Research Article Nanoferrofluid Materials: Advanced Structure Monitoring Using Optical Transmission in a Magnetic Field Serhii Shulyma, Bogdan Tanygin, Valery Kovalenko, and Michail Petrychuk Department of Radiophysics, Taras Shevchenko Kyiv National University, 4G, Acad. Glushkov Ave., Kyiv 03187, Ukraine Correspondence should be addressed to Serhii Shulyma; kiw_88@mail.ru Received 24 December 2016; Revised 20 March 2017; Accepted 12 April 2017; Published 10 May 2017 Academic Editor: Balachandran Jeyadevan Copyright © 2017 Serhii Shulyma et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Te optical transmission of a thin ferrofuid layer was investigated at various optical radiation wavelengths. Te turning on of the durable external magnetic feld pulse leads to nonmonotonic changes of the optical transmission value with minimal value during the feld pulse. Tis phenomenon is related to the formation of columnar nanoparticle aggregates and transformation in the ferrofuid bulk. It was shown that time interval corresponding to the optical transmission minimum is proportional to the laser wavelength, which can be explained with Mie-like optical extinction on the ferrofuid aggregates and its dependence on the diameters of columnar aggregates. Hence, a simple experimental approach was proposed to measure and control the ferrofuid aggregates diameters in submicron spatial dimension ranges. Particularly, this approach could be used for the formation of composite nanomaterials consisting of polymers and magnetic nanoparticles with controlled structural parameters. Tese materials could be reused afer parameters changes (e.g., lattice constant, aggregate size, and magnetic permeability tensor) with a heating/cooling cycle without the need for preparation of a new material from scratch. 1. Background Tere are a large number of recent scientifc reports dedicated to new nanomaterials, their synthesis methods, structures, and applications in various sectors, such as electronics [1, 2], energetics [3, 4], and life sciences [5, 6]. Manufacturing of magnetic single-domain nanoparticles has been an advanced subject of research in the modern nanophysics that are typi- cally suspended in a carrier fuid, forming a ferrofuid (FF). Ferrofuids combine both liquid and magnetic characters [7]. Te new century FF topicality revival is related to new application trends: magnetic targeted in vivo drug delivery [8, 9], local tumor hyperthermia [10], solid body surface polishing [11], programmable lithography mask [12], and others [13, 14]. Te FF properties (magnetic permeability tensor, saturation magnetization, viscosity, and other prop- erties) could be varied by its integral parts changes, for instance, in the carrier liquid and the type and concentration of nanoparticles. However, even without modifcation of such components, the FF properties could vary via magnetic nanoparticle aggregation phenomenon. Tere are two major kinds of FFs [15]: highly stabilized colloid of magnetic single- domain nanoparticles (“classical” FF) [16] and nonclassical FF [17]. Without an external magnetic feld, the classical FF may contain only submicron primary aggregates with confned magnetic fux [18]. Oppositely, nonclassical FF contains large aggregates visible in an optical microscope [18, 19]. Application of an external magnetic feld reversibly produces visible aggregates in both types of a FF [16, 17, 19–21]. Electrical feld [22] and optical radiation [23] may also lead to formation of reversible aggregates. Magnetic feld could produce 1D and 2D long-range ordered self- organized FF aggregate structures, including visible ones [14, 16, 24, 25]. Tey can be used for the formation of micro- and nanostructured magnetic materials, including liquid photonic crystals [25]. Te reversible formation of a periodical magnetic aggregate structure could be used for composite materials with specifcally assigned properties and ability to change properties later for specifc applications. Particularly, the magnetic feld sweep rate variation could be used to change the columnar aggregate diameter [26]. Hindawi Journal of Nanomaterials Volume 2017, Article ID 7251725, 7 pages https://doi.org/10.1155/2017/7251725