3 research outputs found
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
One-Directional Antenna Systems: Energy Transfer from Monomers to J‑Aggregates within 1D Nanoporous Aluminophosphates
A cyanine
dye (PIC) was occluded into two 1D-nanopoporus Mg-containing
aluminophosphates with different pore size (MgAPO-5 and MgAPO-36 with
AFI and ATS zeolitic structure types, with cylindrical channels of
7.3 Å diameter and elliptical channels of 6.7 Å × 7.5
Å, respectively) by crystallization inclusion method. Different
J-aggregates are photophysically characterized as a consequence of
the different pore size of the MgAPO frameworks, with emission bands
at 565 nm and at 610 nm in MgAPO-5 and MgAPO-36, respectively. Computational
results indicate a more linear geometry of the J-aggregates inside
the nanochannels of the MgAPO-36 sample than those in MgAPO-5, which
is as a consequence of the more constrained environment in the former.
For the same reason, the fluorescence of the PIC monomers at 550 nm
is also activated within the MgAPO-36 channels. Owing to the strategic
distribution of the fluorescent PIC species in MgAPO-36 crystals (monomers
at one edge and J-aggregates with intriguing emission properties at
the other edge) an efficient and one-directional antenna system is
obtained. The unidirectional energy transfer process from monomers
to J-aggregates is demonstrated by remote excitation experiments along
tens of microns of distance