DFT characterization of the optical and redox properties of natural pigments relevant to dye-sensitized solar cells

Natural dye as light-harvesting pigments for quasi-solid-state dye-sensitized solar cells

“…As can be seen from Fig. 3, in acidified distilled water extract, one peak was found around 545 nm maximum absorbance which can be associated to the presence of betalain, betalains in acidic environments have strong absorption in the 400-600 nm range due to the color combination of yellow-orange betaxanthins and redpink betacyanins [19,20]. Differently, acidified ethanol extract of Bougainvillea spectabilis shows two absorption peaks around 655 nm (close to 660 nm) and around 420 nm which might indicate the extract contains chlorophyll mixture which shows an absorption peak in between 400-500 nm and 600-700 nm [21] and also the extract has two small peaks between 476 and 545 nm which could be associated with the presence of betalains [22].…”

“…3 and 4, respectively, probably because of a higher solubility in water-polarity effect. But water extracts did not contain chlorophyll absorption since chlorophylls are relatively polar and are thus normally extracted with methanol, ethanol, acetone or other organic solvents miscible with water [20,23]. The acidity of the extract likely influences the solubility of various dyes, leading to extracts with different compositions.…”

Chlorophyll and Betalain as Light-Harvesting Pigments for Nanostructured TiO<sub>2</sub> Based Dye-Sensitized Solar Cells

“…Conversely to the anthocyanins, that present functional groups (-OH), betalains have the requisite functional groups (-COOH) to bind better to the TiO 2 surface [24][25][26], than the functional group (-OH) present in the anthocyanins. The general structure of betalain is shown in Figure 1a.…”

Plasmonic effect of silver nanoparticles intercalated into mesoporous betalain-sensitized-TiO2 film electrodes on photovoltaic performance of dye-sensitized solar cells

“…Betalain has been regarded by many researchers to be a most promising candidate of choice out of the three most exploited dye pigments from plant sources: chlorophylls, anthocyanins, and betalains [9]. Conversely to the anthocyanins, betalains possess essential functional groups (-COOH) to anchor better to the TiO 2 nanoparticles than the functional groups (-OH) present in anthocyanins [10][11][12][13]. Indeed, the interaction between TiO 2 film and carboxylic functions should bring a stronger electronic coupling and rapid forward and reverse electron transfer reactions [9].…”