Advanced Optical Materials最新文献

Lead halide perovskite exhibits great prospects in next-generation display. However, single-cation inorganic perovskite nanocrystals (NCs) still suffer from offset gamut coordinates determined by bandgap, short operating life, and low-efficiency in light-emitting diodes (LEDs), on account of the limitations in lattice stability and defect levels. Here, a thermodynamic co-competition strategy is proposed for fabricating Cs_1−xFA_xPbBr₃ NCs, which reveals the spatial distribution of A-site cations and the improvement of photoelectronic performance. This strategy achieves precise control of NCs in the pure-green range with an accuracy of sub-nanometer, further promotes the comprehensively filling-suppressing effect of incongruous lattice and surface defects. Finally, the high-precision adjusting in electroluminescence is achieved, and the champion device achieves a CIE coordinate of (0.121, 0.788), meeting the pure-green range in BT.2020. Simultaneously, the PeLED demonstrates an EQE exceeding 20% with superior stability, accompanied by 20-fold improvement in lifetime, indicating tremendous potential in next-generation display.

Detection of colorimetric signals is commonly used in various analytical methods and for testing in non-laboratory and resource-limited settings. The performance of colorimetric assays is largely based on nanoparticles and their unique optical properties. Multifunctional nanoparticles combining optical and enzyme-like catalytic properties—known as nanozymes—hold great promise for analytical applications as signal-generating labels. However, the extensive focus on the catalytic properties leaves their unique optical properties overlooked. In this article, the use of the optical and catalytic properties of nanozymes is reviewed for analytical applications relying on the inherent optical properties of nanozymes, the colorimetric detection of a catalytically-formed product, and colorimetric changes of nanoparticles caused by the catalytically-formed product. The impact of the extinction coefficient of nanozymes and reaction products, as well as the kinetic parameters of nanozymes on the sensitivity and limit of detection of assays, are quantitatively evaluated. Finally, the existing limitations and prospects of nanozymes for colorimetric biosensors are summarized.

The burgeoning advancement of information technology has engendered a discernible surge in the examination of neuromorphic devices, notably drawing broader attention to artificial vision systems endowed with sensory recognition capabilities. Current photoelectric synapse devices employed in artificial vision systems are generally well-suited for well-illuminated conditions, yet exhibit diminished sensitivity in weak-light scenarios, resulting in a pronounced deterioration of recognition accuracy. Here, an ultrasensitive photoelectric synaptic transistor based on negative quantum capacitance effect resulted from the 2D semi-metallic graphene layer that partially enclosed within the gate dielectric layer, which manifests a noteworthy reduction in device control voltage and exhibits perception and storage capabilities for weak light of 39.4 nW cm⁻² with detectivity above 10¹⁶ cm Hz^1/2 W⁻¹ is demonstrated. The voltage amplification effect and the concomitant formation of an equivalent local electrostatic field induced by the negative quantum capacitance effect engenders a robust programmable synaptic plasticity for extremely weak light by modifying the control gate. These results represent the inaugural integration of the negative quantum capacitance effect into optoelectronic devices and furnish a robust hardware foundation for developing vision systems in weak-light environments.

Despite the excellent thermometric performance of many developed luminescent nanomaterials, their use has not gone beyond proof-of-concept in vivo experiments to date. An important issue that needs to be resolved before moving toward true biomedical applications of engineered nanothermometers is their potential toxicity and bioaccumulation in the human body considering the ultimate objective of clinical applications. Since most reported nanothermometers currently are not degradable materials and are mainly based on the incorporation of heavy metal ions, these aspects remain of genuine concern in the fields of nanomedicine, nanobiotechnology, nanotoxicology, and nanopharmacology. This work explores the possibility of designing visible, as well as near-infrared, emitting luminescent ratiometric nanothermometers based on appropriate organic dye mixtures embedded in hollow disulfide-bridged periodic mesoporous organosilica (PMO) particles. Such hybrid particles show excellent thermometric performance in the physiological temperature range (20–50 °C), favorable degradability in simulated physiological conditions, as well as no toxicity to healthy normal human dermal fibroblast (NHDF) cells in a wide concentration range. Considering the simplicity of the approach from the synthetic point of view, and the large available library of known fluorescent dyes emitting in various regions of the electromagnetic range, this motif renders a very promising approach to designing novel non-toxic, decomposable, luminescent ratiometric thermometers.

Quasi-2D lead-halide perovskites consist of conducting inorganic layers with tunable thickness (n) separated by large organic spacer cations. Typically, domains with different n and bandgaps are formed within a single film. Here, the crystallization of the films is tuned by mixing Dion-Jacobson (DJ) with Ruddlesden-Popper (RP) spacer cations. Compared to the quasi-2D perovskite film based on solely the DJ type spacer 1,4-phenylenedimethylammonium (PDMA), a film with less defects and more vertically aligned crystallization is achieved by addition of the RP type spacer propylammonium (PA). As the film structure plays an important role in the photophysics, time-resolved photoluminescence (TRPL) and femtosecond transient absorption (TA) are used to investigate the impact of mixing these spacer cations on the dynamics of hot carrier cooling, the occurrence and directionality of energy or electron transfer between the different domains, and the exciton and charge carrier dynamics. Exciton transfer from low-n to high-n domains occurs at a favorable faster rate for the PDMA-based film (0.0640 ps⁻¹) compared to the PA-based film (0.0365 ps⁻¹), while the mixed spacer film demonstrates intermediate behavior (0.0473 ps⁻¹). This study facilitates the design of advanced materials with optimized photophysical characteristics for a next generation of optoelectronic devices.

Quantitative Dynamic Structural Color

In article number 2401152 Nithesh Kumar, Judson D. Ryckman, and co-workers demonstrate an approach to overcome the limited sensitivity and often qualitative nature of structural-color-based sensors and indicators in a scheme referred to as ‘quantitative dynamic structural color’. As illustrated in this cover image, their scheme relies on a spectrally engineered mesoporous metamaterial combined with dichromatic laser illumination. The sensors achieve a well-defined and strongly enhanced color response toward refractometric stimuli including small molecules, vapors, and aerosols.

Defect Suppression in Te-Doped Cs₂ZrCl₆ Perovskite Nanoparticles

Lead-free Cs₂ZrCl₆:Te (CZCT) @ alkyl-terminated silica-oligomer (ASO) core/shell perovskite nanoparticles (PNCs) were designed and synthesized with the highest photoluminescence quantum yield (PLQY) of up to 96% and robust thermal tolerance simultaneously. The high PLQY was attributed to the comprehensive defect suppression through crystallization and surface control. The fabricated white light-emitting diodes based on the CZCT@ASO PNCs exhibit a color coordinate of (0.31, 0.33) and a color rendering index of 86. For further details, see article number 2303079 by Guangguang Huang, Shujie Wang, Zuliang Du, and co-workers from Henan University (the Iron Pagoda in the image representing its culture and spirit).

The design and experimental demonstration of double-step, 1D amorphous germanium grating structures supporting quasi bound-states-in-continuum (quasi-BIC) resonance at 3.2 µm wavelength and its application to third-order sum-frequency generation-based up-conversion are reported. Linear transmission measurements on the fabricated metasurface with loosely focussed excitation spanning 0–3° angles show very good agreement with ideal plane-wave excitation of the periodic photonic structure. TSFG measurements performed on the same structures with tightly focusing mid-infrared signal and pump beams using a reflective-type objective with 15–40° angular excitation show ≈375 times enhancement with significant blue-shift in the resonance feature by ≈300 nm. To understand this excitation angle dependence of the resonance characteristics, a generalized plane-wave expansion (PWE) model is developed by considering varying excitation angle plane-waves incident on the metasurface with a discretized angular spectrum representation used to coherently combine the resultant electric and magnetic fields to obtain the linear transmission characteristics and nonlinear TSFG spectra. The PWE method is found to be particularly effective in modeling linear and nonlinear responses under realistic illumination conditions while ensuring optimal utilization of computational resources. Good agreement is obtained between the PWE simulations, linear transmission, and nonlinear TSFG measurements by considering appropriate angular excitation.

A compact and responsive thermoelectric photodetector is introduced for the mid-infrared. By resonantly coupling mid-infrared light to a Sb₂Te₃-Bi₂Te₃ thermoelectric junction, a thermocouple is formed that is directly heated by narrow-band mid-infrared radiation. Near-perfect absorption is achieved at this hot junction through the resonantly enhanced coupling of light to free-electrons in the Bi₂Te₃ and Sb₂Te₃ materials. The fabricated devices operate at 3.6 µm and demonstrate a responsivity of 10.2 V W⁻¹, a specific detectivity of 4.6  × 10⁶ cm Hz^1/2 W⁻¹, and a bandwidth in the order of 1 kHz. The optimal detection wavelength can be spectrally tuned by changing the resonant cavity dimensions. This work shows a path toward miniaturized mid-infrared detectors and spectrometers with high sensitivity, responsivity, and bandwidth. Importantly, the device presented here is ideal for industrial production, which it is hoped will provide wider access to mid-infrared technologies for chemical sensing, medicine, and security.