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Öğe 0D, 1D, 2D, and 3D Soft and Hard Templates for Catalysis(Elsevier Science Bv, 2017) Bütün, Sultan; Demirci, Şahin; Yaşar, Alper O.; Sağbaş, Selin; Aktaş, Nahit; Şahiner, NurettinCatalytic reactions are generally catalyzed by metal nanoparticles, metal oxides, or their bi- or trimetallic forms with various formulations, morphology, composition, and shapes. The metal nanoparticle catalytic performances are directly related to the surface features of particles such as crystal structure, atomic stacking and order, surface area, roughness and atomic and/or spatial organizations, and the catalyst environments. It's very well-known that the high surface energy of the metal nanoparticles, which is one of the most important challenges to be considered to overcome, leads to aggregation, deactivation, and oxidation problems. Therefore, many templates such as nanoemulsions prepared from surfactant and polymers and nanogels as zero-dimensional (0D) soft templates; cylindrical or tubular natural or synthetic structures derived from again surfactants, polymers, or peptides or self-assembled structures as one-dimensional (1D) templates; graphene oxide, mica, clay, and silicates as two-dimensional (2D) hard templates; and microgel, bulk hydrogel, and cryogels as three-dimensional (3D) soft templates that are used as stabilizing media will be discussed. Regardless of the sizes of templates, various parameters such as morphology, e.g., core-shell, capsules, guiding direction, porosity, and compartmentation features of the templates, have paramount significance on composition, crystallinity, and shape of the resultant nanoparticle to be used as catalyst. Metal nanoparticles, metal oxides, and metal nanoparticles doped with various elements have been extensively investigated due to their unique physical and chemical properties, and even their bi- or trimetallic forms have been under examination due to synergistic potential application of each of the components. The main concern regarding the nanoparticle synthesis is to overcome their agglomeration, due to their high surface area, high energy, and high surface reactivity resulting in strong tendency to aggregate, leading to deactivation and oxidation. There are a variety of methods available in the synthesis of metal nanoparticles to prevent some of these shortcomings with some catalytic performance sacrifices or with some economical infeasibilities. Nevertheless, the key issue with these methods is the control of the particle size and shapes and the morphology and crystallinity. Therefore, a wide range of templates such as nanoemulsions using surfactant and polymers and nanogels as 0D soft templates; cylindrical or tubular natural or synthetic structures derived from again surfactants, polymers, or peptides or self-assembled structures as 1D templates; graphene, mica, clay, and silicates as 2D hard templates; and microgel, bulk hydrogel, and cryogels as 3D soft templates as stabilizing environments and particle compartments will be discussed. In general, polar molecules or polyelectrolytes stabilizers can be used in both controlling the size and preventing the metal nanoparticles from precipitation processes. Water-soluble polymers, including polyelectrolytes, are the commonly employed stabilizing and/or chelating agents in the preparation of metal ultrafine particles.Öğe 4-Nitrofenol ile Boyar Madde Çözelti Karışımlarını Aynı Anda İndirgeme ve Bozundurma Reaksiyonları için Poli(4-Vinil Piridin)-Co İyonik Sıvı Kriyojel Kompozit Katalizörü(Çanakkale Onsekiz Mart Üniversitesi Fen Bilimleri Enstitüsü, 2018) Şahin, Ayşe Demirci; Yıldız, Sema; Şahiner, NurettinBu çalışmada, poli(4-vinil piridin) (p(4-VP)) süper gözenekli kriyojelleri serbest radikalpolimerizasyon tekniği ile kriyojenik koşullarda sentezlenmiştir ve hidroklorik asit ilemuamele edilerek protonlanmıştır (p(4-VP)+Cl-). Hazırlanan kriyojeller, Fourier DönüşümlüKızılötesi Işımalı spektroskopisi (FT-IR), Termogravimetrik Analiz cihazı (TGA), TaramalıElektron Mikroskobu (SEM) ve optik mikroskop ile karakterize edilmişlerdir. P(4-VP)+Clkriyojellerine CoCl2'nin etanol çözeltisinden metal tuzu yüklenerek NaBH4 varlığındaindirgenerek iyonik sıvı (IL) kriyojeller içinde Co metal nanopartikül sentezi yapılmıştır.Kriyojeller içindeki metal miktarları atomik absorpsiyon spektroskopisi (AAS) ilebelirlenmiştir ve p(4-VP)+Cl--Co kriyojel kompozitinin 121,6±7,3 mg/g Co nanopartikülüiçerdiği belirlenmiştir. Hazırlanan p(4-VP)+Cl--Co kompozit kriyojelleri 4-nitro fenol (4-NP),eosin Y (EY), ve metilen mavisi (MM) çözeltilerinin karışımlarını aynı anda indirgeme vebozunma reaksiyonlarında katalizör olarak kullanılmıştır. Buna göre, 4-NP/EY, 4-NP/MB ve4-NP/EY/MB karışımlarındaki herbir molekül için p(4-VP)+Cl--Co kriyojel kompozitkatalizör varlığında %85’in üzerinde dönüşüm elde edilmiştir. Ayrıca, 4-NP, EY ve MMbileşiklerinin çözeltilerinin karışımlarında p(4-VP)+Cl--Co kriyojel kompozit katalizörükullanılarak indirgenme ve/ya bozunma reaksiyonları gerçekleştirilerek dönüşüm% ve bir molkatalizörün dakikada katalizlediği molekülün mol sayısı (TOF) değerleri hesaplanmıştır.Öğe 4-Vinylpyridine-Based Smart Nanoparticles with N-Isopropylacrylamide, 2-Hydroxyethyl Methacrylate, Acrylic acid, and Methacrylic Acid for Potential Biomedical Applications(Bentham Science Publ Ltd, 2011) Şahiner, Nurettin; Özay, Özgür; Aktaş, NahitStimuli-responsive (pH, temperature and magnetic field) 4-vinylpyridine (4-VP)-based nanoparticles in copolymeric formulation with core-shell morphology were synthesized using N-isopropylacrylamide (NIPAM), 2-hydroxyethyl methacrylate (HEMA), acrylic acid (AAc), and methacrylic acid (MAc) as shell-forming monomers. Keeping the 4-VP ratio constant and varying the comonomer amounts produced particles with variant shell thickness. Multi-responsive p(4-VP)-based nanoparticles were further modified by reacting with different functional groups containing bromoalkanes by quaternization. These p(4-VP)-based particles were also utilized to include composite materials by encapsulating separately prepared magnetic ferrites. To demonstrate the potential usage of the synthesized particles and their modified forms as drug delivery devices, naproxene sodium salt as an antibacterial drug was used for in vitro release studies in PBS.Öğe A Comparative Study of Nitrogen Doped Carbon Dots Prepared from Linear Polyethyleneimine (L-PEI) and Branched Polyethyleneimine (B-PEI): Thermal, Optical, Biocompatibility, Sensor, Antibacterial, and Light-Induced Antibacterial Activity(Springer/Plenum Publishers, 2025) Demirci, Şahin; Sağbaş Suner, Selin; Şahiner, Mehtap; Akçalı, Alper; Güven, Olgun; Şahiner, NurettinThe N-doped carbon dots (CDs) prepared in the presence of citric acid (CA) as carbon source, using linear poly(ethylene imine) (L-PEI) and branched poly(ethylene imine) (B-PEI) as nitrogen doping agents were prepared via hydrothermal/solvothermal technique at 250 degrees C in a Teflon-lined autoclave. The zeta potentials of L-PEI CDs and B-PEI CDs were determined as + 9.8 +/- 4 and 0.1 +/- 0.5 mV with 47 +/- 3 and 54 +/- 5 nm sizes, respectively. Bandgap values for L-PEI CDs and B-PEI CDs were estimated as 3.06 and 3.37 eV, respectively. The fluorescence intensities of L-PEI CDs and B-PEI CDs were measured as 59,310(a.u.), and 46,370(a.u.) at 474 and 442 nm, respectively, under 400 and 320 nm excitation wavelengths and 700 V PMT voltage. A higher quantum yield% value was observed for L-PEI CDs with 37 +/- 2.9%. Both L-PEI CDs and B-PEI CDs were found biocompatible up to 1000 mu g/mL concentration with > 80% L929 fibroblast cell viability. The limit of detection (LOD) values for Fe3+ by L-PEI CDs and B-PEI CDs were determined as 0.58 and 2.14 mg/mL, respectively. Both L-PEI CDs and B-PEI CDs at 10 mg/mL concentration resulted in 50% bacterial killing for gram-negative E. coli, gram-positive B. subtilis, and yeast C. albicans microorganisms. Also, the light activation of L-PEI CDs and B-PEI CDs induces almost 70 and 40% bacterial killing for gram-positive B. subtilis in 30 min. Moreover, they have a limit of detection (LOD) value of 0.58 mg/mL for Fe3+ ions, in addition to exhibiting biocompatibility and antibacterial properties.Öğe A comparison study about antibacterial activity of zeolitic imidazolate frameworks (ZIFs) prepared with various metal ions(Elsevier Science Sa, 2022) Demirci, Şahin; Yıldırım, Yıldız; Şahiner, NurettinHerein, the synthesis of zeolitic imidazolate framework particles in water at room temperature using 2-methylimidazole (HmIm) as organic linker, and Co(II), Ni(II), Cu(II), Fe(II), Mg(II), Zn(II), Ce(III), La(III), Fe(III), and Ti (IV) ions is reported. The colors of the prepared ZIF particles varied depending on the metal ions used. The disappearance of N-H-ring-N out of plane bending peak at 1845 cm(-1) and weakening of the N-H bending peak at 1597 cm(-1) in the FT-IR spectrum of HmIm after ZIF synthesis confirmed successful preparation. Higher surface area values were observed for ZIF-Co(II) and ZIF-Zn(II) with values of 1423.4 and 1467.1 m(2)/g, respectively. The prepared ZIF-Fe(II) particles showed magnetic property. The antibacterial activities of ZIF particles also varied depending on metal ions. The highest antibacterial activities were observed for ZIF-Co(II) and ZIF-Cu(II) particles against P. aeruginosa (gram -, ATCC 10145), S. aureus (gram +, ATCC 6538), and C. albicans (fungi, ATCC 10231). The MIC values of ZIF-Co(II) particles were determined as 0.125, 0.25, and 1.0 mg/mL against P. aeruginosa, S. aureus, and C. albicans, whereas MBC values were determined as 0.25, 1.0, and 5.0 mg/mL, respectively. The inhibition zones for P. aeruginosa, S. aureus, and C. albicans in the presence of 10 mg ZIF-Cu(II) particles were measured as 22.7 +/- 1.5, 24.3 +/- 1.1, and 25.7 +/- 0.6 mm, respectively.Öğe A facile method for the preparation of poly (4-vinylpyridine) nanoparticles and their characterization(TÜBİTAK, 2009) Şahiner, NurettinSubmicron size particles were synthesized from 4-vinylpyridine (4-VP) using an oil-in-water emulsion system. Divinyl benzene (DVB) and ethylene glycol dimethacrylate (EGDMA) were utilized as crosslinkers for the synthesis of p(4-VP) hydrogel nanoparticles in sodium dodecyl sulfate (SDS) surfactant systems. Characterization of the particles was made by transmission electron microscopy (TEM) and dynamic light scattering (DLS) methods. To render a positive charge, p(4-VP) particles were reacted with 1-bromo butane (1-BB).Öğe A facile one-pot synthesis of microgels and nanogels of laminarin for biomedical applications(Academic Press Inc., 2021) Can, Mehmet; Şahiner, NurettinHypothesis: Laminarin (LAM) as a nontoxic, biodegradable, and biocompatible marine polysaccharide, has been reported for its ingenious bioactivities such as antioxidant, antitumor antiapoptotic anti-inflammatory, immunomodulatory and dietary fiber activities, and distinct physicochemical structure possess a remarkably promising potential in biomaterial science. Synthesis of LAM-based microgels and bulk hydrogels have been reported in two stages: modification of LAM polysaccharide with polymerizable functional groups and subsequent crosslinking reaction. Therefore, here an easier and more effortless methods to prepare poly(laminarin) (p(LAM)) particles were tackled. Experimental: A direct and facile single step fabrication of micro/nanogels of p(LAM) for the first time by means of reverse micelle microemulsion system were illustrated. Preparation of p(LAM) particles were achieved by the well-known Oxa-Michael addition reaction mechanism using divinyl sulfone as the crosslinker. Findings: P(LAM) particles in 0.3–10 µm size range in spherical morphologies were prepared with 93 ± 7% yield and functionalized with chlorosulfonic acid (CSA) demonstrating their chemical modifiability for variety of agents e.g., targeting ligands. The bare and modified p(LAM) particles showed excellent blood compatibility with hemolytic indices of <1% and blood clotting indices higher than 90%. The reported p(LAM) particles hold great promise as natural alternative surrogates in biomedical applications including drug delivery.Öğe A facile preparation of donut-like supramolecular tannic acid-Fe(III) composite as biomaterials with magnetic, conductive, and antioxidant properties(Taylor & Francis Ltd, 2017) Şahiner, Nurettin; Bütün Şengel, Sultan; Yıldız, MustafaTannic acid (TA) complexes with various metal ions are prepared in buffer solutions by readily adjusting the pH, but there is no normalizing method to produce ferric tannate complexes. In this study, TA-Fe(III) complex was prepared in reverse microemulsion medium by reaction of TA as ligand with Fe(III) in 1: 3 ligand: metal ion molar ratio. The complex was characterized by SEM, AFM, FT-IR, elemental analysis, AAS measurement, and Brunauer-Emmett-Teller (BET) method. Furthermore, magnetic susceptibility was tested with the Gouy method, and electronic spectral studies of TA-Fe(III) complex were completed with solid UV-vis measurements. The thermal stability was also studied by TGA analysis. These studies show that the ligand molecules have octahedral arrangement around Fe(III) and the complex is paramagnetic. The bandgap energy of the complex was calculated as 3.42 eV with solid UV-vis analysis. To determine antioxidant activity of the complex, Total Phenol Content (TPC) and Trolox Equivalent Antioxidant Concentration (TEAC) methods were used. The complex has great antioxidant properties with TPC = 45 +/- 1 mg L-1 GAE and TEAC = 296 +/- 2 mM trolox g(-1) for dry sample. [GRAPHICS] .Öğe A facile synthesis route to improve the catalytic activity of inherently cationic and magnetic catalyst systems for hydrogen generation from sodium borohydride hydrolysis(Elsevier Science Bv, 2015) Şahiner, Nurettin; Seven, FahriyeInherently cationic poly(3-acrylamidoproply)trimethylammonium chloride) (p(APTMACl)) as hydrogel and cryogel as nonporous and superporous structures to use as template for cobalt and Nickel metal nanoparticle preparation and then H-2 production from NaBH4 hydrolysis. Use of p(APTMACl) hydrogels in H-2 generation reactions from hydrolysis is an advantage due to their inherently cationic nature and no requirement for any modification/quaternization steps to load metal salts for in situ metal nanoparticle preparation. However, it is very well known that the metal loading processes of p(APTMACl) hydrogels are very slow. Therefore, the superporous cryogels prepared from p(APTMACl) offered great advantages in terms of swelling, metal absorption for in situ metal nanoparticle preparation, and then higher catalytic activity in hydrolysis of NaBH4. The p(APTMACl) cryogels and their metal composites provide 32, 3600, 1.5, 5.5 and 3.5 fold faster swelling degree, swelling time, metal absorption capacity, metal absorption time and H-2 generation rate, respectively than hydrogels and metal composites. In addition, p(APTMACl)-Co metal composites are shown to have highly useful characteristics in H-2 generation reaction from hydrolysis of NaBH4, due to their innate magnetic character, which allows control by an externally applied magnetic field, and reusability, with almost 80% at the end of 5th use. (C) 2014 Elsevier B.V. All rights reserved.Öğe A New Application for Colloidal Silica Particles: Natural, Environmentally Friendly, Low-Cost, and Reusable Catalyst Material for H2 Production from NaBH4 Methanolysis(Amer Chemical Soc, 2016) Şahiner, Nurettin; Yaşar, Alper O.Metal nanoparticles (NPs) and metal composites (MCs) are generally used as catalysts for the methanolysis reaction of NaBH4. Here, we report the direct use of silica (SiO2) particles as an alternative catalyst for green energy carriers in H-2 generation from the methanolysis of NaBH4. The SiO2 particles of different sizes were synthesized using the very well-known Stober method and then treated with various acids such as hydrochloric acid (HCl), nitric acid (HNO3), sulfuric acid (H2SO4), phosphoric acid (H3PO4), and acetic acid (CH3COOH). The hydrodynamic diameter of prepared SiO2 particles ranged between 200 and 800 nm measured by dynamic light scattering (DLS) with zeta potential values of about -46 and -37 mV. The BET surface area of SiO2 particles was measured between about 4-25 m2 g-1. The catalytic performances of the prepared SiO2 particles in methanolysis of NaBH4 were tested in terms of the effect and the type of treatment agents, acid and base, the hydrodynamic diameter of SiO2 particles, the reusability of the particle as catalyst, the regeneration effects of the particles, the concentration of NaBH4, and temperature. It was found that SiO2 particles are better if not comparable catalysts with metal NPs in terms of high reusability for H-2 production from the methanolysis reaction of NaBH4. The hydrogen generation rate (HGR) value from the methanolysis reaction of NaBH4 catalyzed by SiO2 particles treated with HCl was determined as 34 000 +/- 840 mL H-2 g(-1) min(-1) using 20 mL of 1000 mM NaBH4 and 50 mg of SiO2 as catalyst. The true activity of SiO2 particles treated with HCl was calculated as approximately 60% even after the 10th use. The activation energy (Ea) value for the NaBH4 hydrolysis reaction catalyzed by SiO2 particles was also found to be comparable with the literature at 29.9 +/- 0.4 kJ mol-1. According to the obtained results, the prepared SiO2 particles can be an alternative catalyst instead of metal nanoparticles.Öğe A novel p(AAm-co-VPA) hydrogel for the Co and Ni nanoparticle preparation and their use in hydrogel generation from NaBH4(Elsevier Science Bv, 2012) Sağbaş, Selin; Şahiner, NurettinA novel bulk poly(acrylamide-co-vinyl phosphonic acid) (p(AAm-co-VPA)) hydrogels were synthesized via a photo polymerization technique in macro dimension. Ni and Co nanoparticles inside p(AAm-co-VPA) hydrogel were also prepared by reduction of the metal ions loaded into the hydrogel network from the corresponding metal salt solution in water. The reduction of these bound metal ions within hydrogel matrices were done by treating hydrogel-laden metal ions with NaBH4 to produce novel hydrogel-metal composite catalyst systems. Furthermore, these soft hydrogel composite catalyst systems were employed in the generation of hydrogen from the hydrolysis of sodium boron hydride (NaBH4) in a basic medium. Thermogravimetric analysis (TGA) and atomic absorption spectroscopy (AAS) measurements were employed to determine the metal particle content of p(AAm-co-VPA)-M (M: Co, Ni) composite hydrogels. The effects of different parameters such as the amount of catalyst, the reaction temperature, the type of the metal, the initial concentration of NaBH4 and reusability of the prepared catalyst systems were investigated, and the activation energy for hydrolysis of NaBH, by p(AAm-co-VPA) was found as 23.68 k /mol. (C) 2012 Elsevier B.V. All rights reserved.Öğe A polyphenolic biomacromolecule prepared from a flavonoid: Catechin as degradable microparticles(Wiley, 2021) Sağbaş Suner, Selin; Mohapatra, Subhra; Ayyala, Ramesh S.; Brethanabotla, Venkat R.; Şahiner, NurettinCatechin (CAT) was crosslinked with trimethylolpropane triglycidyl ether(TMPTGE) to obtain degradable poly(CAT) particles in a single step. Sphericalp(CAT) particles with tens of micrometer size range and an isoelectronic pointat pH 1.2 were obtained. The hydrolytic degradation of p(CAT) particles pro-vided sustainable and extended release with 264 mg/g CAT release within10 days at pH 7.4. The antioxidant capacity of 55.0 ± 0.9μg/ml gallic acidequivalent in terms of total phenol content, and 0.88 ± 0.3μmol/g trolox equiv-alent were estimated for p(CAT) particles displaying strong radical scavengingcapability. Blood clotting and hemolysis assays demonstrated dose-dependentblood compatibility revealing higher blood compatibility for p(CAT) particlesup to 10μg/ml concentration. The cytotoxicity results show that p(CAT) parti-cles have almost no toxicity for CCD841 normal colon cells at 250μg/ml con-centration in 24 h incubation time giving ~97% cell viability, whereas CATmolecules only provide ~34% cell viabilityÖğe A Review on Phyto-Therapeutic Approaches in Alzheimer's Disease(MDPI, 2023) Şahiner, Mehtap; Yılmaz, Aynur Sanem; Güngör, Buket; Şahiner, NurettinNeurodegenerative diseases occur due to progressive and sometimes irreversible loss of function and death of nerve cells. A great deal of effort is being made to understand the pathogenesis of neurodegenerative diseases. In particular, the prevalence of Alzheimer’s disease (AD) is quite high, and only symptomatic therapy is available due to the absence of radical treatment. The aim of this review is to try to elucidate the general pathogenesis of AD, to provide information about the limit points of symptomatic treatment approaches, and to emphasize the potential neurologic effects of phytocompounds as new tools as therapeutic agents for disease prevention, retardation, and therapy. This survey also covers the notable properties of herbal compounds such as their effects on the inhibition of an enzyme called acetylcholinesterase, which has significant value in the treatment of AD. It has been proven that phytopharmaceuticals have long-term effects that could protect nervous system health, eliminate inflammatory responses, improve cognitive damage, provide anti-aging effects in the natural aging process, and alleviate dementia sequelae. Herbal-based therapeutic agents can afford many advantages and can be used as potentially as new-generation therapeutics or complementary agents with high compliance, fewer adverse effects, and lower cost in comparison to the traditional pharmaceutical agents in the fight against AD.Öğe A simple gradient centrifugation method for bacteria detection in skim milk(Elsevier Inc., 2023) Solovchuk, Didem Rodoplu; Boyacı, İsmail Hakkı; Tamer, Uğur; Şahiner, Nurettin; Çetin, DemetDevelopment of simple methods for bacteria detection is of great importance, especially in the undeveloped countries where there are limited resources for microbial testing. Herein, we present a simple gradient centrifugation-based optical detection (GCB-OD) method for bacteria testing in skim milk. Our method incorporates capturing bacteria using nanoparticles in Eppendorf tubes, followed by separation of bacteria-captured particles in the sucrose gradient within 6 min of centrifugation. Using a simple mobile phone-setup, images of sucrose-gradients are captured, and optical density of the particle-bound bacteria zones are measured with a MATLAB software, without requirement of a sophisticated optical instrument. In this approach, different nanoparticles are compared according to delta-E (ΔE) color difference value and sedimentation rate to obtain detectable narrow particle-bound bacteria zones. The spherical shaped carbon nanoparticles (CNP) with mean diameters of 119 nm, are found suitable for low concentrations of bacteria detection for having high sedimentation rates comparing to smaller sized particles and having higher ΔE than other particles as well. For CNP-captured bacteria band detection, sucrose-gradient consist of 1 ml of 60–65–70 % (w/v) and 2 ml of 75 % (w/v) sucrose was found suitable. Escherichia coli (E. coli) was used as model fecal indicator bacteria, and the correlation of optical density and E. coli concentration showed linearity in the range of 1.5x100–1.5x104 CFU/ml E. coli in skim milk. The culture plating and transmission electron micrographs were utilized to evaluate bacterial capture performance. The developed simple centrifugation-based method that allows detection of 2 CFU/ml and 3 CFU/ml E. coli in 1XPBS and skim milk, can be useful for microbial testing in resource limited areas.Öğe A simple post modification method for novel porous superabsorbent p(acrylamide) hydrogels and their H2 production(Springer, 2014) Seven, Fahriye; Şahiner, NurettinPoly(Acrylamide) (AAm) hydrogels were synthesized in bulk and reacted with NH2OH center dot HCl to develop a new functional group to confer high swelling, porosity and high metal ion binding abilities. The chemically-modified hydrogels, denoted as amidoximated poly(Acrylamide) (amid-p(AAm)) showed increased water swelling ability of up to 16-fold. The chemical modification induced structural changes were examined by FT-IR spectroscopy, water and pH swelling experiments, optical microscope images, titration studies, and even TG analysis. The amid-p(AAm) hydrogels were used as template for absorption of Co(II) and Ni(II) ions from their aqueous solutions and treated with aqueous NaBH4 for in situ metal nanoparticle preparation of the corresponding ions within the amid-p(AAm) matrices. The amid-p(AAm)-M (M:Co or Ni) composites were then used as catalyst in the hydrolysis of NaBH4 for H-2 generation, and their catalytic performances were investigated. Various parameters for the hydrolysis of NaBH4 such as functionality of polymer matrices, the types of metal nanoparticles, metal catalyst amounts within hydrogel matrices, and temperature were investigated. Considerably low activation energy in comparison to similar studies in the literature were calculated for NaBH4 hydrolysis by amid-p(AAm)Co metal composite systems: E-a=17.26 +/- 0.06.Öğe A soft hydrogel reactor for cobalt nanoparticle preparation and use in the reduction of nitrophenols(Elsevier Science Bv, 2010) Şahiner, Nurettin; Özay, Hava; Özay, Özgür; Aktaş, NahitBulk poly(2-acrylamido-2-methyl-1-propansulfonic acid) (p(AMPS)) hydrogels were prepared by irradiation of an aqueous solution of AMPS in the presence of crosslinker and photoinitiator. These p(AMPS) hydrogel networks were utilized for in situ cobalt nanoparticle synthesis by reduction of metal ions absorbed into the hydrogel network with a reducing agent, i.e., NaBH(4). TEM images confirmed that Co particles are about 100 nm in size. The hydrogel network with embedded Co nanoparticles was utilized as a catalyst in the reduction of 4-nitrophenol (4-NP) and 2-nitrophenol (2-NP) in aqueous media in the presence of an excess amount of NaBH4. The kinetics of the reduction reaction under different reaction conditions was investigated to determine the activation parameters. Activation energies are 27.8 kJ mol(-1) and 39.3 kJ mol(-1) for 4-NP and 2-NP, respectively. It was found that hydrogel-Co composites were 99% active after 5 days storage. (C) 2010 Elsevier B.V. All rights reserved.Öğe A versatile hydrogel template for metal nano particle preparation and their use in catalysis(Elsevier Sci Ltd, 2011) Bütün, Sultan; Şahiner, NurettinWe report the synthesis of a novel bulk hydrogel based on acrylamidoglycolic acid (AAGA) and its use as a template in the preparation of different metal nanoparticles. Furthermore, we demonstrate the efficient utilization of p(AAGA) composite hydrogel as a reactor vessel in the reduction of an organic contaminant, 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The swelling characteristics of the hydrogel at different pH and different concentrations of salts (NaNO3, NaCl) were studied, and experimental molecular mass between crosslink (Me) values was calculated. Experimental parameters that affect the 4-NP reduction rate such as temperature, amount of catalysis, co-catalysis, concentrations of 4-NP and of NaBH4 were investigated. The kinetics of the reduction reaction under different reaction conditions was also evaluated to determine the activation parameters. Activation energy for the reduction of 4-NP was 33.783 kJ mol(-1) and p(AAGA)-Ag composites possessed 88% activity at the end of five repetitive uses. (C) 2011 Elsevier Ltd. All rights reserved.Öğe AChE Inhibition Capability of Nanogels Derived from Natural Molecules: Tannic Acid and Lysine for Alzheimer's Disease(MDPI, 2025) Şahiner, Mehtap; Sağbaş Suner, Selin; Şahiner, NurettinBackground/Objectives: Tannic acid (TA), a known natural polyphenolic acid with many bioactivities including antioxidants, antibacterial, and antiviral, can be combined with a natural essential amino acid L-lysine (LYS) in nanogel formulations to produce p(TA-co-LYS) (p(TA-co-LYS)) nanogels. Methods: A 1:1 mole ratio of TA:LYS was used to prepare corresponding spherical nanogels employing formaldehyde as a linker via the Mannich reaction. Results: The attained p(TA-co-LYS) particles were in 283 +/- 57 nm size ranges (via SEM analysis) and possessed smooth surfaces. The zeta potential measurements of p(TA-co-LYS) nanogels suspension at different solution pHs revealed the isoelectric point (IEP) of pH 4.9, suggesting that the particles are negatively charged at the physiological pH range (e.g., at 7.4). In addition to the antioxidant efficacy of nanogels confirmed by three different tests, p(TA-co-LYS) particles showed significant Fe(II) ion chelating capacity at 350 mu g/mL concentrations compared to bare TA, which is 21%, whereas the LYS molecule had a chelating capacity of 100% at the same concentrations. Moreover, it was found that p(TA-co-LYS) nanogels inhibited the Acetylcholinesterase enzyme (AChE) at a concentration-dependent profile, e.g., at 333 mu g/mL concentration of p(TA-co-LYS), 57.2% of the enzyme AChE activity was inhibited. Furthermore, the minimum inhibition concentrations of p(TA-co-LYS) nanogels of Gram-negative Escherichia coli (ATCC 8739) and Gram-positive Staphylococcus aureus (ATCC 6538) were determined as 12.5 mg/mL. Conclusions: As cytotoxicity studies of p(TA-co-LYS) nanogels on L929 fibroblast cells also ascertained that these particles can be safely used in many biomedical applications, including antioxidant materials, drug delivery devices, and enzyme inhibitors.Öğe Akıllı Mikrojellerle Kaplanmış Ham Pirina ve Yeşil Ceviz Kabuğunun ve Bunların Kompostlarının Kök-ur Nematodu Mücadelesinde Kullanılma Potansiyellerinin Araştırılması(2018) Kavdır, Yasemin; Şahiner, Nurettin; Gözel, UğurBirçok ülkede olduğu gibi Türkiye'de de domates kök-ur nematoduna karşı çok yoğun olarak nematisit kullanılmaktadır. Bu nematisitlerin ve fumigantların doğru kullanılmadığında insan ve çevre sağlığına çok zararlı oldukları bilinmektedir. Bu nedenle alternatif mücadele yöntemleri büyük önem taşımaktadır. Bu çalışmada pirina ve yeşil ceviz kabuğu (YCK) direk olarak, ekstrakte edilerek, kompost yapılarak ve ceviz içindeki juglon maddesi ve ekstrakları polimerle kaplanarak toprağa uygulanmış ve kök-ur nematodları (Meloidogyne spp.) populasyonunda oluşan farklılıklar ile domates gelişimi üzerine etkileri belirlenmiştir. Laboratuar, kontrollü atmosfer, açık hava saksı denemesi, tarla denemesi ve yüksek tünel denemesi olarak uygulamalar denenmiştir. Saksılarda, kök-ur oranı ve yumurta paketi oluşumu üzerine en etkili pirina ve YCK dozu %2 olmuştur. YCK ve pirina kompostu denemesinde kompost uygulanan bitkilerde kök ve boy gelişimi daha fazla olmuştur. Bitki köklerindeki urlanma da kontrole oranla daha az olmuştur. YCK kompostunun % 6 dozunda uygulanması topraktaki kök-ur nematodu sayısını % 88.4 oranında azaltmıştır. Saksı denemesinde YCK ekstraktı uygulanan topraklarda infektif larvaların azalma oranları %8.9 ile %38.1 arasındadır iken pirina ekstraktı uygulanan saksılarda bu oran %26.8-46.1 arasında değişmiştir. Çalışmada, ayrıca pirina, juglon ve YCK ekstraklarının uygulamasında taşıyıcı sistem olarak kullanılmak üzere CMC kullanılmıştır. 0.2Pirjel, 0.1Cjel ve 33Jugçöz uygulamaları domates bitkisine zarar vermeden %0 uygulamasına göre topraktaki nematod sayısını ve kök-ur oranını düşürmüştür. En etkin ve bitki gelişimine en zararsız uygulama 0.2Pirjel olmuştur. Tarla denemesinde %1 pirina ve YCK, %2 pirina ve YCK kompostu denenmiştir. YCK kompostu uygulamasında nematod sayısı en düşük bulunmuş ve ortalama 43.42 adet /100 g?dır. Kontrol parsellerinde M. incognita; sayısı %161 artarken, YCK uygulamasında %120, pirina uygulamasında %122, pirina kompostu uygulamasında %129 ve YCK kompostu uygulamasında ise %155 azalma meydana gelmiştir. Yüksek tünel denemesinde en yüksek domates verimi 5349 kg da-1 ile pirina kompostu uygulamasında bulunmuş ve bunu pirina uygulaması (4815 kg da-1) izlemiştir. Her iki denemede de maksimum M. incognita populasyonu kontrol parsellerinde bulunmuştur.Öğe Alpha-Glucosidase Enzyme Immobilized Dextran-Co Metal Nanoparticle Cryogel Composite Systems as Dual Catalyst with Enhanced Stability and Catalytic Activity(John Wiley and Sons Inc, 2023) Demirci, Şahin; Şahiner, NurettinHere, dextran (Dex) cryogels were prepared and used for the immobilization of α-Glu enzyme via two different techniques of entrapment and covalent linking. The entrapment of α-Glu enzyme within Dex cryogels (α-GluE@Dex) during the synthesis process caused almost 70 % activity loss. On the other hand, the Dex cryogels with α-Glu enzyme immobilized via covalent linking (α-GluC@Dex) maintained 91±1.1 % activity and afforded 10 consecutive usages and could be stored at 25 °C for 10 days with more than 50 % activity. Moreover, we prepared Cobalt (Co) metal nanoparticle containing Dex-Co cryogel composite to be used to immobilize the α-Glu enzyme via covalent linking to attain an α-GluC@Dex-Co catalyst system with dual catalytic performance e. g., enzymatic and chemical reduction of the substrate and its’ by-product for the first time. The prepared α-GluC@Dex-Co cryogels system was used for enzymatic hydrolysis of 4-nitrophenyl-α-D-glucopyranoside to glucose and 4-nitrophenol, and then the reduction of 4-nitrophenol to 4-aminophenol catalyzed by the Co metal nanoparticles present as co-catalyst within the cryogel network. The enzymatic activity of α-GluC@Dex-Co cryogels was calculated as 72±3.1 % and the cryogel reduced the enzymatic reaction by-product of 4-nitrophenol to 4-aminophenol in 7 min in the presence of NaBH4.
