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In this research, we have demonstrated a one-step electrochemical deposition of dendritic gold nanostructures (DGNs) on a graphite rod (GR) electrode without any template, seeds, surfactants, or stabilizers. Three electrochemical methods, namely, constant potential amperometry (CPA), pulse amperometry, and differential pulse voltammetry, were used for DGN synthesis on GR electrode and further application in enzymatic glucose biosensors. Formed gold nanostructures, including DGNs, were characterized by a field emission scanning electron microscopy. The optimal concentration of HAuCl4 (6.0 mmol L−1), duration of DGNs synthesis (400 s), electrodeposition potential (−0.4 V), and the best electrochemical method (CPA) were determined experimentally. Then the enzyme, glucose oxidase, was adsorbed on the surface of DGNs and covalently cross-linked with glutaraldehyde vapor. The enzymatic glucose biosensor based on DGNs electrodeposited at optimal conditions and modified with glucose oxidase showed a quick response (less than 3 s), a high saturation current (291 μA), appropriate linear range (up to 9.97 mmol L−1 of glucose, R2 = 0.9994), good repeatability (RSD 2.4, 2.2 and 1.5% for 2, 30, 97 mmol L−1 of glucose), low limit of detection (0.059 mmol L−1, S/N = 3) and good stability. Additionally, this biosensor could be successfully applied for glucose determination in real samples with good accuracy. These results proved the principle of enzymatic glucose biosensor development based on DGNs as the basis for further investigations.

Surface plasmon resonance technique is highly sensitive to various processes taking place on a metal film and it has emerged as a powerful label-free method to study molecular binding processes taking place on a surface. Another important but less explored area of applications is the use of hybrid methods which combine electrochemistry with optical methods for better monitoring and understanding of biochemical processes. A detection method based on surface plasmon resonance was developed for ampicillin, applying electrochemical techniques for the elaboration and characterization of the aptasensing platform used in this study. Ampicillin is a broad-spectrum β-lactam antibiotic, used both in human and veterinary medicine for the treatment and prevention of primary respiratory, gastrointestinal, urogenital, and skin bacterial infections. It is widely used because of its broad spectrum and low cost. This widespread use can result in the presence of residues in the environment and in food leading to health problems for individuals who are hypersensitive to penicillins. The gold chip was functionalized through potential-assisted immobilization, using multipulse amperometry, first with a thiol-terminated aptamer, as a specific ligand and secondly, using the same procedure, with mercaptohexanol, used to cover the unoccupied binding sites on the gold surface in order to prevent the nonspecific adsorption of ampicillin molecules. After establishing the optimal conditions for the chip functionalization, different concentrations of ampicillin were detected in real time, in the range of 2.5–1000 μmol L−1, with a limit of detection of 1 μmol L−1, monitoring the surface plasmon resonance response. The selectivity of the aptasensor was proven in the presence of other antibiotics and drugs, and the method was successfully applied for the detection of ampicillin from river water.

This review (with (318) refs) describes progress made in the design and synthesis of morphologically different metal oxide nanoparticles made from iron, manganese, titanium, copper, zinc, zirconium, cobalt, nickel, tungsten, silver, and vanadium. It also covers respective composites and their function and application in the field of electrochemical and photoelectrochemical sensing of chemical and biochemical species. The proper incorporation of chemical functionalities into these nanomaterials warrants effective detection of target molecules including DNA hybridization and sensing of DNA or the formation of antigen/antibody complexes. Significant data are summarized in tables. The review concludes with a discussion or current challenge and future perspectives. Graphical abstract ᅟ

In this study, we produced a nanocomposite composed of Ni-Pd bimetallic nanoparticles with precise morphologies that are adorned on multiwall carbon nanotubes. Electrochemical impedance spectroscopy (EIS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to evaluate the produced material. FE-SEM and HR-TEM analysis confirmed the uniform distribution of Ni-Pd across f-MWCNT surfaces. The findings reveal that incorporating Ni-Pd nanoparticles on the surface of f-MWCNT can improve catalytic activity over Ni NPs. The manufactured electrode has garnered a lot of interest in detecting and quantifying dopamine because of its demonstrated potential for instantaneous response, real-time measurements, increased selectivity, and sensitivity. Dopamine (DA) electrochemical activity in the presence of phosphate buffer solution (PBS) as an electrolyte at pH 7 was tested utilizing CV, DPV, and amperometry techniques to explore the sensor’s performance. The finding presented here reveals a simple strategy for creating a modified electrode. The Ni-Pd/f-MWCNT-modified electrode sensor reveals a wide linear range of dopamine (2–400 µM), with a limit of detection (LOD) 0.05 µM, limit of quantification (LOQ) 0.166 µM, and sensitivity 2.116 µA/µM cm2.

In the direct electrochemical sensing of endogenous hydrogen sulfide, the utilization of triple-pulse amperometry (TPA) enables the delivery of distinct cleaning and measurement pulses, effectively mitigating electrode surface passivation due to sulfur deposition. In order to further improve the sensor’s sensitivity and selectivity, gold nanoparticles(nano-Au), platinum nanoparticles (nano-Pt), and poly(3,4-ethylenedioxythiophene) (PEDOT) were separately employed to modify electrodes for constructing electrochemical sensors. Their performance in detecting hydrogen sulfide was evaluated using constant potential amperometry (CPA) alongside TPA. Selectivity coefficients were determined based on current responses to hydrogen sulfide as well as four major interfering substances: ascorbic acid (AA), dopamine (DA), uric acid (UA), and epinephrine (EP). After quantitative comparison, the optimal solution for direct electrochemical sensing of hydrogen sulfide involved employing a PEDOT/nano-Au composite film in conjunction with TPA technology. The sensor responds to hydrogen sulfide in the concentration range 3.0–24.0 µM with a detection limit of 0.035 µM. Furthermore, the sensor demonstrates excellent repeatability and stability, rendering it suitable for continuous electrochemical monitoring of hydrogen sulfide in simulated real biological environments. Graphical Abstract

The 3D NiO hollow sphere/reduced graphene oxide (rGO) composite was synthesized according to the coordinating etching and precipitating process by using Cu 2 O nanosphere/graphene oxide (GO) composite as template. The morphology, structure, and composition of the materials were characterized by SEM, TEM, HRTEM, XPS, and Raman spectra, and the electrochemical properties were studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and amperometry. Moreover, the electrochemical activity of the composite materials with different morphologies were also investigated, which indicating a better combination of the NiO hollow sphere and the rGO. Used as glucose sensing material, the 3D NiO hollow sphere/rGO composite modified electrode exhibits high sensitivity of ~2.04 mA mM −1 cm −2 , quick response time of less than 5 s, good stability, selectivity, and reproducibility. Its application for the detection of glucose in human blood serum sample shows acceptable recovery and R.S.D. values. The outstanding glucose sensing performance should be attributed to the unique 3D hierarchical porous superstructure of the composite, especially for its enhanced electron-transfer kinetic properties.

A biosensor platform based on Au/MXene nanocomposite for sensitive enzymatic glucose detection is reported. The biosensor leverages the unique electrocatalytic properties and synergistic effects between Au nanoparticles and MXene sheets. An amperometric glucose biosensor is fabricated by the immobilization of glucose oxidase (GOx) enzyme on Nafion solubilized Au/ MXene nanocomposite over glassy carbon electrode (GCE). The biomediated Au nanoparticles play a significant role in facilitating the electron exchange between the electroactive center of GOx and the electrode. The GOx/Au/MXene/Nafion/GCE biosensor electrode displayed a linear amperometric response in the glucose concentration range from 0.1 to 18 mM with a relatively high sensitivity of 4.2 μAmM −1 cm −2 and a detection limit of 5.9 μM (S/N = 3). Furthermore, the biosensor exhibited excellent stability, reproducibility and repeatability. Therefore, the Au/MXene nanocomposite reported in this work is a potential candidate as an electrochemical transducer in electrochemical biosensors.

Introducing oxygen-vacancy into the surface of the non-enzymatic sensor is supposed to be an effective way to improve inherently low catalytic activity and specificity of non-enzymatic sensors. In this work, CuO/C was synthesized at different temperatures using metal-organic frameworks as sacrificial templates to receive additional content of oxygen-vacancy. The product with the highest oxygen vacancy was found at 400 °C (named CuO/C-400 °C), which increased catalytically active sites and enhanced the charge-transfer efficiency. The sensing performance was afterward explored by amperometry under an optimal applied potential at 0.5 V (vs. SCE), presenting a broad detection range from 5.0 µM to 25.325 mM (R 2  = 0.9998) with a sensitivity of 244.71 µA mM − 1  cm − 2 , and a detection limit of 1 µM. Furthermore, the reliability and selectivity of CuO/C-400 °C sensors were extensively explored in the presence of artificial serum/saliva samples with gradient glucose concentrations. The human blood samples were also detected with high recoveries compared with the clinical Hexokinase method. Hence, the prepared CuO/C-400 °C sensor with a broad detection range and high selectivity can be applied for the diabetes diagnosis ex vivo without further dilution for real-time analysis in practical applications.

This paper reports the development of a low-cost (< US$ 0.03 per device) immunosensor based on gold-modified screen-printed carbon electrodes (SPCEs). As a proof of concept, the immunosensor was tested for a fast and sensitive determination of S proteins from both SARS-CoV and SARS-CoV-2, by a single disposable device. Gold nanoparticles were electrochemically deposited via direct reduction of gold ions on the electrode using amperometry. Capture antibodies from spike (S) protein were covalently immobilized on carboxylic groups of self-assembled monolayers (SAM) of mercaptoacetic acid (MAA) attached to the gold nanoparticles. Label-free detection of S proteins from both SARS-CoV and SARS-CoV-2 was performed with electrochemical impedance spectroscopy (EIS). The immunosensor fabricated with 9 s gold deposition had a high performance in terms of selectivity, sensitivity, and low limit of detection (LOD) (3.16 pmol L−1), thus permitting the direct determination of the target proteins in spiked saliva samples. The complete analysis can be carried out within 35 min using a simple one-step assay protocol with small sample volumes (10 µL). With such features, the immunoplatform presented here can be deployed for mass testing in point-of-care settings.

In the present work, potato-like silver molybdate (Ag 2 MoO 4 ) microstructures were synthesized through a simple hydrothermal method. The microstructures of Ag 2 MoO 4 were characterized by various analytical and spectroscopic techniques such as XRD, FTIR, Raman, SEM, EDX and XPS. Interestingly, the as-prepared Ag 2 MoO 4 showed excellent photocatalytic and electrocatalytic activity for the degradation of ciprofloxacin (CIP) and electrochemical detection of hydrogen peroxide (H 2 O 2 ), respectively. The ultraviolet-visible (UV-Vis) spectroscopy results revealed that the potato-like Ag 2 MoO 4 microstructures could offer a high photocatalytic activity towards the degradation of CIP under UV-light illumination, leads to rapid degradation within 40 min with a degradation rate of above 98%. In addition, the cyclic voltammetry (CV) and amperometry studies were realized that the electrochemical performance of Ag 2 MoO 4 modified electrode toward H 2 O 2 detection. Our H 2 O 2 sensor shows a wide linear range and lower detection limit of 0.04–240 μM and 0.03 μM, respectively. The Ag 2 MoO 4 modified electrode exhibits a high selectivity towards the detection of H 2 O 2 in the presence of different biological interferences. These results suggested that the development of potato-like Ag 2 MoO 4 microstructure could be an efficient photocatalyst as well as electrocatalyst in the potential application of environmental, biomedical and pharmaceutical samples.