Detection Limit Research Articles

Emissive Hydrazone-Linked Covalent Organic Frameworks as Highly Sensitive and Selective Sensor for the Hydrazine Detection.

Covalent Organic Frameworks (COFs) exhibit a range of exceptional attributes, including notable porosity, outstanding stability, and a precisely tuned π-conjugated network, rendering them highly promising candidates for fluorescence sensors applications. In this study, the synthesis of two emissive hydrazone-linked COFs designed for hydrazine detection is presented. The partially conjugated structure of the hydrazone linkage effectively weakens the fluorescence quenching processes induced by aggregation. Additionally, the incorporation of flexible structural components further reduces conjugation, thereby enhancing luminescent efficiency. Remarkably, these COFs possess a significant abundance of heteroatoms, enabling distinctive interactions with hydrazine molecules, which in turn results in exceptional selectivity and sensitivity for hydrazine detection. The detection limit of these COFs reaches the nanomolar range, surpassing all previously reported COFs, thereby underscoring their superior performance in chemical sensing applications.

Machine Learning-Guided Discovery of Copper(I)-Iodide Cluster Scintillators for Efficient X-ray Luminescence Imaging.

Developing efficient scintillators with environmentally friendly compositions, adaptable bandgaps, and robust chemical stability is crucial for modern X-ray radiography. While copper(I)-iodide cluster crystals show promise, the vast design space of inorganic cores and organic ligands poses challenges for conventional approaches. In this study, we present machine learning-guided discovery of copper(I)-iodide cluster scintillators for efficient X-ray luminescence imaging. Our findings reveal that combining base learning models with fused features enhances model generalization, achieving an impressive determination coefficient of 0.88. By leveraging this approach, we obtain a high-performance Cu(I)-I cluster scintillator, named copper iodide-(1-Butyl-1,4-diazabicyclo[2.2.2]octan-1-ium)2, which exhibit radioluminescence 56 times stronger than that of PbWO4, and enables a detection limit for X-rays of 19.6 nGyair s-1. Furthermore, we demonstrate the versatility of these scintillators by incorporating them as microfillers in the fabrication of flexible composite scintillators for X-ray imaging, achieving a static resolution of 20 lp mm-1 and demonstrating promising performance for dynamic X-ray imaging.

Ultrasensitive Biosensors Detecting m6A in Blood: Achieving Early Screening and Typing of Tumors.

N6-methyladenosine (m6A) modification is one of the most widespread RNA modifications in eukaryotes and is involved in cancer development and progression by regulating oncogene expression. Herein, a reticulated rolling circle amplification (RCA) cascade reaction was used to construct a novel electrochemical biosensor for ultrasensitive detection of m6A, employing ferrocene-tyramine (Fc-Tyr) molecules as electroactive probes. In this strategy, the RCA cascade reaction not only amplifies specific circular DNA in the designed template to reduce the binding with similar nucleic acid sequences but also generates a long ssDNA through multiple repetitions to capture a large number of electrochemical signal probes and achieve the amplification of electrochemical biosensing signals. The developed biosensor demonstrated high selectivity and sensitivity toward m6A in the range of 0.5 pM-150 nM, with a detection limit of 14.07 fM. Meanwhile, total RNA extracted from cell samples was analyzed for m6A expression levels using the developed biosensor and a commercial colorimetric immunoassay, the biosensor and immunoassay showed consistent results. In addition, m6A levels in clinical serum samples were assessed using the developed electrochemical biosensor, which showed that m6A expression was much lower in healthy individuals than in cancer patients, therefore the biosensor is promising for cancer typing. This study provides a new method for rapid and convenient tumor marker detection in clinical practice, as well as a new idea for sensitive detection of other biomolecules.

A handheld fluorescent platform integrated with a Sm(III)-CdTe quantum dot-based ratiometric nanoprobe for point-of-use determination of phosphate.

Phosphate (Pi) is crucial for various physiological processes and aquatic environments, which emphasizes the need for a simple, on-site sensor to promptly detect Pi for human health and environmental conservation. In this study, we propose a dual-emission ratiometric fluorescence sensor for highly sensitive and visual Pi detection. The sensor employs samarium ions (Sm3+) as a core component, with cadmium telluride quantum dots (CdTe QDs) and ofloxacin (OFL) serving as signal carriers. The CdTe-Sm(III)-OFL nanoprobe emits a purple fluorescence resulting from the red fluorescence of CdTe QDs and the blue-green fluorescence of OFL. The fluorescence of OFL is quenched by Sm3+ through fluorescence resonance energy transfer (FRET). Upon Pi interaction, the FRET process is disrupted due to the competitive Pi-Sm3+ binding, which leads to the fluorescence recovery of OFL while the red fluorescence of CdTe remains steady. This enables the construction of a ratiometric fluorescent sensor for Pi detection, manifesting as a color change from purple to blue. The sensor demonstrated a linear response for Pi detection within the range of 0.1-75 μM, with a low detection limit of 17.0 nM. By utilizing the distinct fluorescence responses of various physiological phosphates and employing chemometrics, this innovative dual-emission sensor accurately distinguishes among different physiological phosphates. Furthermore, a portable lab-on-paper device based on CdTe-Sm(III)-OFL, coupled with a smartphone-integrated mini-device, is developed for swift Pi detection using an ordinary smartphone. Analytical performance validated on environmental and biological samples demonstrates the sensor's excellent robustness and adaptability. This study introduces a pioneering approach to fabricate ratiometric fluorescence sensors and customize portable, cost-effective mini-devices for precise target detection, thus opening avenues for advanced sensing strategies in various applications.

Cardiac myosin-binding protein-C: assessing fragmentation patterns to differentiate between forms of myocardial injury

Abstract Background Cardiac myosin-binding protein-C (cMyC) is a novel biomarker of myocardial injury. We hypothesize that fragmentation of cMyC differs according to aetiology of myocardial injury. Assessing the fragmentation pattern of the protein may aid diagnosis of these conditions. Purpose This work represents an examination of cMyC fragmentation in human serum, and studies its utility in differentiating between forms of myocardial injury. Methods Patients who were admitted to a hospital during October-November 2023 with acute myocardial injury were recruited. Acute myocardial injury was defined as a dynamic troponin rise above the 99th centile (Abbott Alinity: cTnI>34ng/L male, cTnI >16ng/L female). Following collection, samples were left at room temperature for 30 minutes and then centrifuged. Serum was separated for cMyC measurement, frozen in liquid nitrogen and stored at -80 °C. Recruited patients were followed up during their inpatient journey. Their final diagnosis was defined using the 4th universal definition of MI by two cardiologists, with a third cardiologist acting as adjudicator, if required. The serum samples were analysed using two separate electrochemiluminescence sandwich ELISA assays detecting different portions of cMyC. One assay formulated for total concentration of cMyC using high affinity mouse N-terminal monoclonal antibodies (mAb) targeting epitopes in close proximity (Limit of Detection (LoD) = 9.0ng/L). The other assay uses a N-terminal and a C-terminal mouse mAb which straddle the major proteolytic cleavage site of cMyC. This assay detects the intact (fuller-length) cMyC (LoD= 14.2ng/L). Both assays perform with good sensitivity, low variability and are capable of detecting cMyC at concentrations well below the 99th centile. Results 11 patient samples were collected with final diagnoses of; type 1 MI (STEMI n=3, NSTEMI n=4), type 4 MI (alcohol septal ablation n=1), acute myocardial injury (myocarditis n=2) and type 2 MI (chest sepsis with known coronary disease n=2). Figure one details the percentage of intact cMyC relative to total cMyC measured in serum for each patient, and is split into their adjudicated diagnosis. The bars display the median and interquartile range (IQR). Our findings suggest that the fragmentation pattern of cMyC could help differentiate between forms of myocardial injury. The ratio of intact: total cMyC was higher in the type 2 MI than any other condition. The results did not reach statistical significance (p = 0.06) due to the small sample size. Conclusions The fragmentation pattern of cMyC is dependent on the type of myocardial injury and could aid in the differentiation between type 2 MI and other forms of myocardial injury.Figure One

A Novel PCR-Free Ultrasensitive GQD-Based Label-Free Electrochemical DNA Sensor for Sensitive and Rapid Detection of Francisella tularensis

Biological warfare agents are infectious microorganisms or toxins capable of harming or killing humans. Francisella tularensis is a potential bioterrorism agent that is highly infectious, even at very low doses. Biosensors for biological warfare agents are simple yet reliable point-of-care analytical tools. Developing highly sensitive, reliable, and cost-effective label-free DNA biosensors poses significant challenges, particularly when utilizing traditional techniques such as fluorescence, electrochemical methods, and others. These challenges arise primarily due to the need for labeling, enzymes, or complex modifications, which can complicate the design and implementation of biosensors. In this study, we fabricated Graphene Quantum dot (GQD)-functionalized biosensors for highly sensitive label-free DNA detection. GQDs were immobilized on the surface of screen-printed gold electrodes via mercaptoacetic acid with a thiol group. The single-stranded DNA (ssDNA) probe was also immobilized on GQDs through strong π−π interactions. The ssDNA probe can hybridize with the ssDNA target and form double-stranded DNA, leading to a decrease in the effect of GQD but a positive shift associated with the increase in DNA concentration. The specificity of the developed system was observed with different microorganism target DNAs and up to three-base mismatches in the target DNA, effectively distinguishing the target DNA. The response time for the target DNA molecule is approximately 1010 s (17 min). Experimental steps were monitored using UV/Vis spectroscopy, Atomic Force Microscopy (AFM), and electrochemical techniques to confirm the successful fabrication of the biosensor. The detection limit can reach 0.1 nM, which is two–five orders of magnitude lower than previously reported methods. The biosensor also exhibits a good linear range from 105 to 0.01 nM and has good specificity. The biosensor’s detection limit (LOD) was evaluated as 0.1 nM from the standard calibration curve, with a correlation coefficient of R2 = 0.9712, showing a good linear range and specificity. Here, we demonstrate a cost-effective, GQD-based SPGE/F. tularensis DNA test suitable for portable electrochemical devices. This application provides good perspectives for point-of-care portable electrochemical devices that integrate sample processing and detection into a single cartridge without requiring a PCR before detection. Based on these results, it can be concluded that this is the first enzyme-free electrochemical DNA biosensor developed for the rapid and sensitive detection of F. tularensis, leveraging the nanoenzyme and catalytic properties of GQDs.

Validation of a smartphone-compatible MIP-based sensor for bisphenol A determination in wastewater samples.

A handheld smartphone-compatible molecularly imprinted polymer (MIP)-based sensor was developed for the analysis of bisphenol A (BPA) in wastewater samples. Sensing elements based on ethylene glycol methacrylate phosphate (EGMP)-containing MIP films were designed and optimized using molecular dynamics simulations. The highly porous MIP films were synthesized via in situ polymerization, employing a fragment-based approach. The colorimetric response was based on the 4-aminoantipyrine method, while the MIP films were further utilized to detect BPA with a smartphone. The proposed sensor exhibited a wide linear range from 5 to 250μM, with a limit of detection (LOD) of 5μM (S/N = 3). Furthermore, the designed analytical system demonstrated excellent analytical performance in terms of selectivity, stability, and reproducibility. During sensor validation, real wastewater samples were successfully tested for BPA, showcasing the feasibility of the smartphone-compatible MIP-based sensor. Recovery values of 87.1-114.6% underscored the efficacy and reliability of the developed sensor system.

Bifunctional SnO2/NiO/rGO nanocomposite electrode for hydrogen evolution reaction and detection of winter wheat cold-resistant RNA.

Aconvenient, non-toxic, and low-cost tin dioxide (SnO2)/nickel oxide (NiO)/reduced graphene oxide (rGO) nanocatalytic electrode was investigated, which can effectively promote the hydrogen evolution reaction and can also be used to construct a sensitive winter wheat cold-tolerant RNA sensor. Due to the good synergy and photocurrent generation between SnO2 and NiO, which accelerates the electron transfer and catalyzes the hydrolysis reaction, the resultant data for the hydrogen evolution reaction in alkaline environment of this material are very impressive, with cathodic current densities of up to 10mAcm-2. The marvelous heterostructures and photovoltaic properties form a signal amplification system, which enables the nanocomposites to have an excellent linear sensitivity in low-concentration RNA solutions. The single-stranded complementary RNA of the target RNA was immobilized on the surface of the nanocomposites, which enabled the materials to recognize the target RNA under enzyme-free conditions. The test results showed that the modified electrode materials had good single detection performance in a wide linear range from 0.1nM to 2mM, with the limit of detection (LOD) of 0.078nM. The developed nanocomposite electrode has good performance in hydrogen evolution and winter wheat cold-resistant RNA detection, and is a bifunctional device with superior performance.

Aggregation-induced emissive copper nanoclusters with peroxidase-like activity for colorimetric detection of cholesterol

Accurate and point-of-care cholesterol detection is of paramount significance for the prevention of cardiovascular diseases. The colorimetric assay based on peroxidase is a commonly used approach for cholesterol detection, without requiring any complicated biomolecular labeling or sophisticated instrumentation. Copper nanoclusters (CuNCs), exhibiting luminescent properties and peroxidase activity, have garnered significant attention in biomedical application recently. Herein, the glutathione-stabilized copper nanoclusters (GSH-CuNCs) were prepared with an easy one-pot method, employing glutathione as both a reducing agent and stabilizer. An optimization of the GSH-CuNCs preparation was carried out to obtain the highest peroxidase-like activity. UV-Vis absorption was measured to explore the steady-state kinetics of the GSH-CuNCs-catalyzed oxidation of 3,3',5,5' - tetramethylbenzidine (TMB) by H2O2. A colorimetric method for cholesterol detection was developed by combining the catalytic reaction of CuNCs and the enzymatic oxidation of cholesterol with cholesterol oxidase (ChOx). Under the optimized conditions, the UV-Vis absorbance of oxidized TMB (oxTMB) is proportional to the concentration of cholesterol within the range of 6.2-187.5 μM, and the limit of detection (LOD) is determined to be 3.0 μM. More importantly, cholesterol levels can be directly distinguished with the naked eye. Furthermore, the practicality of the method for detecting cholesterol in human serum has been verified with promising results. As expected, this simple, cost-effective, and easy-to-operate colorimetric method for cholesterol detection has potential applications in clinical diagnosis and provides valuable insights into the colorimetric sensing based on CuNCs.

A Zn‐MOF With Its Mixed‐Matrix Membranes for Convenient and Efficient Visualization Detection of 3‐Nitrotyrosine Biomarker in Aqueous Media and Practical Application in Serum

ABSTRACTInstant and accurate detection of 3‐nitrotyrosine (3‐NT) biomarker is an important but challenging task in clinical diagnosis, treatment, and monitoring of diseases. Herein, this work reported a Zn (II)–based metal–organic framework (MOF) {[Zn2(BDPT)(DIMB)]}n, denoted as Zn‐BDPT, synthesized by solvothermal method using bis(3,5‐dicarboxyphenyl)terephthalamide (H4BDPT) and 1,4‐di(1H‐imidazol‐1‐yl)butane (DIMB). Neighboring [Zn (COO)2] clusters were connected by BDPT4− units and DIMB to form a (2,4,4)‐connected three‐dimensional (3D) architecture. X‐ray powder diffraction (PXRD) and thermogravimetric (TGA) experiments indicated that Zn‐BDPT had good purity and stability. Zn‐BDPT could selectively and rapidly recognize 3‐NT in an aqueous environment. For rapid economic detection of 3‐NT in actual samples, mixed‐matrix membranes (MMMs) based on Zn‐BDPT were successfully prepared and named Zn‐BDPT@PMMA. The addition of 3‐NT under the UV lamp displayed an evident visible fluorescence quenching effect. Quantitative titration analysis of Zn‐BDPT@PMMA in real serum sample obtained the Ksv value of 1.13 × 104 M−1 and a limit of detection (LOD) of 0.17 μM. This report demonstrated that MOF‐based MMMs could be used as ideal candidate for luminescent probe in actual application.

Colorimetric aptasensing of microcystin-LR using DNA-conjugated polydiacetylene.

Polydiacetylene (PDA) holds promise as a versatile material for biosensing applications due to its unique optical properties and self-assembly capabilities. In this study, we developed a colorimetric detection biosensor system utilizing PDA and aptamer for the detection of microcystin-LR (MC-LR), a potent hepatotoxin found in cyanobacteria-contaminated environments. The biosensor was constructed by immobilizing MC-LR-specific aptamer on magnetic beads, where the aptamer was hybridized with a urease-labelled complementary DNA (cDNA-urease). Upon binding MC-LR, the aptamer undergoes a conformational change to release cDNA-urease. The released cDNA-urease is subsequently captured by PDA bearing a single-stranded DNA (ssDNA). The enzymatic reaction triggers a distinctive color transition of PDA from blue to red. The results demonstrate exceptional sensitivity, with a linear detection range of 5-100ng/mL and a limit of detection as low as 1ng/mL. The practicability of the colorimetric method was demonstrated by detecting different levels of MC-LR in spiked water samples. The recoveries ranged from 77.3 to 102% and the color change, visible to the naked eye, underscores the practical utility for on-site applications. Selectivity for MC-LR over other microcystin variants (MC-RR and MC-YR) was confirmed. The colorimetric detection platform capitalizes on the properties of PDA and nucleic acid, offering a robust method for detecting small molecules with potential applications in environmental monitoring and public health.

Four ecofriendly spectrophotometric methods for the determination of perindopril through derivatization with sulphophtalein dyes: application to tablet analysis

Nowadays, there is a need to expand the bank of spectrophotometric methods for the determination of perindopril in dosage forms for the purposes of routine pharmaceutical analysis, which would be simple, express, «green» and inexpensive. In the present work, perindopril in tablets was quantified via a direct simple, «green», and non-extracting spectrophotometric approach based on the formation of ion-pair complexes with sulphophtalein dyes. The absorbances of the colored reaction products were registered at 405 nm (bromocresol green, BCG), 397 nm (bromocresol purple, BCP, and bromothymol blue, BTB) and 598 nm (bromophenol blue, BPB). To achieve the highest intensity of absorbance, optimum conditions were established by the screening of many experimental factors such as optimal concentration and volume of dyes, and the time consumed for the reaction. Beer’s law was obeyed in the ranges of 0.44–3.96 µg/mL (BCG), 3.00–7.00 µg/mL (BCP), 4.00–12.00 µg/mL (BTB) and 0.44–3.52 µg/mL (BPB). All four methods were validated in accordance with ICH guidelines, confirming specificity and linearity, accuracy and precision, limits of detection and quantification, robustness. These validated methods provide a reliable and green approach for the quantitative analysis of perindopril in tablets, contributing to safer and more sustainable laboratory practices in pharmaceutical analysis.

A portable fluorescence sensing system for timely onsite perfluorooctane sulfonate detection based on an aggregate induced emission fluorescence sensor.

Perfluorooctane sulfonate (PFOS), a ubiquitous persistent organic pollutant, has aroused growing concern due to its adverse effects on human health. Timely onsite monitoring of PFOS in heavily contaminated areas is crucial for effective pollution management and prevention of its spread. However, relevant PFOS detection methods have rarely been reported. Herein, we developed a fluorescence sensing system capable of achieving timely onsite detection of PFOS under outdoor conditions. First, aggregate induced emission (AIE) fluorescence sensors, TPE-PAs, were synthesized. The optimized sensor could selectively interact with PFOS through electrostatic attraction and hydrogen bonding and exhibited prominent fluorescence enhancement after treating with PFOS. There was a good linear relationship between the fluorescence enhancement and PFOS concentration in the range of 0.05-30 ppm, and the limit of detection was measured to be 0.047 ppm. In addition, owing to the AIE fluorescence mechanism and high concentration of TPE-PAs in the sensing medium, the sensor demonstrated excellent anti-interference performance. Second, we developed a portable fluorometer, by modifying the power supply and sample cell of a tiny fluorometer, and further integrated this modified fluorometer, the prepared fluorescence sensor, standard PFOS solutions and other consumables into a portable test system. This test system showed good detection accuracy and reliability and successfully achieved timely onsite PFOS detection in real water samples.

Rapid and sensitive detection of staphylococcal enterotoxin E using a time-resolved fluorescence immunochromatography assay

Staphylococcal food poisoning is a significant foodborne illness caused by staphylococcal enterotoxins (SEs). Immunoassays have become the primary method for rapidly detecting harmful bacteria and toxins because of their excellent sensitivity and specificity. However, these assays have limitations in that they cannot differentiate between types of SEs and do not provide rapid, on-site, quantitative testing. In this study, a time-resolved fluorescence immunochromatography assay (TRFICA) was developed specifically for detecting staphylococcal enterotoxin E (SEE), which is commonly found in dairy products. Compared with a double antibody sandwich enzyme-linked immunosorbent assay, which had a detection limit of 0.028 ng/mL, TRFICA demonstrated comparable sensitivity, enabling SEE quantification with a detection limit as low as 0.081 ng/mL in infant formula. Validation by spiking infant formula samples confirmed no cross-reactivity with analogs (recoveries ranged from 93.17% to 128.77%). Furthermore, with an 8-min reaction time and interpretation delivered by a portable TRFICA strip reader, our method demonstrates potential for use in mobile and on-site detection. This study describes a rapid, easy, and reliable method for detecting trace levels of SEE in infant formula, which could serve as an early screening tool toward preventing food poisoning in infants and children.

Blood pressure and renal function responses in workers exposed to lead for up to six years

Abstract Background Lead is a widespread environmental toxicant. However, there is currently no consensus whether low-level lead exposure raises blood pressure (BP) or induces kidney dysfunction. Purpose The Study for Promotion of Health in Recycling Lead (SPHERL) assessed the BP and renal function (RF) responses for up to six years in the workers without previous occupational lead exposure. Methods BP was the average of 5 consecutive readings and the estimated glomerular filtration rate was derived from serum creatinine (eGFRcrt) and cystatin C (eGFRcys). Blood lead (BL) was measured by inductively coupled plasma mass spectrometry (detection limit 0.5 mg/dL). The statistical methods included multivariable-adjusted mixed models and interval-censored Cox regression analysis. Results The 234 workers analyzed were on average 28.5 years old and included 91.9% men. The baseline BL concentration was 4.35 µg/dL and increased 3.17-fold over follow-up (median: 2.03 years; range: 0.92-6.45 years). The changes in BP and RF were not significantly correlated with the follow-up-to-baseline BL ratio (p≥0.51 and p≥0.18, respectively). The fully-adjusted changes in systolic/diastolic BP associated with a doubling of BL were -0.25/-0.12 mm Hg (CI: -0.94 to 0.44/-0.66 to 0.42 mm Hg). Accordingly, the incidence of stage-1 or -2 hypertension was not associated with the BL change (p≥0.063). Similarly, the changes in eGFRcrt and eGFRcys associated with a 3-fold BL increment were not significant, amounting to -0.70 mL/min/1.73 m2(CI: -1.70 to 0.30 mL/min/1.73 m2) and -1.06 ml/min/1.73 m2 (-2.16 to 0.03 mL/min/1.73 m2). Conclusion The BP and RF responses to an over 3-fold BL increment were small and not significant confirming the safety of modern lead-handing facilities operating under current safety rules.Figure 1Figure 2

SERS Sensor for Acetylcholine Detection Based on Covalent Organic Framework Hybridized Gold Nanoparticles As Nanozymes.

An innovative and potent nanozyme with reductase-like activity was developed by integrating the in situ synthesis of gold nanoparticles (Au NPs) onto the surface of a covalent organic framework (COF). Based on the reductase-like activity of the COF-hybridized Au NPs, this nanozyme could efficiently catalyze the reduction of 4-nitrophenol (4-NPH). Moreover, the prepared nanohybrid was utilized as an excellent surface-enhanced Raman scattering (SERS) substrate for highly sensitive SERS detection by combining the excellent adsorption properties of COFs and the large number of Raman hotspots between the high-density Au NPs. For the first time, 4-NPH was used as an SERS marker to detect the electron receptor acetylcholine (Ach), with high sensitivity; Ach acted as an inhibitor in this catalytic reaction. The linear range of Ach was 1.0 pM to 10 nM, the correlation coefficient was 0.993, the detection limit was approximately 0.3 pM with a signal-to-noise ratio (s/n) of 3, and the acceptable recovery in the serum was 97.2% to 104.5%. The results from this study show that the nanozyme-SERS system has great potential for chemical and bioassay applications.

Dual Recognition Strategy‐Based Transistor Sensor Array for Ultrasensitive and Multi‐Target Detection of Antibiotics

AbstractMulti‐target detection is a notable development direction in the field of analytical methods, boasting significant potential for breakthroughs in complex sample detection. Herein, an extended gate field‐effect transistor (EGFET) sensor array for ultrasensitive and multi‐target detection of antibiotics is developed. To enhance the recognition ability for diverse antibiotics, a dual‐recognition strategy based on tailor‐made molecularly imprinted polymer (MIP) and aptamer is adopted to fabricate the extended gate electrode (sensing electrode). The dual‐recognition strategy‐based EGFET exhibits superior sensitivity, selectivity, and stability compared to single recognition probes due to the synergistic effect of the affinities of MIP and specific aptamer. The developed sensor array can detect three types of antibiotics, including ampicillin, amoxicillin, and kanamycin, at the same time with record‐low detection limit (fM level) and a detection range spanning six orders of magnitude. The practical detection of antibiotics in various samples (tap water, river water, milk, honey, and artificial urine) further validates the feasibility of the sensor array in practical applications. The key advantages of flexibility, high sensitivity and selectivity, and multifunctionality demonstrate the high potential of EGFET sensor array for simultaneous detection of multiple target molecules.

Mercury speciation in environmental samples associated with artisanal small-scale gold mines using a novel solid-phase extraction approach to sample collection and preservation

In artisanal small-scale gold mines (ASGM), mercury (Hg) is known to pollute nearby river waters and sediments where it can be methylated to the highly bioavailable methylmercury (MeHg). The assessment of Hg speciation in water samples has been challenging for many years, with recommended procedures often not adequately allowing for analysis of samples in a suitable timeframe. Using a novel solid-phase extraction (SPE) method for sampling and preservation of Hg species, representative speciation data can be safely and easily collected and retained for up to 4-weeks (MeHg = 115 ± 8% refrigerated and 109 ± 13% unrefrigerated storage; Hg2+ = 100 ± 14% refrigerated and 94 ± 12% unrefrigerated storage). Concentrations of MeHg in environmental water samples and drinking water were below detection limit across two ASGM sites in western Kenya and concentrations of Hg2+ were below drinking water guidelines; however, drinking water sources contribute 20–30% of the tolerable weekly intake of Hg, indicating a need to minimise exposure of Hg from dietary sources to prevent Hg poisoning. Sediments from receiving rivers at ASGM sites showed total Hg concentrations above guideline limits (0.08–1.84 mg kg−1 total Hg) along the length of the river; however, MeHg concentrations fluctuated dependent on the stagnation of the river due to damns and ponds (5.9 ± 14.3 µg kg−1 MeHg). The findings show that SPE can be used as a robust sample collection and preservation approach for Hg speciation, which can better inform mitigation measures, understand ecological and human health implications, and improve environmental monitoring.

Preparation of D-NCCDs and its application in fluorescent/colorimetric dual-mode discrimination of glutamine enantiomers.

Anew type of carbon dots (D-NCCDs) was synthesized by 3, 5-diaminobenzoic acid, N,N-dimethyl-o-phenylenediamine, and D-cysteine. The morphology and structure of D-NCCDs were investigated by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and FT-IR spectra, and the chirality was characterized by circular dichroism. In the presence of hydrogen peroxide, the fluorescence of D-NCCDs at 487nm (λex = 410nm) showed great discrimination ability towards glutamine enantiomers. The ratio of fluorescence intensity (F/F0) to the concentration of D-Gln showed good linearity in the range 0.5-10mM, with a detection limits of 0.11mM. Meanwhile, the color of the solution gradually changed from light yellow to yellow-brown. The UV-Vis absorption ratio (A/A0) at 410nm showed good linearity with the concentration of D-Gln in the range 0.5 to 20mM; the detection limit is 7.7μM. But the fluorescence and absorbance of D-NCCDs showed no significant change after the addition of L-glutamine. Thus, fluorescence and colorimetry dual-mode discrimination of glutamine enantiomers was achieved. The fluorescence enantioselectivity of Gln (FL-Gln/FD-Gln) is 1.62, and the colorimetric enantioselectivity of Gln (AD-Gln/AL-Gln) is 2.14. The chiral discrimination mechanism of D-NCCDs to Gln enantiomers was also investigated systematically. This work not only can discriminate glutamine enantiomers with high sensitivity and convenience, but also offers a new strategy for preparing new dual mode chiral nanoprobes.

A search for water vapor plumes on Europa by spatially resolved spectroscopic observation using Subaru/IRCS

Abstract We present near-infrared high-dispersion spectroscopic observations of Europa using the Infrared Camera and Spectrograph (IRCS) onboard the Subaru Telescope, seeking direct evidence of water plumes on Europa and exploring spatial variations in plume activity. Using the high spectral/spatial resolution and sensitivity of Subaru/IRCS, our observations have enabled a spatially resolved search for water plumes on Europa. Within our detection limits and time of observation, we found no evidence for the presence of water emission. For a rotation temperature of 50 K, we derived an upper limit on the H$_{2}$O abundance of 9.46 $\times$ 10$^{19}$–5.92 $\times$ 10$^{20}$ m$^{-2}$ in each divided slit area and 4.61 $\times$ 10$^{19}$ m$^{-2}$ in the entire area covered by the slit. This upper limit lies below the inferred water abundance from previous UV observations by the Hubble Space Telescope, while being less sensitive by a factor of three compared to the Keck telescope and by one order of magnitude or more than the James Webb Space Telescope observations. Our results align with previous studies and demonstrate that using Subaru/IRCS is an effective strategy for searching for water plumes on Europa with high spatial resolution. Continued observations across different surface areas and orbital phases are essential to fully characterize Europa’s plume activity and complement upcoming space missions.