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

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

Impedance Spectroscopy and Dielectric Properties of Silver Incorporated Indium Sulfide Thin Films

In this study, silver incorporated indium sulfide (In2S3) thin films have been deposited on soda lime glass via spray pyrolysis technique. Structural and electrical properties have been tailored by adding controlled amount of silver acetate into the precursor solution. A phase shift form cubic -In2S3 to AgInS2 has been evidenced from X-ray diffraction spectra (XRD). Molecularity of the samples, meaning (Ag+In)/S ratio, has directly affected the electrical conductivity as well as the dielectric properties. Direct and alternating current conductivities increased with increasing the (Ag+In)/S ratio upto 10% silver incorporation. When the silver amount further increased conductivity decreased due to the pronounced secondary phase formation. The complex impedance analysis was used to determine the effect of silver on the conduction mechanism. It has been observed that frequency exponent of all samples were greater than unity indicating the nanocrystalline nature of the films. The variation of dielectric properties and ac conductivity with frequency revealed that the relaxation process in silver incorporated In2S3 thin films was due to the Maxwell–Wagner type of interfacial polarization in general

Influence of excitation frequency on structural and electrical properties of spray pyrolyzed CuInS2 thin films

This paper reports the cost effective deposition of the copper indium sulfide (CuInS2) thin films under atmospheric conditions via ultrasonic spray pyrolysis. Structural and electrical properties of these films have been tailored by controlling the nozzle excitation frequency and the solution loading. Smoother films have been obtained via 120 kHz excitation frequency compare to the 48 kHz. Band gap energy of the films has also been tailored via excitation frequency. UV-vis-NIR analysis revealed that films deposited at 48 kHz excitation frequency had lower band gap energies. Although, both excitation frequencies resulted chalcopyrite structure, crystallinity of the CuInS2 films was better for 120 kHz. On the other hand, better optical absorption in visible and near infrared region was observed at 48 kHz. Moreover, room temperature electrical conductivity of the samples deposited at 48 kHz excitation frequency was higher than that of samples deposited at 120 kHz. Temperature dependent electrical conductivity data showed that variable range hopping mechanism can be used to explain the conduction of spray pyrolyzed CuInS2 thin films. Electrical mobility as high as 48 cm(2)/Vs has been observed for the sample deposited from 0.51 ml/cm(2) loading at 48 kHz excitation frequency. This value is very close to the mobility of vacuum deposited thin films like amorphous silicon, which is one of the most commonly used semiconductor in electronic and energy applications. (C) 2014 Elsevier B.V. All rights reserved,This study was supported by Republic of Turkey Ministry of Science, Industry and Technology under the research Grant 01072.STZ.2011-2

Nanoporous Pt and Ru catalysts by chemical dealloying of Pt-Al and Ru-Al alloys for ultrafast hydrogen generation

Novel nanoporous catalysts from selective dissolution of alloys have been prepared for fast hydrogen generation from chemical hydrides. Pt and Ru have been used as precious metals in the alloys, while the nonprecious metal is Al. The alloy composition has been arranged by sputtering power of Al, which is varied from 200 to 400 W for Pt-Al and Ru-Al alloys. The influence of particle size on the sputtering power of Al has been demonstrated. The particle size of the Pt nanoparticle decreases from 900 to 90 nm when the sputtering power of Al is increased from 200 to 400 W. However, the particle size of the Ru nanoparticle decreased from 610 to 55 with the same increase in Al sputtering power. The hydrolysis reaction rate of NaBH4 scales with the sputtering power of Al and has been raised from 20 to 90 L min−1gcatalyst−1 for Pt while it increases from 23 to 110 L min−1gcatalyst−1 for Ru. The BET analysis has demonstrated that the measured surface areas of the Pt and Ru nanoparticles are approximately 55.5 and 151 m2 g−1, respectively. Joint like morphology providing the porous structure has been clearly concluded by TEM analysis. The average pore sizes are 1 and 10 nm for the Ru and Pt nanoparticles, respectively. In this study, fast hydrogen generation with lower activation energies of 31.7 and 32.1 kJ mol−1 has been achieved for the Pt and Ru nanoparticles, respectively. The critical parameters demonstrating the high catalytic activity in the hydrolysis reaction of NaBH4 are reported for the catalysts developed by the dealloying process