It depends on the capping groups on the surface of nanoparticles. The major constituent functional groups will be found including the hydroxyl also. The phenolics and flavonoids contribute to the presence of phenolic hydroxyl, ketones, double bond C=C, ethereal linkage, the presence of alkaloids will exhibit the amine function according to its characteristics (primary, secondary, tertiary amines- no peaks). The groups involved are part of the bioreduction process.

What do you exactly mean by crude plant extract? This seems to indicate a number of things. 1) crude indicates that your sample is not pure and contains more than one compound. 2) the nature of the compounds in the extract is dependent on the plant. Based on this you can only look for some general functional groups as indicated by Riaz.