The catalysts with excellent catalytic properties and low-cost are still highly desirable in many fields, such as fuel cells. In respect of this challenge, we have synthesized high-quality platinum nanoparticles loaded nitrogen-doped graphene (Pt/NG) by using formic acid as reduction agent and commercial-available nitrogen-doped graphene (N-graphene) as supporting materials. The morphology and component characterization demonstrate that high-loading Pt nanoparticles with a mean diameter of 2.5 nm were uniformly dispersed on nitrogen-doped graphene. The resulting Pt/NG exhibit higher catalytic activity toward methanol oxidation and hydrogen evolution reaction compared with commercial Pt/C or self-synthesized platinum nanoparticles-loaded graphene. The superior catalytic performance of Pt/NG are discussed, and ascribed to the well-dispersed Pt nanoparticles and abundant edge plane sites on N-graphene. The resultant Pt/NG with high catalytic properties and cost-effective may emerge as a promising high-performance catalyst for fuel cells.The Pt nanoparticles loaded nitrogen-doped graphene (Pt/NG) was efficiently prepared by employing formic acid as the reduction agent free of any surfactant or hydrothermal process. The resultant Pt/NG exhibited superior catalytic activity toward methanol oxidation and hydrogen evolution reaction, which was ascribed to the high Pt loading and nitrogen doping.

•A novel composite, PEI capped N-doped carbon dots (NCDs@PEI), was prepared via a facile microwave-assisted method.•The as-prepared NCDs@PEI exhibited low toxicity and high catalytic effect to the anodic ECL of Ru(bpy)32+ nanosheets.•Reduced graphene oxide (rGO) was introduced to accelerate electron transfer rate and amplify the ECL signal.•The fabricated ECL sensor exhibited multifunctional application in detecting DA, BPA, CT and HQ.A multifunctional solid-state electrochemiluminescence (ECL) sensing platform based on poly(ethylenimine) (PEI) capped N-doped carbon dots (NCDs@PEI) as novel co-reactant of Ru(bpy)32+ nanosheets (RuNSs) was designed for the first time. In this route, RuNSs with large surface-to-volume ratio was used as luminophor, and NCDs@PEI, which was newly synthesized and modified in one step via a facile microwave-assisted method, was served as co-reactant. The as-prepared NCDs@PEI exhibited better catalytic effect to RuNSs than naked NCDs, due to the double enhancement contribution of NCDs and PEI to RuNSs. Simultaneously, reduced graphene oxide (rGO) was further introduced to facilitate the electron transfer and amplify the ECL signal. The developed ECL sensor (NCDs@PEI-rGO/RuNSs/GCE) exhibited desired ECL emission, with about 69-fold enhancement of the ECL intensity in comparison with RuNSs/GCE. When used as ECL probe for dopamine detection, the prepared sensor showed high sensitivity in a wide linear range of 0.01–50 μM with the detection limit of 10 nM. Moreover, the sensing platform also suggested multifunctional application for detecting other compounds including bisphenol A, catechol and hydroquinone.

•A novel H2O2 sensor was developed based on electrospun nitrogen-doped carbon nanoparticles-embedded carbon nanofibers (NCNPFs) film.•The morphology and structure of NCNPFs can be controlled by adjusting the mass concentration of PPy NPs to PAN (wt.%).•NCNPFs-12 wt.% shows highest electrocatalytic activity for H2O2 reduction and excellent sensitivity, selectivity and stability for H2O2 sensing.A novel nonenzymatic electrochemical sensor for the detection of hydrogen peroxide (H2O2) was developed based on free-standing nitrogen-doped carbon nanoparticles-embedded carbon nanofibers (NCNPFs) film, which were prepared by the carbonization of electrospun polypyrrole nanoparticles/polyacrylonitrile (PPy NPs/PAN) composite nanofibers. A series of NCNPFs-x samples with different mass concentration of PPy NPs to PAN (wt.%) were prepared. When the PPy NPs precursor is 12 wt.%, large amount of resulting NCNPs are embedded uniformly in NCNFs substrate without obvious aggregation. The as-obtained NCNPFs-12 wt.% has smaller diameter, higher content of pyrrolic-N and more defective sites, which result in high electrocatalytic activity for H2O2 reduction. The NCNPFs-12 wt.%-based H2O2 sensor shows a fast amperometric response within 2 s, and a wide linear range of 5.0 × 10−6 to 2.7 × 10−2 M with a high sensitivity of 383.9 μA μM−1 cm−2. In addition, this nonenzymatic sensor displays good selectivity, high reproducibility and long-term stability. Because of the remarkable analytical performances, the NCNPFs-12 wt.%-based electrochemical sensor shows potential applications for the detection of H2O2 in human serum and disinfectant samples with satisfactory results.

As advanced catalysts for hydrogen evolution reaction (HER), MoS2-based electrocatalysts have attracted tremendous attention due to their enhanced HER activity. Herein, a facile method is reported to prepare a new type of defect- and S-rich ultrathin MoS2 nanosheet embedded N-doped carbon nanofiber composite (MoS2/NCNFs), which demonstrates a small HER overpotential of 135 mV at 10 mA cm−2 and a large cathodic current density of 65.6 mA cm−2 at only 200 mV. Furthermore, a small Tafel slope of 48 mV dec−1, a large exchange current density of 24.2 μA cm−2, as well as superior cycling stability are obtained. This success of embedding defect- and S-rich ultrathin MoS2 nanosheets in N-doped carbon nanofibers paves a new avenue for highly efficient catalysts for HER in the near future.

A novel one-step strategy is proposed to fabricate three-dimensional (3D) graphene hydrogel (GH) by simultaneous self-assembly and reduction of graphene oxide (GO) at 90 °C under atmospheric pressure, using L-cysteine (L-Cys) as both templating and reducing agent. The preparation process can be completed within 3 h without producing any contamination, which is a fast, facile, economical and green method for the fabrication of GH. The freeze-dried product – graphene aerogel (GA) – has high mechanical strength and thermal stability, with hierarchical pore structure and large specific surface area. More importantly, the as-prepared GA exhibits outstanding adsorption capacity towards organic dyes, which could be a potential candidate for efficient adsorbents in water purification. In addition, the established method is successfully extended to the preparation of platinum nanoparticle (PtNP)-loaded 3D graphene materials via one-step simultaneous reduction and assembly of metal ions and GO. The as-obtained PtNPs/GA with free-standing structure can act as a heterogeneous catalyst for the chemical reduction of p-nitroaniline, which shows excellent catalytic activity. The developed method is promising for preparing other graphene-based multifunctional composite materials.

•A novel N-doped carbon nanodots (N–C dots)-enhanced anodic ECL of Ru(bpy)32+ system was firstly developed.•Based on electron transfer from Ru(bpy)32+* to BPA oxidation product, sensitive and selective analysis of BPA was achieved.•The proposed method was successfully to detect BPA in baby bottle and nipple, indicating its potential prospect.A novel Ru(bpy)32+-based electrochemiluminescence (ECL) sensing platform, using N-doped carbon nanodots (N–C dots) as co-reactant, was established for the sensitive and selective detection of bisphenol A (BPA). N–C dots not only could enhance the ECL signal, but also significantly improved the reproducibility and stability of Ru(bpy)32+ ECL system. The developed ECL sensing system was sensitive to detect BPA based on its efficient quenching effect on Ru(bpy)32+/N−C dots. The N–C dots-enhanced ECL mechanism and BPA-quenched ECL mechanism were investigated. Under the optimum conditions, the inhibited ECL intensity was in good linear relationship versus the concentration of BPA in the range of 0.03–1.0 μM with the detection limit of 10 nM. The relative standard deviation (RSD) for 25 successive measurements with one sensor was 1.1% and for eight different sensors was 2.5%, respectively. The fabricated sensing platform was successfully applied for the detection of BPA in baby bottle and nipple, and relatively satisfactory recoveries were obtained.A novel N-doped carbon nanodots-enhanced anodic ECL of Ru(bpy)32+ system was firstly developed for sensitive and selective detection of bisphenol A.

•A novel high fluorescent (FLQY, 25%) nitrogen and sulfur co-doped carbon dots (N,S/C-dots) are successfully prepared by one-step microwave-assisted method.•The surface state and sizes of N,S/C-dots are uniform, and the FL properties of N,S/C-dots are effectively promoted.•A label-free, selective and reversible FL sensing platform is developed for Hg2+ detection in water and bioimaging in living cells.Nitrogen and sulfur co-doped carbon dots (N,S/C-dots) with high fluorescence quantum yields (FLQY, 25%) was successfully synthesized by a one-step microwave-assisted method. In comparison with nitrogen doped C-dots (N/C-dots) prepared using the same method, the resulting N,S/C-dots featured small particle size, uniform surface state, insensitive FL properties to excitation wavelengths and environmental conditions, negligible cytotoxicity and excellent biocompatibility. Simultaneous doping of N and S effectively promoted electron-transfer and coordination interaction between N,S/C-dots and Hg2+. Thus, when used as fluorescence probe for Hg2+ label-free detection, the resulting N,S/C-dots showed good detection sensitivity and ion selectivity. The limit of detection was 2 μM; among 15 metal ions investigated, only Fe3+ showed interference to the Hg2+ detection. Fortunately, this interference could be effectively shielded using a chelating agent sodium hexametaphoshpate. The applicability of N,S/C-dots as fluorescence probe for Hg2+ detection in lake water and tap water was demonstrated. Finally, based on its favorable features of negligible cytotoxicity and excellent biocompatibility, the N,S/C-dots were successfully applied to probe Hg2+ in living cells, which broaden its application in biological system.

•Four chiral drugs were enantioseparated basically by CE using CM-β-CD.•ITC, NMR and MM were combined to provide deeper understanding of the processes.•The method may be helpful in choosing suitable chiral selectors.•The method can assist to predict chiral CE results before experiments.Four chiral drugs were enantioseparated by native beta-cyclodextrin (β-CD) and negatively charged carboxymethyl-beta-cyclodextrin (CM-β-CD) using capillary electrophoresis coupled with electrochemiluminescence detection (CE-ECL). Using 50 mM pH 5.5 Tris–H3PO4 with 10 mM CM-β-CD as a running buffer, high resolution efficiency could be obtained. With the help of isothermal titration calorimetry (ITC), nuclear magnetic resonance (NMR) and molecular modeling, the chiral recognition mechanism was comprehensively investigated. Thermodynamic parameters data from ITC revealed that CM-β-CD exhibited stronger binding affinity with analytes than β-CD, and that the driving forces of CM-β-CD responsible for chiral recognition were mainly electrostatic interactions between negatively charged CM-β-CD and positively charged analytes. In addition, from both a macroscopic and microscopic point of view, the results of NMR and molecular modeling investigation adequately confirm the conclusion by comparing the stereochemical structures of complexes. Combination of ITC, NMR and molecular modeling techniques not only can assist CE to investigate the chiral discrimination mechanism, but also can predict and guide CE enantioseparation efficiency conversely.Four chiral drugs were enantioseparated by cyclodextrin-mediated capillary electrophoresis, and higher resolution efficiency was obtained using carboxymethyl -beta-cyclodextrinas chiral selector. Isothermal titrational calorimetry, nuclear magnetic resonance and molecular modeling were combined together to investigate the recognition process.

Novel bimetallic PdxCoy alloy nanoparticle (NP)/carbon nanofiber (CNF) composites with superior electrocatalytic performances were successfully prepared by electrospinning Pd and Co precursors, i.e., Pd(acac)2 and Co(acac)2, in polyacrylonitrile followed by a thermal treatment. Uniform dispersion of PdxCoy nanoparticles in carbon nanofibers was achieved. Chemical composition and size of the resulting PdxCoy NPs, which showed a substantial effect on the electrocatalytic properties of PdxCoy/CNF nanocomposites, can be readily controlled by adjusting the feed ratio of metal precursors. In comparison with commercial Pd/C and other state-of-the-art Pd- or Pt-based catalysts, PdxCoy/CNF nanocomposites prepared in this study exhibited much higher electrocatalytic activity and stability in formic acid and methanol oxidation reactions. This improved electrocatalytic performance is very attractive for fuel cell applications and can be attributed to the unique bimetallic Pd–Co alloy formation, a modified electronic structure of Pd in PdxCoy, as well as uniform dispersion and firm embedment of PdxCoy NPs in CNF.Keywords: alloy nanoparticle; carbon nanofibers; embedded nanostructure; formic acid oxidation; PdxCoy

In spite of excellent electrochemical properties, nitrogen-doped carbon nanofibers (NCNFs) have rarely been studied in the field of electroanalysis. In this work, we investigated the electrochemical properties and biosensing performance of NCNFs prepared by a newly proposed approach. The as-obtained NCNFs present a unique free-standing structure with high flexibility which could be convenient for electrode modification. Electrochemical measurements of typical redox species including [Ru(NH3)6]3+/2+, [Fe(CN)6]3–/4–, [Fe(H2O)6]3+/2+, and dopamine indicate that the NCNFs have a larger surface area and faster electron transfer rate compared with carbon nanofibers (CNFs). The presence of high content of pyrrolic-N and abundant defective sites in NCNFs leads to an obvious positive shift of peak potential for oxygen reduction at NCNFs relative to that obtained at CNFs. The unique structure and properties greatly enhance the electrochemical performance of NCNFs. The glucose biosensor based on glucose oxidase/NCNFs shows linear ranges of 0.2–1.2 mM at −0.42 V and 0.05–3 mM at 0.40 V both with high stability. These results suggest that the NCNFs could be a convenient and stable platform for electrochemical biosensors.Keywords: electrochemistry; free-standing structure; glucose biosensing; nitrogen-doped carbon nanofibers;

Novel Pd–Ni alloy nanoparticle/carbon nanofiber (Pd–Ni/CNF) composites were successfully prepared by a simple method involving electrospinning of precursor polyacrylonitrile/Pd(acac)2/Ni(acac)2 nanofibers, followed by a thermal process to reduce metals and carbonize polyacrylonitrile. The nanostructures of the resulting Pd–Ni/CNF nanocomposites were carefully examined by a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), high-angle annular dark field (HAADF)-scanning transmission electron microscopy (STEM), energy dispersive X-ray (EDX), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and X-ray photoelectron spectra (XPS). For all the nanocomposites, the Pd–Ni alloy nanoparticles (NPs) were dispersed uniformly and embedded firmly within the framework or on the surface of CNF. The size, composition, and alloy homogeneity of the Pd–Ni alloy NPs could be readily tailored by controlling the feed ratio of metal precursors and the thermal treatment process. Cyclic voltammetric studies showed enhanced redox properties for Pd–Ni/CNF-based electrodes relative to the Ni-metal electrode and significantly improved electrocatalytic activity for sugar (e.g., glucose, fructose, sucrose, and maltose) oxidation. The application potential of Pd–Ni/CNF-based electrodes in flow systems for sugars detection was explored. A very low limit of detection for sugars (e.g., 7–20 nM), high resistance to surface fouling, excellent signal stability and reproducibility, and a very wide detection linear range (e.g., 0.03–800 μM) were revealed for this new type of Pd–Ni/CNF nanocomposite as the detecting electrode. Such detection performances of Pd–Ni/CNF-based electrodes are superior to those of state-of-the-art nonenzymatic sugar detectors that are commercially available or known in the literature.

•A sensitive ECL sensor was developed by combining Ru(bpy)32+-doped silica (Ru(bpy)32+@SiO2) nanoparticles with graphene.•The proposed sensor exhibited high sensitivity (∼10−13 M) and wide linear range for melamine.•This method was successfully applied to the detection of melamine in milk.A sensitive electrochemiluminescence (ECL) sensor for melamine analysis was fabricated based on Ru(bpy)32+-doped silica (Ru(bpy)32+@SiO2) nanoparticles and graphene composite. Spherical Ru(bpy)32+@SiO2 nanoparticles with uniform size about 55 nm were prepared by the reverse microemulsion method. Since per Ru(bpy)32+@SiO2 nanoparticle encapsulated a great deal of Ru(bpy)32+, the ECL intensity has been greatly enhanced, which resulted in high sensitivity. Due to its extraordinary electric conductivity, graphene improved the conductivity and accelerated the electron transfer rate. In addition, graphene could work as electronic channel improving the efficient luminophor amount participating in the ECL reaction, which further enhanced the ECL signal. This proposed sensor was used to melamine analysis and the ECL intensity was proportional to logarithmic melamine concentration range from 1 × 10−13 M to 1 × 10−8 M with the detect limit as low as 1 × 10−13 M. In application to detect melamine in milk, satisfactory recoveries could be obtained, which indicated this sensor having potential application in melamine analysis in real samples.

•An on-line hyphenated focusing technique combining FASI and DypH was developed in CE-AD.•This CE-based on dual focusing method was used for the detection of two 5-HT3 receptor antagonists.•The proposed method was applied for the analysis of 5-HT3 receptor antagonists in human urine.In the present work, an on-line dual focusing technique based on field-enhance sample injection (FASI) and dynamic pH junction (DypH) was developed for the analysis of two 5-hydroxy-tryptamine type 3 receptor (5-HT3) antagonists ondansetron (Ond) and tropisetron (Tro) by capillary electrophoresis with amperometric detection (CE-AD) system. By preparing the sample in a lower conductivity (FASI condition) and lower pH value (DypH condition) matrix relative to the background electrolyte (BGE) solution, a simple and effective dual focusing approach, FASI–DypH was achieved. In this stacking mode, a large amount of analytes could be electrokinetically injected into the capillary and stacked at the boundary of the sample and the BGE zone as a result of deprotonation and decrease in the electric field. Effects of separation, detection and FASI–DypH focusing conditions were investigated in detail. Under the optimum conditions, good separation for Ond and Tro was achieved within 8 min. In comparison with the conventional CE-AD analysis method, the present dual focusing technique enabled the enhancement factors in terms of peak heights to reach 357-fold and 345-fold for Ond and Tro, respectively. The limits of detection (LODs) (S/N = 3) for Ond and Tro were 2 nM and 5 nM, respectively. The intraday and interday repeatabilities (RSDs) were less than 4.5% and 2.9% for peak height and migration time, respectively. The proposed method was successfully applied for the analysis of Ond and Tro in human urine sample.

Pt nanoparticle (NP)-loaded 1-aminopyrene functionalized reduced graphene oxide composites (Pt/1-AP–rGO) were synthesized by a simple polyol process. The morphology and structure of the resulting composites were characterized by transmission electron microscopy, Raman spectroscopy and X-ray diffraction. In comparison with Pt/–rGO, the resulting Pt/1-AP–rGO exhibited much better dispersibility. Higher dispersion and smaller size of Pt NPs was also observed on 1-AP functionalized rGO. As a result, Pt/1-AP–rGO showed higher catalytic activity, better anti-poisoning ability and stability for methanol oxidation. Meanwhile, it also displayed better electrocatalytic performance toward H2O2. The strategy presented here offers an efficient way for the preparation of high-performance electrocatalysts, which will find promising applications in biosensors and fuel cells.

We report on a novel type of nanocomposite for use in the electrooxidation of formic acid in fuel cells. The material is composed of palladium nanoparticles (Pd-NPs) and carbon nanofibers (CNFs) and was prepared by electrospinning of the precursors Pd(acac)2 and polyacrylonitrile, respectively, followed by thermal treatment to generate in-situ Pd-NPs that are well dispersed within the CNF framework. The nanocomposite was characterized by TEM, high-resolution TEM, SEM, XRD, Raman spectroscopy, and XPS. The size of the Pd-NPs ranges from 12 to 82 nm, depending on the temperature for carbonization (700–1,000 °C). The length and width of the CNF is in the order of tens of micrometers and 300 to 500 nm, respectively. TEM and XPS studies indicate that the Pd-NPs are firmly embedded in the CNF, resulting in a good electrochemical stability of the composite. The electrocatalytic properties of the composite with respect to the oxidation of formic acid were studied by cyclic voltammetry and chronoamperometry. They showed a distinctly improved electrocatalytic activity and stability compared to a commercial Pd-on-carbon catalyst. The Pd/CNF composite carbonized at 900 °C was found to display the best performance.

•CE–ECL technique was developed for the determination of two antipsychotic drugs perphenazine (PPH) and fluphenazine (FPH).•High sensitivity, wide linear range, and good repeatability could be obtained by this method.•The proposed method was applied for the analysis of PPH and FPH in human urine.The coupling of end-column tris (2,2′-bipyridyl) ruthenium (II) electrochemiluminescence (ECL) detection with capillary electrophoresis (CE) was developed for the analysis of two antipsychotic drugs, perphenazine (PPH) and fluphenazine (FPH). The parameters related to CE separation and ECL detection, including the detection potential, the buffer pH value and concentration, the separation voltage, and Ru(bpy)32+ concentration, were investigated in detail. Under optimum conditions, PPH and FPH were well separated and detected within 11 min. The linear ranges were 0.1–5 μM for PPH, and 0.1–7.5 μM for FPH, respectively. The limits of detection of PPH and FPH were 5 and 10 nM (S/N=3). The relative standard deviations (n=3) of the ECL intensity and the migration time were less than 2.5 and 0.65% in a day, and less than 3.4 and 1.7% in different three days. The proposed method was successfully applied to determine PPH and FPH in spiked urine samples with satisfactory results.Based on the fact that the light emission of Ru(bpy)32+ ECL could be enhanced by PPH and FPH containing a tertiary amines group dramatically, CE–ECL has been established for rapid separation and sensitive detection of PPH and FPH. The proposed method was successfully applied to the analysis of two analytes in human urine samples.

Free-standing nitrogen-doped carbon nanofiber (NCNF) films based on polyacrylonitrile (PAN) were prepared simply by the combination of electrospinning and thermal treatment. We reused the nitrogen-rich gas generated as the byproduct of PAN at elevated temperature, mainly NH3, for surface etching and nitrogen doping. The as-obtained NCNFs exhibited a rougher surface and smaller diameter than pristine carbon nanofibers. Despite the decreased total N content, a significant increase in the content of pyrrolic-N was observed for the NCNFs. In application to electrochemistry, the free-standing NCNF films showed comparable catalytic activity with a close four-electron pathway to a commercial Pt/C catalyst in alkaline medium toward oxygen reduction reaction (ORR), which can be attributed to the nitrogen doping and high hydrophilicity. More importantly, the ORR current density on the NCNFs only dropped 6.6% after 10000 s of continuous operation, suggesting an enhanced long-time durability. In addition, the NCNFs also showed better electrocatalytic selectivity than Pt/C. Our work reveals a facile but efficient approach for the synthesis of free-standing NCNF films as a promising alternative to Pt-based electrocatalysts in fuel cells.

Gold dendritic nanostructures with hyperbranched architectures were synthesized by the galvanic replacement reaction between nickel wire and HAuCl4 in aqueous solution. The study revealed that the morphology of the obtained nanostructures strongly depended on experimental parameters such as the HAuCl4 solution concentration, reaction temperature, and time, as well as stirring or not. According to the investigation of the growth process, it was proposed that gold nanoparticles with rough surfaces were first deposited on the nickel substrate and that subsequent growth preferentially occurred on the preformed gold nanoparticles, finally leading to the formation of hyperbranched gold dendrites via a self-organization process under nonequilibrium conditions. The electrochemical experiment results demonstrated that the as-obtained gold dendrites exhibited high catalytic activity toward ethanol electrooxidation in alkaline solution, indicating that this nanomaterial may be a potential catalyst for direct ethanol fuel cells.Keywords: ethanol electrooxidation; galvanic replacement reaction; gold dendritic nanostructures; nickel wire;

Pd nanoparticle-loaded carbon nanofiber composite (Pd/CNF) was prepared via electrospinning and following carbonization treatment. Thanks to this method, the synthesis of CNF and loading Pd nanoparticles were integrated into a simple one-step, and the CNF support did not suffer from any surface functionalization treatment and could keep the robust framework. The morphology and structure of Pd/CNF were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results indicated that uniform Pd nanoparticles were firmly embedded in CNF with face-centered cubic structure. Compared with the commercial Pd/C catalyst, the as-prepared Pd/CNF exhibited higher electrocatalytic activity and better stability toward methanol oxidation.Pd nanoparticle-loaded carbon nanofiber composite (Pd/CNF) was prepared via electrospinning and following carbonization treatment. The electro-oxidation methanol on Pd/CNF paste (PdCFP) electrode was controlled by a diffusion process. PdCFP electrode exhibited enhanced electrocatalytic performance toward methanol electro-oxidation in terms of activity and stability.

This work expanded the knowledge of the use of chemometric experimental design in optimizing of six antihistamines separations by capillary electrophoresis with electrochemiluminescence detection. Specially, central composite design was employed for optimizing the three critical electrophoretic variables (Tris–H3PO4 buffer concentration, buffer pH value and separation voltage) using the chromatography resolution statistic function (CRS function) as the response variable. The optimum conditions were established from empirical model: 24.2 mM Tris–H3PO4 buffer (pH 2.7) with separation voltage of 15.9 kV. Applying theses conditions, the six antihistamines (carbinoxamine, chlorpheniramine, cyproheptadine, doxylamine, diphenhydramine and ephedrine) could be simultaneous separated in less than 22 min. Our results indicate that the chemometrics optimization method can greatly simplify the optimization procedure for multi-component analysis. The proposed method was also validated for linearity, repeatability and sensitivity, and was successfully applied to determine these antihistamine drugs in urine.Highlights► Central composite design was firstly introduced to CE-ECL scheme for optimum ► conditions. ► The optimization procedure for multi-component analysis was greatly simplified. ► The interaction effects are included indicating the experimental design was indispensable.

In the paper, a novel carbon nanofiber paste electrode (CFPE) was fabricated and firstly used as a sensitive amperometric detector in capillary electrophoresis (CE) for the simultaneous determination of three β-blockers: sotalol, alprenolol and atenolol. Compared with the bare carbon paste electrode, the CFPE exhibited enhanced oxidation peak current responses to the analytes due to its excellent electrocatalytic activities, high conductivity and large effective surface area. Subsequently, effects of several important factors such as detection potential, pH and concentration of running buffer, separation voltage and injection time on the analysis were investigated. Under the optimum conditions, the three analytes could be separated and detected in a phosphate buffer (pH 8.5) within 11 min. The linear ranges were 0.1–100 μM for sotalol, 0.2–150 μM for alprenolol and 0.1–50 μM for atenolol and the detection limits were as low as 10−8 M magnitude (S/N=3). Moreover, the CFPE exhibited good repeatability and long-time stability. The proposed method was applied to determine the three β-blockers in spiked urine samples with satisfactory assay results. The good performance, low cost and straightforward preparation method of CFPE demonstrated that it could be used as a detector for CE–amperometric detection system for drug analysis.Highlights► Carbon nanofibers were produced by electrospinning technique. ► A carbon nanofiber paste electrode was fabricated by this electrospun material. ► This electrode was firstly used as a sensitive amperometric detector in CE. ► Proposed method was applied to determine three β-blockers in human urine.

In this paper, the simultaneous determination of dihydroxybenzene isomers (catechol (CC) and hydroquinone (HQ)) was investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) at electrospun carbon nanofiber-modified carbon paste electrode (ECF-CPE) in 0.1 M PBS (pH 7.0) solution. The ECF was prepared by combination of electrospinning and thermal treatment processes, and was modified on the surface of CPE directly without further oxidation treatment and immobilization. Compared to the bare CPE electrode, ECF-CPE exhibits much higher electrocatalytic activity toward the oxidation of dihydroxybenzene isomers with increasing of peak current and decreasing of potential difference (ΔEp) between the oxidation and reduction peaks. CV and DPV results show that the isomers can be detected selectively and sensitively at modified CPE with peak-to-peak separation about 110 mV. Under the optimized condition, the detection limits of CC and HQ are 0.2 and 0.4 μM (S/N = 3) with linear ranges of 1–200 μM in the presence of 50 μM isomer, respectively. The proposed method was successfully applied to the simultaneous determination of CC and HQ in real sample of lake water with reliable recovery. The attractive electrochemical performances and facile preparation method made this novel electrode promising for the development of effective dihydroxybenzene sensor.

The first detailed examination of non-aqueous capillary electrophoresis with electrochemical and electrochemiluminescence detections (NACE-EC/ECL), separation parameters and their interactions via central composite design was presented. This concept was demonstrated by examining the optimization separation conditions of seven antihistamines (chlorpheniramine, cyproheptadine, diphenhydramine, doxylamine, methapyrilene, terfenadine, and triprolidine) by NACE-EC/ECL. To evaluate the NACE separation quality, the chromatography resolution statistic function (CRS−1 function) with regard to the resolution and migration time was established as the response variable. The influences of three experimental variables (buffer apparent pH value (pH*), buffer (TBAP) concentration, and separation voltage) on the response were investigated. A set of optimal conditions was obtained from central composite design: 9.2 mM TBAP in ACN (pH* 4.0) and voltage (12.7 kV), and under these optimum conditions, the seven antihistamines could be well separated in less than 10 min. The obtained electropherograms indicated that the dual EC/ECL detection system was indispensable since the six antihistamines (except for triprolidine) displayed both EC and ECL response, whereas triprolidine only displayed the EC response. This work is instructive for investigators in simplifying the NACE-EC/ECL development procedures for multi-component analysis.

A simple and rapid solution-phase synthesis of dendritic gold nanostructures with hyperbranched architecture is demonstrated in this report. Further investigations revealed that the morphology of the synthesized sample depended on proper parameters such as reagent concentration, reaction temperature, reagent addition sequence and stir. Moreover, the dendritic gold nanostructures exhibited a good electrocatalytic activity toward methanol electro-oxidation. When compared with sea-urchinlike and flowerlike gold nanostructures which were prepared by varying the parameters of experiment, dendritic gold nanostructures showed the highest surface-enhanced Raman scattering (SERS) sensitivity using 4-aminothiophenol (4-ATP) as probe molecules. The dendritic gold nanostructures may find potential applications in catalysis, SERS and biosensor.Graphical abstractDendritic gold nanostructures with hyperbranched architecture, sea-urchinlike and flowerlike gold nanostructures were presented at room temperature. The dendritic gold nanostructures exhibited both a good electrocatalytic activity toward the oxidation of methanol and a good SERS activity.Research highlights► Dendritic, sea-urchinlike and flowerlike gold nanostructures. ► Room temperature. ► Good electro-oxidation of methanol and SERS activity.

A novel electrochemiluminescence (ECL) sensor based on tris(2,2′-bipyridyl) ruthenium(II) (Ru(bpy)32+)/electrospun carbon nanofiber (CNF)/Nafion composite films was demonstrated for the determination of atropine. The voltammetric and ECL behaviors of the presented sensor were investigated. The results indicated that the addition of CNF in the composite films could increase the current and ECL intensity of Ru(bpy)32+, which were subjected to diffusion-controlled processes. Under optimal experimental conditions, the proposed ECL sensor exhibited a wide linear range (r = 0.9967) of 1 × 10−7–1 × 10−4 M with a detection limit (S/N = 3) of 1 × 10−7 M for atropine. The relative standard deviation for 1 × 10−5 M atropine is 2.86% (n = 7), and the present ECL sensor displayed outstanding stability. The ECL sensor was also utilized for the determination of atropine in urine samples, and the recovery was in the range of 81%–88%.

High-yield octahedral gold nanocrystals of ~45 nm in size have been facilely synthesized by one-pot reduction of HAuCl4 using formic acid in cetyltrimethylammonium bromide (CTAB) aqueous solution. The results showed that CTAB can promote the formation of single-crystalline nucleation and preferentially adsorb on the (111) planes of gold nanocrystals, resulting in the formation of octahedral gold nanocrystals. Formic acid acted as not only a mild reducing agent, but also could promote the formation of (111) facet. The octahedral gold nanocrystals exhibited similar cyclic voltammetry (CV) curves to single-crystal Au (111) electrode and excellent electrocatalytic activity for methanol oxidation. This synthetic strategy may open new route for facile synthesis of shape-controlled metal nanoparticles.

A facile wet-chemical method was developed to prepare a novel Pt nanoparticle-loaded carbon nanofiber (Pt/CNF) electrode. Without using any stabilizer or pretreatment procedure, large amounts of Pt nanoparticles could be well deposited on the surface of the electrospun CNF electrode at room temperature, as revealed by scanning electron microscopy (SEM). The effect of the precursor concentration on the formation of Pt catalysts was investigated to optimize the performance of the proposed hybrid electrode. When applied to the electrochemical detection of hydrogen peroxide (H2O2), the Pt/CNF electrode exhibited low overpotential, fast response and high sensitivity. A low detection limit of 0.6 μM with wide linear range of 1–800 μM (R = 0.9991) was achieved at the Pt/CNF electrode, which was superior to that obtained with other H2O2 electrochemical sensors reported previously. In addition, the Pt/CNF electrode showed good selectivity for H2O2 detection in the presence of ascorbic acid (AA), acetaminophenol (AP) and uric acid (UA) under physiological pH condition. The attractive analytical performances and facile preparation method made this novel hybrid electrode promising for the development of effective H2O2 sensors.Highlights► Electrospun carbon nanofiber (CNF) electrode was used as effective supporter for deposition of Pt catalysts without any pretreatment and modification procedure. ► Pt nanoparticles were well dispersed on the CNF electrode via a simple wet-chemical reaction without any surfactant or stabilizer. ► The Pt/CNF electrode exhibited low overpotential for electrochemical reduction of H2O2. ► Fast response, high sensitivity and good selectivity for H2O2 detection were obtained with the Pt/CNF hybrid electrode.

The tricyclic antidepressants (TCA) imipramine (Imi) and trimipramine (Tri) were successfully analyzed by capillary electrophoresis (CE) coupling with Tris(2,2-bipyridyl) ruthenium(II)-based (Ru(bpy)32+) end-column electrochemiluminescence (ECL) detection. The addition of β-CD to the running buffer was found to enable baseline separation of the two analytes and the addition of acetonitrile (ACN) as an organic additive to improve the repeatability and sensitivity of the CE method. Under the optimized separation and detection conditions (50 mM PBS (pH = 7.0) and 2 mM Ru(bpy)32+ in the ECL detection cell, 20 mM Tris (pH = 2.0), 0.2 mM β-CD and 20% ACN (v/v) as running buffer), wide linear ranges of 0.1–5 μM and 0.1–5 μM were achieved, with the correlation coefficients of 0.9990 (n = 8) and 0.9980 (n = 8) for Imi and Tri, respectively. Detection limits 5 nM and 1 nM (S/N = 3) were obtained for Imi and Tri, respectively. The method was also successfully applied for the determination of Imi in pharmaceutical dosage form.

Xanthine (Xa) determination is of considerable importance in clinical analysis and food quality control. Therefore, a sensitive nonenzymatic amperometric sensor for Xa based on carbon nanofibers (CNFs) has been proposed. The CNFs, which were prepared by electrospinning technique and subsequent thermal treatment, were used to modify carbon paste electrode (CNF-CPE) to construct the amperometric sensor device without any oxidation pretreatment. In application to Xa electrochemical determination, the CNF-CPE exhibited high electrocatalytic activity and fast amperometric response. Various experimental parameters, such as pH and applied potential were optimized. Under the optimal conditions, the dynamic linear range of Xa was 0.03–21.19 μM (R = 0.9992) with the detection limit low to 20 nM (S/N = 3). With good selectivity and sensitivity, the present system was successfully applied to estimate the freshness of fish and determine Xa in human urine, which provides potential application in food quality control and clinical analysis.

We have developed a novel nickel nanoparticle-loaded carbon fiber paste (NiCFP) electrode for enzyme-free determination of ethanol. An electrospinning technique was used to prepare the NiCF composite with large amounts of spherical nanoparticles firmly embedded in carbon fibers (CF). In application to electroanalysis of ethanol, the NiCFP electrode exhibited high amperometric response and good operational stability. The calibration curve was linear up to 87.5 mM with a detection limit of 0.25 mM, which is superior to that obtained with other transition metal based electrodes. For detection of ethanol present in liquor samples, the values obtained with the NiCFP electrode were in agreement with the ones declared on the label. The attractive analytical performance and simple preparation method make this novel material promising for the development of effective enzyme-free sensors.

A novel composite electrode has been developed using electrospun carbon nanofibers (CNF) and the ionic liquid 1-butyl-4-methylpyridinium hexaflurophosphate (PFP). The highly pure CNF without any pretreatment exhibited very low background noise and high voltammetric responses. When applied to sensing of biomolecules under physiological conditions, the CNF/PFP electrode provided attractive electrochemical performances, such as high sensitivity and good selectivity for simultaneous detection of dopamine, ascorbic acid and uric acid, guanine and adenine, as well as high signal-to-noise ratio and good stability for amperometric detection of NADH.

A rapid and simple method was demonstrated for the analysis of atropine, anisodamine, and scopolamine by nonaqueous capillary electrophoresis (NACE) coupled with electrochemiluminescence (ECL) and electrochemistry (EC) dual detection. The mixture of acetonitrile (ACN) and 2-propanol containing 1 M acetic acid (HAc), 20 mM sodium acetate (NaAc), and 2.5 mM tetrabutylammonium perchlorate (TBAP) was used as the electrophoretic buffer. Although a short capillary of 18 cm was used, the decoupler was not needed and the separation efficiency was good. The linear ranges of atropine, anisodamine, and scopolamine were 0.5–50, 5–2000, and 50–2000 μM, respectively. For six replicate measurements of 100 μM scopolamine, 15 μM atropine, and 200 μM anisodamine, the RSDs of ECL intensity, EC current, and migration time were less than 3.6%, 4.5%, and 0.3%, respectively. In addition, because the organic buffer was used, the working electrode (Pt) was not easily fouled and did not need reactivation. The method was also applied for the determination of these three alkaloids in Flos daturae extract.

We demonstrate here for the first time the synthesis of squashed dodecahedron gold nanocrystals (SDGn). The SDGn is a singly twinned nanocrystal bound by {110} planes and separated by one {111} twinning plane. An atom structural model and the formation mechanism of SDGn are also proposed.

We have developed a novel electrochemical oxalic acid (OA) sensor based on the palladium nanoparticle-loaded carbon nanofiber (Pd/CNF) composites. These composites with large amounts of spherical nanoparticles well dispersed on the carbon nanofibers (CNF) were produced by combination of electrospinning technique with thermal treatment method. When applied to oxidation of OA, the Pd/CNF modified carbon paste electrode (Pd/CNF-CPE) exhibited high electrocatalytic performances with fast voltammetric responses and notably decreased overpotential compared to the bare and even the CNF modified CPE. A detection limit of 0.2 mM with linear ranges of 0.2–13 mM and 13–45 mM can be obtained at the Pd/CNF-CPE. Based on its high sensitivity and good selectivity, the proposed method was applied to determination of OA in spinach, and the satisfactory results confirmed the applicability of this sensor in practical analysis.

Carbon nanofibers (CNFs), a novel carbon nanomaterial, have the similar conductivity and stability to carbon nanotubes (CNTs). The main distinguishing characteristic of CNFs from CNTs is the stacking of graphene sheets of varying shapes, producing more edge sites on the outer wall of CNFs than CNTs, which can facilitate the electron transfer of electroactive analytes. The unique chemical and physical properties make CNFs exceptional candidates for electrode materials and promising candidates as immobilization substrates. This review is an attempt to give an overview on electrochemical biosensors based on CNFs and their various applications. We discussed the application of CNFs as electrode material in electroanalysis, as well as their functionalization and surface immobilization. Vertically aligned carbon nanofibers (VACNFs) as substrates for the immobilization of biological molecules have also been discussed.

Nonaqueous capillary electrophoresis (NACE) has been widely used in pharmaceutical, environmental, and biological analyses. A great variety of organic solvents are used in NACE, and their physical and chemical properties are different from each other. Therefore, different organic solvents can be selected for NACE according to the different analytes and the detection methods, which extends the application of capillary zone electrophoresis (CZE). In this review, the recent advances in the application of NACE were summarized, including its advantages compared with aqueous CZE, detection methods, sample preconcentration, application in real samples, and future research trends.

A novel and simple method for the direct and quantitative determination of L-tryptophan (Trp), L-tyrosine (Tyr) and L-cysteine (Cys) was proposed in this work. Carbon nanofibers (CNFs), made by electrospinning technique, were used to modify carbon paste electrode (CPE) without any treatment to study the electrochemical behaviors of the three amino acids using cyclic voltammetry (CV) and constant potential amperometric method. The results demonstrated that the CNFs modified carbon paste electrode (CNF-CPE) exhibited high electrocatalytic activity and good analytical performance towards the oxidation of the three amino acids. The linear ranges of Trp, Tyr and Cys were 0.1–119, 0.2–107 and 0.15–64 μM with correlation coefficients of 0.9994, 0.9985 and 0.9996, respectively. All the detection limits of the analytes were 0.1 μM (S/N = 3). In addition, the CNF-CPE displayed good reproducibility, high sensitivity and good selectivity towards the determination of the amino acids, making it suitable for the determination of Trp, Tyr and Cys in clinical and medicine.

Electrospun carbon nanofiber-supported bimetallic PtxAu100−x electrocatalysts (PtxAu100−x/CNF) were prepared by electrochemical codeposition method. The composition of PtAu bimetallic nanoparticles could be controlled by varying the ratio of H2PtCl6 and HAuCl4. Scanning electron microscopy images showed that bimetallic nanoparticles had coarse surface morphology with high electrochemically active surface areas. X-ray diffraction analysis testified the formation of PtAu alloys. PtxAu100−x/CNF electrocatalysts exhibited improved electrocatalytic activities towards formic acid oxidation by providing the selectivity of the reaction via dehydrogenation pathway and suppressing the formation/adsorption of poisoning CO intermediate, indicating that PtxAu100−x/CNF is promising electrocatalyst in direct formic acid fuel cells.

Large-scale arrays consist of dendritic single-crystalline Ag/Pd alloy nanostructures are synthesized for the first time. A simple galvanic replacement reaction is introduced to grow these arrays directly on Ag substrates. The morphology of the products strongly depended on the reaction temperature and the concentration of H2PdCl4 solution. The mechanism of the formation of alloy and the dendritic morphology has been discussed. These alloy arrays exhibit high surface-enhanced Raman scattering (SERS) activity and may have potential applications in investigation of “in situ” Pd catalytic reactions using SERS. Moreover, electrocatalytic measurements suggest that the obtained dendritic Ag/Pd alloy nanostructures exhibit electrocatalytic activity toward the oxidation of formic acid.

A novel nonenzymatic glucose sensor was developed based on the renewable Ni nanoparticle-loaded carbon nanofiber paste (NiCFP) electrode. The NiCF nanocomposite was prepared by combination of electrospinning technique with thermal treatment method. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that large amounts of spherical nanoparticles were well dispersed on the surface or embedded in the carbon nanofibers. And the nanoparticles were composed of Ni and NiO, as revealed by energy dispersive X-ray spectroscopy (EDX) and X-ray powder diffraction (XRD). In application to nonenzymatic glucose determination, the renewable NiCFP electrodes, which were constructed by simply mixing the electrospun nanocomposite with mineral oil, exhibited strong and fast amperometric response without being poisoned by chloride ions. Low detection limit of 1 μM with wide linear range from 2 μM to 2.5 mM (R = 0.9997) could be obtained. The current response of the proposed glucose sensor was highly sensitive and stable, attributing to the electrocatalytic performance of the firmly embedded Ni nanoparticles as well as the chemical inertness of the carbon-based electrode. The good analytical performance, low cost and straightforward preparation method made this novel electrode material promising for the development of effective glucose sensor.

Capillary electrophoresis coupled with electrochemiluminescence detection was developed for the separation and determination of dioxopromethazine hydrochloride (DPZ) enantiomers. Performance parameters of the proposed method were evaluated. An improved separation of DPZ enantiomers could be achieved after adding boric acid to buffer. The enantiomers were completely separated with running buffer of 16.5 mM β-CD in 25 mM tris-H3PO4–40 mM H3BO3 at pH 2.5. The proposed method was successfully applied to the separation and determination of DPZ enantiomers in human urine with a liquid–liquid extraction procedure.

A novel carbon-nanofiber-modified carbon-paste electrode (CNF-CPE) was employed for the simultaneous determination of dopamine (DA), ascorbic acid (AA) and uric acid (UA) with good selectivity and high sensitivity. The CNFs were prepared by combination of electrospinning technique with thermal treatment method and were used without any pretreatment. In application to determination of DA, AA and UA in the ternary mixture, the pristine CNF-CPE exhibited well-separated differential pulse voltammetric peaks with high catalytic current. Low detection limits of 0.04 μM, 2 μM and 0.2 μM for DA, AA and UA were obtained, with the linear calibration curves over the concentration range 0.04–5.6 μM, 2–64 μM and 0.8–16.8 μM, respectively.

Palladium nanoparticle-loaded carbon nanofibers (Pd/CNFs) were prepared by electrospinning and subsequent thermal treatment processes. Pd/CNFs modified carbon paste electrode (Pd/CNF-CPE) displayed excellent electrochemical catalytic activities towards dopamine (DA), uric acid (UA) and ascorbic acid (AA). The oxidation overpotentials of DA, UA and AA were decreased significantly compared with those obtained at the bare CPE. Differential pulse voltammetry was used for the simultaneous determination of DA, UA and AA in their ternary mixture. The peak separation between UA and DA, DA and AA was 148 mV and 244 mV, respectively. The calibration curves for DA, UA and AA were obtained in the range of 0.5–160 μM, 2–200 μM, and 0.05–4 mM, respectively. The lowest detection limits (S/N = 3) were 0.2 μM, 0.7 μM and 15 μM for DA, UA and AA, respectively. With good selectively and sensitivity, the present method was applied to the determination of DA in injectable medicine and UA in urine sample.

Aristolochic acids (AAs) are the main bioactive ingredients in the most of Aristolochia plants, which are used to make dietary supplements, slimming pills and Traditional Chinese Medicines (TCMs). Excessive ingestion of AAs can lead to serious nephropathy. Therefore, quantitative analysis and quality control for the plants containing AAs is of great importance. In this paper, capillary electrophoresis (CE) with electrochemical detection (ED) at a 33 μm carbon fiber microdisk electrode (CFE) has been applied to detect AA-I and AA-II in Aristolochia plants. Under the optimum conditions: detection potential at 1.20 V, 2.0 × 10−2 mol L−1 phosphate buffer solution (PBS) (pH 10.0), injection time 25 s at a height of 17 cm and separation voltage at 12.5 kV, the AA-I and AA-II were baseline separated within 5 min. Low detection limits for AA-I and AA-II were 4.0 × 10−8 mol L−1 and 1.0 × 10−7 mol L−1, respectively. Wide linear ranges were from 4.0 × 10−8 mol L−1 to 1.9 × 10−5 mol L−1 and 1.0 × 10−7 mol L−1 to 5.0 × 10−5 mol L−1 for AA-I and AA-II, respectively. The proposed method has been successfully applied to analyze AAs contents in plant extracts. The results indicated that the contents of AAs in each part of Aristolochia debilis Sieb. Et Zucc. plant were different. Meanwhile, the CE–ED method was utilized for fingerprint analysis of medicine herbs. Six herbs (Radix aristolochiae, Fructus aristolochiae, Herba aristolochiae, Caulis aristolochiae manshuriensis, Caulis clematidis armandii, Caulis akebiae) were well distinguished by comparing their electropherograms obtained by CE–ED method.

An all-purpose approach to immobilize ionic liquids onto solid supports is proposed by chemical grafting on a polyelectrolyte carrier.

A stable and redox active monolayer of para-mercaptodiazoaminobenzene was achieved by direct diazotization on 4-aminothiophenol/Au monolayer. Electrochemical and surface-enhanced Raman scattering spectroscopy measurements were conducted before and after the reaction. The CV result, which exhibits two steps of reversible one-electron and one-proton oxidation and reduction, confirmed the grafting structure on 4-ATP monolayer.

Self-doped poly(o-aminobenzenesulfonic-acid-co-aniline) (abbr. p(oASA-co-Ani)) nanoflowers were prepared by an electrochemical preparation without any other supporting electrolytes. The images of scanning electron microscope show that the nanoflowers are uniform. In addition, the results obtained from the cyclic voltammetry indicate that it exhibits a remarkable electroactivity at an extended pH range from 3 to 13.5.

Carbon nanofibers (CNFs), a novel carbon nanomaterial, have the similar conductivity and stability to carbon nanotubes (CNTs). The main distinguishing characteristic of CNFs from CNTs is the stacking of graphene sheets of varying shapes, producing more edge sites on the outer wall of CNFs than CNTs, which can facilitate the electron transfer of electroactive analytes. The unique chemical and physical properties make CNFs exceptional candidates for electrode materials and promising candidates as immobilization substrates. This review is an attempt to give an overview on electrochemical biosensors based on CNFs and their various applications. We discussed the application of CNFs as electrode material in electroanalysis, as well as their functionalization and surface immobilization. Vertically aligned carbon nanofibers (VACNFs) as substrates for the immobilization of biological molecules have also been discussed.

As advanced catalysts for hydrogen evolution reaction (HER), MoS2-based electrocatalysts have attracted tremendous attention due to their enhanced HER activity. Herein, a facile method is reported to prepare a new type of defect- and S-rich ultrathin MoS2 nanosheet embedded N-doped carbon nanofiber composite (MoS2/NCNFs), which demonstrates a small HER overpotential of 135 mV at 10 mA cm−2 and a large cathodic current density of 65.6 mA cm−2 at only 200 mV. Furthermore, a small Tafel slope of 48 mV dec−1, a large exchange current density of 24.2 μA cm−2, as well as superior cycling stability are obtained. This success of embedding defect- and S-rich ultrathin MoS2 nanosheets in N-doped carbon nanofibers paves a new avenue for highly efficient catalysts for HER in the near future.

A novel one-step strategy is proposed to fabricate three-dimensional (3D) graphene hydrogel (GH) by simultaneous self-assembly and reduction of graphene oxide (GO) at 90 °C under atmospheric pressure, using L-cysteine (L-Cys) as both templating and reducing agent. The preparation process can be completed within 3 h without producing any contamination, which is a fast, facile, economical and green method for the fabrication of GH. The freeze-dried product – graphene aerogel (GA) – has high mechanical strength and thermal stability, with hierarchical pore structure and large specific surface area. More importantly, the as-prepared GA exhibits outstanding adsorption capacity towards organic dyes, which could be a potential candidate for efficient adsorbents in water purification. In addition, the established method is successfully extended to the preparation of platinum nanoparticle (PtNP)-loaded 3D graphene materials via one-step simultaneous reduction and assembly of metal ions and GO. The as-obtained PtNPs/GA with free-standing structure can act as a heterogeneous catalyst for the chemical reduction of p-nitroaniline, which shows excellent catalytic activity. The developed method is promising for preparing other graphene-based multifunctional composite materials.

We have developed a novel electrochemical oxalic acid (OA) sensor based on the palladium nanoparticle-loaded carbon nanofiber (Pd/CNF) composites. These composites with large amounts of spherical nanoparticles well dispersed on the carbon nanofibers (CNF) were produced by combination of electrospinning technique with thermal treatment method. When applied to oxidation of OA, the Pd/CNF modified carbon paste electrode (Pd/CNF-CPE) exhibited high electrocatalytic performances with fast voltammetric responses and notably decreased overpotential compared to the bare and even the CNF modified CPE. A detection limit of 0.2 mM with linear ranges of 0.2–13 mM and 13–45 mM can be obtained at the Pd/CNF-CPE. Based on its high sensitivity and good selectivity, the proposed method was applied to determination of OA in spinach, and the satisfactory results confirmed the applicability of this sensor in practical analysis.