Controlling Nanowire Growth by Light

A wealth of structures for the Ge2H2+ radical cation: comparison of theory and experiment

Five structures of Ge2H2 and Ge2H2+ are investigated in this study. Optimized geometries at the CCSD(T)/cc-pwCVQZ-PP level of theory were obtained. Focal point analyses were performed on these optimized geometries to determine relative energies using the CCSD(T) method with polarized basis sets up to quintuple-zeta. Energy corrections include full T and pertubative (Q) coupled-cluster effects plus anharmonic corrections to the zero-point vibrational energy. Relative ordering in energy from lowest to highest of the five Ge2H2+ structures is butterfly, germylidene, monobridged, trans, then linear. In neutral Ge2H2, the monobridged structure lies lower in energy than the germylidene structure. Fundamental vibrational frequencies and IR intensities were computed for the minima at the CCSD(T)/cc-pwCVTZ-PP level of theory to compare with experimental research. Partial atomic charges and natural bonding orbital analyses indicated that the positive charge of Ge2H2+ is contained in the region of the Ge-Ge bond.

Thermoplasmonic In Situ Fabrication of Nanohybrid Electrocatalysts over Gas Diffusion Electrodes for Enhanced H2O2 Electrosynthesis

Large-scale development of electrochemical cells is currently hindered by the lack of Earth-abundant electrocatalysts with high catalytic activity, product selectivity, and interfacial mass transfer. Herein, we developed an electrocatalyst fabrication approach which responds to these requirements by irradiating plasmonic titanium nitride (TiN) nanocubes self-assembled on a carbon gas diffusion layer in the presence of polymeric binders. The localized heating produced upon illumination creates unique conditions for the formation of TiN/F-doped carbon hybrids that show up to nearly 20 times the activity of the pristine electrodes. In alkaline conditions, they exhibit enhanced stability, a maximum H2O2 selectivity of 90%, and achieve a H2O2 productivity of 207 mmol gTiN-1 h-1 at 0.2 V vs RHE. A detailed electrochemical investigation with different electrode arrangements demonstrated the key role of nanocomposite formation to achieve high currents. In particular, an increased TiOxNy surface content promoted a higher H2O2 selectivity, and fluorinated nanocarbons imparted good stability to the electrodes due to their superhydrophobic properties.

Laser-Driven Growth of Semiconductor Nanowires from Colloidal Nanocrystals

Semiconductor nanowire production through vapor- and solution-based processes has propelled nanowire systems toward a wide range of technological applications. Although vapor-based nanowire syntheses enable precise control over nanowire composition and phase, they typically employ batch processes with specialized pressure management systems, limiting throughput. Solution-based nanowire growth processes have improved scalability but can require even more extensive pressure and temperature management systems. Here, we demonstrate a solution-based nanowire growth process that utilizes the large Young-Laplace interfacial surface pressures and collective heating effects of colloidal metal nanocrystals under irradiation to drive nanowire growth photothermally. Laser irradiation of a solution containing metal nanocrystals and semiconductor precursors facilitates rapid heating, precursor decomposition, and nanowire growth on a benchtop in simple glassware under standard conditions, potentially enabling a range of solution-based experiments including in-line combinatorial identification of optimized reaction parameters, in situ measurements, and the production of nanowires with complex compositions.

Plasmon-driven synthesis of individual metal@semiconductor core@shell nanoparticles

Most syntheses of advanced materials require accurate control of the operating temperature. Plasmon resonances in metal nanoparticles generate nanoscale temperature gradients at their surface that can be exploited to control the growth of functional nanomaterials, including bimetallic and core@shell particles. However, in typical ensemble plasmonic experiments these local gradients vanish due to collective heating effects. Here, we demonstrate how localized plasmonic photothermal effects can generate spatially confined nanoreactors by activating, controlling, and spectroscopically following the growth of individual metal@semiconductor core@shell nanoparticles. By tailoring the illumination geometry and the surrounding chemical environment, we demonstrate the conformal growth of semiconducting shells of CeO₂, ZnO, and ZnS, around plasmonic nanoparticles of different morphologies. The shell growth rate scales with the nanoparticle temperature and the process is followed in situ via the inelastic light scattering of the growing nanoparticle. Plasmonic control of chemical reactions can lead to the synthesis of functional nanomaterials otherwise inaccessible with classical colloidal methods, with potential applications in nanolithography, catalysis, energy conversion, and photonic devices.

MoS2 with Organic Fragment - a New Hybrid Material for Laser Writing

New nanostructured metasurfaces capable change the composition and physical properties upon pulse laser excitation recently received a marked attention for nanophotonic technologies. In this study, well adherent to the metal substrate and significantly thicker nanoplatelet-shaped MoS₂-based arrays were synthesized by one pot hydrothermal way via addition of ethanolamine in the synthesis solution containing ammonium heptamolybdate and thiourea. It was shown that the lightening of this material with green light ns-laser pulses at a suitable fluencies results in the detachment of organic species and compositional transformations to significantly pure MoS₂ material. For characterization the synthesized products scanning electron microscopy (SEM), glancing angle X-ray diffraction (GA-XRD), diffuse reflection, Raman, and time-of-flight secondary ion mass spectrometry (ToF-SIMS) methods before and following green light picosecond laser pulse illumination were applied. We envisaged that these films can be successfully used as metamaterial for laser writing.

Mapping Photoemission and Hot-Electron Emission from Plasmonic Nanoantennas

Understanding plasmon-mediated electron emission and energy transfer on the nanometer length scale is critical to controlling light-matter interactions at nanoscale dimensions. In a high-resolution lithographic material, electron emission and energy transfer lead to chemical transformations. In this work, we employ such chemical transformations in two different high-resolution electron-beam lithography resists, poly(methyl methacrylate) (PMMA) and hydrogen silsesquioxane (HSQ), to map local electron emission and energy transfer with nanometer resolution from plasmonic nanoantennas excited by femtosecond laser pulses. We observe exposure of the electron-beam resists (both PMMA and HSQ) in regions on the surface of nanoantennas where the local field is significantly enhanced. Exposure in these regions is consistent with previously reported optical-field-controlled electron emission from plasmonic hotspots as well as earlier work on low-electron-energy scanning probe lithography. For HSQ, in addition to exposure in hotspots, we observe resist exposure at the centers of rod-shaped nanoantennas in addition to exposure in plasmonic hotspots. Optical field enhancement is minimized at the center of nanorods suggesting that exposure in these regions involves a different mechanism to that in plasmonic hotspots. Our simulations suggest that exposure at the center of nanorods results from the emission of hot electrons produced via plasmon decay in the nanorods. Overall, the results presented in this work provide a means to map both optical-field-controlled electron emission and hot-electron transfer from nanoparticles via chemical transformations produced locally in lithographic materials.