Semiconductor nanoparticles having high luminescence properties that are preferable for applications and uses of biotechnology are provided. With the use of electric charges on the surfaces of particles, the particles and selected polymers are allowed to electrostatically bind to each other, such that the surfaces of the particles are coated. The polymers are allowed to crosslink to each other, resulting in the improved durability of the particles. Further, functional groups contained in the polymers are exposed on the surfaces of the particles. Accordingly, semiconductor nanoparticles that are preferably utilized for applications such as staining and labeling of biopolymers have been synthesized.