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Diffusion of deuterated polystyrene(dPS) is probed in PS matricescontaining stringlike chained nanoparticles (cNP) grafted with PS.This investigation connects prior diffusion studies in model sphericaland cylindrical NP systems and provides insight for technologicalapplications, which typically involve irregularly shaped NPs suchas carbon black. We report that the presence of chained NPs in PSmatrices induces a minimum in the diffusion coefficient (D) with increasing cNP concentration when the key length scale, 2Rg/L≤ 1.5, where Rgis the gyration radius of dPS and Lis the mean length of the impenetrable core of the chainedNPs. When 2Rg/L>1.5, Ddecreases monotonically as the NP concentrationincreases.Note that in all cases 2Rgis larger thanthe diameter of these short-stringy NPs. The diffusion minimum isattributed to anisotropic diffusion in the vicinity of the chainedNPs and requires that the long dimension of the cNP be comparableto or longer than the tracer molecule. Two normalizations are exploredto provide insight about the diffusion mechanism: D/D0where D0is the diffusion coefficient in a pure homopolymer matrix and D/Dewhere Deis an effective diffusion coefficient that accountsfor the distinct dynamics in the PS matrix and PS brush regions. For D/D0, a sharp transition froma diffusion minimum to a monotonic decrease is observed as dPS molecularweight increases, while for D/Dethe transition is more gradual. These studies show not onlythat the NPs act as impenetrable obstacles for polymer diffusion butthat the polymer brush grafted to the cNP provides an alternativepathway to control polymer dynamics. [ABSTRACT FROM AUTHOR]

Nanoparticles readily agglomerate, especially duringnucleation,growth, and calcination processes. In this work, modified carbon black(MCB) has been used to prevent particle agglomeration during the nucleationstep in the preparation of a highly dispersed nano-La(OH)3precursor by a coprecipitation reaction. The surface carboxyl groupsformed on MCB after modification can adsorb and fix positively chargedLa3+ions on the surface. Therefore, nano-La(OH)3nuclei can be uniformly deposited on the MCB surface. After nucleation,La(OH)3particles with a size of about 20 nm with a positivesurface charge still interact strongly with the negatively chargedMCB surface, which effectively prevents their agglomeration duringthe subsequent aging process. Furthermore, due to the release of CO2over a wide temperature range from 400 to 700 °C duringa subsequent calcination process, La2O3particlesobtained by calcination of the La(OH)3precursor can beeffectively isolated at high temperature and prevented from agglomerating.By using MCB as an agglomeration inhibitor in this way, highly dispersedLa2O3nanoparticles with a size of 50 nm havingexcellent photoluminescence ability can be prepared. [ABSTRACT FROM AUTHOR]

Polymer-melt-based manufacturing processes for nanostructures offer high-rate, environmentally friendly, and commercially viable alternatives to solution-based methods. In this work, electrophoresis of a model carbon black and polystyrene system with moderate viscosity was used to investigate the viability of adapting nanoassembly processes to the high viscosity environment of polymer melts. The presence of polystyrene did not prevent deposition of carbon black, but deposition rates decreased at shorter deposition times; deposition was not linear with increasing applied voltage; and greater solution concentrations reduced the critical voltages (i.e., the voltage at which the rate of deposition changed). X-ray photoelectron spectroscopy (XPS) results and comparison of experimental data with Hamaker’s model showed that about 1.6% of the available polystyrene was initially deposited with the carbon black. At voltages above the critical voltage, the deposited mass was less than the Hamaker prediction, indicating the formation of electrically insulating layers on the electrodes. The overall behavior suggests that polymer melt-based processes could be employed for high-rate fabrication of nano-optical devices, biochemical sensors, and nanoelectronics. [ABSTRACT FROM AUTHOR]

The risk of potential human exposure to mixed nanomaterials in consumer, occupational, and medicinal settings is increasing as nanomaterials enter both the workplace and the marketplace. In this study, we investigated the toxicity of mixed engineered carbon black (ECB) and maghemite iron oxide (Fe2O3) nanoparticles in a cellular system to understand the mechanism of toxicity and potential methods of toxicity mitigation. Lung epithelial cells (A549) were exposed to mixed Fe2O3and ECB nanoparticles, mixed Fe2O3and ECB nanoparticles with the addition of l-ascorbic acid, and mixed Fe2O3and surface-oxidized engineered carbon black (ox-ECB) nanoparticles. The nanoparticles were characterized using transmission electron microscopy, nitrogen adsorption surface area measurement (BET), X-ray diffraction, and surface charge measurement. The carbon black nanoparticles were also characterized with a reductive capacity assay and by X-ray photoelectron spectroscopy (XPS). The cellular uptake of nanoparticles was analyzed via transmission electron microscopy and fluorescence microscopy; the cellular uptake of iron was quantified using inductively coupled plasma mass spectrometry (ICP-MS). Both the MTT assay and the ethidium homodimer and calcein AM live/dead assay were used to measure cellular proliferation and cytotoxicity, respectively. The dichlorofluorescein diacetate (DCFH-DA) assay was used to measure the intracellular generation of reactive oxygen species. Results show that both Fe2O3and ECB (or Fe2O3and ox-ECB) were co-internalized in intracellular vesicles. Additionally, after exposure to the mixture of nanoparticles, the amount of acidified lysosomes increased over time. The cellular uptake of Fe2O3nanoparticles was unaffected by mixing with ECB. Significant oxidant production occurred in cells exposed to mixed Fe2O3and ECB, but not in cells exposed to mixed Fe2O3and ox-ECB or in cells exposed to Fe2O3and ECB with the addition of ascorbic acid. Furthermore, exposure to mixed Fe2O3and ECB nanoparticles yielded a dose-dependent decrease in the level of cellular proliferation (MTT assay) and a decrease in cellular viability (ethidium homodimer and calcein AM live/dead assay) that were not seen in the Fe2O3and ox-ECB scenario. The results support the hypothesis that exposure to mixed Fe2O3and ECB nanoparticles produces oxidants that are mediated by the surface reductive capability of ECB when both particle types are colocalized in acidic cellular compartments. This oxidant production mechanism may lead to oxidative stress, but it can be mitigated by an antioxidant such as ascorbic acid or by surface treatment of the ECB to decrease its surface reductive capacity. [ABSTRACT FROM AUTHOR]

Ru and Pt−Ru (Pt:Ru = 1:1) nanoparticles supported on carbon black were prepared by the borohydride reduction method using oleylamine as a stabilizer in an anhydrous ethanol solvent. We investigated the effect of Pt segregation to the surface of alloy nanoparticles on the methanol oxidation reaction (MOR). As-prepared Pt1Ru1/C showed a narrow size distribution and a relatively uniform particle distribution on a carbon support. However, its electrocatalytic activity toward the MOR was poor due to the high surface concentration of Ru. As duration time of heat treatment at 200 °C was increased up to 2 h, the surface composition of Pt atoms was increased without significant particle growth due to thermally induced segregation of Pt atoms, which were revealed by TEM images, X-ray photoelectron spectroscopy (XPS) analysis, changes in the potentials of zero total charge (pztc), and increase in the oxidation charge of “reduced CO2”. In particular, from the combination of CO adlayer oxidation and “reduced CO2” oxidation charges, the increased surface concentration of Pt of alloy catalysts was relatively quantified when compared to its as-prepared state. Cyclic voltammograms in 0.1 M HClO4solution with 0.5 M methanol showed that Pt1Ru1/C annealed for 2 h at 200 °C in a flow of mixture gas of Ar and H2(5 vol %) had a less positive onset potential for the MOR. These results demonstrate a definitive contribution from segregation of Pt atoms to the MOR activity. [ABSTRACT FROM AUTHOR]

The limiting cause of nanoconfinement of rubber molecules for their selective adsorption onto filler surface has been examined by changing: (1) the void size of carbon black aggregates, (2) the atomic scale roughness and chemical character of carbon black surface, and (3) the kind of filler from carbon black to silica. Nanoconfinement of rubber molecules into carbon black aggregate structure occurs at the concave (∼5 nm) formed in between carbon black primary particles. Nanoconfinement is the primary mechanism, whereas chemical interaction between filler and the polymer plays a minor role in the selective adsorption. The new adsorption concept is also examined with silica nanoparticles. [ABSTRACT FROM AUTHOR]

The signal intensity of low-molecular-weight compounds analyzed using surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF-MS) was significantly enhanced when oxidized graphitized carbon black (GCB) particles were used as the desorption/ionization surface. The surface of oxidized GCB contains more carboxylic acid groups than non-oxidized GCB. Carboxylic acid groups enhance the efficiency of the ionization process and the desorption of more hydrophobic compounds. A common pharmaceutical compound, propranolol, was successfully extracted from Baltic Sea blue mussels and quantified using oxidized GCB as the SALDI surface, whereas deuterated propranolol was used as the internal standard. The calibration curve showed a wide linear dynamic range of response (0.1–20 μg/mL) and good reproducibility (RSD < 10%). It was not possible to detect propranolol in Baltic Sea blue mussels when non-oxidized GCB was used as the SALDI surface. [Copyright &y& Elsevier]