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Figure 1. Variable sized/shaped monodisperse magnetic and ferroelectric nanocrystals obtained by our group 
Research
   1. Colloidal Synthesis of Metal Oxide Nanoparticles and Assemblies  The synthesis of metal oxide nanoparticles with controlled morphology and their assemblies into  ordered structures is one of the main research themes in our group. A particular focus has been put in  developing new methodologies in both aqueous and non-aqueous media for the preparation of transition  metal ferrite and perovskite-type colloidal nanocrystals. By achieving control over the size and shape of  these nano-objects, a long term objective of this research topic is to assemble them into highly organized  superlattice structures and superparticles and study their properties for potential technological  applications. 
   2. Metal Oxide Nanotubes and Nanowires  Mono-dimensional oxide nanostructures, such as iron oxides, spinels MFe2O4 and perovskites ABO3  are synthesized in aqueous solutions by a soft-solution approach. Metal oxide nanotubes and nanowires  with tunable length, wall thickness  and diameter are prepared by combining a template method with a  solution-mediated approach. Highly uniform nanotubes are formed within the pores of a porous  membranes through capillary effects as a result of a hydrolysis reaction. This methodology is cost effective,  simple and environmetally friendly (deposition temperatures are as low as 45 oC). Metal oxide nanotubes  are subsequently filled with a second metal or metal oxide phase, thereby generating  nanotube-nanowire  ordered arrays. These nanostructures are being used as templates for the fabrication of hierarchical 1-D  core-shell nanoarchitectures and also integrated into magnetoelectric devices or used for the  photochemical splitting of water molecules.
2. Metal Oxide Nanotubes and Nanowires 
Figure 2. Nanotube and nanowire arrays of perovskites and spinel ferrites obtained by a template-assisted route 
   3. Thin Film and Multilayer Metal Oxide Structures  Another targeted area of interest involves the chemical deposition  of high quality thin films and  multilayered structures. Our research on thin film structures is a key prerequisite for the development of  new functional materials and devices. Recent research efforts have been focused on the soft solution  processing of ferroelectric and magnetic metal oxide thin films with controllable morphology and  predictable properties. These films are furthermore used for the design of complex architectures such as  multicomponent metal oxide films with graded composition and magnetoelectric multilayers. 
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Figure 3. Magnetic and ferroelectric granular thin films and bilayered structures obtained at 45oC 
   4. Scanning Probe Microscopy  An important component of our research is dedicated to the study of the polar ordering and the local  properties of nnaoscale ferroic materials. To this end, scanning probe microscopy (SPM) and piezoresponse  force microscopy (PFM) are components of germane importance in our experimental toolbox for the  characterization of the electromechanical response of ferroelectric and magnetoelectric materials. While most  scanning probe microscopy techniques are used in the study of the converse magnetoelectric effect (changes  in the magnetic structure induced by an electric field), we have developed recently a technique for the  qualitative and quantitative evalauation of the magnetoelectric coupling in nanocomposites by measuring the  piezoelectric response of the material in a magnetic field. This method is simple, easy to use and interpret and  allows for the precise estimation of the local magnetoelctric coupling in nanocomposites with various types of  connectivity schemes between the magnetic and the electrostrictive phases at nanoscale.
Figure 4. AFM topography and PFM phase contrast images of a PbTiO3-Terfenol-D bilayered nanocomposite in the presence of different magnetic fields (H=-2000, 0 and +2000 Oe)  
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Figure 5. Phase and amplitude plots  of the piezoresponse of a PbTiO3-Terfenol-D bilayered nanocomposite in the presence of different magnetic fields
Our research is at the crossroads of synthetic chemistry, materials science, engineering and  nanotechnology being aimed at the design of nanomaterials with precisely controled composition,  microstructure and surface reactivity. We are particularly interested in the study of ferroic properties  (ferroelectricity and magnetism) of low-dimensional systems, as well as the intimate coupling between  these phenomena. To this end, we developed soft-solution chemical routes to produce ferroic and  magnetoelectric multiferroic materials with various topological features (colloidal nanocrystals,  nanotubes and nanorods and thin films) which can be used in different applications, ranging from energy  stoage/conversion and drug delivery to catalysis, sensing  and cellular imaging. 
CARUNTU Research Group
Nanostructured Materials For Energy Applications
Research