Rational Design of Novel Promising Infrared Nonlinear Optical Materials: Structural Chemistry and Balanced Performances.

ConspectusSecond-order nonlinear optical (NLO) materials are currently a hot topic in modern solid-state chemistry and optics because they can produce coherent light by frequency conversion. Noncentrosymmetric (NCS) structure is not only the prerequisite for NLO materials but also a challengeable issue because materials tend to be centrosymmetric (CS) in terms of thermodynamical stability. Among NLO materials, an excellent infrared (IR) candidate should simultaneously meet several strict key conditions including a large NLO coefficient, high laser-induced damage threshold (LIDT), phase-matchable (PM) behavior, and so on. Achieving a balance between the large NLO effect and high LIDT is difficult, as they have contradictory requirements for chemical bonds. Considering the urgent need of the high-power IR laser market and the drawbacks of the available ones, exploring new high-performance IR NLO crystals is necessary while challenging. In this Account, we first briefly introduce the status and advancement of IR NLO crystals and emphasize the criteria of an excellent candidate. Then, we will introduce five simple methods developed by us to discover practical NLO candidates through understanding of the chemical composition-structure-NLO performance relationship. (1) A rarely investigated system with simple chemical compositions as new-type NLO crystals, namely, adducts containing S8 molecules, are developed. Combining a chairlike S8 unit with other units through van der Waals forces has successfully obtained several high-performance NLO adducts. (2) The main trend in exploring new NLO crystals is that the chemical composition is more and more diversified and the structure is more and more complex, and expensive and chemically active alkaline and alkaline earth metals are usually introduced as counter cations. In contrast, the research on systems with simple chemical compositions, simple structures, and low costs has been continuously ignored. The binary M2Q3 (M = Ga, In; Q = S, Se) family with rich acentric modifications has been systematically investigated, and they all exhibit strong SHG effects and high LIDTs. (3) We first proposed the concept of inducing CS structures transformed to NCS ones by partial cation substitution to design novel NLO crystals. Considering the huge number of CS structures in the database compared to the number of NCS structures, it is an attractive method to apply CS structures as the parents to obtain potential NLO materials via partial-substitution-induced symmetry breaking. A series of chalcogenides with high NLO performances have been successfully obtained by us in this way. (4) We investigated the first NLO-active rare earth (RE) chalcophosphates and developed this family systematically, and they demonstrate wonderful comprehensive NLO properties. (5) We created a novel mixed-anion system for NLO applications, namely, chalcogenide borates. Usually, mixed-anion compounds can engender a synergistic effect to obtain desired IR NLO properties. Our recent progress on this system suggests that chalcogenide borates are potential candidates for IR NLO applications, although the study is still in its infancy. Finally, we state the current problems of IR NLO materials and give some perspectives for their future development.

Enabling Gradient-Structured Solid Electrolyte Interphase by a Hydrated Eutectic Electrolyte for High-Performance Zn Metal Batteries.

Aqueous Zn metal batteries are attracting tremendous interest as promising energy storage systems due to their intrinsic safety and cost-effectiveness. Nevertheless, the reversibility of Zn metal anodes (ZMAs) is hindered by water-induced parasitic reactions and dendrite growth. Herein, a novel hydrated eutectic electrolyte (HEE) consisting of Zn(BF4)2·xH2O and sulfolane (SL) is developed to prevent the side reactions and achieve the outstanding cyclability of ZMAs. The strong coordination between Zn2+ and SL triggers the eutectic feature, enabling the low-temperature availability of HEEs. The restriction of BF4 - hydrolysis in the eutectic system can realize favorable compatibility between Zn(BF4)2-based electrolyte and ZMAs. Besides, the newly-established solvation structure with the participation of SL, H2O, and BF4 -, can induce in situ formation of desirable SEI with gradient structure consisting of B,O-rich species, ZnS, and ZnF2, to offer satisfactory protection toward ZMAs. Consequently, the HEE allows the Zn||Zn symmetric cell to cycle over 1650 h at 2 mA cm-2 and 1 mA h cm-2. Moreover, the Zn||NH4V4O10 full batteries can deliver a prolonged lifespan for 1000 cycles with a high capacity retention of 83.4%. This work represents a feasible approach toward the elaborate design of advanced electrolyte systems for next-generation batteries.

Pentanary Oxythiogermanates Ba3MGe3O2S8 (M = Ca, Zn) Featuring [Ge3O2S8]8- Trimers and {[MGe3O2S8]6-}∞ Chains: Structural Chemistry and Physical Properties.

Oxychalcogenides are increasingly attracting wide attention because they contain multiple anions that may combine the advantages of oxides and chalcogenides. In this work, two new pentanary oxythiogermanates, Ba3MGe3O2S8 [M = Ca (1), Zn (2)], were synthesized by a high-temperature solid-state reaction. They crystallize in the orthorhombic space group Pnma, and their structures contain isolated [Ge3O2S8]8- units constructed by one [GeO2S2] and two [GeOS3] tetrahedra that link with M2+ ions to build the {[MGe3O2S8]6-}∞ chain, representing a new type of oxythiogermanate. Notably, a [ZnS5] square pyramid exists in 2. Their structural chemistry and relationship with relevant structures are analyzed. 1 and 2 exhibit wide band gaps of 3.93 and 2.63 eV, birefringences of 0.100 and 0.089 at 2100 nm, respectively, and also obvious photocurrent responses. This work may be extended to a family of AE3MIIMIV3O2Q8 (AE = alkali-earth metal; MII = Ca, Zn, Cd, Hg; MIV = Si, Ge, Sn; Q = S, Se), and further systematic survey on them can be performed to enrich the study of multifunctional oxychalcogenides.

Design of Pentanary Mixed-Chalcogenides Ag2In2SiS6-xSex (x = 1, 2) Based on the Bucket Effect: Local Structural Difference and High-Performance Nonlinear-Optical Properties Realized by Partial Congener Substitution.

Noncentrosymmetric chalcogenides are promising candidates for infrared nonlinear-optical (NLO) crystals, and exploring high-performance ones is a hot topic and challengeable. Herein, the combination of AgQ4, InQ4, and SiQ4 (Q = S, Se) units with different S/Se ratios resulted in the discovery of the tetrahedral chalcogenides Ag2In2SiS4Se2 (1) and Ag2In2SiS5Se (2). They both crystallize in the monoclinic Cc space group with different local structures. Co-occupied S/Se sites only exist in 2, and the arrangement of [In2SiQ3] six-membered rings builds different helical chains and 3D [(In2SiQ6)2-]n polyanionic frameworks in 1 and 2. They show balanced NLO performances, including phase-matchable moderate NLO responses (0.7 and 0.5 × AGS) and enhanced laser-induced damage thresholds (4.5 and 5.1 × AGS). Theoretical calculations reveal that their NLO responses are predominantly contributed by the AgQ4 and InQ4 units.

KREP2S6 (RE = Sm, Gd, Tb, Dy): A Series of Polar Rare-Earth Thiophosphates with High Laser-Induced Damage Thresholds and Moderate Nonlinear-Optical Responses Synergistically Contributed by Isolated P2S6 Units and {[RE2S15]24-}∞ Layers.

As one of the potential candidates of nonlinear-optical (NLO) materials, rare-earth chalcophosphates have demonstrated promising properties. Here, KREP2S6 (RE = Sm, Gd, Tb, Dy) were synthesized using the facile RE2O3-B-S solid-state method. They crystallize with a monoclinic chiral P21 structure, and their layer structures are built by isolated ethane-like P2S6 dimers and RES8 bicapped trigonal prisms built {[RE2S15]24-}∞ layers. By comparing the structures with related ones, the change of the alkali metal or RE3+ ions can cause structural transformation. Their band gaps are tunable between 2.58 and 3.79 eV, and their powder samples exhibit good NLO properties. Theoretical calculations suggest that the NLO properties are mainly contributed by P2S6 units and {[RE2S15]24-}∞ layers synergistically, in which {[RE2S15]24-}∞ layers and P2S6 units dominate the contribution to the band gap and second-harmonic-generation response, respectively. This work enriches the application of rare-earth chalcophosphates as NLO materials.

Polysubstitution Induced Centrosymmetric-to-Noncentrosymmetric Structural Transformation and Nonlinear-Optical Behavior: The Case of Na0.45Ag0.55Ga3Se5.

Obtaining compounds with large nonlinear-optical (NLO) coefficients and wide band gaps is challenging due to their competitive requirements for chemical bonds. Herein, the first member with mixed cations on the A site in the A-M3-Q5 or A-Ag-M6-Q10 (A = alkali metal; M = Ga, In; Q = S, Se, Te) family, viz. Na0.45Ag0.55Ga3Se5 (NAGSe), was obtained by a solid-state reaction. Its structure features [GaSe4] tetrahedra built three-dimensional {[Ga3Se5]-}∞ network, with Na and Na/Ag cations located at the octahedral cavities. Noncentrosymmetric (R32) NAGSe can also be transformed from centrosymmetric RbGa3S5 (P21/c) via multiple-site cosubstitution. NAGSe exhibits the highest NLO response (1.9 × AGS) in the A-Ag-M-Q family. Crystal structure analysis and theoretical calculations suggest that the NLO response is mainly contributed by the regularly arranged [GaSe4] units. This work enriches the exploration of the undeveloped A-M3-Q5 or A-Ag-M6-Q10 family as potential infrared NLO materials.

Nationwide Investigation on Organophosphate Flame Retardants in Tea from China: Migration from Packaging Materials and Implications for Global Risk Assessment.

In this study, we measured 15 common organophosphate flame retardants (OPFRs) in six categories of tea samples across China. OPFRs were found in all the tea samples, with the total concentrations of OPFRs (∑OPFRs) at 3.44-432 ng/g [geometric mean (GM): 17.6 ng/g]. Triphenyl phosphate (TPhP) was the dominant OPFR, accounting for 39.0-76.2% of ∑OPFRs across all tea categories. The potential factors influencing the residual OPFRs in tea were thoroughly examined, including the agricultural environment, fermentation, and packaging of teas. Tea packaging materials (TPMs) were then identified as the primary sources of OPFRs in teas. The migration test revealed that OPFRs with lower molecular weights and log Kow values exhibited a higher propensity for facilitating the migration of OPFRs from TPMs to teas. The estimated daily intakes of OPFRs from teas were relatively higher for the general populations in Mauritania, Gambia, Togo, Morocco, and Senegal (3.18-9.79 ng/kg bw/day) than China (3.12 ng/kg bw/day). The health risks arising from OPFRs in Chinese teas were minor. This study established a baseline concentration and demonstrated the contamination sources of OPFRs in Chinese tea for the first time, with an emphasis on enhancing the hygiene standards for TPMs.

Chlorinated paraffins in takeout food and its packaging in Beijing, China and dietary exposure risk.

Chlorinated paraffins (CPs) are hazardous to humans, and dietary intake acts as the primary pathway for human exposure to CPs. Takeout food is popular worldwide, but the presence of CPs in takeout food and its packaging is unclear. In this study, the concentrations and distributions of short- and median-chain CPs (SCCPs and MCCPs, respectively) were measured in 97 samples of four categories of takeout food and 33 samples of three types of takeout packaging. The SCCP and MCCP median concentrations for the takeout food samples were 248 and 339, 77.2 and 98.2, 118 and 258, 42.9 and 64.4 ng/g wet weight in meat, starch, half meat/half starch, and vegetables, respectively. Takeout food contained higher concentrations of SCCPs than MCCPs. The dominant SCCP and MCCP congener groups in takeout food were C10Cl6-7 and C14Cl7-8, respectively. The CP concentrations in takeout food were lower than those in packaging. The SCCP and MCCP median concentrations, respectively, in packaging were 9750 and 245 ng/g in polypropylene, 2830 and 135 ng/g in paper, and 2060 and 119 ng/g in aluminum foil. The concentrations of SCCPs and MCCPs were comparable in aluminum foil, whereas the concentrations of SCCPs were higher than those of MCCPs in polypropylene and paper. Correlations between CP concentrations in the takeout food and packaging indicated that CPs in packaging were potentially an important source of CPs in the takeout food. A dietary exposure risk assessment showed the takeout food posed a low risk for human exposure to CPs; however, high-frequency consumption may pose a health risk. This study clarified the current contamination situation in takeout food in Beijing, China. The resulting data could be used to prevent human exposure to CPs through dietary intake and to facilitate the market's control over the quality of takeout food.

Artificial utilization of saline-sodic land promotes carbon stock: The importance of large macroaggregates.

Soil aggregates are essential functional units involved in soil carbon sequestration, particularly in saline-sodic soils prone to severe carbon loss. In the present study, the distribution of aggregate-associated carbon fractions and their influencing factors were investigated after artificial utilization of saline soil in the Songnen Plain, Northeast China. Physicochemical properties, enzymatic activities, and bacterial communities were measured in various hierarchical aggregates among two natural land-use types (saline wasteland and degraded grassland) and three anthropogenic land-use types (artificial forest, upland field, and paddy field). The results indicated that, compared to saline wasteland, anthropogenic land use was witnessed an increase in macroaggregate proportions, and PF in large macroaggregates increased the most, while UF and FL were mainly increased in small macroaggregates. After transforming from natural land to anthropogenic land, the aggregate-associated carbon fractions (total organic carbon, readily soluble organic carbon, dissolved organic carbon, and microbial biomass carbon) increased, especially in small macroaggregates. All enzyme activities increased after artificial utilization, hydrolase (urease, amylase, and invertase), catalase, and ß-glucosidase activities were highest in the small macroaggregates. Bacterial biomass was increased in all three aggregate types compared to natural land. Due to the influence of various factors on soil carbon storage, through partial least squares path modeling revealed that large macroaggregates were conducive to carbon storage. These findings suggested that artificial utilization of saline soil can increase large macroaggregate proportions and the abundance of aggregate-associated carbon, resulting in increased soil carbon stocks, with PF having the greatest carbon sequestration capacity.

Ambient Synthesis of Vanadium-based Prussian Blue Analogues Nanocubes for High-performance and Durable Aqueous Zinc-ion Batteries with Eutectic Electrolytes.

Prussian blue analogues (PBAs) have been widely studied in aqueous zinc-ion batteries (AZIBs) due to the characteristics of large specific surface area, open aperture, and straightforward synthesis. In this work, vanadium-based PBA nanocubes were firstly prepared using a mild in-situ conversion strategy at room temperature without the protection of noble gas. Benefiting from the multiple-redox active sites of V3+/V4+, V4+/V5+ and Fe2+/Fe3+, the cathode exhibited an excellent discharge specific capacity of 200 mA h g-1 in AZIBs, which is much higher than those of other metal-based PBAs nanocubes. To further improve the long-term cycling stability of the V-PBA cathode, a high concentration water-in-salt electrolyte (4.5 M ZnSO4 + 3 M Zn(OTf)2), and a water-based eutectic electrolyte (5.55 M glucose + 3 M Zn(OTf)2) were designed to successfully inhibit the dissolution of vanadium and improve the deposition of Zn2+ onto the zinc anode. More importantly, the assembled AZIBs maintained 55% of their highest discharge specific capacity even after 10000 cycles at 10 A g-1 with superior rate capability. This study provides a new strategy for the preparation of pure PBA nanostructures and a new direction for enhancing the long-term cycling stability of PBA-based AZIBs at high current densities for industrialization prospects.

Three-in-One Tetrahedral Functional Units Constructing Diamondlike Ag2In2SiS3.06Se2.94 with High-Performance Nonlinear-Optical Activity.

Exploration of new functional materials with enhanced performance from known ones is always an attractive strategy. A new infrared (IR) nonlinear-optical (NLO) mixed chalcogenide Ag2In2SiS3.06Se2.94 (1), was obtained through partial congener substitution originated from Ag2In2SiS6 (0). 1 crystallizes in the monoclinic space group Cc, and its three-dimensional (3D) polyanionic network is composed of {[In4Si2Se5(S/Se)11]12-}∞ helical chains sharing S/Se(5) corner atoms with cavities embedded with counterion Ag+ ions. It exhibits a much enhanced NLO response compared to that of 0, reaching 1.1 × AgGaS2. Further theoretical analysis results indicate that the large NLO response can be attributed to the synergistic effect of AgQ4 and InQ4 tetrahedral functional motifs. This work not only reports a new high-performance IR NLO material but also enriches the partial ion substitution strategy to obtain new functional materials.

NaREP2Se6 (RE = Y, Sm, Gd-Dy): Quaternary Rare-Earth Selenophosphates with Unique 3D {[REP2Se6]-}∞ Framework Built by RESe8 and P2Se6 Motifs and Multiple Properties.

Rare-earth (RE) chalcophosphates have been widely studied because of their abundant structures. Here, five new RE selenophosphates, NaREP2Se6 (RE = Y, Sm, Gd-Dy), were synthesized by a facile RE oxide-boron-selenium solid-state route. They crystallize in the triclinic P1̅ space group, featuring three-dimensional (3D) structures constructed by RESe8 and P2Se6 motifs, different from common 2D RE chalcophosphates A-RE-P2-Q6 (A = alkali metal; Q = S, Se) system. Their structural chemistry and relationship with related phases are analyzed. Both the size of A and the coordination geometry of RE have important influences on the system's structures. Their optical band gaps are tunable from 1.79 to 2.50 eV, and they exhibit diverse magnetic behaviors, including Van-Vleck-type paramagnetism, antiferromagnetism, and ferromagnetism. Their photocurrent responses and thermal stabilities are analyzed as well. Calculation results suggest that the RESe8 and P2Se6 units make a great contribution to the optical properties. This work enriches the chemistry and multifunctional properties of RE chalcophosphates.

An 'on-off-on' fluorescent switch based on a luminous covalent organic framework for the rapid and selective detection of glyphosate.

Glyphosate, the most used herbicide in the world, has a residue problem that cannot be ignored. However, glyphosate itself does not have fluorescence emission and lacks the conditions for fluorescence detection. In this work, a rapid and selective fluorescence detection method of glyphosate was designed by an 'on-off-on' fluorescent switch based on a luminous covalent organic framework (L-COF). Only the fixed concentration of Fe3+ as an intermediate could trigger the fluorescent switch and no incubation step was required. The proposed method showed good accuracy with a correlation coefficient of 0.9978. The method's limits of detection and quantitation were 0.88 and 2.93 µmol/L, which were lower than the maximum allowable residue limits in some regulations. Environmental water samples and tomatoes were selected as actual samples to verify the application in a complex matrix. A satisfactory mean recovery from 87% to 106% was gained. Furthermore, Fe3+ could induce fluorescence quenching of L-COF through the photo-induced electron transfer (PET) effect, while the addition of glyphosate could block the PET effect to achieve detection. These results demonstrated the proposed method had abilities to detect glyphosate and broaden the application of L-COF.

Impact of outsourced machinery services on farmers' green production behavior: Evidence from Chinese rice farmers.

As an important part of agricultural socialization services, outsourced machinery services are of great significance for promoting the green development of agriculture. Using the field survey data of 1080 rice growers in Sichuan Province, this paper empirically analyzes outsourced machinery services' impact and role path on farmers' green production behavior. Further, it analyzes the difference in influence from the perspective of group heterogeneity. The research results show that: (1) The outsourced machinery services significantly impact farmers' adoption of no-tillage technology, organic fertilizer application technology, and straw returning technology. The conclusion is still stable after considering endogeneity. (2) The outsourced machinery services indirectly affect farmers' green production behavior by promoting off-farm employment and expanding the scale of farmland. (3) The impact of outsourced machinery services on farmers' green production behavior is not significant in the male group and the group whose households own agricultural machinery. In conclusion, the study proposes to increase assistance to outsourced machinery services providers and encourage service entities to actively publicize and popularize green production technologies while providing services, to play an influential role in guiding and educating farmers.

Efficient acousto-optic modulation using a microring resonator on a thin-film lithium niobate-chalcogenide hybrid platform.

This Letter presents the first, to the best of our knowledge, thin-film lithium niobate-chalcogenide based microring acousto-optic modulator where an interdigital transducer and a chalcogenide strip waveguide are integrated on X-cut thin-film lithium niobate. The microring resonator exhibits a high loaded quality factor of 5 × 105. The developed hybrid acousto-optic modulator with an interaction length of 120 µm demonstrates an effective half-wave voltage of only 1.74 V, which corresponds to a voltage-length product of 0.02 V•cm. The performance of the acousto-optic modulator demonstrated on the unsuspended thin-film lithium niobate-chalcogenide waveguide platform is on par with that obtained from an acoustic cavity assisted homogeneous lithium niobate counterpart.

(Na0.74 Ag1.26 )BaSnS4 : A New AgGaS2 -Type Nonlinear Optical Sulfide with a Wide Band Gap and High Laser Induced Damage Threshold.

The development of high-power solid-state lasers is in urgent need of infrared (IR) nonlinear optical (NLO) materials with wide band gaps and high laser-induced damage thresholds (LIDTs). Herein, a new compressed chalcopyrite-like IR NLO crystal (Na0.74 Ag1.26 )BaSnS4 was successfully synthesized using a facile high-temperature solid-state method. Its structure can be considered as a variant of chalcopyrite AgGaS2 (AGS)-type ones. It features a three-dimensional framework constructed by corner-sharing {[(Na/Ag)S4 ]7- }∞ layers and isolated SnS4 tetrahedra with negative cavities occupied by counter ion Ba2+ . (Na0.74 Ag1.26 )BaSnS4 exhibits phase-matchable moderate SHG response (0.31 × AGS), wide band gap (3.70 eV), and high LIDT (6.44 × AGS). Theoretical calculations reveal that the NLO response of (Na0.74 Ag1.26 )BaSnS4 is mainly originated from the synergetic effects of AgS4 and SnS4 tetrahedra, and the inclusion of alkaline and alkaline earth metals is responsible for the wide band gap and high LIDT. Moreover, the discovery of this chalcopyrite-like compound will provide a feasible design strategy for the exploration of new promising IR NLO materials.

Phenylboronic acid-functionalized cross-linked chitosan magnetic adsorbents for the magnetic solid-phase extraction of benzoylurea pesticides.

In this study, a 4-formylphenylboronic acid-modified cross-linked chitosan magnetic nanoparticle (FPBA@CCHS@Fe3 O4 ) was fabricated. The synthesized material was utilized as the magnetic solid-phase extraction adsorbent for the enrichment of six benzoylurea pesticides. In addition to B-N coordination, FPBA@CCHS@Fe3 O4 interacts with benzoylureas through hydrogen bonds and π-π stacking interaction on account of rich active groups (amino and hydroxyl) and aromatic rings in structure. Compared to traditional extraction methods, less adsorbent (20 mg) and reduced extraction time (3 min) were achieved. The adsorbent also exhibited good reusability (no less than 10 times). Coupled with a high-performance liquid chromatography-diode array detector, satisfactory recoveries (89.1-103.9%) and an acceptable limit of detection (0.2-0.7 µg/L) were obtained. Under optimized conditions, the established method was successfully applied to the tea infusion samples from six major tea categories with acceptable recoveries ranging from 76.8 to 110%, indicating its application potential for the quantitative detection of pesticides in complex matrices.

Stepwise Li Substitution Induced Structure Evolution and Improved Nonlinear Optical Performance for Diamond-like Sulfides.

One of the key scientific issues for exploration of novel infrared nonlinear optical (NLO) crystals is to obtain ones with good hybrid NLO behaviors. Herein, we report four diamond-like Ag-based sulfides via stepwise Li substitution of Ag in Ag2ZnSnS4, including Ag2ZnSnS4 (1), (Li1.22Ag0.78)ZnSnS4 (2), (Li1.58Ag0.42)ZnSnS4 (3), and Li2ZnSnS4 (4). With the increase of Li content, the sulfide's noncentrosymmetric crystal structure changes from tetragonal I42m for 1, to orthorhombic Pmn21 for 2 and 3, and to monoclinic Pn for 4. Accordingly, their NLO responses are improved along with the increase of Li content, viz. from non-NLO-active for 1, to non-phase-matchable for 2 and 3, and to phase-matchable for 4. Their optical band gaps also increase regularly. The relationship between their chemical compositions, crystal structures, and NLO activities is investigated by means of chemical structural analysis and theoretical calculation. This work offers a new systematic case for designing promising NLO-active compounds via rarely adopted cation's stepwise partial substitution and understanding the chemical composition-structure-NLO property relationship.

Introduction of Li into Ag-Based Noncentrosymmetric Sulfides for High-Performance Infrared Nonlinear Optical Materials.

The understanding of the structure-performance relationship is beneficial to establish the balance between the second-harmonic generation (SHG) response and laser-induced damage threshold (LIDT) in exploring novel nonlinear optical (NLO) materials. In this work, a facile strategy of partial Li co-occupation with Ag is employed to investigate the structures and NLO performances of the four Ag-based noncentrosymmetric chalcogenides Ag2In2SiS6 (1), (Li0.79Ag1.21)In2SiS6 (2), (Li1.12Ag0.88)In2SiS6 (3), and (Li1.44Ag0.56)In2SiS6 (4). Both the SHG intensity and LIDT are improved as the Li element is introduced, among which 4 exhibits the optimal phase-matchable SHG response of ∼0.8 × AgGaS2 (AGS) and a high LIDT of 4 × AGS. These NLO activities are explained by theoretical calculation and the dipole moment analysis.

Use of 1-octyl-3-methylimidazole hexafluorophosphate modified magnetic hyperbranched polyamideamine as sorbent for the extraction of pyrethroid insecticides from tea infusion.

Magnetic hyperbranched polyamideamine was carboxylated using succinic anhydride and modified further with 1-octyl-3-methylimidazole hexafluorophosphate successively. The morphology and chemical composition of the prepared material was characterized by transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller measurement, X-ray photoelectron spectroscopy, etc. 1-Octyl-3-methylimidazole hexafluorophosphate modified magnetic hyperbranched polyamideamine was used as sorbent in the magnetic solid-phase extraction for the separation and enrichment of five pyrethroid insecticides from tea infusion. The magnetic solid-phase extraction method proposed in this article has low method detection limits (0.53-0.71 ng/mL), acceptable coefficient of determination (0.9992-0.9998), wide linear ranges (2.5-500.0 ng/mL), and good repeatability (intraday: 1.2-6.3%; interday: 1.6-5.4%). In the detection of five pyrethroid insecticides in tea infusion, relative recoveries were in the range from 87.7 to 114.7% with satisfactory relative standard deviations (0.2-7.4%). With the aid of quantum chemistry calculations, the interaction energy between the sorbent and five pyrethroid insecticides was calculated, which proved the necessity of the modification of 1-octyl-3-methylimidazole hexafluorophosphate.