Nanocrystal (NC) self-assembly is a versatile platform for materials engineering at the mesoscale. The NC shape anisotropy leads to structures not observed with spherical NCs. This work presents a broad structural diversity in multicomponent, long-range ordered superlattices (SLs) comprising highly luminescent cubic CsPbBr 3 NCs (and FAPbBr 3 NCs) coassembled with the spherical, truncated cuboid, and disk-shaped NC building blocks. CsPbBr 3 nanocubes combined with Fe 3 O 4 or NaGdF 4 spheres and truncated cuboid PbS NCs form binary SLs of six structure types with high packing density; namely, AB 2 , quasi-ternary ABO 3 , and ABO 6 types as well as previously known NaCl, AlB 2 , and CuAu types. In these structures, nanocubes preserve orientational coherence. Combining nanocubes with large and thick NaGdF 4 nanodisks results in the orthorhombic SL resembling CaC 2 structure with pairs of CsPbBr 3 NCs on one lattice site. Also, we implement two substrate-free methods of SL formation. Oil-in-oil templated assembly results in the formation of binary supraparticles. Self-assembly at the liquid–air interface from the drying solution cast over the glyceryl triacetate as subphase yields extended thin films of SLs. Collective electronic states arise at low temperatures from the dense, periodic packing of NCs, observed as sharp red-shifted bands at 6 K in the photoluminescence and absorption spectra and persisting up to 200 K.

Optically pumped green lasing with an ultra low threshold has been achieved using an InGaN/GaN based micro-disk with an undercut structure on silicon substrates. The micro-disks with a diameter of around 1 μm were fabricated by means of a combination of a cost-effective silica micro-sphere approach, dry-etching and subsequent chemical etching. The combination of these techniques both minimises the roughness of the sidewalls of the micro-disks and also produces excellent circular geometry. Utilizing this fabrication process, lasing has been achieved at room temperature under optical pumping from a continuous-wave laser diode. The threshold for lasing is as low as 1 kW/cm2. Time–resolved micro photoluminescence (PL) and confocal PL measurements have been performed in order to further confirm the lasing action in whispering gallery modes and also investigate the excitonic recombination dynamics of the lasing.

The 1:1:1 reaction of DyCl 3 •6H 2 O, K 3 [Co(CN) 6 ] and bpyO 2 in H 2 O has provided access to a complex with formula [DyCo-(CN) 2) was also precipitated (also in a high yield) using K 3 [Fe(CN) 6 ] instead of K 3 [Co(CN) 6 ]. Their structures have been determined by single-crystal X-ray crystallography and characterized based on elemental analyses and IR spectra. Combined direct current (dc) and alternating current (ac) magnetic susceptibility revealed slow magnetic relaxation upon application of a dc field. μ-SQUID measurements and CASSCF calculations revealed high-temperature relaxation dynamics for both compounds. Lowtemperature magnetic studies show the relaxation characteristics for 1, while for compound 2 the dynamics corresponds to an antiferromagnetically coupled Dy••• Fe pair. High-resolution optical studies have been carried out to investigate the performance of compounds 1 and 2 as luminescence thermometers. For 1, a maximum thermal sensitivity of 1.84% K −1 at 70 K has been calculated, which is higher than the acceptable sensitivity boundary of 1% K −1 for high-performance luminescence thermometers in a broad range of temperature between 40 and 140 K. Further optical studies focused on the chromaticity diagram of compound 1 revealed a temperature shift from warm white (3200 K) at 10 K toward a more natural white color near 4000 K at room temperature.

Microcavities based on group-III nitride material offer a notable platform for the investigation of light-matter interactions as well as the development of devices such as high efficiency light emitting diodes (LEDs) and low-threshold nanolasers. Disk or tube geometries in particular are attractive for low-threshold lasing applications due to their ability to support high finesse whispering gallery modes (WGMs) and small modal volumes. In this article we present the fabrication of homogenous and dense arrays of axial InGaN/GaN nanotubes via a combination of displacement Talbot lithography (DTL) for patterning and inductively coupled plasma top-down dry-etching. Optical characterization highlights the homogeneous emission from nanotube structures. Power-dependent continuous excitation reveals a non-uniform light distribution within a single nanotube, with vertical confinement between the bottom and top facets, and radial confinement within the active region. Finite-difference time-domain simulations, taking into account the particular shape of the outer diameter, indicate that the cavity mode of a single nanotube has a mixed WGM-vertical Fabry-Perot mode (FPM) nature. Additional simulations demonstrate that the improvement of the shape symmetry and dimensions primarily influence the Q-factor of the WGMs whereas the position of the active region impacts the coupling efficiency with one or a family of vertical FPMs. These results show that regular arrays of axial InGaN/GaN nanotubes can be achieved via a low-cost, fast and large-scale process based on DTL and top-down etching. These techniques open a new perspective for cost effective fabrication of nano-LED and nano-laser structures along with bio-chemical sensing applications

Solution-processed lasers are cost-effective, compatible with a vast range of photonic resonators, and suited for a mass production of flexible, lightweight, and disposable devices. The emerging class of lead halide perovskite nanocrystals (LHP NCs) can serve as a highly suitable active medium for such lasers, owing to their outstanding optical gain properties and the suppressed optical nonradiative recombination losses stemming from their defect-tolerant nature. In this work, CsPbBr 3 NCs are embedded within polymeric Bragg reflectors to produce fully solution-processed microcavities. By a systematic parametric optimization of the polymer mirrors, resonators with Q-factors up to 110 can be produced in the green, supporting amplified spontaneous emission (ASE) under continuous wave excitation, with a threshold as low as 140 mW/cm 2 . Angle-dependent reflectivity and luminescence studies performed below the ASE threshold demonstrate the strong spectral and angular redistribution of the CsPbBr 3 NC spontaneous emission when coupled to the cavity mode. Under resonance, amplification of the output intensity by a factor of 9 in the vicinity of the cavity mode and by a factor of 5 in the whole integrated emission along with an increase of the radiative rate accounted by a Purcell factor of 2 is obtained with respect to NCs deposited in reference microcavity structures.