Detection Of Low Concentrations Research Articles

Highly Sensitive and Selective SnO2-Gr Sensor Photoactivated for Detection of Low NO2 Concentrations at Room Temperature.

Chemical nanosensors based on nanoparticles of tin dioxide and graphene-decorated tin dioxide were developed and characterized to detect low NO2 concentrations. Sensitive layers were prepared by the drop casting method. SEM/EDX analyses have been used to investigate the surface morphology and the elemental composition of the sensors. Photoactivation of the sensors allowed for detecting ultra-low NO2 concentrations (100 ppb) at room temperature. The sensors showed very good sensitivity and selectivity to NO2 with low cross-responses to the other pollutant gases tested (CO and CH4). The effect of humidity and the presence of graphene on sensor response were studied. Comparative studies revealed that graphene incorporation improved sensor performance. Detections in complex atmosphere (CO + NO2 or CH4 + NO2, in humid air) confirmed the high selectivity of the graphene sensor in near-real conditions. Thus, the responses were of 600%, 657% and 540% to NO2 (0.5 ppm), NO2 (0.5 ppm) + CO (5 ppm) and NO2 (0.5 ppm) + CH4 (10 ppm), respectively. In addition, the detection mechanisms were discussed and the possible redox equations that can change the sensor conductance were also considered.

Point-of-Care Detection of Carcinoembryonic Antigen (CEA) Using a Smartphone-Based, Label-Free Electrochemical Immunosensor with Multilayer CuONPs/CNTs/GO on a Disposable Screen-Printed Electrode.

In order to identify carcinoembryonic antigen (CEA) in serum samples, an innovative smartphone-based, label-free electrochemical immunosensor was created without the need for additional labels or markers. This technology presents a viable method for on-site cancer diagnostics. The novel smartphone-integrated, label-free immunosensing platform was constructed by nanostructured materials that utilize the layer-by-layer (LBL) assembly technique, allowing for meticulous control over the interface. Detection relies on direct interactions without extra tagging agents, where ordered graphene oxide (GO), carbon nanotubes (CNTs), and copper oxide nanoparticles (CuONPs) were sequentially deposited onto a screen-printed carbon electrode (SPCE), designated as CuONPs/CNTs/GO/SPCE. This significantly amplifies the electrochemical signal, allowing for the detection of low concentrations of target molecules of CEA. The LBL approach enables the precise construction of multi-layered structures on the sensor surface, enhancing their activity and optimizing the electrochemical performance for CEA detection. These nanostructured materials serve as efficient carriers to significantly increase the surface area, conductivity, and structural support for antibody loading, thus improving the sensitivity of detection. The detection of carcinoembryonic antigen (CEA) in this electrochemical immunosensing transducer is based on a decrease in the current response of the [Fe(CN)6]3-/4- redox probes, which occurs in proportion to the amount of the immunocomplex formed on the sensor surface. Under the optimized conditions, the immunosensor exhibited good detection of CEA with a linear range of 0.1-5.0 ng mL-1 and a low detection limit of 0.08 ng mL-1. This label-free detection approach, based on signal suppression due to immunocomplex formation, is highly sensitive and efficient for measuring CEA levels in serum samples, with higher recovery ranges of 101% to 112%, enabling early cancer diagnosis. The immunosensor was successfully applied to determine CEA in serum samples. This immunosensor has several advantages, including simple fabrication, portability, rapid analysis, high selectivity and sensitivity, and good reproducibility with long-term stability over 21 days. Therefore, it has the potential for point-of-care diagnosis of lung cancer.

Low Concentration C2H2 Detection by NiO/SnO2 Nanostructured Heterojunction Based MEMS Sensor

Abstract Low concentration detection and analysis of dissolved characteristic gas Acetylene (C2H2) in oil is one of the effective methods for power transformer condition maintenance to ensure safety. The MEMS gas sensor based on the nanostructured material has become a research hotpot for detecting the C2H2. In this work, SnO2 and NiO thin films were successively deposited by RF sputtering, followed by annealing at different temperatures to prepare NiO/SnO2 heterostructures, and the C2H2 sensor chips were prepared by MEMS (microelectromechanical systems) compatible process by using the SnO2/NiO thin films as sensitive materials. The results showed that the detection limit of the MEMS sensor based on the NiO/SnO2 (NiO/SnO2-2) film annealed at 450℃ was as low as 0.2×10-6 toward C2H2. The sensor exhibits a high response at 260℃ (S=7.9 toward 1.4×10-6 C2H2), which is about 4.5 times that of pure SnO2(1.8). Meanwhile, it has an extremely short response time (13 s and 19 s). This study reveals that dissolved acetylene gas in transformer oil can be detected more efficiently by the sensor with nanostructured heterojunctions as sensitive materials.

Use of natural history museum ungulate specimen hair as biomarkers for environmental trace element contamination.

This study reports the first use of natural history museum ungulate specimens' (common fallow deer, bontebok, Arabian oryx, impala, Dall's sheep, water buffalo, and yak) hair as biomarkers for the determination of environmental trace element contamination and public exposure risk factor assessment. Morphological characteristics of the hair, like diameter and protein structure, were determined using optical microscopy and FTIR spectroscopy, respectively. The levels of thirty-nine (39) elements, sixteen (16) rare earth elements (REEs), and selected isotope ratios (52Cr/53Cr, 144Nd/146Nd, 147Sm/149Sm, 173Yb/172Yb, 206Pb/207Pb, and 206Pb/208Pb) in the hair samples were determined by ICP-MS analysis.A NIST 1643e standard reference material was analyzed for method validation to determine the accuracy of the developed elemental analysis method. The average hair diameter found in samples obtained from common fallow deer (193 ± 72µm), bontebok (148 ± 48µm), Arabian oryx (194 ± 40µm), impala (88 ± 20µm), Dall's sheep (240 ± 68µm), water buffalo (139 ± 17µm), and yak (139 ± 16µm) were recorded. 27Al (1642 ± 1551mg·kg-1), 44Ca (506 ± 272mg·kg-1), 56Fe (730 ± 1391mg·kg-1), 24Mg (108 ± 57mg·kg-1), 39K (720 ± 1591mg·kg-1), 28Si (1125 ± 1163mg·kg-1), 23Na (10,223 ± 9824mg·kg-1), and 66Zn (33 ± 25mg·kg-1) have the highest concentrations detected in the hair samples. Potentially toxic elements and REEs have the lowest concentration in the hair samples. The detection of low concentrations of 75As, 111Cd, 59Co, 52Cr, 53Cr, 60Ni, Pb isotopes, and REEs in all hair samples suggests heavy metal contamination. The plausible sources of the detected elements in ungulate animal hair are likely due to dietary intake, anthropogenic activities, environmental contamination, specimens' preservation practices, or a combination of those sources. The figures of merit highlighted by a high correlation coefficient (R2 ≥ 0.9990), low limit of detection (as low as 1.00 × 10-7mg·kg-1 for 140Ce), and high average percent recoveries (97.0 ± 11.5) of the NIST 1643e standard reference material analyses demonstrate the linearity, high sensitivity, and accuracy of the ICP-MS technique for elemental and isotopic analysis of hair samples.

Development and application of a quadruplex TaqMan real-time fluorescence quantitative PCR assay for four porcine digestive pathogens.

Salmonella, Escherichia coli, Lawsonella intracellularis, and Brachyspira hyodysenteriae are the primary pathogens responsible for gastrointestinal diseases in pigs, posing a significant threat to the health and productivity of pig production systems. Pathogen detection is a crucial tool for monitoring and managing these infections. We designed primers and probes targeting the invA gene of Salmonella, the 23S rRNA gene of Escherichia coli, the aspA gene of Lawsonella intracellularis, and the nox gene of Brachyspira hyodysenteriae. We developed a quadruplex TaqMan real-time quantitative PCR assay capable of simultaneously detecting these four pathogens. This assay demonstrated high sensitivity, with detection limits of 100 copies/μL for the recombinant plasmid standards pEASY-23S rRNA, pEASY-aspA, and pEASY-nox, and 10 copies/μL for pEASY-invA. The standard curves exhibited excellent linearity (R2 values of 0.999, 0.999, 1, and 0.998, respectively) and high amplification efficiencies (93.57%, 94.84%, 85.15%, and 81.81%, respectively). The assay showed high specificity, with no cross-reactivity detected against nucleic acids from Streptococcus suis, porcine epidemic diarrhoea virus (PEDV), porcine transmissible gastroenteritis virus (TGEV), Pasteurella multocida, Clostridium perfringens, Gracilaria parapsilosis, porcine delta coronavirus (PDCoV), porcine group A rotavirus (GARV), and porcine teschovirus (PTV). The assay also exhibited excellent repeatability, with inter- and intra-assay coefficient of variation (CV) ranging from 0.15% to 1.12%. High concentrations of nucleic acids did not interfere with the detection of low concentrations, ensuring robust performance in complex samples. Among 263 diarrhoeic samples, the assay detected Salmonella in 23.95%, Escherichia coli in 26.24%, Lawsonella intracellularis in 33.84%, and Brachyspira hyodysenteriae in 22.43%. This quadruplex TaqMan qPCR assay offers a rapid, sensitive, and specific tool for the simultaneous detection of Salmonella, Escherichia coli, Lawsonella intracellularis, and Brachyspira hyodysenteriae in pigs.

Pyrroloquinoline quinone exhibiting peroxidase-mimicking property for colorimetric assays

BackgroundSmall molecule mimics offer the advantages of easy preparation, good thermodynamic stability, and reproducible catalytic activity. However, most of the reported organic artificial mimics face challenges including low catalytic activity, oxidative self-destruction, and auto-aggregation into inactive dimers. Therefore, novel organic mimics with high catalytic activity as well as good thermal and environmental stability are highly desirable. ResultsWe found that pyrroloquinoline quinone (PQQ), a nutritionally important growth factor, displayed significant peroxidase-like activity to catalyze the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) into blue oxidized TMB (oxTMB) by H2O2. Its catalytic activity surpassed that of other organic small molecules reported previously, including fluorescein derivatives and adenosine/guanosine triphosphate. Based on the reduction of oxTMB by the enzymatically generated ascorbic acid (AA), the PQQ/TMB-based system was used to monitor alkaline phosphatase (ALP) activity with ascorbic acid 2−phosphate (AAP) as the substrate. This sensing system allowed for the determination of ALP with a detection limit of 1 mU/mL. Furthermore, we discovered that PQQ can coordinate with Cu2+ to form metal-organic nanoparticles. The building blocks of two active cofactors endowed the nanoparticles with impressive functionalities for biocatalytic applications. With Cu-PQQ nanoparticles as signal labels, colorimetric immunoassays of prostate specific antigen (PSA) were achieved with a lowest detectable concentration down to 0.1 pg/mL. SignificanceThis work is valuable for the design of novel biosensors by utilizing PQQ as an artificial enzyme because of its high catalytic activity, good stability, ease of storage, and simple chemical structure.

Electroactivated SERS Nanoplatform for Rapid and Sensitive Detection and Identification of Tumor-Derived Exosome miRNA.

Exosomal miRNA expression derived from tumor cells provides a valuable and promising noninvasive modality for the early diagnosis and assessment of the efficacy of cancer treatment. However, accurate detection and identification of miRNA within exosomes have been challenging due to its low abundance and the complexity and tedious extraction with large sample volumes in the separation process. Here, we developed an electrically activated nanoplatform for rapid and sensitive detection and identification of exosome miRNA, through triggering miRNA release by opening exosomes that were captured on the electrode surface using a slightly applied electric field (50 mV), and simultaneously detected them with surface-enhanced Raman spectroscopy (SERS) in situ. The method possessed superior specificity and sensitivity for exosomal miRNA detection, with a low detection concentration of 0.5 nM. The SERS sensor chips also showed a superior sensing performance of exosomal miRNA in complex body fluids such as urine and blood. We found that exosomal miRNA contents derived from tumor cells were significantly higher than those in normal cells, and importantly, the concentrations of exosomes secreted from three different cell lines were distinctly augmented after mild electrical stimulation (ES) treatment. Furthermore, the miRNA expression within exosomes was upregulated after the ES treatment of cells. The developed approach and SERS detection platform for exosomal miRNA are promising for noninvasive and precise screening, classification, and monitoring of cancer.

Developing surface plasmon resonance imaging for discrete particle detection based on a silver layer coated with polyacrylic acid/iodine polyelectrolyte brushes

The detection and analysis of low concentrations of chemical and biological particles presents an enduring challenge in scientific exploration. Among the various techniques employed for this purpose, surface plasmon resonance (SPR) stands as a powerful label-free method with a wide-range applications in advanced detection and sensing. Traditional SPR, while highly effective, encounters inherent limitations when it comes to scrutinizing individual particles. To overcome this limitation, wide-field surface plasmon resonance microscopy emerges as a promising approach, offering real-time detection capabilities for suspended particles in solution. In this study, an innovative wide-field surface plasmon resonance microscope is presented, strategically combining a silver layer coated with polyelectrolyte brushes—polyacrylic acid/iodine, to enhance the detection sensitivity and mitigate silver’s susceptibility to oxidation. It is demonstrated that coating the silver layer with polyacrylic acid/iodine enhances the sensitivity of discrete particle imaging with a high spatial resolution of the recorded image. Since wide-field surface plasmon resonance microscopy can detect discrete particles, a mathematical model is proposed to describe the SPR sensing mechanism based on discrete particles for precisely characterizing and interpreting the experimental observations. This work demonstrates a capability for comprehensive analysis of low concentrations of chemical and biological particles at the single particle level.

Pulse-Driven MEMS NO2 Sensors Based on Hierarchical In2O3 Nanostructures for Sensitive and Ultra-Low Power Detection.

As the mainstream type of gas sensors, metal oxide semiconductor (MOS) gas sensors have garnered widespread attention due to their high sensitivity, fast response time, broad detection spectrum, long lifetime, low cost, and simple structure. However, the high power consumption due to the high operating temperature limits its application in some application scenarios such as mobile and wearable devices. At the same time, highly sensitive and low-power gas sensors are becoming more necessary and indispensable in response to the growth of the environmental problems and development of miniaturized sensing technologies. In this work, hierarchical indium oxide (In2O3) sensing materials were designed and the pulse-driven microelectromechanical system (MEMS) gas sensors were also fabricated. The hierarchical In2O3 assembled with the mass of nanosheets possess abundant accessible active sites. In addition, compared with the traditional direct current (DC) heating mode, the pulse-driven MEMS sensor appears to have the higher sensitivity for the detection of low-concentrations of nitrogen dioxide (NO2). The limit of detection (LOD) is as low as 100 ppb. It is worth mentioning that the average power consumption of the sensor is as low as 0.075 mW which is one three-hundredth of that in the DC heating mode. The enhanced sensing performances are attributed to loose and porous structures and the reducing desorption of the target gas driven by pulse heating. The combination of morphology design and pulse-driven strategy makes the MEMS sensors highly attractive for portable equipment and wearable devices.

Ultrasensitive Room Temperature Formaldehyde Sensors Based on F Doped ZnO Nanostructures Activated by UV Light.

It is urgent to develop an ultrasensitive formaldehyde (HCHO) sensor that can operate at room temperature and has a low detection limit. Metal oxide semiconductors are excellent gas sensitive materials. Therefore, in this paper, we present the synthesis of fluorine (F) doped zinc oxide (ZnO) porous nanomaterials through a straightforward one-pot method with the optimization of F doping levels to achieve the detection of low concentrations of HCHO under UV light at room temperature. Under 375 nm UV light, the sensor exhibits a response value of 386% to 10 ppm of HCHO, which is 2.6 times higher than that of pure ZnO, and its detection limit is as low as 75 ppb. It has excellent selectivity, stability, and moisture resistance, which can meet the requirements of HCHO detection in daily life. Analysis reveals that doping ZnO with F not only increases the material's specific surface area but also introduces active sites. Furthermore, it alters the state of HCHO on the material's surface from physical adsorption to chemical adsorption. The above reasons together enhance the adsorption of HCHO on the gas sensitive material, thereby improving its gas sensitivity performance. Overall, this work demonstrates that F-doped ZnO is a potential material for ultrasensitive HCHO sensors and provides insights into the interpretation of the effect of doping on the gas sensitivity properties of materials.

Feasible synthesis and physicochemical features of a luminescent cadmium-metal organic frameworks (Cd-MOFs) composite, and its functionalization as a turn-off sensor towards selective determination of bisphenol A in food, water, and paper products

In the current study, a cadmium-metal organic frameworks (Cd-MOFs) structure was developed using a chemical process. The work comprised two main stages, initially inspection of the physicochemical features of the structure, and secondly, the application of the prepared Cd-MOFs as a turn-off nanosensor for the spectrofluorimetric determination of bisphenol A (BPA). Field emission scanning electron microscopy (FESEM) revealed the morphological features with the flake-like resembled shape. The elemental peaks for C, O, N, S, and Cd were residing as demonstrated by the energy-dispersive X-ray (EDX) results. The nonporous structure with a surface area of 25 cc/g was determined through the BET surface area results. The fluorescence spectra of Cd-MOFs demonstrated fluorescence emission at 470 nm after excitation at 320 nm. The quenching of the native fluorescence of Cd-MOFs was quantitatively and selectively produced by increasing concentrations of BPA. Therefore, Cd-MOFs have been applied as a turn-off nanosensor for the spectrofluorimetric determination of BPA, for the first time. The proposed approach validates linearity over the concentration range of 0.05–1.0 µg/mL with a detection limit of 0.01 µg/mL, signifying the method’s high sensitivity. Detection of low concentrations of BPA allowed for the real sample analysis in the food industries, including orange juice, tap water, infant feeding bottles, and food contact sheets. Moreover, The excellent eco-friendliness and greenness of the established approach were verified by employing the Analytical GREEnness (AGREE) and complementary Green Analytical Procedure Index (ComplexGAPI). The RGB 12 algorithm has functioned to prove the proposed method is greener, whiter, more sustainable, analytically effective, and less expensive than the reported ones. The proposed approach was validated according to ICH guidelines. This method presents a hopeful approach to quickly and accurately detect and quantify BPA in the food industry, which reinforces food safety and guards consumers’ health.

Target-promoted catalytic DNA molecular circuit network coupled with endonuclease amplification for sensitive and label-free electrochemical aptamer antibiotic assay

Sarafloxacin (SAR) is a common antibiotic that accumulates in animal tissues, which potentially poses health risks to humans via ingestion. Sensitive detection of SAR in animal-derived foods is therefore critical. Traditional SAR detection methods based on HPLC or antibody immunoassays encounter the limitations of cost, sensitivity and operational simplicity. In this study, with the design of a new DNAzyme/catalytic hairpin assembly (CHA) molecular circuit network coupled with endonuclease amplification, we developed an electrochemical aptamer (AP) biosensor with high sensitivity for label-free SAR detection in milk. The sensor functions by specific binding of SAR to APs, which release DNAzyme sequences to initiate the catalytic DNAzyme/CHA molecular circuit network amplification for forming many ssDNAs and dsDNA duplexes. These sequences further hybridize with hairpin signal probes on sensor electrode to create favorable nicking sites for endonuclease, which cleaves hairpin signal probes to liberate lots of G-quadruplex strands to complex with and capture hemin. Subsequent hemin reduction by electrochemistry thus results in dramatically enhanced currents to achieve label-free detection of SAR in linear range between 10 pM and 80 nM with detection limit of 1.62 pM. Our sensor also shows satisfactory reproducibility, repeatability and stability, demonstrates high selectivity for the target SAR against other interfering antibiotics, e.g., norfloxacin, penicillin and gentamicin and can realize detection of low concentrations of SAR in diluted complex milk and human serum samples, thereby underscoring its promises for convenient and sensitive assay of different trace antibiotics.

AuNPs enhanced electrochemical and optical dual-mode fiber optic sensor for trace Hg2+ detection

Efficient and low-concentration detection of heavy metal ions is crucial for healthcare and environmental monitoring. Traditional fiber optic surface plasmon resonance (SPR) sensors face challenges in detecting trace heavy metal ions due to limited sensitivity and the need for complex specific modifications. To overcome these challenges, an innovative electrochemical and optical dual-mode fiber optic sensor for in situ, real-time detection of trace mercury ions is proposed in this paper. The sensor utilizes a reflection-type fiber optic probe coated with thin gold (Au)/indium tin oxide (ITO) film and gold nanoparticles (AuNPs), enabling simultaneous electrochemical and optical interrogation. The coupling effect between the SPR of thin film and the localized surface plasmon resonance (LSPR) of AuNPs significantly improves optical sensitivity, with AuNPs also offering additional active sites for the redox reaction of Hg2+. The ITO film not only facilitates the stripping of Hg2+, leading to sharper stripping peaks but also enhances the ability of the sensor to rapidly respond to anomalous potential changes. Experimental results show that the sensor has a wide dynamic detection range from 10−10 M to 10−5 M, with a limit of detection reaching the pM level. The dual-mode functionality allows the simultaneous collection of voltage, current, and optical information, enabling cross-validation of the detection results and improving the accuracy and reliability of detection.

Wheatstone Bridge MEMS Hydrogen Sensor with ppb-Level Detection Limit Based on the Palladium-Gold Alloy.

On some occasions, such as new energy clinics, monitoring the trace hydrogen at the ppb level is necessary. The traditional resistive hydrogen sensors based on the Pd alloys are very difficult to realize such an extremely low detection limit. To achieve a detection limit at the ppb level and also ensure good stability, a MEMS hydrogen sensor was designed in a suspended Wheatstone bridge structure, with all four resistive arms defined on a sputtered Pd-Au alloy thin film. For the Wheatstone bridge sensor, absolute response (Ra) and relative response (Rs) are defined to describe the sensitivity of the sensor, and the effect of annealing temperature on baseline drift is investigated using the baseline zero drift parameter (DBZD). By testing the sensors across a hydrogen concentration range of 20 ppb to 3 v/v%, the optimal annealing temperature (250 °C) and operating temperature (60 °C) were identified. Under these conditions, the sensor exhibited a detection limit as low as 20 ppb with a power consumption of only 4.6 mW. At the same time, the response and recovery times of the sensor were 6 and 19 s, respectively, toward 3 v/v% hydrogen. After testing over a 100-day period, Ra fluctuated only 0.0026%, indicating that the hydrogen sensor had good long-term stability for low-concentration detection. More results also showed that the sensor has good repeatability, selectivity, and humidity resistance. With the wide measurement range (20 ppb to 3 v/v%), the sensor has the potential to meet hydrogen detection requirements in multiple scenarios.

Perovskite-structured LaFeO3 gas sensor modified by polyoxometalate electron acceptor with high sensitivity and low detection limit for acetone gas☆

Lanthanum ferrite is a representative perovskite-structured rare earth-based bimetallic oxide, which has been widely studied in magnetic materials, sensors, catalysts and batteries. Herein, we designed and prepared polyoxometalate electron acceptor decorated LaFeO3 gas-sensitive composite materials with one-dimensional nanoribbons morphology by electrospinning. The effects of different mass fraction of Keggin type phosphotungstic acid (PW12) on the gas-sensitive properties of LaFeO3 nanoribbons were investigated. The results show that the response value of LaFeO3/PW12 sensor to acetone gas first increases and then decreases with the increase of PW12 content. The LaFeO3/3%PW12 sensor exhibits a maximum response of 3.35 to 5 ppm acetone at 250 °C, a 2.6 times increase in response value and a 90 °C reduction in operating temperature compared to pure LaFeO3 nanoribbons. The LaFeO3/3%PW12 sensor exhibits good linear relation in ppb-level concentrations and the lowest detection concentration is 100 ppb. The sensors also show good repeatability in 6 tests and excellent long-term stability in 30 d. The improvement of the gas sensitive properties of the composite can be attributed to the synergistic effect between the two components. As an electron acceptor, PW12 promotes carrier migration between PW12 and LaFeO3, thereby improving the gas sensing performance of LaFeO3. This work promotes the practical application of polyoxometalate to promote rare earth-based gas sensitive materials in sensing field.

2D CO3O4 Nanosheets for High Selectivity and Response of H2S Gas Sensing Performances

As the demand for selective and sensitive gas sensors continues to escalate, the development of novel materials with enhanced performance becomes increasingly imperative. The present investigation delves into the fabrication and implementation of two-dimensional cobalt oxide (Co3O4) nanostructures as highly proficient gas sensors for the discerning identification of hydrogen sulfide (H2S) within intricate environmental circumstances. The distinct two-dimensional configuration of Co3O4, characterized by its substantial surface-to-volume ratio and abundant accessible active sites, markedly augments gas adsorption and reaction dynamics, resulting in exceptional sensitivity and selectivity toward H2S over other potentially confounding gases. Extensive characterization methodologies, encompassing X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), corroborate the successful synthesis of well-defined nanosheets. The materials exhibited optimal H2S detection at 250 °C, demonstrating significant sensitivity (Response = 214.45) and fast response and recovery times (16.85 s and 46.93 s, respectively). Its performance was further validated through concentration-dependent studies, which showed high accuracy even at low H2S concentrations (0.3–50 ppm). The sensor also displayed excellent selectivity for H2S over other gases, minimal interference from humidity, and maintained stability during cyclic exposure and long-term operation over 30 days. These findings highlight this material as a highly promising sensor for H2S detection due to its superior performance metrics. The incorporation of these nanosheets into a sensor apparatus offers a propitious strategy for the detection of low concentrations of H2S in real-world applications, such as environmental surveillance and industrial safety systems.

Improved the Sensitivity and Limit of Detection of Surface Alloying SERS Sensors by Controlling Mixing Ratio of Trimetallic (Ag-Au-Pd) Nanoparticles

In this study, three different types of hybrid structures SERS sensors made from different mixing ratio of trimetallic (Ag-Au-Pd) nanoparticles of [Au1: Ag1: Pd1] , [Au1: Ag2: Pd1] , [Au1: Ag2: Pd2] in surface alloying forms deposited on macro porous silicon (macroPsi) layer were created and extensively tested. By using a simple and fast immersion process, trimetallic (Ag-Au-Pd) nanoparticles were created utilizing ion reduction of numerous metallic salts on a macro porous silicon (macroPsi) layer. The macroPsi layers were created using a laser assisted etching (LAE) technique for 15 minutes with a constant density of approximately (28mA/c.m2). At a constant concentration (10-3 M) of HAu.Cl4, Ag.NO3 and Pd.Cl2 to synthesize Au-NPs, Ag-NPs and Pd-NPs, immersion processes with various mixing ratios were performed. The hybrid structures of SERS sensors were examined using XRD, FE-SEM, and Raman microscopes. The sensors were tested at different concentrations from 10-6 to 10-12 of MB target molecules. The SERS trimetallic sensors demonstrated a considerable reliance on hot spot zones among trimetallic nanoparticles. Higher enhancement factor with lower detection limit of Raman signal was obtained from [Au1: Ag2: Pd2] hybrid structures SERS sensor of about 1.5×1010 and 10-14 respectively, due to extra ordinary specific surface area and high surface density forming trimetallic nanoparticles . The variations of mixing ratio of trimetallic (Ag-Au-Pd) provide an effective pathway to develop the sensors performance towards detection of lower concentrations.

High-performance PANI sensor on silicon nanowire arrays for sub-ppb NH3 detection

For industrial production and disease diagnosis, real-time detection of low concentrations of NH3 is crucial, necessitating a gas-sensitive sensor compatible with integrated processes and exhibiting excellent performance. Herein, we employed wet etching and rapid in-situ polymerization on silicon nanowire substrates to grow polyaniline fibers, thereby fabricating NH3 gas sensors with p-p heterojunction and three-dimensional network structures. Characterization and gas sensing performance testing were conducted. The results demonstrate the outstanding NH3 detection capabilities of the sensor, providing stable responses down to concentrations as low as 1 ppb, which indicates its LOD is one to two orders of magnitude lower than current similar products. It also exhibits verified selectivity and long-term reliability. The excellent sensing performance is attributed to the high surface area from the silicon nanowire structure and efficient synergy of p-p heterojunction. Additionally, the influence of doping types of the substrates and annealing process were explored. This work serves as a reference for the design of silicon-based gas sensors with high sensitivity, low detection limits, and extended operational lifetimes, suitable for deployment in commercial integrated monitoring systems.

Organic Thin Film Transistor with Aligned Nanowires/Thin Film Hybrid Channel for Low-Concentration Detection of NH3 at Room Temperature

Organic Thin Film Transistor with Aligned Nanowires/Thin Film Hybrid Channel for Low-Concentration Detection of NH₃ at Room Temperature

Zinc oxide-based sensor prepared by modified sol–gel route for detection of low concentrations of ethanol, methanol, acetone, and formaldehyde

Abstract We4 4 We received the acceptance date as 26 September 2024. Could you please update it to reflect this exact date for our project, instead of 1 October 2024? This is very important for our project funding. successfully synthesized zinc oxide (ZnO) nanoparticles using the sol–gel method, followed by their application onto alumina substrates for sensor testing. Comprehensive characterization of the nanomaterials was carried out utilizing XRD, SEM, TEM, UV–VIS-IR, and Photoluminescence (PL) techniques. The nanoparticles displayed a hexagonal wurtzite crystal structure, typical of ZnO. UV–Vis-IR spectroscopy revealed significant absorption in the UV region, with the band gap energy calculated to be 3.22 eV. PL spectra indicated the presence of various defects, such as oxygen vacancies and zinc interstitials, within the ZnO structure. SEM analysis of the deposited film surface showed spherical agglomerates, confirming the nanoscale dimensions, while energy-dispersive x-ray spectroscopy spectra affirmed the high purity of the ZnO films, rich in Zn and O elements. Sensor tests demonstrated the ZnO sensor’s high sensitivity to low concentrations of volatile organic compounds such as ethanol, formaldehyde, methanol, and acetone. Notably, at an operational temperature of 300 °C, the sensor exhibited a remarkable response to 5 ppm of each gas, with the following response and response/recovery times: for methanol, 11.47 and 36 s/57 s; for acetone, 11.54 and 25 s/52 s; for formaldehyde, 0.79 and 53 s/58 s; and for ethanol, 3.88 and 9 s/59 s.