35 research outputs found
Threading Through Macrocycles Enhances the Performance of Carbon Nanotubes as Polymer Fillers
In this work we study the reinforcement of polymers by mechanically
interlocked derivatives of single-walled carbon nanotubes (SWNTs). We compare
the mechanical properties of fibers made of polymers and of composites with
pristine single-walled carbon nanotubes (SWNTs), mechanically interlocked
derivatives of SWNTs (MINTs) and the corresponding supramolecular models.
Improvements of both Young's modulus and tensile strength of up to 200 % were
observed for the polystyrene-MINTs samples with an optimized loading of just
0.01 wt.%, while the supramolecular models with identical chemical composition
and loading showed negligible or even detrimental influence. This behavior is
found for three different types of SWNTs and two types of macrocycles.
Molecular dynamics simulations show that the polymer adopts an elongated
conformation parallel to the SWNT when interacting with MINT fillers,
irrespective of the macrocycle chemical nature, whereas a more globular
structure is taken upon facing with either pristine SWNTs or supramolecular
models. The MINT composite architecture thus leads to a more efficient
exploitation of the axial properties of the SWNTs and of the polymer chain at
the interface, in agreement with experimental results. Our findings demonstrate
that the mechanical bond imparts distinctive advantageous properties to SWNT
derivatives as polymer fillers.Comment: 39 pages, 19 figure
Oxygen vacancies and interfaces enhancing photocatalytic hydrogen production in mesoporous CNT/TiO2 hybrids
We demonstrate a unique route towards hierarchical assemblies of mesoporous TiO2 and CNT/TiO2 photocatalysts by a combination of electrospinning and sol\u2013gel methods. The resulting materials exhibit a mesoporous network of highly crystalline, well-connected inorganic nanocrystals with an order of magnitude higher photocatalytic activity than individualised TiO2 nanoparticles. The in-situ combination of small amounts of MWCNTs with TiO2 to form an electrospun CNT/TiO2 hybrid further enhanced the oxide photoactivity considerably, reaching hydrogen evolution rates of 1218 \u3bcmol/h in water splitting in the presence of sacrificial reagents under UV irradiation. We also discuss the effect of oxygen vacancies on the oxide crystallisation and phase transformation. These vacancies lead to inter-bandgap states and a lower flat band potential that facilitates the photocatalytic process
Gas-to-nanotextile: high-performance materials from floating 1D nanoparticles
Suspended in the gas phase, 1D inorganic nanoparticles (nanotubes and
nanowires) grow to hundreds of microns in a second and can be thus directly
assembled into freestanding network materials. The corresponding process
continuously transforms gas precursors into aerosols into aerogels into
macroscopic nanotextiles. By enabling the assembly of very high aspect ratio
nanoparticles, this processing route has translated into high-performance
structural materials, transparent conductors and battery anodes, amongst other
embodiments. This paper reviews progress in the application of such
manufacturing process to nanotubes and nanowires. It analyses 1D nanoparticle
growth through floating catalyst chemical vapour deposition (FCCVD), in terms
of reaction selectivity, scalability and its inherently ultra-fast growth rates
(107-108 atoms per second) up to 1000 times faster than for substrate CVD. We
summarise emerging descriptions of the formation of aerogels through
percolation theory and multi-scale models for the collision and aggregation of
1D nanoparticles. The paper shows that macroscopic ensembles of 1D
nanoparticles resemble textiles in their porous network structure, high
flexibility and damage-tolerance. Their bulk properties depend strongly on
inter-particle properties and are dominated by alignment and volume fraction.
Selected examples of nanotextiles that surpass granular and monolithic
materials include structural fibres with polymer-like toughness, transparent
conductors, and slurry-free composite electrodes for energy storage.Comment: 36 pages, 25 figure
Interfacial charge transfer in functionalized multi-walled carbon nanotube@TiO2 nanofibres
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\u2032,N\u2032-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