Preparation and characteristic of cobalt phthalocyanine modified carbon paste electrode for bisphenol A detection

A portable optic fiber aptasensor for sensitive, specific and rapid detection of bisphenol-A in water samples

Bisphenol A (BPA) is a known endocrine disruptor and one of the most serious environmental contaminants, often present at low levels in various water sources. Therefore, it is very important and necessary to develop a fast, cost-effective, sensitive, and selective method for on-site detection of BPA. Herein, we developed a portable, evanescent, wave fiber-optic aptasensor for rapid, on-site detection of BPA with high sensitivity and selectivity. In this system, the probe DNA molecule, which is the complementary sequence of a small part of the BPA aptamer, was covalently immobilized onto the optical fiber sensor surface. Using an indirect competitive detection mode, samples containing different concentrations of bisphenol A were premixed with a given concentration of fluorescence-labeled BPA aptamer, which binds to bisphenol A with high specificity. Then, the sample mixture was pumped to the sensor surface, and a higher concentration of BPA led to less fluorescence-labeled BPA aptamer hybridized with surface immobilized probe DNA and thus to a lower fluorescence signal. The developed sensing system exhibits a sensitive response to BPA in the range of 2 nM to 100 nM with a low detection limit of 1.86 nM (0.45 ng ml(-1)) under the optimal conditions. The biosensors showed good reproducibility, stability, and selectivity for BPA detection. Finally, this proposed sensor was successfully employed to determine the presence of BPA in wastewater samples.

Electronic tongue formed by sensors and biosensors containing phthalocyanines as electron mediators: Application to the analysis of red grapes

An electronic tongue formed by voltammetric sensors and biosensors containing phthalocyanines has been developed and used to analyze grapes of different varieties. The sensors are prepared using the carbon paste technique and have been chemically modified with different metallophthalocyanines. In turn, biosensors consist of carbon paste electrodes modified with phthalocyanines combined with tyrosinase or glucose oxidase. The response of the individual sensors towards model solutions of glucose and catechol have demonstrated that the voltammetric responses depend on the nature of the phthalocyanine, evidencing the important role of the electron mediator in the performance of the sensors. The capability of the system to discriminate grapes according to their sugar and their polyphenolic content has been evidenced using Principal Component Analysis. It has been demonstrated that the proposed array of sensors combines the advantages of classical phthalocyanine based sensors — that provide global information about the sample —, with the specificity of the enzyme substrate reaction typical of biosensors. For this reason, the selectivity of the multisensor system and its capability of discrimination is clearly improved when biosensors containing glucose oxidase or tyrosinase are included in the array.

Electrochemical determination of bisphenol A in plastic bottled drinking water and canned beverages using a molecularly imprinted chitosan-graphene composite film modified electrode

Herein, a novel electrochemical sensor based on an acetylene black paste electrode modified with molecularly imprinted chitosan-graphene composite film for sensitive and selective detection of bisphenol A (BPA) has been developed. Several important parameters controlling the performance of the sensor were investigated and optimised. The imprinted sensor offers a fast response and sensitive BPA quantification. Under the optimal conditions, a linear range from 8.0 nM to 1.0 μM and 1.0 to 20 μM for the detection of BPA was observed with the detection limit of 6.0 nM (S/N=3). Meanwhile, the fabricated sensor showed excellent specific recognition to template molecule among the structural similarities and coexistence substances. Furthermore, this imprinted electrochemical sensor was successfully employed to detect BPA in plastic bottled drinking water and canned beverages.

Bioelectronic tongue based on lipidic nanostructured layers containing phenol oxidases and lutetium bisphthalocyanine for the analysis of grapes

In this work, a multisensor system formed by nanostructured voltammetric biosensors based on phenol oxidases (tyrosinase and laccase) has been developed. The enzymes have been incorporated into a biomimetic environment provided by a Langmuir-Blodgett (LB) film of arachidic acid (AA). Lutetium bisphthalocyanine (LuPc2) has also been introduced in the films to act as electron mediator. The incorporation of the enzymes to the floating layers to form Tyr/AA/LuPc2 and Lac/AA/LuPc2 films has been confirmed by the expansion in the surface pressure isotherms and by the AFM images. The voltammetric response towards six phenolic compounds demonstrates the enhanced performance of the biosensors that resulted from a preserved activity of the tyrosinase and laccase combined with the electron transfer activity of LuPc2. Biosensors show improved detection limits in the range of 10(-7)-10(-8) mol L(-1). An array formed by three sensors AA/LuPc2, Tyr/AA/LuPc2 and Lac/AA/LuPc2 has been employed to discriminate phenolic antioxidants of interest in the food industry. The Principal Component Analysis scores plot has demonstrated that the multisensor system is able to discriminate phenols according to the number of phenolic groups attached to the structure. The system has also been able to discriminate grapes of different varieties according to their phenolic content. This good performance is due to the combination of four factors: the high functionality of the enzyme obtained using a biomimetic immobilization, the signal enhancement caused by the LuPc2 mediator, the improvement in the selectivity induced by the enzymes and the complementary activity of the enzymatic sensors demonstrated in the loading plots.

E-assay concept: detection of bisphenol A with a label-free electrochemical competitive immunoassay

A label-free electrochemical immunosensor was developed by electropolymerization of N-(3-(4-(2-(4-hydroxyphenyl)propan-2-yl)phenoxy)propyl) 3-(5-hydroxy-1,4-dihydro-1,4-dioxonaphthalen-2(3)-yl)propionamide (JugBPA). By combination with an antibody directed to bisphenol A (αBPA), this conducting polymer-based biosensor can detect BPA directly with a limit of detection of 2pgmL(-1). Square wave voltammetry shows that the polymer film presents a current decrease upon anti-BPA binding and an opposite current increase upon BPA addition in solution. This electrochemical immunosensor (E-assay) also shows high selectivity towards closely related compounds (bisphenol A dimethacrylate, and dibutyl phthalate). The E-assay concept described here could be a promising tool for simple, low-cost and reagentless on-site environmental monitoring.

Surface-imprinted core-shell Au nanoparticles for selective detection of bisphenol A based on surface-enhanced Raman scattering

Surface-imprinted core-shell Au nanoparticles (AuNPs) were explored for the highly selective detection of bisphenol A (BPA) by surface-enhanced Raman scattering (SERS). A triethoxysilane-template complex (BPA-Si) was synthesized and then utilized to fabricate a molecularly imprinted polymer (MIP) layer on the AuNPs via a sol-gel process. The imprinted BPA molecules were removed by a simple thermal treatment to generated the imprint-removed material, MIP-ir-AuNPs, with the desired recognition sites that could selectively rebind the BPA molecules. The morphological and polymeric characteristics of MIP-ir-AuNPs were investigated by transmission electron microscopy and Fourier-transform infrared spectroscopy. The results demonstrated that the MIP-ir-AuNPs were fabricated with a 2 nm MIP shell layer within which abundant amine groups were generated. The rebinding kinetics study showed that the MIP-ir-AuNPs could reach the equilibrium adsorption for BPA within 10 min owning to the advantage of ultrathin core-shell nanostructure. Moreover, a linear relationship between SERS intensity and the concentration of BPA on the MIP-ir-AuNPs was observed in the range of 0.5-22.8 mg L(-1), with a detection limit of 0.12 mg L(-1) (blank±3×s.d.). When applied to SERS detection, the developed surface-imprinted core-shell MIP-ir-AuNPs could recognize BPA and prevent interference from the structural analogues such as hexafluorobisphenol A (BPAF) and diethylstilbestrol (DES). These results revealed that the proposed method displayed significant potential utility in rapid and selective detection of BPA in real samples.

Self-assembly of tetrakis (3-trifluoromethylphenoxy) phthalocyaninato cobalt(II) on multiwalled carbon nanotubes and their amperometric sensing application for nitrite

In this work, the soluble cobalt phthalocyanine functionalized multiwalled carbon nanotubes (MWCNTs) are synthesized by π-π stacking interaction between tetrakis (3-trifluoromethylphenoxy) phthalocyaninato cobalt(II) (CoPcF) complex and MWCNTs. The physical properties of CoPcF-MWCNTs hybrids are evaluated using spectroscopy (UV-vis, XPS, and Raman) and electron microscopy (TEM and SEM). Subsequently, an amperometric nitrite electrochemical sensor is designed by immobilizing CoPcF-MWCNTs hybrids on the glassy carbon electrode. The immobilized CoPcF complex shows the fast electron transfer rate and excellent electrocatalytic activity for the oxidation of nitrite. Under optimum experimental conditions, the proposed nitrite electrochemical sensor shows the fast response (less than 2 s), wide linear range (9.6 × 10(-8) to 3.4 × 10(-4) M) and low detection limit (6.2 × 10(-8) M) because of the good mass transport, fast electron transfer rate, and excellent electrocatalytic activity.

Cyclic Voltammetric Investigations of Thiazine Dyes on Modified Electrodes

Electrochemical behavior of five progressively alkylated thiazine dyes has been investigated at glassy carbon/montmorillonite and glassy carbon/zeolite electrodes. Quantitative characteristics, associated with the positions of peak potentials (Ea and Ec) and current ratios (ia/ic), are measured with scan rates. The peak current observed in the modified electrodes is dependent on both the porosity and nature and number of sites involved in partitioning the complex into film. The values of diffusion coefficient for different dyes have been calculated from electrochemical data. It is suggested that in clay-modified electrode along with physical diffusion the process of electron hopping seems to be most likely.

A facile electrochemical sensor for nonylphenol determination based on the enhancement effect of cetyltrimethylammonium bromide

A facile electrochemical sensor for the determination of nonylphenol (NP) was fabricated in this work. Cetyltrimethylammonium bromide (CTAB), which formed a bilayer on the surface of the carbon paste (CP) electrode, displayed a remarkable enhancement effect for the electrochemical oxidation of NP. Moreover, the oxidation peak current of NP at the CTAB/CP electrode demonstrated a linear relationship with NP concentration, which could be applied in the direct determination of NP. Some experimental parameters were investigated, such as external solution pH, mode and time of accumulation, concentration and modification time of CTAB and so on. Under optimized conditions, a wide linear range from 1.0 × 10⁻⁷ mol·L⁻¹ to 2.5 × 10⁻⁵ mol·L⁻¹ was obtained for the sensor, with a low limit of detection at 1.0 × 10⁻⁸ mol·L⁻¹. Several distinguishing advantages of the as-prepared sensor, including facile fabrication, easy operation, low cost and so on, suggest a great potential for its practical applications.

An Exfoliated Graphite-Based Bisphenol A Electrochemical Sensor

The use of an exfoliated graphite (EG) electrode in the square wave voltammetric detection of bisphenol A (a model phenolic pollutant) in water, whereby the phenolic electrode fouling challenge is mitigated, is described. The oxidation peak of BPA was observed at about 0.45 V in phosphate buffer solution at pH 10. The current response exhibited a linear relationship with the concentration over a range from 1.56 μM–50 μM. The detection limit was calculated to be 0.76 μM. The EG electrode surface was renewed after each measurement with excellent reproducibility. A real sample application was also investigated.

Remarkable sensitivity for detection of bisphenol A on a gold electrode modified with nickel tetraamino phthalocyanine containing Ni-O-Ni bridges

This work reports the electrocatalysis of bisphenol A on Ni(II) tetraamino metallophthalocyanine (NiTAPc) polymer modified gold electrode containing Ni-O-Ni bridges (represented as Ni(OH)TAPc). The Ni(II)TAPc films were electro-transformed in 0.1 mol L(-1) NaOH aqueous solution to form 'O-Ni-O oxo bridges', forming poly-n-Ni(OH)TAPc (where n is the number of polymerising scans). poly-30-Ni(OH)TAPc, poly-50-Ni(OH)TAPc, poly-70-Ni(OH)TAPc and poly-90-Ni(OH)TAPc films were investigated. The polymeric films were characterised by electrochemical impedance spectroscopy and the charge transfer resistance (R(CT)) values increased with film thickness. The best catalytic activity for the detection of bisphenol A was on poly-70-Ni(OH)TAPc. Electrode resistance to passivation improved with polymer thickness. The electrocatalytic behaviour of bisphenol A was compared to that of p-nitrophenol in terms of electrode passivation and regeneration. The latter was found to passivate the electrode less than the former. The poly-70-Ni(OH)TAPc modified electrode could reliably detect bisphenol A in a concentration range of 7x10(-4) to 3x10(-2)mol L(-1) with a limit of detection of 3.68x10(-9)mol L(-1). The sensitivity was 3.26x10(-4)A mol(-1) L cm(-2).

Sensitivity and selectivity determination of BPA in real water samples using PAMAM dendrimer and CoTe quantum dots modified glassy carbon electrode

Bisphenol A (BPA) is an environmental pollutant to disrupt endocrine system or cause cancer, thus the detection of BPA is very important. Herein, an amperometric sensor was fabricated based on immobilized CoTe quantum dots (CoTe QDs) and PAMAM dendrimer (PAMAM) onto glassy carbon electrode (GCE) surface. The cyclic voltammogram of BPA on the sensor exhibited a well-defined anodic peak at 0.490V in 0.1M pH 8.0 PBS. The determination conditions were optimized and the kinetic parameters were calculated. The linear range was 1.3 x 10(-8) to 9.89 x 10(-6)M with the correlation coefficient of 0.9999. The limit of detection was estimated to be 1 x 10(-9)M. The current reached the steady-state current within about 5s. Furthermore, the fabricated sensor was successfully applied to determine BPA in real water samples.

Amperometric biosensor based on tyrosinase immobilized onto multiwalled carbon nanotubes-cobalt phthalocyanine-silk fibroin film and its application to determine bisphenol A

An amperometric bisphenol A (BPA) biosensor was fabricated by immobilizing tyrosinase on multiwalled carbon nanotubes (MWNTs)-cobalt phthalocyanine (CoPc)-silk fibroin (SF) composite modified glassy carbon electrode (GCE). In MWNTs-CoPc-SF composite film, SF provided a biocompatible microenvironment for the tyrosinase to retain its bioactivity, MWNTs possessed excellent inherent conductivity to enhance the electron transfer rate and CoPc showed good electrocatalytic activity to electrooxidation of BPA. The cyclic voltammogram of BPA at this biosensor exhibited a well defined anodic peak at 0.625 V. Compared with bare GCE, the oxidation signal of BPA significantly increased; therefore, this oxidation signal was used to determine BPA. The effect factors were optimized and the electrochemical parameters were calculated. The possible oxidation mechanism was also discussed. Under optimum conditions, the oxidation current was proportional to BPA concentration in the range from 5.0 x 10(-8) to 3.0 x 10(-6) M with correlation coefficient of 0.9979 and detection limit of 3.0 x 10(-8) M (S/N=3). The proposed method was successfully applied to determine BPA in plastic products and the recovery was in the range from 95.36% to 104.39%.