Labeling ZnO nanoparticles (ZnO NPs) with Rhodamine dye is not as widely standardized as some other dye-conjugation protocols, but it has been reported in several nanomaterials and bioimaging studies.

Rhodamine dyes (such as Rhodamine B or Rhodamine 6G) are commonly used for fluorescence labeling. Labeling ZnO nanoparticles typically involves physical adsorption, covalent attachment, or electrostatic interaction, depending on the surface chemistry of the ZnO NPs and the functional groups of the dye.

• Prepare ZnO NP suspension: Disperse ZnO nanoparticles (10–20 mg) in 10 mL ethanol or water using ultrasonication (10–15 min).
• Prepare Rhodamine dye solution: Dissolve Rhodamine B in ethanol or water (~1 mg/mL).
• Mix: Add the Rhodamine solution to the ZnO suspension in a 1:1 volume ratio (or as needed for fluorescence intensity).
• Incubate: Stir the mixture for 4–12 hours in the dark at room temperature.
• Purify: Centrifuge at 10,000 rpm for 10 min. Wash the pellet with ethanol or water several times to remove unbound dye.
• Characterize: Use UV-Vis, fluorescence spectroscopy, or confocal microscopy to confirm dye attachment.

Thank you for your reply, may i know from your experience whats the common dyes used for labeling ZnO-Np ?