GaNO colloidal nanoparticles synthesis by nanosecond pulsed laser ablation: Laser fluence dependent optical absorption and structural properties

Synthesis of Silicon and Germanium Oxide Nanostructures via Photonic Curing; a Facile Approach to Scale Up Fabrication

Silicon and Germanium oxide (SiOx and GeOx ) nanostructures are promising materials for energy storage applications due to their potentially high energy density, large lithiation capacity (~10X carbon), low toxicity, low cost, and high thermal stability. This work reports a unique approach to achieving controlled synthesis of SiOx and GeOx nanostructures via photonic curing. Unlike conventional methods like rapid thermal annealing, quenching during pulsed photonic curing occurs rapidly (sub-millisecond), allowing the trapping of metastable states to form unique phases and nanostructures. We explored the possible underlying mechanism of photonic curing by incorporating laws of photophysics, photochemistry, and simulated temperature profile of thin film. The results show that photonic curing of spray coated 0.1 M molarity Si and Ge Acetyl Acetate precursor solution, at total fluence 80 J cm-2 can yield GeOx and SiOx nanostructures. The as-synthesized nanostructures are ester functionalized due to photoinitiated chemical reactions in thin film during photonic curing. Results also showed that nanoparticle size changes from ~48 nm to ~11 nm if overall fluence is increased by increasing the number of pulses. These results are an important contribution towards large-scale synthesis of the Ge and Si oxide nanostructured materials which is necessary for next-generation energy storage devices.

Influence of Laser Process Parameters, Liquid Medium, and External Field on the Synthesis of Colloidal Metal Nanoparticles Using Pulsed Laser Ablation in Liquid: A Review

Pulsed laser ablation in liquid, used for nanoparticle synthesis from solid bulk metal targets (a top-down approach), has been a hot topic of research in the past few decades. It is a highly efficient and ‘green’ fabrication method for producing pure, stable, non-toxic (ligand-free), colloidal nanoparticles, which is often challenging using traditional chemical methods. Due to the short time scale interaction between the laser pulses and the target, it is difficult to achieve complete control on the physical characteristics of metallic nanoparticles. Laser process parameters, liquid environment, and external fields vastly effect the shape and structure of nanoparticles for targeted applications. Past reviews on pulsed laser ablation have focused extensively on synthesising different materials using this technique but little attention has been given to explaining the dependency aspect of the process parameters in fine-tuning the nanoparticle characteristics. In this study, we reviewed the state of the art literature available on this technique, which can help the scientific community develop a comprehensive understanding with special insights into the laser ablation mechanism. We further examined the importance of these process parameters in improving the ablation rate and productivity and analysed the morphology, size distribution, and structure of the obtained nanoparticles. Finally, the challenges faced in nanoparticle research and prospects are presented.

Room-Temperature Laser Synthesis in Liquid of Oxide, Metal-Oxide Core-Shells, and Doped Oxide Nanoparticles

Although oxide nanoparticles are ubiquitous in science and technology, a multitude of compositions, phases, structures, and doping levels exist, each one requiring a variety of conditions for their synthesis and modification. Besides, experimental procedures are frequently dominated by high temperatures or pressures and by chemical contaminants or waste. In recent years, laser synthesis of colloids emerged as a versatile approach to access a library of clean oxide nanoparticles relying on only four main strategies running at room temperature and ambient pressure: laser ablation in liquid, laser fragmentation in liquid, laser melting in liquid and laser defect-engineering in liquid. Here, established laser-based methodologies are reviewed through the presentation of a panorama of oxide nanoparticles which include pure oxidic phases, as well as unconventional structures like defective or doped oxides, non-equilibrium compounds, metal-oxide core-shells and other anisotropic morphologies. So far, these materials showed several useful properties that are discussed with special emphasis on catalytic, biomedical and optical application. Yet, given the endless number of mixed compounds accessible by the laser-assisted methodologies, there is still a lot of room to expand the library of nano-crystals and to refine the control over products as well as to improve the understanding of the whole process of nanoparticle formation. To that end, this review aims to identify the perspectives and unique opportunities of laser-based synthesis and processing of colloids for future studies of oxide nanomaterial-oriented sciences.

Evolution of Nonlinear Optical Characteristics of Magnetic Nanoparticle Colloidal Suspensions after Laser-Induced Clusters

In this paper, the nonlinear optical properties of magnetic nanoparticle colloidal solutions were studied by the Z-scan technique using 25 ps laser pulses at a wavelength of 1064 nm. Our results reveal that the formed magnetic nanoparticle clusters under high incident laser intensity will greatly affect the nonlinear optical characteristics of the solution. As the intensity of the pulsed laser decreases, the reverse saturable absorption coefficient and nonlinear refractive index of the sample tend to increase. The evolution of this nonlinear characteristic only occurs in liquid suspension. This is confirmed by fixing particles on a substrate upon which the responses observed in the liquid medium are no longer present. Besides, the possibility of generating optical trapping in the focus of the laser pulses is proposed to explain our experimental results.