ZnO microneedles with hexagonal wurtzite structure were synthesized by carbon thermal reduction method with the mixture of ZnO powder and graphite powder as source materials.Under excitation of near-infrared laser with 800 nm wavelength,two ultraviolet emission bands were observed from a microneedle.The center of the shorter-wavelength band is located at about 392 nm with a small redshift as excitation power increases,which is attributed to the recombination from exciton-exciton scattering.The c...