Poly maximum absorption spectra

Finally, two related studies can be mentioned here. It was noted that when a quartz plate was immersed overnight in a solution of Pb(C104)2 and poly(vinyl alcohol) through which H2S had been bubbled, a film formed on the plate parallel with formation of a colloidal PbS sol [47]. The film was extremely thin (maximum absorbance of <0.015 at 400 nm). The absorption spectrum of this film was similar to that of the PbS sol and consisted of several absorption peaks with an absorption onset of ca. 630 nm (1.97 eV). It is not clear that this is the true bandgap onset, for the same reasons as discussed previously (weak absorption close to the bandgap). The XRD crystal size of the precipitate was ca. 3 nm. 

The steady state absorption and emission spectra of poly(A), poly(dA), and the absorption spectrum of the ribonucleotide monomer adenosine 5 -monophosphate (AMP) are shown in Fig. 1. The absorption spectra of poly(A) and poly(dA) are essentially identical. The AMP absorption spectrum is similar to the polymer spectra, but subtle differences exist. The absorption maximum of both homopolymers is shifted to the blue by several hundred wavenumbers, while the low energy band edge is red-shifted with respect to AMP. Similar shifts are observed at 77 K [15]. 

Fig. 15. Rotatory artifacts that simulate Cotton effects at an absorption band. The dependence of the rotatory artifact on absorbance of p-cresol solutions placed in series with the same poly-L-glutamic acid solution is shown. The concentration of p-cresol was adjusted to give the total absorbance of chromophore plus polypeptide background that appears with each curve. The rotator, poly-L-glutamic acid, was at concentration of 0.5% at pH 7.0 in a 10-cm cell. The rotations are those actually observed, a, in degrees. The rotatory dispersion at Am 2 coincides almost exactly with that for the polypeptide alone, so that it has been omitted from the figure. At Am 4, an interference filter, /, with maximum transmission between 280 and 285 m/i, was placed in the optical path. The absorption spectrum, in arbitrary units, is typical of p-cresol plus poly-L-glutamic acid background. The emission spectrum is represented in arbitrary units, uncorrected for detector response. (Urnes et al., 1961a.)...

The imaging performance of poly(vinyl cinnamate) when exposed by a medium-pressure mercury arc lamp is poor. This is due to the mismatch between the absorption spectrum of the cinnamoyl group (with absorbance maximum at 280 nm) and the spectral emission of the mercury arc. The absorption spectrum of poly(vinyl cinnamate) does not overlap with most of the strong emission lines of a mercury arc lamp. This problem can be overcome by spectral sensitization, for example, with the addition of 5% of Michler s ketone, or by the replacement of the cinnamoyl group with a chromophore such as in poly(vinyl cinnamylidene acetate) (IV) that absorbs at longer wavelengths. ... 

Figure 28 shows the UV—visible spectra of monomer 72. poly-76, and copolymers 77—80. The monomer spectrum was taken in CHCI3. and the polymer spectra were taken in spin-coated films on a quartz substrate. Compound 75 shows the characteristic broad band at 540 nm due to the tt—jt electronic transition of the conjugated cyclic polyene backbone. Copolymers 77—82 containing a chromophore show two maximum absorption values around 390 and 550 nm due to a pendant chromophore and conjugated cyclic polyene backbone, respectively. 

The conjugation length of poly(3-alkylthiophene)s can be determined from the absorption maximum in the electronic spectrum. Whereas regioregular (i.e., head-tail) poy(3-octylthiophene) (POT) displays a maximum at 442 nm in CHCl3/Freon-113 solution, the absorbance maximum of 504 is blue shifted by 114 to 328 nm. This blue shift could arise from a particularly low molecular weight. 

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