Synthesis, characterization and magnetic properties of Co@Au core-shell nanoparticles encapsulated by nitrogen-doped multiwall carbon nanotubes

"Co/Au bilayer thin films were deposited on Si/SiOx substrates using the magnetron sputtering method and used as a catalytic support to grow forests of aligned nitrogen-doped multiwalled carbon nanotubes (N-MWCNT) via chemical vapor deposition (CVD) at 850 °C, using benzylamine (C6H5CH2NH2) as a carbon and nitrogen source. Interestingly, the resulting N-MWCNT contains Co@Au core-shell nanoparticles located at their tips. We found that the metal particle cores consist of cobalt coated by an Au shell of few nanometers. Magnetic measurements revealed a ferromagnetic behavior of the system composed of Co@Au nanoparticles encapsulated inside N-MWCNT. The results are compared with pristine N-MWNT containing only Co nanoparticles encapsulated in their cores.

Statistically coherent calibration of X-Ray Fluorescence Spectrometry for major elements in rocks in minerals.

We applied both the ordinary linear regression (OLR) and the new uncertainty weighted linear regression (UWLR) models for the calibration and comparison of a XRF machine through 59 geochemical reference materials (GRMs) and a procedure blank sample. )e mean concentration and uncertainty data for the GRMs used for the calibrations (Supplementary Materials) (available here) filewere achieved from an up-to-date compilation of chemical data and their processing from well-known discordancy and significance tests. )e drift-corrected XRF intensity and its uncertainty were determined from mostly duplicate pressed powder pellets. )e comparison of the OLR (linear correlation coefficient r∼0.9523–0.9964 and 0.9771–0.9999, respectively, for before and after matrix correction) and UWLR models (r∼0.9772–0.9976 and 0.9970–0.9999, respectively) clearly showed that the latter with generally higher values of r is preferable for routine calibrations of analytical procedures. Both calibrations were successfully applied to rock matrices, and the results were generally consistent with those obtained in other laboratories although the UWLR model showed mostly narrower confidence limits of the mean (slope and intercept) or lower uncertainties than the OLR. Similar sensitivity (∼2.69–46.17 kc·s1·%1 for the OLR and ∼2.78–59.69 kc·s1·%1 for the UWLR) also indicated that the UWLR could advantageously replace the OLR model. Another novel aspect is that the total uncertainty can be reported for individual chemical data. If the analytical instruments were routinely calibrated from the UWLR model, this action would make the science of geochemistry more quantitative than at present

Statistically coherent calibration of X-ray fluorescence spectrometry for major elements in rocks and minerals

"We applied both the ordinary linear regression (OLR) and the new uncertainty weighted linear regression (UWLR) models for the calibration and comparison of a XRF machine through 59 geochemical reference materials (GRMs) and a procedure blank sample. The mean concentration and uncertainty data for the GRMs used for the calibrations (Supplementary Materials) (available here) filewere achieved from an up-to-date compilation of chemical data and their processing from well-known discordancy and significance tests. The drift-corrected XRF intensity and its uncertainty were determined from mostly duplicate pressed powder pellets. The comparison of the OLR (linear correlation coefficient ?0.9523–0.9964 and 0.9771–0.9999, respectively, for before and after matrix correction) and UWLR models (?0.9772–0.9976 and 0.9970–0.9999, respectively) clearly showed that the latter with generally higher values of is preferable for routine calibrations of analytical procedures. Both calibrations were successfully applied to rock matrices, and the results were generally consistent with those obtained in other laboratories although the UWLR model showed mostly narrower confidence limits of the mean (slope and intercept) or lower uncertainties than the OLR. Similar sensitivity (?2.69–46.17?kc·s?1·%?1 for the OLR and ?2.78–59.69?kc·s?1·%?1 for the UWLR) also indicated that the UWLR could advantageously replace the OLR model. Another novel aspect is that the total uncertainty can be reported for individual chemical data. If the analytical instruments were routinely calibrated from the UWLR model, this action would make the science of geochemistry more quantitative than at present.

Pyrrolic nitrogen-doped multiwall carbon nanotubes using ball-milled slag-SiC mixtures as a catalyst by aerosol assisted chemical vapor deposition

We demonstrated that the ball-milled slag-SiC mixture is an effective catalyst to grow pyrrolic nitrogen-doped multiwall carbon nanotubes (N-MWCNTs) by aerosol assisted chemical vapor deposition (AACVD) method. N-MWCNTs synthesized at 800 °C, 850 °C and 900 °C were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, x-ray powder diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). TEM characterizations revealed the presence of a bamboo-like structure, a typical feature of nitrogen-doped carbon nanotubes. The presence of nitrogen was confirmed by the N1s XPS spectrum. Furthermore, a deconvolution of the N1s spectra revealed the presence of N-pyrrolic defects. This nitrogen functionality is investigated concerning the presence of silicon carbide material. Giant nanotubes with large diameters were obtained when SiC was added to the slag to be used as a substrate for N-MWCNTs synthesis. From Raman spectroscopy, the appearance of the D-band was observed, indicating the presence of topological defects that were also observed by TEM. XRD and TEM characterizations demonstrated the presence of Fe _3 C and α -Fe nanoparticles. The N-MWCNTs fabricated here could be used into (electro)catalytic applications or for reinforcing ceramic nanomaterial or polymers