Results 1 - 10 of 1130
Results 1 - 10 of 1130. Search took: 0.019 seconds
|Sort by: date | relevance|
[en] Driven by the urgent demand of high-selectively point-of-care testing device for pesticide, molecular imprinting-photoelectrochemistry (MI-PEC) was introduced into microfluidic paper-based analytical strategy to design a novel paper-based photoelectrochemical (paper-based PEC) protocol. The MI-PEC strategy was constructed based on CdTe quantum dots dotted molecular imprinted polymers (CdTe QDs@MIPs), and triggered by a common ultraviolet lamp (∼365 nm, 50$). The paper-based PEC sensor was fabricated by immobilizing CdTe QDs@MIPs on paper-based screen-printed working electrodes (WEs) via gold nanoparticles (Au NPs), which was electrodeposited on the surface of WE to improve the electron transfer efficiency for high sensitivity. Using S-fenvalerate as model analyte, the produced photocurrent from the proposed paper-based MI-PEC sensor upon ultraviolet radiation decreased with the increasing concentrations of S-fenvalerate solution, and the quenched paper-based MI-PEC showed a low detection limit of 3.2 × 10−9 mol L−1. This study has made a successful attempt in the development of highly selective and sensitive photoelectrochemical sensor for S-fenvalerate monitoring
[en] Highlights: • The Fe(II)/Fe(III) reaction is shown to be facile using a wall-jet electrode and RDE. • Deposition/stripping of iron has equally slow kinetics as in aqueous systems. • An IL based all-iron RFB is reported for the first time, energy efficiency is 37%. • An Zn–Fe complex is shown to form. In an RFB this gives an energy efficiency of 78%. • Problems resulting from the use of redox probes and urea-based DES are demonstrated. -- Abstract: In this paper we report the properties of the Fe(II)/Fe(III) reaction in a deep eutectic solvent based on choline chloride and ethylene glycol. This reaction is shown to be facile using a wall-jet electrode and rotating disc electrode. The deposition and stripping of iron exhibits equally slow kinetics as in aqueous systems. Using these two reactions an all-iron redox flow battery based on ionic liquids is reported for the first time. An energy efficiency of 37% is attained at a current density of 0.5 mA cm−2. A Zn(II)–Fe(II) complex is shown to form when zinc is oxidized by Fe(III). When this complex is applied in a redox flow battery energy efficiencies of 78% are achieved at a current density of 0.5 mA cm−2
[en] This work presents the synthesis and deposition of hybrid sol-gel coating applied on AISI 316Lstainless steel by dipping with the aim of providing corrosion protection to the substrate. On the top of this coating a potentially bioactive glass (58S) made also by sol gel method with tetraethoxysilane (TEOS), triethyl phosphate (TEP) and calcium nitrate as precursors, was applied by spray technique. This method allows the creation of a wide distribution of particles sizes on the target. Coatings were characterized by profilometry and optical and electronic microscopy. The surface integrity and corrosion resistance of the coatings in time is analyzed by electrochemical tests in simulated body fluid (SBF).It is observed some kind of detrimental effect regarding the corrosion behavior between the bioactive dots and the underneath coating. Nevertheless the entire system results promising for further investigation since the addition of 58S bioactive particles by spray method results appealing as it is a simple way to generate bioactive points on the implant surface.
[en] Controlled electrodeposition of silver onto glassy carbon, gold and indium tin oxide-coated glass substrates has been achieved from three room temperature protic ionic liquids (PILs), ethylammonium nitrate, triethylammonium methylsulfonate, and bis(2-methoxyethyl)ammonium acetate. Cyclic voltammetric, chronoamperometric, together with microscopic and X-ray techniques reveal that micro/nanostructured Ag thin films of controlled morphology, size, density, and uniformity can be achieved by tuning the electrodeposition parameters such as potential, time, types of PILs, substrate materials, and ionic liquid viscosity by altering the water content. Chronoamperometric results provide direct evidence that electrodeposition of Ag in protic ionic liquids takes place through a progressive nucleation and diffusion-controlled 3D growth mechanism. The as prepared Ag micro/nanoparticles have been employed as electrocatalysts for oxygen reduction reaction and exhibit excellent catalytic activity. The study provides promise for using protic ionic liquids as alternative electrolytes to conventional aprotic ionic liquids for electrodeposition of metals and nanostructured electrocatalysts.
[en] Highlights: ► Activation of silica gel decreased particle size and enhanced accumulation ability. ► Activated silica gel greatly increased the oxidation signal of quercetin. ► Oxidation was attributed to phenolic hydroxyl groups and transferred two electrons. ► A sensitive and simple electrochemical method was developed for quercetin detection. - Abstract: Silica gel was activated using 6.0 M hydrochloric acid, and then used to modify a carbon paste electrode. The particle size of silica gel was significantly reduced by the activation, as confirmed by scanning electron microscopy measurements. Electrochemical behaviors of K3[Fe(CN)6] on the modified electrode revealed that activated silica gel was capable of facilitating electron transfer and increasing surface area. Chronocoulometry tests indicated that activated silica gel exhibited a strong accumulation efficiency toward quercetin. As a result, activated silica gel displayed remarkable enhancement effect, and greatly increased the oxidation signals of quercetin. The oxidation mechanism of quercetin was also investigated. It was found that the oxidation of quercetin involved two electrons and two protons, occurring at two phenolic hydroxyl groups. The influences of pH value, amount of activated silica gel, accumulation potential and time on the signal enhancement of quercetin were discussed, and a novel electrochemical method was developed for the detection of quercetin. The linear range was from 5 to 100 μg L−1, and the limit of detection was 3.53 μg L−1 after 2 min accumulation. Finally, this method was successfully used in honeysuckle and tea samples.
[en] Graphical abstract: Co-Cu dendritic micro/nanostructure is achieved via electrochemical crystal growth approach. Co, as the inner core structure, is endowed the dendritic shape by affording the large overpotential during the crystal growth process. The shell metal Cu grows onto the inner core template to realize the exquisite smooth external shape or super-dendrite at low or high overpotential. Highlights: ► Dendritic Co-Cu micro/nanostructure is prepared via the electrochemical approach. ► The inner core structure is endowed the dendritic shape by affording the large overpotential. ► Shell metal grows onto inner core template to realize smooth surface/super-dendrite at low/high overpotential. - Abstract: In this study, dendritic Co-Cu is prepared to illustrate a facile strategy to acquire bimetallic dendritic core–shell structure. The core and shell metals are both obtained by electrochemical crystal growth process. The leading parameter, overpotential, endows inner core dendritic shape by surpassing the critical value. Meanwhile, it also determines Cu shell morphology from flat surface to dendritic structure by adopting different value. The Cu dendrite on Co dendritic core constructs a super-dendrite, which is regarded as a higher class of hierarchical structure. Sophisticated techniques such as field-emission scanning electron microscopy, energy dispersive spectroscopy and X-ray powder diffraction are devoted to reveal the external morphology of the as-obtained material and verify the core–shell characteristic.
[en] Graphical abstract: - Abstract: This work presents the results from the development of bio-cathodes for the application on paper-based biofuel cells. Our main goal here is to demonstrate the possibility of using different designs of air-breathing bio-cathodes and ink-based bio-cathodes for this new type of paper based electrochemical cell. The electrochemical performance for the bio-electrocatalytic oxygen reduction reaction was studied by using open circuit voltage and amperometry measurements, as well as polarization curves to probe the four-electron reduction reaction of ambient oxygen catalyzed by bilirubin oxidase (BOx). The electrochemical measurements showed that all procedures allowed the direct electron transfer from the active site of the bilirubin oxidase to the electrode surface with a limiting current density of almost 500 μA cm−2 for an air-breathing BOx cathode and 150 μA cm−2 for an ink based BOx cathode. Under a load of 300 mV a stable current density was obtained for 12 h of continuous operation.
[en] TiOxNy and VOxNy powders have been synthesized using oxide precursors and a conventional nitridation method. It enables to control of oxygen content and surface area. The electrochemical performances of the different powders have been investigated. A strong dependence on the surface area as well as on the nature of the oxynitride has been found. A typical value of 300 μF cm−2 has been determined for VOxNy powders, while TiOxNy powders only show 50 μF cm−2. In this last case it is believed that only double layer capacitance or weak redox reactions participate in charge storage mechanism while for vanadium based oxynitrides, a thin layer below the surface (≈4 Å) is involved in charge storage via faradic reactions. VOxNy electrodes can be operated in different aqueous electrolytes, but only double layer capacitance is measured in neutral electrolytes. The highest capacitance values (≈80 F g−1) are measured in KOH and fair cycling ability is achieved when the electrochemical window is limited, thus avoiding oxidative potentials.