Influence of Electrical and Ionic Conductivities of Organic Electronic Ion Pump on Acetylcholine Exchange Performance

Abstract By using an easy and effective method of depositing conjugated polymers (PEDOT:PSS) on flexible substrates, a new design for organic bioelectronic devices has been developed. The purpose was to build up a system that mimics the motion of neurotransmitters in the synaptic cleft by obtaining an electrical to chemical signal transport. Fourier transform infrared (FTIR) spectroscopy and Raman measurements have demonstrated that electrochemical overoxidation region which separates the pristine PEDOT:PSS electrodes and allows ionic conduction has been achieved successfully. The influence of both electrical and ionic conductivities on organic electronic ion pump (OEIP) performances has been studied. The ultimate goal was to achieve the highest equilibrium current density at the lowest applied voltage via enhancing the electrical conductivity of PEDOT:PSS and ionic conductivity of electrochemically overoxidized region. The highest equilibrium current density, which corresponds to 4.81 × 1017 number of ions of acetylcholine was about 41 μA cm−2 observed for the OEIP with the electrical conductivities of 54 S cm−1. This was a threshold electrical conductivity beyond which the OEIP performances were not changed much. Once Nafion™ has been applied for enhancing the ionic conductivity, the equilibrium current density increased about ten times and reached up to 408 μA cm−2. Therefore, it has been demonstrated that the OEIP performance mainly scales with the ionic conductivity. A straightforward method of producing organic bioelectronics is proposed here may provide a clue for their effortless mass production in the near future

Dealloyed Ruthenium Film Catalysts for Hydrogen Generation from Chemical Hydrides

Thin-film ruthenium (Ru) and copper (Cu) binary alloys have been prepared on a Teflon™ backing layer by cosputtering of the precious and nonprecious metals, respectively. Alloys were then selectively dealloyed by sulfuric acid as an etchant, and their hydrogen generation catalysts performances were evaluated. Sputtering time and power of Cu atoms have been varied in order to tailor the hydrogen generation performances. Similarly, dealloying time and the sulfuric acid concentration have also been altered to tune the morphologies of the resulted films. A maximum hydrogen generation rate of 35 mL min-1 was achieved when Cu sputtering power and time were 200 W and 60 min and while acid concentration and dealloying time were 18 M and 90 min, respectively. It has also been demonstrated that the Ru content in the alloy after dealloying gradually increased with the increasing the sputtering power of Cu. After 90 min dealloying, the Ru to Cu ratio increased to about 190 times that of bare alloy. This is the key issue for observing higher catalytic activity. Interestingly, we have also presented template-free nanoforest-like structure formation within the context of one-step alloying and dealloying used in this study. Last but not least, the long-time hydrogen generation performances of the catalysts system have also been evaluated along 3600 min. During the first 600 min, the catalytic activity was quite stable, while about 24% of the catalytic activity decayed after 3000 min, which still makes these systems available for the development of robust catalyst systems in the area of hydrogen generation. © 2017 by the authors

Investigation of Strain Effects on Photoelectrochemical Performance of Flexible ZnO Electrodes

In this report, the growth of zinc oxide (ZnO) nanocrystals with various morphologies, nanoflower, nanosheet, and nanorod, on flexible stainless steel (SS) foils to be utilized as photoanodes in photoelectrochemical (PEC) solar cells has been presented. It has been aimed to provide flexibility and adaptability for the next generation systems with the incorporation of SS foils as electrode into PEC cells. Therefore, physical deformation tests have been applied to the prepared ZnO thin film photoanodes. These thin films have been thoroughly characterized before and after straining for better understanding the relationship between the morphology, straining effect and photoelectrochemical efficiency. We observed a notable increase in the maximum incident photon-to-current efficiency (IPCE) and durability of all ZnO photoelectrodes after straining process. The increase in IPCE values by 1.5 and 2.5 folds at 370 nm has been observed for nanoflower and nanorod morphologies, respectively after being strained. The maximum IPCE of 69% has been calculated for the ZnO nanorod structures after straining. Bending of the SS electrodes resulted in the more oriented nanorod arrays compared to its flat counterpart, which improved both the light absorption and also the photo-conversion efficiency drastically. The finite-difference time-domain simulations have also been carried out to examine the optical properties of flat and bent ZnO electrodes. Finally, it has been concluded that SS photoanodes bearing ZnO semiconducting material with nanoflower and nanorod morphologies are very promising candidates for the solar hydrogen generator systems in terms of efficiency, durability, flexibility, and lightness in weight

Akso-aksonal iletim için sentetik sinir uçları geliştirilmesi ve asetilkolin iyon pompası olarak test edilmesi

Günümüzde 450 milyondan fazla insan, tedavi edilemeyen nörolojik hastalıklardan küresel olarak muzdarip. Bu hastalıklar, sinir sisteminde bozulmuş elektriksel ve nörokimyasal sinyallerden kaynaklanır. Dünya çapında bu sorunun farkındalığı henüz kazandırılamadı ve bugüne kadar kesin bir tedavi yöntemi bulunamadı. Nörolojik bozukluklarla ilişkili tedavilerin çoğu tıbbi terapi veya elektrik stimülasyonu gibi tedavi yöntemleridir. Bu tedavi yöntemlerinden elde edilen sonuçlar ise maalesef geçici süreliğine etkilidir. Çalışmamızda, bu problemi göz önüne alarak, bir sinir hücresinin işlevini çoğaltan ve sinir sisteminin kusurlu elektrokimyasal iletiminin tamir edilmesine yardımcı olan bir biyomimetik sistemi sunmaktayız. Sinir uyarıları, sinapslar boyunca sinir iletici olarak adlandırılan asetilkolin molekülleri tarafından iletilir. Asetilkolin molekülleri, veziküllerin akson ayağında bulunur. Asetilkolin'in sinaptik yarık içine salınmasından sonra, postsinaptik nöron üzerinde bulunan kolinerjik reseptörlere bağlanır ve postsinaptik hücreler üzerinde uyarılma veya inhibisyona aracılık eder ve bu şekilde sinir sinyalinin taşınmasına neden olur. Grubumuz tarafından geliştirilen sistem, üzerinde PEDOT:PSS bulunan iki elektrot ve yalıtılmış, sadece iyonik taşınmaya izin veren 2 mm'lik aşırı okside bölgeye sahiptir . Esnek yüzeyler üzerinde konjuge polimerlerin (PEDOT:PSS) kaplanmasının kolay ve etkili bir yöntemi kullanılarak, organik biyoelektronik cihazlar için yeni bir tasarım geliştirilmiştir. FTIR ve Raman ölçümleri, PEDOT:PSS elektrotlarını ayıran ve iyonik iletime izin veren elektrokimyasal aşırı oksidasyon bölgesinin başarıyla elde edildiğini göstermiştir. Asetilkolin iyonlarının 4.81x1017 kadarına tekabül eden en yüksek akım yoğunluğunun 54 Scm-1 elektriksel iletkenliği olarak gözlemlenen yaklaşık 41 ?Acm-2 idi. Organik elektronik iyon pompası performansları bu denge iletkenlik değerinin çok ötesinde değişmedi. Nafion ™, iyonik iletkenliği arttırmak için uygulandığında ise, denge akım yoğunluğu yaklaşık on kat artmış ve 408 ?Acm-2'ye ulaşmıştır. Bu nedenle, OEIP performansının esas olarak iyonik iletkenlik ile ölçeklendiği gösterilmiştir. Yakın gelecekte zahmetsizce seri üretim yapmalarını sağlamak için, organik biyoelektronik üretimi basit bir yöntem önerilmiştir.Currently, more than 450 million people are globally suffering from some types of neurological diseases that can hardly be treated. These diseases are caused by distorted electrical and neurochemical signaling in the nervous system. The awareness of this worldwide problem is not brought in yet and definitive treatment has not been introduced so far. Most of therapies associated with neurological disorders are based on medical treatment such as medical therapy or electric stimulation. However, results are temporary and ineffective. The major effect obtained so far, was to conceal the disease and this was just not enough. In our study, by taking into consideration this problem we are presenting a biomimetic system that duplicates the function of a neural cell and helps to reinstitute the defective electrochemical transport of nervous system. Nerve impulses are communicated across synapses by diffusible molecules called neurotransmitters, of which one is acetylcholine. Acetylcholine molecules are contained in the axon foot inside vesicles. After the release of acetylcholine into the synaptic cleft, it binds to the cholinergic receptors located on the postsynaptic neuron and mediate excitation or inhibition on postsynaptic cells and thus causing the transportation of neural signal. The system developed by our group resembles a two electrode structure with PEDOT:PSS deposited on them and a tiny 2 mm overoxidized region that cuts off electrical conductivity thus allowing only ionic transport. By using an easy and effective method of depositing conjugated polymers (PEDOT:PSS) on flexible substrates, a new design for organic bioelectronic devices has been developed. FTIR and Raman measurements have demonstrated that electrochemical overoxidation region which separates the PEDOT:PSS electrodes and allows ionic conduction has been achieved successfully. The influence of both electrical and ionic conductivities on organic electronic ion pump (OEIP) performances has been studied. The highest equilibrium current density, which corresponds to 4.81x1017 number of ions of acetylcholine was about 41 ?A cm-2 observed for the OEIP with the electrical conductivities of 54 Scm-1. The OEIP performances were not changed much beyond this threshold electrical conductivity. Once Nafion™ has been applied for enhancing the ionic conductivity, the equilibrium current density increased about ten times and reached up to 408 ?Acm-2. Therefore, it has been demonstrated that the OEIP performance mainly scales with the ionic conductivity. A straightforward method of producing organic bioelectronics is proposed here giving rise to their effortless mass production in the near future

Indium Sulfide Based Photoelectrodes for All-Vanadium Photoelectrochemical Redox Flow Batteries

The utilization of indium sulfide (In2S3) photo-electrodes in an all-vanadium photoelectrochemical redox flow battery system has been investigated. The In2S3-based photo-electrodes have been prepared via the ultrasonic spray pyrolysis (USP) method. The thickness of the In2S3 photoelectrodes has been altered via increasing the pass number of the USP nozzle from 25 to 75 passes. Each pass delivers 6 mu L.cm(-2) of the precursor solution. Within the scope of the photoelectrochemical oxidation on the In2S3, the vanadium couples of VO2+/V3+ have been proven to be promising redox species. The maximum charge separation and quantum efficiencies of 46% and 20% have been calculated, respectively

Highly efficient 3D-ZnO nanosheet photoelectrodes for solar-driven water splitting: Chalcogenide nanoparticle sensitization and mathematical modeling

Three-dimensional (3D) zinc oxide nanosheets (ZnO-NS), assembled on the FTO coated glass substrates after chemical treatment, have been achieved via a simple yet effective chemical bath deposition technique. The exploration of chalcogenide nanoparticle sensitization on ZnO-NS thin-film photoanodes led us to a spectacular enhancement in the photoelectrochemical conversion efficiency for solar-driven water splitting process as compared to the bare 3D-ZnO-NS. The maximum incident photon-to-charge carrier efficiency of bare 3D-ZnO-NS has been enhanced by approximately four folds as a result of cadmium sulfide (CdS) and cadmium selenide (CdSe) sensitization and the efficiency value have reached to 51% at 550 nm. Besides, the maximum charge injection and charge separation efficiencies of the ZnO eCdSe electrodes have been calculated as 93% and 64%, respectively. Numerical examination of the optical absorption and electrical field distribution has been performed via the finite-difference time-domain (FDTD) method in order to investigate the basis of the enhancement in the photoelectrochemical efficiencies of the 3D-ZnO-NS photoelectrodes. FDTD numerical simulation proved that the accumulation of rectangular 2D-nanosheets of ZnO in 3D-microspherical forms enhanced the light absorption significantly. Moreover, FDTD results also verified that the optical absorption of the ZnO electrodes has been extended from ultraviolet to visible region via CdS and CdSe nanoparticle deposition. (c) 2020 Elsevier B.V. All rights reserved

Zinc Oxide and Metal Halide Perovskite Nanostructures Having Tunable Morphologies Grown by Nanosecond Laser Ablation for Light-Emitting Devices

This work reports a one-pot chemical bath deposition (CBD) method for the preparation of selectively grown, morphology-tunable zinc oxide (ZnO) nanostructures provided via straightforward nanosecond fiber laser ablation. Nanosecond fiber laser ablation is different from lithographic methods due to its simple, time saving, and efficient film scribing abilities. Here, multiple morphologies of the ZnO nanostructures on the same substrate have been grown via laser ablation of the ZnO seeding layer. Selective and controlled ablation of the titanium layer, ZnO growth inhibitor, resulted in systematic growth of nanorod arrays, while the application of extensive fluence energies resulted in the penetration of the laser beam until the glass substrate induced the nanoflake growth within the same CBD environment. The laser penetration depth has been numerically investigated via COMSOL Multiphysics heat module simulations, and the optical variations between two nanostructures (nanorod and nanoflake) have been examined via Lumerical FDTD. The simultaneous growth of two morphologies served as an efficient tool for the enhancement of photoluminescence intensities. It increased the average charge carrier lifetimes of the thin films from approximately 2.01 to 9.07 ns under the same excitation wavelengths. The amplification in PL performances has been accomplished via the capstone of all-inorganic halide perovskite (IHP) deposition that brought a successful conclusion to lifetime responses, which have been increased by 1.4-fold. The development of IHP sensitized nanoscaled multimorphological ZnO thin films can, therefore, be used as potential nanomaterials for light-emitting-device applications

Efficiency enhancement in photoelectrochemical water splitting: defect passivation and boosted charge transfer kinetics of zinc oxide nanostructures via chalcopyrite/chalcogenide mix sensitization

ZnO thin films in nanorod (NR) and nanoflower (NF) morphologies were used as photoelectrode scaffolds for efficient visible-light-driven photoelectrochemical (PEC) water splitting process, where their decoration with copper indium gallium sulfide (CIGS) and indium sulfide (In2S3) layers resulted in significant PEC performance enhancement. ZnO NF/CIGS/In2S3 photoelectrodes exhibited a remarkably high PEC efficiency (∼6.0% applied bias photon-to-current efficiency, 83% incident photon-to-current efficiency) due to the negligible dark current, while ZnO NR/CIGS/In2S3 generated a photocurrent density of 30.0mA.cm-2 at 0.4 V (vs Ag/AgCl), being one of the highest performances reported in the literature for copper-based chalcopyrite photoelectrodes so far. The interfacial photoelectrode-electrolyte charge transport dynamics, investigated via intensity-modulated photocurrent spectroscopy, exhibited a sevenfold increase in charge transfer efficiencies with a significant drop in surface recombination kinetics for ZnO NF after CIGS/In2S3 decoration. The obtained results show consistency with numerically modeled electric field distribution profiles and electron paramagnetic resonance results of ZnO NF, rationalizing the enhanced charge transfer rates for decorated samples and confirming the defect passivating nature of CIGS/In2S3

Tailoring morphology to control defect structures in ZnO electrodes for high-performance supercapacitor devices

Zinc oxide (ZnO) nanostructures were synthesized in the form of nanoparticles, nanoflowers and nanourchins. Structural, electronic and optical characterization of the samples was performed via standard techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence, Raman and ultraviolet-visible (UV-Vis) spectroscopy. Point defect structures which are specific to each morphology have been investigated in terms of their concentration and location via state-of-the-art electron paramagnetic resonance (EPR) spectroscopy. According to the core-shell model, all the samples revealed core defects; however, the defects on the surface are smeared out. Finally, all three morphologies have been tested as electrode materials in a real supercapacitor device and the performance of the device, in particular, the specific capacitance and the storage mechanism, has been mediated by the point defects. Morphology-dependent defective ZnO electrodes enable the monitoring of the working principle of the supercapacitor device ranging from electric double-layer capacitors (EDLC) to pseudo-supercapacitors. © 2020 The Royal Society of Chemistry