6 research outputs found
Molecular Face-Rotating Cube with Emergent Chiral and Fluorescence Properties
Chiral
cage compounds are mainly constructed from chiral precursors
or based on the symmetry breaking during coordination-driven self-assembly.
Herein, we present a strategy to construct chiral organic cages by
restricting the <i>P</i> or <i>M</i> rotational
configuration of tetraphenylethylene (TPE) faces through dynamic covalent
chemistry. The combination of graph theory, experimental characterizations
and theoretical calculations suggests emergent chirality of cages
is originated from complex arrangements of TPE faces with different
orientational and rotational configurations. Accompanied by the generation
of chirality, strong fluorescence also emerged during cage formation,
even in dilute solutions with various solvents. In addition, the circularly
polarized luminescence of the cages is realized as a synergy of their
dual chiral and fluorescence properties. Chirality and fluorescence
of cages are remarkably stable, because intramolecular flipping of
phenyl rings in TPE faces is restricted, as indicated by calculations.
This study provides insight into construct chiral cages by the rational
design through graph theory, and might facilitate further design of
cages and other supramolecular assemblies from aggregation-induced
emission active building blocks
Three-Dimensional and Time-Ordered Surface-Enhanced Raman Scattering Hotspot Matrix
The “fixed” or “flexible”
design of
plasmonic hotspots is a frontier area of research in the field of
surface-enhanced Raman scattering (SERS). Most reported SERS hotspots
have been shown to exist in zero-dimensional point-like, one-dimensional
linear, or two-dimensional planar geometries. Here, we demonstrate
a novel three-dimensional (3D) hotspot matrix that can hold hotspots
between every two adjacent particles in 3D space, simply achieved
by evaporating a droplet of citrate-Ag sols on a fluorosilylated silicon
wafer. In situ synchrotron-radiation small-angle X-ray scattering
(SR-SAXS), combined with dark-field microscopy and in situ micro-UV,
was employed to explore the evolution of the 3D geometry and plasmonic
properties of Ag nanoparticles in a single droplet. In such a droplet,
there is a distinct 3D geometry with minimal polydispersity of particle
size and maximal uniformity of interparticle distance, significantly
different from the dry state. According to theoretical simulations,
the liquid adhesive force promotes a closely packed assembly of particles,
and the interparticle distance is not fixed but can be balanced in
a small range by the interplay of the van der Waals attraction and
electrostatic repulsion experienced by a particle. The “trapping
well” for immobilizing particles in 3D space can result in
a large number of hotspots in a 3D geometry. Both theoretical and
experimental results demonstrate that the 3D hotspots are predictable
and time-ordered in the absence of any sample manipulation. Use of
the matrix not only produces giant Raman enhancement at least 2 orders
of magnitude larger than that of dried substrates, but also provides
the structural basis for trapping molecules. Even a single molecule
of resonant dye can generate a large SERS signal. With a portable
Raman spectrometer, the detection capability is also greatly improved
for various analytes with different natures, including pesticides
and drugs. This 3D hotspot matrix overcomes the long-standing limitations
of SERS for the ultrasensitive characterization of various substrates
and analytes and promises to transform SERS into a practical analytical
technique
Three-Dimensional and Time-Ordered Surface-Enhanced Raman Scattering Hotspot Matrix
The “fixed” or “flexible”
design of
plasmonic hotspots is a frontier area of research in the field of
surface-enhanced Raman scattering (SERS). Most reported SERS hotspots
have been shown to exist in zero-dimensional point-like, one-dimensional
linear, or two-dimensional planar geometries. Here, we demonstrate
a novel three-dimensional (3D) hotspot matrix that can hold hotspots
between every two adjacent particles in 3D space, simply achieved
by evaporating a droplet of citrate-Ag sols on a fluorosilylated silicon
wafer. In situ synchrotron-radiation small-angle X-ray scattering
(SR-SAXS), combined with dark-field microscopy and in situ micro-UV,
was employed to explore the evolution of the 3D geometry and plasmonic
properties of Ag nanoparticles in a single droplet. In such a droplet,
there is a distinct 3D geometry with minimal polydispersity of particle
size and maximal uniformity of interparticle distance, significantly
different from the dry state. According to theoretical simulations,
the liquid adhesive force promotes a closely packed assembly of particles,
and the interparticle distance is not fixed but can be balanced in
a small range by the interplay of the van der Waals attraction and
electrostatic repulsion experienced by a particle. The “trapping
well” for immobilizing particles in 3D space can result in
a large number of hotspots in a 3D geometry. Both theoretical and
experimental results demonstrate that the 3D hotspots are predictable
and time-ordered in the absence of any sample manipulation. Use of
the matrix not only produces giant Raman enhancement at least 2 orders
of magnitude larger than that of dried substrates, but also provides
the structural basis for trapping molecules. Even a single molecule
of resonant dye can generate a large SERS signal. With a portable
Raman spectrometer, the detection capability is also greatly improved
for various analytes with different natures, including pesticides
and drugs. This 3D hotspot matrix overcomes the long-standing limitations
of SERS for the ultrasensitive characterization of various substrates
and analytes and promises to transform SERS into a practical analytical
technique
Three-Dimensional and Time-Ordered Surface-Enhanced Raman Scattering Hotspot Matrix
The “fixed” or “flexible”
design of
plasmonic hotspots is a frontier area of research in the field of
surface-enhanced Raman scattering (SERS). Most reported SERS hotspots
have been shown to exist in zero-dimensional point-like, one-dimensional
linear, or two-dimensional planar geometries. Here, we demonstrate
a novel three-dimensional (3D) hotspot matrix that can hold hotspots
between every two adjacent particles in 3D space, simply achieved
by evaporating a droplet of citrate-Ag sols on a fluorosilylated silicon
wafer. In situ synchrotron-radiation small-angle X-ray scattering
(SR-SAXS), combined with dark-field microscopy and in situ micro-UV,
was employed to explore the evolution of the 3D geometry and plasmonic
properties of Ag nanoparticles in a single droplet. In such a droplet,
there is a distinct 3D geometry with minimal polydispersity of particle
size and maximal uniformity of interparticle distance, significantly
different from the dry state. According to theoretical simulations,
the liquid adhesive force promotes a closely packed assembly of particles,
and the interparticle distance is not fixed but can be balanced in
a small range by the interplay of the van der Waals attraction and
electrostatic repulsion experienced by a particle. The “trapping
well” for immobilizing particles in 3D space can result in
a large number of hotspots in a 3D geometry. Both theoretical and
experimental results demonstrate that the 3D hotspots are predictable
and time-ordered in the absence of any sample manipulation. Use of
the matrix not only produces giant Raman enhancement at least 2 orders
of magnitude larger than that of dried substrates, but also provides
the structural basis for trapping molecules. Even a single molecule
of resonant dye can generate a large SERS signal. With a portable
Raman spectrometer, the detection capability is also greatly improved
for various analytes with different natures, including pesticides
and drugs. This 3D hotspot matrix overcomes the long-standing limitations
of SERS for the ultrasensitive characterization of various substrates
and analytes and promises to transform SERS into a practical analytical
technique
Plasmon-Induced Magnetic Resonance Enhanced Raman Spectroscopy
Plasmon-induced
magnetic resonance has shown great potentials in
optical metamaterials, chemical (bio)-sensing, and surface-enhanced
spectroscopies. Here, we have theoretically and experimentally revealed
(1) a correspondence of the strongest near-field response to the far-field
scattering valley and (2) a significant improvement in Raman signals
of probing molecules by the plasmon-induced magnetic resonance. These
revelations are accomplished by designing a simple and practical metallic
nanoparticle–film plasmonic system that generates magnetic
resonances at visible-near-infrared frequencies. Our work may provide
new insights for understanding the enhancement mechanism of various
plasmon-enhanced spectroscopies and also helps further explore light-matter
interactions at the nanoscale
Plasmon-Enhanced Second-Harmonic Generation Nanorulers with Ultrahigh Sensitivities
Attainment
of spatial resolutions far below diffraction limits by means of optical
methods constitutes a challenging task. Here, we design nonlinear
nanorulers that are capable of accomplishing approximately 1 nm resolutions
by utilizing the mechanism of plasmon-enhanced second-harmonic generation
(PESHG). Through introducing Au@SiO<sub>2</sub> (core@shell) shell-isolated
nanoparticles, we strive to maneuver electric-field-related gap modes
such that a reliable relationship between PESHG responses and gap
sizes, represented by “PESHG nanoruler equation”, can
be obtained. Additionally validated by both experiments and simulations,
we have transferred “hot spots” to the film-nanoparticle-gap
region, ensuring that retrieved PESHG emissions nearly exclusively
originate from this region and are significantly amplified. The PESHG
nanoruler can be potentially developed as an ultrasensitive optical
method for measuring nanoscale distances with higher spectral accuracies
and signal-to-noise ratios