Laser Ablation In Aqueous Solution Research Articles

Uncovering gold nanoparticle synthesis using a microchip laser system through pulsed laser ablation in aqueous solution

A compact, low-power microchip laser system is utilized for pulse laser ablation in liquids, and the impact of solution viscosity on the efficiency of gold nanoparticle ablation in PVP solutions is explored.

Fabrication of Pt nanoparticles by nanosecond pulsed laser ablation in aqueous solution of ethanol using KrF excimer laser

The present paper presents the premiere synthesis of platinum nanoparticles (Pt-NPs) by pulsed laser ablation in aqueous ethanol solution (PLAL) using an excimer nanosecond KrF laser. The impact of the laser fluence, repetition rate (RR) and ethanol concentrations on the optical and morphological properties of the obtained Pt-NPs was investigated. The optical characteristics has been assessed by transmission spectroscopy in the UV/Vis region, and the issues associated to the volatile component’s evaporation are discussed. Detailed information on the morphological properties was acquired via High-Resolution Scanning Transmission Electron Microscopy (HR-STEM). Mean size values in the range of 1.7–2.45 nm with narrow standard deviations from ± 0.6 up to ± 1.1 nm, were established for the synthesized Pt-NPs, that showed a certain level of aggregation. The smallest mean size value, 1.7 nm, was found for the sample produced using 2.3 Jcm−2 laser fluence, 10 Hz RR in 60 % ethanol concentration. The narrowest size distribution (±0.6 nm) was achieved with the same laser fluence and RR in 80 % aqueous ethanol solution. In addition, the metallic character (Pt) of the atoms forming the NPs was confirmed by Direct Analysis in Real Time Mass Spectrometry (DART-MS). The formation of face-centered cubic phase for Pt-NPs with interplanar distances of 0.25 and 0.19 nm for (200) and (111) crystalline planes, respectively, was revealed by X-ray diffraction (XRD). These results are in good agreement with those from HR-STEM analysis, where similar interplanar distances were obtained for individual NPs.

Spectral features of colloidal solutions of elongated gold nanoparticles produced by laser ablation in aqueous solutions

The extinction spectra of colloidal solutions of gold nanoparticles produced by laser ablation in water and aqueous solutions of salts using two near-IR lasers with pulse durations of 200 ns and 1 ps are experimentally investigated. The extinction spectrum of the particles formed by ablation in aqueous solutions is characterised by enhanced optical density in the red and IR regions. This feature is due to the formation of elongated gold nanoparticles, as confirmed by transmission electron microscopy. The surface images of a gold target subjected to multipulse laser ablation exhibit micron and submicron structures.

Laser Synthesis of Composite Nanoparticles of Perovskite BaTiO3 with Au by Laser Ablation in Aqueous Solutions

Laser synthesis of composite nanoparticles of perovskite BaTiO3 and Au nanoparticles has been carried out using laser ablation in water and aqueous solutions. Two approaches were used to this end. Within the first approach, a gold target is subjected to laser ablation in an aqueous colloidal solution of perovskite. In the second approach, a mixture of aqueous colloids of the components is irradiated by a laser. The synthesized particles have been investigated by optical spectroscopy, Raman spectroscopy, and transmission electron microscopy.

Controlled Nitrogen Doping of Graphene Quantum Dots through Laser Ablation in Aqueous Solutions for Photoluminescence and Electrocatalytic Applications

Nitrogen-doped graphene quantum dots (N-GQDs) have promising applications in catalysis and photoluminescence, but many existing synthetic methods require uses of harsh chemicals, long reaction time...

Luminescence Efficiency of Si/SiO2 Nanoparticles Produced by Laser Ablation

Photoluminescence properties of Si(core)/SiO2(shell) nanoparticles produced by pulsed laser ablation in aqueous solution are investigated with the purpose to highlight the microscopic processes that govern the emission brightness and stability. Time resolved spectra evidence that these systems emit a µs decaying band centered around 1.95 eV, that is associated with the radiative recombination of quantum‐confined excitons generated in the Si nanocrystalline core. Both the quantum efficiency and the stability of this emission are strongly dependent on the pH level of the solution, that is changed after the laser ablation is performed. They enhance in acid environment because of the H+ passivation of non radiative defects, located in the Si/SiO2 interface, which causes the growth of IR‐active SiH groups. On the basis of the reported experimental results and previous literature data, we propose that the non radiative defects are located in the suboxide interlayer between Si and SiO2 and their nature is affected by the latter.

SERS, XPS and DFT investigation on palladium surfaces coated with 2,2′-bipyridine monolayers

Palladium surfaces, pretreated with a solution of 2,2′-bipyridine (bpy) as ligand molecule, were SERS-activated by means of laser-ablated Ag colloidal nanoparticles. XPS and Raman measurements, along with DFT simulations, evidenced the species formed on the metal surface as bpy-Pd(OH)2, which appears quite similar, from both structural and spectroscopic points of view, to the bpy-PdCl2coordination compound, whose catalytic activity is well known. Based on these observations, the use of Pd substrates coated with bpy is proposed for reactions of heterogeneous catalysis, instead of using bpy-PdCl2 as homogeneous catalyst. Moreover, palladium nanoparticles could be prepared by laser ablation in aqueous solution of bpy, exhibiting both colloidal stability and catalytic activity.

Nanoaggregates of iron poly-oxo-clusters obtained by laser ablation in aqueous solution of phosphonates

Laser ablation in liquid (LAL) emerged as a versatile technique for the synthesis of nanoparticles with various structures and compositions, although the control over products remains challenging in most cases. For instance, it is still difficult to drive the size of metal oxide crystalline domains down to the level of few atom clusters with LAL. Here we demonstrate that laser ablation of a bulk iron target in aqueous solution of phosphonates gives phosphonate-grafted iron oxo-clusters polymerized into nanoaggregates with Fe:ligand ratio of 2:1, instead of the usual nanocrystalline iron oxides. We attribute this result to the strong ability of phosphonate groups to bind iron oxide clusters and prevent their further growth into crystalline iron oxide. These laser generated poly-oxo-clusters are biocompatible and trackable by magnetic resonance imaging, providing interesting features for use in biological environments, such as nano-vehicles for iron administration. Besides, this method is promising for the generation of atom-scale metal-oxide clusters, which are ubiquitary in chemistry and of interest in biochemistry, catalysis, molecular magnetism and materials science.

Phase transformation of TiO2nanoparticles by femtosecond laser ablation in aqueous solutions and deposition on conductive substrates

Titanium dioxide (TiO2) is a wide bandgap semiconductor that is chemically stable, non-toxic, and economical compared to other semiconductors and has been implemented in a wide range of applications such as photocatalysis, photovoltaics, and memristors. In this work we studied the femtosecond laser ablation of titanium dioxide powders (P25) dispersed either in water or deposited onto a fluoride-doped tin oxide (FTO) substrate. The process was used as a route to induce the phase-transformation of TiO2 nanoparticles which was governed by laser parameters such as ablation time and power. It was observed that upon increase of the ablation time of TiO2 dispersion in water a bandgap widening occurred, leading to the possibility of bandgap engineering of TiO2 using controlled laser parameter profiles.

Controlling the oxidation processes of Zn nanoparticles produced by pulsed laser ablation in aqueous solution

We used online UV-VIS optical absorption and photoluminescence spectra, acquired during and after pulsed laser ablation of a Zinc plate in aqueous solution, to investigate the effect of the laser repetition rate and liquid environment on the oxidation processes of the produced nanoparticles. A transient Zn/ZnO core-shell structure was revealed by the coexistence of an absorption peak around 5.0 eV due to Zn surface plasmon resonance and of an edge at 3.4 eV coming from wurtzite ZnO. The growth kinetics of ZnO at the various repetition rates, selectively probed by the excitonic emission at 3.3 eV, began immediately at the onset of laser ablation and was largely independent of the repetition rate. In addition, we detected an emission at 2.3 eV related to oxygen vacancies, which began to grow after a number of pulses increasing with the used repetition rate. Optical absorption spectra during and after ablation in a mixture of water and ethanol (0%–100%) revealed that the oxidation kinetics of Zn nanoparticles slows down from about 900 s in pure water to at least one week in pure ethanol.

A comparative study of silver nanoparticles synthesized by arc discharge and femtosecond laser ablation in aqueous solution

Silver nanoparticles have been synthesized by arc discharge and femtosecond laser ablation in polyvinylpyrrolidone (PVP) aqueous solution. Both methods are the simple, cost-effective and environment-friendly way to obtain the purity silver nanoparticles. In this study, the structure, composition, morphology, size and distribution, stability, production rate and sintering properties of silver nanoparticles synthesized by both methods were compared. The spherical or pseudo-spherical silver nanoparticles were synthesized by both methods, and the diameters were below 50 nm. The arc discharge-synthesized particle distribution varied with the breakdown voltage, and laser-synthesized particle size mainly depended on the laser energy. PVP solution could cap and stabilize the silver nanoparticles by Ag–O bond, while arc discharge and laser ablation resulted in some level of PVP degradation during processing. Sliver nanoparticle colloids synthesized by both methods had the high negative values of zeta potential and exhibited the good stability. The maximum production rates of the silver nanoparticles synthesized by arc discharge and femtosecond laser ablation were 6.0 and 3.0 mg/min, respectively. In addition, the sintering properties of silver nanoparticles synthesized by both methods were also discussed.

Bismuth and Gold Nanoparticles Prepared by Laser Ablation in Aqueous Solutions

The aim of this work is to report on the preparation of bismuth and gold nanoparticles ablating the corresponding target immersed in different liquid solutions: water and ethanol. The effect of the liquid environment and laser fluence used for ablation on the size and size distribution of the nanoparticles synthesized was investigated. The nanoparticle size was measured by transmission electron microscopy (TEM). In general terms, for both metals, the results obtained reveal smaller sizes as low as approximately 2 nm. The bismuth nanoparticles, as deposited, are highly crystalline in nature and, depending on the conditions of preparation, either Bi or Bi2O3 nanoparticles are obtained in both liquids. UV-Vis measurements show the typical band absorption characteristic of spherical particles of nanometric size. It is worth mentioning that the gold colloids obtained using water are very stable.

Formation of wide bandgap cerium oxide nanoparticles by laser ablation in aqueous solution

Cerium oxide nanoparticles were produced by laser ablation in an aqueous solution. Submicron-sized cerium oxide particles were size-reduced by pulsed-laser irradiation into those having diameters of 3.6nm. It was found that the bandgap of the nanoparticle was larger and the Ce3+ concentration within it was higher than those prepared by other conventional methods. These characteristic structures are likely to originate from additional defect sites in the nanoparticles produced by laser ablation, where O2− ions have a lower coordination with Ce ions, resulting in removal of O atoms and reduction of Ce4+ into Ce3+.

Spectroscopic evidence of positive clusters in Ag colloids obtained by laser ablation in aqueous solutions

We have found evidence of positive cluster formation during the laser ablation process of a silver target in aqueous solutions. In particular, by employing in situ shot-by-shot UV–vis spectroscopy in the early stages of the ablation, we observed a weak and unstable absorption band around 266 nm and a more stable one around 290 nm, which could be assigned to charged clusters like Ag32+ and Ag42+, respectively. Surface-enhanced Raman scattering experiments performed with a test molecule adsorbed on a silver colloid obtained in pure water were compatible with the presence of Ag42+ active sites on the surface of the Ag nanoparticles.

Size Control of Gold Nanoparticles During Laser Ablation In Liquids With Different Functional Molecules

Over the last decade many papers dedicated to the generation of nanoparticles in liquids using laser ablation have been published. They have shown that the nanoparticles size distribution is dependent of the laser fluence and shifts towards smaller sizes when the surfactant concentration is increased. In this paper an alternative approach is presented that permits the control of the size distribution of gold nanoparticles during laser ablation in aqueous solutions containing different surfactant molecules with different shapes and size.

Red luminescence of Eu3+ doped ZnO nanoparticles fabricated by laser ablation in aqueous solution

Fabrication of Eu3+-doped ZnO nanoparticles by laser ablation in liquid medium is reported. Sintered disks made of mixed powders of ZnO and Eu2O3 are used for targets, and surfactant of sodium dodecyl sulfate or LiOH is included in solution. Round-shaped nanoparticles with the diameter of 5∼30 nm are synthesized. When the ZnO host is photoexcited, broad green photoluminescence (PL) of oxygen vacancies in the ZnO host as well as red PL of Eu3+ is observed at room temperature. The red PL peak of Eu3+ included in the ZnO host lattice is different from that of the source material of Eu2O3. Energy transfer from the ZnO host to Eu3+ is demonstrated in site-selectively excited PL spectra and its excitation spectra. This result shows that the liquid-phase laser ablation is useful for doping active centers into nanoparticles.

Platinum Nanoparticles Prepared by Laser Ablation in Aqueous Solutions: Fabrication and Application to Laser Desorption Ionization

Aqueous suspensions of platinum colloidal nanoparticles of varying size and polydispersity have been produced by ablation of a platinum target with a nanosecond Q-switched Nd:YAG laser. Several laser wavelengths (1064, 532, and 266 nm) and stabilizing agents (citrate and polymers PEG, PVA, and PVP) were employed. Laser ablation with the infrared and visible wavelengths leads to spherical amorphous nanoparticles with a bimodal distribution of diameters, featuring a global maximum in the range 5–10 nm and a shoulder extending to 25 nm. Such bimodal distributions plausibly arise from thermal and explosive vaporization mechanisms occurring in different time scales, as proposed in earlier studies. Ultraviolet ablation of Pt at 266 nm, reported here for the first time, produces crystalline nanoparticles of small size (1–4 nm diameter), with a weak onset of larger particles (6–8 nm). The ablation at 266 nm also produced an appreciable yield of large rodlike particles of size ∼10 × 70 nm2, especially in the presence of PEG and PVA. The Pt nanoparticles served to fabricate films capable of assisting the laser desorption ionization (LDI) of a model peptide. The best analytical performance for LDI mass spectrometric detection was obtained with Pt nanoparticles surface-functionalized with citrate and PVA.

Utilization of laser ablation in aqueous solution for observation of photoinduced shape conversion of silver nanoparticles in citrate solutions

Photoinduced shape conversion of silver nanoparticles in citrate solutions was examined using silver nanoparticles prepared by laser ablation. Nowadays, photoinduced shape conversion of silver nanoparticles in citrate solution attracts much attention as a novel technique to produce anisotropic-shaped nanocrystals in a simple manner. So far, the observations of the shape conversion have been carried out using source silver nanoparticles prepared by chemical synthesis. In this work, we demonstrate that silver nanoparticles prepared by laser ablation in liquids are an appropriate system to investigate the photoinduced shape conversion due to the simple preparation method and absence of unnecessary components in colloidal solution. Using this system, we have confirmed that particle size plays a critical role in the shape conversion. In addition, some novel information was obtained: the adsorption conditions of citrate are also important, and polyvinylpyrrolidone promote the conversion rate.

Surface-Enhanced Raman Scattering from Copper Nanoparticles Obtained by Laser Ablation

Copper colloidal nanoparticles are obtained by laser ablation in aqueous solutions of ligands by nanosecond laser pulses at 532 and 1064 nm and examined by localized surface plasmon resonance (LSPR) and surface-enhanced Raman scattering (SERS) spectroscopy, along with transmission electron microscopy (TEM) and zeta potential measurements. This fabrication method, besides providing SERS-active substrates without spectral interferences of reagents, as it generally occurs for the chemical reduction of metal ions, allows obtaining colloidal suspensions which are stable in time because the copper particles are capped by ligand molecules as long as they are formed by laser ablation. This prevents aggregation among metal nanoparticles and probably reduces overall oxidation of the copper surface.

Production of Palladium Nanoparticles by Pulsed Laser Ablation in Water and Their Characterization

Nanosized particles of pure palladium were produced by pulsed laser ablation in aqueous solution, with and without the addition of sodium dodecyl sulfate as the surfactant agent. The work was motivated by the strong catalytic effect of Pd particles in many chemical reactions. The influence of experimental parameters, such as laser energy and beam focusing as well as surfactant concentration, on the laser ablation process, nanoparticle mass yield, and nanoparticle properties was investigated via plasma imaging, UV−visible spectroscopy, transmission electron microscopy/energy dispersive spectroscopy (TEM-EDS) analysis, and measurement of ζ potential. The surface-enhanced Raman scattering activity of nanoparticles was used for the monitoring of their adsorption capability on the metal surface during catalysis processes.