5 research outputs found
Hydrophobic Carbon-Doped TiO<sub>2</sub>/MCF‑F Composite as a High Performance Photocatalyst
A novel
hydrophobic photocatalyst carbon-doped TiO<sub>2</sub>/MCF-F
was prepared by using silica mesoporous cellular foam (MCF) as host
material, glucose as carbon source, and NH<sub>4</sub>F as hydrophobic
modifying agent. It was confirmed that titania nanoparticles were
loaded in pore of MCF by XRD, N<sub>2</sub> sorption isotherms, and
TEM. The loaded titania nanoparticles exhibited higher photocatalytic
performance. UV–vis absorption spectra and XPS suggested carbon
atoms were doped in the lattice of titania by replacing titanium atoms
and narrowed the band gap so that visible light absorption and photocatalytic
activity of the photocatalyst were highly promoted. On the other hand,
water contact angle measurement and XPS proved that the photocatalyst
was endowed with hydrophobic property, which was caused by Si–F
bonds. Carbon-doped TiO<sub>2</sub>/MCF-F photocatalyst showed good
adsorptive ability and photocatalytic activity in the photodegradation
test of methyl orange under visible light
Improved SERS Sensitivity on Plasmon-Free TiO<sub>2</sub> Photonic Microarray by Enhancing Light-Matter Coupling
Highly
sensitive surface-enhanced Raman scattering (SERS) detection was achieved
on plasmon-free TiO<sub>2</sub> photonic artificial microarray, which
can be quickly recovered under simulated solar light irradiation and
repeatedly used. The sensitive detection performance is attributed
to the enhanced matter-light interaction through repeated and multiple
light scattering in photonic microarray. Moreover, the SERS sensitivity
is unprecedentedly found to be dependent on the different light-coupling
performance of microarray with various photonic band gaps, where microarray
with band gap center near to laser wavelength shows a lower SERS signal
due to depressed light propagation, while those with band gap edges
near to laser wavelength show higher sensitivity due to slow light
effect
Fabry–Perot Cavity-Enhanced Optical Absorption in Ultrasensitive Tunable Photodiodes Based on Hybrid 2D Materials
Monolayer
two-dimensional (2D) transition metal dichalcogenides
(TMDs) show interesting optical and electrical properties because
of their direct bandgap. However, the low absorption of atomically
thin TMDs limits their applications. Here, we report enhanced absorption
and optoelectronic properties of monolayer molybdenum disulfide (MoS<sub>2</sub>) by using an asymmetric Fabry–Perot cavity. The cavity
is based on a hybrid structure of MoS<sub>2</sub>/ hexagonal boron
nitride (BN)/Au/SiO<sub>2</sub> realized through layer-by-layer vertical
stacking. Photoluminescence (PL) intensity of monolayer MoS<sub>2</sub> is enhanced over 2 orders of magnitude. Theoretical calculations
show that the strong absorption of MoS<sub>2</sub> comes from photonic
localization on the top of the microcavity at optimal BN spacer thickness.
The n/n<sup>+</sup> MoS<sub>2</sub> homojunction photodiode incorporating
this asymmetric Fabry–Perot cavity exhibits excellent current
rectifying behavior with an ideality factor of 1 and an ultrasensitive
and gate-tunable external photo gain and specific detectivity. Our
work offers an effective method to achieve uniform enhanced light
absorption by monolayer TMDs, which has promising applications for
highly sensitive optoelectronic devices
Molecular Alignment and Electronic Structure of <i>N</i>,<i>N</i>′‑Dibutyl-3,4,9,10-perylene-tetracarboxylic-diimide Molecules on MoS<sub>2</sub> Surfaces
The
molecular orientation of organic semiconductors on a solid
surface could be an indispensable factor to determine the electrical
performance of organic-based devices. Despite its fundamental prominence,
a clear description of the emergent two-dimensional layered material–organic
interface is not fully understood yet. In this study, we reveal the
molecular alignment and electronic structure of thermally deposited <i>N</i>,<i>N</i>′-dibutyl-3,4,9,10-perylene-dicarboximide
(PTCDI-C4) molecules on natural molybdenum disulfide (MoS<sub>2</sub>) using near-edge X-ray absorption fine structure spectroscopy (NEXAFS).
The average tilt angle determination reveals that the anisotropy in
the π* symmetry transition of the carbon <i>K</i>-edge
(284–288 eV range) is present at the sub-monolayer regime.
Supported by ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron
spectroscopy (XPS), and resonant photoemission spectroscopy (RPES)
measurements, we find that our spectroscopic measurements indicate
a weak charge transfer established at the PTCDI-C4/MoS<sub>2</sub> interface. Sterical hindrance due to the C4 alkyl chain caused tilting
of the molecular plane at the initial thin film deposition. Our result
shows a tunable interfacial alignment of organic molecules on transition
metal dichalcogenide surfaces effectively enhancing the electronic
properties of hybrid organic–inorganic heterostructure devices
Surface Functionalization of Black Phosphorus via Potassium toward High-Performance Complementary Devices
Two-dimensional
black phosphorus configured field-effect transistor
devices generally show a hole-dominated ambipolar transport characteristic,
thereby limiting its applications in complementary electronics. Herein,
we demonstrate an effective surface functionalization scheme on few-layer
black phosphorus, through in situ surface modification with potassium,
with a view toward high performance complementary device applications.
Potassium induces a giant electron doping effect on black phosphorus
along with a clear bandgap reduction, which is further corroborated
by in situ photoelectron spectroscopy characterizations. The electron
mobility of black phosphorus is significantly enhanced to 262 (377)
cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> by over
1 order of magnitude after potassium modification for two-terminal
(four-terminal) measurements. Using lithography technique, a spatially
controlled potassium doping technique is developed to establish high-performance
complementary devices on a single black phosphorus nanosheet, for
example, the p–n homojunction-based diode achieves a near-unity
ideality factor of 1.007 with an on/off ratio of ∼10<sup>4</sup>. Our findings coupled with the tunable nature of in situ modification
scheme enable black phosphorus as a promising candidate for further
complementary electronics