating element and, also, aids the sensing material in signal transduction. In recent years, a significant improvement in the substrate production process has been achieved, thanks to the advances in micro- and nanofabrication for micro-electro-mechanical system (MEMS) technologies. In addition, the use of innovative materials and smaller low-power consumption silicon microheaters led to the development of high-performance gas sensors. Various heater layouts were investigated to optimize the temperature distribution on the membrane, and a suspended membrane configuration was exploited to avoid heat loss by conduction through the silicon bulk. However, there is a lack of comprehensive studies focused on predictive models for the optimization of the thermal and mechanical properties of a microheater. In this work, three microheater layouts in three membrane sizes were developed using the microfabrication process. The performance of these devices was evaluated to predict their thermal and mechanical behaviors by using both experimental and theoretical approaches. Finally, a statistical method was employed to cross-correlate the thermal predictive model and the mechanical failure analysis, aiming at microheater design optimization for gas-sensing applications.

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Discovery and Optimization of Selective Inhibitors of Meprin α (Part I)

Pharmaceuticals ◽

10.3390/ph14030203 ◽

2021 ◽

Vol 14 (3) ◽

pp. 203 ◽

Cited By ~ 1

Author(s):

Shurong Hou ◽

Juan Diez ◽

Chao Wang ◽

Christoph Becker-Pauly ◽

Gregg B. Fields ◽

...

Keyword(s):

Inhibitory Activity ◽

De Novo ◽

Selective Inhibitors ◽

Preclinical Development ◽

Starting Point ◽

Good Starting Point ◽

Parallel Screening ◽

Low Cytotoxicity

Meprin α and β are zinc-dependent proteinases implicated in multiple diseases including cancers, fibrosis, and Alzheimer’s. However, until recently, only a few inhibitors of either meprin were reported and no inhibitors are in preclinical development. Moreover, inhibitors of other metzincins developed in previous years are not effective in inhibiting meprins suggesting the need for de novo discovery effort. To address the paucity of tractable meprin inhibitors we developed ultrahigh-throughput assays and conducted parallel screening of >650,000 compounds against each meprin. As a result of this effort, we identified five selective meprin α hits belonging to three different chemotypes (triazole-hydroxyacetamides, sulfonamide-hydroxypropanamides, and phenoxy-hydroxyacetamides). These hits demonstrated a nanomolar to micromolar inhibitory activity against meprin α with low cytotoxicity and >30-fold selectivity against meprin β and other related metzincincs. These selective inhibitors of meprin α provide a good starting point for further optimization.

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A Compact Detection Platform Based on Gradient Guided-Mode Resonance for Colorimetric and Fluorescence Liquid Assay Detection

Sensors ◽

10.3390/s21082797 ◽

2021 ◽

Vol 21 (8) ◽

pp. 2797

Author(s):

Jing-Jhong Gao ◽

Ching-Wei Chiu ◽

Kuo-Hsing Wen ◽

Cheng-Sheng Huang

Keyword(s):

Limit Of Detection ◽

Detection System ◽

Fluorescence Emission ◽

Assay Sensitivity ◽

Detection Range ◽

Current Form ◽

Guided Mode ◽

Spectral Detection ◽

Guided Mode Resonance ◽

Colorimetric Assays

This paper presents a compact spectral detection system for common fluorescent and colorimetric assays. This system includes a gradient grating period guided-mode resonance (GGP-GMR) filter and charge-coupled device. In its current form, the GGP-GMR filter, which has a size of less than 2.5 mm, can achieve a spectral detection range of 500–700 nm. Through the direct measurement of the fluorescence emission, the proposed system was demonstrated to detect both the peak wavelength and its corresponding intensity. One fluorescent assay (albumin) and two colorimetric assays (albumin and creatinine) were performed to demonstrate the practical application of the proposed system for quantifying common liquid assays. The results of our system exhibited suitable agreement with those of a commercial spectrometer in terms of the assay sensitivity and limit of detection (LOD). With the proposed system, the fluorescent albumin, colorimetric albumin, and colorimetric creatinine assays achieved LODs of 40.99 and 398 and 25.49 mg/L, respectively. For a wide selection of biomolecules in point-of-care applications, the spectral detection range achieved by the GGP-GMR filter can be further extended and the simple and compact optical path configuration can be integrated with a lab-on-a-chip system.

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Advances on the Implementation of Circular Economy Techniques in Rural Areas in Colombia under a Sustainable Development Framework

Sustainability ◽

10.3390/su13073816 ◽

2021 ◽

Vol 13 (7) ◽

pp. 3816

Author(s):

Javier Rodrigo-Ilarri ◽

Camilo-A. Vargas-Terranova ◽

María-Elena Rodrigo-Clavero ◽

Paula-A. Bustos-Castro

Keyword(s):

Sustainable Development ◽

Waste Management ◽

Circular Economy ◽

Rural Areas ◽

Development Framework ◽

Starting Point ◽

Management Plans ◽

Good Starting Point ◽

Depressed Regions ◽

First Time

For the first time in the scientific literature, this research shows an analysis of the implementation of circular economy techniques under sustainable development framework in six municipalities with a depressed economy in Colombia. The analysis is based on solid waste data production at a local scale, the valuation of the waste for subsequent recycling, and the identification and quantification of the variables associated with the treatment and final disposal of waste, in accordance with the Colombian regulatory framework. Waste generation data are obtained considering three different scenarios, in which a comparison between the simulated values and those established in the management plans are compared. Important differences have been identified between the waste management programs of each municipality, specifically regarding the components of waste collection, transportation and disposal, participation of environmental reclaimers, and potential use of materials. These differences are fundamentally associated with the different administrative processes considered for each individual municipality. This research is a good starting point for the development of waste management models based on circular economy techniques, through the subsequent implementation of an office tool in depressed regions such as those studied.

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