26 research outputs found
Determination of Critical Micelle Concentration (CMC) of Surfactants Using Environmentally Sensitive Carbonized Polymer Dots
Critical
micelle concentration (CMC) is one of the essential parameters
for surfactants. To accurately measure this value, we prepared a new
type of carbonized polymer dots (CPDs) based on a solvothermal method
of N,N-diethyl-p-phenylenediamine. This CPD exhibits significant fluorescence enhancement
(600Ă—) in various surfactant-contained solutions relative to
its aqueous solution due to the charge transfer (CT) effect. It also
shows a fluorescence change performance in different concentrations
of surfactants, allowing a fluorescence measurement for CMC. Its responsive
mechanism was discussed by the fluorescence lifetime and quantum yield
results. Compared to the previously reported CMC probes, our developed
CPD-based probe has merits in simple preparation, low cost, high availability,
and easy use. This study utilized the CT feature of carbon material
and widened the applications of CPDs for practical detection purposes
Comparison of Shearing Force and Hydrostatic Pressure on Molecular Structures of Triphenylamine by Fluorescence and Raman Spectroscopies
Luminescent mechanochromism (e.g.,
shearing force and hydrostatic
pressure) has been intensively studied in recent years. However, there
are few reported studies on the difference of the molecular configuration
changes induced by these stresses. In this study, we chose triphenylamine,
C<sub>18</sub>H<sub>6</sub>N (TPA), as a model molecule to study different
molecular configuration changes under shearing force and hydrostatic
pressure. Triphenylamine is an organic optoelectric functional molecule
with a propeller-shaped configuration, a large conjugate structure,
and a single molecular fluorescence material. Fluorescence and Raman
spectra of TPA were recorded in situ under different pressures (0–1.9
GPa) produced by the mechanical grinding or using a diamond anvil
cell (DAC). Our results show that the crystal phase of TPA transformed
to the amorphous phase by grinding, whereas no obvious phase transition
was observed under hydrostatic pressure up to 1.9 GPa, indicating
the stability of TPA. Hydrostatic pressure by DAC induces molecular
conformation changes, and the pressure-induced emission enhancement
phenomenon of TPA is observed. By analyzing the Raman spectra at high
pressure, we suggest that the molecular conformation changes under
pressure are caused by the twisted dihedral angle between the benzene
and the nitrogen atom, which is different from the phase transformation
induced by the shearing force of grinding
Ag Nanoparticles Decorated Small-Sized AgTCNQF<sub>4</sub> Nanorod: Synthesis in Aqueous Solution and Its Photoinduced Charge Transfer Reactions
A kind of functional noble metal
nanoparticles and metal/organic
semiconductor composite nanomaterials, Ag nanoparticles (AgNPs, 6–10
nm in diameter) decorated small-sized Ag-tetracyano-<i>p</i>-tetrafluoroquinodimethane (AgTCNQF<sub>4</sub>) nanorods (150–400
nm in length and 60–100 nm in diameter), have been successfully
synthesized through a rapid microemulsion reaction between TCNQF<sub>4</sub> molecules and an AgNP colloid under a soft template of polyÂ(ethylene
glycol)-<i>block</i>-polyÂ(propylene glycol)-<i>block</i>-polyÂ(ethylene glycol). The morphology, chemical structure, and elemental
composition of the prepared AgNPs–AgTCNQF<sub>4</sub> composite
nanorods were studied by transmission electron microscopy, selected-area
electron diffraction, and X-ray photoelectron spectroscopy. The real-time
ultraviolet–visible spectroscopy assisted with two-dimensional
correlation spectroscopic analysis was employed to explore the growth
of AgNPs–AgTCNQF<sub>4</sub> composite nanorods in microemulsion.
These composite nanorods display the photoinduced charge transfer
(CT) property from the monoanion (TCNQF<sub>4</sub><sup>–</sup>) to dianion (TCNQF<sub>4</sub><sup>2–</sup>) selectively
under 532 nm light irradiation. The larger content of AgNPs on the
surface of AgTCNQF<sub>4</sub> led to the higher conversion of dianion
due to the plasmon-assisted photocatalysis. This photoelectric composite
material is promising for the applications of light-writing data storage
and photocatalysis
Highly Efficient Construction of Silver Nanosphere Dimers on Poly(dimethylsiloxane) Sheets for Surface-Enhanced Raman Scattering
We reported a highly efficient and low-cost way to synthesize
silver
nanosphere dimers on a polyÂ(dimethylsiloxane) (PDMS) sheet by using
a stepwise upright assembly method for the “hot spots”
study of surface-enhanced Raman scattering (SERS). The first silver
nanoparticle (NP) layer is almost entirely embedded in PDMS, and the
second-layered silver NPs directionally position the tops of the embedded
particles. The analysis of the localized electric field distributions
of the silver nanosphere dimer presents that the strongest electric
field coupling appears at the gap of two nanospheres when the incident
angle is about 45° and its intensity achieves 400 times enhancement.
The SERS enhancement activity on this novel substrate was determined,
and the results showed that SERS intensities on nanodimers were much
stronger than those on the silver NP monolayer due to the electromagnetic
field coupling of upright NP-NP. By using this novel SERS substrate,
the lowest detection concentration for 4-mercaptopyridine is 4.0 Ă—
10<sup>–14</sup> M
Long-Range Surface Plasmon Field-Enhanced Raman Scattering Spectroscopy Based on Evanescent Field Excitation
The purpose of this paper is to enhance Raman signals in the evanescent field by using the excitation of long-range surface plasmons (LRSPs). A four-phase Kretschmann LRSP resonance (LRSPR) setup composed of a K9 prism/MgF<sub>2</sub> film/silver film/water configuration was constructed. Incident angle-dependent surface-enhanced Raman scattering (SERS) spectra were measured in the evanescent field on this four-phase configuration. The SERS signal obtained under the evanescent field excitation at the LRSPR angle was 15 times higher than that collected based on the conventional SPR configuration. The experimental result also proved that the LRSPs in this evanescent field-enhanced SERS spectroscopy possessed at least 500 nm in the electric field penetration depth, which is longer than the electric field penetration depth of conventional surface plasmons
Plasmon-Driven Dynamic Response of a Hierarchically Structural Silver-Decorated Nanorod Array for Sub-10 nm Nanogaps
Plasmonic nanogaps
serve as a useful configuration for light concentration and local
field amplification owing to the extreme localization of surface plasmons.
Here, a smart plasmonic nanogap device is fabricated by the dynamic
response of an Ag decorated hierarchically structural vertical polymer
nanorod array under the light irradiation. Seven nanorods in one unit
bend because of plasmonic heating effect and they are centrally collected
due to the attraction of the plasmon-induced polaritons, leading to
the significantly enhanced local electromagnetic field at the sub-10
nm gaps among the constricted nanorod tops. Compared with tuning capillarity
in microscale by wetting and drying, using light as external stimuli
is much easier and more tunable in nanoscale. This plasmonic nanogap
device is used for a surface-enhanced Raman scattering (SERS) substrate.
Its hydrophobic surface with a contact angle of 142 degree can make
the probed aqueous solution only access to the Ag tips of nanorods.
Thus, the analytes can be driven to the “hot spot” regions
where located at the tops of nanorods during the solvent evaporation
process, which is beneficial to SERS detection. Discovery of this
smart plasmon-driven process broadens the scope for further functionality
of both the dynamic nanostructure design and the smart plasmonic devices
in the communities of chemistry, biomedicine, and microfluidic engineering
Aptamer-Based Surface-Enhanced Raman Scattering-Microfluidic Sensor for Sensitive and Selective Polychlorinated Biphenyls Detection
A surface-enhanced Raman scattering
(SERS) measurement of 3,3′,4,4′-tetrachlorobiphenyl
(PCB77) with aptamer capturing in a microfluidic device was demonstrated.
To construct the microfluidic chip, an ordered Ag nanocrown array
was fabricated over a patterned polydimethylsiloxane (PDMS) that was
achieved by replicating an anodic aluminum oxide (AAO) template. The
patterned PDMS sheet was covered with another PDMS sheet having two
input channel grooves to form a close chip. The Ag nanocrown array
was used for the SERS enhancement area and the detection zone. PCB
77 aptamers were injected into one channel and the other allows for
analytes (PCBs). The mercapto aptamers captured the targets in the
mixed zone and were immobilized to the SERS detection zone via S–Ag
bonds so as to further improve both the SERS sensitivity and selectivity
of PCB77. Such an aptamer-based microfluidic chip realized a rapid
SERS detection. The lowest detectable concentration of 1.0 Ă—
10<sup>–8</sup> M was achieved for PCB77. This work demonstrates
that the aptamer-modified SERS microfluidic sensor can be utilized
for selective detections of organic pollutants in the environment
Active-Tuned Plasmonic Angle Modulator of Light Beams for Potential Application of 3D Display
We propose a plasmonic angle modulator
device based on the extraordinary
optical transmission (EOT) phenomenon combined with the liquid crystal
(LC)-tuned surface plasmons (SPs). The configuration of this angle
modulator mainly involves an Ag nanograting film for the SP coupling
and a LC layer for continuously tuning SPs via voltage signals. Accordingly,
the directions of the transmission light through the Ag nanograting
film can be tuned continuously, realizing a light beam scanning in
a 5° range at an operation rate of 60 Hz. We expect this active-tuned
plasmonic angle modulator would have potential applications in three-dimensional
(3D) display techniques that strictly require the elaborate and rapid
angle modulation of light beams. In addition, this active-tuned plasmonic
angle modulator can also be applied in other fields, such as photocommunication,
optical detection, beam steering, and so on
Active-Tuned Plasmonic Angle Modulator of Light Beams for Potential Application of 3D Display
We propose a plasmonic angle modulator
device based on the extraordinary
optical transmission (EOT) phenomenon combined with the liquid crystal
(LC)-tuned surface plasmons (SPs). The configuration of this angle
modulator mainly involves an Ag nanograting film for the SP coupling
and a LC layer for continuously tuning SPs via voltage signals. Accordingly,
the directions of the transmission light through the Ag nanograting
film can be tuned continuously, realizing a light beam scanning in
a 5° range at an operation rate of 60 Hz. We expect this active-tuned
plasmonic angle modulator would have potential applications in three-dimensional
(3D) display techniques that strictly require the elaborate and rapid
angle modulation of light beams. In addition, this active-tuned plasmonic
angle modulator can also be applied in other fields, such as photocommunication,
optical detection, beam steering, and so on
A Long-Range Surface Plasmon Resonance/Probe/Silver Nanoparticle (LRSPR-P-NP) Nanoantenna Configuration for Surface-Enhanced Raman Scattering
The purpose of this paper is to enhance Raman signals
with a plasmonic
nanoantenna based on a long-range surface plasmon resonance/probe/silver
nanoparticle (LRSPR-P-NP) sandwich configuration. The finite-difference
time-domain simulation shows that the electromagnetic field at the
gap between the silver film and a silver nanoparticle increases by
a factor of about 2.1 Ă— 10<sup>4</sup>. The resonance condition
of this plasmonic nanoantenna was optimized by incident angle-dependent
surface-enhanced Raman scattering (SERS) spectroscopy under an evanescent
field excitation mode. The SERS signal obtained under the LRSPR-P-NP
configuration at the LRSPR angle was 40 times higher than that collected
on the planar film plasmonic nanoantenna. The enhancement factor of
the LRSPR-P-NP configuration was 9.2 Ă— 10<sup>8</sup>. This plasmonic
nanoantenna was also applied for pH sensing