• PDF / 186,866 Bytes
• 5 Pages / 612 x 792 pts (letter) Page_size
• 2 Downloads / 307 Views

DOWNLOAD

REPORT

---

P.A. Joy National Chemical Laboratory, Pune 411008, India

V. Rao National Metallurgical Laboratory, Jamshedpur 831007, India

P. Ramachandrarao Banaras Hindu University, Varanasi 221005, India (Received 18 September 2002; accepted 6 February 2003)

Matrix-mediated in situ synthesis of monodispersed magnetite and maghemite nanoparticles (2–16 nm) was carried out using the cavities present in gels of globular proteins such as egg white and bovine serum albumin. Under stringent conditions, spatial-charge-distribution-assisted molecular recognition of proteins for inorganic ions led to the site- and polymorph-specific synthesis of superparamagnetic iron oxide particles. A transformation from magnetite to maghemite as a nucleating phase could be observed by partially denaturing the egg white protein, signifying the delicate role of quaternary structure of proteins under different reaction conditions, in determining the size and shape of the polymorph.

I. INTRODUCTION

Nano-sized magnetic particles dispersed in biopolymer matrices are a common occurrence in many living organisms. These nanoparticles exhibit finely tuned functional properties that reflect a remarkable level of control over their nucleation and growth.1 Synthetically, welldispersed nano-sized magnetite particles (size