Synthesis of Orange Emitting Carbon dots as Potential Optical Sensing Receptor for Metal Ions

Carbon dots have gain much interest to be used as sensing receptors due to their unique photoluminescence property, ease to prepare, less toxic, and the option to perform surface modification to suit a sensing application. However, most of the carbon dots reported in the early days are emitting in the blue region with ultra violet (UV) excitation. There has been a lot of effort to red-shift the emission to suit better the sensing applications especially for bio-sensing. UV is often harmful to cells and tissues and the shifting of the excitation to longer wavelengths can reduce this risk. Besides, biological microenvironment often reflects blue background, which wills interference seriously with the blue emitting carbon dots. This paper reports the work performed to red-shift the emission of carbon dots from the conventional blue region into a longer wavelength. The shift is obtained via various strategies and the optimization of the synthesis process to obtain the best yield. This work has successfully isolated carbon dots that emitted orange emission with maximum intensity at 595 nm (orange color). The sensing potential of the carbon dots was tested for the detection of metal ions and found to show different selectivity profiles towards the chosen metal ions. This result suggests that the carbon dots have high potential for in vivo sensing application.