Laser Ablation Of Solids In Liquids Research Articles

Hydrated MoO3 nanoparticles and α-MoO3 nanosheets synthesis by fs laser irradiation

We present a study of the synthesis and characterization of molybdenum oxide nanostructures produced by laser ablation of solids in liquids (LASL). A high purity molybdenum target was ablated in deionized water using femtosecond laser pulses. We found that both nanoparticles and nanosheets composed of molybdenum oxide were formed. The colloid suspension optical absorbance changes with time, as the colloid ages it changes color; a blue shift is observed within a few days of aging. It results in a band gap increase from 2.55 eV up to 2.9 eV for nearly a month of aging, which we computed through the Tauc method. Raman characterization of the nanostructures shows that the synthesized material turns into a hydrated molybdenum oxide (MoO3·nH2O). This is consistent with the band gap evolution, which for early aging corresponds to MoO3 to later achieve the band gap value of a hydrated molybdenum oxide. The nanostructures were also characterized by transmission electron microscopy (TEM) showing that the nanoparticles have a core-shell structure with a raspberry-like shell for medium and small nanoparticles and a smooth homogeneous shell for large nanoparticles. The size distribution peaks at 30–40 nm, with the smallest nanoparticles at 10 nm and the largest at 120 nm. The nanosheets are decorated by tiny nanoparticles. High resolution transmission electron microscopy (HRTEM) images allowed measuring the interplanar distances at the nanosheets, we found the nanosheets are composed by the orthorhombic stable-phase α-MoO3. SAED measurements confirmed the formation of this molybdenum oxide phase. An absorption band at 830 nm that develops in the few first days of aging of the colloid is of interest for photothermal therapy, which gives the reported nanostructures a good potential for biomedical applications.

Antimicrobial evaluation of bismuth subsalicylate nanoparticles synthesized by laser ablation against clinical oral microorganisms

Nowadays, nanotechnology can be useful to generate novel therapeutic compounds with antimicrobial properties for the treatment of different oral infections, such as periodontal diseases. In this work, the antibacterial activity of bismuth subsalicylate nanoparticles (BSS-NPs) synthesized by laser ablation of solids in liquids (LASL) was evaluated against microorganisms taken from subgingival biofilm samples of patients with periodontal disease. The physicochemical characterization of the BSS-NPs was performed using different techniques, such as Ultraviolet–Visible Spectroscopy (UV–Vis); X-Ray Diffraction (XRD); Transmission Electron Microscopy (TEM) and Fourier Transform Infrared Spectroscopy (FT-IR). The evaluation of the antibacterial activity of the BSS-NPs (16.6 µg/mL) against the oral clinical samples, was performed using the colony-forming unit assay. In addition, 16S rRNA sequencing was used to identify sensitive and resistant bacterial genera to the BSS-NPs.The characterization results showed that the synthesized BSS-NPs by laser ablation of solids in liquids maintained the triclinic crystallographic structure, and the vibrational modes of the functional groups of bismuth subsalicylate. Moreover, BSS-NPs presented a quasi-spherical shape, an average size of 4 nm, and water-suspended stability for up to 170 days. Regarding the antimicrobial activity, more than 30 % of the total cultivable bacteria from the oral biofilm samples were inhibited when exposed to BSS-NPs. In addition, sensitive microorganisms to the BSS-NPs such as Aggregatibacter, Streptococcus, Veillonella, Eikenella, Peptostreptococcus, Eubacterium, Prevotella, Selenomonas, Haemophilus, Filifactor, and others, were identified by bioinformatic analysis of 16S rRNA sequencing. Therefore, BSS-NPs have the potential for being used as a new alternative antimicrobial in the treatment of periodontal diseases, reducing the indiscriminate use of antibiotics and preventing the increase of antibiotic resistance.

δ-Bi2O3 nanoparticles obtained by laser ablation of solids in liquids

δ-Bi2O3 nanoparticles (NPs) were successfully synthesized by using the laser ablation of solids in liquids (LASL) technique. This is the first time, to the best of our knowledge, that the δ-Bi2O3 phase is obtained through this synthesis method. A bismuth target immersed in sodium hypochlorite as liquid medium was irradiated with a ns-pulsed Nd:YAG laser. Our results indicate that LASL is a suitable and simple technique to obtaining δ-Bi2O3.

Quantitative analysis of the platinum surface decoration on lanthanum strontium iron oxide thin films via online-LASIL-ICP-MS

Solid oxide fuel cells (SOFCs) are one of the key technologies on the way to environmentally friendly power generation. Current research activities aim to reduce their operational temperature to intermediate temperatures (400–600 °C) to make their application more feasible. In a recent approach, lanthanum strontium iron oxide (LSF) thin film electrodes, a mixed ionic electronic conducting (MIEC) material, was decorated with tiny amounts of platinum nanoparticles, which led to a significant improvement of the oxygen reduction kinetics. To understand this material combination a precise characterization is of major interest, especially the exact amount of platinum on the surface. As the studied model-type thin film electrode requires a platinum current collector buried beneath the LSF to improve in-plane electron conductivity, a method providing quantitative information as well as sufficient depth resolution is needed.In this work, we further improved the recently presented approach of online laser ablation of solids in liquids (LASIL), which enabled in combination with ICP-MS detection a spatially resolved analysis of the sample composition. Careful optimization of laser parameters and carrier solution led to a depth resolution of 30 nm, which allowed a clear separation of the Pt-signals from the surface decoration and the underlying current collector. The amount of platinum on the surface was determined using calibration with a matrix matched standard and validated by another method. Finally, the imaging capabilities of the proposed online-LASIL approach have been employed to assess the homogeneity of the Pt-decoration, indicating significant variations within the investigated area. Thus, further improvements in the electrochemical properties of the investigated LSF electrodes could be anticipated by fabrication of MIECs with a more homogeneous platinum decoration.

Insecticide activity of bifenthrin nanoparticles synthesized by laser ablation of solids in liquids

Organic nanoparticles of bifenthrin (agricultural insecticide) were successfully synthesized by the laser ablation of solids in liquids (LASL) technique, using as liquid medium a solution of a polymeric surfactant at 0.1 %. The results showed that the use of the surfactant improves the stability of the organic nanoparticles 18 times as compared to those synthesized in water. The characterization by UV-Vis spectroscopy allowed evaluating the stability of colloids, as well as determining the concentration of nanoparticles in the medium. In the characterization by TEM and HRTEM was possible to observe nanoparticles with the most probable size of 5 nm and interplanar distances which correspond to the crystalline structure of the starting material. Mass coupled gas chromatography technique was used to corroborate the chemical composition of nanoparticles. Results of biological tests using Drosophila Melanogaster fly, showed that the use of the nanostructured compound is effective in lower doses than those used in agriculture in the form of bulk material.

Synthesis of molybdenum oxide nanoparticles by nanosecond laser ablation

Phothermal therapy (PTT) is one of the most promising techniques to treat cancer. Finding the ideal PTT agent nanomaterial has remained a challenge and has brought the interest of several researchers. In this work, we report the synthesis of molybdenum oxide (MoOx) nanoparticles (NPs), which exhibit absorption in the biological optical window ~840 nm, by using the laser ablation of solids in liquids (LASL) technique with nanosecond (ns) pulses. A Nd:YAG laser was used to synthesize the NPs in deionized (DI) water, free of surfactants or additives, which were optically characterized by absorption spectroscopy and TEM-EDX microscopy. Semi spherical NPs with a suitable average size and shape for potential use as PTT agents were obtained by laser ablation and ablation + fragmentation. The calculated band gap is 3.1 eV, which corresponds to MoO3. Micro-Raman spectroscopy studies determined that these NPs are composed of amorphous molybdenum oxide hydrates (MoO3 · xH2O).

Molybdenum nanoparticles generation by pulsed laser ablation and effects of oxidation due to aging

Molybdenum oxides (MoOx) nanoparticles (NPs) have great optical and electronic features that make them suitable for potential applications such as surface enhanced Raman spectroscopy (SERS) and energy systems. However, there are very few papers that report the synthesis of MoOx NPs by using the laser ablation of solids in liquids (LASL) technique and they lack the explanation for the oxidation process. This work reports on the generation of NPs composed of molybdenum trioxide hydrated (MoO3 · xH2O) (x = 1, 2) by using this method and its oxidation due to aging. A picosecond Nd:YAG laser was used and the per pulse laser fluence was varied from 5 to 20 J/cm2. Spherical NPs were obtained with average diameters from 48 to 141 nm, respectively. The absorption evolution of the obtained colloids was characterized by optical absorption spectroscopy, TEM was used to study the MoOx NPs morphology, size and structure and Raman spectroscopy to determine the material chemical composition.

Synthesis and Characterization of Pd Nanoparticles by Laser Ablation in Water Using Nanosecond Laser

Colloidal solutions of Pd nanoparticles were produced by laser ablation of solids in liquids (LASL) technique. Two different lasers operating at 1064 and 532 nm of wavelength to ablate a Pd foil submerged in water were used. The properties of the obtained nanoparticles were studied and the influence of the wavelength on the nanoparticle size was discussed. The nanoparticles formation mechanism is discussed and compared with the results obtained in previous work using continuous wave (CW) and long pulses lasers. The obtained nanoparticles were characterized by means of transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and UV/VIS absorption spectroscopy. The obtained nanoparticles consisted of crystalline Pd nanoparticles with rounded shape and strong tendency to agglomeration. The size distribution of the nanoparticle range from few nanometers to 40 nm together with the presence of occasional large particles when the infrarred (IR) laser was used.