modifying the surfaces of the nanoparticles 10 as described below is conducted so that the nanoparticles 10 can be firmly incorporated into a network of a metal oxide matrix 50 as can be seen in fig2 b in modifying the surface of the nanoparticles 10 the surfaces of the nanoparticles 10 are coated with the metal oxide that constitutes the matrix 50 coating layer 30 by way of example in an exemplary embodiment when the matrix 50 is formed from a network of silica sio 2 the surface of the nanoparticles 10 is coated with silica fig3 a through 3d are schematic illustrations of an exemplary embodiment of a process of modifying a surface of the nanoparticles 10 according to the present invention first as can be seen in fig3 a a surfactant is dispersed in an organic solvent in an exemplary embodiment the surfactant is a non ionic surfactant that has an ether group as a hydrophilic group and has an alkyl group as a hydrophobic group for example about 50 mole percent mol of polyoxyethylene 5 nonylphenyl ether trade name igepal co 520 which is hereinafter referred to igepal is dispersed in cyclohexane a uniform dispersion may be achieved in the solvent using sonication fig3 a schematically depicts the state of igepal dispersed in the cyclohexane solvent as seen in fig3 b nanoparticles are subsequently mixed in the igepal solution for example the solution in which cdse quantum dots 1 milligram of quantum dots per milliliter of cyclohexane solvent are dissolved is mixed in the igepal solution next as seen in fig3 c an alkaline catalyst.