No abstract

A semiconducting water-soluble core-shell quantum dots (QDs) system capped with thiolated ligand was used in this study for the sensitive detection of glucose in aqueous samples. The QDs selected are of CdSe-coated ZnS and were prepared in house based on a hot injection technique. The formation of ZnS shell at the outer surface of CdSe core was made via a specific process namely, SILAR (successive ionic layer adsorption and reaction). The distribution, morphology, and optical characteristics of the prepared core-shell QDs were assessed by transmission electron microscopy (TEM) and spectrofluorescence, respectively. From the analysis, the results show that the mean particle size of prepared QDs is in the range of 10–12 nm and that the optimum emission condition was displayed at 620 nm. Further, the prepared CdSe/ZnS core shell QDs were modified by means of a room temperature ligand-exchange method that involves six organic ligands, L-cysteine, L-histidine, thio-glycolic acid (TGA or mercapto-acetic acid, MAA), mercapto-propionic acid (MPA), mercapto-succinic acid (MSA), and mercapto-undecanoic acid (MUA). This process was chosen in order to maintain a very dense water solubilizing environment around the QDs surface. From the analysis, the results show that the CdSe/ZnS capped with TGA (CdSe/ZnS-TGA) exhibited the strongest fluorescence emission as compared to others; hence, it was tested further for the glucose detection after their treatment with glucose oxidase (GOx) and horseradish peroxidase (HRP) enzymes. Here in this study, the glucose detection is based on the fluorescence quenching effect of the QDs, which is correlated to the oxidative reactions occurred between the conjugated enzymes and glucose. From the analysis of results, it can be inferred that the resultant GOx:HRP/CdSe/ZnS-TGA QDs system can be a suitable platform for the fluorescence-based determination of glucose in the real samples.

In this study, the applications of CdSe/ZnS quantum dots (QDs) and its role in advanced sensings has been explored. The CdSe/ZnS was synthesized by using hot injection method with the shell ZnS layer was made using successive ionic layer adsorption and reaction (SILAR) method. The morphology of the CdSe/ZnS QDs was studied using Transmission Electron Microscope (TEM) and the average particle size was in 10-12 nm range. The prepared QDs were optically characterized using spectrofluorescence and strong emission was observed at 620 nm. Comparison of the fluorescence emissions of CdSe/ZnS capped with various capping ligands such as L-cysteine, thioglycolic acid (TGA), mercaptopropionic acid (MPA), mercaptosuccinic acid (MSA) and mercaptoundecanoic acid (MUA) were studied. The CdSe/ZnS capped with TGA gave the strongest fluorescence emission compared to others.

Magneticmesoporousɣ-Fe2O3/SiO2 synthesized using an evaporation-induced self-assembly (EISA) approach. The non-ionictriblock copolymer P123 was used as surfactant template with various amounts of iron oxide (1.8g-2.4g) and varied during the synthesis. Characterizations of the surface area and magnetic properties for prepared materials were done using N2-sorption analyses, and a superconducting quantum interference device interfaced with a vibrating sample magnetometer (SQUID-VSM) respectively. From this study, N2-sorption analysis indicated that most of the ɣ-Fe2O3domains of several nanometres were embedded in the silica matrix. In addition, the obtained magneticmesoporouscomposite which contains 2.3g amount ofiron oxide has revealedhigher magnetism saturation value of (4.564 emu/g) compared to other prepared samples which been evaluated by VSM analysis.

Magnetic nanocomposite photocatalyst is an alternative approach for easy separation of catalyst from the treated water by magnetic force. This paper will discuss the performance of dye degradation using two different supported layer; Silica and Activated Carbon that shield between magnetic iron oxide (Fe2O3) and Titanium dioxide (TiO2) photocatalyst. Photocatalytic activity is measure using Methylene Blue (MB) as indicator. The magnetic nanocomposite was synthesis using an evaporation indused self-assembly (EISA) approach and wet synthesis method. The photocatalyst were then characterized using Vibrating Sample Magnetometer (VSM), Brunauer-Emmet-Teller (BET), and Transmission Electron Microscope (TEM) and the effect of dye degradation were characterizing using Ultraviolet-Visible (UV-VIS) spectroscopy. The result showed that activated carbon is the good supporter compare to silica.