Ppb Level Research Articles

Al2O3-Encapsulated TiO2 flower-like spherical mesoporous material for efficient removal of PCl3 traces

Solar energy is considered the most promising sustainable green energy source. Currently, more than 95% of solar energy development and utilization is based on silicon, especially polysilicon. In the production of polysilicon, the PCl3 impurity content must be removed to the ppb level to ensure product performance. Al2O3 has been confirmed to be effective at removing PCl3 at ppm levels, however, it suffers from weak adsorption capacity, slow adsorption rate and low adsorption efficiency in the case of PCl3 in ppb levels. In this work, by encapsulating Al2O3 on TiO2, a flower-like spherical adsorbent ([Al2O3]3[TiO2]1) was prepared. The experimental results show that after introducing TiO2, the adsorption performance of [Al2O3]3[TiO2]1 for PCl3 in ppb levels is significantly improved, 34.1% higher than that before introducing TiO2. Five adsorption–desorption cycles indicate that [Al2O3]3[TiO2]1 has excellent regeneration property. Characterization analysis and density functional theory(DFT) simulations suggest that PCl3 interacts with the adsorbent primarily through charge transfer.

In suit decorating PdPt bimetals on titanium dioxide nanosheets for detecting ppb level of carbon monoxide and hydrogen

The catalyst with strong metal-support interactions often exhibits high catalytic activity. This study aims to prepare sensitive materials with strong metal-MOS interactions and explore their sensitization mechanism. Sn-PdPt/TiO2 was obtained by in-situ decorating PdPt bimetals on the surface of TiO2 NSs using Sn2+ as the reducing agent, and PdPt/TiO2 was prepared by traditional reduction method. Compared with TiO2 sensor, PdPt/TiO2 and Sn-PdPt/TiO2 sensors exhibited higher sensitivity, selectivity, lower operating temperature (200 °C) and detection limit (ppb level) to CO and H2. The sensitization of PdPt bimetal to TiO2 should be ascribed to the high catalytic activity of PdPt bimetal towards O2, H2 and CO, Schottky barrier at the interface between TiO2 and PdPt NPs, and the multiple valence states (Pd0, Pd2+ and Pd4+) of Pd will undergo mutual transformation during gas sensing reactions. And Sn-PdPt/TiO2 sensor exhibited higher sensitivity, selectivity and better stability than those of PdPt/TiO2 sensor, which can be attributed to the introduction of SnO2 and the stronger interaction between PdPt and TiO2 due to the in-situ reduction reaction. This study can provide some reference for preparing the MOS based gas sensing materials with strong metal-support interactions and understanding the sensitization mechanism of PdPt bimetal.

Eco(geno)toxicity of the new commercial insecticide Platinum Neo, a mixture of the neonicotinoid thiamethoxam and the pyrethroid lambda-cyhalothrin

New mixtures of pesticides are being placed on the market to increase the spectrum of phytosanitary action. Thus, the eco(geno)toxic effects of the new commercial mixture named Platinum Neo, as well as its constituents the neonicotinoid Thiamethoxam and the pyrethroid Lambda-Cyhalothrin, were investigated using the species Daphnia magna, Raphidocelis subcapitata, Danio rerio, and Allium cepa L. The lowest- and no-observed effect concentration (LOEC and NOEC) were measured in ecotoxicological tests. While Thiamethoxam was ecotoxic at ppm level, Lambda-Cyhalothrin and Platinum Neo formulation were ecotoxic at ppb level. The mitotic index (MI), chromosomal aberrations and micronucleus [MN] frequency were measured as indicators of phytogenotoxicity in A. cepa plants exposed for 12 h to the different insecticides and their mixture under different dilutions. There were significant alterations in the MI and MN frequency in comparison with the A. cepa negative control group, with Thiamethoxam, Lambda-Cyhalothrin, and Platinum Neo treatments all significantly reducing MI and increasing MN frequency. Thus, MI reduction was found at 13.7 mg L−1 for Thiamethoxam, 0.8 μg L−1 for Lambda-Cyahalothrin, and 2.7:2 μg L−1 for Platinum Neo, while MN induction was not observed at 14 mg L−1 for Thiamethoxam, 0.8 μg L−1 for Lambda-Cyahalothrin, and 1.4:1 μg L−1 for Platinum Neo. The insecticide eco(geno)toxicity hierarchy was Platinun Neo > Lambda-Cyhalothrin > Thiamethoxam, and the organism sensitivity hierarchy was daphnids > fish > algae > A. cepa. Eco(geno)toxicity studies of new pesticide mixtures can be useful for management, risk assessment, and avoiding impacts of these products on living beings.

Simultaneous quantification of Hg(II) and Pb(II) by square wave anodic stripping voltammetry using Bi/graphite electrode

In the present work, we report the synthesis and evaluation of a graphite-supported bismuth film working electrode (BiFE) in the simultaneous quantification of Hg(II) and Pb(II) at ppb levels. The BiFE was synthesized in-situ by electrodeposition in 1 M HNO3 as the supporting electrolyte at −0.5 V potential. A design of experiments and a response surface model (RSM) were developed to optimize the parameter of bismuth concentration ([Bi]) and deposition time (tdep) in the synthesis of the BiFE. The electrodeposition conditions of [Bi] = 3 mM and tdep = 10s proved to be the optimal conditions for the highest sensitivity and selectivity of the synthesized working electrode. For the quantification of Hg(II) and Pb(II), the electrochemical technique of square wave anodic stripping voltammetry (SWASV) was used by applying a deposition potential of −1 V in 1 M acetic acid buffer solution. The optimization of the factors analyzed in the design of experiments allowed the simultaneous detection of Hg(II) and Pb(II) at limiting levels of 1 ppb and 10 ppb, respectively. The calibration curves of Hg(II) and Pb(II) present an R2 of 0.988 and 0.982, respectively.

Enhanced Corrosion Resistance in Aluminum-Based Electrolyzer Components via Stoichiometry Tuned Atomic Layer-Deposited TiOx Films.

Titanium (Ti) is widely used as anode current collectors in proton exchange membrane (PEM)-based water electrolyzers due to its self-passivated oxide layer, which protects it from corrosion in acidic solutions. However, the cost of the material and machining process for Ti is high. A wider utilization of water electrolyzers to produce hydrogen could be favored by the use of less expensive coated aluminum (Al) substrates, which could potentially replace high-cost Ti-based components. It is shown here by depositing a pinhole-free oxygen vacancy-rich titanium oxide (TiOx) protection layer by atomic layer deposition (ALD), the corrosion resistance of Al substrates in acidic environments at oxygen evolution potentials can be enhanced. The optimization of the oxygen vacancy concentration is accomplished by tuning the ALD parameters to achieve ideal stoichiometry and conformal coating on rough substrates. The robustness of the coatings was evaluated at high potentials (2.4 V vs NHE = normal hydrogen electrode) in low pH conditions. A low TiOx dissolution rate of the order of ∼6 nm year-1 was observed. By testing under industrially relevant conditions, i.e., high applied voltages (2.4 V) and low pH, an Al loss at around the zero ppb level was achieved using optimized ALD parameters. It is proposed that a 40 nm TiOx coating on Al may be adequate to provide 60,000 h of durability in a PEM water electrolyzer anode current collector.

Enhanced impregnation of iron‑manganese binary oxide nanoparticles on nylon 6 fibre for rapid and continuous arsenic [As(III)] removal from drinking water

Arsenic in drinking water causes serious health problems and must be brought below the permissible 10 ppb limit rapidly, for on-spot remediation. Household reverse osmosis (RO) units remove As(III) partially. To address this, a post-RO adsorbent is developed based on iron‑manganese binary oxide nanoparticles (IMBNP) impregnated nylon 6 fibre (IMBNP-nylon 6). By optimizing H2SO4 concentration and by reducing temperatures of both IMBNP impregnation and subsequent vacuum drying, IMBNP size on fibre surface could be reduced from 320 to 75 nm. This resulted in increased IMBNP loading on the fibre from 1.4 to 9.3–10 wt%, giving a high adsorption capacity of 48.7 mg As(III)/g of IMBNP-nylon 6 fibre. IMBNP has a synergistic role here, since its MnO2 component oxidises As(III) to As(V), which is more effectively adsorbed by its Fe2O3 component; this in contrast to poor adsorption of As(III), when only Fe2O3 is used. The IMBNP-nylon 6 composite, in continuous fixed bed experiments with feed water of 100 ppb As(III), facilitates removal of arsenic below 10 ppb level, with only 39 s contact time. Overall, this work demonstrates the potential scalability of this technique to treat a large amount of arsenic-containing permeate water in household RO units.

Boron-Salphen Conjugate based Molecular Probe Exhibiting Fluorescence On-Off-On Response in Detection of Cu2+ and ATP through Displacement Approach.

Synthesis and photophysical properties of a fluorescent probe HBD is described. Probe upon interaction with metal ions, anions and nucleoside pyrophosphates (NPPs) showed fluorescence quenching with Cu2+ due to chelation enhanced quenching effect (CHEQ). Moreover, interaction of ensemble HBD.Cu2+ with anions and NPPs showed fluorescence "turn-On" response with ATP selectively. "On-Off-On" responses observed with Cu2+ and ATP is attributed to an interplay between ESIPT and TICT processes. Cyclic voltammogram of probe exhibited quasi-reversible redox behaviour with three oxidation and two reduction potentials and the change in band gaps of probe suggested the interaction with Cu2+ and ATP. The 2 : 1 and 1 : 1 binding stoichiometry for an interaction between probe and Cu2+ (LOD, 62 nM) and ensemble, HBD.Cu2+ with ATP (LOD, 0.4 μM) respectively are realised by Job's plot and HRMS data. Cell imaging studies carried out to detect Cu2+ and ATP in HeLa cells. Also, the output emission observed with Cu2+ and ATP is utilized to construct an implication (IMP) logic gate. Test paper strips showed naked-eye visible color responses to detect Cu2+ and ATP. In real water samples probe successfully detected copper (0.03 μM) between 5-6.5 ppb level (ICP-MS method).

Mesoporous CdO/CdGa2O4 microsphere for rapidly detecting triethylamine at ppb level

Developing fast, accurate and sensitive triethylamine gas sensors with low detection limits is paramount to ensure the safety of workers and the public. However, sensors based on single metal oxide materials still suffer from drawbacks such as low response sensitivity and long response and recovery times. To address these challenges, in this work, a series of mesoporous CdO/CdGa2O4 microspheres were synthesized. We optimized the sensor's sensing performance to triethylamine by fine-tuning the ratio of CdO to CdGa2O4. Among them, CdO:3CdGa2O4-based sensor demonstrates a rapid response time of 2 s to detect 100 ppm of triethylamine, with a high response value of 211 and exceptional selectivity. Furthermore, it exhibits a low detection limit of 20 ppb for triethylamine, making it suitable for practically testing fish freshness. Crucially, electron transfer between the heterojunctions increases the chemically adsorbed oxygen on the materials’ surface, thereby enhancing the sensor's response sensitivity to triethylamine. This discovery provides new insights and methodologies for the design of highly efficient triethylamine gas sensors.

Impurity characterization in diamond for quantum and electronic applications: advances with time-resolved cathodoluminescence

The ultimate purity of synthetic diamond crystals is currently limited by traces of boron and nitrogen. Here we study diamond crystals grown at high-pressure high-temperature, which are made of 3D growth sectors with variable residual impurity contents. The boron concentration is found in the 0.5–6.4 ppb range thanks to continuous cathodoluminescence analysis. Time-resolved cathodoluminescence experiments complete the impurity analysis with measurements of free exciton lifetimes. From them, we deduced an estimate of the nitrogen concentration at the ppb level, from 0.6 to 30 ppb depending on the growth sectors. We identified n-type, p-type and highly compensated regions, which illustrates the potential of cathodoluminescence as a local characterization tool for qualifying diamond for electronic and quantum applications.

The intense charge migration and efficient photocatalytic NO removal of the S-scheme heterojunction composites Bi7O9I3-BiOBr

For purpose of efficient photocatalytic removal of NO molecules, both components of bismuth-rich Bi7O9I3 and BiOBr were typically selected to create binary heterojunction composites Bi7O9I3-BiOBr (BI-BBX) through a facile in-situ synthetic protocol. These composites underwent thorough characterization using a range of analytical methods and were subjected to photocatalytic removal of NO at ppb level under visible light for the first time. These produced composites showed enhanced photocatalytic behavior and the best candidate BI-BB0.2 demonstrated the highest removal efficiency among all tested samples. Density-functional theory (DFT) calculations revealed the intense charge migration at the interface. In addition, the composites surface exhibited a propensity to adsorb and activate O2, H2O, and NO molecules, thus promoting the catalytic conversion of NO to NO2– and further NO3– species. Entrapping experiments and electron spin resonance (ESR) results demonstrated the increased generation of oxygen-containing species O2–, 1O2, and ·OH, which was attributed to the rational creation of heterojunctions with similar crystal structures and efficient migration and separation of generated charge carriers in an S-scheme model. This study provides insight into the design and development of Bi7O9I3-based composites for effective dislodge of NO upon the visible-light irradiation.

Construction of a CoNiHHTP MOF/PHI Z-Scheme Heterojunction for ppb Level NO2 Photoelectric Sensing with 405 nm Irradiation at RT.

Ultrasensitive photoelectric detection of nitrogen dioxide (NO2) with PHI under visible light irradiation at room temperature (RT) remains an ongoing challenge due to the low charge separation and scarce adsorption sites. In this work, a dimensionally matched ultrathin CoNiHHTP MOF/PHI Z-scheme heterojunction is successfully constructed by taking advantage of the π-π interactions existing between the CoNiHHTP MOF and PHI. The amount-optimized heterojunction possesses a record detection limit of 1 ppb (response = 15.6%) for NO2 under 405 nm irradiation at RT, with reduced responsive (3.6 min) and recovery (2.7 min) times, good selectivity and reversibility, and long-time stability (150 days) compared with PHI, even superior to others reported at RT. Based on the time-resolved photoluminescence spectra, in situ X-ray photoelectron spectra, and diffuse reflectance infrared Fourier transform spectroscopy results, the resulting sensing performance is attributed to the favorable Z-scheme charge transfer and separation. Moreover, the Ni nodes favorably present in adjacent metal sites between the lamellae contribute to charge transfer and redistribution, whereas Co nodes could act as selective centers for promoted adsorption of NO2. Interestingly, it is confirmed that the CoNiHHTP MOF/PHI heterojunction could effectively reduce the influence of O2 in the gas-sensitive reaction due to their unique bimetallic (Co and Ni) nodes, which is also favorable for the improved sensing performances for NO2. This work provides a feasible strategy to develop promising PHI-based optoelectronic gas sensors at RT.

Engineering the defect distribution via boron doping in amorphous TiO2 for robust photocatalytic NO removal

Nitric oxide (NO) pollutant can threaten the regional environment and human health. Solar-powered photocatalytic oxidation method is desirable for NO removal (ppb level) at ambient conditions, but suffers from the unsatisfactory activity and poor selectivity due to the sluggish molecular oxygen activation. Herein, we demonstrate that efficient photocatalytic NO removal can be realized by modulating the defects distribution of amorphous TiO2 via boron doping. Theoretical calculations and experimental results reveal that H3BO3 modification can refine the structure of surface oxygen vacancies, promoting electron-rich molecular oxygen activation to •OH. Meanwhile, bulk-phase oxygen defects can be filled by free-state B atoms, accelerating the electron transfer via Ti-O-B bonding. Homogeneous boron-doped amorphous TiO2 achieves about 5 times higher NO removal efficiency (∼50%) than that of amorphous TiO2 (∼9%) without releasing remarkable NO2 (selectivity, ∼97%). This study provides a state-of-the-art approach for robust photocatalytic NO removal by engineering the defect distribution.

Ultrasensitive and selective hydrogen sensing of SnO2 nanofibers decorated with Pd single atoms

Highly accurate and sensitive hydrogen detection particularly at (sub)ppb level is crucial for large-scale use of green hydrogen energy. However, state-of-the-art hydrogen sensors usually have a ppm-level limit of detection (LOD). In this work, SnO2 nanofibers were decorated with Pd single atoms using a scalable two-step annealing method, which remarkably boosted the H2 sensing properties. The Pd-SnO2 nanofiber sensor exhibited a response of 224 to 1000 ppm H2 at the optimum operation temperature of 300°C, which was 107 times higher than that of SnO2, achieving an LOD as low as 0.6 ppb. Moreover, a fast response time of 8.4 s, excellent selectivity, and humidity tolerance were observed. The superior H2 sensing performance of Pd-SnO2 nanofiber was ascribed to excellent catalysis of Pd single atoms and formation of heterojunction.

MOF-derived porous In2O3 nanospheres sensitized by CdS quantum dots: A ppb-level NO2 sensor with ultra-high response at room-temperature

NO2 is one of the most important atmosphere pollutants, causing great harm to the human body at very low concentrations (ppb levels). Herein, a novel fabrication idea for gas sensing materials was reported to detect ppb-level NO2 via MOF-derived porous In2O3 nanospheres (NSs) sensitized by CdS quantum dots (QDs). The good distribution of CdS QDs (2.5–4.0 nm) on porous In2O3 NSs was verified by the transmission electron microscopy and element mapping analyses. In comparison to In2O3 NSs, the CdS@In2O3 composite nanospheres (CNSs) exhibited exceptional responses to ppb-level concentrations of NO2 (S=425.1@100 ppb) at room temperature (RT, 25 °C), while also demonstrating good selectivity and response reproducibility. These improvements in sensing performance were attributed to the synergies of the electronic effects of CdS QDs, MOF-derived porous nanostructures, and enhanced adsorption of NO2 and active O2– by well-dispersed CdS QDs. This work emphasizes that the MOF-derived In2O3 porous NSs sensitized by CdS QDs can accurately detect ppb-level concentrations of the NO2 at RT.

A dilute-and-inject liquid-gas chromatography-mass spectrometry method for the analysis of sixteen polycyclic aromatic hydrocarbons in extra-virgin olive oil

BackgroundPolycyclic aromatic hydrocarbons (PAHs) represent a diverse group of organic compounds characterized by the fusion of two or more benzene rings arranged in various structural forms. Due to their harmful effects on human health, it is essential to implement monitoring systems and preventive measures to regulate human exposure. Given the affinity of PAHs for lipids, extensive research has been focused on their presence in vegetable oils. This study aimed to develop an on-line liquid-gas chromatography (LC-GC) method (using tandem mass spectrometry) with minimized solvent consumption for the determination of 16 PAHs in extra-virgin olive oil (EVOO). ResultsA side-by-side comparison of the selected-ion-monitoring and the pseudo multiple-reaction-monitoring (p-MRM) acquisition modes was performed, in terms of specificity and detectability. The results obtained using the p-MRM mode were superior, and for this reason it was selected. The method was linear over the concentration range 1–200 μg kg−1 (except in five cases, over 2–200 and 5–200 μg kg−1 ranges). Accuracy (at the 2 μg kg−1 and 20 μg kg−1 concentration levels) was in the 86.9–109.3 % range, with an RSD <10 %. Intra-day and inter-day precision (at 2 μg kg−1 and 20 μg kg−1 concentration levels) were in the 1.2–9.7 % and 3.2–10.8 % ranges, respectively. For all the PAHs, a negative matrix effect was observed. Three out of sixteen PAHs were detected in three EVOOs (among ten samples), albeit at the low ppb level. Limits of quantification were satisfactory in relation to EU legislation on the presence of PAHs in vegetable oils. SignificanceA dilute-and-inject LC-GC-tandem mass spectrometry method is herein proposed fulfilling EU legislation requirements; sample preparation was very simple, inasmuch that it involved only a dilution step, thus avoiding extraction, clean-up, and thus a high consumption of organic solvents. In fact, considering both oil dilution and the LC mobile phase, less than 8 mL of solvents were used.

Engineering hierarchical heterostructure material based on multiwalled carbon nanotubes/SnO2 nanorod-flowers for high-efficient ammonia detection

The rational manufacturing of multi-component materials with rich heterostructure is emerging as a possible strategy to develop improved carbon nanotube-based gas sensors. Herein, hierarchical heterostructure of multiwalled carbon nanotubes/SnO2 nanorod-flowers (HMCNS) was synthesized by a facile water-bathing combined hydrothermal approach for highly sensitive ammonia detection. Exploration in the microstructure reveals that hierarchical flowers-like SnO2 consisted of nanorods demonstrates a hollow geometry for wrapping multiwalled carbon nanotubes, featuring a unique three-dimensional (3D) hierarchical architecture. Gas sensor based on SnO2@4.5%CNTs hierarchical heterostructure exhibits highly enhanced ammonia-sensing performances, including ultra-high response of 1650 toward 20 ppm ammonia, good selectivity, 250 ppb level detection, and superior long-term stability. The improvement in ammonia sensing capability could be attributed to the peculiar hierarchical architecture and the creation of Mott-Schottky heterostructure which has been strongly validated by electrochemical research. This work will provide a concise and effective avenue to construct hierarchical composite with Mott-Schottky heterostructure for high-performance ammonia gas sensor.

Sensitive Detection of OCS Using Thermal Conversion Combined with Spectral Reconstruction Filtering Differential Optical Absorption Spectroscopy.

Carbonyl sulfide (OCS) is a toxic gas produced during industrial processes that poses risks to both human health and industrial equipment. Therefore, detecting OCS concentrations plays a crucial role in early hazard warning. This paper presents an online system for detecting OCS at the ppb level using thermal conversion and spectral reconstruction filtering differential optical absorption spectroscopy (SRF-DOAS). First, OCS, which is not suitable for DOAS due to its weak absorption characteristics, is completely transformed into SO2 with strong absorption characteristics under high-temperature conditions. Then, the spectral reconstruction filtering method (SRF) is proposed to eliminate the noise and interference. The core idea of the method is to arrange the spectrum according to the spectral intensity from small to large rather than wavelength, reconstructing the spectrum into a new spectrum with linear characteristics. The reconstructed spectrum can remove noise and interference by linear fitting and retain the characteristic of SO2 oscillation absorption. Next, we demonstrate the ability of the reconstructed spectral method to remove noise and interference by comparing the spectra of the inverse-reconstructed gas mixture and SO2. The relative deviation of 0.88% at 100 ppb and detection limit of 7.26 ppb*m for OCS were obtained using the SRF-DOAS method. Finally, the reliability of the system was confirmed by measurements of OCS concentrations in mixture gas of OCS and air, as well as in human exhaled breath.

Polarization‐Enhanced Narrow‐Band GeS2 2‐D SWIR Spectral Phototransistor

AbstractIntegrated computational spectrometers with gate‐tunable nano heterostructures and reconstruction algorithms are attractive for on‐chip gas‐sensing spectrometers and have enabled versatile spectrum detectors. However, they require the selective and optical filtering capabilities of wavelengths, restricting their efficient implementation in narrow‐band photodetection. In this study, a printable spectral phototransistor is developed with high dynamic detectivity (1012 Jones and 105 Hz at −3 db bandwidth) modulated by a GeS2 nanosheet heterostructure at short‐wave infrared (SWIR) regime. Using the transport mode switching of carriers in a heterostructure and the polarization‐sensitivity of the GeS2 two‐dimension (2‐D) nanosheet, this SWIR spectral phototransistor demonstrates an accurate narrow‐band selective (96.7% accuracy) spectrum detector and performed a deep‐learning analysis of an artificial neural network (ANN). Furthermore, this GeS2 2‐D based spectral phototransistor, characterized by its high in‐plane anisotropy and electrically reconfigurable properties, extends the applicability of narrow‐band photodetection with 15 nm Full Width at Half Maximum (FWHM) to the recognition of trace‐gases at the parts per billion (ppb) level.

Highly efficient degradation and detoxification of antibiotics over C–Dots/siderite heteroaggregates in photo-Fenton systems: The crucial role of C–Dots

The substantial presence of antibiotics in aquatic environments remains as a critical environmental issue that needs to be urgently addressed. In this study, mimetics of C–Dots/siderite heteroaggregates (CSI) were studied in a visible-light-responsive Fenton system as a platform for the degradation of antibiotics in contaminated water. By virtue of the excellent electron transfer of C–Dots, the sustained conversion cycles of Fe(II) → Fe(III) → Fe(II) in CSI were greatly accelerated, and meanwhile the H2O2 utilization was enhanced. The optimized CSI–3 nanocomposite displayed a prominent degradation efficiency towards a series of tetracycline analogs at ppb levels. Density functional theory (DFT) calculations indicated the excellent photo-Fenton catalytic performance of CSI originated from the increased d-band center and electron density, which considerably improves the utilization of H2O2. Both experimental and theoretical studies revealed that the correlated toxicity of degradation intermediates was significantly decreased. Additionally, a continuous flow device integrating the CSI photo-Fenton system maintained a high degradation efficiency after long-term treatment of simulated chlortetracycline wastewater. The presented work thereby confirms a spontaneous remediation process for the decontamination and detoxification of persistent organic pollutants under the action of heteroaggregates formed by engineered nanoparticles and natural minerals.

An ultra-sensitive optical H2S sensor based on thermal conversion combined with UV-DOAS: Dynamic detection from ppm to ppb level

Hydrogen sulfide (H2S) as a common gas plays an important role in both industrial production and clinical pathology. Therefore, the realization of dynamic detection of trace H2S gas is of great significance. In this paper, an ultra-sensitive optical H2S sensor based on thermal conversion and ultraviolet differential optical absorption spectroscopy (UV-DOAS) is developed for dynamic measurement of H2S concentration. The H2S concentration can be derived from the measurement of the change in sulfur dioxide (SO2) concentration before and after conversion. First, the evaluation method of SO2 concentration based on UV-DOAS is presented, and the performance indicators of SO2 concentration measurement are given. Second, the conversion characteristics of H2S under different temperatures and flow rates are investigated, and H2S can be efficiently converted to SO2 in the flowing gas state by controlling the conversion conditions. Finally, the performance indicators of H2S sensor are evaluated. The sensor realizes H2S measurements with a detection limit of 14 ppb * m, while its sensitivity and reliability of measuring H2S concentration increase tenfold, making it suitable for dynamic measurements of trace H2S. In addition, the feasibility of the sensor for applications in atmospheric monitoring and human exhaled breath detection is demonstrated by practical tests.