Flexible transparent electrodes are in significant demand in applications including solar cells, light-emitting diodes, and touch panels. The combination of high optical transparency and high electrical conductivity, however, sets a stringent requirement on electrodes based on metallic materials. To obtain practical sheet resistances, the visible transmittance of the electrodes in previous studies is typically lower than the transparent substrates the electrode structures are built on, namely, the transmittance relative to the substrate is <100%. Here, we demonstrate a flexible dielectric-metal-dielectric-based electrode with ~88.4% absolute transmittance, even higher than the ~88.1% transmittance of the polymer substrate, which results in a relative transmittance of ~100.3%. This non-trivial performance is achieved by leveraging an optimized dielectric-metal-dielectric structure guided by analytical and quantitative principles described in this work, and is attributed to an ultra-thin and ultra-smooth copper-doped silver film with low optical loss and low sheet resistance.

Based on classical nucleation theory, the current entropic reduction model (ERM) of flow-induced crystallization (FIC) treats external work as perturbation on the framework of equilibrium thermodynamics, which, however, obscures the nonequilibrium nature of FIC. In this work, in situ investigation on FIC under strong flow by combining a unique homemade extensional rheometer and ultrafast X-ray scattering reveals a constant critical strain or time for nucleation in isotactic polypropylene melt in a wide temperature range from 130 to 170 °C. Our discovery contradicts the strain–temperature equivalence predicted by ERM but unveils the nonequilibrium nature of FIC. To account for the temperature independence of flow-induced nucleation, a tentative kinetic pathway of nucleation describing stretch-induced hierarchical structural transitions is proposed through which the capability of flow as driving force is justified.

The demand for high‐performance absorbers in the microwave frequencies, which can reduce undesirable radiation that interferes with electronic system operation, has attracted increasing interest in recent years. However, most devices implemented so far are opaque, limiting their use in optical applications that require high visible transparency. Here, a scheme is demonstrated for microwave absorbers featuring high transparency in the visible range, near‐unity absorption (≈99.5% absorption at 13.75 GHz with 3.6 GHz effective bandwidth) in the Ku‐band, and hence excellent electromagnetic interference shielding performance (≈26 dB). The device is based on an asymmetric Fabry–Pérot cavity, which incorporates a monolayer graphene and a transparent ultrathin (8 nm) doped silver layer as absorber and reflector, and fused silica as the middle dielectric layer. Guided by derived formulism, this asymmetric cavity is demonstrated with microwaves near‐perfectly and exclusively absorbs in the ultrathin graphene film. The peak absorption frequency of the cavity can be readily tuned by simply changing the thickness of the dielectric spacer. The approach provides a viable solution for a new type of microwave absorber with high visible transmittance, paving the way towards applications in the area of optics.

Natural enzymes are highly specific biocatalysts that can selectively catalyse specific biological reactions. However, their high preparation cost and easy deactivation of natural enzymes limit their practical applications. In the...

With the rapid development of nanotechnology, new types of fluorescent nanomaterials (FNMs) have been springing up in the past two decades. The nanometer scale endows FNMs with unique optical properties which play a critical role in their applications in bioimaging and fluorescence-dependent detections. However, since low selectivity as well as low photoluminescence efficiency of fluorescent nanomaterials hinders their applications in imaging and detection to some extent, scientists are still in search of synthesizing new FNMs with better properties. In this review, a variety of fluorescent nanoparticles are summarized including semiconductor quantum dots, carbon dots, carbon nanoparticles, carbon nanotubes, graphene-based nanomaterials, noble metal nanoparticles, silica nanoparticles, phosphors and organic frameworks. We highlight the recent advances of the latest developments in the synthesis of FNMs and their applications in the biomedical field in recent years. Furthermore, the main theories, methods, and limitations of the synthesis and applications of FNMs have been reviewed and discussed. In addition, challenges in synthesis and biomedical applications are systematically summarized as well. The future directions and perspectives of FNMs in clinical applications are also presented.

The achievement of perfect light absorption in ultrathin semiconductor materials is not only a long‐standing goal, but also a critical challenge for solar energy applications, and thus requires a redesigned strategy. Here, a general strategy is demonstrated both theoretically and experimentally to create a planar metasurface absorber comprising a 1D ultrathin planar semiconductor film (replacing the 2D array of subwavelength elements in classical metasurfaces), a transparent spacer, and a metallic back reflector. Guided by derived formulisms, a new type of macroscopic planar metasurface absorber is experimentally demonstrated with light near‐perfectly and exclusively absorbed by the ultrathin semiconductor film. To demonstrate the power and simplicity of this strategy, a prototype of a planar metasurface solar cell is experimentally demonstrated. Furthermore, the device model predicts that a colored planar metasurface perovskite solar cell can maintain 75% of the efficiency of its black counterpart despite the use of a perovskite film that is one order of magnitude thinner. The displayed cell colors have high purities comparable to those of state‐of‐the‐art color filters, and are insensitive to viewing angles up to 60°. The general theoretical framework in conjunction with experimental demonstrations lays the foundation for designing miniaturized, planar, and multifunctional solar cells and optoelectronic devices.

Developing electrocatalysts for electrochemical CO2 reduction reaction (CO2RR) with pre-eminent activity and high selectivity at low overpotentials is very significant, but it still remains a formidable challenge. Herein, we report an in situ-activated indium nanoelectrocatalyst derived from InOOH nanosheets for active and selective CO2RR at ultralow overpotentials. Such a catalyst delivers near-unity CO2RR selectivity with formate as the main product, in a wide low-overpotential window of −0.25∼−0.49 V versus reversible hydrogen electrode (vs RHE). Significantly, the CO2RR activity reaches 151 mA cm–2 at −0.45 V vs RHE, comparable to the state-of-the-art Au-based catalysts. Impressively, full-cell CO2 electrolysis implements a record-high electricity-to-fuel energy-conversion efficiency of 76.0% and solar-to-fuel energy-conversion efficiency of 20.7%. Furthermore, in situ synchrotron X-ray diffraction reveals the dynamic formation of nanosized metallic indium, correlating well with CO2RR activity, also evidenced by cyclic voltammetry. Combined with theoretical calculations, it is confirmed that the in situ-generated metallic indium plays a dominant role in promoting formate formation by accelerating the second proton-coupled electron transfer process (*OCHO+ H+ + e – → *HCOOH). Consistent with experimental results, operando Raman spectra further demonstrate that in situ-activated indium nanocatalysts can facilitate formate production even at the thermodynamic potential. This work uncovers nanosized metallic indium as the highly active site and sheds light on the design of superior indium-based catalysts for CO2 electroreduction.

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