Influence of Polar Solvents on Growth of Potentially NLO Active Organic Single Crystal N-Benzyl 2-Methyl-4-Nitroaniline and Efficiency of Terahertz Generation
We report on the growth of N-benzyl-2-methyl-4-nitroaniline (BNA) crystals by solution growth method using certain polar protic and aprotic solvents (single or mixed). It was observed that the morphology of the BNA crystals could be influenced by the solvents used and that the growth was, with certain exceptions, predominant along crystallographic b axis. Attempts to grow large BNA crystals from these solvents showed that majority of these polar solvent molecules tended to get adsorbed preferentially along polar +c and/or –c axes/axis. The bulk and surface qualities of the grown crystals were observed to be influenced by the solvents employed to grow the BNA crystals and the results of THz measurements obtained for the crystals grown from selected solvents were also found to corroborate these observations. A systematic approach has shown that the BNA crystals grown from one of the polar aprotic solvents, which is presumably reported for the first time for this crystal, exhibited relatively higher THz efficiency. It is further understood that this particular solvent could have created a favorable solute – solvent environment at the progressing crystal – solution interface that improved the overall quality of the BNA single crystals and resulted in the significant enhancement in the THz efficiencies.