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The laser synthesis and processing of colloids represents a group of scalable and “green” synthesis methods of crystalline metal oxides, that have recently made encouraging progresses in preparing amorphous as well as defect-rich nanoparticles. The relevant conditions and mechanisms that allow the design of amorphous metal oxides (AMOs) remain unknown. Consequently, in this work the synthesis of Fe-based partially amorphous oxide nanoparticles (NPs) by pulsed laser ablation in water was studied. Furthermore, both laser pulse duration and the number of laser pulse in pulsed laser fragmentation in liquid (LFL) allow a precise control of amorphization of AMOs in water. Hereby, a high-fluence nanosecond-LFL provides a significantly higher amorphization rate, whereas picosecond-LFL always presents minor fractions of crystalline α-Fe even with a higher specific energy input and laser intensity. Consequently, the laser fluence required for the repeated melting and quenching of NP appears to be the decisive parameter to control amorphization. During laser synthesis and processing of colloids, the amorphization of AMOs appears to be linked to the apparent size reduction effect, while a complete full amorphization of AMOs may be attributed to the stronger oxidation effects. This work will stimulate future studies using laser-generated AMO NPs for further functional purposes.

Direct generation of gold nanoparticles on ITO glass using a nanosecond laser is presented and the electrochemical properties of the gold modified ITO electrodes for detection of the ascorbic acid are analyzed. Gold nanoparticles were generated by nanosecond laser pulse irradiation of thin, 3–30 nm thick, gold films. It was found that diameters and the number of generated nanoparticles per unit area strongly depends on the thickness of the gold film when it is less than 10 nm. Furthermore, experiments have shown that the influence of laser processing parameters (the laser pulse energy and pulse number) to the size, the distribution and the area density of generated gold nanoparticles on ITO glass is negligible. Characterization of the electrochemical properties of the gold modified ITO electrodes by nanosecond laser showed that the fabricated electrodes could be employed in electrochemical sensing. Therefore, the demonstrated generation of gold nanoparticles on ITO by using the nanosecond laser approach opens new opportunities for the development of highly sensitive and low-cost electrochemical sensors.

Pulsed laser melting in liquid (PLML) has emerged as a facile approach to synthesize submicron spheres (SMSs) for various applications. Typically lasers with long pulse durations in the nanosecond regime are used. However, recent findings show that during melting the energy absorbed by the particle will be dissipated promptly after laser-matter interaction following the temperature decrease within tens of nanoseconds and hence limiting the efficiency of longer pulse widths. Here, the feasibility to utilize a picosecond laser to synthesize Ge SMSs (200~1000 nm in diameter) is demonstrated by irradiating polydisperse Ge powders in water and isopropanol. Through analyzing the educt size dependent SMSs formation mechanism, we find that Ge powders (200~1000 nm) are directly transformed into SMSs during PLML via reshaping, while comparatively larger powders (1000~2000 nm) are split into daughter SMSs via liquid droplet bisection. Furthermore, the contribution of powders larger than 2000 nm and smaller than 200 nm to form SMSs is discussed. This work shows that compared to nanosecond lasers, picosecond lasers are also suitable to produce SMSs if the pulse duration is longer than the material electron-phonon coupling period to allow thermal relaxation.

Immune responses have to be tightly controlled to guarantee maintenance of immunological tolerance and efficient clearance of pathogens and tumorigenic cells without induction of unspecific side effects. CD4⁺ CD25⁺ regulatory T cells (Tregs) play an important role in these processes due to their immunosuppressive function. Genetic modification of Tregs would be helpful to understand which molecules and pathways are involved in their function, but currently available methods are limited by time, costs or efficacy. Here, we made use of biofunctionalized gold nanoparticles as non-viral carriers to transport genetic information into murine Tregs. Confocal microscopy and transmission electron microscopy revealed an efficient uptake of the bioconjugates by Tregs. Most importantly, coupling eGFP-siRNA to those particles resulted in a dose and time dependent reduction of up to 50% of eGFP expression in Tregs isolated from Foxp3eGFP reporter mice. Thus, gold particles represent a suitable carrier for efficient import of nucleic acids into murine CD4⁺ CD25⁺ Tregs, superior to electroporation.

This work highlights a strategy for the one-step synthesis of FeAu nanoparticles by the pulsed laser ablation of alloy targets in the presence of different solvents. This method allows particle generation without the use of additional chemicals; hence, solvent-metal interactions could be studied without cross effects from organic surface ligands. A detailed analysis of generated particles via transmission electron microscopy in combination with EDX elemental mapping could conclusively verify that the nature of the used solvent governs the internal phase structure of the formed nanoparticles. In the presence of acetone or methyl methacrylate, a gold shell covering a non-oxidized iron core was formed, whereas in aqueous media, an Au core with an Fe₃O₄ shell was generated. This core-shell morphology was the predominant species found in >90% of the examined nanoparticles. These findings indicate that fundamental chemical interactions between the nanoparticle surface and the solvent significantly contribute to phase segregation and elemental distribution in FeAu nanoparticles. A consecutive analysis of resulting Fe@Au core-shell nanoparticles revealed outstanding oxidation resistance and fair magnetic and optical properties. In particular, the combination of these features with high stability magnetism and plasmonics may create new opportunities for this hybrid material in imaging applications.