De Soumi, Asthana Deepak, Thirmal Chinthakuntla, Keshri Sudhir K, Ghosh Ram Krishna, Hundal Geeta, Kumar Raju, Singh Satyendra, Chatterjee Ratnamala, Mukhopadhyay Pritam
School of Physical Sciences, Jawaharlal Nehru University New Delhi - 110067 India
Department of Chemistry, Ashoka University Sonipat Haryana 131029 India.
Chem Sci. 2023 Jan 4;14(10):2547-2552. doi: 10.1039/d2sc06141d. eCollection 2023 Mar 8.
Organic molecules with an active dipole moment have a natural propensity to align in an antiparallel fashion in the solid state, resulting in zero macroscopic polarization. This primary limitation makes the material unresponsive to switching with electric fields, mechanical forces, and to intense laser light. A single-component organic material that bestows macroscopic dipole-driven electro-mechanical and optical functions, , piezoelectric, ferroelectric and nonlinear optical (NLO) activity, is unprecedented due to the design challenges imparted by crystal symmetry and dipole orientations. Herein we report a crystalline organic material that self-assembles with a polar order ( ), and is endowed with a high piezoelectric coefficient ( -47 pm V), as well as ferroelectric and Debye-type relaxor properties. In addition, it shows second harmonic generation (SHG) activity, which is more than five times that of the benchmark potassium dihydrogen phosphate. Piezoelectric force microscopy (PFM) images validated electro-mechanical deformations. Piezoresponse force spectroscopy (PFS) studies confirmed a signature butterfly-like amplitude and a phase loop. To the best of our knowledge, this is the first report of a folded supramolecular π-system that manifests unidirectionally oriented dipoles and exhibits piezoelectricity, ferroelectricity, and has excellent ability to generate second harmonic light. These findings can herald new design possibilities based on folded architectures to explore opto-, electro- and mechano-responsive multifaceted functions.
具有活性偶极矩的有机分子在固态下具有以反平行方式排列的自然倾向，从而导致宏观极化强度为零。这一主要限制使得该材料对电场、机械力和强激光的切换无响应。由于晶体对称性和偶极取向带来的设计挑战，一种赋予宏观偶极驱动的机电和光学功能（即压电、铁电和非线性光学（NLO）活性）的单组分有机材料是前所未有的。在此，我们报告一种结晶有机材料，它以极性有序（ ）自组装，并具有高压电系数（-47 pm V）以及铁电和德拜型弛豫特性。此外，它还表现出二次谐波产生（SHG）活性，其活性是基准磷酸二氢钾的五倍多。压电显微镜（PFM）图像验证了机电变形。压电力谱（PFS）研究证实了标志性的蝴蝶状振幅和相位环。据我们所知，这是首次报道一种折叠超分子π体系，其表现出单向排列的偶极子，并展现出压电性、铁电性以及优异的二次谐波光产生能力。这些发现可为基于折叠结构探索光、电和机械响应的多方面功能带来新的设计可能性。
