•Novel electrochemical sensing platform for toxic TBBPA at pM level.•Remarkable synergetic effects from exfoliated graphene and DDAB composite film.•Good reproducibility, selectivity and accuracy.Graphene nanosheets (GS) were prepared via solvent exfoliation, and then hybridized with dioctadecyldimethylammonium bromide (DDAB). On the single surface of DDAB and GS film, the direct oxidation activities of tetrabromobisphenol A (TBBPA) are improved effectively, and consequently the oxidation signals enhance obviously. Interestingly, the composite of DDAB and GS exhibits remarkable synergetic effects toward the oxidation of TBBPA, and the peak currents of TBBPA further increase greatly on the DDAB-GS composite film. The signal enhancement mechanism was studied using chronocoulometry. It is found that the greatly-increased accumulation efficiency is the main reason. As a result, a novel electrochemical sensing platform was developed for TBBPA. The linear range is from 0.1 to 400 μg L−1, and the detection limit is as low as 41.8 ng L−1 (76.8 pM). The practical applications in water samples manifest that this new determination system is accurate and feasible.

•Solvothermal synthesis of FeOOH structures with different morphologies•Morphology-dependent electrochemistry of FeOOH structures•Morphology-dependent electrochemistry of FeOOH structures towards electroactive species•Perfect interfaces from FeOOH nano-rods for sensitive and simultaneous detection of diethylstilbestrol and bisphenol AFour kinds of iron hydroxide (FeOOH) structures with the morphologies of bulk, nano-sheet, nano-sphere, and nano-rod were synthesized using solvothermal processes. During synthesis different reagents were added to tune the morphology of FeOOH structures. These structures were characterized using TEM and SEM as well as from their Raman and XPS spectra. Voltammetric response of these structures as well as redox probes and endocrine disrupting compounds (EDCs) on these structures based electrodes was investigated. The morphology-dependent electrochemistry of these FeOOH structures was found. The highest redox activity of FeOOH was achieved on the FeOOH nano-rod structure based electrode, which was the best interface as well for the electrochemistry of both redox probes and EDCs. On such an interface, the highest magnitudes of both diethylstilbestrol (DES) and bisphenol A (BPA) were obtained.

•Nanostructured RF polymers with different morphology have been easily prepared.•Signal enhancement ability of RF polymers for amaranth is morphology-dependent.•Highly-sensitive electrochemical sensor has been developed for amaranth at nM level.•The accuracy and practicability of this new method has been tested by HPLC.Three kinds of nanostructured resorcinol-formaldehyde (RF) carbonized polymers were prepared in different acidic solutions such as 0.2 M HCl, 0.2 M H2SO4 and 0.2 M HAc. Measurements of scanning electron microscopy and nitrogen adsorption-desorption isotherms indicated that the morphology and surface area of the prepared polymers were heavily dependent on the used reaction medium. The oxidation behaviors of amaranth revealed that the prepared polymers displayed different electrochemical reactivity toward the oxidation of amaranth. On the surface of RF carbonized polymers, the oxidation signals of amaranth enhanced obviously, and the prepared RF-1 carbonized polymer in 0.2 M HCl was more active for the oxidation of amaranth. As a result, a novel electrochemical sensor with high sensitivity was developed for amaranth. It was used in the drink sample analysis, and the detected results consist with the values that obtained by high-performance liquid chromatography.

•Novel sensing platform for Sunset yellow and Tartrazine at nM level.•Greatly-enhanced oxidation activity toward Sunset yellow and Tartrazine.•Good accuracy and great potential application in the practical sample analysis.It is quite important to develop simple and rapid analytical methods for Sunset yellow and Tartrazine due to their high toxicity and widespread use. Using 1,3,5-benzenetricarboxylate ion (BTC3−) as the ligand and copper ions as the center, Cu-BTC frameworks with high electrochemical activity were prepared, and used to construct a novel detection platform for Sunset yellow and Tartrazine. On the surface of Cu-BTC frameworks, their oxidation signals increase greatly. The signal enhancement mechanism was studied using electrochemical impedance spectroscopy and chronocoulometry. It is found that the prepared Cu-BTC frameworks remarkably enhance the electron transfer ability and accumulation efficiency of Sunset yellow and Tartrazine. The influences of pH values, modification amount of Cu-BTC, accumulation potential and time were investigated, and a highly-sensitive electrochemical sensing system was developed. The linear range is from 0.3 to 50 nM for Sunset yellow, and from 1.0 to 100 nM for Tartrazine. The values of detection limit are evaluated to be 0.05 and 0.14 nM for Sunset yellow and Tartrazine. The sensing platform was used to determine the contents of Sunset yellow and Tartrazine in different drink samples. The results consist with the values that obtained by high-performance liquid chromatography.

•Remarkable signal enhancement ability of Cu-BTC frameworks toward DES and E2.•The electrochemical enhancement mechanism of Cu-BTC frameworks is examined.•Distinctive sensing platform for simultaneous detection of DES and E2 at nM level.It is quite important to monitor environmental estrogens in a rapid, sensitive, simple and cost-effective manner due to their wide existence and high toxicity. Using 1,3,5-Benzenetricarboxylic acid (H3BTC) as the ligand and copper ions as the center, Cu-BTC frameworks with surface area of 654.6 m2/g were prepared, and then used to construct a novel electrochemical sensing platform for diethylstilbestrol (DES) and estradiol (E2). On the surface of Cu-BTC frameworks, two oxidation waves at 0.26 V and 0.45 V are observed for DES and E2, and the oxidation signals are improved greatly. The prepared Cu-BTC frameworks not only enhance the accumulation efficiency of DES and E2, but also improve their electron transfer ability. The influences of pH value, modification amount of Cu-BTC and accumulation time were examined. As a result, a highly-sensitive, rapid and convenient electrochemical method was developed for the simultaneous determination of DES and E2, with detection limit of 2.7 nM and 1.1 nM. The practical applications manifest this new sensing system is accurate and feasible.

Graphene nanosheets (GS) were easily prepared from graphite via a one-step ultrasonic exfoliation approach using N-methyl-2-pyrrolidone (NMP) as the solvent. Compared with the widely used graphene oxide (GO) obtained by multistep chemical oxidation, the NMP-exfoliated GS exhibited apparently better electrochemical activity toward the oxidation of a series of phenols like hydroquinone, catechol, 4-chlorophenol, and 4-nitrophenol. Interestingly, the electrochemical activity of GS toward these phenols can be further enhanced by simply anodizing at 1.8 V for 2 min (denoted as EGS), reflected by the apparently enlarged oxidation peak currents in voltammograms and the obviously reduced charge transfer resistance in electrochemical impedance spectra (EIS). Characterizations by techniques like X-ray photoelectron spectra (XPS), Raman spectra, and atomic force microscopy (AFM) demonstrated that the introduction of new oxygen-containing groups or edge-plane defects and the enhanced surface roughness were responsible for the enhanced activity of EGS. Thereafter, a simple electrochemical method for the highly sensitive detection of phenols was established and the detection limits were 0.012 μM, 0.015 μM, 0.01 μM, and 0.04 μM for hydroquinone, catechol, 4-chlorophenol, and 4-nitrophenol, respectively. The facile synthesis of EGS, together with its high electrochemical activity, thus created a novel platform for developing highly sensitive electrochemical sensing systems.

•Electrospinning is a useful and efficient approach to produce uniform nanostructures.•Lithium-doped NiO nanofibers have high conductivity and large surface areas•Non-enzymatic glucose sensing was achieved on lithium-doped NiO nanofibersLithium-doped NiO nanofibers were synthesized using electrospinning followed by calcinations. The morphology, crystal structure, and electrochemical activities of these nanofibers were characterized, respectively, with scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), and electrochemical techniques. Electrocatalytic oxidation of glucose was found on these nanofibers in 0.1 M NaOH. The catalytic oxidation current was linear with the concentration of glucose in the range of 0.5 to 278 μM. The detection limit was calculated to be 0.1 μM. Lithium-doped NiO nanofiber is thus a potential electrode material for the construction of non-enzymatic glucose sensor.

•PC samples with different morphology and electrochemical activities were prepared.•Highly sensitive electrochemical sensing platform was developed for food colourants.•The accuracy and practicability was testified to be good by HPLC.It is very challenging to develop highly-sensitive analytical platforms for toxic synthetic colourants that widely added in food samples. Herein, a series of porous carbon (PC) was prepared using CaCO3 nanoparticles (nano-CaCO3) as the hard template and starch as the carbon precursor. Characterizations of scanning electron microscopy and transmission electron microscopy indicated that the morphology and porous structure were controlled by the weight ratio of starch and nano-CaCO3. The electrochemical behaviours of four kinds of widely-used food colourants, Sunset yellow, Tartrazine, Ponceau 4R and Allura red, were studied. On the surface of PC samples, the oxidation signals of colourants enhanced obviously, and more importantly, the signal enhancement abilities of PC were also dependent on the starch/nano-CaCO3 weight ratio. The greatly-increased electron transfer ability and accumulation efficiency were the main reason for the enhanced signals of colourants, as confirmed by electrochemical impedance spectroscopy and chronocoulometry. The prepared PC-2 sample by 1:1 starch/nano-CaCO3 weight ratio was more active for the oxidation of food colourtants, and increased the signals by 89.4-fold, 79.3-fold, 47.3-fold and 50.7-fold for Sunset yellow, Tartrazine, Ponceau 4R and Allura red. As a result, a highly-sensitive electrochemical sensing platform was developed, and the detection limits were 1.4, 3.5, 2.1 and 1.7 μg L−1 for Sunset yellow, Tartrazine, Ponceau 4R and Allura red. The practical application of this new sensing platform was demonstrated using drink samples, and the detected results consisted with the values that obtained by high-performance liquid chromatography.

•Compared with RGO, NMP-exfoliated GS possessed lower electron transfer resistance.•Oxidation activity of AC, G and A on NMP-exfoliated GS surface increased greatly.•A highly-sensitive electrochemical sensing platform was constructed for AC, G and A.Graphene nanosheets (GS) were easily prepared by one-step ultrasonic exfoliation of graphite powder in N-methyl-2-pyrrolidone (NMP). Compared with the widely-used reduced graphene oxides that prepared via chemical methods, the NMP-exfoliated GS exhibited higher electron transfer ability. Moreover, the resulting GS displayed higher electrochemical reactivity toward the oxidation of acetaminophen (AC), guanine (G) and adenine (A). In pH 6.5 phosphate buffer, three well-defined oxidation waves at 0.41 V, 0.69 V and 0.96 V were observed, and the oxidation peak currents were greatly enhanced on the surface of GS. As a result, a highly-sensitive electrochemical sensing platform was developed for the simultaneous detection of AC, G and A. The detection limits of AC, G and A on GS-modified electrode were evaluated to be 2.5 nM, 10 nM and 10 nM, respectively. Besides, the proposed method was successfully applied in the detection of tablet and DNA samples.

•Highly-sensitive analytical method was developed for ponceau 4R and tartrazine.•Porous alumina microfibers were prepared and used to enhance the sensitivity greatly.•It was demonstrated with drink samples, and the accuracy was tested by HPLC.Alumina microfibers were prepared and used to construct an electrochemical sensor for simultaneous detection of ponceau 4R and tartrazine. In pH 3.6 acetate buffer, two oxidation waves at 0.67 and 1.01 V were observed. Due to porous structures and large surface area, alumina microfibers exhibited high accumulation efficiency to ponceau 4R and tartrazine, and increased their oxidation signals remarkably. The oxidation mechanisms were studied, and their oxidation reaction involved one electron and one proton. The influences of pH value, amount of alumina microfibers and accumulation time were examined. As a result, a highly-sensitive, rapid and simple electrochemical method was newly developed for simultaneous detection of ponceau 4R and tartrazine. The detection limits were 0.8 and 2.0 nM for ponceau 4R and tartrazine. This new sensor was used in different drink samples, and the results consisted with the values that obtained by high-performance liquid chromatography.

Developing sensitive and simple analytical methods for tetrabromobisphenol A (TBBPA) is very important because TBBPA exists widely in the environment and its biological toxicity is high. Herein, three kinds of acetylene black (AB) films with different morphology and electrochemical reactivity were prepared, and then used to construct different electrochemical sensors for TBBPA. On the surface of AB films, the direct oxidation signals of TBBPA increase greatly, and moreover, the prepared AB films exhibit different enhancement ability toward TBBPA oxidation. The influences of pH value, amount of AB particles and accumulation time were studied on the oxidation signals of TBBPA. As a result, a sensitive electrochemical sensor based on the remarkable enhancement effects of AB film was developed for the rapid detection of TBBPA. The linear range was from 10 to 350 μg L−1, and the detection limit was 6.08 μg L−1 (cal. 11 nM). This new sensing system was used for the analysis of TBBPA in water samples, and good recoveries in the range of 99.3–104.5% were obtained.

•A simple strategy for graphene preparation was developed via one-step exfoliation.•GS/Fe2O3 hybrid and CTAB exhibited notable synergetic signal amplification effects.•An ultrasensitive electrochemical sensing platform was developed for BPA.Graphene nanosheets (GS) were easily prepared via one-step liquid exfoliation of graphite powder in N-methyl-2-pyrrolidone, and then hybridized with porous Fe2O3 microspheres, as confirmed by the measurements of transmission electron microscopy and X-ray diffraction. Scanning electron microscopy tests indicated that the surface roughness of GS-Fe2O3 hybrid was larger, and three-dimensional structure was more abundant. Compared with GS and Fe2O3 microspheres, the resulting GS-Fe2O3 hybrid remarkably increased the oxidation signals of bisphenol A (BPA). Moreover, the oxidation signals of BPA on GS-Fe2O3 hybrid surface was further enhanced greatly after addition of hexadecyltrimethylammonium bromide (CTAB). Based on the synergetic signal amplification of GS-Fe2O3 hybrid and CTAB, a novel electroanalytical method with high sensitivity was developed for BPA, and the limit of detection was as low as 2.5 nM.

•Graphene was prepared by one-step solvent exfoliation as superior electrode material.•Compared with RGO, prepared graphene exhibited stronger signal enhancement.•A widespread and highly-sensitive electrochemical sensing platform was constructed.Graphene was easily obtained via one-step ultrasonic exfoliation of graphite powder in N-methyl-2-pyrrolidone. Scanning electron microscopy, transmission electron microscopy, Raman and particle size measurements indicated that the exfoliation efficiency and the amount of produced graphene increased with ultrasonic time. The electrochemical properties and analytical applications of the resulting graphene were systematically studied. Compared with the predominantly-used reduced graphene oxides, the obtained graphene by one-step solvent exfoliation greatly enhanced the oxidation signals of various analytes, such as ascorbic acid (AA), dopamine (DA), uric acid (UA), xanthine (XA), hypoxanthine (HXA), bisphenol A (BPA), ponceau 4R, and sunset yellow. The detection limits of AA, DA, UA, XA, HXA, BPA, ponceau 4R, and sunset yellow were evaluated to be 0.8 μM, 7.5 nM, 2.5 nM, 4 nM, 10 nM, 20 nM, 2 nM, and 1 nM, which are much lower than the reported values. Thus, the prepared graphene via solvent exfoliation strategy displays strong signal amplification ability and holds great promise in constructing a universal and sensitive electrochemical sensing platform.

Protocatechuic aldehyde (PAL) is a major polyphenolic active ingredient with a variety of biological activities. Herein, the oxidation behavior and mechanism of PAL were studied using different electrode surfaces, and it was found that two-electrons were transferred. Moreover, the silica gel-modified carbon paste electrode (CPE) gave rise to a higher oxidation signal to PAL relative to the unmodified CPE, and a further signal enhancement was observed on the activated silica gel-modified CPE. Based on the remarkable surface enhancement effects of activated silica gel, a new electrochemical method with high sensitivity was developed for the determination of PAL. The linear range was from 5 to 250 μg L−1, and the detection limit was 3.24 μg L−1 (23 nM) after 1 min accumulation. The proposed method was applied in Xiangdan injection samples, and the results were consistent with the values obtained by high-performance liquid chromatography.

Different-shaped aluminas were readily prepared via hydrothermal reaction. It was found that the morphology and the electrochemical sensing properties of alumina were heavily dependent on the reaction time. When extending the reaction time from 6 h to 24 h, the obtained alumina samples changed from amorphous bumps to regular microfibers in diameter of 200 nm, as confirmed by scanning electron microscopy. Transmission electron microscopy observation revealed that longer reaction time was beneficial for the formation of porous and uniform fiber-like structures. Electrochemical tests proved that alumina microfibers were more active for the oxidation of amaranth and exhibited much higher enhancement effect, compared with alumina bumps. On the surface of alumina microfibers, the oxidation peak currents of amaranth increased remarkably. The influences of pH value, amount of alumina microfibers, and accumulation time on the signal enhancement of amaranth were discussed. As a result, a novel electrochemical method was developed for the detection of amaranth. The linear range was from 1 to 150 nM, and the detection limit was 0.75 nM after 1-min accumulation. The analytical application in drink samples was investigated, and the results consisted with the values that obtained by high-performance liquid chromatography.Graphical abstractHighlights► A facile way to tune morphology and sensing properties of alumina was developed. ► Oxidation activities of amaranth on alumina surface were morphology-dependent. ► Alumina microfibers were more active and greatly increased the signal of amaranth. ► Sensitive, rapid, selective and accurate method was developed for amaranth detection.

Platinum nanoparticles with different shapes, such as spheres, rhombs and flowerlike sheets, were in situ deposited on the surface of Pt disk electrode via reduction of 1 mM H2PtCl6 in 0.1 M H2SO4. By variation of reduction potential and time, the morphology and catalytic activity of Pt nanoparticles were readily tuned. Electrochemical tests revealed that the response of chemical oxygen demand (COD) on nano-Pt surface was shape-dependent. Compared with nanospheres and nanorhombs, the flowerlike Pt nanosheets which were deposited at −0.3 V for 2 min greatly increased the response current of COD, displaying strong signal enhancement for COD. The influences of pH value and detection potential were discussed. As a result, a novel electrochemical sensor using flowerlike Pt nanosheets as sensing film was constructed for COD, and the detection limit was 1.83 mg L−1. It was used for different lake water samples, and the results consisted with the values obtained by the national standard method.

It is quite important to monitor synthetic dyes in foods because of their potential harmfulness to human beings. Herein, alumina microfibers with porous structures were prepared via hydrothermal reaction, and then used to construct a highly sensitive platform for the detection of sunset yellow. In pH 6.5 phosphate buffer, an oxidation peak was observed for sunset yellow, and the oxidation peak currents of sunset yellow were greatly increased by alumina microfibers. The influences of pH value, amount of alumina microfibers and accumulation time on the signal enhancement of sunset yellow were discussed. As a result, a novel electrochemical method was developed for the detection of sunset yellow. The linear range was from 0.5 to 100 nM, and the limit of detection was 0.16 nM (72.4 ng L−1) after 2-min accumulation. It was applied in soft drink samples, and the detected results consisted with the values that obtained by high-performance liquid chromatography.

Protocatechuic aldehyde (PAL) is a major polyphenolic active ingredient with a variety of biological activities. Herein, the oxidation behavior and mechanism of PAL were studied using different electrode surfaces, and it was found that two-electrons were transferred. Moreover, the silica gel-modified carbon paste electrode (CPE) gave rise to a higher oxidation signal to PAL relative to the unmodified CPE, and a further signal enhancement was observed on the activated silica gel-modified CPE. Based on the remarkable surface enhancement effects of activated silica gel, a new electrochemical method with high sensitivity was developed for the determination of PAL. The linear range was from 5 to 250 μg L−1, and the detection limit was 3.24 μg L−1 (23 nM) after 1 min accumulation. The proposed method was applied in Xiangdan injection samples, and the results were consistent with the values obtained by high-performance liquid chromatography.