Fig. 4From: Catalytic reduction of 4-nitrophenol with gold nanoparticles synthesized by caffeic acid a–d The 4-NP reduction reaction monitored by UV-visible spectrophotometry. a CA-AuNPs (0.08 mM), b cf-CA-AuNPs (0.08 mM), c CA-AuNPs (0.32 mM), and d cf-CA-AuNPs (0.32 mM). e, f The plot of ln(C t /C 0 ) vs time (sec). e caffeic acid concentration of 0.08 mM and f caffeic acid concentration of 0.32 mMBack to article page