Browsing by Author "Gokturk, Ersen"

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Citation - WoS: 4
Citation - Scopus: 4
Horseradish Peroxidase (HRP) Nanoflowers-Mediated Polymerization of Vinyl Monomers
(Springer, 2024) Ozaydin, Gulbahar; Mirioglu, Muge; Kaplan, Naime; Dadi, Seyma; Ocsoy, Ismail; Gokturk, Ersen
The effects of flower-shaped hybrid nano biocatalyst (hFe-NFs) from coordination between horseradish peroxidase (HRP) enzyme and Fe2+ ions on the free-radical polymerization reactions of three different vinyl monomers (styrene, methylmethacrylate and acrylamide) were investigated. Polymerizations of styrene and methylmethacrylate (MMA) were performed under emulsion conditions using three different surfactants in the presence of acetylacetone (AcAc) and hydrogen peroxide (H2O2) initiator. Polymerization of water soluble acrylamide was accomplished under surfactant-free media. According to the obtained outcomes, hFe-NFs exhibited higher catalytic activity towards polymerization of vinyl monomers compared to the free-HRP enzyme in terms of yields and the number average molecular weights (Mn) of the synthesized polymers. hFe-NFs also demonstrated very high thermal stability. While optimum polymerization of styrene was achieved at room temperature (RT), the highest polymerization yields for acrylamide and MMA were respectively accomplished at 70 and 60 degrees C in which free-HRP enzyme loses its catalytic activity. Preparation of the flower-shaped hFe-NFs, therefore, enables inexpensive and stable catalyst system for free-radical polymerization of vinyl monomers compared to free-HRP enzyme. Increasing catalytic activity and stability of hFe-NFs at higher reaction temperatures are very crucial for utilization of these types of catalysts in both scientific and industrial purposes.
Citation - WoS: 10
Citation - Scopus: 11
Production of Flower-Shaped Nanobiocatalysts From Green Tea and Investigation of Their Peroxidase Mimicking Activity on the Polymerization of Phenol Derivatives
(Wiley, 2024) Kalayci, Berkant; Kaplan, Naime; Dadi, Seyma; Ocsoy, Ismail; Gokturk, Ersen
Enzyme catalyzed reactions are known to be environmental friendly and easy method for many applications. However, utilization of enzymes in a variety of reactions is strictly limited due to their high cost, instability in aqueous solutions, denaturation in organic solvents and high temperatures. For this reason, it is important to discover new generation catalyst systems indicating enzyme-like catalytic activity. Here, we report hybrid organic-inorganic flower-shaped green tea-Cu2+ nanobiocatalyst synthesized from green tea extract as an organic component and copper (II) ions (Cu2+) as inorganic component. The effect of the peroxidase-mimicking activity of green tea-Cu2+ nanobiocatalyst was investigated on the polymerization of phenol and derivatives (guaiacol and salicylic acid) through Fenton-like reaction mechanism. Obtained successful outcomes showed that the synthesized nanobiocatalyst showed very high catalytic activity upon polymerization of phenol and guaiacol. The slight solubility of salicylic acid in water limited to achieve its polymerization under-performed reaction conditions. The yields and molecular weights of the obtained polymers were found to be quite high. While free peroxidase enzymes like horseradish peroxidase (HRP) enzyme loses its catalytic activity at 60 degrees C and above temperatures, green tea-Cu2+ nanobiocatalyst exhibited very high catalytic activity upon polymerization reactions even at 60 degrees C reaction temperature. This outcome provides significant advantages in some reactions requiring high temperatures. In order to understand the origin of the catalytic activity of the green tea-Cu2+ nanoflowers, similar biocatalysts were also synthesized from caffeine and catechin alkaloids which are the active components of green tea. Caffeine-Cu2+ and catechine-Cu2+ nanobiocatalysts also exhibited quite high catalytic activity toward polymerization of phenol and derivatives. We suggest that green tea-Cu2+ and similar types of nanobiocatalysts may expand their utilization in polymer chemistry as promising catalytic agents for radicalic polymerizations.
Citation - WoS: 1
Citation - Scopus: 1
Investigation of the Free-Radical Polymerization of Vinyl Monomers Using Horseradish Peroxidase (HRP) Nanoflowers
(Springer, 2025) Ozaydin, Gulbahar; Mirioglu, Muge; Dadi, Seyma; Ocsoy, Ismail; Gokturk, Ersen
In this study, we report the production of flower-shaped HRP-Cu2+ hybrid nano biocatalyst (HRP-Cu2+ HNF) from the complexation between horseradish peroxidase (HRP) enzyme and Cu2+ ions, and investigate catalytic activity and stability of the obtained nanoflowers on the polymerization of some vinyl monomers (styrene, methylmethacrylate, acrylamide and N-isopropylacrylamide). Polymerizations of these monomers, except water soluble acrylamide, were accomplished under emulsion conditions using cationic, anionic and non-ionic surfactants in the presence of hydrogen peroxide (H2O2) and 2,4-pentanedione mediator. Optimum polymerizations were achieved under the conditions of non-ionic surfactant (tween 40) used. HRP-Cu2+ HNF mediated polymerizations resulted in very high yields and molecular weights (Mn) of the polymers. Optimum polymerization of styrene with 84% of yield (Mn = 319 kDa) was accomplished at room temperature. However, the highest polymerization yields for acrylamide (96%, Mn = 171 kDa) and N-isopropylacrylamide (85%, Mn = 185 kDa) was achieved at 70 degrees C. Similarly, optimum polymerization of methylmethacrylate was accomplished with 84% of yield (Mn = 190 kDa) at 60 degrees C. While free-HRP loses its catalytic activity at 60 degrees C and above temperatures, HRP-Cu2+ HNF showed very high catalytic activity and stability even at 70 degrees C. Increasing activity and stability of hybrid nanoflowers provide significant advantages for both scientific and industrial applications.