Study on the productivity of silicon nanoparticles by picosecond laser ablation in water: towards gram per hour yield

An investigation on the productivity of silicon nanoparticles by picosecond laser ablation in water is presented. A systematic experimental study is performed as function of the laser wave length, fluence and ablation time. In case of ablation at 1064 nm silicon nanoparticles with a mean diameter of 40 nm are produced. Instead, ablation at 355 nm results in nanoparticles with a mean diameter of 9 nm for short ablation time while the mean diameter decreases to 3 nm at longer ablation time. An original model based on the in-situ ablation/photo-fragmentation physical process is developed, and it very well explains the experimental productivity findings. There ported phenomenological model has a general validity, and it can be applied to analyze pulsed laser ablation in liquid in order to optimize the process parameters for higher productivity. Finally, an outlook is given towards gram per hour yield of ultra-small silicon nanoparticles. (C) 2014 Optical Society of Americ

Luminescent silicon nanoparticles prepared by ultra short pulsed laser ablation in liquid for imaging applications

Heavy-metal-free semiconductor material like Silicon Nanoparticle (Si-NPs) is attracting scientists because of their diverse applications in biomedical field. In this work, pulsed laser ablation of silicon in aqueous solution is employed to generate Si-NPs in one step avoiding use of chemical precursors. Characterization by absorption, electron and photoluminescence analysis proves the generation of luminescent Si-NPs. The productivity rate of Si-NPs is investigated by Inductively Coupled Plasma Spectrometry. Furthermore, Si-NPs quantum yield and confocal microscopy studies corroborate the potential use of these biocompatible Si-NPs for imaging applications

Laser assisted synthesis of carbon nanoparticles with controlled viscosities for printing applications

High-quality carbon nanoparticles with controlled viscosity and high aqueous stability were prepared by liquid-phase laser ablation of a graphite target in deionized water. The size distribution was found to vary from 5 nm to 50 nm with mean size of 18 nm, in the absence of any reducing chemical reagents. Efficient generation of short chain polyynes was recorded for high laser repetition rates. Homogeneous and stable nanoparticle suspensions with viscosities ranging from 0.89 to 12 mPa.s were obtained by suspending the nanoparticles in different solvent mixtures such as glycerol–water and isopropanol–water. Optical properties were investigated by absorption and photoluminescence spectroscopy. Raman spectroscopy confirmed graphitic-like structure of nanoparticles and the surface chemistry was revealed by Fourier-transform infrared spectroscopy demonstrating sufficient electrostatic stabilization to avoid particle coagulation or flocculation. This paper present an exciting alternative method to engineer carbon nanoparticles and their potential use as a ligand-free nano-ink for ink jet printing (jetting) applications

Influence of organic solvent on optical and structural properties of ultra-small silicon dots synthesized by UV laser ablation in liquid

Ultra small silicon nanoparticles (Si-NPs) with narrow size distribution are prepared in a one step process by UV picosecond laser ablation of silicon bulk in liquid. Characterization by electron microscopy and absorption spectroscopy proves Si-NPs generation with an average size of 2 nm resulting from an in situ photofragmentation effect. In this context, the current work aims to explore the liquid medium (water and toluene) effect on the Si-NPs structure and on the optical properties of the colloidal solution. Si-NPs with high pressure structure (s.g. Fm3m) and diamond-like structure (s.g. Fd3m), in water, and SiC moissanite 3C phase (s.g. F3m) in toluene are revealed by the means of High-Resolution TEM and HAADF-STEM measurements. Optical investigations show that water-synthesized Si-NPs have blue-green photoluminescence emission characterized by signal modulation at a frequency of 673 cm−1 related to electron–phonon coupling. The synthesis in toluene leads to generation of Si-NPs embedded in the graphitic carbon–polymer composite which has intrinsic optical properties at the origin of the optical absorption and luminescence of the obtained colloidal solution

Taguchi method modelling of Nd:YAG laser ablation of microchannels on cyclic olefin polymer film

This paper presents the development of a model for Nd:YAG laser ablation of cyclic olefin polymer (COP) films. Two Taguchi orthogonal array experimental designs were implemented to produce a model for the prediction of microchannel depth and width produced on ZeonorFilm® ZF14 and ZF16 polymer films via laser ablation. The width and depth of the produced microchannels were measured using 3D optical profilometry. Microchannels produced were seen to range in depth of up to 50 µm, and widths of 112 µm via single-pass laser depending on the grade of COP, with feature size increasing as the number of laser passes increased. The models are discussed in terms of adjusted coefficient of determination, signal to noise ratio and model significance. The effect of the process parameters used such as fluence and scan speed on three different grades of COP was examined with an aim to produce a simple model suitable for predictive control of surface microstructuring of COP

In vitro fibroblast and pre-osteoblastic cellular responses on laser surface modified Ti–6Al–4V

The success of any implant, dental or orthopaedic, is driven by the interaction of implant material with the surrounding tissue. In this context, the nature of the implant surface plays a direct role in determining the long term stability as physico-chemical properties of the surface affect cellular attachment, expression of proteins, and finally osseointegration. Thus to enhance the degree of integration of the implant into the host tissue, various surface modification techniques are employed. In this work, laser surface melting of titanium alloy Ti–6Al–4V was carried out using a CO2 laser with an argon gas atmosphere. Investigations were carried out to study the influence of laser surface modification on the biocompatibility of Ti–6Al–4V alloy implant material. Surface roughness, microhardness, and phase development were recorded. Initial knowledge of these effects on biocompatibility was gained from examination of the response of fibroblast cell lines, which was followed by examination of the response of osteoblast cell lines which is relevant to the applications of this material in bone repair. Biocompatibility with these cell lines was analysed via Resazurin cell viability assay, DNA cell attachment assay, and alamarBlue metabolic activity assay. Laser treated surfaces were found to preferentially promote cell attachment, higher levels of proliferation, and enhanced bioactivity when compared to untreated control samples. These results demonstrate the tremendous potential of this laser surface melting treatment to significantly improve the biocompatibility of titanium implants in vivo

Growth and reproduction of the earthworm Eisenia fetida after exposure to leachate from wood preservatives

Wood preserved with chromated copper arsenate (CCA) and alkaline copper quaternary (ACQ) was mixed with artificial rainwater, to generate leachates containing As, Cr and Cu. Then, leachates were applied to two soils at rates of 13\ufffd169 mg As kg-1 soil (dry weight basis), 12\ufffd151 mg Cr kg-1 and 10\ufffd216 mg Cu kg-1. Metal bioavailability was evaluated after 28 days using the earthworm Eisenia fetida (Savigny). Metal concentrations in earthworm tissue ranged from negligible to 80 mg As kg-1 (dry weight basis), 89 mg Cr kg-1 and 90 mg Cu kg-1, which appeared to be non-lethal to E. fetida. There was less Cu available to earthworms in the Courval soil (pH 7.8) than the Ch\ufffdteauguay soil (pH 6.8), but earthworm previous termgrowth and reproductionnext term were not affected by exposure to Cu from ACQ-treated wood. In contrast, earthworms exposed to As, Cr and Cu from the CCA-treated wood gained weight more quickly in the Courval soil (1.3\ufffd21 mg g-1 initial biomass days) than in the Ch\ufffdteauguay soil (0.2\ufffd7.8 mg g-1 day-1), but fewer than 20% of the cocoons deposited by the faster-growing earthworms hatched by the end of the 56 days ecotoxicology test. It appeared that E. fetida can allocate more energy to previous termgrowth than reproduction,next term delaying cocoon development and hatching in some situations. Further information is needed on the soil factors that may induce such behavior, as it can affect the interpretation of results from the earthworm ecotoxicology test.NRC publication: Ye

Anaerobic and aerobic/anaerobic treatment for tetrachloroethylene (PCE)

NRC publication: Ye

An improved and simplified method for the large-scale purification of pediocin PA-1 produced by Pediococcus acidilactici

NRC publication: Ye

Kinugasa reactions in water: From green chemistry to bioorthogonal labelling

The Kinugasa reaction has become an efficient method for the direct synthesis of \u3b2-lactams from substituted nitrones and copper(I) acetylides. In recent years, the reaction scope has been expanded to include the use of water as the solvent, and with micelle-promoted [3+2] cycloadditions followed by rearrangement furnishing high yields of \u3b2-lactams. The high yields of stable products under aqueous conditions render the modified Kinugasa reaction amenable to metabolic labelling and bioorthogonal applications. Herein, the development of methods for use of the Kinugasa reaction in aqueous media is reviewed, with emphasis on its potential use as a bioorthogonal coupling strategy.Peer reviewed: YesNRC publication: Ye