Unveiling Fundamentals of Multi-Beam Pulsed Laser Ablation in Liquids toward Scaling up Nanoparticle Production.

Pulsed laser ablation in liquids (PLAL) is a versatile technique to produce high-purity colloidal nanoparticles. Despite considerable recent progress in increasing the productivity of the technique, there is still significant demand for a practical, cost-effective method for upscaling PLAL synthesis. Here we employ and unveil the fundamentals of multi-beam (MB) PLAL. The MB-PLAL upscaling approach can bypass the cavitation bubble, the main limiting factor of PLAL efficiency, by splitting the laser beam into several beams using static diffractive optical elements (DOEs). A multimetallic high-entropy alloy CrFeCoNiMn was used as a model material and the productivity of its nanoparticles in the MB-PLAL setup was investigated and compared with that in the standard single-beam PLAL. We demonstrate that the proposed multi-beam method helps to bypass the cavitation bubble both temporally (lower pulse repetition rates can be used while keeping the optimum processing fluence) and spatially (lower beam scanning speeds are needed) and thus dramatically increases the nanoparticle yield. Time-resolved imaging of the cavitation bubble was performed to correlate the observed production efficiencies with the bubble bypassing. The results suggest that nanoparticle PLAL productivity at the level of g/h can be achieved by the proposed multi-beam strategy using compact kW-class lasers and simple inexpensive scanning systems.

Towards laser printing of magnetocaloric structures by inducing a magnetic phase transition in iron-rhodium nanoparticles.

The development of magnetocaloric materials represents an approach to enable efficient and environmentally friendly refrigeration. It is envisioned as a key technology to reduce CO2 emissions of air conditioning and cooling systems. Fe-Rh has been shown to be one of the best-suited materials in terms of heat exchange per material volume. However, the Fe-Rh magnetocaloric response depends on its composition. Hence, the adaptation of material processing routes that preserve the Fe-Rh magnetocaloric response in the generated structures is a fundamental step towards the industrial development of this cooling technology. To address this challenge, the temperature-dependent properties of laser synthesized Fe-Rh nanoparticles and the laser printing of Fe-Rh nanoparticle inks are studied to generate 2D magnetocaloric structures that are potentially interesting for applications such as waste heat management of compact electrical appliances or thermal diodes, switches, and printable magnetocaloric media. The magnetization and temperature dependence of the ink's γ-FeRh to B2-FeRh magnetic transition is analyzed throughout the complete process, finding a linear increase of the magnetization M (0.8 T, 300 K) up to 96 Am2/kg with ca. 90% of the γ-FeRh being transformed permanently into the B2-phase. In 2D structures, magnetization values of M (0.8 T, 300 K) ≈ 11 Am2/kg could be reached by laser sintering, yielding partial conversion to the B2-phase equivalent to long-time heating temperature of app. 600 K, via this treatment. Thus, the proposed procedure constitutes a robust route to achieve the generation of magnetocaloric structures.

Controlling the Oxidation of Magnetic and Electrically Conductive Solid-Solution Iron-Rhodium Nanoparticles Synthesized by Laser Ablation in Liquids.

This study focuses on the synthesis of FeRh nanoparticles via pulsed laser ablation in liquid and on controlling the oxidation of the synthesized nanoparticles. Formation of monomodal γ-FeRh nanoparticles was confirmed by transmission electron microscopy (TEM) and their composition confirmed by atom probe tomography (APT). For these particles, three major contributors to oxidation were analysed: (1) dissolved oxygen in the organic solvents, (2) the bound oxygen in the solvent and (3) oxygen in the atmosphere above the solvent. The decrease of oxidation for optimized ablation conditions was confirmed through energy-dispersive X-ray (EDX) and Mössbauer spectroscopy. Furthermore, the time dependence of oxidation was monitored for dried FeRh nanoparticles powders using ferromagnetic resonance spectroscopy (FMR). By magnetophoretic separation, B2-FeRh nanoparticles could be extracted from the solution and characteristic differences of nanostrand formation between γ-FeRh and B2-FeRh nanoparticles were observed.

Atrofia multisistémica. Presentación de un caso / Multiple system atrophy. A case report

Fundamento: La atrofia multisistémica es un trastorno neurodegenerativo esporádico, que puede comenzar alrededor de los 60 años y ocasiona invalidez progresiva hasta la dependencia total de un cuidador. Presentación de caso: Se presenta el caso de un hombre de 57 años de edad que comenzó con cuadros de inestabilidad para la marcha y torpeza para realizar las actividades cotidianas y se interpretó como una enfermedad de Parkinson con pobre respuesta a la levodopa con bencerazida. Durante su estudio agravó los síntomas neurológicos y al realizar una tomografía axial computarizada de cráneo se evidenció atrofia cerebelosa y frontal que apoyó el diagnóstico de una atrofia multisistémica tipo C. Recibió tratamiento con levodopa con bencerazida, amantadina, y hubo alivio sintomático de la hipotensión ortostática. Conclusiones: El diagnóstico precoz de la enfermedad se dificultó por su comienzo similar a otras enfermedades neurodegenerativas, y su evolución ocasionó pérdida progresiva del validismo del paciente, sin que el tratamiento modificara el curso de la misma.

Background: The multiple system atrophy is a sporadic neurodegenerative disorder that may begin around age 60 and causes progressive disability to total dependence on a caregiver. Case report: A case presentation of a 57 year-old man who started with signs of unsteady gait and clumsiness in performing daily activities and which was interpreted as Parkinson's disease with poor response to levodopa with benserazide. During his study the patient showed worsening neurological symptoms and a computerized tomography of the skull was performed corroborating head and front cerebellar atrophy which supported the diagnosis of multiple system atrophy type C. He received treatment with levodopa together benserazide, and amantadine and a symptomatic relief of orthostatic hypotension was observed. Conclusions: Early diagnosis of the disease was hindered by its similar onset to other neurodegenerative diseases and its evolution caused progressive loss of the patient´s walking ability and the treatment did not modify the course of the disease.