Association of Type 2 Diabetes with Submicron Titanium Dioxide Crystals in the Pancreas

Pigment-grade titanium dioxide (TiO₂) of 200–300 nm particle diameter is the most widely used submicron-sized particle material. Inhaled and ingested TiO₂ particles enter the bloodstream, are phagocytized by macrophages and neutrophils, are inflammatory, and activate the NLRP3 inflammasome. In this pilot study of 11 pancreatic specimens, 8 of the type 2 diabetic pancreas and 3 of the nondiabetic pancreas, we show that particles comprising 110 ± 70 nm average diameter TiO₂ monocrystals abound in the type 2 diabetic pancreas, but not in the nondiabetic pancreas. In the type 2 diabetic pancreas, the count of the crystals is as high as 10⁸–10⁹ per gram

ARTICLE Spinel-type lithium cobalt oxide as a bifunctional electrocatalyst for the oxygen evolution and oxygen reduction reactions

Development of efficient, affordable electrocatalysts for the oxygen evolution reaction and the oxygen reduction reaction is critical for rechargeable metal-air batteries. Here we present lithium cobalt oxide, synthesized at 400°C (designated as LT-LiCoO 2 ) that adopts a lithiated spinel structure, as an inexpensive, efficient electrocatalyst for the oxygen evolution reaction. The catalytic activity of LT-LiCoO 2 is higher than that of both spinel cobalt oxide and layered lithium cobalt oxide synthesized at 800°C (designated as HT-LiCoO 2 ) for the oxygen evolution reaction. Although LT-LiCoO 2 exhibits poor activity for the oxygen reduction reaction, the chemically delithiated LT-Li 1 À x CoO 2 samples exhibit a combination of high oxygen reduction reaction and oxygen evolution reaction activities, making the spinel-type LTLi 0,5 CoO 2 a potential bifunctional electrocatalyst for rechargeable metal-air batteries. The high activities of these delithiated compositions are attributed to the Co 4 O 4 cubane subunits and a pinning of the Co 3 þ /4 þ :3d energy with the top of the O 2 À :2p band

Graphite oxide as a carbocatalyst for the preparation of fullerene-reinforced polyester and polyamide nanocomposites

Graphite oxide (GO) was discovered to catalyze the ring opening polymerization of various cyclic lactones and lactams, such as 3-caprolactone, delta-valerolactone, and epsilon-caprolactam, to their corresponding polyesters or polyamides. The resulting polymers were obtained in moderate number average molecular weights (4.8-12.8 kDa) and in good to excellent yields (39-100%) at GO loadings ranging from 2.5-20.0 wt%. Using powder X-ray diffraction (PXRD) and transmission electron microscopy (TEM), it was determined that the carbon catalyst was retained and homogeneously dispersed within the polymer product, resulting in the formation of a carbon-filled composite. TEM also revealed that the carbon transitioned from the lamellar morphology found in GO primarily to nanometre-sized, multiwalled fullerenes; no other discrete carbon morphologies were observed. The inclusion of the carbon material in the polyesters was found to improve the mechanical stiffness of the polymers by up to 400%, as compared to the neat homopolymer

Effect of Synthesis Conditions on the First Charge and Reversible Capacities of Lithium-Rich Layered Oxide Cathodes

The influence of synthesis temperature and time on the length (capacity) of the plateau region during first charge in the high-capacity lithium-rich layered oxide Li_1.2Mn_0.6Ni_0.2O₂ and on the reversible capacity during subsequent charge–discharge cycles has been systematically investigated. The samples were synthesized by firing a sol–gel precursor obtained at 450 °C at various temperatures (850–1000 °C) for 24 h and at the optimum temperature of 900 °C for 6–72 h. The maximum length of the plateau region during the first charge and, consequently the maximum reversible capacity were achieved with the sample fired at 900 °C for 24 h. In contrast, the sample fired at 1000 °C for 24 h does not show any plateau region. In-depth characterization by X-ray diffraction, aberration-corrected transmission electron microscopy, scanning electron microscopy, inductively coupled plasma analysis, and electrochemical charge–discharge measurements reveals that the actual lithium content in the synthesized samples, compositional inhomogeneities, and the presence of a single <i>C</i>2/<i>m</i> phase vs a <i>C</i>2/<i>m</i> + <i>R</i>3̅<i>m</i> two-phase mixture play a critical role in the length of the plateau region, while particle size and surface area play a minor role. The study demonstrates the benefits of the formation of a single-phase <i>C</i>2/<i>m</i> solid solution with a lithium content of at least 1.16 in order to maximize the discharge capacity

Contact conductance governs metallicity in conducting metal oxide nanocrystal films

Although colloidal nanoparticles hold promise for fabricating electronic components, the properties of nanoparticle-derived materials can be unpredictable. Materials made from metallic nanocrystals exhibit a variety of transport behavior ranging from insulators, with inter- nanocrystal contacts acting as electron transport bottlenecks, to conventional metals, where phonon scattering limits electron mobility. The insulator-metal transition (IMT) in nanocrystal films is thought to be determined by contact conductance. Meanwhile, criteria are lacking to predict the characteristic transport behavior of metallic nanocrystal films beyond this threshold. Using a library of transparent conducting tin-doped indium oxide nanocrystal films with varied electron concentration, size, and contact area, we assess the IMT as it depends on contact conductance and show how contact conductance is also key to predicting the temperature- dependence of conductivity in metallic films. The results establish a phase diagram for electron transport behavior that can guide the creation of metallic conducting materials from nanocrystal building blocks.Funding was provided by the National Science Foundation (NSF) through the Center for Dynamics and Control of Materials: an NSF MRSEC grant DMR- 1720595 (XYG), NSF grant CHE-1905263 (SLG), NASCENT, an NSF ERC (EEC-1160494, CMS), an NSF Graduate Research Fellowship (DGE-1610403 and 2137420, JTB), and a Welch Foundation grant (F-1848, GKO).Center for Dynamics and Control of Material

Facilitating the Operation of Lithium-Ion Cells with High-Nickel Layered Oxide Cathodes with a Small Dose of Aluminum

Layered oxide cathodes with a high Ni content of >0.6 are promising for high-energy-density lithium-ion batteries. However, parasitic electrolyte oxidation of the charged cathode and mechanical degradation arising from phase transitions significantly deteriorate the cell performance and cycle life as the Ni content increases. We demonstrate here a significantly prolonged cycle life with superior cell performance by substituting a small-dose of Al (2 mol %) for Ni in LiNi_0.92Co_0.06Al_0.02O₂; the capacity retention after operating a full cell fabricated with graphite anode for 1000 cycles increases from 47% to 83% on going from the Al-free LiNi_0.94Co_0.06O₂ to the Al-doped LiNi_0.92Co_0.06Al_0.02O₂ cathode. Through in situ X-ray diffraction, we provide the operando evidence that the Al-doping tunes the H2–H3 phase transition process from a two-phase reaction to a quasi-monophase reaction, minimizing the mechanical degradation. Furthermore, secondary-ion mass spectrometry reveals considerably suppressed transition-metal dissolution with Al-doping, effectively preventing sustained parasitic reactions and active Li trapping due to chemical crossover on graphite anodes. This work offers a viable approach for adopting high-Ni cathodes in lithium-ion batteries

Surface Reconstruction in Li-Rich Layered Oxides of Li-Ion Batteries

The performance characteristics of lithium-ion battery cathode materials are governed by the surface structure and chemistry. Synthesis is known to affect the structure of these materials; however, a full understanding of the effects of the surface structure is not well understood. Here, we explore the atomic scale structure of lithium-layered oxides prepared with two different thermal treatments. We show that, under certain thermal treatments, the surface perpendicular to the transition-metal layers is enriched in nickel, which results in Ni occupying the lithium layer of the layered oxide structure. Under both thermal treatments, this surface also shows a reduction of Mn, with some of the reduced Mn occupying sites in the lithium layer. The surface parallel to the transition-metal layers under both treatments shows significant Mn reduction, oxygen loss, and reduced Mn in the lithium layer. The Mn reduction and surface reconstruction are the result of unstable surface terminations and are intrinsic to layered oxides. Synthesis can be tuned to eliminate Ni enrichment at the surface; however, it cannot be tailored to eliminate Mn reduction and surface reconstruction

Microwave-Assisted Synthesis of Pd_<i>x</i>Au_{100–<i>x</i>} Alloy Nanoparticles: A Combined Experimental and Theoretical Assessment of Synthetic and Compositional Effects upon Catalytic Reactivity

Pd_<i>x</i>Au_{100–<i>x</i>} nanoparticle (NP) catalysts with well-defined morphologies and compositions can be rapidly prepared using a simple microwave-assisted synthetic approach. Common Pd­(II) and Au­(III) precursors are coreduced in ethylene glycol to give small and nearly monodisperse (2.5 ± 0.6 nm) NPs with homogeneously alloyed structures in less than 300 s at 150 °C. A comparison of the nucleation and growth processes responsible for the formation of PdAuNPs by microwave and conventional methods revealed faster and more reproducible product formation under microwave-assisted heating. Pd-rich NPs were rapidly formed, into which Au atoms were subsequently incorporated to give the alloyed NPs. The value of <i>x</i> in the Pd_<i>x</i>Au_{100–<i>x</i>}NPs obtained can be finely controlled, allowing the surface electronic structure of the NPs to be broadly tuned. This permits model heterogeneous reaction studies, in which catalytic reactivity can be directly related to Pd:Au composition. Vapor-phase alkene hydrogenation studies using a series of PdAuNPs with varying compositions revealed that Pd₅₉Au₄₁NPs were catalytically the most active. Detailed theoretical studies of the entire hydrogenation reaction catalyzed at randomly alloyed PdAu surfaces were performed using a density functional theory (DFT) approach. Local ensemble effects and longer range electronic effects in the alloys were considered, leading to a prediction for optimal hydrogenation activity by Pd₅₇Au₄₃NPs. PdAuNPs obtained from microwave-assisted syntheses were also found to be more highly active than analogous NPs prepared conventionally. Quantitative solution-state ¹H NMR studies suggest that significantly less PVP was incorporated into PdAuNPs synthesized under microwave heating

Structural and Catalytic Effects of Iron- and Scandium-Doping on a Strontium Cobalt Oxide Electrocatalyst for Water Oxidation

The poor kinetics of the oxygen evolution reaction (OER) are a considerable barrier to the development of water-derived hydrogen fuel. Previous work regarding theoretical calculations of the perovskite SrCoO_3‑δ (SCO) predicts a surface binding energy ideal for OER catalysis but could not be matched to experimental results due to the material’s propensity to form the incorrect trigonal crystal structure. By doping with iron and scandium, X-ray diffraction confirms that we have been able to synthesize a series of SCO catalysts of various crystal structures, culminating in cubic SCO. In doing so, we show that there is a limited correlation between the crystal structure and OER performance in alkaline media. Instead, the use of iron as a dopant is found to decrease the OER overpotential of the SCO by 40 mV in 0.1 M KOH and yield catalysts capable of performing water oxidation at an overpotential of 410 mV at 10 mA/cm². The doped, cubic SCO catalysts are found to be more stable than the undoped material when tested for extended periods, showing only an approximate 3 mV increase in overpotential over a 2 h period at 10 mA/cm². Our results show that proper doping of the B-site cation in SCO allows for tuning the structure, performance, and stability of the oxide as an OER electrocatalyst