Kimya ve Kimyasal İşleme Teknolojileri Bölümü

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https://hdl.handle.net/20.500.12491/10804

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A surface plasmon resonance sensor with synthetic receptors decorated on graphene oxide for selective detection of benzylpenicillin
(Elsevier, 2023) Çelik, Onur; Saylan, Yeşeren; Göktürk, Ilgım; Yılmaz, Fatma; Denizli, Adil
Antibiotic residues in foods, water and the environment reveal antibiotic-resistant bacterial strains, disrupting the ecological balance and causing serious health problems. For these reasons, the detection of antibiotic residues is crucial for the protection of human health. Herein, the detection of benzylpenicillin antibiotic from aqueous and milk sample solutions was carried out by surface plasmon resonance (SPR) sensor using synthetic receptor -molecularly imprinted polymer. The benzylpenicillin-imprinted poly(hydroxyethyl methacrylate-graphene oxide-N-methacryloyl-L-phenylalanine) (MIP-GO) SPR sensor was prepared. Benzylpenicillin detection was performed by MIP-GO SPR sensor in a 1-100 ppb concentration range of benzylpenicillin with 0.9665 linear correlation and 0.021 ppb detection limit. Selectivity analysis showed that the MIP-GO SPR sensor detected the benzylpenicillin molecule 8.16 times more selectively than amoxicillin and 14.04 times more selectively than ampicillin. To examine the imprinting efficiency, non-imprinted poly(hydroxyethyl methacrylate-graphene oxide-N-methacryloyl-L-phenylalanine) (NIP-GO) SPR sensor was also prepared using the same procedure without benzylpenicillin addition. Since graphene oxide (GO) was added to enhance the sensor signal response by increasing sensitivity, the control analyses were performed by a poly(hydroxyethyl methacrylate-N-meth-acryloyl-L-phenylalanine) (MIP) SPR sensor without adding GO. Moreover, repeatability studies of MIP-GO SPR sensor were statistically evaluated and the RSD of intra-day assays less than 1% specified that there was no loss of performance for the benzylpenicillin detection ability even after four cycles. As a real food sample analysis, the benzylpenicillin spiked and unspiked milk samples were evaluated and high-performance liquid chromatography experiments were carried out for validation.
SPR signal enhancement with silver nanoparticle-assisted plasmonic sensor for selective adenosine detection
(IEEE-Inst Electrical Electronics Engineers Inc, 2022) Göktürk, Ilgım; Yücel, Monireh Bakhshpour; Çimen, Duygu; Yılmaz, Fatma; Bereli, Nilay; Denizli, Adil
In this study, we fabricated adenosine imprinted poly(hydroxyethyl methacrylate-N-methacryloyl-L-cysteine methyl ester-silver nanoparticles (AgNPs)-N-methacryloyl-L-phenylalanine methyl ester) (MIP-Ag) sensor. It is a sensitive, simple, low-cost, and label-free adenosine determination in an aqueous solution without the need for any complicated coupling processes. The sensor without the addition of AgNPs (MIP) was prepared for control experiments to examine the effect of incorporated AgNPs to increase the signal response of surface plasmon resonance. Also, non-imprinted (NIP-Ag) sensor were designed using the same polymerization recipe without adding adenosine to evaluate the imprinting efficiency. The characterization studies of MIP-Ag, NIP-Ag and MIP sensors were carried out by atomic force microscopy and contact angle measurements. It was determined that the MIP-Ag sensor detected the target adenosine molecule 5.10 times more selectively than the competitor guanosine and 3.92 times more than thymidine. Imprinting efficiency was determined by comparing the signal response of MIP-Ag and NIP-Ag sensors. Repeatability studies of the MIP-Ag sensor were statistically analyzed for the 1.0 ppm adenosine, and the percent relative standard deviation of the intraday assays of less than 1.0% showed an insignificant decrease in the detection of adenosine after four adsorption-desorption cycles.
Gold-modified molecularly imprinted N-methacryloyl-(l)-phenylalanine-containing electrodes for electrochemical detection of dopamine
(MDPI, 2022) Shama, Nemah Abu; Aşır, Süleyman; Özsöz, Mehmet; Göktürk, Ilgım; Türkmen, Deniz; Yılmaz, Fatma; Denizli, Adil
A molecularly imprinted polymer-based pencil graphite electrode (MIP PGE) sensor, modified with gold nanoparticles, was utilized for the detection of dopamine in the presence of other biochemical compounds using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), depending on its strong electroactivity function. The pulse voltammetry methods recorded the highest response. In addition to the high oxidation rate of DA and the other biomolecule interferences available in the sample matrix used, which cause overlapping voltammograms, we aimed to differentiate them in a highly sensitive limit of detection range. The calibration curves for DA were obtained using the CV and DPV over the concentration range of 0.395-3.96 nM in 0.1 M phosphate buffer solution (PBS) at pH 7.4 with a correlation coefficient of 0.996 and a detection limit of 0.193 nM. The electrochemical technique was employed to detect DA molecules quantitatively in human blood plasma selected as real samples without applying any pre-treatment processes. MIP electrodes proved their ability to detect DA with high selectivity, even with epinephrine and norepinephrine competitor molecules and interferences, such as ascorbic acid (AA). The high level of recognition achieved by molecularly imprinted polymers (MIPs) is essential for many biological and pharmaceutical studies.
Selective amplification of plasmonic sensor signal for cortisol detection using gold nanoparticles
(MDPI, 2022) Yılmaz, Gaye Ezgi; Saylan, Yeseren; Göktürk, İlgim; Yılmaz, Fatma; Denizli, Adil
Herein, gold nanoparticles (AuNP)-modified cortisol-imprinted (AuNP-MIP) plasmonic sensor was developed for signal amplification and real-time cortisol determination in both aqueous and complex solutions. Firstly, the sensor surfaces were modified with 3-(trimethoxylyl)propyl methacrylate and then pre-complex was prepared using the functional monomer N-methacryloyl-L-histidine methyl ester. The monomer solution was made ready for polymerization by adding 2-hydroxyethyl methacrylate to ethylene glycol dimethacrylate. In order to confirm the signal enhancing effect of AuNP, only cortisol-imprinted (MIP) plasmonic sensor was prepared without AuNP. To determine the selectivity efficiency of the imprinting process, the non-imprinted (AuNP-NIP) plasmonic sensor was also prepared without cortisol. The characterization studies of the sensors were performed with atomic force microscopy and contact angle measurements. The kinetic analysis of the AuNP-MIP plasmonic sensor exhibited a high correlation coefficient (R-2 = 0.97) for a wide range (0.01-100 ppb) with a low detection limit (0.0087 ppb) for cortisol detection. Moreover, the high imprinting efficiency (k ' = 9.67) of the AuNP-MIP plasmonic sensor was determined by comparison with the AuNP-NIP plasmonic sensor. All kinetic results were validated and confirmed by HPLC.
Variation of fundamental features of cobalt surface-layered Bi-2212 superconductor materials with diffusion annealing temperature
(Elsevier Science Ltd, 2023) Öz, İlker; Terzioğlu, Cabir; Öz, Muhammed; Ülgen, Asaf Tolga; Türköz, Mustafa Burak; Yıldırım, Gürcan
The present study appears extensively on the role of diffusion annealing temperature intervals 650-850 degrees C on electrical conductivity, flux pinning ability, superconducting and crystallinity quality of Cobalt (Co) surface -layered Bi-2212 compounds with experimental tests including dc resistivity, bulk density, X-ray diffraction, critical current density measurements, and theoretical calculations. Experimental findings display that the Co ions may be replaced mostly by bismuth sites in the crystal lattice as a consequence of appropriate cation -vacancy, electron configurations of the outer shell, chemical valence states, and electronegativity of chemical contents in the main composition. The fundamental characteristic features refine considerably with 650 degrees C annealing temperature due to enhancement of antiferromagnetic spin fluctuations in the clusters of micro -domains, re-ordering of Cu-O bonds, stabilization of system, pairing mechanism, modulation of insulating Bi-O double layers, and orbital hybridization mechanisms. Accordingly, bulk Bi-2212 ceramic obtained at optimum annealing temperature exhibits the best conductivity because of a decrease in systematic crystallinity problems and potential grain boundary interaction problems expected in the system. Likewise, the optimum annealing temperature triggers the artificial nucleation regions for 2D discrete pancakelike Abrikosov vortices to decelerate thermal fluxon movements. Moreover, the X-ray diffraction results indicate that optimum Co ions in crystal lattice significantly improve crystal structure quality, grain alignment distributions in c-axis orientation, the extension of high-Tc Bi-2223 superconducting phase, and average crystallite size parameters. Additionally, the nucleation activation energy is noticed to reduce with optimum Co ions due to enhancement in the nucleation stability and crystallization temperature values to higher temperature zones. Namely, optimum Co ions easily diffusing into the lattice points support the formation of surface nucleation. In contrast, after a critical value of 650 degrees C, the characteristic properties mentioned suppress remarkably. In conclusion, the main characteristic features are extensively improved by the optimum diffusion annealing temperature for usage in novel and feasible market areas.
Simple and fast pesticide nanosensors: Example of surface plasmon resonance coumaphos nanosensor
(MDPI, 2023) Oymen, Beste; Jalilzadeh, Mitra; Yılmaz, Fatma; Aşır, Süleyman; Türkmen, Deniz; Denizli, Adil
Here, a molecular imprinting technique was employed to create an SPR-based nanosensor for the selective and sensitive detection of organophosphate-based coumaphos, a toxic insecticide/veterinary drug often used. To achieve this, UV polymerization was used to create polymeric nanofilms using N-methacryloyl-l-cysteine methyl ester, ethylene glycol dimethacrylate, and 2-hydroxyethyl methacrylate, which are functional monomers, cross-linkers, and hydrophilicity enabling agents, respectively. Several methods, including scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle (CA) analyses, were used to characterize the nanofilms. Using coumaphos-imprinted SPR (CIP-SPR) and non-imprinted SPR (NIP-SPR) nanosensor chips, the kinetic evaluations of coumaphos sensing were investigated. The created CIP-SPR nanosensor demonstrated high selectivity to the coumaphos molecule compared to similar competitor molecules, including diazinon, pirimiphos-methyl, pyridaphenthion, phosalone, N-2,4(dimethylphenyl) formamide, 2,4-dimethylaniline, dimethoate, and phosmet. Additionally, there is a magnificent linear relationship for the concentration range of 0.1-250 ppb, with a low limit of detection (LOD) and limit of quantification (LOQ) of 0.001 and 0.003 ppb, respectively, and a high imprinting factor (I.F.4.4) for coumaphos. The Langmuir adsorption model is the best appropriate thermodynamic approach for the nanosensor. Intraday trials were performed three times with five repetitions to statistically evaluate the CIP-SPR nanosensor's reusability. Reusability investigations for the two weeks of interday analyses also indicated the three-dimensional stability of the CIP-SPR nanosensor. The remarkable reusability and reproducibility of the procedure are indicated by an RSD% result of less than 1.5. Therefore, it has been determined that the generated CIP-SPR nanosensors are highly selective, rapidly responsive, simple to use, reusable, and sensitive for coumaphos detection in an aqueous solution. An amino acid, which was used to detect coumaphos, included a CIP-SPR nanosensor manufactured without complicated coupling methods and labelling processes. Liquid chromatography with tandem mass spectrometry (LC/MS-MS) studies was performed for the validation studies of the SPR.
S-citalopram imprinted monolithic columns for capillary electrochromatography enantioseparations
(WILEY, 2021) Derazshamshir, Ali; Göktürk, Ilgım; Yılmaz, Fatma; Denizli, Adil
In this study, the molecular imprinting method was used to separate enantiomeric forms of chiral antidepressant drug, R,S-citalopram (R,S-CIT) in aqueous solution by CEC system combining the advantages of capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC). For that, an amino acid-based molecularly imprinted monolithic capillary column was designed and used as a stationary phase for selective separation of S-citalopram (S-CIT) for the first time. S-CIT was selectively separated from the aqueous solution containing the other enantiomeric form of R-CIT, which is the same in size and shape as the template molecule. Morphology of the molecularly imprinted (MIP S-CIT) and non-imprinted (NIP S-CIT) monolithic capillary columns was observed by scanning electron microscopy. Imprinting efficiency of MIP S-CIT monolithic capillary column used for selective S-CIT separation was verified by comparing with NIP S-CIT and calculated imprinting factor (I.F:1.81) proved the high selectivity of the MIP S-CIT for S-CIT. Cavities formed for S-CIT form enabled selective (alpha = 2.08) separation of the target molecule from the other enantiomeric R-CIT form. Separation was achieved in a short period of 10 min, with the electrophoretic mobility of 7.68 x 10(-6) m(2)/Vs for R,S-CIT at pH 7.0 10 mM PB and 50% ACN ratio. The performance of both MIP S-CIT and NIP S-CIT columns was estimated by repeating the R,S-CIT separations with intra-batch and inter-batch studies for reproducibility of retention times of R,S-CITs. Estimated RSD values that are lower than 2% suggest that the monolithic columns separate R,S-CIT enantiomers without losing separation efficiency.
Development of molecularly imprinted polymer-based optical sensor for the sensitive penicillin g detection in milk
(WILEY-V C H VERLAG GMBH, 2021) Safran, Volkan; Göktürk, Ilgım; Bakhshpour, Monireh; Yılmaz, Fatma; Denizli, Adil
In this study, selective and sensitive Penicillin G (PEN-G) antibiotic detection from both aqueous solution and milk samples using molecular imprinting technique was performed by surface plasmon resonance sensor. For this purpose, PEN-G imprinted poly(2-Hydroxyethyl methacrylate-N-methacroyl-(L)-cysteine methyl ester-gold nanoparticles-N-methacryloyl-L-phenylalanine methyl ester (MIP-AuNPs) nanosensor was prepared. Control experiments were carried out via the nanosensor without the addition of AuNPs (MIP) to examine the effect of gold nanoparticles (AuNPs) incorporated to increase the surface plasmon resonance signal response. Moreover, to evaluate the imprinting efficiency, non-imprinted (NIP-AuNPs) nanosensor was designed using the same polymerization recipe except the addition of the PEN-G molecule. Characterization studies of MIP, MIP-AuNPs and NIP-AuNPs nanosensors were performed with FTIR-ATR spectrophotometer. Also, MIP-AuNPs and NIP-AuNPs nanosensors were characterized by atomic force microscopy, ellipsometer and contact angle measurements. Imprinting efficiency (I.F: 7.83) for the MIP-AuNPs nanosensor was determined by comparing it with the NIP-AuNPs nanosensor. The MIP-AuNPs nanosensor was 9.87 times more selective for the target PEN-G molecule than amoxicillin, and 16.78-times than ampicillin. In addition, the amount of PEN-G in milk selected as a real sample was measured by spiking 5 ppb PEN-G into the milk.
Sensitive and selective detection of amitrole based on molecularly imprinted nanosensor
(Wiley, 2021) Çakır, Oğuz; Bakhshpour, Monireh; Göktürk, Ilgım; Yılmaz, Fatma; Baysal, Zübeyde
Herein, a surface plasmon resonance (SPR)-based nanosensor was fabricated usingmolecular imprinting technique for the selective and sensitive detection of amitrole, acommonly used highly toxic pesticide. For this purpose, polymeric nanofilms involvingN-methacryloyl-L-tryptophan methyl ester and ethylene glycol dimethacrylate whichare functional monomer and cross-linker, respectively, were prepared on the SPR chipssurface via the ultravoilet polymerization method. The nanofilms were characterized byseveral techniques such as ellipsometry, Fourier transform infrared-attenuated totalreflection, atomic force microscope and contact angle measurements. The kinetic ana-lyses for amitrole detection were examined through amitrole-imprinted and non-imprinted SPR sensor chips. The developed imprinted sensor showed high selectivity tothe amitrole molecule than similar molecules and a good linear relationship for the0.06-11.90 nM concentration range with a low limit of detection value of 0.037 nM.The high imprinting efficiency (I.F: 62.38) of the amitrole-imprinted SPR sensor wasdetermined by comparing it with the non-imprinted SPR sensor. The most suitablemodel of this sensor is the Langmuir adsorption model. To statistically assess the reus-ability of the sensor, intraday experiments were tested three times with five replicates.The relative standard deviation% value less than <1.5 indicates high reproducibility forboth sensor production and reproducibility of the method. The prepared sensor wasalso applied efficiently for the selective detection of the amitrole in spiked samples pre-pared from vegetables to evaluate the matrix effect. As a result, amitrole-imprinted SPRsensors have been estimated to be highly selective, fast responsive, easy to use, reus-able and sensitive in detecting amitrole in both natural source and aqueous solutions.Label-free amitrole detection was performed by an aminoacid-based SPR sensor fabri-cated without the need for complex coupling processes.
Selective dopamine detection by SPR sensor signal amplification using gold nanoparticles
(ROYAL SOC CHEMISTRY, 2021) Türkmen, Deniz; Bakhshpour, Monireh; Göktürk, Ilgım; Aşır, Süleyman; Yılmaz, Fatma
In this study, selective and sensitive detection of the neurotransmitter dopamine (DA) in both aqueous solution and biological samples was performed using a surface plasmon resonance (SPR) sensor based on a molecular imprinting technique. For this, dopamine-imprinted poly(2-hydroxyethyl methacrylate-N-methacroyl-(l)-cysteine methyl ester-gold nanoparticles-N-methacryloyl-l-phenylalanine methyl ester) [PHEMAC-AuNPs/MAPADA] nanoparticles were prepared. Furthermore, to evaluate the imprinting efficiency, non-imprinted [PHEMAC-AuNPs/MAPA] nanoparticles were designed using the same polymerization procedure except for the addition of dopamine molecules. To examine the effect of incorporating AuNPs to increase the SPR signal response, control experiments were carried out via the SPR biosensor produced using [PHEMAC/MAPADA] nanoparticles prepared without the addition of AuNPs. Characterization studies of dopamine- + imprinted [PHEMAC-AuNPs/MAPADA] and non-imprinted [PHEMAC-AuNPs/MAPA] nanoparticles was performed with a zetasizer and an FTIR-ATR spectrophotometer. In addition, dopamine-imprinted [PHEMAC-AuNPs/MAPADA] and non-imprinted [PHEMAC-AuNPs/MAPADA] SPR sensors were characterized by ellipsometer and contact angle measurements. The high imprinting efficiency (I.F: 9.67) of the dopamine-imprinted [PHEMAC-AuNPs/MAPADA] SPR sensor was determined by comparing it with the non-imprinted [PHEMAC-AuNPs/MAPA] SPR sensor. A good linear relationship was obtained in the 0.01-0.5 ppb concentration range with correlation coefficients of 0.9818 and 0.9819, respectively. The dopamine-imprinted [PHEMAC-AuNPs/MAPADA] SPR sensor was 5.53 and 4.59 times more selective for the target molecule dopamine than for epinephrine (EP) and norepinephrine (NE), respectively. The repeatability of the [PHEMAC-AuNPs/MAPADA] SPR sensor was assessed with a 0.5 ppb dopamine solution, with the percent relative standard deviation of the intra-assays (RSD) being less than 1.7%, indicating negligible loss of dopamine sensing capability after four adsorption-desorption cycles with the same sensor.
Effect of borates on the synthesis of nanoscale hexagonal boron nitride by a solid-state method
(Wiley, 2021) Öz, Muhammed; Bozkurt, Çetin; Yılmaz, Binnur Kanbur; Yıldırım, Gürcan
This study delves deeply into the effect of different borates (lithium tetraborate,sodium tetraborate, calcium metaborate, ammonium pentaborate) on the productionand fundamental characteristic features of nanoscale hexagonal boron nitride (hBN)structure with the assistant of standard characteristic measurement methods,namely, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scan-ning and transmission electron microscopy (SEM and TEM). The hBN samples aresynthesized by reaction of powder urea, boron oxide, and different kinds of boratesvia the modified O'Connor method (performed at a relatively lower main heat treat-ment temperature of 1,100 C). All the results obtained show that the usage ofborates affects positively the formation of nanoscale hBN structure. In more detail,the FTIR experiment results reveal that the presence of two strong c peaks appearedat ~1,380 and ~780 cm 1in the spectra points out the conventional BN in-plane andout-of-plane vibrations, respectively. The XRD patterns also confirm the productionof high-ordered hBN as the existence of the main peaks of the corresponding hexag-onal system. As for the SEM examination, it is found that all the hBN materialsexhibit totally different crystallinity quality and microstructural characteristics. ThehBN compound prepared by the sodium tetraborate content shows the most uniformsurface appearance with the smoothest/densest crystal structure, best grain orienta-tions, and finest grain interactions. Hence, the material with strong stretching ofinteratomic bonds shows the highest material (fracture) strength. Moreover, the TEMimages illustrate that all the products are composed of uniform multi-walled nan-otubes and nanorods with an average length of ~250 nm.
Selective detection of penicillin g antibiotic in milk by molecularly imprinted polymer-based plasmonic SPR sensor
(MDPI, 2021) Bakhshpour, Monireh; Göktürk, Ilgım; Bereli, Nilay; Yılmaz, Fatma; Denizli, Adil
Molecularly imprinted polymer-based surface plasmon resonance sensor prepared using silver nanoparticles was designed for the selective recognition of Penicillin G (PEN-G) antibiotic from both aqueous solution and milk sample. PEN-G imprinted sensors (NpMIPs) SPR sensor was fabricated using poly (2-hydroxyethyl methacrylate-N-methacroyl-(L)-cysteine methyl ester)-silver nanoparticles-N-methacryloyl-L-phenylalanine methyl ester polymer by embedding silver nanoparticles (AgNPs) into the polymeric film structure. In addition, a non-imprinted (NpNIPs) SPR sensor was prepared by utilizing the same polymerization recipe without addition of the PEN-G template molecule to evaluate the imprinting effect. FTIR-ATR spectrophotometer, ellipsometer, contact angle measurements were used for the characterization of NpMIPs SPR sensors. The linear concentration range of 0.01-10 ng/mL PEN-G was studied for kinetic analyses. The augmenting effect of AgNPs used to increase the surface plasmon resonance signal response was examined using polymer-based PEN-G imprinted (MIPs) sensor without the addition of AgNPs. The antibiotic amount present in milk chosen as a real sample was measured by spiking PEN-G into the milk. According to the Scatchard, Langmuir, Freundlich and Langmuir-Freundlich adsorption models, the interaction mechanism was estimated to be compatible with the Langmuir model.
Selective recognition of nucleosides by boronate affinity organic-inorganic hybrid monolithic column
(Elsevier, 2021) Ektirici, Sisem; Göktürk, Ilgım; Yılmaz, Fatma; Denizli, Adil
Boronic acids are important ligands used to selectively recognize and enrich compounds containing cis-diol groups such as nucleosides. In the present study, organic-inorganic hybrid [POSS-MAH-BPA] monolithic column was prepared for the first time in the literature as a new boronate affinity system for the recognition of nucleosides. The selectivity of the [POSS-MAH-PBA] boronate affinity monolithic column for the recognition of cis-diol containing adenosine nucleoside from its analogue molecule of deoxyadenosine triphosphate, dATP, noncis-diol containing compound was investigated both by UV and HPLC studies. When the relative selectivity coefficients are compared, the [POSS-MAH-PBA] boronate affinity monolithic column is 4.25 times more selective for adenosine than [POSS-MAH] monolithic column. Besides, to determine endogenous nucleosides in biological fluids, which may serve as non-invasive cancer biomarkers, nucleosides were spiked into the urine solutions and passed through the [POSS-MAH-PBA] boronate affinity monolithic column, and the nucleosides were confirmed by HPLC. The adenosine recognition capability of the [POSS-MAH-PBA] boronate affinity monolithic column with an average enrichment factor of 48.9-fold was apparently superior to that of the [POSSMAH] monolithic column. Methacryl Polyhedral Oligomeric Silsesquioxanes (POSS-MA) with nano-sized stable 3-dimensional architectures provided the advantage of being used as an adsorbent for the monolithic structure by providing high surface area, 507.60 m(2)/g, and enabling vinyl groups to function with amino acid-based MAH monomers capable of providing electrons to coordinate PBA. Recovery results of more than 90% for adenosine showed that the [POSS-MAH-PBA] boronate affinity monolithic column could be a promising adsorbent for selective adsorption of cis-diol containing compounds such as nucleosides.
Temperature dependency on crystallinity and durability of mineral dolomite doped nanocrystalline hexagonal boron nitride
(Springer, 2020) Öz, Muhammed
In this study, Nanocrystalline Hexagonal Boron Nitride powders (n-hBN) were synthesized from boron oxide and urea in the presence of very cheap mineral of dolomite (chemical compound of calcium magnesium carbonate, CaMg(CO3)(2)) followed by a catalytic annealing method and subsequent heat treatment under the ammonia reactive gas atmosphere at different reaction temperatures. Experiments were performed in a tube furnace with controlled atmosphere at 1000 degrees C, 1150 degrees C, 1300 degrees C and 1450 degrees C for 3 h as the weight ratios of 2.5/5.0/3.0 for B2O3/urea/dolomite. Furthermore, the powder n-hBN samples produced were experimentally investigated by means of Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Thermal Gravimetric Analysis (TGA) and High-Resolution Transmission Electron Microscopy (HR-TEM). Instrumental methods pointed out that the samples indicate the boron nitride formation founded on the phase (crystal structure) transition from irregular turbostratic nature to highly crystalline hexagonal morphology. Additionally, it was observed from the results of FTIR and XRD analyses that the optimum reaction temperature was found to be 1450 degrees C for the high crystalline n-hBN structure. In fact, the formation temperature for the boron nitride material was also found to be relatively lower such a value of 1000 degrees C as compared to that of O'Connor method (1600 degrees C). The TGA and DSC examinations also displayed that the thermal dependence of BN in the hexagonal crystal structure was obtained to be stable up to the temperature of 1200 degrees C in the open atmosphere, and the exothermic peak reaching its top point at 1160 degrees C took place at a temperature range of 1050-1300 degrees C.
Electrochromatographic separation of hydrophobic amino acid enantiomers by molecularly imprinted capillary columns
(Elsevier Sci Ltd, 2020) Şarkaya, Koray; Asır, Süleyman; Göktürk, Ilgım; Yılmaz, Fatma; Yavuz, Handan; Denizli, Adil
In the present study, the enantiomeric forms of hydrophobic amino acids (L-tryptophan, L-tyrosine, and L-phenylalanine) were separated by molecularly imprinted capillary columns (MICC) via Capillary Electrochromatography (CEC) for the first time. The monomer ratio, crosslinker ratio, template molecule ratio, the porogen ratio and type, polymerization time, and also the effect of temperature were examined to increase the permeability properties of MICC. FTIR, SEM and BET analyses were realized for the characterization of MICC. The effect of the electric field, organic solvent ratio, and pressure were carried out experimentally to determine the optimum conditions. The separation performances of MICC and the non-imprinted capillary columns (NICC) were compared electrochromatographically.
Separation of histidine enantiomers by capillary electrochromatography with molecularly imprinted monolithic columns
(Wiley-V C H Verlag Gmbh, 2020) Şarkaya, Koray; Aşır, Süleyman; Göktürk, Ilgım; Ektirici, Sisem; Yılmaz, Fatma; Yavuz, Handan; Denizli, Adil
In this study, we aimed to separate the enantiomeric forms of d,l-histidine, one of the essential amino acids, through molecular imprinted monolithic capillary electrochromatography columns prepared using hydrophobic N-methacryloyl-(l)-phenylalanine methyl ester as the functional monomer, and l-histidine as the template molecule. We investigated the effect of monomer ratio, temperature, template molecule mole ratio, crosslinker ratio, and porogen ratio to improve the permeability properties of the monolithic column. Characterization studies of the column were evaluated by attenuated total reflectance-Fourier transform infrared spectroscopy, scanning electron microscopy, and Brunauer-Emmett-Teller analysis. The chromatographic performance of the column was investigated using alkylbenzene-derived compounds. We evaluated some parameters to determine the optimum conditions for electrochromatographic studies such as electric field, organic solvent ratio, and pressure effect. The calculated imprinting factor (2.18) proved that the l-histidine imprinted amino acid-based monolithic column separated d,l-histidine molecules efficiently (percent relative standard deviation < 1.5) from each other using molecular imprinting technique with high-resolution values (resolution value > 1.5). As a result, selective d,l-histidine separation was achieved in less than 10 min at pH 7.0 without using a ligand or extra modification step for the first time.
Real time monitoring and label free creatinine detection with artificial receptors
(Elsevier Science Bv, 2019) Topçu, Aykut Arif; Özgür, Erdoğan; Yılmaz, Fatma; Bereli, Nilay; Denizli, Adil
Molecular imprinting technique is used to design artificial creatinine receptor on the gold surface of surface plasmon resonance (SPR) chip using N-methacryloyl-(L)-histidine methyl ester (MAH), as a functional monomer. Surface characterization of SPR sensor chip is performed with atomic force microscope (AFM), ellipsometry and contact angle measurements. Creatinine imprinted SPR sensor is characterized with a linear range between 1 and 100 mM and limit of detection (LOD) and limit of quantification (LOQ) of creatinine are found 57 mu M and 190 mu M, respectively. N-hydroxysuccinimide (NHS) and creatine molecules are selected to examine the selectivity of creatinine imprinted SPR sensor. Reusability studies of SPR sensor is determined in urine mimic samples.
Molecularly imprinted based surface plasmon resonance nanosensors for microalbumin detection
(Taylor & Francis Ltd, 2019) Esentürk, Meltem Koca; Akgönüllü, Semra; Yılmaz, Fatma; Denizli, Adil
Human serum albumin (HSA) is a major blood plasma protein also found in urine where its existence may be a marker of some types of liver or kidney dysfunction. Herein, we fabricated a novel surface plasmon resonance (SPR) nanosensor for selective, sensitive, and label-free microalbumin detection both in aqueous and urine sample solutions. First, HSA-imprinted nanoparticles were synthesized, which consist of ethylene glycol dimethacrylate and N-methacryloyl-L-leucine methyl ester as a cross-linker and functional monomer. The nanoparticles were characterized by zeta-size and scanning electron microscope analyses and were dropped onto the SPR chip surface to make HSA sensitive nanosensor. Characterization studies of HSA-imprinted SPR chip were carried out by atomic force microscopy, Fourier-transform infrared spectroscopy, contact angle, and ellipsometer. The limit of detection and limit of quantification values of HSA-imprinted SPR nanosensor were calculated as 0.7pM and 1.9pM for the concentration range of 0.15-500nM. Selectivity studies of HSA-imprinted SPR nanosensor were achieved with hemoglobin and transferrin proteins which were chosen as competitor molecules. HSA-imprinted SPR nanosensor was displayed highly selective and sensitive to HSA.
Novel QCM and SPR sensors based on molecular imprinting for highly sensitive and selective detection of 2,4-dichlorophenoxyacetic acid in apple samples
(Elsevier Science Bv, 2019) Çakır, Oğuz; Bakhshpour, Monireh; Yılmaz, Fatma; Baysal, Zübeyde
This study aims to develop molecularly imprinted based quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) sensors for highly sensitive and selective detection of 2,4-dichlorophenoxyacetic acid (2,4-D) and to determine their accuracy and precision by liquid chromatography-tandem mass spectrometry (LC-MS/MS) as a reference technique. Here, we synthesized non-imprinted (NIP) and 2,4-D-imprinted (MIP) [ethylene glycol dimetacrylate-N-metacryloyl-(L)-tryptophan methyl ester-p(EGDMA-MATrp)] polymeric nanofilms by using molecular imprinting technique. MIP and NIP nanofilms were characterized by fourier transform infrared spectroscopy attenuated total reflectance (FTIR-ATR), atomic force microscope (AFM), contact angle and ellipsometer measurements. The molecular imprinting procedures were successfully carried out and it was found that the prepared polymeric surfaces were highly desirable for sensitive recognition by QCM and SPR sensors. Competitive experiments for the sensors revealed that MW nanofilms were found to show more sensitivity and selectivity than NIP ones. The sensor responses have a good linear relationship with 2,4-D concentrations in the range of 0.23-8.0 nM with a limit of detection at 20.17 ng/L for QCM and 24.57 ng/L for SPR sensors. In conclusion, both QCM and SPR sensor systems showed good accuracy and precision, with recovery percentages between 90 and 92% and 87-93%, respectively. Furthermore, they have a fast response time, reusability, high selectivity and sensitivity and low limit of detection.
Polymethacryloyl-L-Phenylalanine [PMAPA]-based monolithic column for capillary electrochromatography
(Oxford Univ Press Inc, 2019) Derazshamshir, Ali; Aşır, Süleyman; Göktürk, Ilgım; Ektirici, Sisem; Yılmaz, Fatma; Denizli, Adil
The ability to detect catecholamines (CAs) and their metabolites is vital to understand the mechanism behind the neuronal diseases. Neurochemistry aims to provide an improved pharmacological, molecular and physiological understanding of complex brain chemistries by analytical techniques. Capillary electrophoresis (CE) is one such analytical technique that enables the study of various chemical species ranging from amino acids and peptides to natural products and drugs. CE can easily adapt the changes in research focus and in recent years remains an applicable technique for investigating neuroscience and single cell neurobiology. The prepared phenylalanine-based hydrophobic monolithic column, Polymethacryloyl-L-phenylalanine [PMAPA], was used as a stationary phase in capillary electrochromatography to separate CAs that are similar in size and shape to each other including dopamine (DA) and norepinephrine (NE) via hydrophobic interactions. Separation carried out in a short period of 17 min was performed with the electrophoretic mobility of 5.54 x 10(-6) m(2) V-1 s(-1) and 7.60 x 10(-6) m(2) V-1 s(-1) for DA and NE, respectively, at pH 7.0, 65% acetonitrile ratio with 100 mbar applied pressure by the developed hydrophobic monolithic column without needing any extra process such as imprinting or spacer arms to immobilize ligands used in separation.

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