Absorption spectra cellulose

The absorption spectrum of nitrocellulose solutions has been examined (Rassow and Aehnelt [135]). It has been established that the capacity to absorb light differs with the origin of the nitrated cellulose. Thus nitrocellulose made from wood pulp gives a slightly different absorption spectrum from that of nitrocotton. 

Experiments by Ellis and Bath [137] on the infra-red absorption spectrum of cellulose have indicated the existence of hydrogen bonds between the hydroxyl groups of the cellulose molecules, probably following the —O—H—O— pattern (see p. 225). 

Inspection of the data in Table II reveals a bathochromic shift of the of the triplet-triplet absorption with increasing solvent polarity, with a further bathochromic shift when the compound is adsorbed on microcrystalline cellulose. No phosphorescence emission in solution is seen from this compound at room temperature, indicating that the radiative lifetime of this triplet state is long. This is consistent with the lowest energy excited triplet state having predominantly (n, n ) character. The shape of the triplet-triplet absorption spectrum also suggests that this is the case(20). 

Another variant of this method has been used by Howell2 for estimating the surface of cellulose accessible to coloured salt such as cobalt chloride. Filter paper is soaked in solutions of different concentrations, and dried the amount of coloured salt on the total surface is thus known, the volume of solution taken up being observed. On examining the absorption spectrum of the now coloured cellulose it is found that, for the first portions of salt deposited, the intensity of the colour increases almost linearly up to a certain critical amount deposited and only slowly thereafter assuming that this critical amount is a layer one molecule thick on the surface, the available surface was found to be about 85 times the apparent surface, as measured microscopically. 

Part of an infrared absorption spectrum from a membrane of bacterial cellulose is shown in Figure 2 (16). The absorption bands refer to the stretching frequencies of the hydrogen-bonded OH groups. Free OH groups would give an absorption band at 3640 cm. 1. All OH groups are... 

Ground-state absorption spectrum for powdered microcrystalline cellulose is also shown in Figure 1. It exhibits R values quite close to unity for visible (Vis) and near infrared (NIR) spectral regions and shows a significative absorption in the ultraviolet (UV). Silica and silicalite also have a reflectance close to unity in the Vis and NIR regions and differ from cellulose by the fact that UV absorption is smaller. In the case of silicas with different porosity, but with the same particle size, significant variations of the reflectance were detected [7]. 

Theoretically, pure cellulose should not have an absorption spectrum. A typical cellulose absorption spectrum is shown in Figure 4.19. The absorption... 

Fig. 18.15 Discoloration of Keyacid Blue (0.1 wt%) stain in electrospun nonwoven mats, (a) Exposed to halogen light ( 13 mW/cm ) over a 24 h. (b) Optical absorption spectrum exposed to halogen light ( 27 mW/cm ) as a function of time. The results show that the cellulose core and Ti02 sheath nanofibers mat exhibited the best photodegradation performance (Reprinted with the permission from Ref. [57]. Copyright 2010 American Chemical Society)...

Fig.I (left). Absorption spectra of suspensions of/ carotene form isolated chromatographically on a DEAE cellulose column (a), or by sequential extraction (b). The absorption spectrum of a mixture of chromatographically isolated pigment and residue after extraction of lipids with J00% acetone is also shown (c).

The elution profile of cytochrome P-448 (absorption at 418 nm) and epoxide hydratase activity from a sodium cholate-solubi-lized hepatic microsomal preparation (from DBA-treated male skates) applied to a DEAE-cellulose column and eluted with Buffer II is shown in Fig. 3. The void volume of the column contained significant amounts of epoxide hydratase activity. Fractions 40-70 (Fig. 3) were combined, and concentrated. The carbon monoxide difference spectrum, which had an absorption maximum at 448 nm in the induced state, is shown in Fig. 4. This form of the cytochrome (i.e.,... 

Figure 10 shows the IR spectrum of a normal cellulose acetate membrane. Figure 11 shows the spectrum of the hydrolyzed membrane. The decrease of absorption around 1,720 cm, and the increase of absorption around 3,200 to 3,500 cm are shown. The first peak correspond to the C = 0 double bond, and the second to the 0 - H single bond. These spectra show the decrease of the acetyl content in the membrane. 

Figure 2 compares ATR spectra of the irradiated and unirradiated sides of a cellulose triacetate film after 24-hour radiation at 253.7 min vacuum. The ATR spectrum of a control cellulose triacetate film, which is identical with that of the unirradiated side in Figure 2, is given in Figure 3. Figure 4 shows the change of infrared absorptions of a cellulose film cast on a NaCl plate upon irradiation at 253.7 min vaccum. The spectra were recorded at 90°C. An increase in OH (3 microns) and a decrease in carbonyl (5.7 microns) absorption were noted. 

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