No abstract

Polymer nanocomposites containing noble metal nanoparticles are promising materials for plasmonic applications. In this paper, we report on a high-resolution negative-tone nanocomposite resist based on poly(vinyl alcohol) where silver nanoparticles and nanopatterns are simultaneously generated by electron-beam lithography. Our results indicate nanostructures with a relatively high concentration of nanoparticles and, consequently, an electromagnetic coupling among the nanoparticles. Therefore, the patternable nanocomposite described in this work may be a suitable material for future plasmonic circuitry.

Optical probes operating in the second near-infrared window (NIR-II, 1,000-1,700 nm), where tissues are highly transparent, have expanded the applicability of fluorescence in the biomedical field. NIR-II fluorescence enables deep-tissue imaging with micrometric resolution in animal models, but is limited by the low brightness of NIR-II probes, which prevents imaging at low excitation intensities and fluorophore concentrations. Here, we present a new generation of probes (Ag 2 S superdots) derived from chemically synthesized Ag 2 S dots, on which a protective shell is grown by femtosecond laser irradiation. This shell reduces the structural defects, causing an 80-fold enhancement of the quantum yield. PEGylated Ag 2 S superdots enable deep-tissue in vivo imaging at low excitation intensities (<10 mW cm −2) and doses (<0.5 mg kg −1), emerging as unrivaled contrast agents for NIR-II preclinical bioimaging. These results establish an approach for developing superbright NIR-II contrast agents based on the synergy between chemical synthesis and ultrafast laser processing.

In this work, a method for the rapid synthesis of metallic microtracks on polyetherimide is presented. The method relies on the photosynthesis of silver nanoparticles on the surface of the polymer substrates from photosensitive silver chloride (AgCl), which is synthesized directly on the polyetherimide surface. The study reveals that the use of AgCl as a photosensitive intermediate accelerates the reactions leading to the formation of silver nanoparticles by up to two orders of magnitude faster than other photodecomposition schemes. The patterning can be conducted under blue light, with notable advantages over UV exposure. Polymers of significant interest to the microelectronics and 3D printing industries can be directly patterned by light using this photography-inspired technique at throughputs high enough to be commercially advantageous. Light exposures as short as a few seconds are sufficient to allow the direct metallization of the illuminated polyetherimide surface. The results show that the silver required for the seed layer is minimal, and the later copper electroless plating results in the selective growth of conductive tracks for circuitry on the light-patterned areas, both on flexible films and 3D printed surfaces. direct metallization [4] of modified photoresists, [5] which has the advantage that it can be directly patterned by UV photolithography [6] without vacuum process steps for the metal deposition. DOIThe metallization of polyimides has received particular attention, due to their mechanical strength, biocompatibility, chemical resistance, and ability to withstand high temperatures. Different approaches have been followed to achieve this metallization, such as embedding silver nanowires, [7] decomposing metalorganic compounds [8] or the activation of a palladium seed layer for future plating. [9] One proposed methodology for the fabrication of metallic tracks on polyimides is surface modification by ion exchange and subsequent plating. [10] This method has the advantage of avoiding any vacuum processing steps. Moreover, the organometallic bonds can be selectively broken by irradiation, enabling direct light patterning. Finally, the use of a photoresist acting as a mold for electroplating can be removed from the manufacturing process. The nanoparticles (NPs) resulting from the photoreduction of the free metallic ions can then be used as seeds for subsequent plating. This also permits patterning by direct laser writing, [11] which could accommodate the selective plating of contoured, 3D surfaces.This manufacturing process has a plethora of advantages, but its industrial implementation has been held back as the photopatterning stage has been too slow to be implemented for mass production. Moreover, the exposure energy must be limited in order to avoid damage to the polymeric substrate. [12] These limitations have triggered a search for new processes in order to obtain faster nanoparticle formation.One approach has been to use assisted photoreduction of the metallic ions with a mild reducing agent [...

The upconversion photoluminescent quantum yield (PLQY) of erbium-doped hexagonal sodium yttrium fluoride (β-NaYF(4): 10% Er(3+) was measured under broadband excitation with full width half maxima ranging from 12 to 80 nm. A novel method was developed to increase the bandwidth of excitation, while remaining independent of power via normalization to the air mass 1.5 direct solar spectrum. The measurements reveal that by broadening the excitation spectrum a higher PLQY can be achieved at lower solar concentrations. The highest PLQY of 16.2 ± 0.5% was achieved at 2270 ± 100 mW mm(-2) and is the highest ever measured.