A big challenge for nonlinear optical (NLO) materials is the application in high power lasers, which needs the simultaneous occurrence of large second harmonic generation (SHG) and high laser induced ...damage threshold (LIDT). Herein we report the preparation of a new Ga2Se3 phase, which shows the SHG intensities of around 2.3 times and the LIDT of around 16.7 times those of AgGaS2 (AGS), respectively. In addition, its IR transparent window ca. 0.59–25 μm is also significantly wider than that of AGS (ca. 0.48–≈11.4 μm). The occurrence of the strong SHG responses and good phase‐matching indicate that the structure of the new Ga2Se3 phase can only be non‐centrosymmetric and have a lower symmetry than the cubic γ‐phase. The observed excellent SHG and phase‐matching properties are consistent with our diffraction experiments and can be well explained by using the orthorhombic models obtained through our high throughput simulations.
A simple but perfect case: A new phase of gallium selenides (δ‐Ga2Se3) has been obtained via solid‐state reactions. δ‐Ga2Se3 is phase‐matchable with large second harmonic generation (SHG) responses, high laser‐induced damage thresholds (LIDTs), and wide transparent range of 0.59–25 μm. These properties are all required for the application of NLO materials with high‐power lasers.
A large nonlinear optical (NLO) coefficient and a wide band gap are two crucial but contradictory parameters that are difficult to achieve simultaneously in a single infrared (IR) NLO compound. A ...salt‐inclusion chalcogenide (SIC), LiLiCs2ClGa3S6 (1), was prepared that presents a nanosized tunnel framework constructed from monotype chalcogenide tetrahedra. Highly oriented covalent GaS4 tetrahedra in the host lead to a moderate second harmonic generation response (0.7 AgGaS2), and ionic guests effectively broaden the band gap to the widest value (4.18 eV) among all IR NLO chalcogenides, thereby achieving a remarkable balance between NLO efficiency and band gap.
The salt‐inclusion chalcogenide LiLiCs2ClGa3S6 is presented, which features a 3D framework composed of Ga3S6 nanosized tunnels. Introduction of an ionic guest to the covalent chalcogenide host produces a material with a moderate nonlinear optical (NLO) coefficient and an ultrawide band gap (Eg). These characteristics are promising for the development of infrared (IR) NLO materials.
Extending photoresponse ranges of semiconductors to the entire ultraviolet-visible (UV)-shortwave near-infrared (SWIR) region (ca. 200-3000 nm) is highly desirable to reduce complexity and cost of ...photodetectors or to promote power conversion efficiency of solar cells. The observed up limit of photoresponse for organic-based semiconductors is about 1800 nm, far from covering the UV-SWIR region. Here we develop a cyanide-bridged layer-directed intercalation approach and obtain a series of two viologen-based 2D semiconductors with multispectral photoresponse. In these compounds, infinitely π-stacked redox-active N-methyl bipyridinium cations with near-planar structures are sandwiched by cyanide-bridged Mn
-Fe
or Zn
-Fe
layers. Radical-π interactions among the infinitely π-stacked N-methyl bipyridinium components favor the extension of absorption range. Both semiconductors show light/thermo-induced color change with the formation of stable radicals. They have intrinsic photocurrent response in the range of at least 355-2400 nm, which exceeds all reported values for known single-component organic-based semiconductors.
We demonstrate herein a promising pathway towards low‐energy CO2 capture and release triggered by UV and visible light. A photosensitive diarylethene ligand was used to construct a photochromic ...diarylethene metal–organic framework (DMOF). A local photochromic reaction originating from the framework movement induced by the photoswitchable diarylethene unit resulted in record CO2‐desorption capacity of 75 % under static irradiation and 76 % under dynamic irradiation.
Low‐energy CO2 capture and release was possible with a metal–organic framework containing a photosensitive diarylethene ligand. The local framework flexibility caused by the photoswitchable diarylethene ligand (see picture) led to a record high CO2‐desorption capacity of 75 % under static irradiation and 76 % under dynamic irradiation.
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•Recent achievements on three main types of middle and far-infrared NLO materials are reviewed.•Materials with double types of anion are promising.•Alkali-metal and Ba chalcogenides ...are studied extensively.•Functional moiety theory is employed to help exploration of NLO materials.
The exploration and development of second-order nonlinear optical (NLO) materials in the middle- and far infrared (MFIR) region are important and high profile topics in the fields of NLO, solid-state chemistry and laser. Common MFIR NLO materials are chalcogenides, halides, and iodates, which have a wide MFIR transparent range and large NLO coefficients. This review summarizes recent achievements on MFIR NLO materials, and specifically focuses on their crystal structures and NLO properties. Compared to known materials, the common choice for cations are alkali-metal Li, Na, K, Rb and Cs, the coin-metal Ag, and the alkali-earth metal Ba. Exploring mixed-anions materials could be one of the most promising solutions to obtaining NLO materials with both large second-harmonic generation (SHG) intensities and high laser induced damage thresholds (LIDTs). This review also summarizes functional moiety theory to elucidate the design of promising NLO materials.
Similarities in sizes, shapes, and physical properties between carbon dioxide (CO2) and acetylene (C2H2) make it a great challenge to separate the major impurity CO2 from products in C2H2 production. ...The use of porous materials is an appealing path to replace current very costly and energy‐consuming technologies, such as solvent extraction and cryogenic distillation; however, high CO2/C2H2 uptake ratio with minor adsorption of C2H2 at standard pressure was only unexpectedly observed in scarce examples in recent years although the related research started early at 1950s, and general design strategies to realize this aim are still absent. This work has successfully developed an efficient PIET strategy and obtained the second highest CO2/C2H2 adsorption ratio for porous materials in a proof‐of‐concept MOF with a photochromism‐active bipyridinium zwitterion. An unprecedented photocontrollable gate effect, owing to change of interannular dihedral after photoinduced generation of radical species, was also observed for the first time. These findings will inspire design and synthesis of porous materials for high efficient gas adsorption and separation.
Using porous materials is a promising technique but a great challenge to achieve high CO2/C2H2 uptake ratio. This work has developed a PIET strategy and obtained the second highest CO2/C2H2 adsorption ratio for porous materials. These findings will promote the development of a new generation of CO2‐selective adsorption technique in C2H2 production and inspire design and synthesis of porous materials for high efficient gas adsorption and separation.
Introduction of photochromic properties into semiconductors confers semiconductors with smart behaviors, color‐related applications, and new modulation approaches. Photochromophores with ...electron‐transfer (redox) behavior, such as viologen and naphthalene diimide, are ideal functional motifs to design photochromic semiconductors owing to good adaptability to the solid matrix, but their reverse reactions are exclusively realized by the thermal mode, which is slow (in dozens of seconds or longer) and thus significantly hinders real applications in the fields that require high‐speed switching. This study reveals that photoexcitation in the electronic absorption band of the π‐aggregate of viologen cation radicals can successfully trigger reverse electron transfer quickly (in 1 s with a continuous‐wave 808 nm laser at a power density of 5 W cm−2; the photothermal effect is excluded), and the first single‐component all‐optically photochromic semiconductor is accordingly discovered. This discovery breaks through a traditional concept that reverse reactions of viologen compounds can not be triggered by the light, and provides a potential approach to realize all‐optical switch of single‐component photochromic smart semiconductors based on electron‐transfer photochromic functional motifs.
This discovery breaks through a traditional concept that reverse reactions of viologen compounds can not be triggered by the light, and provides a potential approach to realize all‐optical switch of single‐component photochromic smart semiconductors based on electron‐transfer photochromic functional motifs.
Feature selection has long been a focal point of research in various fields.Recent studies have focused on the application of random multi-subspaces methods to extract more information from raw ...samples.However,this approach inadequately addresses the adverse effects that may arise due to feature collinearity in high-dimensional datasets.To further address the limited ability of traditional algorithms to extract useful information from raw samples while considering the challenge of feature collinearity during the random subspaces learning process, we employ a clustering approach based on correlation measures to group features.Subsequently, we construct subspaces with lower inter-feature correlations.When integrating feature weights obtained from all feature spaces,we introduce a weighting factor to better handle the contributions from different feature spaces.We comprehensively evaluate our proposed algorithm on ten real datasets and four synthetic datasets,comparing it with six other feature selection algorithms.Experimental results demonstrate that our algorithm,denoted as KNCFS,effectively identifies relevant features,exhibiting robust feature selection performance,particularly suited for addressing feature selection challenges in practice.
Recently, the emergence of photoactive metal–organic frameworks (MOFs) has given great prospects for their applications as photocatalytic materials in visible‐light‐driven hydrogen evolution. Herein, ...a highly photoactive visible‐light‐driven material for H2 evolution was prepared by introducing methylthio terephthalate into a MOF lattice via solvent‐assisted ligand‐exchange method. Accordingly, a first methylthio‐functionalized porous MOF decorated with Pt co‐catalyst for efficient photocatalytic H2 evolution was achieved, which exhibited a high quantum yield (8.90 %) at 420 nm by use sacrificial triethanolamine. This hybrid material exhibited perfect H2 production rate as high as 3814.0 μmol g−1 h−1, which even is one order of magnitude higher than that of the state‐of‐the‐art Pt/MOF photocatalyst derived from aminoterephthalate.
The in visible MOF: A high performance for visible‐light‐driven H2‐evolution is obtained with a new methylthio‐functionalized metal–organic framework (MOF) photocatalyst that is rationally designed and facilely prepared. This approach opens up a new way to achieve photocatalysis based on MOF materials with high quantum efficiency value (up to 8.9 %) and excellent photoactivity.
We evaluated the individual atom contributions to the second harmonic generation (SHG) coefficients of LiCs2PO4 (LCPO) by introducing the partial response functionals on the basis of first principles ...calculations. The SHG response of LCPO is dominated by the metal‐cation‐centered groups CsO6 and LiO4, not by the nonmetal‐cation‐centered groups PO4 expected from the existing models and theories. The SHG coefficients of LCPO are determined mainly by the occupied orbitals O 2p and Cs 5p as well as by the unoccupied orbitals Cs 5d and Li 2p. For the SHG response of a material, the polarizable atomic orbitals of the occupied and the unoccupied states are both important.
Metal centered: The cause for the large second‐harmonic generation (SHG) of LiCs2PO4 is shown to be the metal‐cation‐centered CsO6 and LiO4 groups rather than the nonmetal‐cation‐centered PO4 groups.
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