86 research outputs found

    Media 1: Optimization of the excitation light sheet in selective plane illumination microscopy

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    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

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    Novel poly­(vinyl alcohols) (PVA) functionalized with pendant thermo- and pH-responsive groups were prepared by carbonyl­diimidazole (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 Å) 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

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    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)

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    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)

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    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

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    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 poly­(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

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    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

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    <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>

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    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

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    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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