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Organic dye molecules with excited state proton transfer property gain huge scientific interest owing to the design flexibility and functional diversity. However, the anti-counterfeiting of a single dye molecule through intra- and intermocular excited state proton transfer (ESIPT and ESPT) has yet to be achieved. This study demonstrates a simple and efficient approach to realize the anti-counterfeiting of a single dye molecule in a PMMA film. We control the 1-hydroxypyrene-2-carbaldehyde (HP) to be fluorescent or not through two different solvents based on ESIPT and ESPT mechanisms. Furthermore, we investigate the detailed information of excited-state dynamics for HP in two solvents, aiming at exploring the mechanisms of totally different luminescence property, through the femtosecond transient absorption spectroscopy. Meanwhile, the theoretical TDDFT research sheds light on the correlation between molecular structure and luminescence character. Specifically, the fluorescence of the molecule in acetonitrile is quenched by an ESIPT (127 fs) induced intersystem crossing (11.8 ps) whereas the ESPT (195 fs) and following aldehyde group rotation (26.5 ps) make the molecule to exhibit a strong luminescence property in dimethyl sulfoxide. The results are promising and offer new avenues to realize the greener and sustainable anti-counterfeiting of a single dye molecule. [ABSTRACT FROM AUTHOR]

Inspired by enol-degradation of luciferin, a new dual mode oxygen sensing with alternant change of color and fluorescence has been developed to estimate rapidly the oxygen concentration. Based on the screening of ten methyl ketone molecules with different functional groups, molecule M5 with obvious fluorescence change and high degradation speed is selected and studied in detail by UV-Vis and fluorescence spectroscopy. The degradative mechanism containing four-member ring intermediate has been proved by MS and DFT calculation. And the sensor strip prepared by molecule M5 exhibits high selective and perfect optical properties to detect the oxygen concentration without delicate instrument. This oxygen sensor will not only accelerate the development of oxygen sensor, but will also help to understand the mechanism of luciferin bio-degradation. [ABSTRACT FROM AUTHOR]

The first multi-channel probe giving different signals towards ROS and nitroxyl has been easily synthesized with a rational method which successfully showed blue emission towards peroxynitrite and hypochlorite and green emission towards nitroxyl in solution. The highly efficient oxidation of hypochlorite towards triphenylphosphine was discovered and utilized to distinguish hypochlorite and peroxynitrite with the aid of nitroxyl. A rare photoinduced electron transfer (PET) phenomenon from the donor fluorophore to the acceptor fluorophore was observed and adopted to give the signal of sequence sensing. Furthermore, the probe gave real-time signal selectively towards peroxynitrite and nitroxyl in Hela cells. [ABSTRACT FROM AUTHOR]

A new strategy for red-green-blue (RGB) unimolecular fluorescence switching was demonstrated based on through-bond energy transfer (TBET) mechanism by combining of Rhodamine as acceptor and green fluorescence dye as donor. In this paper, green fluorescence dye 2-(4-aminophenyl)benzothiazoles (PBT) was chosen as an example. And RGB fluorescence property with large stokes shift (260 nm) and good color contrast (red: 625 nm, green: 495 nm, blue: 425 nm) was exhibited in PMMA film and DCM solution. What's more, the switchable through-bond energy transfer mechanism was proved clearly by femtosecond transient absorption spectroscopy and density functional theory (DFT). The strategy will open new method for designing for RGB luminescence, and inspire the development and application of RGB fluorescence switching. [ABSTRACT FROM AUTHOR]

Abstract Organic thermochromic luminescent materials are very promising in applications of thermo-history recording, sensing and anti-counterfeiting. However, the current reported organic thermochromic systems still have the drawbacks of slow responsive speed, low colour contrast and unsatisfactory repeatability. In this paper, we reported a twisted fluorophore based on 1,4-bis[2,2-bisphenyl-vinyl]benzene skeleton with A-D-A structure (OD-CN) , which shows strong solvatochromism in solution with emission shifts up to 135 nm, highly efficient red emission in solid state (660 nm, 11.62%) and unprecedented thermochromic behaviour in linear low density polyethylene matrix with high emission contrast (red to greenish yellow), fast responsiveness (within 1 s) and good repeatability (over 10 times). OD-CN doped LLDPE films show potential applications in anti-counterfeiting and as an example, it was applied as multi-channel anti-counterfeiting printings on paper money. What's more, the strategy of blending fluorophores with solvent effects and solid-state emission into apolar polymer matrixes to realize thermochromisms is general. Graphical abstract Image 1 Highlights • A new emitter (OD-CN) based on twisted skeleton with A-D-A structure is synthesized. • OD-CN exhibits solvatofluorochromisms in solution and red emission in solid state. • The films of OD-CN doped LLDPE show thermochromism with high contrast and fast responsive time and reversibility. • The thermochromic binary films can be used in anti-faking. • Other films of emitters with solvatofluorochromisms and solid-state emission and LLDPE can also present thermochromism. [ABSTRACT FROM AUTHOR]

A bistable electrochromic device based on poly(viologen)s is demonstrated with good overall performance, including bistability (4981 s), switch-on voltage (−1.0 V) and reversibility (≥1000 cycles). Overall, these results imply that the control of the diffusivity of viologens is an effective methodology for achieving excellent bistability and low energy consumption. [Display omitted] • ECDs were fabricated from poly(viologen)s and poly(ferrocene). • The ECD shows good bistable property of 4981 s. • The multi-color device was achieved by mono-layered pixelated-device. [ABSTRACT FROM AUTHOR]