Browsing by Author "Akdoğan, Yaşar"

Now showing 1 - 16 of 16

Adhesion of dopa functionalized gels to spin labeled surfaces
(Izmir Institute of Technology, 2017-07) Göksel, Yaman; Akdoğan, Yaşar; Emrullahoğlu, Mustafa
This study investigates the force free adhesive properties of synthetic polymer in aqueous media using electron paramagnetic resonance (EPR) spectroscopy. Due to poor performance of commercial adhesives in wet environments, scientists are interested in different types of adhesives to overcome this difficulty. On this context, mussels attract attention because of their versatile properties to adhere different types of surfaces from rocks to ship hulls underwater. Adhesion occurs when mussel secretes mussel foot proteins (MFPs) in order to form threads and plaques. Seven types of MFPs are unique in plaque contains high amount of L-3,4-dihydroxyphenylalanine (DOPA) amino acid which is reputed to be responsible for adhesion. In this research, branched polyethylene glycol (PEG) based polymers functionalized with DOPA were synthesized and their force-free adhesive properties to hydrophobic polystyrene and hydrophilic silica nanobeads were investigated in solution. These nanobead surfaces were conjugated with spin label molecules to probe adhesion dynamics using EPR spectroscopy. In addition, gel forms of polymers obtained using NaIO4, FeCl3 and Cr2O7 were used as adhesive materials for EPR measurements. All of these adhesive materials showed adhesion to spin labeled polystyrene (SL-PS) surface. However, non-DOPA containing PEG showed no indication of adhesion thus, demonstrating the importance of DOPA in wet adhesion. In addition, EPR results showed that DOPA based PEG polymers were unable to adhere to spin labeled silica (SL-SiO2) surface. This behavior was attributed to hydration layers around silica nanobeads. These layers formed around hydrophilic SiO2 surface prevent interaction between nanobead surface and polymeric material.
BaTiO3 based ferroelectric materials for electrocaloric cooling applications
(Izmir Institute of Technology, 2018-12) Şanlı, Keriman; Adem, Umut; Akdoğan, Yaşar
The aim of this project was to produce electrocaloric materials and to determine the potential of these materials for electrocaloric cooling applications. The electrocaloric effect (ECE) of lead-free Ba0.8Sr0.2Ti1-xZrxO3 (0 ≤ x ≤ 0.10) ferroelectric ceramics was studied. The phase analysis of each ceramic composition that was synthesized by conventional solid-state reaction technique was performed by X-ray Diffraction. Dielectric measurements were done to determine the phase transition temperatures (Curie temperature, Tc) of all compositions and also construct a phase diagram. ΔT values were calculated indirectly using electrical polarization curves measured at different temperatures and Maxwell's equations. ΔT values that were obtained from different regions of the phase diagram are compared. The most suitable composition for applications was chosen considering the ΔT value, temperature range where relatively large ΔT is preserved and the Curie temperature of all ceramics. Ba0.8Sr0.2Ti0.93Zr0.07O3 ceramic located near the critical point shows the best performance with ΔT value of 0.40 K under 20 kV/cm. In comparison with the lead-free ceramics studied in the literature, Ba0.8Sr0.2Ti1-xZrxO3 system can be considered as one of the best candidates for future electrocaloric cooling technologies.
Functionalization and thickness dependent properties of single layer dichalcogenides
(Izmir Institute of Technology, 2019-12) Kahraman, Zeynep; Şahin, Hasan; Akdoğan, Yaşar
After successful isolation of graphene in 2004, it was found that the layered materials showed different properties when diluted to the monolayer. The layer dependent structural, electronic and vibrational properties of the 1T phase of two dimensional (2D) platinum diselenide are investigated by means of state-of-the-art first-principles calculations. In addition ultra-thin two-dimensional Janus type platinum dichalcogenide crystals formed by two different atoms at opposite surfaces are investigated by performing state-of-the-art density functional theory calculations. While all Janus structures are indirect band gap semiconductors as their binary analogs, their Raman spectra show distinctive features that stem from broken out-of-plane symmetry. Moreover, it was shown that vertically stacked van der Waals heterostructures of binary and ternary (Janus) platinum dichalcogenides offer wide-range electronic features by forming bilayer heterojunctions of type-I, type-II and type-III. On the other hands, Ab initio calculations are performed in order to investigate the structural, vibrational, electronic, and piezoelectric properties of both bare TaS2 and its functionalized structures. Furthermore, the elastic and piezoelectric properties of TaS2 and its derivatives are analyzed. It is revealed that the in-plane piezoelectricity of TaS2 can be enhanced via one-surface fluorination while an additional degree of freedom for the piezoelectricity can be added in all Janus structures due to the broken out-of-plane symmetry. This thesis provides some important results understanding of thickness and functionalization dependent mechanics, vibrational, electronic properties of 2D materials.
Investigation of tribological performance of B4C reinforced aluminium matrix composites
(Izmir Institute of Technology, 2019-06) Serkir, Sevgi; Kandemir, Sinan; Akdoğan, Yaşar
Aluminium, on account of its easy accessibility and superior metallic characteristics, has a wide variety of applications. Increasing demand on the use of aluminium in areas such as automobile, aviation and space industries which requires high performance has led to development of aluminium metal matrix composites. For this purpose, the ceramic reinforcing particles are mostly preferred to provide better mechanical and tribological properties than their conventional counterparts. In this study, aluminium metal matrix composite (AMC) reinforced with 5 wt.%, 10 wt.% and 15wt.% of B4C were fabricated using the powder metallurgy method. In order to obtain the optimum processing parameters necessary for efficient fabrication, several trials, at first place, were studied under different conditions by changing milling parameters such as milling time, milling medium, milling speed and process control agent, and sintering process parameters such as sintering time, sintering temperature. The production of composite powders was carried out using a planetary ball mill in a wet medium for 7 hours with 0.05 wt.% of stearic acid process control agent which helps to avoid contamination and cold welding of ductile Al particle. The milled powders were pressed at 314 MPa at RT and composite samples with a diameter of 30 mm and a height of 4 mm were obtained. The samples were sintered at 550, 575, 600 and 625ºC for one hour under argon atmosphere. The micro-structures of samples were analysed by scanning electron microscopy and the X-ray diffraction techniques. The wear behaviour of sintered composite samples with ball-on-disc dry wear tester and the mechanical behaviour of the samples with Vickers hardness test were investigated.
Measurement of transition metals in soda-lime-silicate glasses by using electron spin resonance (ESR) spectroscopy
(Izmir Institute of Technology, 2017-07) Göktürk, Hakan; Akdoğan, Yaşar; Adem, Umut
Electron spin resonance (ESR) spectroscopy does not appear to have found a wide use when compared with other structural analysis methods, especially spectroscopy techniques, utilized in the glass industry. The method, however, provides a good means for supporting the structural information obtained from other spectroscopic methods. Because of its ability to detect and differentiate the paramagnetic ions at low concentrations, ESR spectroscopy is commonly used as a quantitative and qualitative analysis method for evaluating transition metals. This study showed the behavior and interaction of paramagnetic 3d transition metal ions using ESR spectroscopy for the soda-lime-silicate based glasses. For this reason, it revealed the existence of paramagnetic (Fe3+, Cr3+, Mn2+ and Cu2+) transition metal ions in soda-lime-silicate glass and their spectral trends studied at addition levels up to 2.0% mol. Additionally, ESR spectra of Fe3+-Cr3+, Fe3+-Mn2+ and Fe3+-Cu2+ added soda-lime-silicate glass samples were studied to show the effects of the different transition metals on Fe3+ containing glasses. The final point of study is that the approach to quantify the ESR spectra with the concentration of paramagnetic metal ions in glass. In this way, this study gives structural information about the used glass and so lightens the locations of used metal ions.
Modelling of pore formation in porous materials
(Izmir Institute of Technology, 2017-07) Ülker, Sevkan; Güden, Mustafa; Akdoğan, Yaşar
The purpose of this thesis is to model the expansion behavior of aqueous slurries. Foamed or cellular material made using such method is known, especially in the concrete industry. What appears to be lacking in the literature is the knowledge of pore formation and pore growth in inorganic particles based on aqueous slurry systems that result in the formation of cellular structures. The motivation of this study is to provide a scientific view in identifying and explaining the critical parameters that govern the pore growth and expansion of such slurry based systems. Bubble growth and pore formation are also studied experimentally. Experimental results are used to compare with the empirical study conducted by Kanehira at al. (Kanehira, et al., 2013), and mathematical modeling of pore formation plotted with Wolfram Mathematica software. Experimental procedure consists of three types of aluminum and calcium ratios which provide information about bubble growth and pore formation. These types are 50% aluminum – 50% calcium hydroxide (50/50), 70% aluminum – 30% calcium hydroxide (70/30), and 80% aluminum – 20% calcium hydroxide (80/20). According to the results of studies, mathematical modeling system consists of the pressure difference between the inside and outside of a spherical bubble as the driving force for defining growth. While aluminum ratio increases, bubble growth rate decreases due to release of hydrogen gases which affect bubble expansion phenomenon. In the experimental and mathematical modeling, 50/50 ratio has maximum bubble growth rate compared to 70/30 and 80/20 ratios. The results of experimental and mathematical modeling suggest that viscosity is a very significant parameter which controls the bubble growth rate.
Obtaining and characterization of artificial leather using different types of plasticizers
(Izmir Institute of Technology, 2019-07) Akkuş Altındağ, İffet; Akdoğan, Yaşar; Adem, Umut
Artificial leather is the material which has wide range of use in life from fashion garment, upholstery to technical applications such as defense industries. PVC artificial leather is preferred material by manufacturers because of its low cost and modification can be done easily by using true plasticizers which are fitting for purpose. In this study, number of six different plasticizers which are non-phthalate plasticizers; trioctyl trimelliate (TOTM), tributyl trimelliate (TBTM), dioctyl terephthalate (DOTP), tributyl citrate (TBC), dioctyl adipate (DOA) and dioctyl succinate (Plast BIO) were used for obtaining artificial leather. To characterize the properties of different kinds of plasticizer in artificial leather, mechanical tests including tensile and tear strengths, elongation at break, cold flexibility and effects of migrability tests were applied. Materials were formulated at three degrees of plasticizers ratios. Also, chemical changes during plasticization were observed using FTIR spectroscopy with ATR accessory, according to types and used levels of plasticizers. In conclusion, plasticizers showed different properties, i.e. material with TOTM plasticized had maximum tear and tensile strengths, while DOA and TBC including materials showed maximum elongation under same load. Considering cold flexibility of six plasticizers, DOA, BIO and TBC have more resistance to cold were obtained, respectively. In addition, migration studies showed that plasticizers including TOTM and TBTM have the least migration properties.
Obtaining underwater adhesive materials and characterization of their adhesive properties to different surfaces by ESR spectroscopy
(Izmir Institute of Technology, 2016-07) Kırpat, İklima; Akdoğan, Yaşar
This study describes the design, synthesis and spectral behavior of underwater adhesive materials which adhere to surfaces without any external force. The materials with wet adhesive properties have a wide application field from biomedical implantation and covering to antifouling materials. Mussel’s stickiness to rocks, ships, etc. inspite of strong waves in the sea inspires us to synthesize adhesives materials. Mussels attach to solid surfaces strongly using their threads and plaques. The complex fluid (mussel foot proteins, Mfps) secreted from mussels is solidified in the sea water and forms threads, each equipped with a distal adhesive plaque. Mfps have large amount of L-3,4-dihydroxyphenylalanine (DOPA) amino acid and this amino acid is responsible for adhesion of mussels to underwater surfaces. The presence of stable hydration layers around both the adhesive materials and surface results in strong hydration repulsive forces that undermine adhesion. So far, applied external forces were used to break through or disrupt the hydration layers which prevent adhesion. In this research branched PEG based polymers were modified with different amounts of DOPA in order to obtain underwater adhesive material. Their adhesive properties to spin labeled (SL) nanoparticles were tested without applying an external force by electron spin resonance (ESR) spectroscopy. As model surfaces we synthesized hydrophobic SL-polystyrene and hydrophilic SL-silica nanoparticles. ESR results showed that four arm DOPA modified PEG is able to adhere to SL-polystyrene but not to SL-silica. Moreover, adhesions of the polymers were tested by making hydrogels using iodate (IO3-) and iron (III) (Fe3+) ions. ESR results showed that hydrogels prepared from four arm DOPA modified PEG/IO3- mixture has better adhesive property to SL-polystyrene compare to hydrogels prepared from four arm DOPA modified PEG/Fe3+ mixture and adhesion of IO3- based gel form is better compared to molecule form.
Preparation and characterization of drug loaded cationic albumin nanoparticles
(01. Izmir Institute of Technology, 2021-06) Sözer, Sümeyra Çiğdem; Akdoğan, Yaşar; Emrullahoğlu, Mustafa
Serum albumin protein behaves as a carrier and transporter for both hydrophilic and hydrophobic drugs. Therefore, albumin could be used in the drug carrier systems. Since albumin nanoparticles have a negative charge under physiological conditions, their anionic drug loading and delivering capacities are restricted. This study aims to obtain higher anionic drug loading capacity by producing cationic bovine serum albumin nanoparticles (cBSA NPs). Firstly, the carboxyl groups of amino acids present on the surface of albumin were conjugated with ethylenediamine to change the charge of albumin from negative to positive. Then, cBSA NPs were obtained using the desolvation process. Anionic salicylic acid (SA) was used for drug loading studies of the obtained cBSA NPs. SA loading and releasing experiments were studied with UV-Vis and electron paramagnetic resonance (EPR) spectroscopy. In the UV-Vis, the drug loading capacity of cBSA NPs was found to increase ~2 fold, and drug release was slower compared to BSA NPs. For EPR studies, SA was labeled with stable radicals. Spin labels allow the simultaneous monitoring of bound and free drugs in the same sample. The drug was loaded into nanoparticles using two methods. Based on EPR results, it was found that drug was loaded to cBSA NPs with 50% and 93%, and to BSA NPs with 4% and 15% ratios, by desolvation and incubation, respectively. Thus, UV-vis and EPR measurements showed that cBSA NPs have higher SA loading potential and slower release ability compared to anionic albumin nanoparticles.
Preparation and characterization of serum albumin nanoparticles obtained from modified bovine serum albumin
(01. Izmir Institute of Technology, 2021-07) Özmen Egesoy, Tuğçe; Akdoğan, Yaşar; Demir, Mustafa Muammer
The serum albumin has been used as a drug nanocarrier for a long time due to its rich drug transportation ability. Here, modified bovine serum albumin (BSA) proteins were obtained by conjugation with ethylenediamine and dopamine molecules, separately. Using these modified proteins, new BSA nanoparticles were obtained by a desolvation method. Native BSA has a net negative charge at the physiological condition. However, ethylenediamine conjugation yields a positive charge on it, and thus produces cationic BSA (cBSA) protein. On the other hand, dopamine functionalization (D-BSA) makes BSA eager to coordinate with transition metals. After preparation of modified proteins (cBSA and D-BSA), their nanoparticles were prepared with desolvation method but using different crosslinking mechanisms. For cBSA NPs preparation, a traditional crosslinking agent of glutaraldehyde was used. However, for D-BSA NPs preparation, Fe(III) ions were added to the system to achieve the stable nanoparticle formation. In order to obtain cBSA NPs, several organic solvents were used as desolvating agents. cBSA NPs with an average size around 200 nm were obtained in a high formation yield (54.8%) only through addition of acetonitrile to the cBSA aqueous solution. Similarly, different desolvating agents were studied to obtain D-BSA NPs. The promising results were obtained upon addition of 1:5 (v/v) of water/acetone mixture. After addition of the desolvating agent, Fe(III) ions were added to the solution to interconnect D-BSA with each other. This connection is pH sensitive therefore albumin nanoparticles were stable at basic pH values but not at acidic pH values. By this way, pH sensitive D-BSA NPs around 300 nm particle sizes were obtained.
Preparation of albumin nanoparticles using an ionic liquid based microemulsion-like method
(Izmir Institute of Technology, 2018-06) Demirkurt, Begüm; Akdoğan, Yaşar; Adem, Umut
Rich drug transportation ability of serum albumin protein has inspired scientists to obtain drug nanocarriers from albumin. In the literature, different methods have been developed to prepare albumin nanoparticles and their drug delivery properties have been studied. Here, this study aims to obtain albumin nanoparticles for a first time using ionic liquid (IL) included systems. Goal of this project is using imidazolium based ionic liquids (green solvent) to prepare albumin nanoparticles as alternative solvents for the commonly used organic solvents. The use of volatile, toxic and flammable organic solvents in the albumin nanoparticle production has various negative effects on both human health and environment. Ionic liquids as non-flammable, non-volatile and non-toxic solvent candidates have attracted considerable attention in recent years both in the literature and in industry. Their ability to solve different types of solutes, designability, special mixing ability with water in IL/water binary systems and environmentally friendly properties cause ILs to overtake traditional organic solvents. This thesis study proposed a novel and environmentally friendly microemulsionlike method for producing albumin nanoparticles in IL/water binary systems. Various experimental parameters such as pH effects, albumin concentrations, water amount, surfactant effects, glutaraldehyde effects, homogenizer effects, etc. were investigated to obtain uniform albumin nanoparticles. As a result, we achieved to synthesize uniformly distributed 200 nm average size albumin nanoparticles at pH 9.0 using 1.5% (w/w) of bovine serum albumin (BSA) in 1-butyl-3-methylimidazolium tetrafluoroborate using TX-100/n-butanol surfactant mixture.
Preparation of drug loaded albumin nanoparticles in water / ionic liquids microemulsion systems
(Izmir Institute of Technology, 2021-12) Yıldırım, Barış; Akdoğan, Yaşar
Nanoparticles (NPs) have been used in various applications such as biotechnology, nanomedicine, and drug delivery systems. Many nanoparticle drug delivery systems have been promoted for cancer treatment, and numerous materials have been investigated to use as drug delivery agents to enhance the therapeutic efficiency and safety of anticancer drugs. Albumin is a natural biopolymer and the most abundant protein in blood plasma. Due to its versatile binding capacity of widespread therapeutical drugs, albumin becomes an ideal material to obtain nanoparticles. In this study, the ionic liquid (IL) based emulsification methods were investigated. Instead of classical toxic and volatile solvents, using ILs in microemulsions, environment-friendly media were received to synthesize bovine serum albumin (BSA) NPs. In order to obtain BSA NPs, high-speed homogenizer processing was applied by following crosslinker addition. The IL microemulsions are a thermodynamically stable colloidal dispersion containing spherical droplets (W/IL or IL/W) in submicron sizes that act as nanoreactors for NP formation. Chlorambucil (CHL) was used as a model drug to investigate drug loading and releasing kinetics of BSA NPs as a drug delivery candidate. Results showed that chlorambucil loading capacities and release kinetics depended on the synthesized medium such as anion-type of ILs and surfactants. CHL loaded to the BSA NPs synthesized in hydrophilic IL BmimBF4 in relatively higher amounts and released in the same trend. In addition, the cell viability effect of CHL-loaded BSA NPs synthesized in different types of ILs were investigated. The CHL-loaded BSA NPs synthesized in BmimOTf and BmimPF6 reduced the cancer cell viability more than the used same dose of free CHL.
Processing foam-like porous glass structure using a combined process of glass powder expansion in aqueous environment and sintering process
(Izmir Institute of Technology, 2019-07) Zeren, Doğuş; Güden, Mustafa; Akdoğan, Yaşar
Soda-lime glass foams were formed by the controlled pore structure of inorganic particle-liquid suspensions at room temperature and then sintered at elevated temperatures between 650oC-800 oC. The slurries were prepared using the glass particles below 38 µm (fine), between 38 and 45 µm (medium) and between 45 and 56 µm (coarse) and with 50, 55, and 60 wt% solid content and 2, 3, and 4 wt% carboxymethyl cellulose (CMC) binder addition. The slurries were foamed using an Al-based foaming agent and a calcium hydroxide alkali activator with an amount of 1 wt%. An increase in CMC content and a decrease in particle size shifted the slurries from a Newtonian to a non-Newtonian behavior and slurry stabilization with the CMC addition. The extensively increased initial bubble pressure in high viscosity slurries resulted in higher linear expansion rate initially followed by a bursting of gas bubbles. The maximum foam linear expansion of the slurries increased with CMC addition until about ~5 Pa s and the expansions stayed almost constant over 400% expansion, while the slurries with the viscosity above 50 Pa s could not be foamed. The most effective factor on the maximum expansion was found the solid content followed by CMC content and the least effective factor was determined the particle size. Partial bonding of glass particles and excessive shrinkage of glass particles due to the melting of foam green bodies were seen at 650 and 800 oC sintering temperatures. Prepared foam glasses showed lower compressive strengths and thermal conductivities than the glass foams reported in the literature. Finally, foaming at room temperature with this technique was found to be more advantageous than conventional glass foam production techniques due to ease of pore formation controlling at room temperature.
Production and characterization of porous ceramics for high temperature applications
(Izmir Institute of Technology, 2022-07) Semerci, Tuğçe; Ahmetoğlu, Çekdar Vakıf; Akdoğan, Yaşar
This thesis focuses on the production and characterization of different porous polymer derived ceramic (PDC) components (foams, additively manufactured (AM) honeycombs, and aerogels) and demonstrates their potential for high temperature applications, including gas permeability (up to ~700 o C), molten metal filtration, and heat exchanger. The foams were produced via the replica technique and different pore sizes, ranging from 300 μm to 2 mm, silicon oxycarbide (SiOC) ceramic foams were able to be formed. The average total porosity of the foams was 96 vol% with a specific surface area (SSA) of ~80 m2 /g. AM-made honeycomb-like cellular structures with different cell sizes (578 μm, 1040 μm) were obtained via fused filament fabrication. Finally, SiOC aerogels were synthesized using siloxane resin, then dried at ambient pressure and room temperature. The produced SiOC aerogels showed a total porosity of around 80 vol% and an SSA reaching 250 m2 /g. Regarding the high temperature applications of porous PDC components, initially, the gas permeability of SiOC foams was tested, and the results showed stability up to 700 °C in the air without any loss of functionality, offering reusability even in aggressive environments. In the subsequent studies, filtration of molten aluminum alloy was tested using various porous components. PDC foams demonstrated better performance in comparison to the AM-made cellular structures and commercial SiC foams. Finally, heat exchange analysis was performed to evaluate the heat transfer of SiOC foams, and an increase in pressure drop was found to be directly proportional to the rate of increase in air velocity.
Study of drug transportation by ESR spectroscopy
(Izmir Institute of Technology, 2018-12) Tatlıdil, Duygu; Akdoğan, Yaşar; Emrullahoğlu, Mustafa
The ability to track drug binding and release makes electron spin resonance (ESR) spectroscopy well suited for drug delivery studies. Using the continuous wave cw ESR technique to extract information about the dynamics of the spin labeled drugs we can simultaneously determine the bound and unbound drugs. In this study, ESR technique was used to detect the binding and release of spinlabeled salicylic acid (SLSA) to and from bovine serum albumin (BSA), and to detect different binding interactions between them. We have labeled salicylic acid with stable nitroxide-based tempo radicals to monitor the BSA bound and unbound conditions of the drug. Studying with the different concentrations of SLSA-BSA binding showed that the drug-protein stoichiometry increases significantly in the physiological range of BSA concentration. Also, during the release of SLSA from BSA, there is an unchanging balance between the bound and unbound SLSA. In order to study various drug binding interactions, SL-benzoic acid, SL-phenol, SL-benzene, SL-cyclohexane, SL-hexane and SL-methyl were prepared. We showed that the main conjugation in the binding of these drugs to BSA is hydrophobic interaction. In addition, cationic BSA (cBSA) was prepared to investigate the effect of electrostatic interaction on drug binding. The SLSA loading capacity of cBSA is significantly higher than that of BSA, this result indicates the importance of electrostatic interactions for the drug binding. Finally, we examined the competitive binding behaviors of salicylic acid, ibuprofen and aspirin to BSA. Binding sites of SL-salicylic acid and SL-ibuprofen in BSA show 96% of similarities. In addition, our results showed that binding sites of SL-salicylic acid and SL-aspirin in BSA have 73% of similarities.These results demonstrate that cw ESR spectroscopy with the spin labeling technique is an effective technique for the determination of drug-protein interactions and stoichiometric analysis of drug binding.
Studying dopa adhesion on polystyrene under water
(Izmir Institute of Technology, 2021-06) Yıldız, Remziye; Akdoğan, Yaşar; Emrullahoğlu, Mustafa
Mussels wet adhesive performance has been arousing curiosity for a long time. It is found that 3,4-dihydroxyphenylalanine (DOPA) is responsible for adhesive properties of mussels. Despite a large body of research characterizing the interactions DOPA with hydrophilic surfaces, relatively few works have addressed the mechanism of interactions with hydrophobic surfaces. The benzene ring of DOPA is the main attributor to the adhesion on hydrophobic polystyrene (PS) surface. However, here we showed that two hydroxyl groups of catechol have also effects on wet adhesion. We studied wet adhesive properties of DOPA, tyrosine and phenylalanine functionalized PEG polymers, PEG-(N-Boc-L-DOPA)4, PEG-(N-Boc-L-Tyrosine)4, PEG-(N-Boc-L-Phenylalanine)4, on spin labeled PS nanobeads (SL-PS) by electron paramagnetic resonance (EPR) spectroscopy. Surface coverage ratio of SL-PS upon additions of PEG-(N-Boc-L-DOPA)4, PEG-(N-Boc-L-Tyrosine)4 and PEG-(N-Boc-L-Phenylalanine)4 showed that SL-PS was covered with 70%, 50% and 0%, respectively. This showed that spontaneous wet adhesion on PS increases with the number of amino acids hydroxyl groups. This is also supported with the density functional theory (DFT) energy calculations and ab-initio molecular dynamics (AIMD) simulations. In water, interactions between water molecules and hydroxyl groups on the catechol induce catechol adhesion via π-π stacking between the catechol and double styrene rings which were already tilted out with water.