Electrochemical determination of ciprofloxacin using a MIL-101/reduced graphene oxide-modified electrode.

Ciprofloxacin (CIP) is widely utilised to treat bacterial infections. Currently, CIP is present in water sources at higher concentrations, thus necessitating close monitoring. This study developed electrochemical nano-sensors based on molecularly imprinted polymer (MIP) and reduced graphene oxide (rGO) composites to detect CIP. rGO served as the loading platform for MIP immobilisation on a glassy carbon electrode (GCE). A copolymer thin film, comprised of polyaniline copolymerized with o-phenylenediamine (PAni-co-PDA) was obtained by electro-polymerisation utilizing cyclic voltammetry (CV) under suitable conditions. The performance of the modified GCE was examined utilizing CV mode in a hexacyanoferrate electrolyte as an electrochemical probe. The PAni-co-PDA/rGO-modified GCE exhibited enhanced improvement and efficient electrocatalytic behaviour in the oxidation of CIP with relatively high sensitivity and stability. The sensor was operated in differential pulse voltammetry (DPV) mode. Our best results revealed good linearity response to CIP in the range of 0.001–10.0 μM with an R-squared of 0.949, a detection limit of 0.09 μM (3.3 SD/S), and the calibration plot of ΔI minus the logarithm of the CIP concentration exhibited a sensitivity of –1.521. The sensor demonstrated a conductive polymer-based device that can be utilised for rapid CIP determination in pharmaceutical samples and biological fluids.

We reported a graphene-based electrochemical sensor for sensitively measuring carbendazim, which is one of the effective benzimidazole fungicides popularly used in agriculture. The β-cyclodextrin-functionalized reduced graphene oxide (β-CD–RGO) nanocomposites were synthesized using hydrazine as the reducing agent at room temperature. The as-synthesized nanocomposites were characterized using different analytical methods including UV–visible spectroscopy and Fourier transform infrared spectroscopy. The nanocomposites with a combination of physicochemical properties of RGO and high molecular recognition capability of β-CD were used to modify the surface of a glassy carbon electrode for the electrochemical determination of the drug carbendazim using cyclic voltammetry and differential pulse voltammetry. The current responses of carbendazim on the β-CD–RGO-modified electrode were greatly enhanced compared to that on the bare electrode due to the electrocatalytic effect of β-CD–RGO. It was found that the peak currents increased linearly with the carbendazim concentration in the range between 0.1 and 40 μM. The obtained results suggest that β-CD–RGO composite could be a potential candidate for the preparation of effective electrochemical sensors for carbendazim or similar drugs in the future.

In this paper, we compare reduced graphene oxide (RGO) electrode with multi-walled carbon nanotubes (MWCNT) as modifiers for the sensitive detection of levofloxacin. The RGO-based sensor showed higher currents for levofloxacin compared with the MWCNT-modified (4-fold) and unmodified electrodes (20-fold). A thin-layer adsorptive process was verified for the oxidation of levofloxacin on the RGO-modified electrode which explains the higher currents. Differential pulse voltammetry (DPV), square wave voltammetry (SWV), and amperometric detection using flow-injection analysis (FIA-AMP) were evaluated for levofloxacin determination in urine and pharmaceutical samples. Detection limits of 1.45, 6.70, and 1.90 μmol L−1 and recovery levels of 91, 106, and 103%, respectively were obtained. A relative standard deviation lower than 7.7% indicated proper precision. The FIA-AMP using the RGO-modified electrode presented high analytical frequency (around 100 injections per hour) and thus was selected for the analysis of the samples. Statistically, similar results (95% confidence level) compared with ultra-fast liquid chromatography (UFLC) analysis and recovery level of 96% for the analysis of urine were obtained.

The low cost and profusion of sodium resources make sodium-ion batteries (SIBs) a potential alternative to lithium-ion batteries for grid-scale energy storage applications. However, the use of conv...

Construction of cationic polyfluorinated azobenzene/reduced graphene oxide for simultaneous determination of dopamine, uric acid and ascorbic acid

An easy and sensitive sensor made by carbon paste modified with reduced graphene oxide rGO‐CPE was developed for the detection of hydroxychloroquine (HCQ). Graphene oxide GO was reduced using ethyl acetate. Scanning electron microscope and X‐ray diffraction (XRD) were used for the characterization of rGO powder. The reduction of graphene oxide was confirmed by the disappearance of the identical peak of graphite in the XRD pattern. Herein, the modified electrode rGO‐CPE showed stronger electrochemical activity compared to bare CPE. The electrochemical behavior of HCQ was studied by cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry. The mechanism of the HCQ oxidation in the surface of rGO‐CPE was found to be controlled by an adsorption process with the transfer of 2 electrons. Furthermore, the standard heterogeneous rate constant ( K s ) and the surface concentration of electroactive species ( Γ ) were calculated and the obtained values are 1.03×10 −2 cm s −1 and 1.07×10 −10 mol cm −2 , respectively. Differential pulse voltammetry was used for HCQ quantification as a result a linear relationship between HCQ concentration and the oxidation peak current was obtained in the range from 1.0×10 −7 to 8.0×10 −6 mol L −1 and from 8.0×10 −6 to 1.0×10 −4 mol L −1 , with a detection limit ( LOD ) of 6.29×10 −8 mol L −1 and a sensitivity of 6.42 A L mol −1 cm −2 . Moreover, the rGO‐CPE was successfully applied for the detection of HCQ in wastewater and pharmaceutical samples.

Point of need simultaneous biosensing of pharmaceutical micropollutants with binder free conjugation of manganese stannate micro-rods on reduced graphene oxide in real-time analysis

Introduction There are few selected nanomaterials that are being used as base materials in emerging technologies for possessing exceptional potential. Among such materials, tin oxide (SnO2) is a material with exciting sensing properties such as high sensitivity, good chemical stability, high electron mobility, fast response, and good recovery speed [1]. Electrochemical analysis using SnO2 nanomaterial has been used for the qualitative and quantitative determination of amount of electro active analytes. This method is reported to be highly accurate, reliable and cheap. Several characterization techniques are used to investigate the electrochemical response like Cyclic voltammetry (CV), Differential Pulse Voltammetry (DPV), Square Wave Voltammetry (SWV) or Pulsed Amperiometry (PA) [2]. SnO2 nanowires are hereby reported for the detection of Riboflavin (RF). It is observed that the synthesized nanowires can detect the analyte efficiently. Method SnO2 nanowires were synthesized by template-directed electrodeposition. Copper foil was used as the substrate. The Sn nanowires were electrodeposited into the nanoholes of the polycarbonate membranes by a three-electrode system in a solution containing 0.05 M SnCl2.2H2O and HCl at room temperature. The electrochemical synthesis was performed on a CHI660 electrochemical Workstation. The electrodeposition was performed at -0.7 V (vs saturated Ag/AgCl), with platinum serving as the counter electrode. After SnO2 nanowires were electrodeposited into track etch polycarbonate membranes, the assembly system was annealed in the air at 85oC to form an ordered SnO2 nanowire array. Ag/AgCl as a reference electrode and gold as an auxillary electrode were used to set up the modifications in detection technique. CV, DPV and EIS techniques were used for the successful detection of RF. Moreover, for measuring the pH values, a pH meter with a combined electrode (glass-reference electrode) was used. All potentials are measured against the Ag/AgCl reference electrode at room temperature. Results and Conclusions Field-emission scanning electron microscopy (FE-SEM) is used to characterize the morphologies of the as-prepared products. To demonstrate the chemical composition, EDS analysis was performed. The crystal structure of the as-prepared samples is determined by X-ray diffraction (XRD) with Cu Kα radiation. All these results showed that the nanowires are successfully synthesized in their pure form. Electrochemical studies were carried out by CV and DPV studies. EIS technique also verified about the successful determination of analytes. The developed sensor exhibits good stability, reproducibility and efficiency. Moreover, its practical application was also checked in pharmaceutical samples by the recovery test. For RF content in pharmaceutical samples in the range from 52-150 μM, the developed sensor retains its linearity which indicates that the fabricated sensor not only works well in 0-13 μM range but beyond that range also. Compared with all other existing electrodes reported in the literature, the reported work not only showed remarkably lower detection limit but also the cheapest electrode ever synthesized.

Dual-active-group co-modification of BiOBr for boosting photocatalytic CO2 reduction coupled with ciprofloxacin oxidation

ABSTRACTA novel electrochemical aptasensor is reported for the label-free determination of dopamine by electrochemically reduced graphene oxide and a gold nanocomposite with a ribonucleic acid (RNA) aptamer. The nanocomposite was fabricated by layer-to-layer electrochemical deposition. The aptamer was immobilized on the surface of the gold nanoparticles through the formation of thiol–gold bonds. Dopamine was determined through specific interaction with the immobilized aptamer. The redox activity of the analyte enabled direct electrochemical analysis. The conductivity and structure of the nanocomposite were characterized by cyclic voltammetry and scanning electron microscopy. In contrast to bare or reduced graphene oxide-modified electrodes, the nanocomposite-modified electrode significantly enhanced the current response. The electrochemical aptasensor provided a detection limit of 0.13 µM with a linear dynamic range from 0.5 to 20 µM. In addition, the sensor was shown to provide high selectivity and satisfactory stability for the determination of dopamine in the presence of analogs and in human serum.

ZrO2@C-MOF-808: A carbonized MOF-Based nanocomposite for sensitive electrochemical detection of ulipristal acetate.

In this work, electrochemical biosensors have been developed and quantified the pyrazinamide, isoniazid, rifampicin, ethambutol and streptomycin drugs in various pharmaceutical samples. Electrochemical methods are versatile and powerfull analytical technique of immense value in the area of pharmaceutical analyses. In addition, due to the similarity in the biological and electrochemical reactions, it can be expected that the reduction-oxidation mechanisms occur at the electrode surface. The biologically stimulated molecules can be examined by electroanalysis and they are also outstanding tools for the detection of pharmaceutical complexes in various matrices. Although in the case of a biosensors, the analyte interacts with bioreceptor and the resultant output is measured by a specifically designed transducer. Additionally, a reliable highly sensitive and novel biosensor was developed by using a glassy carbon electrode modified with various nanomaterials. Hence horseradish peroxidase (HRP) - Multiwalled carbon nanotubes (MWCNTs)-Titanium oxide nanoparticles (TiO2NPs) fabricated glassy carbon electrode (GCE) were used for the determination of isoniazid. Similarly, copper oxide nanoparticles (CuONPs)-MWCNTs immobilized with Cytochrome c (Cyt c) on glassy carbon electrode were established for the detection of pyrazinamide. Furthermore, iron oxide nanoparticles (Fe3O4NPs) and MWCNTs composite were immobilized with Coenzyme q (Coen- q) on glassy carbon electrode for the detection of rifampicin. In addition, Cyt c immobilized with ZnONPs and MWCNTs on glassy carbon electrode for the determination of streptomycin. Finally, the glassy carbon electrode fabricated with zinc oxide nanoparticles (ZnONPs) and reduced graphene oxide (RGO) nano composite, was further immobilized with HRP to enhance the electrochemical performance of the modified electrode for the determination of ethambutol. Electrochemical behaviour of these first line anti TB drugs to the developed biosensors were examined by using cyclic voltammetry and differential pulse voltammetry under the optimum experimental conditions such as scan rates, pH, accumulation potential, pulse amplitude, accumulation time, voltage step time, voltage step and deposition time respectively. The prepared biosensors and nanocomposites were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), thermo gravimetry (TGA) and x-ray diffraction (XRD). It was observed that electrochemical methods provided good and effective techniques for the determination of isoniazid, pyrazinamide, rifampicin, ethambutol and streptomycin. Compared to the other analytical methods, the limit of detection and limit of quantifications were found to be 0.0335 μM and 0.1118 μM for isoniazid, 0.0038 μM and 0.0129 μM for pyrazinamide, 0.032 µM, and 0.413 µM for rifampicin, 0.0214 μM and 0.6713 μM for ethambutol, and 0.0028 μM and 0.5628 μM for streptomycin respectively.

Highly electroactive Ce-ZnO/rGO nanocomposite: Ultra-sensitive electrochemical sensing platform for carbamazepine determination

Fabrication of cobalt tungstate/N-rGO nanocomposite: Application towards the detection of antibiotic drug-Furazolidone

Background:Over the past few decades, environmental pollution has appeared to be one of the most crucial global problems. The widespread intensification of numerous hazardous pollutants in the environment need the modern researchers to develop viable, reproducible and cost-effective determination tools for the reliable environmental analysis. The beneficial, as well as perilous, biological compounds are receiving growing interest due to their variable composition which produces advantageous and toxic impacts on human and the environment. Several conventional analytical methods have been established for the pharmaceutical and environmental analysis. However, certain drawbacks limited their practices in the modern rapidly growing era of science and technology. The development of electrochemical sensors has emerged as more beneficial and promising tool as against other traditional analytical approaches, in terms of simplicity, cost-effectiveness, sensitivity, stability and reliability. Nonetheless, the over potential and low anodic/cathodic current response are both considered as bottlenecks for the determination of electroactive entities exploiting electrochemical sensors. Interestingly, these problems can be easily resolved by modifying the electrodes with a variety of conductive materials, especially nanostructures.Objective:This review covers different electrochemical methods, reported in the literature, for the environmental and pharmaceutical analysis through simple and cost-effective nanostructures-based sensors. The electrochemical techniques with different modes and the modification of electrodes with highly conductive and prolific polymeric and nanostructured materials used for the determination of different environmental and pharmaceutical samples are the main prominence of this review. Various kinds of nanomaterials, e.g. metal, metal oxide and their composites, have been synthesized for the fabrication of sensitive electrodes.Conclusion:Nanostructures played a pivotal role in the modification of electrodes, which substantially enhanced the capability and sensitivity of electrochemical sensors. The proper modification of electrodes has materialized the swift detection of electroactive compounds at very low limits and offered the feasible determination procedure without any kind of signal fluctuation and over potential. In crux, due to their enhanced surface area and excellent catalytic properties, nanomaterials recently appeared as the most promising candidates in the field of electrode modification and significantly impacted the detection protocols for various environmental pollutants, viz. pesticides, metal ions and drugs.