Amorphous Quantum Nanomaterials

Abstract

In quantum materials macroscopic behavior is governed in non-trivial ways by quantum phenomena. This is usually achieved by exquisite control over atomic positions in crystalline solids. Here we demonstrate that the use of disordered glassy materials provides unique opportunities to tailor quantum material properties. By borrowing ideas from single molecule spectroscopy, we isolate single delocalized π-electron dye systems in relatively rigid ultrasmall (<10nm diameter) amorphous silica nanoparticles. We demonstrate that chemically tuning the local amorphous silica environment around the dye over a range of compositions enables exquisite control over dye quantum behavior, leading to efficient probes for photodynamic therapy (PDT) and stochastic optical reconstruction microscopy (STORM). Results suggest that efficient fine-tuning of light-induced quantum behavior mediated via effects like spin-orbit coupling can be effectively achieved by systematically varying averaged local environments in glassy amorphous materials as opposed to tailoring well-defined neighboring atomic lattice positions in crystalline solids. Resulting nanoprobes have required features proven to enable clinical translation.

Ultrasmall, Bright, and Photostable Fluorescent Core–Shell Aluminosilicate Nanoparticles for Live‐Cell Optical Super‐Resolution Microscopy

“…We previously demonstrated that brightness enhancements over free dye indeed directly carry over into photon output enhancements in dye blinking. [ 6,24 ] Taken together, these data point to the emergence of an ultrasmall, bright, and photostable nanoparticle platform for SRM. Building on recent advances, e.g., in bright and photostable nanoprobes including upconversion as well as advanced polymer nanoparticles, ultrasmall aC’ dots constitute an attractive platform for bioimaging and SRM that does not contain heavy metals, exhibits on‐off fluorescence cycling characteristics optimal for STORM, and takes advantage of a wide spectral range that can be tailored by dye choice.…”

“…[22,23] We previously introduced a new class of amorphous quantum nanomaterials, in which the incorporation of different amounts of foreign atoms into the amorphous inorganic aluminosilicate glass of an ultrasmall aluminosilicate core and poly(ethylene glycol) (PEG) shell core-shell nanoparticle (aC' dot) alters the quantum behavior of fluorescent dyes covalently encapsulated in the glassy core, leading to substantially altered macroscopic optical behavior. [24,25] After introducing iodine as foreign atoms (iaC' dots), illumination led to increased intersystem crossing (ISC) rates to triplet excited dye states via spinorbit coupling, in turn resulting in improved reactive oxygen species (ROS) generation useful, e.g., in photodynamic therapy (PDT). When introducing thiol groups as foreign atoms (srC' dots), illumination led to dye blinking, which enabled STORM based optical SRM.…”

“…We immobilized biotinylated Cy5 dye (Cy5-biotin), PEG-Cy5-C' dots, and PEG-Cy5-aC' dots on streptavidin-coated glass dishes as described elsewhere, with Hank's balanced salt solution (HBSS) as the imaging buffer (see Supporting Information). [24,34] HBSS is an aqueous buffer routinely used in live-cell imaging. The immobilized single emitters were imaged under different conditions by a total internal reflection fluorescence (TIRF) microscope.…”

“…In the latter particles, under illumination thiol‐dye adducts disrupt dye π‐electron delocalization leading to dark states and associated blinking in the presence of an OS system, whereas such systems quench aC’ dot blinking (vide infra). [ 24 ] In a range of cross experiments with free dyes and aluminum‐free C’ dots we reveal that fourfold coordinated aluminum in the aluminosilicate matrix is responsible for dye blinking, likely via photoinduced redox processes. We demonstrate that dye blinking can be generalized over several dye families covering the visible to near‐infrared (NIR) spectral range, leading to brighter and more photostable SRM probes relative to their parent free dyes.…”

“…[ 33 ] Since we already showed in two separate previous studies that Al is fourfold coordinated in aC’ dots, replacing Si in the silica network, we did not repeat the same solid‐state 27 Al nuclear magnetic resonance (NMR) spectroscopy experiments on aC’ dot samples here. [ 24,25 ] Zeta potential measurements of aC’ dots showed a negative surface charge with an average of −11.9 mV as seen in Figure S2 in the Supporting Information. Characterization results on PEG‐Cy5‐C’ dots used as a reference in this study, i.e., without Al in the core, suggested a hydrodynamic diameter of 5.5 nm with 2.4 Cy5 dyes per particle (Figure S3, Supporting Information).…”