A purification method has been developed that provides for the removal of metal catalysts and impurity carbon from laser-oven-grown single-wall carbon nanotube (SWNT) material. The oxidation rate of SWNTs in air at elevated temperatures is correlated to the metal content of the sample. Sample purity is documented with SEM, TEM, electron microprobe analysis, Raman, and UV-vis-near-IR. We also note that the relative intensity of the electronic transitions in the near-infrared to the continuum absorption at 400 nm in the UV serves as a useful monitor of the perturbation of the sidewall π-electron density of SWNTs due to sidewall substitution and/or oxidation.

A purification method has been developed that provides for the removal of metal catalysts and impurity carbon from laser-oven-grown single-wall carbon nanotube (SWNT) material. The oxidation rate of SWNTs in air at elevated temperatures is correlated to the metal content of the sample. Sample purity is documented with SEM, TEM, electron microprobe analysis, Raman, and UV-vis-near-IR. We also note that the relative intensity of the electronic transitions in the near-infrared to the continuum absorption at 400 nm in the UV serves as a useful monitor of the perturbation of the sidewall π-electron density of SWNTs due to sidewall substitution and/or oxidation.

The growth of a continuous, uniform Au layer on a dielectric nanoparticle is the critical step in the synthesis of nanoparticles such as nanoshells or nanorice, giving rise to their unique geometry-dependent plasmon resonant properties. Here we report a novel, streamlined method for Au layer metallization on prepared nanoparticle surfaces using carbon monoxide as the reducing agent. This approach consistently yields plasmonic nanoparticles with highly regular shell layers and is immune to variations in precursor or reagent preparation. Single particle spectroscopy combined with scanning electron microscopy reveal that thinner, more uniform shell layers with correspondingly redshifted optical resonances are achievable with this approach.

Mass spectrometry imaging (MSI) of tissue implanted with silver nanoparticulate (AgNP) matrix generates reproducible imaging of lipids in rodent models of disease and injury. Gas-phase production and acceleration of size-selected 8 nm AgNP is followed by controlled ion beam rastering and soft landing implantation of 500 eV AgNP into tissue. Focused 337 nm laser desorption produces high quality images for most lipid classes in rat brain tissue (in positive mode: galactoceramides, diacylglycerols, ceramides, phosphatidylcholines, cholesteryl ester, and cholesterol, and in negative ion mode: phosphatidylethanolamides, sulfatides, phosphatidylinositol, and sphingomyelins). Image reproducibility in serial sections of brain tissue is achieved within <10% tolerance by selecting argentated instead of alkali cationized ions. The imaging of brain tissues spotted with pure standards was used to demonstrate that Ag cationized ceramide and diacylglycerol ions are from intact, endogenous species. In contrast, almost all Ag cationized fatty acid ions are a result of fragmentations of numerous lipid types having the fatty acid as a subunit. Almost no argentated intact fatty acid ions come from the pure fatty acid standard on tissue. Graphical Abstract ᅟ.

Survey studies of pressure−temperature-induced transformations of single-wall carbon nanotubes (SWNT) at 1.5, 8.0, and 9.5 GPa and temperatures ranging from 200 to 1500 °C in a piston-cylinder or “Toroid” type high pressure devices have been carried out. It was found that the combined effects of high pressures and high temperatures produce irreversible changes in the SWNT structure, in contrast with the reversible effect of high pressure alone, previously studied by several research groups. The Raman, electron microscopy, and X-ray diffraction data obtained in the present work provide evidence for covalent interlinking of SWNT by sp3 C−C bonds which escalates with the increasing treatment temperature and pressure. The formation of new carbon structures such as nano- and microcrystalline diamond-like (cubic and hexagonal) and nanographite phases under higher pressures (8.0 and 9.5 GPa) has been observed.

Large fullerenes and carbon-coated metal nanoparticles that are formed during the synthesis of carbon nanotubes have been functionalized by the addition of alkyl radicals and isolated by extraction into chloroform. The soluble, functionalized fullerenes have been isolated from raw single-wall carbon nanotube (SWNT) material prepared by laser oven, direct current arc, and high-pressure carbon monoxide production methods. Analyses of the extracted large fullerenes were carried out by thermogravimetric analysis, UV-vis-near-IR, laser desorption ionization mass spectrometry, and high-resolution transmission electron microscopy.

The nonselective nature of glucose pyrolysis chemistry can be controlled by preventing the sugar ring from opening and fragmenting.

Abstract. Experiments that demonstrate quantitatively the importance of laser absorption dynamics for ultraviolet laser ablation of organic materials are presented. Laser pulse transmission measurements have been performed on 0.1 jam spin-coated polyimide films at three ultraviolet wavelengths ( 193 nm, 248 nm, and 355 nm) over the fluence range l0 -3-10 J/cm 2. Target transmission is observed to increase with increasing fluence by a factor of --,5 at 193 nm, and a factor of ~ 10 at 248 nm. In contrast, transmission decreases by approximately one half during 355 nm target irradiation. These results are analyzed theoretically with a two-level model of chromophore absorption. This theory is also applied to reported pulsed UV-laser polyimide ablation data. It is shown that an accurate description of the fluence-dependent film absorption leads to a prediction of the etch depth versus pulse fluence relationship in good agreement with experimental data. PACS : 42.10, 81.60, 82.50 Pulsed ultraviolet-laser ablation has been shown in a multitude of studies to etch organic targets precisely, which in turn has led to widespread application of UV lasers in materials processing, microelectronics, and medicine. In order to optimize these procedures, as well as to assess possible risks of clinical laser use, the laser/material interaction must be well understood. One aspect of photoablation that has only lately become apparent is that the absorptive properties of the target can change during the intense laser irradiation [1][2][3][4]. Recently, two of the current authors presented a theoretical description of such dynamic optical properties [1,5] showing that these absorption changes could account for the commonly noted substantial discrepancy between experimental data and the etch depth versus laser fluence relationship predicted by Beer's law (i.e., the simple "blow-off" model [6] described below).However, other processes such as thermal diffusion could also affect the ablation depth/fluence behavior [7]. A recent theoretical analysis concluded that dynamic target optics were probably more important than thermal diffusion in affecting photoablation [8], yet this issue has not been conclusively resolved. The absolute magnitude of the optical effect cannot be deduced from the reports cited above because those studies were either qualitative in nature or limited in terms of incident laser fluence. For these reasons we have conducted the experiments described here, quantifying the change in absorption for thin films of polyimide (a common photoablation substrate) over a wide range of laser fluences at three distinct ultraviolet wavelengths. This paper thus provides the first quantitative experimental test of the ideas formulated in [1,5], i.e. that proper treatment of the radiation transport to include chromophore saturation and excited-state absorption is extremely important for determination of the etch depth per pulse in organic materials.