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Due to their high refractive index, record optical anisotropy and a set of excitonic transitions in visible range at a room temperature, transition metal dichalcogenides have gained much attention. Here, we adapted a femtosecond laser ablation for the synthesis of WSe2 nanoparticles (NPs) with diameters from 5 to 150 nm, which conserve the crystalline structure of the original bulk crystal. This method was chosen due to its inherently substrate-additive-free nature and a high output level. The obtained nanoparticles absorb light stronger than the bulk crystal thanks to the local field enhancement, and they have a much higher photothermal conversion than conventional Si nanospheres. The highly mobile colloidal state of produced NPs makes them flexible for further application-dependent manipulations, which we demonstrated by creating substrates for SERS sensors.

Transition metal dichalcogenides (TMDCs), particularly molybdenum disulfide (MoS2), have gained significant attention in the field of optoelectronics and photonics due to their unique electronic and optical properties. The integration of TMDCs with plasmonic materials allows to tailor the optical response and offers significant advantages for photonic applications. This study presents a novel approach to synthesize MoS2-Au nanocomposites utilizing femtosecond laser ablation in liquid to achieve tunable optical properties in the near-infrared (NIR) region. By adjusting ablation and fragmentation protocols, we successfully synthesize various core–shell and core–shell–satellite nanoparticle composites, such as MoS2/MoSxOy, MoSxOy/Au, and MoS2/MoSxOy/Au. UV-visible absorption spectroscopy unveils considerable changes in the optical response of the particles depending on the fabrication regime due to structural modifications. Hybrid nanoparticles exhibit enhanced photothermal properties when subjected to NIR-I laser irradiation, demonstrating potential benefits for selective photothermal therapy. Our findings underscore that the engineered nanocomposites not only facilitate green synthesis but also pave the way for tailored therapeutic applications, highlighting their role as promising candidates in the field of nanophotonics and cancer treatment.

The plasmonic sensors based on silver nanoparticles are limited in application due to their relatively fast degradation in the ambient atmosphere. The technology of ion-beam modification for the creation of monocrystalline silver nanoparticles (NPs) with stable plasmonic properties will expand the application of silver nanostructures. In the present study, highly-stable monocrystalline NPs were formed on the basis of a thin silver film by low-energy ion irradiation. Combined with lithography, this technique allows the creation of nanoparticle ensembles in variant forms. The characterization of the nanoparticles formed by ion-beam modification showed long-term outstanding for Ag nanoparticles stability of their plasmonic properties due to their monocrystalline structure. According to optical spectroscopy data, the reliable plasmonic properties in the ambient atmosphere are preserved for up to 39 days. The mapping of crystal violet dye via surface-enhanced Raman spectroscopy (SERS) revealed a strong amplification factor sustaining at least thrice as long as the one of similarly sized polycrystalline silver NPs formed by annealing. The plasmonic properties sustain more than a month of storage in the ambient atmosphere. Thus, ion-beam modification of silver film makes it possible to fabricate NPs with stable plasmonic properties and form clusters of NPs for sensor technology and SERS applications.

The features of polarization control of multiple multiresonances for quasi-trapped modes excited by synchronization of bianisotropic dipole responses in MoS2 disks with a hole are considered. Using numerical calculations with analytical multipole analysis, we showed that the presence of a strong optical anisotropy of MoS2 nanoparticles provides an additional degree of freedom and makes it possible to observe several resonances of electric and magnetic dipoles at once in a narrow spectral range. Based on the simulation results, we obtained the frequency dependences for the dipole polarizabilities of the MoS2 disk with a hole, which can be used to distinguish the contributions of the nonlocal and bianisotropic dipole responses and possessing several features in the near-infrared range. Using the polarizability spectra of single nanoparticles and applying the tuning strategy, the design of the MoS2 metasurface placed in air and supporting three resonances of quasi-trapped modes at once in a narrow spectral range was developed. One of these resonances corresponds to the telecom wavelength of about 1550 nm. The spectrum of light reflection for the MoS2 metasurface is characterized by three narrowband dips corresponding to the wavelengths of the quasi-trapped modes. It was shown that a change in the polarization of a wave normally incident on the metasurface to orthogonal one leads to a change in the type of bianisotropic response excited in each MoS2 disk and to the excitation of three other features in the reflection spectrum of the metasurface at wavelengths close to the initial values.

Photocatalytic CO2 reduction and the production of hydrogen are urgent tasks of green energy. One of the most studied semiconductor photocatalysts for this purpose is titanium dioxide. However, it has a number of fundamental limitations that do not allow its application for such tasks on an industrial scale. Another class of promising materials, which is being investigated very actively, are two-dimensional materials based on MXenes. In this work, we present the first results on photocatalytic hydrogen evolution and CO2 reduction using TiNbC/TiO2 heterostructures with TiNbC contents of 1, 5, and 10%. The approach to the creation of heterostructures proposed in this work may become a significant breakthrough in the search for new highly efficient systems for carbon dioxide reduction and hydrogen production.

Owing to a strong photothermal response in the near-IR spectral range and very low toxicity, titanium nitride (TiN) nanoparticles (NPs) synthesized by pulsed laser ablation in liquids (PLAL) present a novel appealing object for photo-induced therapy of cancer, but the properties of these NPs still require detailed investigation. Here, we have elaborated methods of femtosecond laser ablation from the TiN target in a variety of liquid solutions, including acetonitrile, dimethylformamide, acetone, water, and H2O2, to synthesize TiN NPs and clarify the effect of liquid type on the composition and properties of the formed NPs. The ablation in all solvents led to the formation of spherical NPs with a mean size depending on the liquid type, while the composition of the NPs ranged from partly oxidized TiN to almost pure TiO2, which conditioned variations of plasmonic peak in the region of relative tissue transparency (670–700 nm). The degree of NP oxidation depended on the solvent, with much stronger oxidation for NPs prepared in aqueous solutions (especially in H2O2), while the ablation in organic solvents resulted in a partial formation of titanium carbides as by-products. The obtained results contribute to better understanding of the processes in reactive PLAL and can be used to design TiN NPs with desired properties for biomedical applications.

SnS2 and SnSe2 have recently been shown to have a wide range of applications in photonic and optoelectronic devices. However, because of incomplete knowledge about their optical characteristics, the use of SnS2 and SnSe2 in optical engineering remains challenging. Here, we addressed this problem by establishing SnS2 and SnSe2 linear and nonlinear optical properties in the broad (300–3300 nm) spectral range. Coupled with the first-principle calculations, our experimental study unveiled the full dielectric tensor of SnS2 and SnSe2. Furthermore, we established that SnS2 is a promising material for visible high refractive index nanophotonics. Meanwhile, SnSe2 demonstrates a stronger nonlinear response compared with SnS2. Our results create a solid ground for current and next-generation SnS2- and SnSe2-based devices.

Graphene is a promising building block material for developing novel photonic and optoelectronic devices. Here, we report a comprehensive experimental study of chemical-vapor deposited (CVD) monolayer graphene’s optical properties on three different substrates for ultraviolet, visible, and near-infrared spectral ranges (from 240 to 1000 nm). Importantly, our ellipsometric measurements are free from the assumptions of additional nanometer-thick layers of water or other media. This issue is critical for practical applications since otherwise, these additional layers must be included in the design models of various graphene photonic, plasmonic, and optoelectronic devices. We observe a slight difference (not exceeding 5%) in the optical constants of graphene on different substrates. Further, the optical constants reported here are very close to those of graphite, which hints on their applicability to multilayer graphene structures. This work provides reliable data on monolayer graphene’s optical properties, which should be useful for modeling and designing photonic devices with graphene.

Two-dimensional layers of transition-metal dichalcogenides (TMDs) have been widely studied owing to their exciting potential for applications in advanced electronic and optoelectronic devices. Typically, monolayers of TMDs are produced either by mechanical exfoliation or chemical vapor deposition (CVD). While the former produces high-quality flakes with a size limited to a few micrometers, the latter gives large-area layers but with a nonuniform surface resulting from multiple defects and randomly oriented domains. The use of epitaxy growth can produce continuous, crystalline and uniform films with fewer defects. Here, we present a comprehensive study of the optical and structural properties of a single layer of MoS2 synthesized by molecular beam epitaxy (MBE) on a sapphire substrate. For optical characterization, we performed spectroscopic ellipsometry over a broad spectral range (from 250 to 1700 nm) under variable incident angles. The structural quality was assessed by optical microscopy, atomic force microscopy, scanning electron microscopy, and Raman spectroscopy through which we were able to confirm that our sample contains a single-atomic layer of MoS2 with a low number of defects. Raman and photoluminescence spectroscopies revealed that MBE-synthesized MoS2 layers exhibit a two-times higher quantum yield of photoluminescence along with lower photobleaching compared to CVD-grown MoS2, thus making it an attractive candidate for photonic applications.