Tailoring the molecular structure to suppress extrinsic disorder in organic transistors

In organic field-effect transistors, the structure of the constituent molecules can be tailored to minimize the disorder experienced by charge carriers. Experiments on two perylene derivatives show that disorder can be suppressed by attaching longer core substituents - thereby reducing potential fluctuations in the transistor channel and increasing the mobility at low temperature - without altering the intrinsic transport properties

A novel mertansine conjugate for acid-reversible targeted drug delivery validated through the Avidin-Nucleic-Acid-NanoASsembly platform

: In targeted cancer therapy, antibody-drug-conjugates using mertansine (DM1)-based cytotoxic compounds rely on covalent bonds for drug conjugation. Consequently, the cytotoxic DM1 derivative released upon their proteolytic digestion is up to 1000-fold less potent than DM1 and lacks a bystander effect. To overcome these limitations, we developed a DM1 derivative (keto-DM1) suitable for bioconjugation through an acid-reversible hydrazone bond. Its acid-reversible hydrazone conjugate with biotin (B-Hz-DM1) was generated and tested for efficacy using the cetuximab-targeted Avidin-Nucleic-Acid-NanoASsembly (ANANAS) nanoparticle (NP) platform. NP-tethered B-Hz-DM1 is stable at neutral pH and releases its active moiety only in endosome/lysosome mimicking acidic pH. In vitro, the NP/Cetux/B-Hz-DM1 assembly showed high potency on MDA-MB231 breast cancer cells. In vivo both B-Hz-DM1 and NP/Cetux/B-Hz-DM1 reduced tumor growth. A significantly major effect was exerted by the nanoformulation, associated with an increased in situ tumor cell death. Keto-DM1 is a promising acid-reversible mertansine derivative for targeted delivery in cancer therapy

Dissecting the contributions of composition and mesostructure on the release of thymol from silica-based mesopowders

In pharmaceutics, mesoporous silica (MS)- based powders are used as high capacity sorbents for active agents, sometimes with controlled release properties. In literature, MS powder-adsorbed substances display faster or slower release compared to unformulated compounds. In order to understand this controversial phenomenon, we carried out a comprehensive study by investigating the behavior of thymol (TH, a model compound with acaricide properties against the Varroa destructor bee parasite) in different conditions, as a pure powder and when adsorbed onto four silica-based mesopowders from commercial (Sil-Sol 6035 (R), Neusilin US2 (R), Silica Gel 60737 (R)) and synthetic (MCM-41) origin, and characterized by different chemical composition and nano/mesostructure. All MS-powders displayed high TH loading capacity (between 0.35 and 0.72 g/g SiO2), related to their mesopore volume. Stabilization of physisorbed TH in amorphous form was achieved by all except Neusilin US2 (R). Adsorption onto MCM-41 and SiliSol (R) or Silica Gel 60737 (R) led to tenfold and twofold reduction of sublimation rate at 33 degrees C (the average beehive temperature during treatment), respectively. Adsorption onto the three retentive MS-powders also reduced the energy of activation (Ea) of TH sublimation, providing explanation on the controversial effects on the release of bioactive agents adsorbed onto MS powders described by the literature. In field applications, the effect exerted by the retentive powders should permit to cover the entire Varroa reproduction cycle by a single administration. Reduction of the sublimation Ea brings the additional advantage of reducing sensitivity of the sublimation process to the environment temperature fluctuations

Description of a Sarcoptic Mange Outbreak in Alpine Chamois Using an Enhanced Surveillance Approach

Since 1995, the Alpine chamois (Rupicapra r. rupicapra) population of the Dolomites has been affected by sarcoptic mange with considerable management concerns. In this study, 15 years (2006–2020) of passive surveillance and demographic data were analyzed in order to describe a mange outbreak. Furthermore, an enhanced passive surveillance protocol was implemented in order to evaluate the efficiency of ordinary vs. enhanced surveillance protocol in identifying dead chamois in the field and in reaching a correct diagnosis. Our results confirm the role of mange as a determining factor for chamois mortality, while stressing the importance of a wider view on the factors affecting population dynamics. The enhanced passive surveillance protocol increased the probability of carcass retrieval and identification of the cause of death; however, its adoption may be too costly if applied for long periods on a wide scale. Passive surveillance, in both ordinary and enhanced surveillance protocol, should encompass the use of other strategies in the future to study the eco-epidemiology of the disease in wild Caprinae

Electronic structure of few-layer black phosphorus from μ\mu-ARPES

Black phosphorus (BP) stands out among two-dimensional (2D) semiconductors because of its high mobility and thickness dependent direct band gap. However, the quasiparticle band structure of ultrathin BP has remained inaccessible to experiment thus far. Here we use a recently developed laser-based micro-focus angle resolved photoemission ($\mu$-ARPES) system to establish the electronic structure of 2-9 layer BP from experiment. Our measurements unveil ladders of anisotropic, quantized subbands at energies that deviate from the scaling observed in conventional semiconductor quantum wells. We quantify the anisotropy of the effective masses and determine universal tight-binding parameters which provide an accurate description of the electronic structure for all thicknesses.Comment: Supporting Information available upon reques

The mechanism of NO and N2O decomposition catalyzed by short-distance Cu(I) pairs in Cu-ZSM-5: A DFT study on the possible role of NO and NO2in the [Cu–O–Cu]2+active site reduction

The reactivity between NO and the oxidized form of a short-distance dinuclear Cu-ZSM-5 catalyst (ZCu2O) was investigated. ZCu2O, which contains the [Cu–O–Cu]2+bridge coordinated at the opposite T11 positions of the M6 ring of ZSM-5, is obtained by the spin-forbidden decomposition of N2O on the reduced form of the catalyst, ZCu2, with an activation energy of about 18 kcal mol−1. The further addition of NO to the [Cu–O–Cu]2+unit of ZCu2O occurs in the doublet state without activation energy and gives NO2. After desorption, which requires 39.9 kcal mol−1, NO2decomposes on a second ZCu2O site, giving NO again and O2. Three reaction paths were defined for the latter reaction, with activation energies ranging from about 30 to 42–43 kcal mol−1. Final O2desorption is endothermic. The effect of enthalpy and Gibbs free energy contributions at 298.15 and at 773 K was also shown and discussed. According to the present calculations, the [Cu–O–Cu]2+bridge can easily be broken by reaction with NO but the desorption and further decomposition of NO2are characterized by energetics which make the above mechanism slower than the spin-allowed decomposition of N2O on similar sites, already reported in the literature. The above conclusions were based on a kinetic analysis according to the Energetic Span Model

A DFT study on the mechanism of NO decomposition catalyzed by short-distance Cu(I) pairs in Cu-ZSM-5

The complete NO decomposition catalyzed by short-distance Cu+ pairs in Cu-ZSM-5 was studied by means of DFT calculations. After adsorption of two NO molecules, an hyponitrite species is formed. Further decomposition of hyponitrite occurs with activation energies ranging from about 4 to 24 kcal mol−1, depending on the initial geometry of the substrate-catalyst complex. An oxidized form of the catalyst, [Cu[sbnd]O[sbnd]Cu]2+ and a copper-coordinating N2O molecule are obtained. Further N2O decomposition may occur with oxygen transfer from N2O to [Cu[sbnd]O[sbnd]Cu]2+ and formation of N2 and O2, both adsorbed on the catalyst. Three different kinds of transition states were identified for the latter step, which appears to be rate-determining due to activation energies ranging from 39–40, to 44–45, and to 50–52 kcal mol−1, respectively. After this, N2 desorption occurs easily, whereas O2 desorption is endothermic (from 28.8 to 36.5 kcal mol−1), the highest value being associated to reductive O2 desorption from a peroxide-like complex. It turned out that the best way for N2O elimination is the direct, spin-forbidden decomposition on a reduced Cu+⋯Cu+ pair, with formation of [Cu[sbnd]O[sbnd]Cu]2+ and N2, as already suggested in the literature. The problem of how the reduced catalyst may be regenerated is left open. © 2017 Elsevier B.V