In this paper, the influences of cyanine dye on the photoelectron decay of silver chloride micro-crystal have been studied
with Microwave absorption and dielectric spectrum detection technology. The free photoelectron decay of silver halide
sensitized becomes faster than that of pure silver halide, and the FDT are 86ns and 109ns for silver chloride
sensitized(5.0ml/40g AgCl emulsion) and unsensitized, respectively. The absorption peak of the dye is at about 550nm,
having about 50 nm red shift compared with that in methanol. This indicates that J- aggregate is formed on micro-crystal
surface, moreover the peak of dye J-aggregate becomes sharper, the width of absorption peak narrower with the
increasing of the concentration of dye. Dye J-aggregate increases the concentration of deep electronic trap in the surface
of silver halide micro-crystals.
The time-resolved photoelectron spectra of spectrally sensitized cubic AgCl emulsion are detected with microwave
absorption and dielectric spectrum detection technique. The decay process of photoelectron is accelerated and becomes
faster than that of the unsensitized sample since the concentration of interstitial Agi
+ ions is increased when the dye
molecules are adsorbed onto the surface of crystal. The influence of temperature condition on the photoelectron decay
process is obtained. Results show that the dye adsorption degree is varied when the sensitizing temperature differs, then
the decay dynamic changes. The optimal temperature condition is in 450C in which the adsorption of dye has a larger
influence on crystal property and the photoelectron decay is fastest. When lower or higher than this condition, the
adsorption degree is poor or the dye molecules have a tendency to form bigger dye-aggregates, then the variance of interstitial Agi+ ions is less than that in 450°C and causes a slower photoelectron decay process.
There will be large numbers of carriers coming into being in the interior of silver chloride microcrystals when illumination acts on it. Microwave absorption and dielectric spectrum detection technology with high temporal resolution (1ns) can detect instantaneous decay process of photoelectrons. In this work, the photoelectron decay action of spectral sensitized silver chloride emulsion is measured by microwave absorption and dielectric spectrum detection technology. By analyzing the measured results, it is found that when plentiful dye adsorb on silver chloride microcrystals film, the photoelectron decay of silver chloride emulsion becomes faster than that of pure emulsion. However it is not that the more the dye is adsorbed, the faster the photoelectron decay will be. When the adsorbed dye reaches a certain level, the photoelectron decay becomes slower than the fastest instance. Combining with photoelectron decay kinetics theory it is found that the above results are induced by two kinds of effect from dye adsorption.
The decay curve of free photoelectron in cubic AgCl microcrystals by sulfur sensitization is obtained by microwave absorption dielectric spectrum detection technique. By comparing the free photoelectron decay curves of unsensitized and sensitized sample, we discover that sulfur sensitization centers act as shallow electron trap when sensitization time is 45min. In order to analyze the characteristics of sulfur sensitization center quantitatively, the method of the decay kinetics of photoelectron is used in this paper. We first proposed a model of sulfur-sensitized AgCl microcrystals, and then induced a series of kinetics equation. The characteristics curve of photoelectron decay is obtained by solving the kinetics equation, which is in agreement with the experimental curve. Meanwhile the concentration, trap depth and capture cross-section are obtained by computer simulation, which are 1.12ppm, 0.085eV and 1.46×10-18cm, respectively. Also a possible method to study the mechanism of sulfur sensitization from the perspective of dynamics is suggested.
The photoelectron decay characteristic of AgCl mircrocrystals, which are adsorbed with the green-sensitive cyanine dye, has been obtained by using microwave absorption and phase-sensitive measurement technique. Combined with the absorption spectra of cubic AgCl emulsion sensitized by green-sensitive cyanine dye, the influence of green-sensitive cyanine dye adsorption at various adsorbing concentration on the surface structure of cubic AgCl microcrystals is investigated. It is found that when the concentration is less than 0.02ml(5.0mg/ml)/40g emulsion, the dye J-aggregate is not formed on the surface of silver chloride microcrystals, the surface of AgCl is decorated by the dye, the dye takes place shallow electron trap effect; when the sensitive concentration is more than 0.2ml (5.0mg/ml)/40g emulsion, the dye J-aggregate is formed on the surface of silver chloride microcrystals, the Agi+ of AgCl microcrystal surface is increased, the dye takes place the deep electron trap effect
The characteristic of semi-conduct will be influenced, when environmental conditions act on it. Silver halide
microcrystals, kind of false compositive microcrystals, is a kind of typical photoelectric material. In this work, the silver
chloride microcrystals adsorbing dye are excited by laser with different wavelengths, the photoelectron signals of which
are measured by microwave adsorption dielectric spectrum equipment with a high time resolution (1ns). It is found that
the photoelectron decay time of pure emulsion excited by 355nm and 532nm laser is respective 109ns and 47ns; The
photoelectron decay time of sensitized emulsion with sensitization concentration of 4mg/40g is respective 83ns and 23ns
when it is excited by 355nm and 532nm laser; The photoelectron decay time of sensitized emulsion with sensitization
concentration of 8mg/40g is respective 76ns and 12ns when it is excited by 355nm and 532nm laser. The results show
that the change extent of photoelectron decay are not the same when silver chloride emulsion is excited by laser with
different wavelengths, so the sensitive effect of adsorbed dye is different under different exposal wavelengths.
Microwave absorption and dielectric spectrum detection technology, with high time resolution (less than 1ns), was used
for non-contact measurement of electron property in solid materials. In this paper, the photoelectron decay time-resolved
spectrums of silver halide, which adsorbed the green-sensitive cyanine dyes J-aggregate, are measured by microwave
absorption and dielectric spectrum detection technology. From the experiment, we find that the photoelectron decay time
and the photoelectron lifetime of silver halide, which adsorbed the dye, is shorter than that of the pure silver halide; the
photoelectron decay time of silver bromide is faster than the photoelectron decay time of silver chloride, the free
photoelectron lifetime of silver chloride and silver bromide is 51.66ns and 13.84ns respectively; the variety extent of
silver bromide is bigger than that of the silver chloride after sensitized. The effect of the dye concentration on
photoelectron decay of silver halide is obvious, for silver bromide and silver chloride, the photoelectron decay become
faster while the concentration increases.
Microwave absorption and dielectric spectrum detection technology, with high time resolution (less than 1ns), was used for non-contact measurement of electron property in solid materials. In this paper, the photoelectron decay time-resolved spectra of free electrons in cubic AgCl emulsion sensitized by different concentrations of green-sensitive cyanine dye were measured by dielectric spectrum equipment. At the same time the absorption spectra were obtained by spectrophotometer. Experiments show that when the sensitive concentration is less than 0.02ml(5.0mg/ml)/40g emulsion, the dye J-aggregate is not formed on the surface of silver chloride microcrystals; The photoelectron decay is slower than that of pure cubic AgCl emulsion. when the sensitive concentration is more than 0.2ml (5.0mg/ml)/40g emulsion, the dye J-aggregate is formed on the surface of silver chloride microcrystals; compared to the M-state of dye, the maximal absorption peak of J-aggregate is shifted to longer wavelength about 50nm. The photoelectron decay is faster than that of pure cubic AgCl emulsion.
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