Mg(C3 O4 H2 )(H2 O)2 : A New Ultraviolet Nonlinear Optical Material Derived from KBe2 BO3 F2 with High Performance and Excellent Water-Resistance.

Acquiring high-performance ultraviolet (UV) nonlinear optical (NLO) materials that simultaneously exhibit a strong second harmonic generation (SHG) coefficients, as short as possible SHG phase-matching (PM) wavelength and non-hygroscopic properties has consistently posed a significant challenge. Herein, through multicomponent modification of KBe2 BO3 F2 (KBBF), an excellent UV NLO crystal, Mg(C3 O4 H2 )(H2 O)2 , was successfully synthesized in malonic system. This material possesses a unique 2D NLO-favorable electroneutral [Mg(C3 O4 H2 )3 (H2 O)2 ]∞ layer, resulting in the rare coexistence of a strong SHG response of 3×KDP (@1064 nm) and short PM wavelength of 200 nm. More importantly, it exhibits exceptional water resistance, which is rare among ionic organic NLO crystals. Theoretical calculations revealed that its excellent water-resistant may be originated from its small available cavity volumes, which is similar to the famous LiB3 O5 (LBO). Therefore, excellent NLO properties and stability against air and moisture indicate it should be a promising UV NLO crystal.

Functional keystone taxa promote N and P removal of the constructed wetland to mitigate agricultural nonpoint source pollution.

Characterized by irregular spatial and temporal variations of pollutant loading and complex occurrence mechanisms, agricultural nonpoint source pollution (ANPSP) has always been a great challenge in field restoration worldwide. Returning farmlands to wetlands (RFWs) as an ecological restoration mode among various constructed wetlands was selected to manage ANPSP in this study. Triarrhena lutarioriparia, Nelumbo nucifera and Zizania latifolia monocultures were designed and the water pollutants was monitored. N. nucifera and Z. latifolia could reach the highest TN (53.28 %) and TP (53.22 %) removal efficiency, respectively. By 16s high-throughput sequencing of rhizosphere bacteria, 45 functional species were the main contributors for efficient N and P removal, and 38 functional keystone taxa (FKT) were found with significant ecological niche roles and metabolic functions. To our knowledge, this is the first study to explore the microbial driving N and P removal mechanism in response to ANPSP treated by field scale RFWs.

New Functional Groups Design toward High Performance Ultraviolet Nonlinear Optical Materials.

ConspectusThe invention of the laser is a pivotal milestone in the evolution of modern science and technology. Second-order nonlinear optical (NLO) crystals, which possess the ability to convert frequencies, have found widespread applications in laser science, information transmission, industrial Internet, and other cutting-edge fields within materials and optics. As modern science and technology continue to advance at a rapid pace, existing ultraviolet (UV) and deep ultraviolet (DUV) NLO crystals struggle to meet the ever-growing demands of various applications. Consequently, the development of novel UV and DUV NLO crystals has become an urgent necessity. For a UV NLO crystal to be considered outstanding in the UV/DUV range, it must exhibit three fundamental yet crucial properties: large second-order NLO coefficients, suitable birefringence, and short UV cutoff edge corresponding to a wide band gap. However, these key factors often conflict with one another, making it challenging to achieve a harmonious balance within a single crystal. It is widely believed that these mutually constrained optical properties are codetermined by microscopic NLO-active units and macroscopic structure features. Therefore, how to design high performance UV NLO-active groups to balance these three key properties is an essential scientifically question and serious challenge. In this Account, we present three strategies for designing high-performance UV NLO-active groups: (1) The "tetrahedron partial substitution" strategy by employing various substituents to replace one or more atoms in the traditional nonpolar tetrahedral groups, might achieve the aim of increasing the polarizability anisotropy and hyperpolarizability of the newly formed polar tetrahedral functional groups, such as from SO4 to SO3NH2 or SO3CH3 groups. (2) The "structure-analogue" strategy to develop a range of organic functional groups exhibiting more strong polarizability anisotropy and hyperpolarizability by using inorganic π-conjugated groups, such as BO3 and B3O6 groups, as templates. (3) The "two in one" strategy for integrating groups featuring planar triangle configurations and tetrahedrons to create NLO-active functional groups possessing large band gaps, strong hyperpolarizability, and moderate polarizability anisotropy. These three strategies successfully guide us to design and explore various kinds of organic-inorganic composite NLO crystal materials with excellent performances, like Ba(SO3CH3)2, M(SO3NH2)2 (M = Sr, Ba), C(NH2)3SO3F, KLi(HC3N3O3)·2H2O, KLi(C3H2O4)·H2O, and so on. Finally, we briefly conclude these strategies and propose some prospects for exploring new excellent UV/DUV NLO materials with practical applications. These findings could inspire novel thoughts for researchers designing new UV/DUV NLO materials and providing abundant materials used in UV/DUV regions.

Design of the Ionic Organic Nonlinear Optical Material NH4 [LiC3 H(CH3 )O4 ] with Ultrawide Band Gap and Moderate Birefringence.

Ionic organic crystals containing organic planar π-conjugated units has become one of the hot spots as nonlinear optical (NLO) materials. However, although this type of ionic organic NLO crystals commonly have remarkable second harmonic generation (SHG) responses, they also suffer from overlarge birefringences and relatively small band gaps that be hardly beyond 6.2 eV. Herein, a flexible π-conjugated [C3 H(CH3 )O4 ]2- unit was theoretically revealed, showing great potential for designing NLO crystals with balanced optical properties. Accordingly, through the reasonable NLO-favourable layered design, a new ionic organic material, NH4 [LiC3 H(CH3 )O4 ], was successfully obtained. As expected, it achieves not only a large SHG effect (4×KDP), but also a suitable birefringence (0.06@546 nm) and an ultrawide band gap (>6.5 eV). This study provides a new flexible π-conjugated NLO-active unit, contributing to design more ionic organic NLO materials with excellent balanced optical properties.

Polar Phosphorus Chalcogenide Cage Molecules: Enhancement of Nonlinear Optical Properties in Adducts.

Inorganic adducts are an emerging class of infrared nonlinear optical (NLO) materials. However, although the reported NLO adducts have sufficient birefringences and significant laser-induced damage thresholds (LIDTs), they commonly suffer from weak second harmonic generation (SHG) responses. In this work, a series of polar phosphorus chalcogenide cage molecules with strong hyperpolarizabilities were theoretically screened out to enhance the SHG responses of adducts. Accordingly, (CuI)3 (P4 S4 ), (CuI)3 (P4 Se4 ), (CuBr)7 (P4 S3 )3 and (CuBr)7 (P4 Se3 )3 with target polar cage molecules were successfully synthesized. As expected, they exhibit enhanced SHG responses while keeping moderate birefringences and high LIDTs. Notably, (CuBr)7 (P4 Se3 )3 possesses the largest SHG response (3.5×AGS@2.05 µm) among the known inorganic NLO adducts. Our study confirms that introducing NLO-active cage molecules into adducts is an efficient strategy for high-performance NLO materials.

A field study on the composition, structure, and function of endophytic bacterial community of Robinia pseudoacacia at a composite heavy metals tailing.

Robinia pseudoacacia (R. pseudoacacia) is a well reported plant species for heavy metal phytoremediation, and it was capable to improve Cd uptake efficiency after inoculated with plant growth promoting endophytes. However, the knowledge on R. pseudoacacia associated endophytes in field condition and the relationship between these microbial communities and heavy metal uptake capacities are still scarce. In this study, the characteristics of heavy metal bioaccumulation and translocation in R. pseudoacacia, and the structure and function of its endophytic bacterial communities were revealed. The results showed that heavy metal pollution made microbes more sensitive to the environment as the diversity (Shannon) of endophyte community decreased but the abundance (Chao) increased. Redundancy analysis (RDA) also showed that heavy metals were the key factor affecting the composition of endophyte. In the co-occurrence network, 27 keystone taxa mainly from Actinobacteria, Proteobacteria and Firmicutes occupied the dominant niches, among which 16 OTUs mainly from lactobacillus, bacteroides, staphylococcus, methylorubrum and bifidobacterium were positively related to bioaccumulation and translocation of Cd, Cu, Pb and Zn. Besides, heavy metal stress enhanced the functional adaptability of endophytic bacteria community. Related predicted genes were enriched in immune response, physiological metabolism pathway and stress-resistant enzyme synthesis. This study showed that heavy metal stress enhanced the structural and functional adaptability of endophyte community and keystone taxa played significant role in improving the efficiency of phytoremediation.

Directional Construction of New Nonlinear Optical Bifunctional Units through Molecular Engineering Design Inspired by the B3O7-Typed Configuration.

Studies on new functional structural units with both large hyperpolarizability and high anisotropy are essentially important for finding high-performance nonlinear optical (NLO) materials and enriching the material systems. Under the guidance of the "structure-analogue" strategy, the work utilizes the molecular engineering approach to direct the construction of target units, BC2N5O2 and B(C2N5)2 units. The BC2N5O2 unit with a highly analogous structure to the B3O7 group and its derivate B(C2N5)2 unit with a configuration of B5O10 group are designed as NLO-active units. Furthermore, two compounds with these new NLO-active units, BC2N5H6(OH)2·H2O (I) and B(C2N5H6.5)2(NO3)2 (II), are synthesized, successfully. These compounds exhibit excellent properties with second-harmonic generation (SHG) responses ranging from 0.5 to 5.9 times that of KDP and large birefringence (ΔnI = 0.181 @ 546.1 nm and ΔnII = 0.148 @ 546.1 nm). Theoretical calculations prove that the BC2N5O2 and B(C2N5)2 units make great contributions to the SHG effects and birefringence, which confirms that the BC2N5O2 and B(C2N5)2 units are novel NLO bifunctional units and could be excellent fundamental building blocks to construct amounts of novel NLO and birefringence crystals. Our studies would enlighten the research studies on biguanide complexes of boron.

Be2 (BO3 )(IO3 ): The First Anion-mixed Van der Waals Member in the KBe2 BO3 F2 Family with a Very Strong Second Harmonic Generation Response.

To obtain new nonlinear optical (NLO) materials with a large second harmonic generation (SHG) effect has always been a great challenge. We have synthesized the first metal borate-iodate NLO crystal, Be2 (BO3 )(IO3 ) (BBIO), by multicomponent modification of KBe2 BO3 F2 (KBBF), in which the structural features of KBBF were maintained and (IO3 )- groups were connected to honeycomb [Be2 BO3 O2 ]∞ layers. As the first KBBF family member with mixed anionic groups, BBIO benefited from the synergistic effect of (IO3 )- , (BO3 )3- and (BeO4 )6- groups, and exhibited a very strong SHG response of ≈7.2×KH2 PO4 (KDP, @1064 nm) and a large birefringence (Δn) of 0.172 at 1064 nm. BBIO may, unexpectedly, optimize growth habits via van der Waals forces. This study presents borate-iodate as a new NLO material and it demonstrates opportunities in KBBF structural engineering.

Ba(IO3)F: An Alkaline-Earth-Metal Iodate Fluoride Crystal with Large Band Gap and Birefringence.

An alkaline-earth-metal iodate fluoride, Ba(IO3)F (1), was discovered by introducing F atoms into alkaline-earth-metal iodates via a hydrothermal method. The pseudo-two-dimensional (2D) [BaF]+ layers and [IO3]- anionic groups built the crystal structure, which obviously exhibited large anisotropies. The birefringence of 1 was initially tested to be 0.1256 at 589.3 nm. Besides, compared with most reported metal iodate crystals, 1 possesses a large band gap (Eg = 4.32 eV). Theoretical calculations proved that the excellent optical characteristics can be attributed to [IO3]- anionic groups and [BaO4F4]10- polyhedra.

(NH4 )Bi2 (IO3 )2 F5 : An Unusual Ammonium-Containing Metal Iodate Fluoride Showing Strong Second Harmonic Generation Response and Thermochromic Behavior.

An ammonium-containing metal iodate fluoride compound, (NH4 )Bi2 (IO3 )2 F5 , featuring a two-dimensional double-layered framework constructed by [BiO2 F5 ]6- and [BiO4 F4 ]9- polyhedra, as well as [IO3 ]- groups, was successfully synthesized. The well-ordered alignment of these SHG-active units leads to an extraordinary strong SHG response of 9.2 times that of KDP. Moreover, this compound possesses a large birefringence (Δn=0.0690 at 589.3 nm), a wide energy band gap (Eg =3.88 eV), and a high laser damage threshold (LDT; 40.2×AgGaS2 ). In particular, thermochromic behavior was observed for the first time in this type of compound. Such multifunctional crystals will expand the application of nonlinear optical materials.

Sr[B(OH)4](IO3) and Li4Sr5[B12O22(OH)4](IO3)2: two unprecedented metal borate-iodates showing a subtle balance of enlarged band gap and birefringence.

Two unprecedented metal borate-iodates, Sr[B(OH)4](IO3) (SBIO) and Li4Sr5[B12O22(OH)4](IO3)2 (LSBIO), were synthesized via the strategy of introducing (IO3)- into borates. In particular, the LSBIO possessed a new B12O26 fundamental building block (FBB). The two compounds integrated the advantages of both pure iodates and borates, showing enlarged band gaps and birefringence. Moreover, diverse B-O FBBs achieved the modulation of birefringence. This work reported the first two examples of borate-iodates.