The design and fabrication of supramolecular semiconductor nanowires formed by benzothienobenzothiophene (BTBT)-conjugated peptides

π-Conjugated small molecules based on a [1]benzothieno[3,2-b]benzothiophene (BTBT) unit are of great research interest in the development of solution-processable semiconducting materials owing to their excellent charge-transport characteristics. However, the BTBT π-core has yet to be demonstrated in the form of electro-active one-dimensional (1D) nanowires that are self-assembled in aqueous media for potential use in bioelectronics and tissue engineering. Here we report the design, synthesis, and self-assembly of benzothienobenzothiophene (BTBT)–peptide conjugates, the BTBT–peptide (BTBT-C3–COHN-Ahx-VVAGKK-Am) and the C8-BTBT–peptide (C8-BTBT-C3–COHN-Ahx-VVAGKK-Am), as β-sheet forming amphiphilic molecules, which self-assemble into highly uniform nanofibers in water with diameters of 11–13(±1) nm and micron-size lengths. Spectroscopic characterization studies demonstrate the J-type π–π interactions among the BTBT molecules within the hydrophobic core of the self-assembled nanofibers yielding an electrical conductivity as high as 6.0 × 10−6 S cm−1. The BTBT π-core is demonstrated, for the first time, in the formation of self-assembled peptide 1D nanostructures in aqueous media for potential use in tissue engineering, bioelectronics and (opto)electronics. The conductivity achieved here is one of the highest reported to date in a non-doped state

Fonksiyonel nanomalzemelerin üretimi için kendiliğinden düzenlenen peptitlerin tasarım ve sentezi

Cataloged from PDF version of article.Thesis (Ph.D.): Bilkent University, Department of Materials Science and Nanotechnology, İhsan Doğramacı Bilkent University, 2016.Includes bibliographical references (leaves 146-171).Self-assembling peptides are a class of supramolecular polymers, which exploit noncovalent interactions such as hydrogen bonding, hydrophobic, electrostatic, charge-transfer complex, π-π, and van der Waals interactions to generate well-defined supramolecular nanostructures including nanospheres, nanosheets, nanotubes, and nanofibers. These versatile peptide-based supramolecular nanomaterials have been utilized in variety of applications including catalysis, sensing, light harvesting, optoelectronic, bioelectronic and tissue engineering. In this thesis, use of supramolecular peptide nanofibers formed by specially designed short peptide sequences that can form sheet-like hydrogen bonded structures for controlled synthesis of nanometer scale functional materials were explored. Specifically, n-type and p-type β-sheet forming short peptide sequences were synthesized, which assemble separately into well-ordered nanofibers in aqueous media. These p-type and n-type nanofibers coassemble via hydrogen bonding and electrostatic interactions to generate highly uniform supramolecular n/p-coassembled 1D nanowires. This smart molecular design ensures alternating arrangement of D and A chromophores within n/p-coassembled supramolecular nanowires. Supramolecular n/p- coassembled nanowires were found to be formed by alternating A-D-A unit cells having an association constant of (KA) of 5 x 105 M-1. Moreover, I designed and synthesized β-sheet forming peptide nanofibers to fabricate different metal and metal oxide nanostructures in highly controlled manner using wet chemistry and atomic layer deposition techniques. These hybrid organic-inorganic nanostructures were employed in model Suzuki coupling, alkyne-azide cycloaddition and hydrolysis of ammonia borane reactions.by Mohammad Aref Khalily.Ph.D

Elektrokimyasal Nad/Nadh dönüşümü için yeni mediyatörlerin sentezi.

The synthesis of enantiopure compounds can be achieved by using dehydrogenases as biocatalysts. For instance, reduction reactions of prochiral compounds (ketones, aldehydes and nitriles) into chiral compounds can be achieved by dehydrogenases. These dehydrogenases are cofactor dependent where cofactor is Nicotinamide Adenin Dinucleotite having some restrictions that confines usage of dehydrogenases in organic synthesis including instability of cofactor in water and high cost. Therefore, suitable recycling methods are required and developed which are enzymatic and electrochemical. We will use an electrochemical approach for the regeneration of reduced co-factors. All active compounds; mediator, cofactor and enzyme, will be immobilized on the electrode surface of the constructed reactor surface. Therefore only educts and products will exist in the reactor medium. A gas diffusion electrode will be employed as a counter electrode; which delivers clear protons to the system. Mediator will carry electrons to the cofactor for cofactor regeneration. Then, enzyme will utilize the cofactor and change the substrates to the products in high stereoselectivity. Our aim in this project is the synthesis of mediators and suitable linkers for enzyme, cofactor and mediator immobilization. In the first part of the study, mediators were synthesized which are pentamethylcyclopentadienyl rhodium bipyridine complexes. In the second part of the study, a conductive monomer (SNS) and linker were synthesized for immobilization of the enzyme. In the last part of the study, the reaction of galactitol dehydrogenase with monomer (SNS) was achieved.M.S. - Master of Scienc

Atomic layer deposition of Co3O4 nanocrystals on N-doped electrospun carbon nanofibers for oxygen reduction and oxygen evolution reactions

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are considered as the two crucial reactions in key renewable-energy technologies including fuel cells and water splitting. Despite promising research progress in the preparation of various non-noble metal based electrocatalysts, it is still highly challenging but desirable to develop novel fabrication strategies to synthesize highly active and cost-effective ORR/OER bifunctional electrocatalysts in a precisely controlled manner. Herein, we report atomic layer deposition (ALD) of highly monodisperse Co3O4 nanocrystals of different sizes on N-doped electrospun carbon nanofibers (nCNFs) as high performance bifunctional catalysts (Co@nCNFs) for the ORR and OER. Co@nCNFs (with an average Co3O4 particle size of ∼3 nm) show high ORR performance exhibiting an onset potential of 0.87 V with a low Tafel slope of 119 mV dec-1 approaching that of commercial Pt/C. Similarly, the Co@nCNF electrocatalyst showed remarkable catalytic activity in the OER. The turnover frequency (TOF) value determined at an overpotential of 550 mV for the Co@nCNFs is ∼0.14 s-1 which is ca. 3 and ca. 15-fold higher than those of bulk Co (∼0.05 s-1) and the standard state-of-the-art IrOx (0.0089 s-1) catalyst, respectively. This work will open new possibilities for fabrication of inexpensive non-noble metal materials in highly controlled manner for applications as bifunctional ORR/OER electrocatalysis

Atomic Layer Deposition of Pd Nanoparticles on N-Doped Electrospun Carbon Nanofibers: Optimization of ORR Activity of Pd-Based Nanocatalysts by Tuning Their Nanoparticle Size and Loading

Optimization of size, loading and chemical composition of catalytic nanoparticles is a crucial step to achieve cost-effective and efficient (electro) catalysts. This report elaborates optimization of palladium (Pd) nanoparticle size and loading on the electrospun based N-doped carbon nanofibers (nCNF) towards oxygen reduction reaction (ORR) for the energy devices like fuel cell, metal air batteries. Electrospinning was utilized to produce one-dimensional (1D) polyacrylonitrile nanofibers followed by a two-step carbonization process obtaining well-defined conductive nCNF having diameters in the range of 200–350 nm. As-synthesized nCNF was decorated with discrete Pd nanoparticles ranging from 2.6±0.4 nm to 4.7±0.5 nm via thermal atomic layer deposition (ALD) technique. We found that nCNF deposited Pd nanoparticles having 3.9±0.6 nm size (Pd20/nCNF) showed the best ORR activity with the smallest Tafel slope of 58 mV dec−1 along with four electrons involved in the ORR. In addition, high value at half wave potential (E1/2=806 mV vs. RHE) and exchange current densities (i0=6.998 mA cm−2) at Pd20/nCNF makes it efficient catalyst among other Pd decorated nCNF. Moreover, we found that electrocatalyst with lower loading/density of Pd nanoparticles showed enhanced ORR activity

Atomic Layer Deposition of NiOOH/Ni(OH)(2) on PIM-1-Based N-Doped Carbon Nanofibers for Electrochemical Water Splitting in Alkaline Medium

WOS: 000467235500022PubMed ID: 30637965Portable and flexible energy devices demand lightweight and highly efficient catalytic materials for use in energy devices. An efficient water splitting electrocatalyst is considered an ideal future energy source. Well-aligned high-surface-area electrospun polymers of intrinsic microporosity (PIM-1)-based nitrogen-doped carbon nanofibers were prepared as a free-standing flexible electrode. A non-noble-metal catalyst NiOOH/Ni(OH)(2) was precisely deposited over flexible free-standing carbon nanofibers by using atomic layer deposition (ALD). The morphology, high surface area, nitrogen doping, and Ni states synergistically showed a low onset potential ((HER)=-40 and (OER)=290mV vs. reversible hydrogen electrode), small overpotential at (10) [oxygen evolution reaction (OER)=390.5mV and hydrogen evolution reaction (HER)=-147mV], excellent kinetics (Tafel slopes for OER=50mVdec(-1) and HER=41mVdec(-1)), and high stability (>16h) towards water splitting in an alkaline medium (0.1m KOH). The performance was comparable with that of state-of-the-art noble-metal catalysts (e.g., Ir/C, Ru/C for OER, and Pt/C for HER). Post-catalytic characterization with X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy further proved the durability of the electrode. This study provides insight into the design of 1D-aligned N-doped PIM-1 electrospun carbon nanofibers as a flexible and free-standing NiOOH/Ni(OH)(2) decorated electrode as a highly stable nanocatalyst for water splitting in an alkaline medium

Atomic Layer Deposition of NiOOH/Ni(OH) 2

WOS: 000467235500022PubMed ID: 30637965Portable and flexible energy devices demand lightweight and highly efficient catalytic materials for use in energy devices. An efficient water splitting electrocatalyst is considered an ideal future energy source. Well-aligned high-surface-area electrospun polymers of intrinsic microporosity (PIM-1)-based nitrogen-doped carbon nanofibers were prepared as a free-standing flexible electrode. A non-noble-metal catalyst NiOOH/Ni(OH)(2) was precisely deposited over flexible free-standing carbon nanofibers by using atomic layer deposition (ALD). The morphology, high surface area, nitrogen doping, and Ni states synergistically showed a low onset potential ((HER)=-40 and (OER)=290mV vs. reversible hydrogen electrode), small overpotential at (10) [oxygen evolution reaction (OER)=390.5mV and hydrogen evolution reaction (HER)=-147mV], excellent kinetics (Tafel slopes for OER=50mVdec(-1) and HER=41mVdec(-1)), and high stability (>16h) towards water splitting in an alkaline medium (0.1m KOH). The performance was comparable with that of state-of-the-art noble-metal catalysts (e.g., Ir/C, Ru/C for OER, and Pt/C for HER). Post-catalytic characterization with X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy further proved the durability of the electrode. This study provides insight into the design of 1D-aligned N-doped PIM-1 electrospun carbon nanofibers as a flexible and free-standing NiOOH/Ni(OH)(2) decorated electrode as a highly stable nanocatalyst for water splitting in an alkaline medium

Atomic Layer Deposition of Pd Nanoparticles on N‐Doped Electrospun Carbon Nanofibers: Optimization of ORR Activity of Pd‐Based Nanocatalysts by Tuning Their Nanoparticle Size and Loading

Optimization of size, loading and chemical composition of catalytic nanoparticles is a crucial step to achieve cost‐effective and efficient (electro) catalysts. This report elaborates optimization of palladium (Pd) nanoparticle size and loading on the electrospun based N‐doped carbon nanofibers (nCNF) towards oxygen reduction reaction (ORR) for the energy devices like fuel cell, metal air batteries. Electrospinning was utilized to produce one‐dimensional (1D) polyacrylonitrile nanofibers followed by a two‐step carbonization process obtaining well‐defined conductive nCNF having diameters in the range of 200–350 nm. As‐synthesized nCNF was decorated with discrete Pd nanoparticles ranging from 2.6±0.4 nm to 4.7±0.5 nm via thermal atomic layer deposition (ALD) technique. We found that nCNF deposited Pd nanoparticles having 3.9±0.6 nm size (Pd20/nCNF) showed the best ORR activity with the smallest Tafel slope of 58 mV dec−1 along with four electrons involved in the ORR. In addition, high value at half wave potential (E1/2=806 mV vs. RHE) and exchange current densities (i0=6.998 mA cm−2) at Pd20/nCNF makes it efficient catalyst among other Pd decorated nCNF. Moreover, we found that electrocatalyst with lower loading/density of Pd nanoparticles showed enhanced ORR activity

Facile Synthesis of Three-Dimensional Pt-TiO2 Nano-networks: A Highly Active Catalyst for the Hydrolytic Dehydrogenation of Ammonia-Borane

Three-dimensional (3D) porous metal and metal oxide nanostructures have received considerable interest because organization of inorganic materials into 3D nanomaterials holds extraordinary properties such as low density, high porosity, and high surface area. Supramolecular self-assembled peptide nanostructures were exploited as an organic template for catalytic 3D Pt-TiO2 nano-network fabrication. A 3D peptide nanofiber aerogel was conformally coated with TiO2 by atomic layer deposition (ALD) with angstrom-level thickness precision. The 3D peptide-TiO2 nano-network was further decorated with highly monodisperse Pt nanoparticles by using ozone-assisted ALD. The 3D TiO2 nano-network decorated with Pt nanoparticles shows superior catalytic activity in hydrolysis of ammonia-borane, generating three equivalents of H-2