Poly(acrylic acid) (PAA) was partially grafted with dopamine (PAA-dopa), and then layer-by-layer assembled with poly(vinylpyrrolidone) (PVPON) to prepare hydrogen-bonded (PVPON/PAA-dopa)(n) film. Polydopamine (PDA) was deposited on (PVPON/PAA-dopa)(n) film in the presence of oxidant, and hence the whole (PVPON/PAA-dopa)(n)PDA film was cross-linked. (PVPON/PAA-dopa)(n)PDA could be utilized as a platform to produce the free-standing Janus film because of the easy detaching process and various chemical reactivity of PDA layer. Ag nanoparticles were formed on (PVPON/PAA-dopa)(n)PDA film by electroless metallization. 1H,1H,2H,2H-Perfluorodecanethiol (PFDT) was used to further modify the film through Michael addition. After detaching from the substrate, (PVPON/PAA-dopa)(20)PDA/Ag/PFDT exhibits reversible swellingshrinking behavior as the pH value changes. This free-standing film shows Janus character, one side is hydrophobic, whereas the other side is hydrophilic. In addition, the hydrophobic surface exhibits a surface-enhanced Raman scattering effect, whereas the hydrophilic side does not.