Porous cuprous oxide microcubes for non-enzymatic amperometric hydrogen peroxide and glucose sensing

Using porous cuprous oxide (Cu₂O) microcubes, a simple non-enzymatic amperometric sensor for the detection of H₂O₂ and glucose has been fabricated. Cyclic voltammetry (CV) revealed that porous Cu₂O microcubes exhibited a direct electrocatalytic activity for the reduction of H₂O₂ in phosphate buffer solution and the oxidation of glucose in an alkaline medium. The non-enzymatic amperometric sensor used in the detection of H₂O₂ with detection limit of 1.5 × 10^?6 M over wide linear detection ranges up to 1.5 mM and with a high sensitivity of 50.6 μA/mM. This non-enzymatic voltammetric sensor was further utilized in detection of glucose with a detection limit of 8.0 × 10^?7 M, a linear detection range up to 500 μM and with a sensitivity of ?70.8 μA/mM.     

Microwave-assisted synthesis of organic–inorganic poly(3,4-ethylenedioxythiophene)/RuO2·xH2O nanocomposite for supercapacitor

An organic–inorganic poly(3,4-ethylenedioxythiophene) (PEDOT)/RuO₂·xH₂O nanocomposite (approximately 1 wt.% RuO₂) has been successfully prepared for the first time under microwave irradiation within 5 min with power 900 W via in situ chemical polymerization. The morphology and structure of the resultant material is characterized by transmission electron microscope and Fourier transform infrared. Moreover, the electrochemical properties of the synthesized nanocomposite can be controlled by adjusting the annealing temperature, which is definitely illustrated by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectra. Electrochemical data have shown that the PEDOT/RuO₂·xH₂O nanocomposite annealed at 150 °C possesses the most favorable charge/discharge ability with a specific capacitance of 153.3 F g⁻¹ at a current density of 150 mA g⁻¹ and the high efficient utilization of PEDOT at various current densities. Furthermore, such composite has a less capacitance degradation of 23.8% after 1,000 continuous cycles. The improved electrochemical performance are mainly attributed to the large electroactive surface of nanocomposite and the existence of amorphous RuO₂·xH₂O particles as well as a synergistic effect of the polymer PEDOT and annealed RuO₂·xH₂O. Thus, the PEDOT/RuO₂·xH₂O nanocomposite annealed at 150 °C can act as a promising electroactive material for supercapacitor application.     

Gold Nanoparticles Monolayer Doping PEDOT : PSS Janus Film for Hydrogen Sulfide Sensor

AuNPs monolayer doping Poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT : PSS) film on interdigitated electrode had been fabricated into AuNPs/PEDOT : PSS Janus film sensor to detect hydrogen sulfide (H₂S). The results show that the Janus film sensors have a wide measurement range of H₂S concentration. The sensitivity of PEDOT : PSS/AuNPs sensor grows up with the thickness of Janus film increases. The resistance response of AuNPs Janus film was affected little by the rough surface states of PEDOT : PSS film. In addition, the PEDOT : PSS/AuNPs film sensor had been used again to detect H₂S. This work presents a platform to inspire a novel high sensitive chemiresistive sensor via nanoparticles monolayer.     

Electrochemical detection of cystatin C by oriented antibody immobilization on streptococcal protein G–modified ZIF-8-Cu1−xNix(OH)2@Cu core-shell nanostructured electrode

Herein, we prepared a novel nanostructure involving Cu shell on Zeolitic imidazolate frameworks (ZIF-8) and Cu_1?xNi_x(OH)₂ composite (ZIF-8-Cu_1?xNi_x(OH)₂@Cu) combining sol-gel and co-precipitation method. The morphology, stoichiometry, and structure of the nanocomposite were elucidated by various physicochemical analyses. A poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) coated indium tin oxide (ITO) was modified with the synthesized ZIF-8-Cu_1?xNi_x(OH)₂@Cu nanoparticles (NPs) to obtain an efficient electrode for further antibody immobilization. The ZIF-8-Cu_1?xNi_x(OH)₂@Cu/PEDOT:PSS/ITO was applied for the detection of cystatin C, a promising biomarker of chronic kidney disease (CKD). The electrode was functionalized by streptococcal protein G (SPG) to bind the Fc region of anti-cystatin C in an oriented manner. The synergistic catalytic activities, high surface coverage, enhanced electroactive sites, and excellent redox properties of the proposed electrode lead to excellent electrochemical sensing. The proposed sensor obtained a much lower detection limit (33 pg/mL) for a linear range of 0.1 ng/mL to 1,000 ng/mL with high selectivity, stability, and reproducibility compared with bare ZIF-8/PEDOT:PSS/ITO-based immunosensor. The clinical feasibility of the sensor was confirmed by measuring the human serum in the presence of different concentrations of cystatin C. This work demonstrates a new and facile approach to fabricating a metal-organic framework (MOF) –based nanoimmunosensor for cystatin C, which has significant importance in diagnosing the renal failure.     

Synthesis of Co0.5Mn0.1Ni0.4C2O4⋅n H2O Micropolyhedrons: Multimetal Synergy for High‐Performance Glucose Oxidation Catalysis

Owing to the synergy between metals, trimetal oxalate micropolyhedrons have been synthesized by means of a room‐temperature coprecipitation strategy. The effect of their nanoscale size on their electrochemical performance toward glucose oxidation was investigated. In particular, the Co_0.5Mn_0.1Ni_0.4C₂O₄?n H₂O micropolyhedrons illustrated prominent electrocatalytic activity for the glucose oxidation reaction. Additionally, the Co_0.5Mn_0.1Ni_0.4C₂O₄?n H₂O micropolyhedrons, when used as an electrode material, illustrated an excellent lower limit of detection (1.5 μm ), a wide detection concentration range (0.5–5065.5 μm ), and a high sensitivity (493.5 μA mm ^?1 cm^?2). Further analysis indicated that the effectively improved conductivity may have been due to the small size of the materials, and it was easier to form a flat film when Nafion was coated onto the glassy carbon electrode.     

Designed synthesis of ZnO/PEDOT core/shell hybrid nanotube arrays with enhanced electrochromic properties

Designed growth of zinc oxide (ZnO)/poly(3,4-ethylenedioxythiophene) (PEDOT) core/shell hybrid nanotube arrays has been achieved by electropolymerization technique. The ZnO/PEDOT hybrid nanotubes electropolymerized for 2000-second display enhanced electrochromic properties of the contrast ratio up to 31.3%, a lot higher than those of the pure PEDOT and ZnO/PEDOT hybrid nanorods. Moreover, the coloring efficiency of the hybrid nanotubes increases from 105.2 cm² C⁻¹ of ZnO/PEDOT hybrid nantotube with the electrodeposition time of 1000 seconds to 122.2 cm² C⁻¹ of 2000 seconds at 520 nm. Therefore, the hybrid composite nanotubes fabricated by the in situ electrodeposition techniques may demonstrate huge potential applications in energy-saving technologies such as smart windows.     

Fluorescein Hydrazide-Appended Metal–Organic Framework as a Chromogenic and Fluorogenic Chemosensor for Mercury Ions

In this work, we prepared a fluorescein hydrazide-appended Ni(MOF) (Metal–Organic Framework) [Ni₃(BTC)₂(H₂O)₃]·(DMF)₃(H₂O)₃ composite, FH@Ni(MOF). This composite was well-characterized by PXRD (powder X-ray diffraction), FT-IR (Fourier transform infrared spectroscopy), N₂ adsorption isotherm, TGA (thermogravimetric analysis), XPS (X-ray photoelectron spectroscopy), and FESEM (field emission scanning electron microscopy). This composite was then tested with different heavy metals and was found to act as a highly selective and sensitive optical sensor for the Hg²⁺ ion. It was found that the aqueous emulsion of this composite produces a new peak in absorption at 583 nm, with a chromogenic change to a pink color visible to the naked eye upon binding with Hg²⁺ ions. In emission, it enhances fluorescence with a fluorogenic change to green fluorescence upon complexation with the Hg²⁺ ion. The binding constant was found to be 9.4 × 10⁵ M⁻¹, with a detection limit of 0.02 μM or 5 ppb. This sensor was also found to be reversible and could be used for seven consecutive cycles. It was also tested for Hg²⁺ ion detection in practical water samples from ground water, tap water, and drinking water.     

Enzyme-free amperometric sensing of hydrogen peroxide and glucose at a hierarchical Cu2O modified electrode

In this paper, an enzyme-free amperometric electrochemical sensor was fabricated by casting Nafion-impregnated Cu₂O particles onto a glassy carbon electrode. A dual dependence of peak current on sweeping rate, which can be attributed for the accumulation of reaction products, was observed on the sensor. Electrochemical analysis of the particulate Cu₂O for detecting H₂O₂ and glucose is described, showing remarkable sensitivity in both cases. The estimated detection limits and sensitivities for H₂O₂ (0.0039 μM, 52.3 mA mM⁻¹ cm⁻²) and glucose (47.2 μM, 0.19 mA mM⁻¹ cm⁻²) suggest that the response for H₂O₂ detection was much higher than for glucose detection. Electron microscopy observation suggested that the hierarchical structures of Cu₂O resulting from self-assembly of nanocrystals are responsible for the specific electrochemical properties.     

MXene-based composite electrodes for efficient electrochemical sensing of glucose by non-enzymatic method

A recently discovered 2D transition titanium metal carbides also called as MXenes (Ti₃C₂T_x)-based nanocomposite was prepared with Cu₂O through wet precipitation technique, and these materials were further developed as the electrode for sensing glucose by chronoamperometry technique. The prepared MXene-Cu₂O (Ti₃C₂T_x-Cu₂O) nanocomposite was characterized by XRD, FTIR, UV–Vis spectroscopy, FE-SEM, EDAX, and Raman spectroscopy. Morphological studies of the composites revealed that the micro-octahedral shape of Cu₂O is distributed on the surface of MXene with size larger than bare Cu₂O. Further, the prepared composite material was fabricated as a sensing probe, and the electrochemical activities were examined by cyclic voltammetric analysis (CV) and chronoamperometric (CA) methods. From the CV and CA investigation, the current response was higher for the composite than the bare material (Cu₂O & MXene) in the presence of glucose. The amperometric investigation of MXene-Cu₂O composite for the detection of glucose shows a broad linear range (0.01–30 mM) with a sensitivity of 11.061/μAmM cm^?2 and a detection limit of 2.83 μM. Further, the fabricated sensor exhibits good selectivity with interfering species like NaCl, fructose, sucrose, urea, ascorbic acid, lactose, short response time, stability, good reproducibility, and compatibility with human serum sample. From the investigation, the prepared MXene-Cu₂O composite is a good candidate for the direct detection of glucose molecules and is also well suitable for clinical diagnosis.     

Enzymeless voltammetric hydrogen peroxide sensor based on the use of PEDOT doped with Prussian Blue nanoparticles

An electrochemical sensor for H₂O₂ was developed based on electrochemically deposited Prussian blue (PB) nanoparticles doped poly(3,4-ethylenedioxythiophene) (PEDOT). The PEDOT/PB composite was composed of PEDOT wrapped PB nanoparticles, where the conducting polymer PEDOT not only protected the PB particles to warrant high stability, but also connected them to enhance the electron transfer. Owing to the excellent conductivity of PEDOT and unique electrocatalytic activity of PB, the PEDOT/PB modified electrode exhibited good catalytic activity toward the electrochemical reduction of H₂O₂, and was used for the detection of H₂O₂ in concentrations ranging from 0.5 to 839 μM, with a detection limit of 0.16 μM. Moreover, the sensor also demonstrated excellent reproducibility, selectivity and long-term stability, showing great promise for the fabrication of electrochemical sensors and H₂O₂ related biosensors.

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Graphical abstract An electrochemical non-enzymatic sensor for hydrogen peroxide with excellent stability was developed. It is based on conducting polymer PEDOT doped with Prussian blue nanoparticles.

     

Electrochemical Glyphosate Sensor Based on Hybrid Material SiO2/Sm2O3/Carbon Modified with Meldola Blue

In this work, we have proposed an electrochemical sensor for the detection of pesticides by using a ceramic composite with a SiO₂ surface modified with Sm₂O₃ nanoparticles and C-graphite (SSMG), obtained by the sol-gel process and immobilized by adsorption in Meldola Blue cationic dye (MB). The composite was called (SSMG/MB), which was characterized by spectroscopic, electrochemical techniques, Fourier-transform infrared spectroscopy, and Cyclic Voltammetry. The proposed sensor was applied for the glyphosate electrochemical detection, using Differential Pulse Voltammetry, and, under optimized parameters has presented the linear response for the pesticide in the concentration range from 0.99 to 7.94 (μmol L⁻¹; R²=0.9963; n=8). The calculated values for the detection limit and the quantification limit were 0.15 and 0.49 μmol L⁻¹, respectively. Therefore, the new electrochemical sensor based on SiO₂, NPsSm₂O_3, C-graphite, and MB hybrid material was developed for the first time for glyphosate determination, which has demonstrated high potential for the development of new hybrid devices for environmental control.     

Model-free kinetics applied for the removal of CTMA<Superscript>+</Superscript> and TPA<Superscript>+</Superscript> of the nanostructured hybrid AlMCM-41/ZSM-5 material

The nanostructured hybrid AlMCM-41/ZSM-5 composite was synthesized starting from a hydrogel with molar composition SiO₂:0.32Na₂O:0.03Al₂O₃:0.20TPABr:0.16CTMABr:55H₂O. The cetyltrimethylammonium bromide (CTMABr) and tetrapropylammonium bromide (TPABr) were used as templates. The above mentioned material presents morphological properties with specific characteristics, such as the surface area of the composite which is approximately half of the surface area of the conventional MCM-41. Another interesting feature is the formation of walls with the double of the density of the MCM-41 structure, which characterizes the hybrid material, resulting in a high stability material for catalytic application. The aim of this study is obtain optimized structures of the hybrid material and for this purpose variations in the synthesis time were carried out. A comparative analysis was performed including X-ray diffraction, Fourier transform infrared spectroscopy, and Thermogravimetry measurements. The model-free kinetic algorithms were applied in order to determinate conversion and apparent activation energy of the decomposition of the CTMA⁺ and TPA⁺ species from the hybrid AlMCM-41/ZSM-5.     

Development of copper-stabilized conducting-polymer/polyoxometalate hybrid materials for effective electrochemical charging

A hybrid organic-inorganic material composed of poly (3,4-ethylenedioxythiophene), PEDOT, derivatized with 4-(pyrrol-e1-yl) benzoic acid, PyBA, and Keggin-type copper (II)-salt of H₃PMo₁₂O₄₀ has been proposed here. Such features as good electronic conductivity of PEDOT, hydrophilic and coordination capabilities of PyBA, the ability of copper (II) ions to link PyBA carboxylic groups, and phosphomolybdate anionic sites, as well as high protonic and mixed-valence conductivities of H₃PMo₁₂O₄₀ have been explored here to produce a stable composite material charcterized by reasonable charge propagation dynamics. Characterization and formation of the hybrid ca. 0.6 μm thick PEDOT/PyBA-Cu_xH_yPMo₁₂O₄₀ films have been asessed by FTIR, XRD, AFM, SEM, as well as using electrochemical methods. Among important feautures of the proposed hybrid system is the ability to undergo reversible charging/discharhging (both under voltammetric and galvanostatic conditions) in a manner analogous to what is observed in battery-type cells. Typical parameters, such as specific capacity, energy, and power densities, are provided and discussed.

     

基于碳酸钙-金纳米粒子无机杂化复合物固定硫堇的新方法及其在过氧化氢传感器中的应用

通过静电作用,经碳酸钙-金纳米粒子(CaCO3-AuNPs)无机杂化复合物实现了电活性物质硫堇(Th)在金电极表面的有效固定.AuNPs静电吸附到CaCO3微球表面形成CaCO3-AuNPs无机杂化复合物,该杂化复合物具有微孔结构、大的表面积和好的生物相容性,使得Th的固定量和稳定性大大提高.探讨了Th修饰电极在过氧化...     

Ni4-thiacalix[4]arene sandwiched Mo8 polyoxometalate bimetallic nanoclusters for electrocatalytic glucose oxidation

Available online two new Ni₈Mo₈ bimetallic coordination clusters, [Ni₄(TC4A)]₂[(Mo₅^VMo₃^VIO₂₄)(PO₄)] (+Solvent) (Ni₈PMo₈, H₄TC4A= p-tert-butylthiacalix[4]arene) and [Ni₄(TC4A)]₂[(Mo₅^VMo₃^VIO₂₄)(OH)(CO₃)] (+Solvent) (Ni₈Mo₈), were synthesized by solvothermal method and structurally characterized by single-crystal X-ray diffraction, powder X-ray diffraction, FT-IR spectroscopy, and TGA experiments, respectively. The usage of H₃PMo₁₂O₄₀ as source for Ni₈PMo₈ resulted a sandwich like structure built from two Ni₄-thiacalix[4]arene units and a Mo₈ polyoxometalate with inner spaces of PO₄^3?. Ni₈Mo₈ with the similar structure to that of Ni₈PMo₈ is from H₂MoO₄ starting reagent with OH^? and CO₃^2? anions encapsulated in the center. The two clusters can be directly loaded on carbon paper and utilized as working electrodes which showed distinguishable performances for glucose detection and oxidation. This work provides a better understanding of the structure–property relationships in using substituted polyoxometalates for electrochemical applications and is helpful for building calixarene-based or polyoxometalate-based functional materials.     

Electro-active silver oxide nanocubes for label free direct sensing of bisphenol A to assure water quality

This research, for the first time, demonstrates a direct electrochemical detection of bisphenol A (BPA) using silver oxide (Ag₂O) nanocubes (NCs) modified platinum electrode. The Ag₂O NCs, size ranging from 60 to 100 nm utilized in this research as a smart electro-active sensing platform were pure and synthesized using a cost-effective, affordable, and facile chemical route. The Ag₂O NCs modified electrochemical sensor exhibited a low limit of detection (LOD) as 20 nmol dm^?3, high sensitivity as 95 μA (μmol dm^?3)^?1 cm^?2, and linear dynamic range (LDR) varies from 80 nmol dm^?3- 4.8 μmol dm^?3. This sensor also showed good selectivity, reproducibility, and reusability for BPA detection. The practical application of developed sensor was also tested using real water samples. The outcomes of this research suggested that Ag₂O NCs based sensor can be useful for effective and efficient electrochemical BPA sensing in both real and lab samples.     

CaCl2·6H2O/Expanded graphite composite as form-stable phase change materials for thermal energy storage

In this study, CaCl₂·6H₂O/expanded graphite (EG) composite was prepared as a novel form-stable composite phase change material (PCM) through vacuum impregnation method. CaCl₂·6H₂O used as the PCM was dispersed by surfactant and then, was absorbed into the porous structure of the EG. The surfactant was used to enhance the bonding energy between CaCl₂·6H₂O and EG, which fulfilled the composites with good sealing performance and limited the leakage of the inside CaCl₂·6H₂O. Differential scanning calorimetry and thermal gravimetric analysis show that all the composite PCMs possess good thermal energy storage behavior and thermal stability. Thermal conductivity measurement displays that the conductivities of the samples have been significantly improved due to the highly thermal conductive EG. The thermal conductivity of the sample including 50 mass% CaCl₂·6H₂O (8.796 W m^?1 K^?1) is 14 times as that of pure CaCl₂·6H₂O (0.596 W m^?1 K^?1). Therefore, the obtained composite PCMs are promising for thermal energy storage applications.     

Self‐Assembling of Hybrid Prussian Blue Units in Cinder Matrix: Characterization and Electrocatalysis

Industrial waste cinder (CFe*) has been utilized as a stable anchoring matrix for self‐assembling of Fe(CN)₆^3? as hybrid Prussian blue units (PB, *Fe³⁺Fe^II(CN)₆) on a screen‐printed carbon electrode (SPE) for efficient catalytic applications. The waste cinder was found to be a composite of calcium and iron silicates similar to glass matrix by X‐ray photoelectron spectroscopic (XPS) study. The hybrid PB formations were confirmed by both FT‐IR and electrochemical methods. Most importantly, the free iron (Fe*) ion bound to the non‐bridging oxygen terminals of the silicates was found to play a key role in the PB formation. The self‐assembled PB hybrid on the cinder‐modified screen‐printed electrodes (designated as PBCFe*‐SPE) improved linear detection range and sensitivity for H₂O₂ mediated oxidation than those obtained at a classical PB‐SPE in 0.1 M, pH 2 KCl/HCl base electrolyte at 0.0 V (vs. Ag/AgCl) by amperometric batch analysis.     

The Rapid and Practical Route to Cu@PCR Sensor: Modification of Copper Nanoparticles Upon Conducting Polymer for a Sensitive Non-Enzymatic Glucose Sensor

In this work, rapid, sensitive, practical, and economical strategy for non-enzymatic glucose sensor has been reported based on a modification of copper nanoparticles upon conducting polymer with high surface area (Cu@PCR). Firstly, PCR conducting polymer electrode (PCR) has been successfully fabricated by electrochemical polymerization of a specially synthesized and characterized star-shaped carbazole derivative. Then copper nanoparticles have been successfully electrodeposited on the PCR as a practical method with cyclic voltammetry. The morphologies of the synthesized materials have been characterized by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) measurements. The Cu@PCR sensor platform has been displayed a synergistic effect of high catalytical properties of copper nanoparticles and high electroactive properties of PCR towards the glucose oxidation in alkaline medium. The Cu@PCR sensor platform has shown high sensitivity of 847 μAmM⁻¹cm⁻², good stability (10 weeks), a low detection limit of 0.043 μM, and a fast response of 3 s for the non-enzymatic electrochemical detection of glucose. This organic−inorganic hybrid composite sensor is a promising candidate for the fabrication of a highly sensitive and rapid glucose-sensing with the simple preparation procedure and use of a low-cost precursor.     

Amperometric Glucose Biosensor Based on Pt‐Pd Nanoparticles Supported by Reduced Graphene Oxide and Integrated with Glucose Oxidase

A novel glucose biosensor was developed based on the immobilization of glucose oxidase (GOx) on reduced graphene oxide incorporated with electrochemically deposited platinum and palladium nanoparticles (PtPdNPs). Reduced graphene oxide (RGO) was more hybridized by chemical and heat treatment. Bimetallic nanoparticles were deposited electrochemically on the RGO surface for potential application of the Pd? Pt alloy in biosensor preparation. The as‐prepared hybrid electrode exhibited high electrocatalytic activities toward H₂O₂, with a wide linear response range from 0.5 to 8 mM (R²=0.997) and high sensitivity of 814×10^?6 A/mMcm². Furthermore, glucose oxidase with active material was integrated by a simple casting method on the RGO/PdPtNPs surface. The as‐prepared biosensor showed good amperometric response to glucose in the linear range from 2 mM to 12 mM, with a sensitivity of 24×10^?6 A/mMcm², a low detection limit of 0.001 mM, and a short response time (5 s). Moreover, the effect of interference materials, reproducibility and the stability of the sensor were also investigated.