Spectroelectrochemistry of Intrinsically Conducting Furan-Thiophenes Copolymers

Die elektrochemische Copolymerisation von Furan und Thiophen oder 3-Chlorothiophen wurde erfolgreich realisiert in einer Elektrolytlösung von Bortrifluorid-Diethylether + Ethylether (Verhältnis 1:2) bei konstantem Elektrodenpotenzial. Die Zugabe von Trifluoroessigsäure (TFA) (10 Vol-%) zu Bortrifluorid-Diethylether + Ethylether (Verhältnis 1:2) erniedrigte das Oxidationspotenzial der Monomere; die Polymerisationsgeschwindigkeit erhöhte sich, da TFA die Ionenleitfähigkeit des Elektrolyts vergrößert. Die Homopolymere zeigen nur einen Redoxpeak, verursacht durch Polymeroxidation und - reduktion. Die elektrochemische Copolymerisation wird bei verschiedenen Potenzialen und mit unterschiedlichen Thiophen- oder 3-Chlorothiophenkonzentrationen untersucht. Die Copolymere zeigen ein Redoxpeakpaar, dessen Position sich wesentlich von der der Homopolymere unterscheidet. Mit zunehmendem Polymerisationspotenzial und/oder zunehmender Konzentration an Thiophen- oder 3-Chlorothiophen werden auch mehr Thiophen- oder 3-Chlorothiopheneinheiten in den Copolymerfilm eingebaut. Ein Elektropolymerisationmechanismus wird für die Copolymere vermutet und die Copolymere weisen eine recht gute Langzeitstabilität der Redoxaktivität nach Zyklen in Acetonitril auf. In situ UV-Vis-Spektren der Homo- und Copolymerfilme wurden gemessen und λ1max, welches dem π → π*- Übergang entspricht, wurde bestimmt. Der optische Übergang bei λ2max vom Valenzband in das höhere Bipolaronband wurde ebenfalls bestimmt. Die Bandlücke für die Homo- und Copolymerfilme beim direkten Übergang wurde von der Kante im Absorptionsspektrum abgeschätzt. Die elektrochemische Thermodynamik für die Homo- und Copolymerfilme deutet darauf hin, dass jeweils ein Elektron von den Polymersegmenten, bestehend aus 4 Monomereinheiten, entfernt wird. Die untersuchten leitfähigen Filme zeigen einen Leitfähigkeitssprung mit einer stabilen Leitfähigkeit bis EAg/AgCl= 2 V. Diese Leitfähigkeitsänderung ist reversibel. Polyfuran hat verglichen mit Polythiophen eine geringere Leitfähigkeit und die Leitfähigkeit von Poly(3-chlorothiophen) ist rund eine Zehnerpotenz niedriger als die von Polythiophen. Da das in situ Leitfähigkeitsverhalten der Copolymere nicht die Summe der einzelnen Homopolymere bildet, kann man ausschließen, dass es sich bei den abgeschiedenen Copolymeren um Blockcopolymere handelt. Mit Hilfe der FTIR-Spektroskopie wurden Schwingungsspektren der Homo- und Copolymerfilme aufgenommen. Die Ergebnisse zeigen, dass es zur α-α'-Verknüpfung zwischen den Radikalkationen während der Copolymerisation kommt, was charakteristisch ist für α-substituierte fünfgliedrige heterozyklische Verbindungen. Der Mechanismus der elektrochemischen Degradation von Furan-Thiophen-Copolymeren wird ebenfalls mit Hilfe der gemessenen Spektren beschrieben. Die in situ Resonanz-Raman-Spektroskopie ergab, dass die spektroskopischen Eigenschaften der Copolymere zwischen denen der Homopolymere lagen. Bei höheren Polymerisationspotenzialen und höheren Konzentrationen an Thiophen oder 3-Chlorothiophen werden mehr Thiophen- oder 3- Chlorothiopheneinheiten in die Copolymerketten eingebaut. Es ist offensichtlich, dass die Ramanspektren der Copolymere wesentlich komplexer sind als die der Homopolymere, wodurch die Auswertung erschwert wird. Dennoch erinnern die Ramanspektren der Copolymere an die der Homopolymere. Die spektroelektrochemischen Eigenschaften der Copolymere haben bestätigt, dass deren Charakteristika zwischen denen der Homopolymere liegen, was deutlich macht, dass die Oxidation von Monomeren möglich ist und dass die Copolymerketten demnach aus Furan- und Thiophen- bzw. 3- Chlorothiopheneinheiten bestehen können.Electrochemical copolymerization of furan and thiophene or 3-chlorothiophene was successfully realized in a solvent system consisting of boron trifluoride ethyl ether (BFEE) + ethyl ether (EE) (ratio 1:2) at constant electrode potential. The addition of trifluoroacetic acid (TFA) (10 % by volume) to BFEE + EE (ratio 1:2) decreased the oxidation potential of the monomers; the polymerization rate was also accelerated because TFA increases the ionic conductivity of the electrolyte. The homopolymers have only one redox peak caused by polymer oxidation and reduction. Electrochemical copolymerization both at different potentials and with different thiophene or 3-chlorothiophene concentrations is investigated. The copolymers show one anodic/cathodic peak couple that appears at a position quite different from the positions observed with homopolymers. More thiophene or 3-chlorothiophene units are incorporated into the copolymer film with an increasing polymerization potential of the copolymer and/or with an increasing concentration of thiophene or 3- chlorothiophene in the feed. An electropolymerization mechanism of copolymers has been proposed, and the copolymers show a fairly good long-term stability of the redox activity after cycling in acetonitrile. In situ UV-Vis spectra of the homo- and copolymer films were measured and λ1max which corresponds to the π → π* transition is determined. The optical transition with λ2max from the valence band into the higher bipolaron band is also assigned. The band gap (Eg) for homo- and copolymer films from a direct interband transition is estimated from the absorption edge of the spectrum. The redox thermodynamics of the homo- and copolymer films suggest that one electron is removed from polymer segments containing four monomer units. The studied conducting films show a single conductivity change with a stable conductivity up to EAg/AgCl= 2 V. The conductivity of these films is almost restored when the potential shift direction is reversed. Polyfuran compared to polythiophene, has a lower conductivity and the conductivity of poly(3-chlorothiophene) is around one order of magnitude lower than that of polythiophene. The in situ conductivity properties of the copolymers are not the sum of those of the individual homopolymers. This result may eliminate the possibility that the copolymers can be considered as block copolymers. Vibrational spectra of homo- and copolymer films investigated in this study have been obtained using FTIR spectroscopy. The results indicate that α-α' coupling of radical cations has taken place in the copolymerization. This is a characteristic of α-substituted five-membered heterocyclic compounds. The electrochemical degradation mechanism of furan-thiophene copolymers is also described using the obtained spectra. The in situ resonance Raman spectroscopy of the copolymers shows spectroscopic properties intermediate between those of homopolymers. At higher polymerization potentials and at higher concentrations of thiophene or 3-chlorothiophene in the feed more thiophene or 3-chlorothiophene units are incorporated into the copolymer chains. It is obvious that the Raman spectra of the copolymers are more complex than those of homopolymers, which makes the assignment difficult. However, the in situ Raman spectra of the copolymers are reminiscent of those of the homopolymers. The spectroelectrochemical properties of the copolymers confirmed that the copolymers show intermediate characteristics between the homopolymers, implying that oxidation of monomers is possible and the copolymer chains may accordingly be composed of furan and thiophene or 3-chlorothiophene units

Spectroelectrochemistry of Intrinsically Conducting Selenophene-3- Chlorothiophene Copolymers

The electrochemical copolymerization between selenophene and 3-chlorothiophene monomers was successfully realized. The influence of the applied polymerization potential and the monomer feed ratio on the copolymer properties were investigated, and the results revealed that the obtained polymer films strongly depended on the polymerization conditions. The obtained copolymers showed good redox stability in acetonitrile-based electrolyte solution. Band gap energy of the homo-and copolymer films was estimated and the values were between 1.95-2.11 eV. The electrical conductivity measurements of selenophene-3-chlorothiophene copolymers were successfully achieved using a four-probe technique and generally increased with increasing temperature. Fourier transform infrared (FTIR) characterization disclosed that the bands of homopolymers were retained in the spectra of copolymers with typical assignments suggesting that α-positions in the polymer chains were involved in the polymerization

Removal of Pb(II) Metal Ions from Aqueous Solutions Using Chitosan-Vanillin Derivatives of Chelating Polymers

Our study investigates the removal of Pb(II) ions found in aqueous solutions using chitosan-vanillin polymeric material. The effects of pH, agitation time, adsorbent mass, and initial amount of studied ion on the chelation process have been carried out using batch experiments. The quantity of residual ions has been estimated via atomic absorption spectrometry. The polymers are characterized using infrared spectroscopy, TGA, SEM, and BET surface area. The highest removal of Pb(II) ions achieved by polymers I and II was at pH 6. The Langmuir isotherm worked as the greatest explanation for the experimental outcome with highest chelation capability equal to 23.3 mg g-1 for polymer I and 66.23 mg g-1 for polymer II. Kinetic studies revealed that chemisorption was the rate-determining step, whereas the uptake was natural and endothermic.The Authors thank Imam Abdulrahman Bin Faisal University for providing facilities, financial support, and encouragement

HPLC Analysis of Chemical Composition of Selected Jordanian Medicinal Plants and their Bioactive Properties

Three medicinal plants grown wild in Jordan, namely Achillea santolina L, Achillea fragrantisimma, Asteriscus graveolens (Forssk.) Less, were extracted with ethyl acetate by continuous shaking at room temperature for three days. The antibacterial activity of the crude extract was evaluated. The extracts were analyzed for their phenolic and flavonoids content by HPLC-PDA. The HPLC analysis of the plant extracts revealed the presence of flavonoids and phenolic compounds in the three plant extracts. Results revealed a strong antibacterial activity of A. graveolens against three bacterial strains (B. subtilis, E. coli, and S.aureus). while A. fragrantissima inhibited the growth of B. subtilis. Bioactivities were attributed mainly to the immense content of phenol-based compounds in plants.University and Al-Quds University for providing facilities, and encouragemen

Kinetic Studies on the Removal of Some Lanthanide Ions from Aqueous Solutions Using Amidoxime-Hydroxamic Acid Polymer

Lanthanide metal ions make distinctive and essential contributions to recent global proficiency. Extraction and reuse of these ions is of immense significance especially when the supply is restricted. In light of sorption technology, poly(amidoxime-hydroxamic) acid sorbents are synthesized and utilized for the removal of various lanthanide ions (La3+, Nd3+, Sm3+, Gd3+, and Tb3+) from aqueous solutions. The sorption speed of trivalent lanthanides (Ln3+) depending on the contact period is studied by a batch equilibrium method. The results reveal fast rates of metal ion uptake with highest percentage being achieved after 15–30 min. The interaction of poly(amidoxime-hydroxamic) acid sorbent with Ln3+ ions follows the pseudo-second-order kinetic model with a correlation coefficient R2 extremely high and close to unity. Intraparticle diffusion data provide three linear plots indicating that the sorption process is affected by two or more steps, and the intraparticle diffusion rate constants are raised among reduction of ionic radius of the studied lanthanides

The utilization of leaf-based adsorbents for dyes removal: A review

The presence of organic dyes in the aquatic environment is aserious global problem because of the serious negativeconsequences on the quality of ecosystems. Among various physico-chemical methods, the adsorption could be con-sidered a promising alternative for removing dyes from aqueous media, due to its efficiency, high selectivity, lowcost, ease of operation, simplicity, and availability in a wide range of experimental conditions. However, all these ad-vantages are closely related to the nature of adsorbent material used in the adsorption processes of dyes. The adsor-bent materials available in large quantities requiring a simple preparation will enhance the benefits of theadsorption processes, in agreement with the concepts of green chemistry. This review is focused on the use ofleaf-based materials, in raw or modified forms, as adsorbents for the removal of dyes from aqueous effluents,with applications in the wastewater treatment. This review addresses characterization of leaf-based adsorbents,possible utilization of leaf-based adsorbents (raw and activated forms) for dye removal and possible applicationsin pilot and full scale systems. Also, thermodynamics, equilibrium and kinetic parameters of dye adsorption onleaf-based adsorbents are discussed. The practical utility of leaf-based adsorbents for dye removal, and their possibleuses in the treatment of industrial wastewater are copiously highlighted

The utilization of leaf-based adsorbents for dyes removal: A review

The presence of organic dyes in the aquatic environment is a serious global problem because of the serious negative consequences on the quality of ecosystems. Among various physico-chemical methods, the adsorption could be considered a promising alternative for removing dyes from aqueous media, due to its efficiency, high selectivity, low cost, ease of operation, simplicity, and availability in a wide range of experimental conditions. However, all these advantages are closely related to the nature of adsorbent material used in the adsorption processes of dyes. The adsorbent materials available in large quantities requiring a simple preparation will enhance the benefits of the adsorption processes, in agreement with the concepts of green chemistry. This review is focused on the use of leaf-based materials, in raw or modified forms, as adsorbents for the removal of dyes from aqueous effluents, with applications in the wastewater treatment. This review addresses characterization of leaf-based adsorbents, possible utilization of leaf-based adsorbents (raw and activated forms) for dye removal and possible applications in pilot and full scale systems. Also, thermodynamics, equilibrium and kinetic parameters of dye adsorption on leaf-based adsorbents are discussed. The practical utility of leaf-based adsorbents for dye removal, and their possible uses in the treatment of industrial wastewater are copiously highlighted.Fil: Bulgariu, Laura. Technical University Gheorghe Asachi Of Iasi; RumaniaFil: Escudero, Leticia Belén. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales. Laboratorio de Química Analítica para Investigación y Desarrollo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; ArgentinaFil: Olugbenga, Solomon Bello. Ladoke Akintola University of Technology; NigeriaFil: Munawar, Iqbal. University Lahore; PakistánFil: Jan, Nisar. National Centre Of Excellence In Physical Chemistry; PakistánFil: Kayode Adesina, Adegoke. University of Peshawar; NigeriaFil: Fadi, Alakhras. Imam Abdulrahman Bin Faisal University; Arabia SauditaFil: Michael, Kornaros. University of Patras; GreciaFil: Ioannis, Anastopoulos. University of Patras; Greci