Pulsed Laser Ablation In Liquid Research Articles

Synthesis of low dimensional nanomaterials by pulsed laser ablation in liquid

Synthesis of low dimensional nanomaterials by pulsed laser ablation in liquid

NixFe100-x for urea and oxygen evolution: a matter of compromise

The combination of aqueous electrolysis, either for hydrogen generation or CO2 conversion, with wastewater treatment offers an elegant way to tackle issues associated with our energy transition and the need for clean drinking water. However, it requires an anode capable of doing both the oxidation of the targeted pollutant and the oxygen evolution reaction (OER), as most pollutants are present in too low concentration to be practical for industrial electrolysis. In this study, we focussed on the oxidation of urea on NixFe100-x catalysts. These catalysts were prepared by pulsed laser ablation in liquid, a versatile and green technique to prepare electrocatalysts. Transmission electron microscopy of the nanoparticles indicates the production of monodisperse nanoparticles, with an average diameter increasing from 7.8 ± 2.8 to 19.7 ± 3.9 nm with a higher iron fraction. The composition could be controlled between pure Ni and NiFe bimetallic nanoparticles with up to 56 ± 3% of iron, by controlling the composition of the target. A brief optimisation of the electrode preparation (loading, catalyst-to-carbon ratio) yielded an optimum at about 30 µg/cm2 of catalyst with a catalyst-to-carbon ratio of 20:80. During the electrocatalytic tests, Ni was the best catalyst for urea oxidation, with a maximum peak current of 619 mA/mg. However, Ni75Fe25 was the best OER catalyst, showing a peak current of 1150 mA/mg. The difference increased further during CA at 0.5 V, during which Ni75Fe25 outperformed pure Ni by almost a factor of 3 after 30 min.

Boron nanoparticles (BNPs) produced by ns-laser ablation in water: synthesis and characterization

Boron nanoparticles (BNPs) are attractive nanomaterials for their employment in many applications, such as neutron detection, boron neutron capture therapy, proton boron capture therapy and nuclear fusion. Depending on the specific application, 10B or 11B isotopes can be used.Nevertheless, there are significant challenges in developing suitable BNPs using both conventional chemical synthesis routes and dry fabrication techniques. In this study we report BNPs directly synthetised in water by pulsed Laser Ablation in Liquid (PLAL). Nanoparticles of elemental boron have been generated by laser ablation of a sintered 10B target in MilliQ water by employing ns laser pulse. The ablation resulted in BNPs and boron target micro-fragments with hydrogen gas and boric acid as by-products. Simple washing steps were used to obtain clean BNPs in water. The BNPs showed a narrow size distribution between 3 and 4 nm and their stability in water was induced by a thin layer of boron oxide surrounds BNPs. The BNPs were fully characterized by the chemical and structural point of view employing several techniques. A discussion on boron chemical reactions during laser ablation in water and after the NPs were released in solution was done.

Unique production strategy of Pt/C electrocatalysts via pulsed laser for hydrogen generation: Insights screening by DFT calculations

Design and optimizing the components and structure of highly-active electrocatalysts is a prevalent approach for reducing the input electrical energy consumption and concurrently H2 fuel production. An efficient and sustainable method is a water-electrolyzer for H2 generation, but still restricted by the stable electrode materials. In this study, a green chemistry approach for one-pot production of Pt/C nanospherical with controllable ratios of Pt and C was demonstrated using simple pulsed laser ablation in liquid (PLAL) process, during which Pt target ablation in diverse solvents (water, methanol, ethanol, and 1-propanol) without external carbon source and reducing/capping agents. The carbon-rich solvents are acted as both C-source and solvent, which are decomposed during the PLAL process, producing C, H, and OH ions inside the cavitation bubble which condenses as C-shells on the Pt surface. The optimal Pt/C proportions have the highest electrochemical H2-evolution in acidic media with an overpotential of 59 mV at 10 mA/cm2, Tafel slope of 41 mV/dec, and j0 of 0.686 mA/cm2. The exceptional electrocatalytic concert of optimal Pt/C was further supported by the density functional theory. Optimized C-content in Pt/C reveals good dispersion and strong interaction of C with Pt can make efficient electron transfer, structural stability, and electrochemical durability, resulting in superior electrocatalytic performance in electrolyzer devices.

Influence of environmental conditions on the morphological evolution of bismuth oxide nanostructures via pulsed laser ablation in liquids

Bismuth oxide nanomaterials are increasingly recognized for their promising electronic and optical properties, particularly in electrochemical and biomedical applications. This study demonstrates that various bismuth oxide nanostructures can be synthesized through pulsed laser ablation in liquids (PLAL) by adjusting the concentration of dissolved gases from ambient conditions. Structural and compositional analyses were performed using x-ray diffraction, Raman spectroscopy, FTIR spectroscopy, and morphological investigations were conducted using atomic force microscopy and transmission electron microscopy. Our findings indicate that factors such as dissolved gases, laser fluence, and nanoparticle aging are crucial in determining the final structure and composition of the resulting nanomaterial. The phases observed ranged from spherical metallic bismuth nanoparticles to monoclinic bismuth oxide nanowire bundles, and orthorhombic bismuth carbonate oxide nanosheets. Dissolved gases are shown to influence not only the primary particles formed immediately after ablation, but also significantly impact the aging process of the colloid as well. Additionally, fluence plays an important role in the production of reactive oxygen species, thereby influencing the reactive pathways experienced by the ablated material and its subsequent formation into nanostructures. A notable result, emphasizing the significance of factors such as liquid environment and fluence when performing PLAL on reactive targets like bismuth, is seen in high fluence (20 J/cm2) samples under ambient conditions. These samples initially display an amalgamation of α-Bi2O3 nanowire bundles and carbonate nanosheets, which upon aging, transition to predominantly bismuth oxide nanowire bundles. This contrasts with samples produced in a saturated CO2 environment where bismuth carbonate nanosheets remain highly stable in the colloid.

Synthesis of High Entropy Alloy Nanoparticles by Pulsed Laser Ablation in Liquids: Influence of Target Preparation on Stoichiometry and Productivity

AbstractHigh entropy alloys (HEAs) have a wide range of applications across various fields, including structural engineering, biomedical science, catalysis, magnetism, and nuclear technology. Nanoscale HEA particles show promising catalytic properties. Nevertheless, attaining versatile composition control in nanoparticles poses a persistent challenge. This study proposes the use of pulsed laser ablation in liquids (PLAL) for synthesizing nanoparticles using equiatomic CoCrFeMnNi targets with varied preparation methods. We evaluate the impact of target preparation method on nanoparticle yield and composition as well as the magnetic properties of the nanoparticles. The elemental powder‐pressed heat‐treated target (HEA‐PP), identified as the most time‐efficient and cost‐effective, exhibits noticeable segregation and non‐uniform elemental distribution compared to ball milled hot‐pressed powder (HEA‐BP) and face‐centered cubic (FCC) single crystal (HEA‐SX) alloy targets. From all targets, nanoparticles (sizes from 2 to 120 nm) can be produced in ethanol with a nearly equiatomic CoCrFeMnNi composition and a FCC structure, showing oxidation of up to 20 at.%. Nanoparticles from HEA‐PP exist in a solid solution state, while those from HEA‐BP and HEA‐SX form core‐shell structures with a Mn shell due to inhomogeneous material expulsion, confirmed by mass spectrometry. HEA‐PP PLAL synthesis demonstrates 6.8 % and 15.1 % higher productivity compared to HEA‐BP and HEA‐SX, establishing PLAL of elemental powder‐pressed targets as a reliable, time‐efficient, and cost‐effective method for generating solid solution HEA nanoparticles.

Post-fabrication adjustment of metalloid Mg–C-graphene nanoparticles via Pulsed Laser Ablation for paper electronics and process optimisation

Metalloid nanoparticles (MNPs) possess unique physicochemical properties but are challenging to create through biological or chemical routes. Using Pulsed Laser Ablation in Liquid (PLAL), Mg–C MNPs are fabricated from powders. The produced nanocolloids were ablated after the target was removed to tailor the particle size. MNPs with a mean size 300 nm could be reduced to 60 nm. Alternatively, MNPs with a mean size of 60 nm could be increased to 90 nm. The increase/decrease in size is controlled by the laser processing parameters and showcases the ability of PLAL for real-world applications that require meticulous control of size. The as-fabricated nanocolloids were successfully inkjet printed on paper, achieving a low resistivity of 75 Ω/square after 60 prints, highlighting their potential in printed electronics. To address a historical research gap, this article explored the impact of PLAL processing parameters, including fluence (1–2 J/cm2), pulse width (0.2–0.9 ns), repetition rate (10–20 kHz), and pH, factors often overlooked which is partly limiting applications. The influence of powder vs rod target on the PLAL process was addressed revealing that powders produce better size control and are easier to handle but they produce lower colloid concentrations.

Laser-Synthesized Co-Doped CuO Electrocatalyst: Unveiling Boosted Methanol Oxidation Kinetics for Enhanced Hydrogen Production Efficiency by In Situ/Operando Raman and Theoretical Analyses.

The present study details the strategic development of Co-doped CuO nanostructures via sophisticated and expedited pulsed laser ablation in liquids (PLAL) technique. Subsequently, these structures are employed as potent electrocatalysts for the anodic methanol oxidation reaction (MOR), offering an alternative to the sluggish oxygen evolution reaction (OER). Electrochemical assessments indicate that the Co-CuO catalyst exhibits exceptional MOR activity, requiring a reduced potential of 1.42V at 10 mAcm-2 compared to that of pure CuO catalyst (1.57V at 10 mAcm-2 ). Impressively, the Co-CuO catalyst achieved a nearly 180mV potential reduction in MOR compared to its OER performance (1.60V at 10 mA cm-2 ). Furthermore, when pairing Co-CuO(+)ǀǀPt/C(-) in methanol electrolysis, the cell voltage required is only 1.51V at 10 mAcm-2 , maintaining remarkable stability over 12h. This represents a substantial voltage reduction of ≈160mV relative to conventional water electrolysis (1.67V at 10 mAcm-2 ). Additionally, both in situ/operando Raman spectroscopy studies and theoretical calculations have confirmed that Co-doping plays a crucial role in enhancing the activity of the Co-CuO catalyst. This research introduces a novel synthetic approach for fabricating high-efficiency electrocatalysts for large-scale hydrogen production while co-synthesizing value-added formic acid.

Properties and antibacterial activity of MnFe2O4 nanoparticles obtained by pulsed laser ablation in liquid

In this study, MnFe2O4 nanoparticles (NPs) were fabricated via pulsed laser ablation in liquid. Chemical and structural composition, microstructure, magnetic and antibacterial properties were characterized. Spinel was found as the main crystalline phase, while Fe2O3 and Mn2O3 were observed as the major secondary phases, all identified by X-ray diffractometry (XRD). Observation by Transmission Electron Microscopy (TEM) indicated that most of the nanoparticles were spherical in shape and found in agglomerates, most likely because of their magnetic nature. Moreover, Fast Fourier Transform of selective area electron diffraction patterns pointed at the existence of crystalline particles. The coercive field (Hc) and saturation magnetization (Ms) values determined for these NPs were found to increase with decreasing temperature. Their antibacterial properties were evaluated using the viable bacteria counting technique (colony) for MnFe2O4 concentrations of 100 and 300 μg/mL with Bacillus subtilis, Salmonella typhimurium, Pseudomonas aeruginosa, Klebsiella pneumoniae and Escherichia coli strains.

Unveiling Fundamentals of Multi-Beam Pulsed Laser Ablation in Liquids toward Scaling up Nanoparticle Production.

Pulsed laser ablation in liquids (PLAL) is a versatile technique to produce high-purity colloidal nanoparticles. Despite considerable recent progress in increasing the productivity of the technique, there is still significant demand for a practical, cost-effective method for upscaling PLAL synthesis. Here we employ and unveil the fundamentals of multi-beam (MB) PLAL. The MB-PLAL upscaling approach can bypass the cavitation bubble, the main limiting factor of PLAL efficiency, by splitting the laser beam into several beams using static diffractive optical elements (DOEs). A multimetallic high-entropy alloy CrFeCoNiMn was used as a model material and the productivity of its nanoparticles in the MB-PLAL setup was investigated and compared with that in the standard single-beam PLAL. We demonstrate that the proposed multi-beam method helps to bypass the cavitation bubble both temporally (lower pulse repetition rates can be used while keeping the optimum processing fluence) and spatially (lower beam scanning speeds are needed) and thus dramatically increases the nanoparticle yield. Time-resolved imaging of the cavitation bubble was performed to correlate the observed production efficiencies with the bubble bypassing. The results suggest that nanoparticle PLAL productivity at the level of g/h can be achieved by the proposed multi-beam strategy using compact kW-class lasers and simple inexpensive scanning systems.

Synthesis of Nickel-Based Nanoparticles by Pulsed Laser Ablation in Liquids: Correlations between Laser Beam Power, Size Distribution and Cavitation Bubble Lifetime

Pulsed laser ablation in liquids (PLAL) is a colloidal synthesis technique attracting significant interest from the scientific community due to the quality of the nanoparticles being produced. In this type of synthesis protocol, the cavitation bubble plays a vital role during the synthesis of nanoparticles. This work studied the effect of the laser beam power on cavitation bubble lifetime. Three different laser beam power values (5.8 W, 7.5 W and 10.5 W) were used to irradiate a pure nickel target in de-ionized (DI) water to synthesize nickel-based nanoparticles. The optimal repetition rate maximizing the production of nanoparticles was determined by atomic emission spectroscopy for each laser beam power. It was determined that the optimal repetition rate increased exponentially with laser beam power, while the cavitation bubble lifetime decreased logarithmically with the laser beam power. Moreover, the effect of the laser beam power on the cavitation bubble lifetime also had an effect on the size distribution of the nanoparticles being produced; the smallest size distribution was obtained at the highest laser beam power.

Parallel Diffractive Multi‐Beam Pulsed‐Laser Ablation in Liquids Toward Cost‐Effective Gram Per Hour Nanoparticle Productivity

Nanoparticles (NPs) generated by pulsed‐laser ablation in liquids (PLAL) have benefited many key applications due to their versatility, enlarged surface area, and high purity. However, scaling up NPs production represents one of the main requisites to commercialize this technology. The established upscaling strategy demands high power and repetition rate laser source with fast scanning systems, which are not widely available and costly. Herein, a cost‐effective alternative is proposed, the addition of static diffractive optical elements to achieve parallel processing through the multi‐beam PLAL (MB‐PLAL). In MB‐PLAL, the optimum repetition rate is reduced to compensate laser energy splitting, hence achieving a higher interpulse distance, reducing pulse shielding, and increasing NPs productivity. MB‐PLAL with 11 beams reached a factor 4 productivity increase for iron–nickel alloy (Fe50Ni50) NPs compared to the single‐beam setup (0.4–1.6 g h−1), and a factor 3 increase for gold (Au) NPs (0.32–0.94 g h−1). The scalability of the proposed MB‐PLAL technique setup is confirmed by Au and Fe50Ni50 NPs productivity experiments using 1, 6, and 11 beams, showing a linear increase in productivity.

An overview of the unique absorption and scattering characteristics of gold nanoparticles: experimental and theoretical study

Theoretical prediction of the unusual optical properties shown by the gold (Au) nanomaterials remains challenging. Based on this fact, some colloidal Au nanoparticles (AuNPs) were prepared in ethanol and demonized water using the versatile pulse laser ablation in liquid (PLAL) method and characterized. The pulsed laser irradiation energy-dependent optical absorbance and morphology of these AuNPs were determined. Analytical Mie–Gans scattering model was applied to interpret the experimentally observed absorption spectra of these colloidal AuNPs. In addition, the AuNPs size and shape-dependent absorbance were predicted accurately by fitting the recorded spectra with the analytical model simulation. The results revealed that the dielectric function of the AuNPs played a considerable role to realize the best fit of the experimental absorption data. The average sizes of the AuNPs predicted by the proposed analytical model were tallied well with the experimentally measured ones. It is found that an accuracy of more than 8% on the particle size between experimental and predicted data. It is established that the modified Mie–Gans scattering model can provide a better understanding of the distinct absorption attributes of the colloidal AuNPs synthesized by the PLAL method in various liquid media. Highlights Some AuNPs were prepared in ethanol and deionized water using the PLAL method. The morphology and absorbance of the produced AuNPs were determined. Absorption and scattering traits of these NPs were explained via the modified Mie–Gans model. Proposed AuNPs with distinct optical traits may be beneficial for practical applications.

Mechanistic Study in Gold Nanoparticle Synthesis through Microchip Laser Ablation in Organic Solvents

The utilization of pulsed laser ablation in liquids (PLALs) for preparing gold nanoparticles (Au NPs) in organic solvents holds immense potential across diverse applications. This study introduces a compact and low-power microchip laser (MCL) system (average power 50 mW; pulse energy 0.5 mJ). Due to its compactness, an MCL is advantageous for easy manipulation in organic laboratories during the production of metal nanoparticles (NPs) for research and development purposes. In this research, poly(N-vinyl-2-pyrrolidone) (PVP) is used as a stabilizing agent for the preparation of Au NPs in organic solvents (CH2Cl2, CHCl3, 2-PrOH, MeCN, DMF, EtOH, NMP, and DMSO). Our experimental results demonstrate that the particle size remains consistent across all the organic solvents. This study explores the productivity of Au NPs in different organic solvents, revealing the necessity of multiple laser pulses to generate Au NPs successfully. This phenomenon, known as the ‘incubation effect,’ is linked to the lower pulse energy in the experimental condition and the thermal conductivity of the solvents. The findings emphasize the crucial role of solvent properties in determining the Au NPs productivity in PLAL.

Development of silver nanocubes created by pulsed laser ablation in liquid

This paper describes a simple approach for creating silver (Ag) nanocubes using pulsed laser ablation in a liquid medium. The development of nanocubical formations of Ag obtained by laser ablation using Nd: YAG laser was conducted for 5, 10, 15, and 20[Formula: see text]min. The surface morphological analysis was performed using field-emission scanning electron microscopy (FESEM) to show the formation of silver nanocubes with edge lengths ranging from 150[Formula: see text]nm to 250[Formula: see text]nm. The UV-visible spectroscopy demonstrates that the concentration of Ag nanostructures, evidenced by the characteristic localized surface plasmon resonance band near 400[Formula: see text]nm in the colloidal solution containing Ag nanoparticles, increased with the increasing laser ablation duration from 5[Formula: see text]min to 20[Formula: see text]min. The growth mechanism for Ag nanocubes can be easily understood with the change in laser ablation time from 5 to 10, 15, and then 20[Formula: see text]min. The Ag sheets with no specific shape start to develop after 5 min of laser ablation, and after 10[Formula: see text]min, larger particles form. Then, after 15[Formula: see text]min, a small number of cube-like nanostructures with rough and uneven edges was obtained. At the end of 20[Formula: see text]min, a complete cubic formed with fine and distinct edges and a very large amount of nanocubes. The elemental silver signal was present in Ag nanocubes, as revealed by the energy-dispersive X-ray spectroscopy (EDS) spectra. The produced Ag nanocubes may be used to construct two-dimensional nanocomposites with practical applications in the electrical, optoelectronic, electrochemical, and biological areas.

Effect of Silver Nanoparticles Synthesized by Pulsed Laser Ablation in Liquid on the Hematological, Hepatic, and Renal Functions of Albino Rats

     Silver nanoparticles (Ag-NPs) have unique properties as antibacterial effects against locally isolated clinical Escherichia coli.  In this study, the evaluated the antibacterial activity of AgNPs, which were synthesized by laser ablation, against locally isolated clinical  Escherichia coli on nutrient agar media in vitro. Then assessed the toxicity of the bactericidal dose in albino rats in vivo with hematological, liver, and kidney functions as vital parameters. AgNPs were synthesized by pulsed laser ablation in liquid (PLAL).  AgNPs’ shape and nano size were characterized by atomic force microscopy (AFM), UV-vis spectroscopy, and scanning electron microscopy (SEM). UV peak absorption was observed at 434 nm, which produced an average particle diameter of 28.09 nm. The SEM and AFM topography images of the synthesized nanoparticles showed that they had a spherical shape. Also studied was the toxicity of the synthesized AgNPs in vivo. Four groups of albino rats were used. The liver and kidneys were found to be the main organs that accumulate AgNP. In this study, we examined the influence of intraperitoneally injected AgNPs on blood parameters (complete blood picture) and liver and kidney functions of albino rats. Blood ALP and serum test (GOT and GPT), serum urea and serum creatinine were analyzed at 15, 30, and 60 days after injection of 200 mg/kg of PLAL-synthesized AgNP. The results did not indicate statistically significant differences between the control and treatment groups in blood picture and enzyme levels tested that indicate proper liver function. Additionally, no differences in kidney functions were found during varying time intervals in the blood of rats. Thus, PLAL-synthesized AgNPs could inhibit Escherichia coli bacterial growth.

Effect of Electrode Potential on the Surface Chemical Composition of Au-Pd Nanoparticles

Palladium (Pd) nanoparticles have been investigated for the hydrogen evolution reaction, the hydrogen oxidation reaction, the oxygen reduction reaction, and the methanol and ethanol oxidation reaction. The high methanol/ethanol tolerance of Pd is noteworthy.A powerful approach to further improving the catalytic properties of Pd is through alloying with suitable co-metals. In the case of the ethanol oxidation reaction in alkaline media, Pd alloyed with Au has demonstrated excellent activity exceeding even that of highly active Pt catalysts (1). A complete miscibility, small lattice mismatch, and contrasting properties of Pd and Au make Au-Pd a unique model system. Marked changes in the reactivity of Au-Pd catalysts have been reported when conditioning and operating conditions are altered, which should be related to physico-chemical changes in the nanoparticles. Indeed, dealloying/dissolution and segregation of metals at the surface of nanoparticles (NPs) takes place during conditioning and operation, which have pronounced effect on the activity and stability of NPs. The migration of metals from the bulk to the nanoparticles’ surface may take place during pre-catalytic conditioning and during operation, and can be triggered by the presence of oxidation and reducing agents (2), changes in temperature, and potential cycling (3). Thus, it is critical to investigate the effect of electrode potential on metals dissolution and segregation occurring in alloyed nanoparticles.In the present work, Au-Pd NPs prepared by pulsed laser ablation in liquids were used. Pulsed laser ablation is a simple method to synthesize alloy NPs with high purity out of different material systems and with different compositions. Typically, alloy-metal targets or pressed micro-powder mixture targets are ablated or fragmentated in liquid, respectively. Notably, the technique does not require any surfactant additives to achieve NPs stability in the electrolyte, thus allowing for NPs to remain free of associated contamination from the capping agents. We will show how one can fine-tuned the Au and Pd surface fraction of bimetallic Au-Pd nanoparticles using electrochemistry. The method involves electrochemical cycling in alkaline medium at a suitable upper vertex potential, resulting in a controllable diffusion of Pd atoms from the core to the shell. This preferential outward diffusion of Pd atoms occurs because of the electrochemical adsorption of oxygen atoms at the surface of NPs, which is driven by the application of a potential. This potential has to be positive enough for oxygen atoms to adsorb at the surface of the NPs, and therefore is dependent on the nature of the surface atoms. On AuPd NPs that are enriched with Au atoms, a potential of +1.5 V vs. RHE must be applied to form ca. 1 ML of adsorbed oxygen at the surface of gold and initiate the diffusion of Pd atoms from the core to the NP surface. This approach marks a new avenue in the development of compositionally-controlled electrocatalysts and can be tailored to suit different applications with a simple switch of voltage or a controlled pretreatment.

Multiwavelength SERS of Magneto-Plasmonic Nanoparticles Obtained by Combined Laser Ablation and Solvothermal Methods.

The present study introduces a novel method for the synthesis of magneto-plasmonic nanoparticles (MPNPs) with enhanced functionality for surface-enhanced Raman scattering (SERS) applications. By employing pulsed laser ablation in liquid (PLAL) to synthesize plasmonic nanoparticles and wet chemistry to synthesize magnetic nanoparticles, we successfully fabricated chemically pure hybrid Fe3O4@Au and Fe3O4@Ag nanoparticles. We demonstrated a straightforward approach of an electrostatic attachment of the plasmonic and magnetic parts using positively charged polyethylenimine. The MPNPs displayed high SERS sensitivity and reproducibility, and the magnetic part allowed for the controlled separation of the nanoparticles from the reaction mixture, their subsequent concentration, and their precise deposition onto a specified surface area. Additionally, we fabricated alloy based MPNPs from AgxAu100-x (x = 50 and 80 wt %) targets with distinct localized surface plasmon resonance (LSPR) wavelengths. The compositions, morphologies, and optical properties of the nanoparticles were characterized by using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-vis spectroscopy, and multiwavelength Raman spectroscopy. A standard SERS marker, 4-mercaptobenzoic acid (4-MBA), validated the enhancement properties of the MPNPs and found an enhancement factor of 2 × 108 for the Fe3O4@Ag nanoparticles at 633 nm excitation. Lastly, we applied MPNP-enhanced Raman spectroscopy for the analysis of the biologically relevant molecule adenine and found a limit of detection of 10-7 M at 785 nm excitation. The integration of PLAL and wet chemical methods enabled the relatively fast and cost-effective production of MPNPs characterized by high SERS sensitivity and signal reproducibility that are required in various fields, including biomedicine, food safety, materials science, security, and defense.

Laser-Synthesized Elemental Boron Nanoparticles for Efficient Boron Neutron Capture Therapy

Boron neutron capture therapy (BNCT) is one of the most appealing radiotherapy modalities, whose localization can be further improved by the employment of boron-containing nanoformulations, but the fabrication of biologically friendly, water-dispersible nanoparticles (NPs) with high boron content and favorable physicochemical characteristics still presents a great challenge. Here, we explore the use of elemental boron (B) NPs (BNPs) fabricated using the methods of pulsed laser ablation in liquids as sensitizers of BNCT. Depending on the conditions of laser-ablative synthesis, the used NPs were amorphous (a-BNPs) or partially crystallized (pc-BNPs) with a mean size of 20 nm or 50 nm, respectively. Both types of BNPs were functionalized with polyethylene glycol polymer to improve colloidal stability and biocompatibility. The NPs did not initiate any toxicity effects up to concentrations of 500 µg/mL, based on the results of MTT and clonogenic assay tests. The cells with BNPs incubated at a 10B concentration of 40 µg/mL were then irradiated with a thermal neutron beam for 30 min. We found that the presence of BNPs led to a radical enhancement in cancer cell death, namely a drop in colony forming capacity of SW-620 cells down to 12.6% and 1.6% for a-BNPs and pc-BNPs, respectively, while the relevant colony-forming capacity for U87 cells dropped down to 17%. The effect of cell irradiation by neutron beam uniquely was negligible under these conditions. Finally, to estimate the dose and regimes of irradiation for future BNCT in vivo tests, we studied the biodistribution of boron under intratumoral administration of BNPs in immunodeficient SCID mice and recorded excellent retention of boron in tumors. The obtained data unambiguously evidenced the effect of a neutron therapy enhancement, which can be attributed to efficient BNP-mediated generation of α-particles.

Exotic femtosecond nonlinear optical properties of laser ablated MoS2 quantum dots

Molybdenum disulfide (MoS2) quantum dots (QDs) of sizes 2.05–4.40 nm were synthesized using the femtosecond pulse laser ablation in liquid (PLAL) method. The optical and ultrafast nonlinear optical (NLO) properties of MoS2 QDs were comprehensively studied using photoluminescence and femtosecond Z-scan method. We synthesized these QDs in ethanol (Et) and DI water (DW) with varying ablation times of 20 min and 10 min; the sample names are Et20 and Et10, DW20, and DW10, respectively. The nonlinear absorption (NLA) coefficients [three-photon absorption (3PA)], nonlinear refractive index, etc., of these QDs, were studied using the fs Z-scan method. Interestingly, Et20 possessed saturable absorption (SA) followed by reverse saturable absorption (RSA) due to the free carrier absorption (FCA) with FCA cross-section values of – (0.61–0.89) × 10−18 cm2. While for Et10, DW20, and DW10, we found 3PA, a rare finding for MoS2 QDs. The estimated values of the second hyperpolarizability of these samples were found to be ∼10−30 esu. Due to the strong NLA phenomena, these samples have the optical limiting (OL) onset values in the range of ∼ (5.11–8.43) mJ/cm2, proving the optical limiting application potential of these QDs. The obtained optical, NLO parameters, and Kane energy values of laser-ablated MoS2 QDs suggest that these can be suitable material systems for optoelectronic, NLO switching, logic gates, and other photonic applications.