I have prepared silver nano particles using plant extract. after synthesis, SNPs give fluorescence when observed in UV trans illuminator. but after purification of silver nano particles , SNPs don't give any flourescence
Silver NPs do have luminescence properties, but it depends upon their size and shape. During biosynthesis of Ag NPs, biomolecules could produce strong fluorescence, which will be lost after careful washing with suitable solvents. If the synthesized Ag NPs have innate fluorescence then purification won't change it. It would be wise if synthesized NPs will be scanned by UV -visible and satisfied the characteristic UV maxima of Ag NPs. Kindly do further characterization and check the purity of your plant extract.
Purification does not change the fluorescent properties of silver nanoparticles. Check through TEM, the presence of silver nanopaticles in the solution. Even after that you have to scan properly specially through the range of 350 -500 nm. Hope you will get the result