A novel green approach by photocatalytic oxidative polymerization was developed that addresses and resolves current limitations of chemical polymerization of anilines. This process generates nanoparticles of the conducting polymer poly(N-ethylaniline) (PNETA) and poly-(N-methylaniline) (PNMTA) in a single step by using a catalytic amount of the oxidant in the presence of an organic acid such as DL-(+/-)-Tartaric acid. Poly(N-ethylaniline) nanoparticles doped with tartaric acid show exceptional antimicrobial activity at low concentration. Five compounds have been synthesized. Of these, two compounds have been found to exhibit significant activity against Klebsiella pneumoniae. The minimum inhibitory concentration value was observed at 50 mu g/mL. An extremely simple green approach is described that generates bulk quantities of nanoparticles with average diameter 200nm size of the conducting polymer PNETA in one-step photochemical method using a catalytic amount of ammonium persulfate as oxidant in the presence of organic acid dopant, DL-(+/-)-Tartaric acid. The resultant polymer were characterized by UV-visible, FTIR, XRD, and SEM analysis and their antibacterial activity against Klebsiella pneumoniae has been studied. These polymer nanomaterials show a prominent antimicrobial activity against the tested bacteria and therefore have potential applications in biomedical sciences.