Biomedical subjects

Carlos Alberto Paula Leite

Publications and source records attributed to Carlos Alberto Paula Leite.

3 recordsLinked to original sources

PubMed2006

Cationic latex formation by ionic modification.

Stable cationic latices were prepared by charge inversion of anionic styrene-acrylic copolymer latices upon binding Al3+ and Fe3+ ions. This is achieved by stabilizing the latices with a high-HLB (hydrophile-lypophile balance) nonionic surfactant that imparts strong steric stability to the latex, even in the presence of high concentrations of multivalent counterions while these are bound to the latex anionic sites. The cationic latices thus prepared have good stability properties, and the same procedure should be applicable to essentially any latex-carrying anionic sites. Analytical ESI-TEM images show that particle-bound iron is concentrated at the particle borders, but it is also found in the particle bulk.

Journal Article↗

PubMed2002

Elemental mapping in natural rubber latex films by electron energy loss spectroscopy associated with transmission electron microscopy.

Element distribution maps from Hevea brasiliensis natural rubber latex thin films were obtained, by electron energy-loss spectroscopic imaging in a low-energy (80 kV) transmission electron microscope. C, N, O, P, Na, Ca, Mg, Al, Si, and S maps are presented for latex fractionated by centrifugation, either followed by dialysis or not. Most elements forming non-carbon compounds are concentrated in small, electron-dense spots surrounded by a carbon-rich matrix of polymer, thus showing that the rubber is filled with small particles compatible with the polyisoprene matrix. Ca distribution is unique, since it closely parallels the C distribution, evidencing an important role for -COO(-)-Ca2+-COO- ionic bridges in the structure of natural rubber.

Dialysis↗

PubMed2001

Nanocrystalline Domain Identification in Gold Films, by Backscattered Electron Imaging and Energy-Filtered Transmission Electron Microscopy.

Gold nanocrystallites dispersed in an inhomogeneous gold matrix are detected by high-resolution scanning electron microscopy using a field emission source and backscattered electron detection in the composition mode, as well as by energy-filtered transmission electron microscopy in the plasmon energy region. The identity of the nanocrystalline domains was established by observing the same evaporated gold film samples but using bright-field, dark-field, electron diffractogram, and electron energy loss spectroscopy images in the transmission electron microscope. Comparison of these images shows that backscattered electron and plasmon energy detection can be used to identify crystalline domains in an otherwise chemically uniform sample. Copyright 2001 Academic Press.

Journal Article↗