Automated Particle Analysis of Populations of Silver Halide Microcrystals by Electron Probe Microanalysis under Cryogenic Conditions

Abstract

An automated particle analysis routine is implemented on an electron microprobe for analyzing the chemical composition and projective area of populations of individual silver halide microcrystals. An LN2 cryostage is used to prevent material degradation due to reaction with the impinging electron beam. The background in the EDX spectra is lowered by depositing the microcrystals on a carbon-coated copper grid, mounted in a transmission holder. The ILα/AgLα net X-ray intensity ratio, obtained from a spectrum-fitting algorithm, is used to determine the crystal composition by means of a standard-based calibration curve. The uncertainty on the concentration measurement of individual microcrystals is calculated using the uncertainties on the net X-ray counts and the uncertainties on the calibration curve. The area measurement is optimized by introducing a gray value histogram correction on each individual measurement. Overlapping microcrystals are scrapped from the analysis by defining a maximum shape factor, against which the shape factor of the microcrystal is tested. To minimize problems with drift of the cryostage, spectrum acquisition is carried out immediately after a single microcrystal has been located, based on the backscattered electron image. Several applications are discussed.

Combinatorial approaches for developing upconverting nanomaterials: high-throughput screening, modeling, and applications

“…125 3.4.2 Other optical properties. While upconversion luminescence is the optical property most relevant to the application of UCNPs, these properties must be correlated to the particles' composition and to structural properties such as size, size 19 and confocal microscopes 26 NIR scanner 17,123 Wide-field imaging 125 Wide-/small-angle X-ray scattering (WAXS/SAXS) Crystal phase (WAXS) Lattice strain (WAXS) WAXS with automated sample stages, 95 sample changers 101 Automated WAXS/SAXS synchrotron beamlines 138 Automated TEM [130][131][132]134,135,231 Elemental analysis Composition ICP-OES/MS with autosampler XRF with sample changers 101 Scanning mXRF 138,140 EELS/EDS 127,144,230,232,233 Rutherford back scattering (RBS) 234 distribution, shape, and crystal phase. The electronic structure and optical cross sections of lanthanide-doped nanoparticles are probed spectroscopically with commercial multi-function microplate readers that measure ultraviolet (UV) and visible (vis) absorption (200-1000 nm) on microplates with up to 1536 wells.…”

Quantitative Time-Resolved Monitoring of Nitrate Formation in Sea Salt Particles Using a CCSEM/EDX Single Particle Analysis

“…We have developed and built an automated Time-Resolved Aerosol Collector (TRAC) (33) that takes aerosol samples sequentially onto grid-supported thin films at time intervals short enough to follow significant changes in aerosol properties. It has been demonstrated (34)(35)(36) that the use of the grid-supported ultrathin carbon films as deposition substrates provides exceptional performance in Computer Controlled SEM/EDX single-particle analysis. Grid-supported carbon films of ∼50 nm thickness give very low background in the EDX analysis and thus allow superior automated analysis of particles down to 0.1-0.2 µm size, including semiquantitative detection of low-Z elements: C, N, and O.…”

Evaluation of quantitative procedures for X‐ray microanalysis of environmental particles

“…So, the substrate contributes X-rays to EDX spectra of particles and traditional polycarbonate membranes exhibit intense carbon and oxygen peaks. X-ray interferences could be reduced using grid-supported ultrathin (30260 nm) carbon films having extremely low backscattering coefficients (Gregory et al, 1998). However, the X-ray signal emitted by the metallic TEM grid because of lateral electron scattering can interfere with X-rays characteristic of the particle.…”