Metal-Ion Oxidative Decarboxylations. 9. Reaction Of Benzilic Acid With Cerium(IV) In Acidic Perchlorate And Sulfate Media

The kinetics of oxidation of benzylic acid (HLH) to benzophenone by cerium (IV) has been studied in several media using the stopped-flow technique. In HClO4-Na2SO4-NaClO4 media, which allow for the variation and control of the concentrations of the various Ce(IV) species at constant [H+] and ionic strength, the rate data suggest CeSO42+ as the kinetically relevant species. In HClO4 the observed first-order rate constants, tetrad, first increase with increasing HLH concentration, then decrease slightly at higher substrate concentrations suggesting the intermediacy of two complexes: a reactive [Ce(IV)HL] and a [Ce(IV)(HL)2] which resists reaction. The rate law which best describes the observed kinetics in HClO4 media is given by [formula ommitted] where K7 ′ and K8′ are H+-dependent equilibrium constants for the formation of the 1:1 and 1:2 complexes, respectively. The kinetic parameters kα and kβ are the rate constants for the intramolecular redox reaction of the 1:1 and 1:2 complexes, respectively. The rates in H2SO4 are much slower than those in HClO4 and do not reflect strong complex formation before electron transfer. Whereas H+ had an inhibiting effect in the above-mentioned media, catalysis by H+ was manifest in HClO4-HOAc media, possibly through decreasing acetato complexation of Ce(IV). © 1977, American Chemical Society. All rights reserved

Metal-Ion Oxidative Decarboxylations. 10. Substituent Effects In The Cerium(IV)-Benzilic Acids Reaction

The rates of oxidation by cerium (IV) of several substituted benzylic acids (unsubstituted, 2,2′-dichloro, 4,4′-dichloro, 4,4′-dimethyl, 4,4′-dimethoxy, and 4,4′-dinitro) to the corresponding benzophenones have been studied spectrophotometrically in aqueous H2SO4, aqueous HClO4-HOAc, and acetonitrile. The rates are much slower in H2SO4 than in the other two media, probably because of heavy sulfato complexation of cerium(IV). The px as of the various acids were determined potentiometrically. The Hammett p values in acetonitrile and HClO4-HOAc media, derived from correlations with several sets of σ constants and with the newly determined pKas, are about -0.7 and -0.35 in the two media, respectively. These values rule out the possibility of positive charge development at the benzhydrilic carbon, at or prior to the rate-determining step. Instead, a mechanism involving free (?) radicals is proposed. © 1977, American Chemical Society. All rights reserved

Prediction of Physical Parameters of Pumpkin Seeds Using Neural Network

The design of the machines and equipment used in harvest and post-harvest processing should be compatible with the physical, mechanical and rheological characteristics of the fruits and vegetables. In machine design for agricultural products, several characteristics of relevant products and seeds should be known ahead. Designers can either measure all these design parameters one by one, or they may use intelligent systems to estimate such parameters. Neural networks (NNs) are new computational tools that provide a quick and accurate means of physical properties prediction of agricultural materials, and have been shown to perform well in comparison with traditional methods. In this research, some physical properties of pumpkin (Cucurbita pepo L.) seeds, including linear dimensions, volume, surface and projected area, geometric mean diameter and sphericity were calculated tridimensional in lab conditions. Then, prediction of these parameters was carried out using NNs. The research was divided into two parts; experimental investigation and simulation analysis with NNs. Back Propagation Neural Network (BPNN) and Radial Basis Neural Network (RBNN) structures were employed to estimate physical parameters of the pumpkin seeds. The Root Mean Squared Error (RMSE) was 0.6875 for BPNN and 0.0025 for RBNN structures. The RBNN structure was superior in prediction and could be used as an alternative approach to conventional methods

Metallic Glass Films with Nanostructured Periodic Density Fluctuations Supported on Si/SiO2 as an Efficient Hydrogen Sorber.

Nanostructured metallic glass films (NMGF) can exhibit surface and intrinsic effects that give rise to unique physical and chemical properties. Here, a facile synthesis and electrochemical, structural, and morphologic characterization of Pd-Au-Si based MGs of approximately 50 nm thickness supported on Si/SiO2 is reported. Impressively, the maximum total hydrogen charge stored in the Pd-Au-Si nanofilm is equal to that in polycrystalline Pd films with 1 μm thickness in 0.1 m H2 SO4 electrolyte. The same NMGF has a volumetric desorption charge that is more than eight times and 25 % higher than that of polycrystalline PdNF and Pd-Cu-Si NMGF with the same thickness supported on Si/SiO2 , respectively. A significant number of nanovoids originating from PdHx crystals, and an increase in the average interatomic spacing is detected in Pd-Au-Si NMGF by high-resolution TEM. Such a high amount of hydrogen sorption is linked to the unique density fluctuations without any chemical segregation exclusively observed for this NMGF

Electropolymerization of carbazole and 3,4 (etyhlenedioksithiophene) comonomer on carbon fiber microelectrode

Polikarbozol(PCz) ve poli(3,4 etilen dioksitiyofen)(PEDOT) ikisi de oldukça kararlı polimerlerdir. Fakat Poly(EthylCz) (PECz)’ün iletkenliği PEDOT’a oranla oldukça düşüktür. Polikarbazol ve PEDOT alternatif kopolimerleri sentezlendiğinde PCz’ün iletkenliğinin artırılması, her iki polimerin arasındaki etkileşimden dolayı homopolimerlerden daha üstün özellikleri olan bir kopolimer elde edilmesi amaçlanmıştır. Uç grubu Ecz olan Ecz-BEDOT-Ecz komonomeride sentezlenmiştir. Böylelikle BEDOT komonomeri yapısına Ecz’ü de katılarak komonomerin konjugasyon boyutu uzamıştır. Ecz-BEDOT-Ecz karbon fiber üzerinde polimerleşirken Platin üzerinde tıpkı Ecz homopolimerine benzer şekilde polimerleşmemiş sadece oligomer oluşumu UV spektroskopisinde gözlenmiştir. EBEE’nin karbon fiber üzerine kaplanması 1.3V uygulayarak 100mV/s tarama hızında döngülü voltamogram ile gerçekleştirilmiştir. Bu sonuç kullanılan elektrot tipinin polimeri-zasyon mekanizmasını etkilediğini kanıtlamaktadır. Kaplanan PEBEE’nin elektron transferine ait olan birinci redoks prosesi 0.88V’da, ikinci redoks prosesi ise 1.22V’dadır. Bu ikinci pikin çok daha yüksek olması orada hem komonomerin hemde kopolimerin bu potansiyelde oksitlenebilmesidir. Komonomerdeki ECz uç grubu; kopolimerin fiziksel özelliklerini iyileştirmeye büyük katkısı olmuştur. Elde edilen kopolimerin redoks davranışı Ecz’ün homopolimerine benzer özellik taşımaktadır. PEBEE’nin oksidasyon potansiyeli 0.4V’dur. Dolayısıyla PECz’dan daha küçüktür. Bu veriye dayanarak konjugasyon uzunluğunun arttığını ve elde edilen alternatif kopolimerin iletkenliğinin PECz’den yüksek olduğu sonucunu çıkarabiliriz. PBEDOT’ın oksidasyon potansiyeli düşük olduğundan oda koşullarında saklanamamaktadır. Alternatif kopolimer eldesiyle PBEDOT’ın kararlılığını arttırdığı görülmüştür. PEBEE’ yi homojen olarak karbon fiber üzerine kaplamak için pek çok koşul denenmiş, fakat en homojen kaplamanın  düşük polimerizasyon hızında (20mV/s) ve 50 döngü saysında elde edilebilmiştir. Anahtar Kelimeler: Cz, EDOT, elektropolimerizasyon, iletken polimer, karbon fiber.PEDOT, was initially developed to give a soluble conducting polymer that lacked the presence of undesired a-b, and b-b,couplings within the polymer backbone. Prepared using standard oxidative chemical or electrochemical polymerization methods, PEDOT was initially found to be an insoluble polymer,   yet exhibited some very interesting properties. In addition  to a very high conductivity,, PEDOT was found to be almost transparent in thin, oxidized films and showed a very high stability in the oxidized state. Polycarbazole, among conducting polymers, is attributed with good electroactivity, and useful thermal, electrical andphotophysical properties. However, p®p electron system along its backbone imparts rigidity to the polymer and, therefore, makes it infusible and poorly processable. Due to this reason, it was not initially employed as widely in devices as other conducting polymers. Recent advances in synthesis methods have, however, revived interest in polycarbazole . Investigations related to chemical modification or co-polymerization of carbazole with other monomers have led to the use of polycarbazole and its derivatives as redox catalysts, photoactive devices, sensors, electrochromic display, electroluminescent devices and biosensors . A new co-monomer EBEE has been firstly synthesized, characterized and electropolymerized on CFME and Pt. Side group of monomer play an important role on the physical properties of resulting copolymer and it resembles the behavior of homopolymer of monomer at the end of co-monomer,namely ethylcarbazole. Environmental stability of PBEDOT was increased by incorporation of ECz monomer into structure. For ECz ending monomers CFME seems better substrate than Pt to obtain an electroactive polymer film. EBEE comonomer synthesized first time and electropolymerized on Pt and CFME. ECz was also electropolymerized on CFME in order to compare with Poly(EBEE) and to gain further information. Cyclic voltammogram of electrogrowth  of Poly(EBEE) obtained on CFME ,exhibits two oxidative processes at 0.88V and 1.22 V. Appearance of green color on the electrode surface, higher value of current intensities inaccordance with Pt electrode and increase in the current density with increasing scan number suggests a polymer film on CFME. Although current intensities increase as the scan number increases, deposition process or insoluble film formation could not be detected in any experiments and the color of solution converted to blue when Pt electrode was used as a working electrode. Ex-situ UV of solution was taken during electropolymerization, the results indicated that when it is increased time exposed to potential amount of oligomer increased.This might be due to so-called oligomer approach that accepted recently. In this approach it is suggested that after the formation of a dimer a sequence of subsequent dimerization step leads to the formation of soluble oligomers. All this reaction probably occurs in solution without or only small precipitation on electrode. In our case after dimerization and/or tetramer formation further coupling reaction become very slow due to decrease in the rate constant. Formation of only soluble oligomers was also supported by solution color which turns from light yellow to green as reaction proceeds. In the light of all these results it can be concluded that  solubility of oxidized product of ECz-BEDOT-ECz  on Pt electrode might be due to either characteristic behavior of ECz  or stop of polymerization and/or became very slow at oligomerization level as suggested by oligomer approach. ECz-BEDOT-ECz polymerization mechanism depends on the switching potentials and chemical reaction became important at higher switching potential. The scan rate used have an effect on the homogenity of the resultant film. In literature, it is known that ECz is not electropolymerized in except acidic conditions; however, we observed that ECz can be electropolymerized on CFME under mentioned experimental conditions. CV of PECz coated CFME electrodes in monomer free electrolyte shows two step oxidation at 0.93V and 1.23 V which has promising properties and need to  further investigation. Comparison of results with previous study reveal the fact  that chemical make up play an important role on the properties of resulting polymers. The polymer obtained at 100mV/s and different cycle numbers polymer coating was heteregenous. Regular polymer growth is observed only 20mV/s scan rate with 50cycle. A globular structure resulting from a three dimensional nucleation growth mechanism as observed only in that case. The SEM structure of PEBEE shows small clusters of globules.The morphology of polymers obtained with 100mV/s scan rate were quite different from that of obtained with 20mV/s. Keywords: Cz, EDOT, electropolymerization, carbon fiber microelectrode

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

Morphological and Biochemical Characteristics of Wild Loquat (Eriobotrya japonica Lindl.) Genotypes in Turkey

This study was carried out to determine the pomological and biochemical characteristics of eight different loquat genotypes collected from the Black Sea region (Turkey) in 2018. Totally 20 fruits, at the same ripening stage, were collected from the selected genotypes and tested. Results suggested that there were a high (0.768-0.907) positive and statistically significant correlations among all pomological features (P 0.05). According to the PCA (principal component analysis) analysis of the pomological characteristics, the genotype #1 was superior as compared with other genotypes. Contrary to the pomological characteristics, genotype #1 was found to have the lowest phenolic compounds and it was also moderate in sugar content but a high-grade genotype by organic acids, especially citric acid and malic acid. Furthermore, results suggested that genotypes #3, #4, #7 and #8 were identical and were rich in glucose, succinic acid, and total flavonoid. The results suggested that loquat fruits had a high potential for health benefits. The results are also a preliminary key reference for future studies in terms of loquat cultivation throughout the world and have high potential as a functional food

Bioactive content and antioxidant characteristics of wild (Fragaria vesca L.) and cultivated strawberry (Fragaria × ananassa Duch.) fruits from Turkey

In this study, some biochemical (total soluble solid content, pH, acidity and vitamin C) and in vitro antioxidant activity, total phenolic content, total ellagic acid and concentration of anthocyanins of fifteen wild strawberry genotypes (Fragaria vesca L.) and one commercial strawberry cultivar Camarosa (Fragaria × ananassa Duch.) sampled in Northeastern Turkey were determined. Antioxidant activity of fruit samples was determined by DPPH (2,2-diphenyl-1-picrylhydrazyl) and FRAP (Ferric reducing antioxidant power) assays. Notable differences were found both among wild strawberries and also between wild strawberries and cv. Camarosa. Among the strawberry accessions tested, the total phenolics ranged from 138 mg to 228 mg gallic acid equivalent per 100 g fresh fruit. The total monomeric anthocyanin content was the highest in wild genotype FV-2 (53.51 mg/100 g) while the lowest in FV-6 as 25.11 mg per 100 g fresh weight basis. The total ellagic acid content was between 15.18 and 26.36 mg per 100 g. All wild strawberries had higher antioxidant activity than cv. Camarosa. Thus, it can be concluded that wild strawberry is a good source of polyphenols, ellagic acid and antioxidants