Yury Gogotsi

Bio: Yury Gogotsi is an academic researcher from Drexel University. The author has contributed to research in topics: MXenes & Carbon. The author has an hindex of 171, co-authored 956 publications receiving 144520 citations. Previous affiliations of Yury Gogotsi include Qatar Airways & Clemson University.

Covalent incorporation of aminated nanodiamond into an epoxy polymer network.

Abstract: Outstanding mechanical and optical properties of diamond nanoparticles in combination with their biocompatibility have recently attracted much attention. Modification of the surface chemistry and incorporation into a polymer is required in many applications of the nanodiamond. Nanodiamond powder with reactive amino groups (∼20% of the number of surface carbon atoms in each 5 nm particle) was produced in this work by covalent linking of ethylenediamine to the surface carboxyl groups via amide bonds. The synthesized material was reacted with epoxy resin, yielding a composite, in which nanodiamond particles are covalently incorporated into the polymer matrix. The effect of amino groups grafted on the nanodiamond on the curing chemistry of the epoxy resin was analyzed and taken into consideration. Covalently bonded nanodiamond–epoxy composites showed a three times higher hardness, 50% higher Young’s modulus, and two times lower creep compared to the composites in which the nanodiamond was not chemically linke...

Self-Sensing, Ultralight, and Conductive 3D Graphene/Iron Oxide Aerogel Elastomer Deformable in a Magnetic Field

Abstract: Three-dimensional (3D) graphene aerogels (GA) show promise for applications in supercapacitors, electrode materials, gas sensors, and oil absorption due to their high porosity, mechanical strength, and electrical conductivity. However, the control, actuation, and response properties of graphene aerogels have not been well studied. In this paper, we synthesized 3D graphene aerogels decorated with Fe3O4 nanoparticles (Fe3O4/GA) by self-assembly of graphene with simultaneous decoration by Fe3O4 nanoparticles using a modified hydrothermal reduction process. The aerogels exhibit up to 52% reversible magnetic field-induced strain and strain-dependent electrical resistance that can be used to monitor the degree of compression/stretching of the material. The density of Fe3O4/GA is only about 5.8 mg cm(-3), making it an ultralight magnetic elastomer with potential applications in self-sensing soft actuators, microsensors, microswitches, and environmental remediation.

2D molybdenum and vanadium nitrides synthesized by ammoniation of 2D transition metal carbides (MXenes).

Abstract: MXenes are a rapidly growing class of 2D transition metal carbides and nitrides, finding applications in fields ranging from energy storage to electromagnetic interference shielding and transparent conductive coatings. However, while more than 20 carbide MXenes have already been synthesized, Ti4N3 and Ti2N are the only nitride MXenes reported so far. Here by ammoniation of Mo2CTx and V2CTx MXenes at 600 °C, we report on their transformation to 2D metal nitrides. Carbon atoms in the precursor MXenes are replaced with N atoms, resulting from the decomposition of ammonia molecules. The crystal structures of the resulting Mo2N and V2N were determined with transmission electron microscopy and X-ray pair distribution function analysis. Our results indicate that Mo2N retains the MXene structure and V2C transforms to a mixed layered structure of trigonal V2N and cubic VN. Temperature-dependent resistivity measurements of the nitrides reveal that they exhibit metallic conductivity, as opposed to semiconductor-like behavior of their parent carbides. As important, room-temperature electrical conductivity values of Mo2N and V2N are three and one order of magnitude larger than those of the Mo2CTx and V2CTx precursors, respectively. This study shows how gas treatment synthesis such as ammoniation can transform carbide MXenes into 2D nitrides with higher electrical conductivities and metallic behavior, opening a new avenue in 2D materials synthesis.

Modified MAX Phase Synthesis for Environmentally Stable and Highly Conductive Ti3C2 MXene.

Abstract: One of the primary factors limiting further research and commercial use of the two-dimensional (2D) titanium carbide MXene Ti3C2, as well as MXenes in general, is the rate at which freshly made samples oxidize and degrade when stored as aqueous suspensions. Here, we show that including excess aluminum during synthesis of the Ti3AlC2 MAX phase precursor leads to Ti3AlC2 grains with improved crystallinity and carbon stoichiometry (termed Al-Ti3AlC2). MXene nanosheets (Al-Ti3C2) produced from this precursor are of higher quality, as evidenced by their increased resistance to oxidation and an increase in their electronic conductivity up to 20 000 S/cm. Aqueous suspensions of stoichiometric single- to few-layer Al-Ti3C2 flakes produced from the modified Al-Ti3AlC2 have a shelf life of over ten months, compared to 1 to 2 weeks for previously published Ti3C2, even when stored in ambient conditions. Freestanding films made from Al-Ti3C2 suspensions stored for ten months show minimal decreases in electrical conductivity and negligible oxidation. Furthermore, oxidation of the improved Al-Ti3C2 in air initiates at temperatures that are 100-150 °C higher than that of conventional Ti3C2. The observed improvements in both the shelf life and properties of Al-Ti3C2 will facilitate the widespread use of this material.

Two-Dimensional Titanium Carbide (MXene) as Surface-Enhanced Raman Scattering Substrate

Abstract: Noble metal (gold or silver) nanoparticles or patterned films are typically used as substrates for surface-enhanced Raman spectroscopy (SERS). Two-dimensional (2D) carbides and nitrides (MXenes) exhibit unique electronic and optical properties, including metallic conductivity and plasmon resonance in the visible or near-infrared range, making them promising candidates for a wide variety of applications. Herein, we show that 2D titanium carbide, Ti3C2Tx, enhances Raman signal from organic dyes on a substrate and in solution. As a proof of concept, MXene SERS substrates were manufactured by spray-coating and used to detect several common dyes, with calculated enhancement factors reaching ∼106. Titanium carbide MXene demonstrates SERS effect in aqueous colloidal solutions, suggesting the potential for biomedical or environmental applications, where MXene can selectively enhance positively charged molecules.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Materials for electrochemical capacitors

Abstract: Electrochemical capacitors, also called supercapacitors, store energy using either ion adsorption (electrochemical double layer capacitors) or fast surface redox reactions (pseudo-capacitors). They can complement or replace batteries in electrical energy storage and harvesting applications, when high power delivery or uptake is needed. A notable improvement in performance has been achieved through recent advances in understanding charge storage mechanisms and the development of advanced nanostructured materials. The discovery that ion desolvation occurs in pores smaller than the solvated ions has led to higher capacitance for electrochemical double layer capacitors using carbon electrodes with subnanometre pores, and opened the door to designing high-energy density devices using a variety of electrolytes. Combination of pseudo-capacitive nanomaterials, including oxides, nitrides and polymers, with the latest generation of nanostructured lithium electrodes has brought the energy density of electrochemical capacitors closer to that of batteries. The use of carbon nanotubes has further advanced micro-electrochemical capacitors, enabling flexible and adaptable devices to be made. Mathematical modelling and simulation will be the key to success in designing tomorrow's high-energy and high-power devices.