Mechanism of hologram formation in dichromated gelatin with x-ray photoelectron spectroscopy

The mechanism of hologram formation in dichromated gelatin is studied from all aspects with x-ray photoelectron spectroscopy (XPS). It is indicated that the Cr2p(3/2) XPS spectrum of chromium used for hologram formation shows the property of exhibiting a continuousspectrum during the process of dichromated-gelatin hologramformation. By means of curve fitting and drawing a comparisonbetween the obtained spectra and those of some standard substances, itis found that during the process of hologram formation the valence of chromium used for hologram formation changes from Cr(6+) to a quasi-trivalent state to Cr(4+), and finally to Cr(3+). Accordingly, the corresponding compound experiences a change from (NH(4))(2)Cr(2)O(7) to the transient state close to the feature of Cr(OH)(3) to CrO(2), and finally to Cr(3+), cross linking with the gelatin. The essence of the chemical change at different stages of the process of hologram formation was found, and so the present mechanism, which is determined with comparatively abundant proof, should replace previously reported mechanisms, which were too simple, varied, and sometimes even mutually contradictory. According to the experimental results and the fact that a solid-film reaction, which differs from that of the liquid-phase reaction, was studied, possible chemical-reaction equations of the process of hologram formation are established. This becomes the basis for explaining previous findings and expanding further research.     

Simplified method for preparing methylene-blue-sensitized dichromated gelatin

Methylene-blue-sensitized dichromated gelatin (MBDCG) is a suitable material for recording full-color holograms in a single layer. However, a drying process in an ammonia atmosphere is necessary to prepare the MBDCG plate. This process is time-consuming and unstable. A simplified method for preparing the MBDCG plate is presented in which the MBDCG can be dried without ammonia. Elimination of the drying process is possible when the methylene blue in MBDCG does not separate. This is achieved by a decrease in the concentration of dichromate in the photosensitized solution and the addition of an ammonia solution to the photosensitized solution. Last, the gelatin is allowed to gel. A Lippmann color hologram grating with a diffraction efficiency of more than 80% is obtained by use of this MBDCG.     

One-dimensional diffuser based on a thick layer of dichromated gelatin

A new diffuser capable of scattering light in one direction (one-dimensional diffuser) has been developed and experimentally tested. The diffuser is formed in a thick layer of dichromated gelatin. The scattering indicatrices of the diffuser measured in two mutually perpendicular directions are presented. It is demonstrated that the indicatrix width in one direction is significantly greater than that in the perpendicular direc-tion. However, no zero-order diffraction has been observed. The proposed one-dimensional diffuser exhibits close scattering indicatrices for reading at a wavelength of 0.44 and 0.63 μm.     

Control of the spectral position of dichromated gelatin reflection holograms

Dichromated gelatin (DCG) is one of the best light-sensitive materials for holographic recording. However, strict technological control should be observed during deposition, gelation, and drying of DCG plates and the chemical processing of the recorded structures. Usually, for reflection holograms the gelatin layer should be sealed in order to protect it from ambient humidity, which affects the value and position of the reflection maximum. Herein we give three different recipes for tuning the reflection maximum from 430 to 700 nm by swelling the hologram thickness with a filler material that is commercially available. The mechanism of the hologram swelling, which changes the period of the recorded holographic structure, is also briefly discussed.     

Chemical cleaving method of relief microstructure formation on dichromated gelatin

A chemical cleaving method to improve the resolution of relief modulation in dichromated gelatin is presented. The process (which uses hydroxylamine) yields higher relief resolution and better profile fidelity than a process that uses the enzyme trypsin because it has many fewer cleaving sites. Experiments prove that relief modulation can produce a resolution of as much as 500 lines/mm. With a projection exposure system, a microprism array with a 30-mum-wide, 0.8-mum-high cell is fabricated by this method. A method for forming a continuous relief on dichromated gelatin is also discussed.     

Double-layer method for increasing the bandwidth of UV spectrally responsive holograms in dichromated gelatin

We present a method for increasing the bandwidth of reflection holograms in dichromated gelatin. The recording plate has two dichromated-gelatin layers of different hardness so that their shrinkage at the end of processing is different. We use this method for doubling the bandwidth of holographic mirrors that are designed for solar UV energy concentration. We also study the superposition of two double-layer holograms, which results in UV holographic mirrors with a bandwidth of 60 nm.     

Self-enhancement of holographic gratings in dichromated gelatin and polyvinyl alcohol films

New experimental results concerning real-time hologram recording in dichromated sensitized gelatin and polyvinyl alcohol are presented. Self-enhancement of the holographic gratings observed in the dark in both of these dye-polymer systems is shown.     

Observation of a fast-formed absorption grating and a slowly formed phase grating in undeveloped dichromated gelatin

Real-time diffraction efficiency is measured during hologram formation in undeveloped dichromated gelatin (DCG) film. The main features of real-time diffraction efficiency of undeveloped DCG reveal double peaks with increasing exposure time. Adopting the grating translation technique, we show that the first peak originates from the absorption grating and that the latter is related to the phase grating. To explain such complicated hologram-formation dynamics, we present a phenomenological model for mixed gratings associated with photoinduced refractive-index changes and absorption changes. We have compared the model results with the experimental results, which show good agreement.     

The effect of UV radiation on the properties of diffraction gratings based on dichromated gelatin

Results of experiments on the influence exerted by UV radiation on the height of the surface relief and on the diffraction efficiency of holographic diffraction gratings recorded on dichromated gelatin layers are reported. It is shown that the height of the surface relief substantially increases, which leads to a rise in the diffraction efficiency of the gratings to a value exceeding 25%.     

Comparison of different test methods for determining the mar resistance of clearcoats

This paper presents a number of different methods for determining the mar resistance of automotive clearcoats. The various methods are compared on the basis of measurements on different clearcoat systems and the results discussed with other physical parameters (microhardness, crosslinking density). Micro-scratching tests (individual scratches) were also carried out in addition to more practical tests (simulated car washes).     

Study of the pH dependence of diffraction efficiency of phase holograms in dye sensitized dichromated gelatin

Dichromated gelatin is thought to be a good substitute for photographic emulsions in some uses. The results of a systematic study of the effect of the pH of the developer on the diffraction efficiency of volume holographic gratings recorded in dye sensitized dichromated gelatin are presented.     

地表水中有机磷农残测定的前处理方法比较

分别采用液液萃取法和固相萃取法提取地表水样品中的有机磷农药残留。液液萃取法的方法检出限为0.05~0.2 ng/mL,加标回收率为86%~103%,相对标准偏差为2%~7%;固相萃取法的方法检出限为0.03~0.05 ng/mL,加标回收率为49%~118%,相对标准偏差为5%~18%。液液萃取法处理不同类型基体水样的测试稳定性较好,固相萃取法则对于洁净环境水体中痕量有机磷农药残留的富集更为适用。     

Improving the holographic sensitivity of dichromated gelatin in the blue-green part of the spectrum by sensitization with xanthene dyes

The holographic properties of dichromated gelatin (DCG) sensitized with various xanthene dyes were studied, and results are reported. The sensitivity of dyed DCG in the green part of the spectrum compared with that of pure DCG (215 mJ/cm(2)) was significantly improved by addition of Rhodamine 6G (140 mJ/cm(2)) or Erythrosin B (90 mJ/cm(2)). Diffraction gratings were recorded with a He-Ne laser at 543.5 nm. The maximum diffraction efficiency was found to be 32% at normal incidence of the readout beam; it was 80% at the Bragg angle.     

X-ray diffraction study of the effect of photohardening on the structure of self-developing dichromated gelatin sensitized with Methylene Blue

Peculiarities of the structural organization of self-developing emulsion layers based on dichromated gelatin sensitized with Methylene Blue dye and containing 76% water have been studied by X-ray diffraction. The diffraction patterns I(2θ) of the photolayers are presented. The scattering functions of the amorphous state have been calculated. Differences between the photolayer structures in the exposed and unexposed state are considered. It is shown that recording an image leads to ordering of the photolayer structure that is related to changes in the conformations of gelatin macromolecules.     

Effect of the content of ammonium dichromate in dichromated gelatin on Cr 2P3/2 X-ray photoelectron spectroscopy

The effect of the content of (NH(4))(2)Cr(2)O(7) in dichromated gelatin (DCG) on the binding energy of the Cr 2P(3/2) level was studied with x-ray photoelectron spectroscopy. It was found that the binding energy of the Cr 2P(3/2) level of chromium in DCG is lower than that of pure ammonium dichromate. When the content of (NH(4))(2)Cr(2)O(7) is not greater than 1%, the chromium in DCG has only one state, near 577.5 eV; when this content is between 1% and 20%, the chromium in DCG has two states, near 577.5 and 579.1 eV. The relative contents of these two states change with the content of (NH(4))(2)Cr(2)O(7). As the (NH(4))(2)Cr(2)O(7) content increases, the relative content of the state near 577.5 eV decreases almost linearly, but its absolute content first increases, then reaches a maximum at ~10% (NH(4))(2)Cr(2)O(7), and finally decreases. In addition, the absolute content of the state near 577.5 eV changes very slowly between 5% and 15% (NH(4))(2)Cr(2)O(7). According to these experimental results and holography data reported in the literature, it is inferred that the chromium of the state near 577.5 eV is the chromium that forms the latent image center after exposure and then forms the hologram after development. As a result the basis for the optimum content of (NH(4))(2)Cr(2)O(7) is found, and an approach to increasing sensitivity is suggested through this experiment.