Controlling the optical, electrical and chemical properties of carbon inverse opal by nitrogen doping

Nitrogen-doped carbon inverse opal (CIO-N) is synthesized by a two-step process involving the infiltration of carbon-nitrogen precursors within opals followed by the thermolysis and removal of the opal structure in hydrofluoric acid (HF). Undoped samples exhibit a reflection peak in the red region of the spectrum whereas N-doped samples display shifts to the blue region of the spectrum as the nitrogen content is increased. The degree of crystallinity of CIO-N strongly depends upon the nitrogen content and on the size of the precursor silica particles used to prepare the inverted opals. In addition, the introduction of nitrogen into the samples is able to increase the electrical conductivity by one order of magnitude from 2 to 30 S cm^-1 (at room temperature). All samples are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-Vis) spectroscopy, and electrical conductivity measurements. It is envisaged that CIO-N could have important applications in the fabrication of photonic crystals, photoconducting materials, molecular sensors, field emission devices, capacitors, batteries, among many others. The optical, electrical, and chemical properties of carbon inverse opals are tailored by nitrogen doping. The amount of nitrogen precursor dictates the changes in the physical and chemical properties. The reflected colors of the carbon inverse opal can vary in the visible region from red to blue. In addition, the resistivity can be lowered from 0.30 to 0.02 Ω cm.