Direct electrochemistry and electrocatalysis of nitrite based on nano-alumina-modified electrode

Simple and sensitive electrochemical method for the determination of nitrite, based on a nano-alumina-modified glassy carbon electrode (GCE), is described. Nitrite yields a well-defined oxidation peak whose potential is 0.74 V at the nano-alumina-coated GCE in 0.1 mol L⁻¹ phosphate buffer (pH 5.0). Compared with bare GCE, the nano-alumina-modified GCE has evident catalytic effect towards the oxidation of nitrite, and its peak current can be significantly enhanced. Some of the experimental parameters were optimized for the determination of nitrite. The oxidation peak current was proportional to nitrite concentration in the range of 5.0 × 10⁻⁸–1.1 × 10⁻³ mol L⁻¹, and a detection limit of 1.0 × 10⁻⁸ mol L⁻¹ was obtained. This method has been successfully used to the determination of nitrite in sausage sample. Furthermore, results obtained by the method have been compared with spectrophotometric method.     

Electrochemical determination of nitrite using a gold nanoparticles-modified glassy carbon electrode prepared by the seed-mediated growth technique.

Seed-mediated growth of gold nanoparticles on glassy carbon (GC) surfaces was developed. The field emission scanning electron microscopy (FE-SEM) and electrochemical characterization confirmed the effective attachment of gold nanoparticles on GC surface with such a wet-chemical method. The as-prepared gold nanoparticles attached glassy carbon electrode (Au/GCE) presented excellent catalytic ability toward the oxidation of nitrite. Compared with bare GCE and planar gold electrode, the Au/GCE obviously decreased the overpotential of nitrite oxidation and improved the peak current. The catalytic current was found to be linearly proportional to the nitrite concentration in the range of 1 x 10(-5) - 5 x 10(-3) M, with a detection limit of 2.4 x 10(-6) M. The Au/GCE was successfully applied to the electrochemical determination of nitrite in a real wastewater sample, showing excellent stability and anti-interference ability.     

PdCu合金纳米晶体的制备和电催化活性研究

改变表面活性剂1-十八烯（ODE）和油胺（OLA）或油酸（OA）的配比,以1,2-二羟基十六烷二醇作还原剂同时还原乙酰丙酮铜Cu(acac)2和乙酰丙酮钯Pd(acac)2一步法制备了单分散的球形和米花形的PdCu纳米粒子.透射电子显微镜和XRD等结构表征表明,两种形状的PdCu纳米粒子均为（111）面占优的合金纳米晶体,其平均粒径分别为12.7 ± 0.18 和 20.4 ± 0.31 nm.电化学循环伏安法（CV）测定了两种PdCu合金纳米粒子对甲酸氧化的电催化活性.结果表明,在球形PdCu纳米粒子上得到的甲酸氧化峰电流密度约为米花状纳米粒子（PdCu-B）上的5.6倍.同时,前者显示出了更好的抗CO毒化能力.计时电流测量也表明,球状PdCu纳米粒子比米花状纳米粒子有更好的电催化稳定性能.     

Electrochemical study of brucine on an electrode modified with magnetic carbon-coated nickel nanoparticles

A novel type of glassy carbon electrode modified with magnetic carbon-coated nickel nanoparticles (C-Ni/GCE) was fabricated and the electrochemical properties of brucine were studied using it. The carbon-coated nickel nanoparticles showed excellent electrocatalytic activity for the redox of brucine and an enhanced electron transfer rate. The electrochemical behavior of brucine on the C-Ni/GCE was explored by cyclic voltammetry (CV), and a redox mechanism for brucine was proposed. A series of electrochemical parameters were calculated for brucine by CV and controlled-potential electrolysis. The C-Ni/GCE showed good sensitivity, selectivity and stability, and was applied to determine the concentration of brucine. The differential pulse voltammetry (DPV) response of the C-Ni/GCE showed that the catalytic current was linear with the concentration of brucine in the range of 4.7 × 10⁻⁸ to 2.4 × 10⁻⁴ mol l⁻¹, with a correlation coefficient of 0.998. The detection limit was 1.4 × 10⁻⁸ mol l⁻¹.     

Preparation and characterization of AuPt alloy nanoparticle–multi-walled carbon nanotube–ionic liquid composite film for electrocatalytic oxidation of cysteine

Gold–platinum (AuPt) alloy particles were fabricated directly on multi-walled carbon nanotubes (MWNT)–ionic liquid (i.e., trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide, [P_6,6,6,14][NTf₂]) composite coated glassy carbon electrode (GCE) by electrodeposition method. Scanning electron microscope image showed that they were well-dispersed nanocluster consisting of smaller nanoparticles, and their size was about 70 nm. X-ray diffraction experiment showed that they were single-phase alloy nanomaterial, and the calculated composition was consisting with that obtained by energy dispersive X-ray spectroscopy. The resulting modified electrode (i.e., AuPt–MWNT–[P_6,6,6,14][NTf₂]/GCE) presented high catalytic activity for the electrochemical oxidation of cysteine. The peak potential of cysteine shifted to 0.42 V (versus saturated calomel electrode) in 0.1 M H₂SO₄ and the peak current increased greatly in comparison with that on the corresponding Pt (or Au)–MWNT–[P_6,6,6,14][NTf₂]/GCE. Under the optimized conditions, the oxidation current of cysteine at 0.45 V was linear to its concentration in the range of 5.0 × 10⁻⁷ ∼ 4.0 × 10⁻⁵ M with a sensitivity of 43.8 mA M⁻¹.     

Voltammetric determination of 2-chlorophenol using a glassy carbon electrode coated with multi-wall carbon nanotube-dicetyl phosphate film

Multi-wall carbon nanotubes (MWNT) were dispersed into water in the presence of dicetyl phosphate (DCP), and MWNT-DCP composite film coated glassy carbon electrodes (GCE) were constructed. The electrochemical properties of 2-chlorophenol at a bare GCE and MWNT-DCP modified GCE were compared. It was found that MWNT-DCP modified GCEs significantly enhance the oxidation peak current of 2-chlorophenol and lowers its oxidation overpotential, suggesting great potential in the sensitive determination of 2-chlorophenol. Finally, a sensitive and simple voltammetric method was developed for the determination of 2-chlorophenol. The oxidation peak current increases linearly with the concentration in the range of 1.0 × 10⁻⁷–2.0 × 10⁻⁵ mol L⁻¹, and the detection limit is 4.0 × 10⁻⁸ mol L⁻¹ for 2 min accumulation. The method was successfully used to determine 2-chlorophenol in waste water samples.     

Fabrication of poly(orthanilic acid)–multiwalled carbon nanotubes composite film-modified glassy carbon electrode and its use for the simultaneous determination of uric acid and dopamine in the presence of ascorbic acid

A multiwalled carbon nanotubes (MWNT) modified glassy carbon electrode (GCE) coated with poly(orthanilic acid) (PABS) film (PABS–MWNT/GCE) has been fabricated and used for simultaneous determination of dopamine (DA) and uric acid (UA) in the presence of ascorbic acid (AA) by differential pulse voltammetry (DPV). Scanning electron microscopy, Fourier transform infrared spectra, and electrochemical techniques have been used to characterize the surface morphology of the PABS–MWNT composite film and the polymerization of ABS on electrode surface. In comparison with the bare GCE and the MWNT-modified GCE, the PABS–MWNT composite film-modified GCE, which combines the advantages of MWNT and the self-doped PABS, exhibits good selectivity and sensitivity for the simultaneous and selective determination of UA and DA in the presence of AA. Due to the different electrochemical responses of AA, DA, and UA, PABS–MWNT/GCE can resolve the overlapped oxidation peak of DA and UA into two well-defined voltammetric peaks with enhanced current responses using both cyclic voltammetry (CV) and DPV. The peak potential separations between DA and UA are 170 mV using CV and 160 mV using DPV, respectively, which are large enough for the selective and simultaneous determination of these species. In the presence of 0.5 mM AA, the DPV peak currents are linearly dependent on the concentration of UA and DA in the range of 6–55 and 9–48 μM with correlation coefficients of 0.997 and 0.993, respectively. The detection limits (S/N = 3) for detecting UA and DA are 0.44 and 0.21 μM, respectively. The PABS–MWNT/GCE shows good reproducibility and stability and has been used for the simultaneous determination of DA and UA in the presence of AA in samples with satisfactory results.     

Characterization of gold nanoparticles electrochemically deposited on amine-functioned mesoporous silica films and electrocatalytic oxidation of glucose

This study reports the preparation and characterization of gold nanoparticles deposited on amine-functioned hexagonal mesoporous silica (NH₂–HSM) films and the electrocatalytic oxidation of glucose. Gold nanoparticles are fabricated by electrochemically reducing chloroauric acid on the surface of NH₂–HSM film, using potential step technology. The gold nanoparticles deposited have an average diameter of 80 nm and show high electroactivity. Prussian blue film can form easily on them while cycling the potential between −0.2 and 0.6 V (vs saturated calomel electrode) in single ferricyanide solution. The gold nanoparticles loading NH₂–HSM-film-coated glassy carbon electrode (Au–NH₂–HSM/GCE) shows strong catalysis to the oxidation of glucose, and according to the cathodic oxidation peak at about 0.16 V, the catalytic current is about 2.5 μA mM⁻¹. Under optimized conditions, the peak current of the cathodic oxidation peak is linear to the concentration of glucose in the range of 0.2 to 70 mM. The detection limit is estimated to be 0.1 mM. In addition, some electrochemical parameters about glucose oxidation are estimated.     

Nitric oxide measurement in biological and pharmaceutical samples by an electrochemical sensor

A nitric oxide (NO) electrochemical sensor was developed via one-step construction of gold nanoparticles (GNPs)–chitosan (CS) nanocomposite sensing film on a glassy carbon electrode (GCE) surface. This method is very simple and convenient. The GNPs–CS film which is controllable and stable exhibits catalytic activity to NO oxidation. The anodic peak potential significantly shifted negatively compared with that at bare GCE. The high sensitivity and good stability of developed method have been coupled to a wide linear range from 3.60 × 10⁻⁸ to 4.32 × 10⁻⁵ M for the quantitative analysis of NO. The detection limit of 7.20 nM is much lower than the vast majority of reported methods. This NO sensor has been successfully applied to NO measurement in biological and pharmaceutical samples. Real-time amperometric data show that the addition of L-arginine (L-Arg) can cause a slow release of NO from a whole rat kidney with a maximum concentration of ca. 150 nM. The concentration of NO monitoring from the drug sample was calculated to be ca. 1.60 μM.     

Novel nitrite sensing using a palladium-polyphenosafranine nano-composite.

A novel palladium-polyphenosafranine nano-composite (PPS-Pd) was synthesized by electrochemical co-deposition at a glassy carbon electrode (GCE) for fabrication of a nitrite sensor, PPS-Pd/GCE. This PPS-Pd film was characterized by X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microanalysis (SEM). It was found that the PPS-Pd nano-composite consisted of Pd nanoparticles smaller than 10 nm in diameter which stick together due to the polymer, forming a Pd-embedded PPS layer structure. The sensing ability was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and differential pulse amperometry (DPA). The PPS-Pd/GCE had excellent catalytic activity toward the oxidation of nitrite: high current sensitivity of 0.365 A/M cm(-2), good reproducibility, good stability and fast response. In neutral solutions, a linear concentration range of 1.0 x 10(-6) to 1.1 x 10(-3) M (R(2) = 0.999) with the detection limit (s/n = 3) of 3 x 10(-7) M nitrite was obtained for DPV determination.     

A novel nitrite sensor fabricated through anchoring nickel-tetrahydroxy-phthalocyanine and polyethylene oxide film onto glassy carbon electrode by a two-step covalent modification approach

In this paper, we present a two-step covalent modification approach to fabricate a novel nitrite sensor through anchoring nickel-tetrahydroxy-phthalocyanine (NiPc(OH)₄) and polyethylene oxide (PEO) onto a glassy carbon electrode (GCE). The surface morphology of the prepared NiPc(OH)₄/PEO composite films under different dry conditions was characterized by scanning electron microscopy (SEM). The electrochemical behavior of NiPc(OH)₄/PEO composite film modified GCE toward the catalytic oxidation of nitrite in pH 7.0 phosphate buffer solution (PBS) was investigated by cyclic voltammetry (CV). After drying under an infrared lamp, the fabricated sensor showed a pronounced electrocatalytic activity improvement toward the oxidation of nitrite and led to a significant decrease in the anodic overpotentials compared with bare GCE, which should be ascribed to the synergistic effect of NiPc(OH)₄ and PEO, as well as the enlarged electrochemical effective surface area after drying. Using differential pulse voltammetry (DPV), the sensor gave a linear response to nitrite over the concentration range of 0.1–5,300 μM, with a detection limit of 0.0522 μM. The nitrite sensor exhibits good sensitivity, selectivity, and stability and has been applied for the determination of nitrite in water samples.     

Sensitive voltammetric determination of 2-mercaptobenzimidazole at electropolymerized nickel and copper tetraaminophthalocyanine membrane modified electrode

The voltammetric determination of 2-mercaptobenzimidazole (MBI) was studied by using a glassy carbon electrode (GCE) coated with polymeric nickel and copper tetraaminophthalocyanine (poly-NiTAPc and poly-CuTAPc) membrane. The polymeric membrane decreases the overpotential of oxidation of MBI by 136.2 and 115.0 mV and increases the oxidation peak current by about 3.4 and 3.3 times, while the reduction peak potential shifts positively by 113.0 and 84.1 mV and the peak current increases by about 10 and 7 times in 0.1 mol·l⁻¹ phosphate buffer solution (PBS) at pH = 2.0 for poly-NiTAPc and poly-CuTAPc, respectively, compared to the unmodified GCE. The results indicated that the developed electrode exhibited efficient electrocatalytic activity for MBI with relatively high sensitivity, stability, and long life. The oxidation and reduction peak currents of MBI were linear to its concentrations ranging from 8.0 × 10⁻⁵ to 1.0 × 10⁻³ mol·l⁻¹ at poly-NiTAPc and from 2.0 × 10⁻⁵ to 1.0 × 10⁻³ mol·l⁻¹ at poly-NiTAPc membranes modified electrodes, respectively, with a low limit of detection.     

Analysis of domperidone in pharmaceutical formulations and wastewater by differential pulse voltammetry at a glassy-carbon electrode

The redox characteristics of the drug domperidone at a glassy-carbon electrode (GCE) in aqueous media were critically investigated by differential-pulse voltammetry (DPV) and cyclic voltammetry (CV). In Britton–Robinson (BR) buffer of pH 2.6–10.3, an irreversible and diffusion-controlled oxidation wave was developed. The dependence of the CV response of the developed anodic peak on the sweep rate (ν) and on depolizer concentration was typical of an electrode-coupled chemical reaction mechanism (EC) in which an irreversible first-order reaction is interposed between the charges. The values of the electron-transfer coefficient (α) involved in the rate-determining step calculated from the linear plots of E _p,a against ln (ν) in the pH range investigated were in the range 0.64 ± 0.05 confirming the irreversible nature of the oxidation peak. In BR buffer of pH 7.6–8.4, a well defined oxidation wave was developed and the plot of peak current height of the DPV against domperidone concentration at this peak potential was linear in the range 5.20 × 10⁻⁶ to 2.40 × 10⁻⁵ mol L⁻¹ with lower limits of detection (LOD) and quantitation (LOQ) of 6.1 × 10⁻⁷ and 9.1 × 10⁻⁷ mol L⁻¹, respectively. A relative standard deviation of 2.39% (n = 5) was obtained for 8.5 × 10⁻⁶ mol L⁻¹ of the drug. These DPV procedures were successfully used for analysis of domperidone in the pure form (98.2 ± 3.1%), dosage form (98.35 ± 2.9%), and in tap (97.0 ± 3.6%) and wastewater (95.0 ± 2.9%) samples. The method was validated by comparison with standard titrimetric and HPLC methods. Acceptable error of less than 3.3 % was also achieved. Figure In aqueous media at pH 7.6- 8.4, the DPV and cyclic voltammetry of the drug domperidone (I) at GCE showed an irreversible and diffusion controlled oxidation wave. The values of the electron transfer coefficient (α) involved in the rate determining step were found in the range 0.64± 0.05 confirming the irreversible nature of the peak. The analysis of the drug in pure form and in wastewater samples was successfully achieved     

Fabrication of a Multi-wall Carbon Nanotubes Modified Glassy Carbon Electrode and its Catalytic Effect on the Oxidation of Estradiol, Estrone and Estriol

 Multi-wall carbon nanotubes (MWNT) have been dispersed into water with the emulsification of oil of turpentine and emulsifier OP TX-100. An MWNT-modified glassy carbon electrode (GCE) has been achieved through solvent evaporation of MWNT- dispersion. In pH 2.0 phosphate buffer, MWNT- modified GCE has an obvious catalytic effect on the oxidation of estradiol, estrone and estriol. The oxidation peak current of these estrogens at the modified electrode increases significantly in contrast with that at the bare GCE. The experimental conditions which heavily affect the oxidation peak current of estradiol, such as the solution pH, the amount of MWNT, the scan rate, the adsorption potential and adsorption time, were optimized. The peak current is linear to the concentration in the range of 2.5 × 10⁻⁷ to 5 × 10⁻⁵ mol L⁻¹ estradiol. The detection limit is 1 × 10⁻⁸ mol L⁻¹ after 3 min open-circuit adsorption. The relative standard deviation (RSD) of six measurements using an electrode is 3.2% for 1 × 10⁻⁵ mol L⁻¹ estradiol. The effect of interferences of other organic compounds on the determination of estradiol was examined. Author for correspondence: Department of Chemistry, Wuhan University, Wuhan 430072, P.R. China. E-mail: sshu@whu.edu.cn Received June 19, 2002; accepted January 4, 2003 Published online April 11, 2003     

Determination aminopyrine in pharmaceutical formulations based on APTS-Fe3O4 nanoparticles modified glassy carbon electrode

In this work, 3-aminopropyltriethoxysilane modified Fe₃O₄ nanoparticles (ATPS-Fe₃O₄) were used to modify glassy carbon electrode for aminopyrine determination. ATPS-Fe₃O₄ showed obviously catalytic activity and adsorptivity towards aminopyrine oxidation proven by the increased oxidation peak current and the decreased oxidation peak potential. The best analytical response was obtained by immobilizing 8 μL 3 mg/mL APTS-Fe₃O₄ dispersion with an accumulation time of 200 s at −0.2 V in 0.1 M phosphate buffer solution (pH 9.0). The oxidation peak current of aminopyrine showed linear relationship with its concentration in the range from 0.5 to 100 and 100 to 1600 μM. The detection limit was 0.1 μM (S/N = 3). The proposed method showed satisfactory repeatability and anti-interference ability. The fabricated electrode was successfully applied to determine aminopyrine in pharmaceutical formulations.     

The electrochemical polymerization of <Emphasis Type="Italic">o</Emphasis>-phenylenediamine on <Emphasis Type="SmallCaps">l</Emphasis>-tyrosine functionalized glassy carbon electrode and its application

The polymerization of o-phenylenediamine (OPD) on l-tyrosine (Tyr) functionalized glassy carbon electrode (GCE) and its electro-catalytic oxidation towards ascorbic acid (AA) had been studied in this report. l-Tyrosine was first covalently grafted on GCE surface via electrochemical oxidation, which was followed by the electrochemical polymerization of OPD on the l-tyrosine functionalized GCE. Then, the poly(o-phenylenediamine)/l-tyrosine composite film modified GCE (POPD-Tyr/GCE) was obtained. X-ray photo-electron spectroscopy (XPS), field emission scanning electron microscope (SEM), and electrochemical techniques have been used to characterize the grafting of l-tyrosine and the polymerization and morphology of OPD film on GCE surface. Due to the doping of the carboxylic functionalities in l-tyrosine molecules, the POPD film showed good redox activity in neutral medium, and thus, the POPD-Tyr/GCE exhibited excellent electrocatalytic response to AA in 0.1 mol l⁻¹ phosphate buffer solution (PBS, pH 6.8). The anode peak potential of AA shifted from 0.58 V at GCE to 0.35 V at POPD-Tyr/GCE with a greatly enhanced current response. A linear calibration graph was obtained over the AA concentration range of 2.5 × 10⁻⁴–1.5 × 10^–3 mol l⁻¹ with a correlation coefficient of 0.9998. The detection limit (3δ) for AA was 9.2 × 10⁻⁵ mol l⁻¹. The modified electrode showed good stability and reproducibility and had been used for the determination of AA content in vitamin C tablet with satisfactory results.     

Voltammetric Sensor for the Determination of Parathion Using an Electropolymerized Poly(Carmine) Film Electrode

A voltammetric sensor for the determination of parathion has been developed based on the use of a poly(carmine) film electrode. The reduction of parathion at the poly(carmine) modified glassy carbon electrode (GCE) is studied by cyclic voltammetry (CV) and linear scan voltammetry (LSV). Parathion yields a well-defined reduction peak at a potential of −0.595 V on the poly(carmine) modified GCE in pH 6.0 phosphate buffer solution (PBS). Compared with that on a bare GCE, the reduction peak current of parathion is significantly enhanced. All the experimental parameters are optimized for the determination of parathion. The reduction peak current is linear with the parathion concentration in the range of 5.0 × 10⁻⁸ to 1.0 × 10⁻⁵ mol L⁻¹, and the detection limit is 1.0 × 10⁻⁸ mol L⁻¹.     

Electrochemical behaviors of ofloxacin and its voltammetric determination at carbon nanotubes film modified electrode

A multi-wall carbon nanotubes (MWNTs)-Nafion film-coated glassy carbon electrode (GCE) was fabricated and the electrochemical behavior of ofloxacin on the MWNTs-Nafion film-coated GCE were investigated by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). The oxidation peak current of ofloxacin increased significantly on the MWNTs-Nafion film modified GCE compared with that using a bare GCE. This nano-structured film electrode exhibited excellent enhancement effects on the electrochemical oxidation of ofloxacin. A well-defined oxidation peak attributed to ofloxacin was observed at 0.97 V and was applied to the determination of ofloxacin. The oxidation peak current was proportional to ofloxacin concentration in the ranges 1.0 × 10⁻⁸ to 1.0 × 10⁻⁶ mol/L and 1.0 × 10⁻⁶ to 2.0 × 10⁻⁵ mol/L. A detection limit of 8.0 × 10⁻⁹ mol/L was obtained for 400 s accumulation at open circuit (S/N = 3). This method for the detection of ofloxacin in human urine was satisfactory. __________ Translated from Chinese Journal of Applied Chemistry, 2007, 24(5): 540–545 [译自: 应用化学]     

Electrochemical Determination of 10-Hydroxycamptothecin Using a Multi-Wall Carbon Nanotube-Modified Electrode

We report a sensitive and convenient voltammetric method for the direct determination of 10-hydroxycamptothecin (HCPT). At a multi-wall carbon nanotube (MWNT)-modified electrode, HCPT yields a very sensitive and well-shaped oxidation peak, which can be used as analytical signal for HCPT determination. Compared with the poor electrochemical signal at the unmodified GCE, the electrochemical response of HCPT at the MWNT-modified GCE was greatly improved, as confirmed by the significant peak current enhancement. This result indicates that the MWNT-modified GCE has great potential in the sensitive determination of HCPT. Based on this, a very sensitive and simple electrochemical method was proposed for HCPT determination after all the experimental parameters were optimized. The newly-proposed method possesses very low detection limit (2 × 10⁻⁹ mol L⁻¹) and wider linear range (from 1 × 10⁻⁸ to 4 × 10⁻⁶ mol L⁻¹). Rapid and simple sample analysis is another advantage. Finally, this method was successfully demonstrated using HCPT drugs.     

Electrochemical synthesis of Fe3O4-PB nanoparticles with core-shell structure and its electrocatalytic reduction toward H2O2

The Fe₃O₄-Prussian blue (PB) nanoparticles with core-shell structure have been in situ prepared directly on a nano-Fe₃O₄-modified glassy carbon electrode by cyclic voltammetry (CV). First, the magnetic nano-Fe₃O₄ particles were synthesized and characterized by X-ray diffraction. Then, the properties of the Fe₃O₄-PB nanoparticles were characterized by CV, electrochemical impedance spectroscopy, and superconducting quantum interference device. The resulting core-shell Fe₃O₄-PB-modified electrode displays a dramatic electrocatalytic ability toward H₂O₂ reduction, and the catalytic current was a linear function with the concentration of H₂O₂ in the range of 1 × 10⁻⁷~5 × 10⁻⁴ mol/l. A detection limit of 2 × 10⁻⁸ (s/n = 3) was determined. Moreover, it showed good reproducibility, enhanced long-term stability, and potential applications in fields of magnetite biosensors.