Highly controllable direct femtosecond laser writing of gold nanostructures on titanium dioxide surfaces

High-resolution in situ patterning of perovskite quantum dots via femtosecond laser direct writing

Colloidal quantum dots (QDs) have exhibited great potential for optoelectronic applications, including displays, lasers, anti-counterfeiting and information storage. However, the high-resolution patterning technique of QDs is still a challenge, while precise patterned QDs are of great value for practical applications. Here, a femtosecond laser direct writing strategy was demonstrated for the in situ fabrication of high-resolution-patterned perovskite quantum dots (PQDs) by the laser-induced Marangoni flow to aggregate and deposit the PQDs based on the opto-thermoelectric mechanism. By regulating the laser power and the exposure time, the minimum line width could reach 1.58 μm. Importantly, through the patterning of red, green and blue PQDs, the strategy exhibited the applicability in full-color PQD materials. Moreover, the deposited PQDs can preserve the original photophysical properties including photoluminescence spectra and excited state lifetime. The approach provides a strategy to fabricate high-resolution patterned PQDs in situ, which is a promising alternative in photonic applications including high-resolution displays and anti-counterfeiting.

From Complex Inorganic Oxides to Ag-Bi Nanoalloy: Synthesis by Femtosecond Laser Irradiation

Bimetallic nanoalloys with a wide variety of structures and compositions have been fabricated through many diverse techniques. Generally, various steps and chemicals are involved in their fabrication. In this study, the synthesis of Ag-Bi nanoalloys by femtosecond laser irradiation of an inorganic oxide Ag₂WO₄/NaBiO₃ target without any chemicals like reducing agents or solvent is presented. The interaction between these materials and the ultrashort pulse of light allows the migration of Ag and Bi atoms from the crystal lattice to the particles surfaces and then to the plasma plume, where the reduction of the positively charged Ag and Bi species in their respective metallic species takes place. Subsequently, the controlled nucleation and growth of the Ag-Bi alloyed nanoparticles occurs in situ during the irradiation process in air. Although at the bulk level, these elements are highly immiscible, it was experimentally demonstrated that at nanoscale, the Ag-Bi nanoalloy can assume a randomly mixed structure with up to 6 ± 1 atom % of Bi solubilized into the face-centered cubic structure of Ag. Furthermore, the Ag-Bi binary system possesses high antibacterial activity against Staphylococcus aureus (methicillin-resistant and methicilin-susceptible), which is interesting for potential antimicrobial applications, consequently increasing their range of applicability. The present results provide potential insights into the structures formed by the Ag-Bi systems at the nanoscale and reveal a new processing method where complex inorganic oxides can be used as precursors for the controlled synthesis of alloyed bimetallic nanoparticles.