New paper in Materials Horizons – Thermoresponsive Multicolor-Emissive Materials Based on Solid Lipid Nanoparticles

New paper in Materials Horizons – Thermoresponsive Multicolor-Emissive Materials Based on Solid Lipid Nanoparticles

13 Aug 2021

New publication in Material Horizons journal entitled “Thermoresponsive Multicolor-Emissive Materials Based on Solid Lipid Nanoparticles” authored by Jaume Ramon Otaegui and led by Dr. Claudio Roscini and Dr. Jordi Hernando (UAB).

In this work, the authors reported novel thermoresponsive multicolored fluorescent nanomaterials suitable for the preparation of thermofluorochromic transparent polymeric films and printable waterbased inks. This approach takes advantage of the fluorescence modulation of molecular dyes through the solid-to-liquid transition of phase change-materials (PCMs), recently promisingly exploited to obtain thermofluorochromic bulk materials.

Strategy devised in this work to achieve multicolor thermofluorochromism by a) combining commercially-available fluorophores and phase change materials, b) miniaturizing these mixtures into nanoparticles, and c) integrating several different of the resulting nanostructures in a single platform, which allows the preparation of multicolor-emissive thermally-responsive composites and printable inks using just one type of emitter.

With this novel work, the authors demonstrated for the first time this PCM-based thermally-induced optical modulation is transferred to the nanoscale through the preparation of dye-loaded solid-lipid-nanoparticles (SLPs). These allow obtaining thermofluorochromic highly transparent nanocomposites and water-based inks, impossible to achieve with bulk PCM mixtures. By using one single dye and combining different SLPs made of PCMs of distinct melting point, multistate- and multicolor fluorescent thermoresponsive materials are prepared in a peerless simple fashion. Furthermore, by adding a second dye, thermofluorescent films displaying most of the colors of the CIE 1931 color space are obtained, including nearly pure emitted white light. Finally, SLPs have been easily integrated with NIR-absorbing plasmonic nanoparticles to produce photothermallyresponsive multicolor fluorescent materials, of interest for multithreshold temperature sensing and anticounterfeiting. Overall, the developed approach grants access to new temperature-responsive emissive nanomaterials, with straightforward, tunable and fine control of the optical properties in the solid state that are hard to achieve otherwise.

ABSTRACT: Despite the recent advances in the field of thermofluorochromism, the fabrication of thermoresponsive multicolor-emissive materials in a simple, low-cost and versatile manner still remains a challenge. Herein we accomplish this goal by expanding the concept of matrix-induced thermofluorochromism, where a sudden two state variation of dyes’ emission is promoted by the solid-liquid transition of a surrounding phase change material (e.g., paraffins). We demonstrate that this behavior can be transferred to the nanoscale by the synthesis of dye-loaded solid lipid nanoparticles, different of which can then be combined into a single platform to obtain multicolor thermofluorochromism using a single type of emitter. Because of the reduced dimensions of these particles, they can be utilized to prepare transparent nanocomposites and inkjet-printed patterns showing complex thermoresponsive luminescent signals and applications ranging from smart displays to thermal sensing and high security anti-counterfeiting.

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