Fig. 2From: Catalytic reduction of 4-nitrophenol with gold nanoparticles synthesized by caffeic acidHR-TEM images of CA-AuNPs. Caffeic acid concentrations of a 0.08 mM, b 0.16 mm, c 0.32 mM and d 0.36 mM. The scale bar represents 20 nm in all images. e The relationship between the particle size (nm) measured from HR-TEM images and caffeic acid concentration (mM)Back to article page