A developed colorimetric pH sensor film based on edible materials for real-time monitoring of food freshness is described. The mixed natural dyes from edible plants Clitoria sp and Brassica sp were extracted and incorporated into ι-carrageenan film as a colorimetric pH sensor film for monitoring food spoilage and its freshness. The color changes of the developed colorimetric sensor film were measured with chromametry and UV-vis spectroscopy, respectively. Experimental results show that colorimetric pH sensor film demonstrated statistically significant differences (p < 0.05) between CIE-L*a*b* coordinates color system indicated that the developed colorimetric sensor film was able to give a gradual change in color over a wide pH range. The color of the colorimetric sensor film also changes discretely and linearly with factors that contribute to food spoilage using shrimp and durian samples. Moreover, the developed colorimetric pH sensor film has the potential to be used as a safe, non-destructive testing and also a flexibly visual method for direct assessment of food freshness indicator during storage.

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.

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 laccaseimmobilized microspheres increased upon increasing the epoxy content. Furthermore, poly(GMA-co-nBA) microspheres revealed uniform size below 2 m 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.

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A study is carried out on solid polymer electrolytes (SPEs) based on UV-curable glycidyl methacrylate (GMA) reactive mixtures to determine the lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) effect at different weight percentages. These polymeric systems are discussed considering several factors such as chemical interaction, structural and thermal properties, ionic conductivity, and lithium transference number. Samples are prepared using solution casting technique and are analyzed using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and electrochemical impedance spectroscopy (EIS) characterization methodologies. FTIR spectra show that interaction occurs between electronegative atoms in polymer host and TFSI − ions. XRD diffractogram indicates the amorphous aspect of SPEs, without the presence of LiTFSI peaks. Doping with LiTFSI salt reduces the glass transition temperature of SPEs and increased their ionic conductivity. Identified as the ideal salt concentration for poly(glycidyl methacrylate) (PGMA)-LiTFSI SPE system is 30 wt.% LiTFSI doping level, thus achieving a ionic conductivity of 3.69×10 −8 S cm −1 at ambient temperature and 1.23×10 −4 S cm −1 at 373 K. The ionic conductivity behavior obeys the Vogel-Tamman-Fulcher equation with an activation energy of 0.054 eV.