Controllable Synthesis of Carbon Dots with Excitation‐Wavelength‐Dependent or Independent Photoluminescence for the Selective and Sensitive Detection of Co2+ Ions

Abstract

AbstractFluorescent carbon dots (CDs) with excitation‐wavelength‐dependent and excitation‐wavelength‐independent emission have been prepared with varying amounts citric acid (CA), ethylenediamin end‐capped polyethylenimine (PEI‐EC) and sodium borohydride (NaBH4), their structure, optical and chemical sensing properties have been also systematically investigated. The varying of NaBH4 and PEI‐EC renders the structure and surface state change as well as photoluminescence (PL) properties. The results indicated that NaBH4 made the CDs sensitive to Co2+ ions, whilst the PEI‐EC served to increase their sensitivity. The synergistic roles that both NaBH4 and PEI‐EC played on the selective and sensitive detection of Co2+ were achieved via a simple adjustment of the mass ratios during synthesis. Furthermore, the PL intensity was gradually recovered until completely restored with the addition of chelating agent ethylenediaminetetraacetic acid (EDTA) to the Co2+ quenched CDs solutions. This work provided quantitatively preparation and controllable synthesis of excitation‐wavelength‐dependent or independent CDs for the development of PL based sensors.