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In order to get a better insight into the relationship between molecular structure and photovoltaic performance, six monoazo dye molecules containing benzoic and cinnamic acid moieties were synthesized and their photovoltaic properties were studied. Three of them have not been previously used in solar cells. Spectroscopic measurements of the investigated compounds coupled with theoretical calculations were performed. Short-circuit current density, open-circuit voltage, and fill-factor were determined. It was found that a larger amount of short-circuit current density will be generated if the HOMO-LUMO energy gap is lower, determined by the stability of the molecule and the electronic effect of the donor moiety. Among both series of synthesized dye molecules, the highest obtained values of short-circuit current density were achieved with (2-hydroxynaphthalene-1-ylazo)benzoic acid and (2-hydroxynaphthalene-1-ylazo)cinnamic acid, and thus they were regarded as promising candidates for application in dye-sensitized solar cells.

Disazo pyridone dye, 4-methyl-2,6-dioxo-5-(2-(4-(phenyldiazenyl)phenyl)hydrazono)-1,2,5,6-tetrahydropyridine-3-carbonitrile, is synthesised and thoroughly characterised by a combination of experimental and computational approaches. Fourier Transform-infrared and nuclear magnetic resonance (NMR) spectra prove the existence of the hydrazone form in the solid state and in dimethyl sulphoxide, which is also supported by vibrational and NMR theoretical studies. Ultraviolet (UV) spectral properties, as well as solvatochromism in 19 solvents of different polarity, are investigated. In most of the solvents, the dye is solely present in the hydrazone form, whereas in certain solvents, an acid-base equilibrium exists. Excellent agreement between computational and experimental UV-visible data was established. Frontier Molecular Orbital analysis was performed and proved the existence of intramolecular charge transfer through the dye molecule. A molecular electrostatic potential surface was plotted over the optimised geometry to lighten the reactivity of the investigated molecule.

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Halochromic (pH-responsive) material was obtained by dyeing functionalized viscose fabric with a crude extract from Streptomyces sp. strain NP4. The functionalization of the pristine fabric before dyeing was performed to make cellulose susceptible to coloration with NP4 extract. Two combined pre-treatment protocols were used, oxidation to obtain dialdehyde cellulose and chitosan deposition onto pristine and oxidized cellulose. Functionalization by both protocols made viscose susceptible to dyeing with the notion that the latter deposition of chitosan produced a darker shade on the material. Dyed fabrics showed visual pH responsiveness in the range pH 4-10, with a color change from pink to red (pH 4 to pH 7) and a major color change from red to blue (pH 7 to pH 10) whereby fabric was tested and could withstand 10 color-changing cycles. Cytotoxicity assay con rmed the non-toxic nature of dyed material, which indicates its possible use as wound dressing's indicators.

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