甲基橙-阳离子表面活性剂缔合微粒体系的光谱特性与变色效应

SPECTRAL CHARACTERISTIC OF CETYLTRIMETHYLAMMONIUM BROMIDE-METHYL ORANGE AND ITS HYPOCHROMIC EFFECT

在 p H2 .5 6,4.1 0和 5 .72的 Britton-Robinson介质中 ,甲基橙 ( MO)分别呈红色 ( λmax=5 1 0 nm)、橙色( λmax=470 nm)和黄色 ( λmax=460 nm) .分别加入十六烷基溴化铵 ( CTAB) ,甲基橙在 5 1 0 ,470和 460 nm处吸收峰降低 ,这是由于形成 CTAB-MO缔合物分子并可聚集形成 ( CTAB-MO) n 缔合微粒将吸光分子 MO包裹所致 .( CTAB-MO) n 在 p H2 .5 6,4.1 0和 5 .72的 Britton-Robinson介质中 ,缔合微粒体系分别呈浅红色、橙色和亮黄色 ,在 470和 5 70 ,3 70和 5 3 0 ,3 70和 5 40 nm处各有 2个共振散射峰 .当 [CTAB]≤ [MO]时 ,该缔合微粒体系分别呈浅红色、橙色和亮黄色 ;在 p H2 .5 6的介质中 ,当 [CTAB]≥ 2 [MO]时 ;及在 p H4.1 0和 5 .72 Bri-tton-Robinson介质中 ,[CTAB]≥ 1 .5 [MO]时 ,体系的吸收峰首先紫移到 3 5 6nm再红移到 42 5 nm且逐渐增强 ,经过一系列颜色变化 ,最终都变黄绿色 .共振散射光谱、扫描电镜、透析和乙醇浓度的影响等实验结果表明 ,( CTAB-MO) n 缔合有机微粒是产生其减色效应和增色效应及共振散射效应的根本原因 .[( CTAB-MO) n]n

The spectral characteristic of cetyltrimethylammonium bromide (CTAB)-methyl orange (MO) associated particle system has been investigated.The color of methyl orange solution is red,orange and yellow in pH2.56,4.10 and 5.72 Britton-Robinson buffer solution and its absorption peaks is at 510,470 and 460 nm.With the increasing of the concentration of CTAB,the absorption intensity at 510,470 and 460 nm decreases.The reason for this is that MO and CTAB combine into MO—CTAB associated molecule and the associated molecule is accumulated to (CTAB—MO)_n associated particle which can enwrap MO molecules.The color of the particle system of (CTAB—MO)_n is bright yellow and it has a resonance scattering peaks at 470,525 and 540 nm.When [CTAB]≤[MO],this system is yellow and has a new resonance scattering peaks at 525 nm.However,when [CTAB]≥[MO],the wavelength of resonance scattering peaks is increased and the color becomes green-yellow.Owing to the excessive concentration of CTAB,the color of this system is changing from yellow to green-yellow.That is to say,there is red-move color change effect of particle.In addition,525 nm resonance scattering peaks also take places purple-move.The test of dialysis and the effect of concentration of ethanol demonstrate that the formation of (CTAB—MO)_n particle is ultimate reason for hypochromic and resonance scattering effect.Moreover,both the formation of [(CTAB—MO)_n]_(nucleus) [CTAB_m]_(shell) particle and interface reaction result in change color effect of system of particle.