Gloria Lesly JIMENEZ MIRANDA1, Carlos VAZQUEZ-L.2, Daniel MORALES-M.3, Dominik DOROSZ1
1Faculty of Materials Science and Ceramics, AGH University of Krakow, Al. Mickiewicza 30, 30-059 Krakow, Poland
2Physics department, Cinvestav, Av Instituto Politécnico Nacional 2508, Mexico City, Mexico
3Department of Chemical Sciences, University of Padova, 1, Via Marzolo, Padova, 35131, Italia
Nanomaterials able to convert an external stimulus into a response and then return to their initial state such as magnetic (M)- and photoluminescent (PL)- nanoparticles, have contributed to the development of advanced biomedical technologies, offering less invasive and more efficient solutions. [1] Among these, PL nanoparticles (light-responsive) are particularly promising due to their immediate response. They have been utilized in bioimaging, drug delivery, and optogenetics (OG). OG, though relatively new, is one of the most promising techniques due to its ability to modulate cell activity with high precision. It holds significant potential for treating neurological diseases as well as conditions like blindness, deafness, and heart disease more effectively. [2–4] However, the reliance on visible light limits its application. To overcome this limitation, one promising strategy involves using lanthanide upconversion nanoparticles (Ln-UCNPs) as light nanotransducers. These nanoparticles can convert near-infrared wavelengths (NIR), which offer better tissue penetration and low scattering, into visible light. [5] Despite their exceptional property and the insights gained from conventional heating methods (solvothermal and co-precipitation reactions), Ln-UCNPs still face challenges including low efficiency, relatively large size, morphology control issues, and limited scalability and reproducibility. Previous studies have shown that many of these limitations can be mitigated by using a microwave reactor (MR) with polar-solvents or microwave absorbers like liquid ions (LI). However, their emission efficiency is low. [6]
Based on it, the objectives of this work were as follows: first, to determine if it is possible to develop Ln-UCNPs (α- and β- NaYF4) using non-polar solvents without LI in a closed-vessel MR, meaning a pressurized reaction. Second, to evaluate the influence of different transition metals on the physicochemical properties of α- and β- NaYF4 under optimized conditions. Third, to understand the influence of microwave irradiation on the reaction kinetics to explore other matrices. This approach aims to develop small (<30nm), monodispersed Ln-UCNPs with improved conversion efficiency, which could impact not only biomedical applications but also other fields. The reaction conducted in a closed-vessel MR at 290°C for 30 min, using non-polar solvents and acetylacetonates precursors, resulted in spherical, homogeneous α-NaYF4 nanoparticles with sizes ranging from 20 to 80 nm, depending on the precursor used. The β-NaYF4 phase was favored when a small amount of NaOH was added alongside the Na source. Additionally, the use of co-dopants like Li, Gd, Pt, and Zn influenced not only the structural and morphological properties but also photoluminescent characteristics, including intensity and decay times. These findings demonstrate that a deep understanding of reaction kinetics in a MR not only enables successful tailoring of the NPs but also improves their emission efficiency.
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[3] J.A. Sahel et al., Partial recovery of visual function in a blind patient after optogenetic therapy, Nat Med 27 (2021) 1223–1229.
[4] C. Richter et al., , No light without the dark: Perspectives and hindrances for translation of cardiac optogenetics, Prog Biophys Mol Biol 154 (2020) 39–50
[5] Z. Zhang et al., Modularly Assembled Upconversion Nanoparticles for Orthogonally Controlled Cell Imaging and Drug Delivery, ACS Appl Mater Interfaces 12 (2020) 12549–12556.
[6] R. Krishnan et al., Recent advances in microwave synthesis for photoluminescence and photocatalysis, Mater Today Commun 32 (2022)