Search

Silver nanocrystals (Ag NCs) hold promising antibiotic and antiviral properties in biological systems. The biodistribution of silver nanostructures injected into animals in vivo is currently unknown, remaining as a fundamental issue for potential therapeutic applications. Here, we injected Ag NCs capped with bovine serum albumin (BSA) in live rats to elucidate their fate in several organs including liver, heart and brain. Very significant accumulations of nanoparticles were confirmed by inductively coupled plasma mass spectroscopy (ICPMS) and transmission electron microscopy (TEM) techniques on the liver and heart. In contrast, the brain tissue did not reveal evidence of particles content. Our results suggest that Ag+ permeated across the blood-brain barrier (BBB), and followed swift clearance from the organ.

Gold (Au) nanoparticles can be produced through the interaction of Au(III) ions with oat and wheat biomasses. This paper describes a procedure to recover gold nanoparticles from oat and wheat biomasses using cetyltrimethylammonium bromide or sodium citrate. Extracts were analyzed using UV-visible spectroscopy, high-resolution transmission electron microscopy (HRTEM), and x-ray absorption spectroscopy. The HRTEM data demonstrated that smaller nanoparticles are extracted first, followed by larger nanoparticles. In the fourth extraction, coating of chelating agents is visible on the extracted nanoparticles.

In recent years, an increasing number of laboratories have been applying in situ heating (and ultimately, gas reaction) techniques in electron microscopy studies of catalysts and other nanophase materials. With the advent of aberration-corrected electron microscopes that provide sub-Angström image resolution, it is of great interest to study the behavior of materials at elevated temperatures while maintaining the resolution capabilities of the microscope. In collaboration with Protochips Inc., our laboratory is developing an advanced capability for in situ heating experiments that overcomes a number of performance problems with standard heating stage technologies. The new heater device allows, for example, temperature cycling from room temperature to greater than 1000 degrees C in 1 ms (a heating rate of 1 million Centigrade degrees per second) and cooling at nearly the same rate. It also exhibits a return to stable operation (drift controlled by the microscope stage, not the heater) in a few seconds after large temperature excursions. With Protochips technology, we were able to demonstrate single atom imaging and the behavior of nanocrystals at high temperatures, using high-angle annular dark-field imaging in an aberration-corrected (S)TEM. The new capability has direct applicability for remote operation and (ultimately) for gas reaction experiments using a specially designed environmental cell., ((c) 2009 Wiley-Liss, Inc.)

In this work, we report the synthesis and characterization of Mo-Ni-W oxides. The precursor was prepared from an aqueous solution of ammonium heptamolibdate, ammonium metatungstate, and nickel nitrate with an atomic ratio of 1:1:1 (Mo:W:Ni). The solution was then transferred to a Teflon-lined stainless steel autoclave and heated to 200 degrees C and left at this temperature for 48 h. The resulting material was then washed and dried. The morphology and elemental composition were studied by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. The porosity was studied by the Brunauer, Emmett, and Teller method. The materials synthesized at 200 degrees C remained amorphous and had a specific surface area of 114 m2/g with pore size of 34 A. The average length was 1 microm and the average diameter was 60 nm. The crystalline phase of synthesized material corresponded to W0.4Mo0.6O3 and WO3. After annealing at 550 degrees C for two hours, the material was polycrystalline with a segregated structure of MoO3, WO3; NiMoO4 was observed. The sublimation of the molybdenum oxide was evident when annealed at 900 degrees C for two hours and finally two crystalline phases of material remained; roundish WO3 and elongated particles of NiWO4.

In this work, we studied the shell structure of the Nautilus pompilius Linnaeus by using analytical techniques of scanning (SEM) and transmission electron microscopy (TEM) and X-ray diffraction. The main objective of this study is the structural characterization of Nautilus shell at different length levels, from micron to nano-scale. The results were also used to try to determine the shell structure mechanism of formation. The information obtained in this work will place our particular knowledge a closer step to understand how self-assembly works in nature, and will increase the opportunities of using this information in the future synthesis of new advanced materials.

Pt-Au bimetallic nanoparticles have been synthesized by the polyol method and stabilized with poly(vinylpyrrolidone) (PVP), modifying the temperature of synthesis. Interesting structure changes were observed in the nanoparticles as the temperature was varied. At lower temperatures no bimetallic nanoparticles were detected, but as the temperature increased bimetallic nanoparticles started to appear, commonly obtaining core-shell nanoparticles, always covered by the polymer. This originates the modification of the optical response of the system in the UV-visible region. An absorption peak centered at 520 nm at low temperatures was observed (100-110 degrees C); at higher temperatures (130-170 degrees C) there were non detectable absorption peaks, and finally at the two highest temperatures (180-190 degrees C) the reappearance of an absorption feature centered at 510 nm was noticed. These UV-visible results indirectly imply the composition of the surface of the particle. The structure of the particles has been determined using transmission electron microscopy and high-angle annular dark field (HAADF), the latter being a powerful technique to determine the structural composition of the particles and allowing a direct correlation of the optical response with their structural composition. X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) studies were also performed on the samples and their results support the idea of a Pt(core)-Au(shell) structure with the elements segregated from each other. The combination of these experimental techniques with calculated UV-vis absorption spectra allowed, in a reliable way, the elucidation of the nanoparticles structure and elemental distribution.

Two challenges for effectively exploiting the remarkable properties of single-walled carbon nanotubes (SWNTs) are the isolation of intact individual nanotubes from the raw material and the assembly of these isolated SWNTs into useful structures. In this study, we present atomic force microscopy (AFM) evidence that we can isolate individual peptide-wrapped SWNTs, possibly connected end-to-end into long fibrillar structures, using an amphiphilic alpha-helical peptide, termed nano-1. Transmission electron microscopy (TEM) and well-resolved absorption spectral features further corroborate nano-1's ability to debundle SWNTs in aqueous solution. Peptide-assisted assembly of SWNT structures, specifically in the form of Y-, X-, and intraloop junctions, was observed in the AFM and TEM images.

We report the study of aurothiol nanoclusters using high-resolution electron microscopy, energy loss spectroscopy, X-ray photoelectron spectroscopy, Auger spectroscopy, and microscopy. It is concluded that the sulfur atoms are located on the surface of the gold nanoparticles in both (100) and (111) microfacets. The X-ray photoelectron spectroscopy data show that there is a Au-Au bond as well as a Au-S bond. Auger depth profile measurements made by sputtering of the nanoparticles corroborates that the sulfur is located on the surface of the nanoparticle. Quantitative Auger analysis indicates a ratio Au/S between approximately 1.79 and 1.98.

Maya blue paint was often used in Mesoamerica. The origin of its color and its resistance to acids and biocorrosion have not been fully understood. High-resolution transmission electron microscopy, electron energy loss spectroscopy, and x-ray microanalysis studies of authentic samples show that palygorskite crystals in the paint form a superlattice that probably occurs as a result of mixing with indigo molecules. An amorphous silicate substrate contains inclusions of metal nanoparticles encapsulated in the substrate and oxide nanoparticles on the surface. The beautiful tone of the color is obtained only when both the particles and the superlattice are present.