Low Detection Limit Research Articles

Enhanced Conductivity in Conjugated Microporous Polymers via Integrating of Carbon Nanotubes for Ultrasensitive NO2 Chemiresistive Sensor.

Conjugated microporous polymers (CMPs) present high promise for chemiresistive gas sensing owing to their inherent porosities, high surface areas, and tunable semiconducting properties. However, the poor conductivity hinders their widespread application in chemiresistive sensing. In this work, three typical CMPs (PSATA, PSATB, and PSATT) are synthesized and their chemiresistive gas sensing performance is investigated for the first time. To further improve performance, PSATT are modified on the surface of amino-functionalized multi-walled carbon nanotubes (NH2-MWCNTs) to improve the conductivity. As a result, the obtained material, PSATT-7NC exhibited a high sensitivity of 9766% toward 4 ppm NO2, which is 2.5 times higher than that of pristine PSATT. It also demonstrated remarkable selectivity and excellent long-term stability. Furthermore, the lowest limit of detection (0.79 ppb) among all polymers-based sensors is achieved at a low operating temperature of 100°C. This work provides a valuable strategy into the development of a new material platform for advancing high-performance gas sensing applications.

A Selective Electrochemical Sensor for Bisphenol A Detection Based on Cadmium (II) (bromophenyl)porphyrin and Gold Nanoparticles

Bisphenol A (BPA) is a commonly synthetic chemical mainly used in producing plastic items. It is an endocrine-disrupting compound that causes irreversible health and environmental damage. Developing a simple method for BPA effective quantitative monitoring is emergently necessary. Herein, a novel electrochemical sensor for BPA detection based on [(5,10,15,20-tetrakis(p-bromophenyl) porphyrinato] cadmium (II) [(CdTBrPP)] and gold nanoparticle (AuNPs)-modified screen-printed carbon electrode (SPCE) was elaborated. CdTBrPP was synthesized and then characterized with Ultraviolet–Visible Spectroscopy (UV/vis), Infrared Spectroscopy (IR), and Proton Nuclear Magnetic Resonance Spectroscopy (1H NMR) to confirm its successful synthesis. After drop-coating AuNPs and CdTBrPP on the SPCE, the sensor performance was evaluated using square wave voltammetry (SWV), a linear response in a concentration range from 10−11 M to 10−2 M, with a low detection limit (LOD) of 9.5 pM. The CdTBrPP/AuNPs/SPCE sensor demonstrates a high selectivity and reproducibility, making it a promising candidate for developing a low-cost water-monitoring system for detecting BPA. Additionally, the proposed sensor effectively detected BPA in both tap and mineral water samples.

Biomimetic Honeycomb-like Ti3C2Tx MXene/Bacterial Cellulose Aerogel-Based Flexible Pressure Sensor for the Human-Computer Interface.

The pursuit of efficient and accurate human-computer interface design urgently requires high-performance sensors with pressure sensitivity, a wide detection range, and excellent cycling stability. Herein, a biomimetic honeycomb-like Ti3C2Tx MXene/bacterial cellulose (BC) aerogel with a negative Poisson's ratio (ν = -0.14) synthesized from the bidirectional freeze-drying method is used as the active material for a flexible pressure sensor, which exhibits high sensitivity (20.14 kPa-1), fast response time (100 ms), excellent mechanical durability (5000 cycles), and a low detection limit (responding to a grain of rice weighing about 0.022 g). Moreover, when assembled into the sandwich-structured bending sensor with the aerogel layer at just 0.8 mm in thickness, the aerogel-based device has a wide angular detection range (2.7-156.3°), high sensitivity (0.47 deg-1), and good robustness, proving outstanding electromechanical performance. Significantly, a smart glove consisting of five bending sensors fixed to the proximal knuckles and a flexible circuit board as the signal processing unit was designed for the identification of the shape, demonstrating its promising applications in the field of human-computer interaction.

Portable Electroanalytical Platform Based on Eco-Friendly Biomass-Based Hydrogels with Bimetallic MOF Composites for Trace Acetaminophen Determination.

Accurate acetaminophen (APAP) determination using smartphone-based portable sensing hinges on developing sensing interfaces with effective catalytic performance and high electron transfer efficiency. Herein, we report that various Ni-based bimetallic-organic framework materials (MOFs) were synthesized through the hydrothermal method. These MOFs were incorporated with multiwalled carbon nanotubes (MWCNTs) during the synthesis of chitosan-cationic guar gum hydrogels (HG). The resulting composite conductive hydrogel features a distinctive three-dimensional network structure with a large specific surface area, enhancing APAP enrichment and electrocatalytic activity. Among them, CuNi-MOF-based chitosan-cationic guar gum conductive hydrogel (CHG/CuNi-MOF) has the most desirable capability as a signal amplifier. Under optimal conditions, the sensor constructed with the screen-printed electrode (SPE) using CHG/CuNi-MOF (CHG/CuNi-MOF/SPE) has a wide detection range (0.07-1500 μM), a low detection limit (0.023 μM), and a relatively high sensitivity (0.0450 μA·μM-1·cm-2) for the APAP determination. In addition, CHG/CuNi-MOF/SPE has good stability, repeatability and anti-interference properties, which make it possible to achieve selective determination of targets in complex analysis and ultimately obtain satisfactory recoveries (97.6-104.2%). This work successfully proves the feasibility of the application of MOFs-based conductive hydrogel in the electrochemical detection of phenolics in actual samples.

Inkjet-Printed Graphene–PEDOT:PSS Decorated with Sparked ZnO Nanoparticles for Application in Acetone Detection at Room Temperature

This work presents a simple process for the development of flexible acetone gas sensors based on zinc oxide/graphene/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate). The gas sensors were prepared by inkjet printing, which was followed by a metal sparking process involving different sparking times. The successful decoration of ZnO nanoparticles (average size ~19.0 nm) on the surface of the graphene–PEDOT:PSS hybrid ink was determined by characterizations, including Raman spectroscopy, Fourier transform infrared spectroscopy, field-emission transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffractometry. The ZnO nanoparticle-decorated graphene–PEDOT:PSS with a sparking time of 2 min exhibited the highest response of 71.9% at 10 ppm of acetone, above those of samples treated with other sparking times and the undecorated control. In addition, the optimal sensor revealed high selectivity for acetone over several other kinds of gases, such as ammonia, toluene, dimethylformamide, ethanol, methanol, and benzene, at room temperature. The gas sensor also revealed a low limit of detection (0.4 ppm), high sensitivity (6.18 ppm−1), and high stability (5-week long-term) to acetone. The response and recovery times of the sensor were found to be 4.6 min and 4.2 min, respectively. The acetone-sensing mechanism was attributed to the formation of p-n heterojunctions, which were responsible for the significantly enhanced sensitivity.

Chitosan/platinum nanocubes/Mn(TPDCA)2-modified glassy carbon electrodes for the electrochemical quantification of amlodipine in unprocessed plasma samples

A novel electrochemical probe is developed to detect amlodipine (AMD) in unprocessed plasma samples. The fabrication process involves the synthesis of platinum nanocubes (Pt NCs) and Mn(TPDCA)2 complexes, which are then immobilized them onto the glassy carbon electrode (GCE) surface. The developed electrochemical probe demonstrates exceptional detection performance, with a wide dynamic range, outstanding selectivity, and commendable reproducibility. The linear range and lower limit of detection of the developed method are 53 nM-3.5 µM and 53 nM, respectively. Electrochemical experiments have been conducted to study the kinetics of electrooxidation on the modified electrode, revealing that the process is diffusion-controlled. Furthermore, method validation studies are performed to assess the accuracy, precision, and selectivity of the sensor, demonstrating excellent performance in all these aspects. Consequently, it can be concluded that the sensor is highly suitable for practical applications in drug analysis.

Enhanced Electrochemical Detection of Orthophosphate in Potable Water Using Zinc-Cobalt Oxide Nanocomposite-Modified Nickel Foam Electrodes

Abstract This study presents a novel approach to electrochemical detection of orthophosphate in potable water using hydrothermally synthesized nickel foam electrodes, modified with cobalt oxide (CoOx), zinc oxide (ZnOx), and zinc-cobalt oxide (ZnCoOx) nanocomposites. The incorporation of zinc-cobalt oxide into the electrode significantly enhances its stability and detection capability. In-situ phosphate detection was performed using voltammetric techniques in a highly alkaline environment (pH 14) facilitated by sodium hydroxide (NaOH). Comprehensive electrode characterization, including cyclic voltammetry (0 to 0.6 V at a scan rate of 50 mV/s), electrochemical impedance spectroscopy (105 to 10-2 Hz), scanning electron microscopy, and energy-dispersive X-ray spectroscopy, confirmed the superior performance of the synthesized electrodes. Among the tested configurations, the zinc-cobalt oxide nanocomposite on nickel foam exhibited outstanding sensitivity, with a sensitivity of 0.4 μA/μM across a concentration range of 0 to 40 μM, and an elevated sensitivity of 4.26 μA/μM within the 50 to 100 μM range. The electrode achieved a remarkably low detection limit of 0.171 μM/L (0 to 40 μM detection range) and 0.324 μM/L (50 to 100 μM, detection range), underscoring its potential for highly accurate phosphate detection. These findings highlight the sensor's applicability for diverse practical uses in water quality monitoring.

Real-Time Monitoring of Metal Ions during the Molten Salt Electrolysis Process by Optical Emission Spectrometry Based on Microplasma.

Molten salt electrolysis has been widely used in the production and separation of metals, but it still lacks in situ real-time analysis methods to monitor the electrolysis process. In this work, a microplasma spectroscopic real-time analysis (MIPECA) system is developed based on noncontact direct current (DC) glow discharge. With the MIPECA system, the atomic emission spectroscopy of Li and K could be obtained in situ in LiCl-KCl molten salt, and the impact of different operating conditions on spectral signals was investigated. Then, the characteristic spectra of ten representative elements, including alkali metals (Na, Cs), alkaline earth metals (Mg, Ca, Sr, Ba), transition metals (Ag, Cu, Ni), and lanthanide metals (Ce), were all successfully excited for qualitative analysis. Under the optimal operating conditions, quantitative analysis of Ag, Cs, and Sr was achieved with high sensitivity and low limits of detection (LOD) of about 0.063, 0.021, and 0.073 wt %, respectively. Finally, the electrolysis process of Ag+ in LiCl-KCl molten salt was real-time monitored by using this MIPECA system, showing its application potential in molten salt electrolysis.

Time-Resolved Levodopa Cascade Polymerization Tuned by Bimetallic MOF Fluorescent Nanozyme and Boric Acid for Butyrylcholinesterase Activity Dual-Mode Assay.

A ratiometric fluorescence-photothermal dual-mode assay method is constructed for the detection of butyrylcholinesterase (BChE) activity based on time-resolved levodopa (L-DOPA) cascade polymerization. First, a newly designed bimetallic metal-organic framework (MOF), Eu/Co-DPA (DPA: pyridine-2,6-dicarboxylic acid), is screened out as a fluorescent nanozyme with high catalytic activity and superior luminescence properties. In the presence of boric acid (BA), L-DOPA forms BA-esterified L-DOPA, which is catalyzed by Eu/Co-DPA to form the oligomers with strong blue fluorescence. Meanwhile, the red fluorescence of Eu/Co-DPA is quenched by the oligomers, generating a sensitive turn-on/off ratiometric fluorescence response. As polymerization time increases, Eu/Co-DPA cleaves the borate ester bonds to expose the catechol structures of the oligomers, which facilitates the further oxidation and polymerization of the oligomers, promoting the formation of poly(L-DOPA) nanoparticles with a high photothermal conversion efficiency (30.33%). Then, by using thiocholine (butyrylthiocholine enzymolysis product) to inhibit the catalytic activity of Eu/Co-DPA, BChE activity is detected through the change in fluorescence and photothermal dual signals. Both assay modes have low detection limits (0.021 and 0.024 U L-1) and high accuracy (93.3-105.3% recovery). The detection results of real human serum indicate that both assay modes show 100.0% agreement with the standard method. To our knowledge, this work first combines bimetallic MOFs and a BA regulator to tune the structure of L-DOPA polymers, providing a pathbreaking paradigm for preparing catecholamine-based fluorescence-photothermal organic polymers.

Numerical Investigation of a Microfluidic Biosensor Based on I-Shaped Micropillar Array Electrodes

Micropillar array electrodes offer several advantages, such as enhanced mass transport, lower detection limits, and the potential for miniaturization, making them instrumental in the design and fabrication of electrochemical biosensors. The performance of these biosensors is influenced by electrode geometry, including parameters like shape and height, which affect surface area and overall sensitivity. In this study, we designed a microfluidic electrochemical biosensor featuring micropillar array electrodes, modeled in COMSOL Multiphysics. We compared the response currents of I-shaped and cylindrical micropillar array electrodes. The working electrode (WE), consisting of 100 micropillars with a height of 300 µm, exhibited a sensitivity of 1.61 µA·cm2·mM−1 in cyclic voltammetry, highlighting its effectiveness for analyte detection.

WD‐XRF Determination of Gold in Geological Samples: An Eco‐Friendly Pre‐Concentration Method

ABSTRACTThis study proposes a novel approach for gold analysis in soil and rock samples using wavelength dispersive X‐ray fluorescence. The method offers advantages over traditional techniques like fire assay and MIBK extraction by being less labor‐intensive, environmentally friendly, and achieving lower limits of detection of 20–70 μg/kg depending on matrix of sample. The method involves pre‐concentration steps including aqua regia digestion, evaporation of filtrate and pressed pellet preparation, followed by WD‐XRF analysis to quantify gold content. The instrumental parameters for optimal signal‐to‐background ratio were determined. To ensure precise measurements, the calibration curve was created using specially made pressed pellets of gold‐spiked hematite ore samples. These samples contained known amounts of gold and matched the matrix of the pellets being analyzed. The proposed method demonstrates good accuracy and precision, making it a viable alternative for gold exploration and mining activities.

Method validation and antioxidant activities of Hyperacanthus amoenus and Carissa bispinosa.

Plant foliages used as feed additives pose a health risk due to high oxidant concentrations. Oxidants cause oxidative stress and high rate of morbidities and mortalities. Hence, the aim of the study was to validate the methods to quantify gallic acid (GA) and quercetin (Q) as putative antioxidants, and to evaluate antioxidant activities in feed (F),Hyperacanthus amoenus(HA) andCarissa bispinosa(CB) extracts. Extraction was carried out with 62.5% methanol. Method validations for linearity, accuracy and precision were performed on high performance liquid chromatography. Quantitative analysis of GA and Q and testing of 2,2-diphenyl-2-picrylhydrazyl (DPPH) scavenging activities in the extracts were performed. The lowest limit of detection (LOD) and limit of quantitation (LOQ) of 0.011 µg/mL and 0.032 µg/mL were determined in HA, respectively. The methods were accurate and precise as the relative standard deviations (%RSD) were less than 15%. The GA concentrations in CB and HA extracts were statistically significant (p 0.05) and their values were 0.65 ± 0.03 x 106µg/kg dry weight (DW) (0.13%) and 0.28 ± 0.06 x 106µg/kg DW (0.002%), respectively. All extracts showed very strong radical scavenging activities with their IC50values ranging between 5.87 µg/mL and 6.86 µg/mL.Contribution:These accurate, repeatable, precise and reliable methods can be used to provide a valuable basis for GA and Q analysis in various shrub foliages. Though high GA concentrations have potential to act as antioxidants, they may have adverse health and growth performance effects when used as feed additives, while lower Q concentrations may have no effects on livestock.

Label-Free Liquid Crystal Aptamer Sensors Based on Single-Stranded Nucleic Acid π-Structures for Detecting cTnI.

Cardiac troponin I (cTnI) is a highly sensitive and important serological marker for clinical diagnosis of myocardial injury. Its rapid detection is crucial for the early diagnosis of cardiovascular diseases such as acute myocardial infarction. In this study, based on nucleic acid molecular hybridization and aptamer-specific binding to target molecules, a label-free liquid crystal aptamer sensor based on single-stranded nucleic acid π-structures was developed and applied for the quantitative detection of cTnI. The CP1 and CP2 oligonucleotide chains, complementary to the bases at both ends of the aptamer, are covalently bonded to the sensor substrate via APTES and GA-mediated molecules. The aptamer forms a π-structure with CP1 and CP2 through nucleic acid hybridization, serving as a target molecule capture probe. When cTnI is present in the system, cTnI and the complementary oligonucleotide chains competitively bind with the aptamer, causing the breakdown of the π-structure within the sensor. This reinstates the long-range ordered alignment of the 5CB liquid crystal molecules within the sensor, enabling quantitative measurement of cTnI through variations in optical images. Experimental results show that within the range of 0.01 to 25 ng/mL for cTnI concentration, there is a linear correlation between the brightness area coverage (Br) in the polarized light microscopy images of the sensor and the logarithm of the cTnI concentration, with a correlation coefficient (r). The detection limit is 5.16 pg/mL. This method is label-free, simple to operate, and low-cost, with good specificity and a low detection limit, achieving cTnI detection in serum samples.

The trend of Epstein-Barr virus DNA loads and CD8+ T lymphocyte numbers can predict the prognosis of pediatric liver transplant recipients with PTLD

Abstract Objectives Epstein-Barr virus (EBV) can cause lymphoproliferative disorders (PTLD) in immunodeficiency individuals. The pathogenesis of EBV infection depends on its effective recognition and elimination. Our study investigated the effect of peripheral lymphocyte subsets (PLS) on the elimination of EBV. Methods A retrospective single-center study included 63 patients with 17 pediatric liver transplant recipients with EBV-induced PTLD (PTLD group) and 46 patients diagnosed with EBV-induced mononucleosis (IM group). Dynamic monitoring of PLS with EBV-DNA loads was performed. Results EBV-DNA replicated at a high level (5.2E3∼5.93E7 copies/mL in PBMC) before treatment in all patients in PTLD group. B lymphocytes were the main infected cells. After treatment with Rituximab, the EBV-DNA loads decreased below the lower limit of detection in 10 patients (PTLD-stable disease, PTLD-SD group), and the viral loads replicated at lower level in six patients (PTLD-partial response, PTLD-PR group). In the PTLD-SD group, the percentage of CD3+CD8+ T lymphocytes increased beyond the normal range with the ascending of EBV-DNA loads, then it decreased to the normal range accompanied by the clearance of EBV. In the PTLD-PR group, the CD3+CD8+ T lymphocytes kept in the normal range, while the EBV kept on replication. Conclusions The increased number of CD3+CD8+ T lymphocytes occurred in parallel with the decline in EBV-DNA loads, which is the most useful index in estimating the host capacity of immuno-surveillance against EBV.

Zero-Dimensional Lead-Free Perovskite Single Crystals for the Sensitive Detection of Visible Light and X-Rays.

The excellent performance and facile fabrication process of perovskite semiconductor materials make them highly promising candidates in the field of optoelectronic devices. Whether for visible light or X-rays, detectors with low detection limits can better identify weak light signals, significantly reducing the intensity of the received light source during device operation. In particular, for X-ray detectors, reducing X-ray dosage can greatly enhance the safety of X-ray imaging technology. This work develops detectors with low detection limit based on zero-dimensional (0D) MA3Bi2I9 single crystals. The anisotropy of MA3Bi2I9 and its influence on the detector's performance were investigated in detail. Detectors perpendicular to the (001) crystal plane have better weak light detection capability and require significantly less light intensity compared to devices parallel to the (001) crystal plane. X-ray detector with a limit of detection (LoD) of 0.68 nGyair s‒1 and sensitivity of 5072 μC Gyair‒1 cm‒2 was obtained. The present study offers comprehensive insights into the operational mechanism of layered perovskites, which can provide valuable guidelines for future designs and fabrications of highly sensitive photo and X-ray detectors.

Establishment and application of a rapid new detection method for antimicrobial susceptibility testing of Klebsiella pneumoniae based on MALDI-TOF MS.

The earlier appropriate treatment of Klebsiella pneumoniae infections according to the antimicrobial susceptibility profile based on the minimum inhibitory concentration (MIC) has a great clinical benefit. Our objective was to establish a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS)-based antimicrobial susceptibility test (AST) for K. pneumoniae that produces reliable results within a few hours. Our rapid method is similar to the classical turbidity-based microdilution method. We confirmed, theoretically and experimentally, that MALDI-TOF MS can replace the naked eye in judging the results (MICMS) by "seeing" the bacterial growth in the presence of different concentrations of antibiotics, including determination of the lower limit of bacterial count detection (4 × 105 cfu), the optimal period of incubation (2 h), and bacterial growth curve assay. Based on the study mentioned above, we determined the susceptibility of K. pneumoniae to imipenem. The MICMS and MIC data agreed over 85% (40/46) within 1 dilution range. Susceptibility profiles determined with our rapid method and the reference broth microdilution method were also compared. MICMS resulted in 97.9% (45/46) category agreement, 2.2% minor discrepancies, no major discrepancies, and no very major discrepancies. The summarized category agreement resulted in a kappa coefficient of almost 1 for weighted Cohen's kappa, which could be considered a nearly perfect agreement. It took just 2 h to produce a susceptibility profile with a low failure rate using our new rapid AST method, a work day earlier than the broth microdilution method.IMPORTANCEEmpirical antimicrobial use before antimicrobial susceptibility test (AST) is necessary but risks patient harm and excess costs. It is particularly worrying that the inappropriate use of carbapenems has allowed carbapenem-resistant Klebsiella pneumoniae to become the commonest transmissible carbapenem-resistant Enterobacterales worldwide. Guidelines recommend targeted therapy based on minimum inhibitory concentration results, which directly reflect the effectiveness of antibacterial drugs. The gold standard method of AST relies on visible bacterial growth, causing long turnaround times. Current rapid AST techniques are hampered by factors such as high costs, technological complexities, and limited detection capabilities. We present a novel rapid method and applied to the determination of the susceptibility of K. pneumoniae to imipenem. It took just 2 h to produce a susceptibility profile with a low failure rate, a work day earlier than the standard method. Our method is potentially a faster, more precise, cost-efficient, and user-friendly AST method that can enhance the effectiveness of treatment strategies.

Concentration of strontium and barium by co-precipitation with organic collectors and their x-ray fluorescence determination

The concentration of strontium and barium in the form of complexes with 11 organic reagents by co-precipitation with organic co-precipitants was studied for their subsequent determination by the X-ray fluorescence method. The most effective systems were those including reagents from the group of bisazo-substituted chromotropic acids—Nithchromazo and Chlorophosphonazo III. The complexes of these metals were almost quantitatively co-precipitated in the form of associates with the cations of the Brilliant Green dye when the collector was an associate of an excess of the analytical reagent with the cations of this dye. It was shown that the additional use of polyvinyl butyral as an indifferent co-precipitant allows not only the almost complete extraction of these elements from solutions but also the preparation of emitter concentrates suitable for X-ray fluorescence measurements using the background standard technique. The high efficiency allows reaching very low detection limits (IUPAC): 0.03 µg/mL for Sr and 0.19 µg/mL for Ba, even when working with small-volume samples.

Stable Hydrogen‐Bonded Cobalt‐porphyrin Framework for High‐Performance Electrochemical Detection of Carcinoembryonic Antigen

ABSTRACTThe accurate and sensitive detection of low‐abundance cancer‐related biomarkers in blood remains a key technical challenge in clinical applications. Herein, a simple and accurate sandwich‐type electrochemical immunosensor based on a stable hydrogen‐bonded cobalt‐porphyrin framework (Co‐HOF) was successfully developed for the ultrasensitive detection of the cancer‐related biomarker, carcinoembryonic antigen (CEA). The antibody‐modified Co‐HOF forms a sandwich structure with the CEA aptamer electrode exclusively in the presence of CEA, enabling the specific electrochemical detection of CEA. The electrochemical signal increased linearly with the concentration of CEA, demonstrating a wide linear range (0.001–50 ng mL−1) and a low detection limit (0.22 pg mL−1), surpassing the performance of commercial ELISA kits and most reported detection methods. The sensor was successfully employed for CEA detection in spiked human serum, with recoveries ranging from 85.04% to 105.20%. Additionally, we collected blood samples from colorectal cancer patients and healthy individuals to clinically validate the sensor, observing that CEA levels increased with cancer progression. The sensor detection results showed strong consistency (R2 = 0.995) with those obtained from commercial ELISA kits, demonstrating the proposed sensor's practicality for clinical detection of CEA and related cancer biomarkers.

Gold Nanoparticles Decorated CoAl LDH Monolayer: A Peroxidase-Like Nanozyme for Sensitive Colorimetric Detection of Acetylcholinesterase and Inhibitors.

Monitoring acetylcholinesterase (AChE) activity and its inhibitor is crucial yet challenging for the early diagnosis and treatment of neurological diseases. In this study, we present Au nanoparticle decorated CoAl layered double hydroxide monolayer (Au@CoAl-LDH-m) as a peroxidase-like (POD) nanozyme for the sensitive colorimetric detection of AChE and its inhibitor, thiamine pyrophosphate (TPP). Remarkably, the Au@CoAl-LDH-m nanozyme can catalyze the oxidation of chromogenic substrates through its POD-like activity, which is effectively inhibited by thiocholine (TCh, a catalytic product of AChE), thereby enabling detection of AChE and TPP through a visible colorimetric readout. The approach provides a highly sensitive and specificity assay with a broader linear response range (1-100 mU mL-1 for AChE and 1-1000 ng mL-1 for TPP) and a low detection limit (0.092 mU mL-1 for AChE and 0.201 ng mL-1 for TPP), respectively. These results highlight the significant potential of Au@CoAl-LDH-m for advancing colorimetric sensors in detecting small molecules across various biological applications.

Surface Plasmon-Driven Versatile Enhancement of Chemosensing.

Chemo-sensors have deeply integrated into various facets of our daily lives. To further satisfy the increasing performance demand, the current attempts are mainly centered on materials science approaches, usually involving time-& labor-consuming structure designing, synthesis, and modification. To date, it remains largely unexplored to enhance sensing material performance at the fundamental physical level by strategic exploitation of optical properties. In this work, we proposed a facile and versatile approach for improving the material performance by strategically utilizing the surface plasmon resonance─a characteristic property of optical devices. This approach is revealed to have a dual effect on fluorescence-based chemosensing: it amplifies the collection of fluorescence signals and simultaneously expedites the kinetics of chemical reactions. In this work, we developed a surface plasmon-driven fluorescence-based chemosensor that utilizes the 2,4,6-trisformyl phenol-diethylamine (TFP-I) fluorescent probe for the detection of hydrogen peroxide (H2O2) gas molecules. By harnessing the dual-effect induced by surface plasmons, we achieved outstanding sensing performance for H2O2 gas molecules, characterized by 0.0225 ppt sensitivity and an exceedingly low limit of detection. This study substantiates the applicability of the surface plasmon resonance-based optical effect in the realm of fluorescent chemical materials for sensing performance amplification. Beyond this, it pioneers the strategic harnessing of optical effects to manipulate the performance of chemical materials, particularly for the advancement of sensing capabilities.