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The traditional design strategies for highly bright solid‐state luminescent materials rely on weakening the intermolecular π–π interactions, which may limit diversity when developing new materials. Herein, we propose a strategy of tuning the molecular packing mode by regioisomerization to regulate the solid‐state fluorescence. TBP‐e‐TPA with a molecular rotor in the end position of a planar core adopts a long‐range cofacial packing mode, which in the solid state is almost non‐emissive. By shifting molecular rotors to the bay position, the resultant TBP‐b‐TPA possesses a discrete cross packing mode, giving a quantum yield of 15.6±0.2 %. These results demonstrate the relationship between the solid‐state fluorescence efficiency and the molecule's packing mode. Thanks to the good photophysical properties, TBP‐b‐TPA nanoparticles were used for two‐photon deep brain imaging. This molecular design philosophy provides a new way of designing highly bright solid‐state fluorophores. [ABSTRACT FROM AUTHOR]

Rodents are popular biological models for physiological and behavioral research in neuroscience and rats are better models than mice due to their higher genome similarity to human and more accessible surgical procedures. However, rat brain is larger than mice brain and it needs powerful imaging tools to implement better penetration against the scattering of the thicker brain tissue. Three-photon fluorescence microscopy (3PFM) combined with near-infrared (NIR) excitation has great potentials for brain circuits imaging because of its abilities of anti-scattering, deep-tissue imaging, and high signal-to-noise ratio (SNR). In this work, a type of AIE luminogen with red fluorescence was synthesized and encapsulated with Pluronic F-127 to make up form nanoparticles (NPs). Bright DCDPP-2TPA NPs were employed for in vivo three-photon fluorescent laser scanning microscopy of blood vessels in rats brain under 1550 nm femtosecond laser excitation. A fine three-dimensional (3D) reconstruction up to the deepness of 600 μ m was achieved and the blood flow velocity of a selected vessel was measured in vivo as well. Our 3PFM deep brain imaging method simultaneously recorded the morphology and function of the brain blood vessels in vivo in the rat model. Using this angiography combined with the arsenal of rodent's brain disease, models can accelerate the neuroscience research and clinical diagnosis of brain disease in the future. [ABSTRACT FROM AUTHOR]

Nanoparticle-assisted near-infrared (NIR) bioimaging and two-photon fluorescence microscopy (TPFM) are two important technologies in biophotonic research. In this work, we synthesize the dye named 2-(4-bromophenyl)-3-(4-(4-(diphenylamino)styryl)phenyl)fumaronitrile (TPABDFN), which had a large two-photon absorption cross-section and bright NIR emission. The dyes were then encapsulated with poly(styrene- co -maleic anhydride) (PSMA), forming fluorescent nanoparticles. The TPABDFN-PSMA nanoparticles possessed high chemical and optical stability, good biocompatibility, as well as large two-photon absorption cross-section (5.56 × 10 5 GM). Furthermore, we combined NIR bioimaging and TPFM together, and utilized TPABDFN-PSMA nanoparticles as fluorescent contrast agents for two-photon excited NIR microscopic imaging, with a 1040 nm-femtosecond laser. In vivo angiography of mice ear and brain was performed. Due to the deep penetration capability of both 1040 nm-excitation and NIR emission light, a very large in vivo microscopic imaging depth (∼1.2 mm) was achieved. NIR emissive and biocompatible TPABDFN-PSMA nanoparticles have great potential in disease diagnosis and clinical therapies, where deep-tissue imaging is required. [ABSTRACT FROM AUTHOR]

In this work, a series of new diketopyrrolopyrrole-based dyes have been synthesized by connecting tetraphenylethene to the diketopyrrolopyrrole core. All the four compounds exhibit good aggregation-induced emission property with nonemissive in the solution but strong red fluorescence in the aggregate or solid state. Also, these new dyes exhibit large two-photon absorption cross sections (σ), in which the σ data measured by the open aperture Z-scan technique are determined to be 150, 300, 1140 and 1016 GM for four dyes, respectively. In addition, compound with stilbene and four tetraphenylethene units ( DPP-TPE-3) was used as the luminogen and encapsulated into nanoparticles for cell imaging and two-photon excited fluorescence blood vessels imaging. The result indicates that it can be used as the effective fluorescence probe for bioimaging and has great potential for bioapplications. [ABSTRACT FROM AUTHOR]