Highly efficient heteronuclear polarization transfer using dipolar-echo edited R-symmetry sequences in solid-state NMR.

In solid-state NMR, dipolar-based heteronuclear polarization transfer has been extensively used for sensitivity enhancement and multidimensional correlations, but its efficiency often suffers from undesired spin interactions and hardware limitations. Herein, we propose a novel dipolar-echo edited R-symmetry (DEER) sequence, which is further incorporated into the INEPT-type scheme, dubbed DEER-INEPT, for achieving highly efficient heteronuclear polarization transfer. Numerical simulations and NMR experiments demonstrate that DEER-INEPT offers significantly improved robustness, enabling efficient polarization transfer under a wide range of MAS conditions, from slow to ultrafast rates, outperforming existing methods.

Precise Structural and Dynamical Details in Zeolites Revealed by Coupling-Edited H-O Double Resonance NMR Spectroscopy.

Despite the extensive industrial and research interests in zeolites, their intrinsic catalytic nature is not fully understood due to the complexity of the hydroxyl-aluminum moieties. O NMR would provide irreplaceable opportunities for much-needed fine structural determination given the ubiquitous presence of oxygen atoms in nearly all species; however, the low sensitivity and quadrupolar nature of oxygen-17 make its NMR spectroscopic elucidation challenging. Here, we show that state-of-the-art double resonance solid-state NMR techniques have been combined with spectral editing methods based on scalar (through-bond) and dipolar (through-space) couplings, which allowed us to address the subtle protonic structures in zeolites.

Tetraphenylethylene-based AIE nanoprobes for labeling lysosome by two-photon imaging in living cells.

Lysosomes are essential cellular organelles, serving vital functions in cellular metabolism and degradation. The design of specifically targeting lysosomes probes with aggregation-induced emission (AIE) characteristics using two-photon excitation techniques is significance and challenging work. Here we designed and synthesized two tetraphenylethylene (TPE)-based AIE fluorescence probes, naming TPE-Ma and TPE-Py, with TPE as the matrix and morpholine (Ma) or pyrrolidone (Py) as the targeting group.

A piperazine-substituted phthalocyanine with rapid cellular uptake and dual organelle-targeting for in vitro photodynamic therapy.

The rational design of photosensitizers with rapid cellular uptake and dual-organelle targeting ability is essential for enhancing the efficacy of photodynamic therapy (PDT). However, achieving this goal is a great challenge. In this paper, a novel axial piperazine substituted (PIP) silicon phthalocyanine (PIP-SiPc) has been synthesized.

Morpholinyl silicon phthalocyanine nanoparticles with lysosome cell death and two-photon imaging functions for photodynamic therapy of cancer cells.

The lysosome is an important target for realizing antitumor therapy. Lysosomal cell death exerts significant therapeutic effects on apoptosis and drug-resistance. The development of lysosome-targeting nanoparticles to obtain efficient cancer treatment is challenging.

Multi-technique structural analysis of zinc carboxylates (soaps).

A series of medium- and long-chain zinc carboxylates (zinc octanoate, zinc nonanoate, zinc decanoate, zinc undecanoate, zinc dodecanoate, zinc pivalate, zinc stearate, zinc palmitate, zinc oleate, and zinc azelate) was analyzed by ultra-high-field Zn NMR spectroscopy up to 35.2 T, as well as C NMR and FTIR spectroscopy. We also report the single-crystal X-ray diffraction structures of zinc nonanoate, zinc decanoate, and zinc oleate-the first long-chain carboxylate single-crystals to be reported for zinc.

Solid-State Synthesis of Aluminophosphate Zeotypes by Calcination of Amorphous Precursors.

Because of the growing interest in the applications of zeolitic materials and the various challenges associated with traditional synthesis methods, the development of novel synthesis approaches remains of fundamental importance. Herein, we report a general route for the synthesis of aluminophosphate (AlPO) zeotypes by simple calcination of amorphous precursors at moderate temperatures (250-450 °C) for short reaction times (3-60 min). Accordingly, highly crystalline AlPO zeotypes with various topologies of , , , , , and , ranging from ultra-small to extra-large pores, have been successfully synthesized.

Supercycled R-symmetry sequences for robust heteronuclear polarization transfer in solid-state NMR.

Herein, we introduce supercycle of R-symmetry sequences (SR-sequences) and incomplete supercycle schemes of R-symmetry sequences (iSR-I- and iSR-II-sequences) to improve the robustness of PRESTO for heteronuclear polarization transfer in MAS NMR. The constructions of SR- and iSR-I/II- sequences are based on the different phase-inverted supercycles of R-symmetry sequences, and such supercycles can suppress the influence of CSA, resonance offset and RF mismatch when incorporated into the PRESTO method. Moreover, the SR- and iSR-II-sequences are more efficient in suppressing the interference of homonuclear dipolar coupling.

Direct Detection of Reactive Gallium-Hydride Species on the GaO Surface Solid-State NMR Spectroscopy.

Surface metal hydrides (M-H) are ubiquitous in heterogeneous catalytic reactions, while the detailed characterizations are frequently hindered by their high reactivity/low concentration, and the complicated surface structures of the host solids, especially in terms of practical solid catalysts. Herein, combining instant quenching capture and advanced solid-state NMR methodology, we report the first direct and unambiguous NMR evidence on the highly reactive surface gallium hydrides (Ga-H) over a practical GaO catalyst during direct H activation. The spectroscopic effects of Ga and Ga isotopes on the H NMR signal are clearly differentiated and clarified, allowing a concrete discrimination of the Ga-H signal from the hydroxyl crowd.

O Labeling Reveals Paired Active Sites in Zeolite Catalysts.

Current needs for extending zeolite catalysts beyond traditional gas-phase hydrocarbon chemistry demand detailed characterization of active site structures, distributions, and hydrothermal impacts. A broad suite of homonuclear and heteronuclear NMR correlation experiments on dehydrated H-ZSM-5 catalysts with isotopically enriched O frameworks reveals that at least two types of paired active sites exist, the amount of which depends on the population of fully framework-coordinated tetrahedral Al (Al(IV)-1) and partially framework-coordinated tetrahedral Al (Al(IV)-2) sites, both of which can be denoted as (SiO)-Al(OH). The relative amounts of Al(IV)-1 and Al(IV)-2 sites, and subsequent pairing, cannot be inferred from the catalyst Si/Al ratio, but depend on synthetic and postsynthetic modifications.

Bromopropylate Imidazoliumyl Substituted Silicon Phthalocyanine for Mitochondria-Targeting, Two-Photon Imaging Guided Photodynamic Therapy.

Maximization of phototoxic damage on tumor is essential for effective anticancer photodynamic therapy (PDT). Highly cancer-cell-organelle-specific delivery of efficient photosensitizers (PSs) and is in great demand. In this paper, a novel water-soluble mitochondria targeted cationic bromopropylate imidazoliumyl axially substituted silicon (IV) phthalocyanine (Br-ID-SiPc) is developed to improve PDT efficiency by enhancing the subcellular localization of photosensitizers.

Nature of Five-Coordinated Al in γ-AlO Revealed by Ultra-High-Field Solid-State NMR.

Five-coordinated Als (Al(V)) on the surface of aluminas play important roles when they are used as catalysts or catalyst supports. However, the comprehensive characterization and understanding of the intrinsic structural properties of the Al(V) remain a challenge, due to the very small amount in commonly used aluminas. Herein, the surface structures of γ-AlO and Al(V)-rich AlO nanosheets (AlO-NS) have been investigated and compared in detail by multinuclear high-field solid-state NMR.

Identification of CO adsorption sites on MgO nanosheets by solid-state nuclear magnetic resonance spectroscopy.

The detailed information on the surface structure and binding sites of oxide nanomaterials is crucial to understand the adsorption and catalytic processes and thus the key to develop better materials for related applications. However, experimental methods to reveal this information remain scarce. Here we show that O solid-state nuclear magnetic resonance (NMR) spectroscopy can be used to identify specific surface sites active for CO adsorption on MgO nanosheets.

Solid-State NMR Dipolar and Chemical Shift Anisotropy Recoupling Techniques for Structural and Dynamical Studies in Biological Systems.

With the development of NMR methodology and technology during the past decades, solid-state NMR (ssNMR) has become a particularly important tool for investigating structure and dynamics at atomic scale in biological systems, where the recoupling techniques play pivotal roles in modern high-resolution MAS NMR. In this review, following a brief introduction on the basic theory of recoupling in ssNMR, we highlight the recent advances in dipolar and chemical shift anisotropy recoupling methods, as well as their applications in structural determination and dynamical characterization at multiple time scales (i.e.

Unraveling the Surface Hydroxyl Network on InO Nanoparticles with High-Field Ultrafast Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy.

Hydroxyl groups are among the major active surface sites over metal oxides. However, their spectroscopic characterizations have been challenging due to limited resolutions, especially on hydroxyl-rich surfaces where strong hydroxyl networks are present. Here, using nanostructured InO as an example, we show significantly enhanced discrimination of the surface hydroxyl groups, owing to the high-resolution H NMR spectra performed at a high magnetic field (18.

Revealing Brønsted Acidic Bridging SiOHAl Groups on Amorphous Silica-Alumina by Ultrahigh Field Solid-State NMR.

Amorphous silica-aluminas (ASAs) are important acidic catalysts and supports for many industrially essential and sustainable processes. The identification of surface acid sites with their local structures on ASAs is of critical importance for tuning their catalytic properties but still remains a great challenge and is under debate. Here, ultrahigh magnetic field (35.

Structure Determination of Boron-Based Oxidative Dehydrogenation Heterogeneous Catalysts with Ultra-High Field 35.2 T B Solid-State NMR Spectroscopy.

Boron-based heterogenous catalysts, such as hexagonal boron nitride (-BN) as well as supported boron oxides, are highly selective catalysts for the oxidative dehydrogenation (ODH) of light alkanes to olefins. Previous catalytic measurements and molecular characterization of boron-based catalysts by B solid-state NMR spectroscopy and other techniques suggests that oxidized/hydrolyzed boron clusters are the catalytically active sites for ODH. However, B solid-state NMR spectroscopy often suffers from limited resolution because boron-11 is an = 3/2 half-integer quadrupolar nucleus.

Labeling and Probing the Silica Surface Using Mechanochemistry and O NMR Spectroscopy*.

In recent years, there has been increasing interest in developing cost-efficient, fast, and user-friendly O enrichment protocols to help to understand the structure and reactivity of materials by using O NMR spectroscopy. Here, we show for the first time how ball milling (BM) can be used to selectively and efficiently enrich the surface of fumed silica, which is widely used at industrial scale. Short milling times (up to 15 min) allowed modulation of the enrichment level (up to ca.

Distribution of Aluminum Species in Zeolite Catalysts: Al NMR of Framework, Partially-Coordinated Framework, and Non-Framework Moieties.

The structure of aluminum-containing moieties in and within zeolite H-ZSM-5 catalysts is a complex function of the elemental composition of the catalyst, synthesis conditions, exposure to moisture, and thermal history. Al NMR data collected at field strengths ranging from 7.05 to 35.

Unveiling the Structure and Reactivity of Fatty-Acid Based (Nano)materials Thanks to Efficient and Scalable O and O-Isotopic Labeling Schemes.

Fatty acids are ubiquitous in biological systems and widely used in materials science, including for the formulation of drugs and the surface-functionalization of nanoparticles. However, important questions regarding the structure and reactivity of these molecules are still to be elucidated, including their mode of binding to certain metal cations or materials surfaces. In this context, we have developed novel, efficient, user-friendly, and cost-effective synthetic protocols based on ball-milling, for the O and O isotopic labeling of two key fatty acids which are widely used in (nano)materials science, namely stearic and oleic acid.

Higher Magnetic Fields, Finer MOF Structural Information: O Solid-State NMR at 35.2 T.

The spectroscopic study of oxygen, a vital element in materials, physical, and life sciences, is of tremendous fundamental and practical importance. O solid-state NMR (SSNMR) spectroscopy has evolved into an ideal site-specific characterization tool, furnishing valuable information on the local geometric and bonding environments about chemically distinct and, in some favorable cases, crystallographically inequivalent oxygen sites. However, O is a challenging nucleus to study via SSNMR, as it suffers from low sensitivity and resolution, owing to the quadrupolar interaction and low O natural abundance.

A Practical Review of NMR Lineshapes for Spin-1/2 and Quadrupolar Nuclei in Disordered Materials.

NMR is a powerful spectroscopic method that can provide information on the structural disorder in solids, complementing scattering and diffraction techniques. The structural disorder in solids can generate a dispersion of local magnetic and electric fields, resulting in a distribution of isotropic chemical shift δ and quadrupolar coupling C. For spin-1/2 nuclei, the NMR linewidth and shape under high-resolution magic-angle spinning (MAS) reflects the distributions of isotropic chemical shift, providing a rich source of disorder information.

Structure and Catalytic Characterization of a Second Framework Al(IV) Site in Zeolite Catalysts Revealed by NMR at 35.2 T.

Ultrahigh field Al{H} 2D correlation NMR experiments demonstrate that at least two framework Al(IV) sites with hydroxyl groups can exist in acidic zeolite catalysts in their dehydrated and catalytically active states. In addition to the known Al(IV) at the framework bridging acid site (BAS), a new site created by a second tetrahedral Al atom and its hydroxyl group protons in zeolite HZSM-5 is clearly resolved at 35.2 T field strengths, enabled by recently developed series-connected hybrid (SCH) magnet technology.

Ultrahigh-field Zn NMR reveals short-range disorder in zeolitic imidazolate framework glasses.

The structure of melt-quenched zeolitic imidazole framework (ZIF) glasses can provide insights into their glass-formation mechanism. We directly detected short-range disorder in ZIF glasses using ultrahigh-field zinc-67 solid-state nuclear magnetic resonance spectroscopy. Two distinct Zn sites characteristic of the parent crystals transformed upon melting into a single tetrahedral site with a broad distribution of structural parameters.

Probing Interactions of γ-Alumina with Water via Multinuclear Solid-State NMR Spectroscopy.

Interaction of γ-alumina with water are important in controlling its structure and catalytic properties. We apply solid-state multinuclear NMR spectroscopy to investigate this interaction by monitoring H and O spectra in real-time. Surface-selective detection is made possible by adsorbing O-enriched water on γ-alumina nanorods.