Optimization of physicochemical parameters in the biofabrication of gold nanoparticles using marine macroalgae Padina tetrastromatica and its catalytic efficacy in the degradation of organic dyes

K F Princy,Anu Gopinath

doi:10.1007/s40097-018-0277-2

Abstract

Green synthesis of metallic nanoparticles by means of renewable bioresources has emerged as a new trend in current nanotechnology research with improved environmental safety. In the current study, monodispersed gold nanoparticles (AuNPs) with excellent stability were prepared in a completely green and cost effective manner using aqueous extract of marine macroalgae-Padina tetrastromatica. The influence of reaction conditions such as the quantity of seaweed extract, temperature, precursor metal ion concentration, reaction time and pH on the biosynthesis of nanoparticle was evaluated spectroscopically and also with the help of high resolution transmission electron microscopy (HR-TEM). These physicochemical parameters not only affected the rate of formation but also the size and morphology of resultant nanoparticles. Optimum conditions resulted in the generation of nearly spherical AuNPs having an average particle size of 11.4 nm. The high crystallinity of the biogenic AuNPs was confirmed from characteristic diffraction peaks in XRD profile, clear lattice fringes in the HR-TEM image and bright circular spots in the SAED pattern. The presence of metallic gold was evidenced from EDAX profile. FTIR study revealed the role of secondary metabolites in the bioreduction as well as stabilization of AuNPs. The study also highlights the spectroscopic investigation on the catalytic efficacy of the biosynthesized AuNPs in the reduction reactions of hazardous organic dyes, eosin yellow and Congo red using sodium borohydride, which have a pseudo-first order kinetics. Thus, the biosynthesized metal nanoparticles using renewable marine resources like seaweeds act as promising materials for the application in environmental protection.Graphical abstract

Highlights

Materials and methodsNoble metal nanoparticles are gaining significant attention nowadays due to their attractive optoelectronic properties as against their bulk counterparts
The present study demonstrated the optimized biosynthesis of highly stable and monodispersed AuNPs by a completely green process by means of aqueous extract of marine macroalgae-Padina tetrastromatica as effective reducing and stabilizing agent
Optimization studies revealed that different physicochemical parameters like the quantity of seaweed extract, temperature, metal ion concentration, pH and reaction time greatly affected the rate of formation, size and distribution of nanoparticles

Summary

Materials and methods

Noble metal nanoparticles are gaining significant attention nowadays due to their attractive optoelectronic properties as against their bulk counterparts. Plant mediated nanosynthesis are more beneficial over microbe assisted procedures in the case of easiness, fast rate of synthesis, abundant availability of resources and ecofriendliness It eradicates the complicated procedure of preserving microbial cultures and could be stretched to bulk-scale production. Volume of SWE required for the biosynthesis of AuNPs was optimized by adding varying quantity of extract (1 mL, 2 mL, 3 mL, 4 mL, 5 mL, 8 mL and 10 mL) to 10 mL of 1 mM Chloroauric acid solution at room temperature. The influence of pH on the formation of AuNPs was examined by keeping the pH of the reaction medium (which is obtained by adding 10 mL of 1 mM Chloroauric acid to 2 mL of SWE) at 3.2, 7 and 10, respectively at room temperature.

Results and discussion

Conclusion

Compliance with ethical standards