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Porous graphene (PG) was obtained using one step laser process. Synthesis was carried out by laser ablation of nickel-graphite target under ultra-high flow of argon gas. The field emission scanning electron microscopy (FE-SEM) results showed the formation of a porous structure and the transmission electron microscopy (TEM) revealed that the porosity of PGs increase under intense laser irradiation. Structural characterization study using Raman spectroscopy, X-ray powder diffraction (XRD) and selected area electron diffraction (SAED) technique showed that the obtained PGs display high crystalline structure in the form of few layer rhombohedral graphitic arrangement that can be interpreted as the phase prior to the formation of other carbon nanostructures.

In the recent past, gold nanoparticles synthesized using pulsed laser ablation in biocompatible mediums has attracted scientific and technological interest. In this work, it is found that the gold nanoparticles prepared using laser ablation of gold target in water is inherently non-toxic. These particles have shown that they are photothermally active when excited with 532 nm laser line, in conjunction with the plasmon band. The surface charge of these nanoparticles is found to be negative. The X-ray photoelectron spectroscopy measurements indicated the possibility of partial oxidation of the surfaces of these gold nanoparticles and electron micrographs indicated that the surfaces of these particles are relatively smooth. Raman measurements made with crystal violet as probe molecules using these nanoparticles as substrates and Raman spectra from L929 cells after incubation with these gold nanoparticles have shown that they can enhance the scattered Raman signal.

In this paper, we demonstrate two-dimensional nanohole array substrates prepared using the visible laser ablation technique. We fabricated Au/polymer hybrid thin films where the Au nanoparticles were fixed onto the block copolymer substrate, which was used as the microphase-separated structure. The film was coated with a thin layer of poly(methyl acrylate), and was then irradiated with a nanosecond 532 nm pulsed laser light. The light excited the resonant plasmon absorption band of the Au nanoparticles. The nanoparticles underwent explosive vaporization via a superheated state, resulting in the formation of two-dimensional nanohole arrays on the film surface. The relevant mechanism aspects of the nanohole formation process and the relationship with laser fluence are presented.

In this paper, we investigate experimentally the effect of electric field on the size, optical properties and crystal structure of colloidal nanoparticles (NPs) of aluminum prepared by nanosecond Pulsed Laser Ablation (PLA) in deionized water. The experiments were conducted for two different conditions, with and without the electric field parallel to the laser beam path and the results were compared. To study the influence of electric field, two polished parallel aluminum metals plates perpendicular to laser beam path were used as the electrodes. The NPs were synthesized for target in negative, positive and neutral polarities. The colloidal nanoparticles were characterized using the scanning electron microscopy (SEM), UV–vis absorption spectroscopy and X-ray Diffraction (XRD). The results indicate that initial charge on the target has strong effect on the size properties and concentration of the synthesized nanoparticles. The XRD patterns show that the structure of produced NPs with and without presence of electric field is Boehmite (AlOOH).

Preparation of doped ZnO nanoparticles (NPs) represents a challenging task due to the tendency of self-compensation of the introduced defects by the intrinsic ones. One of the possible ways of achieving reliable p-doping in ZnO is dual acceptor doping, i.e. simultaneous introduction of two types of acceptors. In the present paper the capabilities of laser ablation and post-irradiation processes for preparation of N-doped and Ag-, N-co-doped ZnO NPs were investigated. In order to obtain doped ZnO NPs, Nd:YAG laser ablation of Zn in ammonium nitrate (NH4NO3) solution and sequential laser ablation of Ag and Zn in ammonium nitrate solution were used. The composition, structure and morphology of the prepared NPs were controlled through an additional treatment of the colloids by the second harmonic of the Nd:YAG laser. The influence of the ablation processes sequence and additional laser irradiation parameters on the morphology, structural, optical characteristics and chemical composition of the synthesized NPs was examined. The results obtained reveal that the doping takes place after laser ablation of zinc in ammonium nitrate and silver target in the ZnO colloid in NH4NO3 solution that was confirmed by X-ray photoelectron spectroscopy analysis indicating the substitution of N at O site.

Laser ablation of Zn target in water, ammonium nitrate and cetyltrimethyl ammonium bromide (CTAB) was carried out to synthesize spherical, nanoflakes, nanosquares, nanoflowers and branched nanorods ZnO structures. Morphology of the ZnO nanostructures is controlled by varying ambient condition around laser generated plasma by means of either liquid temperature or addition of surfactant CTAB. In situ heating at temperature to 45, 65 and 85 C resulted in morphology variation from spherical to nanoflakes while ex situ heating at 65 C resulted in aggregation of spherical nanoparticles into nanosquares. Finally, simultaneous variation of CTAB and temperature (in situ and ex situ) generated nanoflakes, nanoflowers, nanosquares and branched nanorods. Highly anisotropic nano-flakes, nano-flowers, nano-squares and branched-nanorods structures display distinct optical absorption and emission behavior.

Nanomaterials of titanium oxide were prepared by pulsed laser ablation of a titanium metal target in distilled water. The ablation was performed at different laser energy (fluence) using a nanosecond pulsed Nd:YAG laser output of 1064 and 532 nm. A post-irradiation of titanium oxide nanocolloids obtained by ablation using 532 nm was carried out to explore its effects on the structure and properties. Analysis of morphology, crystalline phase, elemental composition, chemical state, optical and luminescent properties were performed using Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS), UV–-vis absorption spectroscopy and room temperature photoluminescence spectroscopy. It was found that titanium oxide nanomaterial morphologies and optical properties were determined by ablation wavelength and fluence. Further, nanocolloids prepared by 532 nm ablation showed a crystalline phase change by laser post-irradiation. The results showed that pulsed laser ablation in liquid as well as post-irradiation were effective in modifying the final structure and properties of titanium oxide nanocolloids.

We report the electrochemistry of gold nanoparticles (AuNPs), prepared by Laser Ablation Synthesis in Solution (LASiS), via the electrocatalytic oxidation of glucose upon single nanoparticle collisions at inert microelectrodes. Spherical AuNPs with diameters in the range 20–30 nm, as determined by transmission electron microscopy, were synthesized by LASiS of a gold plate immersed in water. Nanoparticle collisions were electrochemically detected through the AuNP-catalysed oxidation of glucose at carbon fiber microelectrodes in alkaline solution, enabling the electrocatalytic detection of single AuNPs. This approach provides a basis for detecting and understanding the electrocatalytic properties of pristine nanoparticles in aqueous solutions. Keywords: Gold nanoparticles, Laser ablation, Glucose, Electrocatalysis, Nano-impact

Bare nanoparticles synthesized by laser ablation in water have found their application in catalysis, spectroscopy and biomedical research fields. In this perspective, how to efficiently produce stable nanoparticles with controllable size is an important topic and has attracted a lot of interests. Here, we introduce a multiple-pulse laser as the ablation source. By changing the number of sub-pulses, the average size of nanoparticles can be tuned in a broad range from ∼120 nm to ∼4 nm. The demonstration in this article may offer a new approach to fabricate ultrafine nanostructures and also help the scientific study of the mechanism in laser ablation.

Laser ablation in liquids is actively used for generation of clean colloidal nanoparticles with unique shapes and functionalities. The fundamental mechanisms of the laser ablation in liquids and the key processes that control the nanoparticle structure, composition, and size distribution, however, are not yet fully understood. In this paper, we report the results of first atomistic simulations of laser ablation of metal targets in liquid environment. A model combining a coarse-grained representation of the liquid environment (parameterized for water), a fully atomistic description of laser interactions with metal targets, and acoustic impedance matching boundary conditions is developed and applied for simulation of laser ablation of a thin silver film deposited on a silica substrate. The simulations, performed at two laser fluences in the regime of phase explosion, predict a rapid deceleration of the ejected ablation plume and the formation of a dense superheated molten layer at the water-plume interface. The water in contact with the hot metal layer is brought to the supercritical state and transforms into an expanding low density metal-water mixing region that serves as a precursor for the formation of a cavitation bubble. Two distinct mechanisms of the nanoparticle formation are predicted in the simulations: (1) the nucleation and growth of small (mostly ⩽10nm) nanoparticles in the metal-water mixing region and (2) the formation of larger (tens of nm) nanoparticles through the breakup of the superheated molten metal layer triggered by the emergence of complex morphological features attributed to the Rayleigh-Taylor instability of the interface between at the superheated metal layer and the supercritical water. The first mechanism is facilitated by the rapid cooling of the growing nanoparticles in the supercritical water environment, resulting in solidification of the nanoparticles located in the upper part of the mixing region on the timescale of nanoseconds. The computational prediction of the two mechanisms of nanoparticle formation yielding nanoparticles with different characteristic sizes is consistent with experimental observations of two distinct nanoparticle populations appearing at different stages of the ablation process.

Cubic phase zinc peroxide nanoparticles (ZnO 2 NPs) with an average diameter of ca. 9–15 nm have been synthesized via a fast nanosecond pulse laser ablation in liquid technique (PLAL), using H 2 O 2 aqueous solution as the ablation media and a 532 nm pulsed laser as the irradiation source and low-cost zinc powder as the solid target. Both the laser energy and ablation time potentially have a substantial influence on the formation of ZnO 2 NPs. Due to its relatively high oxidation level as well as its hydrophilic wetting behavior, the as-synthesized ZnO 2 NPs exhibit efficient photocatalytic degradation ability of Rhodamine B (RB) whilst remaining stable to photodegradation. The possible mechanisms of the photocatalytic behavior have been discussed in what follows.

We demonstrate the catalytic performance of perovskite-based oxygen reduction reaction (ORR) catalyst based on LaMnO 3+δ nanoparticles (LMO NPs) prepared using the laser ablation synthesis in solution method. The ORR catalytic activity of the post-annealed LMO NPs was similar to that of commercial Pt/C catalysts due to the increased surface area as well as the perovskite crystalline structure of the LMO NPs. The mass and specific activities of the LMO NP catalyst annealed at 800 °C were 20 and 2.2 times higher than those of the bulk LMO, respectively. In a chronoamperometric stability test, our LMO NP catalyst (annealed at 800 °C) outperformed the Pt/C catalyst.

YVO 4 :Eu 3+ nanoparticles were prepared via pulsed laser ablation in water and sodium dodecyl sulfate solution. The particle phase, morphology, and optical properties were evaluated by XRD, TEM, SEM, and PL. Ovoid-like nanoparticles having an average diameter of 97 nm were prepared in water, whereas nearly spherical nanoparticles with an average diameter of 55 nm were obtained in sodium dodecyl sulfate solution. The photoluminescence properties of the YVO 4 :Eu 3+ nanoparticles were affected by the defects in the nanoparticles, as demonstrated by HR-TEM and recovered after annealing at 600 °C for 24 h. Fourier transform infrared spectroscopy revealed that the surfaces of the nanoparticles obtained in sodium dodecyl sulfate solution were covered by surfactant molecules, leading to smaller nanoparticles. These results also provide contributions for the synthesis of oxide nanoparticles in the domain of laser ablation in liquid as single-phase YVO 4 was obtained in this study.

We report about the chemical activity of Gd and Si nanoparticles in the mixture of their colloidal solutions. It was found that mixing of two colloids prepared by laser ablation technique results in the chemical interaction between nanoparticles and formation of silicide phases at room temperature. The phase composition of the resulting products was found to be dependent on the mixing order.

The importance of actinide based nano-structures is well known in the area of biology, nuclear medicine and nuclear industry. Pulsed laser ablation in liquid is recognised as an attractive technique for production of nano-structures of different metals and metal oxides with high purity. In this paper, we report synthesis of uranium-di-oxide nanoparticles by pulsed laser ablation in ethanol. The second harmonic emission of an electro-optically Q-switched nano-second Nd-YAG laser was used as the coherent source here. The structural and optical properties of the fabricated uranium-di-oxide nanoparticles were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive analysis of X-rays (EDX) and UV–Vis–NIR spectrophotometry. The mean size of the particles was found to be dependent on the laser ablation parameters in particular with laser fluence. XRD and TEM analysis confirmed the phase of the synthesised material as pure crystalline uranium-di-oxide with face centred cubic structure. UV–Vis–NIR absorption spectra of the colloidal solution revealed high absorption in the UV regime.

In this work silver nanoparticles suspension of 4.5 nm average size and narrow size distribution was obtained for the first time in a deep eutectic solvent (DES) by using laser ablation targeting a silver metal blank immersed in choline chloride-urea DES. Luminescence properties in both DES and aqueous media of as-synthesized silver nanoparticles are discussed.

Efficient yet, low-cost electrocatalysts are indispensable for electrochemical oxygen reduction reactions (ORR) and oxygen evolution reactions (OER). Here we present laser ablation synthesis in solution in tandem with galvanic replacement reaction (LASiS–GRR), for the first time, as a facile route to synthesize nanocomposites (NCs) of PtCo nanaoalloy (NA) embedded in CoO x matrices as bifunctional electrocatalysts. High resolution TEM reveals PtCo NA of mean sizes ∼8.5–17.7 nm embedded in sponge-shaped CoO x matrices, while electron diffraction and X-ray diffraction data along with energy dispersive X-ray spectrometry (EDX) confirm the NC compositions and crystalline structures. Detailed electrochemistry data indicates outstanding ORR and OER activities for the PtCo/CoO x NCs while exhibiting better stability than the respective standard nanocatalysts. Such activities are ascribed to the shrunken lattice constants of alloyed PtCo that promote oxygen adsorption and the synergic “spillover” effect from high surface area CoO x matrices that accelerate both ORR and OER through symbiotic adsorption/desorption of intermediate species, while preventing aggregation and/or dissolution in alkaline medium. We report a combined overpotential of 756 mV vs. RHE for the PtCo/CoO x NC with 33.3% (molar) Pt content which is the best value ever reported for catalysts supported by carbon black. The enhanced bifunctional catalytic activities of the NCs are attributed to their unique heteronanostructures tailored by our one-pot, “green” synthesis route of LASiS–GRR.

Amine-terminated, ultra-small silicon nanoparticles (Si-NPs) were prepared in one step avoiding the conventional chemical or thermal treatment of Si surface, by introducing organosilane in Si-NPs colloidal solution freshly prepared by ultra-fast laser ablation of silicon target in deionized water. Surface chemistry studies of Si-NPs conducted by Raman and Fourier infrared spectroscopy demonstrated the hydroxyl-terminated surface of Si-NPs. The reactivity of hydroxyl-terminated surface with aminopropyltriethoxysilane in aqueous solution was investigated. Electron microscopy, dynamic light scattering, infrared spectroscopy and stability studies confirmed the successful functionalization of Si-NPs leading to 5nm Si dots covered by aminopropyltriethoxysilane thick layer. Detailed infrared spectroscopy analysis of the Si-O-Si region as a function of immersion time revealed the formation of interfacial Si-O bonds between the organosilane and hydroxyl groups of the nanoparticles. The biocompatible Si nanostructure containing amine functional group prepared using a one-step green protocol opens the route for biomedical applications and successful translation into clinical setting, as bio-labels, contrast agents and vector delivery.

We have developed tandem laser ablation synthesis in solution-galvanic replacement reaction (LASiS-GRR) technique as a facile, green yet, efficient route to synthesize spherical PtCo NAs with varied sizes, compositions and degrees of alloying. The transformative concept here is the ability to design these nanostructured alloys by tuning the high-energy physico-chemical conditions emerging from liquid-confined, laser-induced plasma, and the solution-phase reaction pathways dictated by pH conditions and precursor salt concentrations. The resultant NAs exhibit uniformly alloyed cores with a Pt-rich shell of a few nanometers, as demonstrated by the electron energy loss spectroscopy (EELS) mapping. Such core–shell structure along with high degrees of alloying in these PtCo NAs promote their outstanding electrocatalytic ORR activities in acid electrolytes. Specifically, compared to commercial Pt/C catalysts, the PtCo NAs with Co molar ratio of 22.1% indicate a c.a. 3 and 6-fold increase in mass and specific activities respectively. Such enhanced ORR activities are attributed to the efficacy of tandem LASiS-GRR route to rationally tune size distributions/compositional ratios and alloying degrees of the NAs without the use of any surfactants or reducing agents that are otherwise indispensable in chemical synthesis methods, but harmful for catalytic performances.

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.

Colloidal nanoparticles were prepared from Cu metal in water without any surfactant using a simple one-step laser ablation process with 532 nm Nd-YAG beam irradiation. A surface plasmon band of Cu nanoparticles near 580 nm was not observed; instead, oxidation of the Cu colloidal nanoparticles was noticed. This seems to be due to the partially oxidized copper oxides through the route Cu→Cu2O→CuO. Around 10-nm sized colloidal nanoparticles were agglomerated as a result of oxidation according to the time elapsed, and their sizes were increased to near 200 nm. The agglomeration was confirmed by not only images from transmission electron microscopy but also the long-term observation of the particle size distribution using photon correlation spectroscopy, laser-induced breakdown detection, and field flow fractionation.

In this study, colloidal tungsten oxide nanoparticles were fabricated by pulsed laser ablation of tungsten target using the first harmonic of a Nd:YAG laser (1064 nm) in deionized water. After ablation, a 0.33 g/lit HAuCl4 aqueous solution was added into as-prepared colloidal nanoparticles. In this process, Au3+ ions were reduced to decorate gold metallic state (Au0) onto colloidal tungsten oxide nanoparticles surface. The morphology and chemical composition of the synthesized nanoparticles were studied by AFM, XRD, TEM and XPS techniques. UV–Vis analysis reveals a distinct absorption peak at ∼530 nm. This peak can be attributed to the surface plasmon resonance (SPR) of Au and confirms formation of gold state. Moreover, X-ray photoelectron spectroscopy reveals that Au ions’ reduction happens after adding HAuCl4 solution into as-prepared colloidal tungsten oxide nanoparticles. Transmission electron microscope shows that an Au shell has been decorated onto colloidal WO3 nanoparticles. Noble metal decorated tungsten oxide nanostructure could be an excellent candidate for photocatalysis, gas sensing and gasochromic applications. Finally, the gasochromic behavior of the synthesized samples was investigated by H2 and O2 gases bubbling into the produced colloidal Au/WO3 nanoparticles. Synthesized colloidal nanoparticles show excellent coloration contrast (∼80%) through NIR spectra.

Silver nanoparticles with acetonitrile ligands are produced in a laser ablation flow reactor. Excimer laser ablation produces gas phase metal clusters which are thermalized with helium or argon collisions in the flowtube, and reactions with acetonitrile vapor coordinate this ligand to the particle surface. The gaseous mixture is captured in a cryogenic trap; warming produces a solution of excess ligand and coated particles. TEM images reveal particle sizes of 10–30 nm diameter. UV–vis absorption and fluorescence spectra are compared to those of standard silver nanoparticles with surfactant coatings. Deep-UV ligand absorption is strongly enhanced by nanoparticle adsorption.

Laser ablation in liquids is especially adapted to produce nanoparticles free of any contamination as suited for biological and medical applications. A KrF Excimer laser delivering an UV light at 248 nm and operating at low fluence ( F ~0.5 J/cm 2 ) was used to irradiate a micro-sized powder of selenium dispersed into a de-ionized water solution. To avoid any agglomeration of the selenium nanoparticles during the irradiation, surfactants (SDS and CTAB) were added to the solution and their efficiency was compared. The concentration of surfactants had to be chosen around the critical micellar concentration to produce small selenium nanoparticles (

Ag@Au core-shell nanoparticles are synthesised by pulsed laser ablation in water using low energy laser pulses. The plasmon characteristics of these core-shell nanoparticles are found to be highly sensitive to the thickness of Au coating. In the synthesis, at first silver nanocolloid was prepared by ablating Ag target and then it is followed by ablation of Au target for different time durations to form Ag@Au core-shell nanostructures. The effect of plasmon-plasmon coupling on the absorption spectra is investigated by decreasing the effective distance between the nanoparticles. This is achieved by reducing the total volume of the colloidal suspension by simple evaporation of water, the solvent used. The suitability of these core-shell nanostructures for application as surface enhanced Raman scattering substrates are tested with crystal violet as probe molecules. Influence of plasmon coupling on the enhancement of Raman bands is found to be different for different bands.

In the literature many investigations on colloidal stability and size control of gold nanoparticles are shown but less for ligand-free palladium nanoparticles, which can be promising materials in various applications. Palladium nanoparticles are perspective materials for a manifold of energy application like photo- and electrocatalysis or hydrogen storage. For this purpose, size-controlled nanoparticles with clean surfaces and facile immobilization on catalyst supports are wanted. Laser ablation in saline solution yields ligand-free, charged colloidal palladium nanoparticles that are supported by titania and graphene nanosheets as model systems for photo- and electrocatalysis, respectively. By adjusting the ionic strength during laser ablation in liquid, it is possible to control stability and particle size without compromising subsequent nanoparticle adsorption of supporting materials. A quantitative deposition of nearly 100% yield with up to 18 wt% nanoparticle load was achieved. The average size of the laser-generated nanoparticles remains the same after immobilization on a support material, in contrast to other preparation methods of catalysts. The characterization by X-ray photoelectron spectroscopy reveals a redox reaction between the immobilized nanoparticles and the graphene support.

Titanium dioxide is one of the most important materials today in terms of green technology. In this work, we synthesis ultra-small titanium dioxide nanoparticles (NPs) via a two step process involving infrared laser ablation of a bulk titanium target in DDI water and subsequent irradiation of the colloidal solution with visible light. The as-prepared NPs contain defect states related to oxygen vacancies which lead to visible light sensitization as observed by photodegradation of methylene blue. Irradiation of the colloidal TiO 2 solution, with a 532 nm picosecond laser, lead to fragmentation and ultimate formation of ultra-small (

In this paper, we report on the synthesis of antimony sulfide (Sb 2 S 3 ) semiconductor nanoparticles by pulsed laser ablation in liquid without using any surfactants or capping agents. Different results were obtained in water and organic solvents. In the case of water, Sb 2 S 3 nanoparticles with chemical compositions of stoichiometry were successfully prepared when laser irradiation was performed under the condition with the dissolved oxygen removed by argon gas bubbling. It was shown that thus-obtained Sb 2 S 3 nanoparticles exhibit features of not only low-temperature crystallization but also low-temperature melting at a temperature as low as 200 °C. Nanoparticle-coated Sb 2 S 3 thin films were found to show good visible light absorption and satisfying semiconductor properties (i.e., carrier mobility and density), which are essential for photovoltaic application. On the other hand, in the case of organic solvents (e.g., acetone, ethanol), such unexpected byproducts as CS 2 , CO and CH 4 were detected from the reaction system by GC-MS analysis, which suggests that both Sb 2 S 3 and organic solvents were partially decomposed during laser irradiation. The possible mechanism will be discussed.

Pulsed laser ablation in liquid (PLAL) as a prominent technique for nanofabrication was employed to synthesize palladium (Pd) nanoparticles in different liquids. The synthesis of Pd nanoparticles was developed using a pulsed Nd:YAG laser with its fundamental wavelength output of 1064 nm (10 Hz, 10 ns) in a range of energy fluence (40.5–8 J/cm 2 ). Pure Pd metal target was immersed in distilled water, methanol–water mixture (1:1) and sodium dodecyl sulfate (SDS) to study the effect of the nature of the liquid media. Laser post-irradiation and ultrasonic treatments were applied to the precipitated colloidal solution to investigate their effects on the re-dispersion and stability. The mean size, size distributions, shape, elemental composition, optical properties and stability of nanoparticles synthesized by PLAL were examined by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV–vis absorption spectroscopy. TEM characterizations showed smaller nanoparticles in methanol–water mixture in comparison with the other liquids. Spherical morphology was observed for Pd nanoparticles synthesized in distilled water and methanol–water mixture. In the case of SDS, spherical nanoparticles embedded on the surfactant were observed. The effect of energy fluence was different for each liquid media. Laser post-irradiation and ultrasonic agitation worked as efficient methods to re-disperse the precipitates of NPs and to recover their optical properties.

Bimetallic NiAu and complex NiO:Au nanoparticles were formed by laser ablation of Ni target immersed in the colloidal gold solution. Effect of laser parameters (pulse duration, fluences and ablation times) on size and composition of nanoparticles was investigated by ablating the target with two Nd:YAG lasers at 1064 nm, operating with different pulse durations, 150 ps and 20 ns. Stronger ablation of the Ni target and subsequient synthesis of nanoparticles is achieved with picosecond pulses, compared to the nanoparticles production with nanosecond pulses, because the former ablation induces activation of different reactions between species in the colloidal solution. Shape, size and composition of the synthesized nanopraticles were found to correlate with the concentration of Ni species in the colloidal solution. Higher Ni concentration leads to formation of larger NiAu nanoparticles in form of solid solution. Smaller nanoparticles with lower Ni concentration in the colloidal solution were achieved by their synthesis during nanosecond pulses, when the obtained distribution of composition corresponds to the NiO matrix with incorporated golden nanoparticles. The results also demonstrate that the formation of bimetallic NiAu and complex NiO:Au nanoparticles were possible by means of laser ablation in liquids. (C) 2015 Elsevier B.V. All rights reserved.

Silver nanoparticles have attracted much attention as a subject of investigation due to their well-known properties, such as good conductivity, antibacterial and catalytic effects, etc. They are used in many different areas, such as medicine, industrial applications, scientific investigation, etc. There are different techniques for producing Ag nanoparticles, chemical, electrochemical, sonochemical, etc. These methods often lead to impurities together with nanoparticles or colloidal solutions. In this work, laser ablation of solids in open air conditions (LASOA) is used to produce silver nanoparticles and collect them on glass substrates. Production and deposition of silver nanoparticles are integrated in the same step to reduce the process. The obtained particles are analysed and the nanoparticles formation mechanism is discussed. 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 Ag nanoparticles showing rounded shape with diameters ranging from few to 50 nm

The laser ablation in liquid of carbon-based solid targets is of particular interest thanks to the possibility of obtaining different carbon allotropes by varying the experimental parameters employed. The ablation of a fullerite target in water using a frequency-doubled Nd:glass laser source with a pulse duration of 250 fs and a frequency repetition rate of 10 Hz is presented. The obtained products have been characterized by transmission electron and atomic force microscopies and by X-ray photoelectron and micro-Raman spectroscopies. During the femtosecond laser ablation, the collapse of fullerene cages has been considered with the consequent formation of graphene oxide (GO) and its successive hydrogenation. The process of self-assembling in microtube structures of the formed reduced graphene oxide-fullerene composites has then been reported.

In this paper, pulsed laser ablation method was used for synthesis of colloidal nanoparticles of aluminum and titanium targets in distilled water, ethanol, and acetone as liquid environments. Ultraviolet–visible (UV–vis) absorption spectrophotometer and scanning electron microscope (SEM) were used for characterization of produced nanoparticles. Using image processing technique and analyzing the SEM images, nanoparticles’ mean size and size distribution were achieved. The results show that liquid medium has strong effect on size properties of produced nanoparticles. From the results, it was found that ablation of both metal targets in ethanol medium leads to formation of smaller size nanoparticles with narrower size distributions. The influence of laser fluence was also investigated. According to the results, higher laser fluence produces larger mean size nanoparticles with broader size distribution.

Laser ablation in liquids has been intensively studied in recent years, due to present numerous potentials in laser material micro-processing, including nanomaterials and nanostructures synthesize. Compared to others, typically chemical methods, pulsed laser ablation (PLA) in liquid is a simple and “green” technical method that normally operates in water or organic liquids under ambient conditions. Here, pure Ni nanostrutures were synthesized using PLA method in 30 mL of acetone. A simple fiber pulsed laser setup has been not only employed to reduce the micron Ni particles to nano-sized by the PLA method, but also with no-induced oxidation at room temperature and free additive in liquid. The particle size, spectral analysis and morphology of the products were characterized by UV-vis spectrometry, energy-dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). The TEM image indicates spherical shapes with a narrow size distribution, compared with other methods, with ∼10 nm in diameter respectively.

Nanocomposites based on polyethylene oxide and silver nanoparticles (AgNPs) were developed as new active antimicrobial and antibiofilm coatings. Silver colloids were synthesized by nanosecond-pulsed laser ablation synthesis in solution using an organic solvent to ensure a long-term stability of nanocolloids and a good solubility in polymeric solution. AgNPs were incorporated in a biodegradable polymer matrix for the preparation of composite films. The coatings’ surface chemical composition (assessed by X-ray photoelectron spectroscopy) was correlated with the ion release.

Chemically pure colloidal suspensions of gold and silver nanoparticles were synthesized using pulsed laser ablation. The dependence of laser fluence on the surface plasmon characteristics of the nanoparticles was investigated. Au:Ag colloidal suspensions were prepared by mixing highly monodisperse Au and Ag nanocolloids. The plasmon band of these mixtures was found to be highly sensitive to Au:Ag concentration ratio and wavelength of the laser beam used in the ablation process. The Au:Ag mixture consists of almost spherical shaped nanostructures with a tendency to join with adjacent ones. The surface enhanced Raman scattering activity of the Au, Ag and Au:Ag colloidal suspensions was tested using crystal violet as probe molecules. Enhancement in Raman signal obtained with Au:Ag substrates was found to be promising and strongly depends on its plasmon characteristics.

Scientific research involving nanotechnology has grown exponentially and has led to the development of engineered nanoparticles (NPs). Silica NPs have been used in numerous scientific and technological applications over the past decade, necessitating the development of efficient methods for their synthesis. Recent studies have explored the potential of laser ablation as a convenient way to prepare metal and oxide NPs. Due to its high silica content, low cost, and widespread availability, sugarbeet bagasse is highly suitable as a raw material for producing silica NPs via laser ablation. In this study, two different NP production methods were investigated: laser ablation and NaOH treatment. We developed a novel, one-step method to produce silica NPs from sugarbeet bagasse using laser ablation, and we characterized the silica NPs using environmental scanning electron microscopy (ESEM), energy dispersive spectrometry (EDS), dynamic light scattering (DIS), transmission electron microscopy (TEM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. EDS analysis and XPS confirmed the presence of silica NPs. The NPs produced by laser ablation were smaller (38-190 nm) than those produced by NaOH treatment (531-825 nm). Finally, we demonstrated positive effects of silica NPs produced from laser ablation on the growth of microalgae, and thus, our novel method may be beneficial as an environmentally friendly procedure to produce NPs. (C) 2014 Published by Elsevier B.V.

The production of nanohybrids formed by oxidized multiwalled carbon nanotubes (MWCNTs) and nanoparticles, produced by pulsed laser ablation in liquids process, is described. The use of linkers, obtained by transformation of pyrene-1-butanol, is mandatory to generate an efficient and stable interaction between the two components. Transmission electron microscopy and X-ray photoelectron spectroscopy analysis showed the obtainment of the efficient coverage of the MWCNTs by nanoparticles composed by metal gold and, partially, by oxides.

Palladium nanoparticles are receiving important interest due to its application as catalyst. In this work Pd nanoparticles have been obtained by ablating a Pd target submerged in de-ionized using both, pulsed as well as continuous wave (CW) laser. The influence of laser parameters involved in the formation in nanoparticles has been studied. Crystalline phases, morphology and optical properties of the obtained colloidal nanoparticles were characterized by means of transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and UV/vis absorption spectroscopy. The obtained colloidal suspensions consisted of pure Pd nanoparticles showing spherical shape with diameters ranging from few nanometers to 5–60 nm. The moderate irradiance delivered by the CW laser favours high production of uniform nanoparticles.

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 3.6 nm. It was found that the bandgap of the nanoparticle was larger and the Ce 3+ 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 O 2 − ions have a lower coordination with Ce ions, resulting in removal of O atoms and reduction of Ce 4+ into Ce 3+ .

In this work, nanocomposites based on polyethylene oxide (PEO) and copper nanoparticles (CuNPs) for food packaging application were developed as new active packaging for fresh foodstuffs. Copper colloids were synthesized by femtosecond-pulsed laser ablation synthesis in solution (LASiS) using an organic environment, to ensure a good solubility of nanocolloids in polymeric solution. CuNPs were incorporated in a biodegradable polymer matrix for the preparation of composite films. Besides a deep morphological and spectroscopic characterization, bioactive ions release over time from composite thin films was studied by atomic absorption spectroscopy. Finally, in vivo tests on fresh-cut fruit were carried out to assess the effects of these nanocomposite systems on product quality. CuNPs-PEO composites were found effective to prevent quality decay of fruit salad. In particular, the active films allowed better preserving color and texture of fruit that remained acceptable for 3–4 days more than the control sample.

Crystalline molybdenum oxide nanoparticles (MoO3 NPs) were prepared by laser ablation synthesis in solution (LASiS). The resulting MoO3 NPs are water suspended with average size of 23 nm. Subsequently, in order to produce hole injection layers for solar cells, these nanoparticles were processed as thin films onto indium tin oxide (ITO)/glass substrate using ultrasonic spray deposition, which allows fast and uniform deposition in large areas with controllable thickness and low roughness; the water is removed by heating the substrate during the processing. Moreover, scanning electronic microscopy images pointed out that the bottom of the films is mainly composed of small nanoparticles. Thereafter, the optimized glass/ITO/MoO3NPs/PTB7:PC71BM/Ca/Al solar cells displayed open circuit voltage (Voc) of 0.75 V, short circuit current density (Jsc) of 13 mA/cm2, fill factor (FF) of 58% and power conversion efficiency of 5.7% under AM1.5 illumination, presenting increased stability when compared with devices having polymeric hole transporting layer. Since LASiS method does not require the use of organic precursors/solvents, it is a green route to produce MoO3 NPs. In addition, the ultrasonic spray deposition is a versatile method to achieve homogeneous and transparent thin films from water suspended nanoparticles. The organic solar cell response pointed out the potential use of these procedures to produce hole injection layers for photovoltaic devices.

Small Ni nanoparticles supported on silica nanoparticles were formed by pulsed laser ablation in liquid. Water dispersing surfactant-free silica particles was used here as a solvent, and a bulk Ni metal plate as a target. The nanoparticles formed by laser ablation in water were readily stabilized by the silica particles, whereas Ni nanoparticles prepared in water without silica were found to be precipitated a few hours after aggregation into 5–30 nm particles. The nanoparticles were characterized by TEM, dark-field STEM and optical absorption spectroscopy, which indicated that small 1–3 nm Ni nanoparticles were adsorbed on the surface of silica.

Here we report a study on the third-order nonlinear optical properties of a new class of phenylhydrazones and the influence of silver and gold metal nanoparticles on their nonlinear response. Metal nanoparticles were prepared by laser ablation method. Single beam Z-scan technique with a 7 ns, 10 Hz Nd: YAG laser pulses at 532 nm were employed for the measurements. The compounds exhibit well optical limiting properties. Hence, these compounds are a promising class of materials for the optical device applications.

Since last decade, Pulsed Laser Ablation in Liquid (PLAL) has become an increasingly important technique for the production of the nanoparticles (NPs) since it usually provides high purity nanoparticle systems. This paper reports on the production and fragmentation of titanium oxide TiO 2 nanoparticles by pulsed laser ablation of a titanium target immersed in Sodium Dodecyl Sulfate (SDS) solution using an ultrafast Ti:Sapphire laser. After the production of TiO 2 nanoparticles for 30 min of laser irradiation, second harmonics of the laser wavelength are re-applied for different energies (180,120, 60 µJ) to SDS solution containing TiO 2 colloids in order to fragment relatively large pieces to obtain smaller ones. It was found that size of nanoparticles after the treatment is independent of the initial characteristics of colloids, but depends strongly on laser parameters especially pulse energy and on the presence of chemically active species in the solution. It was reported that particle size and size distribution range can be decreased using second harmonics of Ti:Sapphire laser wavelengths by using different values of energy. Re-irradiation process at average energy value of 180 μJ decreased average particle size from 185 nm to 110 nm. Characterization of the NPs was studied by applying various techniques such as UV–visible (UV–vis.), Transmission Electron Microscope (TEM ) , Dynamic Light Scattering (DLS) and Fourier Transform Infra-Red (FTIR).

Spatially confined laser ablation of silver was used to form long-lived dense plasma for single-shot deposition of a nanoparticle film. The expansion of the ablation plume was restricted by placing a glass substrate at 50 μm from the silver target surface. Time-resolved optical emission spectroscopy showed that the confined plasma is sustained for longer time than for free ablation. A single laser shot is sufficient to produce a layer of silver nanoparticles on the substrate. In absorption the nanoparticle layer displays a surface plasmon resonance which is comparable to films made by conventional pulsed laser deposition in vacuum.

A study is presented of Au nanoparticles (NPs) created by nanosecond pulsed laser ablation of a solid target in double distilled water. The influence was examined of the laser wavelength on the size, shape and optical properties of the resulting NPs. Three different wavelengths: the fundamental (λ = 1064 nm), second (λSHG = 532) and third (λTHG = 355) harmonic of a Nd:YAG laser at the same fluence were utilized to produce various colloids. Ablation at the wavelength of 532 nm was investigated in more detail to reveal the influence of self-absorption by the already created NPs on their characteristics. The colloid produced was irradiated by λirrad = 532 nm (laser energy 40 mJ) at different times up to 25 min after the end of ablation. The initial structure of welded NPs forming wires was modified. Transmission electron microscopy and optical transmission measurements were used to evaluate the shape and size distribution of the NPs.

The generation of nanoparticles using pulsed laser ablation has inherent advantages compared to conventional methods, like the purity and stability of the fabricated nanoparticles, aerosols and colloids. This study addresses the influence of laser parameters such as laser fluence, laser wavelength as well as focusing condition of laser beam on the size and morphology of the gold nanoparticles prepared in de-ionized water by pulsed laser ablation. The optimum conditions at which gold nanoparticles are obtained with controllable average size have been reported as these parameters affected the size, distribution and absorbance spectrum. The effect of laser fluence was studied. The laser fluences were divided into three regions (low, middle and high). A noteworthy change was observed at each region. At low fluences, the size of the nanoparticles decreases as the fluence increases to a certain critical value after which the size of the nanoparticles increases as the fluence increases. Also a significant change in the size distribution of the gold nanoparticles was noticed during the variation of the focusing conditions at gold–water interface.

Size of nanoparticles is an important parameter for their applications. To develop the system for the on-line nanoparticle characterization during their production by a laser, the laser ablation chamber that allows measurement of the surface plasmon resonance spectra during nanoparticle generation process has been designed and fabricated. The mean diameter of nanoparticles was determined using their absorption spectra acquired in the real-time during the ablation experiments. The results were compared with the TEM images analysis and observed differences in size are discussed. The technique was applied to investigate the effect of additional laser irradiation on size distribution in gold colloids prepared by laser ablation in water and in aqueous glucose solution.

Pulsed laser ablation in liquid is an approach for micro-/nanostructure generation directly from bulk materials. It has grown rapidly as a research field of photochemistry and physical chemistry in the last decade, and represents a combinatorial library of constituents and interactions, but the understanding of this library is still insufficient. This review attempts to build up a comprehensive mechanistic scenario of pulsed laser ablation in liquid and illustrate the underlying principles to micro-/nanostructure generation. Various structures produced by this method have been summarized that provide prototypes for potential applications in sensing, optoelectronics, and biomedicine, etc.