Sharina Abu Hanifah

An Electrochemical DNA Microbiosensor Based on Succinimide-Modified Acrylic Microspheres

An electrochemical microbiosensor for DNA has been fabricated based on new acrylic microspheres modified with reactive N-acryloxysuccinimide (NAS) functional groups. Hydrophobic poly(n-butylacrylate-N-acryloxysuccinimide) microspheres were synthesized in an emulsion form with a simple one-step photopolymerization technique. Aminated DNA probe was attached to the succinimde functional group of the acrylic microspheres via covalent bonding. The hybridization of the immobilized DNA probe with the complementary DNA was studied by differential pulse voltametry using anthraquninone-2-sulfonic acid monohydrate sodium salt (AQMS) as the electroactive hybridization label. The influences of many factors such as duration of DNA probe immobilization and hybridization, pH, type of ions, buffer concentrations, ionic strength, operational temperature and non-complementary DNA on the biosensor performance were evaluated. Under optimized conditions, the DNA microbiosensor demonstrated a linear response range to target DNA over a wide concentration range of 1.0 × 10−16 and 1.0 × 10−8 M with a lower limit of detection (LOD) of 9.46 × 10−17 M (R2 = 0.97). This DNA microbiosensor showed good reproducibility with 2.84% RSD (relative standard deviation) (n = 3). Application of the NAS-modified acrylic microspheres in the construction of DNA microbiosensor had improved the overall analytical performance of the resultant DNA microbiosensor when compared with other reported DNA biosensors using other nano-materials for membranes and microspheres as DNA immobilization matrices.

Effects of Gold Nanoparticles on the Response of Phenol Biosensor Containing Photocurable Membrane with Tyrosinase.

The role of incorporation of gold nanoparticles (50-130 nm in diameter) into a series of photocurable methacrylic-acrylic based biosensor membranes containing tyrosinase on the response for phenol detection was investigated. Membranes with different hydrophilicities were prepared from 2-hydroxyethyl methacrylate and n-butyl acrylate via direct photocuring. A range of gold nanoparticles concentrations from 0.01 to 0.5 % (w/w) was incorporated into these membranes during the photocuring process. The addition of gold nanoparticles to the biosensor membrane led to improvement in the response time by a reduction of approximately 5 folds to give response times of 5-10 s. The linear response range of the phenol biosensor was also extended from 24 to 90 μM of phenol. The hydrophilicities of the membrane matrices demonstrated strong influence on the biosensor response and appeared to control the effect of the gold nanoparticles. For less hydrophilic methacrylic-acrylic membranes, the addition of gold nanoparticles led to a poorer sensitivity and detection limit of the biosensor towards phenol. Therefore, for the application of gold nanoparticles in the enhancement of a phenol biosensor response, the nanoparticles should be immobilized in a hydrophilic matrix rather than a hydrophobic material.

Preparation and Characterization of Polymer Electrolyte of Glycidyl Methacrylate-Methyl Methacrylate-LiClO4 Plasticized with Ethylene Carbonate

In the present investigation, we study the properties of the plasticized polyglycidyl methacrylate P(GMA) copolymerized with polymethyl methacrylate P(MMA)-LiClO4 polymer electrolyte prepared by solution casting technique. The electrolyte was characterized using impedance spectroscopy (EIS), Fourier transforms infrared (FTIR), cyclic voltammetry (CV), and X-ray diffraction (XRD). The conductivity was improved from  S cm−1 to  S cm−1 upon the addition of 25 wt.% LiClO4 salt into P(GMA-MMA). The conductivity was improved from  S cm−1 to  S cm−1 upon the addition of 80 wt.% EC into P(GMA-MMA)-LiClO4 The band that belongs to C–O–C is shifted farther than the band of C=O upon the addition of LiClO4 into P(GMA-MMA). The band of C–O–C stretching is shifted to lower wavenumber upon the addition of EC into P(GMA-MMA)-LiClO4. Upon the addition of EC into P(GMA-co-MMA), the intensity of the peaks decreases, implying the amorphous nature of the electrolyte increases with the concentration of the plasticizer. The electrolyte is electrochemically stable at 3.8 V, making it suitable for dye-sensitized solar cell application.

Effects of Temperature and pH on Immobilized Laccase Activity in Conjugated Methacrylate-Acrylate Microspheres

Immobilization of laccase on the functionalized methacrylate-acrylate copolymer microspheres was studied. Poly(glycidyl methacrylate-co-n-butyl acrylate) microspheres consisting of epoxy groups were synthesized using facile emulsion photocuring technique. The epoxy groups in poly(GMA-co-nBA) microspheres were then converted to amino groups. Laccase immobilization is based on covalent binding via amino groups on the enzyme surface and aldehyde group on the microspheres. The FTIR spectra showed peak at 1646 cm−1 assigned to the conformation of the polymerization that referred to GMA and nBA monomers, respectively. After modification of the polymer, intensity of FTIR peaks assigned to the epoxy ring at 844 cm−1 and 904 cm−1 was decreased. The results obtained from FTIR exhibit a good agreement with the epoxy content method. The activity of laccase-immobilized microspheres increased upon increasing the epoxy content. Furthermore, poly(GMA-co-nBA) microspheres revealed uniform size below 2 µm that contributes to large surface area of the microspheres to be used as a matrix, thus increasing the enzyme capacity and enzymatic reaction. Immobilized enzyme also shifted to higher pH and temperature compared to free enzyme.

Effects of ethylene glycol dimethacrylate as cross-linker in ionic liquid gel polymer electrolyte based on poly(glycidyl methacrylate)

ABSTRACT In this study, modified poly(glycidyl methacrylate)-based films for gel electrolyte were prepared by an in situ UV photopolymerization technique. The effects of adding ethylene glycol dimethacrylate (EGDMA) to the polymer host were studied through X-ray diffraction analysis and differential scanning calorimetry. The results from Fourier transform-infrared spectra indicate complete polymerization among the monomers. The addition of EGDMA to the formulation of gel polymer electrolyte increased the loading of 1-butyl-3-methylimidazolium bis(fluoromethylsulfonyl)imide up to 200 wt.% with the highest value of 8.2 × 10−4 S cm−1. All the gel polymer electrolyte membranes obeyed the Arrhenius law.

Role of Salt Concentration Lithium Perchlorate on Ionic Conductivity and Structural of (Glycidyl Methacrylate-co-Ethyl Methacrylate) (70/30) Based on a Solid Polymer Electrolyte

A new solid polymer electrolytes (SPE) comprising copolymer of poly(glycidyl methacrylate, GMA) and (ethyl methacrylate, EMA) as polymer host and LiClO4 as dopant was prepared by solution-casting technique. The copolymer was prepared by photopolymerization method and was characterized using NMR. The SPEs were characterized using electrochemical impedance spectroscopy (EIS), fourier transforms infrared (FTIR) and X-ray diffraction (XRD). The highest conductivity achieved was 4.0x10-4 at 373K with highest conductivity at room temperature (2.7x10ˉ5 S cm-1 at 30 wt. % of LiClO4). The active coordination site for the cation (Li+), three electrons donating functional carbonyl, ether and epoxy group of the GMA-co-EMA host have been evaluated base on their properties that were recorded in (FTIR). The structural analysis showed reduction in copolymer crystallinity phases at its highest conductivity

Polymer electrolyte based on crosslinked poly(glycidyl methacrylate) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

Polymer electrolytes based on crosslinked poly(glycidyl methacrylate) as polymer host and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BmimTFSI) as incorporated salt were prepared by in-situ photopolymerization technique. The complexes with different mass ratio of glycidyl methacrylate (GMA) monomer to BmimTFSI were investigated. The ionic conductivity of the polymer electrolyte was increased and reach the highest value of 7.50 × 10−4 S cm−1 at the ratio of 3:7 (GMA: BmimTFSI). The interaction between the polymer host and ionic liquid was proved by Attenuated Total Reflectance-Fourier Transformation Infra-Red Spectroscopy (ATR-FTIR). Meanwhile, the X-ray diffraction analysis shows the amorphousity of the polymer electrolyte film increase with the ionic liquid ratio.

Photo-polymerization of methacrylate based polymer electrolyte for dye-sensitized solar cell

Abstract The ionic conductivity of poly(glycidyl methacrylate-co-ethyl methacrylate) [P(GMA-co-EMA)]-lithium perchlorate (LiClO4)-ethylene carbonate (EC) electrolyte and photovoltaic performances of dye-sensitized solar cells (DSSC) utilizing the electrolyte were investigated. P(GMA-co-EMA) as a host material of the electrolyte was synthesized by UV-curing and characterized by nuclear magnetic resonance (NMR). P(GMA-co-EMA) based solid polymer electrolyte containing 80 wt% EC exhibited the highest room temperature ionic conductivity. The crystallinity degree of the electrolyte decreases with the EC content, as confirmed by X-ray diffraction (XRD) studies. The electrochemical stability investigated by cyclic voltammetry (CV) reveals that the electrolyte is stable up to 4.8 V. A dye-sensitized solar cell of fluorine tin oxide (FTO)/TiO2-dye/P(GMA-co-EMA)-LiClO4-EC/Pt possessed the photovoltaic effect with a short-circuit current density (Jsc) of 4.85×10-3 mA cm-2 and open circuit voltage (Voc) of 0.4 V, respectively, under light intensity of 100 mW cm-2.

Electrochemical Sunset Yellow Biosensor Based on Photocured Polyacrylamide Membrane for Food Dye Monitoring

An enzyme-based electrochemical biosensor was investigated for the analysis of Sunset Yellow synthetic food dye. A glassy carbon electrode was coated with a poly(acrylamide-co-ethyl methacrylate) membrane to immobilize laccase using a single-step photopolymerization procedure. Poly(acrylamide-co-ethyl methacrylate) membrane was demonstrated to have acceptable water absorption and suitable for biosensor application. Sunset Yellow biosensor exhibited a linear response range from 0.08 to 10.00 µM with a detection limit of 0.02 µM. This biosensor was successfully used to determine Sunset Yellow in soft drinks with recoveries of 99.0–101.6%. The method was validated using high-performance liquid chromatography, indicating the biosensor can be as a promising alternative method for Sunset Yellow detection.

A New Laccase Based Biosensor for Tartrazine

Laccase enzyme, a commonly used enzyme for the construction of biosensors for phenolic compounds was used for the first time to develop a new biosensor for the determination of the azo-dye tartrazine. The electrochemical biosensor was based on the immobilization of laccase on functionalized methacrylate-acrylate microspheres. The biosensor membrane is a composite of the laccase conjugated microspheres and gold nanoparticles (AuNPs) coated on a carbon-paste screen-printed electrode. The reaction involving tartrazine can be catalyzed by laccase enzyme, where the current change was measured by differential pulse voltammetry (DPV) at 1.1 V. The anodic peak current was linear within the tartrazine concentration range of 0.2 to 14 μM (R2 = 0.979) and the detection limit was 0.04 μM. Common food ingredients or additives such as glucose, sucrose, ascorbic acid, phenol and sunset yellow did not interfere with the biosensor response. Furthermore, the biosensor response was stable up to 30 days of storage period at 4 °C. Foods and beverage were used as real samples for the biosensor validation. The biosensor response to tartrazine showed no significant difference with a standard HPLC method for tartrazine analysis.