Large area uniform femtosecond-laser-induced periodic surface structures fabricated on heated LiNbO3:Fe

The influence of laser fluences and scanning speeds on the morphologies of laser-induced periodic surface structures(LIPSS) on heated LiNbO3:Fe(1000○C) surfaces was investigated under femtosecond(fs) laser scanning irradiation. Laser fluence of 8.5 kJ/m2 and scanning speed of 1 mm/s were found to be optimum process parameters, and large-area fs-LIPSS on LiNbO3:Fe with an area of 8 mm×8 mm were fabricated with these parameters. The wettability of laser-textured LiNbO3:Fe changed to be hydrophilic, and the absorptance was improved substantially in the spectral range of 400-2000 nm. This technique is efficient, and environmentally friendly, which will attract tremendous interest in nano-photoelectron and nano-mechanics.

Conceptual Design of a Novel Nozzle Combined with a Clinical Proton Linac for Magnetically Focussed Minibeams

(1) Background: Proton minibeam radiation therapy (pMBRT) is a novel therapeutic approach with the potential to significantly increase normal tissue sparing while providing tumour control equivalent or superior to standard proton therapy. For reasons of efficiency, flexibility and minibeam quality, the optimal implementation of pMBRT should use magnetically focussed minibeams which, however, could not yet be generated in a clinical environment. In this study, we evaluated our recently proposed minibeam nozzle together with a new clinical proton linac as a potential implementation. (2) Methods: Monte Carlo simulations were performed to determine under which conditions minibeams can be generated and to evaluate the robustness against focussing magnet errors. Moreover, an example of conventional pencil beam scanning irradiation was simulated. (3) Results: Excellent minibeam sizes between 0.6 and 0.9 mm full width at half maximum could be obtained and a good tolerance to errors was observed. Furthermore, the delivery of a 10 cm × 10 cm field with pencil beams was demonstrated. (4) Conclusion: The combination of the new proton linac and minibeam nozzle could represent an optimal implementation of pMBRT by allowing the generation of magnetically focussed minibeams with clinically relevant parameters. It could furthermore be used for conventional pencil beam scanning.

Laser solid-phase synthesis of single-atom catalysts

Single-atom catalysts (SACs) with atomically dispersed catalytic sites have shown outstanding catalytic performance in a variety of reactions. However, the development of facile and high-yield techniques for the fabrication of SACs remains challenging. In this paper, we report a laser-induced solid-phase strategy for the synthesis of Pt SACs on graphene support. Simply by rapid laser scanning/irradiation of a freeze-dried electrochemical graphene oxide (EGO) film loaded with chloroplatinic acid (H2PtCl6), we enabled simultaneous pyrolysis of H2PtCl6 into SACs and reduction/graphitization of EGO into graphene. The rapid freezing of EGO hydrogel film infused with H2PtCl6 solution in liquid nitrogen and the subsequent ice sublimation by freeze-drying were essential to achieve the atomically dispersed Pt. Nanosecond pulsed infrared (IR; 1064 nm) and picosecond pulsed ultraviolet (UV; 355 nm) lasers were used to investigate the effects of laser wavelength and pulse duration on the SACs formation mechanism. The atomically dispersed Pt on graphene support exhibited a small overpotential of −42.3 mV at −10 mA cm−2 for hydrogen evolution reaction and a mass activity tenfold higher than that of the commercial Pt/C catalyst. This method is simple, fast and potentially versatile, and scalable for the mass production of SACs.

Polystyrene Thin Films Nanostructuring by UV Femtosecond Laser Beam: From One Spot to Large Surface

In this work, direct irradiation by a Ti:Sapphire (100 fs) femtosecond laser beam at third harmonic (266 nm), with a moderate repetition rate (50 and 1000 Hz), was used to create regular periodic nanostructures upon polystyrene (PS) thin films. Typical Low Spatial Frequency LIPSSs (LSFLs) were obtained for 50 Hz, as well as for 1 kHz, in cases of one spot zone, and also using a line scanning irradiation. Laser beam fluence, repetition rate, number of pulses (or irradiation time), and scan velocity were optimized to lead to the formation of various periodic nanostructures. It was found that the surface morphology of PS strongly depends on the accumulation of a high number of pulses (103 to 107 pulses) at low energy (1 to 20 µJ/pulse). Additionally, heating the substrate from room temperature up to 97 °C during the laser irradiation modified the ripples’ morphology, particularly their amplitude enhancement from 12 nm (RT) to 20 nm. Scanning electron microscopy and atomic force microscopy were used to image the morphological features of the surface structures. Laser-beam scanning at a chosen speed allowed for the generation of well-resolved ripples on the polymer film and homogeneity over a large area.

Sustainable Fabrication of Glass Nanostructures Using Infrared Transparent Mold Assisted by CO2 Laser Scanning Irradiation

Direct thermal imprinting of nanostructures on glass substrates is reliable when manufacturing net-shaped glass devices with various surface functions. However, several problems are recognized, including a long thermal cycle, tedious optimization, difficulties in ensuring high level replication fidelity, and unnecessary thermal deformation of the glass substrate. Here, we describe a more sustainable and energy efficient method for direct thermal imprinting of nanostructures onto glass substrates; we use silicon mold transparent to infrared between 2.5 and 25 μm in wavelength combined with CO2 laser scanning irradiation. The glass strongly absorbed the 10.6 μm wavelength irradiation, triggering substantial heating of a thin layer on the glass surface, which significantly enhanced the filling of pressed glass material into nanostructured silicon mold cavities. For comparison, we conducted conventional direct glass thermal imprinting experiments, further emphasizing the advantages of our new method, which outperformed conventional methods. The thermal mass cycle was shorter and the imprint pattern quality and yield, higher. Our method is sustainable, allowing more rapid scalable fabrication of glass nanostructures using less energy without sacrificing the quality and productivity of the fabricated devices.