We discuss how the controllable carrier influences the localized surface plasmon resonance (LSPR) and charge transfer (CT) in the same system based on ultraviolet-visible and surface-enhanced Raman scattering (SERS) measurements. The LSPR can be easily tuned from 580 to 743 nm by changing the sputtering power of CuS in the Ag and CuS composite substrate. During this process, surprisingly, we find that the LSPR is proportional to the sputtering power of CuS. This observation indicates that LSPR can be accurately adjusted by changing the content of the semiconductor, or even the carrier density. Moreover, we characterize the carrier density through the detection of the Hall effect to analyze the Raman shift caused by CT and obtain the relationships between them. These fundamental discussions provide a guideline for tunable LSPR and the investigation of CT.
Overexpression of the Lens culinaris agglutinin-reactive
fraction of alpha-fetoprotein (AFP-L3) is an essential biomarker for
early diagnosis of hepatocellular carcinoma (HCC). In this study,
we designed a new surface-enhanced Raman spectroscopy active chip
for the detection of AFP with high sensitivity and excellent repeatability.
This chip was composed of a honeycomb gold nanostructure array with
strong electromagnetic field coupling due to the special cavity geometric
characteristics of the honeycomb structure. The honeycomb structure
exhibited extraordinary performance for the specific detection of
AFP in the range of 0.003–3 ng/mL and also determined the proportion
of AFP-L3 with a high degree of accuracy, which has shown great potential
for application in the clinical diagnosis of HCC.
The
central dilemma in label-free in situ surface-enhanced Raman
scattering (SERS) for monitoring of heterogeneously catalyzed reactions
is the need of plasmonically active nanostructures for signal enhancement.
Here, we show that the assembly of catalytically active transition-metal
nanoparticles into dimers boosts their intrinsically insufficient
plasmonic activity at the monomer level by several orders of magnitude,
thereby enabling the in situ SERS monitoring of various important
heterogeneously catalyzed reactions at the single-dimer level. Specifically,
we demonstrate that Pd nanocubes (NCs), which alone are not sufficiently
plasmonically active as monomers, can act as a monometallic yet bifunctional
platform with both catalytic and satisfactory plasmonic activity via
controlled assembly into single dimers with an ∼1 nm gap. Computer
simulations reveal that the highest enhancement factors (EFs) occur
at the corners of the gap, which has important implications for the
SERS-based detection of catalytic conversions: it is sufficient for
molecules to come in contact with the “hot spot corners”,
and it is not required that they diffuse deeply into the gap. For
the widely employed Pd-catalyzed Suzuki–Miyaura cross-coupling
reaction, we demonstrate that such Pd NC dimers can be employed for
in situ kinetic SERS monitoring, using a whole series of aryl halides
as educts. Our generic approach based on the controlled assembly into
dimers can easily be extended to other transition-metal nanostructures.
Perovskite semiconductors as advanced
solar energy-converting materials
are promising catalysts for photoredox organic synthesis. Despite
the high concentration of charge carriers generated on the perovskite
surface, efficient utilization of these nonequilibrium and shambolic
energetic carriers to trigger a chemical reaction remains a hot and
challenging subject. Here, we report a photon-mediated electron shuttle
between paired redox sites on perovskite nanocrystals for the reformation
of highly stable carbon–halogen bonds, where both surface electrons
and holes are utilized simultaneously. The photo-redox cascade can
be effortlessly tailored by precise control of the surface-reducing/-oxidizing
reaction rates, which unlocks the transformation for a wide range
of (het)arenes. This work demonstrates colloidal perovskite photocatalysts
for the direct installation of more than 10 different synthetically
important functional groups onto arenes and heteroarenes.
Excessive thiram residues in food have the potential to negatively impact human health. Hence, the development of a convenient and fast detection method is highly desirable. In this study, an efficient, repeatable, and sensitive surface-enhanced Raman scattering (SERS) active chip was manufactured via a low-cost colloidal lithography technique. The plasmonic structure was composed of a series of silver nanospheres and nanowires. Interestingly, this type structure creates a nanocavity space with a characteristic geometry generating a strong electromagnetic field coupling. The finite-different time-domain software was employed to simulate the electromagnetic field distribute on the nanocavity. Accordingly, SERS active chip that displays ultra-low concentration detection of thiram (10−11 M) was realized. Moreover, the excellent reproducibility of thiram (10−6 M) practical detection on an apple pericarp has great potential for application in food safety.
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