Crystalline silica nanowires

alpha-Cristobalite nanowires of 50-100 nm diameter with lengths of several microns have been synthesized for the first time by the solid-state reaction of fumed silica and activated charcoal. The nanowires have been characterized by x-ray diffraction, electron microscopy, photoluminescence, and Raman scattering. The nanowires are single crystalline as revealed by high-resolution electron microscope images. The crystalline nanowires are clad by an amorphous silica sheath when the carbon to fumed silica ratio in the starting mixture is small. Use of hydrogen along with Ar helps to eliminate the amorphous sheath.