Search

In this paper, large single crystals of diamond were synthesized in a pure Co–C system at 5.6 GPa and 1450–1470 °C. The diamond morphology, nitrogen content, and Co-related optical centres were investigated in depth. The results show that the diamonds are mostly bicrystalline or polycrystalline, with different surface defects, and the grown single crystals exhibit an octahedral morphology, with primarily {111} faces. The colour of the diamonds is brownish green-yellow and the nitrogen content is up to 980 ppm. The photoluminescence (PL) spectra show the presence of Co–V centres at 623 nm (V3Co2)0 and 843 nm (V1Co1+) in the diamonds. The intensity of Co-related optical centres at 623 nm and 843 nm gradually decreased with increases in the annealing temperature, and finally disappeared. Interestingly, Co–N complex defects appeared at 545 nm and 581 nm after annealing at 1700 °C, and the 524 nm Co–N complexes only appeared when the nitrogen almost completely aggregated after annealing up to 1800–1900 °C, and their intensity gradually increased with increasing annealing temperature. Furthermore, when nitrogen was removed from the growth system, the Co-related optical centres did not appear in the type IIa diamonds before and after annealing, which indicates that nitrogen impurities play an important role in the formation of Co-related optical centres. [ABSTRACT FROM AUTHOR]

The local electric field affects the morphology of ionomer films on electrodes and thus the transport phenomena in ionomer films. Therefore, tuning the local electric field is a potential way to reduce the O2 transport resistance in the catalyst layers of fuel cells. This is the first study to explore the transport phenomena in ionomer films at the nanoscale under a local electric field. The results show that the Pt electrodes become more hydrophilic, thereby suppressing the dense arrangement of perfluorosulfonic acid (PFSA) chains that highly hinder O2 transport under a local electric field. Moreover, the water molecules become more ordered, and the side chains of PFSA are better stretched due to the presence of the electric field. Furthermore, the agglomeration of both water molecules and PFSA molecules is suppressed by the electric field, forming an effective PFSA–water interface for O2 transport. Therefore, the more uniform distributions of water and PFSA molecules, more hydrophilic electrodes and better stretching of PFSA side chains in a stronger electric field help form more O2 transport paths and thus reduce the O2 transport resistance. These findings are valuable for the fundamental understanding of transport phenomena at electrolyte–electrode interfaces under an electric field and inspire novel electrode designs with low O2 transport resistance for fuel cells by strengthening the local electric field. [ABSTRACT FROM AUTHOR]

The ability to determine the identity of specific proteins is a critical challenge in many areas of cellular and molecular biology, and in medical diagnostics. Here, we present a macine learning aided microfluidic protein characterisation strategy that within a few minutes generates a three-dimensional fingerprint of a protein sample indicative of its amino acid composition and size and, thereby, creates a unique signature for the protein. By acquiring such multidimensional fingerprints for a set of ten proteins and using machine learning approaches to classify the fingerprints, we demonstrate that this strategy allows proteins to be classified at a high accuracy, even though classification using a single dimension is not possible. Moreover, we show that the acquired fingerprints correlate with the amino acid content of the samples, which makes it is possible to identify proteins directly from their sequence without requiring any prior knowledge about the fingerprints. These findings suggest that such a multidimensional profiling strategy can lead to the development of a novel method for protein identification in a microfluidic format. [ABSTRACT FROM AUTHOR]

Studying the influence of oxygen on the growth and properties of diamond has research significance. In this paper, we created an oxygen-rich environment by adding Ni2O3 to the Fe–Ni–C system. Large single crystals of oxygen-containing diamond were successfully synthesized using the temperature gradient method (TGM) in a China-type large volume cubic high-pressure apparatus (CHPA) at 5.5–6.0 GPa and 1360–1600 °C. The results show that with the increase of the Ni2O3 content in the Fe–Ni–C system, the rate of diamond growth decreased while the conditions for diamond growth were enhanced. The morphology of the diamonds changed from {111}, {110} and {113} mixed faces to {111} dominant face. The IR results show that the presence of Ni2O3 increased the nitrogen content in diamonds from 237 ppm to 543 ppm. When 3.5 wt% Ni2O3 was added, A-centre nitrogen began to appear in the diamonds. The XPS results confirmed that oxygen successfully entered the diamond lattice in the form of C–O, C＝O, O–C＝O and N–O with a high concentration of Ni2O3 additives. Meanwhile, there were no obvious impurity inclusions and cracks in the diamond crystals. In addition, the Raman peak position of the diamond appeared to red shift, and the FWHM increased from 4.93 cm−1 to 5.52 cm−1. [ABSTRACT FROM AUTHOR]

Membrane proteins perform a vast range of vital biological functions and are the gatekeepers for exchange of information and matter between the intracellular and extracellular environment. However, membrane protein interactions can be challenging to characterise in a quantitative manner due to the low solubility and large size of the membrane protein complex with associated lipid or detergent molecules. Here, we show that measurements of the changes in charge and diffusivity on the micron scale allow for non-disruptive studies of membrane protein interactions in solution. The approach presented here uses measurements of key physical properties of membrane proteins and their ligands to characterise the binding equilibrium parameters. We demonstrate this approach for human aquaporins (AQPs), key membrane proteins in the regulation of water homeostasis in cells. We perform quantitative measurements to characterise the interactions between two full-length AQP isoforms and the regulatory protein, calmodulin (CaM), and show that CaM selectively binds AQP0. Through direct measurements of the diffusivity and mobility in an external electric field, the diffusion coefficients and electrophoretic mobilities are determined for the individual components and the resulting AQP0–CaM complex. Furthermore, we obtain directly the binding equilibrium parameters and effective charge of each component. These results open up a route towards the use of microfluidics as a general platform in protein science and open up new possibilities for the characterisation of membrane protein interactions in solution. [ABSTRACT FROM AUTHOR]

The chemical composition can directly tune the transport properties of Cu2Se liquid-like materials, including the carrier concentration, carrier mobility and superionic feature. In this work, the off-stoichiometry effects of both the deficiency and excess of Cu on the phase transition and thermoelectric properties of Cu2+δSe (−0.1 ≤ δ ≤ 0.05) compounds are investigated. The Cu2+δSe samples were synthesized by a high-pressure and high-temperature (HPHT) technique in 30 minutes. Cu2+δSe (−0.1 ≤ δ < 0) existed as a mixture of the monoclinic α-Cu2Se phase and cubic β-Cu2Se phase at room temperature, while only the monoclinic α-Cu2Se phase was detected in the Cu2+δSe (0 ≤ δ ≤ 0.05) compounds. Increasing the Cu content can effectively regulate the carrier concentration and reduce the thermal conductivity from 1.45 W m−1 K−1 (δ = −0.1) to 0.47 W m−1 K−1 (δ = 0.05) at 843 K. The ultralow lattice thermal conductivity of 0.3 W m−1 K−1 was achieved for Cu1.97Se and Cu2.0Se by stoichiometry tuning. A maximum zT value of 1.46 at 843 K was obtained for Cu2.0Se, which is 100% higher than that of Cu1.9Se. This work demonstrates the potential of off-stoichiometry for tuning the TE properties of Ag+ and Cu+ based superionic materials. [ABSTRACT FROM AUTHOR]

The poor electrical conductivity of titanium oxide is a chief hurdle against the enhancement of its thermoelectric properties and increasing its reduction degree is an effective way for advancing its electrical conductivity. Strongly reduced titanium oxides, however, are rarely investigated for their thermoelectric properties so far. Here they were successfully synthesized by the efficient high-pressure and high-temperature (HPHT) method and the first systematic investigations about their thermoelectric properties were conducted. It was revealed that the samples were composed of phases TiO and Ti2O3. The high-pressure modulated morphologies were complicated and the microstructures were rich in lattice defects and nanoscale grains, the characteristics of pressure-modulated samples. Consequently, the electrical resistivity was greatly suppressed compared with that of other semiconductors and the changes in the conducting types of the samples with measurement-temperature were diverse, p → n or n → p → n or n-type all the time. Besides, the common Lorentz number was no longer applicable. The modulation by high-pressure is responsible for these. This work provides prospective strategies about upgrading the thermoelectric properties of titanium oxides under HPHT. [ABSTRACT FROM AUTHOR]

Circular dichroism spectroscopy has become a powerful tool to characterise proteins and other biomolecules. For heterogeneous samples such as those present for interacting proteins, typically only average spectroscopic features can be resolved. Here we overcome this limitation by using free-flow microfluidic size separation in-line with synchrotron radiation circular dichroism to resolve the secondary structure of each component of a model protein mixture containing monomers and fibrils. To enable this objective, we have integrated far-UV compatible measurement chambers into PDMS-based microfluidic devices. Two architectures are proposed so as to accommodate for a wide range of concentrations. The approach, which can be used in combination with other bulk measurement techniques, paves the way to the study of complex mixtures such as the ones associated with protein misfolding and aggregation diseases including Alzheimer's and Parkinson's diseases. [ABSTRACT FROM AUTHOR]

Cu2Se is a p-type semiconducting compound that possesses excellent thermoelectric properties which exhibit great potential for practical applications. In recent years, there have been many ways to improve thermoelectric properties. Reducing the thermal conductivity is a very effective way to obtain high performance thermoelectric materials. In this study, a series of Cu2−xLixSe (x = 0, 0.01, 0.02 and 0.03) polycrystalline bulk samples were successfully prepared by hot-pressing the nanopowders made by hydrothermal synthesis to investigate the doping effects of Li on the phase structure, microstructure and thermoelectric properties of Cu2Se. Compared with the Li-free Cu2Se, the introduction of Li element increases the Seebeck coefficient. Importantly, both nanopores and Li substitution were observed which can reduce κLvia increased scattering phonons. At 973 K, the Cu1.98Li0.02Se sample presented an excellent ZT of 2.14. [ABSTRACT FROM AUTHOR]

In this paper, IIa, Ib, N-doped and N–H co-doped diamonds were studied, and the interaction mechanisms between hydrogen and nitrogen in the diamonds were investigated in detail. The results show that the degree of nitrogen aggregation in the {111} face is higher than that in the {100} face. The N-doped and N–H co-doped crystals exhibit an obvious color difference between the {100} and {111} faces within the same crystal after annealing. The existence of hydrogen is favorable for the aggregation of nitrogen atoms from C-centers to A-centers and B-centers in diamonds. By annealing N–H co-doped diamonds, hydrogen-doped IaA+B type synthetic "natural" diamonds were obtained. [ABSTRACT FROM AUTHOR]

In this paper, we report the influence of oxygen and hydrogen additives in the metal melt on the growth process, morphology, and defect-and-impurity structure of large single-crystal diamonds. The main experiments were performed in the Ni70Mn25Co5–C system at pressure ranging from 5.5 GPa to 6.5 GPa, temperature from 1250 °C to 1550 °C and C6H8O7 concentration from 0 to 1.0 wt%. It was found that the synthesis conditions (temperature and pressure) increase with the increasing quantity of C6H8O7 additive. As the C6H8O7 content was increased from 0 to 0.8 wt%, the presence of oxygen and hydrogen was more likely to cause defects in the {100} surface. A further increase in the C6H8O7 concentration above approximately 0.9 wt% completely terminated the nucleation and growth of the diamonds and led to the crystallization of graphite alone. FTIR, Raman and XPS test results showed that oxygen and hydrogen coexist in the diamond crystal. [ABSTRACT FROM AUTHOR]

Te–Sn co-doped Co4Sb12 bulk polycrystalline materials Co4Sb11.7−xTexSn0.3 have been prepared using a high pressure and high temperature method and then characterized using X-ray diffraction. The aim was to use the disorder of the lattice orientation generated by both high pressure and doping with Te and Sn to reduce the thermal conductivity. The thermoelectric properties were measured at room temperature. As expected, as the synthesis pressure increased, the Seebeck coefficient and electrical resistivity increased, but the thermal conductivity decreased greatly. A minimum thermal conductivity of 2.41 W m−1 K−1 was obtained at room temperature for Co4Sb11Te0.7Sn0.3 synthesized at 3 GPa. [ABSTRACT FROM AUTHOR]

We report a significant enhancement in the figure of merit ZT of bulk BiSbTe3 fabricated by high pressure sintering technique under variable pressures. High pressure intervention during synthesis processes can effectively adjust the thermoelectric transport properties and crystal structures of the reaction products. The novel vibration modes produced by high pressure in Raman spectra can induce a positive role in the reduction of thermal conductivity. Meanwhile, the electrical resistivity can also obtain an efficient decrease due to the effect of high pressure on the texture and the preferred orientation. Because of these positive effects, the maximum ZT has reached 1.4 at 432 K from synthesized BiSbTe3 at 2.5 GPa in a short period. Therefore, we present that the appropriate high-pressure has a positive effect on the thermoelectric transport properties to produce the significant enhancement in thermoelectric properties of BiSbTe3. [ABSTRACT FROM AUTHOR]

Circular dichroism spectroscopy has become a powerful tool to characterise proteins and other biomolecules. For heterogeneous samples such as those present for interacting proteins, typically only average spectroscopic features can be resolved. Here we overcome this limitation by using free-flow microfluidic size separation in-line with synchrotron radiation circular dichroism to resolve the secondary structure of each component of a model protein mixture containing monomers and fibrils. To enable this objective, we have integrated far-UV compatible measurement chambers into PDMS-based microfluidic devices. Two architectures are proposed so as to accommodate for a wide range of concentrations. The approach, which can be used in combination with other bulk measurement techniques, paves the way to the study of complex mixtures such as the ones associated with protein misfolding and aggregation diseases including Alzheimer's and Parkinson's diseases.