A MnOOH‐Polyaniline Nanocomposite Modified Gold Electrode for Electrochemical Sensing of Nitrite

A novel non‐enzymatic nitrite sensor was fabricated by immobilizing MnOOH‐PANI nanocomposites on a gold electrode (Au electrode). The morphology and composition of the nanocomposites were investigated by transmission electron microscopy (TEM ) and Fourier transform infrared spectrum (FTIR ). The electrochemical results showed that the sensor possessed excellent electrocatalytic ability for NO₂⁻ oxidation. The sensor displayed a linear range from 3.0 μmol•L⁻¹ to 76.0 mmol•L⁻¹ with a detection limit of 0.9 μmol•L⁻¹ (S/N = 3), a sensitivity of 132.2 μA •L•mol⁻¹•cm⁻² and a response time of 3 s. Furthermore, the sensor showed good reproducibility and long‐term stability. It is expected that the MnOOH‐PANI nanocomposites could be applied for more active sensors and used in practice for nitrite sensing.     

A Novel Flexible Electrochemical Ascorbic Acid Sensor Constructed by Ferrocene Methanol doped Multi-walled Carbon Nanotube Yarn

An ascorbic acid (AA) electrochemical sensor was fabricated by ferrocene methanol (Fc−OH) modified multi-walled carbon nanotube yarn (CNTY). The prepared sensor (Fc−OH/CNTY) exhibited outstanding flexibility, highly stretchability, excellent bendability and obviously electrocatalytic activity for oxidation of ascorbic acid. The morphology of Fc−OH/CNTY was evaluated by scanning electron microscope. The electrochemical behaviour of Fc−OH/CNTY sensor was studied by cyclic voltammetry and amperometry measurements. Moreover, the influence of Fc−OH concentration, applied potential and electrolyte solution pH were also investigated to obtain the best sensor performance. The prepared sensor exhibited a wide linear range from 3 μM to 3.0 mM toward AA, and a detection limit of 1.32 μM (S/N=3). It also possessed a good lifetime and a fast response speed (2.83 s). In addition, the Fc−OH/CNTY sensor remained 90 % and 60 % of its initial activity after 100 and 500 times bending, respectively, which indicated a potential application on flexible, implantable and/or wearable electrochemical sensors.     

A Nanocomposite Containing Carbon Nano-onions and Polyaniline Nanotubes as a Novel Electrode Material for Electrochemical Sensing of Daidzein

Glassy carbon electrode (GCE) were modified with nanocomposites containing conductive polyaniline nanotubes (PANI_nt) and carbon nano-onions (CNOs). Herein we report a simple and sensitive way for daidzein (DA) determination at concentrations between 1 and 10 μM by linear sweep voltammetry using GCE/PANI_nt/CNOs system. The DA electrochemical behavior was examined in two buffer environments (pH 7.5 and 4.5) using electrodes modified with the oxidized CNOs or their derivatives containing carboxyl and benzylamino functional groups. The direct electrooxidation of DA was observed at +0.65 V and +0.8 V at pH 7.5 and at +0.7 V and +1.1 V vs. Ag/AgCl at pH 4.5.     

A Promising Electrochemical Platform for Dopamine and Uric Acid Detection Based on a Polyaniline/Iron Oxide-Tin Oxide/Reduced Graphene Oxide Ternary Composite

A ternary polyaniline/Fe₂O₃-SnO₂/reduced graphene oxide (PFSG) nanocomposite was prepared using a simple two-step hydrothermal treatment. The composite was applied as a glassy carbon electrode modifier (GCE) to enhance dopamine (DA) and uric acid (UA) detection. The ternary PFSG composite was compared with its binary precursor Fe₂O₃-SnO₂/reduced graphene oxide (FSG). The influence of the modified GCE electrodes on their performance as a sensing platform was determined. GCE/PFSG showed better sensing parameters than GCE/FSG due to the introduction of polyaniline (PANI), increasing the electrocatalytic properties of the electrode towards the detected analytes. GCE/PFSG enabled the detection of low concentrations of DA (0.076 µM) and UA (1.6 µM). The peak potential separation between DA and UA was very good (180 mV). Moreover, the DA oxidation peak was unaffected even if the concentration of UA was ten times higher. The fabricated sensor showed excellent performance in the simultaneous detection with DA and UA limits of detection: LOD_DA = 0.15 µM and LOD_UA = 6.4 µM, and outstanding long-term stability towards DA and UA, holding 100% and 90% of their initial signals respectively, after one month of use.     

电聚合烟酰胺制备电化学传感器：同时测定多巴胺、尿酸和抗坏血酸

用循环伏安法（CV）选择不同电位区间来电聚合烟酰胺（NA）得到了两种聚合物膜修饰电极：poly-niacinamide/GCE (poly-NA/GCE)和poly- nicotinic acid /GCE (poly-NC/GCE)。这两电极都具有显著电化学催化作用,能明显地降低多巴胺（DA）、尿酸（UA）和抗坏血酸(AA)的氧化过电位,并在混合溶液中使这些物质的氧化峰电位距离足够大,可进行三物质的同时测定。poly-NC/GCE的电催化性能更好一些,用差分脉冲伏安法（DPV）测定抗坏血酸,线性范围为75–3000 µmol L-1,电流灵敏度为5.6 mA•L•mol-1;测定多巴胺,线性范围为0.37 – 16 µmol L-1,电流灵敏度为1140 mA•L•mol-1; 测定尿酸,线性范围为0.74 – 230 µmol L-1,电流灵敏度为102 mA•L•mol-1。该电极具有很高的灵敏度、选择性和抗污染能力。     

Highly Sensitive Enzyme-free Sensor Based on a Carbon Paste Electrode Modified with Binary Zinc Oxide/Polyaniline Nanocomposites for Dopamine,Ascorbic Acid and Uric Acid Sensing

Hybrid composites ZnO/PANI were facily synthesized by a sonication process at room temperature. This procedure is non-expensive, time/energy saving and environmentally safe. The as-prepared ZnO/PANI were characterized by FTIR, UV-vis spectroscopies and SEM in order to investigate the structure and morphology of the studied composites. The samples were used to modify carbon paste electrode (CPE) in order to develop electrochemical biosensors (ZnO/PANI/CPE). The sensing properties of the nanoparticles were evaluated for dopamine, ascorbic acid and uric acid non-enzymatic detection. The effect of percentage of polyaniline in the composites and the effect of calcination on the biosensor's response were also examined in the present study. It was revealed that the existence of PANI in ZnO/PANI/CPE largely enhanced the electroactive surface area and therefore the sensitivity for electrochemical sensing. A good electrochemical behavior was noted for ZnO/40 wt% PANI-cal/CPE modified electrode toward DA, AA and UA oxidation. The electroactive surface area of the previously mentioned modified electrode (0.235 cm²) was two times higher than that of the bare electrode (0.117 cm²). The liner relationships between current intensities and concentrations were found to be 0.01–1.4 mM, 0.1–1.3 mM and 0.01–0.12 mM, with detection limit of 0.029 mM, 0.063 mM and 0.007 mM, for DA, AA and UA respectively. In the mixtures of ascorbic acid (AA), dopamine (DA) uric acid (UA) and glucose (Glu) the sensor showed high selectivity of DA with low interference of ascorbic acid by a current change of 14 %. The as-prepared ZnO/PANI/CPE biosensor displayed a good reproducibility and stability.     

An Electrochemical Sensing Platform Based on Graphene Oxide and Molecularly Imprinted Polymer Modified Electrode for Selective Detection of Amoxicillin

An electrochemical sensing platform based on composite material, consisting of molecularly imprinted polymer coated on graphene oxide (MIP-GO), was developed for selective and sensitive analysis of amoxicillin (AMOX). The MIP-GO composite, which was fabricated by sol-gel polymerization after removal of template molecule, was deposited as a thin film on glassy carbon electrode, and then was electrochemically characterized by cyclic voltammetry and differential pulse voltammetry. The linear response for the determination of AMOX was obtained in the concentration range from 5.0×10⁻¹⁰ to 9.1×10⁻⁷ M under the most proper conditions and the detection limit was found to be 2.94×10⁻¹⁰ M.     

Portable Wireless Intelligent Electrochemical Sensor for the Ultrasensitive Detection of Rutin Using Functionalized Black Phosphorene Nanocomposite

To build a portable and sensitive method for monitoring the concentration of the flavonoid rutin, a new electrochemical sensing procedure was established. By using nitrogen-doped carbonized polymer dots (N-CPDs) anchoring few-layer black phosphorene (N-CPDs@FLBP) 0D-2D heterostructure and gold nanoparticles (AuNPs) as the modifiers, a carbon ionic liquid electrode and a screen-printed electrode (SPE) were used as the substrate electrodes to construct a conventional electrochemical sensor and a portable wireless intelligent electrochemical sensor, respectively. The electrochemical behavior of rutin on the fabricated electrochemical sensors was explored in detail, with the analytical performances investigated. Due to the electroactive groups of rutin, and the specific π-π stacking and cation–π interaction between the nanocomposite with rutin, the electrochemical responses of rutin were greatly enhanced on the AuNPs/N-CPDs@FLBP-modified electrodes. Under the optimal conditions, ultra-sensitive detection of rutin could be realized on AuNPs/N-CPDs@FLBP/SPE with the detection range of 1.0 nmol L⁻¹ to 220.0 μmol L⁻¹ and the detection limit of 0.33 nmol L⁻¹ (S/N = 3). Finally, two kinds of sensors were applied to test the real samples with satisfactory results.     

An Electrochemical Sensing Platform for the Detection of Lead Ions Based on Dicarboxyl‐Calix[4]arene

A simple and highly sensitive electrochemical sensor COOH−C4 derived from dicarboxyl‐calix[4]arene modified on a screen printed gold electrode (Au) was developed for the determination of lead ions in water samples. A 3‐mercaptopropionic acid (MPA) monolayer was used as a template on the gold electrode for the surface modification with dicarboxyl‐calixarene. The modified electrodes were surface‐characterized using Fourier Transform infrared spectroscopy (FTIR). The data obtained proved the confirmation of each stage of the electrode modification. The electrochemical analyses of the COOH−C4 electrode showed an enhanced electrocatalytic activity and higher current towards Pb²⁺ ions as compared to the bare Au and MPA/Au electrodes. Under optimum conditions, the differential pulse voltammetry response of COOH−C4 displayed a wide linear response ranging from 280–2500 μg/L for Pb²⁺ with a detection limit of 6.2 μg/L. In addition, the fabricated electrode showed a high selectivity and stability towards the Pb²⁺ ions in presence of possible interfering species. The present method was successfully applied to determine Pb²⁺ ions in real samples with satisfactory precision, with a relative standard deviation of 3.12 % and an acceptable recovery of 92 %, which demonstrated the potential application of dicarboxyl‐calix[4]arene modified on electrodes for heavy‐metal sensing.     

基于碳纳米材料的无酶电化学传感器同时检测抗坏血酸、多巴胺和尿酸

人体中抗坏血酸（AA）、多巴胺（DA）和尿酸（UA）的浓度失调可能导致一系列疾病,如癌症、老年痴呆症、高尿酸血症等,而且这三个物种通常共存于体液中,有接近的氧化还原电位,因此实现三者的同时检测,既具有一定的难度,又具有极其重要的现实意义。近年来用于同时检测AA、DA和UA的电化学传感器取得了令人瞩目的进展,其中碳材料因其成本低廉、导电性好、稳定性好、比表面积大等特点逐渐引起人们的广泛关注。本文综述了基于碳材料构筑的检测AA、DA和UA的无酶电化学传感器的研究进展,对此类电化学传感器的今后发展做了展望。     

Development of a Novel Silver-based Sensing Platform for Detecting Superoxide Anion Released from HeLa Cells Directly

Reactive oxygen species (ROS) have become the focus of research in recent years because they are closely related to many diseases, including cancer. Therefore, detection of ROS released from cells is of particular importance. In this work, the nanocomposites with uniform dispersion of silver nanoparticles were obtained through pyrolyzing a novel silver-based metal-organic framework. As the main active component of the composition, AgNPs can effectively catalyze the decomposition of hydrogen peroxide produced by superoxide anion (O₂ ⋅ ⁻) disproportionation. Then, we designed a superoxide anion sensor (AgNPs@C/GCE) using the above nanocomposite for the first time. The prepared sensor presented excellent catalytic ability and satisfactory detection performance towards O₂ ⋅ ⁻ with a detection range as wide as eight orders of magnitude and a lower detection limit of 1.011×10⁻¹³ M (S/N=3). Furthermore, the sensor can directly measure O₂ ⋅ ⁻ released by human cervical cancer cells (HeLa) under both the normal condition and the inducement by malonic acid. In addition, we explored the effects of different concentrations of stimuli on cells. The results illustrated the high dose malonic acid can cause oxidative stress on cells. Thus, this work has the tremendous potential applications to diagnosis of diseases related to ROS.     

A Boron Doped Diamond Electrode Modified with Nano‐carbon Black for the Sensitive Electrochemical Determination of Chlorogenic Acid

An electrochemical method was developed for the sensitive determination of chlorogenic acid using a boron doped diamond electrode (BDDE) modified with nano‐carbon black (nano‐CB). The active surface areas were found to be 0.059 and 0.146 cm² for the unmodified BDDE, and nano‐CB/BDDE, respectively. Compared with a BDDE, the nano‐CB/BDDE exhibited a well‐defined redox couple for chlorogenic acid. In addition, the plot of the peak current response changing from a square root to a linear dependence on scan rate is attributed to the transition from planar diffusion to surface behaviour. The anodic and cathodic peak separations (ΔE_p) were 97 mV and 14 mV at BDDE and nano‐CB/BDDE, respectively. The decrease in ΔE_p at the proposed electrode indicated that the process of chlorogenic acid was greatly accelerated. Square wave voltammetry (SWV) exhibited a dynamic range in which the current versus the concentration of chlorogenic acid were linear from 2.0×10^?8 to 2.0×10^?6 M with a LOD of 4.1×10^?9 M (based on 3S_b/m). The nano‐CB modified BDDE provided improved electrochemical behavior, high electrocatalytic activity, high sensitivity and good reproducibility.     

2D Leaf-Like Structured ZIF-L Embedded Electrochemically Reduced Graphene Oxide Composite as an Electrochemical Sensing Platform for Sensitively Detecting Benomyl

In this work, a two-dimensional leaf-like framework-L embedded electrochemically reduced graphene oxide (ERGO@ZIF-L) was proposed as an outstanding electrode material for the sensitive electrochemical sensing of benomyl (BM). ZIF-L is surrounded by ERGO, which could effectively ensure the stability and dispersion of ZIF-L. With this unique combination, the prepared ERGO@ZIF-L displayed excellent synergistic characteristics with a large surface area, excellent conductivity, plentiful active sites, and high electrocatalytic properties, thus endowing it with high sensitivity for BM determination. The experimental parameters, such as solution pH, material volume, and accumulation time, were optimized. Under optimal conditions, the BM sensor showed a wide linear range (0.009–10.0 μM) and low-limit detection (3.0 nM). Moreover, the sensor displayed excellent stability, repeatability, and reproducibility, and good anti-interference capability. The method was successfully applied to detect BM in real-world samples.     

Nanomaterials‐based Electrochemical Sensing of Cardiac Biomarkers for Acute Myocardial Infarction: Recent Progress

The development of the methods for early and accurate diagnosis of acute myocardial infarction are needed to facilitate immediate treatment of patients. One of the ways to achieve that is the detection of cardiac biomarkers for myocardial infarction, such as thrombin, cardiac troponins (I and T), myoglobin, etc. Nanotechnology has played an important role in the development of sensitive and efficient electrochemical sensors for cardiac biomarkers. In this review, we discuss recent progress on nanomaterial‐based electrochemical sensing of various cardiac biomarkers for acute myocardial infarction.     

Development of a Novel Molecularly Imprinted Polyvinylimidazole/Functionalized Carbon Black Nanocomposite-based Paste Electrode for Electrochemical Sensing of Imazethapyr in Rice Samples

This paper reports the development of a simple electroanalytical method for imazethapyr (IMT) determination in rice samples based on molecularly imprinted polymer and functionalized carbon black paste electrode (MIP-fCBPE). Carbon black (CB) was functionalized by the insertion of oxygenated functional groups upon acid treatment with HNO₃ and H₂SO₄. The functionalized carbon black (fCB) presented higher performance for IMT determination than the CB without functionalization. The insertion of molecularly imprinted polyvinylimidazole (MIP-VN) in the fCBPE promoted a significant increase in the cathodic peak current even at low proportions (7.5 % w/w) due to the specific binding sites for IMT recognition. For IMT determination, DPV parameters were optimized by the Doehlert matrix applying 0.1 V for 60 s as pre-treatment in acetate buffer solution (pH 3.0) as supporting electrolyte. The proposed method showed low limit of detection (0.03 μmol L⁻¹), a wide linear range (0.10–70.00 μmol L⁻¹), and good precision in terms of repeatability of intraday measures (RSD%=3.6). The method was applied in rice samples after microwave-assisted extraction of IMT and the accuracy of the method was evaluated by addition/recovery assays (96.3–105.7 %), being statistically attested using HPLC-DAD as reference technique.     

Electrochemical Mechanisms in Potentiometric Phosphate Sensing Using Pure Cobalt,Molybdenum and their Alloy for Environmental Applications

Phosphorus (P) is ubiquitous in the environment, but its measurement is costly and time-consuming. Sensor-based measurement shows potential, but selection of right metal remains the major challenge due to strong P species dependence on pH. This study examined the feasibility of pure cobalt, molybdenum, and their electrodeposited alloy, Co₆₃Mo₄₂ (wt %), as phosphate sensors. The cobalt, molybdenum and alloy exhibited mixed potential, Nernst potential, and oxidation-reduction (red-ox) mechanisms, respectively. Alloy showed good selectivity over a wide pH range, but high limit of detection and long response time (8–14 minutes). Yet, alloy provides a new opportunity for improving electrochemical phosphate sensors.     

A 3,5‐DistyrylBODIPY Dye Functionalized with Boronic Acid Groups for Direct Electrochemical Glucose Sensing

The synthesis and characterization of a novel BODIPY dye functionalized with bis‐boronic acid groups to enable direct glucose sensing through selective recognition of carbohydrates is reported. Styrylation with boronic acid groups at the 3,5‐positions of the BODIPY core results in an extension of the π‐conjugation system of the dye and in a red‐shift of the main absorption band from 500 to 637 nm. The functionalized BODIPY dye was adsorbed on a glassy carbon electrode using the drop and dry method. Modified and bare electrodes were characterized using cyclic voltammetry and scanning electrochemical microscopy, while glucose detection was carried out by using differential pulse voltammetry and chronoamperometry. The detection limit was determined to be 1.42 μM. The dye was found to be selective and sensitive towards glucose, since likely interferences have only minor effects on the glucose detection.     

Simple and Inexpensive Electrochemical Platform Based on Novel Homemade Carbon Ink and its Analytical Application for Determination of Nitrite

In this work we present the development of a simple handmade approach for the easy fabrication of three‐electrode electrochemical devices based on newly in‐house developed carbon ink composed of graphite powder and polystyrene. Different proportions of graphite/polystyrene were investigated for the optimization of the ink. The counter and reference electrodes were produced using commercial carbon ink and silver glue. Scanning electron microscopy, electrochemical impedance spectroscopy and cyclic voltammetry were used to investigate the morphology and the electrochemical properties of the sensor. The results showed that the electroactive area of the optimized working electrode was ca . 2.35 times larger than its geometric area. The RSD values obtained for repeatability and reproducibility were 0.20% and 2.78%, respectively, which suggest no significant variation on the electrodes fabricated. The analytical feasibility of the electrode was tested through its application for the determination of nitrite in drinking water. The quantifications were successfully performed at levels below the maximum contaminant level established for nitrite. A limit of detection of 1.42 × 10⁻⁶ mol L⁻¹ and recoveries of ca . 103 % were achieved. The results were validated using ion‐chromatography technique with good agreement. The performance of the unmodified sensor proposed here on nitrite determination was better than some recently reported modified electrodes obtained through complex procedures.     

Co2SnO4/Carbon Nanotubes Composites: A Novel Approach for Electrochemical Sensing of Hydrogen Peroxide

For the first time Co₂SnO₄ (CTO)/Carbon nanotubes (CNT) composites were prepared and used to modify glassy carbon electrodes for the amperometric determination of hydrogen peroxide. The catalytic activity of composites towards the oxidation of hydrogen peroxide was dependent on the quantity of CNT present in the composite and to the pH of the medium. The pure cobalt stannate phase with a ratio of 3 : 1 (CTO:CNT) exhibited the best catalytic activity towards hydrogen peroxide oxidation at low potentials (0.200 and 0.500 V). A linear relationship between current and hydrogen peroxide concentration was obtained with a sensitivity of 95 and 258 μA mM⁻¹ and a detection limit of 0.130 and 0.08 μM respectively.     

基于Au/rGO/FeOOH的新型电化学传感器一步检测亚硝酸盐

亚硝酸盐是一种广泛存在的原料,长期食用会对人体健康不利甚至致癌。因此,简单、灵敏的亚硝酸盐检测方法的开发具有非常重要的意义。本文合成了金/还原氧化石墨烯/羟基氧化铁(Au/rGO/FeOOH)复合材料,并通过SEM、 XRD和EDX等测试进行了材料表征。将合成的复合材料滴涂在氧化氟锡(FTO)电极表面,利用它们的协同催化氧化性能,成功构建了一步检测亚硝酸盐(NO₂^-)的新型电化学传感器。在最佳优化实验条件下, 通过差分脉冲伏安法实现NO₂^-的定量检测, 其线性范围为0.001 ~ 5 mmol·L^-1, 检出限为0.8 μmol·L^-1(S/N = 3), 且响应时间小于2 s。同时, 所制备的传感器表现出良好的选择性和重现性, 也能用于实际样品的测定。