Three-dimensional (3D) laser nanoprinting allows maskless manufacturing of diverse nanostructures with nanoscale resolution. However, 3D manufacturing of inorganic nanostructures typically requires ...nanomaterial-polymer composites and is limited by a photopolymerization mechanism, resulting in a reduction of material purity and degradation of intrinsic properties. We developed a polymerization-independent, laser direct writing technique called photoexcitation-induced chemical bonding. Without any additives, the holes excited inside semiconductor quantum dots are transferred to the nanocrystal surface and improve their chemical reactivity, leading to interparticle chemical bonding. As a proof of concept, we printed arbitrary 3D quantum dot architectures at a resolution beyond the diffraction limit. Our strategy will enable the manufacturing of free-form quantum dot optoelectronic devices such as light-emitting devices or photodetectors.
Photoprinting nanoparticles
Nanoparticle assembly often requires tailored selection of the ligands so that they can selectively bond, as with complementary DNA strands. Alternately, they can be linked together at specified locations using photopolymerization to connect ligands at desired places. However, this process adds to the complexity of making the nanoparticles and is limited by the fidelity of the ligand attachment. Liu
et al
. show that light can be used to desorb surface thiolate ligands from cadmium selenide/zinc sulfide core shell quantum dots (see the Perspective by Pan and Talapin). The resulting trapped holes drive bonding between the particles through the remaining surface ligands. The authors reveal photoprinting of arbitrary three-dimensional architectures at a resolution beyond the diffraction limit and for a range of nanocrystals. Printing can be optically selected based on the size and/or bandgap of the quantum dots. —MSL
Photoexcitation-induced chemical bonding enables high-resolution three-dimensional printing of semiconductor quantum dots.
In photoswitches that undergo fluorescence switching upon ultraviolet irradiation, photoluminescence and photoisomerization often occur simultaneously, leading to unstable fluorescence properties. ...Here, we successfully demonstrated reversible solid‐state triple fluorescence switching through “Pump–Trigger” multiphoton manipulation. A novel fluorescence photoswitch, BOSA‐SP, achieved green, yellow, and red fluorescence under excitation by pump light and isomerization induced by trigger light. The energy ranges of photoexcitation and photoisomerization did not overlap, enabling appropriate selection of the multiphoton light for “pump” and “trigger” photoswitching, respectively. Additionally, the large free volume of the spiropyran (SP) moiety in the solid state promoted reversible photoisomerization. Switching between “pump” and “trigger” light is useful for three‐color tunable switching cell imaging, which can be exploited in programmable fluorescence switching. Furthermore, we exploited reversible dual‐fluorescence switching in a single molecular system to successfully achieve two‐color super‐resolution imaging.
Stable and programmable triple fluorescence switching in the solid state was demonstrated through an alternative “Pump–Trigger” optical manipulation strategy employing a spiropyran‐functionalized distyrylanthracene derivative. The unique switching ability enabled innovative multicolor, tunable, switching cell imaging and two‐color super‐resolution imaging in a single‐molecule system.
In recent years, some studies have been made on the effects of circular RNA (circRNA) in osteoarthritis (OA) and so on; however, its mechanisms remain to be further explored. Studies have shown that ...tumor necrosis factor-alpha can inhibit hsa_circ_0045714 expression in chondrocytes so as to upregulate miR-193b expression. Dual-luciferase reporter assay showed that insulin-like growth factor 1 receptor (IGF1R) is a key target gene of miR-193b. Hsa_circ_0045714 over-expression does not influence miR-193b expression, but can inhibit its transcriptional activity, thereby upregulating IGF1R expression. Hsa_circ_0045714 can promote the expression of type II collagen and aggrecan, and upregulate chondrocyte proliferation, while its linear sequences cannot. IGF1R has similar function, while miR-193b can inhibit the expression of type II collagen and aggrecan, and downregulate chondrocyte proliferation but enhance their apoptosis. IGF1R overexpression can reverse the effect of miR-193b, while miR-193b mimics or IGF1R siRNA can inhibit the function of hsa_circ_0045714. Therefore, hsa_circ_0045714 can regulate extracellular matrix synthesis as well as proliferation and apoptosis of chondrocytes by promoting the expression of miR-193b target gene IGF1R. The findings will provide new proofs for studies on the applications of circRNA in OA and other orthopedic diseases.
Crystallization is a fundamental phenomenon which describes how the atomic building blocks such as atoms and molecules are arranged into ordered or quasi-ordered structure and form solid-state ...materials. While numerous studies have focused on the nucleation behavior, the precise and spatiotemporal control of growth kinetics, which dictates the defect density, the micromorphology, as well as the properties of the grown materials, remains elusive so far. Herein, we propose an optical strategy, termed optofluidic crystallithography (OCL), to solve this fundamental problem. Taking halide perovskites as an example, we use a laser beam to manipulate the molecular motion in the native precursor environment and create inhomogeneous spatial distribution of the molecular species. Harnessing the coordinated effect of laser-controlled local supersaturation and interfacial energy, we precisely steer the ionic reaction at the growth interface and directly print arbitrary single crystals of halide perovskites of high surface quality, crystallinity, and uniformity at a high printing speed of 10
μm s
. The OCL technique can be potentially extended to the fabrication of single-crystal structures beyond halide perovskites, once crystallization can be triggered under the laser-directed local supersaturation.
Before mining, a deep coal seam exists in a state with a high formation temperature and high stress. After mining, the coal body is exposed to oxygen, and the oxidation reaction results in ...significant changes in the micro-structure of the oxidized coal body. To understand the change process, in this paper, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy are employed to test a coal body subjected to flow of hot gas. The evolution patterns of the coal oxidation micro-structure under different temperatures and oxygen conditions are compared and analysed. The results show that in an environment with oxygen, as the temperature increases, the stacking height (Lc) of the coal macromolecular lattice follows an overall increasing trend and has a self-repair capability. During oxidation, the spatial arrangement of the evolution of the coal molecular structure is reversible. In an environment without oxygen, the hydroxyl (–OH) peak height and peak area exceed those of an environment with oxygen, which suggests that the –OH group facilitates coal oxidation. Coal functional groups under high-temperature fracture polymerize constantly, and oxidation produces new functional groups.
The hot deformation behavior of AA2014 forging aluminum alloy was investigated by isothermal compression tests at temperatures of 350–480 °C and strain rates of 0.001–1 s−1 on a Gleeble–3180 ...simulator. The corresponding microstructures of the alloys under different deformation conditions were studied using optical microscopy (OM), electron back scattered diffraction (EBSD) and transmission electron microscopy (TEM). The processing maps were constructed with strains of 0.1, 0.3, 0.5 and 0.7. The results showed that the instability domain was more inclined to occur at strain rates higher than 0.1 s−1 and manifested in the form of local non-uniform deformation. At the strain of 0.7, the processing map showed two stability domains: domain I (350–430°C, 0.005–0.1 s−1) and domain II (450–480 °C, 0.001–0.05 s−1). The predominant softening mechanisms in both of the two domains were dynamic recovery. Uniform microstructures were obtained in domain I, and an extended recovery occurred in domain II, which would lead to the potential sub-grain boundaries progressively transforming into new high-angle grain boundaries. The optimum hot working parameters for the AA2014 forging aluminum alloy were determined to be 370–420 °C and 0.008–0.08 s−1.
Low-dimensional hybrid organic-inorganic perovskites (HOIPs) have attracted significant attention for applications such as solar cells, light-emitting diodes, and photodetectors. Compared with their ...three-dimensional counterparts, low-dimensional perovskites (LDPs) exhibit prominent characteristics such as stronger quantum confinement, remarkable exciton effects, and structural diversity, which are crucial for their nonlinear optical (NLO) properties. However, it remains hard to obtain ideal perovskite crystals with high optical transparency, large NLO responses, and excellent stability simultaneously, which are highly desirable for next-generation integrated photonics. In this work, a wide bandgap (4.2 eV) quasi-1D perovskite single crystal, PEA
3
PbBr
5
·H
2
O, with a considerable second-order NLO coefficient (0.1 pm V
−1
) that is 1/4 times that of the commercial crystal KH
2
PO
4
(KDP), is reported. Power-, wavelength-, and polarization-dependent experiments are implemented, unfolding a high polarization ratio of up to 94%. Moreover, an unexpectedly anomalous green PL phenomenon from the single crystal is discovered. The upconversion emission in the crystal, as well as the time-resolved photoluminescence dynamics, is also investigated. Such a quasi-1D perovskite may provide a new platform for advancing the application of nonlinear optics.
In this work, a new quasi-1D lead bromide perovskite with efficient second-harmonic generation and unexpectedly anomalous green PL phenomenon is developed. The second-order NLO coefficient is about 0.1 pm V
−1
, 1/4 times that of the commercial crystal KH
2
PO
4
(KDP).
A low-profile broadband circularly polarized (CP) patch antenna with wide axial-ratio beamwidth (ARBW) is presented in this paper. The proposed antenna adopts two substrates, one of which is printed ...with a feeding network composed of the Wilkinson power dividers cascaded with the Schiffman phase shifters to contribute to the broadband CP property. A circular patch with four L-shaped branches as a radiator printed on another substrate is employed to obtain wide axial-ratio beamwidths (ARBWs). A wideband CP radiation is achieved by utilizing TM 11 , TM 11+ and TM 31 mode. An antenna prototype with dimensions of 1.03 λ 0 × 1.03 λ 0 × 0.025 λ 0 (λ 0 is the wavelength at the center frequency) is fabricated. The measurement results reveal that a wide relative impedance bandwidth of about 55.6% can be achieved in the 3.26-6.04 GHz, and the CP bandwidth is 33.0% (3.85-5.50 GHz). At 5.0 GHz, the 3 dB ARBWs of the xoz plane and the yoz plane are 148° and 220°, respectively.
