Surface structures consisting of chromatin fibers in isolated barley (Hordeum vulgare) chromosomes revealed by helium ion microscopy

Reflection ion microscopy (RIM) is a technique that uses a low angle of incidence and scattered ions to form an image of the specimen surface. This paper reports on the development of the instrumentation and the analysis of the capabilities and limitations of the scanning RIM in a helium ion microscope (HIM). The reflected ions were detected by their “conversion” to secondary electrons on a platinum surface. An angle of incidence in the range 5–10° was used in the experimental setup. It was shown that the RIM image contrast was determined mostly by surface morphology but not by the atomic composition. A simple geometrical analysis of the reflection process was performed together with a Monte Carlo simulation of the angular dependence of the reflected ion yield. An interpretation of the RIM image formation and a quantification of the height of the surface steps were performed. The minimum detectable step height was found to be approximately 5 nm. RIM imaging of an insulator surface without the need for charge compensation was successfully demonstrated.

Download Full-text

Biosynthesis of Gold Nanoparticles with Serratia marcescens Bacteria

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1132.19 ◽

2015 ◽

Vol 1132 ◽

pp. 19-35

Author(s):

S.O. Dozie-Nwachukwu ◽

J.D. Obayemi ◽

Y. Danyo ◽

G. Etuk-Udo ◽

N. Anuku ◽

...

Keyword(s):

Gold Nanoparticles ◽

Serratia Marcescens ◽

Visible Spectroscopy ◽

X Ray ◽

Color Changes ◽

Transmission Electron ◽

Helium Ion ◽

Ph Conditions ◽

Uv Visible ◽

Ion Microscopy

This paper presents the biosynthesis of gold nanoparticles from the bacteria, Serratia marcescens.The intra-and extra-cellular synthesis of gold nanoparticles is shown to occur over a range of pH and incubation times in cell-free exracts and biomass ofserratia marcescensthat were reacted with 2.5mM Tetrachloroauric acid (HAuCl4). The formation of gold nanoparticles was identified initially via color changes from yellow auro-chloride to shades of red or purple in gold nanoparticle solutions. UV-Visible spectroscopy (UV-Vis), Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray spectroscopy (EDS), Helium Ion Microscopy (HIM) and Dynamic Light Scattering (DLS) were also used to characterize gold nanoparticles produced within a range of pH conditions. The results show clearly that the production of gold nanoparticles from cell-free extracts require shorter times than the production of gold nanoparticles from the biomass.

Download Full-text