4 research outputs found
Multiple Hydrogen Bond Interactions in the Processing of Functionalized Multi-Walled Carbon Nanotubes
In a set of unprecedented experiments combining ābottom-upā and ātop-downā approaches, we report the engineering of patterned surfaces in which functionalized MWCNTs have been selectively adsorbed on polymeric matrices as obtained by microlithographic photo-cross-linking of polystyrene polymers bearing 2,6-di(acetylamino)-4-pyridyl moieties (<b>PS1</b>) deposited on glass or Si. All patterned surfaces have been characterized by optical, fluorescence, and SEM imaging techniques, showing the local confinement of the CNTs materials on the polymeric microgrids. These results open new possibilities toward the controlled manipulation of CNTs on surfaces, using H-bonding self-assembly as the main driving force
Nitrogen-Doped Silver-Nanoparticle-Decorated Transition-Metal Dichalcogenides as Surface-Enhanced Raman Scattering Substrates for Sensing Polycyclic Aromatic Hydrocarbons
The
modification of transition-metal dichalcogenides (TMDs), incorporating
nitrogen (N) doping and silver nanoparticles (Ag<sub>NPs</sub>) decoration
on the skeleton of exfoliated MoS<sub>2</sub> and WS<sub>2</sub>,
was accomplished. The preparation of N-doped and Ag<sub>NPs</sub>-decorated
TMDs involved a one-pot treatment procedure in a vacuum-sputtering
chamber under N plasma conditions and in the presence of a silver
(Ag) cathode as the source. Two different deposition times, 5 and
10 s, respectively, were applied to obtain N-doped with Ag<sub>NPs</sub>-decorated MoS<sub>2</sub> and WS<sub>2</sub> hybrids, abbreviated
as N5-MoS<sub>2</sub>/Ag<sub>NPs</sub>, N10-MoS<sub>2</sub>/Ag<sub>NPs</sub>, N5-WS<sub>2</sub>/Ag<sub>NPs</sub>, and N10-WS<sub>2</sub>/Ag<sub>NPs</sub>, respectively, for each functionalization time.
The successful incorporation of N as the dopant within the lattice
of exfoliated MoS<sub>2</sub> and WS<sub>2</sub> as well as the deposition
of Ag<sub>NPs</sub> on their surface, yielding N-MoS<sub>2</sub>/Ag<sub>NPs</sub> and N-WS<sub>2</sub>/Ag<sub>NPs</sub>, was manifested through
extensive X-ray photoelectron spectroscopy measurements. The observation
of peaks at ā¼398 eV derived from covalently bonded N and the
evolution of a doublet of peaks at ā¼370 eV guaranteed the presence
of Ag<sub>NPs</sub> in the modified TMDs. Also, the morphologies of
N-MoS<sub>2</sub>/Ag<sub>NPs</sub> and N-WS<sub>2</sub>/Ag<sub>NPs</sub> were examined by transmission electron microscopy, which proved
that Ag deposition resulted in nanoparticle growth rather than the
creation of a continuous metal film on the TMD sheets. Next, the newly
developed hybrid materials were proven to be efficient surface-enhanced
Raman scattering (SERS) platforms by achieving the detection of Rhodamine
B (RhB). Markedly, N10-MoS<sub>2</sub>/Ag<sub>NPs</sub> showed the
highest sensitivity for detecting RhB at concentrations as low as
10<sup>ā9</sup> M. Charge-transfer interactions between RhB
and the modified TMDs, together with the polarized character of the
system causing dipoleādipole coupling interactions, were determined
as the main mechanisms to induce the Raman scattering enhancement.
Finally, polycyclic aromatic hydrocarbons such as pyrene, anthracene,
and 2,3-dihydroxynaphthalene, coordinated via ĻāS interactions
with N-MoS<sub>2</sub>/Ag<sub>NPs</sub>, were screened with high sensitivity
and reproducibility. These findings highlight the excellent functionality
of the newly developed N-MoS<sub>2</sub>/Ag<sub>NPs</sub> and N-WS<sub>2</sub>/Ag<sub>NPs</sub> hybrid materials as SERS substrates for
sensing widespread organic and environmental pollutants as well as
carcinogen and mutagen species
A Simple Road for the Transformation of Few-Layer Graphene into MWNTs
We report the direct formation of multiwalled carbon
nanotubes
(MWNT) by ultrasonication of graphite in dimethylformamide (DMF) upon
addition of ferrocene aldehyde (Fc-CHO). The tubular structures appear
exclusively at the edges of graphene layers and contain Fe clusters.
Fc in conjunction with benzyl aldehyde, or other Fc derivatives, does
not induce formation of NT. Higher amounts of Fc-CHO added to the
dispersion do not increase significantly MWNT formation. Increasing
the temperature reduces the amount of formation of MWNTs and shows
the key role of ultrasound-induced cavitation energy. It is concluded
that Fc-CHO first reduces the concentration of radical reactive species
that slice graphene into small moieties, localizes itself at the edges
of graphene, templates the rolling up of a sheet to form a nanoscroll,
where it remains trapped, and finally accepts and donates unpaired
electron to the graphene edges and converts the less stable scroll
into a MWNT. This new methodology matches the long held notion that
CNTs are rolled up graphene layers. The proposed mechanism is general
and will lead to control the production of carbon nanostructures by
simple ultrasonication treatments
Knitting the Catalytic Pattern of Artificial Photosynthesis to a Hybrid Graphene Nanotexture
The artificial leaf project calls for new materials enabling multielectron catalysis with minimal overpotential, high turnover frequency, and long-term stability. Is graphene a better material than carbon nanotubes to enhance water oxidation catalysis for energy applications? Here we show that functionalized graphene with a tailored distribution of polycationic, quaternized, ammonium pendants provides an sp<sup>2</sup> carbon nanoplatform to anchor a totally inorganic tetraruthenate catalyst, mimicking the oxygen evolving center of natural PSII. The resulting hybrid material displays oxygen evolution at overpotential as low as 300 mV at neutral pH with negligible loss of performance after 4 h testing. This multilayer electroactive asset enhances the turnover frequency by 1 order of magnitude with respect to the isolated catalyst, and provides a definite up-grade of the carbon nanotube material, with a similar surface functionalization. Our innovation is based on a noninvasive, synthetic protocol for graphene functionalization that goes beyond the ill-defined oxidationāreduction methods, allowing a definite control of the surface properties