The SiNPs formation was accomplished by wet etching the silicon substrate in an 8 mL solution of 7.6M HF and 0.29M H2O2 in DIW for 15 minutes followed by a thorough wash in DIW. Residues of silver and polystyrene beads were removed with HNO3 and O2 plasma respectively (50 sccm O2, 40 mTorr, 30W, 15 min).