Novel water/gas ratio reducer compounds comprising metal-doped carbon quantum dots, methods of their manufacture, sandstone and limestone gas well compositions containing the water/gas ratio reducer compounds and methods of their use are disclosed. The novel water/gas ratio reducer compounds are useful, inter alia, to decrease Kw/Kg ratio for the reservoir output, reduce the water permeability in the reservoir and/or increase gas permeability in the reservoir use, increase production rate, to increase total output from the reservoir, are more environmentally acceptable, employable at much lower concentrations, are reusable, may be used in a wider range of gas well drilling fluids including, for example, seawater-based drilling fluids and/or more cost-effective in use.

Silicon photonic crystal (10; 10; 10) comprising periodic silicon structures (12) contiguous with voids (14), and a silicon resonant cavity (16) consisting of silicon nanowires (18) entirely made of silicon with uniform doping, said nanowires acting as active medium of the photonic crystal.

Silicon photonic crystal (10; 10; 10) comprising periodic silicon structures (12) contiguous with voids (14), and a silicon resonant cavity (16) consisting of silicon nanowires (18) entirely made of silicon with uniform doping, said nanowires acting as active medium of the photonic crystal.