Tunable Non-linear Refraction Properties and Ultrafast Excited State Dynamics of Dicyanomethylene Dihydrofuran Derivative.

Linpo Yang,Taihui Wei,Feng Li,Shaoming Fang,Zhongguo Li,Yinglin Song,Liming Zhou

doi:10.3389/fchem.2020.522974

Abstract

The third order non-linear optical response of a dicyanomethylene dihydrofuran compound (DCDHF-2V) was investigated using a Z-scan technique in picosecond and nanosecond time regimes. The results show that DCDHF-2V has excellent excited state non-linear refraction properties on both time regimes, and the non-linear refraction index is also solvent-dependent in the nanosecond regime. The excited state relaxation dynamics of DCDHF-2V were demystified via femtosecond transient absorption spectroscopy. The TA spectra reveal that the solvent viscosities have a substantial impact on the excited state relaxation of DCDHF-2V. The exotic photophysical phenomena in DCDHF-2V reported herein can shed new light on future development of small organic non-linear optical materials with large non-linear coefficients and fast response.

Highlights

Conjugated organic molecules have attracted much attention in the field of non-linear optics due to their large non-linear coefficients, ultrafast response rates, large damage thresholds, easy processing, and significant improvement in molecular optical properties through simple substituent changes (Gu et al, 2016; Wu et al, 2017a; Wei et al, 2020)
The UV-vis absorption spectra of the samples in different solvents and the fluorescence emission spectra excited by a 500-nm wavelength are shown in Figure 3, in which the UV-vis spectra were normalized at the position of the strongest absorption peak, and the fluorescence intensity of the samples in different solvents is the actual intensity at the same concentration
The fluorescence intensity of dicyanomethylene dihydrofuran (DCDHF)-2V still increases with the increase of solvent viscosity, indicating that the sample shows stronger fluorescence quantum yield in high-viscosity solvent, which is consistent with the report of the same kind of molecules (Suhina et al, 2016; Qian et al, 2017)

Summary

Introduction

Conjugated organic molecules have attracted much attention in the field of non-linear optics due to their large non-linear coefficients, ultrafast response rates, large damage thresholds, easy processing, and significant improvement in molecular optical properties through simple substituent changes (Gu et al, 2016; Wu et al, 2017a; Wei et al, 2020). The intriguing non-linear optical properties of an organic compound are correlated to its conjugated molecular structure (Kim and Cho, 2009; Xiao et al, 2016; Sadowski et al, 2017; Wu et al, 2017b). It is of great importance to establish the relationship between molecular structure and non-linear optical properties. It is well-known that the fluorescence properties of conjugated organic molecules (excitation and emission wavelength, intensity, lifetime, etc.) are strongly dependent on the structure and relaxation processes of the molecular excitation state (Suhina et al, 2015, 2016; Ahn et al, 2019; Li et al, 2019).

Methods

Results

Conclusion