Fabrication and deposition of copper and copper oxide nanoparticles by laser ablation in open air

The proximity of the “post-antibiotic era”, where infections and minor injuries could be a cause of death, there are urges to seek an alternative for the cure of infectious diseases. Copper nanoparticles and their huge potential as a bactericidal agent could be a solution. In this work, Cu and Cu oxide nanoparticles were synthesized by laser ablation in open air and in argon atmosphere using 532 and 1064 nm radiation generated by nanosecond and picosecond Nd:YVO4 lasers, respectively, to be directly deposited onto Ti substrates. Size, morphology, composition and the crystalline structure of the produced nanoparticles have been studied by the means of field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), the energy dispersive spectroscopy of X-rays (EDS), selected area electron diffraction (SAED) and X-ray diffraction (XRD). The UV-VIS absorbance of the thin layer of nanoparticles was also measured, and the antibacterial capacity of the obtained deposits tested against Staphylococcus aureus. The obtained deposits consisted of porous coatings composed of copper and copper oxide nanoparticles interconnected to form chain-like aggregates. The use of the argon atmosphere contributed to reduce significantly the formation of Cu oxide species. The synthesized and deposited nanoparticles exhibited an inhibitory effect upon S. aureus.Peer ReviewedPostprint (published version

Palladium nanoparticles synthesized by laser ablation in liquids for antimicrobial applications

Antibiotic resistance is a leading cause of death worldwide. In this paper, we explore new alternatives in the treatment of infections. Noble metal nanoparticles could help to mitigate this problem. In this work, palladium nanoparticles were synthesized by laser ablation in order to explore their antimicrobial capacity. To obtain palladium nanoparticles, a palladium plate immersed in water, or methanol, was ablated, using two pulsed lasers that emit radiation with wavelengths of 532 nm and 1064 nm, respectively. Pure Pd-NPs with crystalline microstructure and rounded shape were obtained. The nanoparticles’ size is more homogeneous if the laser wavelength is 532 nm, and it decreases when methanol is used as solvent, reaching mean diameters smaller than 6 nm. With the objective of studying antimicrobial activity against Staphylococcus aureus, the Pd-NPs were immobilized on the surface of titanium discs. The release of palladium ions was recorded during the first seven days, and the cytotoxicity of the immobilized NPs was also tested with L929 mouse fibroblast cell line. Palladium nanoparticles synthesized by means of the infrared laser in methanol showed a strong inhibitory effect on S. aureus and good cytocompatibility, with no toxic effect on fibroblast cells.Peer ReviewedPostprint (published version

Silver nanoparticles produced by laser ablation and re-irradiation are effective preventing peri-implantitis multispecies biofilm formation

Implant-associated infection due to biofilm formation is a growing problem. Given that silver nanoparticles (Ag-NPs) have shown antibacterial effects, our goal is to study their effect against multispecies biofilm involved in the development of peri-implantitis. To this purpose, Ag-NPs were synthesized by laser ablation in de-ionized water using two different lasers, leading to the production of colloidal suspensions. Subsequently, part of each suspension was subjected to irradiation one and three times with the same laser source with which it was obtained. Ag-NPs were immobilized on the surface of titanium discs and the resultant materials were compared with unmodified titanium coupons. Nanoparticles were physico-chemically analysed to determine their shape, crystallinity, chemical composition, and mean diameter. The materials were incubated for 90 min or 48 h, to evaluate bacterial adhesion or biofilm formation respectively with Staphylococcus aureus or oral mixed bacterial flora composed of Streptococcus oralis, Actinomyces naeslundii, Veionella dispar, and Porphyromonas gingivalis. Ag-NPs help prevent the formation of biofilms both by S. aureus and by mixed oral bacterial flora. Nanoparticles re-irradiated three times showed the biggest antimicrobial effects. Modifying dental implants in this way could prevent the development of peri-implantitis.Xunta de Galicia | Ref. ED431C 2019/23Ministerio de Ciencia e Innovación | Ref. PID2020-117900RB-I00Ministerio de Ciencia e Innovación | Ref. EQC2018-004315-PInterreg Atlantic Area | Ref. Bluehuman EAPA_151/201

Influence of laser texturing on the wettability of PTFE

Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer showing excellent thermal and electrical insulation properties and a low coefficient of friction. Due to its large stability, and hydrophobic nature, the wettability of PTFE surfaces can be reduced to transform them into superhydrophobic. In this regard, laser texturing is a fast, simple and versatile method to produce superhydrophobic PTFE surfaces in one-step, and over large areas. In this work, we used a CO2 laser to modify the surface of PTFE samples. We studied the effect of the processing parameters (laser power or irradiance, scanning speed, and spacing -overlapping- between scan lines) on the wettability of textured surfaces using water, mineral oil and ethanol/water solutions as test fluids. Laser-treated surfaces showed a hierarchical micro- and nanotopography with a cotton-like appearance. The higher roughness and large quantity of air pockets make these laser-treated surfaces superhydrophobic, and highly oleophobic. Furthermore, they remain unaltered after being in contact with strong alkali and acid solutions or after slight friction. The self-cleaning performance of these surfaces was also demonstrated. The present findings suggest that CO2 laser texturing of PTFE is suitable for the large-scale preparation of surfaces with low-wettability to different liquids.Agencia Estatal de Investigación | Ref. RTI2018-095490-J-I00Xunta de Galicia | Ref. ED431C 2019/23Xunta de Galicia | Ref. ED481D 2017/010Xunta de Galicia | Ref. ED481B 2016/047-0Xunta de Galicia | Ref. POS-A/2013/16

Re-irradiation of silver nanoparticles obtained by laser ablation in water and assessment of their antibacterial effect

The rapid evolution of resistant bacteria is a huge problem in medicine because makes the treatment of infections more and more difficult. The bactericidal properties of noble metal nanoparticles could be a solution. In this work silver nanoparticles were produced by using two nanosecond Nd:YVO4 lasers operating at 1064 and 532 nm respectively to ablate a silver target submerged in pure de-ionized water. Part of the resulting colloidal solution was injected as a fine stream by a compressed air system and re-irradiated one and three times with the same laser to resize and get uniform nanoparticles. The obtained nanoparticles by ablation and re-irradiation consisted of crystalline Ag nanoparticles with a bimodal size distribution. The particle size has been reduced by subsequent laser re-irradiation with both laser sources, reaching a 40% of mean size reduction. Inhibitory effects on the proliferation of Staphylococcus aureus was demonstrated on silver nanoparticles obtained after re-irradiation with the infrared laser.Postprint (author's final draft

Laser texturing to control the wettability of materials

Many applications of different materials are related to the properties of their surface. Wettability is a key property affecting applications in all fields: adhesives, lubricants, detergents, all types of coatings, implant integration, heat transmission, corrosion, etc. Laser texturing has been demonstrated to be an excellent technique to modify surface wettability of many different materials: polymers, metals, ceramics, or even natural stones. The relative simplicity and robustness of the results, together with the widespread availability of affordable industrial laser sources made laser texturing a very promising tool for modifying the surface of parts in manufacturing plants. In this paper we introduce the basics of the technique and show some examples of applications. On one hand, treating the surface of different polymers for biomedical applications. And on the other hand, the production of surfaces with extreme wettability properties is shown: superhydrophilic, superhydrophobic and omniphobic surfaces were obtained by laser texturing

Laser‐guided corrosion control: a new approach to tailor the degradation of Mg‐alloys

Despite corrosion being commonly seen as a problem to be avoided, applications such as batteries or biodegradable implants do benefit from corrosion‐like phenomena. However, current strategies address corrosion control from a global perspective for a whole component, without considering local adaptations to functionality specifications or inhomogeneous environments. Here, a novel concept is presented: the local control and guidance of corrosion through a laser surface treatment. Immersion tests in saline solution of AZ31 magnesium alloy samples show degradation rates reduced up to 15 times with the treatment, owing to a fast passivation after the induced microstructural modifications. By controlling the treatment conditions, the degradation can be restricted to delimited regions and driven towards specific directions. The applicability of the method for the design of tailored degradation biomedical implants is demonstrated and uses for cathodic protection systems and batteries can also be anticipated.Xunta de Galicia | Ref. ED431C 2019/23Xunta de Galicia | Ref. ED481D 2017/010Xunta de Galicia | Ref. ED481B 2016/047‐0Xunta de Galicia | Ref. ED431B2017/65‐GPCAgencia Estatal de Investigación | Ref. RTI2018-095490-J-I00Agencia Estatal de Investigación | Ref. PID2019-111285RB-I0

Laser Synthesis of Nanomaterials

Nanomaterials, defined as materials with typical dimensions of less than 100 nm in at least one dimension, exhibit very special physicochemical properties that are highly dependent on their size and shape [...

Production of nanoparticles from natural hydroxylapatite by laser ablation

Laser ablation of solids in liquids technique has been used to obtain colloidal nanoparticles from biological hydroxylapatite using pulsed as well as a continuous wave (CW) laser. Transmission electron microscopy (TEM) measurements revealed the formation of spherical particles with size distribution ranging from few nanometers to hundred nanometers and irregular submicronic particles. High resolution TEM showed that particles obtained by the use of pulsed laser were crystalline, while those obtained by the use of CW laser were amorphous. The shape and size of particles are consistent with the explosive ejection as formation mechanism.Ministerio de Educación y Ciencia | Ref. MAT2006-10481Xunta de Galicia | Ref. INCITE08PXIB303225PRXunta de Galicia | Ref. INCITE09E2R303103E

Synthesis and deposition of silver nanoparticles on cp Ti by laser ablation in open air for antibacterial effect in dental implants

Silver nanoparticles have been synthetized and deposited on cp Ti substrates in one-step process by the use of laser ablation in open air. The nanoparticles are produced by ablating Ag foil using two different lasers and an inert gas jet oriented into the interaction zone to prevent oxidation and to direct the ablated material to the substrate. The HRTEM images and FFT confirmed the crystalline nature of the obtained silver nanoparticles with the presence of oxidized ones, while FE-SEM revealed that the nanoparticles were uniformly distributed on Ti substrates. The Ag-containing Ti substrates showed good antibacterial activity against Lactobacillus salivarius.Peer ReviewedPostprint (author's final draft