Synthesis, growth, structural, spectroscopic, crystalline perfection, second harmonic generation (SHG) and thermal studies of 2-aminopyridinium picrate (2APP): A new nonlinear optical material Mohd. Shkir a, b , B. Riscob a , G. Bhagavannarayana a, * a Crystal Growth & X-ray Analysis Activity, CSIR-National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012, India b Dept. of Physics, ARSD College, University of Delhi, New Delhi 110021, India article info Article history: Received 13 January 2012 Received in revised form 26 March 2012 Accepted 16 April 2012 Available online 27 April 2012 Keywords: 2-Aminopyridinium picrate (2APP) Characterization Nonlinear optical properties Thermal analysis abstract Single crystal growth, spectroscopic, relative second harmonic generation (SHG) efficiency and thermal analysis of 2-aminopyridinium picrate (2APP) is reported for the first time. Crystals were grown by the slow evaporation solution technique using methanol as a solvent. The crystal system and lattice parameters were confirmed by single crystal and powder XRD analyses. FT-IR and FT-Raman spectro- scopic studies were carried out to identify the functional groups and vibrational modes present in the grown crystal. Crystalline perfection of the grown crystal was assessed by high-resolution XRD and the results reveal that the crystal is reasonably good. SHG efficiency was measured using Kurtz powder technique. Thermogravimetric (TG) and differential thermal analysis (DTA) studies were carried out and show that the grown single crystal is stable up to 223  C. Ó 2012 Elsevier Masson SAS. All rights reserved. 1. Introduction Search for new nonlinear optical (NLO) materials for tailor made device applications had been increasing from the last few decades because of their potential industrial applications especially in the field of photonics for optical switching, optical modulators, data storage devices, telecommunication, optical information process- ing, and high density optical disk data storage [1,2]. Effective NLO single crystals with efficient optical frequency conversion are the key elements for the development of laser systems. Such systems are of great importance as wide range tunable sources of coherent illumination in ultra-violet, visible and infrared spectral ranges. So, there is a great massive demand to synthesize new NLO materials and grow their single crystals of better perfection. Organic materials show remarkable properties due to their fast and huge nonlinear response over an extensive frequency range, inherent synthetic flexibility and large optical damage threshold for laser power and low frequency dispersion [3,4]. One of the main advantages of organic materials is that they permit one to modify the chemical structure with large physical structural diversity and properties for the desired NLO properties [3,4]. Amino acid family crystals are of great interest due to their attractive nonlinear optical properties [5]. When an organic acid mixed with amino acid, NLO property was found to be increased due to the zwitterionic nature associated with enhanced trans- parency range [6,7]. Picric acid forms molecular charge transfer complexes with aromatic compounds through electrostatic or hydrogen bonding interactions [8,9] and has many reports with many organic molecules [10,11], due to the presence of active p- and ionic bonds [12]. 2-Aminopyridinium picrate (2APP) is a newly invented organic material. As per the authors’ knowledge, except a very few reports on its structural study [13], no other detailed studies are available in the literature on the title material. In the present investigation, crystal growth, structural, spectroscopic, crystal quality, relative SHG efficiency and thermal analysis of 2APP are reported. 2. Experimental 2.1. Synthesis and crystal growth The titled material was synthesized by taking 2-Aminopyridine and picric acid (CDH made) in 1:1 M ratio [13]. * Corresponding author. Tel.: þ91 11 45608261; fax: þ91 11 25726938/52. E-mail address: bhagavan@mail.nplindia.ernet.in (G. Bhagavannarayana). Contents lists available at SciVerse ScienceDirect Solid State Sciences journal homepage: www.elsevier.com/locate/ssscie 1293-2558/$ e see front matter Ó 2012 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.solidstatesciences.2012.04.022 Solid State Sciences 14 (2012) 773e776