Acid-Base Cascades in Zeotype Single Crystal for Sugar Conversion

The chemically catalyzed production of fructose syrup from high concentrations of glucose is crucial for the food industry and biorefining. In this work, a single crystal catalyst was synthesized via protective desilication of zeolite while incorporating indium. Glucose was isomerized in methanol at concentrations as high as 33 wt % before being hydrolyzed with water. The final fructose production was 54.9 %, with 89.1 % selectivity and 93.3 % sugar recovery, the highest isomerization rate at the highest concentration ever reported. Indium was present in the single-crystal catalyst as oxide nanoparticles and boundary framework atoms, and it achieved intelligent cooperation in the production of fructose syrup in methanol by catalyzing isomerization and selective glycosidation, minimizing degradation due to fructose accumulation and eliminating side reactions. This study contributed to the advancement of the industrial practice of chemically catalyzed glucose isomerization.

Solid-state nuclear magnetic resonance of spin-9/2 nuclei 115 In and 209 Bi in functional inorganic complex oxides

Indium and bismuth are technologically important elements, in particular as oxides for optoelectronic applications. ¹¹⁵ In and ²⁰⁹ Bi are both I = 9/2 nuclei with high natural abundances and moderately high frequencies but large nuclear electric quadrupole moments. Leveraging the quadrupolar interaction as a measure of local symmetry and polyhedral distortions for these nuclei could provide powerful insights on a range of applied materials. However, the absence of reported nuclear magnetic resonance (NMR) parameters on these nuclei, particularly in oxides, hinders their use by the broader materials community. In this contribution, solid-state ¹¹⁵ In and ²⁰⁹ Bi NMR of three recently discovered quaternary bismuth or indium oxides are reported, supported by density functional theory calculations, numerical simulations, diffraction and additional multinuclear (²⁷ Al, ^69,71 Ga, and ¹²¹ Sb) solid-state NMR measurements. The compounds LiIn₂ SbO₆ , BiAlTeO₆ , and BiGaTeO₆ are measured without special equipment at 9.4 T, demonstrating that wideline techniques such as the QCPMG pulse sequence and frequency-stepped acquisition can enable straightforward extraction of quadrupolar tensor information in I = 9/2 ¹¹⁵ In and ²⁰⁹ Bi even in sites with large quadrupolar coupling constants. Relationships are described between the NMR observables and local site symmetry. These are amongst the first reports of the NMR parameters of ¹¹⁵ In, ¹²¹ Sb, and ²⁰⁹ Bi in oxides.

Field-stepwise-swept QCPMG solid-state 115In NMR of indium oxide

Experimental and theoretical investigations of indium-115 electric-field-gradient (EFG) tensors of indium(III) oxide, In₂O₃, have been presented. Field-stepwise-swept QCPMG solid-state ¹¹⁵In NMR experiments are carried out at T ​= ​120 ​K, observed at 52.695 ​MHz, and in the range of external magnetic fields between 4.0 and 6.5 ​T. The spectral simulations yield the quadrupolar coupling constant, C_Q value, of 183(2) MHz and the asymmetry parameter, η_Q, of 0.05(5), for In(1), and that of 126(2) MHz and η_Q of 0.86(5) for In(2). Quantum chemical calculations are carried out to provide ¹¹⁵In EFG tensor orientations with respect to the molecular structure. A relationship between operative frequencies and variable ranges of external magnetic fields is briefly discussed for field-swept solid-state ¹¹⁵In NMR.

Experimental and theoretical evidence for hydrogen doping in polymer solution-processed indium gallium oxide

The field-effect electron mobility of aqueous solution-processed indium gallium oxide (IGO) thin-film transistors (TFTs) is significantly enhanced by polyvinyl alcohol (PVA) addition to the precursor solution, a >70-fold increase to 7.9 cm²/Vs. To understand the origin of this remarkable phenomenon, microstructure, electronic structure, and charge transport of IGO:PVA film are investigated by a battery of experimental and theoretical techniques, including In K-edge and Ga K-edge extended X-ray absorption fine structure (EXAFS); resonant soft X-ray scattering (R-SoXS); ultraviolet photoelectron spectroscopy (UPS); Fourier transform-infrared (FT-IR) spectroscopy; time-of-flight secondary-ion mass spectrometry (ToF-SIMS); composition-/processing-dependent TFT properties; high-resolution solid-state ¹H, ⁷¹Ga, and ¹¹⁵In NMR spectroscopy; and discrete Fourier transform (DFT) analysis with ab initio molecular dynamics (MD) liquid-quench simulations. The ⁷¹Ga{¹H} rotational-echo double-resonance (REDOR) NMR and other data indicate that PVA achieves optimal H doping with a Ga···H distance of ∼3.4 Å and conversion from six- to four-coordinate Ga, which together suppress deep trap defect localization. This reduces metal-oxide polyhedral distortion, thereby increasing the electron mobility. Hydroxyl polymer doping thus offers a pathway for efficient H doping in green solvent-processed metal oxide films and the promise of high-performance, ultra-stable metal oxide semiconductor electronics with simple binary compositions.

Tailorable Indirect to Direct Band-Gap Double Perovskites with Bright White-Light Emission: Decoding Chemical Structure Using Solid-State NMR

Efficient white-light-emitting single-material sources are ideal for sustainable lighting applications. Though layered hybrid lead-halide perovskite materials have demonstrated attractive broad-band white-light emission properties, they pose a serious long-term environmental and health risk as they contain lead (Pb²⁺) and are readily soluble in water. Recently, lead-free halide double perovskite (HDP) materials with a generic formula A(I)₂B'(III)B″(I)X₆ (where A and B are cations and X is a halide ion) have demonstrated white-light emission with improved photoluminescence quantum yields (PLQYs). Here, we present a series of Bi³⁺/In³⁺ mixed-cationic Cs₂Bi_1-xIn_xAgCl₆ HDP solid solutions that span the indirect to direct band-gap modification which exhibit tailorable optical properties. Density functional theory (DFT) calculations indicate an indirect-direct band-gap crossover composition when x > 0.50. These HDP materials emit over the entire visible light spectrum, centered at 600 ± 30 nm with full-width at half maxima of ca. 200 nm upon ultraviolet light excitation and a maximum PLQY of 34 ± 4% for Cs₂Bi_0.085In_0.915AgCl₆. Short-range structural insight for these materials is crucial to unravel the unique atomic-level structural properties which are difficult to distinguish by diffraction-based techniques. Hence, we demonstrate the advantage of using solid-state nuclear magnetic resonance (NMR) spectroscopy to deconvolute the local structural environments of these mixed-cationic HDPs. Using ultrahigh-field (21.14 T) NMR spectroscopy of quadrupolar nuclei (¹¹⁵In, ¹³³Cs, and ²⁰⁹Bi), we show that there is a high degree of atomic-level B'(III)/B″(I) site ordering (i.e., no evidence of antisite defects). Furthermore, a combination of XRD, NMR, and DFT calculations was used to unravel the complete atomic-level random Bi³⁺/In³⁺ cationic mixing in Cs₂Bi_1-xIn_xAgCl₆ HDPs. Briefly, this work provides an advance in understanding the photophysical properties that correlate long- to short-range structural elucidation of these newly developed solid-state white-light emitting HDP materials.

Recent advances in solid-state nuclear magnetic resonance spectroscopy of exotic nuclei

We present a review of recent advances in solid-state nuclear magnetic resonance (SSNMR) studies of exotic nuclei. Exotic nuclei may be spin-1/2 or quadrupolar, and typically have low gyromagnetic ratios, low natural abundances, large quadrupole moments (when I > 1/2), or some combination of these properties, generally resulting in low receptivities and/or prohibitively broad line widths. Some nuclides are little studied for other reasons, also rendering them somewhat exotic. We first discuss some of the recent progress in pulse sequences and hardware development which continues to enable researchers to study new kinds of materials as well as previously unfeasible nuclei. This is followed by a survey of applications to a wide range of exotic nuclei (including e.g., ⁹Be, ²⁵Mg, ³³S, ³⁹K, ⁴³Ca, ^47/49Ti, ⁵³Cr, ⁵⁹Co, ⁶¹Ni, ⁶⁷Zn, ⁷³Ge, ⁷⁵As, ⁸⁷Sr, ¹¹⁵In, ¹¹⁹Sn, ^121/123Sb, ^135/137Ba, ^185/187Re, ²⁰⁹Bi), most of them quadrupolar. The scope of the review is the past ten years, i.e., 2007-2017.

Welcoming Gallium- and Indium-Fumarate MOFs to the Family: Synthesis, Comprehensive Characterization, Observation of Porous Hydrophobicity, and CO2 Dynamics

The properties and applications of metal-organic frameworks (MOFs) are strongly dependent on the nature of the metals and linkers, along with the specific conditions employed during synthesis. Al-fumarate, trademarked as Basolite A520, is a porous MOF that incorporates aluminum centers along with fumarate linkers and is a promising material for applications involving adsorption of gases such as CO₂. In this work, the solvothermal synthesis and detailed characterization of the gallium- and indium-fumarate MOFs (Ga-fumarate, In-fumarate) are described. Using a combination of powder X-ray diffraction, Rietveld refinements, solid-state NMR spectroscopy, IR spectroscopy, and thermogravimetric analysis, the topologies of Ga-fumarate and In-fumarate are revealed to be analogous to Al-fumarate. Ultra-wideline ⁶⁹Ga, ⁷¹Ga, and ¹¹⁵In NMR experiments at 21.1 T strongly support our refined structure. Adsorption isotherms show that the Al-, Ga-, and In-fumarate MOFs all exhibit an affinity for CO₂, with Al-fumarate being the superior adsorbent at 1 bar and 273 K. Static direct excitation and cross-polarized ¹³C NMR experiments permit investigation of CO₂ adsorption locations, binding strengths, motional rates, and motional angles that are critical to increasing adsorption capacity and selectivity in these materials. Conducting the synthesis of the indium-based framework in methanol demonstrates a simple route to introduce porous hydrophobicity into a MIL-53-type framework by incorporation of metal-bridging -OCH₃ groups in the MOF pores.

Polyether complexes of groups 13 and 14

Notable aspects of the chemistry of polyether complexes of group 13 and 14 elements are reviewed.

New methods and applications in solid-state NMR spectroscopy of quadrupolar nuclei

Solid-state nuclear magnetic resonance (NMR) spectroscopy has long been established as offering unique atomic-scale and element-specific insight into the structure, disorder, and dynamics of materials. NMR spectra of quadrupolar nuclei (I > (1)/2) are often perceived as being challenging to acquire and to interpret because of the presence of anisotropic broadening arising from the interaction of the electric field gradient and the nuclear electric quadrupole moment, which broadens the spectral lines, often over several megahertz. Despite the vast amount of information contained in the spectral line shapes, the problems with sensitivity and resolution have, until very recently, limited the application of NMR spectroscopy of quadrupolar nuclei in the solid state. In this Perspective, we provide a brief overview of the quadrupolar interaction, describe some of the basic experimental approaches used for acquiring high-resolution NMR spectra, and discuss the information that these spectra can provide. We then describe some interesting recent examples to showcase some of the more exciting and challenging new applications of NMR spectra of quadrupolar nuclei in the fields of energy materials, microporous materials, Earth sciences, and biomaterials. Finally, we consider the possible directions that this highly informative technique may take in the future.