Förster Resonance Energy Transfer from Quantum Dots to Rhodamine B As Mediated by a Cationic Surfactant: A Thermodynamic Perspective

Abstract

Förster resonance energy transfer (FRET) has attracted much attention for its wide applications in the fields of bioimaging, bioanalysis, etc. One of the critical problems in FRET is the construction of suitable donor–acceptor pair. The fluorescent quantum dots (QDs) can well meet the requirements both for a donor and an acceptor, owing to their tunable emission and broad absorption. Besides, the QDs possess high quantum yield, which highly benefits the FRET efficiency. In this work, glutathione-capped CdTe QDs (GSH-CdTe QDs) was chosen as the energy donor (D) and Rhodamine B (RhB) as the energy acceptor (A). However, no FRET occurred when there were only QDs and RhB, even though there was much overlap between the absorption spectrum of RhB and the emission spectrum of QDs. Interestingly, after the addition of a cationic surfactant, cetyltrimethyl­ammonium bromide (CTAB), FRET was induced favorably. Further understanding of this phenomenon was studied by fluorescence spectroscopy, dynamic light scattering, and zeta potential. The results indicated that QDs aggregated and were cross-linked by CTAB due to electrostatic interactions. Then, RhB was trapped in the aggregates. Therefore, QDs and RhB were pulled closer to a reasonable distance and FRET happened prosperously. Notably, thermodynamics in this process was well studied for an in-depth understanding. This work will render the better design of donor–acceptor pairs to overcome the long distances as well as the deep understanding of FRET with spreading applications.

Electrostatically Driven Förster Resonance Energy Transfer between a Fluorescent Metal Nanoparticle and J-Aggregate in an Inorganic–Organic Nanohybrid Material

“…To further confirm the presence of electrostatic interaction between the negatively charged dye and the positively charged surface of AgCAu, we have estimated the relevant thermodynamic parameters for the interaction between AgCAu and S2165 dye (in monomeric form) through fluorescence quenching experiments. We would like to state here that similar type of studies have been performed earlier by other researchers on different inorganic–organic hybrid materials. − Because the fluorescence of AgCAu is quenched in the presence of S2165 dye (Figure a), Stern–Volmer equation can be used to study the variation in F 0 / F against the dye concentration . The Stern–Volmer equation is given by where F 0 and F are the fluorescence intensities of AgCAu in the absence and presence of the dye, respectively, and K SV is the Stern–Volmer constant.…”

Thermodynamic Implications of the Ligand Exchange with Alkylamines on the Surface of CdSe Quantum Dots: The Importance of Ligand–Ligand Interactions

“…The results in Table show that the binding constants in ligand exchange with alkylamines (C 4 Am, C 8 Am, and C 12 Am) decrease as the temperature increases. To illuminate the driving forces in the ligand exchange process, the related thermodynamic parameters were determined by the Van’t Hoff equation: Here, R refers to the gas constant and T represents the absolute temperature. Δ H and Δ S are the enthalpy change and entropy change, respectively.…”

Surfactant-Induced Self-Assembly of CdTe Quantum Dots into Multicolor Luminescent Hybrid Vesicles

“…Similar spectral changes have been observed earlier for oppositely charged fluorophore−surfactant pairs due to ion-pair complexation. 47,48 Therefore, the red shifts in the absorption and PL peak positions with concomitant PL quenching observed in the C1 region of the binary mixture arise mainly due to the formation of surfactant-induced aggregates of QDs via ion-pair complexation. In contrast, the opposite spectral shifts (blue shifts) observed in the C2 region of the binary mixture indicate much less polar local environment around QDs inside the surfactant-induced aggregates in the C2 region compared to that in the C1 region.…”