Figure 9. Photoluminescence spectra of ds-DNA polymerized molecules in tris-HCl buffer, recording with excitation X = 337 nm (curve 1) without UV irradiation, and after UV irradiation at X = 337 nm during 60 min (curve 2), and for next measurements (curves 3,4) with excitation X = 365 nm before (curve 3) and after UV irradiation at X = 365 nm during 60 min (curve 4).
These ds-DNA molecules emit light across the visible range spectrum which is broad. PL spectra ranges from 400 (3.10) to 600 nm (2.06 eV) (Fig. 9). The PL spectral ranges with these wavelengths were obtained for ds-DNA polymerized molecules in network layer absorbed on a nanostructured Si surface  with the intensive PL peak at 2.8 - 2.9 eV. As seen from Fig. 1, UV induced changes in PL spectra are:
- decrease of the intensity of emission at 400-600 nm range (less decreasing of one is at 520 - 600 nm range);
- weak increase of intensity of emission at 450-500 nm range after beginning UV irradiation X = 337 nm during 60 min and next recording of these spectra;
- narrowing of PL bands after UV irradiation because of moving the left edges of spectra to longer wavelengths range;
- the change of PL spectra shape at 400-520 nm range with more observable maxima appearance (Fig. 10).
The UV-induced changes in PL spectra the decomposition of the photoluminescence and absorption spectra, before and after UV irradiation are shown in Fig. 10. The summation curve contains overlays on the experimentally measured spectra. Residuals are scarcely evident.
These ds-DNA polymerized molecules have the absorption and emission spectra well separated (Fig. 9). The absorption of emitted light is now week (these spectra are similar to the semiconductors polymer ). They have strong absorption coefficients (Fig. 3). Intensive emission is now possible through participation of electronic states corresponding to molecular orbital systems in the nucleotide base pairs , and sides of the ladder having a periodic structure with alternating sugar and phosphate groups . Note that a part of electron levels that determine PL spectrum can correspond the formation of DNA molecular networks (Fig.
From the summarized emission sub-bands for PL spectra (Fig. 10 a,b) we detected UV induced shifts of maxima positions in sub-bands (440^ 442, 454^456, 467^470 nm) forming with maxima at 437 and 452 nm (Fig. 10), and stimulating the shift of maximum at 437 ^ 452 nm. In Fig. 10 it's marked as damage. The destruction of sub-band with maximum at 466 nm (2.66 eV) after UV irradiation (Fig. 9, curves 3,4) was also seen.
The quantitative estimation of UV-induced changes of electronic state density can be determined from the conductivity of ds-DNA polymerized molecules in the network layer.
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