Investigating silicon wafer based substrates for dried-droplet analysis by Laser-Induced Breakdown Spectroscopy

Abstract

This work communicates a critical assessment on the analytical capability of the three silicon wafer-based substrates; crystalline silicon (c-Si), oxide-coated silicon (SiO 2 -Si), and nitride-coated silicon (Si 3 N 4 -Si), for drieddroplet analysis by laser-induced breakdown spectroscopy. The methodology consists of loading, drying and analyzing steps. First, nanoliter volume of droplets are manually loaded onto the substrate and dried at room temperature. Then, the dry residue is subjected to high peak power (1.15 GW/cm 2 ) laser pulses focused outside the minimum focal point condition and luminescent plasma is spectroscopically analyzed. Results revealed that nitride-coated substrate exhibits strong enhancements in signal intensity for most emission lines of the analyte species investigated: Cd, Cr, Cu, Mn, and Pb. Surface reflectivity and surface morphology were comparatively investigated to explore enhanced analytical performance of nitride-coated substrates. Experimental conditions were optimized and growth curves for all the elements are found linear with minimum regression constant of 0.96. LOD's of 62 pg Cd, 1.5 pg Cr, 0.5 pg Cu, 2 pg Mn and 11 pg Pb, in absolute amounts, were obtained. The accuracy and precision of the methodology were tested on certified reference water sample (CRM-TMDW), and ICP-multi-element standard sample (ICP-MES). The surface enhancement effect observed on Si 3 N 4 coated substrates has improved the analytical capability of laser-induced breakdown spectroscopy for liquid analysis.

Optimization of different sampling approaches in liquid LIBS analysis for environmental applications

“…18,19 Literature shows that the double pulse technique increases the liquid LIBS signal and thereby its sensitivity by using an extra laser pulse to preheat the plasma-induced by the laser in a liquid environment. [20][21][22][23][24][25] In addition, resonance LIBS by choosing a suitable laser wavelength to employ, circulating the sample through a liquid jet, [26][27][28][29] creation of aerosols 30,31 and liquid droplets, 32,33 liquid to solid transformation using different substrates, [34][35][36][37][38][39][40][41] etc., are the other proposed methods for liquid LIBS analysis till date. Among them, adding the components to the experimental setup is limited by the system cost and complexity, and the liquid jet method is limited by the availability of sample volume.…”

Evaluation of electrosprayed graphene oxide coatings for elemental analysis by thin film microextraction followed by Laser-induced Breakdown Spectroscopy detection

“…. [6][7][8][9][10]. An alternative to circumvent this problem can be the use of sample preparation procedures able to concentrate the target analytes to a level above the detection limits of LIBS.…”

Elemental analysis of levitated solid samples by microwave-assisted laser induced breakdown spectroscopy

“…The techniques used for elemental analysis of microvolume samples are generally coupled with sample introduction systems. Examples of such systems include nano-and micro-nebulisers, 6 paper spray ionisation, 28 piezoelectric microdispensing, 29 capillary electrophoresis, 30 microfluidic systems, 31,32 dried microdroplets on substrates (such as silicon), 33 and matched with laser ablation systems, 34,35 the enchantement of LIBS nanoparticules, 9,15 and electrodynamic balances. 36,37 All these systems are restricted to liquid samples; therefore, dilution is often required.…”