Photoelectrochemical immunoassay of cardiac troponin I based on ZnTCPP/CdIn2S4 type-II heterojunction and co-catalyzed precipitation biolabeling.

CdIn2S4 and zinc tetrakis(4-carboxyphenyl)porphyrin (ZnTCPP) were synthesized by hydrothermal method, and an organic dye-sensitized inorganic semiconductor ZnTCPP/CdIn2S4 type II heterojunction was constructed on a fluorine-doped tin oxide (FTO) substrate electrode. A sandwich immunostructure for signal-attenuation photoelectrochemical (PEC) detection of cardiac troponin I (cTnI) was constructed using the ZnTCPP/CdIn2S4/FTO photoanode and a horseradish peroxidase (HRP)-ZnFe2O4-Ab2-bovine serum albumin (BSA) immunolabeling complex. The bioenzyme HRP and the HRP-like nanozyme ZnFe2O4 can co-catalyze the oxidation of 4-chloro-1-naphthol (4-CN) by H2O2 to produce an insoluble precipitate on the photoanode, thus notably reducing the anodic photocurrent for quantitative determination of cTnI. Under the optimal conditions, the photocurrent at 0 V vs. SCE in 0.1 M phosphate buffer solution (pH 7.40) containing 0.1 M ascorbic acid was linear with the logarithm of cTnI concentration from 500 fg mL-1 to 50.0 ng mL-1, and the limit of detection (LOD, S/N = 3) is 0.15 pg mL-1. Spiked recoveries were 95.1% ~ 104% for assay of cTnI in human serum samples.

Carbon nanotube-interconnected ruthenium phthalocyanine nanoparticles used for real-time monitoring of nitric oxide released from vascular endothelial barrier model.

Real-time monitoring of nitric oxide (NO) is of great importance in diagnosing the physiological functions of neurotransmission, cardiovascular, and immune systems. This study reports the carbon nanotube-interconnected ruthenium phthalocyanine nanoparticle nanocomposite and its applicability in construction of an electrochemical platform, which could real-time detect NO released from the vascular endothelial barrier (VEB) model in cell culture medium. The nanocomposite exhibits regular morphology, uniform particle size, and excellent electro-catalytic activity to electrochemical oxidation of NO. Under optimal conditions, the electrochemical device has high sensitivity (0.871 µA µM-1) and can selectively detect NO down to the concentration of 6 × 10-10 M. The human brain microvascular endothelial cells were cultured onto the Transwell support to construct the VEB model. Upon stimulated by L-arginine, NO produced by the VEB diffuses into the bottom chamber of the Transwell, and is real-time monitored by the electrochemical device. Moreover, evaluation of the NO inhibition by drug is realized using the electrochemical device-Transwell platform. This simple and sensitive platform would be of great interesting for evaluating the endothelial function or its pathological states, and screening the related drugs or chemicals.

Photocurrent Polarity Switchable Sensing of Hyaluronidase Activity by Regulating Electrostatic Interactions between Two Semiconductors.

Photocurrent polarity switchable photoelectrochemical (PEC) sensing has superior accuracy and anti-interference ability to conventional PEC sensing. The development of a novel strategy for photocurrent polarity switchable sensing is of great interest. Herein, a novel strategy for photocurrent polarity switchable sensing is reported by regulating electrostatic interactions between two semiconductor photoactive materials. Hyaluronic acid (HA)-modified CuO nanosheets show a negatively charged surface, which prevents the attachment of CuO nanosheets to negatively charged CdS nanodendrite-modified photoelectrodes because of the strong electrostatic repulsion. In the presence of hyaluronidase (HAase), the specific hydrolysis of HA on the surface of CuO by HAase can yield a positively charged surface, so CuO can be attached to a CdS-modified photoelectrode via electrostatic attraction, leading to photocurrent polarity switching. The photocurrent polarity switchable detection of HAase activity is achieved with an ultralow detection limit of 2 × 10-3 U mL-1 and a wide linear detection range between 0.01 and 100 U mL-1. This work provides a new and effective photocurrent polarity switching strategy for PEC sensing and a simple and efficient method for detecting HAase activity.

Photoelectrochemical aptasensing of lincomycin based on a AgI-carboxylated multiwalled carbon nanotubes-BiOI Z-scheme heterojunction.

Lincomycin (LIN) is a common antibiotic that is widely used in animal husbandry and other fields, and the residual problem caused by its abuse has attracted widespread attention. Herein, a novel AgI-carboxylated multiwalled carbon nanotubes (cMWCNT)-BiOI Z-scheme heterojunction material was synthesized via a one-pot hydrothermal method, modified on a fluorine-doped tin oxide (FTO) electrode surface, and used for detecting LIN. The photocurrent on the AgI-cMWCNT-BiOI/FTO photoelectrode is 4.6 times that on the control AgI-BiOI/FTO photoelectrode. An amino-functionalized LIN aptamer was fixed on the AgI-cMWCNT-BiOI/FTO photoelectrode by the cross-linking reaction between chitosan and glutaraldehyde, and then Ru(NH3)63+ was electrostatically attached to the LIN aptamer to increase the photocurrent response to the LIN binding. When LIN binds competitively with Ru(NH3)63+ to the aptamer, the photocurrent signal can be quantitatively decreased. Under optimized conditions, the anodic photocurrent at 0 V vs KCl-saturated calomel electrode in 0.1 M phosphate buffer (pH 7.0) containing 0.100 M ascorbic acid was linear with the common logarithm of LIN concentration from 10.0 pM to 500 nM, with a limit of detection of 2.8 pM (S/N = 3). Satisfactory recovery results were obtained in the analysis of cow milk samples.

Photoelectrocatalysis Synthesis of Ammonia Based on a Ni-Doped MoS2/Si Nanowires Photocathode and Porous Water with High N2 Solubility.

The synthesis of ammonia through photocatalysis or photoelectrochemistry (PEC) and nitrogen reduction reaction (NRR) has become one of the recent research hotspots in the field, where the catalyzed materials and strategies are critical for the NRR. Herein, a Ni-doped MoS2/Si nanowires (Ni-MoS2/Si NWs) photocathode is prepared, where the Si NWs are formed on the surface of a Si slice by the metal-assisted chemical etching method, and the hydrothermally synthesized Ni-MoS2 nanosheets are then cast-coated on the Si NWs electrode. Porous water with high solubility of N2 is prepared by treating a hydrophobic porous coordination polymer with hydrophilic bovine serum albumin for subsequent aqueous dispersing. The relevant electrodes and materials are characterized by electrochemistry, UV-vis spectrophotometry, scanning electron microscopy/energy dispersive spectroscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller method, and zeta potential method. The uses of the Ni-MoS2/Si NWs photocathode and the porous water with high nitrogen solubility for PEC-NRR give a yield of NH3 of 12.0 mmol h-1 m-2 under optimal conditions (e.g., at 0.25 V vs RHE), and the obtained apparent Faradaic efficiency higher than 100% is discussed from the inherent photocurrent-free photocatalysis effect of the photoelectrodes and the suggested classification of three kinds of electrons in PEC, which may have some reference value in understanding and improving other PEC-based processes.

Photoelectrochemical aptasensing of oxytetracycline based on a BiVO4-carboxylated graphene-WO3 Z-scheme heterojunction.

A new BiVO4-carboxylated graphene (cG)-WO3 Z-scheme heterojunction was constructed on a fluorine-doped tin oxide (FTO) substrate electrode by ultrasonic mixing and cast-coating for determination of oxytetracycline (OTC). Since cG can absorb visible light and well match with the energy levels of WO3 and BiVO4 to promote the charge separation and transfer, the photocurrent on the BiVO4-cG-WO3/FTO photoelectrode is 4.4 times that on the control BiVO4-WO3/FTO photoelectrode. An amino-functionalized OTC aptamer was fixed on the BiVO4-cG-WO3/FTO photoelectrode by the 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide mediated amide reaction, and then hexaammonium ruthenium(III) (Ru(NH3)63+) was attached to the OTC aptamer to increase the photocurrent response to the OTC binding. Under the optimized conditions, the photocurrent on the BiVO4-cG-WO3/FTO photoelectrode at 0 V vs SCE was linear with the common logarithm of OTC concentration from 0.01 nM to 500 nM, with a limit of detection of 3.1 pM (S/N = 3). Satisfactory recovery results were obtained in the analysis of real water samples.

Photoelectrochemical immunoassay of squamous cell carcinoma antigen based on CuO/nitrogen-doped porous carbon-ZnO biolabeling and a type-II In2O3/AgBiS2 heterojunction.

AgBiS2 was hydrothermally synthesized, In2O3 was synthesized by hydrothermal method and calcination, and the type-II In2O3/AgBiS2 heterojunction material of an optimized composition ratio was cast-coated on a fluorine-doped tin oxide (FTO) slice to fabricate an In2O3/AgBiS2/FTO photoanode. The signal-attenuated photoelectrochemistry sandwich immunoassay of squamous cell carcinoma antigen (SCCA) was realized on this photoanode, on the basis of a bovine serum albumin/secondary antibody/CuO nanoparticles/nitrogen-doped porous carbon-ZnO bionanocomposite that can competitively absorb light and deplete the electron donor ascorbic acid as well as show the steric hindrance and p-n quenching effects. Under the optimized conditions (e.g., at a bias of 0 V vs. SCE), the photocurrent was linear with the common logarithm of SCCA concentration from 2.00 pg mL-1 to 50.0 ng mL-1, with a limit of detection (LOD) of 0.62 pg mL-1 (S/N = 3). The immunoassay of SCCA in human serum samples gave satisfactory recovery (92.0~103%) and relative standard deviation (5.1~7.8%) results.

Photoelectrochemistry hydrogen production based on a Pt nanowires-bridged CdS nanorods array of piezoelectricity-triggered Z-scheme junctions.

A vertical CdS nanorods (CdSNR) array is hydrothermally synthesized on an indium tin oxide (ITO) slice, and a novel Pt nanowires (PtNW)/CdSNR/ITO photoanode is then fabricated after the multipoint-bridging of the CdSNR by the photodeposited transverse PtNW. The piezoelectricity (PE)-enhanced photoelectrochemistry based hydrogen production is studied, giving a photocurrent density of 8.13 mA cm-2 and a PE-enhancement factor as high as 2.45 on this photoanode, and a hydrogen yield of 0.132 mmol cm-2 h-1 on a Pt cathode under optimized conditions. A new concept of PE-triggered Z-scheme (or S-scheme) CdSNR-PtNW-CdSNR junctions as the first example of external-field-triggered photoelectric junctions in the field is put forward to discuss the excellent hydrogen-production performance.

Sandwich photoelectrochemical biosensing of concanavalin A based on CdS/AuNPs/NiO Z-scheme heterojunction and lectin-sugar binding.

A CdS/AuNPs/NiO Z-scheme heterojunction was prepared on a fluorine-doped tin oxide (FTO) electrode by hydrothermal synthesis of NiO on FTO, electrodeposition of AuNPs on NiO/FTO electrode and then cast-coating of CdS quantum dots. The CdS/AuNPs/NiO/FTO electrode gave a notably increased photocurrent versus NiO/FTO, CdS/FTO, AuNPs/NiO/FTO, CdS/AuNPs/FTO and CdS/NiO/FTO electrodes. The CdS/AuNPs/NiO/FTO electrode was further cast-coated with chitosan to immobilize d-mannose by Schiff base reaction, and concanavalin A (ConA) and then horseradish peroxidase (HRP) were captured on the electrode surface by lectin-sugar binding. 4-Chloro-1-naphthol (4-CN) was oxidized to form an insoluble precipitate catalyzed by HRP in the presence of H2O2, and the presence of precipitate on the photoelectrode inhibited the photocurrent in the presence of holes scavenger ascorbic acid. The relevant electrodes were characterized by electrochemistry, quartz crystal microbalance (QCM), UV-vis spectrophotometry, scanning electron microscopy/energy dispersive spectroscopy, and transmission electron microscopy. The QCM revealed that the collection efficiency (η) of the 4-CN-electrooxidation precipitate on the electrode can be as high as 91.8%. Under the optimal conditions, the decline of photocurrent responded linearly to the common logarithm of ConA concentration from 50 pM to 500 nM, with a limit of detection of 17 pM (S/N = 3). Satisfactory results were obtained in the detection of real soybean samples.

Tailoring enzymatic loading capacity on 3D macroporous gold by catalytic hairpin assembly and hybridization chain reaction: Application for ultrasensitive self-powered microRNA detection.

It is important to develop effective strategies to construct enzymatic biofuel cell based self-powered biosensors. We report here the facile regulation of enzymatic loading capacity on the bioanode by utilizing a concatenated catalytic hairpin assembly (CHA)/hybridization chain reaction (HCR) and its application for self-powered microRNA-141 (miRNA-141) detection. To construct the bioanode, a concatenated CHA/HCR process triggered by miRNA-141 was conducted on the three-dimensional macroporous gold (3DMG) electrode to generate long double-stranded DNA nanowires for glucose oxidase immobilization. Quartz crystal microbalance study reveals that the enzymatic loading capacity on the bioanode increases at an increasing miRNA-141 concentration, leading to enhanced catalytic performance for glucose oxidation. The short-circuit currents of the assembled glucose/O2 biofuel cells increase at increasing miRNA-141 concentrations, enabling ultrasensitive detection of miRNA-141. The self-powered biosensor features a wide dynamic range for detecting miRNA-141 from 10-17 to 10-11 M, with an ultralow detection limit of 1.3 aM. This work provides a highly sensitive self-powered biosensing platform for miRNA detection.

Preparation of novel HKUST-1-glucose oxidase composites and their application in biosensing.

Copper-based metal-organic frameworks (MOF) and multi-walled carbon nanotubes (HKUST-1-MWCNTs) composite were synthesized by one-step hydrothermal method, and PDA-enzyme-HKUST-1-MWCNTs composite was prepared by one-pot method for the construction of glucose biosensors, which realized the sensitive amperometric detection of glucose at 0.7 V (vs. SCE). The sensitivity of the sensor for glucose detection was 178 µA mM-1cm-2 in the wide linear range of 0.005 ~ 7.05 mM, the detection limit was 0.12 µM and the corresponding RSD was 3.8%. Its high performance is mainly benefitted from the high porosity and large specific surface area of HKUST-1, the good conductivity of MWCNTs, and the excellent adhesion and dispersion of PDA. The strategy of combining PDA and MWCNTs to improve the dispersion and conductivity of MOF is expected to achieve a wider application of MOF-based materials in the electrochemical biosensing field.

Piezoelectricity-enhanced photoelectrochemistry synthesis of H2O2 on an Au nanoparticles modified p-type Sb-doped ZnO nanotubes array.

A p-type Sb-doped ZnO nanorods (p-ZnOSb,NR) array was hydrothermally prepared on indium tin oxide (ITO) and then etched into a p-type Sb-doped ZnO nanotubes (p-ZnOSb,NT) array by hot alkali solution. Further photodeposition of Au nanoparticles (AuNP) yielded a novel AuNP/p-ZnOSb,NT/ITO photocathode. The green synthesis of H2O2 by piezoelectricity-enhanced photoelectrochemistry and oxygen reduction reaction was studied for the first time, giving a H2O2 yield of 15.2 µmol cm-2 h-1, a photocurrent density of -1.05 mA cm-2 and a Faraday efficiency of 79.0% on this photocathode.

Au nanoclusters-decorated WO3 nanorods for ultrasensitive photoelectrochemical sensing of Hg2.

Photosensitizers and enzyme mimics are extensively used in photoelectrochemical (PEC) sensing, but few materials can be used as both photosensitizers and enzyme mimics in PEC sensing. Herein, we report Au nanoclusters (AuNCs) as both photosensitizers and peroxidase mimics for sensitive PEC sensing of Hg2+. It is found that AuNCs can act as photosensitizers to improve the PEC activity of WO3 nanorods; so the WO3/AuNCs composite material can be used as an advanced photosensitive material for PEC detection. AuNCs can also catalyze precipitate formation on the photoelectrode because of their peroxidase mimetic activity, and the interface electron transfer is hindered by the formed precipitate. Thus, the photocurrent of the WO3/AuNCs-based photoelectrode is quenched. When Hg2+ is present, the AuNCs-catalyzed precipitate formation is inhibited by Hg2+ because of the binding of Hg2+ to AuNCs through Hg2+-Au+ interactions. The photocurrent of the WO3/AuNCs-based photoelectrode increases accordingly, enabling "signal on" PEC detection of Hg2+. A broad linear range for Hg2+ detection is achieved between 1.0 pM and 50 nM with a detection limit of 0.2 pM. We have developed an advanced photosensitive material and introduced a simple method for PEC detection of Hg2+.

A Novel Signaling Strategy for an Ultrasensitive Photoelectrochemical Immunoassay Based on Electro-Fenton Degradation of Liposomes on a Photoelectrode.

A signaling strategy can directly determine the analytical performance and application scope of photoelectrochemical (PEC) immunoassays, so it is of great significance to develop an effective signaling strategy. The electro-Fenton reaction has been extensively used to degrade organic pollutants, but it has not been applied to PEC immunoassays. Herein, we report a novel signaling strategy for a PEC immunoassay based on electro-Fenton degradation of liposomes (Lip) on a photoelectrode. Lip vesicles are coated on Au@TiO2 core-shell photoactive material, which can prevent ascorbic acid (AA) from scavenging photogenerated holes. In the presence of a target, the immunomagnetic bead labels are converted to Fe3+ for electro-Fenton reaction, and hydroxyl radicals generated by the electro-Fenton reaction can degrade the Lip vesicles on the photoelectrode. Because of the degradation of Lip vesicles, photogenerated holes can be scavenged more effectively by AA, leading to an increase in photocurrent. Based on the electro-Fenton-regulated interface electron transfer, the sensitive "signal on" PEC immunoassay of a carcinoembryonic antigen is achieved, which features a dynamic range from 0.05 to 5 × 104 pg mL-1 and a detection limit of 0.01 pg mL-1. Our work provides a novel and efficient PEC immunoassay platform by introducing the electro-Fenton reaction into PEC analysis.

Photoelectrochemical sandwich immunoassay of brain glycogen phosphorylase based on methyl orange-sensitized TiO2 nanorods.

The photoelectrochemical immunoassay of glycogen phosphorylase BB (GPBB) was studied. A methyl orange/TiO2 nanorod heterojunction was constructed on a fluorine-doped tin oxide electrode by hydrothermal synthesis, calcination, and chemical adsorption. A sandwich immune structure consisting of GPBB as the first antibody, GPBB, and a CdS@mesoporous silica-ascorbic acid (AA)-GPBB as secondary antibody composite was constructed on each of the selected well surfaces of a 96-well microplate. By adding mercaptoethylamine to structurally destroy the secondary antibody composite and release the electron donor AA, the amplification of photocurrent, and thus the "off-on" photoelectrochemical biosensing of GPBB were realized. The use of the 96-well microplate provides good reproducibility of the assembled immune structures and eliminates the possible effect of the photogenerated hole-induced protein oxidation on the photocurrent. The relevant electrodes and materials were characterized by electrochemistry, UV-vis diffuse reflectance spectra, Fourier transform infrared spectroscopy, X-ray diffractometer, scanning electron microscopy/energy dispersive spectroscopy, transmission electron microscopy and BET method. Under the optimal conditions, the photocurrent was linear with the logarithm of GPBB concentration from 0.005 to 200 ng mL-1 and with a limit of detection of 1.7 pg mL-1 (S/N = 3). Satisfactory results were obtained in the analysis of real serum samples. A sandwich immune structure consisting of GPBB first antibody, GPBB, and a CdS@mesoporous silica-ascorbic acid (AA)-GPBB secondary antibody composite was constructed on each of the selected well surfaces of a 96-well microplate. By adding mercaptoethylamine to structurally destroy the secondary antibody composite and release the electron donor AA, the amplification of photocurrent, and thus the "off-on" photoelectrochemical biosensing of GPBB were realized.

Sensitive photoelectrochemical determination of T4 polynucleotide kinase using AuNPs/SnS2/ZnIn2S4 photoactive material and enzymatic reaction-induced DNA structure switch strategy.

We report here Au nanoparticles (AuNPs)/SnS2/ZnIn2S4 as a high-performance active material for sensitive photoelectrochemical (PEC) determination of T4 polynucleotide kinase (T4 PNK) using an enzymatic reaction-induced DNA structure switch strategy. To construct the PEC biosensor, a double-stranded DNA probe consisting of a CdS quantum dots (QDs)-labeled single-stranded DNA (sDNA) and its complementary DNA (cDNA) is immobilized on the AuNPs/SnS2/ZnIn2S4 photoactive material. T4 PNK can catalyze the phosphorylation of 5'-OH-terminated sDNA in the double-stranded DNA probe when ATP is present, and λ-exonuclease can catalyze the degradation of the phosphorylated sDNA into small fragments. Then the cDNA forms a hairpin structure so that CdS QDs and AuNPs are in close contact, which can induce exciton-plasma interactions between CdS QDs and AuNPs. The exciton-plasma interactions significantly boost the photocurrent, enabling the "signal on" PEC determination of T4 PNK in the range of 10-4 - 1 U mL-1 with a detection limit of 6 × 10-5 U mL-1. The PEC biosensor can also be used to screen enzyme inhibitors.

Controllable sensitization of Zr-MOFs by using CdS and its application for photoelectrochemical detection of alkaline phosphatase.

CdS quantum dots (QDs) are attached onto zirconium-based metal-organic frameworks (Zr-MOFs) with DNA as a bridge to boost the photoelectrochemical (PEC) activity of Zr-MOFs, and the sensitization of Zr-MOFs by using CdS QDs is regulated by the alkaline phosphatase (ALP)-catalyzed hydrolysis of tripolyphosphate, enabling sensitive "signal-on" PEC detection of ALP activity.

Photoelectrochemical sandwich immunoassay of CYFRA21-1 based on In2O3/WO3 type-II heterojunction and CdS quantum dots-polydopamine nanospheres labeling.

Using an In2O3/WO3 type-II heterojunction modified fluorine-doped tin oxide (FTO) electrode as the photoanode and CdS quantum dots (QDs)-polydopamine nanospheres (PDA NSs) as the secondary antibody (Ab2) label, the photoelectrochemistry (PEC) sandwich immunosensing of the lung cancer marker CYFRA21-1 was studied. WO3 nanoplates were prepared by a hydrothermal method, In2O3 nanoporous spheres were prepared by a hydrothermal method followed by calcination, and the In2O3/WO3 type-II heterojunction with high PEC activity was prepared by ultrasonic mixing and cast-coating. PDA NSs with a high surface area can be loaded with abundant Ab2 molecules and many CdS QDs with an energy level well matched with the heterojunction, so the photocurrent signal can be amplified by the formation of a sandwich immunostructure. Through the simulation experiments of photoelectrode-modified chitosan films of varying thickness, the effective transport distance of photogenerated charges is preliminarily discussed. Under the optimized conditions, the photocurrent was linear with the common logarithm of CYFRA21-1 concentration from 100 fg mL-1 to 50 ng mL-1, with a limit of detection of 56 fg mL-1 (S/N = 3). The immunoassay of CYFRA21-1 in human serum samples gave satisfactory recovery results.

A TetR family transcriptional regulator, SP_2854 can affect the butenyl-spinosyn biosynthesis by regulating glucose metabolism in Saccharopolyspora pogona.

BACKGROUND: Butenyl-spinosyn produced by Saccharopolyspora pogona exhibits strong insecticidal activity and a broad pesticidal spectrum. Currently, important functional genes involve in butenyl-spinosyn biosynthesis remain unknown, which leads to difficulty in efficiently understanding its regulatory mechanism, and improving its production by metabolic engineering. RESULTS: Here, we identified a TetR family transcriptional regulator, SP_2854, that can positively regulate butenyl-spinosyn biosynthesis and affect strain growth, glucose consumption, and mycelial morphology in S. pogona. Using targeted metabolomic analyses, we found that SP_2854 overexpression enhanced glucose metabolism, while SP_2854 deletion had the opposite effect. To decipher the overproduction mechanism in detail, comparative proteomic analysis was carried out in the SP-2854 overexpressing mutant and the original strain, and we found that SP_2854 overexpression promoted the expression of proteins involved in glucose metabolism. CONCLUSION: Our findings suggest that SP_2854 can affect strain growth and development and butenyl-spinosyn biosynthesis in S. pogona by controlling glucose metabolism. The strategy reported here will be valuable in paving the way for genetic engineering of regulatory elements in actinomycetes to improve important natural products production.

Anodic Stripping Voltammetric Analysis of Trace Arsenic(III) on a Au-Stained Au Nanoparticles/Pyridine/Carboxylated Multiwalled Carbon Nanotubes/Glassy Carbon Electrode.

A Au-stained Au nanoparticle (Aus)/pyridine (Py)/carboxylated multiwalled carbon nanotubes (C-MWCNTs)/glassy carbon electrode (GCE) was prepared for the sensitive analysis of As(III) by cast-coating of C-MWCNTs on a GCE, electroreduction of 4-cyanopyridine (cPy) to Py, adsorption of gold nanoparticles (AuNPs), and gold staining. The Py/C-MWCNTs/GCE can provide abundant active surface sites for the stable loading of AuNPs and then the AuNPs-initiated Au staining in HAuCl4 + NH2OH solution, giving a large surface area of Au on the Aus/Py/C-MWCNTs/GCE for the linear sweep anodic stripping voltammetry (LSASV) analysis of As(III). At a high potential-sweep rate of 5 V s-1, sharp two-step oxidation peaks of As(0) to As(III) and As(III) to As(V) were obtained to realize the sensitive dual-signal detection of As(III). Under optimal conditions, the ASLSV peak currents for oxidation of As(0) to As(III) and of As(III) to As(V) are linear with a concentration of As(III) from 0.01 to 8 µM with a sensitivity of 0.741 mA µM-1 and a limit of detection (LOD) of 3.3 nM (0.25 ppb) (S/N = 3), and from 0.01 to 8.0 µM with a sensitivity of 0.175 mA µM-1 and an LOD of 16.7 nM (1.20 ppb) (S/N = 3), respectively. Determination of As(III) in real water samples yielded satisfactory results.