Fabrication of conductive copper structures on the surface of various dielectric materials is quite important in many fields of science.

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.

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The present brief review focuses on the features of the Layer-by-Layer (LbL) synthesis of coatings containing hydroxyapatite nanoparticles and assesses their use in solving several biomedical problems. This work provides the state-of-art of this field. This method is based on the sequential chemical adsorption of reagents on the substrate surface that makes it possible to apply nanolayers of the specified composition on the surface of a wide range of substrates of complex shape, to control the thickness of the synthesized layers accurately at the nanometer level. It also enables the modification of surface characteristics, including roughness, hydrophilicity, and surface charge, and allows artificially constructed multilayers consisting of hybrid organic and inorganic substances to be obtained. The experimental material presented in the review demonstrates the effectiveness of LbL synthesis for creating new 3D scaffolds as bone substitutes, coatings on the surface of metal implants, and drug delivery systems. A promising direction for the development of LbL synthesis is the creation of methods that involve ion-substituted hydroxyapatites as reagents. Success in this area can pave the way for significant advances in biomedicine and open new opportunities for creating a new generation of structures that mimic the structural, compositional, and mechanical properties of the bone mineral phase.

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