Scaffold-like 3D networks fabricated via the organogelation of β-diketone-boron for fluorescent sensing organic amine vapors

Ingenious fluorescent probes for biogenic amine and their applications in bioimaging and food spoilage detection

Food safety issues have received much attention. Biogenic amines are considered important markers of food spoilage. Accurate detection of biogenic amines is important for food quality monitoring. Herein, we developed two coumarin-difluoroboron β-diketonate hybrid probes, 1 and 2, for detection of amines. Both probes possess large conjugated structures and donor-acceptor-donor configuration, exhibiting solvatochromic effects due to intramolecular charge transfer mechanism. Upon reaction with amines, the boron atom in difluoroboron unit can interact with lone pair electrons of nitrogen atom, thus resulting in significant changes in absorption and fluorescence properties. These probes were successfully utilized to image amine in live cells and liver tissues. Moreover, by photographing probe-loaded food extract supernatant, we establish the relationship between color parameters and food storage time, which can easily indicate food spoilage process. This work and its findings hold promise for providing potential strategies for real-time and convenient detection of food freshness.

Room temperature tunable multicolor phosphorescent polymers for humidity detection and information encryption

Amorphous polymer-based room temperature phosphorescence (RTP) materials exhibiting tunable emission colors have received tremendous attention and are extremely challenging to prepare. Herein, polyacrylamide-based RTP materials with tunable multicolor emission were prepared via copolymerizing phosphor with concentration dependent luminescence colors and acrylamide with different molar ratios. The hydrogen bonding interactions and chemically crosslinked structures in these polymers effectively restrict the mobility of phosphors and activate efficient RTP emission. The molar ratio of phosphor and acrylamide has a significant influence on the photophysical properties of these polymers, which can be used to fabricate multicolor materials. In addition, the RTP intensity decreases with increasing humidity due to the disassociation of hydrogen bonding by adsorption of water, manifesting as a humidity sensor. Benefiting from the distinguishable RTP lifetimes and the responsiveness to humidity, triple encoding for information encryption is successfully realized.

A polymer with tunable multicolor was prepared via copolymerizing a phosphor with concentration dependent luminescence and acrylamide based on chemical crosslinking and hydrogen bonding interactions for humidity detection and information encryption.

o-Hydroxydibenzoylmethanate of boron difluoride: A complex with multi-stimuli-responsive emission effects

The structural, luminescence and chemosensor properties of boron difluoride o-hydroxydibenzoylmethanate (1) have been investigated. In the concentrated solution, PE (polyethylene) matrix, and crystals of 1, one observes the formation of J-aggregates. The crystal structure of 1 is in compliance with that of J-aggregates of the "brickwork type" consisting of dimers that comprise excimer traps. In time-resolved luminescence spectra of 1 in PE films and crystals, one observes luminescence bands corresponding to the luminescence of excimer J-aggregates. At application of external stimuli on the crystals of 1 (heating, grinding), one observes changes in the luminescence spectrum caused by redistribution of intensities of excimer and J-aggregate bands. 1 could act as an optic chemosensor for probing amines vapors with different response rates and different sensitivities controlled by their morphologies.

Synthesis, photophysical and solvatochromic properties of diacetoxyboron complexes with curcumin derivatives

Five novel diacetoxyboron complexes of β-diketones incorporated curcumin moiety were designed and synthesized. Their photophysical behaviors were investigated by UV-vis absorption and fluorescence spectroscopy in different solvents and solid state. It was observed that their fluorescence spectra yielded a blue to yellow-green emission in solution and emitted a yellow to red emission in solid state. Especially, the complex 3b displayed the strongest emission and the highest quantum efficiency (Φ_u = 0.98) in toluene among these complexes. The CIE coordinate of the complex 3b in solid state was positioned in an ideal red region of the chromaticity diagram. The maximal emission of these complexes exhibited a large wavelength shift and Stokes shift increased with the increase of the solvent polarity. Their dipole moment differences between the ground and excited states were also estimated by using the Lippert-Mataga equation. Meanwhile, their HOMO, LUMO energy levels and energy band gaps were calculated by cyclic voltammetry.

H- and J-aggregates formed from a nontraditional π-gelator depending on the solvent polarity for the detection of amine vapors

A tert-butyl carbazole-modified difluoroboron β-diketonate complex (TCbzB) has been synthesized. Although no traditional gelation group was involved in TCbzB, it could form organogels in the mixed solvents of o-dichlorobenzene/cyclohexane (v/v = 1/5 or 1/2), toluene/cyclohexane (v/v = 1/2) and chlorobenzene/cyclohexane (v/v = 1/2). Interestingly, an orange organogel was obtained in o-dichlorobenzene/cyclohexane (v/v = 1/2) with relatively high polarity and red organogels were gained in the other three mixed solvents with relatively low polarity. TCbzB self-assembled into H-aggregates and J-aggregates in orange and red organogels, respectively, and the corresponding xerogels emitted yellow and red light, respectively, under UV illumination. The red emission of the xerogel-based film could be quenched significantly by gaseous n-propylamine and aniline because of the decomplexation of the difluoroboron β-diketonate complex by n-propylamine and the weak interactions between aniline and boron difluoride units.

Luminescent organogels based on triphenylamine functionalized β-diketones and their difluoroboron complexes

New organogelators based on triphenylamine functionalized β-diketones and their difluoroboron complexes were synthesized.