We report a simple, high-yield, method of producing homogeneous dispersions of unfunctionalized and nonoxidized graphene nanosheets in ortho-dichlorobenzene (ODCB). Sonication/centrifugation of various graphite materials results in stable homogeneous dispersions. ODCB dispersions of graphene avert the need for harsh oxidation chemistry and allow for chemical functionalization of graphene materials by a range of methods. Additionally, films produced from ODCB-graphene have high conductivity.

Neutrons are unique particles to probe samples in many fields of research ranging from biology to material sciences to engineering and security applications. Access to bright, pulsed sources is currently limited to large accelerator facilities and there has been a growing need for compact sources over the recent years. Short pulse laser driven neutron sources could be a compact and relatively cheap way to produce neutrons with energies in excess of 10 MeV. For more than a decade experiments have tried to obtain neutron numbers sufficient for applications. Our recent experiments demonstrated an ion acceleration mechanism based on the concept of relativistic transparency. Using this new mechanism, we produced an intense beam of high energy (up to 170 MeV) deuterons directed into a Be converter to produce a forward peaked neutron flux with a record yield, on the order of 10(10)  n/sr. We present results comparing the two acceleration mechanisms and the first short pulse laser generated neutron radiograph.

We demonstrate a high yield method of functionalizing graphene nanosheets through nitrene addition of azido-phenylalanine [Phe(N(3))] to exfoliated micro-crystalline graphite (microG). This method provides a direct route to highly functionalized graphene sheets. TEM analysis of the product shows few layer (n < 5) graphene sheets. The product was determined to have 1 phenylalanine substituent per 13 carbons.

Table-top laser–plasma ion accelerators have many exciting applications, many of which require ion beams with simultaneous narrow energy spread and high conversion efficiency. However, achieving these requirements has been elusive. Here we report the experimental demonstration of laser-driven ion beams with narrow energy spread and energies up to 18 MeV per nucleon and ∼5% conversion efficiency (that is 4 J out of 80-J laser). Using computer simulations we identify a self-organizing scheme that reduces the ion energy spread after the laser exits the plasma through persisting self-generated plasma electric (∼1012 V m−1) and magnetic (∼104 T) fields. These results contribute to the development of next generation compact accelerators suitable for many applications such as isochoric heating for ion-fast ignition and producing warm dense matter for basic science.

Ultrasmall copper nanoparticles are produced by N,N,N',N'-tetramethyl-p-phenylenediamine (TMPDA) reduction of aqueous Cu(2+) on a hydrophobically immobilized sodium dodecylbenzenesulfonate (SDBS) surfactant template in the presence of sodium citrate at room temperature. Single-walled carbon nanotubes (SWNTs) act as a scaffold controlling the size of the SDBS micelle, which in turn confines a limited number of copper ions near the nanotube surface. TMPDA reduction forms copper nanoparticles as confirmed by X-ray photoelectron spectroscopy and electron diffraction, whose size was determined by atomic force microscopy and transmission electron microscopy to be approximately 2 nm. Particles formed in the absence of the SWNT immobilizer range from 2 to 150 nm.

We present a full characterization of a short pulse laser-driven neutron source. Neutrons are produced by nuclear reactions of laser-driven ions deposited in a secondary target. The emission of neutrons is a superposition of an isotropic component into 4p and a forward directed, jet-like contribution, with energies ranging up to 80 MeV. A maximum flux of 4.4 Â 10 9 neutrons/sr has been observed and used for fast neutron radiography. On-shot characterization of the ion driver and neutron beam has been done with a variety of different diagnostics, including particle detectors, nuclear reaction, and time-of-flight methods. The results are of great value for future optimization of this novel technique and implementation in advanced applications. V

With the development of several novel heating sources, scientists can now heat a small sample isochorically above 10,000 K. Although matter at such an extreme state, known as warm dense matter, is commonly found in astrophysics (e.g., in planetary cores) as well as in high energy density physics experiments, its properties are not well understood and are difficult to predict theoretically. This is because the approximations made to describe condensed matter or high-temperature plasmas are invalid in this intermediate regime. A sufficiently large warm dense matter sample that is uniformly heated would be ideal for these studies, but has been unavailable to date. Here we have used a beam of quasi-monoenergetic aluminum ions to heat gold and diamond foils uniformly and isochorically. For the first time, we visualized directly the expanding warm dense gold and diamond with an optical streak camera. Furthermore, we present a new technique to determine the initial temperature of these heated samples from the measured expansion speeds of gold and diamond into vacuum. We anticipate the uniformly heated solid density target will allow for direct quantitative measurements of equation-of-state, conductivity, opacity, and stopping power of warm dense matter, benefiting plasma physics, astrophysics, and nuclear physics.

Oxidation of graphite may be carried out by reaction with meta-chloroperoxybenzoic acid to yield graphite epoxide. Scanning tunneling microscopy (STM) showed that the functionalization occurs at the edges rather than on the basal plane of the graphite. Quantification of the epoxide content is possible through the deepoxidation reaction using MeReO3/PPh3.