Synthesis and Ultrafast Broadband Optical Limiting Properties of a Two-Branched Twistacene

Abstract

A novel two-branched twistacene (PyDN) has been designed and synthesized for application on ultrafast optical limiting. This twistacene exhibits excellent two photon absorption and two photon absorption-induced excited singlet state absorption, which was systematically investigated with a femtosecond Z-scan experiment, transient absorption spectrum, and two-photon excited fluorescence experiments. The admirable two photon absorption is attributed to the high degree of π electron delocalization in twistacene which is caused by introduction of two strong donors. The excited singlet state absorption cooperates with two-photon absorption to provide an excellent ultrafast optical limiting behavior with high linear transmittance, where the thresholds are 2.3–5.3 mJ/cm2 in the spectral region of 532–800 nm of femtosecond laser and 133 mJ/cm2 for picosecond pulse at 532 nm. These thresholds are lower than that of most of the optical limiters reported previously, which indicates PyDN is a promising candidate for ultrafast optical limiting.

Excellent Nonlinear Optical Limiting Behavior of Tetra (C60) Lanthanum Phthalocyanine in Solid Poly(methyl methacrylate) Films

“…The OA Z-scan data can be theoretically fitted by using the transmittance equation for the RSA absorption process: 0.25em T OA = prefix∑ m = 0 ∞ true[ prefix− β eff I 0 L eff / ( 1 + ( z z 0 ) 2 ) true] m false( m + 1 false) 3 / 2 where T OA refers to the measured hole transmittance and L eff is the effective thickness of the sample. L eff = [1-exp(−αL)]/α, where α is the linear absorption rate of the sample.…”

“…The appearance of the PET/ET process is mainly due to the generation of an effective electron transfer path inside the constructed D−A molecule. 35,36 The OA Z-scan data can be theoretically fitted by using the transmittance equation 11 for the RSA absorption process:…”

“…Liu et al prepared perfluorinated gallium phthalocyanine (F16PcGa) axially grafted few-layer black phosphorus (BP) nanosheets (F16PcGa–BP). The results showed that covalent modification of BP can effectively suppress the tendency of BP to form aggregates, and covalent modification of BP with Pcs can significantly improve the third-order nonlinear optical (NLO) performance. , Pcs are usually impacted by the intermolecular aggregation effect, which typically reduces the effective nonlinear absorption by shortening the excited state lifetime and adding relaxation pathways. Therefore, it is essential to design the structure of Pcs to improve their solubility.…”

Synthesis, Photophysical, and Optical Limiting Properties of Twistacene-Functionalized Arenes

“…Among them, the smallest twistacene is 9,14-diphenyldibenzo­[ de , qr ]­tetracene, which can be regarded as an electron-rich motif. − In general, the sp-hybridized alkyne bond is a covalent bond linker, which can not only promote molecular coplanarity but also increase the π–π* transition within the molecules. , When the alkyne group is connected with the twistacene, the as-formed derivatives might possess excellent solubility in organic solvents, enhanced charge transfer, and broadband optical limiting ability. Although many derivatives resulting from such twistacenes with positive nonlinear optical responses have been prepared, − systematic examination of the effect of the connection mode of alkyne bonds on the nonlinear optical performance and absorption mechanism is unprecedented.…”

“Hot exciton” fluorescence and charge transport of fine-tuned twistacenes: theoretical study on substitution effect and intermolecular interactions

“…Due to the significant fluorescence enhancement of the twisted acenes, these dendrimers presented strong blue light in diluted solution with good quantum yields, except for the case of 1,2,3,4,5,6-hexa(2-(5,12-diphenyl-6:7,10:11-bis-(4′- tert -butyl benzo)tetracene)) benzene. Another new two-branched twistacene (PyDN) was designed and synthesized by Han et al 17 The degree of π electron delocalization in PyDN was improved by the electron-donating groups and thus could lead to two-photon absorption, suggesting its potential for application in ultrafast optical limiting materials. According to Kasha's rule, the reverse intersystem crossing (RISC) of traditional TADF is the process from the first triplet state (T1) to the first excited singlet state (S1) of a molecule.…”