Feed aggregator

TOC Graphic

The Journal of Physical Chemistry CDOI: 10.1021/acs.jpcc.7b06093

TOC Graphic

LangmuirDOI: 10.1021/acs.langmuir.7b01519
Energy & FuelsDOI: 10.1021/acs.energyfuels.7b01119

Efforts to relocate artefacts to sites of origin could stall after gold robbery at national park.

Nature News doi: 10.1038/nature.2017.22479

Sports organizations are only starting to understand the harm that can be inflicted by high-contact activities. Science must play its part in highlighting the problem and in aiding diagnosis.

Nature 548 371 doi: 10.1038/548371a

Panel sought to help businesses and state and local governments prepare for the effects of global warming.

Nature News doi: 10.1038/nature.2017.22484

TOC Graphic

The Journal of Physical Chemistry CDOI: 10.1021/acs.jpcc.7b04974

TOC Graphic

The Journal of Physical Chemistry CDOI: 10.1021/acs.jpcc.7b07421

Since the discovery of Dirac physics in graphene, research in 2D materials has exploded with the aim of finding new materials and harnessing their unique and tunable electronic and optical properties. The follow-on work on 2D dielectrics and semiconductors has led to the emergence and development of hexagonal boron nitride, black phosphorus, and transition metal disulfides. However, the spectrum of good insulating materials is still very narrow. Likewise, 2D materials exhibiting correlated phenomena such as superconductivity, magnetism, and ferroelectricity have yet to be developed or discovered. These properties will significantly enrich the spectrum of functional 2D materials, particularly in the case of high phase-transition temperatures. They will also advance a fascinating fundamental frontier of size and proximity effects on correlated ground states. Here, a broad family of layered metal thio(seleno)phosphate materials that are moderate- to wide-bandgap semiconductors with incipient ionic conductivity and a host of ferroic properties are reviewed. It is argued that this material class has the potential to merge the sought-after properties of complex oxides with electronic functions of 2D and quasi-2D electronic materials, as well as to create new avenues for both applied and fundamental materials research in structural and magnetic correlations.

Thumbnail image of graphical abstract

Metal thiophosphates (MTPs) are a class of cleavable insulating materials with a common P2S6 structural framework. They span a very wide variety of transition metal cations, thus exhibiting ferroelectricity, magnetism, and optoelectronic properties, as well as rich solid state chemistry that can combine various properties within a single bulk, quasi-2D, or prospectively 2D crystal. In this respect, MTP compounds can be viewed as a layered analog to complex oxides.

Near-infrared (NIR)-light-triggered photothermal therapy (PTT) usually requires hyperthermia to >50 °C for effective tumor ablation, which can potentially induce inflammatory disease and heating damage of normal organs nearby, while tumor lesions without sufficient heating (e.g., the internal part) may survive after treatment. Achieving effective tumor killing under relatively low temperatures is thus critical toward successful clinical use of PTT. Herein, we design a simple strategy to fabricate poly(ethylene glycol) (PEG)-modified one-dimensional nanoscale coordination polymers (1D-NCPs) with intrinsic biodegradability, large surface area, pH-responsive behaviors, and versatile theranostic functions. With NCPs consisting of Mn2+/indocyanine green (ICG) as the example, Mn-ICG@pHis-PEG display efficient pH-responsive tumor retention after systemic administration and then load Gambogic acid (GA), a natural inhibitor of heat-shock protein 90 (Hsp90) that plays an essential role for cells to resist heating-induced damage. Such Mn-ICG@pHis-PEG/GA under a mild NIR-triggered heating is able to induce effective apoptosis of tumor cells, realizing low-temperature PTT (~43 °C) with excellent tumor destruction efficacy. This work not only develops a facile approach to fabricate PEGylated 1D-NCPs with tumor-specific pH responsiveness and theranostic functionalities, but also presents a unique low-temperature PTT strategy to kill cancer in a highly effective and minimally invasive manner.

Thumbnail image of graphical abstract

A one-dimensional (1D) PEGylated nanoscale coordination polymer (NCPs) is fabricated via a one-step method. After loading gambogic acid (GA), such Mn-ICG@pHis-PEG/GA displays efficient pH-responsive tumor retention after systemic administration. Owing to the GA-induced down-regulation of Hsp90 to overcome the thermal-resistance of tumor cells, highly effective in vivo destruction of tumors is relized with Mn-ICG@pHis-PEG/GA under low-temperature PTT at 43 °C.

TOC Graphic

LangmuirDOI: 10.1021/acs.langmuir.7b01826

Polymer zwitterions are generally regarded as hydrophilic and repellant or “slippery” materials. Here, a case is described in which the polymer zwitterion structure is tailored to decrease water solubility, stabilize emulsion droplets, and promote interdroplet adhesion. Harnessing the upper critical solution temperature of sulfonium- and ammonium-based polymer zwitterions in water, adhesive droplets are prepared by adding organic solvent to an aqueous polymer solution at elevated temperature, followed by agitation to induce emulsification. Droplet aggregation is observed as the mixture cools. Variation of salt concentration, temperature, polymer concentration, and polymer structure modulates these interdroplet interactions, resulting in distinct changes in emulsion stability and fluidity. Under attractive conditions, emulsions encapsulating 50–75% oil undergo gelation. By contrast, emulsions prepared under conditions where droplets are nonadhesive remain fluid and, for oil fractions exceeding 0.6, coalescence is observed. The uniquely reactive nature of the selected zwitterions allows their in situ modification and affords a route to chemically trigger deaggregation and droplet dispersion. Finally, experiments performed in a microfluidic device, in which droplets are formed under conditions that either promote or suppress adhesion, confirm the salt-responsive character of these emulsions and the persistence of adhesive interdroplet interactions under flow.

Thumbnail image of graphical abstract

Dipole–dipole interactions of polymer zwitterions promote adhesion between emulsion droplets, which exhibit responsiveness to both environmental and chemical triggers. Oil-in-water emulsions stabilized by polymer zwitterions become adhesive and gel under conditions where the polymers are insoluble in the aqueous phase. These interdroplet interactions are modulated by temperature, salt concentration, polymer concentration, zwitterion type, and reactions conducted at the oil–water interface.

Lead telluride has long been realized as an ideal p-type thermoelectric material at an intermediate temperature range; however, its commercial applications are largely restricted by its n-type counterpart that exhibits relatively inferior thermoelectric performance. This major limitation is largely solved here, where it is reported that a record-high ZT value of ≈1.83 can be achieved at 773 K in n-type PbTe-4%InSb composites. This significant enhancement in thermoelectric performance is attributed to the incorporation of InSb into the PbTe matrix resulting in multiphase nanostructures that can simultaneously modulate the electrical and thermal transport. On one hand, the multiphase energy barriers between nanophases and matrix can boost the power factor in the entire temperature range via significant enhancement of the Seebeck coefficient and moderately reducing the carrier mobility. On the other hand, the strengthened interface scattering at the intensive phase boundaries yields an extremely low lattice thermal conductivity. This strategy of constructing multiphase nanostructures can also be highly applicable in enhancing the performance of other state-of-the-art thermoelectric systems.

Thumbnail image of graphical abstract

A new strategy of constructing multiphase nanostructures can enhance the thermoelectric power factor and reduce the lattice thermal conductivity simultaneously. Through this strategy, it is reported that a record-high ZT value of ≈1.83 can be achieved at 773 K in n-type PbTe-4%InSb composites. Furthermore, the mechanisms introducing multiphase nanostructures are also highly applicable in other thermoelectric systems.

TOC Graphic

LangmuirDOI: 10.1021/acs.langmuir.7b01102

TOC Graphic

The Journal of Physical Chemistry CDOI: 10.1021/acs.jpcc.7b06012

This study describes a conductive ink formulation that exploits electrochemical sintering of Zn microparticles in aqueous solutions at room temperature. This material system has relevance to emerging classes of biologically and environmentally degradable electronic devices. The sintering process involves dissolution of a surface passivation layer of zinc oxide in CH3COOH/H2O and subsequent self-exchange of Zn and Zn2+ at the Zn/H2O interface. The chemical specificity associated with the Zn metal and the CH3COOH/H2O solution is critically important, as revealed by studies of other material combinations. The resulting electrochemistry establishes the basis for a remarkably simple procedure for printing highly conductive (3 × 105 S m−1) features in degradable materials at ambient conditions over large areas, with key advantages over strategies based on liquid phase (fusion) sintering that requires both oxide-free metal surfaces and high temperature conditions. Demonstrations include printed magnetic loop antennas for near-field communication devices.

Thumbnail image of graphical abstract

This study describes a conductive ink formulation that exploits electrochemical sintering of Zn microparticles in aqueous solutions at room temperature, with relevance to emerging classes of biologically and environmentally degradable electronic devices. The resulting electrochemistry establishes the basis for a remarkably simple procedure for printing highly conductive features in degradable materials at ambient conditions over large areas.

TOC Graphic

The Journal of Physical Chemistry CDOI: 10.1021/acs.jpcc.7b04494

A cascade amplification release nanoparticle (CARN) is constructed by the coencapsulation of β-lapachone and a reactive-oxygen-species (ROS)-responsive doxorubicin (DOX) prodrug, BDOX, in polymeric nanoparticles. Releasing β-lapachone first from the CARNs selectively increases the ROS level in cancer cells via NAD(P)H:quinone oxidoreductase-1 (NQO1) catalysis, which induces the cascade amplification release of DOX and overcomes multidrug resistance (MDR) in cancer cells, producing a remarkably improved therapeutic efficacy against MDR tumors with minimal side effects.

Thumbnail image of graphical abstract

A cascade amplification release nanoparticle is constructed by loading β-lapachone and a reactive-oxygen-species-responsive doxorubicin (DOX) prodrug in polymeric nanoparticles. The selective cascade amplification release of β-lapachone and DOX in cancer cells remarkably increases the selectivity of chemotherapy and overcomes the multidrug resistance (MDR) in cancer cells, producing a remarkably enhanced therapeutic efficacy against MDR tumors with minimal side effects.

Nanoscale manipulation of materials' physicochemical properties offers distinguished possibility to the development of novel electronic devices with ultrasmall dimension, fast operation speed, and low energy consumption characteristics. This is especially important as the present semiconductor manufacturing technique is approaching the end of miniaturization campaign in the near future. Here, a superior metal–insulator transition (MIT) of a 1D VO2 nanochannel constructed through an electric-field-induced oxygen ion migration process in V2O5 thin film is reported for the first time. A sharp and reliable MIT transition with a steep turn-on voltage slope of <0.5 mV dec−1, fast switching speed of 17 ns, low energy consumption of 8 pJ, and low variability of <4.3% is demonstrated in the VO2 nanochannel device. High-resolution transmission electron microscopy observation and theoretical computation verify that the superior electrical properties of the present device can be ascribed to the electroformation of nanoscale VO2 nanochannel in V2O5 thin films. More importantly, the incorporation of the present device into a Pt/HfO2/Pt/VO2/Pt 1S1R unit can ensure the correct reading of the HfO2 memory continuously for 107 cycles, therefore demonstrating its great possibility as a reliable selector in high-density crossbar memory arrays.

Thumbnail image of graphical abstract

A 1D vanadium dioxide nanochannel is constructed via electric-field-induced ion transport and related solid-state redox reaction in V2O5 thin film. A superior metal–insulator transition of VO2 with sharp transition, fast switching speed, low energy consumption, and excellent reproducibility is demonstrated. The VO2 nanostructure can act as a promising candidate for the selector element in high-density crossbar memory arrays.

Heteroepitaxial growth of lattice mismatched materials has advanced through the epitaxy of thin coherently strained layers, the strain sharing in virtual and nanoscale substrates, and the growth of thick films with intermediate strain-relaxed buffer layers. However, the thermal mismatch is not completely resolved in highly mismatched systems such as in GaN-on-Si. Here, geometrical effects and surface faceting to dilate thermal stresses at the surface of selectively grown epitaxial GaN layers on Si are exploited. The growth of thick (19 µm), crack-free, and pure GaN layers on Si with the lowest threading dislocation density of 1.1 × 107 cm−2 achieved to date in GaN-on-Si is demonstrated. With these advances, the first vertical GaN metal–insulator–semiconductor field-effect transistors on Si substrates with low leakage currents and high on/off ratios paving the way for a cost-effective high power device paradigm on an Si CMOS platform are demonstrated

Thumbnail image of graphical abstract

Thick (19 µm), crack-free, and pure GaN-on-Si is achieved by strain engineering and metal–organic chemical vapor deposition. A record-low threading dislocation density of 1.1 × 107 cm−2 and vertical trench-gate normally off metal–insulator–semiconductor field-effect transistor are achieved for the first time in GaN-on-Si.

Pages

Zircon - This is a contributing Drupal Theme
Design by WeebPal.