6 research outputs found
Local Enhancement of Exciton Emission of Monolayer MoS<sub>2</sub> by Copper Phthalocyanine Nanoparticles
Monolayer transition-metal
dichalcogenides (1L-TMDs) provide ideal
platforms to study light emission using two-dimensionally confined
excitons. Recent studies have shown that the exciton emissions of
1L-TMDs can be conveniently modulated by developing heterostructures
with zero-dimensional nanoparticles (NPs) or quantum dots. In this
study, we synthesized organic semiconducting copper phthalocyanine
(CuPc) NPs with sizes in the range of 30–70 nm by a re-precipitation
method and decorated the chemical vapor deposition-grown 1L-MoS<sub>2</sub> with these NPs. This hybrid system exhibited a 6 times larger
local photoluminescence (PL) at the positions of the CuPc NPs compared
with the pristine 1L-MoS<sub>2</sub> sample. The PL enhancement and
spectral modification of the 1L-MoS<sub>2</sub> decorated with CuPc
NPs were attributed to the p-doping effect of the CuPc NPs, confirmed
by spectral analysis and field-effect transistor measurements
Charge Transport in MoS<sub>2</sub>/WSe<sub>2</sub> van der Waals Heterostructure with Tunable Inversion Layer
Despite numerous
studies on two-dimensional van der Waals heterostructures,
a full understanding of the charge transport and photoinduced current
mechanisms in these structures, in particular, associated with charge
depletion/inversion layers at the interface remains elusive. Here,
we investigate transport properties of a prototype multilayer MoS<sub>2</sub>/WSe<sub>2</sub> heterojunction <i>via</i> a tunable
charge inversion/depletion layer. A charge inversion layer was constructed
at the surface of WSe<sub>2</sub> due to its relatively low doping
concentration compared to that of MoS<sub>2</sub>, which can be tuned
by the back-gate bias. The depletion region was limited within a few
nanometers in the MoS<sub>2</sub> side, while charges are fully depleted
on the whole WSe<sub>2</sub> side, which are determined by Raman spectroscopy
and transport measurements. Charge transport through the heterojunction
was influenced by the presence of the inversion layer and involves
two regimes of tunneling and recombination. Furthermore, photocurrent
measurements clearly revealed recombination and space-charge-limited
behaviors, similar to those of the heterostructures built from organic
semiconductors. This contributes to research of various other types
of heterostructures and can be further applied for electronic and
optoelectronic devices
Simple and Integrated Spintip-Based Technology Applied for Deep Proteome Profiling
Great
efforts have been taken for developing high-sensitive mass
spectrometry (MS)-based proteomic technologies, among which sample
preparation is one of the major focus. Here, a simple and integrated
spintip-based proteomics technology (SISPROT) consisting of strong
cation exchange beads and C<sub>18</sub> disk in one pipet tip was
developed. Both proteomics sample preparation steps, including protein
preconcentration, reduction, alkylation, and digestion, and reversed
phase (RP)-based desalting and high-pH RP-based peptide fractionation
can be achieved in a fully integrated manner for the first time. This
easy-to-use technology achieved high sensitivity with negligible sample
loss. Proteomic analysis of 2000 HEK 293 cells readily identified
1270 proteins within 1.4 h of MS time, while 7826 proteins were identified
when 100000 cells were processed and analyzed within only 22 h of
MS time. More importantly, the SISPROT can be easily multiplexed on
a standard centrifuge with good reproducibility (Pearson correlation
coefficient > 0.98) for both single-shot analysis and deep proteome
profiling with five-step high-pH RP fractionation. The SISPROT was
exemplified by the triplicate analysis of 100000 stem cells from human
exfoliated deciduous teeth (SHED). This led to the identification
of 9078 proteins containing 3771 annotated membrane proteins, which
was the largest proteome data set for dental stem cells reported to
date. We expect that the SISPROT will be well suited for deep proteome
profiling for fewer than 100000 cells and applied for translational
studies where multiplexed technology with good label-free quantification
precision is required
Simple and Integrated Spintip-Based Technology Applied for Deep Proteome Profiling
Great
efforts have been taken for developing high-sensitive mass
spectrometry (MS)-based proteomic technologies, among which sample
preparation is one of the major focus. Here, a simple and integrated
spintip-based proteomics technology (SISPROT) consisting of strong
cation exchange beads and C<sub>18</sub> disk in one pipet tip was
developed. Both proteomics sample preparation steps, including protein
preconcentration, reduction, alkylation, and digestion, and reversed
phase (RP)-based desalting and high-pH RP-based peptide fractionation
can be achieved in a fully integrated manner for the first time. This
easy-to-use technology achieved high sensitivity with negligible sample
loss. Proteomic analysis of 2000 HEK 293 cells readily identified
1270 proteins within 1.4 h of MS time, while 7826 proteins were identified
when 100000 cells were processed and analyzed within only 22 h of
MS time. More importantly, the SISPROT can be easily multiplexed on
a standard centrifuge with good reproducibility (Pearson correlation
coefficient > 0.98) for both single-shot analysis and deep proteome
profiling with five-step high-pH RP fractionation. The SISPROT was
exemplified by the triplicate analysis of 100000 stem cells from human
exfoliated deciduous teeth (SHED). This led to the identification
of 9078 proteins containing 3771 annotated membrane proteins, which
was the largest proteome data set for dental stem cells reported to
date. We expect that the SISPROT will be well suited for deep proteome
profiling for fewer than 100000 cells and applied for translational
studies where multiplexed technology with good label-free quantification
precision is required
Photocurrent Switching of Monolayer MoS<sub>2</sub> Using a Metal–Insulator Transition
We
achieve switching on/off the photocurrent of monolayer molybdenum
disulfide (MoS<sub>2</sub>) by controlling the metal–insulator
transition (MIT). N-type semiconducting MoS<sub>2</sub> under a large
negative gate bias generates a photocurrent attributed to the increase
of excess carriers in the conduction band by optical excitation. However,
under a large positive gate bias, a phase shift from semiconducting
to metallic MoS<sub>2</sub> is caused, and the photocurrent by excess
carriers in the conduction band induced by the laser disappears due
to enhanced electron–electron scattering. Thus, no photocurrent
is detected in metallic MoS<sub>2</sub>. Our results indicate that
the photocurrent of MoS<sub>2</sub> can be switched on/off by appropriately
controlling the MIT transition by means of gate bias
ZnO Nanowire Arrays on 3D Hierachical Graphene Foam: Biomarker Detection of Parkinson’s Disease
We report that vertically aligned ZnO nanowire arrays (ZnO NWAs) were fabricated on 3D graphene foam (GF) and used to selectively detect uric acid (UA), dopamine (DA), and ascorbic acid (AA) by a differential pulse voltammetry method. The optimized ZnO NWA/GF electrode provided a high surface area and high selectivity with a detection limit of 1 nM for UA and DA. The high selectivity in the oxidation potential was explained by the gap difference between the lowest unoccupied and highest occupied molecular orbitals of a biomolecule for a set of given electrodes. This method was further used to detect UA levels in the serum of patients with Parkinson’s disease (PD). The UA level was 25% lower in PD patients than in healthy individuals. This finding strongly implies that UA can be used as a biomarker for PD