Ablation efficiency of gold at fs/ps laser treatment in water and air

A comparison of single-pulse laser ablation of gold target by pulses with a 0.3–10 ps duration and a wavelength of 515 nm in air and in water was performed. The radiation was focused on the sample surface through the objectives with numerical apertures NA = 0.65 and 0.25. The influence of the medium, pulse duration, and spot size on the crater morphology was studied. A significant difference in crater morphology was found for different lenses. The ablation efficiency was studied by measuring the profiles of single-shot pulse craters using scanning force microscopy. The contribution of filamentation to the ablation process is shown quantitatively.

Changes in the electrical conductivity of glass, quartz, Au, C, and MoS2 films under influence of continuous proton injection

Changes in the electrical conductivity of a wide range of materials with different crystal-chemical types and electrophysical properties (quartz, glass, molybdenum disulfide, graphite, gold) under continuous proton injection are studied. Film samples of layered MoS2 and graphite compounds were obtained on rough surfaces of glass or quartz by mechanical rubbing of powder. Gold films are formed on glass substrates by magnetron sputtering of a gold target. To create a continuous stream of protons injected into the test sample, a stationary ion source with a cold cathode and a magnetic field forming an ion beam of relatively low intensity was used. The current in the ion beam is up to 1.2 mA, the pressure of hydrogen in the chamber is ~10 – 2 Pa, the energy of hydrogen ions is from 1 to 4 keV. The experimental results indicate that under conditions of continuous proton injection, the electrical conductivity of thin films with a layered structure (MoS2 and graphite) increases sharply (by 4 – 5 orders of magnitude). This effect increases when the temperature decreases from ~ 293 to ~ 77 K, as well as when the number of charges supplied to the sample increases. In the case of continuous injection of protons into massive dielectrics (glass, quartz) and thin films of gold, no noticeable change in electrical conductivity was detected.

Formation of Periodic Nanoridge Patterns by Ultrashort Single Pulse UV Laser Irradiation of Gold

A direct comparison of simulation and experimental results of UV laser-induced surface nanostructuring of gold is presented. Theoretical simulations and experiments are performed on an identical spatial scale. The experimental results have been obtained by using a laser wavelength of 248 nm and a pulse length of 1.6 ps. A mask projection setup is applied to generate a spatially periodic intensity profile on a gold surface with a sinusoidal shape and periods of 270 nm, 350 nm, and 500 nm. The formation of structures at the surface upon single pulse irradiation is analyzed by scanning and transmission electron microscopy (SEM and TEM). For the simulations, a hybrid atomistic-continuum model capable of capturing the essential mechanisms responsible for the nanostructuring process is used to model the interaction of the laser pulse with the gold target and the subsequent time evolution of the system. The formation of narrow ridges composed of two colliding side walls is found in the simulation as well as in the experiment and the structures generated as a result of the material processing are categorized depending on the range of applied fluencies and periodicities.

Laser-Assisted Synthesis of Composite Nanoparticles of Perovskite BaTiO3 in Aqueous Solutions and Their Optical Properties

Experimental results are presented on laser-assisted synthesis of composite nanoparticles of perovskite BaTiO3 with gold nanoparticles using the technique of laser ablation in water and aqueous solution of hydrogen peroxide. Nanoparticles of BaTiO3 are generated by near IR laser radiation with pulse durations of 170 fs, 1 ps, and 200 ns. Nanoparticles of barium titanate BaTiO3 (BTO) have tetragonal structure for all used pulse durations. Two ways of synthesis are tested. In the first one a gold target is ablated in the colloidal solution of BaTiO3 nanoparticles. The second way consists of laser exposure of the mixture of colloidal solutions of nanoparticles of BaTiO3 and Au. Synthesized composite nanoparticles are characterized by optical spectroscopy, Raman spectroscopy, X-Ray diffractometry, and Transmission Electron Microscopy. Composite BaTiO3‑Au nanoparticles have the absorption band in the visible range of spectrum and demonstrate plasmonic luminescence.

MAP Kinases Pathways in Gastric Cancer

Gastric cancer (GC) is turning out today to be one of the most important welfare issues for both Asian and European countries. Indeed, while the vast majority of the disease burden is located in China and in Pacific and East Asia, GC in European countries still account for about 100,000 deaths per year. With this review article, we aim to focus the attention on one of the most complex cellular pathways involved in GC proliferation, invasion, migration, and metastasis: the MAP kinases. Such large kinases family is to date constantly studied, since their discovery more than 30 years ago, due to the important role that it plays in the regulation of physiological and pathological processes. Interactions with other cellular proteins as well as miRNAs and lncRNAs may modulate their expression influencing the cellular biological features. Here, we summarize the most important and recent studies involving MAPK in GC. At the same time, we need to underly that, differently from cancers arising from other tissues, where MAPK pathways seems to be a gold target for anticancer therapies, GC seems to be unique in any aspect. Our aim is to review the current knowledge in MAPK pathways alterations leading to GC, including H. pylori MAPK-triggering to derail from gastric normal epithelium to GC and to encourage researches involved in MAPK signal transduction, that seems to definitely sustain GC development.

INCLUSIVE PRODUCTION OF INTERMEDIATE MASS FRAGMENTS IN 20Ne+Ag,Au INTERACTIONS AT 20-60 MeV/nucleon

Energy spectra and angular distributions of intermediate mass fragments were measured at 20, 30, 40, 50 and 60 MeV/nucleon incident energies. Assuming two prevailing origins, fragmentation and evaporation (or fission), the measured energy spectra and angular distributions are reproduced by emission from two moving sources. The dependence of the parameters extracted for the sources on the fragment charge and on the incident energy is discussed. The distinctive role of fission in the case of the gold target is stressed. Xuclear fragmentation cross sections deduced from the moving source analysis are given and discussed for the two systems.

Gold Nanoparticles in Liquid Based on Photonic Crystal Fiber PCF for Sensors Application

The effect of laser wavelength on gold nanoparticle (Au NPs) fabrication is reported by using the laser ablation in the liquid method in the ethanol. The Pulsed Laser ablation in liquid technique of the gold target was ablated using an Nd:YAG laser nanopulsed nanosecond after that the investigation of the gold NPs was tested by the AFM (Atomic Force Microscopy), and the (XRD) X-ray diffraction. The results showed the characteristics of prepared NPs, depending on XRD, AFM. NPs obtained by 532 nm laser possess better properties than that achieved by 1064 nm laser according to the highest intensity of shorter wavelengths.