Squaraine-sensitized composite of a reduced graphene oxide/TiO₂ photocatalyst: π–π stacking as a new method of dye anchoring

Abstract

We synthesized a near infra-red (NIR) absorbing squaraine dye (VJ-S) showing a strong absorption and emission. Photocatalytic activity of VJ-S/r-NGOT in visible light wavelengths is much higher than that of r-NGOT alone.

Visible light sensitization of TiO2 nanoparticles by a dietary pigment, curcumin, for environmental photochemical transformations

“…[1][2][3] Various strategies have been attempted to increase the visible light absorption of wide bandgap semiconductors such as doping with metal or nonmetal elements, 4-8 surface deposition of noble metals for plasmon effects, [9][10][11] and coupling with smaller bandgap semiconductors, 12-14 quantum dots 15,16 and dyes. [17][18][19] Among them, dye sensitization has been successfully demonstrated for many applications such as photocatalytic hydrogen production 20,21 and dye-sensitized solar cells. 22 In particular, ruthenium-based dyes have been widely used because of their high visible light absorption efficiency and stability in acidic aquatic environments.…”

Photosensitive Hybrid Nanostructured Materials: The Big Challenges for Sunlight Capture

“…Squaraine dyes, based on squaric acid (diketocyclobutenediol), are gaining interest in several applications, including red light and NIR harvesting in DSCs and organic solar cells, owing to their high absorptivity in the region around 600-800 nm and to their easy structure tunability [68]; nonetheless, their use in photocatalytic systems has been limited. Two examples are: a zwitterionic squaraine dye, anchored through π-π interaction to graphene in TiO 2 /rGO nanocomposites, active in H 2 production [69], and squaraines featuring dodecyl spacers and carboxylic or phosphonate anchoring groups, coupled with Pt/TiO 2 or Re(I)/TiO 2 to obtain photocatalysts tested in H 2 evolution and CO 2 reduction [68].…”

“…Indeed, in some cases, both pathways have a similar probability to be active, even if one can be kinetically favored. In addition, although dyes are commonly associated with indirect CT, some visible light-absorbing molecules are predicted to prefer a direct electron injection [49,69,100]. Direct photosensitization should result in a more efficient electron transfer to the conduction band; on the other hand, the back electron transfer (recombination) might also be favored [97].…”

Pyrrolyl Squaraines–Fifty Golden Years

“…It has also been possible that the some pyrrole-derived polysquaraines, such as that derived from pyrrole itself, can be used as black colour materials in toners and inks just because they are produced as black intractable powders [40]. One interesting study improved the holographic data storage characteristics of a known photopolymer by adding the polysquaraine derived from 3-octylpyrrole [46]; there is one reported example of near-infrared thermochromism in a pyrrole-derived polysquaraine [62], and one reporting improved photocatalytic activity with the inclusion of a pyrrolyl squaraine dye [68].…”

“…Electrical conductivity measurements have exclusively been undertaken on pyrrole-derived polysquaraines. However, pyrrolyl squaraine dyes have undergone cyclic voltammograms to measure their redox chemistry [23,33,39,49,51,53,57,63,68] as have pyrrole-derived poysquaraines [30,41,49,50,54]. It is also worth noting that current density verses voltage (or J-V) curves have been measured, particularly on organic photovoltaics containing pyrrolyl squaraines [35,45,48,51,67].…”