Theoretical and experimental study of the nanoparticle-driven blue phase stabilisation

B. Rožič; V. Tzitzios; E. Karatairi; U. Tkalec; G. Nounesis; Z. Kutnjak; G. Cordoyiannis; R. Rosso; E.G. Virga; I. Muševič; S. Kralj

doi:10.1140/epje/i2011-11017-8

EPJ

Theoretical and experimental study of the nanoparticle-driven blue phase stabilisation

B. Rožič¹, V. Tzitzios², E. Karatairi³^,4, U. Tkalec¹^,5, G. Nounesis³, Z. Kutnjak¹, G. Cordoyiannis¹^,6, R. Rosso⁷, E.G. Virga⁷, I. Muševič¹ and S. Kralj¹^,8

¹ Condensed Matter Physics Department, Jožef Stefan Institute, Jamova cesta 39, 1000, Ljubljana, Slovenia
² Institute of Materials Science, National Centre for Scientific Research “Demokritos,”, 15310, Aghia Paraskevi, Greece
³ Institute of Radioisotopes and Radiodiagnostic Products, National Centre for Scientific Research “Demokritos,”, 15310, Aghia Paraskevi, Greece
⁴ Department of Materials Science, University of Patras, 26500, Patras, Greece
⁵ NAMASTE Centre of Excellence, Jamova 39, 1000, Ljubljana, Slovenia
⁶ EN FIST Centre of Excellence, Dunajska 156, 1000, Ljubljana, Slovenia
⁷ Dipartimento di Matematica and SMMM, Università di Pavia, via Ferrata 1, I-27100, Pavia, Italy
⁸ Department of Physics, University of Maribor, Koroška cesta 160, 2000, Maribor, Slovenia

Received: 5 October 2010
Accepted: 17 January 2011
Published online: 22 February 2011

Abstract

We have studied theoretically and experimentally the effects of various types of nanoparticles (NPs) on the temperature stability range $\Delta$ T _BP of liquid-crystalline (LC) blue phases. Using a mesoscopic Landau-de Gennes type approach we obtain that the defect core replacement (DCR) mechanism yields in the diluted regime $\Delta$ T _BP(x) $\propto$ 1/(1 - xb) , where x stands for the concentration of NPs and b is a constant. Our calculations suggest that the DCR mechanism is efficient if a local NP environment resembles the core structure of disclinations, which represent the characteristic property of BP structures. These predictions are in line with high-resolution ac calorimetry and optical polarising microscopy experiments using the CE8 LC and CdSe or aerosil NPs. In mixtures with CdSe NPs of 3.5nm diameter and hydrophobic coating the BPIII stability range has been extended up to 20K. On the contrary, the effect of aerosil silica nanoparticles of 7.0nm diameter and hydrophilic coating is very weak.

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EPJ

Theoretical and experimental study of the nanoparticle-driven blue phase stabilisation

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