New paper in Advanced Optical Materials – Solid Materials with NIR‐Induced Fluorescence Modulation

New paper in Advanced Optical Materials – Solid Materials with NIR‐Induced Fluorescence Modulation

3 Sep 2020

New publication in Advanced Optical Materials journal entitled “Solid Materials with Near‐Infrared‐Induced Fluorescence Modulation” authored by Jaume Ramon Otaegui and led by Dr. Claudio Roscini and in collaboration with Dr. Jordi Hernando from Chemistry Department in the UAB.

In this work, the authors reported a conceptually novel strategy to achieve NIR-induced fluorescence modulation in solid materials that relies on two main principles: i) the capacity of phase change materials to reversibly alter the optical properties of molecular emitters upon solid-liquid transition and ii) the photothermal heating generated by NIR-absorbing plasmonic nanostructures to induce Phase Change Materials (PCMs) melting. Multiple advantages derive from this approach: i) the strategy directly applies to readily available, unfunctionalized emitters and PCMs, thus preventing the tedious synthesis of complex photoresponsive molecules such as NIR-absorbing photochromes, ii) second, by using noble metal nanostructures as NIR absorbers, their stimulation can be decoupled from emitter excitation to minimize photodegradation and destructive readout, while larger NIR-induced responses with lower irradiation intensities can be generated.

The published methodology is highly versatile, as it can make use of a large number of emitters and operate under multiple fluorescence modulation mechanisms deriving from phase-controlled dye-PCM, dye-dye, and even dye-additive interactions (e.g., fluorescent molecular rotors, AIE, ACQ, photoinduced electron transfer). To successfully demonstrate the versatility of this approach, thermofluorescent materials were fabricated undergoing fast, slow, and irreversible NIR-response, allowing writing patterns of high and controllable resolution.

ABSTRACT: Solid molecular materials modulating their luminescent properties upon irradiation are typically based on photochromic dyes. Despite these are potentially interesting for applications such as anticounterfeiting, bioimaging, optical data storage, and writable/erasable devices, key features are preventing their use in marketable products: the lack of straightforward strategies to obtain near infrared (NIR) radiation‐responding photochromic dyes and the dramatic response modification these molecules suffer in solids. Herein a photochrome‐free approach is reported to achieve solid materials whose luminescence modulation is induced by NIR radiation. This strategy is based on the capacity of phase change materials (PCMs) to modify the emission properties of fluorescent dyes upon photothermally induced interconversion between their solid and liquid states. The preparation of several NIR‐responsive thermofluorochromic materials of high fatigue resistance and nondestructive readout is illustrated and this approach is extended to different commercially available dyes, taking advantage of distinct fluorescence modulation mechanisms, providing, thus, color tunability. The modulation response is straightforwardly tuned by simply varying the irradiation power density, the gold nanoshell concentration, and/or the PCM type. This tunability allows to accomplish NIR‐activated multistate thermofluorochromic materials and fast/slow/irreversible responses in NIR‐writings/drawings of good spatial resolution, which can be of interest for barcodings, anticounterfeiting technologies and (re)writable devices.

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