Nanoparticle-enhanced Laser-induced Breakdown Spectroscopy Research Articles

Sensitivity and stability improvement on slippery surface-aggregated substrate for trace heavy metals detection using NELIBS

The sensitive and stable detection of trace heavy metals in liquid is crucial given its profound impact on various aspects of human life. Currently, nanoparticle-enhanced laser-induced breakdown spectroscopy (NELIBS) with dried droplet method (DDM) is widely applied for heavy metals detection. Nevertheless, the coffee ring effect (CRE) in DDM affects the stability, accuracy, and sensitivity of NELIBS. Here, we developed a slippery surface-aggregated substrate (SS substrate) to suppress the CRE and enrich analytes, and form a plasmonic platform for NELIBS detection. The SS substrate was prepared by infiltrating perfluorinated lubricant into the pores of PTFE membrane. The droplet, with targeted elements and gold nanoparticles, was dried on the SS substate to form the plasmonic platform for NELIBS analysis. Then, trace heavy metal elements copper (Cu) and manganese (Mn) were analyzed by NELIBS. The results of Cu (RSD = 5.60%, LoD = 3.72 μg/L) and Mn (RSD = 7.42%, LoD = 6.37 μg/L), illustrated the CRE suppression and analytes enrichment by the SS substrate. The results verified the realization of stable, accurate and sensitive NELIBS detection. And the LoDs succeeded to reach the standard limit of China (GB/T 14848-2017). Furthermore, the results for groundwater detection (relative error: 5.92% (Cu) and 4.74% (Mn)), comparing NELIBS and inductively coupled plasma mass spectrometry (ICP-MS), validated the feasibility of the SS substrate in practical applications. In summary, the SS substrate exhibits immense potential for practical application such as water quality detection and supervision.

Interface self-assembly of plasmonic nanolayer for sensitive detection of heavy metals in water using NELIBS

Nowadays, high-stable and ultrasensitive heavy metal detection is of utmost importance in water quality monitoring. Nanoparticle-enhanced laser-induced breakdown spectroscopy (NELIBS) shows high potential in hazardous metal detection, however, encounters unstable and weak signals due to nonuniform distribution of analytes. Herein, we developed an interface self-assembly (ISA) method to create a uniformly distributed gold nanolayer at a liquid-liquid interface for positive heavy metal ions capture and NELIBS analysis. The electrostatically self-assembled Au nanoparticles (NPs)-analytes membrane was prepared at the oil-water interface by injecting ethanol into the mixture of cyclohexane and Au NPs-analytes water solution. Then, the interface self-assembled Au NPs-analytes membrane was transformed onto a laser-processed superhydrophilic Si slide for detection. Three heavy metals (cadmium (Cd), barium (Ba), and chromium (Cr)) were analyzed to evaluate the stability and sensitivity of the ISA method for NELIBS. The results (Cd: RSD ​= ​3.6 ​%, LoD ​= ​0.654 ​mg/L; Ba: RSD ​= ​3.4 ​%, LoD ​= ​0.236 ​mg/L; Cr: RSD ​= ​7.7 ​%, LoD ​= ​1.367 ​mg/L) demonstrated signal enhancement and high-stable and ultrasensitive detection. The actual sample detection (Cd: RE ​= ​7.71 ​%, Ba: RE ​= ​6.78 ​%) illustrated great reliability. The ISA method, creating a uniform distribution of NP-analytes at the interface, has promising prospects in NELIBS.

Comparison of three nanoparticle deposition techniques potentially applicable to elemental mapping by nanoparticle-enhanced laser-induced breakdown spectroscopy

In this study, we compared the applicability of three nanoparticle deposition techniques (spray coating, spark discharge nanoparticle generation, magnetron sputtering) towards elemental mapping by nanoparticle-enhanced laser-induced breakdown spectroscopy (NE-LIBS). It was found that sputtering followed by a thermal treatment at 550 °C can provide a homogenous, practical and controllable way of NE-LIBS sample preparation with gold nanoparticles. The laser ablation properties of the created NP layer was also studied in detail and it was established that a 200 μm laser spot size is good compromise between the NE-LIBS signal enhancement and the spatial resolution required for mapping. A signal enhancement of about a factor of 10 with good repeatability (ca. 5 %RSD) in a line scanning demonstration was achieved on glass for Si detection. For samples that are fairly temperature and vacuum stable, this approach allows the signal enhancement to be used in mapping applications.

Elemental analysis of liquid samples by nanoparticle-enhanced laser-induced breakdown spectroscopy: using ordered nano-arrays with a tunable nanoparticle size and inter-particle distance

NELIBS analysis of liquid samples using ordered nanoparticle arrays with a precisely tunable nanoparticle size and inter-particle distance, which provide excellent homogeneity to ensure signal reproducibility and enhancement.

Nanoparticle-enhanced laser-induced breakdown spectroscopy for serum element analysis using an Ag NP-coated filter paper substrate

NELIBS using an Ag NP paper substrate achieves effective spectral enhancement, enabling serum analysis with limited sample preparation.

Plasma Parameters During Nanoparticle-Enhanced Laser-Induced Breakdown Spectroscopy (NELIBS) in the Presence of Nanoparticle-Protein Conjugates.

Nanoparticle-enhanced laser-induced breakdown spectroscopy (NELIBS) is an optical emission technique based on the laser-induced plasma (LIP) on a sample after the deposition of plasmonic nanoparticles (NPs) on its surface. The employment of the NPs allows an enhancement of the signal with respect to the one obtained with the conventional laser-induced breakdown spectroscopy (LIBS) enabling an extremely high sensitivity and very low limits of detection compared with the LIBS performance. Recently, NELIBS was used for monitoring the NP protein corona formation. As a matter of fact, the NPs in the presence of proteins adsorbed on the surface change their surface properties, therefore the sensing of protein corona formation was possible because of the strong dependence of NELIBS effects on the NP organization on the substrate, which in turn is deeply affected by the surface properties of the NPs. A correlation was found between NELIBS enhancement and the structure of the NP-protein conjugate in terms of protein content absorbed on the NP surface. An interesting question that was not yet exploited regards the role of LIP during the NELIBS when the NPs are covered with proteins. Since the presence of organic matter can strongly quench the LIP emission, the study of the LIP properties during protein corona sensing by NELIBS is of interest for two main reasons: (i) to understand whether the plasma parameters can vary in the presence of proteins adsorbed on the NP surface and (ii) to investigate how and if the plasma parameters themselves can influence the NELIBS processes. With this aim, the study of plasma parameters, i.e., electron densities and temperatures, during the sensing of NP protein corona by NELIBS is presented and discussed. The NPs used during these experiments were ultrapure gold NPs (AuNPs) produced by pulsed laser ablation in liquid, which are stable without any stabilizer. The human serum albumin protein is used to form AuNP-protein conjugates further deposited on a titanium target in NELIBS measurements. Dynamic light scattering, surface plasmon resonance spectroscopy, and laser Doppler electrophoresis for ζ-potential determination were employed to monitor the protein coverage of NP surface in the conjugate solutions before the NELIBS measurements.

Evaporative self-assembling bioconcentrators onto superhydrophobic micropyramidal arrays as rapid and intelligent blood cancer filtering platforms

Harnessing the power of artificial intelligence (AI) for rapid and accurate cancer diagnosis is invaluable for medical practice, but technically challenging due to the low sensitivity and low selectivity of traditional bio-analytical methods. Here, we explored an AI-driven filtering method integrated with a plasmonic bioconcentrator for rapid, sensitive, and accurate blood cancer diagnosis. The bioconcentrator were sequentially dual-assembled by sequentially depositing multi-walled carbon nanotubes and core-shell gold silicon dioxide nanoparticles onto a laser-fabricated superhydrophobic surface with micropyramidal arrays. The laser spectroscopic sensing technique, nanoparticle-enhanced laser-induced breakdown spectroscopy, was applied to obtain the fingerprint information of serum samples from four types blood cancers and one health control. Furthermore, the principal component analysis and support vector machine algorithms were performed to discriminate the serum samples for AI-driven filtering. The results demonstrated that the integration of AI-driven filtering with bioconcentrator enabled sensitive and accurate diagnosis of blood cancers with several minutes. Rapid, cost-effective, and personalized cancer treatment could be envisioned by the AI-driven cancer filtering with the plasmonic bioconcentrator.

Drying Acoustically Levitated Droplets as Signal-Amplifying Platforms for Ultrasensitive and Multimode Laser Sensing.

Ultrasensitive sensing to trace atomic and molecular analytes has gained interest for its intimate relation to industrial sectors and human lives. One of the keys to ultrasensitive sensing for many analytical techniques lies in enriching trace analytes onto well-designed substrates. However, the coffee ring effect, nonuniform distribution of analytes onto substrates, in the droplet drying process hinders the ultrasensitive and stable sensing onto the substrates. Here, we propose a substrate-free strategy to suppress the coffee ring effect, enrich analytes, and self-assemble a signal-amplifying (SA) platform for multimode laser sensing. The strategy involves acoustically levitating and drying a droplet, mixed with analytes and core-shell Au@SiO2 nanoparticles, to self-assemble an SA platform. The SA platform with a plasmonic nanostructure can dramatically enrich analytes, enabling enormous spectroscopic signal amplification. Specifically, the SA platform can promote atomic detection (cadmium and chromium) to the 10-3 mg/L level by nanoparticle-enhanced laser-induced breakdown spectroscopy and can promote molecule detection (rhodamine 6G) to the 10-11 mol/L level by surface-enhanced Raman scattering. All in all, the SA platform, self-assembled by acoustic levitation, can intrinsically suppress the coffee ring effect and enrich trace analytes, enabling ultrasensitive multimode laser sensing.

Different nanoparticle shapes for nanoparticle-enhanced laser-induced breakdown spectroscopy: nanosphere and nanorod effects

Comparison between nanosphere and nanorod plasmonic coupling with the laser electromagnetic field in terms of signal enhancement obtained during NELIBS.

High-sensitivity analysis of mercury in medicinal herbs using nanoparticle-enhanced laser-induced breakdown spectroscopy combined with argon purging

In this work, nanoparticle-enhanced LIBS combined with argon purging was used to improve the analytical sensitivity of Hg in medicinal herbs.

Improvement in signal sensitivity and repeatability using copper nanoparticle-enhanced laser-induced breakdown spectroscopy

In the present work, the sensitivity and repeatability of the emission spectra have been investigated using nano-enhanced laser-induced breakdown spectroscopy (NELIBS). The colloidal solution of copper nanoparticles was produced by using the laser ablation technique at the fundamental wavelength of Nd: YAG laser at 100 mJ and deposited on the surface of standard aluminum alloy in different concentrations. With varying laser irradiances (10 GW/cm2 to 35 GW/cm2) and nanoparticles surface concentration (6.4 μL/cm2 to 57.7 μL/cm2), emission spectra were acquired from laser-induced plasma. On average the signal enhancement up to 50 times was achieved at a laser irradiance of 28.3 GW/cm2 and at NPs concentration of 45 μL/cm2. A decrease in relative standard deviations (RSD) from 28% to 16% for manganese and 18% to 10% for aluminum emission lines was achieved at laser irradiance of 10.5 GW/cm2 and surface concentration of 19.2 μL/cm2.

High sensitivity analysis of soil by laser-induced breakdown spectroscopy with Ag nanoparticles

Various studies have been conducted to improve the detection sensitivity of metallic elements in soil using laser-induced breakdown spectroscopy (LIBS) by controlling environmental parameters or assisting with other methods, which inevitably increases the cost and complexity of LIBS. In this study, a simple LIBS assisted with self-synthetic Ag nanoparticles enhancement method was proposed to achieve sensitive analysis of the metallic elements in soil samples. The calibration curves of Fe, Mn, Cu, and Zn using LIBS and nanoparticle-enhanced LIBS were established. The limits of detection of Fe, Mn, Cu, and Zn in the soil were 28.4 ppm, 6.3 ppm, 0.34 ppm, and 2.4 ppm, respectively, and the relative errors were all below 4%, which were better than those of conventional LIBS. These results show that Ag nanoparticles can promote further development of LIBS elemental analysis in soil.

Graphene thin film microextraction and nanoparticle enhancement for fast LIBS metal trace analysis in liquids

Several strategies have been effectively tested in the past to improve the Laser Induced Breakdown Spectroscopy (LIBS) signal for the analysis of liquid samples, 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 performances of LIBS towards the analysis of solutions. Among the various strategies, the most promising and versatile appears to be Thin Film Microextraction (TFME) using carbon-based adsorbents.Another sample pre-treatment procedure, Nanoparticle-Enhanced LIBS (NELIBS), has gained significant interest due to its relative simplicity and effectiveness. This methodology uses a deposition of silver nanoparticles (AgNPs) on the sample to greatly increase the emission of the LIBS plasma.In this work, we investigate for the first time the possibility of combining TFME and NELIBS. We developed TFME supports by depositing an aqueous graphene nano-sheets (aq-GRA) prepared by Pulsed Laser Ablation in Liquid (PLAL) on a glass substrate. The preparation of the supports was optimized with regards to the substrate nature, deposition method, sorbent volume and drying method. Then, the TFME supports were tested for the extraction of Chromium from aqueous solution at different extraction times and analyte concentration. Subsequently, the TFME supports were treated with a deposition of silver nanoparticles (AgNP) to test the feasibility of the NELIBS approach.We observed an enhancement in the emission lines of Cr when the AgNPs were applied, as well as a lower estimated LOD value when compared to plain graphene TFME supports.

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 of copper in solution by laser-induced breakdown spectroscopy based on nanoparticle chip

We report a highly sensitive electrolytic copper (Cu) detection method using nanoparticle enhanced laser-induced breakdown spectroscopy (NELIBS) for metal smelting processes. The sulfate solution Cu with content ranging from 10 to 50 g/L was prepared and measured on the nanoparticle chip. The experimental results showed that the Cu spectral line intensity of NELIBS increased 5.5 to 9.4 times compared with typical LIBS without nanoparticles. The calibration curve was established based on the spectral line intensity at Cu I 327.40 nm according to the different Cu content in the solution. The determination coefficient R2 of the calibration curve was 0.99. The method of laser-induced breakdown spectroscopy based on drying liquid droplets on the nanoparticle chip can be applied to the rapid determination of Cu content in the copper electrolyte.

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.

Retraction: Determination of cadmium in rice using nanoparticle-enhanced laser-induced breakdown spectroscopy combined with film preparation

Retraction of ‘Determination of cadmium in rice using nanoparticle-enhanced laser-induced breakdown spectroscopy combined with film preparation’ by Jinming Niu et al., J. Anal. At. Spectrom., 2020, 35, 2990–2996, DOI: 10.1039/D0JA00354A.

Gold Nanoparticle-Enhanced Laser-Induced Breakdown Spectroscopy and Three-Dimensional Contour Imaging of an Aluminum Alloy

In the present work, nanoparticle-enhanced laser-induced breakdown spectroscopy was used to analyze an aluminum alloy. Although LIBS has numerous advantages, it suffers from low sensitivity and low detection limits compared to other spectrochemical analytical methods. However, using gold nanoparticles helps to overcome such drawbacks and enhances the LIBS sensitivity in analyzing aluminum alloy in the current work. Aluminum was the major element in the analyzed samples (99.9%), while magnesium (Mg) was the minor element (0.1%). The spread of gold nanoparticles onto the Al alloy and using a laser with different pulse energies were exploited to enhance the Al alloy spectral lines. The results showed that Au NPs successfully improved the alloy spectral lines intensity by eight times, which could be useful for detecting many trace elements in higher matrix alloys. Under the assumption of local thermodynamic equilibrium, the Boltzmann plot was used to calculate the plasma temperature. Besides, the electron density was calculated using Mg and H lines at Mg(I) at 285.2 nm and Hα(I) at 656.2 nm, respectively. Three-dimensional contour mapping and color fill images contributed to understanding the behavior of the involved effects.

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.