Hierarchically Porous Carbon Photonic Structures

Hierarchically porous carbon holds promise for many applications involving not only electrical, catalytic, power storage and related functionalities but, despite absorption in the visible and near-infrared, also optical and sensing uses are envisaged. In this paper, the self-assembly of heterogeneous core-shell and hollow carbon spheres based on polystyrene cores, their optical properties and their response to humidity are described. The remarkable high quality of the crystals permits to exploit their singular optical properties among which a very high sensitivity to adsorption of guest materials stands out. In this regard, an original characterization of the system response is performed by means of the photonic bandgap variation with the relative gas pressure. Controlled pyrolysis enables to create and tune the features of the porosity brought about by degassing and the restructuring of the carbon lattice. Functionality associated with diverse pore populations reveals sensitivity to diverse ranges of humidity owing to selective adsorption of water in different size pores.