Light-Emitting Nanophotonic Designs Enabled by Ultrafast Laser Processing of Halide Perovskites.

Nanophotonics based on resonant nanostructures and metasurfaces made of halide perovskites have become a prospective direction for efficient light manipulation at the subwavelength scale in advanced photonic designs. One of the main challenges in this field is the lack of large-scale low-cost technique for subwavelength perovskite structures fabrication preserving highly efficient luminescence. Here, unique properties of halide perovskites addressed to their extremely low thermal conductivity (lower than that of silica glass) and high defect tolerance to apply projection femtosecond laser lithography for nanofabrication with precise spatial control in all three dimensions preserving the material luminescence efficiency are employed. Namely, with CH3 NH3 PbI3 perovskite highly ordered nanoholes and nanostripes of width as small as 250 nm, metasurfaces with periods less than 400 nm, and nanowire lasers as thin as 500 nm, corresponding to the state-of-the-art in multistage expensive lithographical methods are created. Remarkable performance of the developed approach allows to demonstrate a number of advanced optical applications, including morphology-controlled photoluminescence yield, structural coloring, optical- information encryption, and lasing.

Hybrid Perovskite Terahertz Photoconductive Antenna.

Hybrid organic-inorganic perovskites, while well examined for photovoltaic applications, remain almost completely unexplored in the terahertz (THz) range. These low-cost hybrid materials are extremely attractive for THz applications because their optoelectronic properties can be chemically engineered with relative ease. Here, we experimentally demonstrate the first attempt to apply solution-processed polycrystalline films of hybrid perovskites for the development of photoconductive terahertz emitters. By using the widely studied methylammonium-based perovskites MAPbI3 and MAPbBr3, we fabricate and characterize large-aperture photoconductive antennas. The work presented here examines polycrystalline perovskite films excited both above and below the bandgap, as well as the scaling of THz emission with the applied bias field and the optical excitation fluence. The combination of ultrafast time-resolved spectroscopy and terahertz emission experiments allows us to determine the still-debated room temperature carrier lifetime and mobility of charge carriers in halide perovskites using an alternative noninvasive method. Our results demonstrate the applicability of hybrid perovskites for the development of scalable THz photoconductive devices, making these materials competitive with conventional semiconductors for THz emission.

Biocompatible pH-Degradable Functional Capsules Based on Melamine Cyanurate Self-Assembly.

Development of adaptive self-regulating materials and chemical-biological systems-self-healing, self-regulating, etc.-is an advanced modern trend. The very sensitive pH-controlled functionality of supramolecular assemblies is a very useful tool for chemical and biochemical implementations. However, the assembly process can be tuned by various factors that can be used for both better functionality control and further functionalization such as active species, e.g., drugs and dyes, and encapsulation. Here, the effect of a dye, sodium fluorescein (uranine) (FL), on the formation of a self-assembled melamine cyanurate (M-CA) structure is investigated and calculated with density functional theory (DFT) and molecular dynamics. Interestingly, the dye greatly affects the self-assembly process at early stages from the formation of dimers, trimers, and tetramer to nucleation control. The supramolecular structure disassembly and subsequent release of trapped dye occurred under both high- and low-pH conditions. This system can be used for time-prolonged bacterial staining and development of supramolecular capsules for the system chemistry approach.

Flexible Perovskite CsPbBr3 Light Emitting Devices Integrated with GaP Nanowire Arrays in Highly Transparent and Durable Functionalized Silicones.

The architecture of transparent contacts is of utmost importance for creation of efficient flexible light-emitting devices (LEDs) and other deformable electronic devices. We successfully combined the newly synthesized transparent and durable silicone rubbers and the semiconductor materials with original fabrication methods to design LEDs and demonstrate their significant flexibility. We developed electrodes based on a composite GaP nanowire-phenylethyl-functionalized silicone rubber membrane, improved with single-walled carbon nanotube films for a hybrid poly(ethylene oxide)-metal-halide perovskite (CsPbBr3) flexible green LED. The proposed approach provides a novel platform for fabrication of flexible hybrid optoelectronic devices.

Tunable Mie Resonances of Tin-based Iodide Perovskite Islandlike Films with Enhanced Infrared Photoluminescence.

The ability of light manipulation at a sub-wavelength scale of metal halide perovskite-based nanostructures through nanophotonic design were employed for advanced optical and optoelectronic applications. While these nanostructures could be efficiently tuned in the visible spectral range, their operation at infrared wavelengths is still challenging. Herein, we illustrate that islandlike films of lead-free CH3NH3SnI3 can generate strong and tunable Mie-type resonances in the near-infrared spectral range. Two critical factors contribute to the Mie resonance properties-the microscale geometry is crucial for the initiation of Mie resonances in the particles, while the concentration of free holes formed via the oxidation of Sn2+ to Sn4+ modulates the spectral position of Mie resonances. Moreover, coupling the Mie resonances to the photoluminescence peak wavelength results in the enhancement of the photoluminescence intensity. This study offers a platform for the implementation of optically resonant perovskite nanostructures as tunable light emitters for infrared photonics and optoelectronics.

Optically Active Hybrid Materials Based on Natural Spider Silk.

Spider silk is a natural material possessing unique properties such as biocompatibility, regenerative and antimicrobial activity, and biodegradability. It is broadly considered an attractive matrix for tissue regeneration applications. Optical monitoring and potential control over tissue regrowth are attractive tools for monitoring of this process. In this work, we show upconversion modification of natural spider silk fibers with inorganic nanoparticles. To achieve upconversion, metal oxide nanoparticles were doped with low concentrations of rare-earth elements, producing potentially biocompatible luminescent nanomaterials. The suggested approach to spider silk modification is efficient and easy to perform, opening up sensing and imaging possibilities of biomaterials in a noninvasive and real-time manner in bio-integration approaches.

Upconversion metal (Zr, Hf, and Ta) oxide aerogels.

A major obstacle in developing upconversion aerogels is the incompatibility of the highly-developed porosity and the crystal structure required for converting light to a shorter wavelength. We propose a novel method for creating a sol-gel procedure for synthesizing metal (Zr, Hf, and Ta) oxide upconverison aerogels uniformly doped with Er3+ and Yb3+ by precisely adjusting the calcination conditions.