查看更多>>摘要：The complex oxides with the ordered perovskite-like structure were carefully examined as enzyme-free electrochemical sensors with a stable and sensitive response to the hydrogen peroxide for the first time. The ordered perovskites PrBaCo2O6-8 (PBC) and PrBaCo1.9Ni0.1O6-8 (PBCN) were synthesized by glycine-nitrate combustion method and characterized by means of XRD, SEM and XPS. Thermogravimetry and iodometric titration were implemented to evaluate the average oxidation states of B-site transition metals and the oxygen non-stoichiometry. Electrochemical properties of double perovskites towards H2O2 were comprehensively studied by a combination of cyclic voltammetry and chronoamperometry in an alkaline media. The PBCN-based electrode is shown to possess a considerable sensitivity (1078.31 mu A cm-2 mM-1) with a suitable detection limit and linear range. In addition, the influence of more oxidized forms of B-site cations, oxygen vacancies, and diffusion coefficient values at peroxide electrocatalytic properties were discussed.
查看更多>>摘要：A new chemiresistive sensor for detection of hexanal, as a volatile organic compound, was constructed based on a nanocomposite of gold nanoparticles and molecularly imprinted polymers. Changes in volatile organic compounds levels are associated to a variety of health problems like cancers. The nanocomposite was drop casted on the surface of an interdigitated electrode and the electrical response and resistance change of the sensor were analyzed by fast Fourier transform cyclic voltammetry in the presence of different concentrations of hexanal gas. The ability of the sensor to detect hexanal in the headspace of different biological matrices like cell culture medium, serum, plasma, urine, and saliva was also examined. The calculated limit of detection and linear range of the sensor were determined as 1.1 ppm and 2.5-300 ppm respectively. The sensor showed three times more sensitivity to hexanal than other volatile organic compounds with similar carbon atom number in the selectivity test.
查看更多>>摘要：We report on a hollow NiCoSe2/C prepared through a step-by-step derivatization method as high-performance supercapacitor electrode. Hollow nickel-cobalt bimetallic layered hydroxide (NiCo-LDH) derived from a typical zeolitic imidazolate framework (ZIF-67) was selenized to NiCoSe2 via in situ selenylation, which was then coated with a layer of carbon via the hydrothermal method by using glucose as the carbon source. The electrochemical performances of the as-synthesized NiCoSe2/C are investigated, and the results indicate that the hol low NiCoSe2/C exhibits considerable specific capacity of 232.6 mAh g(-1) at 1 A g(-1), good rate capability of 72.6% and high capacity retention of 88.3% after 5,000 cycles. Compared with ZIF-67, NiCo-LDH and NiCoSe2, the greatly enhanced electrochemical performances of the NiCoSe2/C can be due to the hollow nanostructure of NiCoSe2, enhanced electrical conductivity by the introduction of Se and C, and inhibited volume changes during the redox cycling from the protection of the carbon layer.
查看更多>>摘要：Adenine and guanine, whose current concentrations are considered an important parameter for the diagnosis of various diseases, also play a key role in the storage of genetic information. Thus, accurate and sensitive determination of deoxyribonucleic acids is of great importance for clinical diagnosis. Conducting polymers and various nanoparticle-based composites have good electrical conductivity and improved sensitivity. Therefore, in this study, a novel voltammetric sensing platform based on the combination of silane-modified magnetitemetal organic framework-carbon nanotube (magnetite MOF@CNT) and electropolymerizable anthracene-carbazole compound (3) was constructed for simultaneous determination of adenine and guanine. MALDI-TOF and 1H NMR spectroscopic methods were used to elucidate the structure of compound 3. Also, the characterization of magnetite MOF@CNT nanohybrid was carried out by transmission electron microscope (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Raman, Fourier-transform infrared (FTIR), X-ray diffraction (XRD) spectroscopies. A glassy carbon electrode (GCE) was firstly modified with magnetite MOF@CNT nanohybrid then electropolymerization of compound 3 was performed on modified GCE (magnetite MOF@CNT-pC). The voltammetric sensor behaviors of adenine and guanine were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in phosphate buffer (pH 7.0). Under the optimized conditions, voltammetric responses were linearly increased in the concentration ranges from 0.5 to 35.0 mu M for simultaneous determination of adenine and guanine with the limit of detections (LODs) as 285.0 and 244.0 nM, respectively. The real sample analyses were successfully carried out for the determination of adenine and guanine in calf thymus sperm with validation by HPLC. The newly constructed magnetite MOF@CNT-pC sensor platform offers a promising candidate for simultaneous voltammetric determination of adenine/guanine and could be applied in widespread fields such as microbiology or biotechnology.
Reyes-Morales, JoshuaGlasscott, Matthew W.Pendergast, Andrew D.Goines, Sondrica...
8页
查看更多>>摘要：Obtaining mechanistic insight into interfacial electron and ion transfer processes remains imperative to developing a comprehensive understanding of synthetic and biological processes. There is fundamental interest in the coupled electron-ion transfer processes characteristic of heterogeneous reactions at three-phase boundaries comprised of two immiscible liquids and a solid electrode surface. To probe reactivity at the three-phase boundary, we report a multifaceted analysis of ferrocene (Fc) oxidation in toluene droplets of diverse sizes. In one experiment, we study Fc oxidation in a large toluene macrodroplet. In a second experiment, we study Fc oxidation in an array of toluene microdroplets. We performed each experiment with and without an ionic liquid, trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)amide. Upon Fc oxidation in the oil phase without supporting electrolyte, the ferrocenium cation (Fc(+)), which is soluble in water, is expelled from the oil phase to maintain charge neutrality. Because Fc is only slightly soluble in water (similar to 40 mu M), reversing the scan to reduce Fc(+) in the aqueous phase generates a Fc precipitate adjacent to the three-phase boundary. This observation was confirmed by correlated optical microscopy. Increasing the voltammetric scan rate elucidated sequential versus concerted ion transfer mechanisms, which are shown to be highly dependent on the droplet size and the presence of trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)amide in the toluene phase. Differences in voltammetric responses are supported by finite element simulations.
Ketwong, TulakarnHalabaso, Eric RabangThi Kim Anh NguyenAreeprasert, Chinnathan...
11页
查看更多>>摘要：This study reports a comparative study on the integration of double-layer capacitive activated carbon with CuO, which imposes pseudocapacitive activity to the electrode materials, for supercapacitor application in the presence of different electrolytes. The activated carbon was prepared from different pilot-scale char production procedures. The CuO/activated char (CuO/AC) electrode material with an exceptional electrochemical performance was efficiently produced by slow pyrolysis or by hydrothermal carbonization through the chemical activation to produce activated biochar (ABC) or activated hydrochar (AHC). The specific surface area and total pore volume of the produced ABC was 810-1008 m(2) g(-1) and 0.53-0.79 cm(3) g(-1), respectively. In a three-electrode cell, the CuO/ABC electrode material exhibited superior specific capacitances of 495 and 274F g(-1) in 2 M KOH and 1 M Na2SO4 electrolytes, respectively. The energy density of the symmetric supercapacitor produced in KOH electrolyte was 11.42 Wh kg(-1) with power density of 600 W kg(-1) and could maintain up to 6.17 Wh kg(-1) at 6,000 W kg(-1). In Na2SO4 aqueous electrolyte, the cells achieved the maximum energy density of 6.01 Wh kg(-1) at 700 W kg(-1). In the cyclic stability test, the initial capacitance was retained at 92.7% after 5,000 cycles by using Na2SO4 as the electrolyte, signifying that CuO/ABC is a promising electrode material which can be mass production from pilot-scale to perform the excellent electrochemical energy storage capacity with outstanding long-cycling life.
查看更多>>摘要：A new ceramic carbon polyaniline electrode material, namely Sonogel-Carbon-polyaniline (SNG-C-PANI), was synthesized using high-power ultrasound. The synthesis conditions were optimized by means of a full factorial design. The electroactivity of polyaniline, previously characterized by means of Raman spectroscopy, is retained into the sonogel matrix. After the synthesis and the subsequent characterization, the electrode material was applied in the electrochemical determination of a benchmark analyte, 4-chloro-3-methylphenol (PCMC), providing excellent figures of merit, e.g. high sensitivity (5.19 x 103 +/- 110 mu A/mM center dot cm2) and low limit of detection (0.36 mu M), as well as suitable selectivity and reproducibility (%RSD < 4%). Besides the electroactive surface can be restored by performing a cyclic electrochemical treatment or simple mechanical polishing, minimizing fouling phenomena commonly found in conducting polymer layer-based sensors. The electrochemical detection of other chlorophenols of interest was also performed, obtaining remarkable analytical results. Finally, the electrochemical sensor was successfully applied in spiked tap water analyses.
查看更多>>摘要：Volatile organic compounds (VOCs) are a major constituent of human breath which is being investigated as potential targets to be sensed in e-nose biosensors. Limonene is found in the breath of cirrhotic liver patients and can be used for early diagnosis using electrochemical biosensors. In the current study, electrochemical detection of limonene was performed using monolayer thiolated gold nanoparticles. Three different types of monolayer thiol capped AuNPs were synthesized by the modified biphasic method with the different molar ratios (2:1 and 1:1) of hydrogen tetrachloroaurate (III) (HAuCl4-2H(2)O) and thiol groups: dodecanethiol, decanethiol, and hexanethiol. Thiol capped AuNPs were characterized physiochemically and for electrochemical sensing at different factors such as pHs, scan rate, current stability. Based on the best presented electrochemical results, hexanethiol AuNPs were selected as a sensor for analyzing the electrochemical detection of limonene as an analyze. Hexanethiol capped AuNPs based biosensing platform showed high sensitivity with a LOD of 0.2 mmol L-1 as observed via its DPV, and high specificity when was used against another VOC standard. The sensor was also used to detect limonene in the real breath sample of the clinical patient, besides testing the lab standard of limonene. The breath sample of cirrhotic patients was collected and tested for the presence of limonene by using GC-MS. The quantity of limonene measured via GC-MS was 800 ppm in cirrhotic patients and electrochemical sensor measurements of limonene were almost the same providing confidence over quantitative detection of the synthesized hexanethiol capped AuNPs based biosensing platform in this study.
查看更多>>摘要：The review presents the application potential of elimination voltammetry with linear scan (EVLS) in the electroanalysis of organic and inorganic electroactive substances. This innovative method can be considered a software tool that transforms the total current-voltage records measured at different scan rates into elimination functions providing new useful information about a given electrode process. Some EVLS functions are capable of separating overlapped voltammetric signals, identifying the adsorbed state of the analyze, and detecting the preceding chemical reaction before the electron transfer. EVLS finds use in solving the mechanisms of electrode processes and determining significant physicochemical parameters, such as charge transfer coefficients and electrochemical equilibrium protonation constants. This review selects and draws attention to certain problems that may accompany EVLS in voltammetric experiments on solid electrodes.
查看更多>>摘要：The interactions between nucleic acids and nanomaterials have been often utilized to design the electrochemical biosensor due to easy preparation, adsorptive tunability and high sensitivity. In this study, we have prepared a new electrochemical biosensor for Pb2+ detection based on GR5 DNAzyme/Ti3C2Tx Mxenes modified glassy carbon electrode (GR5 DNAzyme/Ti3C2Tx Mxenes-GCE). GR5 DNAzyme is an RNA-cleavage-type DNAzyme that shows high specificity towards Pb2+. With the presence of Pb2+, the cleavage of GR5 DNAzyme is activated at a ribo-adenine (rA) site in the substrate stranded DNA, leading to the unwinding of double-helix structure. This can enhance the adsorptive property of Ti3C2Tx Mxenes toward GR5 DNAzyme, which favors the ion intercalation into the Ti3C2Tx Mxenes and induces the increase of oxidation peak current. Therefore, we have successfully applied GR5 DNAzyme/Ti3C2Tx Mxenes-GCE to detect Pb2+ with a linear range from 0.5 to 32 nM and a detection limit of 0.1 nM. This electrochemical biosensor is simple, sensitive and selective for Pb2+ determination that it should find some potential applications in food safety inspection and environmental monitoring.
NSTL
Elsevier