Low Low Limit Of Detection Research Articles

A nanopore-based label-free CRISPR/Cas12a system for portable and ultrasensitive detection of zearalenone

BackgroundFood safety has become a serious global concern. Therefore, there is a need for effective detection technologies in this field. Currently, the development of effective on-site detection techniques is extremely important for food safety. However, the traditional on-site detection methods currently lack effective signal amplification. Herein, the aim of this study was to construct a nanopore-based label-free CRISPR/Cas12a system for the detection of Zearalenone (ZEN). The method is expected to be highly sensitive for portable detection of ZEN in food. ResultsThe proposed strategy was mainly involved three steps, including the displacement of the target DNA, the triggering of the cleavage of hairpin DNA probes (probes 1) by the trans-cleavage of CRISPR/Cas12a, and the generation of a measurable nanopore current signal. The probes 1 and DNA after the cleavage of probes 1 (probes 2) produce different characteristic nanopore signals as they pass through the nanopore. The established method achieved a low limit of detection (LOD) of 6.52 fM for ZEN and a wide liner range under optimized conditions. Furthermore, the practical applicability of this method was verified in real maize samples and showed good recoveries (90.68–101.98 %) and low relative standard deviations (RSD) (9.21–9.72 %). Therefore, this method is a promising option for rapid and ultrasensitive detection of ZEN. Significance and noveltyThe study presented a portable nanopore-based CRISPR/Cas12a signal amplification detection system for the detection of ZEN in food, which had a low LOD and the advantages of rapid, portability, and on-site detection potential. In conclusion, the method presented a promising prospect and universal platform for the detection of ZEN and other mycotoxins, offering a novel insight into on-site food safety detection.

A highly sensitive ratiometric near-infrared nanosensor based on erbium-hyperdoped silicon quantum dots for iron(Ⅲ) detection

Ratiometric fluorescent detection of iron(Ⅲ) (Fe3+) offers inherent self-calibration and contactless analytic capabilities. However, realizing a dual-emission near-infrared (NIR) nanosensor with a low limit of detection (LOD) is rather challenging. In this work, we report the synthesis of water-dispersible erbium-hyperdoped silicon quantum dots (Si QDs:Er), which emit NIR light at the wavelengths of 810 and 1540 nm. A dual-emission NIR nanosensor based on water-dispersible Si QDs:Er enables ratiometric Fe3+ detection with a very low LOD (0.06 μM). The effects of pH, recyclability, and the interplay between static and dynamic quenching mechanisms for Fe3+ detection have been systematically studied. In addition, we demonstrate that the nanosensor may be used to construct a sequential logic circuit with memory functions.

Nano-Photonic Crystal D-Shaped Fiber Devices for Label-Free Biosensing at the Attomolar Limit of Detection.

Maintaining both high sensitivity and large figure of merit (FoM) is crucial in regard to the performance of optical devices, particularly when they are intended for use as biosensors with extremely low limit of detection (LoD). Here, a stack of nano-assembled layers in the form of 1D photonic crystal, deposited on D-shaped single-mode fibers, is created to meet these criteria, resulting in the generation of Bloch surface wave resonances. The increase in the contrast between high and low refractive index (RI) nano-layers, along with the reduction of losses, enables not only to achieve high sensitivity, but also a narrowed resonance bandwidth, leading to a significant enhancement in the FoM. Preliminary testing for bulk RI sensitivity is carried out, and the effect of an additional nano-layer that mimics a biological layer where binding interactions occur is also considered. Finally, the biosensing capability is assessed by detecting immunoglobulin G in serum at very low concentrations, and a record LoD of 70 aM is achieved. An optical fiber biosensor that is capable of attaining extraordinarily low LoD in the attomolar range is not only a remarkable technical outcome, but can also be envisaged as a powerful tool for early diagnosis of diseases.

Oxygen Vacancy-Induced Low-Valence reactive species enabling High-Efficient nonenzymatic glucose detection

NiCo2O4 (NCO), a typical spinel-type transition metal oxide, emerges as a promising candidate for non-electroenzymatic glucose sensors because of its stable structure and low overpotential. However, the practical applications of NCO are hindered by its limited intrinsic activity for glucose detection. Herein, we intentionally incorporated low-valence redox species into NCO nanowires by modulating the oxygen vacancies (VO-NCO NWs), thereby facilitating glucose oxidation reactivity. The concentration of low-valence species increases with the generated oxygen vacancies, which enriches the reactive redox species and enhances the intrinsic electrical conductivity, thereby improving the catalytic activity. Consequently, the optimized VO-NCO NWs exhibit highly efficient glucose detection with high sensitivity up to 19.65 mA·mM−1·cm−2, which is 4.6 times higher than that of the pristine NCO NWs, as well as a low limit of detection (LOD) of 0.15 μM. Furthermore, a flexible miniaturized three electrode (FMTE) assembled with optimized VO-NCO NWs provides a high sensitivity of 15.89 mA·mM−1·cm−2 and a low LOD of 0.18 μM in synthetic sweat. Under various bending conditions, the FMTE demonstrates good mechanical flexibility, with no discernible alterations in the response current. These findings provide a promising protocol for the dynamic monitoring of sweat composition to reveal human physiological health status.

Real-time biomolecule detection using GMR chip-based sensor with green-synthesized Fe3O4/rGO nanocomposites as magnetic labels

The availability of a rapid, low-cost, and easy-to-use device to monitor the bovine serum albumin (BSA) level in human blood and urine is vital in early disease detection. This work reports a biosensor system based on a giant magnetoresistance (GMR) chip as a transducer integrated with Fe3O4/rGO magnetic labels for BSA protein detection. The commercial chip AAL024 is utilized as the GMR sensor, combined with an Arduino microcontroller (AM) and a basic differential amplifier to acquire the digital output voltage. The Fe3O4/rGO nanocomposites were synthesized by a hybrid process based on the green synthesis route utilizing plant extracts. The nanocomposites exhibit superparamagnetic behavior, affecting the magnetic label detection quality. In investigating sensor performance, Fe3O4/rGO nanocomposites can generate sufficient stray fields under a 4 Oe of bias magnetic field (HB). A larger net stray field is produced by a higher concentration of magnetic labels, which suggests that there are more Fe3O4 nanoparticles attached to the sensor surface. Further, the effectiveness of the biosensor was evaluated by detecting the BSA protein. As a result, a high sensitivity of 22.98 mV/(mg/mL) and a low limit of detection (LOD) of 0.3 mg/mL were obtained in detecting Fe3O4/rGO(5:1)/BSA with a voltage signal that can be collected in 30 s. Besides its high sensitivity, low LOD, and fast detection, the sensor exhibits remarkable reproducibility and stability, as evidenced by the relative signal deviation (RSD) range of 1.1 – 5.6%. These findings demonstrate that the GMR chip-based sensor integrated with Fe3O4/rGO magnetic labels provides a simple biosensor system with real-time electronic readout.

Enhanced Potentiometric Hydrogen Sensing Response Based on the Ba0.5Sr0.5Co1-yFeyO3-δ Electrode with Unusual Polarity.

In this work, unusual potentiometric hydrogen sensing of mixed conducting Ba0.5Sr0.5Co0.8Fe0.2O3-δ was reported. Inspired by the unusual polarity, a dual sensing electrode (SE) potentiometric hydrogen sensor was fabricated by pairing Ba0.5Sr0.5Co0.8Fe0.2O3-δ with electronic conducting ZnO to enhance the hydrogen response. Hydrogen sensing measurements suggested that significantly higher response, larger sensitivity, and lower limit of detection (LOD) were achieved by the dual SE sensor when compared with the single SE sensor based on Ba0.5Sr0.5Co0.8Fe0.2O3-δ or ZnO. A high response of 97.3 mV for 500 ppm hydrogen and a low LOD of 2.5 ppm were obtained by the dual SE sensor at 450 °C. Furthermore, the effect of the Fe doping concentration in Ba0.5Sr0.5Co1-yFeyO3-δ (y = 0.2, 0.5, and 0.8) on hydrogen sensing response was investigated. The potentiometric response values to hydrogen increased monotonically with increasing Fe doping concentration. With the Fe/Co atomic ratio increased from 0.25 to 4, the responses to 500 ppm hydrogen raised by 69.6 and 94% at 350 and 450 °C, respectively. The sensing behaviors of unusual Ba0.5Sr0.5Co1-yFeyO3-δ may be ascribed to the predominant surface electrostatic effect. These results show that mixed conducting Ba0.5Sr0.5Co1-yFeyO3-δ is desirable for developing high-performance dual SE hydrogen sensors.

First report for fluorometric determination of kasugamycin based on amino acid-functionalized bimetallic nanoclusters

A rapid and straightforward turn-off fluorescence sensor has been developed for the detection of kasugamycin (KASN) using tryptophan-capped silver/gold bimetallic nanoclusters (Trp@Ag-Au NCs). The sensor's parameters, including reaction time and solvent type, were optimized to enhance its performance. The fluorescence emission of Trp@Ag-Au NCs is quenched upon the addition of KASN due to the aggregation of the Trp@Ag-Au NCs induced by the electrostatic and non-covalent interactions between the negatively charged Trp@Ag-Au NCs and the positively charged KASN. The sensor exhibited excellent sensitivity for KASN detection, demonstrating a linear concentration range from 0.5 to 500 µM and a low limit of detection (LOD) of 0.14 µM, determined at a signal-to-noise ratio of 3. These values indicate the sensor's ability to accurately detect KASN even at low concentrations. To evaluate its practical utility, spike recovery analysis was performed in synthetic samples, confirming its effectiveness in real-world sample matrices. The optimized sensor parameters, wide linear range, low LOD, and successful application in various samples highlight the sensor's potential for practical use in various applications, including food safety and biomedical research. Its simplicity, rapidity, and sensitivity make it a promising tool for the detection of KASN.

A Single Set of Well‐Designed Aptamer Probes for Reliable On‐site Qualitative and Ultra‐Sensitive Quantitative Detection

AbstractAptamer‐based probes are pivotal components in various sensing strategies, owing to their exceptional specificity and versatile programmable structure. Nevertheless, numerous aptamer‐based probes usually offer only a single function, limiting their capacity to meet the diverse requirements of multi‐faceted sensing systems. Here, we introduced supersandwich DNA probes (SSW‐DNA), designed and modified on the outer surface of nanochannels with hydrophobic inner walls, enabling dual functionality: qualitative detection for on‐site analysis and quantitative detection for precise analysis. The fragmented DNAs resulting from the target recognition, are subsequently identified through lateral flow assays, enabling robust on‐site qualitative detection of microcystin‐LR with an impressively low limit of detection (LOD) at 0.01 μg/L. Meanwhile, the nanochannels enable highly sensitive quantification of microcystin‐LR through the current analysis, achieving an exceptionally low LOD at 2.5×10−7 μg/L, with a broad dynamic range spanning from 1×10−6 to 1×102 μg/L. Furthermore, the process of target recognition introduces just a single potential error propagation, which reduces the overall risk of errors during the entire qualitative and quantitative detection process. This sensing strategy broadens the scope of applications for aptamer‐based composite probes, holding promising implications across diverse fields, such as medical diagnosis, food safety, and environmental protection.

A Single Set of Well-Designed Aptamer Probes for Reliable On-site Qualitative and Ultra-Sensitive Quantitative Detection.

Aptamer-based probes are pivotal components in various sensing strategies, owing to their exceptional specificity and versatile programmable structure. Nevertheless, numerous aptamer-based probes usually offer only a single function, limiting their capacity to meet the diverse requirements of multi-faceted sensing systems. Here, we introduced supersandwich DNA probes (SSW-DNA), designed and modified on the outer surface of nanochannels with hydrophobic inner walls, enabling dual functionality: qualitative detection for on-site analysis and quantitative detection for precise analysis. The fragmented DNAs resulting from the target recognition, are subsequently identified through lateral flow assays, enabling robust on-site qualitative detection of microcystin-LR with an impressively low limit of detection (LOD) at 0.01 μg/L. Meanwhile, the nanochannels enable highly sensitive quantification of microcystin-LR through the current analysis, achieving an exceptionally low LOD at 2.5×10-7 μg/L, with a broad dynamic range spanning from 1×10-6 to 1×102 μg/L. Furthermore, the process of target recognition introduces just a single potential error propagation, which reduces the overall risk of errors during the entire qualitative and quantitative detection process. This sensing strategy broadens the scope of applications for aptamer-based composite probes, holding promising implications across diverse fields, such as medical diagnosis, food safety, and environmental protection.

Universal smartphone-assisted label-free CRISPR/Cas12a-DNAzyme chemiluminescence biosensing platform for on-site detection of nucleic acid and non-nucleic acid targets

The clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein (Cas) (CRISPR/Cas) system enables sensitive and specific detection of biomolecules, thanks to its programmability, high fidelity, and powerful signal amplification capabilities. Herein, a universal smartphone-assisted label-free G-quadruplex (G4) DNAzyme-based chemiluminescence CRISPR/Cas12a biosensing platform (G4CLCas) is firstly described that achieves on-site, ultrasensitive visual detection of nucleic acid and non-nucleic acid targets. The G4CLCas-based sensing platform relies on Cas12a trans-cleavage activation that triggers the cleavage of the G4 DNAzyme, resulting in chemiluminescence signals off/on compared to that of the control. Chemiluminescence signals are captured as images that are quantitatively analyzed and visualized using a smartphone-assisted imaging cartridge. Under optimal conditions, G4CLCas achieves a low limit of detection (LOD) of 8.6 aM (∼5.2 copies/μL) for monkeypox virus (MPXV) DNA within the linear concentration range of 10–300 aM and can accurately quantify viral DNA in spiked samples. G4CLCas can also detect non-nucleic acid targets, whereby it achieves a low LOD value of 84.3 nM for adenosine triphosphate (ATP) within the linear concentration range of 2–2000 μM. Here, a label-free, portable, on-site CRISPR/Cas12a chemiluminescence biosensing platform based on the G4 DNAzyme substrates is proposed with potential applications in clinical detection and bioanalytical chemistry research.

Cu-Based Nanoneedle Array for Electrochemical Detection of Nitrate

The extensive usage of nitrogen-based fertilizers, food preservatives and explosive chemicals in various industries has led to the accumulation of nitrate in the ecosystems, especially in soil and water bodies. Several severe environmental and human health issues, including eutrophication, diseases related to N-nitroso compounds (such as Cancer, Parkinson and Gastritis) and blue-baby syndrome (methemoglobinemia), have arisen from the excessive nitrate concentration in the environment. Consequently, various government and regulatory agencies, such as the U.S. Environmental Protection Agency (EPA), have established the maximum nitrate ion concentration in drinkable water at 44 mg/L (0.71 mM). In this context, an accurate monitoring of the level of nitrate becomes important in environmental pollution control, food, clinical analysis, and other industries. While the spectroscopy techniques are of the most use due to its high precision and low limit of detection (LOD), these methods frequently require skilled workforces and specific instrumentations to operate. The electrochemical sensors benefit from recent developments of new nanomaterials to detect nitrate with a quick response, ability of continuously monitoring, small and simple instrumentation as well as easy to use. Several studies have utilized different strategies to fabricate Cu-based nanostructures (such as nanoparticles, nanoclusters, nanowires, and single-crystals) to achieve a low LOD. However, the sensitivity that has been achieved so far is still relatively low compared to the requirements for the real sampling applications.In this work, we utilized a one-step electrodeposition method to prepare Cu-based nano-array electrodes with high active surface sites, aiming for a fast and sensitive electrochemical detection of nitrate. The morphology of the array can be fine-tuned between nanoneedle and nanowire structures (Figure 1a and 1b). The x-ray diffraction (XRD) measurements indicate that the Cu-based nanoneedle array exhibited an abundant Cu(220) facet than the nanowire systems, which is usually associated with the active edge sites on copper (Figure 1c). The nanoneedle array was used for nitrate sensing via Cyclic Voltammetry methods which showed a sensitivity of 2.8 μA/μM*cm2, about 5-fold higher than the Cu foil control electrode (Figure 1d). The main reason of the sensitivity enhancement is that the nanoneedle structure resulted in a 30 times enrichment in the surface area compared to the Cu foil as shown in the electrochemical surface area (ECSA) measurement. Overall, our study provides a novel and convenient design of highly ordered Cu nanoneedle array structure for the sensitive electrochemical detection of nitrate. Figure 1

A triple-aptamer tetrahedral DNA nanostructures based carbon-nanotube-array transistor biosensor for rapid virus detection

Outbreaks of infectious viruses cause enormous challenges to global public health. Recently, the coronavirus disease 2019 (COVID-19) induced by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has severely threatened human health and resulted in the global pandemic. A strategy to detect SARS-CoV-2 with both fast sensing speed and high accuracy is urgently required. Here, rapid detection of SARS-CoV-2 antigen using carbon-nanotube-array-based thin-film transistor (CNT-array-based TFT) biosensors merged with tetrahedral DNA nanostructures (TDNs) and triple aptamers is demonstrated for the first time. Compared with CNT-network-based TFT biosensors and metal-electrode-based CNT-TFT biosensors, the response of CNT-array-based TFT biosensors can be enhanced up to 102% for SARS-CoV-2 receptor-binding domain (RBD) detection, which is supported by its sensing mechanism. By combining TDNs with triple aptamers, the biosensor has realized the wildtype SARS-CoV-2 RBD detection in a broad detection range spanning eight orders of magnitude with a low limit of detection (LOD) of 10 aM (6 copies/μL) owing to the improved protein capture efficiency. Moreover, the triple-aptamer biosensor platform has achieved the detection of SARS-CoV-2 Omicron RBD in a low LOD of 6 aM (3.6 copies/μL). Additionally, the CNT-array-based TFT biosensors have exhibited excellent specificity, enabling identification among SARS-CoV-2 antigen, SARS-CoV antigen and MERS-CoV antigen. The platform of CNT-array-based TFT biosensors combined with TDNs and triple aptamers provides a high-performance and rapid approach for SARS-CoV-2 detection, and its versatility by altering specific aptamers enables the possibility for rapid virus detection.

Electrochemical Immunosensor for Ultra-Low Detection of Human Papillomavirus Biomarker for Cervical Cancer.

Human papillomavirus (HPV) is the causative agent for cervical cancer. Of the various types of HPV, the high-risk HPV-16 type is the most important antigenic high-risk HPV. In this work, the antigenic HPV-16 L1 peptide was immobilized on a glassy carbon electrode and used to detect several concentrations of the anti-HPV-16 L1 antibody, and vice versa. Two electrode platforms were used: onion-like carbon (OLC) and its polyacrylonitrile (OLC-PAN) composites. Both platforms gave a wide linear concentration range (1.95 fg/mL to 6.25 ng/mL), excellent sensitivity (>5.2 μA/log ([HPV-16 L1, fg/mL]), and extra-ordinarily low limit of detection (LoD) of 1.83 fg/mL (32.7 aM) and 0.61 fg/mL (10.9 aM) for OLC-PAN and OLC-based immunosensors, respectively. OLC-PAN modified with the HPV-16 L1 protein showed low LoD for the HPV-16 L1 antibody (2.54 fg/mL, i.e., 45.36 aM), proving its potential use for screening purposes. The specificity of detection was proven with the anti-ovalbumin antibody (anti-OVA) and native ovalbumin protein (OVA). An immobilized antigenic HPV-16 L1 peptide showed insignificant interaction with anti-OVA in contrast with the excellent interaction with anti-HPV-16 L1 antibody, thus proving high specificity. The application of the immunosensor as a potential point-of-care (PoC) diagnostic device was investigated with screen-printed carbon electrodes, which detected ultra-low (ca. 0.7 fg/mL ≈ 12.5 aM) and high (ca. 12 μg/mL ≈ 0.21 μM) concentrations. This study represents the lowest LoD reported for HPV-16 L1. It opens the door for further investigation with other electrode platforms and realization of PoC diagnostic devices for screening and testing of HPV biomarkers for cervical cancer.

Design of multifunctional fluorescent self-assembly system for sensing Hg2+, volatile acids and being applied as anti-counterfeit materials through the transformation of ACQ-to-AIE

An AIE self-assembly system (APNP) was constructed based on 2, 9-diamino- 1,10-phenanthroline (APhen). APNP could form fluorescent organogels in some solvents along with the formation of microbelt and microrod. The self-assembly behaviors of APNP in different solvents were studied by multiple technologies. The formation of the gel mainly benefited from hydrogen bonding. Even APhen as basic skeleton possessed the sizably conjugated structure, π-π stacking interaction between them was effectively prohibited due to the large steric hindrance at the terminal, which was successfully induced the transformation from ACQ to AIE. Solution APNP possessed highly selective and ultrafast detection of Hg2+ with a low limit of detection (LOD) of 1.57 nM. Gel APNP in THF/H2O (v/v, 5/1) also exhibited selective response to Hg2+ by showing multimode signal expression including colour, gel state and emission. APNP could detect volatile acids in solution, gel and film states via protonation of the 1, 10-phenanthroline group. Especially for gaseous TFA, film APNP could rapidly detect TFA gases with a very low LOD of 7.95 ppb within 0.5 s. The present study will provide a new way to achieve AIE fluorescent materials from ACQ materials.

Toward femtomolar detection of heavy metal ions using uniform liquid crystal films with 1 × 1 cm2 active regions

Photoresist grids (PGs) hosting uniform ligand-doped liquid crystal (LC) films with large active regions of 1 × 1 cm2 are fabricated in this work. The length and thickness of the meshes of the PGs are optimized by studying the anchoring energy of the alignment layers of the LC films. The PGs hosting the LC films exhibit the significant transition of optical signals from dark to bright after the binding of ligand and Hg2+ reorients the LC. The optimized PGs hosting the LC films have an extremely low limit of detection (LOD) of 5.0 ± 0.4 femtomolar (fM) for detecting Hg2+ in aqueous solutions. The LOD is 2 × 106 times lower than those of current LC sensors, and 24 times lower than those of current electrochemical sensors. Without using a polarized optical microscope, the image of a PG hosting an LC film is clearly observed by naked eyes when the film is exposed to an aqueous solution with 5.0 ± 0.4 fM Hg2+. The extremely low LOD and real naked-eye detection are great achievements for the practical applications of LC sensors.

Visual detection and highly sensitive quantification of antibiotic meropenem in pharmaceutical and human plasma samples using gold nanoparticles

ABSTRACT Meropenem is a broad-spectrum β-lactam antibiotic effective against a wide variety of gram-positive and gram-negative organisms, and has been extensively used in the intensive care unit (ICU) for severe infections caused by susceptible microorganisms that are resistant to other available drugs. A novel visual detection and highly sensitive method for meropenem quantification has been developed for the first time, based on the aggregation of citrate-capped gold nano particles (AuNPs) induced by the interaction with meropenem, leading to the change in surface plasmon resonance (SPR) properties of AuNPs. By naked eyes, one can detect meropenem trace by the visual change of gold solution color from red to blue, corresponding to the shift of absorbance maximum in the UV-Vis spectrum from 520 nm to 660 nm. Quantification of meropenem is possible through a linear relationship between the optical absorption ratio A660/A520 and the logarithm of meropenem concentrations. The present method has high recovery (97.6–101.5%), high precision (RSD<4.5%), and selectivity over other possible interferences such as glucose, sucrose, lactose, and sodium carbonate. This method has been successfully applied to determine meropenem in several pharmaceutical samples with a very low limit of detection (LOD) of 0.06 mg/L. Cross-checks with HPLC-DAD method show a good agreement between the two methods. For blood analysis, in combination with liquid-liquid extraction, the developed method presents high specificity, low LOD of 0.64 mg/L, and applicability to analysis of plasma samples taken from patients treated with meropenem under intensive care.

Crumpled graphene/Ni(OH)2 nanocomposites applied as electrochemical sensors for glucose and persistent contaminants

Different Ni depositions on acetate were performed using adsorption and electrochemical deposition methods. The optimization of the Ni deposition was carried out taking into account the best electrocatalytic behavior for glucose oxidation in an alkaline medium employing chronoamperometry. The best electrochemical behavior was achieved using electrochemical deposition through the application of 0.7 V for 30 s in a Ni+2 aqueous solution, followed by the cycling in KOH aqueous solution, in order to lead to thin films of CG homogeneously decorated with 3.79 ± 0.04 nm Ni(OH)2 nanoparticles. The glucose detection was optimized for the CG/Ni(OH)2 thin films reaching a low limit of detection (LD) of 0.34 ± 0.04 μmol L−1 for a wide linear range of detection (LRD) from 1 to 1000 μmol L−1 with good reproducibility, repeatability and low interferents effect. The CG/Ni(OH)2 thin films also exhibited very low LD for n-acetylcysteine, hydrochlorothiazide, and famotidine (0.54 ± 0.07, 2.38 ± 0.45, and 0.91 ± 0.48 μmol L−1, respectively) and a wide LRD (from 1 to 1000 μmol L−1).

Universal N2O Reaction Gas To Remove Spectral Interferences of Nonmetallic Impurity Elements by Inductively Coupled Plasma Tandem Mass Spectrometry Analysis of High-Purity Magnesium Alloys.

Using N2O as a universal reaction gas, a new strategy was proposed for the highly sensitive interference-free simultaneous determination of nonmetallic impurity elements in high-purity magnesium (Mg) alloys by ICP-MS/MS. In the MS/MS mode, through O-atom and N-atom transfer reactions, 28Si+ and 31P+ were converted to the oxide ions 28Si16O2+ and 31P16O+, respectively, while 32S+ and 35Cl+ were converted to the nitride ions 32S14N+ and 14N35Cl+, respectively. The ion pairs formed via the 28Si+ → 28Si16O2+, 31P+ → 31P16O+, 32S+ → 32S14N+, and 35Cl+ → 14N35Cl+ reactions by the mass shift method could eliminate spectral interferences. Compared with the O2 and H2 reaction modes, the present approach delivered much higher sensitivity and lower limit of detection (LOD) of the analytes. The accuracy of the developed method was evaluated via standard addition method and comparative analysis by sector field ICP-MS (SF-ICP-MS). The study indicates that in the MS/MS mode, use of N2O as reaction gas can provide interference-free conditions and sufficiently low LODs for analytes. The LODs of Si, P, S, and Cl could reach down to 17.2, 4.43, 10.8, and 31.9 ng L-1, respectively, and the recoveries were in the range of 94.0-106%. The determination results of the analytes were consistent with those obtained by SF-ICP-MS. This study presents a systematic method for the precise and accurate quantification of Si, P, S, and Cl in high-purity Mg alloys by ICP-MS/MS. The developed method provides valuable reference that can be expanded and applied to other fields.

Sex Pheromone Receptor-Derived Peptide Biosensor for Efficient Monitoring of the Cotton Bollworm Helicoverpa armigera.

The cotton bollworm, Helicoverpa armigera (H. armigera), causes damage to a wide range of cultivated crops and is one of the pests with the greatest economic importance for global agriculture. Currently, the detection of H. armigera is based on manual sampling. A low limit of detection (LOD), convenient, and real-time monitoring method is urgently needed for its early warning and efficient management. Here, we characterized the amino acid sequence in the sex pheromone receptors (SPRs) recognizing the pheromone components of H. armigera by three-dimensional (3D) modeling and molecular docking. Next, sex pheromone receptor-derived peptides (SPRPs) were synthesized and conjugated to nanotubes by chemical connection. The modified nanotubes were used to fabricate a sensor capable of real-time monitoring of gaseous sex pheromone compounds with a low LOD (∼10 ppb for Z11-16:Ald) and selectivity, and the sensor was able to detect a single live H. armigera. Furthermore, the developed biosensor allowed direct monitoring of the pheromone release dynamics by female H. armigera and showed that the release was instantly reduced in response to light. Here, we report the first demonstration of a biosensing method for detecting gaseous sex pheromones and live H. armigera. The findings show the great potential of the SPRP sensor for broad applications in insect biology study and infestation monitoring.

Comparison study on ZnO and CuO gas sensing characteristics: Temperature modulated-dual selectivity towards benzene and xylene vapours

The selective detection of gaseous benzene, toluene, ethylbenzene, and xylene (BTEX) is challenging due to their similar molecular structures. In addition, BTEX vapours are extremely hazardous and carcinogenic. Thus, in the current study, n-type ZnO and p-type CuO nanostructures were synthesized utilizing various bases by a simple hydrothermal method. Among the tested sensors, the ZnO–NaOH-based sensor displayed a temperature dual-mode selectivity toward benzene with responses (Ra/Rg) of 2.5 and 24 at 5 and 100 ppm, respectively at 75 °C, and Ra/Rg ≈ 142 toward xylene vapour at 100 ppm at an operating temperature of 150 °C. While the CuO-based sensors showed poor response, sensitivity and selectivity towards tested analytes. Moreover, the ZnO–NaOH based sensor revealed enormous sensitivity of 1.21 ppm−1 and low limit of detection (LoD) of 0.018 ppm (i.e., 18 ppb) toward xylene. The ultra-sensitivity, selectivity, low LoD of ZnO–NaOH based sensor toward benzene and xylene are associated with the improved VO observed in the in-situ photoluminescence and electron paramagnetic resonance studies, and as well as the x-ray photoelectron spectroscopy analyses. The ZnO–NaOH-based sensor, which was stored for roughly 18 months (547 days), demonstrated a reliable repeatability and long-time operation stability for 22 h exposure to xylene. The superior sensitivity, stability, and selectivity indicate openly that the strategy of using various bases is a striking method for fabricating a temperature dual-mode selectivity for the detection of benzene and xylene vapours.