Low LOD Research Articles

Boosting the sensitivity for tau protein detection with a bifunctional nanoenzyme signal amplifier

The trace amounts of tau protein in the blood are considered a significant biomarker in the early diagnosis of Alzheimer's disease. Herein, an electrochemical biosensor has been developed that utilizes a bifunctional nanoenzyme signal amplifier (Nanosa), which incorporates hybridization chain reaction (HCR) amplification and peroxide-mimicking nanoenzymes enhancement to enable ultrasensitive detection of tau. The Nanosa utilizes a peroxide-active MoS2/Au substrate on which DNA aptamer and hairpin probes are fixed as signal amplifiers capable of triggering HCR. The Fc molecules were initially aggregated at the electrode interface through HCR amplification, and were tested by adding an electrolyte solution containing hydrogen peroxide (H2O2). Under the catalysis of a peroxide nanoenzyme, the electrochemical signal of Fc molecules was further enhanced. The bifunctional Nanosa can not only achieve the pre-enrichment of Fc molecules at the electrode interface but also catalyze the enhancement of its electrochemical signal. The well-designed and optimized poly adenine tail not only as an electrode coupling agent but also as an excellent antifouling coating. The ingenious design of the Nanosa-based biosensing strategy enables the ultrasensitive analysis of tau with a broad linear range from 0.1 pg/mL to 100 ng/mL and a lower LOD of 33.4 fg/mL. Meanwhile, the outstanding analytical performance of this Nanosa-based biosensing strategy enables its successful application in determining tau levels in real plasma samples, and showed good agreement with results obtained using a commercial ELISA kit.

Ultrasensitive electrochemical sensor for fenitrothion based on MIL-125 derived iron/titanium bimetallic oxides doped porous carbon composite

Fenitrothion (FT) is a common organophosphorus pesticide widely used in agricultural. Residues of fenitrothion in crops can adversely affect human health. In this work, modified MIL-125-Fe was prepared by changing the solvent ratios and further etching with iron nitrate, followed by high-temperature pyrolysis to obtain modified-TiO2/FeTiO3-doped nitrogen-containing carbon framework (m-TiO2/FeTiO3@NCF). The porous carbon material of m-TiO2/FeTiO3@NCF was used to modify the GCE to produce FT electrochemical sensor. Under optimized conditions, the sensor exhibited good detection performance for FT with a low LOD of 0.96 nM and a wide detection linear range of 1–9000 nM, and also exhibited good reproducibility (RSD = 2.08 %), repeatability (RSD = 1.09 %) and anti-interference performance. The sensor was successfully applied in real sample tests showing the recovery rates of 98.7 %–101.2 %. The present study provides a new idea for the rapid and accurate detection of FT.

Carboxyethylsilanetriol-Coated Magnetic Nanoparticles as an Ultrasensitive Immunoplatform for Electrochemical Magnetosensing of Cotinine.

In the present study, an innovative and simple electrochemical magneto biosensor based on carboxyethylsilanetriol-modified iron oxide (Fe3O4) magnetic nanoparticles was designed for ultrasensitive and specific analysis of cotinine, an important marker of smoking. Anticotinine antibodies were covalently immobilized on carboxylic acid-modified magnetic nanoparticles, and the cotinine-specific magnetic nanoparticles created a specific surface on the working electrode surface. The use of magnetic nanoparticles as an immobilization platform for antibodies provided a large surface area for antibody attachment and increased sensitivity. In addition, the advantages of the new immobilization platform were reusing the working electrode numerous times, recording repeatable and reproducible signals, and reducing the necessary volume of biomolecules. The specific interaction between cotinine and cotinine-specific antibody-attached magnetic nanoparticles restricted the electron transfer of the redox probe and changed the impedimetric response of the electrode correlated to the concentration of cotinine. The magneto biosensor had a wide detection range (2-300 pg/mL), a low LOD (606 fg/mL), and an acceptable recovery (97.24-105.31%) in real samples. In addition, the current biosensor's measurement results were in good agreement with those found by the standard liquid chromatography (HPLC) and enzyme-linked immunosorbent assay (ELISA) methods. These results showed that a simple impedimetric immunosensing platform was generated for the cotinine analysis.

Ionic liquid-functionalized mesoporous multipod silica for simultaneously effective extraction of aflatoxin B1 and its two precursors from grain

BackgroundAflatoxin B1 (AFB1) and its precursors contaminate food and agricultural products, posing a significant risk to food safety and human health, but simultaneous and effective extraction and determination of AFB1 and its precursors with varied structures is still a challenging task. ResultsIn this study, a bisimidazolium-type ionic liquid functionalized mesoporous multipod silica (SiO2@mPMO-IL(im)2) was fabricated to extract AFB1 and its two precursors, i.e., averantin and sterigmatocystin. The SiO2@mPMO-IL(im)2 could simultaneously extract three targets with varied structures based on the multipods, mesopores, and multifunctional groups. The density functional theory calculations further verified the multiple interactions between SiO2@mPMO-IL(im)2 and targets. The fabricated SiO2@mPMO-IL(im)2 could effectively extract and determine three targets in grains by combing with dispersive solid-phase extraction and high-performance liquid chromatography. Good linearity (r2 > 0.9978), low LODs (0.9–1.5 μg kg−1) and LOQs (3.0–4.5 μg kg−1), satisfactory spiked recoveries (92.5%–106.8%) and high precisions (RSD<6.4%) were observed. Significance and noveltyThis work demonstrates the feasibility of SiO2@mPMO-IL(im)2 for simultaneous and effective extraction of toxins with varied structures and provides a promising sample preparation for the analysis of AFB1 and its precursors in grain samples.

Desitometric Development and Validation for Simultaneous Determination of Antiretroviral Drugs Lamivudine, Zidovudine and Nevirapine in Fixed-Dose Combination Tablets

A cutting-edge high-performance thin layer chromatography (HPTLC) approach designed for simultaneous measurement of tablets containing drugs like lamivudine, nevirapine, and zidovudine. Chromatograms were performed employing chloroform and methanol (8:2 v/v) on pre-coated silica gel aluminum thin-layer chromatography (TLC) plates. The data was quantified using the optical density absorbance mode at 271 nm. The Rf values for lamivudine, zidovudine, and nevirapine were 0.140, 0.523, and 0.678, respectively. Linearity was found for lamivudine, zidovudine and nevirapine at concentrations of 150 to 900 ng band-1, 300 to 1800 and 200 to 1200 ng band-1, respectively. Lamivudine had a lower limit of detection (LLoD) of 27.36 ng band-1 and a lower limit of quantitation (LLoQ) of 82.91 ng band-1, whereas zidovudine had LoQs of 64.13 ng band-1 and 194.34 ng band-1. For nevirapine, the values were 35.52 and 107.64 ng band-1, respectively. Lamivudine had a lower LoD of 27.36 ng band-1 and a lower LoQ of 82.91 ng band-1, whereas zidovudine had LoQs of 64.13 and 194.34 ng band-1. For nevirapine, the values were 35.52 and 107.64 ng band-1, respectively. The recovery, specificity, and accuracy of this device have been demonstrated. This new formulation evaluated market tablet formulations of the above drugs (Duovir, Cipla Ltd.). The developed method demonstrated the ability to simultaneously identify these drugs from quantitative data without interference.

Improving gallic acid detection in plant samples: Fabrication and optimization of a sensitive and selective NiO-supported carbon paste electrode

In this study, we successfully prepared a modified nickel oxide (NiO) carbon paste electrode to detect gallic acid (GA). NiO nanoparticles were synthesized by the simple, organic solvent-free chemical coprecipitation method, and the electrochemical properties of the electrode and GA were thoroughly investigated using CV, SWV, and EIS, while morphological properties were examined using ICP-OES, TEM, SEM, and XRD. Excellent catalytic characteristics are displayed by the developed material which facilitates the interaction of the target with the electrode surface. The obtained electrochemical information showed that the incorporation of NiO nanoparticles to the carbon paste electrode effectively facilitates electron transfer processes and enriches the catalytic response of the carbon paste electrode. The fabricated NiO/CPE sensor showed a satisfactory linear relationship between peak current and GA concentration in the broad range of 0.2–100 μM and 100–200 μM with a low detection limit of 0.04 μM and limit of quantification of 0.12 μM at pH 3 of BRBS as supporting electrolyte. The selectivity of the proposed method was satisfactory, with acceptable stability, considerable repeatability, and accurate reproducibility. Moreover, the good practicability performance could be effectuated at the NiO/CPE sensor for the quantitative analysis of GA in bourtree, walnut, primrose, and chamomile tea samples. The results were compared with the standard DPPH test and statistical processing of the results was performed, which confirmed the excellent agreement between the two methods. The developed method can provide a cost-effective, rapid, selective, and sensitive means for GA monitoring. When compared to other works, the developed technique has a wider linear range and lower LOD and LOQ, which makes this work a very important reference for the highly sensitive analysis of GA in the field of food safety.

Abstract 5023: Analytical validation of the Oncomine™ Dx Express Test using liquid biopsy samples as an IUO assay in a CAP/CLIA lab

Abstract Introduction: The Oncomine™ Dx Express Test (ODxET) is a next-generation sequencing (NGS) test. It can be used as an investigational use only (IUO**) test to detect somatic DNA and RNA alterations in human cell-free total nucleic acid (cfTNA) isolated from plasma samples. This study outlines the analytical validation of the ODxET for relevant single nucleotide variants (SNV) and insertion/deletions (INDEL) in liquid biopsy specimens. The Ion Torrent Genexus™ platform has a short turnaround time with minimal operator input. This study was performed in a College of American Pathologists (CAP™) accredited and Clinical Laboratory Improvement Act (CLIA) licensed laboratory. Methods: Forty-seven unique samples (39 clinical, 3 derived, 2 reference and 3 commercially available DNA controls) were analyzed. All experiments began with sample extraction, except the lower input limit of detection (LLOD). We evaluated limit of detection, variant calling accuracy, and precision. Two control NIST™ samples were sequenced with 3 technical replicates each for INDEL and SNVs analytical accuracy. The LOD was evaluated at both the target input of 2ng/µl (40ng), and the minimum input,0.33ng/µl (6.6ng) with allele frequency (AF) levels at 1%, 0.5%, and 0.25%. The 39 clinical plasma samples were used for variant calling accuracy. Inter-assay reproducibility was assessed by sequencing DNA controls across four runs by different operators over multiple days/systems. Intra-assay repeatability was assessed by sequencing 4 samples in replicate on the same run by one operator on the same day/system. Results: The analytical accuracy and NPV was 100% for SNV/INDEL variants. The 40ng input LOD sensitivity was 96% for SNVs at 0.5% AF and 100% for INDELs at 0.25% Minimum AF. The lower input LOD sensitivity was 89% for SNVs and 100% for INDEL at 1% AF. Variant calling accuracy on samples with pre-characterized data was 100% for the 13 positive samples. Specificity was &amp;gt;99% for all samples including both healthy donor and positive samples. Repeatability was 100% for INDELs and &amp;gt;96% for SNVs, reproducibility was 100% for both variant classes. Conclusion: This validation study to estimate analytical accuracy, limit of detection, variant calling accuracy and precision has demonstrated that the ODxET assay is highly robust in detecting SNV and INDEL mutations in plasma samples and is suitable for use in a CAP/CLIA laboratory as an IUO assay.**=In Vitro Diagnostic use only. Not available in all regions including North America. Citation Format: Juan C. Espinoza, Rajendra Ramsamooj, Akemi Yuki, John Williamson, Diarra Hassell, Madhu Jasti, Suzanne Salazar, David Ginzinger. Analytical validation of the Oncomine™ Dx Express Test using liquid biopsy samples as an IUO assay in a CAP/CLIA lab [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5023.

A ratiometric fluorescent probe with 1,2,4-triazole recognition unit for fluoride ion detection based on synchronous fluorescence spectroscopy

As an important inorganic chemical with wide applications and high toxicity, the detection of fluoride-containing products and environmental samples has gained the most interest. In this work, a ratiometric fluorescent probe (NIN2) is constructed with a triazole group as the new recognition site for the detection of F−. The synchronous fluorescence technology was introduced to obtain the well discrimination of two emission bands. The value of wavelength intervals (Δλ = λem. - λex.) is optimized to be set as 70 nm with the minimized overlap of two emission bands centered around 380 nm and 470 nm, respectively. In this way, NIN2 can detect F− in the region of 0–0.2 μM with a good linear relationship (R2 = 0.9989) and low LOD value (36 nM). Only F− can induce obvious ratiometric response (I470nm/I380nm) from 0.2 to 3.4 while the ratios of the samples containing other cations and anions are as low as the blank sample. For investigating the recognition mechanism of triazole, 1H, 13C and 19F NMR spectral technologies were used to verify the interaction between triazole and F−. Furthermore, the DFT calculation was also performed to discuss the electronic transition of NIN2 before and after interaction with F−. We believe this work provides a new recognition moiety for detecting F−.

Hypersensitized electrochemical sensing of Hg(II) based on phase engineering of Co doped MoSe2 nanosheets: Insight in dynamic phase change induced by the chemical interaction between Se and Hg(II)

Transition metal dichalcogenides (TMDs) are regarded as promising nanomaterials for electrochemical detection to heavy metal ions due to their variable performance. However, their detection performances are still limited by inferior conductivities and adsorption ability. In this work, the defects and phase engineering strategy are proposed to utilize cobalt (Co) doped MoSe2 nanosheet for electrochemical detection of Hg ion (Hg(II)). Through Co doping, we successfully achieved the phase transition of MoSe2 from the 2 H phase of semiconductor to the 1 T phase of conductor. Moreover, the 1 T MoSe2 is demonstrated to show a better adsorption and catalytic ability for Hg(II) detection than that of 2 H MoSe2. As a result, the MoSe2 containing atomic ratio of Co is 10% (named CM10) owning suitable content of 1 T phase has a superior sensitivity of 52.17 μA μM−1 and a low LOD of 3.96 nM for Hg(II). More importantly, combining with the characterization of X-ray photoelectron spectroscopy (XPS) and density-functional theory (DFT) calculation, it is found that the Hg(II) adsorption will also lead to the phase change of MoSe2, and the change state in the samples after the adsorption of Hg(II) will be more accurate to be responsible for the improvement of catalytic ability.

A modified Prussian blue biosensor with improved stability based on the use of self-assembled monolayers and polydopamine for quantitative L-glutamate detection.

Aminiature L-glutamate (L-Glu)biosensor is describedbased on Prussian blue (PB) modification with improved stability by using self-assembled monolayers (SAMs) technology and polydopamine (PDA). A gold microelectrode (AuME) was immersed in NH2(CH2)6SH-ethanol solution, forming well-defined SAMs via thiol-gold bonding chemistry which increased the number of deposited Prussian blue nanoparticles (PBNPs) and confined them tightly on the AuME surface. Then, dopamine solution was dropped onto the PBNPs surface and self-polymerized into PDA to protect the PB structure from destruction. The PDA/PB/SAMs/AuME showed improved stability through CV measurements in comparison with PB/AuME, PB/SAMs/AuME, and PDA/PB/AuME. The constructed biosensor achieved a high sensitivity of 70.683 nAµM-1cm-2 in the concentrationrange 1-476µM L-Gluwith a low LOD of 0.329µM and performed well in terms of selectivity, reproducibility, and stability. In addition, the developed biosensor was successfully applied to the determination of L-Glu in tomato juice, and the results were in good agreement with that of high-performance liquid chromatography (HPLC). Due to its excellent sensitivity, improved stability, and miniature volume, the developed biosensor not only has a promising potential for application in food sample analysis but also provides a good candidate for monitoring L-Glu level in food production.

Study of the ZnO/MoS2 heterostructures-based gas sensor for humidity-independent response

In this study, several strategies including coating with a hydrophobic MoS2 layer, UV light illumination, raising temperature, alternating current (AC), and four-probe measurement have been systematically studied to overcome humidity dependence response behavior for the ZnO sensor. Catalyst-free CVD method was used to prepare pure ZnO nanorods and ZnO/MoS2 heterostructures, and the prototypes were then fabricated on the substrates with Pt interdigital (ID) electrodes, respectively. The gas sensing properties of two sensors were systematically investigated. The ZnO/MoS2 heterostructures-based sensor with four-probe measurement operating at 150 °C shows stable responses during a wide humidity variation range. Furthermore, the ZnO/MoS2 sensor obtains excellent sensing performance to NO2 with a high sensitivity of 12.6 %/ppm and high sensor responses at 150 °C and UV light illumination. Additionally, a low theoretical LoD of 6.5 ppb NO2 is achieved for ZnO/MoS2 heterostructures-based sensor.

Enhanced oxidase mimic activity of raspberry-like N-doped Mn3O4 with oxygen vacancies for efficient colorimetric detection of gallic acid coupled with smartphone

The content of gallic acid (GA) is positively correlated with the quality grade of tea. Here, we developed a colorimetric method based on raspberry-like N-doped Mn3O4 nanospheres (N-Mn3O4 NSs) with oxidase-like activity for GA assay. Modulating the electronic structure of Mn3O4 by N doping could promote the catalysis ability, and the produced oxygen vacancies (OVs) can provide high surface energy and abundant active sites. The N-Mn3O4 NSs presented low Michaelis-Menten constant (Km) of 0.142 mM and maximum initial velocity (Vmax) of 9.8 × 10−6 M s−1. The sensor exhibited excellent analytical performance towards GA detection, including low LOD (0.028 μM) and promising linear range (5 ∼ 30 μM). It is attributed that OVs and O2− participated in TMB oxidation. Based on the reaction color changes, a visualized semi-quantitative GA detection could be realized via a smartphone-based system. It could be applied for evaluating GA quality in market-purchased black tea and green tea.

Transformational Modulation of Fluorescence to Room Temperature Phosphorescence in Metal-Organic Frameworks with Flexible C-S-C Bonds.

Photoluminescent metal-organic frameworks (MOFs) have been a subject of considerable interest for many years. However, the regulation of excited states of MOFs at the single crystal level remains restricted due to a lack of control methods. The singlet-triplet emissive property can be significantly influenced by crystal conformational distortions. This review introduces an intelligent responsive MOF material, denoted as LIFM-SHL-3a, characterized by flexible C-S-C bonds. LIFM-SHL-3a integrates elastic structural dynamics with fluorescence and room temperature phosphorescence (RTP) modulation under heating conditions. The deformable carbon-sulfur bond essentially propels the distortion of molecular conformation and alters the stacking mode, as illustrated by single-crystal-to-single-crystal transformation detection. The deformation of flexible C-S-C bonds leads to different noncovalent interactions in the crystal system, thereby achieving modulation of the fluorescence (F) and RTP bands. In the final state structure, the ratio of fluorescence is 66.7%, and the ratio of RTP is 32.6%. This stands as a successful demonstration of modulating F/RTP within the dynamic MOF, unlocking potential applications in optical sensing and beyond. Especially, a PL thermometer with a relative sensitivity of 0.096-0.104%·K-1 in the range of 300-380 K and a H2S probe with a remarkably low LOD of 125.80 nM can be obtained using this responsive MOF material of LIFM-SHL-3a.

Point-and-shoot: portable Raman and SERS detection of organic gunshot residue analytes

Raman spectroscopy is one of many tools available to verify the molecular composition of an analyte. Due to its non-destructive nature and its ability to accurately discern differences in closely related molecular structures, it has become invaluable in many fields, including its potential for forensic gunshot residue detection. Firearm-related fatalities in the United States continue to rise and many of them remain unsolved. This necessitates tools that are better equipped to aid in the investigation of firearm-related crimes, capable of high-throughput analysis yet remaining sensitive to give accurate and valuable information. The comparative downside of Raman spectroscopy to neighboring techniques like mass spectrometry and nuclear magnetic resonance is its lower sensitivity. Surface-enhanced Raman spectroscopy allows for the benefits of Raman spectroscopy alongside the added lower limit of detection with the simple application of nanoparticles, typically gold. Unfortunately, these benefits have seen little on-site application due to the difficulty of translating methods from conventional tabletop Raman spectrometers to point-and-shoot portable Raman spectrometers which have even lower sensitivities (higher limits of detection). Herein, we outline a versatile methodology for the detection of 6 organic gunshot residue components (diphenylamine (DPA), ethyl centralite (EC), 2,4-dinitrotoluene (2,4-DNT), 2-nitrodiphenylamine (2-nDPA), 4-nitrodiphenylamine (4-nDPA), and N-nitrosodiphenylamine (N-nDPA)) in liquid-phase that allows us to detect millimolar concentrations of these analytes. Furthermore, we report calculated vibrational assignments for these 6 analytes in solution, alongside detailed peak-by-peak analyses on a portable instrument. We showed signal enhancement and lower LODs through our data processing as well as a proof-of-concept SERS enhancement in a complex liquid-phase matrix, with an increased sensitivity of 700% when using SERS.

Aptasensor Integrated with Two-Dimensional Nanomaterial for Selective and Sensitive Electrochemical Detection of Ketamine Drug.

Ketamine is one of the most commonly abused drugs globally, posing a severe risk to social stability and human health, not only it is being used for recreational purposes, but this tasteless, odourless, and colourless drug also facilitates sexual assaults when it is mixed with drinks. Ketamine abuse is a threat for safety, and this misuse is one of the main uses of the drug. The crucial role of ketamine detection is evident in its contributions to forensic investigations, law enforcement, drug control, workplace integrity, and public health. Electrochemical sensors have gained considerable interest among researchers due to their various advantages, such as low cost and specificity, and particularly screen-printed paper-based electrode (SPBE) biosensors have gained attention. Here, we reported an ePAD (electrochemical paper-based analytical device) for detecting the recreational drug ketamine. The advantages of using a paper-based electrode are that it reduces the electrode's production costs and is disposable and environmentally friendly. At the same time, nanographite sheets (NGSs) assisted in amplifying the signals generated in the cyclic voltammetry system when ketamine was present. This ePAD was developed by immobilizing a ketamine aptamer on NGS electrodes. The characterization of proper synthesized NGSs was performed by Scanning Electron Microscopy (SEM), XRD (X-ray Diffraction), Fourier-transform infrared spectroscopy (FTIR), and UV-Vis spectroscopy. Electrochemical techniques, including cyclic voltammetry (CV) and linear sweep voltammetry (LSV), were employed to validate the results and confirm each attachment. Furthermore, the versatility of the proposed sensor was explored in both alcoholic and non-alcoholic beverages. The developed sensor showed a low LOD of about 0.01 μg/mL, and the linear range was between 0.01 and 5 μg/mL. This approach offers a valid diagnostic technique for onsite service with minimal resources. This cost effective and portable platform offers desirable characteristics like sensitivity and selectivity and can also be used for POC (point of care) testing to help in the quick identification of suspicious samples and for testing at trafficking sites, amusement parks, and by the side of the road.

Controlled construction of 2D hierarchical core-shell ZnO/MnO2 nanosheets on Nitinol fiber with enhanced adsorption performance for selective solid-phase microextraction of trace polycyclic aromatic hydrocarbons in water samples

BackgroundPolycyclic aromatic hydrocarbons (PAHs) are an important class of potentially toxic persistent organic pollutants in environmental water. Their concentrations are usually too low to allow for direct determination with analytical instruments, and the preconcentration is required prior to instrumental analysis. Solid phase microextraction (SPME) is considered as a high-performance green sample preparation technique for volatile and non-volatile organic compounds due to its high enrichment factor. In fact, the nature of SPME coatings governs the adsorption performance. Therefore, more efforts have devoted to the controlled construction of novel long-life SPME fibers with enhanced adsorption performance and improved adsorption selectivity. Results2D hierarchical core-shell ZnO/MnO2 nanosheets (NSs) were constructed on a Nitinol (NiTi) fiber substrate by layer-by-layer assembly for enhanced and selective SPME of PAHs. Firstly, hexagonal ZnO NSs were electrodeposited on the NiTi substrate. Subsequently smaller secondary MnO2 NSs were uniformly grown on the surface of ZnO NSs by a facile hydrothermal oxidation process. ZnO NSs were well protected by the chemically stable MnO2 shell, making the coating highly durable and efficient for SPME application. Meanwhile, the ZnO/MnO2 NSs coating demonstrated superior adsorption performance for PAHs. After the optimization of SPME conditions, the proposed SPME-HPLC-UV method exhibited good analytical performance for preconcentrating and determining trace PAHs with wide linear ranges (0.03–200 μg L−1) and low LODs (0.005–0.112 μg L−1) as well as good repeatability (1.4%-6.9%) and fiber-to-fiber reproducibility (5.3%-7.1%). Moreover, the proposed method showed good precision and recovery in the preconcentration and determination of target PAHs in real water samples. SignificanceAs compared with representative commercially available fibers, the NiTi@ZnO/MnO2 NSs fiber showed enhanced adsorption efficiency and improved adsorption selectivity for PAHs. The constructed fiber can be used as an alternative to commercial fibers for the adsorption and preconcentration of target PAHs in the environmental water samples. Moreover, the preparation strategy is expected to provide new insights into the precisely controlled construction of the efficient and stable core-shell bimetallic oxide nanostructures on the superielastic NiTi-based fibers.

Indium nanocubes based recyclable fluorescent chemosensor for sustainable environmental monitoring: pH-induced fluorescence transition and selective detection of Pd(II) ions

Rapid modern industrialization and urbanization have escalated heavy metal pollution, with palladium (Pd2+) raising significant concerns due to its extensive usage in catalysis, hydrogen storage, and electronics, thereby imposing substantial risks on the environment and human health. In this study, we report a highly fluorescent indium nanocubes based chemosensor (InNCs) functionalized with perylene tetracarboxylic acid (PTCA) and 4-(pyridyl)ethenyl benzene (PEB). The InNCs exhibited emission maximum at 415 nm (λex ∼ 350 nm) with robust chemical and photo-stability, and acted as a fluorogenic probe for selective recognition of Pd2+ in aqueous medium. The fluorescence sensing properties of InNCs were thoroughly assessed via different techniques including steady-state absorption, emission and time-resolved emission spectroscopic methods. Among the various competitive analytes, only Pd2+ could induce a significant fluorescence quenching in the probe. This “turn-off” fluorescence sensing demonstrated a remarkably low LoD of ∼65 nM. Notably, with the addition of EDTA, the probe displayed good recyclability upto 4 cycles. The sensory probe was successfully employed as a reusable platform to estimate Pd(II) in different real water and soil samples with considerable accuracy (∼ 5–10 % error). Moreover, the probe exhibited a pH-induced fluorescence transition, indicating its potential to be applied as a pH sensor. The Pd(II) binding and pH-sensing mechanisms have also been elucidated through density functional theory (DFT) calculations.

Gold nanoparticles with natural polymer synthesized by plasma–liquid interactions: Size-control, characterization and colorimetric detection of melamine based on the size effect of gold nanoparticles

This work reports the synthesis of size-controlled gold nanoparticles as AuNP colloids in aqueous solutions with capping natural polymer matrices – the sodium salt of carboxymethyl cellulose, using a liquid-phase plasma process. The effects of the solution plasma process discharge time, concentrations of gold(III) chloride trihydrate precursor (0.06–2.5 mmol/L) and correlations of the precursor/CMC ratios on the characteristics on the synthesized Au NPs, including size distribution and optical absorption properties, were investigated. The average size (20–90 nm) and form (spherical, hexagonal and triangular) of the AuNPs can be change depending on the initial concentration of Au3+ and the ratios of precursor/CMC on the process synthesis. Gold nanoparticles were used to study a straightforward colorimetric detection of melamine. Melamine caused the AuNPs to agglomerate in aqueous solution, changing their visible color from red to blue. The prepared AuNPs can be used for the detection of melamine with a low LOD and an extremely wide linear range (0.005–0.21 μM.).

Glucose detection via photoelectrochemical sensitivity of 3D CuO-TiO2 heterojunction nanotubes/Ti combined with chemometric tools

High sensitivity and low detection limit are important targets for biosensors. Using 3D hydrogen titanate nanotubes/Ti as precursor, CuO-TiO2 heterojunction nanotubes/Ti (CuO-TiO2NTs/Ti) photoelectrode was prepared to fabricate photoelectrochemical (PEC) glucose sensor. The prominent Ti foil substrate, 3D mesoporous structure, and CuO-TiO2 heterojunction of this PEC sensor can effectively improve the separation efficiency of charge carriers, facilitate electron transfer, and generate strong photoelectronic signals. Under visible light irradiation, the CuO-TiO2NTs/Ti electrode exhibited high sensitivity, low LOD, and good selectivity. Through density functional theory simulation, the enhanced electron-hole separation and improved PEC properties were illuminated in the CuO-TiO2 heterojunction. Associated with chemometric tools, the accuracy of the sensitivity was significantly improved, which could enhance the practical application capability of PEC biosensors.

Sensitive dual-signal detection and effective removal of tetracycline antibiotics in honey based on a hollow triple-metal organic framework nanozymes

In this work, a colorimetric/fluorescent dual-signal mode sensor is proposed for the sensitive, selective and accurate detection and removal of tetracycline antibiotics (TCs). A triple-metal MOF of NiCoFe is successfully synthesized and controllable adjusted the shape of the hollow structure for the first time, and then modified with TCs aptamer. The as-prepared triple-atom MOF (apt-NiCoFe-MOF-74) exhibits well-defined hollow morphology, high crystallinity, and high surface areas endow their alluring adsorption and removal performances for TCs. More attractively, this triple-metal MOF show a good peroxidase-like activity and strong fluorescence property at 540 nm of apt-NiCoFe-MOF-74 when excitation wavelength was 370 nm. Inspire by this, a dual-signal output biosensor is constructed and the linear absorbance response is well correlated with wide range and low LOD for TCs. The biosensor provided an universal method with satisfactory sensitivity and accuracy for TCs analysis in real food samples.