A new insight into photoinduced charge transfer processes across carbon nanotube@TiO₂ 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 TiO₂ results in hole-doped oxMWCNTs and reduced TiO₂. The latter is inferred from femto- and nanosecond transient absorption spectroscopy performed with oxMWCNT@TiO₂ 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 TiO₂ in these hybrids.

In this research work, the gas phase CO2 photocatalytic reduction using water as electron donor has been performed using hierarchical assemblies of mesoporous TiO2 1-D nanofibres synthesised by a combination of electrospinning and sol–gel methods. In order to compare the effect of the crystallisation step on oxygen vacancies and conductivity, two different annealing conditions have been undertaken: under a high Ar flow (“TiO2 Fibres-A” sample) and under static Ar (“TiO2 Fibres B” sample). Moreover, these materials have been compared with individualised TiO2 nanoparticles prepared by a sol-gel procedure. CO and H2 are detected as major products with all photocatalysts, with lower amounts of CH4 and CH3OH. The TiO2 nanofibres exhibit better results than the sol-gel photocatalyst, behaviour that may be ascribed to an improved nanocrystals connection, which favours a fast charge transport along the grain boundaries, as measured by electrochemical impedance spectroscopy (EIS). The highest CO2 reduction activity is achieved with the TiO2 Fibres B catalyst, which gives rise to ca. 4 and 2.5 times higher H2 and CO production, respectively, than the TiO2 Fibres-A one. This sample is composed of a mixture of anatase and rutile crystalline phases (80:20), leading to a decrease in the electron-hole recombination rate observed by photoluminescence (PL) measurements

Electrospun TiO₂ single-nanofibres are employed as photodetectors with state-of-the-art performance: high sensitivity in the UV (responsivity of 90 A W⁻¹ for 375 nm wavelength), response time of ∼5 s and light polarisation sensitivity.

Hybridisation is a powerful strategy towards the synthesis of next generation multifunctional materials for environmental and sustainable energy applications. Here, we report a new inorganic/nanocarbon hybrid material prepared by atomically controlled deposition of a monocrystalline TiO₂ layer that conformally coats a macroscopic carbon nanotube (CNT) fiber. Through X-ray diffraction, Raman spectroscopy and photoemission spectroscopy we detect the formation of a covalent Ti–O–C bond at the TiO₂/CNT interface and a residual strain of approximately 0.7–2%, which is tensile in TiO₂ and compressive in the CNT. It arises after deposition of the amorphous oxide onto the CNT surface previously functionalized by the oxygen plasma used in ALD. These features are observed in samples of different TiO₂ thicknesses, in the range from 10 to 80 nm. Ultraviolet photoemission spectroscopy on a 20 nm-thick TiO₂ coated sample gives a work function of 4.27 eV, between that of TiO₂ (4.23 eV) and the CNT fiber (4.41 eV), and the presence of new interband gap states that shift the valence band maximum to 1.05 eV below the Fermi level. Photoelectrochemical measurements demonstrate electron transfer from TiO₂ to the CNT fiber network under UV irradiation. Electrochemical impedance spectroscopy measurements reveal a low resistance for charge transfer and transport, as well as a large capacitance. Our results point to the fact that these hybrids, in which each phase has nanometric thickness and the “current collector” is integrated into the material, are very different from conventional electrodes and can provide a number of superior properties.

The assembly of 3-dimensional covalent organic frameworks on the surface of carbon nanotubes is designed and successfully developed for the first time via the hybridization of imine-based covalent organic frameworks (COF-300) and oxidized MWCNTs by one-pot chemical synthesis. The resulting hybrid material ox-MWCNTs@COF exhibits a conformal structure that consists of a uniform amorphous COF layer covering the ox-MWCNT surface. The measurements of individual hybrid nanotube mechanical strength performed with atomic force microscopy provide insights into their stability and resistance. The results evidence a very robust hybrid tubular nanostructure that preserves the benefits obtained from COF, such as CO₂ adsorption. Further digestion of the organic structure with aniline enables the study of the interplay between the hybrid interface and its nanomechanics. This new hybrid nanomaterial presents exceptional mechanical and electrical properties, merging the properties of the CNT template and COF-300.