A mesoporous amorphous crystalline nanopowder (NP) Si–SiO2 with a specific surface area (SSA) of 35 m2/g was produced by pulsed electron beam evaporation (PEBE) of a compact of micron commercial SiO2 powder (0.9 m2/g). Si semimetal nanoparticles (NPles) reduced in for vacuum (≈4 Pa) had a marked effect on the thermal and luminescent properties of the Si–SiO2 nanoparticles compared to the properties of amorphous SiO2 NPles produced earlier by PEBE evaporation of a target compound made from NP Aerosil 90 (Degussa). Photocatalytic capabilities of Si–SiO2 nanoparticles were evaluated. NPles Si–SiO2 showed high antioxidant activity on HELA cancer cells.