Background: Gold nanoparticles (GNPs) of different sizes and shapes are very important
for technological applications. They possess unique catalytic behavior under mild conditions and also
they are considered catalysts of choice due to higher stability and negligible poisoning as compared
to other metal nanoparticles (NPs).
Objective: The main aim of the work is to synthesize GNPs using the flower extract of the harmful
invasive wild growing plant, Lantana camara as a reducing and stabilizing agent under ambient conditions
and use them for catalytic applications.
Methods: The as-synthesized GNPs were characterized using various spectroscopic, microscopic and
diffractometric techniques. UV-vis spectroscopy was used to monitor the progress of the catalytic
dye reduction reactions.
Results: UV-vis spectroscopic results indicated that optical properties of GNPs can be tuned by varying
the concentration of extract in the reaction medium. Zeta potential measurement confirmed that
the surfaces of these GNPs are negatively charged which imparts stability to the colloids. Microscopic
results confirmed that varying the concentration of flower extract; size and shape of the formed
GNPs can be systematically tuned. Selected area electron diffraction analysis of spherical and polygonal
GNPs indicated that spherical GNPs are mainly polycrystalline in nature whereas polygonal
GNPs are single crystalline.X-ray diffraction analyses confirmed the formation of pure face-centered
cubic gold. These GNPs showed excellent catalytic activity in the borohydride reduction of organic
Conclusion: At higher extract concentration, spherical GNPs are formed predominantly. But when
the concentration of extract is lowered, GNPs of mixed morphology are formed. Further lowering in
the concentration of extract resulted in polygonal GNPs only. These gold nanoparticles can be used
as an efficient catalyst for borohydride reduction of toxic organic dyes in an aqueous medium.