3 research outputs found
Plasmonic nanocrystals with complex shapes for photocatalysis and growth: Contrasting anisotropic hot-electron generation with the photothermal effect
In plasmonics, and particularly in plasmonic photochemistry, the effect of
hot-electron generation is an exciting phenomenon driving new fundamental and
applied research. However, obtaining a microscopic description of the
hot-electron states represents a challenging problem, limiting our capability
to design efficient nanoantennas exploiting these excited carriers. This paper
addresses this limitation and studies the spatial distributions of the
photophysical dynamic parameters controlling the local surface photochemistry
on a plasmonic nanocrystal. We found that the generation of energetic electrons
and holes in small plasmonic nanocrystals with complex shapes is strongly
position-dependent and anisotropic, whereas the phototemperature across the
nanocrystal surface is nearly uniform. Our formalism includes three mechanisms
for the generation of excited carriers: the Drude process, the surface-assisted
generation of hot-electrons in the sp-band, and the excitation of interband
d-holes. Our computations show that the hot-carrier generation originating from
these mechanisms reflects the internal structure of hot spots in nanocrystals
with complex shapes. The injection of energetic carriers and increased surface
phototemperature are driving forces for photocatalytic and photo-growth
processes on the surface of plasmonic nanostructures. Therefore, developing a
consistent microscopic theory of such processes is necessary for designing
efficient nanoantennas for photocatalytic applications
Colloidal titanium nitride nanobars for broadband inexpensive plasmonics and photochemistry from visible to mid-IR wavelengths
Developing colloidal plasmonic nanomaterials with high carrier density that show optical resonances and photochemical activity extending from the visible to the mid-infrared (MIR) ranges remains a challenging pur-suit. Here, we report the fabrication of titanium nitride (TiN) nanobars obtained using a two-step procedure based on a wet chemical route synthesis of TiO2 nanowires and their subsequent high temperature annealing in ammonia flow. Electromagnetic simulations of the resulting TiN nanobars reveal a rich set of optical resonances featuring transverse, longitudinal and mixed transverse-longitudinal plasmonic modes that cover energies from the visible to MIR region. TiN nanobars decorated with Pt co-catalyst nanocrystals show enhanced photocatalytic hydrogen evolution activity in comparison to both isotropic TiN nanospheres of similar size and TiN nanocubes under near infrared excitation at 940 nm due to the enhanced hot electron generation. We also demonstrate that plasmonic TiN nanobars can be used for the detection of furfural molecular vibrations by providing a strong surface enhanced infrared absorption (SEIRA) effect in the MIR region.Web of Science104art. no. 10798
Local photochemical nanoscopy of hot-carrier-driven catalytic reactions using plasmonic nanosystems
Nanoscale investigation of the reactivity of photocatalytic systems is crucial for their fundamental understanding and improving their design and applicability. Here, we present a photochemical nanoscopy technique that unlocks the local spatial detection of molecular products during plasmonic hot-carrier-driven photocatalytic reactions with nanometric precision. By applying the methodology to Au/TiO2 plasmonic photocatalysts, we experimentally and theoretically determined that smaller and denser Au nanoparticle arrays present lower optical contribution with quantum efficiency in hot-hole-driven photocatalysis closely related to the population heterogeneity. As expected, the highest quantum yield from a redox probe oxidation is achieved at the plasmon peak. Investigating a single plasmonic nanodiode, we unravel the areas where oxidation and reduction products are evolved with subwavelength resolution (∼200 nm), illustrating the bipolar behavior of such nanosystems. These results open the way to quantitative investigations at the nanoscale to evaluate the photocatalytic reactivity of low-dimensional materials in a variety of chemical reactions.Web of Science1712114381142