Influence of the polymer structure over self‐assembly and thermo‐responsive properties: The case of PEG‐b‐PCL grafted copolymers via a combination of RAFT and ROP

During the last years, the field of drug delivery has experienced a growing interest toward the so‐called thermo‐responsive polymers: synthetic materials that, due to the specific hydrophilic–lipophilic balance of their repeating units, exhibit a lower critical solution temperature (LCST) in water associated to a characteristic coil–globule transition. In this work, thermo‐responsive amphiphilic block copolymers are synthesized via reversible addition‐fragmentation transfer (RAFT) polymerization starting from thermo‐responsive monomers and a hydrophobic biodegradable macromonomer, oligo(caprolactone)methacrylate (CL₃MA), produced via ring opening polymerization (ROP). The obtained copolymers exhibit an interesting self‐assembly behavior leading to nanoparticles (NPs) as long as temperature is kept below the LCST. Otherwise, once this value is overcome, the destabilization of the NPs causes the formation of hydrophobic superstructures that enhance the release of an entrapped lipophilic drug. This characteristic behavior has been systematically studied and related to the copolymer structure. In particular, the self‐assembly behavior as well as temperature‐triggered NP destabilization have been related to the relative length of the two blocks constituting the copolymers and to their hydrophilic–lipophilic balance (HLB). Finally, the efficacy of the thermo‐responsive triggered drug release has been tested in the case of Paclitaxel (PTX). © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2919–2931     

Preparation of photoluminescent PMMA doped with tris(pyrazol-1-yl)borate lanthanide complexes

The neutral homoleptic Ln(III) complex Ln(Tp)₃ (Ln=Sm, Eu, Tb, Yb; Tp=hydrotris(pyrazol-1-yl)borate) were used as dopants for the preparation of novel photoluminescent poly(methyl methacrylate) glasses indicated as Ln(Tp)₃@PMMA. The doped polymers containing samarium, europium and terbium derivatives showed emission associated to f–f transitions in the visible range upon excitation with UV light, while a NIR emission was obtained from Yb(Tp)₃@PMMA. The maximum incident wavelength able to induce emissions from the Ln(Tp)₃-doped polymers depends upon the choice of the lanthanide ion. No meaningful antenna-effect was instead observed using dysprosium as metal centre.     

Effect of nature and location of defects on bandgap narrowing in black TiO2 nanoparticles

The increasing need for new materials capable of solar fuel generation is central in the development of a green energy economy. In this contribution, we demonstrate that black TiO(2) nanoparticles obtained through a one-step reduction/crystallization process exhibit a bandgap of only 1.85 eV, which matches well with visible light absorption. The electronic structure of black TiO(2) nanoparticles is determined by the unique crystalline and defective core/disordered shell morphology. We introduce new insights that will be useful for the design of nanostructured photocatalysts for energy applications.     

Global air quality and climate

Emissions of air pollutants and their precursors determine regional air quality and can alter climate. Climate change can perturb the long-range transport, chemical processing, and local meteorology that influence air pollution. We review the implications of projected changes in methane (CH(4)), ozone precursors (O(3)), and aerosols for climate (expressed in terms of the radiative forcing metric or changes in global surface temperature) and hemispheric-to-continental scale air quality. Reducing the O(3) precursor CH(4) would slow near-term warming by decreasing both CH(4) and tropospheric O(3). Uncertainty remains as to the net climate forcing from anthropogenic nitrogen oxide (NO(x)) emissions, which increase tropospheric O(3) (warming) but also increase aerosols and decrease CH(4) (both cooling). Anthropogenic emissions of carbon monoxide (CO) and non-CH(4) volatile organic compounds (NMVOC) warm by increasing both O(3) and CH(4). Radiative impacts from secondary organic aerosols (SOA) are poorly understood. Black carbon emission controls, by reducing the absorption of sunlight in the atmosphere and on snow and ice, have the potential to slow near-term warming, but uncertainties in coincident emissions of reflective (cooling) aerosols and poorly constrained cloud indirect effects confound robust estimates of net climate impacts. Reducing sulfate and nitrate aerosols would improve air quality and lessen interference with the hydrologic cycle, but lead to warming. A holistic and balanced view is thus needed to assess how air pollution controls influence climate; a first step towards this goal involves estimating net climate impacts from individual emission sectors. Modeling and observational analyses suggest a warming climate degrades air quality (increasing surface O(3) and particulate matter) in many populated regions, including during pollution episodes. Prior Intergovernmental Panel on Climate Change (IPCC) scenarios (SRES) allowed unconstrained growth, whereas the Representative Concentration Pathway (RCP) scenarios assume uniformly an aggressive reduction, of air pollutant emissions. New estimates from the current generation of chemistry-climate models with RCP emissions thus project improved air quality over the next century relative to those using the IPCC SRES scenarios. These two sets of projections likely bracket possible futures. We find that uncertainty in emission-driven changes in air quality is generally greater than uncertainty in climate-driven changes. Confidence in air quality projections is limited by the reliability of anthropogenic emission trajectories and the uncertainties in regional climate responses, feedbacks with the terrestrial biosphere, and oxidation pathways affecting O(3) and SOA.     

Selective O-acylation of unprotected N-benzylserine methyl ester and O,N-acyl transfer in the formation of cyclo[Asp-Ser] diketopiperazines

The synthesis of two diastereomeric cyclo[Asp-N-Bn-Ser] diketopiperazines (2a and 2b) was investigated. Initial formation of the Boc-aspartyl-N-benzyl serine isopeptide methyl esters (4a and 4b) was observed, which derive from the selective O-acylation of unprotected (S)- or (R)-N-benzylserine. This unexpected O-acylation is preferred over the formation of the tertiary amide and the resulting ester bond is stable in solution to O,N-acyl transfer. The O,N-acyl migration is then triggered by cleavage of the Boc protecting group and treatment with base, which also promotes immediate cyclization to the diketopiperazines.     

Community structure in large-scale cortical networks during motor acts

The purpose of the present work is to evaluate the community structure of the cortical network subserving the neurophysiologic processes in simple motor acts.To this end, we studied the topological properties of the functional brain connectivity in the frequency domain. The functional networks were estimated by means of the imaginary coherence from a dataset of high-resolution EEG recordings (4094 cortical sources) in a group of healthy subjects (n = 10) during a finger extension task. The analysis of the community structure was addressed through a particular detection algorithm that optimizes the modularity, a function related to the level of internal clustering inside the communities in the network. The principal results indicate that the cortical network changes its structural organization during the motor execution with respect to a baseline condition. Notably in the Beta band (12.5–30 Hz), the level of intra-module connectivity decreases, while inter-module connectivity increases reflecting the need for a neural integration of distant regions. Notably, this distributed interaction involves anatomical regions belonging to both the hemispheres including pre-motor and primary motor areas in the frontal and central part of the cortex as well as parietal associative regions, which are related to the planning, selection and execution of actions.     

Effect of graphitization on the wettability and electrical conductivity of CVD-carbon nanotubes and films

The use of carbon nanomaterials in various applications requires precise control of their surface and bulk properties. In this paper, we present a strategy for modifying the surface chemistry, wettability, and electrical conductivity of carbon tubes and films through annealing in a vacuum. Experiments were conducted with 60-300 nm nanotubes (nanopipes), produced by noncatalytic chemical vapor deposition (CVD) in a porous alumina template, and with thin films deposited by the same technique on a glassy carbon substrate having the same structure and chemistry of the CNTs. The surface of the as-produced CVD-carbon, treated with sodium hydroxide to remove the alumina template, is hydrophilic, and the bulk electrical conductivity is lower by a factor of 20 than that of fully graphitic multiwalled nanotubes (MWNT) or bulk graphite. The bulk electrical conductivity increases to the conductivity of graphite after annealing at 2000 degrees C in a high vacuum. The analysis of CNTs by transmission electron microscopy (TEM) and Raman spectroscopy shows the ordering of carbon accompanied by an exponential increase of the in-plane crystallite size, L(a), with increasing annealing temperature. Environmental scanning electron microscopy (ESEM) was used to study the interaction of CNT with water, and contact angle measurements performed using the sessile drop method on CVD-carbon films demonstrate that the contact angle increases nearly linearly with increasing annealing temperature.