Solid Materials with Near‐Infrared‐Induced Fluorescence Modulation

Abstract

which are exploited in high-density data storage [13,14] and information processing, [15] white light generation, [16] (bio) sensing and imaging, [17-20] anticounterfeiting technologies, [21,22] and photowritable/erasable fluorescent inks, [23] among other areas. For many of these applications, the use of near-infrared (NIR) radiation to achieve luminescence modulation would be highly beneficial, e.g., to reach higher penetration depths with lower photodamage for (bio)imaging probes [18,24] or to develop advanced security inks for anticounterfeiting. [25] Currently, most common methodologies applied to achieve fluorescence modulation are based on the reversible interconversion of photochromic dyes. [9,10,11-18,19-21] However, these systems suffer from important drawbacks that are limiting their application in commercial products. On one hand, the interconversion of photochromic dyes are generally based on isomerization processes that involve large polarity and geometrical changes, which are often detrimentally affected by the surrounding matrix when these compounds are transferred from solution to the solid state. This is especially the case for photoswitchable luminescent materials based on T-type photochromes, [26] for which novel strategies are being developed to favor dye (photo) isomerization in solid matrices (e.g., by covalently attaching bulky moieties to increase the surrounding free volume [22,27] or by using photoisomersable compounds with minimal conformational changes [26,28]). On the other hand, photochromic dyes typically operate under highly energetic UV or visible radiation (e.g., spiropyrans) which contributes significantly to fast dye degradation. [29] Actually, making photochromic compounds sensitive to NIR radiation still remains a challenge that requires intricate synthetic procedures [30-33] and/or multiphoton excitation under high irradiation powers. [34-40] As such, their incorporation into more complex systems to attain NIR-induced luminescence modulation has been largely hampered to date. As an alternative to photochromic-based systems, we report herein a conceptually different strategy to obtain NIR-driven fluorescence modulation in the solid state, which takes advantage of a) the recent discovery by us [41-43] and others [44-47] that the emission of selective dyes dispersed in phase change materials (PCMs) can be thermally varied upon solid-to-liquid 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 radi...

The modulation effect of pi–pi interactions on the electronic and photochromic properties of viologen complexes containing N,N′-bis(carboxyethyl)-4,4′-bipyridinium

“…In 1952, Hirshberg et al discovered that spiropyrans can undergo reversible color change under light irradiation, which is called photochromism, that is, photochromic phenomenon. 1 Photochromic materials are a new type of functional materials developed in recent years, 2 and play an increasingly important role in daily life, industry and military fields, which can be used to make photochromic accessories, 3 ultraviolet sensors, 4 optical storage devices, 5 recording media, 6 nonlinear optical materials 7 and so on. As the superior electron acceptors of photochromic materials, viologen compounds, defined as N , N ′-bisubstituted-4,4′-bipyridinium dications, are one of the first choices for the construction of redox photochromic complexes due to the reason that they can be easily photoreduced accompanied by obvious color changes.…”

Tunable Thermofluorochromic Sensors Based on Conjugated Polymers

“…The 20-carbon inert paraffin eicosane (EC, melting point T m EC = 36.5 °C [82] ), already used to thermally modulate the aggregation and therefore fluorescence of small molecular dyes, [59,60,64] was first chosen as a PCM in our work and mixed with 0.01 wt% MEH-PPV (EC/MEH_0.01, see the Supporting Information for experimental details). In the solid state (20 °C), the mixture showed a broad emission band at λ max = 603 nm and a shoulder at 640 nm characteristic of the aggregated polymer (Figure S1, Supporting Information).…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] Specially relevant are those whose emission can be controlled with temperature, as luminescence transition is a quite universal method to control the aggregation of the embedded fluorophores and their luminescence (e.g., by switching between monomeric and excimer emission upon dye aggregation). [59][60][61][62][63][64][65][66][67][68] Following this approach, up to now organic nonpolymeric PCMs have been successfully combined with small molecular fluorophores to yield single-color emission switching (off/on or on/off), [59,61,65] while multicolored thermal responses, with coarse color tunability, could only be accomplished by using different fluorescent molecules. [62,66,68] Although conjugated polymers are known to manifest highly medium-dependent emission properties, to our knowledge the only so far reported examples of PCM-based thermofluorochromism using a semiconductive polymer (polydiphenylacetylene) only provided a single-color on/off fluorescence modulation, and/or it required additional chemical functionalization to improve its miscibility with the surrounding PCM.…”

Novel Fluorescent Polyurethane Coating on Fabric with Acid‐Base Indicating Function in Solution

“…The main reason is that the polymer matrix can restrict the movement of fluorescent substances. [10,11] And reduce the non-radiative quantum transition. On the other hand, excellent processability and stability is bought to the fluorescent substance by the polymers.…”

“…For most fluorescent polymers, the abilities to obtain fluorescence emission with special luminescence properties and high quantum yield under the condition of low fluorescent substance content for them is common. The main reason is that the polymer matrix can restrict the movement of fluorescent substances [10,11] . And reduce the non‐radiative quantum transition.…”