Interfacial charge transfer in functionalized multi-walled carbon nanotube@TiO₂ nanofibres

Abstract

A new insight into photoinduced charge transfer processes across carbon nanotube@TiO interfaces has been gained based on experimental details from transient absorption spectroscopy. We show that photoinduced, interfacial hole transfer to carboxylic acid-functionalized multiwalled carbon nanotubes (oxMWCNTs) from TiO results in hole-doped oxMWCNTs and reduced TiO. The latter is inferred from femto- and nanosecond transient absorption spectroscopy performed with oxMWCNT@TiO dispersions and complemented with investigations using methyl viologen and N,N,N',N'-tetramethyl-p-phenylenediamine as an electron scavenger and a hole scavenger, respectively. The results of ultraviolet photoemission spectroscopy (UPS) of the compounds corroborate the findings, highlighting the strong coupling between oxMWCNTs and TiO in these hybrids.

Towards Long‐Term Thermal Stability of Dye‐Sensitized Solar Cells Using Multiwalled Carbon Nanotubes

“…The Raman modes of the pure anatase phase are observed at 144 (E g1 ), 395 (B 1g ), 514 (A 1g ), and 641 cm −1 (E g3 ). These modes are absent in the observed spectra of the two samples before thermal aging owing to the adsorption of the dye molecules on the TiO 2 surface . After thermal aging, three bands are observed in the spectrum of the control cell at about 390, 508, and 635 cm −1 , which arise from a slight shift in the Raman peaks of the anatase phase.…”

“…These modes are absenti nt he observed spectra of the two samples before thermala ging owing to the adsorption of the dye molecules on the TiO 2 surface. [45][46][47][48][49] After thermal aging, three bands are observed in the spectrum of the control cell at about 390,5 08, and 635 cm À1 ,w hich arise from as light shifti n the Raman peaks of the anatase phase.T his is directly related to the heat-induced desorption of the dye from the TiO 2 particles during the aging test. [43,45,46] Generally,there is an equilibrium between the dye dissolved in the electrolyte and the dye adsorbed on the surface of the TiO 2 .T he dye adsorption/desorptione quilibrium kinetics are influenced by temperature, and more desorption of the dye from the surface of TiO 2 can arise at high temperatures, that is, around 80 8C.…”

Preparation and Characterization of Defective TiO2. The Effect of the Reaction Environment on Titanium Vacancies Formation

“…The PL emission of maximum intensity in the high-energy region was observed at 400 nm for all samples, which was equal to 3.10 eV. It corresponds to indirect band-to-band recombination across the bandgap [59]. Other emission peaks in the visible light region were detected at 485 nm (2.56 eV) and 530 nm (2.24 eV).…”

“…Other emission peaks in the visible light region were detected at 485 nm (2.56 eV) and 530 nm (2.24 eV). The emission in the 380-700 nm range could be assigned to the transition of electrons from the defect states to the valence band of titanium(IV) oxide [60] as well as trapped holes [59]. The emission in the blue region at 480 nm is related to indirect recombination via defects [60].…”

Embedded carbon in a carbon nitride hollow sphere for enhanced charge separation and photocatalytic water splitting

“…Graphitic carbon allotropes such as quantum dots, 46,47 graphene, [48][49][50][51] carbon nanotubes 52,53 and carbon black 54 were reported to be able to accept the photogenerated electrons from the conduction band of a photocatalyst, thus accelerating charge separation. A strong interaction between the carbon allotropes and the matrix is usually highly required for efficient interfacial charge transfer.…”