Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü / Department of Material Science & Nanotechnology Engineering

Permanent URI for this collectionhttps://gcris3.etu.edu.tr/handle/20.500.11851/279

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Türkiye Yüzyılı’nda Bilim Teknoloji
(Memur-Sen, 2023) Sultansoy, Saleh
[No Abstract Available]
A New Perspective for Nanoconfined Polymer Crystals
(Polymer Science and Technology Association & Middle East Technical University, 2024) Duran Durmuş, Hatice
Nanoporous hard templates provide a two-dimensional confined space in which self- organization processes such as crystallization, protein secondary structure formation, and phase separation can be fundamentally different from those obtained in thin films and in bulk. A particular advantage of hard templates is that they provide a range of parameter space (pore diameter, curvature, nature of pore walls) that can induce or manipulate nucleation and crystal growth. Nowadays, a broad range of soft materials can be formed into nanotubes utilizing nanoporous hard templates containing arrays of self-ordered cylindrical nanopores. Understanding the crystallization, thermodynamics, and dynamics of soft materials under confinement allows for their rational design as functional devices with tunable mechanical strength, processability, and electronic and optical properties. The principal focus of this lecture is finding the basic underlying principles that give rise to nucleation and crystal growth in a range of soft materials (crystallizable polymers, amphiphilic molecules, liquid crystals, low-molecular-weight liquids, and biopolymers) under hard confinement. The confining geometry is also important since curvature affects Laplace pressure. In this context, we provide a detailed analysis of the impact of compartmentalization, space, curvature, interfacial interaction, and molecular weights on the nano-crystallization process.
Designing of PLA Biocomposites Filled with Biomass Resources for 3D Printing Applications
(Polymer Science and Technology Association & Middle East Technical University, 2024) Salamcı, Elifnaz; Yıldız, Tuğçe; Öçalan, Sude Pelin; Duran Durmuş, Hatice
Polylactic acid (PLA) stands out as one of the most preferred materials in 3D printing applications, but PLA loses its dimensional stability due to its low glass transition temperature and melting temperature. To modify the thermal and mechanical properties of PLA, composites of PLA and biomass materials obtained at varying amounts of recycled PLA (0.5 wt.%, 1 wt.%, 3 wt.%, and 5 wt.%) were prepared through the internal mixing method. The structural (GPC, FTIR, XRD, SEM) and thermal (TGA, DSC) characterizations of the composites were developed. It was observed that the addition of biomass enhances the thermal stability and degree of crystallinity of PLA. The SEM images revealed a uniform distribution of biomass within the PLA matrix. Surface modification will be performed in order to improve the interaction between PLA and biomass.
Thin Film and Surface Characterization with X-ray photoelectron spectroscopy (XPS)
(2024) Duran, Hatice
XPS, or X-ray Photoelectron Spectroscopy, is a technique used to analyze the chemical composition, chemical state, and electronic state of elements present in a material with high sensitivity to the surface. It measures elemental composition at the parts-per-thousand range and is able to provide information about the oxidation state of materials. In an upcoming lecture, I will cover the working principles, advantages, limitations, and application areas of this widely-used method in the analysis of surface chemical structure. I will also present examples of chemical analysis on different surfaces, such as metal, metal oxide, and polymer, to provide a better understanding of the subject.
Improving the Antimicrobial Properties of Polypropylene Meshes Used in Hernia Surgeries with Amine-Functional Polymer Coatings
(Polymer Science and Technology Association & Middle East Technical University, 2024) Özaydın, Hilal Meva; Kılıç, Yusuf Alper; Duran, Hatice
Polypropylene (PP) meshes utilized in hernia surgeries are prone to infection-related complications due to their inherent susceptibility to bacterial colonization. This study focuses on developing a method to functionalize PP meshes with specific amine-functional polymers (Poly(2-(dimethylamino)ethyl methacrylate) and poly[(dimethylaminoethyl methacrylate)-co-(ethyleneglycol dimethacrylate)]) to enhance their antimicrobial properties. The aim is to introduce positively charged amino groups onto the mesh surface, facilitating interaction with bacterial cell membranes, leading to bacterial cell death, and imparting antibacterial characteristics. The modified PP meshes were characterized using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), and Water Contact Angle (WCA) measurements. Antimicrobial activity of poly- DMAEMA and poly-DMAEMA-EGDMA (quaternary amine) coated PP meshes will be assessed using the agar diffusion method against both Gram-positive (Escherichia coli) and Gram-negative (Staphylococcus aureus) bacteria. This approach offers a promising solution to enhance postoperative healing by augmenting the antimicrobial properties of meshes employed in hernioplasty, thereby minimizing the risk of postoperative infections.
Investigating the Charge Transport Properties of Nucleic Acid Analogues with Density Functional Theory
(2023) Gültaktı, Çağlamaz Akın; Ören, Ersin Emre
In terrestrial organisms, DNA carries genetic information and plays roles in protein synthesis and evolution through mutations. Besides its importance in life, DNA is also a significant building block for nanotechnology applications, especially for molecular electronics with their self-assembly ability and tunable electronic conductivity. Even though they can act as transistors, rectifiers etc. with their electronic characteristics, integration of DNA to electronic devices have some difficulties within currently available technologies due to its unstable behavior in high temperatures (above ~70 oC). By using nucleic acid analogues, which have similar properties with DNA but have more structural stability in higher temperatures, we may overcome this limitation. Here, we showed that nucleic acid analogues can create different charge transport pathways by using molecular dynamics and DFT (Gaussian 09, B3LYP/631G(d,p)) calculations. First of all, the necessary force field parameters for the analogues are generated by using antechamber based on bsc1 and gaff force fields, and partial charges are calculated with DFT (Gaussian 09, B3LYP/6-31G(d,p)) for unknown parts of the nucleic acids. After the MD simulations, we classified the conformations with clustering algorithms among 50,000 different molecular structures. We select the representative conformation of each different cluster to see the effect of different conformations on the overall charge transport properties of the molecule. Our research shows that different conformations of the same molecule and the density of states in the electrode coupled region of the DNA affect the charge transport properties. We showed that modifying DNA with the analogues can decrease the conductance up to 10 times.
Detection of the Coordinates of the Bee Swarm in the Sky Through Image Processing
(2023) Karahan, Mehmet; Lacınkaya, Furkan; Inal, Mertcan; Dilmen, Alperen; Akay, Ahmet Nuri; Kasnakoğlu, Coşku
By scattering pollen to flowers, bees allow plants and trees to bear fruit and disperse their seeds. This important task of bees in life continues the oxygen cycle, which is vital for humans. To put it briefly, a large part of life on earth depends on bees doing their job. In recent years, there has been an annual decrease in the number of bee colonies. For this reason, it is of great importance to keep the bee population under control and to prevent its decline. In this study, the x and y coordinates of a bee swarm in the sky were obtained using the MATLAB program. For this purpose, erosion, one of the morphological image processing methods, was used. In this way, objects other than bees in the photograph used in image processing were removed. With the developed algorithm, the coordinates were determined in the photograph where only the bees were visible. The obtained coordinates are written on the command line of the MATLAB program. Thus, the instantaneous location of the bees could be determined properly.
Strategies To Prepare 2d Mxenes
(Springer Singapore, 2024) Yeltik, A.; Yilmaz, A.; Perkgoz, N.K.; Ay, F.; Rouhi, S.
MXenes have rapidly become a key focus in contemporary materials research, particularly because of their unique structural and electrical properties since their discovery. Consequently, they find application across various domains such as supercapacitors, batteries, and hydrogen storage. However, a significant challenge lies in optimizing existing methodologies or devising novel ones to enable high-quality, cost-effective, and scalable production, thereby broadening their potential applications. This section delves into the diverse range of top-down and bottom-up approaches employed for the production of 2D MXenes today. In addition to conventional wet-chemical synthesis methods, it elucidates innovative techniques like halogen etching, thermal reduction, UV-induced selective etching, and algae extraction, which have surfaced in recent years. Furthermore, it provides intricate insights into the optimization of process parameters within the chemical vapor deposition method utilized for synthesizing 2D MXenes. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.
Citation - Scopus: 4
Decarbonizing the Industry With Green Hydrogen
(Wiley, 2024) Altaf, C.T.; Demir, O.; Colak, T.O.; Karagöz, E.; Kurt, M.; Demirci Sankır, Nurdan; Sankır, Mehmet
Perseverance to reduce global greenhouse gas emissions and backward economic and ecological issues of excessive use of carbon-based fuels is more preponderant than any other environmental- related policies. In this respect, hydrogen (H2) appears to be a revolutionary in decarbonizing the common and energy-intensive industrial applications along with its use in transportation. Nations agree to explore a diverse range of innovations to integrate green H2 into the common industrial plants. Energy-intensive industrial sectors emitting large amounts of carbon dioxide (CO2) annually need widespread analysis and investigations to reform the adaptation to carbon-neutral resources. This chapter plunges into these energy-intensive, yet crucial for human needs, applications such as ammonia (NH3), iron/steel, cement, and oil refining. These sectors can be assisted with green H2 as an energy source with its high energy density and as a potential carbon-neutral feedstock for the chemical industry. © 2024 Scrivener Publishing LLC.
Citation - Scopus: 1
Towards Green Hydrogen Generation
(wiley, 2024) Sankır, Mehmet; Demirci Sankır, Nurdan
Readers will find a multidisciplinary approach elucidating all the important features of green hydrogen so that science researchers and energy engineers as well as those in economics, political science and international relations, will also find value. Energy sources and generation is the foremost concern of all governments, NGOs, and activist groups. With Green New Deals and reduced or net zero emission goals being implemented on a global scale, the quest for economic, scalable, efficient, and sustainable energy systems has reached a fever pitch. No one energy source ticks all the boxes and new energy technologies are being developed all the time as potential disruptors. Enter green hydrogen with zero emissions. Hydrogen is a rare gas in nature and is often found together with natural gas. While hydrogen is the most abundant element in the known universe, molecular hydrogen is very rare in nature and needs to be produced-and produced in large quantities, if we are serious about the Green Deal. This book has been organized into three parts to introduce and discuss these crucial topics. Part I discusses the Green Deal and the current state and challenges encountered in the industrialization of green hydrogen production, as well as related politics. Chapters in this section include how to decarbonize the energy industry with green hydrogen, and one that describes a gradual shift in the approach of hydrogen production technologies from non-renewable to renewable. Part II is devoted to carbon capturing and hydrogen. Chapters on biomass mass waste-to-hydrogen conversion and related efficient and sustainable hydrogen storage pathways, life cycle assessment for eco-design of biohydrogen factory by microalgae, and metal oxide-based carbon capture technologies are all addressed in this section. The third and final part of the book was designed to present all features of green hydrogen generation. Chapters include PEM water electrolysis and other electrolyzers, wind-driven hydrogen production, and bifunctional electrocatalysts-driven hybrid water splitting, are introduced and thoroughly discussed. Audience: This book is directed to researchers and industry professionals in energy engineering, chemistry, physics, materials science, and chemical engineering, as well as energy policymakers, energy economists, and others in the social sciences. © 2024 Scrivener Publishing LLC.
Citation - WoS: 11
Citation - Scopus: 10
Solar-Driven Calcination of Clays for Sustainable Zeolite Production: Co2 Capture Performance at Ambient Conditions
(Elsevier Sci Ltd, 2024) Pasabeyoglu, Pelin; Deniz, Erdem; Moumin, Gkiokchan; Say, Zafer; Akata, Burcu
This study presents the environmentally sustainable synthesis of zeolites from solar-calcined kaolin and halloysite, emphasizing their application in CO2 capture due to their distinctive porous structures and chemical attributes. Expanding upon prior research that utilized solar energy for kaolin calcination, we now explore halloysite as an alternative clay mineral for zeolite production and CO2 capture. Employing a solar simulator, halloysite was calcined at temperatures ranging from 700 to 1000 degrees C, resulting in the synthesis of zeolites 4A and 13X via hydrothermal methods. The synthesized zeolites were characterized using X-ray diffraction (XRD), low angle XRD (LA-XRD), transmission electron microscopy (TEM), and field-emission scanning electron microscopy (FE-SEM), and Brunauer-Emmett-Teller (BET) surface area measurements. Notably, the presence of Al-Si spinel, which crystallizes at elevated solar calcination temperatures, persisted within the zeolite 13X matrix, inducing a secondary mesoporous phase. The observed hysteresis in 13X samples, rather than confirming the mesoporous character of zeolite 13X, indicates a tandem effect of mesoporous Al-Si spinel with microporous zeolite 13X, exemplifying systems known as micro/mesoporous zeolitic composites (MZCs). The correlation obtained between the interplanar distances calculated from LA-XRD and pore size distributions acquired from the BJH desorption branches highlights LA-XRD as an alternative analysis method for assessing mesoporosity. While the microporosity of Al-Si spinel possessing 13X samples positively correlates with CO2 capture performance, mesoporosity appears to have minimal impact. Among the zeolites synthesized using solar energy, zeolite 4A (LTA) demonstrates superior CO2 capture capability, achieving an adsorption capacity of 2.15 mmol/g at 25 degrees C and 1 bar. This study highlights the potential of solar energy in producing eco-friendly zeolites from kaolin and halloysite for improved CO2 capture, advancing sustainable environmental solutions.
Alternative Scenarios for the Lhc Based Electron-Proton Collider
(Tubitak Scientific & Technological Research Council Turkey, 2024) Akay, Ahmet Nuri; Dagli, Burak; Ketenoglu, Bora; Ozturk, Arif; Sultansoy, Saleh
Construction of the ERLC (twin LC) collider tangential to LHC will allow investigating ep collisions at essentially higher center-of-mass energies than ERL-50 and LHC based ep collider. Luminosity estimations show that values well exceeding 10 34 cm-2s-1 - 2 s - 1 can be achieved for ERLC and HL-LHC based ep colliders. Certainly, proposed ep colliders have great potential for clarifying QCD basics and new physics search in addition to providing precise PDFs for adequate interpretation of the LHC experimental data. Another alternative to the ERL-50 is to construct an e-ring with the same energy and length. In this case, luminosity of order 1034cm-2s-1 34 cm - 2 s - 1 can be reached. The advantage of this option is that the mu -ring can be installed instead of the e-ring as a next stage, which will allow to reach a much higher center of mass energy.
Citation - WoS: 1
Citation - Scopus: 1
Transformation of Fly Ash-Based Oxide Particles Into a Functional Silica-Alumina Aerogel and Its Potential Application as an Anti-Icing Surface
(Amer Chemical Soc, 2024) Bedir, Esra; Çitoğlu, Senem; Duran, Hatice
Lightweight, surface hydrophobic, highly insulating, and long-lasting aerogels are required for energy conservation and ice-repellent applications. Here, we present the conversion of fly ash to a silica-alumina aerogel (SAA) by utilizing its high silica content. The extracted silica component replaces expensive precursors typically used in conventional aerogel production. Ice adhesion performance was compared to that of polypropylene (PP), an insulating commodity polymer. First, we removed some salt impurities and heavy metals via water and alkaline washing protocols. Then, we produced SAA via the ambient pressure drying method by using trimethylchlorosilane (TMCS) as an adhesion promoter. The newly produced SAA has a surface area of 810 m(2) g(-1) and shows hydrophobic properties with a contact angle of 140 +/- 5 degrees. The thermal conductivity of SAA is 0.0238 W m(-1) K-1 with C-P = 1.1922 MJ m(-3) K-1. The ice adhesion strength of the PP substrate was calculated as 188.30 +/- 51.24 kPa, while the ice adhesion strength of the SAA was measured as 1.21 +/- 0.40 kPa, which was about 150 times lower than that of PP. This indicated that SAA had icephobic properties since ice adhesion strength was less than 10 kPa. This study demonstrates that fly ash-based SAA can be utilized as an economical material with a large surface area and exceptional thermal insulation capacity and is free of harmful compounds (heavy metals), making it potentially suitable as an anti-ice thermal insulation material.
Citation - WoS: 2
Citation - Scopus: 2
Muon Ring and Fcc-ee/Cepc Based Antimuon-Electron Colliders
(Institute of Physics, 2024) Akturk, D.; Dagli, B.; Sultansoy, S.
Recently, the construction of an antimuon-electron collider, μTRISTAN, at KEK has been proposed. We argue that the construction of a similar muon ring tangential to FCC-ee and CEPC will give an opportunity to realize antimuon-electron collisions at higher center-of-mass energies. Moreover, the same ring may be used later to realize energy-frontier antimuon-proton colliders based on FCC-pp and SppC. Similarly, the change of the electron ring in the μTRISTAN project into the proton ring will give the opportunity to investigate lepton-hadron collisions at ∼2 TeV center-of-mass energies. In this paper the main parameters of the proposed colliders have been studied. It is shown that sufficiently high luminosities can be achieved for all proposals under consideration. Copyright © 2024 The author(s)
Design and Production of Mesh Patterned Photoelectrode With Maskless Laser Lithography and Device Performance of Perovskite Derived/Zno Nras Based Photodetector
(Springer, 2024) Eroğlu, Ayşe Nur; Altaf, Çiğdem Tuç; Demirci Sankır, Nurdan; Sankır, Mehmet
This study reports the design and fabrication of environmentally friendly, portable, robust, and stable self-powered photoelectrochemical photodetector (PEC-PD) devices based on the heterojunction of ZnO nanorod arrays (NRA) in a mesh pattern and inorganic halide perovskites (IHP). First, the effects of distance between the center of lines in a mesh pattern on the material properties and device performance were revealed. The mesh patterned ZnO NRAs-based PEC-PD device exhibited a fast response time (tau rise/tau decay = 100/75 ms) under UV-light illumination with 367 nm of wavelength at no applied bias. The best-performing mesh pattern was then used as a sub-layer for lead-based CsPbBr3-CsPb2Br5 dual-phase and lead-free Cs2AgBiBr6 double perovskite to construct self-powered p-n junction and PEC-PD devices. Upon the deposition of Cs2AgBiBr6, the maximum photocurrent value was enhanced about 13.65 times as compared to mesh patterned pristine ZnO NRAs under AM 1.5 illumination at + 5 V of applied potential. Responsivity (RS) and Detectivity (D*) values of the mesh patterned pristine ZnO NRAs-based PD have been increased from 0.24 mAW-1 and 3.0 x 108 Jones to 3.08 mAW-1 and 7.63 x 108 Jones with Cs2AgBiBr6 layer, respectively. Furthermore, 69.18 mAW-1 of RS and 1.71 x 1010 Jones of D* value have been observed at 382 nm wavelength and + 5 V for mesh patterned ZnO NRAs/Cs2AgBiBr6 photoelectrode.
Citation - WoS: 1
Citation - Scopus: 1
Silica Nanoparticles Tailored With a Molecularly Imprinted Copolymer Layer as a Highly Selective Biorecognition Element
(Wiley-V C H Verlag Gmbh, 2024) Oluz, Zehra; Yazlak, Mustafa Gokturk; Kursun, Tugana Talya; Nayab, Sana; Glasser, Günnar; Yameen, Basit; Duran, Hatice
Molecularly imprinted silica nanoparticles (SP-MIP) are synthesized for the real-time optical detection of low-molecular-weight compounds. Azo-initiator-modified silica beads are functionalized through reversible addition-fragmentation chain transfer (RAFT) polymerization, which leads to efficient control of the grafted layer. The copolymerization of methacrylic acid (MAA) and ethylene glycol dimethacrylate (EDMA) on azo initiator-coated silica particles (approximate to 100 nm) using chain transfer agent (2-phenylprop-2-yl-dithiobenzoate) is carried out in the presence of a target analyte molecule (l-Boc-phenylalanine anilide, l-BFA). The chemical and morphological properties of SP-MIP are characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller surface analysis, and thermogravimetric analysis. Finally, SP-MIP is located on the gold surface to be used as a biorecognition layer on the surface plasmon resonance spectrometer (SPR). The sensitivity, response time, and selectivity of SP-MIP are investigated by three similar analogous molecules (l-Boc-Tryptophan, l-Boc-Tyrosine, and l-Boc-Phenylalanine) and the imprinted particle surface showed excellent relative selectivity toward l-Boc-Phenylalanine (l-BFA) (k = 61), while the sensitivity is recorded as limit of detection = 1.72 x 10(-4) m.
Citation - WoS: 3
Citation - Scopus: 3
Dialoxygenation: a Preclinical Trial for Transforming the Artificial Kidney Into an Oxygenator
(Lippincott Williams & Wilkins, 2025) Karacanoglu, Dilek; Bedir, Esra; Nakip, Ozlem Saritas; Kesici, Selman; Duran, Hatice; Bayrakci, Benan
Critically ill patients sometimes require tandem application of extracorporeal membrane oxygenation (ECMO) and continuous renal replacement therapy (CRRT) which is easier and cheaper. We aimed to transform the kidney membrane into a lung membrane by adding hydrogen peroxide (H2O2) to the dialysate as the oxygen source. A solution containing H2O2 and a dialysate fluid mixture was used as the final dialysate. Starting with 100% H2O2 solution and gradually reducing the volume of H2O2, respectively: 50%, 10%, 5%, 4%, 3%, 2%, and 1%. PRISMAFLEX system, Prismaflex M60 set and a bag of packed red blood cells (pRBCs) were the prototype. blood flow rate was about 40 ml/minute and the dialysis rate was about 200 ml/m2/minute/1.73 m2. blood sampling times were; at the beginning (T0), at 15th (T1), 30th (T2), 60th (T3) minutes. Amongst eight attempts H2O2 concentration that increased the partial oxygen pressure (pO2) level significantly in a reasonable period, without any bubbles, was 3%. Methemoglobinemia was not observed in any trial. After the test with 3%, H2O2 in the dialysate fluid decreased progressively without any H2O2 detection at post-membrane blood. Three percent H2O2 solution is sufficient and safe for oxygenation in CRRT systems. With this new oxy-dialysate solution, both pulmonary and renal replacement can be possible via a single membrane in a simpler manner.
Citation - WoS: 11
Citation - Scopus: 14
Zinc Oxide Nanoflake/Reduced Graphene Oxide Nanocomposite-Based Dual-Acting Electrodes for Solar-Assisted Supercapacitor Applications
(Royal Soc Chemistry, 2024) Altaf, Cigdem Tuc; Colak, Tuluhan Olcayto; Rostas, Arpad Mihai; Socaci, Crina; Lazar, Mihaela Diana; Demirci Sankır, Nurdan; Sankır, Mehmet
There is an ever-growing requirement for systems that enable both conversion and storage of solar energy in the same device, thereby reducing the need for grid electricity and fossil fuels. Although photo-supercapacitors (PSCs) potentially meet this requirement, it is essential to develop high-performance devices in which conversion and storage can be achieved on the same electrode. This study investigated two-electrode PSC systems based on three-dimensional (3D) zinc oxide (ZnO) nanoflakes/reduced graphene oxide (rGO) nanocomposites to meet the need for in situ solar energy conversion/storage. To better understand the effect of rGO and 3D ZnO nanoflakes separately, three different compositions have been studied, in which the weight percent of rGO changes from 8 to 32%. The energy density increases as the amount of rGO increases, but the composite material loses its light sensitivity above a critical value. Therefore, the electrodes containing 16% rGO exhibited higher performance than those containing 32% and 8% rGO. As a result, the (16%) rGO/ZnO-based PSC exhibited superior performance compared to the other samples, with its ability to maintain 100% of its performance at 40 000 cycles, its areal capacitance of 40 mF cm-2 and energy density values of 22 mu W h cm-2, which were 170% higher than under dark condition measurements. There is an ever-growing requirement for systems that enable both conversion and storage of solar energy in the same device, thereby reducing the need for grid electricity and fossil fuels.
Citation - WoS: 3
Citation - Scopus: 2
Flexible Self-Powered Manganese Doped Zinc Oxide Nanorod and Perovskite Quasi-Solid State Uv-Photodetector With Excellent Stability and High Performance
(Elsevier Science Sa, 2024) Karagoz, Emine; Altaf, Cigdem Tuc; Sankir, Nurdan Demirci; Sankir, Mehmet
Flexible, self-powered, and fast-responsive photoelectrochemical photodetector (PEC-PD) devices are needed in optoelectronic applications. Although the PD devices constructed from heterojunction of zinc oxide (ZnO) and inorganic halide perovskite (CsPbBr3)-type perovskite displayed astonishing performance in the field, the sensitivity of the perovskite layer to environmental conditions restricts the wide application. Herein, we present a study for the preparation of a wide light spectrum (367-499 nm) sensitive PEC-PD devices built from the heterostructure of Mn-doped ZnO nanorod (ZnONR) and CsPbBr3 on both rigid and flexible substrates using ionic conductive polymer electrolyte. The PEC-PD performance parameters of the self-powered PEC-PD device such as responsivity (R), Detectivity (D*), and sensitivity (S%) have been calculated as 95.12 mAW-1, 2.83x1012 Jones and 8.04x106%, respectively. In addition to these parameters, the fast light response for rise/decay time (tau rise/ tau decay) which is an important parameter for PD applications was (10.62 ms/42.9 ms) observed. The resulting PEC-PD device demonstrated durability over 2500 cycles under simulated sunlight and upon 500 bending cycles at different angles.
A Fabrication Method for Memristors With Graphene Top Electrodes and Their Characterization
(2024) Onay, Selin; Çayla, Ömer R.; Büke, Göknur; Köymen, Itır
In recent years, there has been extensive research on the memristor, a non-volatile memory device that demonstrates effective emulation of biological synapses. The implementation of graphene as a top electrode in memristive switching systems presents an intriguing alterna- tive to conventional materials such as Platinum. Graphene, as a carbon-derived material, pos- sesses a remarkable area- to-volume ratio, biocompatibility, adsorption capabilities, and high electrical conductivity and thereby offers a promising avenue for the fabrication of biosen- sors with superior characteristics. This study reports a novel fabrication method of utilizing graphene as a top electrode in memristive devices. Characterization results of micrometric devices as well as larger memristive devices are also discussed. Larger devices show promising results to be used as memristive sensors. Microstructures have been fabricated successfully through developing a process flow and patterning graphene using photolithography and lift- off. E-beam evaporation and sputtering were used for depositing bottom metal electrodes and active layer respectively. Graphene was produced using the chemical vapor deposition (CVD) method and subsequently transferred using the fishing technique. Ultimately Pt/ TiO2/TiOx/Graphene memristive devices were fabricated.

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