Wide Detection Research Articles

A metal-organic framework-based sensor for specific detection of tetracycline in milk

Molecularly imprinted fluorescent sensors are of interest to researchers due to their specificity, high sensitivity, and stability. In this study, the fluorescence-imprinted sensor (NH2-MIL-53/MIP) for the detection of tetracycline (TC) in animal-derived foods was developed based on the characteristics of luminescent metal-organic frameworks (MOFs) and molecularly imprinted polymers (MIPs). The MOFs provide fluorescence sensing signals and large specific surface areas, while the MIPs provide the specific recognition sites for TC. As a result, the sensor exhibits a wide detection range (0.05–50 μg/mL), high sensitivity (LOD of 0.006 μg/mL), fast detection speed and good selectivity. The sensing principle can be attributed to photoinduced electron transfer. Furthermore, the sensor can determine TC in milk with good recovery rates (95.05–104.71 %). This work addresses the limitation of current molecularly imprinted sensors such as slow corresponding speed and limited detection capability, providing valuable insights for target determination in complex systems.

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.

Development of piezoresistive poly(ɛ-caprolactone) sensor with unique flexibility and sensing performance for rehabilitative application

ABSTRACT Piezoresistive sensor is applied extensively in rehabilitative monitoring, to help with patients’ physical and mental health recovery. However, the manufacturing complexity of hierarchical structure in sensing element remains a major limitation to piezoresistive sensor. Here, we report a scalable and simple method for the preparation of piezoresistive sensing element. Based on biocompatible poly(ɛ-caprolactone) (PCL), uniaxial cold stretching resulted in a flexible sheet-like element with unique hierarchical geometries comprising highly aligned multiscale ridges on sheet’s double sides. This leads to higher mechanical elasticity of the hierarchitectured PCL element and enhanced resistance against plastic deformation due to the improved Young’s modulus. Further assembly of the piezoresistive sensor demonstrates a wide detection range of 25–4.7 × 104 Pa with rapid response and the high sensitivity of 1.37 kPa−1 at small pressure loadings. The sensor shows successful application in the monitoring physiological signals including pulse, speaking, face expression and limb motion.

Biomimetic Electronic Skin for Robots Aiming at Superior Dynamic-Static Perception and Material Cognition Based on Triboelectric-Piezoresistive Effects.

Empowering robots with tactile perception and even thinking as well as judgment capabilities similar to those of humans is an inevitable path for the development of future robots. Here, we propose a biomimetic electronic skin (BES) that truly serves and applies to robots to achieve superior dynamic-static perception and material cognition functionalities. First, the microstructured triboelectric and piezoresistive layers are fabricated by a facile template method followed by selected self-polymerization treatment, enabling BES with high sensitivity and a wide detection range. Further, through laminated-independent triboelectric and piezoresistive parts for perceiving dynamic and static pressures simultaneously, the BES is capable of supporting the robot hand to monitor the entire process during object grasping. Most importantly, by further combining a neural network model, an intelligent cognition system is constructed for real-time cognition of the object material species via one touch of the robot hand under arbitrary pressures, which goes beyond the human cognition ability.

Enhanced polyvinyl alcohol ionic conductive hydrogel with feather keratin extracted via deep eutectic solvent for wearable strain sensor

The extraction of keratin from discarded feathers for the preparation of poly (vinyl alcohol) (PVA) ionic conductive hydrogels with enhanced mechanical properties shows promise for applications in green flexible electronics. Here, we first extracted feather keratin (FK) from duck feather fibers using the lactic acid/l-cysteine deep eutectic solvents. Subsequently, the composite ionic conductive hydrogel composed of FK, PVA, and CaCl2 was constructed by a one-pot freeze-thawing strategy. The introduction of FK resulted in a denser structure of the fabricated hydrogel, which significantly enhanced its mechanical properties, including high elongation at break of 639.3%, high breaking strength of 270 kPa, and durable fatigue resistance. Impressively, the hydrogel-based wearable strain sensor demonstrated high strain sensing sensitivity (GF = 1.26), wide strain detection range (5%–200%), fast response, and stable reliability, enabling it to accurately monitor and distinguish the difference in electrical signals generated by large and tiny human motions. This work provides a reliable method for the green extraction of FK and the design of high-performance PVA hydrogel-based flexible electrical devices.

C─H···π interaction induced H‐aggregates for wide range water content detection in organic solvents

AbstractJ‐aggregation and H‐aggregation are identified as two classical models of functionally oriented non‐covalent interactions, and significant attention has been drawn by researchers. However, due to the scarcity of single‐crystal examples of H‐aggregation, a comprehensive understanding of the relationship between its stacking mode and optical behaviour has been hindered. In recent studies, two polyaromatic Schiff base compounds, Cl‐Salmphen and H‐Salmphen, were successfully synthesized, and both were found to exhibit H‐aggregation. In the findings, H‐Salmphen was shown to display typical C─H···π interactions, characteristic of Aggregation‐Induced Emission (AIE) active molecules, whereas its halogenated counterpart was identified as behaving similar to Aggregation‐Caused Quenching (ACQ) active molecules. These types of results suggest that identical intermolecular interactions can produce differing optical behaviours. Light was shed, at least in part, on the formation mechanisms of H‐type aggregates and their luminescence properties from these observations. Additionally, the high optical signal‐to‐noise ratio inherent to H‐aggregates was utilized for the exploration of water content detection. As an outcome, a high‐performance fluorescent filter paper was developed, enabling easy real‐time detection using a smartphone.

Electrochemical detection of heavy metal ions in water using MWCNT/ZnO nanocomposite

A nanocomposite of multi-walled carbon nanotubes (MWCNTs) decorated with zinc oxide nanoparticles (ZnO NPs) was fabricated via an in-situ hydrothermal approach and implemented as a modified electrode for stripping voltammetric detection of dissolved heavy metal ions. The MWCNT/ZnO exhibited a high specific surface area of 53 m2/g and charge transfer conductivity amplified to 26 S/cm. By square wave voltammetry, the nanocomposite sensor achieved wide linear detection of Cu(II) from 1 to 800 ppb, Pb(II) from 5 to 1000 ppb, and Hg(II) from 1 to 900 ppb, along with low limits of detection reaching 0.8, 1.2, and 0.7 ppb, respectively. The 3–5X enhanced sensitivity versus an unmodified screen-printed carbon electrode confirms performance gains supplied by the tailored hybrid interface. Selectivity testing produced distinct, well-resolved oxidation peaks for each metal ion target that remained unaffected by high off-target concentrations of Mn(II), Co(II), and Fe(III) interferents. Accurate spike recoveries between 95% and 102% were obtained from quantifying ternary mixtures across various Cu(II):Pb(II):Hg(II) compositions, substantiating the capability for simultaneous multianalyte analysis. The simple preparation, high sensitivity and selectivity, and accuracy for direct water testing validates the nanocomposite as a practical portable sensor for on-site toxic heavy metal detection.

Synthesis, properties, and applications of all-solid-state reference electrode based on AgTi2(PO4)3

High-density AgTi2(PO4)3 as a solid electrolyte was synthesised by a high-temperature solid-state process. The optimal sintering temperature was determined to obtain the best structural and electrical performance. Based on the as-prepared AgTi2(PO4)3 fast-ion conductor, a new type of all-solid-state reference electrode was prepared, and its electrochemical properties, such as cyclic voltammetry curves and potentials at varying pH, were investigated. A pH sensor was designed by combining an AgTi2(PO4)3 reference electrode with an Ir/IrO2 pH electrode. This pH sensor exhibited a good linear response to pH values in aqueous solutions and simulated seawater samples. In addition, a metal ion sensor, comprising the as-fabricated solid-state reference electrode, a Pt counter electrode, and a glassy carbon working electrode, was employed to quantify Cu2+, Hg2+, and Pb2+ concentrations using differential-pulse anodic stripping voltammetry. The resulting peak currents correlated with the metal ion concentrations and exhibited a low detection limit, good linearity, and wide detection range, which is suitable for performing chemical analysis in harsh marine environments.

Colloidal quantum dots-modified electrochemical sensor for high-sensitive extracellular vesicle detection

Small extracellular vesicles (sEVs), primarily referring to exosomes, have emerged as potent tools for investigating pathological mechanisms and facilitating precise diagnostics owing to their ability to transfer informative molecules between cells and their accessibility from diverse biological fluids. Despite the multitude of biomedical applications, achieving enhanced specificity and sensitivity in detecting trace sEV samples continues to pose a significant challenge. Considering the potential of electrochemical sensing in efficient molecular detection, this study proposes a viable strategy for specifically recognizing sEVs by targeting their membrane proteins. Additionally, it demonstrates sensitive and quantitative detection of sEVs based on the unique performance of PbS colloidal quantum dots (CQDs) nanomaterials. The good immobilization of target proteins on the chemically modified electrode is achieved through the synergistic effect of the charge–discharge mechanism and strong suspension bonds of PbS CQDs. The results obtained from the analysis of differential pulse voltammetry demonstrate rapid and highly sensitive electrochemical responses. The CD63 antibody-modified sensor can achieve highly sensitive detection of sEVs, providing a wide linear detection range (102 ∼ 108 particles mL−1) and a low detection limit (19 particles mL−1). The established method is ultimately employed to differentiate the sEVs originating from distinct tumor cells, thereby demonstrating its potential in membrane-biomarker-based diagnostics. Consequently, the presented electrochemical sensor demonstrates remarkable efficiency in quantifying EVs with exceptional specificity and sensitivity, thereby offering extensive prospects for applications in EV analysis and point-of-care tests.

One-pot synthesis of cerium-organic framework@carbon black composites for simultaneous detection of dopamine, uric acid, and acetaminophen

Accurate identification of dopamine (DA), uric acid (UA), and acetaminophen (APAP) is critical to safeguarding human health. However, their simultaneous detection is still challenging due to their similar oxidation potentials. In this work, a series of new composites based on cerium-organic framework (Ce-MOF) and carbon black (CB) were constructed by one-pot method at room temperature. The introduction of CB can significantly affect the conductivity and specific surface area of the composites. The optimal composite Ce-MOF-COOH/CB0.4 can identify DA, UA, and APAP simultaneously with low detection limit of 0.030, 0.045, and 0.057 μM and wide detection range of 2.5–310.0, 3.0–305.0, and 2.5–617.0 μM, respectively. Furthermore, density-functional theory (DFT) calculation was performed to explore the influence of functional groups (-NH2 or –COOH) on the sensing performance. It was found that the introduced functional groups can obviously enhance the host-guest interactions through the formation of strong hydrogen bonds, which is beneficial for promoting sensing performance. In addition, the constructed electrode could also detect DA, UA, and APAP in real samples, which indicated its potential for practical applications. This study provides a feasible approach to utilize MOFs as electrochemical sensors for simultaneously detection of biomolecules.

Highly sensitive flexible pressure sensor based on a 1D/2D hybrid aerogel

Wearable pressure sensors with highly sensitive and wide detection ranges are essential for human motion monitoring. In this work, a self-assembled hybrid aerogel was obtained by polyacrylonitrile nanofibers, polyaniline, and reduced graphene oxide. Based on the complementation of 1D and 2D nanomaterials, the aerogel acted like a spring under lower pressure and a membrane under higher pressure, showing great potential in human motion monitoring. According to the wide detection range of the aerogel, an artificial hand was designed to recognize different spatial pressures such as grasping a pen, holding a bottle, and shaking hands. These signal outputs could be precisely reflected by voltage change and further converted to RGB values. Meanwhile, a shoe pad was prepared to monitor foot pressure and the resistance change could be converted to color scale signals. This work provides a new strategy for 1D/2D hybrid nanomaterials-based aerogel with wide pressure ranges in flexible electronics.

Porous nanofibers and micro-pyramid structures array for high-performance flexible pressure sensors

Flexible pressure sensors have attracted extensive research interest as smart wearable devices’ core components. However, developing flexible pressure sensors with high sensitivity and wide pressure detection range remains a great challenge. Utilizing electrospinning and mould transfer technology, this paper presents a novel ‘sandwich’ flexible pressure sensor composed of a sensitive layer of poly (lactic acid) (PLA) porous nanofiber network film and electrodes made of polydimethylsiloxane (PDMS) micro-pyramid structure array film. Through ultrasonic treatment, carbon black particles penetrate into the PLA porous nanofiber film, which effectively enhances the conductivity of the PLA film. Due to the complex conductive pathways formed by the ultra-high specific surface area of the PLA porous nanofibers and the three-dimensional amplification structure of the PDMS micro-pyramid arrays, the sensor has a high sensitivity of 54.06 kPa−1, a wide detection range of 0–56 kPa, an ultra-low detection limit of 2.5 Pa and excellent durability (10000 cycles). Impressively, the sensor is able to accurately monitor various physiological activities of the human body in real time, which is believed to be a strong impetus for the development of the next generation of wearable products.

Chiral Viologen-Derived Water-Stable Small Band Gap Lead Halides: Synthesis, Characterization, and Optical Properties.

Chiral organic-inorganic metal halides (OIMHs) are attractive for their potential applications in chiral optoelectronics and spintronics, such as circular polarized light emitters, detectors, and chiral-induced spin selectivity. Here, we report three pairs of chiral OIMHs with great water stability constructed from chiral viologens. These OIMHs contain either 1D or 0D structures, however, with small band gaps around 2 eV. Circular dichroism (CD) spectroscopy on transparent thin films of two OIMH pairs showed a wide CD response covering most of the visible light range. Although the chiral center is not directly attached to the pyridinium in these chiral viologens, the chirality is still successfully transferred into both the band gap and the exciton absorption ranges. Liquid and solid CD studies of the chiral viologens further indicate that the chiral induction inside these OIMHs is possibly through chiral crystallization. This work demonstrated the design strategy of water-stable, small band gap chiral OIMHs through chiral viologens. These low-dimensional chiral materials may provide an interesting system to investigate chiral induction, and their broad CD response may enable their potential application as circular photodetectors with a wide detection range.

An unlabeled electrochemical sensor for the simultaneous detection of homocysteine and uric acid based on molecularly imprinted recognition for prediction of cardiovascular disease risk

An unlabeled molecular imprinted electrochemical sensor was developed for simultaneous detection of homocysteine and uric acid, based on gold nanoparticles and molecularly imprinted polymer composites modified glass carbon electrode. Gold nanoparticles stably enhanced the electron transfer and improved the sensitivity by acting as a base for enhancing signal for molecularly imprinted polymers. Specific molecular imprinting cavities based on electropolymerization with dopamine were formed to specifically and simultaneously identify homocysteine and uric acid. Combining the good sensitivity of electrochemistry and the excellent selectivity of molecularly imprinted polymer, the difference in peak current position was used to achieve simultaneous detection of homocysteine and uric acid. For this reason, the developed sensor showed the wide detection range of 5.00 × 10−3-1.00 × 103 μmol/L for homocysteine and 5.00 × 10−1-5.00 × 103 μmol/L for uric acid, with the LOD of 5.64 × 10−5 μmol/L and 0.128 μmol/L (S/N = 3). The developed sensor with easy preparation, great selectivity and short detection time could be used in simultaneous detection of homocysteine and uric acid in serum.

Novel electrochemical platform based on C3N4-graphene composite for the detection of neuron-specific enolase as a biomarker for lung cancer

Lung cancer remains the leading cause of cancer mortality worldwide. Small cell lung cancer (SCLC) accounts for 10–15% of cases and has an overall 5-years survival rate of only 15%. Neuron-specific enolase (NSE) has been identified as a useful biomarker for early SCLC diagnosis and therapeutic monitoring. This work reports an electrochemical immunosensing platform based on a graphene-graphitic carbon nitride (g-C3N4) nanocomposite for ultrasensitive NSE detection. The g-C3N4 nanosheets and graphene nanosheets were synthesized via liquid exfoliation and integrated through self-assembly to form the nanocomposite. This nanocomposite was used to modify screen-printed carbon electrodes followed by covalent immobilization of anti-NSE antibodies. The unique properties of the graphene-g-C3N4 composite facilitated efficient antibody loading while also enhancing electron transfer efficiency and electrochemical response. Systematic optimization of experimental parameters was performed. The immunosensor exhibited a wide linear detection range of 10 pg/mL to 100 ng/mL and low limit of detection of 3 pg/mL for NSE along with excellent selectivity against interferences. Real serum matrix analysis validated the applicability of the developed platform for sensitive and accurate NSE quantifica-tion at clinically relevant levels. This novel graphene-g-C3N4 nanocomposite based electro-chemical immunoassay demonstrates great promise for early diagnosis of SCLC.

Efficient DNA walker guided by ordered cruciform-shaped DNA track for ultrasensitive and rapid electrochemical detection of lead ion

The rational design of DNA tracks is an effective pathway to guide the autonomous movement and high-efficiency recognition in DNA walkers, showing outstanding advantages for the cascade signal amplification of electrochemical biosensors. However, the uncontrolled distance between two adjacent tracks on the electrode could increase the risk of derailment and interruption of the reaction. Hence, a novel four-way balanced cruciform-shaped DNA track (C-DNT) was designed as a structured pathway to improve the effectiveness and stability of the reaction in DNA walkers. In this work, two kinds of cruciform-shaped DNA were interconnected as a robust structure that could avoid the invalid movement of the designed DNA walker on the electrode. When hairpin H2 was introduced onto the electrode, the strand displacement reaction (SDR) effectively triggered movements of the DNA walker along the cruciform-shaped track while leaving ferrocene (Fc) on the electrode, leading to a significant enhancement of the electrochemical signal. This design enabled the walker to move in an excellent organized and controllable manner, thus enhancing the reaction speed and walking efficiency. Compared to other walkers moving on random tracks, the reaction time of the C-DNT-based DNA walker could be reduced to 20 min. Lead ion (Pb2+) was used as a model target to evaluate the analytical performance of this biosensor, which exhibited a low detection limit of 0.033 pM along with a wide detection ranging from 0.1 pM to 500 nM. This strategy presented a novel concept for designing a high-performance DNA walker-based sensing platform for the detection of contaminants.

Vacuum-solvent thermal synthesis of nickel foam-supported CuO-based sensor electrode for good electrochemical detection of nitrite

Given the bad effect of superfluous nitrites on biology/environment, engineering the fast, sensitive, and real-time quantification of nitrites matters to safeguard both the eco-system and human public health. Here, a CuO nanocatalyst self-supported on nickel foam (CuO@NF) was crafted via facilely fusing a vacuum solvent recipe with ambient thermal annealing. Various characterizations show that hollow sea urchin-like CuO structures were arrayed on substrate to feature a 3D porous motif and large specific surface area. Such traits promise the effective local wetting and enrichment of nitrite to augment the nitrate capture/contact capacity, underlying a highly sensitive electrochemical determination of nitrite. Specifically, a wide linear detection range can span 0.5 to 4250 μM, with a stable current response at a concentration as low as 0.5 μM nitrite. The detection limit or sensitivity is approximately 0.0287 mM or 2.402 mAmM−1 cm−2, respectively. This electrode was also successfully applied to detect the nitrite in complex samples like pickled vegetables with satisfactory recovery rates. Our study shows that the self-supported CuO sensor provides an ingenious tactic to build high-efficiency binderless electrodes for the electrochemical sensing applications.

Chameleon-like Response Mechanism of Gold-Silver Bimetallic Nanoclusters Stimulated by Sulfur Ions and Their Application in Visual Fluorescence Sensing.

Herein, 2-mercapto-5-benzimidazolesulfonate acid sodium salt dihydrate (MBZS)-protected gold-silver bimetallic nanoclusters, named MBZS-AuAg NCs, were synthesized. Interestingly, we found that MBZS-AuAg NCs solutions can exhibit different fluorescence color changes under sulfide stimulation. A series of modern analytical testing techniques were used to explore the interaction mechanism between MBZS-AuAg NCs and sulfide. Sulfide ions can not only cause MBZS-AuAg NCs to exhibit rich fluorescence color changes similar to those of a chameleon but also have four linear relationships between the response intensity and sulfide concentration. A wide-range sulfide fluorescence sensing platform was constructed based on four linear segments with different fluorescence color responses. This sensing platform can be directly used for the determination of S2- with a detection limit as low as 11 nM. The portable test paper based on MBZS-AuAg NCs can realize the visual and rapid detection of gaseous hydrogen sulfide with a detection limit of 100 ppb (v/v). The wide detection range of the proposed method not only allows it to be used as an alternative method for sulfide detection in environmental samples but also has potential applications in the rapid detection and early warning of hydrogen sulfide gas in industrial and mining scenarios.

Surface plasmon resonance temperature sensor based on the conjoined-tube hollow-core anti-resonant fiber with ultra-high temperature sensitivity

A surface plasmon resonance (SPR) temperature sensor based on the conjoined-tube hollow-core anti-resonant fiber (HC-ARF) is designed and analyzed. The conjoined-tube HC-ARF contains two connecting tubes with a cross arrangement in the cladding. The SPR temperature sensor is constructed by inserting a metal into one of the inner layer tubes and injecting a thermo-sensitive liquid into the hollow core of the HC-ARF to enhance the temperature sensitivity by exploiting the SPR effect. The effects of the structural parameters and thermo-sensitive media and metals on the sensing properties such as the temperature sensitivity, peak loss, resolution, amplitude sensitivity, and figure of merit (FOM) are analyzed systematically. Numerical analysis reveals ultra-high temperature sensitivity of 38.8 nm/°C and FOM of 673.84∘C−1, which are approximately 10 times higher than those of sensors described in the recent literature. In addition, the sensor is capable of detecting a wide temperature range from −5∘C to 60°C with good linearity. The SPR temperature sensor with high precision, a wide temperature detection range, a simple and easily modifiable structure, as well as good manufacturing tolerance has large potential in high-precision temperature monitoring in the petrochemical and biomedical industries.

Novel flexible capacitive pressure sensor with a wide detection range enabled by carboxyl iron particle-paraffin wax/silicone composite

The emergence of flexible capacitive pressure sensors has prominently accelerated the development of flexible electronics. However, most capacitive pressure sensors reported so far have limited detection ranges, which greatly restricts their application scenarios. In this work, a novel flexible capacitive pressure sensor with a wide detection range was produced by employing the carboxyl iron particle-paraffin wax (CIP-PW)/silicone composite as the dielectric layer. Due to the introduction of phase-changing PW and magnetic CIPs, the resultant CIP-PW/silicone composite exhibits magnetism and temperature-controllable mechanical properties, which therefore provides the capacitive pressure sensor with a tunable effective detection range in the frequency range of 0.1–5 Hz. To be specific, the sensor could achieve an effective detection range of 0.2–350 kPa, much wider than other capacitive sensors reported. This merit is further demonstrated by monitoring finger and arm movements as well as walking status. In addition to the physical contact sensing, the sensor exhibits a contactless sensing capacity, and could be used to monitor finger movements without direct contact. In virtue of the wide detection range and bimodal sensing capacity, the current capacitive pressure sensor shows greatly promising in the fields of wearable devices, e-skin, robotics and so on.