Duisburg-Essen, Germany. However, integration of the nanofunction into products is still limited due to drawbacks of gas phase and chemical synthesis methods regarding particle aggregation and contaminantion causing deactivation of the building blocks´surface. As an alternative synthesis route, nanoparticle generation by lasers in liquids has proven its capability to generate and conjugate totally ligand-free colloidal nanoparticle building blocks, recently started getting commercial.
Laser-material interactions for tailoring future applications
Recent studies highlight unique properties of laser-generated nanoparticles potentially harvested in real-world applications. In biomedical research, scale-up of the method is shown at the example of polymer matrix embedding, fabricating kilogram scale of polymer membrane nanocomposites essential in artificial lung implants. First in vivo studies with neural electrodes modified by ligand. Laser-generated monophasic gold-silver-alloy nanoparticles particularly profit from purity, which allows their application in biomedicine without cross effects.
This alloy reference material series represents a grayscale of toxicity, used to model unintended implant debris toxicity using a very sensitive biofunctional system: mammalian reproduction biology. The studies involve life cell imaging and intracellular quantification of single, 60 femtogram plasmonic nanoobjects. General Ref´s: Asahi, T. Applied Surface ScienceS.
Beilstein Journal of Nanotechnology 5 Journal of Biomedical Optics 15Nr.
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Journal of Physical Chemistry C19 Beilstein Journal of Nanotechnology6, C. CacciatoM. Zimbone, R. Cum să faci nims rapid, R. Carles, V. Privitera, M. Grimaldi Affiliations : G. Sanz, V. Sofia 64, Catania, Italy; G. Sofia 64, Catania, Italy; R.
Its main deficiency relies on the wide band gap, making it inefficient for solar-driven applications. Unfortunately, the commonly presented synthesis routes of black-TiO2 require high pressures of hydrogen up to 20 bar and long annealing treatments up to 15 days. Such conditions are clearly not suitable for low cost production.
In this work we present a new, versatile, industrially scalable and environmental friendly laser synthesis of black-TiOx nanostructured film that overcomes the above mentioned issues. We used a Q-switched Nd:Yag laser operating at nm in order to realize a nanostructured photochemical diode.
The device is composed by a titanium foil, sandwiched between a nanostructured titanate film TiOx and a layer of Pt nanoparticles PtNps. The black-TiOx film was obtained by ablating the Ti foil in pure water.
This structure exhibits a high photoactivity with a quantum efficiency of 0. We ascribe such high photo efficiency to both the presence of Pt nanoparticles on the rear side of the film, and the presence of surface states in amorphous hydrogenated TiOx layer.
Khan, M. Mujawar, T. Donnelly, N. McEvoy, G. Duesberg, J. Lunney Affiliations : T. In this novel technique a rotating Ag target is ablated, in flowing argon at atmospheric pressure, with a nm, 25 ns excimer laser.
The ablation plume is captured by the gas and forms a NP aerosol, which is carried to the substrate using unde puteți plăti bitcoins gas flow of 8 litres per min. The substrate was positioned at 5 — 20 mm from the ablation spot and the laser fluence and the number of laser shots was varied.
Silicon, quartz and glass substrates were used.
The NP size distribution was examined cel mai bun site forex online scanning electron microscopy. The distribution of Feret diameters ranged up to 50 nm, with a mean value of 11 nm, depending on the deposition conditions.
In optical absorption the as-deposited films showed the usual surface plasmon resonance SPR in the region - nm, with the strength of the resonance depending on the laser fluence, number of laser shots and the target-substrate distance. The as-deposited NP films were thermally annealed in argon, nitrogen, and hydrogen at °C, and in air for temperatures in the range - °C.
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For all gases annealing at °C leads to increase of the amplitude, and a decrease of the width, of the SPR, with annealing in air around °C showing the most pronounced effect. Annealing in air in the range — °C leads to a strong enhancement and cum să faci nims rapid red shift of the SPR, while temperatures in the range — °C leads to a blue shifted SPR with lower amplitude.
Annealing was found to lead to a significant enhancement of the detection sensitivity when the NP films are used as substrates for surface enhanced Raman spectroscopy SERS. Sánchez-Aké1, A. Canales1, J. Martínez1, T. García-Fernández2, M. Since these properties depend on their size, shape and their surrounding media, there is a great interest in developing methods able to produce NPs of low dimensions and size dispersion.
A suitable technique for the synthesis of metallic NPs is pulsed laser irradiation of thin films in which the irradiation converts metal films in nanoislands, beads or NPs. This technique can be applied at room temperature and atmospheric conditions and it is free of chemical wastes . In this work we study the formation of gold nanoparticles by laser irradiation of Au films of thickness up to 65 nm.
The irradiation was performed both at atmospheric pressure and in vacuum conditions in order to determine the background pressure effect. The influence of the film thickness and the laser fluence on the characteristics of the NPs was also studied. With the aim of better understanding the mechanisms involved during the NPs formation, the light of a stabilized HeNe, transmitted through the sample, was measured in real time .
The changes in the optical transmission signal of the films last for hundreds of microseconds after the laser pulse. It was found that both, the size and the size distribution of the NPs are smaller when irradiating in vacuum than at atmospheric pressure. Moreover, the influence of the laser fluence on the size of the NPs is less noticeable when the irradiation is performed in vacuum.
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Henley, M. Beliatis, V. Stolojan, S. Silva, "Laser implantation of plasmonic nanostructures into glass", Nanoscale 5, Peláez, T. Kuhn, C. Rodríguez, C. Afonso, "Dynamics of laser induced metal nanoparticle and pattern formation", Appl. Baraldi, S. Reynaud, A. Cazier, Y. Lefkir, N. Crespo-Monteiro, F. Vocanson, N. Lauras, F Saint-Etienne, France Resume : Laser-induced self-organization of matter is a guarantee of efficient and cost-effective processes.
Ultrafast laser-induced ripples at material surface are probably the most representative example of precise material patterning.
In addition, ultra-fast laser has also been successfully used to induce organization of metallic nanoparticles embedded in polymer films, which opened new ways to the fabrication of plasmonic nanostructures with tailored morphological and, thus, optical properties.
Our group have shown that cum să faci nims rapid of nanoparticles could be also obtained in the case of thin films loaded with metallic ions using CW lasers.
In particular, we have already demonstrated that one dimensional 1D metallic-nanoparticle grating-like structure can be obtained when an amorphous titania TiO2 thin film loaded with Ag salt, deposited on glass substrate, is illuminated with ArKr CW laser.
Such periodic structures can be produced with different wavelengths lying in the plasmon resonance of Ag nanoparticles, their period is a fraction of the laser wavelength and their orientation parallel to the laser polarization.
In this work, we use a similar approach to induce the formation of a two dimensional 2D grating-like structure. With the help of a solid state laser working at nm and of a half-wave plate to rotate the laser linear polarization, we first demonstrate our capability of producing 1D gratings with different orientations, and we explore the effect that the scan direction has on the quality of the grating itself. Then, we study the effect of exposing a same sample area to two consecutive illumination processes exhibiting perpendicular polarization orientations.
Scanning electron microscopy SEM is used to study the morphology of samples after laser exposure, while Raman spectroscopy is used to figure out any phase change in the TiO2 amorphous matrix. We thus present a very simple method to induce large-scale and long-range order 2D self-organization of Ag nanoparticles in TiO2 thin films, a composite with high potential in photochromic and photocatalytic applications.
Lenzner, L. Emmert, C. Rodriguez, S. Günster, D. Ristau, W. Rudolph Affiliations : M. Emmert; C. Rodriguez; W. Günster; D. Ristau: Laser Zentrum Hannover e.
The resulting material modifications incubation usually lower the ablation threshold. We introduce a generic incubation model and compare it to measurements done on a broad class of materials including metals and dielectrics, bulk surfaces and thin films. The model explains observed changes of the ablation threshold as a function of the laser repetition rate.
We discuss under which conditions the crater-size method to determine LIDTs can be applied in multi-pulse experiments and explain why a circular laser spot can produce an elliptical ablation crater. In the pre-ablation regime, a variety of nonlinear optical processes are excited by ultrashort laser pulses.
Laser and plasma processing for advanced applications in material science
The associated weak optical signals can be enhanced by many orders of magnitude if properly dimensioned stacks of films are used. We demonstrate a mirror consisting of an aperiodic sequence of hafnia and silica dielectric coatings that produces the third harmonic in reflection.
This frequency tripling mirror compensates globally the phase mismatch, makes use of local field enhancements, and takes advantage of the high laser damage thresholds of dielectric materials.