153 research outputs found
Electronic Structure of Twisted Bilayers of Graphene/MoS<sub>2</sub> and MoS<sub>2</sub>/MoS<sub>2</sub>
Vertically
stacked two-dimensional multilayer structures have become a promising
prototype for functionalized
nanodevices due to their wide range of tunable properties. In this
paper we performed first-principles calculations to study the electronic
structure of nontwisted and twisted bilayers of hybrid graphene/MoS<sub>2</sub> (Gr/MoS<sub>2</sub>) and MoS<sub>2</sub>/MoS<sub>2</sub>.
Both twisted bilayers
of Gr/MoS<sub>2</sub> and MoS<sub>2</sub>/MoS<sub>2</sub> show significant
differences in band structures from the nontwisted ones with the appearance
of the crossover between direct and indirect
band gap and gap variation. More interestingly, the band structures
of twisted Gr/MoS<sub>2</sub> with different rotation angles are very
different from each other, while those of MoS<sub>2</sub>/MoS<sub>2</sub> are very similar. The variation of band structure with rotation
angle in Gr/MoS<sub>2</sub> is, indeed, originated from the misorientation-induced
lattice strain and the sensitive band-strain dependence of MoS<sub>2</sub>
Visualization 1: Graphics processing unit–assisted real-time three-dimensional measurement using speckle-embedded fringe
Measurement result of a shaking paper Originally published in Applied Optics on 01 August 2015 (ao-54-22-6865
Visualization 1: Adaptive step-size strategy for noise-robust Fourier ptychographic microscopy
The evolution of the amplitude reconstructions of an USAF resolution target with an adaptive step-size. Originally published in Optics Express on 05 September 2016 (oe-24-18-20724
Staged Self-Assembly of Colloidal Metastructures
We demonstrate sequential assembly of chemically patchy
colloids such that their valence differs from stage to stage to produce
hierarchical structures. For proof of concept, we employ ACB triblock
spheres suspended in water, with the C middle band electrostatically
repulsive. In the first assembly stage, only A–A hydrophobic
attraction contributes, and discrete clusters form. They can be stored,
but subsequently activated to allow B–B attractions, leading
to higher-order assembly of clusters with one another. The growth
dynamics, observed at a single particle level by fluorescence optical
microscopy, obey the kinetics of stepwise polymerization, forming
chains, pores, and networks. Between linked clusters, we identify
three possible bond geometries, linear, triangular, and square, by
an argument that is generalizable to other patchy colloid systems.
This staged assembly strategy offers a promising route to fabricate
colloidal assemblies bearing multiple levels of structural and functional
complexity
Organic Stealth Nanoparticles for Highly Effective <i>in Vivo</i> Near-Infrared Photothermal Therapy of Cancer
In recent years, a wide range of near-infrared (NIR) light absorbing nanomaterials, mostly inorganic ones, have been developed for photothermal therapy (PTT) of cancer. In this work, we develop a novel organic PTT agent based on poly-(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS), a conductive polymer mixture with strong NIR absorbance, for <i>in vivo</i> photothermal treatment of cancer. After being layer-by-layer coated with charged polymers and then conjugated with branched polyethylene glycol (PEG), the obtained PEDOT:PSS-PEG nanoparticles are highly stable in the physiological environment and exhibit a stealth-like behavior after intravenous injection with a long blood circulation half-life. As a result, an extremely high <i>in vivo</i> tumor uptake of PEDOT:PSS-PEG attributed to the tumor-enhanced permeability and retention effect is observed. We further use PEDOT:PSS-PEG as a PTT agent for <i>in vivo</i> cancer treatment and realize excellent therapeutic efficacy in a mouse tumor model under NIR light irradiation at a low laser power density. Comprehensive blood tests and careful histological examination reveal no apparent toxicity of PEDOT:PSS-PEG to mice at our treated dose within 40 days. To our best knowledge, this work is the first to use systemically administrated conductive polymer nanoparticles for highly effective <i>in vivo</i> PTT treatment in animals and encourages further explorations of those organic nanomaterials for cancer theranostic applications
Media 3: High-speed transport-of-intensity phase microscopy with an electrically tunable lens
Originally published in Optics Express on 07 October 2013 (oe-21-20-24060
Spatial scaling of soil salinity indices along a temporal coastal reclamation area transect in China using wavelet analysis
<p>High spatial variability of soil salinity in coastal reclamation regions makes it difficult to obtain accurate scale-dependent information. The objectives of this study were to describe the spatial patterns of saline-sodic soil properties (using soil pH, electrical conductivity (EC<sub>1:5</sub>) and sodium ion content (<i>SIC</i>) as indicators) and to gain knowledge of the scaling relationships between those variables. The soil pH, EC<sub>1:5</sub> and <i>SIC</i> data were measured at intervals of 285 m along a 13,965-m temporal transect in a coastal region of China. The spatial variability of soil pH was weak but it was strong for soil EC<sub>1:5</sub> and <i>SIC</i> at the measurement scale. There was a significant positive correlation between soil EC<sub>1:5</sub> and <i>SIC</i>, while correlations between soil pH and either EC<sub>1:5</sub> or <i>SIC</i> were weak and negative. For each saline-sodic soil parameter, the variability changed with the decomposition scales. The high-variance area at the larger scales (≥570 m) occupied less than 10% of the total area in the local wavelet spectrum, which meant that the spatial variations of the salinity indicators were insignificant at these scales. For local wavelet coherency, at a scale of 1500–2800 m and a sampling distance of 0–4500 m, the covariance was statistically significant between any two of the saline-sodic soil parameters.</p
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Dynamic Charge Carrier Trapping in Quantum Dot Field Effect Transistors
Noncrystalline semiconductor materials
often exhibit hysteresis in charge transport measurements whose mechanism
is largely unknown. Here we study the dynamics of charge injection
and transport in PbS quantum dot (QD) monolayers in a field effect
transistor (FET). Using Kelvin probe force microscopy, we measured
the temporal response of the QDs as the channel material in a FET
following step function changes of gate bias. The measurements reveal
an exponential decay of mobile carrier density with time constants
of 3–5 s for holes and ∼10 s for electrons. An Ohmic
behavior, with uniform carrier density, was observed along the channel
during the injection and transport processes. These slow, uniform
carrier trapping processes are reversible, with time constants that
depend critically on the gas environment. We propose that the underlying
mechanism is some reversible electrochemical process involving dissociation
and diffusion of water and/or oxygen related species. These trapping
processes are dynamically activated by the injected charges, in contrast
with static electronic traps whose presence is independent of the
charge state. Understanding and controlling these processes is important
for improving the performance of electronic, optoelectronic, and memory
devices based on disordered semiconductors
Media 3: Transport-of-intensity phase imaging using Savitzky-Golay differentiation filter - theory and applications
Originally published in Optics Express on 11 March 2013 (oe-21-5-5346
MOESM1 of Microbial community compositions in different functional zones of Carrousel oxidation ditch system for domestic wastewater treatment
Additional file 1: Table S1. Characteristics of the six representative full-scale WWTPs. Table S2: Raw and trimmed reads, Good’s coverage, Chao1, ACE, Shannon, Simpson, and plus numbers of OTUs of the activated sludge samples
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