In the present article, we synthesise the Sm(DBM)3phen (SmDP), silica nanoparticles (SiNP) and Sm(DBM)3phen functionalized SiNPs (SiNP_SmDP), which were prepared using the modified Stober method. SEM images revealed an average Si NPs diameter of ∼324 nm. The absorption spectra of the samples showed broad absorption bands in the UV-blue region. Photoluminescence spectra revealed the broadband emission of SiNP centred at 435 nm; and sharp emission peaks corresponding to SmDP due to Sm3+ ion at 567 nm, 609 nm, and 650 nm ascribed due to the transitions 4G5/2 → 6H5/2, 4G5/2 → 6H7/2, and 4G5/2 → 6H9/2, respectively. The SiNP_SmDP's emission spectra consist of amalgam emission with broadband due to SiNP; and sharps peaks due to SmDP complex. Under 405 nm laser excitation, the opto-thermal properties of SiNP_SmDP were explored in the range 293K–313K temperature. CIE coordinate analysis illustrates how colour perception varies with temperature. The maximum sensitivities values are 0.00816 K−1, 1.6326%K−1 and 0.00974 K−1, 3.43743%K−1 corresponding to the transitions 4G5/2 → 6H5/2: 4G5/2 → 6H7/2 and 4G5/2 → 6H5/2: 4G5/2 → 6H9/2 of Sm3+ ions.