Application of abrupt cut-off models in the analysis of the capacitance spectra of conjugated polymer devices

In this paper, a detailed study of the capacitance spectra obtained from Au/doped-polyaniline/Al structures in the frequency domain (0.05 Hz–10 MHz), and at different temperatures (150–340 K) is carried out. The capacitance spectra behavior in semiconductors can be appropriately described by using abrupt cut-off models, since they assume that the electronic gap states that can follow the ac modulation have response times varying rapidly with a certain abscissa, which is dependent on both temperature and frequency. Two models based on the abrupt cut-off concept, formerly developed to describe inorganic semiconductor devices, have been used to analyze the capacitance spectra of devices based on doped polyaniline (PANI), which is a well-known polymeric semiconductor with innumerous potential technological applications. The application of these models allowed the determination of significant parameters, such as Debye length (≈20 nm), position of bulk Fermi level (≈320 meV) and associated density of states (≈2×10¹⁸ eV⁻¹ cm⁻³), width of the space charge region (≈70 nm), built-in potential (≈780 meV), and the gap states’ distribution.     

Understanding the inactivation process of organophosphorus herbicides: A DFT study of glyphosate metallic complexes with Zn2+, Ca2+, Mg2+, Cu2+, Co3+, Fe3+, Cr3+, and Al3+

Glyphosate is the active component of one of the top‐selling herbicides, which is also a potent EPSP synthase inhibitor. The herbicide is absorbed by living tissue and translocated via the phloem, to plant roots and rhizomes. When applied directly into the soil it has low activity, due to the high adsorption by soil constituents. Understanding the specific interactions between metals in the soil and glyphosate is the main step in understanding the low activity of the herbicide when applied directly into the ground and not pulverized. We can observe there is a stability order for both tetrahedral and octahedral complexes between glyphosate and metals: Zn>Cu>Co>Fe>Cr>Al>Ca>Mg. © 2012 Wiley Periodicals, Inc.     

Renormalization for piecewise smooth homeomorphisms on the circle

In this work we study the renormalization operator acting on piecewise smooth homeomorphisms on the circle, that turns out to be essentially the study of Rauzy–Veech renormalizations of generalized interval exchange maps with genus one. In particular we show that renormalizations of such maps with zero mean nonlinearity and satisfying certain smoothness and combinatorial assumptions converge to the set of piecewise affine interval exchange maps.     

Shadows and strong gravitational lensing: a brief review

For ultra compact objects, light rings and fundamental photon orbits (FPOs) play a pivotal role in the theoretical analysis of strong gravitational lensing effects, and of BH shadows in particular. In this short review, specific models are considered to illustrate how FPOs can be useful in order to understand some non-trivial gravitational lensing effects. This paper aims at briefly overviewing the theoretical foundations of these effects, touching also some of the related phenomenology, both in general relativity and alternative theories of gravity, hopefully providing some intuition and new insights for the underlying physics, which might be critical when testing the Kerr black hole hypothesis.     

A note on gradient k-Yamabe solitons

Annals of Global Analysis and Geometry - In this paper we provide some triviality results for gradient k-Yamabe solitons under different assumptions. In fact, under either growth or integral...     

Thionin adsorption on silicon (1 0 0): Structural analysis

In the search of new photoactive species that may be of use either in energy conversion or in photodynamic therapy, we studied the functionalization of silicon (1 0 0) with thionin using the glutaraldehyde coupling reaction. Surface properties were obtained by ellipsometric measurements, atomic force microscopy, and luminescence spectroscopy, which indicated the formation of a well organised monolayer in the silicon surface. In addition, the comparison of Raman spectroscopy data with first-principles pseudopotential calculations of the vibrational modes of the thionin molecule also indicate the formation of a monolayer of intact thionin molecules. Therefore, the simple functionalization process (involving only mild aqueous solution chemistry) described here works well and can be used to construct smooth monolayers of photoactive molecules with functional amine groups.