Introducing carbon dots to moderate the blue emission from zinc vanadium oxide hydroxide hydrate nanoplates

The relative intensity of the blue component of the total emission from light-emitting diodes (LEDs) can be an important factor when assessing their biological safety. Carbon quantum dots (CQDs) are compatible with many materials and present a high density of multiple surface states; the incorporation of such CQDs thus offers a route to modifying the emission from a given LED matrix. Here we report the fabrication of stable CQD/zinc pyrovanadate (Zn₃(OH)₂V₂O₇·2H₂O) nanoplate composites via a facile hydrothermal route. Structural and morphological analyses confirm that the nanoplates are hexagonal phase and grew normal to the [0001] direction. X-ray photoemission spectroscopy, Raman and infrared spectroscopy demonstrate that the CQDs combine with nanoplates via surface carbon-oxygen bonds. Wavelength resolved photoluminescence measurements show that the relative intensity of the blue (2.93 eV) component of the emission associated with the nanoplates is significantly reduced by incorporating CQDs. We suggest that this reduction arises as a result of preferential trapping of the higher energy photoelectrons by surface defects on the CQDs.