With the rapid development of information technology, the demand for optoelectronic functional materials is increasing. Nonlinear optical materials are needed as basic materials in the optoelectronic ...industry, such as optical switches, optical communication, optical information processing, optical computers, laser technology, and so on. Therefore, nonlinear optical materials have received extensive attention in recent decades, but for nonlinear optical materials, the difficulty in their synthesis is the synthesis of noncentrosymmetric crystal structures. In this paper, three new compounds, namely Ag2(H2bpz)2.5(PF6)(OH)·H2O (1), Ag2(H2bpz)2.5(SbF6)(OH)·H2O (2), and Ag(H2bpz)(NO3)·H2O (3), have been synthesized and characterized by X-ray single-crystal diffractometry; compounds 1 and 2 crystallize in a noncentrosymmetric space group. It is worth noting that the characterization results show that, through a simple hydrothermal reaction, we have successfully verified the feasibility of the theory of synthesizing noncentrosymmetric structures. In addition, compounds 1 and 2 synthesized by our simple method show second-harmonic generation, and it is phase-matchable.
Display omitted
•3D triptycene scaffold with versatile functionality for constructing TADF emitters.•Combined excellent film-formation quality and photoluminescent efficiency of 92%.•Doped and ...non-doped OLEDs with EQE up to 21.2% and 15.6% and low efficiency roll-off.
Thermally activated delayed fluorescence (TADF) materials with high luminescence efficiencies, short lifetimes, excellent thermal stability and high-quality film formation are highly desired to realize efficient organic light emitting diodes (OLEDs) with low efficiency roll-off. Herein, two asymmetric TADF molecules consisting of triptycene-fused benzophenone serving as an electron acceptor, and dimethylacridin and phenoxazine as electron donors are reported. The comparative study reveals that the introduction of triptycene scaffold strengthens the molecular rigidity and the intermolecular interactions in aggregated states, which endow the titled materials with significantly improved thermal stability, film formation quality and mechanofluorochromism behaviors. The triptycene-imbedded compound TCO-DMAC emits fast efficient delay fluorescence with photoluminescence quantum yield (PLQY) of 0.92 and short lifetime of 4.94 μs in doped evaporated film, based on which the bluish-green doped OLED achieved an external quantum efficiency (EQE) of 21.2%, a current efficiency (CE) of 57.3 cd/A, a power efficiency (PE) of 62.3 lm/W, and a maximum brightness of 15780 cd/m2. It is worth mentioning that the evaporated neat film of TCO-DMAC exhibit high PLQY of 0.69 and short delay fluorescence lifetime of 4.37 μs. The non-doped OLED achieved an external quantum efficiency (EQE) of 15.6%, a turn-on voltage of 2.8 V and a maximum brightness of 13830 cd/m2 with only minor efficiency roll-off of 3.8% at a high luminance of 1000 cd/m2.
Cerium element with a unique electric structure can be used to modify semiconductor photocatalysts to enhance their photocatalytic performances. In this work, Ce-doped TiO
(Ce/TiO
) was successfully ...achieved using the sol-gel method. The structural characterization methods confirm that Ce was doped in the lattice of anatase TiO
, which led to a smaller grain size. The performance test results show that the Ce doped in anatase TiO
significantly enhances the charge transport efficiency and broadens the light absorption range, resulting in higher photocatalytic performance. The Ce/TiO
exhibited a photocurrent density of 10.9 μA/cm
at 1.0 V vs. Ag/AgCl, 2.5 times higher than that of pure TiO
(4.3 μA/cm
) under AM 1.5 G light. The hydrogen (H
) production rate of the Ce/TiO
was approximately 0.33 μmol/h/g, which is more than twice as much as that of the pure anatase TiO
(0.12 μmol/h/g). This work demonstrates the effect of Ce doping in the lattice of TiO
for enhanced photocatalytic hydrogen production.
14 new structures of isoxazole-moiety-containing quinazoline derivatives(3a~3n) were synthesized for the first time and characterized by IR, (1)H NMR, (13)C NMR, ESI-MS. Subsequently, their in vitro ...anticancer activity against A549, HCT116 and MCF-7 cell lines was preliminarily evaluated using the MTT method. Among them, most compounds showed good to excellent anticancer activity, especially 3d, 3i, 3k and 3m exhibited the more potent anticancer activity against A549, HCT116 and MCF-7 cell lines, which can be regarded as the promising drug candidates for development of anticancer drugs.
Display omitted
•New ionic TADF emitters based on O/S-fused arylphosphonium electron acceptors.•Simultaneously attaining high PLQYs, short exciton lifetimes, and high RISC rates.•Realizing ...solution-processed OLEDs with high EQEs and small efficiency roll-offs.
Ionic thermally activated delayed fluorescence (iTADF) materials are newly emerging as promising candidates for constructing solution-processed electroluminescence devices. Developing iTADF materials with high emission efficiency, short exciton lifetime, and fast reverse intersystem crossing (RISC) is crucial for achieving stable and efficient organic light-emitting diodes (OLEDs), but it remains challenging. Here we report two high-performance iTADF emitters, namely DMAC-TPPOBF4 and DMAC-TPPSBF4, which consist of a conventional acridine as the electron-donor and newly developed oxygen/sulfur-fused arylphosphonium derivatives as the electron-acceptor. DMAC-TPPOBF4 and DMAC-TPPSBF4 exhibit high photoluminescence quantum yields of 77 % and 83 %, coupled with short exciton lifetimes of 1.2 and 1.1 μs, and RISC rate constants reaching up to 2.60 × 106 and 2.73 × 106 s−1, respectively. Theoretical and experimental investigations demonstrate that the imbedding of bridging heteroatoms into the phosphonium cation is pivotal for enhancing emission efficiency through molecular skeleton rigidification, as well as for accelerating the RISC process by capitalizing on the non-metal heavy-atom effect. Eventually, solution-processed OLEDs utilizing DMAC-TPPSBF4 realize a peak external quantum efficiency (EQE) of 17.8 % and show a minor efficiency roll-off of 7.3 % (EQE = 16.5 %) even at a practical high luminance of 1000 cd/m2.
Display omitted
•H2 and O2 were produced at separate times in water-organic solvent systems.•H4SiW12O40 was an efficient electron-coupled-proton buffer in the present systems.•Organic solvents could ...regulate the redox property of silicotungstic acid in water.•A high yield of hydrogen (∼85%) was obtained in a water-ethanol system (V/V = 1:1).•Semihydrogenation of organic compounds could be achieved under mild conditions.
H2 and O2 were produced at separate times from water electrolysis by using silicotungstic acid as an electron-coupled-proton buffer. It was found that the redox property of silicotungstic acid in water could be regulate by the introduction of organic solvents (acetonitrile, DMF and ethanol). The redox wave of silicotungstic acid at ∼0.02 V vs. RHE moved in the negative direction, which was good for the production of hydrogen. A high yield of hydrogen (∼85%) was obtained in a water-ethanol system (V/V = 1:1), which was higher than that in water (∼45%). And the introduction of ethanol didn’t affect the rate of hydrogen evolution. Moreover, the semihydrogenation of organic compounds could be achieved in the present system under mild conditions. The conversion of phenylacetylene and acetophenone are 97% and 80% under optimum reaction conditions, while the selectivity of styrene and 1-phenylethanol are 80% and 82%, respectively.
In this work, two spiro‐type compounds are investigated with similar molecular structure and stacking structure. By simply altering the acceptor's heteroatoms, a strategy to enhance room temperature ...phosphorescence (RTP) performance is presented. The intersystem crossing process can effectively be accelerated by reducing the energy gap between the singlet and triplet states (ΔEST) through adjusting the molecular energy level. Besides, thermally activated delayed fluorescence (TADF) is emerging in dilute solution due to such small ΔEST. This is helpful for deeply understanding the mechanism of competition in different radiative decay pathways (RTP and TADF).
Through investigating two donor‐acceptor molecules with similar geometry and packing structure, a method can be put forward to enhance the room temperature phosphorescence performance through reducing ΔEST by tuning excited states level. When small ΔEST is obtained, reverse intersystem crossing process is also accelerated. Not only can phosphorescence be enhanced, but also thermally activated delayed fluorescence is induced.
The sparse representation based classification (SRC) method attracts much attention in recent years, due to its promising result and robustness for face recognition. Different from the previous ...improved versions of SRC which emphasize more on sparsity, we focus on the decision rule of SRC. SRC predicts the label of a given test sample based on the residual which measures the representational capability of the training data of each class. Such decision rule is the same as the nearest feature classifiers (NFCs), but not optimal for SRC which is based on the mechanism of sparsity. In this paper, we first review the NFCs, and rewrite them in a unified formulation. We found that the objective of NFCs is different from SRC but they use the same decision rule. In order to capture more discriminative information from the sparse coding coefficient, we propose a new decision rule, sum of coefficient (SoC), which matches well with SRC. SoC is based on the fact that the sparse coefficient reflects the similarities between data, which are able to take full advantage of sparsity for classification. SoC can be regarded as the voting decision rule which is widely used in ensemble learning, i.e. Adaboost, Bagging. We compare our method with the original SRC on three representative face databases and show that SoC is much more discriminative and accurate.
String Similarity Search: A Hash-Based Approach Hao Wei; Yu, Jeffrey Xu; Can Lu
IEEE transactions on knowledge and data engineering,
2018-Jan.-1, 2018-1-1, 20180101, Letnik:
30, Številka:
1
Journal Article
Recenzirano
String similarity search is a fundamental query that has been widely used for DNA sequencing, error-tolerant query autocompletion, and data cleaning needed in database, data warehouse, and data ...mining. In this paper, we study string similarity search based on edit distance that is supported by many database management systems such as Oracle and PostgreSQL. Given the edit distance, ed(s, t), between two strings, s and t, the string similarity search is to find every string t in a string database D which is similar to a query string s such that ed(s, t) ≤ τ for a given threshold τ. In the literature, most existing work takes a filter-and-verify approach, where the filter step is introduced to reduce the high verification cost of two strings by utilizing an index built offline for D. The two up-to-date approaches are prefix filtering and local filtering. In this paper, we study string similarity search where strings can be either short or long. Our approach can support long strings, which are not well supported by the existing approaches due to the size of the index built and the time to build such index. We propose two new hash-based labeling techniques, named OX label and XX label, for string similarity search. We assign a hash-label, H s , to a string s, and prune the dissimilar strings by comparing two hash-labels, H s and H t , for two strings s and t in the filter step. The key idea is to take the dissimilar bit-patterns between two hash-labels. We discuss our hash-based approaches, address their pruning power, and give the algorithms. Our hash-based approaches achieve high efficiency, and keep its index size and index construction time one order of magnitude smaller than the existing approaches in our experiment at the same time.
In this work, a simple one-step hydrothermal method was employed to prepare the Ce-doped Fe
O
ordered nanorod arrays (CFT). The Ce doping successfully narrowed the band gap of Fe
O
, which improved ...the visible light absorption performance. In addition, with the help of Ce doping, the recombination of electron/hole pairs was significantly inhibited. The external voltage will make the performance of the Ce-doped sample better. Therefore, the Ce-doped Fe
O
has reached superior photoelectrochemical (PEC) performance with a high photocurrent density of 1.47 mA/cm
at 1.6 V vs. RHE (Reversible Hydrogen Electrode), which is 7.3 times higher than that of pristine Fe
O
nanorod arrays (FT). The Hydrogen (H
) production from PEC water splitting of Fe
O
was highly improved by Ce doping to achieve an evolution rate of 21 μmol/cm
/h.
