Abstract
Ti3C2 nanosheet is a newly discovered two-dimensional (2D) clan. It turns out to have encouraging applications for electromagnetic shielding and energy storage. Here, Ag@ Ti3C2 hybrids are precisely synthesized by using the one-step solution processing method. Also, their ultrafast broadband nonlinear optical responses in the visible region are studied systematically through nanosecond open-aperture Z-scan and transient absorption techniques. The mechanism of two-photon absorption (TPA) is disclosed in the visible region (409–532 nm). When the laser energy is low and the wavelength is longer than 400 nm, nonlinear absorption cannot happen. Meanwhile, as the laser energy increases, two photons will be absorbed by the electrons in the valence band and the electrons will jump to the conduction band. The process is named as two-photon absorption which will make the specimen show reverse saturable absorption (RSA) properties. What is more, the ultrafast carrier dynamics of the specimen are studied by using the transient absorption. The result shows that the decay contains two phases: the fast and then the slow one. The two phases first come from electron–phonon and then from phonon–phonon interactions, respectively. The electron transfer and charge carrier trapping processes are further verified by the outcomes of similar measurements on Ag@ Ti3C2 hybrids. Besides, the two decay processes increase together with the pump fluence. These results show that Ti3C2 nanosheet has potential applications in broadband optical limiter.
Highlights
(2D) materials to promote the research of modern nonlinear optics owing to their layers of atomic structure, strong light–mater interaction and huge nonlinear optical effect [1]
The breakthrough of hybridizing NPs for nonlinear optical (NLO) application has emerged in the past several years in terms of their defect states, surface control, and excellent plasmonic properties [18,19,20]
Ti3 C2 nanosheet pumped at 400 nm with a fluence of 6.4 × 10 mW/cm . (b,d) Time and wavelength wavelength resolved transient absorption data of Ag@Ti3C2 and Ti3C2 nanosheet
Summary
With the discovery of graphene, much attention has been placed on two-dimensional (2D) materials to promote the research of modern nonlinear optics owing to their layers of atomic structure, strong light–mater interaction and huge nonlinear optical effect [1]. They have been found to have numerous applications in photonics and optoelectronics [2]. In visible light region, silver (Ag) can act as an excellent dopant accompanied by functional advantages of increasing the excited absorption cross-section and promoting absorption in the excited state Silver nanoparticles, though they oxidize rapidly in the air, are favored for their bactericidal properties. The carrier dynamics of this hybrid are investigated with femtosecond transient absorption experiments which can be used to study the decaying channels at various energy levels with multiple probe wavelengths
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