Rodney S. Ruoff

Bio: Rodney S. Ruoff is an academic researcher from Ulsan National Institute of Science and Technology. The author has contributed to research in topics: Graphene & Graphene oxide paper. The author has an hindex of 164, co-authored 666 publications receiving 194902 citations. Previous affiliations of Rodney S. Ruoff include Texas State University & North Carolina State University.

Ripening of silver nanoparticles on carbon nanotubes

Abstract: An electrostatic-force-directed-assembly technique was used to coat multiwalled carbon nano-tubes (MWCNTs) with aerosol Ag nanoparticles produced from a mini-arc plasma source. The deposition of Ag nanoparticles onto CNTs was confirmed by transmission electron microscopy (TEM), high-resolution TEM, scanning electron microscopy, and X-ray photoelectron spectroscopy. Ripening of Ag nanoparticles on CNTs was observed via successive TEM imaging after heating the nanoparticle–nanotube hybrid structures in air to three different temperatures ranging from 100°C to 300°C. With temperatures at and above 200°C, the areal density of Ag nanoparticles decreased and the average particle size increased. In particular, migration and coalescence of Ag nanoparticles have been observed at this relatively low temperature, which suggests a van der Waals nanoparticle–nanotube interaction.

Inductively heated synthesized graphene with record transistor mobility on oxidized silicon substrates at room temperature

Abstract: We report chemical vapor-deposited (CVD) graphene field-effect transistors (GFETs) on conventional SiO2/Si substrate with high-performance comparable to GFETs on boron nitride under practical ambient conditions. The fabricated GFET statistics reveal maximum carrier mobility of ∼17 800 cm2/V-s. Intrinsic graphene features such as three-region output characteristics including soft current saturation have also been observed, in addition to over ten-fold gate modulation. Low-temperature studies indicate that impurity scattering is the limiting transport mechanism. Our results on graphene, synthesized by an inductively heated CVD system, suggest that the prospects of GFETs on oxidized silicon are comparable to those on ideal surfaces, e.g., hBN at room temperature.

Site-Specific Deposition of Au Nanoparticles in CNT Films by Chemical

Abstract: There has been no attempt to date to specifically modify the nodes in carbon nanotube (CNT) networks If the nodes can be modified in favorable ways, the electrical and/or thermal and/or mechanical properties of the CNT networks could be improved In an attempt to influence the performance as a transparent conductivefilm,goldnanoparticlescappedwiththeaminoacidcysteine(Au-CysNP)havebeenselectivelyattached atthenodesofmultiwalledcarbonnanotubes(MWCNTs)networksThesenanoparticleshaveanaveragediameter of 5 nm as observed by TEM FTIR and XPS were used to characterize each step of the MWCNT chemical functionalization process The chemical process was designed to favor selective attachment at the nodes and not the segments in the CNT networks The chemical processing was designed to direct formation of nodes where the gold nanoparticles are The nanoparticles which were loosely held in the CNT network could be easily washed awaybysolvents,whilethoseboundchemicallyremainedTEMresultsshowthattheCys-AuNPsarepreferentially located at the nodes of the CNT networks when compared to the segments These nanoparticles at the nodes were also characterized by a novel technique called diffraction scanning transmission electron microscopy (D- STEM) confirming their identity Four-probe measurements found that the sheet resistance of the modified CNT networks was half that of similarly transparent pristine multiwalled CNT networks

Controlled deposition of nanotubes on opposing electrodes

Abstract: We report a method of depositing individual 'templated carbon nanotubes' (T-CNTs) on opposing electrodes so that they are suspended across 100 µm deep trenches, and in separate experiments across low profile (70 nm thick) opposing electrodes. The geometry of the electrodes with deep trenches was chosen to be essentially identical to that in a micro-electromechanical system (MEMS) testing stage used for mechanical loading of nanostructures. An electric field was used to attract the T-CNTs dispersed in a solvent and critical point drying was employed to protect them from breaking or deforming. The real-time potential change in the circuit was monitored as a means of characterizing the deposition of an individual T-CNT across this deep trench. For the case of sequential deposition on electrodes that are 70 nm above the substrate surface, a method was developed for counting the number of sequentially deposited T-CNTs. Simultaneous video recording of the deposition of T-CNTs confirmed the measured real-time potential changes for both cases. It was found that the resistance of the circuit changed as each new T-CNT was deposited for the sequential deposition; up to five T-CNTs were sequentially detected. This approach allows for controlled deposition of one-dimensional nanostructures for their potential use in NEMS devices, and may be useful for large-scale integration.

The rise of graphene

Abstract: Graphene is a rapidly rising star on the horizon of materials science and condensed-matter physics. This strictly two-dimensional material exhibits exceptionally high crystal and electronic quality, and, despite its short history, has already revealed a cornucopia of new physics and potential applications, which are briefly discussed here. Whereas one can be certain of the realness of applications only when commercial products appear, graphene no longer requires any further proof of its importance in terms of fundamental physics. Owing to its unusual electronic spectrum, graphene has led to the emergence of a new paradigm of 'relativistic' condensed-matter physics, where quantum relativistic phenomena, some of which are unobservable in high-energy physics, can now be mimicked and tested in table-top experiments. More generally, graphene represents a conceptually new class of materials that are only one atom thick, and, on this basis, offers new inroads into low-dimensional physics that has never ceased to surprise and continues to provide a fertile ground for applications.

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。

Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene

Abstract: We measured the elastic properties and intrinsic breaking strength of free-standing monolayer graphene membranes by nanoindentation in an atomic force microscope. The force-displacement behavior is interpreted within a framework of nonlinear elastic stress-strain response, and yields second- and third-order elastic stiffnesses of 340 newtons per meter (N m(-1)) and -690 Nm(-1), respectively. The breaking strength is 42 N m(-1) and represents the intrinsic strength of a defect-free sheet. These quantities correspond to a Young's modulus of E = 1.0 terapascals, third-order elastic stiffness of D = -2.0 terapascals, and intrinsic strength of sigma(int) = 130 gigapascals for bulk graphite. These experiments establish graphene as the strongest material ever measured, and show that atomically perfect nanoscale materials can be mechanically tested to deformations well beyond the linear regime.