Enhanced Laser Induced Breakdown Spectroscopy Research Articles

Solid substrate assisted enhanced laser induced breakdown spectroscopy for metal element analysis in aqueous solution

Due to plasma quenching caused by the dense water medium, laser-induced breakdown spectroscopy (LIBS) faces challenges such as strong continuous background radiation, weak and broadened characteristic spectral lines when directly...

Nano objects evaluation for nanoparticle enhanced laser induced breakdown spectroscopy analysis of polymers using a handheld device

Polymer additives are essential to provide essential properties to the plastic materials. Some of the mainly employed additives contain metals essential to measure like Sb, Pb or P. Laser Induced Breakdown Spectroscopy suffers a lack of sensitivity for these elements and especially when using handheld devices. The recent developments in Nanoparticles Enhanced Laser Induced Breakdown Spectroscopy (NELIBS) have led to improvement of signals mainly in conductive materials. In this work we prepared and evaluate nano-objects with different shapes and size to improve element signals on plastic samples. Ellipsoid, bipyramids and spheres increased significantly sensitivity of most additives i.e. P, Sb, Mg and Pb. The obtained gold ellipsoids nano-objects were of small dimensions and gave best signal enhancement. The NELIBS also increased the CaF molecular band signal by a factor of 2. These results indicate that the NELIBS can be used in quantitative analytical application for plastics even for difficult elements like fluorine.

Rapid and Reliable Detection of Lithium in Water Sources Using Surface Enhanced Laser Induced Breakdown Spectroscopy (SENLIBS) on Aluminium Substrate

Lithium is one of the most important materials in re-chargeable battery as well as pharmaceutical and automotive industry. Due to the increasing demand for lithium for industrial production and daily usage, the reliable detection and recovery of lithium, a non-renewable metal, from water resources is an essential requirement. In this work, we performed lithium detection using surface enhanced laser induced breakdown spectroscopy on aluminium (Al) substrate for three different matrices, sea, river and municipal water. We also examined the matrix effect on sensitivity of lithium detection. Lithium spiked samples in different concentration (0- 100 ppm) was dried on an Al surface. The specific emission line of Li 670 nm was used for quantitative analysis. The intensity of Li was obtained about 15 times on Al substrate better than microscope glass. The limit of detection (LOD) value achieved to 0.138 ppm. No significant matrix effect was observed in the different water sources. Good reliability was obtained for intra and inter-day precision methods with RSD is <3.7% and<7.3% respectively in all water samples. Total analysis time including sample preparation is approximately in 1 min. We demonstrated that SENLIBS method provides rapid, high accuracy and repeatability of sensitive Li detection in different water sources.

Plasma Formation And Its Sustainment In Time And Space In Microwave Enhanced Laser Induced Breakdown Spectroscopy

The transient and unstable plasma generation in the laser-induced breakdown is potentially resolved by the addition of microwaves. The laser and microwave technology combination extends the plasma lifetime and enhanced its emission intensity and volume. The expansion of the plasma started a few seconds after the initial formation of the plasma seed and the absorption of the microwave by the plasma also started to take effect. Large dome-shaped plasma is then briefly sustained until the end of the microwave duration. As the plasma expands, the plasma drifts away from the sample surface which is a good indication of the non-ablation effect of the microwave energy. The expansion of the plasma by microwaves enhances the breakdown of the plasma but potentially regulates the formation of toxic ablation fumes.

Effect of plasma temperature and electron number density on signal enhancement observed in nanoparticle enhanced LIBS

The present work aims to understand the signal enhancement observed in nanoparticle (NP)-enhanced laser induced breakdown spectroscopy (NELIBS) due to changes in the plasma parameters as a result of improved atomization and excitation. A systematic study on signal enhancements during NELIBS using simultaneous spectroscopy and imaging is investigated by varying the experimental parameters like particle size and laser fluence. We have observed similar enhancements in spectroscopy and imaging channels regardless of NP size at different laser fluences. Although the plume size in NELIBS was marginally more prominent than the LIBS at the same laser fluence, the corresponding intensity in NELIBS is significantly higher. This agrees with the hypothesis of efficient atomization and excitation of plasma in the case of NELIBS. Therefore, we performed a sensitivity analysis using simulated LIBS signal to understand changes in experimentally observable plasma parameters (excitation temperature and electron number density) on signal enhancement. We have shown that the enhancements in the emission intensities of typically one order of magnitude can be explained as a result of the change in electron number density and plasma temperature. A comparison of the expected enhancement due to this change with experimental observation for a Cu I line is also presented.

Detection enhancement at parts per billion level of aluminum in water droplets by a combination of acoustic levitation and nanoparticle enhanced laser induced breakdown spectroscopy

Nowadays, detecting metals dissolved in water is a paramount health concern, due to the sustained contamination of water reservoirs for human consumption. Limits of detection in the sub-ppm range are required, but a simple and fast method suitable to measure such levels is not easy to implement. Laser induced breakdown spectroscopy (LIBS) is a simple technique and can be employed on field, but its lack of sensitivity at sub-ppm has restricted its application. With the recent use of metallic nanoparticles to enhance the plasma emission, ppb limits of detection are achieved. In combination with liquid droplet acoustic levitation, this work demonstrate that few ppb limit of detection is possible measuring directly in the liquid sample without any pretreatment. When limits of detection obtained with and without the use of metallic nanoparticles are compared, improvements up to three orders of magnitude were obtained for aluminum dissolved in water, keeping similar relative standard deviations in the range of 10–20%. It is also important to note that after optimization, excitation energies as low as 1 mJ are sufficient to generate spectra with signal to noise ratios around 7 at concentrations below 1 ppb. The resulting spectra are suitable to be analyzed for quantification, opening the real possibility of its implementation on field applications.

Sensing nanoparticle-protein corona using nanoparticle enhanced Laser Induced Breakdown Spectroscopy signal enhancement

Recently nanoparticle enhanced Laser Induced Breakdown Spectroscopy (NELIBS) is getting a growing interest as an effective alternative method for improving the analytical performance of LIBS. On the other hand, the plasmonic effect during laser ablation can be used for a different task rather than elemental analysis.In this paper, the dependence of NELIBS emission signal enhancement on nanoparticle-protein solutions dried on a reference substrate (metallic titanium) was investigated. Two proteins were studied: Human Serum Albumin (HSA) and Cytochrome C (CytC). Both proteins have a strong affinity for the gold nanoparticles (AuNPs) due to the bonding between the single free exterior thiol (associated with a cysteine residue) and the gold surface to form a stable protein corona. Then, since the protein sizes are vastly different, a different number of protein units is needed to cover AuNP surface to form a protein layer. The NP-protein solution was dropped and dried onto the titanium substrate. Then the NELIBS signal enhancement of Ti emission lines was correlated to the solution characteristics as determined with Dynamic Light Scattering (DLS), Surface Plasmon Resonance (SPR) spectroscopy and Laser Doppler Electrophoresis (LDE) for ζ-potential determination. Moreover, the dried solutions were studied with TEM (Transmission Electron Microscopy) for the inspection of the inter-particle distance. The structural effect of the NP-protein conjugates on the NELIBS signal reveals that NELIBS can be used to determine the number of protein units required to form the nanoparticle-protein corona with good accuracy. Although the investigated NP-protein systems are simple cases in biological applications, this work demonstrates, for the first time, a different use of NELIBS that is beyond elemental analysis and it opens the way for sensing the nanoparticle protein corona.

Effect of spherical gold nanoparticles size on nanoparticle enhanced Laser Induced Breakdown Spectroscopy

Recently the use of nanoparticles (NPs) for enhancing Laser ablation based analytical techniques, is getting a growing interest in analytical atomic spectroscopy. This technique is based on the deposition of NPs on the sample surface before the laser irradiation. The effect of the coupling of NPs plasmon with the laser pulse allows a notable improvement of the analytical signal. In this study, different sizes of spherical gold nanoparticles (AuNPs), 10 nm, 40 nm, 60 nm and 100 nm, have been employed to clarify the role of the NPs size on the signal enhancement during Laser Induced Breakdown Spectroscopy (LIBS). Therefore, a systematic investigation of the Nanoparticle Enhanced LIBS (NELIBS) have been done by varying the key experimental parameters as NPs surface concentration, laser fluence and laser spot size. The experimental results show that improvement of the emission signal during NELIBS occurs at specific NPs surface concentration and that this critical concentration depends on the NP size. When the concentration has been optimized for each NP size, the plasmon-enhanced ablation is moderately affected by the NPs size.

Enhanced laser induced breakdown spectroscopy signal intensity in colloids: An application for estimation of Cu and Cr in aqueous solution

A fast and sensitive estimation of Cu and Cr in aqueous solution by laser induced breakdown spectroscopy (LIBS) was realized by using a simple pre-treatment methodology of aqueous solution. Sodium hydroxide (NaOH) is added to the sample to raise the pH (>12) of the solution to form hydroxides of metals which leads to formation of colloids. This colloidal solution is spread over a filter paper, dried in air and subsequently subjected to LIBS. The LIBS signal intensity was found to be two orders of magnitude higher than the solution without adding NaOH. Under optimized experimental conditions, linear calibration plots were obtained in the range of 0.05–0.8 μg/mL of Cu and Cr, with good correlation coefficients (R2 > 0.995) using Yb as an internal standard. The detection limits of Cu and Cr were found to be 0.020 and 0.025 μg/mL respectively. Tap and rain water samples spiked with Cu and Cr are analysed by the proposed method and recoveries are in the range of 93–117%.

High enhancement factor in low-power unipolar discharge arc assisted laser induced plasma spectroscopy

The enhanced laser induced breakdown spectroscopy is highly desirable for the quantitatively detection with low limit of detection (LOD) and high accuracy. Higher enhancement factor is always obtained from discharge assisted laser-induced breakdown spectroscopy with enough higher energy injection in comparison to the normally standard laser induced breakdown spectroscopy (LIBS), which means dangerous with high voltage and elevated power. Here, a low power (10 W) injected unipolar discharge arc is proven to greatly enhance the LIBS with a large enhancement factor up to 13.8 when the discharged electric arc followed by a laser induced plasma are simultaneously applied on a silicon wafer, which is comparative or larger than those results with high-power (kW) and high voltage (kV) being applied. Furthermore, the enhanced technique is applied on an actual qualitative detection of cadmium in soil. The lines of Cd II (214.44 nm) from soil is enhanced as compared to a LIBS measurement. Accordingly, the LOD of the typical emission line is reduced to 23.5 ppm by the unipolar discharge arc assisted laser induced breakdown spectroscopy (UD-LIBS), which is 2.45-fold lower than that from the normal LIBS. The pre-ionization of the environment and the surface by the modulated discharge arc to directly make the Inverse Bremsstrahlung (IB) absorption with higher absorption coefficient dominate the initial stage of plasma formation rather than the multi-photon absorption process, thus make both electron density and the temperature of plasma raising are the main mechanism of spectral enhancement, which is further proved by the evolution dynamics images of two plasma overlapping processes under an in-situ intensified charge-coupled device (ICCD) based photographic system. The simple, portable, commercial highly enhancement way is greatly benefit to the actual applications.

Investigating double pulse nanoparticle enhanced laser induced breakdown spectroscopy

Several strategies have been effectively tested in the past to improve the Laser Induced Breakdown Spectroscopy (LIBS) signal, involving peculiar experimental configurations, such as Double Pulse LIBS (DP-LIBS). Recently, sample treatment has proven to be a viable and simple way to enhance the LIBS performances; in particular, the Nanoparticle-Enhanced LIBS (NELIBS) methodology uses a deposition of metal nanoparticles (NPs) on the sample to greatly increase the emission of the LIBS plasma.In this work, we investigate the possibility of combining, for the first time, DP-LIBS with NELIBS. The chosen set-up uses two parallel non-collinear laser pulses to ensure the activation of NPs during both pulses, while maintaining the low-pressure environment typical of DP-LIBS. The two laser beams are spatially separated so that the second beam is focused within the shock wave generated by the first one. This configuration allows the exploitation of the combined enhancement of both DP-LIBS and NELIBS.Several tests on copper targets have been performed to determine the best set-up for the maximum magnitude of the signal enhancement by adjusting different parameters such as pulse energies and offset distances. Commercially available silver NPs and NPs prepared by pulsed laser ablation in liquid have been tested and their performances compared with standard DP-LIBS.

Nanoparticle enhanced laser ablation and consequent effects on laser induced plasma optical emission

In this paper the plasmon enhanced ablation for elemental analysis is investigated with several experiments in order to point out the crucial questions concerning the laser matter interaction under the effect of plasmonic coupling between the nanoparticle (NP) system and the laser ablation pulse. The correlation between the electromagnetic field enhancement and the signal enhancement during NP enhanced laser induced breakdown spectroscopy (NELIBS), as well as the laser matter interaction at the nanoscale, is discussed in the case of noble metal NPs deposited on metal samples. The results suggest that, while laser pulse energy is concentrated in the space between the NPs, the NP system is shielded by the field enhancement distribution after the laser pulse interacts with the plasmons of the NP system. Finally the comparison of the laser energy transfer to the sample between NELIBS and conventional LIBS is discussed.

Nanoparticle enhanced laser induced breakdown spectroscopy of liquid samples by using modified surface-enhanced Raman scattering substrates

An assessment of the feasibility of using modified surface enhanced Raman scattering substrates (Ag nanoparticles on indium‑tin-oxide glass) for quantitative nanoparticle-enhanced laser induced breakdown spectroscopy (NELIBS) was carried out. Substrates were prepared with different surface coverage from various nanoparticle sizes, and their laser ablation behaviour was tested in detail. It was found that use of those combinations are most beneficial in terms of the signal enhancement factor, which provide the shortest interparticle distances. With the application of 266 nm laser wavelength, long (ms-range) gate width, and optimized laser pulse energy, the best NELIBS signal enhancement was found to be about a factor of three. By using liquid sample deposition by spraying, which was found to provide an even distribution of liquid samples on the substrate surface, successful calibration for Mn, Zn and Cr was performed. The NELIBS signal repeatability from five repeated measurements was found to be comparable to that of LIBS (5–10% RSD). These observations indicate that the NELIBS signal enhancement approach can be used in quantitative analytical applications for liquid samples, if i) the substrate fabrication procedure has good repeatability, ii) surface coverage and nanoparticle size is tightly controlled, iii) a homogenous liquid sample deposition is achieved.

Application of gold nanoparticles embedded in the amyloids fibrils as enhancers in the laser induced breakdown spectroscopy for the metal quantification in microdroplets

In this work Nanoparticle Enhanced Laser Induced Breakdown Spectroscopy (NELIBS) has been employed for quantitative metal detection using amyloid fibrils coated with gold nanoparticles as enhancers. Amyloid fibrils represent, from one hand, an extremely interesting system for novel technologies, ranging from water purification to medical applications, and on the other hand, an ideal system for investigating the performance of laser-matter interaction in biological systems. The results obtained in this work show the potentiality of NELIBS for the quantification at sub-ppm (mg/kg) level of metallic elements (Cr, Pb, Tl and Cd) even in the protein and/or biological environment, employing amyloid fibrils with gold nanoparticles. Moreover, the single-shot measurements reveal the promising use of this technique in applications where high sensitivity and/or limitation in the sample amount are demanded.

Research on spectral characteristics of laser-induced plasma by combining Au-nanoparticles and magnetic field confinement on Cu

In order to enhance the intensity of emission spectra of laser-induced plasma, a method of combining magnetic field enhanced laser induced breakdown spectroscopy(LIBS) with nanoparticle enhanced LIBS (NELIBS) was proposed. Laser-induced breakdown of copper was respectively performed by using traditional LIBS, magnetic field-enhanced LIBS, NELIBS, and the combination of the magnetic field enhanced LIBS and NELIBS.Some parameters including electron temperature, electron density and signal-to-noise ratio were obtained and analyzed. The experimental results show that when the Au-nanoparticles(Au NPs) are combined with magnetic field in LIBS, the spectral intensity of plasma is effectively enhanced and, the signal-to-noise ratio is significantly improved, and the optimum is achieved when the laser pulse energy is 80 mJ; the electron temperature and the electron density do not change obviously, the ability of using LIBS to detect trace elements is significantly improved.

Nanoparticle Enhanced Laser Induced Breakdown Spectroscopy for Improving the Detection of Molecular Bands

Enhancement of molecular band emission in laser-induced plasmas is important for improving sensitivity and limits of detection in molecular sensing and molecular isotope analysis. In this work we introduce the use of Nanoparticle Enhanced Laser Induced Breakdown (NELIBS) for the enhancement of molecular band emission in laser-induced plasmas, and study the underlying mechanisms responsible for the observed enhancement. The use of Ag nanoparticles leads to an order of magnitude enhancement for AlO (B2Σ+→Χ+Σ+) system emission from an Al-based alloy. We demonstrate that the mechanism responsible for the enhancement of molecular bands differs from that of atomic emission, and can be traced down to the increased number of atomic species in NELIBS which lead to AlO molecular formation. These findings showcase the potential of NELIBS as a simple and viable technology for enhancing molecular band emission in laser-induced plasmas.

Perspective on the use of nanoparticles to improve LIBS analytical performance: nanoparticle enhanced laser induced breakdown spectroscopy (NELIBS)

In this paper, the new approach for Laser Induced Breakdown Spectroscopy (LIBS) based on nanoparticle deposition on the sample surface is reviewed from both fundamental and application points of view.

Nanoparticle Enhanced Laser Induced Breakdown Spectroscopy: Effect of nanoparticles deposited on sample surface on laser ablation and plasma emission

In this paper the use of metallic nanoparticles (NPs) for improving Laser Induced Breakdown Spectroscopy (LIBS) is discussed. In the case of conductors an emission signal enhancement up to 1–2 orders of magnitude was obtained depositing NPs on the sample surface by drying a micro-drop of colloidal solution. The basic mechanisms of Nanoparticle Enhanced LIBS (NELIBS) were studied and the main causes of this significantly large enhancement were found to be related to the effect of NPs on the laser ablation process, in terms of a faster and more efficient production of seed electrons with respect to conventional LIBS. The characteristics of NELIBS-produced plasma were investigated by emission spectroscopy and spectrally resolved images. In spite of similar plasma parameters, the NELIBS plasma was found to have larger emission volume and longer persistence than the LIBS one. A method to determine NP concentration and size was also proposed, which involved depositing NPs on non-interacting substrates, and proved the feasibility of LIBS as a fast detection tool for a preliminary characterization of NPs.