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Herein, a series of La3+-doped BaSnO 3 nanorods (Ba 1-x La x SnO 3) were prepared by sol-gel method and were developed as electrochemical sensor for the electrochemical detection of ethylvanillin (EVA). The Ba 1-x La x SnO 3 sensor exhibited better electrocatalytic detection performance than that of GCE and BaSnO 3 , which is ascribed to the enhancement of conductivity and active sites after the introduction of La3+. The optimized Ba 0.995 La 0.005 SnO 3 sensor exhibited a linear range from 0.05 μ M to 130 μ M and a low limit of detection (LOD) of 8.6 nM. Mechanistic study demonstrated that the electrochemical oxidation process of EVA is involved the diffusion control process of two electrons and the same number of protons. Additionally, the proposed sensor for EVA demonstrated good anti-interference ability, repeatability (RSD ∼2.70 %), reproducibility (RSD ∼2.99 %), and stability (RSD ∼2.44 %). Moreover, the Ba 0.995 La 0.005 SnO 3 sensor has good recoveries (100.4 %–102.4 %) for the detection of EVA in real milk powder extraction sample. The as-fabricated Ba 0.995 La 0.005 SnO 3 sensor provide the possibility to detect the EVA in the real sample. • La doped BaSnO 3 based electrochemical sensor for ethyl vanillin. • La doping improved conductivity and active sites. • The superior performance of the electrochemical sensor is presented. • The sensor was successfully applied to detect ethyl vanillin in milk powder. [ABSTRACT FROM AUTHOR]

A novel sensor for sensitive determination of hydroquinone (HQ) and catechol (CC) was proposed using a Fe3O4 microspheres-graphene oxide (Fe3O4-GO) composites modified glassy carbon electrode (GCE) which was further encapsulated with chitosan (Chit-Fe3O4-GO/GCE). The excellent electrocatalytic performance is probably related to the strong synergistic effect of the composites. The proposed sensor shows a linear response for HQ and CC in wide concentration ranges from 1.5 to 150 µM and 1 to 410 µM, with detection limits ( S/ N=3) of 20 and 250 nM, respectively. Additionally, the sensor exhibits good selectivity and stability in tap water samples. [ABSTRACT FROM AUTHOR]

Abstract: In this report, a voltammetric sensor for simultaneous determination of hydroquinone (HQ) and catechol (CC) was developed at a glassy carbon electrode modified with graphene (GR/GCE). The separation of oxidation and reduction peak (ΔE) is decreased from 281 to 31mV for HQ and from 250 to 26mV for CC at GR/GCE, respectively. Separation of the oxidation peak potentials for HQ and CC was about 112mV in 0.10M acetate buffer solution (pH 4.5), and the anodic currents for the oxidation of both HQ and CC are greatly increased at GR/GCE, which makes it suitable for simultaneous determination of these compounds. Under the optimized condition, the anodic peak current of HQ is linear with the concentration of HQ from 1×10−6 to 5×10−5 M in the presence of 5×10−5 M CC. A detection limit of 1.5×10−8 M (S/N =3) can be achieved. At the same time, the anodic current of CC is linear with the concentration of CC from 1×10−6 to 5×10−5 M with a detection limit of 1.0×10−8 M (S/N =3) in the presence of 5×10−5 M HQ. The proposed sensor was successfully applied to the simultaneous determination of HQ and CC in tap water, and the results are satisfactory. [ABSTRACT FROM AUTHOR]

Highlights: [•] Metal-organic framework MIL-101 modified carbon paste electrode was fabricated. [•] The electrode enhances the electron transfer of [Fe(CN)6]3-/4- redox couple. [•] The electrode shows excellent electrocatalysis for the oxidation of DA and UA. [•] The novel electrode is attractive for electrochemical sensing application. [ABSTRACT FROM AUTHOR]

Hollow peanut-shaped NiFe 2 O 4 /CoFe 2 O 4 twinned nano-spherical shell composite materials have interconnected electron channels and excellent electrochemical performance, which prompted the use of this unique spatial structure to fabricate efficient electrochemical sensors. In this work, N-doped carbon dots (NCDs) incorporated into magnetic NiFe 2 O 4 /CoFe 2 O 4 nanoparticle shell (NiFe 2 O 4 /CoFe 2 O 4 /NCDs) modified glassy carbon electrode (GCE) was applied to construct a dual-template molecularly imprinted polymer (MIP) based electrochemistry sensor (NiFe 2 O 4 /CoFe 2 O 4 /NCDs/MIP/GCE) for the simultaneous detection of catechin (CA) and theophylline (TPH). MIP was fabricated by an in-situ electrochemical polymerization strategy based on the theoretical exploration and density functional theory (DFT) computer directional simulation to screen out the optimal functional monomer (L-arginine) and the optimal ratio between the dual template molecules (CA and TPH) and functional monomer. The materials were characterized by SEM, TEM, XRD, XPS, and TGA. Besides, electron binding energy, binding constant, and imprinting factor were investigated. With the optimal conditions, the proposed electrochemical dual detection system showed outstanding analytical performance for the simultaneous sensing of CA and TPH, with an ultralow detection limit (LOD, S/N = 3) of 1.3 nM for CA in 0.01–1 μM (R2 = 0.9956) and 1–50 μM (R2 = 0.9928), as well as a LOD of 20.0 nM for TPH in the linear range of 0.1–100 μM (R2 = 0.9939), respectively. Also, the selectivity and anti-interference performances of the fabricated sensor were performed by differential pulse voltammetry and chronoamperometry, and successfully detected the analyte from tea drinks and human urine samples with the recovery rates ranging from 98.22% to 104.76% and relative standard deviations (RSD) were 1.19%–3.81%, demonstrated the sensor has excellent stability, repeatability, and reproducibility, which paves the way for other platforms to use this nanomaterial for the detection of antioxidant in the filed food safety. • A dual template electrochemical molecularly imprinted sensor based on DFT theory guide was proposed. • Fabricate the MIP sensor based on peanut twin-like NiFe 2 O 4 /CoFe 2 O 4 /NCDs nanospheres. • The adsorption position and the electron distribution of the bonding groups were determined by molecular modeling. • Highly sensitivity MIP sensor for the simultaneous detecting of CA and TPH with ultralow LOD. [ABSTRACT FROM AUTHOR]

A novel sensing system was constructed by biomass carbon/MOF-derived Co 3 O 4 /FeCo 2 O 4 (BC/Co 3 O 4 /FeCo 2 O 4) composite decorated with glassy carbon electrode (GCE) for exploiting to determine dopamine (DA), acetaminophen (AC), and xanthine (XA) simultaneously. The BC/Co 3 O 4 /FeCo 2 O 4 composite was synthesized via a facile in-situ growth process and calcination treatment, coupled with hydrothermal reaction. This composite could appreciably enlarge the electrochemically active surface area of as-prepared sensor to promote electron transfer resulting in enhanced response signals. Applying BC/Co 3 O 4 /FeCo 2 O 4 /GCE sensor under the optimum conditions, the differential pulse voltammetry (DPV) current responses vs. concentration are linear in the wider ranges of 0.1–250 μM, 0.1–220 μM, and 0.5–280 μM, along with low detection limits (LOD, S/N = 3) of 0.04587 μM, 0.02886 μM, and 0.1209 μM for DA, AC and XA correspondingly. Moreover, the proposed sensor exhibited a satisfying selectivity, stability and reproducibility as well. Finally, this sensor had been utilized to detect DA, AC and XA successfully in real samples with satisfactorily apparent recoveries, providing a promising application for further sensing analysis. (A) The preparation process of BC/Co3O4/FeCo2O4 composite and (B) simultaneous detection of DA, AC and XA on BC/Co3O4/FeCo2O4/GCE. Image 1 • A novel electrochemical sensor based on MOF-derived Co 3 O 4 /FeCo 2 O 4 incorporated porous biomass carbon was constructed. • The proposed sensor showed preferable electrochemical sensitivity and practicality. • Simultaneous detection of dopamine, acetaminophen and xanthine in human serum samples could be achieved. • The detection limits (S/N = 3) were as low as 0.04587 μM, 0.02886 μM, and 0.1209 μM, respectively. [ABSTRACT FROM AUTHOR]

Schematic illustration of the formation of the MWCNTs−COOH/UiO-66-NH 2 /MWCNTs−COOH/GCE and the high selectivity electrochemical sensing for detecting Cd2+ and Pb2+ • An in situ growth method of UiO-66-NH 2 was developed. • Three-layer assembly of MWCNTs-COOH/UiO-66-NH 2 /MWCNTs-COOH film was fabricated. • Potentiostatic electrodeposition is a unique driving force for thin film manufacturing. • These structures of the sensor reveal high selectivity towards Pb2+ and Cd2+. • Effective rapid and simultaneous quantitative detective of Pb2+ and Cd2+ in water. In this work, an effective strategy for the fabrication of novel layer-by-layer multilayer films modified electrodes in electrochemical sensor applications. Glassy carbon electrode (GCE) surface has been modified with various multilayer films which were prepared by continuous repeated alternating electrodeposited of carboxylated multi-walled carbon nanotubes (MWCNTs−COOH) and Zr-metal-organic frameworks (UiO-66-NH 2). Newly constructed three-layer assembly of MWCNTs−COOH/UiO-66-NH 2 /MWCNTs−COOH/GCE as voltammetric sensor was adapted to simultaneous detection Cd2+ and Pb2+ by square-wave anodic stripping voltammetry (SWASV). Meanwhile, the formation of MWCNTs−COOH/UiO-66-NH 2 /MWCNTs−COOH/GCE is supported by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), X-ray photoelectron spectra (XPS), X-ray diffraction patterns (XRD), and Fourier transform infrared spectra (FT-IR), which have been researched to estimate the effect of their electrochemical detection. Here, combined the abundant adsorption sites of UiO-66-NH 2 with excellent conductivity ability of MWCNTs−COOH, and the dominant characteristics of the chelation mechanisms between amine groups and heavy metal cations, which strengthened its electrocatalytic activity. Results show that three-layer film modified GCE (MWCNTs−COOH/UiO-66-NH 2 /MWCNTs−COOH/GCE) can acquire the optimal simultaneous detection performances as the higher sensitivities to Cd2+ (0.2528 μA ppb−1) and Pb2+ (0.3012 μA ppb−1), the lower level detection limits to Cd2+ (0.090 ppb) and Pb2+ (0.071 ppb), as well as the superior linear relativity, respectively. Finally, excellent stability, repeatability and reproducibility of three-layer film modified GCE allow this sensing platform to work in practical application. The strategy that used layer by layer electrodeposition to assemble multilayer films will provide great potential for advanced applications in environment, biomedicine, human health and energy field. [ABSTRACT FROM AUTHOR]