Tenth-Order Multiphoton Excitation and Saturable Second Harmonic Generation in Polyoxometalate-Exfoliated Molybdenum Disulfide
Tenth-Order Multiphoton Excitation and Saturable Second Harmonic Generation in Polyoxometalate-Exfoliated Molybdenum Disulfide
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DOI：
10.1021/acs.jpcc.2c05739
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发表时间：
2022-10
期刊：
影响因子：
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通讯作者：
M. Steves;A. Jawaid;Ariel Struzyk;R. Torsi;J. Robinson;R. Vaia;K. Knappenberger
中科院分区：
文献类型：
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作者：
M. Steves;A. Jawaid;Ariel Struzyk;R. Torsi;J. Robinson;R. Vaia;K. Knappenberger
在非线性光学和能量转换材料方面，纳米材料有望取代传统的块体晶体。在本研究中，我们观察到了氧化还原剥离法制备的胶体MoS2纳米片中可饱和的二次谐波产生和高阶(高达10)的多光子光致发光。傅里叶变换非线性光学光谱学通过二维非线性激发/检测相关谱实现了对这些高阶信号的分辨。对非线性干涉图的互补建模为观测到的高阶信号提供了机制，其中包括与谐波能量共振的跃迁饱和和多光子吸收的多个竞争级数。化学气相沉积制备的MoS2中没有观察到的可饱和二次谐波产生和高次多光子光致发光与氧化还原剥落过程中形成的多金属氧酸盐簇有关。进一步的研究表明，多金属氧酸盐可以在其他胶体半导体中引起高阶非线性光学效应，并在谐波能量处产生共振，这为彻底改变具有分子吸附的纳米材料的非线性光学响应提供了一条普遍的途径。这种响应部分归因于多金属氧酸盐物种与纳米材料之间的界面电荷转移。傅里叶变换非线性光学光谱学为解决传统非线性光学测量中被遮挡的分子吸附效应提供了一条途径。
Nanomaterials are promising alternatives to traditional bulk crystals for nonlinear optics and energy conversion materials. In this study, we report the observation of saturable second harmonic generation and high-order (up to 10th) multiphoton photoluminescence in colloidal MoS2nanoflakes prepared by redox exfoliation which generates polyoxometalate clusters. Fourier transform nonlinear optical spectroscopy enabled the resolution of these high-order signals through two-dimensional nonlinear excitation/detection correlation spectra. Complementary modeling of the nonlinear interferograms suggested mechanisms for the observed high-order signals, which involve saturation of transitions resonant with the harmonic energy and multiple competing orders of multiphoton absorption. The saturable second harmonic generation and high-order multiphoton photoluminescence, which were not observed in MoS2prepared by chemical vapor deposition, are related to the formation of polyoxometalate clusters during the redox exfoliation process. Further studies demonstrated that polyoxometalates can induce high-order nonlinear optical effects in other colloidal semiconductors with resonances at the harmonic energy, suggesting a general route to drastically alter the nonlinear optical response of nanomaterials with molecular adsorbates. This response is due in part to the interfacial charge transfer between polyoxometalate species and the nanomaterial. Fourier transform nonlinear optical spectroscopy offers a route to resolving the effects of molecular adsorbates, which are obscured in traditional nonlinear optical measurements.