Gold Nanobipyramids for Near-Infrared Fluorescence-Enhanced Imaging and Treatment of Triple-Negative Breast Cancer.

There is an imminent need for novel strategies for the diagnosis and treatment of aggressive triple-negative breast cancer (TNBC). Cell-targeted multifunctional nanomaterials hold great potential, as they can combine precise early-stage diagnosis with local therapeutic delivery to specific cell types. In this study, we used mesoporous silica (MS)-coated gold nanobipyramids (MS-AuNBPs) for fluorescence imaging in the near-infrared (NIR) biological window, along with targeted TNBC treatment. Our MS-AuNBPs, acting partly as light amplification components, allow considerable metal-enhanced fluorescence for a NIR dye conjugated to their surfaces compared to the free dye. Fluorescence analysis confirms a significant increase in the dye's modified quantum yield, indicating that MS-AuNBPs can considerably increase the brightness of low-quantum-yield NIR dyes. Meanwhile, we tested the chemotherapeutic efficacy of MS-AuNBPs in TNBC following the loading of doxorubicin within the MS pores and functionalization to target folate receptor alpha (FRα)-positive cells. We show that functionalized particles target FRα-positive cells with significant specificity and have a higher potency than free doxorubicin. Finally, we demonstrate that FRα-targeted particles induce stronger antitumor effects and prolong overall survival compared to the clinically applied non-targeted nanotherapy, Doxil. Together with their excellent biocompatibility measured in vitro, this study shows that MS-AuNBPs are promising tools to detect and treat TNBCs.

Flexible, Free-Standing Polymer Membranes Sensitized by CsPbX3 Nanocrystals as Gain Media for Low Threshold, Multicolor Light Amplification.

Lead halide perovskite nanocrystals (NCs) are highly suitable active media for solution-processed lasers in the visible spectrum, owing to the wide tunability of their emission from blue to red via facile ion-exchange reactions. Their outstanding optical gain properties and the suppressed nonradiative recombination losses stem from their defect-tolerant nature. In this work, we demonstrate flexible waveguides combining the transparent, bioplastic, polymer cellulose acetate with green CsPbBr3 or red-emitting CsPb(Br,I)3 NCs in simple solution-processed architectures based on polymer-NC multilayers deposited on polymer micro-slabs. Experiments and simulations indicate that the employment of the thin, free-standing membranes results in confined electrical fields, enhanced by 2 orders of magnitude compared to identical multilayer stacks deposited on conventional, rigid quartz substrates. As a result, the polymer structures exhibit improved amplified emission characteristics under nanosecond excitation, with amplified spontaneous emission (ASE) thresholds down to ∼95 µJ cm-2 and ∼70 µJ cm-2 and high net modal gain up to ∼450 and ∼630 cm-1 in the green and red parts of the spectrum, respectively. The optimized gain properties are accompanied by a notable improvement of the ASE operational stability due to the low thermal resistance of the substrate-less membranes and the intimate thermal contact between the polymer and the NCs. Their application potential is further highlighted by the membrane's ability to sustain dual-color ASE in the green and red parts of the spectrum through excitation by a single UV source, activate underwater stimulated emission, and operate as efficient white light downconverters of commercial blue LEDs, producing high-quality white light emission, 115% of the NTSC color gamut.

Unraveling the Radiative Pathways of Hot Carriers upon Intense Photoexcitation of Lead Halide Perovskite Nanocrystals.

The slowdown of carrier cooling in lead halide perovskites (LHP) may allow the realization of efficient hot carrier solar cells. Much of the current effort focuses on the understanding of the mechanisms that retard the carrier relaxation, while proof-of-principle demonstrations of hot carrier harvesting have started to emerge. Less attention has been placed on the impact that the energy and momentum relaxation slowdown imparts on the spontaneous and stimulated light-emission process. LHP nanocrystals (NCs) provide an ideal testing ground for such studies as they exhibit bright emission and high optical gain, while the carrier cooling bottleneck is further pronounced compared to their bulk analogues due to confinement. Herein, the luminescent properties of CsPbBr3, FAPbBr3, and FAPbI3 NCs in the strong photoexcitation regime are investigated. In the former two NC systems, amplified spontaneous emission is found to dominate over the radiative recombination at average carrier occupancy per nanocrystal larger than 5-10. On the other hand, under the same photoexcitation conditions in the FAPbI3 NCs, a longer lived population of hot carriers results in a competition between hot luminescence, stimulated emission, and defect recombination. The dynamic interplay between the aforementioned three emissive channels appears to be influenced by various experimental and material parameters that include temperature, material purity, film morphology, and excitation pulse width and wavelength.

Robust Hydrophobic and Hydrophilic Polymer Fibers Sensitized by Inorganic and Hybrid Lead Halide Perovskite Nanocrystal Emitters.

Advances in the technology and processing of flexible optical materials have paved the way toward the integration of semiconductor emitters and polymers into functional light emitting fabrics. Lead halide perovskite nanocrystals appear as highly suitable optical sensitizers for such polymer fiber emitters due to their ease of fabrication, versatile solution-processing and highly efficient, tunable, and narrow emission across the visible spectrum. A beneficial byproduct of the nanocrystal incorporation into the polymer matrix is that it provides a facile and low-cost method to chemically and structurally stabilize the perovskite nanocrystals under ambient conditions. Herein, we demonstrate two types of robust fiber composites based on electrospun hydrophobic poly(methyl methacrylate) (PMMA) or hydrophilic polyvinylpyrrolidone (PVP) fibrous membranes sensitized by green-emitting all-inorganic CsPbBr3 or hybrid organic-inorganic FAPbBr3 nanocrystals. We perform a systematic investigation on the influence of the nanocrystal-polymer relative content on the structural and optical properties of the fiber nanocomposites and we find that within a wide content range, the nanocrystals retain their narrow and high quantum yield emission upon incorporation into the polymer fibers. Quenching of the radiative recombination at the higher/lower bound of the nanocrystal:polymer mass ratio probed is discussed in terms of nanocrystal clustering/ligand desorption due to dilution effects, respectively. The nanocomposite's optical stability over an extended exposure in air and upon immersion in water is also discussed. The studies confirm the demonstration of robust and bright polymer-fiber emitters with promising applications in backlighting for LCD displays and textile-based light emitting devices.

Lead halide perovskites and other metal halide complexes as inorganic capping ligands for colloidal nanocrystals.

Lead halide perovskites (CH3NH3PbX3, where X = I, Br) and other metal halide complexes (MX(n), where M = Pb, Cd, In, Zn, Fe, Bi, Sb) have been studied as inorganic capping ligands for colloidal nanocrystals. We present the methodology for the surface functionalization via ligand-exchange reactions and the effect on the optical properties of IV-VI, II-VI, and III-V semiconductor nanocrystals. In particular, we show that the Lewis acid-base properties of the solvents, in addition to the solvent dielectric constant, must be properly adjusted for successful ligand exchange and colloidal stability. High luminescence quantum efficiencies of 20-30% for near-infrared emitting CH3NH3PbI3-functionalized PbS nanocrystals and 50-65% for red-emitting CH3NH3CdBr3- and (NH4)2ZnCl4-capped CdSe/CdS nanocrystals point to highly efficient electronic passivation of the nanocrystal surface.