Urchin‐like Ag Nanowires as Non‐enzymatic Hydrogen Peroxide Sensor

Urchin‐like Ag nanowires were prepared by reacting AgNO₃(aq) with Cu metal in the presence of cetyltrimethylammonium chloride and HNO₃(aq) on a screen printed carbon electrode at room temperature. The diameters of the nanowires were about 100 nm, while the lengths were up to 10 μm. Cyclic voltammetric experiments using the Ag nanowires as the working electrode showed electrocatalytic H₂O₂ reduction. The electrode exhibited a high sensitivity of 4705 μA mM^‐1 mg^‐1 cm^‐2 from 50 μM to 10.35 mM and a measurable detection limit of 10 μM in amperometric detection. This is the first report on Ag NWs for non‐enzymatic H₂O₂ sensing.     

MOF‐Derived Spinel NiCo2O4 Hollow Nanocages for the Construction of Non‐enzymatic Electrochemical Glucose Sensor

Non‐enzymatic glucose sensor is greatly expected to take over its enzymatic counterpart in the future. In this paper, we reported on a facile strategy to construct a non‐enzymatic glucose sensor by use of NiCo₂O₄ hollow nanocages (NiCo₂O₄ HNCs) as catalyst, which was derived from Co‐based zeolite imidazole frame (ZIF‐67). The NiCo₂O₄ HNCs modified glassy carbon electrode (NiCo₂O₄ HNCs/GCE), the key component of the glucose sensor, showed highly electrochemical catalytic activity towards the oxidation of glucose in alkaline media. As a result, the proposed non‐enzymatic glucose sensor afforded excellent analytical performances assessed with the aid of cyclic voltammetry and amperometry (i–t). A wide linear range spanning from 0.18 μΜ to 5.1 mM was achieved at the NiCo₂O₄ HNCs/GCE with a high sensitivity of 1306 μA mM^?1 cm^?2 and a fast response time of 1 s. The calculated limit of detection (LOD) of the sensor was as low as 27 nM (S/N=3). Furthermore, it was demonstrated that the non‐enzymatic glucose sensor showed considerable anti‐interference ability and excellent stability. The practical application of the sensor was also evaluated by determination of glucose levels in real serum samples.     

Facile Non‐enzymatic Lactic Acid Sensor Based on Cobalt Oxide Nanostructures

In this study, we have investigated the effect of counter anions on the morphology of cobalt oxide nanostructures. The nanostructures of cobalt oxide are prepared by a low temperature aqueous chemical growth method. The morphology of cobalt oxide nanostructure material was investigated by scanning electron microscopy and the crystalline structure was studied by powder X‐ray diffraction technique. The cobalt oxide nanostructures exhibit the nanowire, lump, bundle of the nanowire and flower‐like morphologies. The XRD study has revealed a cubic phase of cobalt oxide nanostructures. The electro‐catalytic properties of cobalt oxide nanostructures were explored through cyclic voltammetry and amperometric techniques by sensing of lactic acid in the alkaline media. The cobalt oxide nanostructures prepared from cobalt nitrate have shown a well‐resolved redox peak. The proposed mechanism for the non‐enzymatic lactic acid sensor is elucidated by considering the morphology and cyclic voltammetry response. The limit of detection for the sensor was found to be 0.006 mM and it exhibits a linear range from 0.05–3 mM of lactic acid as shown by cyclic voltammetry. The amperometric response has shown the excellent current‐concentration response and the linear range of sensor was found to be 0.1 mM to 5.5 mM. The lactic acid sensor is stable, selective and can be used for practical applications. This study provides an excellent alternative analytical tool for the determination of lactic acid.     

Nanostructured Gold Microelectrodes for Non‐enzymatic Glucose Sensor

A novel, highly stable, selective, and sensitive non‐enzymatic glucose sensor was developed by simple and effective modification procedure. The modification of gold microelectrodes by electrochemically deposited gold nanoparticles resulted in increase of surface area up to 37 %. The nanostructured surfaces of the gold microelectrodes obtained by different modifications were studied by confocal microscopy, atomic force microscopy, and scanning electron microscopy. The gold nanoclusters exhibit great electrocatalytic properties toward glucose with a wide linear range from 0.5 to 50 mM, with a limit of detection 218 μM, and sensitivity of 185.2 mA mM^?1cm^?2. Moreover, the modified microelectrodes display good reproducibility, stability, and selectivity in the presence of poisoning compounds. Due to the small dimensions of gold microelectrodes and a very small volume of the sample, the microelectrodes make a contribution to miniaturisation of the system.     

Biomass‐derived Nitrogen and Phosphorus Co‐doped Hierarchical Micro/mesoporous Carbon Materials for High‐performance Non‐enzymatic H2O2 Sensing

Nitrogen and phosphorus co‐doped hierarchical micro/mesoporous carbon (N,P‐MMC) was prepared by simple thermal treatment of freeze‐dried okra in the absence of any other additives. The 0.96 wt % of N and 1.47 wt % of P were simultaneously introduced into the graphitic framework of N,P‐MMC, which also possesses hierarchical porous structure with mesopores centered at 3.6 nm and micropores centered at 0.79 nm. Most importantly, N,P‐MMC carbon exhibits excellent catalytic activity for electrocatalytic reduction of H₂O₂, resulting in a new strategy to construct non‐enzymatic H₂O₂ sensor. The N,P‐MMC‐based H₂O₂ sensor displays two linear detection range about 0.1 mM–10 mM (R²=0.9993) and 20 mM–200 mM (R²=0.9989), respectively. The detection limit is estimated to be 6.8 μM at a signal‐to‐noise ratio of 3. These findings provide insights into synthesizing functional heteroatoms doped porous carbon materials for biosensing applications.     

A Highly Sensitive and Selective Non-enzymatic Hydrogen Peroxide Sensor Based on Nanostructured Co3O4 Thin Films Using the Sol-gel Method

In this work we report an easy and efficient way to fabricate nanostructured cobalt oxide (Co₃O₄) thin films as a non-enzymatic sensor for H₂O₂ detection. Co₃O₄ thin films were grown on ITO glass substrates via the sol-gel method and characterized with several techniques including X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and optical absorbance. The Co₃O₄ thin films’ performance regarding hydrogen peroxide detection was studied in a 0.1 M NaOH solution using two techniques, cyclic voltammetry (CV) and amperometry. The films exhibited a high sensitivity of 1450 μA.mM⁻¹.cm⁻², a wide linear range from 0.05 μM to 1.1 mM, and a very low detection limit of 18 nM. Likewise, the Co₃O₄ thin films produced showed an exceptional stability and a high selectivity.     

Sensitive and Selective Sensing of Hydrogen Peroxide with Iron‐Tetrasulfophthalocyanine‐Graphene‐Nafion Modified Screen‐Printed Electrode

We developed a novel iron‐tetrasulfophthalocyanine‐graphene‐Nafion (FeTSPc‐GR‐Nafion) modified screen‐printed electrode to determine hydrogen peroxide (H₂O₂) with high sensitivity and selectivity. The nanocomposite film (FeTSPc‐GR‐Nafion) exhibits an excellent electrocatalytic activity towards oxidation of H₂O₂ at a potential of +0.35 V in the absence of enzyme. A comparative study reveals that the FeTSPc‐GR complexes play a dual amplification role. Amperometric experiment indicates that the sensors possess good sensitivity and selectivity, with a linear range from 2.0×10^?7 M to 5.0×10^?3 M and a detection limit of 8.0×10^?8 M. This sensor has been successfully used to develop the glucose biosensor and has also been applied to determine H₂O₂ in sterile water.     

Amperometric Detection of Hydrogen Peroxide Using Glassy Carbon Electrodes Modified with Chromium Hexacyanoferrate/Single‐Walled Carbon Nanotube Nanocomposites

Chemical functionalization of single‐walled carbon nanotubes (SWNTs) has constructed plenty of new structures with useful properties. But the modification was often confined to organic molecules, either by covalence or noncovalence. In this report, SWNTs were successfully functionalized with one kind of electroactive inorganic compounds: chromium hexacyanoferrate (Cr hcf). The resulting Cr hcf/SWNTs nanocomposites were confirmed by Field‐emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), UV‐vis absorption spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. Cr hcf crystallites are observed to be finely attached to the SWNTs. The electrochemical properties of Cr hcf/SWNTs nanocomposites were also investigated. The nanocomposites modified glassy carbon (GC) electrode shows high electrocatalytic activity towards the reduction of H₂O₂ and the amperometric responses show a linear dependence on the concentration of H₂O₂ in a range of 0.5 μM to 10 mM (R=0.9989). In addition, the sensor has good stability and reproducibility.     

FeS2 Grown Pencil Graphite as an In‐expensive and Non‐enzymatic Sensor for Sensitive Detection of Uric Acid in Non‐invasive Samples

While most electrochemical uric acid (UA) sensors are developed on the conventional electrodes and involve either multiple steps based synthesis routes and/or complicated fabrication processes, this paper is the first demonstration of direct growth of pyrite FeS₂ on pencil‐graphite electrode (PGE) for non‐enzymatic UA sensing. FESEM images of the pyrite FeS₂‐PGE reveal mesoporous microspherical structure of pyrite FeS₂ along with graphite flakes of PGE and EDX, Raman spectroscopic data validate growing of pyrite FeS₂ on PGE. The pyrite FeS₂‐PGE sensor exhibited detection limit of 6.7 μM, excellent linearity, reproducibility, selectivity over glucose, urea, ascorbic acid with the sensitivity of 370 μA mM^?1 cm^?2 in the range of 10–725 μM of UA. These improved analytical performances can be attributed to high conductivity of the pyrite FeS₂, larger electro‐active surface area of the mesoporous microspherical pyrite FeS₂ grown on PGE (than only PGE) and abundance in defect sites originating from both the pyrite FeS₂ as well as functional groups of pencil graphite. Furthermore, the sensor was validated against UA in urine sample and the result supports well with the UA concentration achieved from colorimetric technique. Development of this low cost, non‐enzymatic, sensitive and highly selective pyrite FeS₂‐PGE bases UA sensor is a significant step in the development of practically viable sensors for point‐of‐care applications in clinical and pharmaceutical analyses.     

Synthesis of Ferrocene Based Naphthoquinones and its Application as Novel Non‐enzymatic Hydrogen Peroxide

At present, a highly sensitive hydrogen peroxide (H₂O₂) sensor is fabricated by ferrocene based naphthaquinone derivatives as 2,3‐Diferrocenyl‐1,4‐naphthoquinone and 2‐bromo‐3‐ferrocenyl‐1,4‐naphthoquinone. These ferrocene based naphthaquinone derivatives are characterized by H‐NMR and C‐NMR. The electrochemical properties of these ferrocene based naphthaquinone are investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) on modified glassy carbon electrode (GCE). The modified electrode with ferrocene based naphthaquinone derivatives exhibits an improved voltammetric response to the H₂O₂ redox reaction. 2‐bromo‐3‐ferrocenyl‐1,4‐naphthoquinone show excellent non‐enzymatic sensing ability towards H₂O₂ response with a detection limitation of 2.7 μmol/L a wide detection range from 10 μM to 400 μM in H₂O₂ detection. The sensor also exhibits short response time (1 s) and good sensitivity of 71.4 μA mM^?1 cm^?2 and stability. Furthermore, the DPV method exhibited very high sensitivity (18999 μA mM^?1 cm^?2) and low detection limit (0.66 μM) compared to the CA method. Ferrocene based naphthaquinone derivative based sensors have a lower cost and high stability. Thus, this novel non‐enzyme sensor has potential application in H₂O₂ detection.     

Fe修饰多壁碳纳米管电极高效产H2O2

为提高电芬顿(Electro-Fenton)体系H2O2的产率, 制备了多壁碳纳米管(MWNT)电极, 并与石墨/气体扩散(GDC)电极进行了比较. 结果表明, MWNT电极H2O2产率高于GDC电极. 采用电沉积方法, 制备了Fe修饰MWNT(Fe-MWNT)电极, 发现Fe对MWNT电极的修饰不仅可以提高体系的H2O2产率, 而且电流效率可以提高8%左右, 与GDC电极的电流效率接近. Fe-MWNT电极有望成为一种新型的阴极材料应用于Electro-Fenton体系中.     

H2O2氧化降解海藻酸钠

研究了清洁高效的氧化剂H2O2对海藻酸钠的降解,探讨了溶液pH值、反应温度、H2O2用量及金属离子浓度对降解速度的影响. 结果表明,随着溶液pH值的降低、反应温度的升高及H2O2用量的增加,降解速度加快. 当反应pH=5.3、反应温度50 ℃、H2O2用量0.5%时,反应2 h即可降低海藻酸钠的分子量. 4 mg/L的Cu2+或Fe2+可明显加快降解速度,反应30 min的粘度变化相当于不加Cu2+或Fe2+时300 min的变化. GPC结果表明,海藻酸钠被氧化降解后,分子量下降,分布变宽;FTIR显示降解前后海藻酸钠的糖环结构没有改变,主要是糖苷键的断裂.     

Binderless Solution Processed Zn Doped Co3O4 Film on FTO for Rapid and Selective Non‐enzymatic Glucose Detection

A simple solution based deposition process has been used to fabricate Zn doped Co₃O₄ electrode as an electrocatalyst for non‐enzymatic oxidation of glucose. XRD, HRTEM, SEM, EELS, AFM, EIS was used to characterise the electrode. The addition of Zn as dopant on Co₃O₄ resulted in enhanced electrochemical performance of Zn:Co₃O₄ material compared to pristine Co₃O₄ due to increased charge transferability. The as prepared electrode showed fast response (<7 s) time, good sensitivity (193 μA mM⁻¹ cm⁻²) in the linear range of 5 μM–0.62 mM, good selectivity towards glucose at a relatively lower applied potential of +0.52 V in 0.1 M NaOH solution. A detection limit of ∼2 μM was measured for the Zn:Co₃O₄ electrode. The applied fabrication method resulted in good inter and intra electrode reproducibility as was shown by the lower relative standard deviation values (R.S.D). The electrode retained 70 % of initial current response after 30 days. Although the as prepared Zn:Co₃O₄ electrodes did not result in highest reported sensitivity, and lowest limit of detection; the ease of fabrication and scalability of production, good inter and intra electrode reproducibility makes it a potential candidate for commercial application as glucose sensor.     

MnO2/Graphene Nanocomposites for Nonenzymatic Electrochemical Detection of Hydrogen Peroxide

MnO₂/graphene nanocomposites with different morphologies were synthesized and the petal‐shaped nanosheet MnO₂/graphene composite was developed as an electrode material for nonenzymatic hydrogen peroxide (H₂O₂) sensor. The morphology, structure, composition, and hydrophilicity of the resulting products were characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), and the contact angle tests. In addition, the fabricated MnO₂/graphene composites could be used as catalysts for the electrochemical oxidation of H₂O₂. Cyclic voltammogram (CV) experiments indicated that MnO₂/graphene‐modified electrode showed good electrocatalytic activity towards both the oxidation and reduction of H₂O₂ in a neutral environment. Amperometric response results illustrated that this nonenzymatic sensor had excellent anti‐interference ability and displayed two linear ranges from 10 to 90 µM and from 0.2 to 0.9 mM with a detection limit of 2 µM.     

Copper‐based Metal‐organic Framework for Non‐enzymatic Electrochemical Detection of Glucose

A non‐enzymatic electrochemical glucose sensor based on a Cu‐based metal‐organic framework (Cu‐MOF) modified electrode was developed. The Cu‐MOF was prepared by a simple ionothermal synthesis, and the characterizations of the Cu‐MOF were studied by Fourier transform infrared spectroscopy (FT‐IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), single‐crystal X‐ray powder diffraction (SCXRD), and X‐ray powder diffraction (XRD). Electrochemical behaviors of the Cu‐MOF modified electrode to glucose were measured by differential pulse voltammetry (DPV). The electrochemical results showed that the Cu‐MOF modified electrode exhibited an excellent electro‐catalytic oxidation towards glucose in the range of 0.06 μM to 5 mM with a sensitivity of 89 μA/mM cm² and a detection limit of 10.5 nM. Moreover, the fabricated sensor showed a high selectivity to the oxidation of glucose in coexistence with other interferences. The sensor was satisfactorily applied to the determination of glucose in urine samples. With the significant electrochemical performances, MOFs may provide a suitable platform in the construction of kinds of electrochemical sensors and/or biosensors and hold a great promise for sensing applications.     

Synthesis of PtxSn/MWCNTs and their Application in Non‐enzymatic Glucose and Hydrogen Peroxide Sensors

Pt_xSn/MWCNTs (x=1, 2, 3) nanocomposites were synthesized by chemical reduction. Comparing all of the materials, the results revealed that the best material was Pt₃Sn/MWCNTs. The sensor based on Pt₃Sn/MWCNTs exhibited excellent catalytic activities towards glucose and hydrogen peroxide. Sensing of glucose had a double‐linear range: one was between 50 μM and 550 μM, the other was between 1.35 mM and 16.35 mM. These were due to the fact that more and more intermediate species were adsorbed onto the electrode surface with increasing concentration of glucose, which limited the following glucose oxidation. Meanwhile, the sensor also had a linear response range between 0.05 mM and 18.95 mM for hydrogen peroxide. Furthermore, the glucose and hydrogen peroxide sensors exhibited excellent selectivity, stability, and reproducibility. Thus the sensors had potential utilities in the detection of glucose and hydrogen peroxide.     

Electrochemically Prepared Three‐dimensional Porous Nitrogen‐doped Graphene Modified Electrode for Non‐enzymatic Detection of Hydrogen Peroxide

A facile and green electrochemical method for the fabrication of three‐dimensional porous nitrogen‐doped graphene (3DNG) modified electrode was reported. This method embraces two consecutive steps: First, 3D graphene/polypyrrole (ERGO/PPy) composite was prepared by electrochemical co‐deposition of graphene and polypyrrole on a gold foil. Subsequently, the ERGO/PPy composite modified gold electrode was annealed at high temperature. Thus 3DNG modified electrode was obtained. Scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS) and Raman spectroscopy were used to characterize the structure and morphology of the electrode. The electrode exhibits excellent electroanalytical performance for the reduction of hydrogen peroxide (H₂O₂). By linear sweep voltammetric measurement, the cathodic peak current was linearly proportional to H₂O₂ concentration in the range from 0.6 μM to 2.1 mM with a sensitivity of 1.0 μA μM⁻¹ cm⁻². The detection limit was ascertained to be 0.3 μM. The anti‐interference ability, reproducibility and stability of the electrode were carried out and the electrode was applied to the detection of H₂O₂ in serum sample with recoveries from 98.4 % to 103.2 %.     

SnCl4催化丙酮与过氧化氢反应制取大环过氧化物

H₂O₂与过渡金属构成的催化体系可选择性地氧化烃类化合物,如芳烃的羟基化和烯烃的环氧化等^[1～3],且H₂O₂在应用中无环境污染,是一种颇有前途的氧化剂.有关金属催化H₂O₂与酮类化合物反应的报道很少.     

Magnetite Nanorods Stabilized by Polyaniline/Reduced Graphene Oxide as a Sensing Platform for Selective and Sensitive Non‐enzymatic Hydrogen Peroxide Detection

In this study, magnetite nanorods stabilized on polyaniline/reduced graphene oxide (Fe₃O₄@PANI/rGO) was synthesized via a wet‐reflux strategy. The possible formation of Fe₃O₄@PANI/rGO was morphologically and structurally verified by field emission scanning electron microscopy (FE‐SEM), Fourier transform infrared (FT‐IR) spectroscopy, Raman spectroscopy, X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS). Furthermore, the thermal stability of Fe₃O₄@PANI/rGO was measured by a thermogravimetric analyzer (TGA); the composite had good thermal stability owing to the ceramic nature of Fe₃O₄. The Fe₃O₄@PANI/rGO has been applied as a potential sensing platform for electrochemical detection of hydrogen peroxide (H₂O₂). By the combined efforts of extended active surface area, active carbon support, more catalytic active sites and high electrical conductivity, the Fe₃O₄@PANI/rGO exhibited an improved performance toward the non‐enzymatic detection of H₂O₂ in 0.5 M KOH with a fast response time (5 s), high sensitivity (223.7 μA mM^?1 cm^?2), low limit of detection (4.45 μM) and wide linear range (100 μM–1.5 mM). Furthermore, the fabricated sensor exhibited excellent recovery rates (94.2–104.0 %) during real sample analysis.     

Design of a New Non‐enzymatic Sensor Based on a Substituted A2BO4+δ Perovskite for the Voltammetric Detection of Glucose

Instant determination of glucose levels is necessary to monitor the treatment of diabetes. The next generation of electrochemical sensors aims to eliminate the use of enzymes because of their lack of stability and the complex procedure to immobilize them on the electrode. In this paper Pr_1.92Ba_0.08Ni0.₉₅Zn_0.05O_4+δ perovskite, a A₂BO_4+δ type, was tested, for the first time for non enzymatic detection of glucose. It was synthesized by a sol‐gel method. The obtained crystallized powder was structurally characterized by XRD, morphologically characterized by SEM and EDX and electrochemically characterized. A monoclinic crystallographic system was formed. The presence of Pr₂O₃ during synthesis and calcination is in agreement with the formation of defects in the crystalline network and the disproportionation of Ni^III sites into Ni^II and Ni^IV, due to the substitution of Pr by Ba. The oxido‐reduction of Ni^II sites is observed by cyclic voltammetry. The electrocatalytic oxidation of glucose through the electrooxidized Ni^II site was observed on a gold electrode, at 481 mV. The analytical performance of this glucose sensor is good in comparison to previously published ABO₃ perovskite modified electrodes, in terms of dynamic range (1.5 μM–7000 μM) and detection limit (0.5 μM). Its application to human serum shows that there is no interference for glucose detection.