Carbon microrod material derived from human hair and its electrochemical supercapacitor application

Here, Turkish human hair fibers were used as a carbon source at the synthesis of human hair-sourced activated carbons (HHC). During the synthesis of HHCs sodium carbonate (Na2CO3) was added to the synthesis process for an elevated activation by calcination at different temperatures. Then obtained HHCs utilized for the modification of carbon paste electrode to evaluate the supercapacitance performance of this activated HHC. Electrochemical investigation of the HHC modified electrodes have been carried out by employing differential pulse voltammetry (DPV), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. The pore and surface properties and chemical structure of the HHCs were investigated by scanning electron microscopy (SEM), Brunauer-Emmett and Teller (BET) analysis and Raman spectroscopy. HHCs displayed a Type-IV isotherm, which indicates the existence of micro-mesoporous structure on the surface. Carbonization of the waste hair was performed by calcination to improve the pore facilities at three different temperatures (200-250-300 degrees C). The sample was named HHC-250 (HHC calcinated at 250 degrees C) exhibited the best charge storage capacity when used at the modification of carbon paste electrode, among other HHCs with a 26.88 F g(-1) specific capacitance value (in 6 M KOH at a scan rate of 100 mV s(-1)). Also, a very attainable supercapacitance stability was achieved from HHC-250 modified electrode after 1000 cycles. The presented electrode system exhibited an energy density of 3.73W h kg(-1). This work can serve as a guideline for optimizing the performance of hair like biomass-derived carbons by matching their pore properties and detailed electrochemical performance investigations

Biomass Based Materials in Electrochemical Supercapacitor Applications

Biomass is the general term for organic substances derived from living organisms (plants and animals). Since, biomass is a renewable, sustainable, innovative, low cost and carbon-neutral energy source, the applications of nano-micro particles produced from biomass in electrochemical applications have emerged. A large number of carbon-based materials, such as featured activated carbon, carbon nanotube, C-dots, biochar, hybrid carbon-metal/metal oxide … etc. can be produced from divergent types of biomass. With the growing energy need in the world, supercapacitors have also developed considerably besides the energy generation and storage methods. The supercapacitor is an energy storage system that can work reversibly to provide high energy in a short time. In these systems, electrode structure and surface properties are crucial for energy capacity enhancement. In this sense, electrode modifications with the above-mentioned biomass-based nano-micro structures are widely used in supercapacitor applications

A biochar-modified carbon paste electrode

The present work examıned the use of biochar derived from tea waste as a novel electrode material. For the fabrication of the biochar electrode, suitable amounts of biochar and graphite were mixed with mineral oil for the first time. The electrochemical performance of the biochar-modified carbon paste electrode (BCPE) was measured by various cyclic voltammetric reactions for several redox systems. The factors affecting the electrode kinetics of BCPE surfaces were examined and optimized. The BCPE was applied as transducer in a glucose biosensor. The results reflect the effective properties of composite electrodes and the electrochemical properties of biochar showing that the BCPE could be used for various electrochemical applications

MoS2/Chitosan/GOx-Gelatin modified graphite surface: Preparation, characterization and its use for glucose determination

Graphene-like new generation of two dimensional (2D) nanomaterials, in particular the family of transition metal dichalcogenides (TMDCs) have been attracting a wide range of research interest. Among the family of TMDCs, molybdenum disulfide (MoS2) has been the most used one for biosensor applications. In this work, we detail the preparation of MoS2/chitosan composite modified pencil graphite electrode (MoS2/Chitosan/PGE) and its use as glucose biosensor after the modified electrode were immobilized with glucose oxidase (GOx)-gelatin (MoS2/Chitosan/GOx-Gelatin/PGE). This electrode was compared with the unmodified electrode in terms of electrochemical performance. Superior electrochemical responses were achieved including good electroactivity and sensitive glucose biosensing. For the MoS2/Chitosan/GOx-Gelatin modified PGE, a linear glucose concentration range was obtained from 10 mu M to 800 mu M with the equation of y = 0.0008x + 0.0547 (R2 = 0.9992) and a limit of detection (LOD) value of 3.18 mu M. The relative standard deviation (RSD%) was calculated as 3.77% at 200 mu M glucose (n = 5). The biosensor was tested in the presence of dopamine and ascorbic acid and our results presented the high selectivity of this novel MoS2/Chitosan/GOx-Gelatin modified PGE as a glucose biosensor

Mikro boyutta pH temelli potansiyometrik glikoz biyosensör

Günümüzdeki bilimsel ve teknik ilerlemeler, biyosensör teknolojisinde önemli gelişmelere yol açarak biyosensörlerin gıda teknolojileri, çevre, farmasi ve klinik teşhis, biyokimya, analitik kimya gibi alanlarda yaygın olarak kullanılmasına neden olmuştur. Potansiyometrik biyosensörlerin hazırlanmasında kullanılan iyon-seçici sensör teknolojisindeki gelişmeler ve sensör materyallerin sayılarının artması, yeni tip potansiyometrik biyosensörlerin geliştirilmesini de hızlandırmıştır. Nitekim, bu çalışmada, kompozit pH sensörüne dayalı yeni bir mikro boyutlu potansiyometrik glikoz biyosensörünün geliştirilmesi ele alınmıştır. Glikoz oksidaz, biyotanıma elemanı olarak kompozit tabaka üzerinde immobilize edildi. Kompozit pH algılama esaslı glikoz biyosensör matriksinin yüzeyi ilk olarak elektrokimyasal tanımlama için dönüşümlü voltametri ve elektrokimyasal impedans spektroskopisi kullanılarak incelendi. Yüksek elektron transfer hızı, biyosensörün kararlı bir tepki davranışına sahip olduğunu ve glikozun saptanması için uygun bir potansiyometrik sensör olduğunu göstermektedir. Glikozun potansiyometrik tespiti için 2x10-5 mol/L saptama sınırı ile 5x10-5 ila 1x10-1 mol/ L konsantrasyon aralığında lineer bir cevap elde edildi. Biyosensör hızlı bir tepki süresi (10 s) gösterdi, iyi bir kararlılığa ve uzun bir ömre sahipti

Graphene-metallic nanocomposites as modifiers in electrochemical glucose biosensor transducers

anik, ulku/0000-0002-3607-7208; Tepeli Buyuksunetci, Yudum/0000-0002-4717-7933WOS: 000397826400001Graphene sheets and three different graphene-metallic nanocomposites including graphene-copper (graphene-Cu), graphene-nickel (graphene-Ni) and graphene-platinum (graphene-Pt) were prepared and characterized in the first place. Then the electrochemical performances of these nanocomposites were tested in glucose biosensor transducers, which were formed by combining these metallic nanocomposites with glucose oxidase enzyme and glassy carbon paste electrode (GCPE). This is the first work that includes the usage of these graphene-Me nanocomposites as a part of glucose biosensor transducer. Fabricated amperometric biosensors linear ranges were obtained as follow: For the plain graphene, the linear range was found in the concentration range between 50 mu Mand 800 mu Mwith the RSD (n= 3 for 50 mu M glucose) value of 12.86% and LOD value of 7.2 mu M. For graphene-Pt modified glucose biosensor, the linear range was between 10 mu M and 600 mu M with the RSD (n= 3 for 50 mu M glucose) value of 3.45% and LOD value of 3.06 mu M. in the case of graphene-Ni modified glucose biosensor, the values were 25 mu M to 600 mu M with the RSD (n= 3 for 50 mu M glucose) value of 8.76% and LOD value of 24.71 mu M and for graphene-Cu modified glucose biosensor linear range was 25 mu M to 400 mu M with the RSD (n= 3 for 50 mu M glucose) value of 3.93% and LOD value of 2.87 mu M

Electrochemical properties of coumarin 500 encapsulated in a liquid crystal guided electrospun fiber core and their supercapacitor application

Here, we first report a study on coumarin 500 and liquid crystal including polyacrylonitrile nanofibers in terms of synthesis, characterizations, and supercapacitor performances. SEM, POM, FTIR, and DSC measurements showed that liquid crystal was inserted into the fine polyacrylonitrile nanofibers successfully. Because a strong molecular interaction took place between coumarin 500 and liquid crystal and coumarin 500 was sensitive to the polarity of the medium, the liquid crystal behaved as a guide material for coumarin 500, and it was expected that coumarin 500 was oriented by the director of the liquid crystal along the core of the fiber. The average polyacrylonitrile nanofiber size was between 0.19 to 0.25 mu m, and liquid-crystal-doped and liquid-crystal +coumarin-500-doped fibers exhibited a similar distribution, which is approximately in the 0.30 to 0.60 mu m interval. This proved that the fibers maintained their structure after modifications. Electrochemical evaluation of the different composite nanofibers showed that there was not a significant current increase upon liquid crystal addition into polyacrylonitrile nanofibers at voltammograms. C-s values were enhanced after the coumarin 500 addition into liquid-crystal-doped nanofiber and obtained as 410.60 F/g with a specific energy value of 57.03 Wh/kg. Additionally, the long-term charge-discharge test of the liquid-crystal+coumarin-500-doped polyacrylonitrile graphite electrode showed a very steady distribution between 100th and the 2500th cycles with a 14.12% Cs deviation. This is attributed to the stable and robust network of the PAN nanofiber and the synergetic effect between liquid crystal and coumarin 500 in the nanofiber net

Development of MoS2 and Au nanoparticle including disposable CEA-based immuno-cytosensor platforms

In this study, an electrochemical biosensor for determination of Carcinoembryonic antigen (CEA) biomarker using human breast ductal adenocarcinoma (MCF-7) and human ovarian adenocarcinoma (SK-OV-3) cancer cells was presented. Disposable pencil graphite electrodes (PGE) has been modified with Au nanoparticle (Au NP) and MoS2 nanostructure dispersed chitosan (Cs) matrix. Therefore, the electrochemical interaction between the antibody-electrode surface was facilitated. Under optimal conditions, the immunosensor exhibited high sensitivity toward CEA biomarker in the low concentration range 0.01-10 ng mL(-1), with the detection limit of 1.93 ng mL(-1) and relative standard deviation of 4.65 (n = 5). The results indicated that even very small changes in CEA concentration can be sensed with the presented system. Also, recovery of the immunosensor found as 98 +/- 3% in the real sera samples containing dopamine and ascorbic acid. It has a great potential in the clinical screening of divergent cancer biomarkers. Experiments were conducted to determine the number of normal cell hGF and cancer cells adhered and attached on immuno-cytosensor surfaces. CEA-positive MCF-7 cells have shown great potential for adhesion and attachment to MoS2/Cs/Au/Anti-CEA/CEA surface better than CEA-negative cells. The developed immuno-cytosensor exhibited very promising results for the future biosensor studies

Syntheses, crystal structures, hirshfeld surface analyses and electrochemical etoposide/camptotechin sensor applications of acetaldehyde oxime derivatives

(E)-2-(4-Hydroxyphenyl)-2-oxoacetaldehyde oxime monohydrate (I) and (E)-2-(4 Nitropheny1)-2oxoacetaldehyde oximes (II) were synthesized from 4'-hydroxyacetophenone and 4'-nitroacetophenone, respectively. Their structures were elucidated by elemental analyses, H-1 NMR, UV-Vis and also their molecular and crystal structures were determined by single crystal X-ray analysis. They belong to monoclinic system P 2(1)/n space group with a = 6.8198 (3) angstrom, b = 7.3846 (3) angstrom, c = 16.4706 (5) angstrom, beta = 94.300 (3)degrees, Z = 4 and V = 827.15 (6) angstrom(3) (for I) and a = 7.1557 (3) angstrom, b = 14.5338 (5) angstrom, c = 8.6311 (3) angstrom, beta = 108.321 (3)degrees, Z = 4 and V = 852.13 (5) angstrom(3) (for II). Hirshfeld surface analyses of the crystal structures indicate that the most important contributions for the crystal packings are from H center dot center dot center dot H (35.0%) and H center dot center dot center dot O/O center dot center dot center dot H (33.9%) contacts (for I) and H center dot center dot center dot O/O center dot center dot center dot H (40.9%) and H center dot center dot center dot H (19.4%) contacts (for II). Hydrogen bonding and van der Waals contacts are the dominant interactions in the crystal packings. Comparing the limit of detection achieved in this work with the therapeutic ranges of etoposide/camptotechin verifies the possibility of using both oxime I and II based electrodes as sensors. However GCPE/I electrode exhibited the best electrochemical improvement on the etoposide determination in terms of both sensitivity and limit of detection (C) 2022 Elsevier B.V. All rights reserved