Elucidating the electronic properties of single-wall carbon nanohorns

Single-walled carbon nanohorns are an allotrope of carbon with promising properties for a variety of applications. Despite their promise, the majority carrier type (i.e. electrons or holes) that defines the electronic properties of this novel semiconductor is poorly understood and so far only indirect measurements have been employed to arrive at contradictory results. Here, we directly determine the majority carrier type in single-wall carbon nanohorns for the first time by means of thermopower measurements. Using this direct method, we show that SWCNH films exhibit a positive Seebeck coefficient indicating that SWCNHs behave as p-type semiconductors. This result is further corroborated by intentionally tuning the hole or electron concentrations of SWCNH layers via redox doping with molecular electron acceptors and donors, respectively. These results provide a framework for both measuring and chemically tuning the majority carrier type in this emerging nanocarbon semiconductor

Trained Immunity as a Trigger for Atherosclerotic Cardiovascular Disease—A Literature Review

Atherosclerosis remains the leading cause of cardiovascular diseases and represents a primary public health challenge. This chronic state may lead to a number of life-threatening conditions, such as myocardial infarction and stroke. Lipid metabolism alterations and inflammation remain at the forefront of the pathogenesis of atherosclerotic cardiovascular disease, but the overall mechanism is not yet fully understood. Recently, significant effects of trained immunity on atherosclerotic plaque formation and development have been reported. An increased reaction to restimulation with the same stimulator is a hallmark of the trained innate immune response. The impact of trained immunity is a prominent factor in both acute and chronic coronary syndrome, which we outline in this review

Charge-Gating Dibenzothiophene-S,S-dioxide Bridges in Electron Donor–Bridge–Acceptor Conjugates

The synthesis of a series of new electron donor–bridge–acceptor (D–B–A) conjugates (18–20) comprising electron-donating zinc(II) porphyrins (ZnPs) and electron-accepting fullerenes (C60s) connected through various co-oligomer bridges containing both dibenzothiophene-S,S-dioxide and fluorene units is reported. Detailed investigations using cyclic voltammetry, absorption, fluorescence, and femto/nanosecond transient absorption spectroscopy in combination with quantum chemical calculations have enabled us to develop a detailed mechanistic view of the charge-transfer processes that follow photoexcitation of ZnP, the bridge, or C60. Variations in the dynamics of charge separation, charge recombination, and charge-transfer gating are primarily consequences of the electronic properties of the co-oligomer bridges, including their electron affinity and the energy levels of the excited states. In particular, placing one dibenzothiophene-S,S-dioxide building block at the center of the molecular bridge flanked by two fluorene building blocks, as in 20, favors hole rather than electron transfer between the remote electron donors and acceptors, as demonstrated by exciting C60 rather than ZnP. In 18 and 19, in which one dibenzothiophene-S,S-dioxide and one fluorene building block constitute the molecular bridge, photoexcitation of either ZnP or C60 results in both hole and electron transfer. Dibenzothiophene-S,S-dioxide is thus shown to be an excellent building block for probing how subtle structural and electronic variations in the bridge affect unidirectional charge transport in D–B–A conjugates. The experimental results are supported by computational calculations

Tetrahedral to Octahedral Nickel(II) as an Initiation Step in Metallaphotoredox Catalysis

In this work we seek to understand the pre-catalytic initiation steps in a classic metallaphotoredox catalysis paring Ir(III) ((Ir[dF(CF$_{3}$)ppy]$_{2}$(dtbbpy))PF$_{6}$) and Ni(II) ((4,4\u27-dtbbpy)NiCl$_{2}$) in dimethoxyethane. We use a combination of transient X-ray and optical absorption spectroscopies to track both nuclear and electronic excited-state dynamics, revealing two steps. First, photoexcitation produces the expected intramolecular oxidation of the iridium center, Ir(III), to Ir(IV)(dtbbpy)$^{\bullet -}$ correlated to the Ir metal-to-ligand charge transfer state. Second, interaction with Ir(IV)(dtbbpy)$^{\bullet -}$ drives the tetrahedral Ni(II) starting material to an unexpected octahedral Ni(II) species. We conclude by proposing the identity of the octahedral Ni(II) and suggest both an electron and an energy transfer mechanism for producing it that are equally consistent with our observations

Effectiveness of Lifestyle Modification vs. Therapeutic, Preventative Strategies for Reducing Cardiovascular Risk in Primary Prevention—A Cohort Study

Background: Cardiovascular diseases (CVD) are still the leading cause of death in developed countries. The aim of this study was to calculate the potential for CV risk reduction when using three different prevention strategies to evaluate the effect of primary prevention. Methods: A total of 931 individuals aged 20–79 years old from the Bialystok PLUS Study were analyzed. The study population was divided into CV risk classes. The Systematic Coronary Risk Estimation (SCORE), Framingham Risk Score (FRS), and LIFE-CVD were used to assess CV risk. The optimal prevention strategy assumed the attainment of therapeutic goals according to the European guidelines. The moderate strategy assumed therapeutic goals in participants with increased risk factors: a reduction in systolic blood pressure by 10 mmHg when it was above 140 mmHg, a reduction in total cholesterol by 25% when it was above 190 mg/dL, and a reduction in body mass index below 30. The minimal prevention strategy assumed that CV risk would be lowered by lifestyle modifications. The greatest CV risk reduction was achieved in the optimal model and then in the minimal model, and the lowest risk reduction was achieved in the moderate model, e.g., using the optimal model of prevention (Model 1). In the total population, we achieved a reduction of −1.74% in the 10-year risk of CVD death (SCORE) in relation to the baseline model, a −0.85% reduction when using the moderate prevention model (Model 2), and a −1.11% reduction when using the minimal prevention model (Model 3). However, in the low CV risk class, the best model was the minimal one (risk reduction of −0.72%), which showed even better results than the optimal one (reduction of −0.69%) using the FRS. Conclusion: A strategy based on lifestyle modifications in a population without established CVD could be more effective than the moderate strategy used in the present study. Moreover, applying a minimal strategy to the low CV risk class population may even be beneficial for an optimal model

Dipole Moment and Charge Reorganization in Photoredox Catalysts

We report evidence of excited-state ion pair reorganisation in a cationic iridium (III) photoredox catalyst in 1,4-dioxane. Microwave-frequency dielectric-loss measurements allow us to assign both ground and excited-state molecular dipoles and excited-state polarizability volumes. These measurements show significant changes in ground-state dipole moment between [Ir[dF(CF_{3})ppy]_{2}(dtbpy)]PF_{6} (10.74 Debye) and [Ir[dF(CF_{3})ppy]_{2}(dtbpy)]BAr^{F}_{4} (4.86 Debye). Photoexcitation of each complex results in population of highly mixed ligand centered and metal-to-ligand charge transfer states. Relaxation to the lowest lying excited-state leads to a negative change in the dipole for [Ir[dF(CF_{3})ppy]_{2}(dtbpy)]PF_{6}, and a positive change in dipole for [Ir[dF(CF_{3})ppy]_{2}(dtbpy)]BAr^{F}_{4}. These observations are consistent with a sub-nanosecond reorganization with the PF_{6}^{-} counter-ion. Taken together, these observations suggest contact-ion pair formation in [Ir[dF(CF_{3})ppy]_{2}(dtbpy)]PF_{6}. The ion pair reorganisation we observe with the PF_{6}^{-} may modify both the thermodynamic potential available for electron transfer and inhibit oxidative catalysis, providing a possible mechanism for recently observed trends in similar complexes

Charge-Gating Dibenzothiophene‑<i>S</i>,<i>S</i>‑dioxide Bridges in Electron Donor<b>–</b>Bridge<b>–</b>Acceptor Conjugates

The synthesis of a series of new electron donor–bridge–acceptor (D–B–A) conjugates (<b>18</b>–<b>20</b>) comprising electron-donating zinc­(II) porphyrins (ZnPs) and electron-accepting fullerenes (C₆₀s) connected through various co-oligomer bridges containing both dibenzothiophene-<i>S</i>,<i>S</i>-dioxide and fluorene units is reported. Detailed investigations using cyclic voltammetry, absorption, fluorescence, and femto/nanosecond transient absorption spectroscopy in combination with quantum chemical calculations have enabled us to develop a detailed mechanistic view of the charge-transfer processes that follow photoexcitation of ZnP, the bridge, or C₆₀. Variations in the dynamics of charge separation, charge recombination, and charge-transfer gating are primarily consequences of the electronic properties of the co-oligomer bridges, including their electron affinity and the energy levels of the excited states. In particular, placing one dibenzothiophene-<i>S</i>,<i>S</i>-dioxide building block at the center of the molecular bridge flanked by two fluorene building blocks, as in <b>20</b>, favors hole rather than electron transfer between the remote electron donors and acceptors, as demonstrated by exciting C₆₀ rather than ZnP. In <b>18</b> and <b>19</b>, in which one dibenzothiophene-<i>S</i>,<i>S</i>-dioxide and one fluorene building block constitute the molecular bridge, photoexcitation of either ZnP or C₆₀ results in both hole and electron transfer. Dibenzothiophene-<i>S</i>,<i>S</i>-dioxide is thus shown to be an excellent building block for probing how subtle structural and electronic variations in the bridge affect unidirectional charge transport in D–B–A conjugates. The experimental results are supported by computational calculations

PCET-Based Ligand Limits Charge Recombination with an Ir(III) Photoredox Catalyst

Upon photoinitiated electron transfer, charge recombination limits the quantum yield of photoredox reactions for which the rates for the forward reaction and back electron transfer are competitive. Taking inspiration from a proton-coupled electron transfer (PCET) process in Photosystem II, a benzimidazole-phenol (BIP) has been covalently attached to the 2,2′-bipyridyl ligand of [Ir(dF(CF3)ppy)2(bpy)][PF6] (dF(CF3)ppy = 2-(2,4-difluorophenyl)-5-(trifluoromethyl)pyridine; bpy = 2,2′-bipyridyl). Excitation of the [Ir(dF(CF3)ppy)2(BIP-bpy)][PF6] photocatalyst results in intramolecular PCET to form a charge-separated state with oxidized BIP. Subsequent reduction of methyl viologen dication (MV2+), a substrate surrogate, by the reducing moiety of the charge separated species demonstrates that the inclusion of BIP significantly slows the charge recombination rate. The effect of ∼24-fold slower charge recombination in a photocatalytic phthalimide ester reduction resulted in a greater than 2-fold increase in reaction quantum efficiency.Fil: Sayre, Hannah. University of Princeton; Estados UnidosFil: Ripberger, Hunter H.. University of Princeton; Estados UnidosFil: Odella, Emmanuel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Arizona State University; Estados UnidosFil: Zieleniewska, Anna. National Renewable Energy Laboratory; Estados UnidosFil: Heredia, Daniel Alejandro. Arizona State University; Estados Unidos. Universidad Nacional de Río Cuarto. Instituto para el Desarrollo Agroindustrial y de la Salud. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto para el Desarrollo Agroindustrial y de la Salud; ArgentinaFil: Rumbles, Garry. National Renewable Energy Laboratory; Estados UnidosFil: Scholes, Gregory D.. University of Princeton; Estados UnidosFil: Moore, Thomas A.. Arizona State University; Estados UnidosFil: Moore, Ana L. Arizona State University; Estados UnidosFil: Knowles, Robert R.. University of Princeton; Estados Unido