The adsorption of molecules usually increases capacity and/or strength with the doping of surfaces with transition metals; furthermore, carbon nanostructures, i.e., graphene, carbon nanotubes, fullerenes, graphdiyne, etc., have a large specific area for gas adsorption. This review focuses on the reports (experimental or theoretical) of systems using these structures decorated with transition metals for mainly pollutant molecules’ adsorption. Furthermore, we aim to present the expanding application of nanomaterials on environmental problems, mainly over the last 10 years. We found a wide range of pollutant molecules investigated for adsorption in carbon nanostructures, including greenhouse gases, anticancer drugs, and chemical warfare agents, among many more.

A microscopic model is presented to account for the diffraction efficiency of photorefractive gratings generated in semiconductor multiple quantum wells. The material equations are solved for the steady state, under rather general conditions, with respect to an applied electric field parallel to the layer planes. Previously obtained results for the space-charge field are obtained from the present solution after suitable approximations. The dependence of the diffraction efficiency on the relevant physical parameters is subsequently determined. We exhibit a comparison of the variation of the diffraction efficiency with the applied electric field with available experimental data. The agreement is reasonably good. On the other hand, the experimental dependence of the diffraction efficiency on grating spacing follows a trend similar to that of the space-charge field that we predicted, as we should expect. These results represent an improvement with respect to previous approaches, in which only partial agreement was obtained.

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