Rosamaria W. C. Li

A novel soluble poly(fluorenylenevinylene) conjugated polymer: synthesis, characterization and application to optoelectronic devices

We report the synthesis and characterization of poly(9,9-dioctyl-1,4-fluorenylenevinylene), PDO14FV. This polymer is a novel poly(arylenevinylene) with fluorene units and long chain substituents that ensure solubility in organic solvents. PDO14FV presents green photoluminescence and yellow–green electroluminescence. The estimated ionization potential of PDO14FV is 5.3 eV and its estimated electroaffinity 2.5 eV. Organic light-emitting diodes based on PDO14FV were constructed, showing electroluminescent intensity onset at ca. 6 V.

A conductive polymer based electronic nose for early detection of Penicillium digitatum in post-harvest oranges.

We describe the construction of an electronic nose, comprising four chemiresistive sensors formed by the deposition of thin conductive polymer films onto interdigitated electrodes, attached to a personal computer via a data acquisition board. This e-nose was used to detect biodeterioration of oranges colonized by Penicillium digitatum. Significant responses were obtained after only 24 h of incubation i.e. at an early stage of biodeterioration, enabling remedial measures to be taken in storage facilities and efficiently distinguishing between good and poor quality fruits. The instrument has a very low analysis time of 40 s.

Efficient organic light-emitting diodes with fluorine-doped tin-oxide anode and electrochemically synthesized sulfonated polyaniline as hole transport layer

In this work we report efficiency measurements on light-emitting diodes with electrochemically synthesized sulfonated polyaniline as hole transport layer. The anode used in our devices is fluorine-doped tin oxide, the blocking layer is electrochemically synthesized poly(9,9-dioctyl-1,4-fluorenylenevinylene) and the electron transporting material and emitter is tris-(8-hydroxyquinoline) aluminum. Sulfonated polyaniline based devices presented efficiency of 0.79 cd/A.

Identification of Four Wood Species by an Electronic Nose and by LIBS

This paper presents two complementary methods capable of identifying four wood species (Cedrela fissilis, Ocotea porosa, Hymenolobium petraeum, and Aspidosperma subincanum) both by their volatile organic compounds and by the presence of 10 chemical elements: Al, B, Ca, Mg, Zn, Cu, Mn, Fe, Na, and Si. The volatile compounds were detected by an electronic nose formed by an array of three different conductive polymer gas sensors. The elemental determination was made by laser-induced breakdown spectrometry (LIBS). The emissions measured were treated by principal component analysis (PCA). Leave-one-out analysis showed a rate of hits of 100%.

Investigation of the conformational changes of a conducting polymer in gas sensor active layers by means of polarization-modulation infrared reflection absorption spectroscopy (PM-IRRAS).

Polarization-Modulation Infrared Reflection Absorption Spectroscopy (PM-IRRAS) was employed to observe the changes in the molecular conformation of poly(2-phenyl-1,4-xylylene) (PPPX) films that occurred after exposure to organic solvent vapors. The PPPX films were supported on solid matrixes by casting, spin-coating, and Langmuir-Blodgett (LB) techniques. The results show that the polymer is sensitive to the solvent vapors, which affect some of the vibration dipole moments, as detected by PM-IRRAS. The sensitivity depends on the method employed to immobilize the polymer, with more significant changes in films formed using techniques that result in a less systematically organized conformation. This feature enables the use of surface vibration spectroscopy to detect organic solvent vapors and may be applied in an artificial nose.

Ion Jelly: a novel sensing material for gas sensors and electronic noses

Although ionic liquids (ILs) are promising materials for electrochemical gas sensors, their practical application is somehow limited since it is difficult to confine a liquid in micro-devices. The gelation of ILs induced by a biopolymer such as gelatin originates quasi-solid materials named Ion Jelly which are dimensionally stable and fairly conductive. In this paper we describe chemoresistive gas sensors having different ion jellies as an active layer and an electronic nose formed by an array of such sensors. The performance of this e-nose was demonstrated by its ability to detect and correctly sort eight common volatile solvents.

Electrochemical syntheses of poly(4,7-benzofuran vinylene) (PBFV) and poly(4,7-benzothiophene vinylene) (PBTV)

Poly(4,7-benzofuran vinylene) (PBFV) and poly(4,7-benzothiophene vinylene) (PBTV) were obtained by the cathodic reduction of 4,7-bis(dibromomethyl)benzofuran and 4,7-bis(dibromomethyl)benzothiophene at a stirred mercury pool cathode. Spectroscopic and thermal analysis data, doping and conductivity measurements are also presented.

Synthesis, properties, and applications of poly( p -phenylene vinylene)S

Publisher Summary This chapter discusses the synthesis, properties, and applications of poly(p-phenylene vinylene) (PPV). The infrared (IR) spectrum of unsubstituted PPV has been studied in detail and assignments made to almost all the observed bands. PPV oligomers present optical absorption and luminescence spectra whose peaks are redshifted with increasing chain length. PPV and its derivatives are conventionally used in the form of thin films operating as active layers in light-emitting diodes (LEDs), photodetectors, and other optoelectronic devices. An important characteristic of devices constructed with PPV is that they operate with the polymer layer submitted to high electric-field strengths. To permit device operation at low voltages, on the order of a few volts, the polymer film thickness is reduced to around 102 nm. The production of high-quality polymer thin films constitutes an important step in the device construction process. PPV-based devices are commonly constructed in a multilayer structure in which the polymer film is sandwiched between charge injection electrodes; hence, the polymer/electrode interface plays an important role in the performance of the devices and is discussed in the chapter for different classes of materials.

Electrochemical synthesis of poly(4,4′-biphenylene ethylene)s

Abstract Three novel poly(4,4′-biphenylene ethylene)s (PBPE)s, substituted at the 2,2′-positions by electron-withdrawing or donating groups, were obtained via the cathodic reduction of 4,4′-bis(bromomethyl)biphenyl and corresponding derivatives at a stirred mercury pool cathode. Spectroscopic and thermal analysis data are also presented.

Electrochemical synthesis of poly(4,4′-biphenylenevinylene)s (PBPVs)

A series of three 2,2′-substituted 4,4′-dimethylbiphenyls have been prepared either by Grignard or Ullmann reactions and their benzylic bromination with NBS gave the corresponding 4,4′-bis(dibromomethyl)biphenyls. The cathodic reduction of these compounds, at a stirred mercury pool cathode led to the desired poly(4,4′-biphenylenevinylene)s, PBPVs, in good yields and in very smooth conditions. The obtained polymers have been spectroscopically characterized. After doping with iodine vapours, they exhibited electrical conductivities of the same magnitude as those observed for parent PPVs. Thermal analysis data (DSC and TG) are also presented and show their thermal stability both in air or nitrogen atmosphere.