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MATERIALS AND CRYSTALS

Comparative Analysis of the Structural and Morphological Features of Biogenic and Synthesized Goethite Nanoparticles A. A. Novakovaa,*, A. V. Dolzhikovaa,**, V. M. Novikovb,***, N. M. Boevab, and E. A. Zhegalloc a Moscow

State University, Moscow, Russia of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry, Russian Academy of Sciences, Moscow, Russia c Borissiak Paleontological Institute, Russian Academy of Sciences, Moscow, Russia *e-mail: [email protected] **e-mail: [email protected] ***e-mail: [email protected] b Institute

Received May 19, 2017

Abstract―A comparative analysis of the relationship between the morphological forms and magnetic properties of natural goethite particles from the crust of weathering of the Far East and Vietnam basalts and pure, chemically synthesized goethite particles was performed using Mössbauer spectroscopy, X-ray diffraction analysis, and scanning electron microscopy. It is shown how the shape of biogenic goethite particles affects their magnetic properties, which significantly differ from the magnetic properties of chemically synthesized samples. DOI: 10.1134/S1063774517060189

INTRODUCTION Currently, not only geologists but also physicists, chemists, and biologists are greatly interested in the role of bacteria and organic materials in the mineral formation. The study of the products of natural biomineralization processes is important both for understanding the formation conditions of nanominerals and for modeling new biochemical processes in nanotechnologies. The basic source of natural bionanominerals is crusts of weathering. Currently, a crust of weathering is considered to be a complex of rocks formed under continental subaerial conditions as a result of physical and chemical changes in the rocks in the upper part of lithosphere under influence of various climatic, geological structural, geomorphological, hydrogeochemical, and biochemical factors [1]. The biogenic factor of crust of weathering manifests itself in the effect of organic matter, microorganisms, and products of their metabolism on the initial rock. In this paper, we report the results of a comparative analysis of the morphological and physical properties of nanoparticles of biogenic goethites from the crust of weathering of basalts from Russia (Far East) and Vietnam [2, 3] with the characteristics of hydrothermally synthesized goethite, whose parameters are closest to those provided by natural geological conditions [4, 5].

EXPERIMENTAL The purpose of this study was to establish the influence of the morphology, sizes, and phase composition of particles of natural (biogenic) and synthesized goethites on their magnetic state. The particle morphology and sizes were determined by scanning electron microscopy (SEM) on CamScan-4 (Cambridge) and TESCAN VEGA IIXMU (Tescan) microscopes. To study the morphology of hydrothermally synthesized particles, we used a double-beam Quanta 3D FEG scanning electron microscope (FEI). X-ray diffraction analysis was performed on a PANanalitical