Target-modulated sensitization of upconversion luminescence by NIR-emissive quantum dots: a new strategy to construct upconversion biosensors

Abstract

We herein used Ag2Se QDs as a target-modulated sensitizer for UCNPs and the target thrombin as the sensitizing switch to construct a biosensor with enhanced SBR and assay sensitivity, circumventing the limited LRET efficiency of UCNPs.

Doping Lanthanide Ions in Colloidal Semiconductor Nanocrystals for Brighter Photoluminescence

“…26 Organic dyes and SNCs offer instead broadband absorption capabilities and tunability of the absorption range. [20][21][22] Strategies based on the use of these moieties leverage the same principle: absorption of the energy in the form of photons by the donor (dye/SNC) and its funneling to the Ln 3+ ions (acceptors) within the lanthanide-based nanoparticle mainly via a Förster resonance energy transfer (FRET) transfer process. Importantly, for effective FRET to occur, the donor should be as close as possible to the acceptor: an aspect that limits the applicability of these approaches in tandem with the growth of a protective shell -which reduced surface quenching phenomena (see Section 4.3), but also increases the donor-acceptor distance.…”

“…Different strategies have been developed to overcome the hurdle of poor emission brightness (Table ), such as the engineering of complex-core/multiple-shells architectures and coupling with highly absorbing moieties, including plasmonic nanoparticles, , organic molecules, , or semiconductor nanocrystals (SNCs). , The first strategy leverages the concept of energy transfer from a sensitizer (the ion absorbing the optical energy) to an activator (the ion to which the absorbed energy is transferred and that re-emits it in the form of photon). The use of core/shell architectures generally aims to increase the total number of sensitizers per particle, minimize the losses during the sensitizer-to-activator energy transfer processes, and limit surface quenching phenomena. , Unfortunately, the low absorption coefficient of lanthanide ions poses an intrinsic limit to this approach.…”

“…The limitation of this approach is that no broadband absorption is achievable, with the absorption wavelength being dictated by the Ln 3+ employed . Organic dyes and SNCs offer instead broadband absorption capabilities and tunability of the absorption range. − Strategies based on the use of these moieties leverage the same principle: absorption of the energy in the form of photons by the donor (dye/SNC) and its funneling to the Ln 3+ ions (acceptors) within the lanthanide-based nanoparticle, mainly via a Förster resonance energy transfer (FRET) transfer process. Importantly, for effective FRET to occur, the donor should be as close as possible to the acceptor: an aspect that limits the applicability of these approaches in tandem with the growth of a protective shell, which reduced surface quenching phenomena (see section ) but also increases the donor–acceptor distance. , The enhancement of the absorption achievable with these approaches is sizable, but it does not directly translate to a betterment of the brightness of Ln 3+ emission, because the additional step of energy transfer heavily impacts the final efficiency of sensitization.…”

“…Different strategies have been developed to overcome the hurdle of poor emission brightness (Table 1), such as the engineering of complex-core/multiple-shells architectures and coupling with highly absorbing moieties, including plasmonic nanoparticles, 17,18 organic molecules, 19,20 or semiconductor nanocrystals (SNCs). 21,22 The first strategy leverages the concept of energy transfer from a sensitizer (the ion absorbing the optical energy) to an activator (the ion to which the absorbed energy is transferred and that re-emits it in the form of photon). The use of core/shell architectures generally aims to increase the total number of sensitizers per particle, minimize the losses during the sensitizer-to-activator energy transfer processes, and limit surface quenching phenomena.…”

Colloidal stability and aggregation kinetics of nanocrystal CdSe/ZnS quantum dots in aqueous systems: Effects of ionic strength, electrolyte type, and natural organic matter

“…Among the various types of nanoparticles, quantum dots (QDs), which are semiconductor nanoscale crystals, encompass a wide range of areas of application owing to their optical and electronic properties [1]. Their capacity of fluorescence in different spectral regions, with a superior excitation enhancement, high quantum yield, and elevated photobleaching threshold, makes them suitable for potential applications in biomedical imaging [2,3], biomarkers and biosensors [4][5][6][7], site-specific gene medical treatment and site-specific drug delivery or targeting [8,9], diagnosis and therapy [10,11], nanophotocatalysis [12][13][14][15], and luminescence based-probes [16,17]. In addition, QDs are used in various applications in electronics industries such as solar cells [18][19][20][21], visual and display technologies such as light emitting diodes [22][23][24], and information technologies such as quantum information processing (QIP) for storing, processing and communicating data [25].…”