摘要
用吸收光谱和反射光谱技术研究了黑白片感红染料 798( 3,3′—二羟乙基— 5,5′—二甲氧基— 9—乙基—噻碳菁氯盐 )在甲醇、水及KBr水溶液中的聚集效应和吸附于AgBr表面的吸附态性质 .其在甲醇中以单分子态存在的最大吸收波长λmax为 560nm .在 2 5℃水溶液中 (浓度范围 5× 1 0 - 6～ 2 .5× 1 0 - 5 mol/dm3) ,存在二聚平衡 (λD=52 0mm) ,其标准平衡常数K—O( 2 98K) =1 .2 8× 1 0 - 5ΔrG—Om( 2 98K) =2 7.9kJ/mol、ΔrH—Om( 2 98K) =35.2kJ/mol、ΔrS—Om( 2 98K) =2 4 .5J/(K·mol) .2 5℃的吸附等温线表明 798在AgBr上为多层吸附 ,第一吸附层的饱和吸附量是 0 .73μmol/g(按单分子染料单元计算 ) ,吸附态的表面反射光谱表明 ,只在第一层中存在J—聚集状态。
The aggregation behavior of 3.3′ dihydroxy ethyl 5.5′ dimethoxy 9 ethylthiacarbocyanine chloride (dye 798) in CH 3OH, H 2O solution and its adsorbed state on AgBr surface was studied by the absorption and reflection spectra and by the adsorption isotherms at 25 ℃. NO J absorption ,but only dimer monomer equilibrium was observed form the absorption spectra of aqueous solutions of the dye in the experimental concentration range, the dimerzation constant K —O (298 K),Δ rG —O m(298 K) ,Δ rH —O m(298 K)and Δ rS —O m(298 K) were found spectrophotometrically to be 1.28×10 -5 , 27.9 kJ/mol, 35.2kJ/mol and 24.5 J/(K·mol), respectively. The adsorption isotherm obtained at 25 ℃ indicated that the adsorption of dye 798 on the surface of AgBr was of multilayer type with a saturated capacity of 0.73 μmol/g(AgBr)(expressed as monomer units of the dye )in the first adsorbed layer. The surface reflection spectra showed that after the J band had reached critical intensity(λ J a=640nm),the further addition of dye only caused H aggregate and monomer formation. This indicated that only the dye molecules in the first adsorbed layer existed as J aggregates ,the adsorption states in subsequent dye layers were different. The J aggregates of cyanine dye play an important role in spectral sensitization to photographic emulsion, especially in ultra sensitization. The study of aggregation behavior has been an important aspect of spectral sensitization studies. The aggregation behavior of photographic sensitizing dye 798 used in monochrome in solution and the results of studying the adsorbed state on the surface of silver bromide and its aggregation thermodynamic properties were reported. All above will play an important role in using dye reasonably in productions and further understanding sensitizing mechanism .
出处
《分析测试技术与仪器》
CAS
2000年第2期101-105,共5页
Analysis and Testing Technology and Instruments
