Direct Femtosecond Laser Fabrication of Chemically Functionalized Ultra-Black Textures on Silicon for Sensing Applications

Abstract

Here, we present the single-step laser-assisted fabrication of anti-reflective hierarchical surface textures on silicon locally functionalized with a photoluminescent (PL) molecular nanolayer. Using femtosecond-laser ablation of commercial crystalline Si wafers placed under a layer of a solution containing rhodamine 6G (R6G) a triethoxysilyl derivative, we fabricated ordered arrays of microconical protrusions with self-organized nanoscale surface morphology. At the same time, the laser-induced temperature increase facilitated surface activation and local binding of the R6G derivative to the as-fabricated nanotextured surface. The produced dual-scale surface textures showed remarkable broadband (visible to near-IR) light-absorbing properties with an averaged reflectivity of around 1%, and the capping molecular nanolayer demonstrated a strongly enhanced PL yield. By performing a pH sensing test using the produced nanotextured substrate, we confirmed the retention of sensory properties of the molecules attached to the surface and validated the potential applicability of the high-performing liquid-assisted laser processing as a key technology for the development of innovative multifunctional sensing devices in which the textured substrate (e.g., ultra-black semiconductor) plays a dual role as a support and PL signal amplifier.

Noble-Metal Nanoparticle-Embedded Silicon Nanogratings via Single-Step Laser-Induced Periodic Surface Structuring

“…Specifically, for catalytic reactions driven by sunlight radiation, the realization of light-absorbing supports is highly demanded. Such "ultra-black" surfaces provide a convenient pathway to trap and enhance broadband optical radiation within the functional surface layer loaded with noble-metal NPs, facilitating their catalytic performance [21][22][23][24][25]. The mechanism is based on light localization by nanostructures made of dielectric and semiconductor materials characterized by rather low optical losses and high refractive index such as Si, Ge, TiO 2 , etc.…”

Light Harvesting Nanoprobe for Trace Detection of Hg2+ in Water

“…Microfluidic devices using optical sensors are characterized by a limit of detection (LOD), which is at least tenfold higher than the MPC values in drinking water recommended by WHO for the most toxic metals: Hg [ 3 ] and Pb [ 4 ]. Alternative ultrasensitive techniques such as surface-enhanced Raman scattering [ 5 , 6 , 7 , 8 ] or surface-enhanced fluorescence [ 9 , 10 , 11 , 12 ] allow for the determination of significantly lower analyte concentrations; however, they require powerful and expensive equipment, both for measurements and for the fabrication of nanostructured enhancing substrates, which limits the use of such sensors devices for monitoring water quality in problematic regions, as in the active gold mining and processing industry, for example.…”

Hierarchical Conical Metasurfaces as Ultra‐Broadband Perfect Absorbers from Visible to Far‐Infrared Regime

“…While the homogeneous hierarchical structures combine surface structures of multiple scales and types that exhibit diverse light responses, [18][19][20] has the potential to facilitate ultrabroadband and wide-angle absorption. According to the scales of the structures relative to various functions, the structures can be classified into three types.…”