Light Control over Chirality Selective Functionalization of Substrate Supported Carbon Nanotubes

in Journal of Physical Chemistry. C, Nanomaterials and interfaces (2022), 126(23), 9803-9812

Diazonium reactions with carbon nanotubes form optical sp3 defects that can be used in optical and electrical circuits. We investigate a direct on-device reaction supported by confined laser irradiation ... [more ▼]

Diazonium reactions with carbon nanotubes form optical sp3 defects that can be used in optical and electrical circuits. We investigate a direct on-device reaction supported by confined laser irradiation and present a technique where an arbitrary carbon nanotube can be preferentially functionalized within a device by matching the light frequency with its transition energy. An exemplary reaction was carried out between (9,7) nanotube and 4-bromobenzenediazonium tetrafluoroborate. The substrate supported nanotubes of multiple semiconducting chiralities were locally exposed to laser light while monitoring the reaction kinetics in situ via Raman spectroscopy. The chiral selectivity of the reaction was confirmed by resonant Raman spectroscopy, reporting a 10 meV E22 transition energy red-shift only of the targeted species. We further demonstrated this method on a single tube (9,7) electroluminescent device and show a 25 meV red-shifted emission of the ground state E11 compared to the emission from the pristine tubes. [less ▲]

An Atomistic Study of the Thermoelectric Signatures of CNT Peapods

in Journal of Physical Chemistry. C, Nanomaterials and interfaces (2021), 125(25), 1372113731

Carbon-based nanomaterials such as carbon nanotubes (CNTs) have a great potential for applications in the development of high performance thermoelectric (TE) materials because of their low-cost and for ... [more ▼]

Carbon-based nanomaterials such as carbon nanotubes (CNTs) have a great potential for applications in the development of high performance thermoelectric (TE) materials because of their low-cost and for being environmentally friendly. Pristine nanotubes have, however, high electrical and thermal conductivities so that further nanoscale engineering is required to exploit them as TE materials. We investigate electron and phonon transport in CNT peapods to elucidate their potential advantage over pristine CNTs as basic TE elements. We show that the electron and phonon transport properties are sensitively modified by C60 encapsulation, when the CNT–C60 intermolecular interaction is strong enough to produce a periodic buckling of the CNT walls. Moreover, the phonon transmission is strongly suppressed at low and high frequencies, leading to a reduction of the phonon contribution to the overall thermal conductance. A similar effect has also been observed in the recently proposed phononic metamaterials. We obtain in general a larger TE figure of merit over a broad temperature range for the CNT peapod when compared with the pristine CNT, achieving an increase by a factor of 2.2 at 575 K. Our findings show an alternative route for the enhancement of the TE performance of CNT-based devices. [less ▲]

Subtle Fluorination of Conjugated Molecules Enables Stable Nanoscale Assemblies on Metal Surfaces

in Journal of Physical Chemistry. C, Nanomaterials and interfaces (2018), 122(33), 10

In molecular self-assembly on surfaces, the structure is governed by the intricate balance of attractive and repulsive forces between molecules as well as between molecules and the substrate. Frequently ... [more ▼]

In molecular self-assembly on surfaces, the structure is governed by the intricate balance of attractive and repulsive forces between molecules as well as between molecules and the substrate. Frequently, repulsive interactions between molecules adsorbed on a metal surface dominate in the low-coverage regime, and dense self-assembled structures can only be observed close to full monolayer coverage. Here, we demonstrate that fluorination at selected positions of conjugated molecules provides for sufficiently strong, yet nonrigid, H···F bonding capability that (i) enables the formation of stable nanoscale molecular assemblies on a metal surface and (ii) steers the assemblies’ structure. This approach should be generally applicable and will facilitate the construction and study of individual nanoscale molecular assemblies with structures that are not attainable in the high-coverage regime. [less ▲]

First-Principles Study of Alkoxides Adsorbed on Au(111) and Au(110) Surfaces: Assessing the Roles of Noncovalent Interactions and Molecular Structures in Catalysis

in Journal of Physical Chemistry. C, Nanomaterials and interfaces (2017), 121

Microscopic understanding of molecular adsorption on catalytic surfaces is crucial for controlling the activity and selectivity of chemical reactions. However, for complex molecules, the adsorption ... [more ▼]

Microscopic understanding of molecular adsorption on catalytic surfaces is crucial for controlling the activity and selectivity of chemical reactions. However, for complex molecules, the adsorption process is very systemspecific and there is a clear need to elaborate systematic understanding of important factors that determine catalytic functionality. Here, we investigate the binding of eight molecules, including seven alkoxides and one carboxylate, on the Au(111) and Au(110) surfaces. Our density-functional theory calculations including long-range van der Waals interactions demonstrate the significant role of these “weak” noncovalent forces on the adsorption structures, energetics, and relative adsorbate stabilities. Interestingly, the binding energy trends are insensitive to the surface structure. Instead, the adsorption stability depends strongly on the structural and chemical characteristics of the molecules: linear vs branching configurations, number of unsaturated C−C bonds, bidentate adsorption, and the presence of electronegative atoms. Our calculations help establish the influence of individual and collective chemical factors that determine the catalytic selectivity of alkoxides. [less ▲]

Single Second Laser Annealed CuInSe2 Semiconductors from Electrodeposited Precursors as Absorber Layers for Solar Cells

in Journal of Physical Chemistry. C, Nanomaterials and interfaces (2014), 118 (3)

Interaction of Isophorone with Pd(111): A Combination of Infrared Reflection-Absorption Spectroscopy, Near-Edge X-ray Absorption Fine Structure, and Density Functional Theory Studies

in Journal of Physical Chemistry. C, Nanomaterials and interfaces (2014), 118(48), 27833-27842

Atomistic level understanding of interaction of alpha,beta-unsaturated carbonyls with late transition metals is a key prerequisite for rational design of new catalytic materials with the desired ... [more ▼]

Atomistic level understanding of interaction of alpha,beta-unsaturated carbonyls with late transition metals is a key prerequisite for rational design of new catalytic materials with the desired selectivity toward C-C or C-O bond hydrogenation. The interaction of this class of compounds with transition metals was investigated on alpha,beta-unsaturated ketone isophorone on Pd(111) as a prototypical system. In this study, infrared reflectionabsorption spectroscopy (IRAS), near-edge X-ray absorption fine structure (NEXAFS) experiments and density functional theory calculations including van der Waals interactions (DFT+vdW) were combined to obtain detailed information on the binding of isophorone to palladium at different coverages and on the effect of preadsorbed hydrogen on the binding and adsorption geometry. According to these experimental observations and the results of theoretical calculations, isophorone adsorbs on Pd(111) in a flat-lying geometry at low coverages. With increasing coverage, both C-C and C-O bonds of isophorone tilt with respect to the surface plane. The tilting is considerably more pronounced for the C-C bond on the pristine Pd(111) surface, indicating a prominent perturbation and structural distortion of the conjugated p system upon interaction with Pd. Preadsorbed hydrogen leads to higher tilting angles of both p bonds, which points to much weaker interaction of isophorone with hydrogen-precovered Pd and suggests the conservation of the in-plane geometry of the conjugated pi system. The results of the DFT+vdW calculations provide further insights into the perturbation of the molecular structure of isophorone on Pd(111). [less ▲]

Carbon Nanotube Wins the Competitive Binding over Proline-Rich Motif Ligand on SH3 Domain

in Journal of Physical Chemistry. C, Nanomaterials and interfaces (2011), 115(25), 12322-12328

The binding competition between a proline-rich motif (PRM) ligand and a hydrophobic nanoparticle, the single-wall carbon nanotube (SWCNT), at the binding pocket of SH3 domain, has been investigated by ... [more ▼]

The binding competition between a proline-rich motif (PRM) ligand and a hydrophobic nanoparticle, the single-wall carbon nanotube (SWCNT), at the binding pocket of SH3 domain, has been investigated by molecular dynamics simulations. It is found that the SWCNT has a very high probability of occupying the binding pocket of the SH3 domain, which prevents the PRM ligand from binding to the pocket. The binding free energy landscapes show that the SWCNT has similar to 0.6 kcal/mol stronger binding affinity than the ligand in the three-way binding competition (SWCNT + ligand + protein). The potent binding affinity between the SWCNT and the SH3 domain is shown to be mainly from the pi-pi stacking interactions between the CNT and aromatic residues in the binding pocket. Our findings show that the existence of hydrophobic particles can greatly reduce the possibility of the regular binding of the ligand with the target protein, suggesting potential toxicity to proteins by hydrophobic nanoscale particles. [less ▲]

Desorption of H2O from Flat and Stepped Pt(111)

in Journal of Physical Chemistry. C, Nanomaterials and interfaces (2009), 113(2), 691-697

To investigate the effect of steps on H2O binding on a nominal Pt(111) surface, we used thermal desorption spectroscopy of water adsorbed on purposefully nanostructured surfaces: a rippled surface ... [more ▼]

To investigate the effect of steps on H2O binding on a nominal Pt(111) surface, we used thermal desorption spectroscopy of water adsorbed on purposefully nanostructured surfaces: a rippled surface containing densely packed (100)-microfaceted and (111)-microfaceted steps was created using grazing incidence ion bombardment, and a surface with triangular mounds mainly consisting of (111)-microfaceted steps was fabricated through hornoepitaxial growth. These morphologies are determined by scanning tunneling microscopy. We find two additional high -temperature H2O desorption peaks using the rippled surface, whereas only the peak with the highest desorption temperature is present on the (111)-microfaceted mound. Thus, water preferentially binds to steps and especially favors (111)-microfaceted ones. Furthermore, the large step concentration on our nanostructured surfaces precludes the coexistence of a condensed and a diluted phase in a monolayer of water and suppresses the formation of crystalline ice multilayers during heating. [less ▲]