Fabrication of an electrochemical sensor based on the electrodeposition of Pt nanoparticles on multiwalled carbon nanotubes film for voltammetric determination of ceftriaxone in the presence of lidocaine, assisted by factorial-based response-surface methodology

A glassy carbon electrode (GCE) is modified with platinum nanoparticle (PtNPs) decorated multiwalled carbon nanotube (MWCNT). The modified electrode is applied for the determination of ceftriaxone (CFX) in the presence of lidocaine. Different methods were used to characterize the surface morphology of the modified electrode. The electrochemical behavior of CFX was investigated at GCE, MWCNT/GCE and PtNPs/MWCNT/GCE. A factorial-based response-surface methodology was used to find out the optimum conditions with minimum number of experiments. Under the optimized conditions, oxidation peak currents increased linearly with CFX concentration in the range of 0.01–10.00 μM with a detection limit of 9.01 nM. The results prove that the modified electrode is also suitable for the determination of CFX in pharmaceutical and clinical preparations.     

A uric acid sensor based on electrodeposition of nickel hexacyanoferrate nanoparticles on an electrode modified with multi-walled carbon nanotubes

An electrode sensitive to uric acid was prepared by electrodeposition of nickel(II) hexacyanoferrate(III) on the surface of a glassy carbon electrode modified with multi-walled carbon nanotubes. The morphology of the material was characterized by scanning electron microscopy and Fourier transform infrared spectrometry. The modified electrode were characterized via cyclic voltammetry and amperometry (i - t). It exhibited efficient electron transfer ability and a strong and fast (< 3?s) response towards uric acid which is linear in the range from 0.1???M to 18???M, with a lower detection limit of 50 nM (at an S/N ratio of 3). In addition, the electrode exhibited good reproducibility and long-term stability.

Sensitive and selective molecularly imprinted electrochemical sensor based on multi-walled carbon nanotubes for doxycycline hyclate determination

An electrochemical sensor for doxycycline hyclate(DC)detection with high sensitivity and good selectivity is reported.The sensor was fabricated by electro-polymerization of molecularly imprinted polymers(MIPs)in the presence of DC onto multi-walled carbon nanotubes modified glassy carbon electrode(MWCNTs/GCE).The MWCNTs can significantly increase the current response of the sensor,leading to enhanced sensitivity.The MIPs provide selective recognition sites for DC detection.The experimental parameters,such as the polymer monomer concentration,supporting electrolyte pH,the time for electro-polymerization and the incubation time of the sensor with DC were optimized.Under optimized experimental conditions,the sensor displayed a linear range of 0.05μmol/L-0.5μmol/L towards DC detection,with the detection limit of 1.3×10^-2μmol/L.The sensor was successfully applied for recovery test of DC in human serum samples.     

Anodic stripping voltammetric determination of mercury using multi-walled carbon nanotubes film coated glassy carbon electrode

An electrochemical method for the determination of trace levels of mercury based on a multi-walled carbon nanotubes (MWNT) film coated glassy carbon electrode (GCE) is described. In 0.1 mol L^–1 HCl solution containing 0.02 mol L^–1 KI, Hg²⁺ was firstly preconcentrated at the MWNT film and then reduced at –0.60 V. During the anodic potential sweep, reduced mercury was oxidized, and then a sensitive and well-defined stripping peak at about –0.20 V appeared. Under identical conditions, a MWNT film coated GCE greatly enhances the stripping peak current of mercury in contrast to a bare GCE. Low concentrations of I^– remarkably improve the determining sensitivity, since this increases the accumulation efficiency of Hg²⁺ at the MWNT film coated GCE. The stripping peak current is proportional to the concentration of Hg²⁺ over the range 8×10^–10–5×10^–7 mol L^–1. The lowest detectable concentration of Hg²⁺ is 2×10^–10 mol L^–1 at 5 min accumulation. The relative standard deviation (RSD) at 1×10^–8 mol L^–1 Hg²⁺ was about 6% (n=10). By using this proposed method, Hg²⁺ in some water samples was determined, and the results were compared with those obtained by atomic absorption spectrometry (AAS). The two results are similar, suggesting that the MWNT-film coated GCE has great potential in practical analysis.     

Disposable paper-based electrochemical sensor based on stacked gold nanoparticles supported carbon nanotubes for the determination of bisphenol A

This work reports a new type of disposable electrochemical sensor for the determination of bisphenol A (BPA). The working electrodes were fabricated by sputtering gold nanoparticles on commercial art paper and then modifying the gold layer with multi-walled carbon nanotubes (MWCNTs). The electrode in their intermediated and final stage was characterized by atomic force microscope, scanning electron microscope and electrochemical techniques. To perform electrochemical analysis, the resulting electrode was integrated with a homemade paper-based analytical device, which could also ensure the immobilization of MWCNTs on the electrode surface without any functionalization. The determination of BPA was investigated by linear sweep voltammetry (LSV). A wide linearity in the range from 0.2 to 20 mg/L with a detection limit of 0.03 mg/L (S/N = 3) was obtained. The between-sensor reproducibility was 5.7% (n = 8) for 0.5 mg/L BPA. The proposed sensor showed good resistance against interferences and was applied to detect BPA leached from real plastic samples with satisfying results. This disposable sensor is readily mass-produced and has been verified to serve as an attractive alternative to screen-printed electrodes for practical applications.     

Highly selective tryptophan enantiomers electrochemical chiral sensor based on poly-lysine and functionalized multi-walled carbon nanotubes

Journal of Solid State Electrochemistry - A novel electrochemical chiral sensor was reported for recognizing tryptophan enantiomers based on multi-walled carbon nanotubes functionalized by...     

Nonenzymatic glucose voltammetric sensor based on gold nanoparticles/carbon nanotubes/ionic liquid nanocomposite

In this paper, a novel nonenzymatic glucose voltammetric sensor based on a kind of nanocomposite of gold nanoparticles (GNPs) embedded in multi-walled carbon nanotubes (MWCNTs)/ionic liquid (IL) gel was reported. The surface morphology of this nanocomposite was characterized using X-ray photoelectron spectrometer (XPS), scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. It can be found that most of GNPs lie close to the ektexine of MWCNTs and the others have obviously inserted the inner of MWCNTs through the defects or ends of MWCNTs, due to the attraction between GNPs and MWCNTs as well as the repulsion between GNPs and IL. Voltammetry was used to evaluate the electrocatalytic activities of the nanocomposite biosensor toward nonenzymatic glucose oxidation in alkaline media. The GNPs embedded in MWCNTs/IL gel have strong and sensitive voltammetric responses to glucose, owing to a possible synergistic effect among GNPs, MWCNTs and IL. Under the optimal condition, the linear range for the detection of the glucose is 5.0-120 μM with the correlation coefficient of 0.998, based on the oxidation peak observed during cathodic direction of the potential sweep. The kinetics and mechanism of glucose electro-oxidation were intensively investigated in this system. This kind of nanocomposite biosensor is also highly resistant toward poisoning by chloride ions and capable of sensing glucose oxidation in the presence of 20 μM uric acid and 70 μM ascorbic acid. This work provides a simple and easy approach to the detection of glucose in body fluid with high sensitivity and excellent selectivity.     

Imprinted sol-gel electrochemical sensor for the determination of benzylpenicillin based on Fe3O4@SiO2/multi-walled carbon nanotubes-chitosans nanocomposite film modified carbon electrode

In this work, we developed a novel graphene-assisted matrix solid-phase dispersion (GA-MSPD) method for extraction of polybrominated diphenyl ethers (PBDEs) and their methoxylated (MeO-) and hydroxylated (OH-) analogs from environmental samples. We found that grinding the solid sample with chemically converted graphene (CCG) powder yielded a tight contact and sufficient dispersion of the sample matrix due to the large surface area and flexible nanosheet morphology of CCG. The resultant blend was eluted using a two-step elution strategy: PBDEs and MeO-PBDEs were eluted firstly by hexane/dichloromethane and analyzed by GC-ECD, and then OH-PBDEs were eluted by acetone and determined by LC-ESI-MS/MS. The GA-MSPD conditions were optimized in detail. Better recoveries were obtained with GA-MSPD than with other sorbents (C18 silica, Florisil and carbon nanotubes) and other extraction techniques (Soxhlet and accelerated solvent extraction). Other advantages of GA-MSPD, including reduced consumption of sorbent and solvent, good selectivity and short extraction time, were also demonstrated. In analysis of soil samples, the method detection limits of five PBDEs, ten MeO-PBDEs and ten OH-PBDEs were in the range of 5.9-28.7, 14.3-46.6, and 5.3-212.6 pg g(-1) dry weight, respectively. The proposed method was successfully applied to the extraction of PBDEs, MeO-PBDEs and OH-PBDEs from different kinds of spiked environmental samples, including soil, tree bark and fish.     

Intensified electrochemical hydrogen storage capacity of multi-walled carbon nanotubes supported with Ni nanoparticles

The electrochemical hydrogen storage properties of Ni-supported multi-walled carbon nanotube (Ni/MWCNT) electrodes were investigated using charge/discharge (C&D) and cyclic voltammetry (CV) techniques. Nickel NPs were deposited on the MWCNT surface, which was first chemically oxidized by H₂SO₄ and HNO₃ (3:1, v/v). Hydrogen storage was carried out by using the Ni/MWCNT electrode as the working electrode in the electrochemical cell. A set of various current densities were applied to the cell to produce (C&D) cycles, and it became optimum corresponding to 1.5 mA current. According to the electrochemical test results, the highest electrochemical discharge capacity of 1625 mAh g^?1 was obtained for the electrode with ratio of 4:1 (MWCNTs to Ni) in the initial cycle, which corresponded to 6.07 wt% H₂. The storage capacity was increased and reached to 4909 mAh g^?1 (18.34 wt% H₂) after 20 cycles, and the electrode maintained the specific capacity as cycling continued. Thus, the Ni/MWCNT electrode displays an excellent cycle stability and a high capacity reversibility. CV measurements also showed that the electrochemical adsorption and desorption amount of hydrogen was increased by Ni loading onto the CNTs and indicated that the electrochemical hydrogen adsorption of the electrode has an activated period.     

基于多壁碳纳米管和纳米金修饰电极测定特殊序列DNA的电化学生物传感器的制备

基于多壁碳纳米管和纳米金复合膜修饰电极制备了特殊序列的靶DNA的电化学生物传感器.该传感器以六氨基合钌为杂交指示剂,用差示脉冲伏安法进行检测DNA杂化,其响应信号与靶DNA浓度在1.0×10<'-12>～1.0×10<'-7>mol/L范围内呈线性关系,检测限达3.5×10<'-13>mol/L.该传感器能区分单碱基错配的靶DNA.     

Development of an acetylspiramycin sensor based on a single-walled carbon nanotubes film electrode

A simple and sensitive sensor is described for the determination of acetylspiramycin (ASPM) based on a single-wall carbon nanotubes (SWNTs)-dihexadecyl hydrogen phosphate (DHP) film coated glassy carbon electrode (GCE). Compared with a bare GCE, the SWNTs-DHP film modified GCE exhibits excellent enhancement effects on the electrochemical oxidation of ASPM. A well-defined oxidation peak of ASPM occurs at 0.89 V in 0.1 mol·L⁻¹ phosphate buffer (pH 5.5), which was used to determine ASPM. The electrochemical behavior of ASPM at the SWNTs-DHP modified GCE was examined by cyclic voltammetry and differential pulse voltammetry. The experimental parameters were optimized and a direct electrochemical method for the determination of ASPM is proposed. Under optimum conditions, the oxidation peak current is linear to the concentration of ASPM in the range of 5.0–100 μg·mL⁻¹, with a detection limit of 1 μg·mL⁻¹. The SWNTs-DHP film modified electrode also provides an efficient way of eliminating interferences from some inorganic species in the solution. This sensor was successfully utilized to determine ASPM in drugs.     

Highly sensitive voltammetric sensor based on catechol-derivative-multiwall carbon nanotubes for the catalytic determination of captopril in patient human urine samples

A new catechol-derivative compound, N-(3,4-dihydroxyphenethyl)-3,5-dinitrobenzamide, was synthesized and used to construct a modified-carbon nanotubes paste electrode. The electro-oxidation of captopril at the surface of the modified electrode was studied using cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. Under the optimized conditions, the differential pulse voltammetric peak current of captopril increased linearly with captopril concentration in the ranges of 6.4×10(-8) to 3.2×10(-48) mol L(-1). The detection limit was 3.4×10(-8) mol L(-1) captopril. The diffusion coefficient and kinetic parameters (such as electron transfer coefficient and the heterogeneous rate constant) for captopril oxidation were also determined. The RSD% for 0.5 and 10.0 μmol L(-1) captopril were 2.1% and 1.6%, respectively. The proposed sensor was successfully applied for the determination of captopril in human patient urine and tablet samples.     

A highly sensitive nonenzymatic glucose sensor based on NiO-modified multi-walled carbon nanotubes

A highly sensitive and selective glucose biosensor has been constructed by using highly dispersed NiO nanoparticles supported on well-aligned MWCNTs (NiO/MWCNTs) as sensing interface. The NiO/MWCNTs nanocomposite was synthesized by magnetron sputtering deposition of NiO nanoparticles on vertically aligned carbon nanotubes. The nanocomposite electrode showed high electrochemical activity towards the oxidation of glucose in 0.20 M NaOH solution. At an applied potential of +0.50 V, it gives a fast response time (< 5 s) and a linear dependence (R?=?0.997) on the glucose concentration up to 7.0 mM with an extraordinarily high sensitivity of 1.77 mA mM^-1 cm^-2 and a detection limit of 2 μM. The interference by the oxidation of common interfering species such as ascorbic acid, dopamine, uric acid, lactose, and fructose is effectively avoided. The electrode was used to analyze glucose concentration in human serum samples. It allows highly sensitive, stable, and fast amperometric sensing of glucose, which is promising for the development of nonenzymatic glucose sensors.     

Sensitive voltammetric determination of tyrosine using multi-walled carbon nanotubes/4-aminobenzeresulfonic acid film-coated glassy carbon electrode

A chemically modified electrode is constructed based on the multi-walled carbon nanotubes (MWNTs)/4-aminobenzeresulfonic acid (4-ABSA) film-coated glassy carbon electrode. The electrocatalytic oxidation of tyrosine (Tyr) is investigated on the surface of the MWNTs/4-ABSA-modified electrode using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The prepared modified electrode shows voltammetric responses with high sensitivity and selectivity for Tyr in optimal conditions, which makes it very suitable for sub-micromolar detection of Tyr. A sensitive oxidation peak at +0.64 V is employed to determine Tyr. Good linear relationship between the oxidation peak current and the Tyr concentration in the range of 1 × 10⁻⁷ to 5 × 10⁻⁵ mol/L is obtained in phosphate buffer solution with pH 7.0. By use of modified electrode, the voltammetric detection limit for Tyr in DPV measurements is 8 × 10⁻⁸ mol/L (S/N = 3). Good sensitivity, selectivity and stability of the low-cost modified electrode make it very suitable for the determination of trace amounts of Tyr in pharmaceutical and clinical preparations.     

An innovative electrochemical approach for voltammetric determination of levodopa using gold nanoparticles doped on titanium dioxide nanotubes

Catalytic nanotubes made from titanium dioxide (TiO₂-NTs) and covered with gold nanoparticles (Au-NPs) were prepared via galvanic deposition of the Au-NPs on the TiO₂-NTs. The morphology and surface characteristics of the resulting electrodes were investigated using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The results indicated that the Au-NPs were homogeneously deposited on the surface of TiO₂-NTs which consist of individual tubes of about 40?C80?nm in diameter. The AuNPs with a size of 80?C100?nm are well-dispersed on the surface of the TiO₂-NTs. The electro-catalytic activity of the electrodes towards the electro-oxidation of levodopa was studied by cyclic voltammetry, differential puls voltammetry. The results showed that the electrodes exhibit a considerably higher activity toward the oxidation of levodopa. The oxidation peak current linearly depends on the concentration of levodopa in the 10 to 70???M concentration range. Levodopa was determined by the method in pharmaceutical preparations, and results were found to be satisfactory.

Hydrogen peroxide sensor based on a stainless steel electrode coated with multi-walled carbon nanotubes modified with magnetite nanoparticles

Multi-walled carbon nanotubes (MWCNTs) were decorated with magnetite (Fe₃O₄) nanoparticles and then used to modify a stainless steel electrode. The Fe₃O₄/MWCNTs composite was characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and X-ray diffraction patterns. Electrochemical properties of the modified electrode revealed a substantial catalytic activity for the reduction of hydrogen peroxide. The relationship between peak current and the concentration of hydrogen peroxide was linear in the range from 0.06?mmol?L^?1 to 0.36?mmol?L^?1, and the lowest detectable concentration is 0.01?mmol·L^?1 (S/N?=?3). The modified stainless steel electrode displays excellent stability.

Copper nanoclusters conjugated silica nanoparticles modified on carbon paste as an electrochemical sensor for the determination of dopamine

An electrochemical sensor based on modification of carbon paste electrode by glutathione‐capped copper nanoclusters silica nanoparticles (CuNCs/SiO₂NPs) composite for determination of dopamine in the presence of ascorbic acid was presented. Transmission electron microscopy, scanning electron microscopy, energy dispersive X‐Ray analysis, X‐ray photoelectron spectroscopy, Fourier‐transform infrared spectroscopy, X‐ray diffraction and electrochemical impedance spectroscopy were used for characterization of the developed electrode. The electrochemical behavior of dopamine on CuNCs/SiO₂NPs/carbon paste electrode was investigated by cyclic voltammetry and differential pulse voltammetry. Dopamine was determined in the range of 10.0 – 900.0 μM, and the limit of detection was obtained as 0.43 μM. The electrochemical behaviors of the coexisting electroactive species, which often cause interference with the determination of dopamine, were investigated. The results show that the developed electrode does not show any interference with respect to coexisting species, even in the presence of ascorbic acid. The developed electrochemical sensor was further employed for the determination of dopamine in human blood plasma, with a good recovery.     

An electrochemical sensor prepared by sonochemical one-pot synthesis of multi-walled carbon nanotube-supported cobalt nanoparticles for the simultaneous determination of paracetamol and dopamine

Multi-walled carbon nanotubes (MWCNTs) functionalized by cobalt nanoparticles were obtained using a single step chemical deposition method in an ultrasonic bath. The composite material was characterized using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The electroactivity of the cobalt-functionalized MWCNTs was assessed in respect to the electrooxidation of paracetamol (PAR) and dopamine (DA). It was found that the carbon nanotube supported cobalt nanoparticles have significantly higher catalytic properties. The proposed electrode has been applied for the simultaneous determination of PAR and DA. The modified electrode could resolve the overlapped voltammetric waves of PAR and DA into two well-defined voltammetric peaks with peak to peak separation of about 203 mV. On the other hand, the presence of potential drug interfering compounds AA and UA did not affect the voltammetric responses of PAR and DA. The current of oxidation peaks showed a linear dependent on the concentrations of PAR and DA in the range of 5.2 × 10⁻⁹–4.5 × 10⁻⁷ M (R² = 0.9987) and 5.0 × 10⁻⁸–3.0 × 10⁻⁶ M (R² = 0.9999), respectively. The detection limits of 1.0 × 10⁻⁹ M and 1.5 × 10⁻⁸ M were obtained for PAR and DA, respectively. The proposed electrode showed good stability (peak current change: 4.9% with and RSD of 2.6% for PAR; 5.5% with and RSD of 3.0% for DA over 3 weeks), reproducibility (RSD 2.3% for PAR and RSD 1.5% for DA), repeatability (RSD 2.25% for PAR and RSD 2.50% for DA) and high recovery (99.7% with an RSD of 1.3% for PAR; 100.8% with an RSD of 1.8% for DA). The proposed method was successfully applied to the determination of PAR and DA in pharmaceuticals.