Different electrochemical effect on photoluminescence in single-doped/dual-doped carbon quantum dots

Due to their application potential in novel optoelectronic devices, several methods have been used to understand or tune the photophysical properties of doped carbon quantum dots (CQDs). Spectroelectrochemical method is one of excellent means, which has been demonstrated in nitrogen-doped CQDs film to efficiently manipulate their photoluminescence. However, the role of different doping elements are still unclear. Therefore, in this work the optical properties of sulfur-doped CQDs (S-CQDs), sulfur-nitrogen co-doped CQDs (S,N-CQDs) and fluorine-nitrogen co-doped CQDs (F,N-CQDs) films were investigated by spectroelectrochemical method. Compared with S,N-CQDs and F,N-CQDs, S-CQDs have a more obvious photoluminescence (PL) enhancement phenomenon under the same bias voltage, and their PL intensity increases by 100% and 55.8% at +2.0 V and −2.0 V, respectively. We believe that the above PL enhancement is related to the weakening of the inter-molecular π-π interaction after electrochemical charges implantation and single-doped CQDs are more conducive to this process. In addition, the onset potential of PL enhancement is also affected by the doping element.