Detection Limit Of Sensor Research Articles

Environmentally Benign Synthesis of Magnetic Fe3O4 Nanoparticle/Carbon Black/Copper‐Quercetin Rods for Sensitive, Disposable Electrochemical Sensor for Mitoxantrone

AbstractPhenolic compounds have a variety of activities but are most famous for their antioxidant and metal‐chelating properties. We explore the green synthesis and application of Fe3O4 nanoparticles, carbon black (CB), and copper‐quercetin (Cu−Q) composite for a disposable electrochemical sensor for mitoxantrone. Fe3O4 was synthesised using Camellia sinensis leaf extract. The copper‐quercetin was synthesised by titrating copper acetate solution with quercetin monohydrate solution at room temperature. Equal amounts of Fe3O4, CB, and Cu−Q were mixed to form Fe3O4‐CB/Cu−Q. The Fe3O4‐CB/Cu−Q/SPE has the lowest detection limit (55.47 pM) compared to previous mitoxantrone sensors. The average recovery was 102.2 %, with an RSD of 4.67 % in serum. The sensor maintained an average accuracy of 98.99 % in the presence of the interfering agent. The detection limit of the new sensor is about five times lower than that of the previous Fe3O4 and carbon black electrode. Therefore, it can be suggested that the Copper‐quercetin complex contributed significantly to the electrode's sensitivity. This research is the first to report the three oxidation potentials for mitoxantrone consistent with mitoxantrone's complex oxidation mechanism. Also, this is the first report on using copper‐quercetin as an electrode material for electrode chemical detection. Furthermore, this is the first green‐derived sensor for mitoxantrone.

A Novel Rhodamine‐Tetraphenylporphyrin Fluorescence Probe for Imaging Mercury In Vitro and In Vivo

ABSTRACTA highly selective fluorescent sensor Por‐RBO for determination of Hg2+ was designed and synthesized with Rhodamine B and Tetraphenylporphyrin. The sensor can determine the Hg2+ of a solution within the pH 5.0–8.0, free from interference of other metal ions. When detected in buffer solution, the fluorescence was the strongest when five times the concentration of Hg2+ ion was added. Calculated by fluorescence titration method, the detection limit of sensor Por‐RBO for Hg2+ ion was as low as 0.12 μmol/L. The geometries of Por‐RBO and Por‐RBO‐Hg2+ were optimized at the B3LYP/6‐31G** level by density functional theory. The charge distribution, orbital interactions, and bonding characteristics were analyzed and compared in detail to discuss the recognition mechanism and structure–fluorescence property relationships. The results of cell fluorescence imaging and CCK‐8 experiments indicate that the sensor Por‐RBO exhibits lower cytotoxicity. Por‐RBO can be used for fluorescence distribution imaging of Hg2+ in living cells.

Asymmetric Nanopore Sensor for Logic Detection of Dam and M.SssI Methyltransferases in Combination of DNA Walker and Autocatalytic Hybridization Reaction.

The detection of DNA methyltransferase (MTase) was crucial for understanding gene expression regulation, cancer mechanisms, and various biological processes, contributing significantly to disease diagnosis and drug development. Herein, a nanopore sensor based on cascaded signal amplification of DNA walker and autocatalytic hybridization reaction (AHR) was developed for the ultrasensitive determination of various MTases. In the presence of Dam MTase, the hairpin structure HD underwent methylation and cleavage by DpnI endonuclease, forming T-DNA fragments. These T-DNA fragments were used to activate the DNA walker, which moved across the surface of magnetic beads step by step, generating a large quantity of initiator I by cleaving the substrate. The initiator I subsequently activated the AHR. The AHR included a hybridization chain reaction (HCR) amplifier and a catalytic hairpin assembly (CHA) convertor. The HCR amplifier generated multiple novel CHA triggers, which activated the CHA convertor. This, in turn, stimulated the HCR amplifier, creating an AHR circuit that resulted in the formation of numerous DNA nanowires. These DNA nanowires were adsorbed onto the G4-PAMAM-modified nanopore surface under the influence of an electric field, thereby altering the surface charge of the nanopore and changing the ionic rectification curve. The detection limit of the Dam MTase nanopore sensor reached 0.0002 U/mL. By modification of the recognition sites of the probes, this nanopore system could also be used for the detection of M.SssI MTase. Moreover, a four-input parallel concatenated logic circuit (AND//INHIBIT-OR) had been constructed and applied for the multivariate detection of Dam MTase and M.SssI MTase, presenting a novel conceptual model for advancing the construction of nanopore logic gate systems and their applications in biosensing.

Highly sensitive and low-temperature triethylamine sensor based on in situ growth of hierarchical α-MoO3 flowers

To challenge high working temperature of present triethylamine (TEA) sensor, well-defined hierarchical α-MoO3 flowers were in situ grown on Al2O3 tubes through a simple solvothermal method. The α-MoO3 flowers were about 3 μm in diameter consisted of overlapping nanosheets with average thickness of ∼30 nm, growing radially from the center of the flowers. The α-MoO3 flowers in situ grew on Al2O3 tubes to constitute the thin film sensors, which exhibited improved gas-sensing performance to TEA compared to the thick film sensors painted with the powder of α-MoO3 produced in the same reaction system. The average response value of the α-MoO3 thin film sensors to 10 ppm TEA was 243.5 at relatively low operating temperature of 133 °C, which was 4.5 times as high as that of the thick film sensors (54.2). And the detection limit of the thin film sensors to TEA is further decreased to 0.001 ppm compared to the α-MoO3 thick film ones. The superior TEA-sensing capability should be attributed to the hierarchical nanostructure grown in situ that supplies more active sites for gas molecule adsorption and electron transfer. The synthesized α-MoO3 flowers with hierarchical nanostructure are promising material for trace TEA detection in practical application.

MXene-based self-adhesive, ultrasensitive, highly tough flexible hydrogel pressure sensors for motion monitoring and robotic tactile sensing

With the rapid development of artificial intelligence and human–computer interaction fields, wearable electronic devices represented by flexible pressure sensors have a wider range of application scenarios. In this paper, we used a composite hydrogel made by one-pot polymerization using a combination of acrylamide (AM), sodium carboxymethyl cellulose (CMC), dopamine (DA), and MXene (Ti3C2Tx). The composite hydrogel has the advantages of self-adhesion, high sensitivity, large detection range (0–500 kPa), low detection limit, high toughness (compression > 90 %), stability (more than 6700 s) and other advantages of hydrogel flexible pressure strain sensor. Sodium carboxymethyl cellulose (CMC), as a multifunctional thickener and gelling agent, significantly improves rheological properties and viscosity in hydrogels, forms crosslinked structures to enhance mechanical properties and provides reliable toughness for pressure sensors. Dopamine (DA), which is rich in catechol groups, can adhere to the material surface through oxidative polymerization to enhance bond strength. Hydrogel pressure sensors for human motion detection can accurately track joint movement, respond sensitively to changes in knocks and touches, and display specific characters such as Morse code. The technology extends to robotic systems, where pressure-activated electrical signals are used to control robot movements. Therefore, it has a very promising application in the field of human–computer interaction, human-body movement signal detection, etc. PAM/CMC/DA/MXene hydrogel pressure sensors have excellent mechanical, electrical, and adhesion properties, which provide a more reliable solution for the fields of flexible wearable e-skin, human–computer interaction, and tactile sensing.

CHARACTERIZATION AND ELECTROCHEMICAL BEHAVIOUR OF BORON DOPED DIAMOND IN DETECTING AMODIAQUINE

Amodiaquine (AQ) is an essential medicine in treating malaria. Yet, the threat of drug resistance and toxicity necessitates accurate measurement of AQ in the human body. This research determines the amodiaquine (AQ) detection performance of boron-doped diamond (BDD) working electrodes. The study utilizes different pulse velocity (DPV) methods to analyze the AQ reaction behavior of BDD. The research demonstrates the reaction mechanism: Two electrons are transferred, and irreversible oxidation reactions occur. The sensor limit of detection (LOD) is measured to determine the performance of working electrodes for AQ detection. The LOD is calculated between 0.0645 µM and 0.3 µM, and changes in analytical concentrations relative to maximum current are calculated. The LOD of the BDD electrode is 1.5×10–8 M, lower than previous research on AQ sensors, showing the effectivity of the BDD electrode as an AQ sensor.

Evaluation of reflective fiber-optic surface plasmon resonance sensor for monitoring scale deposition.

A reflective surface plasmon resonance (SPR) sensor was evaluated for real-time monitoring of scale deposition. The sensor consists of an optical fiber, only 5mm at the gold-coated tip of the sensing area. The effect of silica growth on the sensor response was evaluated using a Na2SiO3 solution. The sensitivity of the sensor to silica was 1.6 ± 0.3nm per one immersion in the solution of 1000mg/L (as SiO2) at 85°Cand subsequnt air drying, as indicated by theSPR peak shift. The amount of silica deposited on the gold surface was measured by the quartz crystal microbalancemethod, and the SPR sensitivity of 0.089nm/ng to silica mass was obtained. The detection limit (3σ) of the SPR sensor was 17ng, correspondingto a thickness of 2.5nm for amorphous silica. The SPR sensor wastested in geothermal brine sampled at the Sumikawa Geothermal Power Plant, where a clear SPR shift was observed, suggesting the effectiveness of the SPR sensor for scale monitoring.

High-Yield WS2 Synthesis through Sulfurization in Custom-Modified Atmospheric Pressure Chemical Vapor Deposition Reactor, Paving the Way for Selective NH3 Vapor Detection.

Nanostructured transition metal dichalcogenides have garnered significant research interest for physical and chemical sensing applications due to their unique crystal structure and large effective surface area. However, the high-yield synthesis of these materials on different substrates and in nanostructured films remains a challenge that hinders their real-world applications. In this work, we demonstrate the synthesis of two-dimensional (2D) tungsten disulfide (WS2) sheets on a hundred-milligram scale by sulfurization of tungsten trioxide (WO3) powder in an atmospheric pressure chemical vapor deposition reactor. The as-synthesized WS2 powders can be formulated into inks and deposited on a broad range of substrates using techniques like screen or inkjet printing, spin-coating, drop-casting, or airbrushing. Structural, morphological, and chemical composition analysis confirm the successful synthesis of edge-enriched WS2 sheets. The sensing performance of the WS2 films prepared with the synthesized 2D material was evaluated for ammonia (NH3) detection at different operating temperatures. The results reveal exceptional gas sensing responses, with the sensors showing a 100% response toward 5 ppm of NH3 at 150 °C. The sensor detection limit was experimentally verified to be below 1 ppm of NH3 at 150 °C. Selectivity tests demonstrated the high selectivity of the edge-enriched WS2 films toward NH3 in the presence of interfering gases like CO, benzene, H2, and NO2. Furthermore, the sensors displayed remarkable stability against high levels of humidity, with only a slight decrease in response from 100% in dry air to 93% in humid environments. Density functional theory and Bayesian optimization simulations were performed, and the theoretical results agree with the experimental findings, revealing that the interaction between gas molecules and WS2 is primarily based on physisorption.

Dye-sensitized NiO photocathode sensor based on signal-sensitive change strategy for MC-LR detection.

A novel photoelectrochemical (PEC) sensor for the detection of microcystic toxins (MC-LR) was developed on the basis of signal-sensitive change strategy. NiO nanoarray as a basic photoactive material was grown directly on the ITO glass electrode via calcination after hydrothermal reaction, while dye N719 was used to sensitize the electrode for enhancing visible light absorption, and the first signal-on stage was obtained. In the meantime, p-type Cu2O was applied as the signal probe attached to probe DNA (DNA2) to improve the sensitivity, and the second "signal-on" stage appeared because of its synergistic effect with NiO nanoarrays. The PEC signal decreases after the target analyte MC-LR is modified on the electrode due to the stronger affinity between MC-LR and its complementary aptamer DNA; part of the Cu2O-DNA2 will dissociate from the electrode. This sensitive signal change strategy allows the detection limit of the MC-LR sensor to be as low as 1.7pM, which offers an optional method for the sensitive and selective detection of other target molecules, with potential applications in environmental monitoring and toxin determination.

High sensitivity and ultra-low detection limit of violet phosphorus-based formaldehyde gas sensor by ultrasonic-assisted laser ablation

Formaldehyde (HCHO) pollution has emerged as a progressively critical environmental concern, with the detection of formaldehyde at trace levels being an indispensable requirement. Violet phosphorus (VP) nanoplates, recognized as innovative two-dimensional materials, are promising candidates for gas sensing due to their rich active sites and substantial specific surface area. This work pioneered the use of ultrasonic-assisted laser ablation in the synthesis of VP nanoplates. The as-produced VP nanoplates had the lateral dimension of 6.5 μm and the thickness of 2–6 nm (1–5 layers), which was strongly influenced by the ablation techniques employed and the processing parameters. The VP nanoplates demonstrated excellent sensitivity towards formaldehyde: gauge factor is 7.23 × 109; and resistance response is 144.6 % for detecting 20 ppb of formaldehyde. The detection limit is only 3 ppb. This work employed experiments and calculations to study the sensing mechanism. The binding energy between VP/G and HCHO is −1.276 eV, demonstrating the strong chemical adsorption. This paper provided a novel approach to fabricate VP nanoplates with superior formaldehyde sensitivity and ultra-low detection limitation, thereby showcasing significant potential for applications in detecting of air pollution.

High sensitivity and ultra-low detection limit of ethylene glycol gas sensor based on 0D carbon dots modified ZnO in multicolor light illumination

Ethylene glycol (EG) is a widely used material, but its vapor is harmful to human health already in low concentrations. Thus, highly sensitive EG gas sensors are urgently needed. Herein, a series samples of ZnO and carbon dots (CDs) were synthesized at different ratios through a simple mechanical grinding method. The senor made using ZnO/CDs2 exhibits an ultra-high response (Ra/Rg) to 100 ppm EG up to 2798, 1378 and 467, and extremely low detection limit as low as 21 ppb, 13 ppb and 2 ppb, under UV light, visible light, and infrared light, respectively, as well as excellent repeatability and long-term stability. Especially, under UV light irradiation, the response of ZnO/CDs2 to 100 ppm EG is 24 times that of pure ZnO (Ra/Rg = 114.7), and more than 71 times that of 9 other gases. The outstanding gas sensing performance of ZnO/CDs2 can be attributed to the excellent light response ability of CDs at first, which greatly enriches the electron concentration in ZnO/CDs under light irradiation. Furthermore, the photo-induced electron transfer (PET) property of CDs and the p-n heterojunction formed at the interface between ZnO and CDs play a key role in rapid electron transport and transfer, avoiding a large number of electron hole recombination.

Metal-Organic Framework-Derived Au-Doped In2O3 Nanotubes for Monitoring CO at the ppb Level.

Achieving selective detection of ppb-level CO is important for air quality testing at industrial sites to ensure personal safety. Noble metal doping enhances charge transfer, which in turn reduces the detection limit of metal oxide gas sensors. In this work, metal-organic framework-derived Au-doped In2O3 nanotubes with high electrical conductivity are synthesized by pyrolysis of the Au-doped metal-organic framework (In-MIL-68) as a template. Gas-sensing experiments reveal that the detection limit of 0.2% Au-doped In2O3 nanotubes (0.2% Au, mass fraction) is as low as 750 ppb. Meanwhile, the sensing material shows a response value of 18.2 to 50 ppm of CO at 240 °C, which is about 2.8 times higher than that of pure In2O3. Meanwhile, the response and recovery times are short (37 s/86 s). The gas-sensing mechanism of CO is uncovered by in situ DRIFTS through the reaction intermediates. In addition, first-principles calculations suggest that Au doping of In2O3 significantly enhances its adsorption energy for CO and improves the electron transfer properties. This study reveals a novel synthesis pathway for Au-doped In2O3 nanotubular structures and their potential application in low concentration CO detection.

Ultrasensitive detection of H2O2 via electrochemical sensor by graphene synergized with MOF-on-MOF nanozymes.

An electrochemical sensor was developed for the detection of hydrogen peroxide (H2O2),utilizing the synergistic effects of graphene (Gr) and MOF-on-MOF nanozymes (FeCu-NZs). Initially, Fe-MOF with peroxide-like activity is synthesized using a solvothermal method. Subsequently, the organic ligand on its surface binds Cu2+, enhancing the enzyme-like activity further. The resulting FeCu-NZs exhibit a distinctive electrochemical signal in response to H2O2. Moreover, integrating FeCu-NZs with Gr significantly amplifies the electrochemical signal and effectively reduces the sensor's detection limit. The developed sensor exhibited linear ranges of 0.1-3800 μM, with a limit of detection (LOD) of 0.06 μM. Additionally, FeCu-NZs catalyze H2O2 to generate abundant •OH radicals, and colorimetric detection of H2O2 is facilitated using the color rendering principle of 3,3',5,5'-tetramethylbenzidine (TMB). Notably, this detection method was applied to determine H2O2 concentrations in real samples, achieving a recovery exceeding 95.7%. In summary, this research provides a practical platform for the construction of traditional nanozymes and the integration of electrochemical systems, which have broad applications in food analysis, environmental monitoring, and medical diagnosis.

Ultra-sensitive strain sensor based on Sagnac interferometer with different length panda fiber

A high-sensitivity harmonic Vernier effect (HVE) strain sensor is fabricated by cascading Sagnac interferometer (SI) and Fabry-Perot interferometer (FPI). SI is fabricated by the panda fiber (PF). PF is a typical polarization maintaining fiber (PMF) that has two pressure zones, making it particularly sensitive to strain. SI1, SI2, and SI3 are constructed using PF with lengths of 20 cm, 50 cm, and 80 cm, respectively. They have interference spectra similar to sine waves in the wavelength range of 1250 nm to 1650 nm. Research has found that the sensitivity of SI is directly proportional to the effective PF length under strain action. In addition, if the strain acts on the entire length of the PF, the strain sensitivities of SI1, SI2, and SI3 are 30.4 pm/με, 28.4 pm/με, and 30.1 pm/με, respectively, which are relatively close. Then, FPI is fabricated by splicing single mode fiber (SMF) and quartz capillary, and it is an “SMF-Capillary-SMF” sandwich structure, and the free spectral range (FSR) of FPI is approximately half of that of SI2. FPI and SI2 are cascaded to produce a first-order HVE sensor, further amplifying the strain sensitivity of SI2. The intersection point of the internal envelope based on the HVE sensor spectrum can provide accurate spectral wavelength position and drift, and the strain sensitivity of the HVE sensor reaches 293.0 pm/με, improving the strain sensitivity of SI2 by 10.3 times. The detection limit of the HVE sensor is 0.5 µε as the strain varies from 0 to 700 µε. This HVE strain sensor is relatively easy to manufacture, low-cost, linear and reliable, and can achieve high sensitivity strain measurement. It has certain application value in the field of strain measurement.

Low level carbon monoxide detection using chemically reduced graphene oxide deposited ZnO nanorods

Carbon monoxide (CO) is a toxic and extremely dangerous gas commonly produced from partial combustion of fossil fuels from automobiles, industries and power plants, etc. Prolonged inhalation of CO with higher concentration (150–200 ppm) causes convulsions, respiratory arrest and even may lead to death. Therefore, a low-cost highly sensitive CO sensor with low detection limit is needed for environmental and biomedical applications. A resistive CO gas sensor was fabricated using zinc oxide nanorods (ZnO NRs). The sensor sensitivity, response, and detection limit have been enhanced by depositing reduced graphene oxide (rGO). The maximum sensitivity was obtained with 25 µl rGO loading at ∼190 °C operating temperature. The sensor demonstrated high selectivity towards the interfering gases like nitric oxide, acetone, alcohol and ammonia. rGO loaded ZnO NRs based CO gas sensor exhibited sensitivity 0.9 ppm-1 with lower limit of detection ∼14.3 ppb.

Optical Aptamer-Based Cytokine Nanosensor Detects Macrophage Activation by Bacterial Toxins.

Overactive or dysregulated cytokine expression is a hallmark of many acute and chronic inflammatory diseases. This is true for acute or chronic infections, neurodegenerative diseases, autoimmune diseases, cardiovascular diseases, cancer, and others. Cytokines such as interleukin-6 (IL-6) are known therapeutic targets and biomarkers for such inflammatory diseases. Platforms for cytokine detection are, therefore, desirable tools for both research and clinical applications. Single-walled carbon nanotubes (SWCNT) are versatile nanomaterials with near-infrared fluorescence that can serve as transducers for optical sensors. When functionalized with an analyte-specific recognition element, SWCNT emission may become sensitive and selective toward the desired target. SWCNT-aptamer sensors are easily assembled, inexpensive, and biocompatible. In this work, we introduced a nanosensor design based on SWCNT and a DNA aptamer specific to IL-6. We first evaluated several SWCNT-aptamer constructs based on this simple direct complexation method, wherein the aptamer both solubilizes the SWCNT and confers sensitivity to IL-6. The sensor limit of detection, 105 ng/mL, lies in the relevant range for pathological IL-6 levels. Upon investigation of sensor kinetics, we found rapid response within seconds of antigen addition which continued over the course of 3 h. We found that this sensor construct is stable and the aptamer is not displaced from the nanotube surface during IL-6 detection. Finally, we investigated the ability of this sensor construct to detect macrophage activation caused by bacterial lipopolysaccharides (LPS) in an in vitro model of disease, finding rapid and sensitive detection of macrophage-expressed IL-6. We are confident that further development of this sensor will have novel implications for diagnosis of acute and chronic inflammatory diseases, in addition to contributing to the understanding of the role of cytokines in these diseases.

Natural Hydrogen in the Northern Perth Basin, WA Australia: Geospatial Analysis and Detection in Soil Gas for Early Exploration

The scope of this work is to empirically check and prove the practical applicability of the Primordially Hydridic Earth (PHE) concept for early exploration of the resources of naturally occurring hydrogen. With the PHE concept postulates interpreted within the local geological, tectonic, petrological and geophysical context, the reconnaissance plan, as well as the field exploration and data acquisition programs, were put together and implemented in the field. The results obtained from the surface (<1m deep) soil gas survey performed in Western Australia (WA) resulted in values of hundreds of ppm H<sub>2</sub>, including three samples with a concentration of hydrogen exceeding the gas sensor detection limit of 2,000 parts per million (ppm) (the all-Australia record). Similarly, several of the shallow soil samples used for obtaining headspace gas extracts yielded dozens % H<sub>2</sub>, which was established utilizing Gas Chromatography (GC) technology. The latter tests established the all-Australia record of 58.3% (norm.) H<sub>2</sub> concentration from 15 m depth, being the highest reading from the area of research. At one location, a concentration of He exceeding 8,000ppm was detected in a 1m surface soil gas sample analyzed by the independent lab. The most important outcome was finding natural hydrogen where it was expected and predicted. On the other hand, H<sub>2</sub> concentrations exceeding the natural background of 1-3ppm were not detected in the soil gas readings outside of the areas identified using the PHE concept as a theoretical foundation. It may be stated that overall, the practical application of the PHE concept along with the thoroughly planned utilization of carefully selected exploration techniques brings satisfactory results.

Room temperature acetone gas sensing performance of ZnS-NiO nanocomposite sensor enhanced by UV activation for diabetes detection

Metal oxide semiconductors are popular in gas sensor applications.Current metal oxide-based acetone sensors struggle to deliver ppb-level acetone sensing at low temperatures for biological use. This study synthesizes 4mol% ZnS combined with NiO for acetone sensing. Nanoparticles were studied using FE-SEM, XPS, XRD, and UV-Vis spectroscopy. Mixed ZnS and NiO resulted in rapid gas channel movement and n-p heterojunction development, which increased acetone sensitivity. ZnS-NiO showed a gas sensing response of 163% for 20 ppm acetone at room temperature under UV irradiation, which is 2.3 times higher than pristine NiO (70% at 180 ∘C). ZnS improves sensor selectivity. Heterojunction sensor reaction and recovery times were 20 and 14 seconds, respectively. The composite sensor detection limit was 0.1 ppm. The increased sensitivity validates the n-p heterojunction. The sensor’s higher response values and lower detection limit point to breath analyzer applications such as diabetes detection.

Ag/Fe3O4 bifunctional nanocomposite for SERS detection of non-steroidal anti-inflammation drug diclofenac

In this work, a bifunctional nanocomposite based on silver and iron oxide nanoparticles (AgNPs/Fe3O4) was prepared and then used as SERS substrate (surface-enhanced Raman spectroscopy) for sensing diclofenac which is one of the most widely used non-steroid anti-inflammation drugs. AgNPs/Fe3O4 nanocomposite was synthesized by combining co-precipitation of iron oxide and in-situ reduction of silver nanoparticles. Morphology and structural studies revealed a conjugated structure in which silver nanoparticles (80 nm in diameter) were surrounded by iron oxide nanoparticles (18 nm in diameter). There is a slight blue-shift in position of plasmon peak from 405 nm for silver nanoparticles to 375 nm for AgNPs/Fe3O4 nanocomposite. Even the saturation magnetization (Ms) of the Ag/Fe3O4 nanocomposite only reached 28 emu.g-1 but still good enough for immobilizing nanocomposite structures onto the substrate. The use of AgNPs/Fe3O4 nanocomposite as SERS substrate for sensing application was demonstrated with using diclofenac as a model. The detection limit and enhancement factor of the SERS-based diclofenac sensor were found to be 10-12 M and 2.6×1010, respectively. Such kind of bifunctional nanocomposite will probably help us to avoid time-consuming process to immobilize metal nanoparticles onto the surface, and also allow us to regenerate the substrate for multiple uses.

Defect-rich cypress-leaf-like Cu2+1O@NiF for high-performance non-invasive glucose detection with low detection limit

Non-invasive detection of body fluid glucose concentration is of great significance in the diagnosis and treatment of diabetes, which poses a new challenge to the reduction of the detection limit of glucose sensors. In this work, a novel non-enzymatic glucose sensor (defect-rich cypress-leaf-like Cu2+1O@NiF) was proposed by rapid electrodeposition of cypress-leaf-like Cu2+1O on the surface of nickel foam (NiF) substrate. Due to the high electrochemical active surface area and abundant defects of cypress-leaf-like Cu2+1O providing more catalytic active sites, the prepared non-enzymatic sensor has an ultra-low detection limit (0.9 nM), high sensitivity (88,419.4 μA∙mM−1∙cm−2 (1 nM-0.5 μM) and 2095.5 μA∙mM−1∙cm−2 (1 μM-4.33 mM)) and wide linear range (1 nM-4.33 mM) with good selectivity, reproducibility and stability. Furthermore, the obtained sensors exhibited high detection stability, accuracy and recovery for glucose detection of human body fluid samples, which means that the defect-rich cypress-leaf-like Cu2+1O@NiF electrode is an ideal candidate for non-invasive glucose sensors.