Abstract: The present disclosure relates to a method of preparing silicon carbon nanocrystals (SiC-NCs) in a size-dependent manner by reacting a compound of the Formula I: R1Si(X1)3, with a compound of the Formula II Si(X2)4(II) under conditions for the hydrolysis and condensation of the compound of the Formula I and the compound of the Formula II to form a siloxane polymer comprising repeating units of the Formula III: —[(R1SiO1.5)x(SiO2)y]—, followed by thermal processing of the siloxane polymer under conditions to form SiC-NC's. Optionally the SiC-NC's are liberated to provide free standing SiC-NC's.