Biogenic Platinum Nanoparticles’ Production by Extremely Acidophilic Fe(III)-Reducing Bacteria

Takahiro Matsumoto,Idol Phann,Naoko Okibe

doi:10.3390/min11111175

Abstract

Platinum nanoparticles (Pt(0)NPs) are expected to play a vital role in future technologies as high-performance catalysts. The microbiological route for Pt(0)NPs’ production is considered a greener and simpler alternative to conventional methods. In order to explore the potential utility of extreme acidophiles, Fe(III)-reducing acidophilic bacteria, Acidocella aromatica and Acidiphilium crytpum, were tested for the production of bio-Pt(0)NPs from an acidic solution. Bio-Pt(0)NPs were successfully formed via a simple one-step reaction with the difference in the size and location between the two strains. Intact enzymatic activity was essential to exhibit the site for Pt(0) crystal nucleation, which enables the formation of well-dispersed, fine bio-Pt(0)NPs. Active Ac. aromatica cells produced the finest bio-Pt(0)NPs of mean and median size of 16.1 and 8.5 nm, respectively. The catalytic activity of bio-Pt(0)NPs was assessed using the Cr(VI) reduction reaction, which was shown to be in a negative linear correlation with the mean particle size under the conditions tested. This is the first study reporting the recruitment of acidophilic extremophiles for the production of Pt(0)NPs. Acidophilic extremophiles often inhabit metal-rich acidic liquors in nature and are expected to become the promising tool for metal nanotechnology.

Highlights

Metal nanoparticles (NPs) have recently gained increasing attention owing to their potential for technological innovation in various sectors, including energy, catalysis, pharmaceuticals, optics, and photonics industries
“Green” hydrogen is produced via the water electrolysis reaction, wherein Pt plays a vital role as the reaction catalyst
Ac. aromatica strain PFBC (DSM 27026T) and A. cryptum strain SJH were chosen in this study as Fe(III)-reducing acidophiles which are tolerant to a number of heavy metals [22,23]

Summary

Introduction

Metal nanoparticles (NPs) have recently gained increasing attention owing to their potential for technological innovation in various sectors, including energy, catalysis, pharmaceuticals, optics, and photonics industries. The size of biogenic metal NPs can be controlled by modifying conditions such as concentrations of electron donors and reaction inhibitors [5,6]. Among those microorganisms or plants as the template for NPs’ production, a number of bacterial species possess the ability to reduce soluble metal species to zero-valent nanometal. Broadly defined as microorganisms that grow optimally at pH < 3, have potential in metal NPs’ production from such highly acidic liquors but are rarely studied in this regard. We report the Pt(0)NPs’ production using the two Fe(III)-reducing, extreme acidophiles, Ac. aromatica and A. crytpum

Microorganisms

Particle Size Analysis Using Image-J

Findings

Conclusions