Anne Bonhomme

Molecularly imprinted polymer-based electrochemical sensor for the sensitive detection of glyphosate herbicide

ABSTRACT A sensitive electrochemical molecularly imprinted sensor was developed for the detection of glyphosate (Gly), by electropolymerisation of p-aminothiophenol-functionalised gold nanoparticles in the presence of Gly as template molecule. The extraction of the template leads to the formation of cavities that are able to specifically recognise and bind Gly through hydrogen bonds between Gly molecules and aniline moieties. The performance of the developed sensor for the detection of Gly was investigated by linear sweep voltammetry using a hexacyanoferrate/hexacyanoferrite solution as redox probe, the electron transfer rate increasing when concentration of Gly increases, due to a p-doping effect. The molecularly imprinted sensor exhibits a broad linear range, between 1 pg/L and 1 µg/L and a quantification limit of 0.8 pg/L. The selectivity of the proposed sensor was investigated towards the binding of Gly metabolite, aminomethylphosphonic acid, revealing excellent selectivity towards Gly. The developed sensor was successfully applied to detect Gly in tap water samples.

Aflatoxin B1 Detection Using a Highly-Sensitive Molecularly-Imprinted Electrochemical Sensor Based on an Electropolymerized Metal Organic Framework

A sensitive electrochemical molecularly-imprinted sensor was developed for the detection of aflatoxin B1 (AFB1), by electropolymerization of p-aminothiophenol-functionalized gold nanoparticles in the presence of AFB1 as a template molecule. The extraction of the template leads to the formation of cavities that are able to specifically recognize and bind AFB1 through π-π interactions between AFB1 molecules and aniline moities. The performance of the developed sensor for the detection of AFB1 was investigated by linear sweep voltammetry using a hexacyanoferrate/hexacyanoferrite solution as a redox probe, the electron transfer rate increasing when the concentration of AFB1 increases, due to a p-doping effect. The molecularly-imprinted sensor exhibits a broad linear range, between 3.2 fM and 3.2 µM, and a quantification limit of 3 fM. Compared to the non-imprinted sensor, the imprinting factor was found to be 10. Selectivity studies were also performed towards the binding of other aflatoxins and ochratoxin A, proving good selectivity.

Sensitive Potentiometric Determination of Amphetamine with an All-Solid-State Micro Ion-Selective Electrode

ABSTRACT The development of amphetamine-ion-selective microelectrodes using electrochemical polymerization and microfabrication technologies is reported in this study. The microelectrodes include polypyrrole films electrochemically polymerized and doped with cosane anion ([3,3′-Co(1,2-C2B9H11)2]−) as the internal solid contact layer between the polymeric sensitive membrane and platinum working microelectrode. Several poly(vinyl chloride)-type membranes with different compositions of plasticizers/ionophore were drop casted on the conducting polymer layer, polypyrrole[3,3′-Co(1,2-C2B9H11)2]. Potentiometric measurements were performed to calibrate the response of the developed chemical sensors. The sensor was highly sensitive to amphetamine using a membrane composition of 26 wt% poly (vinyl chloride), 63 wt% di-butyl phthalate, 6 wt% sodium tetraphenylborate, and 5 wt% dibenzo-18-crown 6-ether. A high and linear response was demonstrated within the concentration range from 10−5 to 10−3 M with a slope of 53 mV/decade and a limit of detection of 4 × 10−5 M. A Reilley diagram shows that the sensor signal is stable for a working pH between 1.50 and 8.50. The chemical sensor was highly selective to amphetamine when compared to other interfering ions and compounds including K+, Na+, , D,L-phenylalanine, caffeine, (±)-epinephrine bitartrate salt, and N-formylamphetamine using the fixed interference method with coefficients of selectivity (Log ) from −1.40 to −1.15.

Characterization of surfactant complex mixtures using Raman spectroscopy and signal extraction methods: Application to laundry detergent deformulation.

This paper presents the analysis of surfactants in complex mixtures using Raman spectroscopy combined with signal extraction (SE) methods. Surfactants are the most important component in laundry detergents. Both their identification and quantification are required for quality control and regulation purposes. Several synthetic mixtures of four surfactants contained in an Ecolabel laundry detergent were prepared and analyzed by Raman spectroscopy. SE methods, Independent Component Analysis and Multivariate Curve Resolution, were then applied to spectral data for surfactant identification and quantification. The influence of several pre-processing treatments (normalization, baseline correction, scatter correction and smoothing) on SE performances were evaluated by experimental design. By using optimal pre-processing strategy, SE methods allowed satisfactorily both identifying and quantifying the four surfactants. When applied to the pre-processed Raman spectrum of the Ecolabel laundry detergent sample, SE models remained robust enough to predict the surfactant concentrations with sufficient precision for deformulation purpose. Comparatively, a supervised modeling technique (PLS regression) was very efficient to quantify the four surfactants in synthetic mixtures but appeared less effective than SE methods when applied to the Raman spectrum of the detergent sample. PLS seemed too sensitive to the other components contained in the laundry detergent while SE methods were more robust. The results obtained demonstrated the interest of SE methods in the context of deformulation.

Effect of Perfluorinated-Hexaethylene Glycol Functionalization of Gold Nanoparticles on the Enhancement of the Response of an Enzymatic Conductometric Biosensor for Urea Detection

In conductometric enzymatic biosensors, enzymatic reaction is confined close to the interdigitated electrode surface, because enzyme is cross-linked in contact with this surface in the presence or absence of nanoparticles. The effect of the use of a new type of doubly-functionalized gold nanoparticles (PF-HEG-Au NPs) on the response of conductometric biosensor based on interdigitated electrodes (IDEs), for the detection of enzymatic substrates was studied. Gold nanoparticles (AuNPs) were first synthesized following the citrate process, with an average diameter of 14 nm. AuNPs were then functionalized with 11-mercaptoundecylhexaethyleneglycol (HEG) and then with 1H,1H,2H,2H-perfluorodecanethiol (PF). The doubly-functionalized AuNPs were characterized using TEM, UV-Vis spectrophotometry and FTIR spectroscopy. Urease, mixed with these doubly functionalized AuNPs, was then cross-linked with glutaraldhedyde vapor on the IDE surface. In the presence of urea, the conductometric response was measured in a differential mode. The best sensitivities for urea detection were obtained with PF-HEG-Au NPs (520 µS /mM and 0.5µM of detection limit), as compared to 284µS/mM and 2µM of detection limit with bare Au NPs, PF-AuNPs and HEG-AuNPs, and 1.07µS/mM and 100 µM of detection limit with urease directly crosslinked on IDEs.When stored in phosphate buffer (5 mM, pH 6.7) at 4 °C, the biosensor with PF-HEG-Au NPs showed good stability for more than 12 days.

Voltammetric glucose biosensor based on glucose oxidase encapsulation in a chitosan-kappa-carrageenan polyelectrolyte complex

In this work, a new design of voltammetric glucose biosensor, based on the encapsulation of glucose oxidase (GOx) in a chitosan/κ‑carrageenan (CHIT/CAR) polyelectrolyte complex (PEC) using a simple coacervation process is presented. A conductometric monitoring of this is performed. Spectroscopic and morphological characterization of the PEC film encapsulating GOx is carried out. Compared to biosensors based on a chitosan film, a more sensitive voltammetric detection of glucose is obtained. Using square wave voltammetry (SWV), the CHIT/CAR PEC based biosensor exhibits a wide linearity range from 5 μM to 7 mM glucose with a detection limit of 5 μM. Excellent selectivity against ascorbic acid, uric acid and urea is observed and the applicability of the biosensor for glucose detection in spiked saliva samples was demonstrated.

Voltammetric Sensor Based on a Double-Layered Molecularly Imprinted Polymer for Testosterone

ABSTRACT A novel strategy to improve the sensitivity of molecularly imprinted polymer sensors based on a double-layered molecularly imprinted polymer hybrid film-modified gold electrode was investigated for the determination of testosterone. A conductive poly(anilinomethyltriethoxysilane) film was electrodeposited on the surface of the electrode, and a molecularly imprinted polysiloxane thin film was formed on the conductive layer by a sol-gel process to enhance the electrochemical response. The performance of the sensor for testosterone was investigated by square-wave voltammetry in the presence of a hexacyanoferrate/ferrite as a redox probe. The prepared sensor provided high recognition for testosterone with a broad linear range from 10 to 100 fM and a low detection limit of 10 fM. Good sensitivity, selectivity, and stability were observed with relative standard deviations less than 5%. Good recovery of testosterone was obtained when the sensor was used for the determination of testosterone in fortified urine.

Fabrication of new polypyrrole/silicon nitride hybrid materials for potential applications in electrochemical sensors: Synthesis and characterization

ABSTRACT In this research, an efficient fabrication process of conducting polypyrrole (PPy)/silicon nitride (Si3N4) hybrid materials were developed in order to be employed as transducers in electrochemical sensors used in various environmental and biomedical applications. The fabrication process was assisted by oxidative polymerization of pyrrole (Py) monomer on the surface of Si/SiO2/Si3N4 substrate in presence of FeCl3 as oxidant. To improve the adhesion of PPy layer to Si3N4 surface, a pyrrole-silane (SPy) was chemically bonded through silanization process onto the Si3N4 surface before deposition of PPy layer. After Py polymerization, Si/SiO2/Si3N4-(SPy-PPy) substrate was formed. The influence of SPy concentration and temperature of silanization process on chemical composition and surface morphology of the prepared Si/SiO2/Si3N4-(SPy-PPy) substrates was studied by FTIR and SEM. In addition, the electrical properties of the prepared substrates were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). It was found that the best silanization reaction conditions to get Si/SiO2/Si3N4-(SPy-PPy) substrate with high PPy adhesion and good electrical conductivity were obtained by using SPy at low concentration (4.3 mM) at 90°C. These promising findings open the way for fabrication of new hybrid materials which can be used as transducers in miniaturized sensing devices for various environmental and biomedical applications.

Large area in situ fabrication of Poly(pyrrole)-nanowires on flexible thermoplastic films using Nanocontact printing

Highly efficient nano-engineering tools will certainly revolutionize the biomedical and sensing devices research and development in the years to come. Here, we present a novel high performance conducting poly(pyrrole) nanowires (PPy-NW) patterning technology on thermoplastic surfaces (poly(ethylene terephthalate (PETE), poly(ethylene 2,6-naphthalate (PEN), polyimide (PI), and cyclic olefin copolymer) using nanocontact printing and controlled chemical polymerization (nCP-CCP) technique. The technique uses a commercial compact disk as a template to produce nanopatterned polydimethylsiloxane (PDMS) stamps. The PDMS nanopatterned stamp was applied to print the PPy-NWs and the developed technology of nCP-CCP produced 3D conducting nanostructures. This new and very promising nanopatterning technology was achieved in a single step and with a low cost of fabrication over large areas.