Mechanism of Hologram Formation in Dichromated Gelatin with X-Ray Photoelectron Spectroscopy

Abstract

The mechanism of hologram formation in dichromated gelatin is studied from all aspects with x-ray photoelectron spectroscopy (XPS). It is indicated that the Cr 2p(3/2) XPS spectrum of chromium used for hologram formation shows the property of exhibiting a continuous spectrum during the process of dichromated-gelatin hologram formation. By means of curve fitting and drawing a comparison between the obtained spectra and those of some standard substances, it is found that during the process of hologram formation the valence of chromium used for hologram formation changes from Cr6+ to a quasi-trivalent state to Cr4+, and finally to Cr3+. Accordingly, the corresponding compound experiences a change from (NH4)2Cr2O7 to the transient state close to the feature of Cr(OH)3 to CrO2, and finally to Cr3+, 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.

Facile Synthesis of Smart Magnetic Graphene for Safe Drinking Water: Heavy Metal Removal and Disinfection Control

“…The broad Cr2p 3/2 peak could be deconvoluted into two peaks at binding energies of 577.3 and 580.1 eV, which are characteristic of Cr(III) and Cr(VI). 55,56 This adsorption phenomenon is further supported by the SEM image of Cr(VI)-adsorbed SMG (SMG-Cr(VI)) (Supporting Information Figure S7b), which possesses wrinkled GO sheets (Supporting Information Figure S7a) with a rough surface. The energy dispersive X-ray pattern (Supporting Information Figure S7c) shows the presence of C, O, Cr, and Fe in SMG-Cr(VI).…”

Hybrid process of latent image formation in silver halide sensitized gelatin: differential hardening with microvoids

“…For many authors the index modulation in DCG holograms is caused by rearrangement of gelatin molecule chains during the development steps due to the hardness di erential [14]. Furthermore, evidence has been given of the transformation of Cr ‡6 into Cr ‡3 , with Cr ‡5 [15] and Cr ‡4 [16] being the intermediate species involved in the process.…”

Cyclic allylic sulfide based photopolymer for holographic recording showing high refractive index modulation

“…Such nice features, pushed Covestro to develop commercial high performance Bayfol® HX photopolymers for holography 10–12 . However, the modulation of the refractive index (∆n) reachable by photopolymer is still limited if compared to dichromated gelatins 13,14 or silver halides, 15 which are the reference holographic materials in terms of this property. This prevents the use of photopolymers in some fields, such as dispersing elements for high‐performances spectrographs or high efficiency and thin lenses.…”