Ferromagnetic carbon-coated Fe nanoparticles (core size of 15 nm, saturated magnetization of Ms=218 emu g(-1) and coercivity of Hc=62 Oe), fabricated at a mild temperature, demonstrate a strong ability to effectively remove more than 95 wt% of Cr(VI) in waste water via carbon shell physical adsorption, which is much higher than the commercially available Fe NPs.
We suggest optimally designed one-dimensional metal/photonic crystal structures for the excitation of optical Tamm plasmon polaritons, which show strongly enhanced electromagnetic field intensities compared to those due to conventional surface plasmon excitations. We assume that the photonic crystal is made of weakly nonlinear optical materials and calculate the reflectance and the electromagnetic field distribution precisely, using the invariant imbedding method generalized to nonlinear media. We find field intensity enhancement factors as large as 3,000 at the metal/photonic crystal interface. We verify that due to this strong enhancement, nonlinear optical effects such as optical bistability can be observed for very small values of the incident wave power. Our results imply that using our structure, very strong surface enhanced Raman scattering signals can be achieved and optical switching devices can be operated in much lower threshold light intensities.
The
UV plasmonic properties of Al shallow pit arrays (ASPA) are investigated
by experimental and simulative methods. ASPA with various periods
are fabricated by the hard anodization (HA) technique. The measured
reflectance spectra of ASPA exhibit a reflectance pit in the UV region,
which is red shifted with the increasing period of ASPA and refractive
index of the surrounding medium. The dependence of reflectance on
the period and refractive index calculated by the finite difference
time domain (FDTD) method exhibits the identical evolution trends
with measurement results. The angle-dependent reflectance spectrum,
spatial electric field, and surface charge distribution calculated
by FDTD reveal that ASPA sustains propagating surface plasmons (SPs),
the UV reflectance pit corresponds to the propagating SPs mode,
and the total field inside the Al shallow pit and its proximity region
is enhanced with increasing the period of ASPA, which reveals the
origin of the higher sensing performance of ASPA with bigger period
and is in accordance with the measured results.
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