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

Abstract

Here, we show that direct femtosecond laser nanostructuring of monocrystalline Si wafers in aqueous solutions containing noble-metal precursors (such as palladium dichloride, potassium hexachloroplatinate, and silver nitrate) allows for the creation of nanogratings decorated with mono- (Pd, Pt, and Ag) and bimetallic (Pd-Pt) nanoparticles (NPs). Multi-pulse femtosecond-laser exposure was found to drive periodically modulated ablation of the Si surface, while simultaneous thermal-induced reduction of the metal-containing acids and salts causes local surface morphology decoration with functional noble metal NPs. The orientation of the formed Si nanogratings with their nano-trenches decorated with noble-metal NPs can be controlled by the polarization direction of the incident laser beam, which was justified, for both linearly polarized Gaussian and radially (azimuthally) polarized vector beams. The produced hybrid NP-decorated Si nanogratings with a radially varying nano-trench orientation demonstrated anisotropic antireflection performance, as well as photocatalytic activity, probed by SERS tracing of the paraaminothiophenol-to-dimercaptoazobenzene transformation. The developed single-step maskless procedure of liquid-phase Si surface nanostructuring that proceeds simultaneously with the localized reduction of noble-metal precursors allows for the formation of hybrid Si nanogratings with controllable amounts of mono- and bimetallic NPs, paving the way toward applications in heterogeneous catalysis, optical detection, light harvesting, and sensing.

A Laser-Printed Surface-Enhanced Photoluminescence Sensor for the Sub-Nanomolar Optical Detection of Mercury in Water

“…The SEPL effect coming from the efficient light intensity localization by the laser-textured interface containing a light-emitting nano-layer of chemosensory molecules allowed us to reach the detection limit of mercury ions of 100 pM which is two orders of magnitude lower compared to this molecular probe's sensitivity in solution. The fabrication technique is upscalable, inexpensive, and flexible regarding the ability to control the surface nano-morphology of Si [23,27,[40][41][42], the amount and type of loading noble-metal nanoparticles [31,43,44], as well as the type of molecular probe. This opens up pathways for the on-demand development of various multi-functional chemosensing platforms with expanded functionality.…”

“…Inherently weak optical signals from quantum emitters can be empowered by placing them onto specially designed substrates via a phenomenon referred to as surfaceenhanced photoluminescence (SEPL). SEPL originates from the interaction between light, luminescent species, and optically resonant nanostructures made of plasmon-supporting noble metals [22] or high-index low-loss semiconductors (such as Si and Ge) [23][24][25][26][27]. This technique has received wide attention in recent years due to a significant improvement in sensing performance as a result of the ability to reliably detect an analytical signal from a small number of quantum emitters, which in some cases can give single-molecule sensitivity [28].…”

Femtosecond laser processing of silicon in liquid: diverse nanomorphologies and applications

“…Additionally, it is possible to sequentially or simultaneously deposit different noble-metal nanoparticles on a single substrate by replacing the functionalizing solution containing the corresponding metal salts in a liquid cell or by using a bimetallic solution, respectively. In work 32 , the simultaneous bimetallic deposition of Pd and Pt NPs is demonstrated, which is promising for heterogeneous catalysis. The sequential deposition of gold and silver nanoparticles also allows 33 for the excitation of plasmonic fields at the plasmon wavelength of each respective metal.…”