![malvern zetasizer ns malvern zetasizer ns](https://flowcore.hsc.wvu.edu/media/15838/nanosight-1-april-2019.jpeg)
Also, the emission intensity of CDs became stronger with the decreasing concentration. Interestingly, we have found that by diluting CD solution with deionized water, the blue-shift of the maximum emission peak from 480 to 440 nm was observed.
![malvern zetasizer ns malvern zetasizer ns](https://docplayer.net/docs-images/111/196126660/images/20-2.jpg)
However, the excitation-independent property of CDs is rarely observed. Many possible reasons have been reported to explain this phenomenon, such as size, element doping, solvent polarity, defects, surface states, surface groups or surface passivation. Under different excitation wavelengths, CDs have different photoluminescence (PL) peaks from violet to red. One special property of CDs is the dependence of emission peak with excitation wavelength. Up to now, various synthetic methods have been developed for the preparation of CDs, such as the electrochemical oxidation of graphite, the hydrothermal method, and the microwave-assisted synthesis. Inspired by these properties, the CDs possess various potential applications, such as drug delivery, fluorescent ink, sensors, optoelectronics, photocatalysis, and light-emitting devices. Meanwhile, CDs, which are not larger than 10 nm, have unique photophysical characteristics, such as high photostability, good biocompatibility, excellent optical properties and low environmental hazards. Typically, a CD has a core of graphite or amorphous carbon framework, and the surface of which is coated with oxygen-containing groups, polymers and other species. Carbon dots, as a fluorescent material in the carbon nanomaterial family, have drawn increasing concerns in the past few years.