Explore the vast range of titles available.

A voltammetric sensor is described for the determination of L-cysteine (Cys). A pencil graphite electrode (PCE) was modified with a Co(II)-Al(III) layered double hydroxide (LDH) to obtain a disposable, inexpensive and sensitive sensor for Cys. The LDH was electrochemically deposited on the PGE by chronoamperometry. The electrochemical behavior of the modified PGE was investigated by cyclic voltammetry, differential pulse voltammetry, electrochemical impedance spectroscopy, and linear sweep voltammetry. The structure and morphology of the electrodes surface were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. Experiments were conducted in optimal condition, scan rate of 10 mV. s −1 and the oxidation peak potential 0.15 V vs. saturated calomel electrode. The sensor has a linear response in the 100 pM to 0.1 μM Cys concentration range and a 100 pM detection limit. It was used to quantify Cys in a drug sample. Graphical abstract Schematic presentation of pencil graphite electrode modification with Co-Al layered double hydroxide nanaocatalyst by chronoamperometry, and its usage as an electrochemical sensor for L-cysteine determination.

We present a highly sensitive and selective nano-biosensor for rapid, stable and highly reproducible detection of ascorbic acid (AA) in the presence of dopamine, uric acid and other interferences by a three-layer sandwich arrangement of nitrogen-doped functionalized graphene (NFG), silver nanoparticles (AgNPs) and nanostructured polyaniline (PANI) nanocomposite. The enhanced AA electrochemical properties of the NFG/AgNPs/PANI electrode is attributed to the superior conductivity of the NFG-PANI and the excellent catalytic activity of AgNPs. The critical modification of the AgNPs-grafted NFG-PANI coated on very low-cost fluorine doped tin oxide electrode (FTOE) increased the charge transfer conductivity of the electrode (the resistance drops down from 11,000 Ω to 6 Ω). The nano-biosensor was used to accurately detect AA in vitamin C tablets with the recovery of 98%. The sensor demonstrated a low detection limit of 8 µM (S/N = 3) with a very wide linear detection range of 10–11,460 µM, good reproducibility and excellent selectivity performance for AA detection. The results demonstrate that this nanocomposite is a promising candidate for rapid and selective detection of AA in practical clinical samples.

Screening for hepatitis B is one of the most severe liver virus infections in the world, and due to the effect of early detection and treatment of hepatitis B disease, fast and sensitive analytical devices are highly needed. A highly sensitive voltammetric genosensor is described for hepatitis B virus (HBV) detection by depositing electrochemically Pd(II)-Al(III)-layered double hydroxide (LDH) in a short time by chronoamperometry (CA) technique on the surface of the fluorinated tin oxide electrode (FTO) that is reported for the first time. The complementary DNA sequence of the amino-labeled DNA was fixed as a probe on the carboxylic group-directed LDH film. The electrochemical behavior of the designed genosensor by the attached DNA virus was investigated using the differential pulse voltammetry (DPV), cyclic voltammetric (CV), and electrochemical impedance spectroscopy (EIS) techniques in the presence of the Fe(CN)63–/4– and at the optimum conditions has a wide linear range (1 fM to 1 μM) with the experimental detection limit of 1 fM. This genosensor was successfully implemented to measure the DNA of HBV in human serum. This modified electrode has high sensitivity and short production time, which can be a candidate for the production of a portable hepatitis B diagnostic kit.Graphical abstract

In this work, F-doped Li4Ti5O12 in the form of Li4Ti5O12-xFx (0 ≤ X ≤ 0.4) is successfully synthesized via a solid-state reaction between TiO2 (anatase), Li2CO3, and LiF. The synthesized powder is used as the anode in Li-ion batteries. X-ray diffraction (XRD) results show that the F−-doping does not change the spinel-type structure, and it has successfully doped into the crystal structure of Li4Ti5O12. The morphological and electrochemical characterization of synthesized powders is tested with the scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and charge-discharge techniques. Among the modified samples, Li4Ti5O11.7F0.3 delivers the highest capacity and cyclability. The Li4Ti5O11.7F0.3 (LTOF0.3) has a capacity of 139.7 and 134.7 mAh g−1 in the first and 100th cycles with 1 C, respectively. The retention of capacity after 100 cycles charge and discharge with 1 C for LTO and LTOF0.3 is 90.8 and 96.3%, respectively.

In this work, Ni 3 (BTC) 2 metal–organic framework (MOF) based on the nickel (II) and benzene 1,3,5-tricarboxylic acid (H 3 BTC) was synthesized on a nickel foam (NiBTC/Ni foam) using an electrochemical synthesis technique. This technique allows the formation of crystal layers overgrowing the porous Ni support at the room temperatures in a short synthesis time. The influence of some important parameters such as solvent, voltage, and synthesis time on the MOF production was investigated. The structure and morphology of the MOFs were characterized by X-ray diffraction and scanning electron microscopy. The coordination between nickel (II) and carboxylate moieties of the linker has been characterized using Fourier transform infrared spectroscopy, and the surface area of the MOF was measured by Brunauer–Emmett–Teller nitrogen adsorption–desorption technique. The thermal stability was examined with thermal gravimetric analysis method. After synthesis and characterizations, the performance of Ni foam and NiBTC/Ni foam for the electrochemical hydrogen evolution reaction (HER) were compared by the linear sweep voltammetry, electrochemical impedance spectroscopy, and the chronoamperometry. The results showed that NiBTC/Ni foam has a more catalytic activity for HER.

Natural polymers such as cellulose have interesting tribo- and piezoelectric properties for paper-based energy harvesters, but their low performance in providing sufficient output power is still an impediment to a wider deployment for IoT and other low-power applications. In this study, different types of celluloses were combined with nanosized carbon fillers to investigate their effect on the enhancement of the electrical properties in the final nanogenerator devices. Cellulose pulp (CP), microcrystalline cellulose (MCC) and cellulose nanofibers (CNFs) were blended with carbon black (CB), carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs). The microstructure of the nanocomposite films was characterized by scanning electron and probe microscopies, and the electrical properties were measured macroscopically and at the local scale by piezoresponse force microscopy. The highest generated output voltage in triboelectric mode was obtained from MCC films with CNTs and CB, while the highest piezoelectric voltage was produced in CNF-CNT films. The obtained electrical responses were discussed in relation to the material properties. Analysis of the microscopic response shows that pulp has a higher local piezoelectric d33 coefficient (145 pC/N) than CNF (14 pC/N), while the macroscopic response is greatly influenced by the excitation mode and the effective orientation of the crystals relative to the mechanical stress. The increased electricity produced from cellulose nanocomposites may lead to more efficient and biodegradable nanogenerators.

A voltammetric sensor is described for the determination of L-cysteine (Cys). A pencil graphite electrode (PCE) was modified with a Co(II)-Al(III) layered double hydroxide (LDH) to obtain a disposable, inexpensive and sensitive sensor for Cys. The LDH was electrochemically deposited on the PGE by chronoamperometry. The electrochemical behavior of the modified PGE was investigated by cyclic voltammetry, differential pulse voltammetry, electrochemical impedance spectroscopy, and linear sweep voltammetry. The structure and morphology of the electrodes surface were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. Experiments were conducted in optimal condition, scan rate of 10 mV. s.sup.-1 and the oxidation peak potential 0.15 V vs. saturated calomel electrode. The sensor has a linear response in the 100 pM to 0.1 [mu]M Cys concentration range and a 100 pM detection limit. It was used to quantify Cys in a drug sample.

In this study, graphene oxide was electrochemically deposited and reduced on a graphite sheet. The electrode surface morphology was studied by scanning electron microscopy. The performance of the modified electrode in detecting dopamine was investigated. The results indicate that the electrodeposition of reduced graphene oxide onto the electrode surface increases the dopamine oxidation current, decreases the overpotential, and reduces the charge transfer resistance. The efficiency of dopamine detection by this modified electrode was evaluated using cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. The effects of electrolyte pH, potential scan rate, electrode reproducibility, and selectivity were investigated. Furthermore, for the stability test, the chronoamperometry technique was performed, and the results demonstrated that the electrode has excellent stability. This electrode provides a low detection limit of 68 nM and a wide linear range from 0.1 to 1000 µM. For real sample analysis, measurements were successfully conducted on a dopamine ampule as a cardiovascular drug. This nanosensor takes advantage of a simple and rapid fabrication process at a low cost.

The use of renewable energy, especially water resources, through hydrogen evolution reduction (HER) is an important topic in research. In this survey, carbon cloth electrode (CCE) was applied as the working electrode, and NiBTC, Ni, Ni-Pt, and Ni-PtBTC were in situ electrosynthesized on the surface CCE as modifiers electrodes. After microstructural characterization of each modified electrode by field emission scanning electron microscopy (FE-SEM), their elemental analysis was accomplished by energy-dispersive X-ray analysis. The electrocatalytic performance of each presented modified CCEs toward HER was compared by linear scanning voltammetry and Tofel plot slope. Among these modified carbon cloth electrodes, Ni-PtBTC-modified CCE was shown the highest electroactive properties with an onset potential of 170 mV and Tafel slope of 40 mV dec −1 . The results showed a minimum charge transfer resistance ( R ct ) of 112.3 Ω cm 2 for Ni-PtBTC-modified CCE, and this modified electrode showed good stability under HER conditions despite low amount of platinum. Graphical abstract

This paper presents a dynamic model to study triboelectric charge accumulation in a variable capacitive structure with metal–dielectric interface. The presented model addresses a serious flaw of current published theoretical works related to modeling of triboelectric energy harvesters. Electrostatic analysis of the device in the contact and non-contact modes is performed. Based on the analysis of the non-contact mode, a novel technique is introduced to measure stable parasitic triboelectric charge density on the surface of the dielectric layer. Theoretical analysis for positive and negative charge accumulation is performed separately and key characteristic equations of both cases are extracted. A new measurement technique is developed to assess triboelectric charge build-up on the surface of the dielectric layer by employing a simple bridge rectifier as a test circuit. Based on the measured data, a time-dependent exponential model is suggested for triboelectric charge accumulation on the surface of the dielectric layer. The presented dynamic model is a vital asset in modeling dynamic output of triboelectric nanogenerators (TENG’s). The results show that failure to consider triboelectric charge dynamics in modeling of TENG’s would result in more than 50% error in the simulated output characteristics. Graphical abstract Charge accumulation A new surface charge evaluation technique is introduced. Triboelectric charge accumulation on the surface of dielectrics is calculated and modeled using a simple half-wave rectifier. To get to the model, discrete charge-time points are measured. The dynamic charge model presents an essential asset in simulation of the output performance of TENG’s. positive and negative charge build up is measured.