NLOphoric Azo Dyes Studied Using Z‐Scan. Issue 20 (23rd May 2022) - Ramugade, Supriya H.
Abstract: Disperse Red 343((E)‐N‐(2‐((2, 6‐dicyano‐4‐methylphenyl) diazenyl) ‐ 5 ‐ (diethylamino) phenyl)methanesulfonamide, 1 a ), Disperse Red177((E) ‐ methyl3‐((2‐cyanoethyl)(4‐((6‐nitrobenzo [d]thiazol‐2‐yl)diazenyl) phenyl) amino) propanoate, 1 b ), Disperse Blue 165((E) ‐ N ‐ (2 ‐ ((2, 6 ‐ dicyano ‐ 4 ‐nitrophenyl)diazenyl)‐5‐ (diethylamino) phenyl) acetamide, 1 c ), Disperse Blue 165.1((E) ‐ N ‐ (5 ‐ (benzyl (ethyl) amino) ‐ 2 ‐ ((2‐cyano ‐ 4, 6‐dinitrophenyl) diazenyl) phenyl) acetamide, 1 d ), Disperse Blue 366 ((E) ‐ 2 ‐ ((4‐ (diethylamino) ‐ 2 ‐ methylphenyl) diazenyl) ‐ 5 nitroisophthalonitrile, 1 e ), and Disperse Blue 148((E) ‐ methyl 3‐(ethyl (4 ‐ ((5 ‐ nitrobenzo [c]I sothiazol‐3‐yl) diazenyl) phenyl) amino) propanoate, 1 f ) were examined in solvents for their non‐linear optical properties using Z‐scan technique. Because of their CT characteristics, they have shown positive solvatochromism. As observed in nonpolar solvents, the ground states are more stable than their excited states. Changes in solvating the low‐lying ground state and the state above generate the bathochromic shift in vertical excitation. The dye 1 b produces the maximum x 3 ( 7 . 95 × 10 - 13 e . s . u . ) due to strong NO2 donor‐ п‐ acceptors systems in DMSO. We found a positive nonlinear refractive index (η2 ) in both series using the closed aperture (valley‐peak) compared to the other five disperse dyes. Dye 1 c (with two cyano groups) has a ′larger nonlinear susceptibility (χ 3 )′ in DMSO than in the other two solvents (acetone, ethanol). Dye 1 a –1 f showed LDT (9.109, 6.553, 4.641, 6.44) W/m 2 respectively. The "nonlinear absorptive coefficient (β), nonlinear refractive index (η2 ), third‐order nonlinear optical susceptibility χ (3) and optical limiting (OL)" of acetone, ethanol, and DMSO are determined using the Z‐scan technique, and the results are significantly better than earlier known dyes. Abstract : Dye 1 c has shown higher nonlinear susceptibility in DMSO than the other solvents as correlated to demonstrate that entire azo dyes have significant NLO characteristics. In nitro substituted azo dyes, β values increased in dyes 1 b and 1 c. Due to charge separation, azo dyes result in non‐centrosymmetry structures with enhanced NLO properties.