Mechanistic Aspects of Quantum Dot Based Probing of Cu (II) Ions: Role of Dendrimer in Sensor Efficiency |
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Authors: | Srabanti Ghosh Amiya Priyam Subhash C Bhattacharya Abhijit Saha |
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Institution: | (1) UGC-DAE Consortium for Scientific Research, Kolkata Centre, III/LB-8, Bidhananagar, Kolkata, 700098, India;(2) Department of Chemistry, Jadavpur University, Kolkata, 700032, India |
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Abstract: | Selective quenching of luminescence of quantum dots (QDs) by Cu2+ ions vis-à-vis other physiologically relevant cations has been reexamined. In view of the contradiction regarding the mechanism,
we have attempted to show why Cu2+ ions quench QD-luminescence by taking CdS and CdTe QDs with varying surface groups. A detailed study of the solvent effect
and also size dependence on the observed luminescence has been carried out. For a 13% decrease in particle diameter (4.3 nm
→3.7 nm), the quenching constant increased by a factor of 20. It is established that instead of surface ligands of QDs, conduction
band potential of the core facilitates the photo-induced reduction of Cu (II) to Cu (I) thereby quenching the photoluminescence.
Taking the advantage of biocompatibility of dendrimer and its high affinity towards Cu2+ ions, we have followed interaction of Cu2+-PAMAM and also dendrimer with the CdTe QDs. Nanomolar concentration of PAMAM dendrimer was found to quench the luminescence
of CdTe QDs. In contrast, Cu2+-PAMAM enhanced the fluorescence of CdTe QDs and the effect has been attributed to the binding of Cu2+-PAMAM complex to the CdTe particle surface. The linear portion of the enhancement plot due to Cu2+-PAMAM can be used for determination of Cu2+ ions with detection limit of 70 nM. |
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Keywords: | CdTe Nanoparticles Cu2+ions PAMAM dendrimer Photoluminescence (PL) |
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