Temperature features of non-radiative energy transfer in hybrid associates of CdS/TGA quantum dots with methylene blue m
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RESEARCH PAPER
Temperature features of non-radiative energy transfer in hybrid associates of CdS/TGA quantum dots with methylene blue molecules Mikhail S. Smirnov
Received: 2 September 2019 / Accepted: 10 July 2020 © Springer Nature B.V. 2020
Abstract The paper presents the study results of non-radiative resonance energy transfer of electronic excitation from colloidal CdS quantum dots passivated with thioglycolic acid (CdS/TGA QDs) with an average size of 2.9 nm to methylene blue (MB+ ) molecules in temperature ranging from 300 to 80 K. In an aqueous MB+ and colloidal CdS/TGA QDs mixture, the increase in (MB+ )2 dimers fraction and shift of the absorption band peaks of monomers (MB+ ) from 662 to 676 nm and dimers (MB+ )2 from 606 to 590 nm were found. It is concluded that the hybrid associates of CdS/TGA+MB+ and CdS/TGA+(MB+ )2 are formed. Luminescence quenching at CdS/TGA QDs band and MB+ luminescence enhancement under increase in MB+ molecules concentration were observed. A decrease in average lifetime of CdS/TGA QDs luminescence from 25 to 4 ns was found for MB+ concentration of 42 μM. The Stern–Volmer constant, determined from the data
This work was prepared in the framework of State support of the major scientific schools of Russian Federation (project 2613.2020.2). M. S. Smirnov () Voronezh State University, Voronezh, 394018, Russia e-mail: smirnov m [email protected] M. S. Smirnov Federal State Budget Educational Institution of Higher Education, Voronezh State University of Engineering Technologies, Voronezh, 394036, Russia
on luminescence quenching, is 0.36 ∗ 106 M−1 . It is concluded that there is non-radiative resonance energy transfer (FRET) from the luminescence center of CdS/TGA quantum dots to MB+ molecule. Decreasing in temperature value to 80 K led to an increase in the luminescence intensity by 12 times. At the same time, the average lifetime of luminescence for pure CdS/TGA QDs increases from 25 to 72 ns. The Stern–Volmer constant increased to 0.64 ∗ 106 M−1 . It is concluded that its increase is due to an increase in average lifetime of CdS/TGA QD luminescence. In the framework of FRET theory, the rate constant of non-radiative energy transfer was estimated for an even distribution of CdS/TGA quantum dots and MB molecules in solution. Its is much smaller (6.7 ∗ 104 s−1 ) than the experimentally determined value (2.5∗108 s−1 ). This fact confirms the conclusion about the formation of CdS/TGA+MB hybrid system with effective FRET. Keywords Quantum dots · Methylene blue · Luminescence · Hybrid associates · Non-radiative resonance energy transfer · Colloids
Introduction Small sizes and size-dependent properties for colloidal semiconductor quantum dots (QDs), such as photostability, wide excitation range, and possibility of additional functionalization by surface ligands,
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provide a wide range of potential applications (Jr 1998; Coe et al. 2002; Rakovich et al. 2010; Ren et al. 2014; Wang et al. 2007). One of the active developing research areas is related to the use of QDs as the b
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