Synthesis and characterization of polymer/silica/QDs fluorescent nanocomposites with potential application as printing toner

In this work cadmium telluride quantum dots (CdTeQDs) were prepared via one-pot synthesis microwave assisted. Afterwards, CdTeQDs/silica (SiO2)/nigrosine (nigro)/poly (styrene co-methyl methacrylate) (PSCMM) fluorescent nanocomposite (CSNP) powders were prepared via ultrasonic treatment and post drying at 60 °C. The samples were characterized by UV-vis absorbance, x-ray diffraction (XRD) and transmission electron microscopy (TEM). Finally, successful printing tests were performed on security paper at 130 °C. These results show the potential of this nanocomposite to be used as security toner. This printing toner configuration is reported for first time

Deposition of Size-Selected Cu Nanoparticles by Inert Gas Condensation

Nanometer size-selected Cu clusters in the size range of 1–5 nm have been produced by a plasma-gas-condensation-type cluster deposition apparatus, which combines a grow-discharge sputtering with an inert gas condensation technique. With this method, by controlling the experimental conditions, it was possible to produce nanoparticles with a strict control in size. The structure and size of Cu nanoparticles were determined by mass spectroscopy and confirmed by atomic force microscopy (AFM) and scanning electron transmission microscopy (STEM) measurements. In order to preserve the structural and morphological properties, the energy of cluster impact was controlled; the energy of acceleration of the nanoparticles was in near values at 0.1 ev/atom for being in soft landing regime. From SEM measurements developed in STEM-HAADF mode, we found that nanoparticles are near sized to those values fixed experimentally also confirmed by AFM observations. The results are relevant, since it demonstrates that proper optimization of operation conditions can lead to desired cluster sizes as well as desired cluster size distributions. It was also demonstrated the efficiency of the method to obtain size-selected Cu clusters films, as a random stacking of nanometer-size crystallites assembly. The deposition of size-selected metal clusters represents a novel method of preparing Cu nanostructures, with high potential in optical and catalytic applications

Synthesis of Fe nanoparticles functionalized with oleic acid synthesized by inert gas condensation

In this work, we study the synthesis of monodispersed Fe nanoparticles (Fe-NPs) in situ functionalized with oleic acid. The nanoparticles were self-assembled by inert gas condensation (IGC) technique by using magnetron-sputtering process. Structural characterization of Fe-NPs was performed by transmission electron microscopy (TEM). Particle size control was carried out through the following parameters: (i) condensation zone length, (ii) magnetron power, and (iii) gas flow (Ar and He). Typically the nanoparticles generated by IGC showed diameters which ranged from ∼0.7 to 20 nm. Mass spectroscopy of Fe-NPs in the deposition system allowed the study of in situ nanoparticle formation, through a quadrupole mass filter (QMF) that one can use together with a mass filter. When the deposition system works without quadrupole mass filter, the particle diameter distribution is around +/−20%. When the quadrupole is in line, then the distribution can be reduced to around +/−2%

Size-Selected Ag Nanoparticles with Five-Fold Symmetry

Silver nanoparticles were synthesized using the inert gas aggregation technique. We found the optimal experimental conditions to synthesize nanoparticles at different sizes: 1.3 ± 0.2, 1.7 ± 0.3, 2.5 ± 0.4, 3.7 ± 0.4, 4.5 ± 0.9, and 5.5 ± 0.3 nm. We were able to investigate the dependence of the size of the nanoparticles on the synthesis parameters. Our data suggest that the aggregation of clusters (dimers, trimer, etc.) into the active zone of the nanocluster source is the predominant physical mechanism for the formation of the nanoparticles. Our experiments were carried out in conditions that kept the density of nanoparticles low, and the formation of larges nanoparticles by coalescence processes was avoided. In order to preserve the structural and morphological properties, the impact energy of the clusters landing into the substrate was controlled, such that the acceleration energy of the nanoparticles was around 0.1 eV/atom, assuring a soft landing deposition. High-resolution transmission electron microscopy images showed that the nanoparticles were icosahedral in shape, preferentially oriented with a five-fold axis perpendicular to the substrate surface. Our results show that the synthesis by inert gas aggregation technique is a very promising alternative to produce metal nanoparticles when the control of both size and shape are critical for the development of practical applications

Clinical characteristics associated with the severity of Clostridium [Clostridioides] difficile infection in a tertiary teaching hospital from Mexico

Background: Clostridium difficile infection (CDI) is a leading cause of healthcare-associated diarrhea worldwide. In this study, risk factors associated with the development of severe-complicated and recurrent outcomes in CDI patients in different age groups, including the non-elderly, were assessed in a third-level hospital. Methods: CDI cases were detected by clinical data and polymerase-chain-reaction (PCR). Clinical, demographic, epidemiological, and microbiological risk factors for CDI were evaluated. Results: During the study period, 248 out of 805 patients with nosocomial diarrhea were diagnosed with CDI and the majority were severe-complicated cases (87.90%). Female gender (OR 3.19, 95% CI 1.19e8.55, p ¼ 0.02) and lymphoma (OR 3.95, 95% CI 1.03e15.13, p ¼ 0.04) were risk factors for severe-complicated CDI. Mature adulthood (51e60 years) (OR 5.80, 95% CI 1.56e21.62, p ¼ 0.01), previous rifampicin use (OR 7.44, 95% CI 2.10e26.44, p ¼ 0.00), and neoplasm (solid malignant neoplasm or hematological malignancies) (OR 4.12, 95% CI 1.01e16.83, p ¼ 0.04) were risk factors for recurrent infection. Autoimmune disorders (OR 6.62, CI 95% 1.26e34.73, p ¼ 0.02), leukemia (OR 4.97, 95% CI 1.05e23.58, p ¼ 0.04), lymphoma (OR 3.79, 95% CI 1.03e12.07, p ¼ 0.04) and previous colistin treatment (OR 4.97, 95% CI 1.05e23.58, p ¼ 0.04) were risk factors for 30-day mortality. Conclusion: Newly identified risk factors for recurrent CDI were rifampicin treatment and age between 51 and 60 years; colistin treatment was identified as a risk factor for 30-day mortality. Previously identified risk factors for severe-complicated CDI were confirmed, but with a major impact on non-elderly patients

Dynamics of pick-up ions in collisionless velocity shears

We study the motion of charged particles in large-scale velocity shears that are produced in the interaction of magnetized plasma winds and plasma obstacles. The purpose of the analysis is to account for the observation of strongly energetic contaminant ions in the region of interaction of the solar wind with planetary/cometary non-magnetic ionospheric obstacles (Venus, Mars, comets). The convective electric field set up by the streaming plasma is incorporated to the equation of motion of ions born in a velocity shear. Neglecting collisions and the back reaction of the contaminant particles on the wind, the trajectories of the particles are computed as a function of the shear properties as well as of the mass of the ions and the magnetic field configuration. For a linear dependence of the wind velocity across the shear, the problem is solved analytically and we find that the particle velocity can have either a purely oscillatory behavior or grow exponentially with time depending on the value of a dimensionless parameter proportional to the product of the velocity gradient and the cyclotron frequency of the ion trajectories. In the latter case a strong acceleration of the contaminant ions can be achieved. Adopting magnetic field and flow properties appropriate for cometary and planetary environments, we explore the potential importance of the mechanism discussed to explain the presence of superthermal ions and filamentary structures in such regions