吖啶橙受溶液pH和浓度变化的光谱研究

利用荧光光谱分析仪研究吖啶橙受溶液pH和浓度变化的吸收光谱和荧光光谱的变化。实验表明,当改变吖啶橙溶液pH和浓度时,它的吸收光谱和荧光光谱发生位移。吖啶橙为1×10-6mol/L时,不同pH的吖啶橙溶液均在(490±3)nm出现一个强吸收峰,pH=6.5,吸收光谱的λm ax=430 nm,发生蓝移;而荧光光谱的λm ax随pH增大发生红移,荧光强度减弱。在浓吖啶橙溶液中,不同pH的吖啶橙溶液的吸收光谱的形状基本相同,出现两个吸收峰,λm ax1分别为(455±3)nm和(430±3)nm,λm ax2分别为(505±4)nm和(510±2)nm,吸收光谱红移;荧光光谱的λm ax均为(535±2)nm,荧光强度荧光很弱。pH相同或相近时,吖啶橙溶液的吸收光谱蓝移和荧光光谱红移,浓度越大,荧光强度越弱。还探讨了吖啶橙在水溶液中的赋存状态,结果表明,在稀溶液中,吖啶橙主要以单体的形式存在;在高浓度吖啶橙溶液中则以吖啶橙单体、二聚体,甚至多聚体形式存在。这说明溶液pH主要影响到吖啶橙分子基态的质子化和氢键的形成能力,使得分子的基态与激发态之间的能量间隔发生了变化,吖啶橙被质子化,则引起发光光谱向短波方向移动,而离解作用,则引起发光光谱向长波方向移动;吖啶橙浓度变化影响吖啶橙在水溶液赋存状态,引起吸收光谱向短波方向移动或向长波方向移动。

Study on the spectra of acridine orange influencing by different concentration and pH in aqueous solution

The magnitude of λmax in absorption and fluorescence spectra is investigated on changing the pH and concentration of acridine orange in aqueous solution.These experiments demonstrate that the λmax in absorption and fluorescence spectra is shifted.When acridine orange is 1×10-6 mol/L,λmax in absorption spectra is(490±3) nm in the different solution,except that pH is 6.5,λmax is 430 nm,which shift to the direction of short wavelength.The λmax in fluorescence spectra shift to the direction long wavelength with the increasing of pH,and the fluorescence intensity is weakened.However,two absorption peaks are presented and the shape of peak is similar by changing pH when the concentration of acridine orange is respectively 1×10-4 mol/L and 1×10-3 mol/L.One(λmax1) in absorption and fluorescence spectra are respectively(455±3) nm and(430±3)nm,the other(λmax2) are(505±4) nm and(510±2) nm,which shift to the direction of long wavelength.The λmax in fluorescence spectra is(535±2) nm,which shifts to the direction of long wavelength,and the fluorescence intensity is weakened as well.The λmax in absorption and fluorescence spectra is shifted if pH was equivalent.The fluorescence intensity is weaker in high concentrated solution.The form of acidine orange in aqueous solution is examined by measuring the fluorescence intensity in different concentration of acridine orange.The result shows that acridine orange is monomer in 1×10-6 mol/L,and maybe be the mixture of monomer in 1×10-5 mol/L,and is dimer and polymer in 1×10-4 mol/L and 1×10-3 mol/L.These demonstrate that the protonization and bond formation of the ground-state molecules of acidine orange are influenced by changing pH,the energy gap was changed between ground state and excited state.If acridine orange is protonized,the λmax in fluorescence spectra is shifted to the direction of short wavelength.When it is deprotonized,the λmax in fluorescence spectra is shifted to the direction of long wavelength.The λmax in absorption and fluorescence spectra is shifted to the direction of short or long wavelength because of the form of acridine orange in different concentration solution.