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.
Highlights
The nanomaterials maintain the special characteristics, which include the substantial surface area, superior reaction surface activity, and higher catalytic efficiency, to mention some [1]
In the presence of glucose, glucose oxidase (GOx) loaded onto the substrate catalyzes the available glucose into gluconic acid by means of an oxidation process using the oxygen molecule as an electron acceptor and in turn produces H2 O2 simultaneously
The biocompatible property is contributed by property is contributed by the oleic acid (OA) and thioglycolic acid (TGA) groups, as we found from our earlier studies that any the groups, as we found from our earlier studies that any ligand which has the functional ligand which has the functional groups in its structure such as amine, thiol, or unsaturation was groups in to its maintain structure such amine,anti-oxidative thiol, or unsaturation wasThis observed to maintain inbuilt observed someasinbuilt properties
Summary
The nanomaterials maintain the special characteristics, which include the substantial surface area, superior reaction surface activity, and higher catalytic efficiency, to mention some [1]. For the majority of biosensor-related applications, the previously reported nanomaterials include gold [4], carbon nanotubes [5], magnetic iron oxide [6], titania [7], silica [8], and quantum dots (QDs) [9,10,11,12,13,14]. Among all these nanomaterials, QDs have been found to be more favorable for sensor applications as they exhibit broad excitation and narrow emission wavelengths, in addition to allowing their emission wavelengths to be fine-tuned. The fluorescence emission wavelengths of QDs are mostly influenced by the changes in particle sizes and surface covered ligands as the charges are strongly inclined by the nature of ligands and all of which responsible for the biomolecule interactions [16]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
