Gaseous Analytes Research Articles

Photoactivated Pd-Loaded WO3 for Enhanced H2 S Sensing

In this article, pristine WO3 and Pd-loaded WO3 are synthesized via facile hydrothermal method and integrated with the Internet of Things (IoT)-enabled portable resistance readout circuit for real-time sensing performance measurement of the fabricated sensor toward <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{H}_{{2}}\text{S}$ </tex-math></inline-formula> . A series of characterizations are performed to investigate the crystal structure, surface morphology, active surface area, and elemental composition of the synthesized materials. Pristine WO3 nanoplates show a 9.13 sensing response toward 100-ppm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{H}_{{2}}\text{S}$ </tex-math></inline-formula> exposure, while loading of 0.25 and 0.5 mol% Pd further improves the response up to 14.37 and 23.45, respectively. However, further loading of Pd (1 mol%) on WO3 nanoplates reduces the sensing response to 15.29. The fabricated 0.5 mol% Pd-loaded WO3 sensor is investigated under thermal and photoenergy excitations. Moreover, the temperature optimization of 0.5 mol% Pd-loaded WO3 exhibits a higher sensing response of 47.8 at 100 °C. Furthermore, under visible and ultraviolet (UV) illumination, the 0.5 mol% Pd-loaded WO3 sensor response increases from 47.8 to 57.3 and 63. The fabricated 0.5 mol% Pd-loaded WO3 sensor exhibits remarkable response, shorter response–recovery time, and ultraselectivity toward analyte gas.

Investigations of methane gas sensor based on biasing operation of n-ZnO nanorods/p-Si assembled diode and Pd functionalized Schottky junctions

In this work, we developed methane gas sensors based on zinc oxide nanorod (n-ZnO-NR) arrayed assembly, synthesized using aqueous phase deposition on p-Si(100) substrates, fabricated as pn junction besides chemical sensitization by Pd (Pdcat/n-ZnO-NR) and Pd-30wt%Ag (Pd–Agcat/n-ZnO-NR) forming Schottky junctions. These sensors are evaluated under reducing methane [CH4] gas with varying concentration (100–10,000 ppm or 0.01–1.0%) mixed with synthetic air under optimum temperature (≤200–230 °C) for thermal activation and UV A (365 nm) light activation supplemented with 50–100 °C, following increased electrical conductivity, bandgap narrowing, decreased barrier height, under biasing operation. The performance metrics include a high response (R; 45–80%), low limit of detection (LOD; 80–270 ppm), fast response-recovery times (<1–67 s), and strong binding constants (0.012–0.021), quantified from saturation current, transient response, and Langmuir adsorption isotherm, respectively. Every factor inducing a change in oxygen content of analyte gas atmosphere above ZnO include: (1) surface chemical reaction with chemisorbed oxygen ions on pristine and Pdcat or Pd-Agcat modified n-ZnO-NR yields electron donors increasing sensor conductance; (2) effective free carrier concentration and amplified interface-dipole allowing reduced barrier height and electron tunneling at high reverse bias prevailing depletion-driven mechanism; (3) faster electron transport shortening the response time due to weakened oxygen ion adsorption removed by analyte gas molecules; and finally, (4) in-depth study of thermal and UV activated processes is supported with space charge model and band-bending theory perspectives.

Electronic nose based on multiple electrospinning nanofibers sensor array and application in gas classification

To mimic the human olfactory system, an electronic nose (E-nose, also known as artificial olfactory) has been proposed based on a multiple gas sensor array and a pattern recognition algorithm. Detection of volatile organic components (VOCs) has many potential applications in breath analysis, food quality estimation, and indoor and outdoor air quality monitoring, etc. In this study, a facile single-needle electrospinning technology was applied to develop the four different semiconductor metal oxide (MOS) nanofibers sensor arrays (SnO2, CuO, In2O3 and ZnO, respectively). The array shows a smooth surface and constant diameter of nanofiber (average of 150 nm) resulting in high sensitivity to multiple target analyte gases. Five human health related VOCs gases were measured by fabricated E-nose and different response patterns were obtained from four MOS nanofibers sensors. Combined with feature extraction from the response curves, a principal component analysis (PCA) algorithm was applied to reduce the dimension of feature matrix, Thus, the fabricated E-nose system successfully discriminated five different VOCs gases. Real-time and non-invasive gas monitoring by E-nose is very promising for application in human health monitoring, food monitoring, and other fields.

Obtaining of ZnO/Fe2O3 Thin Nanostructured Films by AACVD for Detection of ppb-Concentrations of NO2 as a Biomarker of Lung Infections

ZnO/Fe2O3 nanocomposites with different concentration and thickness of the Fe2O3 layer were obtained by two-stage aerosol vapor deposition (AACVD). It was shown that the ZnO particles have a wurtzite structure with an average size of 51-66 nm, and the iron oxide particles on the ZnO surface have a hematite structure and an average size of 23-28 nm. According to EDX data, the iron content in the films was found to be 1.3-5.8 at.%. The optical properties of the obtained films were studied, and the optical band gap was found to be 3.16-3.26 eV. Gas-sensitive properties at 150-300 °C were studied using a wide group of analyte gases: CO, NH3, H2, CH4, C6H6, ethanol, acetone, and NO2. A high response to 100 ppm acetone and ethanol at 225-300 °C and a high and selective response to 300-2000 ppb NO2 at 175 °C were established. The effect of humidity on the magnitude and shape of the signal obtained upon NO2 detection was studied.

Silk and its composites for humidity and gas sensing applications.

Silk fibroin (SF) is a natural protein largely used in the textile industry with applications in bio-medicine, catalysis as well as in sensing materials. SF is a fiber material which is bio-compatible, biodegradable, and possesses high tensile strength. The incorporation of nanosized particles into SF allows the development of a variety of composites with tailored properties and functions. Silk and its composites are being explored for a wide range of sensing applications like strain, proximity, humidity, glucose, pH and hazardous/toxic gases. Most studies aim at improving the mechanical strength of SF by preparing hybrids with metal-based nanoparticles, polymers and 2D materials. Studies have been conducted by introducing semiconducting metal oxides into SF to tailor its properties like conductivity for use as a gas sensing material, where SF acts as a conductive path as well as a substrate for the incorporated nanoparticles. We have reviewed gas and humidity sensing properties of silk, silk with 0D (i.e., metal oxide), 2D (e.g., graphene, MXenes) composites. The nanostructured metal oxides are generally used in sensing applications, which use its semiconducting properties to show variation in the measured properties (e.g., resistivity, impedance) due to analyte gas adsorption on its surface. For example, vanadium oxides (i.e., V2O5) have been shown as candidates for sensing nitrogen containing gases and doped vanadium oxides for sensing CO gas. In this review article we provide latest and important results in the gas and humidity sensing of SF and its composites.

Ratiometric optical oxygen sensor based on perovskite quantum dots and Rh110 embedded in an ethyl cellulose matrix

Ratiometric optical sensor gas sensing continues to develop optical sensing techniques and materials used in various industrial and environmental applications. This research focuses on a new ratiometric optical sensor using the development of new material of FAPbI3 perovskite QDs and a simple method to detect oxygen (O2) gas. FAPbI3 perovskite QDs are used as an indicator of oxygen gas, and rhodamine 110 (Rh 110) is a reference material in a ratiometric optical sensor. All of the sensing and reference materials are embedded in an ethyl cellulose (EC) matrix and coated on the surface of the filter paper. Using a UV LED with a central wavelength of 380 nm as the excitation light source, the emission spectra results show that the emission wavelengths of the oxygen-sensitive dye (O2) FAPbI3 perovskite QDs do not overlap with the Rh 110 reference signal. Thus, oxygen concentration can be measured using a ratiometric fluorescence reference-based approach. The sensing signal will be obtained in the presence of analyte gas in the ratiometric sensitivity of R0/R100, where R0 and R100 represent the luminescence intensity detected in 100% nitrogen and 100% oxygen concentrations, respectively. The experimental results show the optical oxygen sensor's sensitivity as R0/R100 = 12.7. In addition, the response time and recovery of the oxygen gas sensor produced are 75 s and 93 s, respectively. The use of a new type of FAPbI3 perovskite QDs material has been successfully developed in the optical ratiometric sensor for oxygen gas. The sensor proposed in this study has a low cost and easy fabrication process. The effect of spurious fluctuations in the excitation source intensity can be suppressed by the ratiometric optical sensing method.

Array Point Discharge as Enhanced Tandem Excitation Source for Miniaturized Optical Emission Spectrometer.

A new compact tandem excitation source was designed and constructed by using an array point discharge (ArrPD) microplasma for a miniaturized optical emission spectrometer through coupling a hydride generation (HG) unit as a sample introduction device. Three pairs of point discharges were arranged in sequence in a narrow discharge chamber to construct the ArrPD microplasma, for improved excitation capability owing to the serial excitation. Besides, the discharge plasma region was greatly enlarged, therefore, more gaseous analytes could be intercepted to enter into the microplasma for sufficient excitation, for improved excitation efficiency and OES signal. To better understand the effectiveness of the proposed ArrPD source, a new instrument for simultaneous detection of atomic emission and absorption spectral responses was also proposed, designed, and constructed to reveal the excitation and enhancement process in the discharge chamber. Under the optimized conditions, the limits of detection (LODs) of As, Ge, Hg, Pb, Sb, Se, and Sn were 0.7, 0.4, 0.05, 0.7, 0.3, 2, and 0.08 μg L-1, respectively, and the relative standard deviations (RSDs) were all less than 4%. Compared with a commonly used single point discharge microplasma source, the analytical sensitivities of these seven elements were improved by 3-6-fold. Certified Reference Materials (CRMs) were successfully analyzed with this miniaturized spectrometer, which features low power, compactness, portability, and high detectability, and is thereby a great prospect in the field of elemental analytical chemistry.

Amperometric sensor for gaseous H2O2 based on copper redox mediator incorporated electrolyte

The determination of gases and other volatile compounds using electrochemical gas sensors remains a challenge with respect to sensitivity and selectivity. Many real-life situations require fast, sensitive, and yet easy-to-operate sensors for gaseous hydrogen peroxide (H2O2) that can operate at room temperature. Herein, we present an H2O2 gas sensor comprising a polyacrylic acid and NaOH gel electrolyte that included Cu(II) ions acting as a redox mediator and commercially available screen-printed carbon electrodes. Aqueous polyacrylate gel electrolyte containing Cu(II) provided for sensing material that enabled the accumulation and stabilization of the gaseous analyte and via redox interaction with Cu(II) its fast and sensitive detection. The designed sensor exhibited good sensitivity in the low mg m−3 range with a wide linear response in the examined concentration range of 10–100 mg m−3 and a rapid detection after only 2 min accumulation under ambient conditions. Sensor's relatively simple setup and solid electroanalytical performance have strong application potential in emerging fields such as clinical diagnostics, explosive detection, environmental monitoring and occupational health and safety.

Application of Titanium Carbide MXenes in Chemiresistive Gas Sensors.

The titanium carbide MXenes currently attract an extreme amount of interest from the material science community due to their promising functional properties arising from the two-dimensionality of these layered structures. In particular, the interaction between MXene and gaseous molecules, even at the physisorption level, yields a substantial shift in electrical parameters, which makes it possible to design gas sensors working at RT as a prerequisite to low-powered detection units. Herein, we consider to review such sensors, primarily based on Ti3C2Tx and Ti2CTx crystals as the most studied ones to date, delivering a chemiresistive type of signal. We analyze the ways reported in the literature to modify these 2D nanomaterials for (i) detecting various analyte gases, (ii) improving stability and sensitivity, (iii) reducing response/recovery times, and (iv) advancing a sensitivity to atmospheric humidity. The most powerful approach based on designing hetero-layers of MXenes with other crystals is discussed with regard to employing semiconductor metal oxides and chalcogenides, noble metal nanoparticles, carbon materials (graphene and nanotubes), and polymeric components. The current concepts on the detection mechanisms of MXenes and their hetero-composites are considered, and the background reasons for improving gas-sensing functionality in the hetero-composite when compared with pristine MXenes are classified. We formulate state-of-the-art advances and challenges in the field while proposing some possible solutions, in particular via employing a multisensor array paradigm.

Flexible, Low-Cost, and Room Temperature Ammonia Sensor Based on Polypyrrole and Functionalized MWCNT Nanocomposites in Extreme Bending Conditions

We report a flexible and room temperature ammonia sensor based on polypyrrole/functionalized multiwalled carbon nanotubes (Ppy/f-MWCNTs). This nanocomposite has been synthesized by the in-situ chemical oxidative polymerization method and finally loaded on a transparent poly(vinylidene fluoride) (PVDF) membrane substrate. The entire flexible sensor fabrication process was cost-effective and easy to operate, making it ideal for commercial production on a wide scale. The optimized Ppy/f-MWCNT-based flexible sensor demonstrates improved sensing characteristics (26.5% for 100 ppm) with a low response time of 16 s and high response toward ammonia compared with pristine Ppy. In addition, high repeatability and long-term stability were also observed over a concentration range of 5–200 ppm. It shows high response toward ammonia among various gaseous analytes. Furthermore, the flexible sensor was mechanically robust and could produce a high response value even in extreme bending conditions. The flexible Ppy/f-MWCNT-based flexible sensors offer potential applications in advanced wearable devices to detect ammonia in the ambient environment.

One-dimensional In2O3 nanofibers patterned onto functionalized catalytic electrodes: A novel approach for selective xylene detection

Remarkable efforts have been devoted for enhancing gas selectivity of chemiresistors via tuning the sensing materials. However, the selective detection of low reactive gases remains challenging. Herein, we report a new strategy for selective detection of low reactive gases by patterning nanofibers and tuning the catalytic property of electrode. In this approach, straight single In2O3 nanofibers are patterned onto Au, Pt, and ITO interdigitated electrodes (IDEs) via direct-write near-field electrospinning; the resulting low coverage of the sensing materials (∼0.12%) exposes the electrode to analyte gases. The gas sensing characteristics of the sensors are determined by the catalytic activity of each electrode. Furthermore, the functionalization of Pt IDE with Au nanoparticles could achieve extremely high selectivity and response toward xylene. The sensing properties and mechanisms of the nanopatterned sensors are investigated regarding electrode composition, degree of electrode exposure, and catalyst location on the electrode and/or sensing materials. The key strategies for achieving high selectivity are the conversion of low reactive xylene gas into more reactive intermediate species while highly reactive interference gases are completely oxidized at open catalytic electrodes. Catalyst functionalization and exposure of electrodes can provide new guidelines for designing high performance gas sensors for new applications.

Mid-Wave Infrared Graphene Photodetectors With High Responsivity for On-Chip Gas Sensors

On-chip integration of mid-wave infrared (MWIR) absorption spectroscopy gas sensors is a powerful approach to massproducing compact and inexpensive devices and systems. Moreover, this approach opens new horizons for sophisticated applications in environmental monitoring, quality control, and Internet-of-Things networks. Nonetheless, further development of integrated photonic devices that can operate at the MWIR band is essential. Towards that end, we propose an MWIR graphene photodetector that is integrated into silicon-on-sapphire (SOS) slot waveguides for on-chip absorption spectroscopy applications. This configuration boosts the electric field distribution of the guided mode, which enhances the effective absorption of graphene. In addition, the presence of the guided mode in the slotted air region permits significant interaction with the analyte gas, which is a significant advantage for absorption spectroscopy. The sensing performance of the device is quantified by investigating its minimum detectable concentration of the three most prevalent greenhouse gases in the U.S.: carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Numerical results reveal that sub-ppb detection of these gases is achievable at the chip scale. These promising findings pave the way for the emergence of novel designs of portable, inexpensive, and highly sensitive sensors that are integrated into miniaturized electronic–photonic chipsets.

Enhanced transverse magneto-optical Kerr effect using ferromagnetic metal perforated with nanopore arrays.

Enhancement of transverse magneto-optical Kerr effects (T-MOKEs) based on surface plasmon resonance has attracted wide attention because of their high sensing performance. Most studies, however, mainly focus on prism-based magnetoplasmonic structures or architectures that incorporate a noble metal lattice and ferromagnetic layer, hindering device fabrication, miniaturization, and integration into a microfluidic sensing configuration. Herein, we propose a single Co6Ag94 ferromagnetic-metal layer perforated with a square nanopore array system with a pronounced T-MOKE magnitude 51 times higher than that of a smooth film, and with potential to detect gaseous analytes. The proposed system is sufficient to detect gaseous media for early environmental monitoring and enables an accessible pathway for magneto-optical sensor design.

The Ti0.2V1.8C MXene Ink-Prepared Chemiresistor: From Theory to Tests with Humidity versus VOCs

The 2D structure of MXenes attracts wide research attention toward an application of these materials in gas sensors. These structures are extremely sensitive to minor variations in their composition, which are employed for tuning their functional properties. Here, we consider the partially substituted MXenes of the composition of TixV2-xC, where x = 0.2, via quantum chemical calculations, and test their chemiresistive characteristics as a receptor component of the planar-type sensor and on-chip multisensor array. We thoroughly discuss the synthesis process of Ti0.2V1.8AlC MAX-phase and the corresponding MXenes, to prepare functional inks and, furthermore, deposit the films by microextrusion printing over an array of planar multi-electrode structures at the surface of a pen-sized chip. The crystal structure of the obtained materials is evaluated via X-ray diffraction analysis. The developed chip has been exposed upon few gaseous analytes, of alcohol VOCs, NH3, and H2O, of a 500–16,000 ppm concentration, at room temperature to ensure that we could observe the positive chemiresistive effect matured from resistance enhancing, with up to 10% vs. water vapors. The calculations carried in the framework of the density-functional theory for V2C, Ti2C, and Ti0.2V1.8C crystals ensured that the variations in their electronic structure were almost consistent with the experiment fundings: the most prominent effect is observed in relation to the H2O vapors. Therefore, these Ti0.2V1.8C structures could be considered for applying them in room temperature-operated hygrometers.

Polyethyleneimine-Starch Functionalization of Single-Walled Carbon Nanotubes for Carbon Dioxide Sensing at Room Temperature.

There is an ever-growing interest in the detection of carbon dioxide (CO2) due to health risks associated with CO2 emissions. Hence, there is a need for low-power and low-cost CO2 sensors for efficient monitoring and sensing of CO2 analyte molecules in the environment. This study reports on the synthesis of single-walled carbon nanotubes (SWCNTs) that are functionalized using polyethyleneimine and starch (PEI-starch) in order to fabricate a PEI-starch functionalized SWCNT sensor for reversible CO2 detection under ambient room conditions (T = 25 °C; RH = 53%). Field-emission scanning electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy are used to analyze the physiochemical properties of the as-synthesized gas sensor. Due to the large specific surface area of SWCNTs and the efficient CO2 capturing capabilities of the amine-rich PEI layer, the sensor possesses a high CO2 adsorption capacity. When exposed to varying CO2 concentrations between 50 and 500 ppm, the sensor response exhibits a linear relationship with an increase in analyte concentration, allowing it to operate reliably throughout a broad range of CO2 concentrations. The sensing mechanism of the PEI-starch-functionalized SWCNT sensor is based on the reversible acid-base equilibrium chemical reactions between amino groups of PEI and adsorbed CO2 molecules, which produce carbamates and bicarbonates. Due to the presence of hygroscopic starch that attracts more water molecules to the surface of SWCNTs, the adsorption capacity of CO2 gas molecules is enhanced. After multiple cycles of analyte exposure, the sensor recovers to its initial resistance level via a UV-assisted recovery approach. In addition, the sensor exhibits great stability and reliability in multiple analyte gas exposures as well as excellent selectivity to carbon dioxide over other interfering gases such as carbon monoxide, oxygen, and ammonia, thereby showing the potential to monitor CO2 levels in various infrastructure.

Terahertz Spectroscopic Molecular Sensor for Rapid and Highly Specific Quantitative Analytical Gas Sensing

Quantitative analytical gas sampling is of great importance in a range of environmental, safety, and scientific applications. In this article, we present the design, operation, and performance of a recently developed tabletop terahertz (THz) spectroscopic molecular sensor capable of rapid (minutes) and sensitive detection of polar gaseous analytes with near "absolute" specificity. A novel double-coil absorption cell design and an array of room-temperature sorbent-based preconcentration modules facilitate quantitative THz detection of light polar volatile compounds, which often challenge the capabilities of established gas sensing techniques. Acetone, ethanol, methanol, acetaldehyde, formaldehyde, and isoprene are detected at low parts-per-billion to high parts-per-trillion levels. This work evaluates performance-limiting factors for THz spectroscopy-based chemical identification: (1) spectral signal to noise and (2) preconcentrator efficiency.

Surface Enhancement Using Black Coatings for Sensor Applications.

The resolution of a quartz crystal microbalance (QCM) is particularly crucial for gas sensor applications where low concentrations are detected. This resolution can be improved by increasing the effective surface of QCM electrodes and, thereby, enhancing their sensitivity. For this purpose, various researchers have investigated the use of micro-structured materials with promising results. Herein, we propose the use of easy-to-manufacture metal blacks that are highly structured even on a nanoscale level and thus provide more bonding sites for gas analytes. Two different black metals with thicknesses of 280 nm, black aluminum (B-Al) and black gold (B-Au), were deposited onto the sensor surface to improve the sensitivity following the Sauerbrey equation. Both layers present a high surface roughness due to their cauliflower morphology structure. A high response (i.e., resonant frequency shift) of these QCM sensors coated with a black metal layer was obtained. Two gaseous analytes, H2O vapor and EtOH vapor, at different concentrations, are tested, and a distinct improvement of sensitivity is observed for the QCM sensors coated with a black metal layer compared to the blank ones, without strong side effects on resonance frequency stability or mechanical quality factor. An approximately 10 times higher sensitivity to EtOH gas is reported for the QCM coated with a black gold layer compared to the blank QCM sensor.

Strategies to combat the fouling and surface texture issues associated with fabric-based colorimetric sensors

Colorimetric arrays are low-cost, portable options for numerous sensing applications and are bolstered by the possibility of using high-quality smartphone imaging for signal readouts. Despite advances in the use of colorimetric sensors in the biomedical, environmental, and food safety fields, reliable fabric-based colorimetric sensors for wearable applications have not yet been fully developed. There are two major issues that attenuate the sensitivity and selectivity of fabric-based wearable colorimetric sensors in comparison to their paper-based counterparts. First, wearable colorimetric sensors are subject to fouling by body oils and other biomolecules during wear. Second, fabric surfaces are highly rough and textured, which reduces the efficacy of portable imaging and complicates signal readout. In this work, a fabric-based colorimetric sensing platform is developed based on optimized chemistry and post-image processing. A colorimetric array on natural fabrics was created via sol-gel chemistry and encapsulated using photoinitiated chemical vapor deposition. This fabrication strategy yields sensors with robust color fastness, antifouling ability, fast colorimetric response, recoverability, and mechanical stability when it is exposed to a model gaseous analyte, ammonia. Moreover, it is found that the texture problem introduced by the fabric substrate can be mitigated by image pixel manipulation after the images are captured. The accuracy for classifying different pH levels by the fabric sensor array is improved after the image sharpening technique is applied. These successful demonstrations of both qualitative and quantitative analysis of vapor and aqueous solutions sensing illustrate the practical suitability of this fabric-based sensing platform, which is appealing to advanced wearable monitoring.

Palladium/Graphene Oxide Nanocomposite for Hydrogen Gas Sensing Applications Based on Tapered Optical Fiber.

Gaseous pollutants such as hydrogen gas (H2) are emitted in daily human activities. They have been massively studied owing to their high explosivity and widespread usage in many domains. The current research is designed to analyse optical fiber-based H2 gas sensors by incorporating palladium/graphene oxide (Pd/GO) nanocomposite coating as sensing layers. The fabricated multimode silica fiber (MMF) sensors were used as a transducing platform. The tapering process is essential to improve the sensitivity to the environment through the interaction of the evanescent field over the area of the tapered surface area. Several characterization methods including FESEM, EDX, AFM, and XRD were adopted to examine the structure properties of the materials and achieve more understandable facts about their functional performance of the optical sensor. Characterisation results demonstrated structures with a higher surface for analyte gas reaction to the optical sensor performance. Results indicated an observed increment in the Pd/GO nanocomposite-based sensor responses subjected to the H2 concentrations increased from 0.125% to 2.00%. The achieved sensitivities were 33.22/vol% with a response time of 48 s and recovery time of 7 min. The developed optical fiber sensors achieved excellent selectivity and stability toward H2 gas upon exposure to other gases such as ammonia and methane.

Learning from Headspace Sampling: a Versatile High-Throughput Reactor for Photochemical Vapor Generation.

Inspired by the headspace sampling (HS) device, a versatile high-throughput photochemical reactor with twenty vessels serving as both the photochemical vapor generator and the HS device was developed for the rapid and sensitive determination of mercury, nickel, and selenium by coupling photochemical vapor generation (PVG) to atomic fluorescence spectrometry (AFS) or point discharge optical emission spectrometry (μPD-OES). The photochemical reactor utilized a specially designed annular UV lamp around which the vessels containing sample solution were automatically rotated and irradiated to yield gaseous analyte species. Subsequently, the species escaped into the headspace of vessels prior to introduction to the atomic spectrometer. Compared with the conventional flow injection (FI) or continuous flow (CF) PVG, the developed PVG-HS method possesses several unique advantages including high throughput (260 pcs h-1), high sensitivity, and the elimination of matrix interference from transition metal ions and the memory effect associated with the quantification of mercury. Limits of detection (LODs) of 0.002, 0.007, and 0.01 μg L-1 were obtained for Hg (II), Ni (II), and Se (IV) by PVG-HS-AFS, respectively, and 0.02 and 0.2 μg L-1 were obtained for Hg (II) and Ni (II) by PVG-HS-μPD-OES, respectively. The practicality of the reactor was evaluated by the detection of Hg (II), Ni (II), and Se (IV) in five certified reference materials, including water (GBW08603, GBW08607, and GBW(E)080395), National Research Council Canada dogfish liver (DOLT-5), fish protein (DORM-4), and three river water samples with good recoveries (92-106%).