Enhancement of single upconversion nanoparticle imaging by topologically segregated core-shell structure with inward energy migration

Abstract

Manipulating topological arrangement is a powerful tool for tuning energy migration in natural photosynthetic proteins and artificial polymers. Here, we report an inorganic optical nanosystem composed of NaErF4 and NaYbF4, in which topological arrangement enhanced upconversion luminescence. Three architectures are designed for considerations pertaining to energy migration and energy transfer within nanoparticles: outside-in, inside-out, and local energy transfer. The outside-in architecture produces the maximum upconversion luminescence, around 6-times brighter than that of the inside-out at the single-particle level. Monte Carlo simulation suggests a topology-dependent energy migration favoring the upconversion luminescence of outside-in structure. The optimized outside-in structure shows more than an order of magnitude enhancement of upconversion brightness compared to the conventional core-shell structure at the single-particle level and is used for long-term single-particle tracking in living cells. Our findings enable rational nanoprobe engineering for single-molecule imaging and also reveal counter-intuitive relationships between upconversion nanoparticle structure and optical properties.

A Surfactant-Free and General Strategy for the Synthesis of Bimetallic Core–Shell Nanocrystals on Reduced Graphene Oxide through Targeted Photodeposition

“…Bimetallic core–shell heterostructured nanocrystals (HNCs) with well-defined structures, disparate phases, and phase boundaries or interfaces have showed superior physicochemical properties as compared to their monometallic counterparts. − Owing to these properties, they have been widely used in various applications, including catalysis, − energy, spectroscopy, imaging, sensors, bioresearch, and medicine . In particular, the bimetallic core–shell HNCs have shown great potential for electrocatalytic reactions, such as hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and carbon dioxide reduction reaction (CO 2 RR). − It is worth mentioning that the HNCs grown on supports are favorable for the catalytic reactions since it is beneficial for inhibiting the catalyst aggregation .…”

Squaraine Dye-Sensitized Upconversion with Enhanced Stability and Minimized Aggregation-Caused Quenching

“…The process of enhancing the emission of UCNPs with a dye is termed “dye-sensitized upconversion” . Dye-sensitized upconversion has been demonstrated in several studies. ,,,− However, all the NIR fluorophores for dye-sensitized upconversion, such as IR-806 and Cy7.5, have been based on the cyanine skeleton which has a methine group with differing numbers of carbon atoms and two aromatic side chains. , Due to the poor chemical stability and photostability of the methine group, ,, it is difficult to obtain dye-sensitized upconversion for single particle measurement in which a high irradiance (∼KW/cm 2 ) is used. ,, In addition, aggregation-caused quenching (ACQ) in polar solutions diminishes the ability of cyanine dyes to act as antennae to enhance UCL emission . Recently, a steric hindrance strategy , was developed to improve cyanine dyes’ chemical stability and reduce ACQ for dye-sensitized upconversion.…”

“…38,39 Due to the poor chemical stability and photostability of the methine group, 31,40,41 it is difficult to obtain dye-sensitized upconversion for single particle measurement in which a high irradiance (∼KW/ cm 2 ) is used. 25,42,43 In addition, aggregation-caused quenching (ACQ) in polar solutions diminishes the ability of cyanine dyes to act as antennae to enhance UCL emission. 44 Recently, a steric hindrance strategy 45,46 was developed to improve cyanine dyes' chemical stability and reduce ACQ for dyesensitized upconversion.…”

“…In polar solvents, organic dyes on the surface of UCNPs can form aggregates, weakening the dye-sensitization effect. 43 We investigated the effect of polarity on the upconversion performance of dye-sensitized UCNPs by adding the polar solvent DMSO to the nonpolar solvent CHCl 3 , CHCl 3 /DMSO (3:1, v/v) (see Supporting Information 1.2). As shown in Figure 3e, DMSO (25%, v/v) quenched the luminescence of IR-806-UCNPs 5.7-fold compared to the luminescence in CHCl 3 .…”

Selectively Manipulating Interactions between Lanthanide Sublattices in Nanostructure toward Orthogonal Upconversion

“…A multilayer core–shell nanostructure (MLCS) has been shown to be a powerful design for both fundamental research and application of UCNPs . By taking advantage of the MLCS designs, energy migration and luminescence dynamics can be easily probed. − It is also able to realize the orthogonal excitation–emission colors conveniently by using suitable dopants and chemical compositions in an MLCS nanostructure. ,− More importantly, such designs allow for the spatial control of dopants on the nanosized scale, providing a versatile nanoplatform toward diversities of frontier applications. − Thus, it would be highly desirable to construct the dual-lanthanide sublattices and finely manipulate their interfacial interactions in a single nanoparticle through rational nanostructure design and selection of lanthanide dopants with suitable doping contents.…”