Graphene and its derivatives for laser protection

The development of functional materials for laser protection is an extremely important research field for the safety and security of users. To achieve simultaneous protection against both pulsed and continuous wave (cw) or quasi-cw lasers, significant research effort has been invested into state-of-the-art broadband optical limiting (OL) materials and processes in an attempt to achieve some measure of protection from such laser beams in the past decades. As the first truly two-dimensional material, graphene is being considered as an ideal material for modern photonic, optoelectronic and electronic devices because of its fantastic physical properties. Graphene shows ultrafast carrier relaxation dynamics and ultra-broadband resonate nonlinear optical (NLO) response due to their extended pi-conjugate system and the linear dispersion relation holding for their electronic band structure. Almost all types of graphene-based materials described in this review exhibit strong broadband OL response. The dominant limiting mechanism of graphene is non-linear scattering, which is very effective in liquid suspensions rather than in solid state hosts. In contrast to the pure graphene, the solubilized graphene and its derivatives optically limits through nonlinear absorption mechanism, nonlinear scattering as well as the photoinduced electron transfer and/or energy transfer between graphene and organic/polymeric species. This review describes systematically the OL mechanisms and the recent achievements on the graphene-based functional materials (i.e., graphene nanostructures, graphene composites, and covalently modified graphene) for OL applications. The future major ongoing areas of effort have also been suggested. (C) 2016 Elsevier Ltd. All rights reserved.