Bulk optical-quality single crystal of 2, 6-diaminopyridinium 4-nitrophenolate 4-nitrophenol (DAPNP) with dimensions of 22 x 15 x 8 mm(3) was successfully grown by the controlled slow cooling solution growth method. Thermogravimetric (TG) and differential thermal analysis (DTA) were carried out to characterize the thermal behaviors of the grown crystals. Its specific heat was determined and dielectric properties from 298.15 to 353.2 K have also been investigated. Second-harmonic generation (SHG) on powder samples indicated that DAPNP is a phase-matchable material and its SHG coefficient is 11.5 times larger than that of urea. (C) 2011 Elsevier B.V. All rights reserved.