Electropolymerization And Characterization Of Synthesized Thiophene And Nonylbithiazole Based Comonomers

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2006Thesis (PhD) -- İstanbul Technical University, Institute of Science and Technology, 2006Bu çalışmada yeni elektron alıcı verici alıcı türündeki bis(3,4-etilen-dioksitiyofen)-(4,4’-dinonil-2,2’-bitiyazol) komonomerinin sentezi, karakterizasyonu ile karbon fiber, Pt elektrotlar ve İTO kaplı cam üzerine elektrokimyasal polimerizasyonu çalışılmıştır. Polimerin 0.1 M’lık Et4NBF4 / CH2Cl2 elektrolit çözelti ortamındaki döngülü voltametrisi cok iyi ve tersinir redoks davranışı göstermektedir. Ayrıca bu komonomer hem p-katkılandırma hem de n-katkılandırma özelliklerine sahiptir. Polimerin yarı dalga (E1/2) potansiyeli Ag/AgCl referans elektroda karşı 0.303 V ve 0.814 V değerlerinde olduğu gözlemlenmiştir. Polimer elektrokromiktir: -* geçişleri için başlangıç potansiyelinden (Eg) değeri 1,75V ve λmax `değeride 2.15 eV dur. Polimerin homojen ve kaliteli filmi 0.25 s `den daha az zamanda anahtarlama özelliği ile kararli optik ozellikler sunmaktadir. Morfolojik çalışmalar ise polimerin karbon fiber mikroelektrot yüzeyine homojen ve sürekli şekilde biriktirildiğini göstermektedir. Bütün bu özellikler polimerin elektronik cihazlarda kullanıma elverişli olduğunun bir göstergesidir. Karbon fiber mikroelektrot/poli (3,4-etilen-dioksitiyofen)-(4,4’-dinonil-2,2’-bitiyazol)`in kapasitif davranışı ilk defa sabit akımda 5C cm-2 yük ile hazırlanmış olan polimer filmin dikdortgen şekil gösteren döngülü voltamogramında farkedilmiştir. Polimer filmin spesifik kapasitansı yaklaşık olarak ~340 mF cm-2 elde edilmistir. İki adet eşdeğer devre, elektrokimyasal impedans verileri ile önerilen bileşenlerin nümerik değerlerini bulabilmek icin eşleştirilmistir. Filmin sabit akımda yükleme/boşaltma özelliği, çözücünün ve biriktirme yükünün filmin kapasitif davranışı üzerindeki etkisi de incelenmiştir. Elektrokimyasal olarak farkli biriktirme yükleri ile hazırlanmış filmlerın morfolojisi FE-SEM ile görüntülenmiştir.In this study, the synthesis and characterization of a novel donor acceptor donor type bis(3,4-ethylene-dioxythiophene)-(4,4’-dinonyl-2,2’-bithiazole) comonomer and its electrochemically prepared polymer on carbon fiber, Pt button and ITO plate is reported. Cyclic voltammetry of the polymer in 0.1 M Et4NBF4/CH2Cl2 exhibits a very well defined and reversible redox processes and this comonomer can be either p-doped or n-doped. The half-wave oxidation potentials of the polymer (E1/2) were observed at 0.303 V and 0.814 V versus Ag/AgCl. The polymer is electrochromic; the onset for the  to * transition (Eg) of 1.75 eV with a λmax at 2.15 eV and the homogeneous and high quality film of the polymer is stable of its optical properties offering fast switching time which is less than 0.25s. The morphological studies reveal that the polymer was deposited as a continuous and very well adhering film to surface of the carbon fiber microelectrode. All these properties make this polymer favorable for use in electronic devices. Capacitive behavior of the carbon fiber microelectrode/poly(3,4-ethylene-dioxythiophene)-(4,4’-dinonyl-2,2’-bithiazole) film was firstly noticed from CV experiments which exhibit a rectangular shape, for a galvanostatically prepared polymer film with a charge of 5 C cm-2 which specific capacitance value was obtained about ~340 mF cm 2. The electrochemical impedance data were fitted two equivalent circuit models to find out numerical values of the proposed components. The galvanostatic charge/discharge characteristic of a film was investigated and the morphology of the films electrodeposited at different deposition charges were monitored using FE-SEM engineering.DoktoraPh

Nonylbithiazol centered comonomer synthesis and electrochemical characterization

Bu çalışmada yeni elektron alıcı-verici-alıcı türündeki bis(3,4-etilen-dioksitiyofen)-(4,4’-dinonil-2,2’-bitiyazol) komonomerinin sentezi, karakterizasyonu ile karbon fiber, Pt elektrot ve İTO kaplı cam üzerine elektrokimyasal polimerizasyonu çalışılmıştır. Polimerin 0.1 M’lık Et4NBF4 /DCM elektrolit çözelti ortamındaki döngülü voltamogramı çok iyi ve tersinir redoks davranışı göstermektedir. Ayrıca bu komonomer hem p-katkılandırma hem de n-katkılandırma özelliklerine sahiptir. Polimerin yarı dalga  (E1/2) potansiyeli Ag/AgCl referans elektroda karşı 0.303 V ve 0.814 V değerlerinde olduğu gözlemlenmiştir. Polimer elektrokromiktir: p-p* geçişlerinin başlangıcından band aralığı (Eg) değeri 1.75V olarak hesaplanmıştır ve λmax `değeri de 2.15 eV dur. Polimerin homojen ve kaliteli filmi 0.25 s`den daha az zamanda anahtarlama özelliği ile kararlı optik özellikler sunmaktadır. Morfolojik çalışmalar ise polimerin karbon fiber mikro elektrot yüzeyine homojen ve sürekli şekilde biriktirildiğini göstermektedir. Bütün bu özellikler polimerin elektronik cihazlarda kullanıma elverişli olduğunun bir göstergesidir. Karbon fiber mikroelektrot/poli (3,4-etilen-dioksitiyofen)-(4,4’-dinonil-2,2’-bitiyazol)`in kapasitif davranışı ilk önce sabit akımda (5C cm-2) yük ile hazırlanmış olan polimer filmin dikdörtgen şekil gösteren döngülü voltamogramında fark edilmiştir. Polimer filmin spesifik kapasitansı yaklaşık olarak ~340 mF cm?2 elde edilmiştir. İki adet eşdeğer devre, elektrokimyasal empedans verileri ile önerilen bileşenlerin nümerik değerlerini bulabilmek için eşleştirilmiştir. Filmin sabit akımda yükleme/boşaltma özelliği, çözücünün ve biriktirme yükünün filmin kapasitif davranışı üzerindeki etkisi de incelenmiştir. Elektrokimyasal olarak farklı biriktirme yükleri ile hazırlanmış filmlerin morfolojisi FE-SEM ile görüntülenmiştir. Anahtar Kelimeler: EDOT, iletken polimerler, karbon fiber, EES, süperkapasitör, eşdeğer devre.Since the first appearance of the conducting polymers in the late 70s, many researchers have been focused on the conducting polymers to commercialize them with applications such as thin film transistors, polymer light-emitting diodes (LEDs), and electrochromic devices. The poly(alkylbithiazoles) has received considerable attention because of its n-doping capability and usage in light emitting diode construction, this new class of conjugated polymer exhibit interesting thermochromic and electrochemical behavior especially nonyl derivative shows unusual optical properties. The most general use of carbon fibers is to reinforce composite materials due to its unique properties such as high strength, high modulus and low density. In order to achieve this, the surface properties them were studied recently and modification surfaces by electropolymerizing 3-methyl thiophene, ter-thiophene, pyrrole, EDOT and their copolymers and by electrocopolymerizing acrylamide, carbazole, thiophene, carbazole, pyrrole, carbazole, indole onto the fibers have investigated in detail. Conducting polymers, such as polypyrrole, polyaniline, polythiophene, and their derivatives, were reported as electrode materials for supercapacitors. Supercapacitors can be classified into two types the double-layer which store the energy within the electrochemical double-layer at the electrode-electrolyte interface and the redox supercapacitors. For redox supercapacitors, among several types of electrode materials employing of conducting polymers has received much attention due to their use in both aqueous and organic electrolytes and their wide potential working range. The electrochemical impedance spectroscopy (EIS) is one of the most effective and the reliable method to extract information about electrochemical characteristics of the electrochemical system for instance double-layer capacitance, diffusion impedance, determination of the rate of the charge transfer and charge transport processes, solution resistance etc. EIS was used to explain behavior of the polymer coated electrodes by established theories employing two models which are known as uniform and porous medium. In this study, the synthesis and characterization of a novel donor acceptor donor type ENBTE comonomer and its electrochemically prepared polymer on carbon fiber, Pt button and ITO plate is reported. Cyclic voltammetry of the polymer in 0.1 M Et4NBF4/CH2Cl2 exhibits a very well defined and reversible redox processes and this comonomer can be either p-doped or n-doped. The half-wave oxidation potentials of the polymer (E1/2) were observed at 0.303 V and 0.814 V versus Ag/AgCl. The polymer is electrochromic; the onset for the p to p* transition (Eg) of 1.75 eV with a ?max at 2.15 eV and the homogeneous and high quality film of the polymer is stable of its optical properties offering fast switching time which is less than 0.25s. The morphological studies reveal that the polymer was deposited as a continuous and very well adhering film to surface of the carbon fiber microelectrode. All these properties make this polymer favorable for use in electronic devices. Capacitive behavior of the carbon fiber microelectrode/PENBTE film was firstly noticed from CV experiments which exhibit a rectangular shape, for a galvanostatically prepared polymer film with a charge of 5 C cm-2 which specific capacitance value was obtained about ~340 mF cm-2. EIS studies revealed that high capacitance values observed in lower frequency region. The electrochemical impedance data were fitted two equivalent circuit models to find out numerical values of the proposed components. Simulation results showed that proposed electrical equivalent circuit was successfully applied to the experimental data to explain the interface between the carbon fiber microelectrode, the polymer film and the electrolyte. The slope the galvanostatic charge/discharge curve is 0.9985 and -0.9998 respectively indicates that IR drop is negligible and triangular shape of the charge discharge curve is typical for ideal capacitor behavior suggest that very good capacitive performance. The galvanostatic charge/discharge characteristic of a film was investigated and the morphology of the films electrodeposited at different deposition charges were monitored using FE-SEM. From the obtained results, we can conclude the employed comonomer in polymer electrode shows very good capacitive behavior on carbon fiber microelectrode. The measured capacitance values are quite promising for supercapacitor constructions with a good engineering. Keywords: EDOT; carbon fiber, conducting polymer; equivalent circuit EIS, supercapacitors

Performance comparison of CVD grown carbon nanofiber based on single- and multi-layer graphene oxides in melt-compounded PA6.6 nanocomposites

In the present study, newly design hybrid nanostructures were produced by growing long carbon nanofibers (CNF) on single- and multi-layer graphene oxide (GO) sheets in the presence of catalyst by chemical vapor deposition (CVD). Chemical composition analysis indicated the formation of Fe-C bonds by the deposition of carbon atoms on catalyst surface of Fe2O3 and increasing in C/O atomic ratio confirming CNF growing. These hybrid additives were distributed homogeneously through polyamide 6.6 (PA6.6) chains by high shear thermokinetic mixer in melt phase. Spectroscopic studies showed that the differences in the number of graphene layer in hybrid structures directly affected the crystalline behavior and dispersion state in polymer matrix. Flexural strength and flexural modulus of PA6.6 nanocomposites were improved up to 14.7% and 14% by the integration of 0.5 wt% CNF grown on multi-layer GO, respectively, whereas there was a significant loss in flexural properties of single-layer GO based nanocomposites. Also, the integration of 0.5 wt% multi-layer GO hybrid reinforcement in PA6.6 provided a significant increase in tensile modulus about 24%. Therefore, multi-layer GO with CNF increased the degree of crystallinity in nanocomposites by forming intercalated structure and acted as a nucleating agent causing the improvement in mechanical properties

New hybrid nano additives for thermoplastic compounding: CVD grown carbon fiber on graphene

Nano additives have unique characteristics widely used in high technology applications due to their ultrahigh mechanical and thermal properties. They are not preferred in price sensitive sectors especially in automotive applications because of their high cost. On the other hand, there is a growing interest to use graphene as a reinforcing agent in composite production. At this point, graphene platelet (GNP) produced from the recycle source was used as a template for carbon nanofiber production by using chemical vapor deposition (CVD) technique to overcome commercialization harrier. This bicomponent and novel structure is a good candidate to be used as a reinforcing agent in compound formulations. This produced hybrid additive was dispersed in thennoplastic resin by thennokinetic mixer to get homogeneous dispersion and provide strong interfacial interactions. In the current work, the outstanding properties of graphene with carbon fibers were combined into one type structure. With the further research, the number of graphene layer were adjusted in this hybrid structure to bring a new insight in graphene and its composite applications. After the fabrication of graphene and carbon fiber-based reinforcements with different graphene sources, mechanically and thermally improved Polyamide 6.6 were developed at very low loadings by a thermokinetic high shear mixer. This developed technology will utilize an innovation to produce advanced thermoplastic prepregs including graphene and its hybrid additives with high mechanical properties and increased recycling degree by decreasing manufacturing costs

PVA/PANI/rGO ternary electrospun mats as metal-free anti-bacterial substrates

Successful performance of biocompatible hybrid systems in various biomedical applications such as wound healing patches, and scaffolds for stem cell preparation have been reported. However, relatively poor structural properties and further bacterial infection have been the major drawbacks for their commercialization. In order to improve the antimicrobial property of such structures, transition metals have been previously added to the media. However, the potential risk of metal pollution as well as hardship of processing has put this approach into obsolescence. Herein the ternary polyvinyl alcohol/reduced graphene oxide/polyaniline fibrous nanocomposites, as substitute for transition metal-containing nanocomposites, were prepared via electrospinning. The mats' structural properties (e.g. rheological, morphological, electrical and mechanical properties) and their antibacterial properties against E. coli bacteria cultures after two different treatments (including thermal and acid doping approaches) were systematically investigated. It was shown that in addition to significant structural improvement, an over 80% antibacterial property enhancement in treated mats in comparison to pristine PVA fibers were achieved. Finally the interaction and main effect analyses were used for suggesting the optimum antibacterial specimen conditions

Multilayer thin films of Zinc (II) Phthalocyanine loaded Poly(D, L-lactide-co-glycolide) nanocapsules by layer-by-layer self assembly

Systematic design and controlled distribution of drug loaded nanoparticles in molecular level are highly challenging by traditional techniques. In this study, encapsulation of photodynamically active hydrophobic molecule, zinc (II) phthalocyanine, by biocompatible and biodegradable copolymer poly (D, L- lactide-co-glycolide) is achieved by co-solvent evaporation method. The average size of the drug-loaded nanoparticles is obtained below 100 nm for the first time for thin film assembly with 86% yield which is stated as crucial for the efficiency of drug delivered. These nanospheres are further studied for multilayer thin film coatings by dip-spin layer-by-layer self-assembly. As a scalable and controlled method, LbL offered a uniform distribution of hydrophobic photosensitizers ZnPc loaded PLGA capsules below 10 nm precisely. Light absorbance-transmittance spectroscopy and quartz-crystal microbalance measurements are performed for thin film growth and adsorption kinetics, respectively. Besides, the thickness of layers, the stability of thin film structures and homogeneous distribution of nanoparticles on the surface are controlled and investigated by surface profiler, dynamic light scattering, and scanning electron microscopy measurements respectively. Prepared multilayer thin film coatings are promising candidates for tumors on the skin or just under the skin by photodynamic therapy applications

Selective electrochemical sensor for theophylline based on an electrode modified with imprinted sol-gel film immobilized on carbon nanoparticle layer

A novel electrochemical sensor based on an imprinted hybrid sol-gel film for selective and sensitive determination of theophylline was developed. The imprinted hybrid sol-gel film was prepared by using a new organosilane synthesized as a functional precursor, theophylline as a template and tetraethoxysilane as a matrix forming precursor. The mixture was allowed to hydrolyze, and then spin coated on glassy carbon electrode covered by carbon nanoparticles with sulfonic acid groups that were introduced for immobilization of imprinted sol-gel film and for enhancement of electronic transmission. The morphology and performance of the imprinted film were investigated in detail by scanning electron microscopy, FTIR Spectroscopy, cyclic voltammetry and differential pulse anodic stripping voltammetry. Molecularly imprinted sol-gel was employed to achieve a suitable conformation for electrochemical oxidation of theophylline and also to improve the selectivity of the sensor. The results showed that the imprinted film exhibited selectivity toward theophylline compared to the random sol-gel film prepared in the absence of the template. The imprinted sensor was also successfully employed to detect theophylline in a drug sample

Investigation of pH and concentration influence on layer-by-layer self-assembly for nickel(II)phthalocyanine-tetrasulfonic acid tetrasodium salt coatings

Porphyrins and phthalocyanines are widely studied molecules for various functional applications. Researchers have investigated these photoactive compounds for electrochemical, sensor, semiconductor and photodynamic therapy purposes. Layer-by-layer (LbL.) self-assembly is preferred for its simple, environmentally-friendly and water-based features compared to other coating techniques in the literature. Coating thickness can be controlled on the order of nanometers by LbL mechanism. Multilayer thin film formation of diverse phthalocyanine-based molecules is examined in terms of molecular orientation and temperature dependency by the LbL, method. However, as well as concentration and temperature, the pH of the coating medium is another challenging parameter in the LbL approach. Film thickness and layer distribution are influenced by pH value, changing ionic density and hence the strength of electrostatic interactions during LbL assembly. In this study, layer-by-layer deposition of branched poly(ethyleneimine)/nickel(II)phthalocyanine-tetrasulfonic acid tetrasodium salt (NiPcTS) coating pair is studied. Impact of pH and concentration of NiPcTS on thin film properties are tested for four different pH conditions. Corresponding analysis is made by UV-vis spectroscopy, surface profiler and quartz-crystal microbalance. LbL deposition of NiPcTS is homogeneously controlled and 98 nm thick films are obtained in the presence of acidic media