Rationalization of dye uptake on titania slides for dye-sensitized solar cells by a combined chemometric and structural approach / Valentina Gianotti; Giada Favaro; Luca Bonandini; Luca Palin; Gianluca Croce; Enrico Boccaleri; Emma Artuso; Wouter Van Beek; Claudia Barolo; Marco Milanesio. -In: CHEMSUSCHEM. -ISSN 1864-ISSN -5631. -7:11(2014, pp. 3039-3052. Original Citation:Rationalization of dye uptake on titania slides for dye-sensitized solar cells by a combined chemometric and structural approach A model photosensitizer (D5) for application in Dye-sensitized Solar Cells has been studied by a combination of X-ray diffraction, theoretical calculations and spectroscopic/chemometric methods. The conformational stability and flexibility of D5 and molecular interactions between adjacent molecules was characterized to obtain the driving forces governing D5 uptake and grafting process, and to infer the most likely arrangement of the molecules on the surface of titanium oxide. A spectroscopic/chemometric approach was then used, yielding information about the correlations between three variables governing the uptake itself: D5 concentration, dispersant (chenodeoxycholic acid, CDCA) concentration and contact time. The obtained regression model shows that large uptakes can be obtained at high D5 concentrations, when CDCA is present and contact time is high, or, in absence of CDCA, only if contact time is smaller, suggesting how to optimize dye uptake and photovoltaic device preparation.

Layered double hydroxides are versatile materials used for intercalating bioactive molecules, both in pharmaceutical and cosmetic fields, with the purpose of protecting them from degradation, enhancing their water solubility to increase bioavailability, and/or obtaining modified release properties. The crystal chemistry of hydrotalcite-like compounds is investigated by X-ray powder diffraction (XRPD) and hyphenated TGA-GC-MS to shed light on the mechanisms involved in ion exchange and absorption of contaminants, mainly carbonate anions. XRPD demonstrated that the presence of carbonate is able to drive the intercalation of organic molecules into LDH, since CO3 contaminated samples tend to assume d-spacing roughly multiple of LDH-CO3 d-spacing. TGA-GC-MS allowed distinguishing and quantifying intercalated and surface adsorbed organic molecules, confirming the presence and amount of carbonate, especially at low (ppm) concentrations and separating the different types and strength of adsorption, in relation with the temperature of elimination. Also the importance of the intercalation method on the carbonate absorption was examined. This is probably due to the fact that the larger molecules leave some voids in the packing and the carbonate can occupy these voids during the intercalation. Finally the presence of adsorbed and not intercalated organic guest was quantified by TGA-GC-MS.

The Inside Cover picture underlines the link between solar energy and a sustainable economy. The sunny sky represents the environment in which we live and the dye‐sensitized solar cell one of the tesserae needed to build the puzzle of a sustainable future. The optimization of DSC modules is facilitated through the chemical sciences represented by the molecule of D5, the topic of the paper, and through a deep comprehension of the molecular mechanism, represented by the 3D energetic landscape obtained by a combination of theoretical and experimental techniques. More details can be found in the Full Paper by Gianotti et al. on page 3039 (DOI: ).