New eco-friendly carbon dot structures (CDs) were synthesized with hydrothermal method from ocimum basilicum in a single step. Structure, morphology and optical analyzes of these new CDs were performed with TEM, XRD, FTIR, XPS, UV-Vis. absorption and steady-state fluorescence measurements. It was determined that nano-sized CDs structures with high fluorescence properties were obtained by the analysis results. The sensor application of CDs was studied using various metal ions with different charges. The results showed that these ocimum basilicum based CDs were sensitive and selective only for Fe 3 + and Al 3 + ions. LOD values of Fe 3 + and Al 3 + ions were calculated as 0.12 μM and 0.78 μM, respectively. As a result of interference and response time studies, it was determined that CDs have a highly selective and rapid response for Fe 3 + and Al 3 + ions. It was observed that CDs have practical applicability with real sample tests. The results obtained showed that this new CDs exhibit both "turn-off" (for Fe 3 + ions) and "turn-on" (for Al 3 + ions) detection simultaneously.