Use of Mass Spectrometric Vapor Analysis To Improve Canine Explosive Detection Efficiency

The detection of explosives is crucial for civilian safety and environmental protection. The detection in harsh conditions, such as different pH values, is rarely reported. In this paper, using an AIE-active hyperbranched polymer (hb-P1a), the pH effect on explosive detection in aqueous was first studied. The hb-P1a aggregates are highly sensitive to explosive in acid to basic media, indicating that they are tolerant to various pH conditions. Improved detection efficiency of the polymer was recorded in the acid solution (K up to 8.26 × 104 M-1). Furthermore, the prototype devices of hb-P1a in filter papers could sense the PA in varying pH solutions. These advantages make the polymer a good candidate for explosive detection in various practical applications.

Download Full-text

Fresnel interference in point-projection imaging of purple membrane

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100140609 ◽

1995 ◽

Vol 53 ◽

pp. 846-847

Author(s):

X. Zhang ◽

J. Spence ◽

W. Qian ◽

D. Taylor ◽

K. Taylor

Keyword(s):

Detection Efficiency ◽

Mean Free Path ◽

Purple Membrane ◽

Unit Cell Dimension ◽

Experimental Point ◽

Membrane Thickness ◽

Low Energies ◽

Channel Plate ◽

Point Projection ◽

Inelastic Mean Free Path

Experimental point-projection shadow microscope (PPM) images of uncoated, unstained purple membrane (PM, bacteriorhodopsin, a membrane protein from Halobacterium holobium) were obtained recently using 100 volt electrons. The membrane thickness is about 5 nm and the hexagonal unit cell dimension 6 nm. The images show contrast around the edges of small holes, as shown in figure 1. The interior of the film is opaque. Since the inelastic mean free path for 100V electrons in carbon (about 6 Å) is much less than the sample thickness, the question arises that how much, if any, transmission of elastically scattered electrons occurs. A large inelastic contribution is also expected, attenuated by the reduced detection efficiency of the channel plate at low energies. Quantitative experiments using an energy-loss spectrometer are planned. Recently Shedd has shown that at about 100V contrast in PPM images of thin gold films can be explained as Fresnel interference effects between different pinholes in the film, separated by less than the coherence width.

Download Full-text

Effect of energy filtering on micro-diffraction in the SEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010017075x ◽

1994 ◽

Vol 52 ◽

pp. 604-605

Author(s):

James F. Mancuso ◽

Leo A. Fama ◽

William B. Maxwell ◽

Jerry L. Lehman ◽

Hasso Weiland ◽

...

Keyword(s):

Detection Efficiency ◽

Ccd Camera ◽

High Gain ◽

Microchannel Plate ◽

Electrostatic Energy ◽

Energy Filtering ◽

Electron Channelling ◽

Low Energy Electrons ◽

Low Sensitivity ◽

Angular Field Of View

Micro-diffraction based crystallography is essential to the design and development of many classes of ‘crafted materials’. Although the scanning electron microscope can provide crystallographic information with high spatial resolution, its current utility is severely limited by the low sensitivity of existing diffraction techniques (ref: Dingley). Previously, Joy showed that energy filtering increased contrast and pattern visibility in electron channelling. This present paper discribes the effect of energy filtering on EBSP sensitivity and backscattered SEM imaging.The EBSP detector consisted of an electron energy filter, a microchannel plate detector, a phosphor screen, optical coupler, and a slow scan CCD camera. The electrostatic energy filter used in this experiment was constructed as a cone with 5 coaxial electrodes. The angular field-of-view of the filter was approximately 38°. The microchannel plate, which was the initial sensing component, had high gain and had 50% to 80% detection efficiency for the low energy electrons that passed through the retarding field filter.

Download Full-text

Trace nanoanalysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100172437 ◽

1994 ◽

Vol 52 ◽

pp. 940-941

Author(s):

D. E. Newbury ◽

R. D. Leapman

Keyword(s):

High Performance ◽

Secondary Ion Mass Spectrometry ◽

Detection Efficiency ◽

Volume Element ◽

And Performance ◽

Trace Constituents ◽

Secondary Ion ◽

Concentration Levels ◽

Structure Properties

Trace constituents, which can be very loosely defined as those present at concentration levels below 1 percent, often exert influence on structure, properties, and performance far greater than what might be estimated from their proportion alone. Defining the role of trace constituents in the microstructure, or indeed even determining their location, makes great demands on the available array of microanalytical tools. These demands become increasingly more challenging as the dimensions of the volume element to be probed become smaller. For example, a cubic volume element of silicon with an edge dimension of 1 micrometer contains approximately 5×1010 atoms. High performance secondary ion mass spectrometry (SIMS) can be used to measure trace constituents to levels of hundreds of parts per billion from such a volume element (e. g., detection of at least 100 atoms to give 10% reproducibility with an overall detection efficiency of 1%, considering ionization, transmission, and counting).

Download Full-text