Two-dimensional metal-organic frameworks (MOFs) demonstrate the advantages of organo-inorganic nature such as operation efficiency, and stability for optical sensing. For achieving high selectivity and operational performance optical properties of MOFs nanosheets can be varied by choosing the metal centers and the linking ligands. According to 2D nature, the material could be exfoliated up to monolayer height, which drastically increases the effective surface area of the sensor. The existing challenge is to preserve the lateral size of the membrane while reducing the height of the material. In this work, we have overcome the described challenge and obtained high-quality 2D MOF layers with a record for MOF aspect ratio (21300:1) and demonstrated unique optical sensitivity to solvents of varied polarity. Developed method of membrane fabrication opens the way to produce scalable and freestanding 2D MOF-based atomically thin chemo-optical sensors by an industry-oriented approach.
The integration of metal-organic frameworks (MOFs) as coordination polymers into the field of nonlinear optics and light conversion has recently attracted significant attention. However, the challenge of achieving high endurance and efficiency for light conversion throughout the entire visible range using a single MOF crystal persists. In this work, we present the design of a non-centrosymmetric MOF based on a 1,3,5-benzenetricarboxylic acid ligand and Erbium (Er) ions, which demonstrates efficient and simultaneous generation of multiple second and third optical harmonics (SHG, THG) across a wavelength range of 400 to 750 nm. Through a combination of optical experiments we have confirmed the effectiveness of SHG and THG in the MOF single crystals. These phenomena are caused by the specific MOF space group and the associated dipole moment. The observation of coherent light conversion throughout the entire visible range by MOF single crystals under ambient conditions enables the realization of multicolor (up to 3) emission, which is essential for modern laser technologies.
The resonant high-index nanostructures open opportunities for control many optical effects via optically-induced electric and magnetic Mie resonances, mostly localized inside the structures. Especial interest such nanostructures represent for quantum emitters placed inside, that makes possible enhancement of quantum source emission through resonant coupling to localized modes. We have proposed the concept of active dielectric nanoantennas based on nanodiamonds with embedded NV-centers. The study of theoretically dependence of optical properties of this system on the spectral position of the resonant modes has demonstrated that that at some sizes of the diamond spherical particles and certain position of the dipole in the sphere the Purcell factor can achieve the value of 30. We have demonstrated experimentally that the photoluminescence properties of the NV-centers can be controlled via scattering resonances and observed a decrease of the NV-centers lifetime in the studied diamond particles, as compared to nonresonant nanodiamonds. These results are in a good agreement with our theoretical calculations for the average Purcell factor for multiple NV-centers within a nanoparticle. The simplicity of the proposed concept compared to existing photonic cavity systems and applicability for a wide range of color centers in diamond make active diamond nanoantenna an effective tool for creating controllable emitting elements in the visible range for future nanophotonic devices.
We demonstrate that a hybrid c-Si/Au nanocavity can serve as a multifunctional sensing platform for nanoscale (about 100 nm) thermometry with high accuracy (>0.4 K) and fast response (<0.1 second), controlled local optical heating up to 1200 K and also provide Raman scattering enhancement (>10^4 fold). The system has been tested in the experiment on thermally induced unfolding of BSA molecules, plased inside the hybrid nanocavity. Moreover, numerical modeling reveal, that two possible operation modes of the system: with and without considerable optical heating at the nanometer scale, while other functionalities (nanothermometry, RS enhancement, and tracing the events) are preserved. These regimes make the hybrid nanocavity more versatile sensing system than fully plasmonic counterparts. The simplicity and multifunctionality of the hybrid nanocavity make it a promising platform for photochemistry and photophysics applications.
The recently discovered ultralow-threshold nonlinear refraction of low-intensity laser radiation in dielectric nanostructures has an atypical dependence on radiation intensity in the pulsed and continuous modes. We first carry out quantitative measurements of the dependence of the nonlinear response of liquid dielectric nanostructures on the low-intensity radiation and then devise a theoretical explanation. The theory suggests that the nonlinearity is of photoinduced nature instead of a thermal one and depends directly on the nanoparticles electronic structure and the relationship between permittivities of dielectric matrix and nanoparticles.
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