Cross-sectional transmission electron microscopy micrographs, atomic force microscopy images, and UV-vis spectra reveal significant differences in the size and distribution of the AgNPs into the films as well as the maximal absorbance and wavelength position of the localized surface plasmon resonance absorption bands before and after thermal post-treatment.
Furthermore, many polyphenols including flavonols demonstrated maximal absorbance at the wavelengths between 270 and 290 nm [ 52].
Other than those facts, flavonols and various polyphenols have been shown to exert maximal absorbance at variable wavelengths between 270 and 290 nm.
Although gold colloid in this size range has maximal absorbance in the visible wavelengths, there are several variants of AuNPs that are of similar size 25-600 nm) and absorb optimally in the NIR region, permitting translation of this delivery method for PTT.
The resulting visual pigments vary in spectral sensitivity, with the wavelength of maximal absorbance (λmax) ranging from the ultraviolet (UV) to the yellow.
The wavelength of maximal absorbance of a visual pigment (λmax) is determined by the interactions between the opsin protein and its chromophore, via a process known as spectral tuning [ 14].
AlamarBlue™ (Serotec, Oxford, UK) was added to the culture medium at a final concentration of 10% (v-v) and after 24 hours, absorbance was measured at the two different wavelengths of maximal absorbance of the reduced and oxidized forms of AlamarBlue™, 570 and 600 nm using Victor 1420 Multilabel Counter (Perkin-Elmer, Wellesley, USA).
The wavelengths showing maximal absorbance changes between oxy-Ngb and met-Ngb species were used to determine the autoxidation rates.
The value obtained for both compounds (33 600 ± 200 M–1cm–1) was the same within experimental error; however, the wavelengths of maximal absorbance were different (280 nm for 3 and 300 nm for 4).
The regeneration of ATP from PEP and ADP was coupled to the oxidation of NADH and was observed as a decrease in absorbance at 380 nm (the maximal absorbance for NADH is at 340 nm, but 380 nm wavelength was used so that the signal remained within the linear range of the spectrophotometer for the duration of the experiment).
