Showing papers by "Richard E. Russo published in 2020"

Coal Discrimination Analysis Using Tandem Laser-Induced Breakdown Spectroscopy and Laser Ablation Inductively Coupled Plasma Time-of-Flight Mass Spectrometry

Abstract: The contribution and impact of combined laser ablation inductively coupled plasma time-of-flight mass spectrometry (LA-ICP-TOF-MS) and laser-induced breakdown spectroscopy (LIBS) were evaluated for...

Dynamic characteristics of multi-charged ions emitted from nanosecond laser produced molybdenum plasmas

Abstract: Diagnostics of plasma–wall interaction processes provide important information on nuclear fusion devices. Elucidation of the charge state distribution and temporal evolution of multi-charged ions is essential to improve laser ablation-based diagnostics of the plasma–wall interaction processes. Molybdenum is a material of interest in fusion and has been used as the plasma-facing material of the first wall in the EAST tokamak. In this work, the dynamic characteristics of multi-charged ions emitted from a molybdenum plasma produced by a Q-switched Nd:YAG nanosecond laser (wavelength 1064 nm, pulse width 7 ns) were studied using time of flight mass spectroscopy under a pressure of 6 × 10−4 Pa. The charge state distribution and temporal evolution of the multi-charged ions at various laser power densities from 0.85 GW cm−2 to 7.9 GW cm−2 were systematically investigated. This power density range is commensurate with that used in LIBS and LIAS diagnostics of the plasma–wall interaction process in EAST tokamaks. The ion charge state was found to increase with laser power density and the observed maximum charge state was up to seven at the highest laser power density used in these experiments. The higher charged ions had greater velocities indicating that separation took place between the different charged ions during the plasma expansion process. The origin of multi-charged ions is attributed to step-wise ionization due to plasma shielding from strong laser absorption in the plasma and the reduction of the ablation rate with the increase in laser power density. The velocities between these multi-charged ions were related to the acceleration of the transient plasma sheath during the laser interaction with the target and plasma.

Detection of E. coli labeled with metal-conjugated antibodies using lateral-flow assay and laser-induced breakdown spectroscopy

Abstract: This study explores the adoption of laser-induced breakdown spectroscopy (LIBS) for the analysis of lateral-flow immunoassays (LFIAs). Gold (Au) nanoparticles are standard biomolecular labels among LFIAs, typically detected via colorimetric means. A wide diversity of lanthanide-complexed polymers (LCPs) are also used as immunoassay labels but are inapt for LFIAs due to lab-bound detection instrumentation. This is the first study to show the capability of LIBS to transition LCPs into the realm of LFIAs, and one of the few to apply LIBS to biomolecular label detection in complete immunoassays. Initially, an in-house LIBS system was optimized to detect an Au standard through a process of line selection across acquisition delay times, followed by determining limit of detection (LOD). The optimized LIBS system was applied to Au-labeled Escherichia coli detection on a commercial LFIA; comparison with colorimetric detection yielded similar LODs (1.03E4 and 8.890E3 CFU/mL respectively). Optimization was repeated with lanthanide standards to determine if they were viable alternatives to Au labels. It was found that europium (Eu) and ytterbium (Yb) may be more favorable biomolecular labels than Au. To test whether Eu-complexed polymers conjugated to antibodies could be used as labels in LFIAs, the conjugates were successfully applied to E. coli detection in a modified commercial LFIA. The results suggest interesting opportunities for creating highly multiplexed LFIAs. Multiplexed, sensitive, portable, and rapid LIBS detection of biomolecules concentrated and labeled on LFIAs is highly relevant for applications like food safety, where in-field food contaminant detection is critical. Graphical abstract.

Molecular laser-induced breakdown spectroscopy

Abstract: This chapter focuses on molecular laser-induced breakdown spectroscopy (LIBS). Of interest are applications in diverse fields that include plasma diagnostics, combustion diagnostics, molecular plasma spectroscopy, and selected astrophysics spectra analyses. Laser ablation molecular isotopic spectrometry (LAMIS) reveals favorable measurement opportunities for identification of atomic isotope compared to direct isotope spectroscopy. For selected molecules of different atomic isotope composition, or for isotopologues, the presented summary discusses LAMIS advantages. LIBS experiments convey formation of diatomic molecules primarily due to recombination. The analysis of diatomic emission spectra reveals excitation temperatures up to 10 kK following laser-induced optical breakdown. Cyanide (CN), aluminum monoxide (AlO), titanium monoxide, Swan bands of C2, and hydroxyl molecules are frequently recorded in nanosecond LIBS investigations over and above the usual atomic emission spectra. The CN molecule occurs within the first few hundred nanoseconds after optical breakdown, and Abel inversion of CN line-of-sight data determines the spatial distributions of molecular signals. For nanosecond LIBS, expansion dynamics and shockwave phenomena explain the measured radial distributions for CN and also for hydrogen. Chemical equilibrium distribution computations assess deviation from thermodynamic equilibrium. This chapter also communicates measurements of AlO ablation spectra and associated analysis with line strength data. Analysis of astrophysics C2 Swan spectra provides further challenges, but in turn can serve as a gauge for chemical analysis with molecular LIBS.