Ultrafast Laser Excitation Improves LIBS Performance for the Analysis of Optically Trapped Single Nanoparticles Owing to Characteristic Interaction Mechanisms

Abstract

Owing to the exceedingly small mass involved, complete elemental characterization of single nanoparticles demands a highly precise control of signal background and noise sources. LIBS has demonstrated remarkable merits for this task, providing a unique tool for the multielemental analysis of particles on the attogram−picogram mass scale. Despite this outstanding sensitivity, the air plasma acting as a heat source for particle dissociation and excitation is a meddling agent, often limiting the acquisition of an accurate sample signature. Although thermal effects associated with ultrashort laser pulses are known to be reduced when compared to the widely used nanosecond pulse duration regime, attempts to improve nanoinspection performance using ultrafast excitation have remained largely unexplored. Herein, picosecond laser pulses are used as a plasma excitation source for the elemental characterization of single nanoparticles isolated within optical traps in air at atmospheric pressure. Results for picosecond excitation of copper particles lead to a mass detection limit of 27 attogram, equivalent to single particles 18 nm in diameter. Temporally and wavelength-resolved plasma imaging reveals unique traits in the mechanism of atomic excitation in the picosecond regime, leading to a deeper understanding of the interactions occurring in single nanoparticle spectroscopy.

In situ online detection of atmospheric particulate matter based on laser induced breakdown spectroscopy: a review

“…To address these issues, future directions include the use of ultrafast LIBS (ULIBS) to enhance laser ablation efficiency, signal intensity, and stability, thereby improving sensitivity. 119 LIF can enhance the detection capabilities of organic compounds and isotopes, complementing LIBS. LIBS-LIF combinations enhance multi-information analysis for comprehensive and accurate detection.…”

“…On the other hand, the longlived plasma provides time for molecule formation. 67 To address the limitations of traditional LIBS technology in discerning isomers, Wan et al conducted a semi-quantitative analysis of four primary lead isotopes ( 204 Pb + , 206 Pb + , 207 Pb + , and 208 Pb + ) and nine stable tin isotopes ( 114 Sn + , 115 Sn + , 116 Sn + , 117 Sn + , 118 Sn + , 119 Sn + , 120 Sn + , 122 Sn + , and 124 Sn + ) in welding fume samples with varying lead concentrations, utilizing LIBS and single particle aerosol mass spectrometry (SPAMS) techniques. 46 The researchers rst used a soldering iron to melt tin wire samples with different lead contents, creating smoke samples with varying lead concentrations.…”

Ultrashort and short-pulse laser ablation for chemical element analysis and thin film deposition of complex materials

“…UV single-pulse and double-pulse fs-LIBS depth profiling of multilayered thin film samples with nanometer depth resolution has been reported [18]. For single nanoparticles of sub-femtogram mass that were trapped by optical tweezer in gas background and ablated by picosecond laser pulses, LIBS signals have been detected [19].…”

Atomic spectrometry update: review of advances in atomic spectrometry and related techniques

“…Results showed that plasmon-enhanced ablation was only moderately affected by the variation in NP shape, providing similar enhancement values for the different types of AuNPs. Burgos-Palop et al 100 used ultrafast (ps) laser excitation to investigate optically trapped single NPs in LIBS. They found a higher number of analyte-related lines and reduced presence of air components in the spectra.…”