Dynamical Studies of Color Sensitization in Photography

首次在飞秒时间尺度上研究了溴化银纳米晶的光谱增感和超增感效应。测量了吸附在不同形状（立方体和八面体）的溴化银纳米晶体（边缘到边缘距离为40至900 nm）上的染料1的J聚集体的无湮灭荧光[1]。观察到非常快的非指数荧光衰减的快速组件从0.4到2.5 ps，和从1.1到5.5 ps的平均衰减时间，这取决于AgBr颗粒的类型和大小。立方颗粒上的平均荧光衰减时间是八面体颗粒上的几倍，通过时间分辨荧光各向异性测量研究了八面体AgBr微晶上J聚集体的超快激发能量转移[2]。各向异性衰减是双相的，具有两个时间常数：0.15 ps和2-7 ps。短时间常数几乎与染料覆盖率无关，而第二个在较高的染料覆盖率下变得较慢。在初级电子注入AgBr（0.7ps）之前，{111}表面上外延排列的J聚集体之间发生了超快激发转移（0.1ps）.

Spectral sensitization and supersensitization of the silver bromide nanocrystals were studied in the femtosecond timescale for the first time. An annihilation-free fluorescence from J-aggregates of dye 1 adsorbed on the silver bromide nanocrystals (edge to edge distance from 40 to 900 nm) of different shapes (cubic and octahedral) was measured [1]. Very fast non-exponential fluorescence decays were observed with a fast component from 0.4 to 2.5 ps, and an average decay time from 1.1 to 5.5 ps, depending on the type and size of AgBr grains. The average fluorescence decay time is several times longer on the cubic grains than that on the octahedral grains.By time-resolved fluorescence anisotropy measurement the ultrafast excitation-energy transfer of the J-aggregates on the octahedral AgBr microcrystal is studied [2]. The anisotropy decays are biphasic with two time constants of 〜0.15 ps and 2-7 ps. The short time constant is almost independent of the dye coverage, while the second one becomes slower at higher dye coverages. An ultrafast excitation transfer (O.1ps) is suggested to take place between epitaxially arranged J-aggregates on the {111} surface prior to the primary electron injection to AgBr (0.7 ps).