Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, F-13013, Marseille, France.
Ultrafast and Microspectroscopy Laboratories and ARC Centre of Excellence in Exciton Science, School of Chemistry, University of Melbourne, Melbourne, 3010, Australia.
Sci Rep. 2019 Feb 8;9(1):1670. doi: 10.1038/s41598-018-38229-4.
Ferroelectric nanocrystals have considerable interest for applications in nanophotonics, optical memories and bio-imaging. Their crystalline nature at the nanoscale remains however poorly known, mostly because structural investigation tools on single nanocrystals are lacking. In this work we apply polarization resolved second harmonic generation (P-SHG) imaging on isolated Barium Titanate (BaTiO) nanocrystals to unravel their crystalline nature, exploiting the sensitivity of polarized SHG to local non-centrosymmetry and nanocrystals surface responses. We evidence crystalline heterogeneities in BaTiO nanocrystals manifested by a centrosymmetric shell around the tetragonal core of the crystals, corroborating hypotheses from previous ensemble structural investigations. This study shows that in contrast to bulk materials, nanocrystals exhibit a complex composition, which is seen to be reproducible among nanocrystals. P-SHG appears furthermore as a powerful methodology that reports structural behaviors in nanoscale dielectrics materials, at the individual nanoparticle scale.
铁电纳米晶体在纳米光子学、光学存储和生物成像等应用中具有相当大的兴趣。然而，它们在纳米尺度上的晶体性质仍然知之甚少，主要是因为缺乏针对单个纳米晶体的结构研究工具。在这项工作中，我们应用偏振分辨二次谐波产生（P-SHG）成像技术对孤立的钛酸钡（BaTiO）纳米晶体进行研究，以揭示其晶体性质，利用偏振 SHG 对局部非中心对称和纳米晶体表面响应的敏感性。我们证明了 BaTiO 纳米晶体中的晶体不均匀性，表现为晶体四方核周围的中心对称壳，这与以前的整体结构研究的假设相符。这项研究表明，与体材料相比，纳米晶体表现出复杂的组成，这种组成在纳米晶体之间是可重复的。P-SHG 还表现为一种强大的方法，可在单个纳米颗粒尺度上报告纳米级介电材料的结构行为。
