An Approach for Optimizing the Shell Thickness of Core−Shell Quantum Dots Using Photoinduced Charge Transfer

Abstract

Photoinduced charge-transfer dynamics between CdSe quantum dots (QDs) possessing varying monolayers of ZnS and hole scavengers such as phenothiazine (PT) and N-methylphenothiazine (NMPT) were investigated for optimizing the shell thickness of core−shell quantum dots. Spectroscopic investigations indicate that phenothiazine binds onto the surface of bare CdSe QDs, resulting in the photoluminescence quenching, and two monolayers of ZnS prevent the electron-transfer process. Methodologies presented here can provide quantitative information on the optimum shell thickness of core−shell QDs, which can suppress the undesired electron transfer and provide maximum luminescence yield.

Biokinetics and In Vivo Distribution Behaviours of Silica-Coated Cadmium Selenide Quantum Dots

“…Trioctylphosphine oxide (TOPO)-capped QDs were synthesized by following a reported procedure [10,21]. A pot mixture containing CdO (0.067 g, 0.52 mmol), dodecylamine (3.8 g, 20.72 mmol), TOPO (2.7 g, 6.9 mmol) and tetradecylphosphonic acid (0.40 g, 1.44 mmol) was heated to 300°C under vacuum, until CdO dissolves completely to produce an optically clear solution.…”

Fluorescence Quenching of CdS Quantum Dots by 4‐Azetidinyl‐7‐Nitrobenz‐2‐Oxa‐1,3‐Diazole: A Mechanistic Study

“…[31][32][33][34][35] Exciton dissociation of QDs by Fçrster resonance energy transfer (FRET) is a dynamic quenching process, whereas the quenching of QD emission by charge transfer (electron and/or hole) can proceed through either dynamic or static quenching mechanisms. [28,29,36] There are some cases where both dynamic and static quenching mechanisms contribute to QD exciton quenching. [37] Quenching processes are also dependent on the nature of quencher and the QD.…”

“…[37] Quenching processes are also dependent on the nature of quencher and the QD. [29,36] Herein, we address some important issues concerning fluorescence quenching of the QDs by organic molecules, in particular, the static vs dynamic nature of the quenching and the energy transfer vs other mechanisms of quenching by investigating the fluorescence quenching of hexadecylamine capped CdS QDs by a highly fluorescent nitrobenzoxadiazole derivative, 4-azetidinyl-7-nitrobenz-2-oxa-1,3-diazole (NBD, Figure 1). The nitrobenzoxa-diazole derivatives belong to the family of electron donor-acceptor (EDA) molecules and are extremely popular candidates as fluorescent probes in biological applications.…”

“…The literature suggests different scenarios arising from fluorescence quenching of the QDs by organic molecules involving a charge transfer mechanism, [29,36] indicating that it can be a static or a dynamic process. Our case, where the individual lifetime components do not change but their relative contributions vary with change in the quencher concentration is similar to the quenching of CdTe QDs by pyromellitimide derivative (PI-CA), [28] is indicative of a static charge transfer quenching mechanism in accordance with the literature, which clearly suggest that the influence of charge transfer interaction on the lifetime is highly dependent on the nature of the quantum dot and the quencher.…”

Cellular uptake and subcellular localization of highly luminescent silica-coated CdSe quantum dots – In vitro and in vivo

“…QDs were synthesized by following a reported procedure [25,26]. Cadmium oxide (0.067 g, 0.52 mmol), dodecylamine (3.8 g, 20.72 mmol), trioctylphosphine oxide (2.7 g, 6.9 mmol) and tetradecylphosphonic acid (0.40 g, 1.44 mmol) was heated to 300°C under vacuum, until CdO dissolves completely to produce an optically clear solution.…”