High-contrast flicker luminescence on dynamic covalent structure based nanoaggregates

A simple AIE chemosensor based on diphenyl imidazole scaffold for 2,4,6-trinitrophenol detection and dye absorption

Fluorescent material exhibiting aggregation-induced emission (AIE) has demonstrated to be a facile and effective method to detect 2,4,6-trinitrophenol (TNP) due to its excellent features. In this study, a novel diphenyl imidazole-based fluorescent material (DINP) was successfully synthesized via a facile method. Fluorescence spectra showed that DINP had a typical AIE effect in DMSO/water solution, and the fluorescence emission was effectively quenched by TNP without being affected by other explosives. The Stern-Volmer quenching constant of 2.70 × 10⁵ M^-1 and detection limit of 7.2 × 10^-8 M demonstrated that the DINP aggregates could serve as potential chemosensor for TNP detection. The mechanism behind the quenching of fluorescence could be ascribed to the formation of ground state complex. In addition, fluorescent test strips and TLC plate prepared with the aggregates provided an easy and low cost method for TNP detection in the aqueous solution. Especially, DINP was applied to quantitatively detect the content of TNP in real water samples. Furthermore, the aggregates exhibited good selective adsorptive performance to rhodamine B dye in aqueous solution with high adsorption efficiency of 98 % in a few minutes.

Lighting up solid states using a rubber

It is crucial and desirable to develop green and high-efficient strategies to regulate solid-state structures and their related material properties. However, relative to solution, it is more difficult to break and generate chemical bonds in solid states. In this work, a rubbing-induced photoluminescence on the solid states of ortho-pyridinil phenol family was achieved. This rubbing response relied on an accurately designed topochemical tautomerism, where a negative charge, exactly provided by the triboelectric effect of a rubber, can induce a proton transfer in a double H-bonded dimeric structure. This process instantaneously led to a bright-form tautomer that can be stabilized in the solid-state settings, leading to an up to over 450-fold increase of the fluorescent quantum yield of the materials. The property can be repeatedly used due to the reversibility of the tautomerism, enabling encrypted applications. Moreover, a further modification to the structure can be accomplished to achieve different properties, opening up more possibilities for the design of new-generation smart materials.

Changes in molecular properties due to stimuli response are critically important for the development of new materials. However, most processes are slow or inefficient in the solid state. Here the authors demonstrate property switching in the solid state using a rubbing-induced tautomerism in multiple hydrogen-bonded donor-acceptor couples.

A Fluorescence-Phosphorescence-Phosphorescence Triple-Channel Emission Strategy for Full-Color Luminescence

Organic luminogens constitute promising prototypes for various optoelectronic applications. Since gaining distinct color emissions normally requires the alternation of the conjugated backbone, big issues remain in material synthetic cost and skeleton compatibility while pursuing full-color luminescence. Upon a facile one-step coupling, three simple but smart perchalcogenated (O, S, and Se) arenes are synthesized. They exhibit strong luminescent tricolor primaries (i.e., blue, green, and red, respectively) in the solid state with a superior quantum yield up to >40% (5-10 times higher than that in corresponding solutions). The properties originate from a fluorescence-phosphorescence-phosphorescence triple-channel emission effect, which is regulated by S and Se heavy atoms-dependent intersystem crossing upon molecular packing, as well as Se-Se atom interaction-caused energy splittings. Consequently, full-color luminescence, including a typical white-light luminescence with a Commission Internationale de I'Eclairage coordinate of (0.30, 0.35), is realized by complementarily incorporating these tricolor luminescent materials in the film. Moreover, mechanochromic luminescent color conversions are also observed to achieve the fine-tuning of the luminescent tints. This strategy can be smart to address full-color luminescence on the same molecular skeleton, showing better material compatibility as an alternative to the traditional multiple-luminophore engineering.

Fluorescence to multi-colored phosphorescence interconversion of a novel, asterisk-shaped luminogen via multiple external stimuli

Photoluminescence from blue fluorescence to green, yellow, and orange phosphorescence can be switched via multiple stimuli on an asterisk-shaped compound.

Photoexcitation-controlled self-recoverable molecular aggregation for flicker phosphorescence

Chemical systems with external control capability and self-recoverability are promising since they can avoid additional chemical or energy imposition during the working process. However, it remains challenging to employ such a nonequilibrium method for the engineering of optoelectronic function and for visualization. Here, we report a functional molecule that can undergo intense conformational regulation upon photoexcitation. It enables a dynamical change in hydrophobicity and a follow-up molecular aggregation in aqueous media, accordingly leading to an aggregation-induced phosphorescence (AIP) behavior. This successive performance is self-recoverable, allowing a rapid (second-scale cycle) and long-standing (>10³ cycles) flicker ability under rhythmical control of the AIP. Compared with traditional bidirectional manipulations, such monodirectional photocontrol with spontaneous reset profoundly enhances the operability while mostly avoiding possible side reactions and fatigue accumulation. Furthermore, this material can serve as a type of luminescent probe for dynamically strengthening visualization in bioimaging.