Ppb-level Detection Research Articles

Nanoscale Bimetallic AuPt-Functionalized Metal Oxide Chemiresistors: Ppb-Level and Selective Detection for Ozone and Acetone.

As the most widely used gas sensors, metal oxide semiconductor (MOS)-based chemiresistors have been facing great challenges in achieving ppb-level and selective detection of the target gas. The rational design and employment of bimetallic nanocatalysts (NCs) are expected to address this issue. In this work, the well-shaped and monodispersed AuPt NCs (diameter ≈ 9 nm) were functionalized on one-dimensional (1D) In2O3 nanofibers (NFs) to construct efficient gas sensors. The sensor demonstrated dual-selective and ppb-level detection for ozone (O3) and acetone (C3H6O) at different optimal working temperatures. For the possible application exploitation, a circuit was designed to monitor O3 concentration and provide warnings when the concentration safety limit (50 ppb) was exceeded. Moreover, simulated exhaled breath measurements were also carried out to diagnose diabetes through C3H6O concentration. The selective detection for O3 and C3H6O was further analyzed by principal component analysis (PCA). The drastically enhanced sensing performances were attributed to the synergistic catalytic effect of AuPt NCs. Both the "spillover effect" and the Schottky barrier at the interfaces of AuPt NCs and In2O3 NFs promoted the sensing processes of O3 and C3H6O.

A dual-responsive bio-amicable fluorophore for trace level recognition of Zn2+ and Cd2+: Prefatory diagnosis of neoplastic disease from urine and ALS from saliva

A fluorogenic and electrochemical chemosensor BHMMP has been synthesized for aqueous phase ppb level detection of Zn2+ and Cd2+. The chemosensor exhibited distinct CHEF-based turn-on fluorometric transformation upon the addition of Zn2+ and Cd2+ respectively. Distinct fluorogenic response of BHMMP in presence of urinary excreted Zn2+ and human salivary Cd2+ indorsed the chemosensor towards a prefatory diagnostic tool for urinary Neoplastic disease and salivary Amyotrophic Lateral Sclerosis (ALS). The bio-compatibility of BHMMP was validated through in-vitro detection of Zn2+ and Cd2+ distinctively in the MCF-7 cancer cell line. BHMMP exhibited a paper-strip-based distinct fluorogenic response upon the addition of a trace amount of Zn2+ and Cd2+. A lumino-readable ‘information storage system’ was developed which strengthened the on-field applicability of BHMMP. The sensing response was rejuvenated by the addition of EDTA2−, which showcased a design of a four-input-three-output ‘fishtail’ mimicking logic gate circuitry. Sensing phenomena were corroborated through, Photoluminescence, ESI-MS, cyclic voltammetry, 1H NMR, FTIR, and DLS along with an in-silico approach. Additionally, synthesized ‘H’ type organic nano aggregate out of BHMMP (BHMMP-ONA) exhibited F− scavenging efficiency in a wide range of contaminated water samples. Therefore, the multichannel applications of this probe are expected to find imminent effectiveness in the realm of point-of-care testing.

Enhanced room temperature NO2 sensing performance based on N-doped carbon nanosheets@ZnO nanoplates by morphology transition and white light illumination

Highly-sensitive gas sensors operating at room temperature (RT) have been pursued by researchers due to their high security, energy saving and long-term stability. Herein, N-doped carbon nanosheets-incorporated zinc oxide (NCZ) was synthesized via solution calcination combined with hydrothermal method and utilized for ppb level detection of NO2 at RT. Intriguingly, the construction of N-doped carbon nanosheets was accompanied by generation of ZnO nanoparticles, and then be transferred into mesoporous nanoplates. The as-synthesized NCZ(120)-300 nanocomposites demonstrated high sensitivity to 3 ppm NO2 (|Rg-R0|/R0=∼28.2), along with fast response/recovery (60 s/129 s) speed, excellent selectivity and cyclic stability. In particular, the morphology transition of ZnO greatly enhanced the RT NO2 sensing performance of the as-prepared sensor. Meanwhile, the white light illumination further ameliorated the sensor’s properties involving ∼ 2.1 times enhancement of sensitivity and shorter recovery process (accelerated from 563 s to 129 s). These enhancements are ascribed to the heterostructure between ZnO nanoplates and N-doped carbon nanosheets, and the modulation of electron structure by photo-generated electron-hole pairs. In addition, the 2D N-doped carbon nanosheets and mesoporous ZnO nanoplates offer numerous active adsorption-sites, which improved the surface chemical activity of NCZ(120)-300.

The sampling and phase characterisation of black mass

“Black mass” is the industry term used to describe a type of e-waste comprising crushed and shredded battery cells. It is an intermediate product in the recycling of spent, end-of-life, batteries. It comprises a mixture of metals including; lithium, manganese, cobalt and nickel, which are valuable recycling commodities, of increasing strategic and economic importance to meet future global demands in the “battery revolution”. The objective of this “phase characterisation” investigation was to provide an indicative profile of the morphological characteristics, grain size, composition and textural variability for a natural state (unprepared) and prepared (powdered) sample of black mass from Europe. It is envisaged that this is relevant to: (a) develop a pragmatic sampling strategy to ensure a non-biased, representative sample is provided for assaying; (b) determine the optimal processing route (e.g., hydrometallurgical, pyrometallurgical); (c) identify the presence of payable phases; (d) identify phases that may hinder metal recovery or penalty components; (e) develop assay procedures; and (f) assist in the identification of hazards and the mitigation of risks. The techniques used were: (1) visual examination and binocular microscopy; (2) manual scanning electron microscopy (SEM); (3) automated scanning electron microscopy with linked energy dispersive spectrometers (SEM-EDS), to characterise the phases present and particle types (using AMICS); (4) X-ray computed tomography (X-CT) to provide the 3D morphology of the particles; and (5) laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) to detect and quantify the phases that cannot be detected using automated SEM-EDS and X-CT. The results demonstrated that automated SEM-EDS can be used to characterise and quantify the phases present, and the phase chemistry allows the particle types to be assigned back to the primary battery components. Some phases identified are at present not linked back to the original components and further work is needed to refine the compositional groups, with the analysis of additional samples from different feeds/streams in Europe, China and USA. Interactive SEM-EDS analysis also demonstrated that there is a high-resolution chemical variability within the individual particle categories. X-CT imaging demonstrated the complex 3D textures and morphology of the particles, which is potentially significant during sample preparation and chemical analysis. Neither automated nor manual interactive analysis can determine the presence / abundance of the light elements, such as lithium. However, LA-ICP-MS was successful in detecting and quantifying lithium. Furthermore, LA-ICP-MS was able to determine contents of 67 other non-metals and metals at a 20-micron scale with ppm to ppb level detection limits.

ZIF-8 derived ZnO@CeO2 heterojunction for ppb-level acetone detection

The development of high sensitivity acetone gas sensor is of great significance for air quality monitoring and diagnosis of diseases. Herein, ZIF-8 derived ZnO@CeO2 heterojunction was prepared by simple hydrothermal method to achieve ppb level detection of acetone. ZnO was decorated on the surface of CeO2 matrix by using ZIF-8 as sacrificial template, which was beneficial to enlarge the specific surface area and generate abundant oxygen vacancies (OV). ZnO@CeO2-1 min composites show excellent sensing performance towards acetone detection, with low detection limit (240 ppb), high response (32 for 100 ppm acetone) and good stability. Particularly, the electronic modulation of ZnO@CeO2 heterojunction increases the resistance variation during the sensing process, and OV increases the carrier concentration of sensitive materials, providing more active sites. The synergistic effect of the construction of ZnO@CeO2 heterostructure and the surface Ov can effectively improve the sensing performance. Our study provides an ingenious strategy to produce ZnO@CeO2 nanostructures as well as new insights for the detection of acetone.

Hydrogen sensor with ppb-level detection limit prepared by Pd-modified and Bi-doped oxidized Ni foam

In this work, we propose a hydrogen sensor to realize ppb-level hydrogen detection at a lower temperature. To fabricate the sensor, foamed nickel was thermally oxidized in bismuth oxide vapor to form the Bi-doped oxidized nickel foam, and Pd nanoparticles were further deposited on its surface by magnetron sputtering. This sensor possesses a unique phenomenon, that is, the response of the sensor does not decline due to repeated hydrogen charging and discharging as same as most hydrogen sensors, but keeps increasing and reaches balance eventually. The Bi3+ doping leads to a reduction in the thickness of the NiO hole accumulation layer, which contributes to the high response. The Bi5+ self-doping occurring during the repeated cycle test further promotes oxygen adsorption, so that the sensor response is continuously improved. As a result, the response of the Pd-Bi-OFN sensor to 1% hydrogen is as high as 580% in the air, and the detection limit is as low as 20 ppb at a lower temperature of 75 °C. Meanwhile, the sensor possesses high selectivity, great humidity stability, and long durability. This work provides an outstanding guidance to fabricate reliable ppb-level hydrogen sensors.

A room-temperature and ppb-level NO2 sensor based on n-CdS/p-CuO heterojunction modified with rGO nanosheets

In this work, novel mesoporous heterostructure of CdS/CuO/rGO composites was synthesized by a green and ultra-low-cost hydrothermal method. More importantly, the sensor shows significantly higher response of 12.46, which is about 5.3 times and 1.5 times of the CdS (2.36) and CdS/CuO (8.22) sensors, respectively. Besides, the fabricated sensors have ultra-low limit of detection (LOD) of 50 ppb, ensuring the ppb-level detection to NO2 gas in practical applications. Besides, the CdS/CuO/rGO sensor has excellent reversibility, good selectivity to NO2 gas against other gases (such as NH3, H2, CO and SO2), and reliable stability. The improvement of the gas sensing properties for CdS/CuO/rGO sensor is mainly ascribed to the existence of numerous active sites, which are able to enhance the adsorption capacity of target gas, improving the affinity for gas molecules. Furthermore, the heterojunction formed between CdS/CuO/rGO composites can provide conductive channel to accelerate carrier transfer to further improve the performance of the sensor. It is no doubt that our work will provide potential applications for improving gas sensing performance of a room-temperature NO2 sensor.

Ppb-level butanone sensor based on porous spherical NiO and the influence of silver modification

In this work, porous spherical UG-NiO nanomaterials is synthesized through a one-step hydrothermal process, and the samples are modified with precious metal silver (Ag) for ppb-level detection to butanone. The gas-sensitive test results show that the response of UG -NIO to 100 ppm of 2-butanone is 4 times that of U-NiO, and the response of modified 3.9% [email protected] to 100 ppm butanone is 3.1 timesthan that of UG-NiO. And both synthetic UG-NiO and [email protected] -NiO can detect 2-butanone at ppb level. Meanwhile, synthetic samples are characterized via X-ray diffraction measurements (XRD), the energy dispersive spectrometer (EDS) and scanning electron microscopy (SEM). Finally, the response mechanism is further explained by DFT.

Conductometric ppb-level triethylamine sensor based on macroporous WO3-W18O49 heterostructures functionalized with carbon layers and PdO nanoparticles

Effective detection of triethylamine (TEA) is considerable in view of human health and environment. However, both ppb-level detection and rapid response/recovery speed under extreme conditions such as high relative humidity and wide detection ranges remain challenging for TEA gas sensing. Herein, a facile one-spot solvothermal approach is used to synthesize urchin-like WO3-W18O49 heterostructures assisting with glucose modification and PdO functionalization. Benefiting from the hierarchical macroporous structure, synergistic effects, various heterojunctions along with sensitization of PdO, the sensor based on hierarchical WO3-W18O49 urchin with PdO and carbon decorating exhibits appealing TEA sensing performance including rapid response /recovery time (1 s/2 s) to 100 ppm TEA at 325 °C, high selectivity, superior anti-humidity property and extremely low detection limitation (50 ppb), which are much better than previously reported TEA sensors. Our research results open a facile pathway for the development of high-performance gas sensors in terms of real-time and ppb-level detection.

Hydrogen Sensor with Ppb-Level Detection Limit Prepared by Pd-Modified and Bi-Doped Oxidized Ni Foam

Hydrogen Sensor with Ppb-Level Detection Limit Prepared by Pd-Modified and Bi-Doped Oxidized Ni Foam

A Triethylamine Gas Sensor Based on Snse Nanofibers with Ppb-Level Detection Limit

A Triethylamine Gas Sensor Based on Snse Nanofibers with Ppb-Level Detection Limit

Optimization of Light-Analyte Interaction in Si3n4/Polymer Hybrid Waveguide for Sensitive Sensing of Pyridine Vapor with Ppb-Level Detection Limit

Optimization of Light-Analyte Interaction in Si3n4/Polymer Hybrid Waveguide for Sensitive Sensing of Pyridine Vapor with Ppb-Level Detection Limit

The ppb-level formaldehyde detection with UV excitation for yolk-shell MOF-derived ZnO at room temperature

The ppb-level detection at room temperature, urgently demanded in application, is such a promising and challenging technology for formaldehyde sensing. This research has achieved the yolk-shell structural Zn-MOF and MOF-derivates via adjusting the ratio of metal ions to organic-ligand in solvothermal process and subsequent calcination. Under the synergistic effect of yolk-shell MOF-derived structure and assistance of UV irradiation of 8.31 mW/cm2, the sensors exhibit superb sensing performance to formaldehyde even at room temperature about 20 ℃, i.e., the response/ recovery time and sensitivity of MOF-derived ZnO are respectively 6 s/22 s and ~ 14.05–100 ppm formaldehyde. More notably, the detection limit is as low as 100 ppb. The relevant mechanism is summarily interpreted as follows: (i) Yolk-shell structure MOF-derived ZnO with mesoporous provides affluent oxygen vacancies and excellent adsorption capacity; (ii) UV radiation produces the electron-hole pairs to increase intra-grain conductivity and facilitate the capture of oxygen ions at room temperature.

Feather-Shaped InGaN Nanorods for Selective ppb-Level Detection of NO2 Gas at Room Temperature

Feather-Shaped InGaN Nanorods for Selective ppb-Level Detection of NO₂ Gas at Room Temperature

UV Illumination as a Method to Improve the Performance of Gas Sensors Based on Graphene Field-Effect Transistors.

The ability to detect and recognize airborne chemical species is essential to enable applications in security, health, and environmental monitoring. Here, we report a sensing platform based on graphene field-effect transistor (GFET) devices combined with optical illumination for the detection of volatile compounds. We compare the change in resistance of GFET sensors upon exposure to analytes such as ethanol, dimethyl methylphosphonate (DMMP), and water vapors with and without the presence of a local illuminating ultraviolet (UV) light-emitting diode (LED). Our results show that UV illumination acts as a control knob for the electronic transport properties of graphene, increasing the device's response to ethanol, water, and DMMP, up to a factor of 54, and enabling ppb-level detection of DMMP at 800 ppb without chemical functionalization of the graphene layer. The sensing response can be optimized to reveal an analyte-specific interplay between the induced changes in carrier concentration and mobility of the GFET. These findings provide a pathway to enhancing the sensitivity of GFET sensors and a differentiation channel to improve their selectivity.

NiO-functionalized In2O3 flower-like structures with enhanced trimethylamine gas sensing performance

NiO-functionalized In2O3 flower-like structures were successfully synthesized via a simple one-step hydrothermal route and applied in gas sensors for trimethylamine (TMA) detection. By virtue of the unique 3D hierarchical flower-like structures, p-n heterojunctions and the catalytic activity of NiO, NiO-functionalized In2O3 shows enhanced TMA gas sensing performance. Specifically, the sensor fabricated from 0.05-NiO-In2O3 composites with well-defined flower-like structures shows the highest response of about 20.5 to 10 ppm TMA at 200 °C, which is 4.7 times higher than that of the pure In2O3 flower-like structures (4.4 to 10 ppm TMA). Besides, this sensor shows good reproducibility and stability, high selectivity and a ppb-level detection limit of 1.5 to 0.5 ppm (500 ppb) TMA, providing a widely applicable strategy to improve the gas sensing properties of metal oxides semiconductors.

Impact of Device Configurations on Sensing Performance of WS2-Based Gas Sensors: A Review

As 2D materials are aggressively penetrating the arena of conventional metal oxides-based gas sensors, tungsten disulfide (WS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) as a ‘beyond graphene and beyond MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layered material’ is appearing with shining visibility owing to its exquisite electronic, surface, optical, physicochemical and thermal properties. Micromechanically exfoliated or homogeneously/heterogeneously synthesized mono/few-layer(s) of this transition metal di-chalcogenide (TMDCs), with excellent tunability of almost all the properties, have intrigued worldwide gas sensor researchers to demonstrate various device configurations using WS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> leading to ultrahigh sensitivity with ppb level detection capacity even at room temperature. This review article presents a holistic overview of the WS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> based gas sensors encompassing the impact(s) of the different device architectures (viz. planar, Schottky, heterojunctions, field-effect, and heterojunction bipolar transistors) on the gas sensing performance indices (like sensitivity, selectivity, response/recovery time, humidity effect and baseline drift). Starting with the brief overview of the sensing mechanism of WS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , followed by elaborate discussions on the unique features/advantages and bottlenecks of each of the innovative device architecture investigated, this review concludes by focusing the possible direction to circumvent the most common challenges (like slow and incomplete recovery, vulnerability to humidity and oxidation), that slacken the commercial viability of such devices.

Room temperature ppb level detection of chlorine using peripherally alkoxy substituted phthalocyanine/SWCNTs based chemiresistive sensors

Carbon nanotubes (CNTs) have created their niche in the area of gas sensing applications because of their unique mechanical and electronic properties. Their long recovery time and inadequate or temperature-based recovery result in substandard sensing properties. In this account, to overcome these issues and to highlight the application of CNTs in trace level identification and sensitive detection of chlorine (Cl2), operating at room temperature; a hybrid of single-walled carbon nanotubes anchored with peripheral alkoxy substituted phthalocyanine has been prepared. The as-prepared samples have been characterized for their morphological properties via transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), and structural properties via Raman, UV–vis, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS) techniques. Moreover, N2-adsorption analysis reveals that Brunauer-Emmett-Teller (BET) surface area for hybrid increases more than three-fold in comparison to SWCNTs-COOH. At room temperature, gas sensing properties of fabricated hybrid sensors exhibit remarkable Cl2 sensing characteristics with a limit of detection up to 1.33 ppb. Moreover, the nature of the interaction between hybrid sensors and gas analytes has been explored based on spectroscopic studies.

Ultra-fast and low detection limit of H2S sensor based on hydrothermal synthesized Cu7S4-CuO microflowers

In this work, Cu7S4-CuO microflowers were successfully synthesized through a simple hydrothermal route. The influence of S doping amount on the corresponding microstructures and gas sensing properties of the composites are investigated. In the comparative gas sensing test, the sensor fabricated from Cu7S4-CuO (S/Cu = 27 mol%) microflowers exhibited the highest response (156–50 ppm) to hydrogen sulfide with a fast response and recovery time. Furthermore, Cu7S4-CuO (S/Cu =27 mol%) microflowers gas sensor not only showed superior hydrogen sulfide selectivity compared with other gases, but also ppb-level detection limit (100 ppb-16.2) at 225 °C, even lower detection limit (50 ppb-1.8). The synergistic effects between CuO and Cu7S4, more surface adsorbed oxygen, and active sites were regarded as the main reasons for the ultrasensitive and selective hydrogen sulfide detection.

Batch fabrication of formaldehyde sensors based on LaFeO3 thin film with ppb-level detection limit

High-performance formaldehyde sensors act a significant role in environmental monitoring and industrial gas analysis. However, the traditional side-heating type gas sensors fabricated by handicraft-like brush-painting or drop-casting methods still suffer from poor detection limits and the difficulty of massive fabrication, which hinders the further practical applications of gas-sensing devices. Herein, the uniform LaFeO3 thin film prepared through a facile sol-gel method combining with spin coating is proposed to achieve batch-fabricated gas sensors for the detection of gaseous formaldehyde. The fabricated gas sensor exhibits a low detection limit as low as 50 ppb toward gaseous formaldehyde, which is lower than the guideline value (80 ppb) limited by World Health Organization. Furthermore, the gas-sensing properties of batch-fabricated thin film gas sensors reveal satisfactory uniformity and replicability with low device-to-device deviation. The maximum variation of baseline resistance between different batch samples is only 5.4%, and the maximum drift of the response value toward formaldehyde is only 6.5%. The favorable gas-sensing performances and high replicability for the sensors might be attributed to the controllable fabrication process that can be completely compatible with the well-established semiconductor technics. This work will open up an effective pathway to prompt high-performance formaldehyde sensors with ppb-level detection limits toward practical applications.