Halide-perovskite microlasers have demonstrated fascinating performance owing to their low-threshold lasing at room temperature and low-cost fabrication. However, being synthesized chemically, controllable fabrication of such microlasers remains challenging, and it requires template-assisted growth or complicated nanolithography. Here, we suggest and implement an approach for the fabrication of microlasers by direct laser ablation of a thin film on glass with donut-shaped femtosecond laser beams. The fabricated microlasers represent MAPbBr x I y microdisks with 760 nm thickness and diameters ranging from 2 to 9 μm that are controlled by a topological charge of the vortex beam. As a result, this method allows one to fabricate single-mode perovskite microlasers operating at room temperature in a broad spectral range (550–800 nm) with Q-factors up to 5500. High-speed fabrication and reproducibility of microdisk parameters, as well as a precise control of their location on a surface, make it possible to fabricate centimeter-sized arrays of such microlasers. Our finding is important for direct writing of fully integrated coherent light sources for advanced photonic and optoelectronic circuitry.
Ordered hybrid nanostructures for nanophotonics applications are fabricated by a novel approach via femtosecond laser melting of asymmetric metal-dielectric (Au/Si) nanoparticles created by lithographical methods. The approach allows selective reshaping of the metal components of the hybrid nanoparticles without affecting the dielectric ones and is applied for tuning of the scattering properties of the hybrid nanostructures in the visible range.
Carefully designed micro-and nanocarriers can provide significant advantages over conventional macroscopic counterparts in biomedical applications. The set of requirements including a high loading capacity, triggered release mechanisms, biocompatibility, and biodegradability should be considered for the successful delivery realization. Porous calcium carbonate (CaCO3) is one of the most promising platforms, which can encompass all the beforehand mentioned requirements. Here, we study both the particles formation and biological applicability of CaCO3. In particular, anisotropic differently shaped CaCO3 particles were synthesized using green sustainable approach based on co-precipitation of calcium chloride and sodium carbonate/bicarbonate at different ratios in the presence of organic additives. The impact of salts concentrations, reaction time, as well as organic additives was systematically researched to achieve controllable and reliable design of CaCO3 particles. It has been demonstrated that the crystallinity (vaterite or calcite phase) of particles depends on the initial salts' concentrations. The loading capacity of prepared CaCO3 particles is determined by their surface properties such as specific surface area, pore size and zetapotential. Differently shaped CaCO3 particles (spheroids, ellipsoids, toroids) were used to evaluate their uptake efficiency on the example of C6 glioma cells. The results show that the ellipsoidal particles possess a higher probability for internalization by cancer cells. All tested particles were also found to have a good biocompatibility. The capability to design physicochemical properties of CaCO3 particles has a significant impact on drug delivery applications, since the particles geometry substantially affects cell behavior (internalization, toxicity) and allows outperforming standard spherical counterparts.
mostly based on fluorescent (FL) agents of high brightness and combines exceptional optical properties with biocompatibility, biodegradability, and precise targeting both in vivo and in vitro. This includes inorganic semiconductor quantum dots, [2] carbon nanodots, [3] organic molecular dyes, [4] and genetically encoded universal FL proteins. [5] Additional specific class of extrinsic FL nanoprobes is amyloidbinding small molecule ligands (thioflavin T, Congo red and more) employed for tracking the kinetics of amyloid fibrils growth. [6] Each of the imaging agents has its inherent mechanism of photon emission, which defines its figures of merit for bioimaging: FL spectral region, quantum yield (QY), and photobleaching. [7,8] For instance, quantum dots and organic dye molecules exhibit FL in the visible range and have very high QY exceeding 90%. However, the organic molecular dyes are limited for long-term bioimaging applications because of photobleaching issues. The biocompatibility is another basic parameter of any biolabels, which is especially critical for some organic dyes and inorganic semiconductor quantum dots, containing heavy metals. Recently found FL carbon nanodots are biocompatible but have a low QY. [9] The green fluorescence protein (GFP) and its homologues are the only molecules, known until today, having biological origin FL and providing unique biocompatibility. These proteins exhibit pronounced FL with QY reaching 90% covering the entire visible spectrum, which makes them unique FL tags [10] among unlimited number of nonfluorescent peptide and protein biomolecules. [1,2,5,7] Alternative composition-insensitive visible FL was recently found in biological and bioinspired nanostructures characterized by specific ordering of biomolecules into antiparallel β-sheets structures. This includes a wide variety of diverse biomolecular compositions, such as amyloidogenic proteins, [11,12] PEGylated peptides, [13,14] nonaromatic biogenic, and synthetic peptides [15] and recently natural silk fibrils. [16] The basic features of these FL nanostructures are similar fibrillar morphology, original β-sheets secondary structure, and identical visible FL optical spectrum. These common structural and optical properties enable to relate all of them to a wide class of thermodynamically stable disease-and nondiseased-related amyloid structures. [17][18][19] Such β-sheet structures and visible FL can also Nanoscale bioimaging is a highly important scientific and technological tool, where fluorescent (FL) proteins, organic molecular dyes, inorganic quantum dots, and lately carbon dots are widely used as light emitting biolabels. In this work, a new class of visible FL bioorganic nanodots, self-assembled from short peptides of different composition and origin, is introduced. It is shown that the electronic energy spectrum of native nonfluorescent peptide nanodots (PNDs) is deeply modified upon thermally mediated refolding of their biological secondary structure from native metastable to stable β-sheet rich structure. This ...
The ability to manipulate small objects with focused laser beams has opened a venue for investigating dynamical phenomena relevant to both fundamental and applied science. Nanophotonic and plasmonic structures enable superior performance in optical trapping via highly confined near-fields. In this case, the interplay between the excitation field, re-scattered fields and the eigenmodes of a structure can lead to remarkable effects; one such effect, as reported here, is particle trapping by laser light in a vicinity of metal surface. Surface plasmon excitation at the metal substrate plays a key role in tailoring the optical forces acting on a nearby particle. Depending on whether the illuminating Gaussian beam is focused above or below the metal-dielectric interface, an order-of-magnitude enhancement or reduction of the trap stiffness is achieved compared with that of standard glass substrates. Furthermore, a novel plasmon-assisted anti-trapping effect (particle repulsion from the beam axis) is predicted and studied. A highly accurate particle sorting scheme based on the new anti-trapping effect is analyzed. The ability to distinguish and configure various electromagnetic channels through the developed analytical theory provides guidelines for designing auxiliary nanostructures and achieving ultimate control over mechanical motion at the micro- and nano-scales.
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