86 research outputs found
Media 1: Optimization of the excitation light sheet in selective plane illumination microscopy
Originally published in Biomedical Optics Express on 01 March 2015 (boe-6-3-881
Dual Thermoresponsive and pH-Responsive Poly(vinyl alcohol) Derivatives: Synthesis, Phase Transition Study, and Functional Applications
Novel polyÂ(vinyl alcohols) (PVA)
functionalized with pendant thermo- and pH-responsive groups were
prepared by carbonylÂdiimidazole (CDI)-mediated couplings of <i>N</i><sup>1</sup>,<i>N</i><sup>1</sup>-diethylethane-1,2-diamine
(DEEDA) with controllable modification degree. Nuclear magnetic response
(NMR) and IR have verified the successful modification of PVA. The
macro- and microscopic phase transition behavior of the obtained PVA-DEEDA-<i>t</i> (<i>t</i> = 10, 30, 70, and 90 h) was thoroughly
characterized using various techniques, including turbidity measurement,
NMR, and dynamic light scattering (DLS). PVA-DEEDA-<i>t</i> is demonstrated to possess tunable lower critical solution temperature
(LCST) between 58 and 24 °C. LCST is dependent on solution pH
and degree of PVA modification (14.1–20.9%). By combining DLS
and DOSY characterizations, it can be concluded that both coil-to-globule
transition and aggregation occurred to PVA-DEEDA-<i>t</i> during phase transition, while only coil-to-globule transition can
be detected for the pristine PVA. 2D NOESY proved that the −NH–
segment on PVA-DEEDA-<i>t</i> is in close (<5 Ã…)
proximity to the main chain of PVA, as evidenced by the appearance
of NOE signal between −NH– on DEEDA and −CH<sub>2</sub>–CH– chain of PVA when the temperature increased
above LCST. To exploit the functional applications, the PVA-DEEDA-90
h was transformed into gel and film forms. PVA-DEEDA-90 h gel obtained
by adding borax enabled controlled drug (e.g., RhB) release due to
its temperature- and pH-dependent permeability. The PVA-DEEDA-90 h
film was also casted on ITO glass, creating a smart surface with tunable
wettability and interfacial ion transportation with high sensitivity
toward the pH and temperature
Highly Alloyed PtRu Nanoparticles Confined in Porous Carbon Structure as a Durable Electrocatalyst for Methanol Oxidation
The
state-of-the-art carbon-supported PtRu catalysts are widely
used as the anode catalysts in polymer electrolyte fuel cells (PEMFCs)
but suffer from instability issues. Severe ruthenium dissolution occurring
at potentials higher than 0.5 V vs NHE would result in a loss of catalytic
activity of PtRu hence a
worse performance of the fuel cell. In this work, we report an ultrastable
PtRu electrocatalyst for methanol oxidation by confining highly
alloyed PtRu nanoparticles in a hierarchical porous carbon structure.
The structural characteristics, e.g., the surface composition and
the morphology evolution, of the catalyst during the accelerated degradation
test were characterized by the Cu-stripping voltammetry and the TEM/SEM
observations. From the various characterization results, it is revealed
that both the high alloying degree and the pore confinement of PtRu
nanoalloys play significant roles in suppressing the degradation processes,
including Ru dissolution and particle agglomeration/migration. This
report provides an opportunity for efficient design and fabrication
of highly stable bimetallic or trimetallic electrocatalysts in a large
variety of applications
Media 2: Snapshot hyperspectral retinal camera with the Image Mapping Spectrometer (IMS)
Originally published in Biomedical Optics Express on 01 January 2012 (boe-3-1-48
Media 1: Snapshot hyperspectral retinal camera with the Image Mapping Spectrometer (IMS)
Originally published in Biomedical Optics Express on 01 January 2012 (boe-3-1-48
Polystyrenesulfonate Threaded in MIL-101Cr(III): A Cationic Polyelectrolyte Synthesized Directly into a Metal–Organic Framework
Incorporation of an ion-exchange
polymer in a metal–organic
framework (MOF) is an attractive strategy to achieve fast ion exchange
by increasing surface area and porosity of the material. Synthesis
of a cationic polyelectrolyte in a MOF is reported here for the first
time. Sodium polyÂ(4-styrenesulfonate) threaded in MIL-101 (NaPSS∼MIL-101)
is synthesized directly with polymerization in situ of the MOF. NaPSS∼MIL-101
exhibits superior exchange kinetics, high selectivity with co-ion
rejection, reversibility, and durability. The polyelectrolyte threaded
in MOF has a larger specific volume compared to its bulk state and
possesses advantageous properties. The fixed charges of the polyelectrolyte
are exposed for full interaction with solvated ions and solvent, without
the need of swelling or restructuring the porous framework
Media 2: Multiview optical resolution photoacoustic microscopy
Originally published in Optica on 20 October 2014 (optica-1-4-217
Phenolic resin as a carbon source for the synthesis of monometallic Mo and bimetallic CoMo carbides via carbothermal reduction route
<p>It was the first time that phenolic resin (PR) was used as a carbon source for the synthesis of nanostructured monometallic Mo and bimetallic CoMo carbides via carbothermal reduction route. The results showed that phase-pure β-Mo<sub>2</sub>C can be formed under an Ar atmosphere at 900°C or a H<sub>2</sub> atmosphere above 700°C. However, almost pure CoMo carbides (Co<sub>3</sub>Mo<sub>3</sub>C and Co<sub>6</sub>Mo<sub>6</sub>C) can be obtained only under a H<sub>2</sub> atmosphere at a low temperature of 630°C for 24 and 48 h, respectively. The role of PR in the preparation process has been investigated and a detailed formation mechanism was proposed based on the experimental results.</p> <p></p
Plasmon-Mediated Generation of Reactive Oxygen Species from Near-Infrared Light Excited Gold Nanocages for Photodynamic Therapy <i>in Vitro</i>
We have performed fundamental assays of gold nanocages (AuNCs) as intrinsic inorganic photosensitizers mediating generation of reactive oxygen species (ROS) by plasmon-enabled photochemistry under near-infrared (NIR) one/two-photon irradiation. We disclosed that NIR light excited hot electrons transform into either ROS or hyperthermia. Electron spin resonance spectroscopy was applied to demonstrate the production of three main radical species, namely, singlet oxygen (<sup>1</sup>O<sub>2</sub>), superoxide radical anion (O<sub>2</sub><sup>–•</sup>), and hydroxyl radical (<sup>•</sup>OH). The existence of hot electrons from irradiated AuNCs was confirmed by a well-designed photoelectrochemical experiment based on a three-electrode system. It could be speculated that surface plasmons excited in AuNCs first decay into hot electrons, and then the generated hot electrons sensitize oxygen to form ROS through energy and electron transfer modes. We also compared AuNCs’ ROS generation efficiency in different surface chemical environments under one/two-photon irradiation and verified that, compared with one-photon irradiation, two-photon irradiation could bring about much more ROS. Furthermore, <i>in vitro</i>, under two-photon irradiation, ROS can trigger mitochondrial depolarization and caspase protein up-regulation to initiate tumor cell apoptosis. Meanwhile, hyperthermia mainly induces tumor cell necrosis. Our findings suggest that plasmon-mediated ROS and hyperthermia can be facilely regulated for optimized anticancer phototherapy
Living Growth Kinetics of Polymeric Micelles on a Substrate
Living growth of micelles on the substrate is an intriguing
phenomenon;
however, little is known about its growth kinetics, especially from
a theoretical viewpoint. Here, we examine the living growth kinetics
of polymeric micelles on a hydrophobic substrate immersed in an aqueous
solution. The block copolymers first assemble into short cylinder
seeds anchored on the substrate. Then, the small aggregates of block
copolymers in the solutions fuse onto the active ends of the anchored
seeds, leading to micelle growth on the substrate. A theoretical model
is proposed to interpret such living growth kinetics. It is revealed
that the growth rate coefficient on the substrate is independent of
the copolymer concentration and the multistep feedings; however, it
is significantly affected by the surface hydrophobicity. Brownian
dynamics simulations further support the proposed growth mechanism
and the kinetic model. This work enriches living assembly systems
and provides guidance for fabricating bioinspired surface nanostructures
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