Abstract Molecular room‐temperature phosphorescent (RTP) materials with long‐lived excited states have attracted widespread attention in the fields of optical imaging, displays, and sensors. However, accessing ultralong RTP systems remains challenging and examples are still limited to date. Herein, a thermally activated delayed fluorescence (TADF)‐assisted energy transfer route for the enhancement of persistent luminescence with an RTP lifetime as high as 2 s, which is higher than that of most state‐of‐the‐art RTP materials, is proposed. The energy transfer donor and acceptor species are based on the TADF and RTP molecules, which can be self‐assembled into two‐component ionic salts via hydrogen‐bonding interactions. Both theoretical and experimental studies illustrate the occurrence of effective Förster resonance energy transfer (FRET) between donor and acceptor molecules with an energy transfer efficiency as high as 76%. Moreover, the potential for application of the donor–acceptor cocrystallized materials toward information security and personal identification systems is demonstrated, benefitting from their varied afterglow lifetimes and easy recognition in the darkness. Therefore, the work described in this study not only provides a TADF‐assisted FRET strategy toward the construction of ultralong RTP, but also yields hydrogen‐bonding‐assembled two‐component molecular crystals for potential encryption and anti‐counterfeiting applications.
In this paper, ZnO thin films with a polycrystalline preferential orientation and low surface roughness were successively achieved on Si (100) substrate by RF magnetron sputtering techniques under optimized experimental parameters. In our sputtered samples, the average grain size is around 15~23 nm calculated from Scherrer Formula, and transmittance in visible range was over 80% measured by spectrophotometer, d33 equal to 27.5 pV/m measured by Piezoelectric Force Microscopy (PFM), surface roughness is below 3.00 nm and a good (002) plane orientation growth observed from XRD patterns. All the excellence properties of the ZnO thin films we acquired signal them are promising materials to be applied in electronic devices.
The traditional concept of the synthesis of semiconductor nanocrystals (NCs) by solvent routes usually performed under high temperatures, causes the semiconductor materials to nucleate and grow into various shaped NCs in solution. Therefore, these methods are named as "solvent-thermal approachs". In this work, we describe a simple and reproducible strategy for the synthesis of PbS NCs at temperatures even as low as −20 °C by using frozen and solidified precursors. With the aid of alkylamines, nano-sized PbS could also nucleate and grow at such low temperatures within a short time (a few seconds). The experimental results not only break people's traditional thinking but also provide a significant and novel direction in the engineering of the synthesis of NCs. In addition, we further systematically investigated the effect of two types of temperatures (the mixing temperature of the precursors and the ripening temperature of the PbS NCs). Combining this with different alkylamines, we found an obvious competition between a growth kinetic process caused by the alkylamines and a thermodynamic process induced by the temperature, which formed variously shaped monodispersed PbS NCs, including flower-, star-, sphere-, truncated octahedron-, cuboctahedron-, quasi cube-, cube-shaped and some hollow PbS NCs. Furthermore, this competition process could also provide a facile and cost-effective route to synthesize size-tunable but shape-permanent PbS NCs and their self-assembly superlattices in the same reaction systems, which is still a major challenge at present. Afterward, both the formation mechanisms of the PbS nanostructures synthesized below room temperature and the shape transformation depending on two types of temperature and alkylamines are systematically discussed.
Ho 3 + -doped and Ho3+/Yb3+-codoped lead bismuth gallate (PBG) oxide glasses were prepared and their spectroscopic properties were investigated. The derived Judd–Ofelt intensity parameters (Ω2=6.81×10−20 cm2, Ω4=2.31×10−20 cm2, and Ω6=0.67×10−20 cm2) indicate a higher asymmetry and stronger covalent environment for Ho3+ sites in PBG glass compared with those in tellurite, fluoride (ZBLAN), and some other lead-contained glasses. Intense frequency upconversion emissions peaking at 547, 662, and 756 nm as well as infrared emissions at 1.20 and 2.05 μm in Ho3+/Yb3+-codoped PBG glass were observed, confirming that energy transfer between Yb3+ and Ho3+ takes place, and a two-phonon-assisted energy transfer from Yb3+ to Ho3+ ions was determined by the calculation using phonon sideband theory. The 1.20 μm emission observed was primarily due to the weak multiphonon deexcitation originated from the small phonon energy of PBG glass (∼535 cm−1). A large product of emission cross-section and measured lifetime (9.93×10−25 cm2 s) was obtained for the 1.20 μm emission and the gain coefficient dependence on wavelength with population inversion rate (P) was performed. The peak emission cross-section for 2.05 μm emission was calculated to be 4.75×10−21 cm2. The relative mechanism of Ho3+-doped and Ho3+/Yb3+-codoped PBG glasses on their spectroscopic properties was also discussed. Our results suggest that Ho3+/Yb3+-doped PBG glasses are a good potential candidate for the frequency upconversion devices and infrared amplifiers/lasers.
Responsive luminescent materials that reversibly react to external stimuli have emerged as prospective platforms for information encryption applications. Despite brilliant achievements, the existing fluorescent materials usually have low information density and experience inevitable information loss when subjected to mechanical damage. Here, inspired by the hierarchical nanostructure of fluorescent proteins in jellyfish, we propose a self-healable, photoresponsive luminescent elastomer based on dynamic interface-anchored borate nanoassemblies for smart dual-model encryption. The rigid cyclodextrin molecule restricts the movement of the guest fluorescent molecules, enabling long room-temperature phosphorescence (0.37 s) and excitation wavelength-responsive fluorescence. The building of reversible interfacial bonding between nanoassemblies and polymer matrix together with their nanoconfinement effect endows the nanocomposites with excellent mechanical performances (tensile strength of 15.8 MPa) and superior mechanical and functional recovery capacities after damage. Such supramolecular nanoassemblies with dynamic nanoconfinement and interfaces enable simultaneous material functionalization and self-healing, paving the way for the development of advanced functional materials.
This paper reports mechanical properties of P-doped hydrogenated nanocrystalline silicon (nc-Si:H) films prepared by PECVD in different conditions. The basic mechanical properties of nanocrystalline silicon thin films are evaluated from load, hardness and modulus curves using a nanoindentation instrument. The effect of P-doping rate and types of substrates on mechanical properties is discussed. It is indicated that proper phosphorus-doped nanocrystalline silicon films have lower carrying capacity, but they hold ideal interface combination strength and lower surface roughness; Nanocrystalline silicon thin films on glass substrates have better distortion coordination and film-substrate bonding strength compared to films on silicon substrates. In addition, it is also expected that the thickness of thin films can be roughly estimated by the first obvious step's position on the Load-depth curves.
Inorganic indium‐based halide double perovskites (DPs) are environmentally friendly alternatives to lead‐based halide perovskites in light‐emitting diodes, but commonly suffer from low quantum efficiency and harsh synthesis conditions. Herein, a large‐scale green method using water as solvent is developed for the synthesis of 3D Cs 2 NaInCl 6 and 0D Cs 2 InCl 5 ·H 2 O with/without Sb 3+ dopant at room temperature. The transformation between Cs 2 InCl 5 ·H 2 O and Cs 2 NaInCl 6 products is controlled by the concentration of eco‐friendly NaCl, where excess Cl − and Na + ions play important roles in inhibiting In 3+ hydrolysis and promoting Cs 2 NaInCl 6 crystallization, respectively. The obtained Cs 2 NaInCl 6 :Sb and Cs 2 InCl 5 ·H 2 O:Sb exhibit highly luminescent self‐trapped exciton‐related blue (450 nm; photoluminescence quantum yield [PLQY] ≈85%) and yellow (610 nm; PLQY ≈88%) emissions, which are comparable to those obtained by previous methods. Tunable cold/warm white light with a PLQY of up to ≈73% is achieved by the rational assembly of two components with highly overlapped excitation wavelength ranges. Each component demonstrates remarkable stability against humidity and heat. This composite shows great potential in solid‐state lighting for general illumination.
Efficient and stable inorganic lead-free halide perovskites have attracted tremendous attention for next-generation solid-state lighting. However, single perovskite phosphors with strong, tunable-color-temperature white-light emission are rare. Here, a doping strategy was developed to incorporate Sb3+ and Bi3+ ions into Cs2NaInCl6 single crystals. Blue and yellow emission for white light with a 77% quantum yield was observed. The dual-emission originates from different [SbCl6]3– octahedron-related self-trapped excitons (STEs). The blue emission is attributable to limited Jahn–Teller deformation from Sb3+ doping. Large-radii Bi3+ increase the deformation level of the [SbCl6]3– octahedron, enhancing yellow STE emission. Density functional theory calculations indicated that the Bi3+ doping forms a sub-band level, which produces yellow STE emission. Tuning between warm and cold white light can be realized by changing the Sb3+/Bi3+ doping ratio, which suggests a unique interaction mechanism between Sb3+ and Bi3+ dopants, as well as Bi3+-induced lattice distortion in double perovskites.
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