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Tenofovir disoproxil fumarate (TDF) is an antiretroviral medication with significant curative effects, so its quantitative detection is important for human health. At present, there are few studies on the detection of TDF by electrochemical sensors. This work can be a supplement to the electrochemical detection of TDF. Moreover, bare electrodes are susceptible to pollution, and have high overvoltage and low sensitivity, so it is crucial to find a suitable electrode material. In this work, zirconium oxide (ZrO2) that has a certain selectivity to phosphoric acid groups was synthesized by a hydrothermal method with zirconyl chloride octahydrate as the precursor. A composite modified glassy carbon electrode for zirconium oxide-chitosan-multiwalled carbon nanotubes (ZrO2-CS-MWCNTs/GCE) was used for the first time to detect the TDF, and achieved rapid, sensitive detection of TDF with a detection limit of sub-micron content. The ZrO2-CS-MWCNTs composite was created using sonication of a mixture of ZrO2 and CS-MWCNTs solution. The composite was characterized using scanning electron microscopy (SEM) and cyclic voltammetry (CV). Electrochemical analysis was performed using differential pulse voltammetry (DPV). Compared with single-material electrodes, the ZrO2-CS-MWCNTs/GCE significantly improves the electrochemical sensing of TDF due to the synergistic effect of the composite. Under optimal conditions, the proposed method has achieved good results in linear range (0.3~30 μM; 30~100 μM) and detection limit (0.0625 μM). Moreover, the sensor has the merits of simple preparation, good reproducibility and good repeatability. The ZrO2-CS-MWCNTs/GCE has been applied to the determination of TDF in serum and urine, and it may be helpful for potential applications of other substances with similar structures. [ABSTRACT FROM AUTHOR]

Preparation of MnS/Co 3 S 4 ErGO/GCE and schematic diagram of its electrochemical response to DA. This protocol used a two-step ion exchange method to prepare MnS/Co 3 S 4 heterostructures, with self-made cobalt chloride bicarbonate (CO (CO 3) 0.35 C 0.20 (OH) 1.10) as the precursor, sodium disulfide monohydrate as the sulfur source, and manganese chloride as the manganese source. The obtained MnS/Co 3 S 4 -ErGO was modified on a glassy carbon electrode, exhibiting electrochemically ultrasensitive ability for the redox reaction of DA determination at nanomolar concentration. [Display omitted] • An ultrasensitive DA determination sensor at nanomolar level is presented. • High selectivity, selective and good reproducibility of the sensor is obtained. • Good linear concentration ranges of DA with low LOD (2.0 nM) is observed. • The sensor is successfully applied to the detection of DA in real samples. An ultrasensitive and selective electrochemical sensor has been constructed for the quantitative assay of dopamine (DA) based on hollow tubular manganese-cobalt sulfide (MnS/Co 3 S 4) hybrids embedded on electrochemically reduced graphene oxide (ErGO). The MnS/Co 3 S 4 heterostructures were created by two-step ion exchange method, of which Co 9 S 8 with hollow tubular structures was fabricated by solvothermal method using the self-made cobalt chloride carbonate hydroxide (CO(CO 3) 0.35 Cl 0.20 (OH) 1.10) as precursor and sodium disulfide monohydrate as sulfur source and manganese chloride as manganese source. The MnS/Co 3 S 4 -ErGO/GCE could exhibit strong catalytic ability for the redox reaction of DA. Under the optimal conditions, the developed sensor exhibits a wide linear response for DA ranging from 6.0 nM to 20.0 μM by second-order derivative linear sweep voltammetry (SDLSV), with a detection limit of 2.0 nM. In addition, the developed method exhibited high sensitivity and selectivity, good reproducibility and low-cost. It is a very promising analytical method for the determination of DA in pharmaceutical and biological samples. [ABSTRACT FROM AUTHOR]

Acyclovir (Acyclovir, ACV) is an antiviral drug which, despite its favorable safety profile, can have systemic adverse effects, following improper use. This study prepared a clay-like two-dimensional transition metal carbide Ti 3 C 2 by etching Ti 3 AlC 2 with LiF and HCl. Carboxylated multi walled carbon nanotubes (Carboxylated multi-walled carbon nanotubes, MWCNTs-COOH) were combined with Ti 3 C 2 using chitosan (Chitosan, CS) as solvent and ultrasonic treatment. The nanocomposite was then modified onto the surface of a glassy carbon electrode (Glassy carbon electrode, GCE) to develop an electrochemical sensor for the detection of ACV. The Ti 3 C 2 -CS-MWCNTs-COOH/GCE nanocomposite was characterized by X-ray diffractometry (X-ray diffractometry, XRD), scanning electron microscope (Scanning electron microscope，SEM), and cyclic voltammetry (Cyclic voltammetry，CV), as well as the electrochemical impedance method (Electrochemical impedance，EIS). The successful preparation of Ti 3 C 2 -CS-MWCNTs-COOH, and the good electrochemical performance of the electrode were verified. Linear scanning voltammetry (Linear scan voltammetry，LSV) was used to quantify the ACV. The linear range of the method is wider than other works (0.05 ∼ 20.0 and 20.0 ∼ 500.0 μM), with a low detection limit (0.088 μM). The sensor achieves sensitive detection of ACV and can be used for the analysis of ACV in pharmaceutical and urine dosage forms, with recoveries of 95.5∼97.6% and 95.6∼97.5%, respectively. For the first time, this sensor utilizes clay-like Ti 3 C 2 with a larger specific surface area in combination with MWCNTs-COOH for ACV detection, which exhibits excellent immunity to interference, repeatability, reproducibility, and stability. This method provides a rapid and sensitive method for the determination of ACV, and lays foundations for developing miniaturized field rapid test detectors. [Display omitted] • Ti 3 C 2 -CS-MWCNTs-COOH/GCE sensor is for electrochemical determination of acyclovir. • Clay-like Ti 3 C 2 has higher conductivity, larger specific surface area and higher security than accordion-like Ti 3 C 2. • Wide linear range (0.05–20.0 µM and 20.0–500.0 µM), low detection limit (0.088 µM) are obtained. • The developed sensor could be used for the detection of acyclovir in urine and pharmaceuticals. [ABSTRACT FROM AUTHOR]

In this paper, a sensitive electrochemical sensor based on MnO 2 nanoparticles functionalized carboxylated multi-walled carbon nanotubes (MnO 2 -c-MWCNTs) was prepared for the determination of curcumin. The synthesized materials have been fully characterized by instruments, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical behavior of curcumin on the MnO 2 -c-MWCNTs modified glassy carbon electrode (MnO 2 -c-MWCNTs/GCE) was investigated in detail by CV and chronocoulometry (CC). The electrochemical reaction mechanism of curcumin on the modified electrode was also discussed. In 0.1 M H 2 SO 4 solution, the peak current showed a good linear dependence on curcumin concentration in the range of 0.01–1 μM and 1–80 μM, The method has high sensitivity (3.30 μA μM−1 cm−1), and the detection limit is 6.0 nM. At the same time, the MnO 2 -c-MWCNTs/GCE has good anti-interference ability and stability. In addition, the sensor was used for the accurate and rapid determination of curcumin in commercial food samples, which shows its good potential for practical application. [Display omitted] • A novel sensor MnO 2 -c-MWCNTs/GCE was prepared which for the stable determination of curcumin. • High selectivity, repeatability and reproducibility of the sensor were obtained. • Good linear concentration ranges of 0.01–1 μM and 1–80 μM curcumin with low LOD (6.0 nM) were observed. • The sensor was successfully applied to the detection of curcumin in nanomolarity in real samples. [ABSTRACT FROM AUTHOR]