Formulation and characterization of ionically crosslinked gellan gum hydrogels using trilysine at low temperatures for antibody delivery.

Research of the nontraditional polysaccharide gellan gum (GG) is a growing space for the development of novel drug delivery systems due to its tunable physic-mechanical properties, biocompatibility, and stability in a wide range of environments. Unfortunately, high temperature crosslinking is often required, representing a limiting factor for the incorporation of thermosensitive therapeutic agents. Here, we demonstrated that GG can be crosslinked at a low temperature (38 °C) using a simple fabrication process that utilizes trilysine as an alternative to traditional mono- or divalent ion crosslinkers.

Structural characterization of tin in toothpaste by dynamic nuclear polarization enhanced Sn solid-state NMR spectroscopy.

Stannous fluoride (SnF) is an effective fluoride source and antimicrobial agent that is widely used in commercial toothpaste formulations. The antimicrobial activity of SnF is partly attributed to the presence of Sn(II) ions. However, it is challenging to directly determine the Sn speciation and oxidation state within commercially available toothpaste products due to the low weight loading of SnF (0.

Spatially Directed Pyrolysis via Thermally Morphing Surface Adducts.

Combustion is often difficult to spatially direct or tune associated kinetics-hence a run-away reaction. Coupling pyrolytic chemical transformation to mass transport and reaction rates (Damköhler number), however, we spatially directed ignition with concomitant switch from combustion to pyrolysis (low oxidant). A 'surface-then-core' order in ignition, with concomitant change in burning rate,is therefore established.

Inductively Coupled Nonthermal Plasma Synthesis of Size-Controlled γ-AlO Nanocrystals.

Gamma alumina (γ-AlO) is widely used as a catalyst and catalytic support due to its high specific surface area and porosity. However, synthesis of γ-AlO nanocrystals is often a complicated process requiring high temperatures or additional post-synthetic steps. Here, we report a single-step synthesis of size-controlled and monodisperse, facetted γ-AlO nanocrystals in an inductively coupled nonthermal plasma reactor using trimethylaluminum and oxygen as precursors.

An Atomistic Picture of Boron Oxide Catalysts for Oxidative Dehydrogenation Revealed by Ultrahigh Field B-O Solid-State NMR Spectroscopy.

Boron oxide/hydroxide supported on oxidized activated carbon (B/OAC) was shown to be an inexpensive catalyst for the oxidative dehydrogenation (ODH) of propane that offers activity and selectivity comparable to boron nitride. Here, we obtain an atomistic picture of the boron oxide/hydroxide layer in B/OAC by using 35.2 T B and O solid-state NMR experiments.

Formation of a Strong Heterogeneous Aluminum Lewis Acid on Silica.

Al(OC(CF ) )(PhF) reacts with silanols present on partially dehydroxylated silica to form well-defined ≡SiOAl(OC(CF ) ) (O(Si≡) ) (1). Al NMR and DFT calculations with a small cluster model to approximate the silica surface show that the aluminum in 1 adopts a distorted trigonal bipyramidal coordination geometry by coordinating to a nearby siloxane bridge and a fluorine from the alkoxide. Fluoride ion affinity (FIA) calculations follow experimental trends and show that 1 is a stronger Lewis acid than B(C F ) and Al(OC(CF ) )(PhF) but is weaker than Al(OC(CF ) ) and Pr Si .

Attached Nitrogen Test by C-N Solid-State NMR Spectroscopy for the Structure Determination of Heterocyclic Isomers.

Differentiation of heterocyclic isomers by solution H, C, and N NMR spectroscopy is often challenging due to similarities in their spectroscopic signatures. Here, C{N} solid-state NMR spectroscopy experiments are shown to operate as an "attached nitrogen test", where heterocyclic isomers are easy to distinguish based on one-dimensional nitrogen-filtered C solid-state NMR. We anticipate that these NMR experiments will facilitate the assignment of heterocyclic isomers during synthesis and natural product discovery.

Semiconducting silicon-phosphorus frameworks for caging exotic polycations.

A series of novel semiconductors AAeSiPX (A = Na, K, Rb, Cs; Ae = Sr, Ba; X = Cl, Br, I) is reported. Their crystal structures feature a tetrahedral Si-P framework with large zeolite-like pores hosting two types of cations, monoatomic A and unprecedented octahedral X@Ae. Mixing of the A and Ba cations was detected by single crystal X-ray diffraction and confirmed by multinuclear solid state NMR.

A Heterogeneous Palladium Catalyst for the Polymerization of Olefins Prepared by Halide Abstraction Using Surface R Si Species.

The silylium-like surface species [ Pr Si][(R O) Al-OSi≡)] activates (N^N)Pd(CH )Cl (N^N=Ar-N=CMeMeC=N-Ar, Ar=2,6-bis(diphenylmethyl)-4-methylbenzene) by chloride ion abstraction to form [(N^N)Pd-CH ][(R O) Al-OSi≡)] (1). A combination of FTIR, solid-state NMR spectroscopy, and reactions with CO or vinyl chloride establish that 1 shows similar reactivity patterns as (N^N)Pd(CH )Cl activated with Na[B(Ar ) ]. Multinuclear C{ Al} RESPDOR and H{ F} S-REDOR experiments are consistent with a weakly coordinated ion-pair between (N^N)Pd-CH and [(R O) Al-OSi≡)].

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.

Active Sites in a Heterogeneous Organometallic Catalyst for the Polymerization of Ethylene.

Heterogeneous derivatives of catalysts discovered by Ziegler and Natta are important for the industrial production of polyolefin plastics. However, the interaction between precatalysts, alkylaluminum activators, and oxide supports to form catalytically active materials is poorly understood. This is in contrast to homogeneous or model heterogeneous catalysts that contain resolved molecular structures that relate to activity and selectivity in polymerization reactions.

Revealing the Surface Structure of CdSe Nanocrystals by Dynamic Nuclear Polarization-Enhanced Se and Cd Solid-State NMR Spectroscopy.

Dynamic nuclear polarization (DNP) solid-state NMR (SSNMR) spectroscopy was used to obtain detailed surface structures of zinc blende CdSe nanocrystals (NCs) with plate or spheroidal morphologies which are capped by carboxylic acid ligands. 1D Cd and Se cross-polarization magic angle spinning (CPMAS) NMR spectra revealed distinct signals from Cd and Se atoms on the surface of the NCs, and those residing in bulk-like environments, below the surface. Cd cross-polarization magic-angle-turning (CP-MAT) experiments identified CdSeO, CdSeO, and CdSeO Cd coordination environments on the surface of the NCs, where the oxygen atoms are presumably from coordinated carboxylate ligands.

B-MWW Zeolite: The Case Against Single-Site Catalysis.

Boron-containing materials have recently been identified as highly selective catalysts for the oxidative dehydrogenation (ODH) of alkanes to olefins. It has previously been demonstrated by several spectroscopic characterization techniques that the surface of these boron-containing ODH catalysts oxidize and hydrolyze under reaction conditions, forming an amorphous B (OH) O (x=0-6) layer. Yet, the precise nature of the active site(s) remains elusive.