Polyoxometalates with tunable third-order nonlinear optical and superbroadband optical limiting properties

In order to tune the intrinsic third-order nonlinear optical (NLO) properties of polyoxometalates (POMs), we adopted a strategy of substituting addenda atoms of POMs to obtain a class of polyoxomolybdovanadates, [TBA](3)[VMO5O19] (V1Mo8), [TBA](4)[V8Mo2O28]center dot 2CH(3)CN (V8Mo2) and [TBA](4)[HV(9)Moo(28)]center dot 2CH(3)CN (V9Mo1) (TBA = tetrabutylammonium). Their structures were determined by single crystal X-ray diffraction and further characterized by FT-IR, Raman, UV-vis, diffuse reflection, HR MS, XPS, ICP-MS, CHN analysis and so on. The Z-scan curves of all compounds in a suspension of propanetriol demonstrate typical nonlinear absorption (NLA) irradiated by a laser at 532 nm and 1064 nm, which can be tuned by the substitution of addenda atoms in POMs. Among those, V8Mo1 possesses the smallest transmittance and largest nonlinear absorption coefficient. V8Mo1-doped organically modified silica (ORMOSIL) gel glasses have NLA and optical limiting (OL) properties that could be tuned by changing the doping concentration of V8Mo1. In particular, V8Mo1 exhibits an unusual superbroadband OL performance in the visible and long-wavelength near-infrared regions (532-2150 nm). To the best of our knowledge, this is the first example of a super-broadband optical limiter based on crystalline metal cluster compounds. Our current work not only provides a series of polyoxomolybdovanadates and V8Mo1-doped gel glasses with tunable third-order NLO properties and superbroadband OL performance but also affords a feasible strategy to tune the third-order NLO properties of POMs via the substitution of addenda atoms.

Automated summary

In this study, we employed a strategy of substituting addenda atoms of polyoxometalates (POMs) to obtain a class of polyoxomolybdovanadates with tunable third-order nonlinear optical (NLO) properties. Among these compounds, V8Mo1 showed the best nonlinear absorption performance and could be doped into organically modified silica gel glasses to exhibit exceptional broadband optical limiting (OL) properties.