Electron Microscopy of Colloidal Systems

Abstract

VOLUME 2 1, NO. 4, APRIL 1949 475 one after the illumination had been corrected. In the latter procedure, the point representing the quality on the trichroic ratio graph was brought to the same location on the graph within a reasonable tolerance. There was one exception to this. In one case, the variation consisted of an intensity difference with the illuminance from a ribbon filament at one twentieth that of the first pair. This was brought to the quality represented by the point further along the line representing variation of the reference point with intensity level. It was found that the same reference point was not valid for the tungsten arc which contains lines of the mercury spectrum superposed on the tungsten spectrum, at least with the photocell filters listed for Type B films. The method was satisfactory for variations of quality produced by changing from tungsten filament to a 4.5-ampere and a 10-ampere arc and from transparent to vertical illumination. (A sheet of this test on Kodachrome film was shown at St. Louis as a color slide.} Probably the system can be used with a tungsten arc but with its own reference points on the graph; this has been tested by only a fe\v trials. This relative!}' new' system has proved valuable in routine work;it saves much time and justifies the confidence with w'hich exposed film is sent off for processing.

Hydrothermal synthesis of well-crystallised boehmite crystals of various shapes

“…The authors presented optical microscopy and TEM images of thin plates with hexagonal or elongated profiles. Turkevich and Hillier 20 provided TEM images showing aluminium oxide monohydrate crystals as ellipsoid plates with sharp points at each end. The structural regularity of the crystal was evidenced by the Bragg reflections in some areas of the plates.…”

Synthesis of Au/TiO<SUB>2</SUB> Core-shell Structure Nanoparticles and the Crystallinity of TiO<SUB>2</SUB> Shell

“…TiO 2 coating was preformed by utilizing the Stober method. 18) TOAA was used as a coating reagent. For the preparation of ethanol solution suspending gold sol, 0.4 mM of MUA-coated gold sol (stock solution, 0.3 ml) was mixed with 9.7 ml of ethanol including some water.…”

Uso de nanobastões de ouro para o desenvolvimento de aulas práticas de nanotecnologia

“…8,9 Descritas pela primeira vez por Faraday em 1857, as nanoesferas de ouro são usualmente sintetizadas a partir de uma reação de redução aquosa de ácido cloroáurico (HAuCl 4 ) por citrato de sódio. 10,11 Já os nanobastões de ouro são frequentemente sintetizados pelo método mediado por sementes, descrito por Murphy e colaboradores em 2001, 12,13 no qual os nanobastões são preparados à partir da adição de nanoesferas recobertas por citrato (sementes), à uma solução contendo HAuCl 2 em elevadas concentrações, resultante da redução de HAuCl 4 por ácido ascórbico (C 6 H 8 O 6 ) na presença do surfactante brometo de cetiltrimetilamônio (CTAB) e íons de prata. O CTAB é essencial para a síntese controlada em forma de bastões, devido ao fenômeno de ligação preferencial às diferentes faces dos bastões após o início do crescimento das sementes.…”