We have demonstrated an easy chemical oxidation approach toward fluorescent carbon dots (CDs) using arc-synthesized carbon by-products. The as-synthesized CDs possess a strong excitation-independent photoluminescence emission located at ca. 502 nm and strong upconversion fluorescence under long wavelength radiation (from 900 to 550 nm). Importantly, the CD-based device has been investigated and exhibits excellent photoresponse under UV irradiation, highlighting the potential for optoelectronic applications.