Molecular afterglow materials with ultralong‐lived excited states have attracted considerable interest owing to their promise for light‐emitting devices, optical imaging, and anti‐counterfeiting ...applications. However, the realization of ultralong afterglow emission in low‐dimensional micro/nanostructures has remained an open challenge, limiting progress toward new‐generation photonic applications. In this work, new types of mono/binuclear metal–organic halide micro/nanocrystals with tunable afterglow properties, made possibly by the rational control over both ultralong‐lived room‐temperature phosphorescence and thermally activated delayed fluorescence, are developed. Interestingly, the mono/binuclear coordination complexes present excitation‐dependent luminescence across a wide range (wavelength > 150 nm) with broad emission color differences from blue to yellow owing to the multiple long‐lived excited states. The 1D binuclear metal–organic microrods further exhibit excitation‐dependent optical waveguide and space/time dual‐resolved afterglow emission properties, endowing them with great potential in wavelength‐division multiplexing information photonics and logic gates. Therefore, this work not only communicates the first example of wide‐range tunable ultralong afterglow of low‐dimensional metal–organic micro/nanocrystals under ambient conditions but also provides a new route to achieve optical communications and photonic logic compilation at the micro/nanoscale.
New metal–organic halide micro/nanocrystals with tunable afterglow luminescence, which exhibit excitation‐dependent optical waveguide properties across a wide color range, as well as space/time dual‐resolved afterglow, are developed. They have great potential in wavelength‐division multiplexing information photonics and optical logic gates.
Long-persistent luminescence based on purely inorganic and/or organic compounds has recently attracted much attention in a wide variety of fields including illumination, biological imaging, and ...information safety. However, simultaneously tuning the static and dynamic afterglow performance still presents a challenge. In this work, we put forward a new route of organic-doped inorganic framework to achieve wide-range and multicolor ultralong room-temperature phosphorescence (RTP). Through a facile hydrothermal method, phosphor (tetrafluoroterephthalic acid (TFTPA)) into the CdCO
(or Zn
(OH)
CO
) host matrix exhibits an excitation-dependent colorful RTP due to the formation of diverse molecular aggregations with multicentral luminescence. The RTP lifetime of the doped organic/inorganic hybrids is greatly enhanced (313 times) compared to the pristine TFTPA. The high RTP quantum yield (43.9%) and good stability guarantee their easy visualization in both ambient and extreme conditions (such as acidic/basic solutions and an oxygen environment). Further codoped inorganic ions (Mn
and Pb
) afford the hybrid materials with a novel time-resolved tunable afterglow emission, and the excitation-dependent RTP color is highly adjustable from dark blue to red, covering nearly the whole visible spectrum and outperforming the current state-of-the-art RTP materials. Therefore, this work not only describes a combined codoping and multicentral strategy to obtain statically and dynamically tunable long-persistent luminescence but also provides great opportunity for the use of organic-inorganic hybrid materials in multilevel anticounterfeiting and multicolor display applications.
Persistent luminescence has attracted great attention due to the unique applications in molecular imaging, photodynamic therapy, and information storage, among many others. However, tuning the ...dynamic persistent luminescence through molecular design and materials engineering remains a challenge. In this work, the first example of excitation‐dependent persistent luminescence in a reverse mode for smart optical materials through tailoring the excited‐state proton transfer process of metal cytosine halide hybrids is reported. This approach enables ultralong phosphorescence and thermally activated delayed fluorescence emission colors highly tuned by modulation of excitation wavelength, time evolution, and temperature, which realize multi‐mode dynamic color adjustment from green to blue or cyan to yellow‐green. At the single crystal level, the 2D excitation/space/time‐resolved optical waveguides with triple color conversion have been constructed on the organic‐metal halide microsheets, which represent a new strategy for multi‐dimensional information encryption and optical logic gate applications.
Reversed excitation‐dependent persistent luminescence can be obtained in metal cytosine halides by controlling the process of excited‐state proton transfer (ESIPT). The metal cytosine halides further exhibit multi‐mode (excitation/space/time) triple‐color luminescent conversion, which have promising applications in multi‐dimensional information encryption and photonic logic gates.
Semiconductor photocatalysts have recently received growing attention, but still meet the challenges of a weak separation ability of photogenerated electrons and holes, which leads to energy loss. In ...this work, we utilize ultralong-lived triplet excitons to promote the separation of electron-hole pairs and to realize the efficient transformation from excitons to carriers. Room temperature phosphorescent (RTP) carbon dots (CDs) were selected as a model system, which were highly dispersed onto g-C
3
N
4
and exhibited largely enhanced photocatalytic and electrochemical activities compared with those of typical fluorescent CD systems. Both experimental and density functional theory calculations show that the ultralong-lived triplet excitons from RTP CD@g-C
3
N
4
serve as an “energy sustained-release capsule” and thus effectively regulate the recombination of excitons and boost the intrinsic photocatalytic performances (including water splitting and dye degradation). Therefore, this work provides a new design strategy to use ultralong-lived triplet excitons as high-efficiency photocatalysts.
Functional textiles are widely concerned because of their potential applications in various fields, water-repellent textiles play a vital role in functional textiles because of their huge practical ...needs. However, the realization of water-repellent finishing agent with high stability and heat resistance has remained an open challenge, limiting the further application of water-repellent textiles. Herein, waterborne polyurethane (WPU) is prepared by introducing C = C bonds into polyurethane (PU) side chains using trimethylolpropane monoallyl ether (TMPME) as a grafting agent by self-emulsification. As a seed emulsion, WPU is further copolymerized with acrylate monomers to prepare waterborne polyurethane/acrylate (WPUA). Interestingly, the WPUA emulsions with obvious core–shell structure exhibit excellent storage stability and heat resistance, which can cover the fabric surface and form a thin film. The static contact angle up to 151° imparts excellent water repellency to the fabric. Thus, a water-repellent finishing agent was successfully assembled, which possesses high reference value for designing and preparing such materials.
Graphical Abstract
An InGaN/GaN superlattice (SL) with Mg-doped barriers was designed and inserted into the InGaN-based blue light-emitting diodes (LEDs) as a hole gathering layer (HGL) to promote hole injection into ...the active region. The fabricated LEDs with the SL HGL show 36.4% increase in light output power at an injection current of 200 mA. Meanwhile, the efficiency droop is also mitigated effectively, as compared to the traditional LEDs. The improved performance is attributed to increased hole injection efficiency and decreased electron leakage into the p-type region.
Evaporation processes of a fuel droplet under sub- and supercritical ambient conditions have been studied using molecular dynamics (MD) simulations. Suspended n-dodecane droplets of various initial ...diameters evaporating into a nitrogen environment are considered. Both ambient pressure and temperature are varied from sub- to supercritical values, crossing the critical condition of the chosen fuel. Temporal variation in the droplet diameter is obtained and the droplet lifetime is recorded. The time at which supercritical transition happens is determined by calculating the temperature and concentration distributions of the system and comparing with the critical mixing point of the n-dodecane/nitrogen binary system. The dependence of evaporation characteristics on ambient conditions and droplet size is quantified. It is found that the droplet lifetime decreases with increasing ambient pressure and/or temperature. Supercritical transition time decreases with increasing ambient pressure and temperature as well. The droplet heat-up time as well as subcritical to supercritical transition time increases linearly with the initial droplet size d0, while the droplet lifetime increases linearly with d02. A regime diagram is obtained, which indicates the subcritical and supercritical regions as a function of ambient temperature and pressure as well as the initial droplet size.
•A die attach adhesive was designed with cross-linked epoxy-silicone and fused silica.•Both high thermal conductivity and low viscosity are achieved.•Similar refractive indexes of matrix and filler ...results in high transmittance.•Epoxy-silicone improves the adhesion to the bonding surfaces comparing with silicone.•The improved thermal, optical and reliability performance of LEDs are achieved.
High thermal conductivity, low viscosity and high transparency are desired properties of die attach adhesives (DAA) for LEDs to achieve high thermal and optical performance as well as good reliability. However, it is challenging for DAAs with thermally conductive fillers to keep a low viscosity and high transparency. In this paper, a novel DAA with designed hyper-branched epoxy-silicone and surface modified fused silica was formulated to improve the thermal conductivity without sacrificing high transparency and low viscosity. Compared with a widely used commercial DAA, 165% thermal conductivity improvement and 83% viscosity reduction are achieved, resulting in 26% thermal resistance reduction, 7% light extraction enhancement, and 14% less lumen degradation in accelerate aging test for mid-power LED packages.
Photo‐controllable persistent luminescence at the single crystal level can be achieved by the integration of long‐lived room temperature phosphorescence (RTP) and photochromism within metal–organic ...frameworks (MOFs) for the first time. Moreover, the multiblock core–shell heterojunctions have been prepared utilizing the isostructural MOFs through an epitaxial growth process, in which the shell exhibits bright yellow afterglow emission that gradually disappears upon further irradiation, but the core does not show such property. Benefitting from combined persistent luminescence and photochromic behavior, a multiple encryption demo can be facilely designed based on the dynamic manipulating RTP via reversible photochromism. This work not only develops new types of dynamically photo‐controllable afterglow switch, but also provides a method to obtain MOFs‐based optical heterojunctions towards potential space/time‐resolved information encryption and anti‐counterfeiting applications.
Multiblock core–shell MOFs heterojunctions were prepared through an epitaxial growth process, in which the shell exhibits both persistent luminescence and photochromic properties. The bright yellow afterglow in MOFs shell can be detected before irradiation but almost disappears after coloration upon continuous UV irradiation.
•A criterion for the multi-component transition to diffusive mixing is proposed.•Increasing ambient pressure does not necessarily accelerate the phase transition.•Light fuel components increase the ...minimum pressure of the diffusive mixing zone.•The supercritical transition temperature has a maximum value at a certain pressure.•The top temperature of supercritical transition decreases with decreasing pressure.
For a multi-component hydrocarbon mixture under supercritical conditions, the mechanism and criterion for the transition of the dominant mixing mode from evaporation to diffusion are not well established. In this paper, phase transition processes of three-component hydrocarbon fuel (5.3 wt% isooctane, 25.8 wt% n-dodecane and 68.9 wt% n-hexadecane) droplets in sub- and supercritical nitrogen environments were studied using molecular dynamics, in comparison with those of single-component n-hexadecane droplets. The initial diameters of the droplets were 25.5 nm (three-component) and 26.5 nm (single-component), respectively. Based on the quantitative Voronoi tessellation, a new criterion, which was a combination of two dimensionless critical values of Hc = 0.85 and Wc = 0.35, was proposed to determine the transition of the dominant mixing mode from evaporation to diffusion during fuel-ambient gas mixing. Results indicated that when the ambient pressure ranged from 2 MPa to 10 MPa and the ambient temperature ranged from 750 K to 1200 K,the density difference between the vapor phase and the liquid phase decreased gradually with increasing ambient pressure or decreasing ambient temperature. And the dominant mixing mode gradually transitioned from evaporation to diffusion. Increasing the ambient pressure did not necessarily promote the occurrence of phase transition, while increasing ambient temperature accelerated the phase transition monotonically. Light fuel components increased the minimum pressure of the diffusive mixing zone. A major finding was that under a certain ambient pressure, the supercritical transition temperature had not only a minimum but also a maximum.
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