Thermoelectric materials realize direct conversion between thermal and electrical energy. An important strategy for improving their efficiency is to embed nanoparticles into semiconductors to make heterostructural films. However, the sizes of the particles synthesized using current thermal annealing methods are not well controlled. Here, we use a chemical reducing method to synthesize diameter controlled silver/copper nanoparticles with bonding to a substrate. Next, a thin oxide layer is grown on the particles using Atomic Layer Deposition coating. Combined with the chemistry we developed previously, a molecular semiconductor (Sb₂Te₃/Te) layer could be covered on top eventually by spin coating to obtain a heterostructural film. With this method we avoid high temperature processes and can get diameter controlled particles, which are crucial to the performance of the materials. Overall, this work shows the possibility of engineering multiphases to further improve thermoelectric performance through a low-temperature solution process route.