Yıldız, Ümit Hakan
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Yildiz, U. Hakan
Yildiz, U.
Yildiz, U. H.
Yildiz, Umit Hakan
Yıldız, Ü. Hakan
Yıldız, Ü. H.
Yıldız, Ü.
Yildiz, Ümit Hakan
Yildiz, U.
Yildiz, U. H.
Yildiz, Umit Hakan
Yıldız, Ü. Hakan
Yıldız, Ü. H.
Yıldız, Ü.
Yildiz, Ümit Hakan
Job Title
Email Address
hakanyildiz@iyte.edu.tr
Main Affiliation
04.01. Department of Chemistry
Status
Current Staff
ORCID ID
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WoS Researcher ID
Sustainable Development Goals
1NO POVERTY
0
Research Products
2ZERO HUNGER
1
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3GOOD HEALTH AND WELL-BEING
11
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4QUALITY EDUCATION
1
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5GENDER EQUALITY
0
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6CLEAN WATER AND SANITATION
4
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7AFFORDABLE AND CLEAN ENERGY
12
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8DECENT WORK AND ECONOMIC GROWTH
1
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9INDUSTRY, INNOVATION AND INFRASTRUCTURE
21
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10REDUCED INEQUALITIES
0
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11SUSTAINABLE CITIES AND COMMUNITIES
0
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12RESPONSIBLE CONSUMPTION AND PRODUCTION
4
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13CLIMATE ACTION
10
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14LIFE BELOW WATER
1
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15LIFE ON LAND
0
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16PEACE, JUSTICE AND STRONG INSTITUTIONS
0
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17PARTNERSHIPS FOR THE GOALS
0
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Documents
67
Citations
1252
h-index
20
This researcher does not have a WoS ID.
Scholarly Output
79
Articles
47
Views / Downloads
158565/26183
Supervised MSc Theses
16
Supervised PhD Theses
6
WoS Citation Count
646
Scopus Citation Count
703
Patents
0
Projects
8
WoS Citations per Publication
8.18
Scopus Citations per Publication
8.90
Open Access Source
48
Supervised Theses
22
| Journal | Count |
|---|---|
| ACS Applied Materials & Interfaces | 4 |
| Sensors and Actuators, B: Chemical | 3 |
| International Journal of Biological Macromolecules | 3 |
| Analytica Chimica Acta | 2 |
| Analytical Chemistry | 2 |
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79 results
Scholarly Output Search Results
Now showing 1 - 10 of 79
Article Citation - WoS: 19Citation - Scopus: 19Visual Detection of Al3+ Ions Using Conjugated Copolymer-Atp Supramolecular Complex(Elsevier Ltd., 2016) Tu, Meng-Che; Rajwar, Deepa; Ammanath, Gopal; Alagappan, Palaniappan; Yıldız, Ümit Hakan; Liedberg, BoA colorimetric Al3+ sensor based on fluorescence recovery of a conjugated copolymer-ATP complex is proposed. An optimized ratio of two polythiophene (PT) monomers is utilized to synthesize copolymer (CP) that yielded maximized colorimetric response for Al3+ in deionized (DI) and tap water. The electrostatic disassembly of CP-ATP upon addition of Al3+ led to an evident visual color change. The lowest concentration of Al3+ for naked eye observation is around 4 μM, which is below the threshold levels in drinking water according to European Economic Community (EEC) standard. Besides, the proposed assay showed a similar response to Al3+ in tap water. The proposed methodology showed selective and sensitive detection for Al3+ in analytically relevant concentration ranges without involving sophisticated instrumentation, illustrating the applicability for on-site drinking water monitoring.Article Cryofixation Strategy for Fabrication of Robust Gelatin-Polyester Conductive Biocomposites(Taylor & Francis Inc, 2026) Koksal, Busra; Onder, Ahmet; Yildiz, Umit HakanThe development of mechanically robust and electroconductive biomaterials is critical for advancing tissue engineering strategies, particularly in neural, cardiac and musculoskeletal applications. Here, we report a polycaprolactone (PCL)-gelatin conductive polymer (poly(3,4-ethylenedioxythiophene):polystyrene sulfonate, PEDOT:PSS) biocomposite with tunable mechanical and electrical properties, fabricated via the cryofixation process relying on rapid reaction between isocyanate-terminated PCL, gelatin and PEDOT:PSS. Two isocyanate sources, hexamethylene diisocyanate (HDI) or isophorone diisocyanate (IPDI) were employed to obtain reactive end-functionalized PCLHDI and PCLIPDI. The cryofixation (at -18 degrees C) of PCLHDI or PCLIPDI, gelatin and PEDOT:PSS was found to occur in unfrozen microdomains and enabled the resultant gel with an inherited network of ice, thereby increasing porosity. Electroconductivity was introduced via the incorporation of PEDOT:PSS, yielding conductive cryogels with porous morphology. The resulting scaffolds exhibited a Young's modulus of 637 Pa and electrical conductivity of 197 mu S/cm, alongside biocompatible nature of gelatin-based gels. This multifunctional platform offers significant promise for the engineering of electrically active tissues.Conference Object Citation - WoS: 3Citation - Scopus: 3Halloysite Nanotube Loaded Polyamide Nanocomposites: Structural, Morphological, Mechanical, Thermal and Processing Behaviors(American Institute of Physics, 2023) Akar, Alinda Öykü; Yıldız, Ümit Hakan; Tayfun, ÜmitIn this study, the polyamide 6 (PA) matrix was reinforced with the purified, fine ground and amino-silane treated halloysite nanotubes (HNT) at different concentrations. The preparation of composites was carried out using a lab-scale twin-screw micro-compounder with loading ratios at 0.5, 1, 3, and 20% by weight, and the test samples were prepared by the injection-molding process. According to mechanical test results, additions of HNT to the PA matrix caused slight improvements in tensile strength and Youngs' modulus parameters. The optimum concentrations for all of the additives used were estimated by comparison of mechanical test data. The addition of aminosilane-modified HNT resulted in a higher impact performance at high loading levels up to 3% concentrations. Further addition of HNT caused a reduction in the mechanical parameters of composites. Thermal studies revealed that the glass transition temperature of PA shifted to higher values after HNT mineral inclusions. Thermo-mechanical results showed that storage moduli of PA exhibited improvement with an increase in HNT content. The distributions of HNT clay into the PA phase were visualized with SEM images. Based on these observations, a high level of dispersion homogeneity was achieved for lower filling ratios. According to melt-flow and force measurements, composites filled with 20% of HNT displayed a remarkable increase in exerted force during melt-blending. © 2023 Author(s).Master Thesis Investigation of Ion Transport Properties of Organic Electrochemical Transistors(01. Izmir Institute of Technology, 2022) Küçüktartar, Tuğçe; Yıldız, Ümit HakanOrganic electrochemical transistors (OECTs) comprise large amplification in current response while operating at low voltages and have high transconductance due to its volumetric capacitance created by ion injection from electrolyte through the whole organic semiconductor channel. OECTs are switchable by doping and de-doping of active channel via application of positive or negative gate bias. One of the most common organic material for OECTs is the conductive polymer, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). PEDOT:PSS offers prominent advances because of their coupled electronic and ionic conductance, morphology and optical properties. Although the complex working principle of OECT has been tried to be elaborated with several models in literature, the conduction of ions and electrons in the channel has not been fully elucidated. In this thesis, the transformations between un-doped, doped and de-doped state investigated systematically based on the electrical (OECT), structural and morphological characterization of PEDOT:PSS thin film. Measurements were conducted with different dopant molecules and the repeatability of the device was investigated. As a result, the most stable drain and gate voltage range in which the device works has been determined. In addition, the X-ray photoelectron spectroscopy (XPS) investigation performed which is revealed that the density of the bipolaron formation of PEDOT:PSS in the doped state increase as compared to its natural form in the de-doped state. XPS mapping on OECT devices suggested that ions migration is homogeneously generated by applied bias.Article Citation - WoS: 43Citation - Scopus: 46Glucuronoxylan-Based Quince Seed Hydrogel: a Promising Scaffold for Tissue Engineering Applications(Elsevier, 2021) Güzelgülgen, Meltem; Özkendir İnanç, Dilce; Yıldız, Ümit Hakan; Arslan Yıldız, AhuNatural gums and mucilages from plant-derived polysaccharides are potential candidates for a tissue-engineering scaffold by their ability of gelation and biocompatibility. Herein, we utilized Glucuron-oxylanbased quince seed hydrogel (QSH) as a scaffold for tissue engineering applications. Optimization of QSH gelation was conducted by varying QSH and crosslinker glutaraldehyde (GTA) concentrations. Structural characterization of QSH was done by Fourier Transform Infrared Spectroscopy (MR). Furthermore, morphological and mechanical investigation of QSH was performed by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The protein adsorption test revealed the suitability of QSH for cell attachment. Biocompatibility of QSH was confirmed by culturing NIH-3T3 mouse fibroblast cells on it. Cell viability and proliferation results revealed that optimum parameters for cell viability were 2 mg mi(-1)of QSH and 0.03 M GTA. SEM and DAPI staining results indicated the formation of spheroids with a diameter of approximately 300 pm. Furthermore, formation of extracellular matrix (ECM) microenvironment was confirmed with the Collagen Type-I staining. Here, it was demonstrated that the fabricated QSH is a promising scaffold for 3D cell culture and tissue engineering applications provided by its highly porous structure, remarkable swelling capacity and high biocompatibility. (C) 2021 Published by Elsevier B.V.Article Citation - WoS: 35Citation - Scopus: 44Current Trends and Challenges in Point-Of Urinalysis of Biomarkers in Trace Amounts(Elsevier, 2022) Yeasmin, Sanjida; Ammanath, Gopal; Önder, Ahmet; Yan, Evelias; Yıldız, Ümit Hakan; Palaniappan, Alagappan; Liedberg, BoUrinalysis enables non-invasive point-of-care (POC) testing of numerous biomarkers at their physiological and elevated levels, obviating the need for sophisticated equipment or trained personnel. POC urinalysis is used to identify biomarkers that are rich in urine (greater than 1 μM), such as lactate, uric acid, glucose, ions, and adenosine. Urine also contains biomarkers such as small molecules, nucleic acids, neurotransmitters, and drugs in trace amounts (less than 1 μM). These biomarkers are of significant importance for health care monitoring, diagnosis of various disorders (cancer, metabolic diseases, etc.) and illicit drug control (cocaine, steroids, etc.). While POC detection of urinary biomarkers at higher concentration (μM to mM) levels is feasible, direct assaying of biomarkers in nM to fM levels is challenging, as assay responses are typically masked by interferences from the urine sample matrix. This report is a consolidated review of emerging trends and challenges in the POC urinalysis for detecting biomarkers that are less abundant in urine. The sensing mechanisms, analytical device fabrication, discrete and integrated sample pre-treatment procedures for POC assaying of urinary markers in trace amounts are elaborated. Subsequently, the utilization of smart data analytics for facilitating personalized urinalysis is presented. A comprehensive outlook on associated challenges in POC urinalysis of biomarkers in trace amounts is further provided, which would facilitate the advancement of POC urinalysis for a wide range of healthcare applications.Article Citation - WoS: 7Citation - Scopus: 7A Perspective on Polythiophenes as Conformation Dependent Optical Reporters for Label-Free Bioanalytics(American Chemical Society, 2022) Sinsinbar, Gaurav; Palaniappan, Alagappan; Yıldız, Ümit Hakan; Liedberg, BoPoly(3-alkylthiophene) (PT)-based conjugated polyelectrolytes (CPEs) constitute an important class of responsive polymers with excellent optical properties. The electrostatic interactions between PTs and target analytes trigger complexation and concomitant conformational changes of the PT backbones that produce distinct optical responses. These conformation-induced optical responses of the PTs enable them to be utilized as reporters for detection of various analytes by employing simple UV-vis spectrophotometry or the naked eye. Numerous PTs with unique pendant groups have been synthesized to tailor their interactions with analytes such as nucleotides, ions, surfactants, proteins, and bacterial and viral pathogens. In this perspective, we discuss PT-target analyte complexation for bioanalytical applications and highlight recent advancements in point-of-care and field deployable assays. Subsequently, we highlight a few areas of critical importance for future applications of PTs as reporters, including (i) design and synthesis of specific PTs to advance the understanding of the mechanisms of interaction with target analytes, (ii) using arrays of PTs and linear discriminant analysis for selective and specific detection of target analytes, (iii) translation of conventional homogeneous solution-based assays into heterogeneous membrane-based assay formats, and finally (iv) the potential of using PT as an alternative to conjugated polymer nanoparticles and dots in bioimaging.Doctoral Thesis Characterization of Conjugated Polyelectrolytes for Nucleic Acid Sensing, Gene Delivery and Imaging(01. Izmir Institute of Technology, 2022) Yücel, Müge; Yıldız, Ümit Hakan; Yıldız, Ümit HakanIn this thesis, cationic derivatives of poly(3-alkylmethoxythiophene) (PT) which are a class of conjugated polyelectrolytes (CPE), have been synthesized. PT has been polymerized via FeCl3 oxidative polymerization, were treated in a set of solvents to elaborate coil conformation of polymer chain in different physicochemical environment. Spectroscopic and scattering techniques have ascertained that ethylene glycol is a good solvent for PT regarding Flory-Huggins theory. The smaller interaction parameter of PT with respect to ethylene glycol than water drives a thermodynamically driven ultra-small particle (Pdot) formation in aqueous phase by a rapid nanophase separation between PTrich ethylene glycol and PT-poor water phase. All CPEs have been then employed to prepare single polymer chain polymer dots (Pdot) by “nanophase separation” method. As a next step, Pdots have been characterized in terms of optical and colloidal properties that they possess in the backbone conformations altered by solvation effect. Regarding their colloidal characteristic, translocation of Pdot into cancerous cells was analyzed compared to healthy cells by 2D cell culture and co-culture studies. It has reported that Pdots have ability to penetrate through nuclear envelope in hepatocellular carcinoma whereas accumulate around nucleus of healthy liver cells in cytoplasm. Additionally, Pdots were studied in breast cancer cell lines to understand the behavior of Pdot staining in 2D cell culture of invasive and non-invasive breast cancer types. The findings suggest that Pdots are prone to penetrate into the invasive cancerous cells attributed to the greater deformations on nucleus membrane of triple negative breast cancer cells. In a next application, the enhanced photophysical property of PT exhibited in ethylene glycol media allows PT to be utilized as a fluorescent probe for determination of single nucleotide polymorphism by a non-amplification-based protocol. Fluorescence emission at specific wavelengths resulted from very distinct conformations of PT chain is the key elements for the SNP detection assay. The evaluation of optical data obtained from the probe with principal component analysis proves the separation of healthy individuals from patients with an overall 96% accuracy.Article Citation - WoS: 11Citation - Scopus: 12Colorimetric and Fluorometric Profiling of Advanced Glycation End Products(American Chemical Society, 2022) Ammanath, Gopal; Delachi, Carla Giorgia; Karabacak, Soner; Ali, Yusuf; Boehm, Bernhard O.; Yıldız, Ümit Hakan; Alagappan, Palaniappan; Liedberg, BoProfiling of advanced glycation end products (AGEs) is an emerging area of clinical significance for disease diagnosis and prognosis. Typically, concentrations of AGEs are estimated in laboratories by trained personnel using sophisticated equipment. Herein, a facile approach for colorimetric and fluorometric profiling of AGEs is reported for rapid and on-site analysis. The concentrations of AGE levels in plasma are estimated via changes in optical properties of polythiophenes (PTs) upon interaction with aptamers (Apts) in the presence and in the absence of AGEs. To validate the proposed approach, glyceraldehyde-derived AGEs (AGE class 1 [AGE1]), the biomarker associated with cardiovascular diseases and diabetes, are used as a model system. Colorimetric analysis yielded linear responses for AGE1 for clinically relevant concentration ranges between 1.5 and 300 μg/mL with a limit of detection (LOD) of ∼1.3 μg/mL. Subsequently, an approach utilizing PTs with four different pendant groups in conjunction with four different Apts is demonstrated for qualitative colorimetric profiling and for quantitative fluorometric profiling of up to four AGEs in clinical matrices. Principal component analysis (PCA) of fluorometric responses of AGE-spiked samples yielded distinct responses for the different AGEs tested. Thus, the proposed approach ascertains rapid profiling of spiked AGEs in plasma samples without the requirement of preanalytical processing and advanced instrumentation, thereby facilitating on-site diagnosis.Article Citation - WoS: 6Citation - Scopus: 7Utilization of Electrospun Polystyrene Membranes as a Preliminary Step for Rapid Diagnosis(John Wiley and Sons Inc., 2016) Işık, Tuğba; Horzum, Nesrin; Yıldız, Ümit Hakan; Liedberg, Bo; Demir, Mustafa MuammerRecent advances in clinical practice drive deoxyribonucleic acid (DNA) as an important class of biomarker. Monitoring the change in their concentration suggests the initiation and/or progression of various disorders. However, low quantity of DNA biomarkers in body fluids requires a delicate isolation methodology that provides efficient separation and easy handling. This study describes a newer-generation separation technology relying on electrospun fibers of sub-micrometer diameter of a commodity polymer for DNA biomarkers in simulative serum. Fibrous polystyrene membranes are prepared by electrospinning and they are subjected to post-modification with Au. The composite membranes may provide a convenient environment for the removal of bovine serum albumin (BSA) from BSA and DNA mixtures. The eluent can be used as an efficient tool for detection of DNA biomarkers associated with diagnosis of numerous life-threatening diseases.