Display omitted •The tartrazine photodegradation by modified and unmodified SiNWs was studied.•The modification of SiNWs was carried out by nanoparticles of Pt, Pd, Ag, Au and Cu.•The Cu-modified SiNWs give the highest photocatalytic activity.•The enhancement of the photocatalytic activity by the treatment of Cu-modified SiNWs with H2O2 is shown. In this work we investigated the tartrazine photodegradation by modified and unmodified silicon nanowires (SiNWs). SiNWs were elaborated by one-step metal-assisted electroless chemical etching of silicon substrate in HF/AgNO3 aqueous solution. The modification of SiNWs was carried out by nanoparticles of platinum, palladium, silver, gold and copper in chemical solutions of PtO2, PdCl2, AgNO3, AuCl3 and CuSO4, respectively. The results show that Cu-modified silicon nanowires give the highest photocatalytic activity compared to the unmodified SiNWs and SiNWs modified with nanoparticles of Au, Pt, Pd and Ag.