Transition metal dichalcogenide nanospheres for high-refractive-index nanophotonics and biomedical theranostics

Abstract

Recent developments in the area of resonant dielectric nanostructures have created attractive opportunities for concentrating and manipulating light at the nanoscale and the establishment of the new exciting field of all-dielectric nanophotonics. Transition metal dichalcogenides (TMDCs) with nanopatterned surfaces are especially promising for these tasks. Still, the fabrication of these structures requires sophisticated lithographic processes, drastically complicating application prospects. To bridge this gap and broaden the application scope of TMDC nanomaterials, we report here femtosecond laser-ablative fabrication of water-dispersed spherical TMDC (MoS 2 and WS 2 ) nanoparticles (NPs) of variable size (5 to 250 nm). Such NPs demonstrate exciting optical and electronic properties inherited from TMDC crystals, due to preserved crystalline structure, which offers a unique combination of pronounced excitonic response and high refractive index value, making possible a strong concentration of electromagnetic field in the NPs. Furthermore, such NPs offer additional tunability due to hybridization between the Mie and excitonic resonances. Such properties bring to life a number of nontrivial effects, including enhanced photoabsorption and photothermal conversion. As an illustration, we demonstrate that the NPs exhibit a very strong photothermal response, much exceeding that of conventional dielectric nanoresonators based on Si. Being in a mobile colloidal state and exhibiting superior optical properties compared to other dielectric resonant structures, the synthesized TMDC NPs offer opportunities for the development of next-generation nanophotonic and nanotheranostic platforms, including photothermal therapy and multimodal bioimaging.

Tunable optical properties of transition metal dichalcogenide nanoparticles synthesized by femtosecond laser ablation and fragmentation

“…As a result, the obtained MoO 3− x NPs demonstrate more bright photothermal properties compared to MoS 2 NPs the similar properties of which are 2 times greater than for Si NPs conventionally used in theranostics. 45…”

“…12,33 It inspired researchers to shift their attention to their bulk counterparts 34 since they preserve the advantages of monolayers, namely, large optical constants, 6 an asymmetrical optical response, 23,35 and excitonic dielectric function, 36 thanks to weak vdW bonding between layers. As a result, layered materials have already demonstrated great results in subdiffractional guiding, 23,37 integrated circuits, 38 strong light-matter coupling, [39][40][41] resonance nonlinear processes, 28,42 polaritonic transport, 23,43 anisotropic metasurfaces, 31,44 and photothermal conversion, 45 especially, in the case of transition metal dichalcogenides (TMDCs). In addition, recent works 40,[45][46][47][48] establish the fabrication processes of TMDC nanostructures that are compatible with widespread complementary metal oxide technologies.…”

“…As a result, layered materials have already demonstrated great results in subdiffractional guiding, 23,37 integrated circuits, 38 strong light-matter coupling, [39][40][41] resonance nonlinear processes, 28,42 polaritonic transport, 23,43 anisotropic metasurfaces, 31,44 and photothermal conversion, 45 especially, in the case of transition metal dichalcogenides (TMDCs). In addition, recent works 40,[45][46][47][48] establish the fabrication processes of TMDC nanostructures that are compatible with widespread complementary metal oxide technologies. 49 In this regard, special attention should be devoted to the laser ablation method for the creation of spherical TMDC nanoparticles.…”

High-refractive index and mechanically cleavable non-van der Waals InGaS3

“…Although, its refractive index is only about ~18 % higher than of traditional TiO 2 41 , we show that InGaS 3 planar waveguides have by 55 % stronger field confinement achieved at 40 % lower thickness than TiO 2 waveguides. Hence, we expect that alldielectric nanostructures, such as waveguides 42 , Mie-resonance nanoparticles 43 , and subwavelength metasurfaces 44 based on InGaS 3 would benefit greatly from its higher refractive index. Additionally, it exhibits an out-of-plane optical anisotropy (Δn 0.1), in contrast to conventional high-refractive index materials, which may greatly extend its scope of applications.…”

Multigram-Scale Production of Hybrid Au-Si Nanomaterial by Laser Ablation in Liquid (LAL) for Temperature-Feedback Optical Nanosensing, Light-to-Heat Conversion, and Anticounterfeit Labeling

“…This provides a pathway for the preparation of nanomaterials with a wide range of morphologies, structures and compositions (including metastable and nonequilibrium phases) . Laser irradiation of LAL-generated dispersions can further expand the method functionality, allowing for the high-performance preparation of diverse hybrid nanomaterials for photovoltaics, , photothermal conversion, ,− catalysis, − nonlinear optics, sensing, − and medical applications. , …”