NOVELTY - A population of nanoparticles comprises several core/shell nanocrystals include: a semiconductor core; an intermediate semiconductor shell layer disposed over the semiconductor core; an external semiconductor shell layer disposed over the intermediate semiconductor shell layer; and a thiol-based hydrophilic organic layer or a functionalized organophosphorus-based hydrophilic layer in direct contact with the external semiconductor shell layer; where the population of nanoparticles has an alpha on value of less than 1.4.    USE - As population of nanoparticles (claimed) in fields including biology, analytical and combinatorial chemistry, medical diagnostics, genetic analysis, solar energy conversion, displays, and single molecule spectroscopy.    ADVANTAGE - The population of nanoparticles has an alpha on value of less than 1.4; is capable of undergoing fluoresence resonance energy transfer (FRET) with donor moieties or acceptor moieties; has a FRET efficiency of greater than 20%; and has an on-time fraction of greater than 0.8. The nanoparticles have modulated, reduced or no fluorescent intermittency (i.e. non-blinking); reduced or absent spectral shifting; low to no photobleaching; high quantum yield; and sufficient FRET efficiency.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for production of a population of nanoparticles involving:    (1) process A: providing a mixture including several nanocrystal cores and at least one coordinating solvent; adding a first intermediate shell precursor alternately with a second intermediate shell precursor in layer additions to form an intermediate shell layer on each of the nanocrystal cores; adding a first external shell precursor alternately with a second external shell precursor in layer additions to form an external shell layer on each of the nanocrystal cores; adding an aqueous solution comprising thiol-based hydrophilic ligands; and maintaining the mixture under conditions that cause the nanocrystals to migrate into an aqueous phase; and    (2) process B: providing a mixture comprising several nanocrystal cores, functionalized organophosphorous-based hydrophilic ligands and at least one coordinating solvent; adding a first intermediate shell precursor alternately with a second intermediate shell precursor in layer additions to form an intermediate shell layer on each of the nanocrystal cores; and adding a first external shell precursor alternately with a second external shell precursor in layer additions to form an external shell layer on each of the nanocrystal cores.