Crystal Growth and Kinetic Behaviour of Pseudoalteromonas espejiana Assisted Biosynthesized Gold Nanoparticles.

Rashmi Gupta,Amit Kumar Nayak,Badr Aldahmash,Saud Alarifi,Saad Alkahtani,Sabya Sachi Das,Md Saquib Hasnain,Bader Almutairi,Gourav Kumar,Abdullah Alkahtane,Gadah Albasher

doi:10.1155/2020/6501294

Abstract

Pseudoalteromonas espejiana (P. espejiana) is a marine bacterium known for its high resistance to alkalinity. The ability of P. espejiana to reduce Au (III) and biosynthesize gold nanoparticles (AuNPs) is found positive and was confirmed using UV-VIS, EDS, SEM, and TEM studies. Previously, many studies have been reported regarding the crystalline nature of AuNPs; therefore, this research aims at studying the crystal growth behaviour of AuNPs through DLS and TEM studies. Spherically shaped and monodispersed, AuNPs ranging between 5 to 160 nm were obtained with an average particle size of 62 nm. Also, to achieve maximum production of AuNPs, the reaction kinetic study was performed using an ICP-OES method and the effect of various parameters including pH, temperature, rpm, and concentration of substrate was analyzed. During the biosynthesis process, an appropriate phase of nucleation, crystal growth, and saturation was observed and this helped to determine the rate constants and order of reaction. The parameters such as pH profile (pH 9), temperature (30°C), agitation speed (150 rpm), and enzyme substrate ratio (2 : 3) were found to be the best fits for maximum production of low size AuNPs. This demonstrates that in initial few hours, a quick conversion of the ionic gold precursor takes place into metallic gold nuclei, trailed by crystal growth via coalescence of small nuclei. Subsequently, it can be concluded that coalescence processes drive the crystal growth process of AuNPs over a time interval and finally leads to saturation and no newer particle formation in the solution.

Highlights

In the field of material science, nanotechnology is unremittingly carving its own zone as an emerging field of research
It was further characterized by DLS which gave an average particle size of 62 nm with net particle charge of -25.6 analyzed by zeta potential analyzer approving the stability of the
The best enzyme to substrate relation comes out to be 1⁄2E: 1⁄2CA = 2 : 3 since maximum UV-VIS absorbance was observed as illustrated in Figure 2, which demonstrated that 2 units of enzymes is able to reduce 3 fractions of substrate successfully to synthesize the AuNPs

Summary

Introduction

In the field of material science, nanotechnology is unremittingly carving its own zone as an emerging field of research. Applicability of nanoparticles (NPs) and nanomaterials is evolving rapidly; specially on the biomedical front from cell imaging, targeted drug delivery and cancer diagnostics to therapeutic applications [1,2,3,4,5,6,7,8]. Both the physical and chemical methods, or either of any, can be significantly applied for the synthesis of NPs [9,10,11].

Objectives

Results

Conclusion