Silica Nanoparticle Architecture Determines Radiative Properties of Encapsulated Fluorophores

Abstract

Silica nanoparticles with embedded fluorescent molecules are used in a variety of applications requiring the observation of single nanoprobes. We describe a class of fluorescent, core–shell silica nanoparticles with a radius of ∼15 nm, narrow particle size distribution, and controlled internal architecture. Particles covalently encapsulating multiple rhodamine molecules are over 20 times brighter than the single dye molecule in water. The photophysical behavior of rhodamine can be manipulated by small changes in the internal architecture of particles with otherwise similar composition, leading to 3-fold enhancement of quantum efficiency per dye with no observable energy transfer between neighboring dyes. This enhancement of quantum efficiency per dye is due to a uniform 2-fold enhancement in radiative rate and a variable reduction in nonradiative rate which varies inversely with the degree of rotational mobility of the dye allowed by the particle architecture. These results demonstrate a practical method for synthesizing highly fluorescent silica nanoparticles and an effective methodology for selectively modifying the photophysical properties of fluorophores.

Absorption and Emission Spectra of a Flexible Dye in Solution: A Computational Time-Dependent Approach

“…Both the solute GS and EES FFs were parameterized by the JOYCE package, 50,51 through a least square minimization of the functional I intra (5) where N geom is the number of the sampled conformations, Q K is the K th normal coordinate and U g is the QM computed energy in the g th geometry, with respect to the absolute minimum (g = 0). The QM Hessian matrix H KL and the FF Hessian are evaluated at g = 0.…”

“…Organic dyes 1 have recently attracted a growing attention, thanks to their wide range of applications, that covers different fields in both materials [2][3][4][5][6][7][8][9][10][11] and life sciences. [12][13][14][15] In particular, the high selectivity and specificity of some fluorescent molecules in detecting particular molecular targets and/or in modulating the responses to different external stimuli are often exploited to investigate the structural and dynamic properties of a wide variety of complex systems like, e.g., polymeric materials, DNA structures, protein conformations or lipid aggregates.…”

“…19,23 In order to reproduce the overall line shapes and their complex features and to reach a more reliable comparison with experimental observations, it is mandatory to take nuclear motions (both of the chromophore and of its environment) into the proper account. [23][24][25][26][27] In the case of flexible molecules in condensed phases, some sampling of large parts of the potential energy surfaces (PES) becomes mandatory 5,15,[28][29][30] and the most suitable approach is based, in our opinion, on molecular dynamics (MD) simulations followed by proper averaging (and smoothing) of TDDFT results for a sufficient number of representative snapshots. Implicit solvation methods, such as the Polarizable Continuum Model (PCM 31 ), offer the undeniable advantage of correctly describing the average polarization of the environment and its effect on the chromophore without any explicit sampling of solvent coordinates, but they are, of course, unable to capture specific solvent effects especially in the cybotactic region.…”

Fluorescent Dyes Used in Polymer Carriers as Imaging Agents in Anticancer Therapy

“…They incorporated hydrophobic rhodamine 6G molecules inside the SiNPs by using two compounds as precursors with a different lipophilicity i.e., more hydrophobic phenyltriethoxysilane (PTES) [PhSi(OCH 3 )] which keeps the organic dye in the silica matrix and [Si(OR) 4 ] (TEOS) which can turn into a hydrophilic comopound, thus it allows obtained SiNPs to be dispersed in an aqueous solution [373]. All SiNPs have approximately the same size and composition but selected dyes (e.g., fluorescein, pyrene) [374,375] might exhibit different photophysical properties [376]. The silica matrix provides embedded dyes an effective barrier to protect them against the surrounding environment and both photobleaching and photodegradation phenomena can be minimized [377].…”

Molecular fluorescence in silica particles doped with quercetin-Al3+ complexes

“…Many studies have been reported about dye-doped silica nanospheres, and the increase of fluorophore emission intensity and photo stability when the dye molecule is entrapped in the solid structure are effects that have been observed. [5][6][7] The flavonoid quercetin forms complexes with Al 3+ resulting in species with high fluorescent quantum yield because excited state intramolecular proton transfer (ESIPT) process in quercetin is inhibited. 8 These complexes have been studied in methanolic solution 8,12 and they can be interesting systems to investigate the interaction of silica nanoparticles and to be used as probes for Al In the present work, the quercetin-Al 3+ complexes are studied in two types of colloidal silica matrices, using steadystate and time-resolved fluorescence and UV-Vis absorption techniques.…”