Imprinted Sol-gel Film Research Articles

Application of a nanostructured platform and imprinted sol-gel film for determination of chlorogenic acid in food samples

Chlorogenic acid (CGA) is a polyphenol derivative that widely exists in higher plants like fruits, vegetables, black teas, and some traditional Chinese medicines. In this work, we have proposed a sensitive and selective electrochemical sensor for detection of CGA. The sensor was based on a glassy carbon electrode (GCE) modified with a functional platform by grafting vinyltrimethoxysilane (VTMS) in multi-walled carbon nanotubes (MWCNTs) and covered by a molecularly imprinted siloxane (MIS) film prepared using the sol-gel process. The VTMS was grafted onto the surface of the MWCNTs via in situ free radical polymerization. The MIS was obtained from the acid-catalyzed hydrolysis/condensation of a solution consisting of tetraethoxysilane (TEOS), phenyltriethoxysilane (PTEOS), (3-aminopropyl)trimethoxysilane (APTMS), and CGA as a template molecule. The modification procedure was evaluated by differential pulse voltammetry (DPV) and scanning electron microscopy (SEM). Under optimized operational conditions, a linear response was obtained covering a concentration ranging from 0.08μmolL−1 to 500μmolL−1 with a detection limit (LOD) of 0.032μmolL−1. The proposed sensor was applied to CGA determination in coffee, tomato, and apple samples with recoveries ranging from 99.3% to 108.6%, showing a promising potential application in food samples. Additionally, the imprinted sensor showed a significantly higher affinity for target CGA than the non-imprinted siloxane (NIS) sensor.

SPR Enhanced molecular imprinted sol–gel film: A promising tool for gas-phase TNT detection

An innovative surface plasmon resonance (SPR) approach for the detection of 2,4,6-trinitrotoluene (TNT) gas traces, obtained using an engineered molecular imprinted sol–gel film as recognition layer onto a plasmonic gold grating, is here proposed. The SPR substrate combined with the sol–gel matrix is able to trap gas phase TNT molecules from a TNT-saturated environment (4.9ppb). Taking advantage of the azimuthally-controlled grating-coupled SPR, this sensing platform demonstrates the potentiality to detect TNT traces <1ppb with a sensitivity of 0.47°/ppb.

Selective electrochemical sensor for theophylline based on an electrode modified with imprinted sol–gel film immobilized on carbon nanoparticle layer

A novel electrochemical sensor based on an imprinted hybrid sol–gel film for selective and sensitive determination of theophylline was developed. The imprinted hybrid sol–gel film was prepared by using a new organosilane synthesized as a functional precursor, theophylline as a template and tetraethoxysilane as a matrix forming precursor. The mixture was allowed to hydrolyze, and then spin coated on glassy carbon electrode covered by carbon nanoparticles with sulfonic acid groups that were introduced for immobilization of imprinted sol–gel film and for enhancement of electronic transmission. The morphology and performance of the imprinted film were investigated in detail by scanning electron microscopy, FTIR Spectroscopy, cyclic voltammetry and differential pulse anodic stripping voltammetry. Molecularly imprinted sol–gel was employed to achieve a suitable conformation for electrochemical oxidation of theophylline and also to improve the selectivity of the sensor. The results showed that the imprinted film exhibited selectivity toward theophylline compared to the random sol–gel film prepared in the absence of the template. The imprinted sensor was also successfully employed to detect theophylline in a drug sample.

Electrochemical sensor based on a carbon nanotube-modified imprinted sol–gel for selective and sensitive determination of ß2-agonists

We describe a molecularly imprinted electrochemical sensor for selective and sensitive determination of β2-agonists. It is making use of a combination of single-wall carbon nanotubes (SWNTs) with a molecularly imprinted sol–gel. The SWNTs were introduced in order to enhance electron transport and sensitivity. The imprinted sol–gel film with its specific binding sites acts as a selective recognition element and as a preconcentrator for β2-agonists. The morphology of the imprinted film was characterized by scanning electron microscopy. The optimized sensor displays high sensitivity and excellent selectivity for the β2-agonists as shown for their determination in human serum samples.

Highly Selective Molecular Recognition and Ultrasensitive Detection of 3,4-dichloroaniline Based on Molecularly Imprinted Sol-Gel Film Combined with Multi-Walled Carbon Nanotubes

This paper developed an electrochemiluminescence (ECL) method for detecting ultratrace levels of the highly toxic organic pollutant, 3,4-dichloroaniline (3,4-DCA), in water. This method has not been used previously for 3,4-DCA detection, and is based on a 96-well micro-plate modified with molecularly imprinted sol-gel films combined with multi-walled carbon nanotubes (MIF-MWCNTs). The increase in the ECL signal intensity was proportional to the 3,4-DCA concentration within a certain range, and an excellent response was obtained for 3,4-DCA concentrations ranging from 4 × 10−11 to 6 × 10−9 mol L−1, with a low detection limit (LOD) of 1 × 10−11 mol L−1. The detection sensitivity of the present method is higher than those of the most commonly used chromatography methods, with the recovery of 3,4-DCA from spiked samples of water ranging from 83.3 to 110.5%. Thermodynamic analysis showed that the adsorption of 3,4-DCA by the MIF-MWCNTs occurred spontaneously as an exothermic and entropy decreasing process (ΔH = −32.49 kJ mol−1, ΔS = −117.89 J mol−1). Kinetic equation fitting demonstrated that the adsorption of 3,4-DCA could be fitted by an intraparticle diffusion model, and that the adsorption isotherm data fitted the Freundlich model.

Fabrication, characterization and sensing properties of Cu(II) ion imprinted sol–gel thin film on QCM

Cu(II)-molecularly imprinted sol–gel films (Cu(II)-MISGF), coated on a quartz crystal microbalance (QCM) chip, were fabricated using a sol–gel procedure. Co-hydrolysis and co-condensation of Cu(II) (templates), 3-aminopropyltrimethoxysilane (APTS, functional monomer) and tetraethoxysilane (TEOS, cross-linking agent) were performed with acid and base catalysis. The properties of the Cu(II)-MISGF were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and the electrochemical methods of cyclic voltammetry (CV). Microstructural observations revealed that the acid-catalyzed system yielded more mechanically stable thin films. A combined Cu(II)-MISGF-QCM with flow injection analysis (FIA) method was utilized to investigate the sensing performance of the Cu(II)-MISGF, with special emphasis on the most important properties of sensitivity, selectivity and response time. The Cu(II)-MISGF-QCM sensor, at a TEOS/APTS molar ratio of 10, exhibited excellent selectivity and rapidly responded to Cu(II) ions.

Effects of Physical Parameters on Bacterial Cell Adsorption onto Pre-Imprinted Sol-Gel Films

Organically modified silica (ORMOSILS) thin films produced by sol-gel method were imprinted with two bacterial strains as whole cells in order to develop an easy, fast and specific probe to detect and specifically identify these micro-organisms when present in water samples. An important feature of the imprinting process was the molecular finger-prints left by these microorganisms alongside morphology, into imprinted film cavities. The films also showed high selectivity toward the imprinted template and were able to discriminate between two very close bacterial species (E. coli and S. typhimurium). In addition, several central physical parameters of the experimental water solution were examined (i.e., pH, ionic strength and the organic load exemplified by NaCl and TOC concentration, respectively). The method sensitivity to different bacterial concentrations was studied by confocal microscopy (CLSM) and quartz crystal microbalance (QCM) tools. Results showed that increased bacterial concentrations favor rapid adsorption onto imprinted sol-gel films with high affinity, while low pH, increased organic load and high ionic concentrations (i.e., seawater) interfere with bacteria re-adsorption, reducing detection capability. Under average drinking water chemical composition the method proved to be highly efficient.

Rapid Detection of Staphylococcal Enterotoxin B by Two-Dimensional Molecularly Imprinted Film-Coated Quartz Crystal Microbalance

We fabricated a two-dimensional (2D) molecularly imprinted sol-gel thin film-coated quartz crystal microbalance (QCM) for the rapid detection of staphylococcal enterotoxin B (SEB) by combining organosilanes and the template protein SEB on the surface of piezoelectric quartz crystal (PQC) Au-electrode by in-situ immobilization. The detection process was monitored by the QCM's frequency shift (Δf). The working range of this method was 1.0 × 10−1–1.0 × 103 µg/mL. The detection limit was 6.1 ng/mL, which was lower than that of the PQC immunosensor, and the detection period was within 0.5 h. The reproducibility of the imprinted film-coated QCM was satisfactory due to no significant statistical difference (P > 0.05) in the rapid detection of SEB between intra- and inter-batch. The selectivity of the imprinted sol-gel film showed that it could discriminate the template molecule from its analogues and other guest molecules. Compared with immunochip, the imprinted film-coated QCM is more advantageous in terms of simplicity, rapidity, low cost, and sensitivity. Moreover, in real sample analysis, the recoveries of this method were 89.4–106.63%, which can be considered a favorable and applicable method for the rapid determination of SEB in real samples.

Electrochemical imprinted sensor for determination of oleanic acid based on poly (sodium 4-styrenesulfonate-co-acrylic acid)-grafted multi-walled carbon nanotubes-chitosan and cobalt hexacyanoferrate nanoparticles

A novel sensitive and selective imprinted electrochemical sensor for the determination of oleanic acid was constructed on a carbon electrode by stepwise modification of functional multi-walled carbon nanotubes, cobalt hexacyanoferrate nanoparticles and a thin imprinted sol–gel film. The fabrication of a homogeneous porous poly (sodium 4-styrenesulfonate-co-acrylic acid)-grafted multi-walled carbon nanotubes/SiO2–chitosan nanocomposite film was conducted by controllable electrodeposition technology. The surface morphologies of the modified electrodes were characterized by scanning electron microscope. The performance of the imprinted sensor was investigated by cyclic voltammetry, square wave voltammetry and electrochemical impedance spectroscopy in detail. The imprinted sensor displayed high sensitivity and selectivity towards oleanic acid. A linear relationship between the sensor response signal and the logarithm of oleanic acid concentrations ranging from 1.0×10−8 to 1.0×10−3molL−1 was obtained with a detection limit of 2.0×10−9molL−1. It was applied to the determination of oleanic acid in real capsule samples successfully.

Electrochemical Sensor for Detection of Trichlorfon Based on Molecularly Imprinted Sol–Gel Films Modified Glassy Carbon Electrode

Thin films of molecularly imprinted sol–gel polymer with specific binding sites for trichlorfon were prepared, fixed on glassy carbon electrodes and used as recognition material. The binding characteristic of the imprinted films to trichlorfon was evaluated by equilibrium binding experiments; and, the morphology was studied by scanning electronic microscope. A novel electrochemical sensor for determination of trichlorfon was developed based on the reaction between trichlorfon and the molecularly imprinted sol–gel film, which was a modified glassy carbon electrode. The sensor displayed excellent selectivity and high sensitivity. The linear response range of the sensor was 10−8 –10−6 g mL−1, and the limit of detection was 2.8 × 10−9 g mL−1. The relative standard deviation for the determination of 10−7 g mL−1 trichlorfon was 3.5%. The sensor was applied to the determination of trichlorfon in vegetables with satisfactory results.

A High Throughput and High Selective Chemiluminescence Method for Quantification of Bifenthrin Based on Molecularly Imprinted Film

One novel highly cross-linked, shape-controllable molecularly imprinted sol-gel film (MISF) with good thermal and chemical stability and three-dimensional network porous structure has been developed. The binding characteristic of the imprinted film to bifenthrin was evaluated by equilibrium binding experiments and imprinting-induced promotion of binding. The MISF was modified into the wells of 96 micro-well plate combined with chemiluminescence (CL) technology to establish the molecular imprinting-chemiluminescence (MI-CL) sensor. The high throughput and high selective detection sensor of bifenthrin was applied in vegetable and food samples with satisfactory results.

Synthesis and Application of Molecularly Imprinted Sol-Gel Film for Simultaneous Determination of Multi-Component Pesticide Residue

In this paper, three kinds of molecularly imprinted sol-gel film (MISF) which have good thermal and chemical stability and three-dimensional network porous structure have been developed. The material was synthesized by sol-gel technology using lambda-cyhalothrin, trichlorphon and beta-cyfluthrin as model analytes. The special structural behavior makes the material have good capability to seizure and capture template molecules which enhanced the MISF’s recognition efficiency and the property of separation and enrichment. The material was environmental friendly and easy to operate. The binding characteristic of the imprinted film to the three pesticides was evaluated by equilibrium binding experiments. The SEM of the three MISF has been performed to characterize the morphology of MISF. The MISFs were combined with chemiluminescence (CL) technology by modifying the sol-gel into 96 micro-well plate to establish one molecular imprinting- chemiluminescence (MI-CL) sensor which realized high selectivity, sensitivity and high throughput simultaneous assay of three pesticides. The proposed method was successfully applied to the simultaneous determination of multi-component pesticide residue in foodstuff.

A sensitive and selective sensor‐coated molecularly imprinted sol–gel film incorporating β‐cyclodextrin‐multi‐walled carbon nanotubes and cobalt nanoparticles‐chitosan for oxacillin determination

A sensitive and selective imprinted electrochemical sensor for the determination of oxacillin was developed based on indium tin oxide electrode. The proposed sensor was decorated with imprinted sol–gel film and cobalt nanoparticles‐chitosan/β‐cyclodextrin‐multiwalled carbon nanotubes nanocomposites. The surface morphologies of the modified electrodes were characterized by scanning electron microscopy and transmission electron microscope. The stepwise assembly process and electrochemical behavior of the novel sensor were characterized by differential pulse voltammetry, cyclic voltammetry and Amperometric i‐t response. The imprinted sensor displayed excellent selectivity toward oxacillin. Meanwhile, the introduced cobalt nanoparticles‐chitosan and β‐cyclodextrin‐multi‐walled carbon nanotubes exhibited noticeable amplified electrochemical response signal. The differential voltammetric anodic peak current was linear to oxacillin concentration in the range from 2.0 × 10−7 to 1.0 × 10−4 mol·l−1, and the detection limit was 6.9 × 10−9 mol·l−1. The proposed imprinted sensor was applied to the determination of oxacillin in human blood serum samples successfully. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Electrochemical determination of l-phenylalanine at polyaniline modified carbon electrode based on β-cyclodextrin incorporated carbon nanotube composite material and imprinted sol–gel film

A sensitive and selective electrochemical sensor based on a polyaniline modified carbon electrode for the determination of l-phenylalanine has been proposed by utilizing β-cyclodextrin (β-CD) incorporated multi-walled carbon nanotube (MWNT) and imprinted sol–gel film. The electrochemical behavior of the sensor towards l-phenylalanine was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and amperometric i–t curve. The surface morphologies of layer-by-layer assembly electrodes were displayed by scanning electron microscope (SEM). The response mechanism of the imprinted sensor for l-phenylalanine was based on the inclusion interaction of β-CD and molecular recognition capacity of the imprinted film for l-phenylalanine. A linear calibration plot was obtained covering the concentration range from 5.0×10−7 to 1.0×10−4molL−1 with a detection limit of 1.0×10−9molL−1. With excellent sensitivity, selectivity, stability, reproducibility and recovery, the electrochemical imprinted sensor was used to detect l-phenylalanine in blood plasma samples successfully.

A High Throughput Chemiluminescence Method Based On Molecularly Imprinted Sol-gel Films For Determination Of Sibutramine

A novel and high throughput chemiluminescence (CL) method for determination of sibutramine was originally developed based on potassium permanganate-hydrochloric acid-(tween-80) CL system. Molecularly imprinted sol-gel film (MIF) was synthesized and used as selective material to improve the selectivity of CL. In the proposed procedure, sibutramine molecule was adsorbed into the MIF, and then potassium permanganate, hydrochloric acid and tween-80 were added in wells of a 96well plate, Based on which, sibutramine was oxidized and CL was produced and detected by a photomultiplier tube (PMT). The CL intensity was correlated linear with the concentration of sibutramine over the range of 5.0 × 10 -8 -1.0 × 10

Electrochemical fabrication of molecularly imprinted porous silicate film electrode for fast and selective response of methyl parathion

A methyl parathion-templated molecularly imprinted porous silicate thin film was electrodeposited onto a glassy carbon electrode using tetraethylorthosilicate sol as the silicon precursor and vinyltriethoxysilane as the functional monomer. The surface morphology and crystallinity of the imprinted film were characterized by scanning electron microscope and X-ray diffraction. The binding performance of the film with methyl parathion was examined with voltammetric techniques. The results show that the imprinted sol–gel film gives fast, sensitive and selective response to methyl parathion. The good selectivity of the film allows fine discriminations of methyl parathion from interferants, which including parathion, α-hydroxyl-4-nitrophenyl-dimethyl-phosphonate, p-nitrophenol and nitrobenzene. A linear range for methyl parathion determination was found from 1.0 × 10 −8 to 1.0 × 10 −5 mol l −1 with an estimated detection limit of 8.9 × 10 −9 mol l −1 (S/N = 3). This imprinted sol–gel film electrode was proved to be a versatile sensing tool for the selective detection of methyl parathion in real samples.

Novel layer-by-layer assembly molecularly imprinted sol–gel sensor for selective recognition of clindamycin based on Au electrode decorated by multi-wall carbon nanotube

A novel sensitive molecularly imprinted electrochemical sensor was constructed for selective detection of clindamycin by combination of a multi-wall carbon nanotube (MWNT) layer with a thin molecularly imprinted sol–gel film. The sensor was fabricated onto Au electrode via stepwise modification of MWNT and a thin sol–gel film of molecularly imprinted polymers (MIP) by using electrodeposition method. The molecularly imprinted film displayed excellent selectivity towards clindamycin. Due to such combination, the sensor responded quickly to clindamycin. The response peak current was linear to the concentration of clindamycin in the range from 5.0 × 10 −7 mol L −1 to 8.0 × 10 −5 mol L −1, and the detection limit was 2.44 × 10 −8 mol L −1. This imprinted sensor was applied to the determination of clindamycin in human urine samples successfully. These results revealed that the imprinted sensor fulfilled the selectivity, sensitivity, speed and simplicity requirements for clindamycin detection, and provided possibilities of clinical application in physiological fluids.

Highly selective molecular recognition and high throughput detection of melamine based on molecularly imprinted sol–gel film

Multimode reader has been generally applied in immunoassay, and in the proposed paper, the 96 well micro-plate was modified with molecularly imprinted melamine sol–gel film, based on which the highly selective and high throughput detection of melamine was achieved. Melamine was imprinted into silica sol–gel films directly using phenyltrimethoxysilane and methyltrimethoxysilane as functionalized organosilicon precursors. The binding characteristic of the imprinted film to melamine was evaluated by equilibrium binding experiments and the morphology was studied by scanning electronic microscope (SEM). Scatchard analysis was carried out to estimate the binding parameters of the imprinted film. The proposed method exhibited excellent selectivity because of specific recognition of MM by molecularly imprinted film. Under the optimum conditions, the chemiluminescence (CL) intensity had a linear relationship against the concentration of melamine over the range of 0.1–50 μg mL −1 with a lower detection limit of 0.02 μg mL −1.

Smart electrochemical sensor for some neurotransmitters using imprinted sol–gel films

A hybrid sol–gel material formed by acid hydrolysis of a mixture of tetraethylorthosilicate (TEOS) and phenyltriethylorthosilicate (PTEOS) as functional monomers was imprinted by tyramine and dopamine as template molecules for the purpose of molecular recognition. Imprinted materials were spin coated as thin films on the surface of glassy carbon electrodes and then were characterized using cyclic voltammetry (CV). After extraction of the encapsulated molecules, imprinted films were tested in solutions of their templates and other molecules. Rebinding experiments were followed by electrochemical characterization using square wave voltammetry (SWV). Imprinted films showed higher affinities toward their template molecules compared to other structurally similar molecules especially for tyramine imprinted film. With the exception of tyramine and norepinephrine, the interference level did not exceed 5% for all compounds studied for dopamine-imprinted films. Tyramine-imprinted films however showed high affinity to tyramine with dopamine 40% interference. Some factors related to the rebinding ability process like pH of solution, concentration of template were studied. The sensing surface lifetime extended to 2 weeks with decay in response signal that ranged from 22%, 40% to 60% for dopamine, tyramine and norepinephrine, respectively. The standard deviation from the mean of measurements for the repeated experiments is 7.4%. Electrochemical impedance spectroscopy (EIS) measurements confirmed the results obtained by electrochemical measurements. Morphological characteristics of the imprinted thin films and their thickness were investigated using scanning electron microscope (SEM).

Electrodeposited sol–gel-imprinted sensing film for cytidine recognition on Au-electrode surface

A novel thin molecularly imprinted sol–gel film with specific recognition for cytidine was electrodeposited on the surface of piezoelectric quartz crystal (PQC) Au-electrode. In this method, a sufficiently negative potential was applied to the electrode surface to generate hydroxyl ions, which play the role of the catalyst for the hydrolysis and condensation of 3-(aminopropyl)trimethoxysilane (APTMS). The process of the preparation of the imprinted sol–gel film was investigated in detail by using the piezoelectric quartz crystal impedance (PQCI) technique and cyclic voltammetry. The thickness of the imprinted film was controlled easily by adjusting the applied potential and the deposited time. The binding capacity and the selectivity of the electrodeposited imprinted sol–gel film were also studied in detail by using PQCI, electrochemically impedance technique and capacitance technique. The electrodeposited imprinted sol–gel film exhibited high selectivity toward cytidine in comparison to interfering substances. The dissociation constant ( K d) in the nanomolar range indicated a strong imprinted interaction existing between the electrodeposited sol–gel-imprinted film and the template cytidine.