The luminescent nanoparticle can be modified by reaction with a linker Xa???Rn???Yb where X and Y can be reactive moieties such as carboxylic acid groups, phosphonic acid groups, sulfonic acid groups, amine containing groups etc., a and b are independently 0 or 1 where at least one of a and b is 1, R is a carbon, nitrogen or oxygen containing group such as ???CH2, ???NH??? or ???O???, and n is 0-1