Portable electrochemical sensing platform based on amidated GO-MOF and PEDOT:PSS for high-efficient detection of ponceau 4R.

A promising electrochemical sensing platform for the detection of ponceau 4R in food has been fabricated based on the carboxylated graphene oxide (GO-COOH), metal-organic framework (MOF) UIO-66-NH2, and poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). To this end GO-COOH was covalently coupled with UIO-66-NH2 through amide reaction, endowing the material (GO-CONH-UIO-66) unique hierarchical pores and high chemical stability and as a result improving the conductivity of MOF and the dispersion of GO. After the addition of PEDOT:PSS into GO-CONH-UIO-66, the continuity and conductivity of the composite (PEDOT:PSS/GO-CONH-UIO-66) have been further enhanced, due to the high conductivity, favorable film-forming, and hydrophilic properties of PEDOT:PSS. Systematic electrochemical experiments confirm that the PEDOT:PSS/GO-CONH-UIO-66/GCE shows satisfactory electrochemical sensing properties towards the detection of ponceau 4R, with a wide linear detection range of 0.01-30 µM, a low limit of detection of 3.33 nM, and a high sensitivity of 0.606 µA µM-1 cm-2. The PEDOT:PSS/GO-CONH-UIO-66 sensing platform was successfully used to detect ponceau 4R in beverage, and the detection results were compared with  high-performance liquid chromatography. As a result, the PEDOT:PSS/GO-CONH-UIO-66 composite shows a promising application prospect for rapid detection of ponceau 4R in food and will play significant role in food safety detection and supervision.

Fabrication of rGO/MXene-Pd/rGO hierarchical framework as high-performance electrochemical sensing platform for luteolin detection.

A  nanocomposite of rGO/MXene-Pd/rGO with hierarchical structure based on Ti3C2Tx MXene, Pd nanoparticles, and reduced graphene oxide (rGO) was synthesized by a green approach. Ti3C2Tx MXene decorated with Pd nanoparticles (MXene-Pd) was prepared first. Then, graphene oxide (GO), MXene-Pd, and GO were coated on the surface of the glassy carbon electrode (GCE) in sequence. After each coating of the GO layer, the GO nanosheets were reduced to rGO electrochemically. The fabricated rGO/MXene-Pd/rGO hierarchical framework performs a pie structure with MXene-Pd as the stuffing and rGO nanosheets as the crust, which will be beneficial to the enhancement of its electrochemical sensing performance. As compared with other electrodes, the rGO/MXene-Pd/rGO/GCE exhibited higher electrocatalytic activity and better sensing performance for luteolin detection, with a wide linear range of 6.0 × 10-10 to 8 × 10-7 M and 1.0 × 10-6 to 1.0 × 10-5 M (oxidation peak potential Epa = 0.34 V vs. SCE), a low detection limit of 2.0 × 10-10 M, and a high sensitivity of 112.72 µA µM-1 cm-2. Moreover, the fabricated sensor also showed high selectivity, reproducibility, and repeatability toward the detection of luteolin. The real sample analysis for luteolin in honeysuckle was successfully carried out by rGO/MXene-Pd/rGO and verified with high-performance liquid chromatography (HPLC) analysis techniques with acceptable results. All the above tests indicate the promising application prospect of the rGO/MXene-Pd/rGO framework for luteolin detection in honeysuckle and other herbs containing luteolin.

High-efficient electrooxidation of ethylene glycol and ethanol on PdSn alloy loaded by versatile poly(3,4-ethylenedioxythiophene).

Developing a novel catalyst with lower noble-metal loading and higher catalytic efficiency is significant for promoting the widespread application of direct alcohol fuel cells (DAFCs). In this work, poly(3,4-ethylenedioxythiophene) (PEDOT) supported the PdSn alloy (PdSn/PEDOT) were simply synthesized and their electrocatalytic performance toward the oxidation of ethylene glycol and ethanol (EGOR and EOR) were investigated in alkaline media, respectively. In comparison with other control catalysts, the optimized Pd4Sn6/PEDOT catalyst exhibits the highest mass activity (7125/4166 mA mgPd-1) and specific activity (26/15 mA cm-2) towards EGOR/EOR. The mass activity of Pd4Sn6/PEDOT for EGOR and EOR are 11.9 and 10.9 times higher than commercial Pd/C, respectively. Moreover, chronoamperometry (CA) and successive cyclic voltammetry (CV) tests show that the CO resistance ability and durability of the Pd4Sn6/PEDOT catalyst were superior to Pd4Sn6, Pd/PEDOT and commercial Pd/C catalysts, which can be attributed to the d-band center of Pd can be effectively downshifted and the interface strain effect between electrons caused by the conjugated structure between PEDOT groups. This work provides an effective strategy for the development of highly efficient anode catalysts of DAFCs.

Engineering the highly efficient heterogeneous catalyst based on PdCu nanoalloy and nitrogen-doped Ti3C2Tx MXene for ethanol electrooxidation.

Improving the electrocatalytic performance by modulating the surface and interface electronic structure of noble metals is still a research hotspot in electrocatalysis. Herein, we prepared the heterogeneous catalyst based on the well-dispersed PdCu nanoalloy and the N-doped Ti3C2Tx MXene support (PdCu/N-Ti3C2Tx) via in situ growth of PdCu nanoparticles on the fantastic N-Ti3C2Tx sheets. By exploring the electrocatalytic properties of ethanol oxidation reaction (EOR), the composition optimized Pd1Cu1/N-Ti3C2Tx delivers higher mass activity/specific activity/intrinsic activity (2200.7 mA mgPd-1/13.1 mA cm-2/2.2 s-1), anti-poisoning ability and stability than those of Pd/N-Ti3C2Tx, Pd1Cu1/Ti3C2Tx and commercial Pd/C, which can be attributed to the modified surface electronic features of Pd by the participation of Cu atoms and N-Ti3C2Tx MXene, as well as the "metal-carrier" effect between the PdCu nanoalloy and N-Ti3C2Tx heterogeneous interface. Furthermore, the conductivity of N-Ti3C2Tx MXene can be improved by N-doping, and the abundant terminal groups (-O, -OH, -F and N) on the N-Ti3C2Tx surface can promote the electron exchange between PdCu and N-Ti3C2Tx. This work provides an effective strategy for engineering heterogeneous electrocatalysts for enhanced electrocatalytic EOR by adjusting the interfacial electronic structure of noble metals.

Fabrication of hierarchical Ru/PEDOT:PSS/Ti3C2Tx nanocomposites as electrochemical sensing platforms for highly sensitive Sudan I detection in food.

In our paper, a promising electrochemical sensing platform was fabricated with titanium carbide (Ti3C2Tx), poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), and ruthenium nanoparticles (RuNPs). First, the Shandong pancake structural PEDOT:PSS/Ti3C2Tx was prepared by physical stirring. PEDOT:PSS as the dispersant was embedded into the Ti3C2Tx nanosheets, increasing the degree of dispersion of the Ti3C2Tx nanosheets and further improving the specific surface area of the composite material. Then, RuNPs were supported on the surface of PEDOT:PSS/Ti3C2Tx to form the hierarchical ternary nanocomposite of Ru/PEDOT:PSS/Ti3C2Tx. The prepared Ru/PEDOT:PSS/Ti3C2Tx nanocomposite exhibited promising electrochemical sensing properties toward Sudan I detection with a wide detection range of 0.01 âˆ¼ 100 µM and a high sensitivity of 482.43 µA mM-1 cm-2. Moreover, the Ru/PEDOT:PSS/Ti3C2Tx sensing platform has been successfully applied for Sudan I detection in ketchup and chili paste, implying the promising application prospect of Ru/PEDOT:PSS/Ti3C2Tx in food safety testing.

One-pot synthesis of porous Pd-polypyrrole/nitrogen-doped graphene nanocomposite as highly efficient catalyst for electrooxidation of alcohols.

Herein, a ternary-nanocomposite Pd-polypyrrole/nitrogen-doped graphene (Pd-PPy/NGE) has been prepared facilely by the one-pot method. In simple terms, PPy was in-situ polymerized on the surface of NGE with PdCl42- as the oxidant, and simultaneously Pd nanopaticles were loaded on the surface of PPy or embedded in PPy particles. The obtained Pd-PPy/NGE nanocomposite exhibits promising electrocatalytic properties toward the oxidation reaction of alcohols in alkaline medium. Especially, the optimized Pd-PPy/NGE (1:50) catalyst possesses mass activity of 2176.7, 1192.7 and 498.9 mA mgPd-1 toward ethylene glycol, methanol and ethanol electrooxidation, respectively, which are 4.3, 6.7 and 2.9 times of those for commercial Pd/C catalyst. Moreover, the Pd-PPy/NGE (1:50) also shows higher anti-poisoning ability and operating stability than the Pd/C catalyst. The promising electrocatalytic performance of the Pd-PPy/NGE (1:50) for alcohols oxidation can be ascribed to the well dispersion of Pd nanoparticles, the porous and stable three dimentional structure of the composite, and the synergistic effect between different components. The structural randomness of the conducting polymer and the potential synergistic effect between the metal nanoparticles and various supports would provide broad development space for these composites as electrocatalysts in direct alcohol fuel cell.

Sandwich-structured PEDOT:PSS/MXene-PdAu/PEDOT:PSS film for highly sensitive detection of shikonin in lithospermum erythrorhizon.

Promising electrochemical sensing platforms can be constructed by two-dimensional (2D) inorganic materials, metal nanoparticles and conducting polymers (CPs) via suitable and effective composite-structural fabrication. Herein, a sandwich-structured composite film was fabricated with MXene (Ti3C2Tx), PdAu nanoparticles and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). In the fabrication, PdAu nanoparticles were first loaded on the surface of MXene nanosheets by one-pot method, preventing self-stacking and improving the dispersion of MXene nanosheets. And then, the PEDOT:PSS/MXene-PdAu/PEDOT:PSS sandwich structure was obtained with PEDOT:PSS as the upper and lower layers and MXene-PdAu as the interlayer. Indeed, the upper PEDOT:PSS film can permeate between MXene-PdAu particles and contribute to the continuity of MXene nanosheets, forming a complete conducting three-dimensional framework. The formed PEDOT:PSS/MXene-PdAu/PEDOT:PSS framework exhibits promising electrochemical sensing properties towards shikonin detection with a wide range of 0.001-35 µM, a low detection limit of 0.33 nM and a high sensitivity of 5.685 µA µM-1 cm-2. Furthermore, this sensing platform performs favorable selectivity and stability. In the actual sample testing, the sensing platform was used for shikonin detection in Lithospermum erythrorhizon and performed comparable results with high-performance liquid chromatography (HPLC), indicating the promising application prospect of PEDOT:PSS/MXene-PdAu/PEDOT:PSS film for the qualitative and quantitative analysis of shikonin.

Robust poly(3,4-ethylenedioxythiophene) granules loaded Cu/Ni-doped Pd catalysts for high-efficiency electrooxidation of ethylene glycol.

In our work, poly(3,4-ethylenedioxythiophene) (PEDOT) granules supported Cu/Ni-doped Pd electrocatalysts (PdCu/PEDOT and PdNi/PEDOT) were synthesized for ethylene glycol (EG) oxidation in alkaline medium. The amorphous PEDOT granules as the catalyst supports provide plenty of attachment sites for PdCu and PdNi nanoparticles. The optimized Pd1Cu3/PEDOT and Pd7Ni3/PEDOT catalysts both perform superior mass-based activity, area-based activity and intrinsic activity for EG oxidation as compared to other control samples. Moreover, chronoamperometry and long-term cyclic voltammetry tests demonstrate that the Pd1Cu3/PEDOT catalyst performs optimal anti-poisoning capability and catalytic durability. The outstanding electrocatalytic performance can be attributed to the favourable dispersion of Pd1Cu3 and Pd7Ni3 nanoparticles on the PEDOT granules and the synergistic effects between Pd, Cu/Ni atoms and the electron-rich conjugated structure of PEDOT. In summary, this work synthesized two Pd/PEDOT-based electrocatalysts with promising catalytic application prospect in direct ethylene glycol fuel cell (DEGFC), which may provide some theoretical support for the design and synthesis of competent electrocatalysts for DEGFC.

Caffeic acid polymer rapidly modified sponge with excellent anti-oil-adhesion property and efficient separation of oil-in-water emulsions.

The efficient treatment of high stability emulsion with small diameter and the prevention of oil contamination of materials are serious issues in the process of emulsion separation. In order to address those issues, we reported a fast and versatile hydrophilic surface coating technology that uses oxidants and diamines to synergistically promote the polymerization of caffeic acid (CA). It was found that amino groups can not only accelerate the polymerization of CA, but also promote the deposition of polymers on the sponge surface. Using silica nanoparticles to improve the roughness, superhydrophilic melamine sponge could be prepared, which exhibited excellent superhydrophlic-underwater superolephobic and anti-oil-adhesion properties. DFT simulation was employed to explore the potential mechanism of the anti-oil adhesion ability. In addition, combined with the mechanical compression strategy, the sponge exhibited a high efficiency of 99.10% with a permeation flux of 19080 ±â€¯700 Lm-2 h-1 in emulsion separation just under the action of gravity. Moreover, based on the interaction between the surfactant and the surface of the material, the separation mechanism was discussed. Overall, this work provided an advanced method for the preparation of superhydrophilic sponge with anti-oil-fouling performance, which showed great potential in dealing with practically challenging emulsified wastewater.

Functional group-rich hyperbranched magnetic material for simultaneous efficient removal of heavy metal ions from aqueous solution.

In order to achieve the purpose of simultaneous removal of coexisting heavy metal ions, in this work, functionalized magnetic mesoprous nanomaterials (Fe3O4-HBPA-ASA) with high density and multiple adsorption sites were designed and prepared. The obtained Fe3O4-HBPA-ASA was characterized by SEM, FTIR, VSM, TGA and zeta potential. Cu(II), Pb(II) and Cd(II) were chosen as the model heavy metal ions, the adsorption experiments showed that Fe3O4-HBPA-ASA showed hightheoretical adsorption capacitiesin individual system, and the maximum adsorption capacity was 136.66 mg/g, 88.36 mg/g and 165.46 mg/g, respectively. In the binary and ternary systems, the competitive adsorption leads to a decrease in the adsorption capacity of Cu(II), Pb(II) and Cd(II). However, in the ternary system with a concentration lower than 15 mg/L, the simultaneous removal rate was still higher than 90%. The adsorption isotherms and kineticswere well fitted by Langmuir and pseudo-second-order models, respectively. The XPS and density functional theory (DFT) analysis have confirmed that the adsorption of metal ions was related to various types of functional groups on the surface of Fe3O4-HBPA-ASA, while the adsorption mechanisms of Cu(II), Cd(II) and Pb(II) were different.

Novel graphene flowers modified carbon fibers for simultaneous determination of ascorbic acid, dopamine and uric acid.

A novel and sensitive carbon fiber electrode (CFE) modified by graphene flowers was prepared and used to simultaneously determine ascorbic acid (AA), dopamine (DA) and uric acid (UA). SEM images showed that beautiful and layer-petal graphene flowers homogeneously bloomed on the surface of CFE. Moreover, sharp and obvious oxidation peaks were found at the obtained electrode when compared with CFE and glassy carbon electrode (GCE) for the oxidation of AA, DA and UA. Also, the linear calibration plots for AA, DA and UA were observed, respectively, in the ranges of 45.4-1489.23 µM, 0.7-45.21 µM and 3.78-183.87 µM in the individual detection of each component. By simultaneously changing the concentrations of AA, DA and UA, their oxidation peaks appeared at -0.05 V, 0.16 V and 2.6 V, and the good linear responses ranges were 73.52-2305.53 µM, 1.36-125.69 µM and 3.98-371.49 µM, respectively. In addition, the obtained electrode showed satisfactory results when applied to the determination of AA, DA and UA in urine and serum samples.

Clean method for the synthesis of reduced graphene oxide-supported PtPd alloys with high electrocatalytic activity for ethanol oxidation in alkaline medium.

In this article, a clean method for the synthesis of PtPd/reduced graphene oxide (RGO) catalysts with different Pt/Pd ratios is reported in which no additional components such as external energy (e.g., high temperature or high pressure), surfactants, or stabilizing agents are required. The obtained catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), induced coupled plasma atomic emission spectroscopy (ICP-AES), and electrochemical measurements. The HRTEM measurements showed that all of the metallic nanoparticles (NPs) exhibited well-defined crystalline structures. The composition of these Pt-Pd/RGO catalysts can be easily controlled by adjusting the molar ratio of the Pt and Pd precursors. Both cyclic voltammetry (CV) and chronoamperometry (CA) results demonstrate that bimetallic PtPd catalysts have superior catalytic activity for the ethanol oxidation reaction compared to the monometallic Pt or Pd catalyst, with the best performance found with the PtPd (1:3)/RGO catalyst. The present study may open a new approach for the synthesis of PtPd alloy catalysts, which is expected to have promising applications in fuel cells.

A one-pot 'green' synthesis of Pd-decorated PEDOT nanospheres for nonenzymatic hydrogen peroxide sensing.

We developed a novel nonenzymatic biosensor based on palladium/poly(3,4-ethylenedioxythiophene) (Pd/PEDOT) nanocomposite modified glassy carbon electrode (GCE) for the detection of hydrogen peroxide (H2O2). Pd/PEDOT has been successfully fabricated by a facile one-pot 'green' method using H2PdCl4 as an oxidant and a source of metal nanoparticles without any surfactants and templates. The as-synthesized PEDOT nanospheres are quite uniform in size (~60 nm) without aggregation and provide a good platform for anchoring the Pd nanoparticles (NPs). Pd NPs (~4.5 nm) are homogenously dispersed on surface of PEDOT nanospheres. The Pd/PEDOT nanospheres on GCE exhibit a good electrocatalytic activity towards the H2O2 reduction. The electrochemical response of Pd/PEDOT to H2O2 exhibits a low detection limit of 2.84 µM in the range of 2.5×10(-3)-1.0 mM with a high sensitivity, good repeatability, acceptable reproducibility and good long-term stability. The good recoveries achieved in spiked human urine samples demonstrated the potential application of Pd/PEDOT for H2O2 detection.

An amperometric biosensor based on ascorbate oxidase immobilized in poly(3,4-ethylenedioxythiophene)/multi-walled carbon nanotubes composite films for the determination of L-ascorbic acid.

An amperometric L-ascorbic acid (AA) biosensor fabricated by immobilizing ascorbate oxidase (AO) in poly(3,4-ethylenedioxythiophene) (PEDOT) and multi-walled carbon nanotubes (MWCNTs) composite films was reported for the first time. The entrapment of AO in PEDOT/MWCNTs composite films was performed during an electrochemical polymerization process. The influence of various experimental conditions was examined for determining the optimum analytical performance. The response of the biosensor towards AA under the optimized conditions is linear from 0.05 to 20 mM with a detection limit of 15 µM (S/N = 3). The biosensor shows a response time of 20 s and a sensitivity of 23.95 mA M(-1) cm(-2). The apparent Michaelis-Menten constant (K(m)) and apparent activation energy (E(a)) are 19.5 mM and 21 kJ mol(-1), respectively. Moreover, the biosensor exhibits good anti-interferent ability, good reproducibility and remarkable storage stability.