Electrochromic properties of spiropyran-terthiophene adaptive polymers

Adaptive materials have the ability to modify their behaviour or characteristics in response to external stimuli, for example through electrochemical changes, macroscopically in the molecular structure. These materials may have only one form with binding skills whilst others are passive. In principle this material can be switched ‘on’ and ‘off’ using external stimuli [3]. In this field hybrid Polythiophenes substituted with Spiropyrans are an important representative class of conjugated polymers that form environmentally and thermally stable materials and stimulate deep interest for their optoelectronic and reversible properties. An enhancement in the electronic and photonic properties of the materials and the creation of new functions, such as new sensory materials or new biocompatible structures, critically depends on the synthesis of polythiophene [1,4]. This problem can be bypassed with some synthetically procedures that have been developed by our group and published on previous outputs. In this work the new family of hybrid spiropyran-terthiophenes moieties has been fully characterized and analyzed. An important aspect emerged in the study consists is the charge transfer during the processes of activation and deactivation of the material [2]. It has been observed spectroelectrochemically that a consistent charge transfer occurs while the activated surface is stimulated with an external potential. The kinetics of activation and deactivation has been detected at different potentials. This plays a remarkable role in the complete description of the properties of the structure under different conditions, especially during the electrochemical activation of the material in an electrolytical cell. This offers the possibility of inducing dramatic changes to the bulk properties of the active system by electrochemical stimulus. Herein we present the electrochemical and spectrelectrochemical behaviour of our materials. BIBLIOGRAPHY 1. S. Gambhir, K. Wagner, D. L. Officer, Towards functionalised terthiophene-based polymers. Synthetic Metals 154, 2005: 117-120. 2. S. Hammes-Schiffer, A. V.Soudakov. Proton-coupled electron transfer in solution, Proteins and electrochemistry. Journal of Physical Chemistry B, 2008, 14108-14123. 3. A. Radu, S. Scarmagnani, R. Byrne, C. Slater, K. T. Lau, D. Diamond, Photonic modulation of surface properties: a novel concept in chemical sensing. Journal of Physics D: Applied Physics, 40, 2007, 7238-7244. 4. H. Mehenni, L. H. Dao, Synthesis and characterization of novel conducting homopolymers based on β-styryl terthiophene. Canadian Journal of Chemistry, 86, 2008, 1010-1018

Electro- and photo- chromism of hybrid conducting polymers

Polythiophenes are an important representative class of conjugated polymers that form some of the most environmentally and thermally stable materials that can be used as electrical conductors, nonlinear optical devices, polymer LEDs, electrochromic windows, sensors, solar cells, polymer electronic interconnects, nanoelectronic and optical devices.1 Gaining control over the structure, properties, and function in polythiophenes continues to make the synthesis of polythiophenes a critical subject in the development of new advanced materials. An enhancement in the electronic and photonic properties of the materials and the creation of new functions, such as new sensory materials, critically depends on the synthesis of the polythiophene.4 This leads to the exciting prospect that the properties of polythiophenes can be selectively engineered through synthesis and assembly. Herein, we show the incorporation of molecular photochromic switches, such as benzospiropyran, into the polythiophene backbone. These are an intriguing class of organic molecules, which allow the control of molecular structure and function with light.2, 3 This offers the possibility of inducing dramatic changes to the bulk properties of a system by photonic irradiation. More importantly, benzospiropyran forms photo- reversible transition metal ion complexes. Herein, we present our work on the electro-chemical and optical properties of these hybrid materials

Fermion mass hierarchy from the Klein-Gordon equation

I discuss some simple considerations and a quantization rule deal- ing with tensor and scalar gravitons starting from the analysis of gravitational waves inducing electromagnetic ¯elds in cavities. A further important quan- tization rule providing the exact mass values for the elementary fermions by relating the Klein-Gordon equation to the metric properties of the space- time of this propagating graviton is reached. As a consequence of the previous analysis I deduce some cosmological implications and forecast the existence of new particles detectable through experiments running at the LHC facilities

Visible spectroelectrochemical characterization of geobacter sulfurreducens biofilms on optically transparent indium tin oxide electrode

We report visible spectroelectrochemical (SEC) characterization of cytochrome c552 (cyt c552) in viable Geobacter sulfurreducens biofilms on tin-doped indium oxide (ITO) electrodes poised at 0.24 V vs.. SHE. G. sulfurreducens biofilms were grown in minimal medium with acetate as electron donor (turnover conditions), followed by 24 hours incubation in electron donor-depleted medium (non-turnover conditions). The electronic absorption spectra of G. sulfurreducens biofilms showed the lowest energy absorption band in the reduced state at 552 nm, which indicated excess of cyt c552 in the biofilm. The spectra under non-turnover conditions displayed gradual reduction of the cyt c552, following the step-wise decrease of electrode potential from 0.0 V to -0.6 V vs.. standard calomel electrode (SCE). The spectral changes were fully reversible in both positive and negative direction of the scan potential, with average midpoint potential value of -0.42 V vs.. SCE. Confocal microscopy analysis revealed that the thickness of biofilms under turnover conditions and non-turnover conditions was approximately 35 and 3.5 µm, respectively. This is the first study to observe the reversible redox conversion of cyt c552 in viable G. sulfurreducens biofilms

Polymer sensors and actuators: synthesis and characterization of polythiophenes modified with benzospiropyran derivatives

The aim of this thesis is to understand the basic physico/chemical behaviour of novel nitrospiropyran-substituted-(poly)terthiophene materials. Attractive characteristics that distinguish these materials include electrochemical/photochemical-switching processes. Understanding the fundamental behaviour of these new derivatives is the key to taking advantage of these characteristics. The stimuli induced isomerisation between the colourless spiropyran and the highly coloured merocyanine is the key-process studied in this research. Chapter 2 reports the electrochromic behaviour of spiropyran, through irreversible electrooxidative isomerisation in at least two merocyanine isomers. The molecular photophysical processes of the electrochemically-generated polymer are reported and the properties studied. In Chapter 3 a new monomer, which differs by a single methylene group in the linking ester-linker functionality from the previous one, will be introduced. A nitrospiropyran was used as a reference, and a detailed spectroscopy analysis will help in the description of the thermodynamic properties. Chapter 4 highlights how the polymeric molecular switches can bind an important extracellular protein, fibronectin, and explores by means of microscopy the on-demand tuning of the protein adhesion. A new derivative is presented in Chapter 5, wherein a spiropyran moiety is intercalated between two thiophenes. The electrochemical and optical switching of the spiropyran and thiophene groups were investigated. In Chapter 6 three new spiropyran-based derivatives are presented, and routes to multi-modal switching behavior are explored via photochemical, electrochemical and chemical stimuli, such as pH. Their reversibility and their properties are investigated using both spectroscopic and electroanalytical methods. The final chapter outlines future work and initial progress related to the integration of spiropyran-thiophene polymers into photo-electro active portable analytical devices

An experiment revealing the motion of the earth through a medium

The results of a simple experiment are reported. Circuits, like data-loggers, containing FET electronic components reveal a particular signal when working in the tri-state mode (floating pin). Time series recorded by two identical circuits (antennae) at distances of thousands of kilometers show identical daily spectrograms and correlation time delay. In particular the daily correlation time delay curve confirms, over the 99.99 % confi- dence limit, the motion of the Earth through a medium filled with a field generating the signal fluctuations. Such a field appears homogeneously distributed all around the Earth orbit as proved by the best fit with a simple model providing a flux speed of about 37 ± 4 km/s in the direction of the motion of the Earth in the solar frame system. Some final considerations are formulated by analyzing the power spectrum of the signal apparently different from both a Lorentzian and a Planckian distribution. This seems to exclude that the origin of the signal could be ascribed to respectively Random Telegraph Noise (RTN) and particles obeying the Bose-Einstein statistics

Analysis of fabric evolution and metamorphic reaction progress at Lago della Vecchia-Valle d'Irogna, Sesia-Lanzo Zone, Western Alps

The Lago della Vecchia-Valle d'Irogna rocks are part of the Eclogitic Micaschists Complex (EMC) of the Sesia-Lanzo Zone, western Austroalpine domain. The 1:10,000 scale map includes metaintrusive, minor micaschist, banded gneiss, and metabasic boudins. The multiscale structural analysis reveals successive magmatic and tectono-metamorphic stages: during M0 the metaintrusive protoliths emplaced; D1 took place under eclogite-facies conditions; during D2 stage, a pervasive foliation developed under retrograde blueschist-facies conditions; D3–D4 and D5 structures developed under greenschist-facies conditions; during M6 andesitic dykes intruded. The mapped degree of fabric evolution (FE) and metamorphic transformation (MT) related to D2-foliation shows that the MT was not only controlled by bulk rock and mineral compositions, but also by FE. The development of a pervasive blueschist-facies D2-foliation is in contrast with the eclogitic dominant fabric generally recorded in the EMC. This difference suggests that FE and MT are potentially responsible for km-scale heterogeneities in the tectono-metamorphic record

Density Distribution Maps: A Novel Tool for Subcellular Distribution Analysis and Quantitative Biomedical Imaging

open5noSubcellular spatial location is an essential descriptor of molecules biological function. Presently, super-resolution microscopy techniques enable quantification of subcellular objects distribution in fluorescence images, but they rely on instrumentation, tools and expertise not constituting a default for most of laboratories. We propose a method that allows resolving subcellular structures location by reinforcing each single pixel position with the information from surroundings. Although designed for entry-level laboratory equipment with common resolution powers, our method is independent from imaging device resolution, and thus can benefit also super-resolution microscopy. The approach permits to generate density distribution maps (DDMs) informative of both objects’ absolute location and self-relative displacement, thus practically reducing location uncertainty and increasing the accuracy of signal mapping. This work proves the capability of the DDMs to: (a) improve the informativeness of spatial distributions; (b) empower subcellular molecules distributions analysis; (c) extend their applicability beyond mere spatial object mapping. Finally, the possibility of enhancing or even disclosing latent distributions can concretely speed-up routine, large-scale and follow-up experiments, besides representing a benefit for all spatial distribution studies, independently of the image acquisition resolution. DDMaker, a Software endowed with a user-friendly Graphical User Interface (GUI), is also provided to support users in DDMs creation.openIlaria De Santis; Michele Zanoni; Chiara Arienti; Alessandro Bevilacqua; Anna TeseiIlaria De Santis; Michele Zanoni; Chiara Arienti; Alessandro Bevilacqua; Anna Tese