Reliable production of nanoparticles (NPs) by magnetron sputtering in a gas aggregation source (GAS) is of great interest because of many potential applications. The technique is an environmentally friendly approach with low consumption of materials and a minimal exhaust of by-products. In this study, the fabrication of Ag and Cu nanoparticles is investigated in dependence on the deposition parameters in the GAS. Special attention is given to the effect of the adjustable magnetic field (MF - a not much studied parameter) on the formation of Cu nanoparticles. Decrease of the MF from 83 to 35 mT results in changes in the shape and size distribution of the NPs. MF also strongly affects the NPs deposition rate (DR). Electromagnetic trapping of the NPs in the vicinity of the magnetron target is proposed to be responsible for the changes in DR and polydispersity. The highest DR was reached at 45 mT. In the second part of the study, GAS is successfully utilized for the fabrication of metal/polymer nanocomposites with the potential to be used in the field of oily water purification and biomedicine. Two types of functional nanocomposite coatings are developed. First, hard Ag/a:C-H nanocomposites are fabricated by the simultaneous deposition of Ag NPs by GAS and hydrocarbon matrix by PECVD. The strategy allows independent control of the matrix properties and the amount of embedded NPs so that mechanical and antibacterial properties of the coatings can be properly tuned. Second, superwettable nanocomposites with the wettability ranging from superhydrophobic to superamphiphilic are obtained on the filtration membranes by a step-by-step deposition process. PECVD from hexamethyldisiloxane is used for the deposition of thin films of either organosilicon plasma polymer or silicon dioxide by mixing the precursor with Ar or O2. The films are combined with Cu NPs. Modified membranes are used for the gravity-driven separation of the water/oil mixtures with the efficiency above 99.97%.