4 research outputs found
Facet-Dependent Diol-Induced Density of States of Anatase TiO<sub>2</sub> Crystal Surface
Owing to their fundamental
importance and practical applications,
anatase TiO<sub>2</sub> crystals with well-defined {001} and {101}
facets attracted intensive research interests. In this study, we systematically
investigated solvent dependence of the photoreaction of the different
coexposed crystal facets during noble metal photodeposition. By examining
the deposition position in each solvent, we revealed that solvents
play a pivotal role on the facet selectivity. On the basis of density
functional theory calculations, the solvent molecules were found to
modify both the crystal facet electronic structure and the {001}–{001}
heterojunction. These modifications are not only the origin of diverse
charge-carrier pathways but are also responsible for carrier accumulation
at specific facets that increase their reductive power. These findings
are vital for a better understanding of photocatalytic materials and
an improved design for the next-generation materials
Surface Density-of-States Engineering of Anatase TiO<sub>2</sub> by Small Polyols for Enhanced Visible-Light Photocurrent Generation
Enhancement
of visible-light photocurrent generation by sol–gel
anatase TiO<sub>2</sub> films was achieved by binding small polyol
molecules to the TiO<sub>2</sub> surface. Binding ethylene glycol
onto the surface, enhancement factors up to 2.8 were found in visible-light
photocurrent generation experiments. Density functional theory calculations
identified midgap energy states that emerge as a result of the binding
of a range of polyols to the TiO<sub>2</sub> surface. The presence
and energy of the midgap state is predicted to depend sensitively
on the structure of the polyol, correlating well with the photocurrent
generation results. Together, these results suggest a new, facile,
and cost-effective route to precise surface band gap engineering of
TiO<sub>2</sub> toward visible-light-induced photocatalysis and energy
storage
Remote Excitation of Tip-Enhanced Photoluminescence with a Parallel AgNW Coupler
Tip-enhanced photoluminescence (TEPL) microscopy allows
for the
correlation of scanning probe microscopic images and photoluminescent
spectra at the nanoscale level in a similar way to tip-enhanced Raman
scattering (TERS) microscopy. However, due to the higher cross-section
of fluorescence compared to Raman scattering, the diffraction-limited
background signal generated by far-field excitation is a limiting
factor in the achievable spatial resolution of TEPL. Here, we demonstrate
a way to overcome this drawback by using remote excitation TEPL (RE-TEPL).
With this approach, the excitation and detection positions are spatially
separated, minimizing the far-field contribution. Two probe designs
are evaluated, both experimentally and via simulations.
The first system consists of gold nanoparticles (AuNPs) through photoinduced
deposition on a silver nanowire (AgNW), and the second system consists
of two offset parallel AgNWs. This latter coupler system shows a higher
coupling efficiency and is used to successfully demonstrate RE-TEPL
spectral mapping on a MoSe2/WSe2 lateral heterostructure
to reveal spatial heterogeneity at the heterojunction
Length-Controllable Gold-Coated Silver Nanowire Probes for High AFM-TERS Scattering Activity
Tip-enhanced Raman scattering (TERS) microscopy is an
advanced
technique for investigation at the nanoscale that provides topographic
and chemical information simultaneously. The TERS probe plays a crucial
role in the microscopic performance. In the recent past, the development
of silver nanowire (AgNW) based TERS probes solved the main tip fabrication
issues, such as low mechanical strength and reproducibility. However,
this fabrication method still suffers from low control of the protruded
length of the AgNW. In this work, a simple water–air interface
electrocutting method is proposed to achieve wide controllability
of the length. This water cutting method was combined with a succedent
Au coating on the AgNW surface, and the probe achieved an up to 100×
higher enhancement factor (EF) and a 2× smaller spatial resolution
compared to pristine AgNW. Thanks to this excellent EF, the water-cut
Au-coated AgNW probes were found to possess high TERS activity even
in the nongap mode, enabling broad applications