Trace Detection Research Articles

Trace detection of SF6 gas decomposition component H2S based on Pr6O11-In2O3

Sulfur hexafluoride (SF6) from Gas Insulated Switchgear (GIS) will decompose and produce hydrogen sulfide (H2S) in the event of equipment failure. Therefore, the detection of H2S can determine whether the equipment has malfunctioned. Due to the low concentration of the SF6 decomposition product H2S and its application in industrial environments, sensors must have a low detection limit and rapid response time. Considering that the oxides of rare earth elements can improve the sensing characteristics, praseodymium oxide (Pr6O11)-indium oxide (In2O3) was prepared. The impact of Pr6O11 doping on In2O3 was investigated through characterization methods. To validate its feasibility for use in GIS, the best sensor (F3) exhibits good sensing characteristics for H2S in the SF6 and air ambient. The responses to 10 parts per million (ppm) H2S at 190°C were 146.6 in SF6 and 190.8 in air. In SF6 ambient, the F3 sensor demonstrated a low detection limit (50 parts per billion (ppb)). The good sensing characteristics are attributed to the doping of rare earth elements, which induces an increase in the proportion of defect oxygen and accelerate the chemical reaction. The sensing characteristics of the material can be attributed to the doping of Pr6O11 and the electronic effect. This study provides a novel approach for detecting H2S generated from SF6 decomposition.

Trace detection of cadmium (II) ions based on an excessively tilted fiber grating

Cadmium (Cd2+) ion is one of the most crucial industrial pollutants that cause serious harm to the human body. We proposed and experimentally demonstrated a highly sensitive Cd2+ sensor based on hydrogel coated excessively tilted fiber grating. The hydrogel with the functional monomer of the allyl thiourea can specifically bind to Cd2+, and hence forming a complex. The grating excites high order cladding modes, and ensures a sufficient interaction between the light and hydrogel binding to Cd2+, providing highly sensitive monitoring. The results show that the sensor can detect 0-160 pM Cd2+ in aqueous solution. The maximum sensitivity is 10600 nm/µM, and the minimum detection concentration is 20 pM (about 0.004 ppb), which is much less than that of the international standard (3 ppb). The proposed sensor exhibits high sensitivity, ultra-low detection limit, specificity, and a compact structure, offering potential as a tool for Cd2+ detection in aqueous solution.

A novel fluorescent probe based imprinted polymer-coated magnetite for the detection of imatinib leukemia anti-cancer drug traces in human plasma samples

Myeloid leukemia is a chronic cancer, which associated with abnormal BCR-ABL tyrosine kinase activity. Imatinib (IMB) acts as a tyrosine kinase inhibitor and averts tumor growth in cancer cells by controlling cell division, so it is urgent to develop an effective assay to detect and monitor its IMB concentration. Therefore, an innovative fluorescent biomimetic sensor is a promising sensing material that constructed for the efficient recognition of IMB and displays excellent selectivity and sensitivity stemming from molecularly imprinted polymer@Fe3O4 (MIP@Fe3O4). The detection strategy depends on the recognition of IMB molecules at the imprinted sites in the presence of coexisting molecules, which are then transferred to the fluorescence signal. The synthesized MIP@Fe3O4 was characterized using Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Furthermore, computational studies of the band gap (EHOMO-ELUMO) of the monomers, IMB, and their complexes were performed. These results confirmed that the copolymer is the most appropriate and has high stability (Binding energy; 0.004 x 10-19 KJ) and low reactivity. A comprehensive linear response over IMB concentrations from 5 × 10-6 mol/L to 8 × 10-4 mol/L with a low detection limit of 9.3 × 10-7 mol/L was achieved. Furthermore, the proposed technique displayed long-term stability (over 2 months), high intermediate precision (RSD<2.1 %), good reproducibility (RSD <1.9 %), and outstanding selectivity toward IMB over analogous molecules with similar chemical and spatial structure (no interference by 100 to 150-fold of the competitors). Owing to these merits, the proposed fluorescence sensor was utilized to detect IMB in drug tablets and human plasma, and satisfactory results (99.3–100.4 %) were obtained. Thus, the synthesized fluorescence sensor is a promising platform for IMB sensing in various applications.

Dual-responsive luminescent dye@MOF hybrids for ratiometric trace detection, colorimetric visualization, and precise discrimination of tetracycline antibiotics

In this work, dual-responsive luminescent Her@Zn-Bim hybrids are developed by herniarin (Her) dye encapsulation engineering within a layered host MOF (Zn-Bim). The pore confinement effect of the Zn-Bim host effectively isolates the guest dye molecules, therefore affording bright blue dye emission for Her@Zn-Bim hybrids. Upon exposure to tetracycline antibiotics (TCs), the hybrid undergoes a significant quenching of the blue emission, concurrent with the appearance of a distinct green emission. This dual-emission response is very fast and sensitive, facilitating real-time ratiometric detection of TCs with a low limit of detection of 7.81 nM. Notably, the ratiometric luminescence response manifests as a readily observable blue-to-green color switching, enabling straightforward and colorimetric visualization of TCs. Visual and semiquantitative monitoring of TCs is achieved using a readily available smartphone installed with a color-analysis app. Furthermore, in conjunction with principal component analysis, the Her@Zn-Bim hybrids demonstrate efficient discrimination of four TCs with high structural and chemical similarities, even in complex mixture systems. The mechanisms underlying the luminescent responses of the hybrids towards TCs are carefully elucidated. These hybrid sensors, featuring high sensitivity, fast response, colorimetric visualization, and precise discrimination capability, hold promising potential for practical applications in sensing TCs.

Surface confinement–induced electrochemiluminescence enhancement of Au nanoclusters for ultrasensitive detection of a soluble urokinase-type plasminogen activator receptor

In this study, gold nanoclusters (Au NCs) anchored on the surface of 2D Zn-containing hydroxyl double salt (Zn-HDS) with surface confinement–induced electrochemiluminescence (SC-ECL) improvement were used as an intensive ECL emitter to construct a biosensor for ultrasensitive detection of soluble urokinase-type plasminogen activator receptor (suPAR) related to cardiovascular disease in chronic nephritis patients. Impressively, SC-ECL of Au NCs/Zn-HDS nanocomposites exhibited fast electrochemical excitation and efficient radiation transition, showing 4.9 times stronger ECL emission and 10.9 times higher ECL efficiency than those of pure Au NCs. This improvement was attributed to the matched energy level of Zn-HDS and Au NCs, enabling electron–hole pairs of Au NCs to be trapped by the energy levels of Zn-HDS. Moreover, a bipedal DNA walker was generated through target-induced DNA strand displacement and catalytic hairpin assembly (CHA), which was attached to a stable DNA cubic track through electrostatic attraction of positively charged SH-PEG-NH3+ to improve walking efficiency and further boost detection sensitivity. Consequently, the proposed sensing platform achieved trace detection of suPAR ranging from 0.700 pg/mL to 80.0 ng/mL with a low detection limit of 0.344 pg/mL and was successfully applied to detect suPAR in patient serum. This work synthesized a highly efficient metal nanocluster-based ECL emitter, showing great potential in constructing ultrasensitive biosensors for early disease diagnosis.

Laser Parallel Nanofabrication of Dual‐Au‐Nanoholes on Microsphere‐Lens‐Array for Polarization‐Dependent SERS

AbstractHigh‐efficient fabrication of well‐ordered nanostructures on flexible substrates is a challenge to surface‐enhanced Raman spectroscopy (SERS) for analytical fingerprinting trace‐detection. In this work, a laser parallel nanofabrication method is reported via incident‐angle‐dependent photonic nanojet ablating Au film on the bottom surface of microsphere‐lens‐array (MLA), for combination with formed dual Au‐nanoholes (MLA/2‐AuNHs) as the flexible SERS substrates. The process parameters, i.e., pulsed laser energy, MLA diameter, Au film thickness, and laser incident angle, are optimized for high finish‐quality of dual‐AuNHs with a diameter of ≈875 nm and a tip gap of ≈90 nm. The SERS substrate demonstrates the limit of detection down to 10−11 M for 4‐nitrobenzenethiol molecules by the multiple optical regulations, including self‐aligned focusing to the hotspots and directional antenna, the strongly localized surface plasmon resonances, and optical whispering‐gallery modes for resonance energy transfer. The flexible PDMS film supporting the rigid MLA holds the SERS performance of MLA/2‐AuNHs with high flexibility. Moreover, the MLA/2‐AuNHs SERS substrate exhibits differential responses to orthogonally polarized excitation, by which the background noises can be eliminated to improve the Raman spectrum. The present work opens new opportunities to fabricate dielectric‐metal flexible SERS substrates by laser parallel nanofabrication via MLA for Raman trace detection.

Fluorescence Detection of Pb2+ in Environmental Water Using Biomass Carbon Quantum Dots Modified with Acetamide-Glycolic Acid Deep Eutectic Solvent.

In this study, a novel green fluorescent probe material, nitrogen-doped carbon quantum dots (N-CQDs), was prepared by a one-step hydrothermal synthesis method using walnut green skin as a carbon source and acetamide-glycolic acid deep eutectic solvent (AGADES) as a modifier. By covalent coupling, the amide chromophore in AGADES is designed to cover the surface of walnut green skin carbon quantum dots (W-CQDs), forming a fluorescence energy resonance effect and improving the fluorescence performance of the carbon quantum dots. The prepared N-CQDs have a uniform particle size distribution, and the fluorescence quantum efficiency has increased from 12.5% to 32.5%. Within the concentration range of 0.01~1000 μmol/L of Pb2+, the linear detection limit is 1.55 nmol/L, which can meet the trace detection of Pb2+ in the water environment, and the recycling rate reaches 97%. This method has been successfully applied to the fluorescence detection and reuse of Pb2+ in actual water bodies, providing new ideas and methods for the detection of heavy metal ions in environmental water.

Rapid Sample Pretreatment Facilitating SERS Detection of Trace Weak Organic Acids/Bases in Simple Matrices.

Surface-enhanced Raman spectroscopy (SERS) is a powerful tool for highly sensitive qualitative and quantitative analyses of trace targets. However, sensitive SERS detection can only be facilitated with a suitable sample pretreatment in fields related to trace amounts for food safety and clinical diagnosis. Currently, the sample pretreatment for SERS detection is normally borrowed and improved from the ones in the lab, which yields a high recovery but is tedious and time-consuming. Rapid detection of trace targets in a complex environment is still a considerable issue for SERS detection. Herein, we proposed a liquid-liquid extraction method coupled with a back-extraction method for sample pretreatment based on the pH-sensitive reversible phase transition of the weak organic acids and bases, where the lowest detectable concentrations were identical before and after the pretreatment process. The sensitive (μg L-1 level) and rapid (within 5 min) SERS detection of either koumine, a weak base, or celastrol, a weak acid, was demonstrated in different drinking water samples and beverages. Furthermore, target generality was demonstrated for a variety of weak acids and bases (2 < pKa < 12), and the hydrophilicity/hydrophobicity of the target determines the pretreatment efficiency. Therefore, the LLE-BE coupled SERS was developed as an easy, rapid, and low-cost tool for the trace detection of the two types of targets in simple matrices, which paved the way toward trace targets in complex matrices.

Highly sensitive and selective laser-based BTEX sensor for occupational and environmental monitoring

A mid-infrared laser-based sensor is designed and demonstrated for trace detection of benzene, toluene, ethylbenzene, and xylene isomers at ambient conditions. The sensor is based on a distributed feedback inter-band cascade laser emitting near 3.29 µm and an off-axis cavity-enhanced absorption spectroscopy configuration with an optical gain of 2800. Wavelength tuning and a deep neural network (DNN) model were employed to enable simultaneous and selective BTEX measurements. The sensor performance was demonstrated by measuring BTEX mole fractions in various mixtures. At an integration time of 10 s, minimum detection limits of 11.4, 9.7, 9.1, 10, 15.6, and 12.9 ppb were achieved for benzene, toluene, ethylbenzene, m-xylene, o-xylene, and p-xylene, respectively. The sensor can be used to detect tiny BTEX leaks in petrochemical facilities and to monitor air quality in residential and industrial areas for workplace pollution.

The Detection of Trace Metal Contaminants in Organic Products Using Ion Current Rectifying Quartz Nanopipettes.

While ion current rectification (ICR) in aprotic solvent has been fundamentally studied, its application in sensing devices lacks exploration. The development of sensors operable in these solvents is highly beneficial to the chemical industry, where polar aprotic solvents, such as acetonitrile, are widely used. Currently, this industry relies on the use of inductively coupled plasma mass spectrometry (ICP-MS) and optical emission spectroscopy (OES) for the detection of metal contamination in organic products. Herein, we present the detection of trace amounts of Pd2+ and Co2+ using ion current rectification, in cyclam-functionalized quartz nanopipettes, with tetraethylammonium tetrafluoroborate (TEATFB) in MeCN as supporting electrolyte. This methodology is employed to determine the concentration of Pd in organic products, before and after purification by Celite filtration and column chromatography, obtaining comparable results to ICP-MS within minutes and without complex sample preparation. Finite element simulations are used to support our experimental findings, which reveal that the formation of double-junction diodes in the nanopore enables trace detection of these metals, with a significant response from baseline even at picomolar concentrations.

Optimization of cotton SERS substrates based on different weave structures for surface trace detection

Cotton fabrics have been used to fabricate Surface-enhanced Raman spectroscopy (SERS) substrates due to their excellent properties such as flexibility, hygroscopicity, and large-scale production. The morphology of the SERS substrate has a great influence on the deposition of noble metal nanoparticles and affects the Raman-enhanced signal. Although numerous research reports have been conducted on SERS substrates made from cotton, there has been limited exploration on the impact of the weave structure of cotton fabric on SERS performance. Herein, the cotton SERS substrates were prepared by depositing silver nanoparticles (Ag NPs) on cotton fabrics with different weave structures by a simple vacuum-thermal evaporation method. The influence of substrate morphology on the deposition arrangement of Ag NPs and the enhancement of SERS performance was explored. The analysis findings demonstrate that the cotton SERS substrate displays exceptional Raman signal enhancement performance. Thereinto, the satin SERS substrate exhibited a stronger Raman signal due to its smoother surface favoring the deposition of Ag NPs. The limit of detection for p-aminothiophenol (PATP) was established at a low of 10−8 M, with an RSD value of 9.96%. Moreover, the satin SERS substrate demonstrated an enhancement factor of 5.18 × 105. In addition, it has excellent mechanical flexibility and good hygroscopicity, and thiram on the apple surface can be detected by simple wiping. Cotton SERS substrates show great potential in food safety analysis and monitoring. More importantly, this study provides assistance for the selection of SERS substrates for traditional cotton fabrics, and further promotes the broadening of the application fields of smart cotton fabrics.

The effect of fingerprint enhancement methods applied on adhesive surfaces on DNA recovery: a preliminary study

The presence of body fluids such as blood, saliva, semen or urine during fingerprint research on the evidence taken from the crime scene makes it necessary to protect biological materials to examine the evidence in multiple ways. Therefore, it is crucial that fingerprint development (FD) techniques do not disrupt the structure of biological materials during FD procedures. In this sense, it is essential to determine whether biological material or fingerprints should be the priority during the collection of evidentiary materials, to determine the systematic order and to determine whether the FD methods to be applied cause damage to the genetic material used in the identification of individuals and to evaluate them in terms of their evidentiary quality. This study investigated the effects of the application of trace detection methods on DNA profiling processes in evidence where fingerprints and biological samples are found at the same time. In this study, blood, saliva, semen and urine samples were taken from a male individual who signed an informed consent form at the laboratory stage. The samples were applied 50 µL on the adhesive tape surface. After application, the samples were treated with crystal violet (CV) and sticky side (SS) fingerprint development chemicals suitable for the surface type. The prepared samples were dried under room conditions. After 1 day and 45 days under normal room conditions, silica-based DNA extraction was performed. After extraction, DNA quantification was performed using the fluorimetry method. In the study, biological samples with known DNA content were used to focus on DNA quantification. Among the fresh samples prepared in the study, DNA recovery was higher in the SS-treated urine, blood and saliva samples and in the CV-treated semen sample group compared to the other groups. This shows that chemical treatment of some biological samples on adhesive tape increases the efficiency of DNA recovery. When the 45-day waiting samples were compared with the control group samples, DNA recovery decreased in CV-treated urine and blood samples, while DNA recovery increased in SS-treated urine and blood samples. In semen samples, both CV and SS treatment negatively affected DNA recovery. In saliva samples, DNA recovery increased ~2-fold in the CV-treated sample group, while SS treatment caused a ~75% decrease in DNA recovery. The results show that the non-porous adhesive tape does not adversely affect the amount of DNA in terms of STR profiling of latent FD chemicals used on the surfaces and that adhesive tape treated with fingerprint enhancement chemicals can actually be used for advanced forensic genetic analyses for DNA extraction on surfaces.

Automatic ultrasensitive lateral flow immunoassay based on a color-enhanced signal amplification strategy

Lateral flow immunoassays (LFIAs) are an essential and widely used point-of-care test for medical diagnoses. However, commercial LFIAs still have low sensitivity and specificity. Therefore, we developed an automatic ultrasensitive dual-color enhanced LFIA (DCE-LFIA) by applying an enzyme-induced tyramide signal amplification method to a double-antibody sandwich LFIA for antigen detection. The DCE-LFIA first specifically captured horseradish peroxidase (HRP)-labeled colored microspheres at the Test line, and then deposited a large amount of tyramide-modified signals under the catalytic action of HRP to achieve the color superposition. A limit of detection (LOD) of 3.9 pg/mL and a naked-eye cut-off limit of 7.8 pg/mL were achieved for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleoprotein. Additionally, in the inactivated virus detections, LOD equivalent to chemiluminescence (0.018 TCID50/mL) was obtained, and it had excellent specificity under the interference of other respiratory viruses. High sensitivity has also been achieved for detection of influenza A, influenza B, cardiac troponin I, and human chorionic gonadotrophin using this DCE-LFIA, suggesting the assay is universally applicable. To ensure the convenience and stability in practical applications, we created an automatic device. It provides a new practical option for point-of-care test immunoassays, especially ultra trace detection and at-home testing.

Large-scale SU-8 Micro-Pole-Arrays decorated with Hierarchical Metal-Dielectric-Metal nanostructures as sensitive 3D SERS substrates

Dielectric layer-mediated surface-enhanced Raman scattering (SERS) substrates are currently explored for ultrasensitive detection and expected to provide uniform SERS response by the virtue of three-dimensional micro-nanostructures, dielectric layer, and plasmonic metal nanostructures. For this purpose, the present work reports on the development of the metal-dielectric-metal (MDM) three-dimensional (3D) micro-pole-arrays structure based on SU-8 colloid lithography. By utilizing the large-scale periodic arrangement characteristics of SU-8 colloidal lithography, along with the hot spot effect created by the nano-gap between MDM, we successfully prepared an array of SERS substrates that exhibit both periodicity and multi-dimensional plasmonic coupling effect. Compared to a single metal nanoparticle substrate, the SERS activity of the substrate is significantly enhanced, and the substrate has trace detection ability (LOD of detection of 10−12 mol/L for R6G). The enhancement factor (EF) is 5.72 × 107. Periodicity ensures that the prepared substrate has good reproducibility (RSD < 8 %) and stability. Furthermore, the substrate modified with HS-β-CD demonstrated potential for rapid trace SERS detection of polychlorinated biphenyls (PCB-77) (LOD of 10−8 mol/L for PCB-77). The results indicate that the proposed substrate has the potential for application in the preparation of SERS sensors with high sensitivity and uniformity.

Colorimetric and SERS dual-mode detection of GSH in human serum based on AuNPs@Cu-porphyrin MOF nanozyme

BackgroundRapid and accurate detection of glutathione content in human blood plays an important role in real-time tracking of related diseases. Currently, surface-enhanced Raman scattering/spectroscopy (SERS) combined with nanozyme material has been proven to have excellent properties in the detection applications compared to many other methods because of it combines the advantages of trace detection capability of SERS and efficient catalytic activity of nanozymes. However, there are still existing problems in real sample detection, and to achieve quantitative detection is still challenging. ResultsIn this study, gold nanoparticles (AuNPs) were synthesized in situ on the surface of two-dimensional Cu-porphyrin metal-organic framework (MOF) nanosheets to produce the AuNPs@Cu-porphyrin MOF nanozyme, which exhibited both oxidase-like activity and SERS detection ability. On one hand, the intrinsic oxidase-like activity of the nanozyme could be inhibited due to the chelation of glutathione (GSH) and Cu, which thus led to the visual color change of the solution. On the other hand, the abundant Raman “hot spots” at the nanogap generated by Au NPs and the internal standard (IS) signal provided by Cu-meso-tetra (4-carboxyphenyl) porphine (Cu-TCPP) MOF improved the sensitivity and quantitative accuracy of detection. Significance and noveltyA dual-mode signal output sensor based on the nanozyme was thus established, which could be used in the trace detection of GSH. Such a dual-mode sensor possesses excellent detection performance, with the advantage of both wide detection range from 1 to 300 μM in the colorimetric detection mode and high sensitivity with LOD of 5 nM in the SERS detection mode, and can be applied to GSH detection in actual serum samples with reliable results.

A dual‐responsive luminescent sensor for efficient detection of 3‐nitrotyrosine and dipicolinic acid biomarkers based on copper(II) organic framework

The trace detection of biomarkers in real samples has profound a most important significance in the early diagnosis and daily monitoring of diseases. Based on the ligand pre‐design strategy, a novel 3D CuMOF, with the formula of {[Cu4(BTPB)(μ2‐OH)2(H2O)5]·3H2O}n, was fabricated by using the hexacarboxyl ligand of 1,4‐bis(2,4,6‐tricarboxylpyrid‐5‐yl)benzene (H6BTPB) and tetranuclear {Cu4(COO)4(μ2‐OH)2} SBUs. Benefiting from the robust framework and unique luminescence performance, the prepared CuMOF displays great potential as a dual‐responsive efficient luminescent sensor in “turn‐off” detection of 3‐nitrotyrosine (3‐NT) biomarker and “turn‐on” detecting the anthrax biomarker of dipicolinic acid (DPA), with detection limits (LOD) for 3‐NT and DPA being 110.8 ng/ml and 85.2 ng/ml, respectively. Additionally, the practicality and compatibility of such developed sensors were verified by quantifying 3‐NT and DPA biomarkers in diluted serum and urine samples with satisfactory recoveries. Further, the theoretical calculations of energy levels as well as the spectral overlap between the analytes and CuMOF were conducted to elucidate the possible sensing mechanisms. This work demonstrated that MOFs‐based luminescent sensors are evolving as an efficacious and equable approach for the detection of biomarkers in real samples.

CuCo2O4 nanoneedle arrays growth on carbon cloth as a non-enzymatic electrochemical sensor with low detection limit ketoprofen recognition.

An electrochemical sensor for detecting ketoprofen was constructed by in-situ grown copper cobaltate (CuCo2O4) nanoneedle arrays on a carbon cloth (CC) substrate. The resulting porous nanoneedle arrays not only expose numerous electrochemically active sites but also significantly enhance the electrochemical apparent active area and current transmission efficiency. By leveraging its electrochemical properties, the sensor achieves an impressive detection limit for ketoprofen of0.7 pM, with a linear range spanning from 2 pM ~ 2 µM. Furthermore, the sensor exhibits remarkable reproducibility, anti-interference capabilities, and stability. Notably, the developed sensor also performed ketoprofen detection on real samples (including drug formulations and wastewater) and demonstrated excellent recognition ability. These exceptional performances can be attributed to the direct growth of CuCo2O4 nanoneedle arrays on the CC substrate, which facilitates a robust electrical connection, provides abundant electrocatalytic active sites, and expands the apparent active area. Consequently, these improvements contribute to the efficient trace detection capabilities of the ketoprofen sensor.

Sub-PPB Detection with Gas-Phase Multiphoton Electron Extraction Spectroscopy under Ambient Conditions.

Multiphoton electron extraction spectroscopy (MEES) is an advanced analytical technique that has demonstrated exceptional sensitivity and specificity for detecting molecular traces on solid and liquid surfaces. Building upon the solid-state MEES foundations, this study introduces the first application of MEES in the gas phase (gas-phase MEES), specifically designed for quantitative detection of gas traces at sub-part per billion (sub-PPB) concentrations under ambient atmospheric conditions. Our experimental setup utilizes resonant multiphoton ionization processes using ns laser pulses under a high electrical field. The generated photoelectron charges are recorded as a function of the laser's wavelength. This research showcases the high sensitivity of gas-phase MEES, achieving high spectral resolution with resonant peak widths less than 0.02 nm FWHM. We present results from quantitative analysis of benzene and aniline, two industrially and environmentally significant compounds, demonstrating linear responses in the sub-PPM and sub-PPB ranges. The enhanced sensitivity and resolution of gas-phase MEES offer a powerful approach to trace gas analysis, with potential applications in environmental monitoring, industrial safety, security screening, and medical diagnostics. This study confirms the advantages of gas-phase MEES over many traditional optical spectroscopic methods and demonstrates its potential in direct gas-trace sensing in ambient atmosphere.

Mid-infrared trace detection with parts-per-quadrillion quantitation accuracy: Expanding frontiers of radiocarbon sensing

Detection sensitivity is a critical characteristic to consider during selection of spectroscopic techniques. However, high sensitivity alone is insufficient for spectroscopic measurements in spectrally congested regions. Two-color cavity ringdown spectroscopy (2C-CRDS), based on intra-cavity pump-probe detection, simultaneously achieves high detection sensitivity and selectivity. This combination enables mid-infrared detection of radiocarbon dioxide ([Formula: see text]CO[Formula: see text]) molecules in room-temperature CO[Formula: see text] samples, with 1.4 parts-per-quadrillion (ppq, 10[Formula: see text]) sensitivity (average measurement precision) and 4.6-ppq quantitation accuracy (average calibrated measurement error for 21 samples from four separate trials) demonstrated on samples with [Formula: see text]C/C up to [Formula: see text]1.5[Formula: see text] natural abundance ([Formula: see text]1,800 ppq). These highly reproducible measurements, which are the most sensitive and quantitatively accurate in the mid-infrared, are accomplished despite the presence of orders-of-magnitude stronger, one-photon signals from other CO[Formula: see text] isotopologues. This is a major achievement in laser spectroscopy. A room-temperature-operated, compact, and low-cost 2C-CRDS sensor for [Formula: see text]CO[Formula: see text] benefits a wide range of scientific fields that utilize [Formula: see text]C for dating and isotope tracing, most notably atmospheric [Formula: see text]CO[Formula: see text] monitoring to track CO[Formula: see text] emissions from fossil fuels. The 2C-CRDS technique significantly enhances the general utility of high-resolution mid-infrared detection for analytical measurements and fundamental chemical dynamics studies.

Ultrasensitive solid-state electrochemiluminescence sensor based on lotus root shaped carbon fiber, CdSe QDs and Fe3O4 synergically amplify Ru(bpy)32+ luminophore signal for detection of cyfluthrin.

An efficient and innovative electrochemiluminescence (ECL) sensor was developed for trace detection of cyfluthrin.The sensor utilized materials such as lotus root shaped carbon fiber (Co CNFs), cadmium selenide quantum dots (CdSe QDs), and Fe3O4 to amplify Ru(bpy)32+ signals. Co CNFs, with its large specific surface area and porosity, served the purpose of not only enhancing the stability of the sensor by fixing CdSe QDs and Ru(bpy)32+ on the Co CNFs/GCE, but also facilitating electron transfer. CdSe QDs was involved in the luminescence reaction and collaborated with Ru(bpy)32+ to enhance the sensor's sensitivity, while Fe3O4 promoted electron transfer in the system due to its large surface area. The solid-state ECL sensor achieved satisfactory signal under the synergistic action of these components. The ECL signal of the sensor was quenched by cyfluthrin, and a favorable linear relationship was observed between the sensor and cyfluthrin in the concentration range 1 × 10-12 to 1 × 10-6 M. The detection limit of the sensor was 3.3 × 10-13 M (S/N = 3). The utilization of lotus root shaped carbon fiber, CdSe QDs, and Fe3O4 in the Ru(bpy)32+ system demonstrated a synergistic effect for cyfluthrin detection, presenting a new approach for the rapid determinationanalysis of pesticide residues in foods.