Application of functionalized silver nanoparticles as a biochemical sensor for selective detection of lysozyme protein in milk sample.

Silver nanoparticles (AgNPs) functionalized with glutamic acid (GA) was used as a biochemical sensing probe in colorimetry for detection of lysozyme protein in milk samples. The method is based on the color change of AgNPs/GA from yellow to reddish-yellow differentiated with naked eyes for qualitative determination and red shift of localized surface plasmon resonance (LSPR) absorption signal intensity of AgNPs/GA in visible region used for quantitative determination of lysozyme. The control experiments were performed to demonstrate the electrostatic force of interactions between AgNPs/GA and protein molecule. A wide linear range of 3-150 nM with limit of detection of 1.5 nM was acquired for quantitative determination of lysozyme using AgNPs/GA as a biochemical sensing probe. The advantages of using AgNPs/GA as a biochemical sensing probe are simple, label-free and economic for determination of lysozyme from milk samples.

Sucrose capped gold nanoparticles as a plasmonic chemical sensor based on non-covalent interactions: Application for selective detection of vitamins B1 and B6 in brown and white rice food samples.

We report simple and selective method for detection of vitamins B1 and B6 in brown and white rice samples using localized surface plasmon resonance (LSPR) of sucrose capped gold nanoparticles (AuNPs) as a chemical sensor colorimetrically. Here, detection is based on the color change of AuNPs from pink to blue followed by a red shift of LSPR absorption band in UV-vis region with the addition of vitamins B1 and B6 into the NPs solution. A good linear range was observed in the range of 25-1000 ngmL-1 with detection limit of 8 ngmL-1 for B1 and 50-1000 ngmL-1 with detection limit of 15 ngmL-1 for vitamins B6. The employment of AuNPs for detection of B1 and B6 vitamins in rice food samples showed remarkable abilities in terms of the simplicity, low cost, stability, reproducibility and sensitivity.

Experimental and theoretical approaches for the selective detection of thymine in real samples using gold nanoparticles as a biochemical sensor.

We report a simple, selective and cost effective method for the qualitative and quantitative determination of thymine in a DNA standard and urine samples using gold nanoparticles (AuNPs) as a label-free colorimetric biochemical sensor. The mechanism for the detection of thymine is demonstrated via the color change of the AuNPs from pink to blue, followed by the shift of the localized surface plasmon resonance (LSPR) absorption band to a higher wavelength with the introduction of an analyte. The selective detection of thymine was experimentally verified by performing a control experiment with nucleobases, other biomolecules, metal ions and anions. In addition, the computation density functional theory (DFT) and time dependent density functional theory (TD-DFT) using the Gaussian (C.01) program highlighted that the electrostatic potential behavior of the thymine molecule facilitated a non-covalent interaction toward gold for the selective detection of analytes, and the computation was also used to calculate a UV-Vis absorption band as well. The calculated absorption band of the AuNPs with thymine, obtained using TD-DFT, was found to be very close to the experimental data. The omnicapped truncated tetrahedral (ν 3-tetrahedral) Au20 cluster structure was considered as the model for the AuNP optimization. The linear range obtained for the quantitative determination of thymine was found to be 10-1200 ng mL-1 with a limit of detection of 3 ng mL-1. The advantages of using the AuNPs as a biochemical sensor are that they provide a facile and low cost method and are selective for the qualitative and quantitative determination of thymine in a DNA standard and in urine samples in comparison to chromatographic and electrochemical methods.

Removal of endrin and dieldrin isomeric pesticides through stereoselective adsorption behavior on the graphene oxide-magnetic nanoparticles.

A novel stereoselective removal behavior of isomeric endrin and dieldrin pesticides from sample solution is demonstrated using nanocomposite of graphene oxide (GO) and iron oxide (Fe3O4) magnetic nanoparticles (MNPs). The removal efficiency of endrin and dieldrin was found higher when GO-MNPs was used as a separating probe than the individual use of GO and MNPs. The removal efficiency of both the pesticides was found to be more favorable when the dosage amount of GO-MNPs was 30 mg for 30-min contact time with pH 4.0 at room temperature. The good correlation of determination (R 2) with 0.975 and 0.973 values obtained for endrin and dieldrin, respectively demonstrated a well fitting of Langmuir adsorption isotherm model. The higher removal percentage (86.0%) and higher slope value of Langmuir adsorption isotherm were estimated for endrin compared to dieldrin (74.0%). The reason for higher adsorption percentage of endrin is due to the endo-position of oxygen atom in molecule favors more interaction of molecules with GO-MNPs compared to the exo-position of oxygen present in dieldrin. In addition, the higher value of R 2 for endrin and dieldrin demonstrated better suitability of pseudo-first-order and pseudo-second-order kinetic models, respectively. The advantages of the present method are use of simple UV-vis spectrophotometry for monitoring and low-cost use of GO-MNPs nanomaterial for the removal of pesticides from sample solution.