Restriction‐In‐Motion of Surface Ligands Enhances Photoluminescence of Quantum Dots—Experiment and Theory

Abstract

molecular processes within individual cells, [1] they present challenges, especially in maintaining their fluorescence properties after exposure to the excitation light for a period of time. Generally, it is well known that commonly employed organic fluorophores suffer from photobleaching, low quantum yields, and aggregationinduced self-quenching, some of which can be attributed to the organic nature of these fluorophores.One class of nonorganic fluorophores with promising optical properties are quantum dots (QDs), which are semiconductor nanocrystals. QDs have nanoscale dimensions, small enough to induce quantum confinement. [2] This unique characteristic allows for manipulating QDs' fluorescent properties for specific applications by changing their sizes. [3] The optical properties of QDs include broad and continuous absorption spectra, narrow and symmetric emission spectra, high photochemical stability, and the ability to emit a tunable size-specific color that depends on the adjustable bandgap of the semiconductor core. [4] Compared to conventional fluorophores, QDs have higher quantum yield and reduced susceptibility to photobleaching, thus allowing for extendedThe relationship between emission and ligand restriction of a series of ZnSe/ ZnS quantum dots (QDs) encapsulated in nanoparticles is investigated systematically via experiments and quantum theory. The QDs have a ZnSe core and a ZnS shell, capped with hydrophobic ligands (triotylphosphine oxide/ hexadecylamine), allowing them to be entrapped in a model biomembrane, bicelle, made of zwitterionic dipalmitoyl and dihexanoyl phosphatidylcholines and charged dipalmitoyl phosphatidylglycerol. Enhanced photoluminescence is observed upon encapsulation, depending on the QD-to-lipid ratio. Transmission electron microscopy and small-angle X-ray scattering confirm that QDs are preferably situated at the rim of bicellar discs. A simplified quantum dissipation heat-bath theory is proposed to correlate the enhancement with slower nonradiative processes caused by the restriction-in-motion (RIM) of the surface ligands. However, Förster resonance energy transfer due to QD aggregation counteracts the effect.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/admi.202102079.

Cellular Localization, Aggregation, and Cytotoxicity of Bicelle-Quantum Dot Nanocomposites

“…The first physical characterization of NANO 2 -QD can be found in the previous report, 9 where QDs are found to be localized to the outer rim of bicelles and show increased fluorescence. 9 In this study, CdSe/ZnS quantum dots (QDs) were encapsulated within bicelles for delivery into cells maintained in cell culture.…”

“…The first physical characterization of NANO 2 -QD can be found in the previous report, 9 where QDs are found to be localized to the outer rim of bicelles and show increased fluorescence. 9 In this study, CdSe/ZnS quantum dots (QDs) were encapsulated within bicelles for delivery into cells maintained in cell culture. We took advantage of the high electron density of QDs to determine their uptake and location in the cell at the ultrastructural level by transmission electron microscopy (TEM).…”

“…Lipid nanoparticles (LNPs) have been heavily investigated regarding their structural stability, − enhanced cellular uptake, the function of therapeutic carriers, , and the capability of entrapped hydrophobic species to yield unique functions. , In the past, the majority of LNPs studied for biological applications were liposomes (vesicles) or micelles. − As increasingly sophisticated molecular complexes are developed for therapeutics and diagnostics, novel LNPs with improved features for targeted cellular delivery are urgently needed. The robust preparation, well-defined nanostructure, and high therapeutic efficacy make bicellar derivatives an excellent candidate as a novel targeting theranostic LNP carrier.…”