Silver nanowires as plasmonic compensators of luminescence quenching in single up-converting nanocrystals deposited on graphene

Localized three-photon upconversion enhancement in silver nanowire networks and its effect in thermal sensing

The quest for enhancing the upconversion luminescence (UCL) efficiency of rare-earth doped materials has been a common target in nanophotonics research. Plasmonic nanoarchitectures have proven potential for amplifying UCL signals, prompting investigations into localized enhancement effects within noble metal nanostructures. In this work we investigate the localized enhancement of UCL in silver nanowire (AgNW) networks coated with upconversion nanoparticles (UCNPs) by employing hyperspectral microscopy to unveil distinctive regions of local enhancement. Our study reveals that three-photon upconversion processes predominantly occur at hot-spots in nanowire junctions, contributing to heightened luminescence intensity on AgNW networks. Intriguingly, our findings demonstrate that enhancement on AgNWs introduces significant artifacts for thermometry based on ratiometric analysis of the emission spectra, resulting in the observation of artificial thermal gradients. To address this challenge, we developed correction methods that were successfully applied to mitigate this effect, enabling the generation of accurate thermal maps and the realization of dynamic thermal measurements. We quantified the distance-dependent enhancement profiles and studied the effect of temperature by exploiting the heat dissipation under varying electrical voltages across the electrically percolated AgNW networks. The observations were confirmed through numerical calculations of the enhancement factor and the energy transfer rates. This comprehensive investigation sheds light on the complex interplay between plasmonic nanostructures, three-photon upconversion processes, and their influence on thermal sensing applications. The presented hyperspectral method not only allows a direct visualization of plasmonic hot-spots but also advances our understanding of localized enhancements. The correction methods applied to analyze the emission spectra also contribute to the refinement of accurate temperature mapping using UCNPs, thereby enhancing the reliability of this thermal sensing technology.

Intertumoral and intratumoral barriers as approaches for drug delivery and theranostics to solid tumors using stimuli-responsive materials

The solid tumors provide a series of biological barriers in cellular microenvironment for designing drug delivery methods based on advanced stimuli-responsive materials. These intertumoral and intratumoral barriers consist of perforated endotheliums, tumor cell crowding, vascularity, lymphatic drainage blocking effect, extracellular matrix (ECM) proteins, hypoxia, and acidosis. Triggering opportunities have been drawn for solid tumor therapies based on single and dual stimuli-responsive drug delivery systems (DDSs) that not only improved drug targeting in deeper sites of the tumor microenvironments, but also facilitated the antitumor drug release efficiency. Single and dual stimuli-responsive materials which are known for their lowest side effects can be categorized in 17 main groups which involve to internal and external stimuli anticancer drug carriers in proportion to microenvironments of targeted solid tumors. Development of such drug carriers can circumvent barriers in clinical trial studies based on their superior capabilities in penetrating into more inaccessible sites of the tumor tissues. In recent designs, key characteristics of these DDSs such as fast response to intracellular and extracellular factors, effective cytotoxicity with minimum side effect, efficient permeability, and rate and location of drug release have been discussed as core concerns of designing paradigms of these materials.