SnO2 nanoparticle-coated ZnO nanotube arrays for high-performance electrochemical sensors

Dual-recognition driven sensing platform based on a BSA-Cu NP nanozyme combined with smartphone-assistance for fluorometric/colorimetric monitoring of dopamine

Developing a highly sensitive approach for neurotransmitter analysis is of vital significance due to their essential role in clinical diagnosis and treatment of disease. Herein, bovine serum albumin templated copper nanoparticles (BSA-Cu NPs) with peroxidase-mimicking activity are designed and synthesized for dopamine detection through the fluorometric/colorimetric dual-mode technique. The experimental results suggest that as-fabricated BSA-Cu NPs can strongly catalyze the decomposition of hydrogen peroxide to produce oxidized substances, accompanied by remarkable color changes of chromogenic agent 3,3',5,5'-tetramethylbenzidine from colorless to blue, revealing peroxidase-like activities of BSA-Cu NPs. However, owing to the strong binding affinity between dopamine (DA) and BSA-Cu NPs, the catalytic activities of synthesized BSA-Cu NPs are inhibited, leading to a significant decrement of absorption peak signal. Meanwhile, the strong fluorescence of BSA-Cu NPs exhibits remarkable quenching due to photo-induced electron transfer. Besides, by integrating paper strips and smartphone software analysis, an intelligent recognition of DA is also fabricated. On the basis of these phenomena, a fluorometric/colorimetric approach based on the BSA-Cu NP nanozyme combined with smartphone-assisted analysis is constructed for detecting dopamine with a detection limit of 5 nM, and 5 nM, respectively. Moreover, the recognition of dopamine in human serum samples is also successfully realized which is verified using high performance liquid chromatography, demonstrating its promising potential in bioanalysis and clinical disease diagnosis.

Cu2O-SnO2-PDA heterozygous nanozyme doped hydrogel mediated conglutinant microenvironment regulation for wound healing therapy

Bacterial infection significantly hinders the wound healing process. Overuse of antibiotics has led to the rise of drug resistance in bacteria, making the development of smart medical dressings that promote wound healing without antibiotics, a critical need. In this study, Cu₂O-SnO₂-PDA (PCS) nanoenzymes with Fenton-like activity and high photothermal conversion efficiency were developed. These nanoenzymes were then incorporated into a hydrogel through cross-linking of acrylamide (AM) and N-[Tris-(hydroxymethyl)methyl] acrylamide (THMA), forming a tough, highly-adhesive, and self-healing composite hydrogel (AT/PCS) with antimicrobial properties. The AT/PCS hydrogel exhibits excellent mechanical strength and adhesion, facilitating increased oxygen levels and strong adherence to the wound site. Moreover, it effectively regulates the wound microenvironment by combining synergistic chemodynamic therapy (CDT) and photothermal therapy (PTT) for antibacterial treatment. The AT/PCS hydrogel enhances collagen deposition and expedites wound healing in a rat model, largely due to its potent antibacterial properties.

A Semi-Automatic Environmental Monitoring Device for Mercury and Cobalt Ion Detection

A syringe-based, semi-automatic environmental monitoring device is developed for on-site detection of harmful heavy metal ions in water. This portable device consists of a spring-embedded syringe and a polydimethylsiloxane (PDMS) membrane-based flow regulator for semi-automatic fix-and-release fluidic valve actuation, and a paper-based analytical device (PAD) with two kinds of gold nanoclusters (AuNCs) for sensitive Hg2+ and Co2+ ion detection, respectively. The thickness of the elastic PDMS membrane can be adjusted to stabilize and modulate the flow rates generated by the pushing force provided by the spring attached to the plunger. Also, different spring constants can drastically alter the response time. People of all ages can extract the fix-volume sample solutions and then release them to automatically complete the detection process, ensuring high reliability and repeatability. The PAD comprises two layers of modified paper, and each layer is immobilized with bovine serum albumin-capped gold nanoclusters (R-AuNCs) and glutathione-capped gold clusters (G-AuNCs), respectively. The ligands functionalized on the surface of the AuNCs not only can fine-tune the optical properties of the nanoclusters but also enable specific and simultaneous detection of Hg2+ and Co2+ ions via metallophilic Au+ -Hg2+ interaction and the Co2+ -thiol complexation effect, respectively. The feasibility of the device for detecting heavy metal ions at low concentrations in various environmental water samples is demonstrated. The Hg2+ and Co2+ ions can be seen simultaneously within 20 min with detection limits as low as 1.76 nm and 0.27 µm, respectively, lower than those of the regulatory restrictions on water by the US Environmental Protection Agency and the European Union. we expect this sensitive, selective, portable, and easy-to-use device to be valid for on-site multiple heavy metal ion pollution screenings in resource-constrained settings.

Rapid and sensitive colorimetric detection of dopamine based on the enhanced-oxidase mimicking activity of cerium(iv)

A fast and sensitive approach for colorimetric determination of DA based on the enhanced oxidase-like catalytic activity of Ce⁴⁺ by DA was developed.

Rational Construction of 3D-Networked Carbon Nanowalls/Diamond Supporting CuO Architecture for High-Performance Electrochemical Biosensors

Tremendous demands for highly sensitive and selective nonenzymatic electrochemical biosensors have motivated intensive research on advanced electrode materials with high electrocatalytic activity. Herein, the 3D-networked CuO@carbon nanowalls/diamond (C/D) architecture is rationally designed, and it demonstrates wide linear range (0.5 × 10^-6 -4 × 10^-3 m), high sensitivity (1650 µA cm^-2 mm^-1 ), and low detection limit (0.5 × 10^-6 m), together with high selectivity, great long-term stability, and good reproducibility in glucose determination. The outstanding performance of the CuO@C/D electrode can be ascribed to the synergistic effect coming from high-electrocatalytic-activity CuO nanoparticles and 3D-networked conductive C/D film. The C/D film is composed of carbon nanowalls and diamond nanoplatelets; and owing to the large surface area, accessible open surfaces, and high electrical conduction, it works as an excellent transducer, greatly accelerating the mass- and charge-transport kinetics of electrocatalytic reaction on the CuO biorecognition element. Besides, the vertical aligned diamond nanoplatelet scaffolds could improve structural and mechanical stability of the designed electrode in long-term performance. The excellent CuO@C/D electrode promises potential application in practical glucose detection, and the strategy proposed here can also be extended to construct other biorecognition elements on the 3D-networked conductive C/D transducer for various high-performance nonenzymatic electrochemical biosensors.

Enhanced electrochemical sensing of dopamine in the presence of AA and UA using a curcumin functionalized gold nanoparticle modified electrode

In the present study, a electrochemical sensor for the determination of dopamine was developed with green synthesised gold nanoparticles using curcumin as a reducing and, functionalizing agent.

Bouquet-Like Mn2SnO4 Nanocomposite Engineered with Graphene Sheets as an Advanced Lithium-Ion Battery Anode

Volume expansion is a major challenge associated with tin oxide (SnO _x), which causes poor cyclability in lithium-ion battery anode. Bare tin dioxide (SnO₂), tin dioxide with graphene sheets (SnO₂@GS), and bouquet-like nanocomposite structure (Mn₂SnO₄@GS) are prepared via hydrothermal method followed by annealing. The obtained composite material presents a bouquet structure containing manganese and tin oxide nanoparticle network with graphene sheets. Benefiting from this porous nanostructure, in which graphene sheets provide high electronic pathways to enhance the electronic conductivity, uniformly distributed particles offer accelerated kinetic reaction with lithium ion and reduced volume deviation in the tin dioxide (SnO₂) particle during charge-discharge testing. As a consequence, ternary composite Mn₂SnO₄@GS showed a high rate performance and outstanding cyclability of anode material for lithium-ion batteries. The electrode achieved a specific capacity of about 1070 mA h g^-1 at a current density of 400 mA g^-1 after 200 cycles; meanwhile, the electrode still delivered a specific capacity of about 455 mA h g^-1 at a high current density of 2500 mA g^-1. Ternary Mn₂SnO₄@GS material could facilitate fabrication of unique structure and conductive network as advanced lithium-ion battery.

A facile one-pot green synthesis of gold nanoparticle-graphene-PEDOT:PSS nanocomposite for selective electrochemical detection of dopamine

A facile one-pot and green method was developed to prepare a nanocomposite of gold nanoparticle (AuNP), graphene (GP) and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). Graphene was first electro-exfoliated in a polystyrene sulfonate solution, followed by a one-step simultaneous in situ formation of gold nanoparticle and PEDOT. The as-synthesized aqueous dispersion of AuNP-GP-PEDOT:PSS was thereafter used to modify the glassy carbon electrode (GCE). For the first time, the quaternary composite between AuNP, GP, PEDOT and PSS was used for selective determination of dopamine (DA) and uric acid (UA) in the presence of ascorbic acid (AA). In comparison to a bare GCE, the nanocomposite electrode shows considerably higher electrocatalytic activities toward the oxidation of DA and UA due to a synergistic effect between AuNP, GP, PEDOT and PSS. Using differential pulse voltammetry (DPV), selective determination of DA and UA in the presence of AA could be achieved with a peak potential separation of 110 mV between DA and UA. The sensor exhibits wide linear responses for DA and UA in the ranges of 1 nM to 300 μM and 10 μM to 1 mM with detection limits (S/N = 3) of 100 pM and 10 μM, respectively. Furthermore, the proposed sensor was also successfully used to determine DA in a real pharmaceutical injection sample as well as DA and UA in human serum with satisfactory recovery results.

A facile one-pot green synthesis of gold nanoparticle-graphene-PEDOT:PSS nanocomposite was successfully demonstrated.

ZnO nanotubes supported molecularly imprinted polymers arrays as sensing materials for electrochemical detection of dopamine

In this study, ZnO nanotubes (ZNTs) were prepared onto fluorine-doped tin oxide (FTO) glass and used as supports for MIPs arrays fabrication. Due to the imprinted cavities are always located at both inner and outer surface of ZNTs, these ZNTs supported MIPs arrays have good accessibility towards template and can be used as sensing materials for chemical sensors with high sensitivity, excellent selectivity and fast response. Using K₃[Fe(CN)₆] as electron probe, the fabricated electrochemical sensor shows two linear dynamic ranges (0.02-5μM and 10-800μM) towards dopamine. This proposed electrochemical sensor has been applied for dopamine determination with satisfied recoveries and precision. More complex human urine samples also confirmed that the proposed method has good accuracy for dopamine determination in real biological samples. These results suggest potential applicability of the proposed method and sensor in important molecule analysis.

Detection of Nitric Oxide from Living Cells Using Polymeric Zinc Organic Framework-Derived Zinc Oxide Composite with Conducting Polymer

Sensitive and selective detection of nitric oxide (NO) in the human body is crucial since it has the vital roles in the physiological and pathological processes. This study reports a new type of electrochemical NO biosensor based on zinc-dithiooxamide framework derived porous ZnO nanoparticles and polyterthiophene-rGO composite. By taking advantage of the synergetic effect between ZnO and poly(TTBA-rGO) (TTBA = 3'-(p-benzoic acid)-2,2':5',2″-terthiophene, rGO = reduced graphene oxide) nanocomposite layer, the poly(TTBA-rGO)/ZnO sensor probe displays excellent electrocatalytic activity and explores to detect NO released from normal and cancer cell lines. The ZnO is immobilized on a composite layer of poly(TTBA-rGO). The highly porous ZnO offers a high electrolyte accessible surface area and high ion-electron transport rates that efficiently catalyze the NO reduction reaction. Amperometry with the modified electrode displays highly sensitive response and wide dynamic range of 0.019-76 × 10^-6 m with the detection limit of 7.7 ± 0.43 × 10^-9 m. The sensor probe is demonstrated to detect NO released from living cells by drug stimulation. The proposed sensor provides a powerful platform for the low detection limit that is feasible for real-time analysis of NO in a biological system.

Surface defect engineering: gigantic enhancement in the optical and gas detection ability of metal oxide sensor

By using surface defect engineering, the gigantic enhancement in UV and gas detection abilities of nanosensors can be achieved.

Wireless Hydrogen Smart Sensor Based on Pt/Graphene-Immobilized Radio-Frequency Identification Tag

Hydrogen, a clean-burning fuel, is of key importance to various industrial applications, including fuel cells and the aerospace and automotive industries. However, hydrogen gas is odorless, colorless, and highly flammable; thus, appropriate safety protocol implementation and monitoring are essential. Highly sensitive hydrogen-gas leak detection and surveillance systems are needed; additionally, the ability to monitor large areas (e.g., cities) via wireless networks is becoming increasingly important. In this report, we introduce a radio frequency identification (RFID)-based wireless smart-sensor system, composed of a Pt-decorated reduced graphene oxide (Pt_rGO)-immobilized RFID sensor tag and an RFID-reader antenna-connected network analyzer to detect hydrogen gas. The Pt_rGOs, produced using a simple chemical reduction process, were immobilized on an antenna pattern in the sensor tag through spin coating. The resulting Pt_rGO-based RFID sensor tag exhibited a high sensitivity to hydrogen gas at unprecedentedly low concentrations (1 ppm), with wireless communication between the sensor tag and RFID-reader antenna. The wireless sensor tag demonstrated flexibility and a long lifetime due to the strong immobilization of Pt_rGOs on the substrate and battery-independent operation during hydrogen sensing, respectively.

Metallic Sn spheres and SnO2@C core-shells by anaerobic and aerobic catalytic ethanol and CO oxidation reactions over SnO2 nanoparticles

SnO₂ has been studied intensely for applications to sensors, Li-ion batteries and solar cells. Despite this, comparatively little attention has been paid to the changes in morphology and crystal phase that occur on the metal oxide surface during chemical reactions. This paper reports anaerobic and aerobic ethanol and CO oxidation reactions over SnO₂ nanoparticles (NPs), as well as the subsequent changes in the nature of the NPs. Uniform SnO₂@C core-shells (10 nm) were formed by an aerobic ethanol oxidation reaction over SnO₂ NPs. On the other hand, metallic Sn spheres were produced by an anaerobic ethanol oxidation reaction at 450 °C, which is significantly lower than that (1200 °C) used in industrial Sn production. Anaerobic and aerobic CO oxidation reactions were also examined. The novelty of the methods for the production of metallic Sn and SnO₂@C core-shells including other anaerobic and aerobic reactions will contribute significantly to Sn and SnO₂-based applications.

Graphene-based nanoprobes for molecular diagnostics

In recent years, graphene has received widespread attention owing to its extraordinary electrical, chemical, optical, mechanical and structural properties. Lately, considerable interest has been focused on exploring the potential applications of graphene in life sciences, particularly in disease-related molecular diagnostics. In particular, the coupling of functional molecules with graphene as a nanoprobe offers an excellent platform to realize the detection of biomarkers, such as nucleic acids, proteins and other bioactive molecules, with high performance. This article reviews emerging graphene-based nanoprobes in electrical, optical and other assay methods and their application in various strategies of molecular diagnostics. In particular, this review focuses on the construction of graphene-based nanoprobes and their special advantages for the detection of various bioactive molecules. Properties of graphene-based materials and their functionalization are also comprehensively discussed in view of the development of nanoprobes. Finally, future challenges and perspectives of graphene-based nanoprobes are discussed.

Fabrication of SnO2-SnO nanocomposites with p-n heterojunctions for the low-temperature sensing of NO2 gas

In this report, the fabrication of a novel SnO2-SnO nanostructure with p-n heterojunctions has been achieved through a facile one-pot and low-cost hydrothermal process. The structure and properties of the nanocomposite were analyzed with X-ray techniques and electron microscopy. HRTEM characterization showed that the p-n heterojunctions were formed with small n-type SnO2 nanocrystals dispersed on the surface of large p-type SnO crystals. Compared to the single SnO2-based material, a gas sensor fabricated from the SnO2-SnO composite exhibited an enhanced sensing performance for NO2 gas detection, with a limit of detection and sensitivity of 0.1 ppm and 0.26 ppm(-1), respectively, at a relatively low operating temperature (50 °C). Moreover, the p-n heterojunctions exhibited high sensing selectivity for NO2. Such a high sensing sensitivity and a low operating temperature make the SnO2-SnO p-n nanomaterial a promising gas sensor for practical NO2 gas detection. The improved sensing response characteristics of the hybrid material could be attributed to the p-n junctions formed through the in situ growth of SnO2 nanocrystals on SnO nanoplates. The present study is helpful for the design of novel gas sensing materials and the development of NO2 gas sensors.

One-pot synthesis of fluorescent and cross-linked polyphosphazene nanoparticles for highly sensitive and selective detection of dopamine in body fluids

Highly cross-linked and monodisperse polyphosphazene (PZS) nanoparticles exhibiting strong fluorescence were prepared by the facile one-pot polycondensation of hexachlorocyclotriphosphazene and 4′,5′-dibromofluorescein (DBF).

A three dimensional Pt nanodendrite/graphene/MnO2 nanoflower modified electrode for the sensitive and selective detection of dopamine

A highly sensitive and selective electrochemical sensor: a 3D hierarchical ternary composite including a Pt nanodendrite/reduced graphene oxide/MnO₂ nanoflower modified electrode.