Solid-state Spectroscopy Research Articles

Time-Dependent Solvent-Driven Solid-State Fluorescence-based Numeric Coding.

Controllable solid-state transformations can provide a basis for novel functional materials. Herein, we report a series of solid-state systems that can be readily transformed between amorphous, co-crystalline, and mixed crystalline states via grinding or exposure to solvent vapors. The present solid materials were constructed using an all-hydrocarbon macrocycle, cyclo[8](1,3-(4,6-dimethyl)benzene) (D4d-CDMB-8) (host), and neutral aggregation-caused quenching dyes (guests), including 9,10-dibromoanthracene (1), 1,8-naphtholactam (2), diisobutyl perylene-3,9-dicarboxylate (3), 4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (4), 4,7-di(2-thienyl)-benzo[2,1,3]thiadiazole (5), and 4-imino-3-(pyridin-2-yl)-4H-quinolizine-1-carbonitrile (6). Seven co-crystals and six amorphous materials were obtained via host-guest complexation. Most of these materials displayed turn-on fluorescence emission (up to 20-fold enhancement relative to the corresponding solid-state guests). The interconversion between amorphous, co-crystalline states, and crystalline mixtures could be induced by exposure to solvent vapors or by subjecting to grinding. The transformations could be monitored readily by means of single-crystal and powder X-ray diffraction analyses, as well as solid-state fluorescent emission spectroscopy. The externally induced structural interconversions resulted in time-dependent fluorescence changes. This allowed sets of privileged number array codes to be generated.

Crystallization Behavior of Heterotrinuclear ZnII–LnIII–ZnII Complexes Bearing Two Tripodal Nonadentate Ligands: Possibility for Absolute Spontaneous Resolution

Crystal structures and crystallization behaviors of a series of heterotrinuclear ZnII–LnIII–ZnII complexes, [(L)ZnLnZn(L)]NO3 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, and Y; H3L = 1,1,1-tris[(3-methoxysalicylideneamino)methyl]ethane), were examined. Because the trinuclear complex cation has two asymmetric centers (Δ and Λ) at the ZnII sites resulting from the twist of the tripodal ligand arms, it was confirmed from the single-crystal X-ray diffraction (SC-XRD) analysis that these complexes have homochiral structures (i.e., Λ,Λ- or Δ,Δ-enantiomer) in the solid state. Among the series of compounds, various types of spontaneous resolution were observed, which were classified by the SC-XRD analysis (using the Flack parameter) or solid-state circular dichroism spectroscopy. The latter technique was used to determine the chirality of every single crystal and that of an entire bulk mixture of microcrystals obtained in a particular crystallization process. It was found that the TbIII complex, [(L)ZnTbZn(L)]NO3·2MeOH (Zn–Tb–Zn), exclusively deposited the left-handed Λ-conglomerate in every crystallization experiment. This phenomenon may be termed “absolute spontaneous resolution.” It was also notable that only the lanthanoid(III) ions with an even number of 4f electrons (Eu, Tb, Ho, and Lu) exhibited this unusual phenomenon. It was also attempted to deposit the opposite-handed Zn–Tb–Zn Δ-conglomerate, which could not be isolated from the ambient crystallization. Seeding of a crashed single-crystal Δ-conglomerate of [(L)ZnYZn(L)]NO3·2MeOH (Zn–Y–Zn), which was isomorphic to Zn–Tb–Zn, into a saturated methanolic solution of Zn–Tb–Zn gave, for the first time, crystals of the corresponding Δ-conglomerate.

New mixed ligand complexes of lanthanide metal cations containing acesulfame/nicotinamide. Synthesis and structural characterizations

The mixed ligand complexes containing acesulfame and nicotinamide ligands of rare earth metal cations Eu3+, Tb3+, Ho3+, Er3+ and Yb3+ were synthesized and their structural characterizations were examined. The complexes' thermal decomposition steps and structural properties were investigated by chemical analysis, infrared spectroscopy, mass analysis, and solid-state UV-vis spectroscopy and thermal analysis methods. According to the results obtained, it is suggested that the metal cations have six coordination sphere. It is recommended that the geometry of the complexes is distorted octahedral with two nicotinamide ligands that make neutral coordination over the nitrogen atom of the pyridine group, two aqua ligands and two monoanionic monodentate acesulfame ligands that coordinated via the acidic imine nitrogen. The coordination compounds perform charge balances with an anionic acesulfame situated the coordination sphere. Except for the Er3+ metal cation complex, it has been determined that all other structures have one hydrate water. From the thermal analysis curves, it was obtained that oxide derivatives of each metal cation were formed in the reaction pots as the last degradation products of Ho3+, Er3+ and Yb3+ complexes. It has been suggested that sulfate salts of related metal cations remain as thermal decomposition products in Eu3+ and Tb3+ metal cation-centered structures.

Tailoring structure for improved sodium mobility and electrical properties in V2O5–Nb2O5–P2O5 Glass(es)-(Ceramics)

This study investigates the influence of structural modifications induced by the introduction of Nb2O5 on the thermal, (micro)structural, and electrical properties of quaternary system 35Na2O–10V2O5-(55–x)P2O5-xNb2O5 (x = 0–40 mol%). Non-monotonic trends in DC conductivity and activation energy are attributed to the facilitating effect of Nb2O5 on the transport of Na + ions, confirming the mixed glass former effect. The results demonstrate that the electrical conductivity mechanism is purely ionic, with V2O5 acting as both, glass modifier and network-former with vanadate units being in predominantly 4-fold coordination and without actively participating in the conduction process. Complementary Raman and IR-ATR spectroscopic studies in combination with solid-state impedance spectroscopy (SS-IS) reveal a strong correlation between structural and electrical properties indicating that the enhancement in conductivity is driven by the formation of mixed niobate-phosphate glass network. The increase in conductivity is followed by a gradual transition of glass structure from a predominantly phosphate glass network (x ≤ 10, Region I) into a mixed niobate-phosphate glass network (10 ≤ x ≤ 20, Region II). The conductivity increases by a factor of ∼4.5 within the series reaching the highest value of 3.29 × 10−10 Ω−1 cm−1 for Nb-20 glass. In the predominantly niobate network (x ≥ 25, Region III), the 3D clustering of NbO6 octahedra hinders the transport of Na + ions. The scaling features of the conductivity spectra additionally confirm the ionic mechanism of electrical transport and provide insight into the local dynamics of Na+ ions.

Li-Ion Transfer Mechanism of Gel Polymer Electrolyte with Sole Fluoroethylene Carbonate Solvent.

Although gel polymer electrolytes (GPEs) represent a promising candidate to address the individual limitations of liquid and solid electrolytes, their extensive development is still hindered due to the veiled Li-ion conduction mechanism. Herein, the related mechanism in GPEs is extensively studied by developing an in situ polymerized GPE comprising fluoroethylene carbonate (FEC) solvent and carbonate ester segments (F-GPE). Practically, although with high dielectric constant, FEC fails to effectively transport Li ions when acting as the sole solvent. By sharp contrast, F-GPE demonstrates superior electrochemical performances, and the related Li-ion transfer mechanism is investigated using molecular dynamics simulations and 7 Li/6 Li solid-state nNMR spectroscopy. The polymer segments are extended with the swelling of FEC, then an electron-delocalization interface layer is generated between abundant electron-rich groups of FEC and the polymer ingredients, which works as an electron-rich "Milky Way" and facilitates the rapid transfer of Li ions by lowering the diffusion barrier dramatically, resulting in a high conductivity of 2.47× 10-4 Scm-1 and a small polarization of about 20mV for Li//Li symmetric cell after 8000h. Remarkably, FEC provides high flame-retardancy and makes F-GPE remains stable under ignition and puncture tests.

Solution-state nuclear magnetic resonance spectroscopy of crystalline cellulosic materials using a direct dissolution ionic liquid electrolyte.

Owing to its high sustainable production capacity, cellulose represents a valuable feedstock for the development of more sustainable alternatives to currently used fossil fuel-based materials. Chemical analysis of cellulose remains challenging, and analytical techniques have not advanced as fast as the development of the proposed materials science applications. Crystalline cellulosic materials are insoluble in most solvents, which restricts direct analytical techniques to lower-resolution solid-state spectroscopy, destructive indirect procedures or to 'old-school' derivatization protocols. While investigating their use for biomass valorization, tetralkylphosphonium ionic liquids (ILs) exhibited advantageous properties for direct solution-state nuclear magnetic resonance (NMR) analysis of crystalline cellulose. After screening and optimization, the IL tetra-n-butylphosphonium acetate [P4444][OAc], diluted with dimethyl sulfoxide-d6, was found to be the most promising partly deuterated solvent system for high-resolution solution-state NMR. The solvent system has been used for the measurement of both 1D and 2D experiments for a wide substrate scope, with excellent spectral quality and signal-to-noise, all with modest collection times. The procedure initially describes the scalable syntheses of an IL, in 24-72 h, of sufficient purity, yielding a stock electrolyte solution. The dissolution of cellulosic materials and preparation of NMR samples is presented, with pretreatment, concentration and dissolution time recommendations for different sample types. Also included is a set of recommended 1D and 2D NMR experiments with parameters optimized for an in-depth structural characterization of cellulosic materials. The time required for full characterization varies between a few hours and several days.

A colloidal hydrogel-based drug delivery system overcomes the limitation of combining bisphosphonates with bioactive glasses: in vitro evidence of a potential selective bone cancer treatment allied with bone regeneration

Bisphosphonates are a class of drugs that induce bone cancer cell death and favor bone regeneration, making them suitable for bone cancer treatment. However, when combined with bioactive glasses to enhance bone regeneration, a chemical bond between biphosphonates and the glass surface inactivates their mechanism of action. A new colloidal hydrogel-based drug delivery system could overcome that limitation once bisphosphonates, such as zoledronic acid (ZA), are incorporated into hydrogel micelles, avoiding their interaction with the glass surface. In this work, we proposed formulations based on a poloxamer 407 thermo-responsive hydrogel matrix containing holmium-doped bioactive glass nanoparticles and different concentrations (0.05 and 5 mg/mL) of ZA. We characterized the influence of the glass and the ZA on the hydrogel properties. In addition, a drug concentration screening was performed, and biological characterizations evaluated the best result. The biological characterization consisted of evaluating cytotoxicity and in vitro bone regeneration ability through cell migration and quantification of genes related to osteogeneses through RT-PCR. The results suggest that the addition of glasses and ZA to the poloxamer did not significantly influence the sol-gel transition of the hydrogels (around 13 °C) regardless of the ZA content. However, the ZA at high concentration (PL-ZA100) decreased the enthalpy of gel formation from 68 to 43 kJ.mol−1 when compared with the pure hydrogel formulation (PL), suggesting a water structurer role of ZA, which is withdrawn when glass particles are added to the system (PL-BG5Ho-ZA100). Solid-state 31P nuclear resonance spectroscopy results showed that part of the ZA is chemically bonded to the glass surface, which explains the withdrawal in the water structurer role of ZA when the glasses were incorporated into the hydrogel. Besides, based on the drug release results, we proposed a model where part of the ZA is “free,” encapsulated in the hydrogel matrix, while another part of the ZA is bonded to the glass surface. Finally, considering the in vitro results and our proposed model, the ratio between “free” and “bonded” ZA in our drug delivery systems showed in vitro evidence of a cancer treatment that selectively kills osteosarcoma cells while still favoring an osteogenic microenvironment. By overcoming the limitation of combining bisphosphonates with bioactive glasses, hydrogel-based drug delivery systems can be a solution for the development of new formulations proposed for bone cancer treatment in conjunction with bone regeneration.

Possible implementation of salicylate anions in lead detoxification

The water-soluble coordination polymer of formula {[Pb(Sal)2(H2O)]n} (SaLead), was obtained from the reaction between Pb(NO3)2 and the potassium salt of salicylic acid (SalH), an anti-inflammatory drug, which is also use as food preservation, in cosmetics etc. The compound was characterized by melting point, Attenuated Total Reflectance-Fourier Transform Infra-Red (ATR-FTIR) spectroscopy and X-ray diffraction crystallography (XRD) in solid state and in solution by Ultra Violet (UV) and 1H NMR spectroscopies. The binding affinity of SalK to Pb(II) ions towards SaLead was determined in order to examine its possible implementation in lead detoxification. The in vitro non-toxic behaviour of SalK and its complex SaLead was evaluated against normal human fetal lung fibroblast cells (MRC-5). The corresponding IC50 values are 260 ± 13 and > 1600 μM respectively. The non-genotoxic in vitro activity of SaLead was confirmed with the micronucleus (MN) assay, while its in vivo non-toxicity behaviour was evaluated with Allium cepa and Artemia salina assays.

O-doped and nitrogen vacancies 3D C3N4 activation of peroxydisulfate for pollutants degradation and transfer hydrogenation of nitrophenols with water

A three-dimensional carbon nitride co-modified through oxygen doping and nitrogen vacancies was prepared via an ordinary hydrothermal and thermal polymerization reaction of dicyandiamide and polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer (PEPE-C3N4). The electronic structure of carbon and nitrogen was proven through solid-state nuclear magnetism and electron loss energy spectroscopy. Density functional theory calculations revealed reduced band gap and altered charge density. The results show that the PEPE-C3N4 constructed by O-doped and nitrogen vacancy released electrons to activate peroxodisulfate (PDS), in which the 1% PEPE-C3N4 in the photocatalytic PDS system showed about 12 and 30 times increase of the photodegradation of 2-mercaptobenzothiazole (MBT) and bisphenol A (BPA), respectively, compared to graphite-phase carbon nitride (g-C3N4). The degradation products of MBT and BPA were named according to applying liquid chromatography-mass spectrometry and conceivable degradation pathways proposed. Furthermore, 1% PEPE-C3N4 had the highest hydrogen production activity (8275.74 μmol•h−1•g−1); it completely hydrogenates 4-nitrophenol to 4-aminophenol after 2.5 h of simulated sunlight. Additionally, biomass was used instead of TEOA to measure the coupling operation of H2 generation and selective oxidation of 5-hydroxymethylfurfural (HMF) to 2, 5-furandicarboxaldehyde (DFF). The optimized PEPE-C3N4 demonstrated high efficiency for selective oxidation of HMF to DFF with simultaneous H2 co-production (1176.84 μmol•h−1•g−1 for H2 and 357.67 μmol•h−1•g−1 for DFF), 5.31 and 2.36 times more excellent than that of g-C3N4, respectively. This study outlines a way to devise photocatalysts for organic pollutant degradation and biomass value-added co-production of hydrogen.

Spectroscopic identification of Ca-bearing uranyl silicates formed in C–S–H systems

Portland cement-based grouts used for radioactive waste immobilisation contain a Ca- and Si-rich binder phase, known as calcium–silicate–hydrate (C–S–H). Depending on the blend of cement used, the Ca/Si ratio can vary considerably. A range of C–S–H minerals with Ca/Si ratios from 0.6 to 1.6 were synthesised and contacted with aqueous U(VI) at 0.5 mM and 10 mM concentrations. Solid-state 29Si MAS-NMR spectroscopy was applied to probe the Si coordination environment in U(VI)-contacted C–S–H minerals and, in conjunction with U LIII-edge X-ray absorption spectroscopy analysis, inferences of the fate of U(VI) in these systems were made. At moderate or high Ca/Si ratios, uranophane-type uranyl silicates or Ca-uranates dominated, while at the lowest Ca/Si ratios, the formation of a Ca-bearing uranyl silicate mineral, similar to haiweeite (Ca[(UO2)2Si5O12(OH)2]·3H2O) or Ca-bearing weeksite (Ca2(UO2)2Si6O15·10H2O) was identified. This study highlights the influence of Ca/Si ratio on uranyl sequestration, of interest in the development of post-closure safety models for U-bearing radioactive waste disposal.

Ionic liquid dynamics and electrical conductivity under confinement within micro and nanocellulose ionogels

To investigate the effect of cellulose matrix on the diffusion and conductivity properties of the ionogels formed with the BMIMCl ionic liquid (IL), two types of samples were made with micro (CMC) and nano (CNC) cellulose. The cellulose interactions with IL were studied by 1H and 13C NMR solid-state spectroscopy. The cation [BMIM]+ self-diffusion coefficient was calculated based on Fast Field Cycling 1H NMR relaxation measurements. The ionic conductivity was measured by the thermal scanning conductometry method. The NMR spectra at room temperature revealed that cation in the CNC-based ionogel interacts more strongly with the cellulose chain than in the CMC-based ionogel through the methyl group at the end of the alkyl chain. Despite this, the cellulose matrix's influence on the cations' dynamics and electrical conductivity are comparable in both ionogels. The diffusion coefficient is reduced by about two times and the conductivity by about 30% compared with bulk IL.

Solid-state fluorescent 3,3-diarylallylidene indolinones by pseudo-five-component synthesis

One-pot syntheses of 3,3-diarylallylidene indolinones are achieved by pseudo-four- and pseudo-five-component reactions. The title compounds are obtained as a mixture of E/Z-configured isomers. The photophysical characteristics are assessed by absorption and solid-state emission spectroscopy. Irrespective of their configuration, the 3,3-diarylallylidene indolinones fluoresce in the solid state for electron-withdrawing and weakly electron-releasing remote p-phenyl substituted dyes with concomitantly Boc substitution of the lactam moiety. DFT and TD DFT calculation reproduce and rationalize the electronic structure of the longest wavelength absorption and emission bands.

Neptunium Alkoxide Chemistry: Expanding Alkoxides to the Transuranium Elements.

Two oxo-containing neptunium(IV) tert-butoxides, [Np3O(OtBu)10] (1) and [K4Np2O(OtBu)10] (2), were synthesized using the ligand substitution between neptunium(IV) silylamides and HOtBu, whereas the salt metathesis between [NpCl4(DME)2] (DME = dimethoxyethane) and various amounts of LiOtBu resulted in the formation of oxo-free alkoxides [Np(OtBu)4(py)2] (3; py = pyridine) and [Li(THF)]2[Np(OtBu)6] (4; THF = tetrahydrofuran). These complexes are the first structurally characterized neptunium(IV) alkoxides using single-crystal X-ray diffraction and solid-state absorption spectroscopy, which provide data for the development of anhydrous metal-organic neptunium chemistry.

Modulated self-assembly of three flexible Cr(III) PCPs for SO2 adsorption and detection.

Modulated self-assembly protocols are used to develop facile, HF-free syntheses of the archetypal flexible PCP, MIL-53(Cr), and novel isoreticular analogues MIL-53(Cr)-Br and MIL-53(Cr)-NO2. All three PCPs show good SO2 uptake (298 K, 1 bar) and high chemical stabilities against dry and wet SO2. Solid-state photoluminescence spectroscopy indicates all three PCPs exhibit turn-off sensing of SO2, in particular MIL-53(Cr)-Br, which shows a 2.7-fold decrease in emission on exposure to SO2 at room temperature, indicating potential sensing applications.

Quantum interferometric spectroscopy of a biexciton

Fourier transform spectroscopy with classical interferometry corresponds to the measurement of a single-photon intensity spectrum from the viewpoint of the particle nature of light. In contrast, the Fourier transform of two-photon quantum interference patterns provides the intensity spectrum of the two photons as a function of the sum- or difference frequency of the constituent photons. This unique feature of quantum interferometric spectroscopy offers a different type of spectral information from the classical measurement and may prove useful for nonlinear spectroscopy with two-photon emission. Here, we report the experimental demonstration of two-photon quantum interference of biphotons emitted via biexcitons in the semiconductor CuCl. Besides applying Fourier transform to quantum interference patterns, we reconstruct the intensity spectrum of the biexciton luminescence in the two-photon sum- or difference frequency. We discuss the connection between the reconstructed spectra and exciton states in CuCl as well as the capability of quantum interferometry in solid-state spectroscopy.

Carbazole-based aggregation-induced phosphorescent emission-active gold(I) complexes with various phosphorescent mechanochromisms.

A series of carbazole-containing gold(I) complexes modified with different substituents were successfully designed and synthesized, and their molecular structures were characterized by nuclear magnetic resonance spectroscopy and mass spectrometry. The aggregation-induced behaviors of these gold(I) complexes were studied by ultraviolet/visible and photoluminescence spectroscopy. Meanwhile, their mechanical force-responsive emissive properties were also investigated via solid-state photoluminescence spectroscopy. Interestingly, all these gold(I)-based luminogenic molecules were capable of exhibiting aggregation-induced phosphorescent emission phenomena. Furthermore, their solids of three gold(I) complexes displayed contrasting mechano-responsive phosphorescence features. More specifically, trifluoromethyl or methoxyl-substituted luminophores 1 and 3 demonstrated mechanochromic behaviors involving blue-shifted phosphorescence changes, and their mechanoluminochromic phenomena were reversible. However, the solid-state phosphorescence of phenyl-substituted luminophor 2 was not sensitive to external mechanical force.

Coordination Patterns of the Diphosphate in IDP Coordination Complexes: Crystal Structure and Chirality

The knowledge of accurate geometrical parameters from X-ray diffraction studies in the solid state of metal nucleotide is very important for understanding the relationship between structures and properties, including biochemical processes and even enzyme-metal-substrate interactions. The research is also very necessary to precisely and controllably design the functional materials. Here, seven types of coordination polymers of inosine 5'-diphosphate nucleotide (IDP) with transition metals, {[Zn(HIDP)(azpy)(H2O)2]·4H2O}n (1), {[Cd2(IDP)2(bpda)2]·[Cd(H2O)6]·11H2O}n (2), {[Cd3(IDP)2(4,4'-bipy)2(H2O)3]·6H2O}n (3), {[Cd2(IDP)2(bpe)2(H2O)2]·(H2bpe)·26H2O}n (4), {[Cu3(IDP)2(azpy)2(H2O)5]·5H2O}n (5), {[Cu3(IDP)2(bpe)2(H2O)5]·9H2O}n (6), and {[Co(HIDP)(azpy)(H2O)2]·7H2O}n (7) [4,4'-bipy = 4,4'-bipyridine, azpy = 4,4'-azopyridine, bpe = 1,2-bis(4-pyridyl)ethene, and bpda = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene], were designed, synthesized, and firmly characterized using single-crystal X-ray diffraction. The coordination patterns of the diphosphate group of IDP in these complexes were studied by crystallographic analysis, namely, open, close, and open-close hybrid types. We have investigated the diverse coordination patterns of the diphosphate group and its spatial relationship relative to the pentose ring on the basis of two conformational parameters, the pseudorotation phase angle and the degree of puckering. Crystallographic studies clearly reveal the correlation between the backbone torsion angle (ω' and φ) of the sugar-diphosphate and the conformational preference of the pentose ring, i.e., the signs of the backbone torsion angles ω' and φ are both plus (+) or minus (-), the conformation of the pentose ring is envelope form (E), while when one of the two signs is plus (+) and the other is minus (-), the pentose ring is in the twist form (T). This is the first time elucidation of the coordination pattern of diphosphate relative to the conformation of the pentose ring in nucleotide metal complexes, which are different from the other inorganic or organic diphosphate compounds. The chirality of these coordination polymers was examined by combining solid-state circular dichroism spectroscopy measurements with the explanation of their crystal structures. The results presented in this paper are very important for understanding their nucleotide coordination chemistry, their supramolecular chemistry, and even their biochemistry.

Blue Light-Excitable Broadband Yellow Emission in a Zero-Dimensional Hybrid Bismuth Halide with Type-II Band Alignment

Zero-dimensional (0D) organic-inorganic hybrid metal halides have captured broad interest in the lighting and display fields because of their unique electronic structures and splendid broadband emission properties. However, the blue light-excitable broadband yellow emissions have been rarely reported in 0D hybrid metal halides. Here, we design a new 0D bismuth hybrid, (4cmpyH)2BiCl5 (1, 4cmpy = 4-(chloromethyl)pyridine), featuring isolated edge-sharing bioctahedral [Bi2Cl10]4- dimers surrounded by rigid, conjugated, and luminescent organic [4cmpyH]+ cations. This material is able to show intrinsic broadband yellow emissions under blue light (468 nm) excitation with a long lifetime of 22.33 μs and a photoluminescence (PL) quantum yield of 5.56%. Solid-state UV-vis spectroscopy studies prove that introducing organic π-conjugated groups into hybrid systems leads to absorption in the visible light region, in favor of photoexcitation by visible light. By comparing the PL data of 1 and the organic template at room temperature and measuring variable-temperature PL spectra of 1, the blue light-excited broadband emission of 1 can be attributed to the synergistic emissions of intramolecular π → π* and n → π* transitions in the organic cations and triple self-trapped exciton (STE) states centralized at the highly distorted Bi-Cl lattices. Moreover, density functional theory calculations reveal a type-II band alignment in 1 with an indirect band gap of 2.64 eV, which is together determined by organic cations and inorganic bioctahedral units. To the best of our knowledge, our work represents the first report on the blue light-excitable STE emission in 0D Bi-based metal halides, which will largely promote the rapid development of novel high-performance yellow light-emitting materials.

Structural, Electrical and Optical Properties of Mg-Ni Thin Films for Hydrogen Storage Applications

Using the magnetron sputtering technique, Mg-Ni (150nm) bilayer thin films were deposited onto the simple, and ITO coated glass substrates. To obtain proper mixing and inter diffusion of thin film structure, annealing of the prepared thin films was made at constant temperature 523 K. The surface morphology of thin films confirms the uniform deposition of the Mg-Ni thin films on substrates. The Raman spectroscopy of thin films shows that the intensity of Raman peaks is decreased as the hydrogen pressure increases and variation in the intensity peak confirms the existence of hydrogen in the prepared film. The d.c. conductivity of thin films were observed at different hydrogen pressure (10 - 40 psi) for both the as-deposited and annealed thin films and the variation in the conductivity after hydrogenation was found out. In Uv-Vis spectroscopy, it was found that the optical bandgap of thin films increases with the increase of hydrogen pressure. The deviations in the structural, electrical and optical properties after hydrogenation indicate that Mg-Ni thin films may be used for solid state hydrogen storage applications. HIGHLIGHTS Preparation of Mg-Ni bilayer thin films using magnetron sputtering technique Finding the opportunity to use Mg-Ni bilayer thin film as solid-state hydrogen storage materials Raman spectroscopy for confirming the presence of hydrogen in Mg-Ni bilayer thin films Effect of hydrogen on conductivity and optical energy bandgap of Mg-Ni bilayer thin films GRAPHICAL ABSTRACT

Self-Assembly of a U(VI)-Containing Polytungstate Tetramer with Lewis Acid-Base Catalytic Activity for a Dehydration Condensation Reaction.

A novel U(VI)-containing polytungstate (U-POW) tetramer, {K1.37Na26.63[K2(UO2)4Cl0.5(OH)5.5(γ-SiW10O36)4]}·ca66H2O (U4), was synthesized using the Keggin-type precursor [γ-SiW10O36]8- and UO2(NO3)2. U4 was further characterized by single-crystal X-ray diffraction, FT-IR, Raman spectroscopy, solid-state diffuse reflection spectroscopy, ICP-OES, ESI-MS, TGA, and PXRD. The central {K2(UO2)4Cl0.5(OH)5.5} chromophore was constructed dexterously from four uranyl, four halves of K ions, 5.5 bridging μ2-OH, and disordered Cl ions, and was further stabilized by four {γ-SiW10} moieties to construct the tetramer [K2(UO2)4Cl0.5(OH)5.5(γ-SiW10O36)4]28-. Notably, U4 could work as an effective bifunctional Lewis acid-base catalyst for the synthesis of pyrazoles via the condensation of hydrazines with 1,3-diketones under mild conditions, which is attributed to the synergetic effect of the Lewis acidity of U(VI) and the Lewis basicity of {γ-SiW10}.