Aggregation induced emission-active two-photon absorption zwitterionic chromophore for bioimaging application

Small-molecule fluorogenic probes for mitochondrial nanoscale imaging

Mitochondria are inextricably linked to the development of diseases and cell metabolism disorders. Super-resolution imaging (SRI) is crucial in enhancing our understanding of mitochondrial ultrafine structures and functions. In addition to high-precision instruments, super-resolution microscopy relies heavily on fluorescent materials with unique photophysical properties. Small-molecule fluorogenic probes (SMFPs) have excellent properties that make them ideal for mitochondrial SRI. This paper summarizes recent advances in the field of SMFPs, with a focus on the chemical and spectroscopic properties required for mitochondrial SRI. Finally, we discuss future challenges in this field, including the design principles of SMFPs and nanoscopic techniques.

Novel red light-emitting two-photon absorption compounds with large Stokes shifts for living cell imaging

Three novel donor-π-acceptor two-photon absorption compounds (1PZPy, 2PZIm, 3CZPy) bearing the 10-butyl-10H-phenothiazine (9-butyl-9H-carbazole) donor, the pyridinium (benzimidazolium) acceptor, and the 2,5-divinylthiophene π-bridge were synthesized and fully characterized by ¹H NMR, ¹³C NMR, FT-IR, and HRMS. The linear and nonlinear photophysical properties were systematically investigated. Their absorption properties show a strong solvent dependence, while the emission properties are nearly independent of solvent polarity. All of them possess large Stokes shifts (Δλ=149-190 nm in H₂O). 1PZPy and 3CZPy exhibit red fluorescence emission centered at about 635 and 660 nm, respectively. The two-photon absorption cross-sections measured by the open aperture Z-scan technique are determined to be 486 (1PZPy), 601 (2PZIm), and 753 GM (3CZPy) in DMF. The density functional theory calculations were further carried out to reveal their electronic structures. All the target compounds are verified to have low cytotoxicity in the working solution and good capability for one- and two-photon excitation fluorescence imaging, suggesting their potential application in bioimaging. Moreover, they show the organelle targeting ability in living cells with the high Pearson's coefficients above 0.94 for the endoplasmic reticulum.

Flexible and Transparent Oligothiophene-o-Carborane-Containing Hybrid Films for Nonlinear Optical Limiting Based on Efficient Two-Photon Absorption

Structure-property relationship for fluorophores with favorable nonlinear optical (NLO) properties are promising topics in organic chemistry and material science. Herein, a series of terthiophene-o-carborane dyads and triads covalently linked with different end-capping styles were readily synthesized and comprehensively investigated. Quantitative values of the crystal and packing structures, photophysical parameters including aggregation-induced emission (AIE) and two-photon absorption (2PA) were provided. Significant impact of carborane unit for introducing the AIE characteristic has been investigated in contrast to the parent oligothiophene. All the obtained fluorophores exhibit maximum absorption around 370 nm in THF and emit bright reddish photoluminscence with absolute fluorescence quantum yields above 16% in solid states. Intramolecular charge communication between oligothiophene and carborane plays important roles in the related NLO properties. These results are supported well by the time-dependent DFT theoretical calculations. Effective 2PA cross sections (δ_2PA = 95-355 GM@650 nm) and transition dipole moments of the derivatives are variable for different end-capping styles. Their potential applications as optical limiting materials based on the 2PA mechanism in solutions and doped PDMS films were further evaluated. Taken together, this work provides an understanding of their structure-property relationship, and flexible PDMS films as outstanding candidates for practical applications in optical limiting.