Na4Sn4(C2O4)3F6 and NaSnC2O4F·H2O: two tin(II) fluoride oxalates display large birefringence.

Birefringent materials play an important role in laser techniques as an essential part of optical devices. Therefore, the exploration of high-performance birefringent materials has been a central focus of researchers. Herein, two tin(II) fluoride oxalates Na4Sn4(C2O4)3F6 and NaSnC2O4F·H2O were gained by the combination of birefringence-active groups of Sn2+ with stereochemically active lone pairs and planar π-conjugated [C2O4]2- groups. These groups assemble into low-dimensional structures of 0D [C2O4F4]6- clusters and 1D [SnC2O4F]∞- chains in Na4Sn4(C2O4)3F6, and double [Sn2(C2O4)2F2]∞2- chains in NaSnC2O4F·H2O, which gives rise to the large birefringence of 0.160@546 nm and 0.189@546 nm, respectively. Detailed structure-property analysis and theoretical calculations indicate that strong optical anisotropy can be induced by the rational arrangement of the Sn2+-polyhedra and [C2O4]2- groups.

A2Hgx(SeO3)y (A = K, Rb, Cs): Three Alkali Metal Mercury Selenites Featuring Unique 1D [HgOm(SeO3)n]∞ Chains.

Herein, three alkali metal mercury selenites, K2Hg2(SeO3)3, Rb2Hg2(SeO3)3, and Cs2Hg3(SeO3)4, were successfully obtained by a hydrothermal method. The three compounds featured same one-dimensional (1D) [HgOm(SeO3)n]∞ chain structure that consisting of distorted Hg-O polyhedra and SeO3 triangular pyramids with stereochemically active lone pair (SCALP) electrons. Interestingly, the rich coordination environment of Hg atoms and the size difference of alkali metal cations lead to diverse arrangement of SeO3 groups, which makes them exhibit different birefringence. The band gaps of the three compounds indicate that they are potential ultraviolet (UV) optical materials. Detailed theoretical calculations demonstrate that the combined effects of SeO3 triangular pyramids and Hg-O polyhedra are responsible for the optical characteristics of the reported compounds.

A Ratiometric Fluorescent Probe Based on RhB Functionalized Tb-MOFs for the Continuous Visual Detection of Fe3+ and AA.

In this study, a red-green dual-emitting fluorescent composite (RhB@MOFs) was constructed by introducing the red-emitting organic fluorescent dye rhodamine B (RhB) into metal-organic frameworks (Tb-MOFs). The sample can be used as a ratiometric fluorescent probe, which not only avoids errors caused by instrument and environmental instability but also has multiple applications in detection. The results indicated that the RhB@MOFs exhibited a turned-off response toward Fe3+ and a turned-on response for the continuous detection of ascorbic acid (AA). This ratiometric fluorescent probe possessed high sensitivity and excellent selectivity in the continuous determination of Fe3+ and AA. It is worth mentioning that remarkable fluorescence change could be clearly observed by the naked eye under a UV lamp, which is more convenient in applications. In addition, the mechanisms of Fe3+- and AA-induced fluorescence quench and recovery are discussed in detail. This ratiometric probe displayed outstanding recognition of heavy metal ions and biomolecules, providing potential applications for water quality monitoring and biomolecule determination.

A Novel Dye-Modified Metal-Organic Framework as a Bifunctional Fluorescent Probe for Visual Sensing for Styrene and Temperature.

A novel fluorescent probe (C460@Tb-MOFs) was designed and synthesized by encapsulating the fluorescent dye 7-diethylamino-4-methyl coumarin (C460) into a terbium-based metal-organic framework using a simple ultrasonic impregnation method. It is impressive that this dye-modified metal-organic framework can specifically detect styrene and temperature upon luminescence quenching. The sensing platform of this material exhibits great selectivity, fast response, and good cyclability toward styrene detection. It is worth mentioning that the sensing process undergoes a distinct color change from blue to colorless, providing conditions for the accurate visual detection of styrene liquid and gas. The significant fluorescence quenching mechanism of styrene toward C460@Tb-MOFs is explored in detail. Moreover, the dye-modified metal-organic framework can also achieve temperature sensing from 298 to 498 K with high relative sensitivity at 498 K. The preparation of functionalized MOF composites with fluorescent dyes provides an effective strategy for the construction of sensors for multifunctional applications.

Novel Mn4+-Activated K2Nb1-xMoxF7 (0 ≤ x ≤ 0.15) Solid Solution Red Phosphors with Superior Moisture Resistance and Good Thermal Stability.

Nowadays, Mn4+-activated fluoride red phosphors with excellent luminescence properties have triggered tremendous attentions for enhancing the performance of white light-emitting diodes (WLEDs). Nonetheless, the poor moisture resistance of these phosphors impedes their commercialization. Herein, we proposed the dual strategies of "solid solution design" and "charge compensation" to design K2Nb1-xMoxF7 novel fluoride solid solution system, and synthesized the Mn4+-activated K2Nb1-xMoxF7 (0 ≤ x ≤ 0.15, x represents the mol % of Mo6+ in the initial solution) red phosphors via co-precipitation method. The doping of Mo6+ not only significantly improve the moisture resistance of the K2NbF7: Mn4+ phosphor without any passivation and surface coating, but also effectively enhance the luminescence properties and thermal stability. In particular, the obtained K2Nb1-xMoxF7: Mn4+ (x = 0.05) phosphor possesses the quantum yield of 47.22% and retains 69.95% of its initial emission intensity at 353 K. Notably, the normalized intensity of the red emission peak (627 nm) for the K2Nb1-xMoxF7: Mn4+ (x = 0.05) phosphor is 86.37% of its initial intensity after immersion for 1440 min, prominently higher than that of the K2NbF7: Mn4+ phosphor. Moreover, a high-performance WLED with high CRI of 88 and low CCT of 3979 K is fabricated by combining blue chip (InGaN), yellow phosphor (Y3Al5O12: Ce3+) and the K2Nb1-xMoxF7: Mn4+ (x = 0.05) red phosphor. Our findings convincingly demonstrate that the K2Nb1-xMoxF7: Mn4+ phosphors have a good practical application in WLEDs.

Hg3(SeO3)2(SO4): A UV Nonlinear Optical Mercury Selenite Sulfate Constructed by Neat [Hg6O8(SeO3)4]∞ Layers and SO4 Tetrahedra.

A novel mercury selenite sulfate named Hg3(SeO3)2(SO4) has been successfully synthesized under a mild hydrothermal method. Hg3(SeO3)2(SO4) crystallizes in a monoclinic space group P21 and features a unique three-dimensional (3D) frame structure formed by [Hg6O8(SeO3)4]∞ layers and SO4 tetrahedra, which enables it to exhibit a comprehensive performance of a moderate second-harmonic generation (SHG) response of approximately 1.3 times that of baseline KH2PO4 (KDP), a moderate birefringence (0.118@546 nm), and a wide band gap (4.70 eV), which indicates that it has potential for application as an ultraviolet (UV) nonlinear optical material. Detailed theoretical calculations show that the Hg2+-based polyhedra with large polarizability and deformability and the SeO3 groups with stereochemically active lone pair (SCALP) electrons are the main contributors to moderate optical properties.

Host-Guest Symmetry and Charge Matching in Glycine-Templated Metal Sulfate-Oxalates Obtained by a Solvent-Free Method.

Two metal sulfate-oxalates, (Hgly)2·Zn(SO4)(C2O4) (1) and Hgly·In(SO4)(C2O4)(gly) (2), were prepared under solvent-free conditions, where gly = glycine. They have similar layered structures despite the fact that aliovalent metal ions are used as structural nodes. Notably, glycine molecules play dual roles as a protonated cation and a zwitterionic ligand in compound 2. The two compounds display moderate second-harmonic-generation (SHG) responses, confirming their noncentrosymmetric structures. Theoretical calculations were performed to reveal the origin of their SHG responses.

A Novel Dual-Emission Fluorescence Probe Based on CDs and Eu3+ Functionalized UiO-66-(COOH)2 Hybrid for Visual Monitoring of Cu2.

In this work, CDs@Eu-UiO-66(COOH)2 (denoted as CDs-F2), a fluorescent material made up of carbon dots (CDs) and a Eu3+ functionalized metal-organic framework, has been designed and prepared via a post-synthetic modification method. The synthesized CDs-F2 presents dual emissions at 410 nm and 615 nm, which can effectively avoid environmental interference. CDs-F2 exhibits outstanding selectivity, great sensitivity, and good anti-interference for ratiometric sensing Cu2+ in water. The linear range is 0-200 µM and the limit of detection is 0.409 µM. Interestingly, the CDs-F2's silicon plate achieves rapid and selective detection of Cu2+. The change in fluorescence color can be observed by the naked eye. These results reveal that the CDs-F2 hybrid can be employed as a simple, rapid, and sensitive fluorescent probe to detect Cu2+. Moreover, the possible sensing mechanism of this dual-emission fluorescent probe is discussed in detail.

A Ratiometric Fluorescent Sensor Based on Dye/Tb (III) Functionalized UiO-66 for Highly Sensitive Detection of TDGA.

Thiodiglycolic acid (TDGA) is a biomarker for monitoring vinyl chloride exposure. Exploring a facile, rapid and precise analysis technology to quantify TDGA is of great significance. In this research, we demonstrate a fluorescent sensor based on dual-emissive UiO-66 for TDGA detection. This ratiometric fluorescent material named C460@Tb-UiO-66-(COOH)2 was designed and synthesized by introducing organic dye 7-diethylamino-4-methylcoumarin (C460) and Tb3+ into UiO-66-(COOH)2. The as-obtained C460@Tb-UiO-66-(COOH)2 samples showed highly selective recognition, excellent anti-interference and rapid response characteristics for the recognition of TDGA. The detection limit is 0.518 mg·mL-1, which is much lower than the threshold of 20 mg·mL-1 for a healthy person. In addition, the mechanism of TDGA-induced fluorescence quenching is discussed in detail. This sensor is expected to detect TDGA content in human urine.

A Novel Turn-On Fluorescence Probe Based on Cu(II) Functionalized Metal-Organic Frameworks for Visual Detection of Uric Acid.

As an important biomarker in urine, the level of uric acid is of importance for human health. In this work, a Cu(II) functionalized metal-organic framework (Cu2+@Tb-MOFs) is designed and developed as a novel fluorescence probe for wide-range uric acid detection in human urine. The study shows that this fluorescence platform demonstrated excellent pH-independent stability, high water tolerance, and good thermal stability. Based on the strong interaction between metal ions and uric acid, the designed Cu2+@Tb-MOFs can be employed as efficient turn-on fluorescent probes for the detection of uric acid with wide detection range (0~104 µM) and high sensitivity (LOD = 0.65 µM). This probe also demonstrates an anti-interference property, as other species coexisted, and the possibility for recycling. The sensing mechanisms are further discussed at length. More importantly, we experimentally constructed a molecular logic gate operation based on this fluorescence probe for intelligent detection of uric acid. These results suggest the Cu(II) functionalized metal-organic framework can act as a prominent candidate for personalized monitoring of the concentration of uric acid in the human urine system.

Sharp Enhancement of Birefringence in Antimony Oxalates Achieved by the Cation-Anion Synergetic Interaction Strategy.

Birefringent materials with large birefringence play an important role in in laser science and technology owing to their ability to modulate polarized light. However, the lack of systematic and effective synthesis strategies severely hinders the development of novel superior birefringent materials. Herein, the cation-anion synergetic interaction strategy was proposed to successfully synthesize two excellent UV birefringent materials, RbSb(C2O4)F2·H2O and [C(NH2)3]Sb(C2O4)F2·H2O. Both compounds feature unprecedented [Sb(C2O4)F2]∞- anionic chains composed of planar π-conjugated [C2O4]2- units and a distorted SbO4F2 complex with stereochemically active lone pairs, which induce a large optical anisotropy. Remarkably, further enhancement of birefringence in [C(NH2)3]Sb(C2O4)F2·H2O was achieved via cation-anion synergetic interactions between the [C(NH2)3]+ cationic groups and [Sb(C2O4)F2]∞- anionic chains. It exhibited a giant birefringence of 0.323@546 nm, twice larger than that of its analogue RbSb(C2O4)F2·H2O (0.162@546 nm). A detailed structural analysis and theoretical calculations revealed that the cation-anion synergetic interaction strategy is an effective strategy for the efficient exploration of superior birefringent materials, which will guide the further exploration of new structure-driven functional materials.

Tin Chloride Sulfates A3Sn2(SO4)3-xCl1+2x (A = K, Rb, Cs; x = 0, 1) as Multifunctional Optical Materials.

The series of alkali-metal tin chloride sulfates A3Sn2(SO4)3-xCl1+2x (A = K, Rb, Cs; x = 0, 1), K3Sn2(SO4)3Cl, Rb3Sn2(SO4)2Cl3, and Cs3Sn2(SO4)2Cl3, were successfully synthesized through an improved mild hydrothermal method. Interestingly, in addition to the cation size effect, the structure-directing effect of anions induces different symmetries in the three title compounds, with K3Sn2(SO4)3Cl being noncentrosymmetric, while Rb3Sn2(SO4)2Cl3 and Cs3Sn2(SO4)2Cl3 are centrosymmetric. Powder second-harmonic generation (SHG) measurements indicate that K3Sn2(SO4)3Cl is a nonlinear optical material that is type I phase matchable with a weak SHG response (0.1× KDP). Photoluminescence tests reveal that the three title compounds emit strong greenish yellow, orange, and salmon light, respectively, under UV excitation, indicating that they are promising inorganic solid fluorescent materials. Simultaneously, a detailed structural analysis of all the known tin(II) halide sulfates has been performed, which will guide the systematic exploration of high-performance tin(II)-based functional materials in the future.

Highly Dispersed Mo Sites on Pd Nanosheets Enable Selective Ethanol-to-Acetate Conversion.

The fermentation of biomass allows for the generation of major renewable ethanol biofuel that has high energy density favorable for direct alcohol fuel cells in alkaline media. However, selective conversion of ethanol to either CO2 or acetate remains a great challenge. Especially, the ethanol-to-acetate route usually demonstrates decentoxidation current density relative to the ethanol-to-CO2 route that contains strongly adsorbed poisons. This makes the total oxidation of ethanol to CO2 unnecessary. Here, we present a highly active ethanol oxidation electrocatalyst that was prepared by in situ decorating highly dispersed Mo sites on Pd nanosheets (MoOx/Pd) via a surfactant-free and facile route. We found that ∼2 atom % of Mo on Pd nanosheets increases the current density to 3.8 A mgPd-1, around 2 times more active relative to the undecorated Pd nanosheets, achieving nearly 100% faradic efficiency for the ethanol-to-acetate conversion in an alkaline electrolyte without the generation of detectable CO2, evidenced by in situ electrochemical infrared spectroscopy, nuclear magnetic resonance, and ion chromatography. The selective and CO2-free conversion offers a promising strategy through alcohol fuel cells for contributing comparable current density to power electrical equipment while for selective oxidation of biofuels to useful acetate intermediate for the chemical industry.

Bi3+-Doped BaYF5:Yb,Er Upconversion Nanoparticles with Enhanced Luminescence and Application Case for X-ray Computed Tomography Imaging.

In this work, BaYF5:20%Yb3+/2%Er3+/x%Bi3+ (abbreviated as BaYF5:Yb,Er,Bix, where x = 0-3.0) upconversion nanoparticles (UCNPs) with various doping concentrations of Bi3+ were synthesized through a simple hydrothermal method. The influence of the doping amount of Bi3+ on the microstructures and upconversion luminescence (UCL) properties of the BaYF5:Yb,Er,Bix UCNPs was studied in detail. The doping concentration of Bi3+ has little influence on the microstructures of the UCNPs but significantly impacts their UCL intensities. Under excitation of a 980 nm near-IR laser, the observed UCL intensities for the BaYF5:Yb,Er,Bix UCNPs display first an increasing trend and then a decreasing trend with an increase in the ratio x, giving a maximum at x = 2.5. A possible energy-transfer process and simplified energy levels of the BaYF5:Yb,Er,Bix UCNPs were proposed. The potential of the BaYF5:Yb,Er,Bix UCNPs as contrast agents for computerized tomography (CT) imaging was successfully demonstrated. An obvious accumulation of BaYF5:Yb,Er,Bix in tumor sites was achieved because of high passive targeting by the enhanced permeability and retention effect and relatively low uptake by a reticuloendothelial system such as liver and spleen. This work paves a new route for the design of luminescence-enhanced UNCPs as promising bioimaging agents for cancer theranostics.

(NH4)3[B(OH)3]2(COOH)3: a graphite-like UV nonlinear optical material with a large birefringence via structural optimization.

A novel noncentrosymmetric (NCS) metal-free formic-borate, (NH4)3[B(OH)3]2(COOH)3, has been discovered, which exhibits an infrequent graphite-like structure. The alliance of two types of π-conjugated planar anions BO33- and COOH- produced an optimized layered structure to maximize the anisotropic polarizability, resulting in an extremely large birefringence (0.156@546 nm), larger than that of the classical commercial UV birefringent material α-BBO (0.122@546 nm). This strategy that structural optimization could enhance birefringence will guide the discovery of large birefringence materials, especially in the UV region.

Two amino acid-templated metal phosphates: surfactant-thermal synthesis, water stability, and proton conduction.

Two new metal phosphates, namely, Zn(HPO4)(C6H11NO2) (1) and (C5H10NO2)Ga4(PO4)4F·3H2O (2), were prepared under surfactant-thermal conditions. Single-crystal X-ray diffraction analyses reveal that compound 1 has a zigzag-chain structure decorated with homoproline and compound 2 has a three-dimensional zeolite-like structure templated by proline. Notably, compound 2 remains stable in both boiling water and aqueous solutions with a pH range of 2-12. It shows a proton conductivity of 8.89 × 10-4 S cm-1 at 85 °C and 95% relative humidity.

Two-stage evolution from phosphate to sulfate of new KTP-type family members as UV nonlinear optical materials through chemical cosubstitution-oriented design.

KTiOPO4 (KTP) is a classic commercial nonlinear optical (NLO) crystal, but its narrow bandgap (3.52 eV) prevents its practical application in the ultraviolet (UV) region. Many trials to widen the narrow bandgap of KTP have failed in the past few decades. A chemical cosubstitution strategy was implemented to design new members of the KTP-type family as potential UV NLO materials. First, a novel centrosymmetric KTP-type compound NH4SbFPO4·H2O with a sharply enlarged bandgap (5.01 eV) was obtained through three-site aliovalent substitution. Second, the noncentrosymmetric NH4SbF2SO4 was synthesized by the introduction of more F- anions to destroy the crystal symmetry and SO42- to replace PO43- for balancing the charge in NH4SbFPO4·H2O, which realized the transformation from a visible phosphate system to solar blind UV sulfate system for KTP-type family NLO materials. The preliminary experimental results indicated that NH4SbF2SO4 is a promising solar blind UV NLO material. The first-principles calculations revealed that the sharply enlarged bandgap resulted from the substitution of the transition metal cations with the main group metal cations and the introduction of F- anions with high electronegativity.

Terbium-based metal-organic frameworks: highly selective and fast respond sensor for styrene detection and construction of molecular logic gate.

Volatile organic compounds (VOCs) are extremely harmful to the human body and environment, thus it is greatly meaningful and urgent to detect VOCs. In this work, terbium-based metal-organic frameworks (Tb-MOFs) have been prepared successfully via a facile and efficient route. These well-constructed Tb-MOFs architectures exhibit characteristic green emission of Tb3+ ion upon excitation of UV light. It is noteworthy that the Tb-MOFs can act as a convenient and efficient luminescent sensor for VOCs. Especially, the Tb-MOFs displayed high selectivity and superior sensitivity towards the sensing of styrene solution and vapor through fluorescence quenching mechanism. The Tb-MOFs can realize fast detection for styrene vapor with a response time of 30 s. The mechanism of fluorescence quenching of Tb-MOFs induced by styrene was also discussed. More importantly, we have designed a logic gate operation with the combination of the sensor for the intelligent detection of styrene. This developed type of lanthanide luminescent metal-organic frameworks (Ln-MOFs) based on the combination of fluorescence sensor and logic gate has a great application prospect in the detection of VOCs in daily life.

Co0.8Zn0.2MoO4/C Nanosheet Composite: Rational Construction via a One-Stone-Three-Birds Strategy and Superior Lithium Storage Performances for Lithium-Ion Batteries.

CoMoO4 has gained great attention as an anode material for lithium-ion batteries owing to its high theoretical capacity of 980 mAh g-1 and relatively high electrochemical activity. Unfortunately, CoMoO4 anode also has some drawbacks such as low electronic/ionic conductivity, inferior cyclic stability, and relative severe volumetric expansion during the lithiation/delithiation process, greatly inhibiting its further development and application. Herein, we report Co0.8Zn0.2MoO4/C nanosheet composite constructed via a novel and facile one-stone-three-birds strategy. The preparation of the Co0.8Zn0.2MoO4/C nanosheet is based on the following two-step process: the formation of Co/Zn nanosheet precursors derived from Co/Zn-ZIF rhombic dodecahedra via solvothermal pretreatment, followed by a calcination treatment with molybdic acid (H2MoO4) in air. The as-prepared Co0.8Zn0.2MoO4/C is monoclinic crystal structured composite with the in situ formed active carbon, which is well-defined nanosheet with a rough surface and mean thickness of 60-70 nm for a single sheet. This Co0.8Zn0.2MoO4/C nanosheet composite possesses a larger surface area of 37.60 m2 g-1, showing a mesoporous structure. When used as anode materials, the as-obtained Co0.8Zn0.2MoO4/C composite can deliver as high as a discharge capacity of 1337 mAh g-1 after 300 cycles at 0.2C and still retain the capacity of 827 mAh g-1 even after 600 cycles at 1C, exhibiting outstanding lithium storage performances. The higher capacity and superior cyclic stability of the Co0.8Zn0.2MoO4/C composite should be ascribed to the synergistic effect of the substitution of Zn2+, in situ composited active carbon and the as-constructed unique microstructure for the Co0.8Zn0.2MoO4/C composite. Our present work provides a facile one-stone-three-birds strategy to effectively construct the architectures and significantly enhance electrochemical performances for other transition metal electrode materials.

Rb3SbF3(NO3)3: an excellent antimony nitrate nonlinear optical material with a strong second harmonic generation response fabricated by a rational multi-component design.

A novel antimony fluoride nitrate, Rb3SbF3(NO3)3, fabricated by a rational multi-component design, has been successfully synthesized by a rapid evaporation concentration method. This title compound crystallizes in a polar noncentrosymmetric (NCS) space group (P21) and presents a complicated three-dimensional (3D) network composed of SbO3F3, Rb-centered distorted polyhedra and π-conjugated planar triangular NO3 groups. Rb3SbF3(NO3)3 is a potential UV nonlinear optical material due to its large phase-matchable second harmonic generation (SHG) response of approximately 2.2 times that of KH2PO4 (KDP) and a wide band gap of 3.75 eV. Theoretical calculation analysis was used to rationalize the large SHG effect, which originates from the multi-component synergistic effect including moderately polarizable Rb+ cations, a stereochemically active lone pair effect of Sb3+ and NO3 groups with a π-conjugated planar triangular structure.