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The ease of synthesis, readily modifiable structure and high stability of 1,3-bis(2-pyridylimino)isoindole (BPIs) compounds make pincer ligands suitable candidates for many potential applications.

This article describes three novel electrochemical biosensing platforms developed to determine the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) spike antigen protein: glutaraldehyde, SARS-CoV-2 spike antibody and bovine serum albumin

Novel 4, 4?-((((2-(3, 4-dicyanophenoxy)-5-methyl-1, 3-phenylene) bis (methylene)) bis (4-methyl-3, 1-phenylene)) bis (oxy)) -bridged ball-type phthalocyanines were achieved from 4, 4?-((((2-(3, 4-dicyanophenoxy)-5-methyl-1, 3-phenylene) bis (methylene)) bis (4-methyl-3, 1-phenylene)) bis (oxy)) diphthalonitrile through appropriate transition metal (II) acetate salts in 2-dimethylaminoethanol. The new tris-phthalonitrile precursor was achieved from 3,3?-((2-hydroxy-5-methyl-1,3-phenylene) bis (methylene)) bis (4-methylphenol), and 4-nitrophthalonitrile with the presence of catalyst potassium carbonate in dimethylformamide at 50?C. The structural verification of the compounds was accomplished by proton-nuclear magnetic resonance, matrix-assisted laser desorption/ionization time-of-flight mass, infrared, and ultraviolet–visible spectroscopic methods. The BTCuPc electrode material exhibited a specific capacitance of 265 F.g?1 at a scan rate of 5 mV.s?1 in 3.0 M KCl aqueous electrolyte. In addition, a wide operating potential range (1.5 V) was achieved in the aqueous electrolyte. © 2022 Elsevier B.V., Türkiye Bilimler Akademisi; Marmara Üniversitesi: FYL-2022-10221, Özer Bekaroğlu gratefully acknowledges the Turkish Academy of Science (TUBA) , Türkiye for the partial financial support. The authors are grateful for the Scientific Research Projects Commission of Marmara University Türkiye supporting the supporting chemical and service purchases with the FYL-2022-10221 grant numbers. Computer time provided by TUBITAK ULAKBIM TRUBA Resources, Türkiye is gratefully acknowledged.

In this study, Ce/Cr redox flow battery system (RFB), which had redox pair indifferent oxidation states, was performed in aqueous acidic medium for thefirst time in the literature. At Ce/Cr RFB system, optimization of acid (H2SO4),and active ion (Cr(III) and Ce(III) ions) concentration were executed by usingdifferential pulse voltammetry and electrochemical impedance spectroscopymethods. The mass transfer type for positive electrolyte was determined byusing of cyclic voltammetric method. Both chemical stability and changes onsurface morphology of pencil graphite electrode were analyzed with scanningelectron microscope. Cyclic charge/discharge test was performed for this novelelectrolyte composition. Cell potential and the highest discharge capacityvalues were also determined as 1.52 V and 21.2 mAh L1, respectively, at0.8 mA cm2charge current density and 0.2 mA cm2discharge current den-sity. Obtained data in this work can open a new perspective for the using ofthe alternative redox couples for the redox flow batteries.

In this study, an anodically pretreated pencil graphite electrode (Ptre/PGE) which has oxygen-containing groups was used for the electrochemical determination of Allura Red (AR) by differential pulse voltammetry (DPV) method for the first time in the literature. In order to be more selective and sensitive the pencil graphite electrode, the anodic pretreatment process was performed by applying a constant +1.8 V potential for 250 s in pH 9 phosphate buffer solution using chronoamperometry method. The characterisation studies of the sensor were performed using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM) methods. Interference effects of sunset yellow, tartrazine, amaranth, aspartame, glucose, gelatin, and ascorbic acid on AR determination with Ptre/PGE were investigated. The limit of detection and quantitation values was found as 75 and 251 nmol L−1, respectively. The Ptre/PGE has been used for the determination of AR in cherry juice and energy drink samples, where it provides recovery ranging from 98.40% to 100.8%.

In this work, a novel one-step environmentally benign procedure for preparing nitrogen-doped graphene electrodes for high performance supercapacitors has been demonstrated for the first time, called Yucel’s method. N-doped graphene-based electrodes were synthesized in a short time, at room temperature, one step (no need for a second process for doping) and low-cost by the using of Yucel's method without harmful oxidizing and reducing chemicals. During the production of N-doped graphene-based electrodes by this method, which functional group will form on the graphene surface is determined by controlling the applied potential range. Also, a detail mechanism has been proposed for the incorporation of these functional groups on the graphene structure produced by Yucel’s method for the first time in literature. Since the chemical and morphological structure of each electrode is different, specific capacitance values are also different. The electrodes synthesized in a narrower synthesis potential range have shown higher capacity thanks to the catalytic effects of oxygenated functional groups (NO2, ▬COOH, ▬OH etc.) on their surfaces. Indeed, the relations between N including functional groups and specific capacitance properties of the electrodes were investigated in detail. After electrochemical, spectroscopic, and microscopic characterization of the materials, cyclic charge–discharge tests were carried out for 1000 cycles. The specific capacitance of the electrodes changed from 178 mF.cm−2 to 2034 mF.cm−2 in 10 mA.cm−2 current density as a function of the mesoporous structure. This structure type becomes more accessible for electrolyte penetration as the number of cycles increases.

In this work, symmetrical supercapacitors in the form of coin cell types were produced by using S-doped graphene powders. Sulfur doped graphene powders were prepared by cyclic voltammetry in different potential ranges for selective modification of powders by functional groups. S-Doped graphene powders were also characterized by spectroscopic, microscopic, and electrochemical methods. The formation of graphene layers was supported by scanning electron microscopic and Raman spectroscopic analyses. Functional groups formed on the graphene surface were identified by X-ray photoelectron spectroscopy. The electrodes formed with compositions consisting of binding material at 5%, conductive material at 5% and S-doped graphene powder at 90% were used in cyclic charge–discharge tests of the supercapacitors to determine the specific capacitance of them. The highest specific capacitance of the supercapacitors was determined as 176 F/g−1, with a capacity loss of 5% at the end of 1000 cycles in A-SG3M.

Graphene-based negative electrodes in lithium-ion batteries have recently been the focus of interest. In this study, sulfur (S)–doped graphene powders in different functionality have been prepared in one step by using Yucel’s method for the first time in the literature and they have been used as anode materials of Li-ion batteries. By changing the scanned potential during the preparation of S-doped graphene powders, the graphenic surface is covalently doped by –C-S-C- and –C-SOx-C- (x:2, 3) groups at different amount. When the potential has been scanned in wider potential range (- 1.0 and 2.5 V), 48 sp2-hybridized carbon rings have been determined on the powders by using Raman analysis. It is the lowest as 16 for graphenic powder prepared at narrower potential range (1.5 and 2.5 V) and chronoamperometric method. S-doped graphene powders have been investigated by microscopic methods. Electrochemical properties of the prepared S-doped graphene powders and their potential use in Li-ion batteries have been assessed. At a 50-mA/g current density, the 915-mAh/g specific capacity has been determined as the highest discharge capacity in the powder which was prepared by the chronoamperometric method. Specific capacities of 710 mAh/g, 594 mAh/g, and 642 mAh/g have been observed in the powders prepared between - 1.0–(+ 2.5 V), 0.6–(+ 2.5 V), and 1.5–(+ 2.5 V) samples, respectively. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.

The rapid and accurate determination of phosphate is necessary for human health and the environment. In this study, three species of inorganic phosphate were sensitively determined by the use of po...

We have fabricated inverted-type perovskite solar cells employing CH3NH3PbI3-xClx perovskite in the form of ITO/PEDOT:PSS/Perovskite/PCBM/Al. The effects of UV radiation on ITO/PEDOT:PSS substrates have been investigated for perovskite solar cells. ITO/PEDOT:PSS substrates were exposed to UV radiation for 5 to 15 min. The perovskite solar cells fabricated on UV-irradiated ITO/PEDOT:PSS substrates exhibited better performance as compared to those fabricated on substrates employing non-treated PEDOT:PSS. We used photovoltaic characterization, UV-VIS absorption, sheet resistance, X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), and external quantum efficiency (EQE) characterization techniques to investigate the effect of UV irradiation of ITO/PEDOT:PSS substrates on the performance of perovskite solar cells. The devices fabricated on ITO/PEDOT:PSS (UV irradiated for 10 min) exhibited the best device performance of all. We achieved a 9% increase in the overall power conversion efficiency for the devices fabricated on substrates exposed to UV radiation.

The electropolymerization of L-cystine was performed on a pencil graphite electrode (PGE) in order to improve the redox properties for the determination of folic acid (FA). The characterization stu...

The rapid and accurate determination of tartrazine is necessary for human health and environment. In this study, a sensor platform was developed for the electrochemical determination of tartrazine....

In this work, a novel aqueous electrolyte system consisting of cobalt and vanadium for redox flow battery was prepared to increase the cell voltage of the system for the first time in the literature. Electrolyte systems were characterized by using of cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy to determine the effects of sulfuric acid and active ion concentration on the performance of the battery. Optimum sulfuric acid concentration was determined as 4.0 M for anolyte and catholyte. The effect of diffusion on mass transfer mechanism was higher than that of adsorption in each electrolyte of the flow battery system. Cyclic charge-discharge tests were carried out for the prepared novel electrolyte system. Discharge capacities of the electrolyte were determined as 430.1, 417.4, and 428.7 mAh for first cycle, second cycle, and third cycle, respectively. The cell potential of the redox flow battery in the electrolyte system during the charging process increased to 2.35 V which was also relatively higher than those of aqueous vanadium redox flow battery and aqueous iron flow battery. Obtained redox flow battery composition with its high cell potential can bring a new approach for the different application areas in the electrochemical energy storage.

Molybdenum blue was electrodeposited on a pencil graphite electrode (PGE) by cyclic voltammetry and it was used in the detection of phosphate ions for the first time in the literature. Polyvinyl chloride was used as a coating agent for the modified electrodes to improve their stability. The characterization of the electrodes was done by using microscopic and electrochemical methods. Parameters affecting the analytical response of the electrode in differential pulse voltammetry such as concentration of supporting electrolyte, immersion time, operation temperature and thickness of film were optimized before the analysis of a soil sample containing phosphate. The prepared electrode exhibited high sensitivity for phosphate. The limit of detection (LOD) and limit of quantification (LOQ) were determined as 2.19 × 10−8 M (S/N = 3) and 7.30 × 10−8 M (S/N = 10), respectively. Quantification of phosphate in soil samples was confirmed by spectroscopic analysis.

Titanium glycerolate precursors were prepared from a novel starting material and using glycerol as a chelating ligand and solvent via a developed method. This method and optimization of process parameters provided morphology control, and rod-like anatase particles with a high surface area and large aspect ratio were synthesized.

A novel copper(II) phthalocyanine (CuPc)-modified multiwalled carbon nanotube-based electrode was prepared for the sensitive electrochemical detection of bisphenol A, by the modification of a pencil graphite electrode via the adsorption method. The synthesized novel CuPc was characterized by spectroscopic methods and the electrodes were characterized by electrochemical, spectroscopic and microscopic methods. The limit of detection (LOD, S/N = 3) was calculated as 0.0189 μM for bisphenol A. The experimental parameters such as pH and adsorption time were optimized for the electrochemical detection of bisphenol A. The detection was done in real samples, with a high recovery value (>98%), indicating the useful application of modified electrodes as electrochemical sensors for bisphenol A. The electrodes showed excellent repeatability and stability in the differential pulse voltammetric detection of bisphenol A. The prepared novel sensor can be used for the detection of bisphenol A in many environmental analyses due to its simplicity, low cost, environmental friendliness and high sensitivity.

Graphene is a material with various application potentials Graphene is a unique material with superiorities and has been applied in various fields for different purposes. Although studies on the utility of graphene oxide in the biomedical field are available, no evaluation has yet been done regarding the utility of sulfur doped (S-doped) graphene. The study focuses on the effect of blending the poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) membrane with sulfur heteroatom doped graphene and the evaluation of biological responses to S-doped graphene/PHBHHx. PHBHHx membranes were blended with 1%, 0.5%, 0.1% (w/v) S-doped graphene. The morphological (SEM and Microscopy), chemical (FTIR and Raman spectroscopy), and surface area (BET) characterizations of S-doped graphene/PHBHHx membranes were performed. The presence of S groups on the surface was determined with the EDS results. Besides, the swelling profile and biodegradation tendency of the membranes were evaluated. The differentiation of protein adhesion, cell viability, cell adhesion, and cell proliferation by the increasing content of S-doped graphene was examined. The contact angle analysis revealed that modification of PHBHHx with S-doped Graphene reduced the free surface energy of PHBHHx membranes. Blending with S-doped Graphene has decreased the polarity of the PHBHHx membrane. The protein adsorption on the PHBHHx membrane was determined as 10.12 ± 0.247 mg/ml. Protein absorption on 1%, 0.5% and 0.1% S-doped graphene/PHBHHx membranes were determined as 11.34 ± 0.551 mg/ml, 9.91 ± 0.294 mg/ml and 9.48 ± 0.093 mg/ml, respectively. The cell attachment to the surface decreased with the increasing amount of S-doped graphene, however, PHBHHx membranes with graphene did not affect cytotoxicity. S-doped graphene blended PHBHHx membrane seems like a suitable patch for biomedical treatments as a hydrophobic membrane where less cell adhesion and proliferation are required like the prevention of peritoneal adhesion.

In this work, titanium dioxide thin films in rutile and anatase forms were prepared on pencil graphite and indium tin oxide electrodes, respectively by using an electrochemical method in one-step and room temperature. X-ray diffraction analyses were performed on the as prepared samples. The surface morphology of the electrodeposited TiO2 electrodes was characterized by scanning electron microscope and atomic force microscope. We have observed that the choice of the substrate affects the form of the electrodeposited thin TiO2 layers as rutile and anatase. When the pencil graphite electrode was used as a substrate rutile form of TiO2 was obtained on the electrode surface whereas anatase form of TiO2 was obtained when indium thin oxide electrode surface was used. We have also fabricated inverted type organic solar cells by employing TiO2 layer as an electron transport layer. We achieved a power conversion efficiency of 2.3%.

Sunset Yellow (E110) is an azo food artificial dye and has a wide range of applications. When ingested in excess, it can lead to many serious health problems, so it is significant to rapidly determine Sunset Yellow. In this study, a modified electrode was developed by making use of electroactive properties of Sunset Yellow. Using a chronoamperometry method, an electrochemically prepared graphene oxide modified pencil graphite electrode was prepared in one-step by applying a + 1.9 V constant potential for 60 seconds in 5.0 M sulfuric acid. Cyclic voltammetry, electrochemical impedance spectroscopy, X-ray powder diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy were used to characterize the electrochemical properties and surface morphology of the modified electrode. Electrochemical measurements were carried out using differential pulse voltammetry. The influence of pH on the electrochemical determination of Sunset Yellow was investigated. The effects of possible substances that may interfere and the repeatability and reproducibility of the developed sensor platform were examined. Under the optimized conditions, the limits of detection and quantitation were 0.057 µM and 0.19 µM, respectively. The applicability of the developed protocol to real samples was investigated and good recovery values were achieved. The developed sensor platform stands out with features such as short preparation and analysis time, simplicity, low cost, sensitivity and selectivity.

In the present work, novel redox ion-pairs (as cobalt and chromium) have been used in aqueous medium for the first time in the literature as electrolyte component of redox flow battery system. The electrochemical performance of the Co(II) and Cr(III) redox species as anolyte and catholyte was investigated by cyclic charge-discharge tests, respectively. Electrochemical behaviors of Cr(III) solutions in sulfuric acid solution were determined by using differential pulse voltammetry, electrochemical impedance spectroscopy and cyclic voltammetry via a typical three-electrode system. Morphological analyses of surface of pencil graphite electrode, which was used as anode in differential pulse voltammetric analysis, were done by scanning electron microscopy. Discharge capacity of the battery system consisting of 1.0 M Cr(III) as anolyte (negative electrolyte) and 1.0 M of Co(II) as catholyte (positive electrolyte) in 4.0 M of sulfuric acid was determined as 682.5 mAh (1.4 Ah L-1) with 4 mA cm(-2) charge current density and 0.4 mA cm(-2) discharge current density. Voltage efficiency, energy efficiency and coulombic efficiency of the battery were 70.1%, 53.8% and 57.2%, respectively. The discharge cell potential of the battery was also determined as 1.40 V.

A novel silicate-based protective film was formed on negative electrodes and compared of the performance in various electrolyte systems of lead-acid batteries. The sodium silicate-based coating for the negative electrode component of a gel valve-regulated lead-acid (gel-VRLA) battery was applied for the first time in the literature. The battery system was produced by sodium silicate-coated negative electrodes and lead oxide positive electrodes in various kinds of electrolyte. Electrochemical characterization of cells and battery prototypes were done by cyclic voltammetric (CV) analysis, electrochemical impedance spectroscopic (EIS) analysis, and cyclic charge-discharge tests. The surface morphologies of silicate-coated electrodes were investigated by scanning electron microscopic analysis after cyclic voltammetric analysis and charge-discharge tests. The coating of silicate on the surface of negative electrodes increased the corrosion resistance of a VRLA battery according to the Tafel polarization curves. Indeed, sulfation on the negative electrode component of the battery have significantly reduced with silicate coatings of them. Besides, the prepared novel silicate-based protective film have increased the battery performance of a VRLA. Silicate-based coatings for electrodes can be used for industrial battery production for many different battery types due to their amazing anti-corrosion properties in acidic media.

This work presents the preparation and characterization studies of gold nanoparticle/poly(methylene blue) (GNP/PMB)-modified pencil graphite electrode (PGE) and its use for electrochemical determination of nitrite. The working electrode (PGE) was functionalized by electropolymerization of methylene blue (MB) and modified with gold nanoparticles (GNPs) to produce the final (GNP/PMB/PGE) electrode in a two-step procedure. Characterization and morphology studies of GNP/PMB/PGE were performed by electrochemical impedance spectroscopy, cyclic voltammetry, X-ray photoelectron spectroscopy, Fourier transform Infrared spectroscopy, and scanning electron microscopy techniques. The highest peak current response was obtained for nitrite at pH 5.0. A wide linear relationship between the concentration and the oxidation peak currents of nitrite was observed in the concentration range of 5–5000 μM. The limit of detection (0.314 μM, S/N = 3) and reproducibility (RSD = 2.38% for N = 10) have been identified. Finally, the electrode platform was successfully applied to commercial sausage and mineral water samples.

The production of catalysts that display strong efficiencies in aqueous media for the electrochemical carbon dioxide reduction reaction (CO2RR) is essential both for a healthy world and for realistic application of energy waste to generate value-added fuels. In this study, thiophene functionalized metal-free (poly-H2Por) and cobalt porphyrin-based (poly-CoPor) organometallic catalysts were easily attached on the pencil graphite electrode surface via electrochemical polymerization method and these, porphyrin coated, pencil graphite electrodes (PGE) were used as electrocatalysts for electrochemical CO2 reduction for the first time in the literature. To reveal the electrochemical activity of CO2RR, the electropolymerized catalysts were investigated with linear sweep voltammetry in 0.1 M KHCO3 solution. The results showed that, the electrode which is modified with poly-CoPor decreased the overpotential of CO2RR, according to bare pencil graphite electrode, from −1.35 V to −0.63 V.

This article is the first to report the direct, one-step synthesis of molybdenum blue (MB) in solid state, via application of cyclic voltammetry. Electrochemical synthesis of MB was carried out in a three-electrode cell in 1.0 M sulfuric acid and at the appropriate amount of sodium molybdate dihydrate. Both a pencil graphite electrode and a platinum plate electrode were used as working electrodes. The structure of electrochemically synthesized MB was characterized using such techniques as Ultraviolet-visible spectroscopy, Fourier Transform Infrared Spectroscopy, Resonance Raman Spectroscopy, Scanning Electron Microscopy, Energy-Dispersive X-Ray Spectroscopy, X-Ray Powder Diffraction, X-ray Fluorescence Spectroscopy, and X-Ray Photoelectron Spectroscopy. In addition, the electrochemical behavior of the synthesized MB was examined via cyclic voltammetry. Finally, the determination of phosphate was conducted using a UV–vis spectrometer with electrochemically synthesized MB.

Herein, a novel coumarin-based fluorescent probe (FS3) was designed, synthesized, and characterized. It exhibited significant fluorescence quenching in the presence of Zn2+ ions. Just a minor alteration occurred in the fluorescence intensity of FS3 in the presence of other metals studied. The limit of detection for the determination of Zn2+ by FS3 was calculated to be 3.43 × 10−9 M. Since the Job’s graph of 1/(F0–F) and 1/[Zn2+] had a linear fit, it was determined that the binding stoichiometry between the FS3 and Zn2+ was 1:1. The association constant of the system was found to be 2.39 × 104 M−1 and confirmed by ESI-MS and FT-IR. It was demonstrated that the developed highly reversible sensor system works by performing real sample analysis. Moreover, the FS3 which has shown no toxicity and displayed a strong fluorescence image will act as an efficient and non-destructive sensor for the determination of Zn2+ in living organisms.

We investigated the use of an overoxidized nanofiber polypyrrole (OONfPPy) modified pencil graphite electrode (PGE) as a sensor for the determination of dopamine (DA) in this work. The performance of the modified electrode was studied using differential pulse voltammetric method. The surface of the modified electrode was characterized by an electrochemical impedance spectroscopy (EIS) and scanning electron microscope (SEM). The calculated electroactive areas of the bare electrode and OO(10)NfPPy(5)PGE were found to be 4.54 x 10(-8) cm(2) and 1.05 x 10(-6) cm(2), respectively. The sensor (OO(10)NfPPy(5)PGE) showed a high selectivity to DA with a detection limit of 6.95 x 10(-9) M (S/N= 3). To demonstrate the validity of the sensor for the determination of DA, pharmaceutical and human serum samples were performed.

WOS: 000406286800016, In this study, a novel polysiloxane-based gel agent (PSGA) was synthesized by using poly(dimethylsiloxane-co-alkylmethylsiloxane) and used as a gel agent for gel-valve-regulated lead-acid batteries. A PSGA was characterized by Fourier transform infrared, zeta meter, scanning electron microscopy, and energy-dispersive X-ray analysis. The electrochemical characterization of the gel system for the optimization of some parameters, such as concentration of gel agent, stirring rate, and agitation time, was conducted by cyclic voltammetric and electrochemical impedance spectroscopic analyses. The optimum concentration of the gel agent was determined as 6 wt% of the PSGA to form the best gel structure. The mechanical parameters related to the formation of a suitable gel structure were also investigated. The optimum stirring rate and agitation time were determined as 500 rpm and 2.5 h, respectively. The charge-discharge tests were applied to the gel system, and the highest capacity was determined in the PSGA-based gel system as 10 mAh at the end of the 100th cycle. The capacity of non-gelled system was the lowest., SAN-TEZ program of the Ministry of Science, Industry and Technology, Republic of Turkey [00897. STZ. 2011-1]; Anadolu University; Ericsson Turkey, This work was supported by the SAN-TEZ program (No. 00897. STZ. 2011-1) of the Ministry of Science, Industry and Technology, Republic of Turkey; Anadolu University; and Ericsson Turkey. Y. Sahin thanks Prof. Dr. Kadir Pekmez, Prof. Dr. Ender Suvaci, and Oktay Uysal for their supports to this study. M. Gencten thanks the TUBITAK-BIDEB.

A novel gel electrolyte system used in lead-acid batteries was investigated in this work. The gel systems were prepared by addition of different amount of Al2O3, TiO2 and B2O3 into the gelled system consisting of 6 wt% fumed silica and 30 wt% sulfuric acid solution for the first time. The anodic peak currents and peak redox capacities of the gel electrolytes were characterized by cyclic voltammetric method. When B2O3 and Al2O3 were used as additives in fumed silica based gel electrolyte system, the anodic peak currents and peak redox capacities decreased. However, the investigated parameters in cyclic voltammetry (anodic peak current and capacities) increased by the adding of 3.0 wt% of TiO2 in the fumed silica based gel system. The solution and charge transfer resistances of the gel electrolytes were investigated by electrochemical impedance spectroscopy. While the solution resistances were lower in gel systems having different amount additives than pure fumed silica based gel, the charge transfer resistance was the lowest in gel electrolytes consisting fumed silica and fumed silica-TiO2. The morphological differences of gelled systems were elucidated by scanning electron microscopic and optic microscopic analysis. The battery performances were studied by obtaining discharge curves of prepared gel electrolytes. The performance of gelled systems were higher than that of non-gelled electrolyte at room temperature. The mixture of fumed silica-TiO2 was suggested an alternative gel formulation for gel valve-regulated lead acid batteries. TiO can be a useful additive for gel-VRLA batteries.

In this study, the effect of temperature on the electrochemical behaviors of gel electrolyte systems was investigated for valve regulated lead-acid battery at 0≤ T ≤50 o C. Fumed silica and mixture of fumed silica and TiO 2 were used as gel electrolytes. TiO 2 has a good combination with fumed silica. They were characterized by cyclic voltammetry, electrochemical impedance spectroscopy and battery tests. The anodic peak currents and redox capacities of the gel electrolytes increased with increasing of temperature. The highest anodic peak current and redox capacity were observed at 30 o C in fumed silica and at 40 o C in fumed silica:TiO 2 based gel systems. The solution and charge transfer resistance values decreased in fumed silica:TiO 2 gel system by increasing temperature. In battery tests, discharge curves were obtained for each gel system at 0, 25 and 50 o C. The discharge time of mixture gel electrolyte system was higher than that of fumed silica based gel electrolyte at low (0 o C) and high (50 o C) temperatures. The best performance was obtained in fumed silica based gel electrolyte at 25 o C.

In this study, one-step preparation method of different heteroatom (-S, -N, -Cl) doped graphene oxide electrodes were achieved as electrode materials for the purpose of high-capacity supercapacitors. Microscopic, spectroscopic, and electrochemical methods were used to characterize the prepared electrodes. Formation of -ClO2, -ClO3, -SOx (x:2, 3) and -NO2 groups on the graphene oxide-based electrodes were determined by X-ray photoelectron spectroscopy analysis. Detail reaction mechanisms were suggested for the formation of these groups on the electrode surface for the first time in the literature. Different surface properties of graphene oxide structures in the electrodes were investigated by scanning electron microscopy and atomic force microscopy. Electrochemical behaviors of the prepared electrodes were characterized by cyclic voltammetry and electrochemical impedance spectroscopy. Sulphur, nitrogen, and chlorine doped graphene oxide electrodes were used as electrode materials for supercapacitor applications. Since different heteroatom doped graphene oxide-based electrodes showed different capacitive behavior. Areal capacitances of -S, -N and -Cl doped graphene oxide electrodes were determined as 206.4 mF.cm−2, 533.2 mF.cm−2 and 1098 mF.cm−2, respectively with 10 mA.cm−2.

In this work, we aimed to prepare three different metallo phthalocyanine/functionalized-multiwalled carbon nanotube/polyaniline/pencil graphite electrode (MPc/f-MWCNT/PANI/PGE) modified electrodes with high specific capacitance, high energy and power densities, and long cycle life for supercapacitors. In this concept, ZnPc/f-MWCNT/PANI/PGE, CuPc/f-MWCNT/PANI/PGE, and NiPc/f-MWCNT/PANI/PGE electrode materials were prepared by electrochemical method. The surface and structural properties of the prepared electrodes were investigated with Fourier-transform infrared spectroscopy (FT-IR), Scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy (EDS), Atomic force microscope (AFM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area and electrical conductivity analyses. The electrochemical properties of these electrode materials were examined by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge (GCD) analyses. The effects of preparation parameters and composite composition of the electrodes on electrochemical performance were investigated. The NiPc/f-MWCNT/PANI/PGE electrode has higher specific capacitance (325 F/g) than ZnPc/f-MWCNT/PANI/PGE (278 F/g), CuPc/f-MWCNT/PANI/PGE (282 F/g), f-MWCNT/PANI/PGE (162 F/g), and PANI/PGE (126 F/g) electrodes. In addition, all MPc/f-MWCNT/PANI/PGE electrodes have long-cycle life and maintained approximately 100% of its capacitance after 1000 charge-discharge cycles. As a result, the prepared MPc/f-MWCNT/PANI/PGE electrodes significantly removed the disadvantages of the components, and the synergistic effects between the components considerably improved supercapacitor performance of the electrodes.

In this study; an easy, practical, and selective sensor has been developed for the electrochemical determination of riboflavin. To prepare the modified electrode, the gold nanoparticle was deposited on the pencil graphite electrode (AuNP/PGE) by the method of chronoamperometry at −3.0 V for 30 s in 0.5 M H2SO4 solution containing 10 mM tetrachloroaurate. Functionalized multi-walled carbon nanotube (f-MWCNT) solution was dropped on prepared AuNP/PGE and the functionalized multi-walled carbon nanotube/gold nanoparticle/pencil graphite electrode (f-MWCNT/AuNP/PGE) was prepared for measurements. Characterization studies of the prepared sensor were performed using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) methods. The surface morphology of the prepared sensor was investigated by field emission scanning electron microscopy (FESEM). Differential pulse voltammetry (DPV) was used to carry out electrochemical measurements in phosphate buffer solution pH 4.0. Limit of detection (LOD) and limit of quantitation (LOQ) values were found to be 0.0352 and 0.118 μmol l−1, respectively. The fabricated sensor showed excellent anti-interference ability against ascorbic acid (AA) and glucose (G). The applicability of the constructed sensor to real samples was investigated and good recovery values were achieved. As a result, it has been seen that the modified electrode is applicable in applications of riboflavin determination.