Abstract: A polyheterosiloxane composition includes (A) a first metal (M1), (B) a second metal (M2), and (C) siloxy units having the formula (R13SiO1/2), (R12SiO2/2), (R1SiO3/2), and/or (S1O4/2). R1 is independently a hydrocarbon or halogenated hydrocarbon group including 1 to 30 carbon atoms. The mole fractions of (A), (B), and (C) relative to each other is of the formula [(M1)]a[(M2)]b[R13SiO1/2]m[R12SiO2/2]d[R1SiO3/2]t[SiO4/2]q, wherein a and b are each independently from 0.001 to 0.9, each of m, d, t, and q are independently from zero to 0.9 so long as m, d, t, and q are not all zero and the sum of a+b+m+d+t+q?1. At least one of (M1) and (M2) is a lanthanide metal. The composition exhibits a quantum yield of at least 0.05% and is formed using a method including reacting (A?) a metal (M3) alkoxide, (B?) an optional hydrolyzable metal (M4) salt, (C?) a silicon-containing material and (D) water.