•Hollow CuCo2O4 anchored on porous reduced graphene oxide (PrGO) was prepared.•The hollow CuCo2O4 polyhedron possessed plentiful catalytic active sites.•CuCo2O4/PrGO composite showed high electrocatalytic activity for glucose oxidation.•The CuCo2O4/PrGO based glucose sensor exhibited high sensitivity and application feasibility.A hollow CuCo2O4 polyhedron/porous reduced graphene oxide (PrGO) composite was prepared by simple thermolysis-induced transformation of heterobimetallic zeolitic imidazolate frameworks/porous graphene oxide (Cu-Co-ZIFs/PGO). In this strategy, the PGO was suitable for Cu-Co-ZIFs growing and anchoring, and the framework acted as sacrificial template during the formation of morphology-inherited hollow polyhedrons. In the obtained composite, PrGO sheets not only provided conduction path, but also served as protective agent to prevent the aggregation of crystals. The hollow rhombic dodecahedral CuCo2O4 possessed plentiful active sites and high electrocatalytic activity. When the composite was optimized and used for glucose sensing, it displayed good performance with a wide linear range of 0.5–3354 μM, a low detection limit of 0.15 μM (S/N = 3), a high sensitivity of 2426 μA mM−1 cm−2 and short response time (<3 s). Moreover, it could resist the interference of coexistent substances from serum sample etc. Thus the composite modified glassy carbon electrode was a promising enzyme-free glucose sensor.Figure optionsDownload full-size imageDownload high-quality image (112 K)Download as PowerPoint slide

A direct Z-scheme BiOI–CdS photocatalyst has been successfully synthesized by an electrostatic interaction mechanism and used for selective photoelectrochemical sensing of Cu2+. The BiOI–CdS photocatalyst shows higher photocatalytic activity and photoelectrochemical performance than pure CdS and BiOI. The photocurrent intensity generated by the BiOI–CdS-3 electrode is about 62 and 10 times of those induced by BiOI and CdS under visible-light irradiation, respectively. The enhanced photocatalytic activity is attributed to the formation of a hierarchical direct Z-scheme BiOI–CdS photocatalyst and its high Brunauer–Emmett–Teller (BET) specific surface area, which benefit the efficient spatial separation of charge and capture of visible-light. Moreover, a photoelectrochemical sensor is developed based on the selective replacement reaction between Cu2+ and CdS. The photoelectrochemical sensor is easily fabricated and presents good selectivity, acceptable detection range (0.1–100 μM) and detection limit (0.02 μM). It has been applied to the detection of Cu2+ ions in drinking water with a satisfactory result.

•A novel quercetin imprinted polymer-based electrochemical sensor was fabricated.•3D Pd/pGN-CNTs composite was used for the MIP sensor construction.•Density functional theory was used to explore the interaction between quercetin and p-ABA.•The sensitive and selective MIP sensor could be used for real sample detection.A novel molecularly imprinted electrochemical sensor for quercetin (QR) was fabricated via electropolymerization of para-aminobenzoic acid (p-ABA) on a three-dimensional (3D) Pd nanoparticles-porous graphene-carbon nanotubes composite (Pd/pGN-CNTs) modified glassy carbon electrode. The 3D Pd/pGN-CNTs composite was prepared by a facile one-pot hydrothermal method and it exhibited high conductivity, large surface as well as excellent electrocatalysis. The imprinting factor (IF) of MIP sensor toward QR was 3.14, which is higher than those of its analogues (i. e. morin, catechin, rutin, luteolin, and kaempferide). Based on the synergistic effect of the nanocomposite and the molecularly imprinted poly(p-ABA), the resulting electrochemical sensor presented high sensitivity and selectivity. Its linear response range was 0.01–0.50 μM, and the low detection limit was 5.0 nM (S/N = 3). The sensor also showed good reproducibility and stability. It was successfully applied to the detection of QR in food and medicine samples. In addition, theoretical calculations based on density functional theory (DFT) was conducted, and the result indicated that there was strong hydrogen bond between the QR and p-ABA.A novel QR molecularly imprinted electrochemical sensor was fabricated via electropolymerization of para-aminobenzoic acid (p-ABA) on a 3D Pd nanoparticles-porous graphene-carbon nanotubes composite (Pd/pGN-CNTs) modified glassy carbon electrode, showing high sensitivity and selectivity to QR.Download high-res image (133KB)Download full-size image

•IL-OMC was used as support to improve the conductivity of MoS2.•3D Pd/MoS2-IL-OMC composite was employed for constructing quercetin sensor.•The sensor showed high sensitivity and stability in sensing quercetin.A quercetin (QR) sensor based on Pd/MoS2-ionic liquid functionalized ordered mesoporous carbon (Pd/MoS2-IL-OMC) composite is developed. The Pd/MoS2-IL-OMC composite is prepared by using IL as anchor and OMC as substrate. MoS2 nanosheets are in situ grown on IL-OMC surface and then Pd nanoparticles are prepared on MoS2 nanosheets via chemical reduction method. As the nanocomposite combines the high conductivity of IL-OMC and the electrocatalytic activity of Pd nanoparticles and MoS2, the resulting sensor exhibits good performance towards QR, better than MoS2-IL-OMC and Pd/IL-OMC nanocomposites modified electrodes. The electrochemical sensor allows for the selective determination of QR, with a detection limit of 8.0 nM (S/N = 3), a linear range of 0.020 μM–10 μM, and a sensitivity of 150.1 μA μM−1 cm−2. It also shows good reproducibility and stability, and can be applied to the detection of QR in real samples.A 3D Pd/MoS2-IL-OMC nanocomposite is prepared and used for the electrochemical detection of QR; it presents good performance.Download high-res image (114KB)Download full-size image

A stable graphene (GR)/CdS:Mn photocatalyst was synthesized through a simple and straightforward one-pot hydrothermal method, and it exhibited enhanced photoelectrochemical (PEC) response to glutathione. The catalyst was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and UV-vis diffuse reflectance spectroscopy. It showed efficient separation of photogenerated charge carriers and low photo-corrosion. The doped Mn2+ effectively improved the band structure of CdS. Meanwhile, the introduced GR greatly enhanced and facilitated visible light absorption as well as electron transport. The GR/CdS:Mn based PEC sensor displayed more sensitive photocurrent response to glutathione than the pure CdS, CdS:Mn and GR/CdS based sensors. Furthermore, the response of the sensor was rapid and stable. The details of the additions and specific effects of each component were discussed. Under the optimized conditions, it presented wide detection range of 0.01 μM to 100 μM, low detection limit, as well as good reproducibility. The sensor could be applied to the determination of glutathione in tomato and ketchup samples.

•MWNTs-PDA@MIP for the electrochemical determination of VA was prepared.•PDA promoted the dispersion of MWNTs and anchored long-chain [VOIm]PF6 monomer.•MWNTs-PDA@MIP of VA improved the density of imprinted sites.•SWNTs-COOH was applied to enhance the response signal.•The resulting sensor exhibited sensitive and selective response to VA.A highly selective electrochemical sensor was constructed for the detection of vanillin (VA). It was fabricated by molecular imprinting on the surface of polydopamine-functionalized multi-walled carbon nanotubes (MWNTs-PDA), followed by coating on a carboxyl single-walled carbon nanotubes modified electrode. The molecularly imprinted polymer was synthesized with 1-vinyl-3-octylimidazole hexafluoride phosphorus ([VOIm]PF6) as monomer, VA as template and ethylene glycol dimethacrylate as cross-linker. The carboxyl single-walled carbon nanotube was introduced for improving conductivity and sensitivity. The sensor could recognize VA from its analogs and possible coexistent substances. The response peak current and VA concentration showed good linear relationship in the range of 0.2 μM–10 μM, with a sensitivity of 1.22 μA/μM mm2. The detection limit was 0.1 μM (S/N = 3). It was applied to the determination of VA in real samples with satisfactory results.

A novel poly(indole-co-3-methylthiophene)–ionic liquid (i.e., 1-allyl-3-vinylimidazolium bis((trifluoromethyl)sulfonyl)imide) (P(In–3-MeT)/IL) composite film was electrodeposited on a stainless steel wire for headspace solid phase microextraction. The obtained P(In–3-MeT)/IL coating was rough and showed a cauliflower-shape. It had high thermal stability (up to 450 °C) and mechanical stability and could be used for at least 180 times in solid phase microextraction (SPME) without a decrease in extraction performance. The coating exhibited high extraction capacity for some polycyclic aromatic hydrocarbons (e.g. naphthalene, 1-methylnaphthalene, acenaphthene, biphenyl, fluorene and phenanthrene) due to the strong hydrophobic and π–π interactions between the analytes and P(In–3-MeT)/IL. Through coupling with GC, good linearity (correlation coefficients higher than 0.9994), wide linear ranges (0.05–50 μg L−1) and low limits of detection (6.25–25.2 ng L−1) were achieved for these analytes. The reproducibility (defined as RSD) was 3.5–5.5% and 4.5–7.2% for single fiber (n = 5) and fiber-to-fiber (n = 5), respectively. The SPME-GC method was successfully applied for the determination of three real samples, and the recoveries for standards added were 86.8–105% for mosquito-repellent incense, 89.9–110% for cigarettes and 82.3–103% for industrial lubricant.

A novel core–shell heterostructure of CuxO nanoparticles@zeolitic imidazolate framework (CuxO NPs@ZIF-8) was successfully prepared through facile pyrolysis of a nanocrystalline copper-based metal–organic framework [nHKUST-1, i.e., Cu3(BTC)2 (BTC = 1,3,5-benzene-tricarboxylate)]@ZIF-8, based on the different thermal stability of the two metal–organic frameworks (MOFs). The small CuxO NPs derived from nHKUST-1 were uniformly dispersed inside the host material and provided active sites, while ZIF-8 kept the original structure as the molecular sieving shell. Owing to the proper pore shape and pore size of ZIF-8, H2O2 could diffuse through the shell, but bigger molecules could not pass. Thus, the composite material exhibited high selectivity when it was used to construct a H2O2 sensor. In addition, the sensor showed an extended linear detection range (from 1.5 to 21442 μM), low detection limit (0.15 μM), and high sensitivity, due to the good electrocatalysis of CuxO NPs and the synergistic effect of the core–shell structure.Keywords: core−shell structure; CuxO; electrocatalysis; hydrogen peroxide; metal−organic frameworks; ZIF-8

In this work, highly dispersed AuPd alloy nanoparticles (NPs, 3–6 nm) decorated amino-functionalized Zr(IV)-based metal–organic framework (i.e. UiO-66-NH2) was prepared via a novel adsorption/reduction method in ethanol-water solution. In this process, the UiO-66-NH2 acted as both supporting platform and protective agent. The pores of UiO-66-NH2 could limit the aggregation and migration of AuPd alloy NPs. The resulting AuPd/UiO-66-NH2 catalyst possessed large specific surface area and excellent stability and dispersity in aqueous media. When it was used to construct a nitrite sensor, the composite material exhibited higher catalytic activity than the metal counterparts (i.e., Au/UiO-66-NH2 and Pd/UiO-66-NH2) due to the strong metallic synergistic effect. The electrochemical study demonstrated that the AuPd/UiO-66-NH2 based sensor had an extended linear response concentration range of 0.05–5666 μM for nitrite detection, with a detection limit of 0.01 μM. It was successfully applied to determine nitrite in sausage and pickle samples.

•A three-dimensional porous material (MWCNTs-rGO-IL) was synthesized by self-assembly.•A new PANI-MWCNTs-rGO-IL composite coating was prepared by electrochemical method.•It presented high thermal stability and extraction selectivity for alcohols.In this work, ionic liquid (IL, i.e. 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate), carboxyl multiwall carbon nanotubes (MWCNTs) and reduced graphene oxide (rGO) were used to prepare three-dimensional porous material (MWCNTs-rGO-IL) by one-step self-assembly, then it was co-electrodeposited with polyaniline (PANI) on stainless steel wires by cyclic voltammetry. The resulting coating (PANI-MWCNTs-rGO-IL) was characterized by using FT-IR and scanning electron microscopy etc, and it showed porous structure and had high thermal stability. Furthermore, it was found to be very suitable for the headspace solid-phase microextraction of alcohols (i.e. octanol, nonanol, geraniol, decanol, undecanol and dodecanol). By coupling with gas chromatography, wide linear ranges and low limits of detection (i.e. 2.2–28.3 ng L−1) were obtained for the alcohols. The coating also presented good repeatability and reproducibility; the relative standard deviations for intra-fiber and fiber-to-fiber were less than 5.6% (n = 5) and 7.0% (n = 5) respectively. In addition, the proposed method was successfully applied to the determination of alcohols in tea drinks, and the recoveries for standards added were 85.6–114%.

•A novel MWCNT@IL/PANI fiber was prepared by electrochemical method.•It showed high thermal stability.•It exhibited high selectivity and extraction efficiency toward target analytes.The present work reports the electrochemical fabrication of an ionic liquid functionalized multiwalled carbon nanotubes–polyaniline (MWCNT@IL/PANI) nanocomposite coating and its application in the headspace-solid phase microextraction (HS-SPME) and gas chromatography (GC) determination of benzoic acid esters (i.e., methyl benzoate, ethyl benzoate, propyl benzoate and butyl benzoate). The MWCNTs was firstly functionalized with amine-terminated IL (MWCNT@IL) through chemical reduction, and then was doped in PANI during the electropolymerization of aniline. The resulting coating was characterized by infrared spectroscopy, field emission scanning electron microscopy and thermo gravimetry. It showed net-like structure and had high thermal stability (up to 330 °C). Furthermore, it presented high selectivity for the four benzoic acid esters and thus suited for their HS-SPME–GC determination. Results showed that under optimized extraction conditions, the detection limits were less than 6.1 ng L−1 (S/N = 3) and the linear detection ranges were 0.012–50 μg L−1 (R ≥ 0.9957) for these analytes. The relative standard deviations (RSDs) were lower than 6.4% for five successive measurements with one fiber, and the RSDs for fiber-to-fiber were 4.4–9.6% (n = 5). The developed method was successfully applied to the determination of these benzoic acid esters in perfume samples.

In this work, a composite material of Au nanoparticles (Au NPs) encapsulated in N-doped porous carbon (Au@NPC) was prepared through a one-pot thermolysis of Au NPs@zeolitic imidazolate framework (Au@ZIF-8) precursor. The obtained Au@NPC possessed a high specific surface area as well as superior thermal and chemical stability. The NPC shell functioned as a barrier to effectively prevent Au NPs from dissolution, migration and aggregation during the carbonization process and electrochemical testing, while it allowed the transit of electrolyte to the Au NPs surface. The core–shell structure and Au content were related to the preparation conditions. When the concentration of Au NPs was 0.5 mg mL−1, the resulting Au@ZIF-8 could be carbonized to form a core–shell structure. The size of the encapsulated multi-core Au NPs slightly increased with enhancing carbonizing temperature (e.g. from 600 to 800 °C), while the Au content and surface area of the obtained composite material also increased. On this basis, a sensitive and stable electrochemical sensor was constructed for the detection of hydrazine. Under the optimized conditions, a linear dynamic range of 80 nM to 466.28 μM, with a satisfactory sensitivity of 2035.4 μA mM−1 cm−2 and a comparable detection limit of 8 nM (S/N = 3), was obtained. Moreover, it only lost 4.7% activity after one-month storage. This strategy could also be used to prepare other metal–carbon composite materials for constructing sensors.

•A netlike graphene-MWCNTs composite was prepared by in situ hydrothermal process.•A MIP was supported on the composite for RT detection.•The obtained modified electrode had high sensitivity and selectivity to RT.•The RT in buckwheat tea and orange juice was determined.In this paper, a novel molecularly imprinted composite film modified electrode was presented for rutin (RT) detection. The modified electrode was fabricated by electropolymerization of pyrrole on a graphene-multiwalled carbon nanotubes composite (G-MWCNTs) coated glassy carbon electrode in the presence of RT. The netlike G-MWCNTs composite, prepared by in situ hydrothermal process, had high conductivity and electrocatalytic activity. At the resulting MIP/G-MWCNTs/GCE electrode RT could produce a sensitive anodic peak in pH 1.87 Britton-Robinson buffer solution. The factors affecting the electrochemical behavior and response of RT on the modified electrode were carefully investigated and optimized. Under the selected conditions, the linear response range of RT was 0.01–1.0 μmol L−1 and the detection limit (S/N=3) was 5.0 nmol L−1. The electrode was successfully applied to the determination of RT in buckwheat tea and orange juice samples, and the recoveries for standards added were 93.4–105%.The novel rutin imprinted polypyrrole-graphene-multiwalled carbon nanotubes composite film coated glassy carbon electrode shows high sensitivity and selectivity to rutin.

In this paper, ionic liquid functionalized graphene nanoribbons were prepared by using 1-(3-aminopropyl)-3-methylimidazolium bromide as reducing and functionalizing reagent. Then hollow PdAg alloy nanoparticles were assembled on the composite through electrostatic interaction. The resultant hybrid material showed excellent electrocatalysis to nifedipine and thus it was used for constructing an electrochemical sensor for nifedipine. Result showed that the peak current of nifedipine was linear to its concentration in the range of 10 to 4000 nM with a detection limit of 4 nM (S/N = 3). The sensor possessed desirable reproducibility, stability and selectivity. It was successfully applied to the determination of nifedipine in real samples, and the recovery was 97.6%–101%.

•4-Nonyl phenol imprinted copolymer based sensor is prepared by voltammetry.•Nitrogen-doped graphene nanoribbons and ionic liquid are used to enhance sensitivity.•The composite film presents good performance in sensing 4-nonyl phenol.A novel electrochemical sensor was presented for the determination of 4-nonyl-phenol (NP), which was constructed by molecularly imprinted polymer (MIP), nitrogen-doped graphene nanoribbons (NGNRs) and ionic liquid (IL). The NGNRs were prepared by unzipping multiwalled carbon nanotubes, followed by hydrothermal treatment with ammonium–NaOH solution. The MIP was prepared by electropolymerization at the NGNRs-IL composite film modified electrode, using NP as template, o-phenylenediamine and o-toluidine as copolymerization monomers. The resulting sensor MIP/NGNRs-IL/GCE showed good performance. Under the optimized conditions, the peak current was linear to NP concentration in the range from 0.04 to 6 μM. The sensitivity and detection limit were 3.4 μA/μM and 8 nM (S/N = 3), respectively. The electrochemical sensor was applied to the determination of NP in real samples and satisfactory results were obtained.The electrochemical sensor based on molecularly imprinted poly (o-phenylenediamine-co-o-toluidine)– nitrogen-doped graphene nanoribbons–ionic liquid composite film shows high sensitivity and selectivity to 4-nonyl-phenol.Note: o-phenylenediamine (oPD), o-toluidine (OTD), nitrogen-doped graphene nanoribbons (NGNRs), ionic liquid (IL) and 4-nonyl-phenol (NP).

•A novel hydrophobic PANI-PPO coating was prepared by electrochemical method.•Acidic ionic liquid was used in the preparation of PANI-PPO coating.•The coating showed netlike structure.•It had high extraction capability toward carbamate pesticides.A nanostructural polyaniline-poly(propylene oxide) (PANI-PPO) composite coating was electrochemically synthesized on a stainless steel wire, by using acidic ionic liquid 1-sulfobutyl-3-methylimidazolium hydrosulfate as supporting electrolyte. The coating showed strong hydrophobicity and allowed for the direct immersion solid-phase microextraction of carbamate pesticides (i.e. 2-(1-methylethoxy) phenyl methylcarbamate, m-tolyl-n-methylcarbamate, 2-(1-methylethyl) phenyl methylcarbamate, 2-(1-methylpropyl) phenol methylcarbamate and 2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate) in complex matrices. Moreover, this coating could be used for at least 120 times of extraction. When it was coupled with gas chromatography for the determination of these carbamate pesticides the linear ranges were about 0.1–100 μg L−1 and the detection limits were 0.012–0.048 μg L−1. It also displayed acceptable repeatability and reproducibility. When a fiber was used for five successive measurements the relative standard deviations (RSDs) were smaller than 8.7%, and the RSDs for fiber-to-fiber were 5.7–12.9% (n = 5). The practical feasibility of the proposed method was evaluated by determining carbamate pesticides in vegetable samples and the recoveries for standards added were 79.8–108.8%.

Multiwalled carbon nanotubes (MWCNTs) were non-covalently functionalized with poly(imidazolium ionic liquids) (PILs), and the resulting PIL/MWCNTs composite suspension was coated on electrodeposited polyaniline (PANI) film to fabricate a novel solid-phase microextraction coating (PANI-PIL/MWCNTs). The coating showed porous structure and had large specific surface area (231 m2 g−1, determined by the Brunauer–Emmett–Teller N2 adsorption method). Its adsorption properties were explored by preconcentrating benzene derivatives from water samples prior to gas chromatography-flame ionization detection. The results showed that the PANI-PIL/MWCNTs composite had high enrichment capacity for the analytes and high stability for repeatable use, due to the synergistic effect of PANI and PIL/MWCNTs. Hence, a detection method was developed for them, and good linearity (correlation coefficients higher than 0.9953), low limits of detection (17.7–32.6 ng L−1) and high precision (relative standard deviations less than 6.5% (n = 5)) were achieved. The method was applied to the determination of the benzene derivatives in real samples with recoveries of 84.0–106.9%.

In this work, a three-dimensional hybrid film with in- and out-of-plane pores was fabricated by using porous graphene as framework structure and porous PdCu alloy nanoparticles as building blocks. The porous PdCu alloy nanoparticles were prepared by chemical dealloying with acetic acid. The hierarchical pores had abundant active catalytic sites, and the material exhibited remarkable catalytic activity toward the oxidation of hydrazine. Based on this hybrid film, an electrochemical sensor of melamine was developed by further introducing melamine imprinted electro-polymer of para-aminobenzoic acid. Melamine was detected by differential pulse voltammetry using hydrazine as electrochemical probe. The detection signal was amplified due to the catalytic oxidation of hydrazine at this hybrid film. The linear determination range was 0.01–1 μM and the detection limit was 2 nM (S/N = 3). The sensor displayed high recognition capacity toward melamine and also showed good reproducibility and stability. It is promising in the determination of melamine in real samples.Keywords: hydrazine; melamine; molecularly imprinted polymer; porous graphene; porous PdCu alloy

•A novel AuPd alloy nanoparticles−graphene hybrid modified electrode was prepared.•It presented high electrocatalysis to the oxidation of vanillin.•Vanillin can produce a sensitive oxidation peak at the hybrid film.•The electrode showed good performance when used to sense vanillin.In this work, graphene oxide was reduced to graphene with an endogenous reducing agent from dimethylformamide, and then AuPd alloy nanoparticles were electrodeposited on the graphene film. The obtained AuPd–graphene hybrid film was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and voltammetry. The electrochemical behavior of vanillin was studied using the AuPd–graphene hybrid based electrode. It presented high electrocatalytic activity and vanillin could produce a sensitive oxidation peak at it. Under the optimal conditions, the peak current was linear to the concentration of vanillin in the ranges of 0.1–7 and 10–40 μM. The sensitivities were 1.60 and 0.170 mA mM−1 cm−2, respectively; the detection limit was 20 nM. The electrode was successfully applied to the detection of vanillin in vanilla bean, vanilla tea and biscuit samples.

In this work, a novel poly(aniline-co-m-aminobenzoic acid)–ionic liquid composite coating is presented for the head-space solid phase microextraction (HS-SPME) of aryl halides (i.e. chlorobenzene, bromobenzene, 1,4-dichlorobenzene, 4-bromotoluene, and 1,2,4-trichlorobenzene). This coating was prepared on a platinum wire by electrochemical deposition in an aqueous solution containing 0.1 mol L−1 aniline, 0.1 mol L−1m-aminobenzoic acid, 0.02 mol L−1 1-butyl-3-methylimidazolium tetrafluoroborate and 1.0 mol L−1 HNO3. It showed high mechanical stability, thermal stability (up to 320 °C) and durability (repetitively used for more than 120 times). When it was applied to the HS-SPME and gas chromatographic detection of aryl halides, it presented high repeatability and sensitivity. Under the optimized conditions (i.e. extraction temperature: 30 °C; extraction time: 30 min; stirring rate: 600 rpm; NaCl concentration: 0.35 g mL−1), the linear detection ranges were 0.2–100 μg L−1 with correlation coefficients above 0.9922; the detection limits were 0.01–0.05 μg L−1 (S/N = 3). The relative standard deviations (RSDs) of chromatographic peak areas were smaller than 5.3% for five successive measurements with a single fiber, and the fiber to fiber RSD was 2.4–9.5% (n = 3) for different aryl halides (50 μg L−1). This method was successfully applied to the determination of real samples (i.e. moth balls) and the recoveries for the standard added were 85.7 % to 121%.

•A hydrophilic surface-imprinted polymer based sensor was fabricated for fenitrothion.•RAFT chain-transfer agent modified AuNPs were prepared by click chemistry.•Hydrophilic fenitrothion imprinted polymer on AuNPs was prepared by RAFTPP.•The sensor showed high selective and sensitive response to fenitrothion.A novel water-compatible fenitrothion imprinted polymer was prepared on Au nanoparticles (AuNPs) by click chemistry and reversible addition–fragmentation chain transfer (RAFT) precipitation polymerization (RAFTPP). The RAFT chain-transfer agent was synthesized on the surface of AuNPs using click chemistry, then an imprinted polymer with hydrophilic polymer brushes was prepared on the RAFT chain-transfer agent modified AuNPs by RAFTPP, mediated by hydrophilic polyethylene glycol macromolecular cochain-transfer agent. The obtained molecularly imprinted material showed improved accessibility to fenitrothion and recognition property in water medium. When the material was immobilized on an ionic liquid functionalized graphene coated glassy carbon electrode for the electrochemical determination of fenitrothion, the resulting electrochemical sensor presented linear response in the range of 0.01−5 μM, with a sensitivity of 6.1 μA/μM mm2. The low limit of detection was 8 nM (S/N=3). The sensor was successfully applied to the determination of real samples and the recovery for standard added was 95−108%.

AgPd nanoparticles were assembled on ionic liquid-functionalized graphene by electrostatic interaction to form a graphene–metal composite. The resulting hybrid nanomaterial was characterized by transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and ultraviolet-visible absorption spectrophotometry. The AgPd nanoparticles were confirmed to be alloy and they were well dispersed on the ionic liquid-functionalized graphene sheets. The hybrid nanomaterial showed striking electrocatalytic activity toward the reduction of trichloroacetic acid (TCA). At the hybrid nanomaterial modified glassy carbon electrode, TCA exhibited a cathodic peak at about −0.65 V (vs. SCE) in pH 7 phosphate buffer solution, which was further enhanced by cetyltrimethylammonium bromide. Under the optimal conditions, the determination of TCA was performed with a linear range of 0.5–50 μM and a detection limit of 0.2 μM (S/N = 3).

•A polyaniline–polypyrrole coating is prepared by the electrochemical method.•It shows reticulate structure and has large surface area and high mass-transport rate.•When it is used for SPME, it presents high durability and extraction efficiency for esters.•This is a new way to make use of different monomers to prepare SPME fibers.A novel polyaniline–polypyrrole (PANI–PPY) composite film coated stainless steel wire was prepared by cyclic voltammetry. Firstly, PANI was electrodeposited on a stainless steel wire from a solution containing 0.1 M aniline and 1 M HNO3, after the PANI coating was dried in air PPY was electrodeposited on it from a solution containing 0.1 M pyrrole and 0.1 M p-methylbenzene sulfonic acid. The resulting PANI–PPY fiber showed reticulate structure and had large specific surface area. When it was used for the headspace solid-phase microextraction of several esters (i.e. methyl anthranilate, ethyl-o-aminobenzoate, dimethyl phthalate, methyl laurate, and diethyl phthalate), followed by gas chromatographic determination, it presented higher extraction capability in comparison with PPY and PANI coatings. Under the optimized conditions, the linear ranges were 0.07−300 μg L−1 and the detection limits were 0.05−0.38 μg L−1 for different esters. The PANI–PPY fiber also showed high durability, after being used for about 160 times its extraction capacity only changed a little. The proposed method was successfully applied to the determination of these esters in real samples and the recoveries were 90–102%.

A poly(p-phenylenediamine-co-aniline) composite coating was prepared on a stainless steel wire through electrochemical method. The coating was characterized by scanning electron microscopy, Fourier transform infrared spectrophotometry and thermogravimetry. It showed thin slice shape and netlike microstructure, and thus it had large surface area and large extraction capacity. When the resulting fiber was used for the headspace solid-phase microextraction of some derivatives of benzene (i.e. chlorobenzene, 1,3-dimethylbenzene, 1,2-dimethylbenzene, 2-chlorotoluene, 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene), followed by gas chromatographic (GC) analysis, it presented better performance than the polyaniline coated stainless steel wire. Under the optimized conditions, the GC peak areas were linear to their concentration in the ranges of about 0.5–500 μg L−1, with correlation coefficients of 0.9911–0.9989; the detection limits were 0.2–0.88 μg L−1(S/N=3). The run-to-run RSD was smaller than 5.5% (n=5), and the fiber-to-fiber RSD was 3.5%–12.7% (n=3). The fiber was quite stable and durable; after it was used for about 140 times, its extraction efficiency kept almost unchanged. The developed method was successfully applied to the determination of the derivatives of benzene in waste water, and the recoveries were 86.9%–107.7%.Highlights► A poly(p-phenylenediamine-co-aniline) coating is prepared by electrochemical method. ► It shows porous slice shape and has large surface area and high adsorption capacity. ► When it is used for SPME, it presents much better performance than PANI coating. ► This is a new way to make use of different monomers to prepare SPME fibers.

Macrolide antibiotics generally shows slow electron-transfer rate and produces insensitive redox peaks at conventional electrodes. In this paper, we studied the electrochemical behavior of midecamycin, one of macrolide antibiotics, at a multi-walled carbon nanotube (MWNT) modified gold electrode. It was found that MWNT could adsorb midecamycin and promote its direct electron-transfer. Hence midecamycin exhibited a more sensitive anodic peak at the modified electrode. The electrochemical process showed the feature of a mixed-control system of diffusion and adsorption. Under the optimized conditions (i.e. pH 7.0 phosphate supporting electrolyte, 5 μl 0.5 mg ml−1 multi-walled carbon nanotube suspension for Ø = 2.0 mm electrode, accumulation at −0.8 V for 150 s), the anodic peak current was linear to midecamycin concentration in the range of 5 × 10−7 to 2 × 10−5 M, with a correlation coefficient of 0.998. For a 5 × 10−6 M midecamycin solution, ten repetitive measurements gave a relative standard deviation of 2.2%. This method was successfully applied to the determination of midecamycin in medicine tablet and the recovery was 97.5–104.0%.Graphical abstractOwing to the catalysis and adsorption of multi-walled carbon nanotube (MWNT) macrolide antibiotics midecamycin can present direct electron-transfer phenomenon and produce a sensitive anodic peak at a MWNT film coated gold electrode.Highlights► Multi-walled carbon nanotube (MWNT) promotes the electron-transfer of midecamycin. ► Direct electrochemistry of midecamycin is achieved at MWNT modified electrode. ► A sensitive voltammetry is developed for midecamycin

A novel modified electrode was fabricated, which comprised of hydrophobic ionic liquid (i.e. trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide, [P6,6,6,14][NTf2]), multiwalled carbon nanotubes (MWNTs) and cationic genimi surfactant (i.e. C12H25N(CH3)2–C4H8–N(CH3)2C12H25Br2, C12–C4–C12). Cyclic voltammetry and linear sweep voltammetry were used to investigate the electrochemical behaviour of Sudan І. The components showed good synergic interaction in sensing Sudan І, thus the modified electrode presented higher sensitivity. After optimising the experimental conditions, the anodic peak current of Sudan I was linear to its concentration in the range of 0.05–2 μmol l−1, and the detection limit was 0.03 μmol l−1 in pH 4.5 potassium biphthalate buffer with acetonitrile. The modified electrode had good stability and repeatability. It was applied to the detection of Sudan І in hot chilli powder and ketchup samples, and the recovery was acceptable.

Gold–platinum (AuPt) alloy particles were fabricated directly on multi-walled carbon nanotubes (MWNT)–ionic liquid (i.e., trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide, [P6,6,6,14][NTf2]) composite coated glassy carbon electrode (GCE) by electrodeposition method. Scanning electron microscope image showed that they were well-dispersed nanocluster consisting of smaller nanoparticles, and their size was about 70 nm. X-ray diffraction experiment showed that they were single-phase alloy nanomaterial, and the calculated composition was consisting with that obtained by energy dispersive X-ray spectroscopy. The resulting modified electrode (i.e., AuPt–MWNT–[P6,6,6,14][NTf2]/GCE) presented high catalytic activity for the electrochemical oxidation of cysteine. The peak potential of cysteine shifted to 0.42 V (versus saturated calomel electrode) in 0.1 M H2SO4 and the peak current increased greatly in comparison with that on the corresponding Pt (or Au)–MWNT–[P6,6,6,14][NTf2]/GCE. Under the optimized conditions, the oxidation current of cysteine at 0.45 V was linear to its concentration in the range of 5.0 × 10−7 ∼ 4.0 × 10−5 M with a sensitivity of 43.8 mA M−1.

A novel alcohol sensor was proposed in the present work, which was based on the pulsed electrodeposition of PtRuNi ternary alloy nanoparticles on multi-walled carbon nanotubes (MWNTs)–ionic liquid (IL, i.e. 1-octyl-3-methylimidazolium hexaflurophosphate, OMIMPF6) gel film. The composition, morphology and catalytic activity of the obtained nanoparticles were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy and voltammetry, respectively. The PtRuNi–MWNT–IL coated glassy carbon electrode was proved to be suitable for detecting alcohol. The analytical characteristics of the resulting sensor, in terms of poison tolerance, response time, linear range, detection limit, sensitivity, reproducibility and long-term stability were explored and satisfying results were obtained. For comparison, the electrodes with PtRuCo, PtRu and Pt nanoparticles were also prepared and studied.

The simultaneous voltammetric determination of catechol (CC) and hydroquinone (HQ) has been achieved at a mesoporous carbon CMK-3 modified electrode in phosphate buffer solution (pH 7.0). At the electrode both CC and HQ can cause a pair of quasi-reversible and well-defined redox peaks and their peak potential difference increases. In comparison with multi-walled carbon nanotubes (MWCNTs) and Vulcan XC-72 carbon modified electrodes the CMK-3 modified electrode shows larger peak currents and higher adsorbed amounts for the two dihydroxybenzene isomers. This is related to the higher specific surface area of CMK-3. Under the optimized conditions, the linear concentration ranges for CC and HQ are 5 × 10−7 to 3.5 × 10−5 M and 1 × 10−6 to 3 × 10−5 M, respectively. In the presence of 5 μM isomer, the linear concentration range of CC (or HQ) is 5 × 10−7 to 2.5 × 10−5 M (or 5 × 10−7 to 2.0 × 10−5 M). The sensitivity for CC or HQ is 41 A M−1 cm−2 or 52 A M−1 cm−2, which is close to that without isomer. The detection limits (S/N = 3) for CC and HQ are 1 × 10−7 M after preconcentration on open circuit for 240 s.

We report here for the first time on the fabrication of highly dispersed PtM (M = Ru, Pd and Au) nanoparticles on composite film of multi-walled carbon nanotubes (MWNTs)–ionic liquid (IL, i.e., trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide) by using ultrasonic-electrodeposition method. The PtM nanoparticles are characterized by scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction, and we find that they are well-dispersed and exhibit alloy properties. Electrochemical experiments show that the PtRu(1:1, i.e., ratio of c(H2PtCl6)/c(RuCl3))–MWNT–IL nanocomposite modified glassy carbon electrode (PtRu(1:1)–MWNT–IL/GCE) has smaller electron transfer resistance and larger active surface area than PtRu(1:1)/GCE, PtRu(1:1)–MWNT/GCE, PtPd(1:1)–MWNT–IL/GCE and PtAu(1:1)–MWNT–IL/GCE. The PtRu(1:1)–MWNT–IL/GCE also presents stronger electrocatalytic activity toward the glucose oxidation than other electrodes. At −0.1 V, the electrode responds linearly to glucose up to 15 mM in neutral media, with a detection limit of 0.05 mM (S/N = 3) and detection sensitivity of 10.7 μA cm−2 mM−1. Meanwhile, the interference of ascorbic acid, uric acid, acetamidophenol and fructose is effectively avoided. The as-made sensor was applied to the determination of glucose in serum and urine samples. The results agreed closely with the results obtained by a hospital. This novel nonenzyme sensor thus has potential application in glucose detection.

The direct electron transfer and electrocatalysis of hemoglobin (Hb) entrapped in polyvinyl alcohol (PVA)–room temperature ionic liquid (i.e., 1-octyl-3-methylimidazolium hexafluorophosphate [OMIM]PF6) composition has been investigated by using cyclic voltammetry and chronocoulometry. It is found that the composition can promote the direct electron transfer of Hb and the heterogeneous electron transfer rate constant (ks) of immobilized Hb is enhanced to 19.9 s−1. The immobilized Hb also shows high electro-catalytic activity towards the redox of oxygen, hydrogen peroxide and nitrite. The Michaelis constants (Km) decrease to 1.2 × 10−4 M (for hydrogen peroxide) and 9.4 × 10−3 M (for nitrite). The surface concentration of electroactive Hb is estimated and it is ca. 1.4 × 10−10 mol cm−2, meaning that several layers of immobilized Hb take part in the electrochemical reaction. When gold nanoparticles (GNP) is introduced into the composition, the resulting PVA–GNP–[OMIM]PF6 composition presents better performance. The electrochemical characteristic of immobilized Hb is improved further. Thus PVA–GNP–[OMIM]PF6 composition is more suitable for the immobilization of Hb. Therefore, it is a good strategy to prepare novel composition for protein immobilization by using several materials with different function.

The voltammetric and electrocatalytic behavior of horseradish peroxidase (HRP) immobilized on a cationic gemini surfactant (i.e. C12H25N(CH3)2–C12H24–N(CH3)2C12H25Br2, C12–C12–C12)–polyvinyl alcohol (PVA) composite film-coated glassy carbon electrode (GCE) has been studied. It is found that on the novel composite film HRP presents excellent electroactivity and can exhibit a pair of well-defined voltammetric peaks in 0.10 M pH 7.0 phosphate buffer solution (PBS). The immobilized HRP also presents good bioelectrocatalytic activity, and it can catalyze the reduction of oxygen (O2), hydrogen peroxide (H2O2), nitrite ion (NO2−) and trichloroacetic acid (TCA). For H2O2 the catalytic current is linear to its concentration in the range of 0.195–97.5 μM, and the detection limit is down to 6.5 × 10−8 M. The response shows Michaelis–Menten feature and the apparent Michaelis–Menten constant is estimated to be 110.5 μM. Similarly, the electrode can sense NO2− and TCA. In addition, it is observed that the spacer group of gemini surfactant affects the electroactivity of HRP significantly. A spacer group with higher flexibility and hydrophility is favorable to the electron transfer of HRP. UV–vis spectrum indicates that the structure of HRP in the PVA–C12–C12–C12 film is similar to that of native HRP. Thus the C12–C12–C12–PVA composite possesses good biocompatibility and has promising application in fabricating biosensor and bioelectronics.

Gold−platinum nanoparticles (AuPt NPs) were fabricated on chitosan (Ch)−ionic liquid (i.e., trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide, [P(C6)3C14][Tf2N]) film by using an ultrasonic electrodeposition method for the first time. Ch acted as an adsorbent for the metal ions, and [P(C6)3C14][Tf2N] played a dual role of matrix and stabilizer in the formation of the nanoparticles. The obtained AuPt NPs were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. It was found that they were well-dispersed on the composite surface, and their diameters were 10−20 nm. Furthermore, they exhibited the features of an alloy, and the atomic ratio of Au/Pt in the alloy NPs was close to the concentration ratio of AuCl4−/PtCl62− in the solution. Electrochemical observation showed that the AuPt−Ch−[P(C6)3C14][Tf2N] modified glassy carbon electrode (GCE) had a large electroactive surface area and small electron transfer resistance. When the ratio of AuCl4−/PtCl62− was around 3:1, the resulting electrode (i.e., Au3Pt1−Ch−[P(C6)3C14][Tf2N]/GCE) displayed high catalytic activity to the reduction of hydrogen peroxide (H2O2). Chronoamperometric experiments showed that at an applied potential of 0.05 V (vs SCE), the reduction current of H2O2 was linear to its concentration in the range of 5−355 nM, and the detection limit was found to be 0.3 nM on the basis of the signal-to-noise ratio of 3. The as-prepared nonenzyme hydrogen peroxide sensor exhibited excellent stability, repeatability, and selectivity.

A novel method, based on the coupling of ionic liquid-based headspace single-drop microextraction (SDME) with gas chromatography (GC), is developed for the determination of chlorobenzene derivatives. For the SDME of five chlorobenzene derivatives, a 1.0 μL 1-octyl-3-methylimidazolium hexafluorophosphate microdrop is exposed for 20 min to the headspace of a 15 ml aqueous sample containing 20% (w/v) NaCl placed in 25 ml vial at 40 °C. Then, the extractant is directly injected into the injector block of the GC instrument. To avoid ionic liquid leaking into the chromatographic column, a small glass tube is placed in the injection block. Under optimized operation conditions, linear relation between peak areas and analyte concentrations up to 1.5 mg L−1 has been obtained The detection limits range from 0.1 to 0.5 μg L−1 for the various analytes. The relative standard deviations at 1.0 μg L−1 range from 7.7 to 12.4%, and the enrichment factors from 41 to 127. The method is simple and sensitive, and does not suffer from the influence of a solvent peak. Its applicability is demonstrated by the determination of chlorobenzenes in wastewater samples.

A novel composite material comprised of gemini surfactant (i.e. dodecyl-α,ω-bis (dimethylcetylammonium bromide), C16–C12–C16) and hydrophobic room temperature ionic liquid (i.e. 1-octyl-3-methylimidazolium hexafluorophate, OMIMPF6) has been fabricated. This composite material suits for the immobilization of horseradish peroxides (HRP). The ultraviolet–visible spectra and reflectance absorption infrared spectra of the HRP immobilized in the C16–C12–C16–OMIMPF6 material are almost the same as those of native HRP. When it is coated on a glassy carbon (GC) electrode, the resulting electrode C16–C12–C16–OMIMPF6–HRP/GC exhibits a pair of well-defined, stable and reversible voltammetric peaks in 0.10 M pH 7 phosphate buffer solutions. When the hydrophobic action of ionic liquid and gemini surfactant used increases, more immobilized HRP can undergo electrochemical reaction and the voltammetric peaks become larger. In addition, the C16–C12–C16–OMIMPF6–HRP/GC electrode shows good catalytic response to dissolved oxygen and H2O2. The cathodic peak current of the electrode is linear to H2O2 concentration in the range of 5.82 μM to 388 μM. The apparent Michaelis–Menten constant is estimated to be 0.159 mM. The electrode has good stability and reproducibility. Hence, the composite material has potential applications in fabricating biosensors and bioelectronics.

Pt nanoparticles were deposited on mesoporous carbon material CMK-3. Glucose oxidase (GOx) was immobilized in the resulting Pt nanoparticles/mesoporous carbon (Pt/CMK-3) matrix, and then the mixture was cast on a glassy carbon electrode (GCE) using gelatin as a binder. The glucose biosensor exhibited excellent current response to glucose after cross-linking with glutaraldehyde. At 0.6 V (vs. SCE) the response current was linear to glucose concentration in the range of 0.04–12.2 mM. The response time (time for achieving 95% of the maximum current) was 15 s and the detection limit (S/N = 3) was 1 μM. The Michaelis–Menten constant (Kmapp) and the maximum current density (imax) were 10.8 mM and 908 μA cm−2, respectively. The activation energy of the enzymatic reaction was estimated to be 22.54 kJ mol−1. The biosensor showed good stability. It achieved the maximum response current at about 52 °C and retained 95.1% of its initial response current after being stored for 30 days. In addition, some fabrication and operation parameters for the biosensor were optimized in this work. The biosensor was used to monitor the glucose levels of serum samples after being covered with an extra Nafion film to improve its anti-interferent ability and satisfied results were obtained.

An ionic liquid (i.e. 1-butyl-3-methylimidazolium hexafluophosphate, BMIMPF6)–single-walled carbon nanotube (SWNT) paste coated glassy carbon electrode (BMIMPF6–SWNT/GCE) has been fabricated. The electrode shows good electro-catalysis to the reduction of methylparathion (MP) and MP can accumulate effectively on it. Thus, MP can produce a sensitive cathodic peak on the BMIMPF6–SWNT/GCE. Parameters influencing the voltammetric response of MP are optimized for MP determination. Under the selected experimental conditions (i.e. solution pH 7.0; accumulation time, 180 s; accumulation potential, on open-circuit; the ratio of SWNT to BMIMPF6 1:20 (mg μL−1)), the peak current is linear to MP concentration over the range of 2.0 × 10−9 to 4.0 × 10−6 M. The detection limit is 1.0 × 10−9 M. Therefore, this system is quite sensitive in comparison with other electrochemical methods. In addition, it is found that the hydrolysate of MP (i.e. p-nitrophenol, PNP) can also produce a sensitive cathodic peak under this condition. But the peaks of MP and PNP do not overlap with each other. Hence they can be determined simultaneously. This electrode has been applied to the determination of MP and PNP in real samples.

A hybrid film is fabricated by casting hemoglobin (Hb)–carbon nanoparticles (CNPs)–polyvinyl alcohol (PVA) suspension on glassy carbon electrode (GCE). The resulting film shows a three-dimensional nanoporous structure. In the hybrid film, the ultraviolet visible (UV–Vis) absorption spectra of Hb keep almost unchanged. The organic–inorganic hybrid material can promote the direct electron transfer of Hb. A pair of well-defined and quasireversible peaks with a formal potential of −0.348 V (vs saturated calomel electrode) is obtained, which is caused by the electrochemical reaction of the Fe(III)/Fe(II) couple of Hb. The electron transfer rate constant (ks) is estimated to be 3.9 s−1. The immobilized Hb exhibits high stability and excellent electrochemical catalysis to the reduction of oxygen (O2), hydrogen peroxide (H2O2), and nitrite (\(NO^{ - }_{2} \)). The catalytic currents are linear to the concentrations of H2O2 and \(NO^{ - }_{2} \) from 1.96 to 112 μM and from 0.2 to 1.8 mM, respectively. Therefore, the hybrid film may be a good matrix for protein immobilization and biosensor fabrication.

A novel composite film modified glassy carbon electrode has been fabricated and characterized by scanning electron microscope (SEM) and voltammetry. The composite film comprises of single-wall carbon nanotube (SWNT), gold nanoparticle (GNP) and ionic liquid (i.e. 1-octyl-3-methylimidazolium hexafluorophosphate), thus has the characteristics of them. The resulting electrode shows good stability, high accumulation efficiency and strong promotion to electron transfer. On it, chloramphenicol can produce a sensitive cathodic peak at −0.66 V (versus SCE) in pH 7.0 phosphate buffer solutions. Parameters influencing the voltammetric response of chloramphenicol are optimized, which include the composition of the film and the operation conditions. Under the optimized conditions, the peak current is linear to chloramphenicol concentration in the range of 1.0 × 10−8–6.0 × 10−6 M, and the detection limit is estimated to be 5.0 × 10−9 M after an accumulation for 150 s on open circuit. The electrode is applied to the determination of chloramphenicol in milk samples, and the recoveries for the standards added are 97.0% and 100.3%. In addition, the electrochemical reaction of chloramphenicol and the effect of single-wall carbon nanotube, gold nanoparticle and ionic liquid are discussed.

The direct electrochemistry of glucose oxidase (GOD) entrapped in nano gold particles (NAs)-N,N-dimethylformamide (DMF)-1-butyl-3-methylimidazolium hexafluophosphate (BMIMPF6) composite film on a glassy carbon electrode (NAs-DMF-GOD (BMIMPF6)/GC) has been investigated for first time. The immobilized GOD exhibits a pair of well-defined reversible peaks in 0.050 M pH 5 phosphate solutions (PS), resulting from the redox of flavin adenine dinucleotide (FAD) in GOD. The peak currents are three times as large as those of GOD-NAs-DMF film coated GC electrode (i.e. NAs-DMF-GOD (water)/GC). In addition, the NAs-DMF-GOD (BMIMPF6) composite material has higher thermal stability than NAs-DMF-GOD (water). Results show that ionic liquid BMIMPF6, DMF and NAs are requisite for GOD to exhibit a pair of stable and reversible peaks. Without any of them, the peaks of GOD become small and unstable. Upon the addition of glucose, the peak currents of GOD decrease and a new cathodic peak occurs at −0.8 V (versus SCE), which corresponds to the reduction of hydrogen peroxide (H2O2) generated by the catalytic oxidation of glucose. The peak current of the new cathodic peak and the glucose concentration show a linear relationship in the ranges of 1.0 × 10−7 to 1.0 × 10−6 M and 2.0 × 10−6 to 2.0 × 10−5 M. The kinetic parameter Imax of H2O2 is estimated to be 1.19 × 10−6 A and the apparent Km (Michaelis–Menten constant) for the enzymatic reaction is 3.49 μM. This method has been successfully applied to the determination of glucose in human plasma and beer samples, and the average recoveries are 97.2% and 99%, respectively.

The direct electrochemistry and electrocatalysis of horseradish peroxidase (HRP) immobilized on a gelatin – N, N-dimethylformamide (DMF) – hydrophobic ionic liquid (i.e. 1-octyl-3-methylimidazolium hexafluorophsohate) gel film coated glassy carbon electrode has been studied for the first time. The immobilized HRP exhibits a pair of well-defined quasi-reversible peaks in pH 7.0 phosphate buffer solutions, which results from the direct electron transfer between the enzyme and the underlying electrode. In this case there is about 2.7% of the immobilized HRP undergoing the electrochemical reaction, which corresponds to multi-layer of HRP on the electrode surface. The HRP immobilized has higher thermal stability than in gelatin hydrogel. Experiment results also show that the voltammetric behavior of the enzyme electrode depends on the type of room temperature ionic liquid (RTIL) used. When a more hydrophobic RTIL is adopted, the resulting enzyme electrode gives better performance. In the presence of hydrogen peroxide, the enzyme electrode shows sensitive response. The sensitivity of the catalytic peak is up to 1.38 A cm−2 M−1 and the Michaelis constant is down to 6.84 × 10−5 M, which are superior to that reported elsewhere. In addition, the UV–visible spectra of HRP entrapped in different films and the mass transfer of hydrogen peroxide are discussed as well.

Glucose oxidase (GOD) immobilized in nanogold particles (NAs)-N,N-dimethylformamide (DMF) composite film on glassy carbon (GC) electrode exhibits a pair of quasi-reversible and unstable peaks due to the redox of flavin adenine dinucleotide (FAD) of GOD. When ionic liquids (ILs) 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) or trihexyltetradecylphosphorium bis (trifluoromethylsulfony) (P666,14 NTf2) is introduced in the film, the peaks become small. But ILs 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) and 1-octyl-3-methylimidazolium hexafluorophate (OMIMPF6) make the peaks large and stable. In different composite films the formal potential (E0′) of GOD is different. UV–vis spectra show that the GOD dispersed in these films almost retains its native structure and there are weak interactions between ILs and GOD. Electrochemical impedance spectra display that NAs can promote the electron transfer between FAD and GC electrode; and ILs can affect the electron transfer through interacting with GOD. The thermal stability of GOD entrapped in NAs-DMF-ILs composite films is also influenced by ILs, and it follows such order as: in NAs-DMF-OMIMPF6 > in NAs-DMF-BMIMPF6 ≈ in NAs-DMF-BMIMBF4 > in NAs-DMF. In addition, GOD immobilized in NAs-DMF-OMIMPF6 and NAs-DMF-BMIMPF6 films shows good catalytic activity to the oxidation of glucose. The Imax of H2O2 and the apparent Km (Michaelis–Menten constant) for the enzymatic reaction are calculated.

This study reports the preparation and characterization of gold nanoparticles deposited on amine-functioned hexagonal mesoporous silica (NH2–HSM) films and the electrocatalytic oxidation of glucose. Gold nanoparticles are fabricated by electrochemically reducing chloroauric acid on the surface of NH2–HSM film, using potential step technology. The gold nanoparticles deposited have an average diameter of 80 nm and show high electroactivity. Prussian blue film can form easily on them while cycling the potential between −0.2 and 0.6 V (vs saturated calomel electrode) in single ferricyanide solution. The gold nanoparticles loading NH2–HSM-film-coated glassy carbon electrode (Au–NH2–HSM/GCE) shows strong catalysis to the oxidation of glucose, and according to the cathodic oxidation peak at about 0.16 V, the catalytic current is about 2.5 μA mM−1. Under optimized conditions, the peak current of the cathodic oxidation peak is linear to the concentration of glucose in the range of 0.2 to 70 mM. The detection limit is estimated to be 0.1 mM. In addition, some electrochemical parameters about glucose oxidation are estimated.

The voltammetric behavior of tannic acid (TA) on a single-wall carbon nanotubes (SWNTs) modified glassy carbon electrode has been investigated by cyclic voltammetry. TA can generate a well-defined anodic peak on the modified electrode at around 0.42 V (vs. SCE) in 0.10 M phosphate buffer solutions (pH = 4.0). The electrochemical reaction involves 1e transfer, accompanied by one proton. The electrode process is controlled by adsorption. The parameters affecting the response of TA, such as solution pH, accumulation time and accumulation potential are optimized for the determination of TA. Under the optimum conditions, the peak current changes linearly with the TA concentration in the range of 5.0 × 10−8–1.0 × 10−6 M. The lowest detectable concentration of TA is 8.0 × 10−9 M after 180 s accumulation. This method has been successfully applied to the determination of TA in tea and beer samples. In addition, the influence of potential interferents is examined. In the presence of bovine serum albumin, the peak current of TA decreases linearly due to the formation of a super-molecular complex.

•SAM and electropolymerization were combined to fabricate novel PEDOT@AuNPs coating.•PEDOT and AuNPs showed synergistic adsorption/affinity for PAHs.•The coating showed good stability, long lifetime, high sensitivity and selectivity.In this work, a novel poly(3,4-ethylenedioxythiophene)@Au nanoparticles (PEDOT@AuNPs) hybrid coating was prepared and characterized. Firstly, the monomer 3,4-ethylenedioxythiophene was self-assembled on AuNPs, and then electropolymerization was performed on a stainless steel wire by cyclic voltammetry. The obtained PEDOT@AuNPs coating was rough and showed cauliflower-like micro-structure with thickness of ∼40 μm. It displayed high thermal stability (up to 330 °C) and mechanical stability and could be used for at least 160 times of solid phase microextraction (SPME) without decrease of extraction performance. The coating exhibited high extraction capacity for some environmental pollutants (e.g. naphthalene, 2-methylnaphthalene, acenaphthene, fluorene and phenathrene) due to the hydrophobic interaction between the analytes and PEDOT and the additional physicochemical affinity between polycyclic aromatic hydrocarbons and AuNPs. Through coupling with GC detection, good linearity (correlation coefficients higher than 0.9894), wide linear range (0.01–100 μg L−1), low limits of detection (2.5–25 ng L−1) were achieved for these analytes. The reproducibility (defined as RSD) was 1.1–4.0% and 5.8–9.9% for single fiber (n = 5) and fiber-to-fiber (n = 5), respectively. The SPME-GC method was successfully applied for the determination of three real samples, and the recoveries for standards added were 89.9–106% for lake water, 95.7–112% for rain water and 93.2–109% for soil saturated water, respectively.

A direct Z-scheme BiOI–CdS photocatalyst has been successfully synthesized by an electrostatic interaction mechanism and used for selective photoelectrochemical sensing of Cu2+. The BiOI–CdS photocatalyst shows higher photocatalytic activity and photoelectrochemical performance than pure CdS and BiOI. The photocurrent intensity generated by the BiOI–CdS-3 electrode is about 62 and 10 times of those induced by BiOI and CdS under visible-light irradiation, respectively. The enhanced photocatalytic activity is attributed to the formation of a hierarchical direct Z-scheme BiOI–CdS photocatalyst and its high Brunauer–Emmett–Teller (BET) specific surface area, which benefit the efficient spatial separation of charge and capture of visible-light. Moreover, a photoelectrochemical sensor is developed based on the selective replacement reaction between Cu2+ and CdS. The photoelectrochemical sensor is easily fabricated and presents good selectivity, acceptable detection range (0.1–100 μM) and detection limit (0.02 μM). It has been applied to the detection of Cu2+ ions in drinking water with a satisfactory result.

In this work, a novel poly(aniline-co-m-aminobenzoic acid)–ionic liquid composite coating is presented for the head-space solid phase microextraction (HS-SPME) of aryl halides (i.e. chlorobenzene, bromobenzene, 1,4-dichlorobenzene, 4-bromotoluene, and 1,2,4-trichlorobenzene). This coating was prepared on a platinum wire by electrochemical deposition in an aqueous solution containing 0.1 mol L−1 aniline, 0.1 mol L−1m-aminobenzoic acid, 0.02 mol L−1 1-butyl-3-methylimidazolium tetrafluoroborate and 1.0 mol L−1 HNO3. It showed high mechanical stability, thermal stability (up to 320 °C) and durability (repetitively used for more than 120 times). When it was applied to the HS-SPME and gas chromatographic detection of aryl halides, it presented high repeatability and sensitivity. Under the optimized conditions (i.e. extraction temperature: 30 °C; extraction time: 30 min; stirring rate: 600 rpm; NaCl concentration: 0.35 g mL−1), the linear detection ranges were 0.2–100 μg L−1 with correlation coefficients above 0.9922; the detection limits were 0.01–0.05 μg L−1 (S/N = 3). The relative standard deviations (RSDs) of chromatographic peak areas were smaller than 5.3% for five successive measurements with a single fiber, and the fiber to fiber RSD was 2.4–9.5% (n = 3) for different aryl halides (50 μg L−1). This method was successfully applied to the determination of real samples (i.e. moth balls) and the recoveries for the standard added were 85.7 % to 121%.

AgPd nanoparticles were assembled on ionic liquid-functionalized graphene by electrostatic interaction to form a graphene–metal composite. The resulting hybrid nanomaterial was characterized by transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and ultraviolet-visible absorption spectrophotometry. The AgPd nanoparticles were confirmed to be alloy and they were well dispersed on the ionic liquid-functionalized graphene sheets. The hybrid nanomaterial showed striking electrocatalytic activity toward the reduction of trichloroacetic acid (TCA). At the hybrid nanomaterial modified glassy carbon electrode, TCA exhibited a cathodic peak at about −0.65 V (vs. SCE) in pH 7 phosphate buffer solution, which was further enhanced by cetyltrimethylammonium bromide. Under the optimal conditions, the determination of TCA was performed with a linear range of 0.5–50 μM and a detection limit of 0.2 μM (S/N = 3).