Synthesis of imprinted gels which sensitive to specific target molecules and the effect of the physical parameters on the sensitivity

Moleküler algılama; farklı türden molekülün bulunduğu bir ortamda, sadece belli bir molekülün, çoğunlukla zayıf fiziksel etkileşmeler aracılığıyla algılayıcı sisteme dönüşümlü olarak bağlanması ve salıverilmesi olarak tanımlanır. Biyolojik sistemlerde gözlemlenen moleküller arası özgün etkileşmelerin taklit edilerek endüstriyel amaçlı çalışmalara uygulanması son 20 yılın hızlı gelişen, disiplinler arası çalışma sahası haline gelmiştir. Yapay polimerler ya da polimerik jeller çok farklı özelliklere sahip monomerlerle sentezlenebilmektedir ve bunların özel bir teknikle (kalıplama tekniği) sentezlenmesi durumunda, biyolojik sistemlerde olduğu gibi, doğal seçici sistemlere benzer davranış gösteren yapay sistemlerin geliştirilebileceği düşünülebilir. Bu çalışmada hedef molekül olarak belirlenen floresans özelliğe sahip piranin molekülüne duyarlı jel sentezlenmesi ve bu jelin moleküler algılama kabiliyetinin jelin kompozisyonuna ve sıcaklık, pH, iyon derişimi gibi çevresel faktörlere bağlılığının araştırılması hedeflenmiştir. Karakterizasyon yöntemi olarak floresans spektroskopisi tekniği kullanılmıştır. Bu yöntemin en önemli üstünlükleri etkileşmeler hakkında oldukça zengin bilgi vermesi, uygulama kolaylığı ve maliyetinin düşük olmasıdır. Bu yöntem ile elde edilen spektrumlar değerlendirilerek jellerin Hafıza kabiliyetleri belirlenmiştir. Bu işlem bu tez kapsamında önerdiğimiz “Hafıza Parametresi” modeli ile gerçekleştirilmiştir. Hedef molekülün jele difüzyonu sonrası, jellerden alınan spektrumlarda meydana gelen dalgaboyu kaymaları yoluyla jellerin algılama kabiliyetleri tanımlanmıştır. Bu yolla tanımlanan ve ölçülen hafıza parametresinin kalıplanmamış jellerde sıfıra yakın çıkarken kalıplanmış jellerde en az 0.6 olarak bulunmuştur. Tezde sıcaklık, hedef molekül ve tuz derişimi, pH gibi parametrelerin algılama sürecine olan etkileri de ayrıntılı olarak tartışılmaktadır.  Anahtar Kelimeler: Moleküler algılama, moleküler kalıplama, floresans spektroskopisi, polimerik jeller.The molecular recognition is defined as reversible adsorption -by means of weak physical interactions- of a specific molecule from a medium in which different kinds of molecules are exist together. Imitating the specific interactions available in the biological systems, and applying them to industrial applications have been one of rapidly developing interdisciplinary fields of last 20 years. Synthetic polymers or polymeric gels can be synthesized with monomers which have different functional peripheral groups. The physical interactions, like electrostatic, van der Waals, hydrogen bonding, and hydrophilic or hydrophobic, having different nature are possible between the polymer chains themselves, and also between the polymer chains and the solvent molecules. One of the most important properties of polymeric gels is undergoing phase transitions between collapsed and swollen states as a result of external stimuli. Namely, they are the smart materials which respond to external stimuli. This phase transition can be induced by temperature, solvent composition, pH, ionization degree of network, electric field or light. By synthesizing the polymeric gels with a special technique called as imprinting technique, it is possible to construct artificial systems showing similar behaviors with natural selective systems as in the biological systems. In these systems there are three different interactions between the target molecule and the host molecule. These are the covalent, non-covalent and semi-covalent (hybrid) interactions. The targets can be ions and molecules such as metals, small organic molecules like aminoacids, peptide, sugar and large organic molecules like polypeptide, proteins. In this work it is aimed to synthesis imprinted gels which can recognize the target molecule, pyranine, which is a fluoroprobe, and to study the strength of the recognition as a function of the composition of the gels and the environmental factors such as the concentration of the target molecule, temperature, pH and the concentration of the replacement molecules (NaCl). In these studies fluorescence technique was used as the experimental technique for characterization. Also absorption measurements were done to verify some of the fluorescence measurements. No stable dependence of the recognition on the concentration of the target molecules was observed. This is due to both the absence of replacement molecules and the loose network structure of the gel because of the small amount of crosslinker molecules. Since the network structure is very loose, the gel can not keep its initial conformation when it is collapsed. This means that the volume of the collapsed gel is smaller than the initial volume and also the size of the cavities in the gel is smaller. So this change in the sizes of the cavities destroys the imprinting effect. It was observed that at 60oC, although the gels were in collapsed state, the diffused amount of target molecules was the highest. And also the diffusion into the imprinted gel was much bigger than that of the random gel. At this temperature the imprinted gel has the most convenient conformation for the target molecules. But the random gel is not. Its volume is smaller than that of its initial volume. This smaller volume obstructs the diffusion into the random gel. It was observed that the diffusion into the gels at pH=4 is bigger than the other pH values. Since the pH of the conditions of synthesize of the gels were also around 4, it can be concluded that the microstructures of the gels became the most appropriate conformation at this pH value. Presence of the replacement molecules affects the diffusion of target molecules. At moderate concentrations of replacement molecules they bring the target molecules close to each other via the bridges constructed by the electrostatic interactions between Na+ and . In this case the fluorescence maximum of the target molecules is observed at both 430nm and 506nm. At high concentrations they separate the clusters and the fluorescence spectrum shift to 515 nm completely. The absorption experiments showed that the number of functionality groups of the target molecules was 3.1±0.9 for imprinted gel and 0.9±0.1 for the random gel. These values are very close the values given in literature. The ?Recognition Parameter? was defined first time in terms of the shifts in the wavelength of the fluorescence spectra of the gel in which the target molecules were diffused. It was calculated that it was almost zero for non-imprinted gels while it becomes bigger than 0.6 for imprinted gels.  Keywords: Molecular recognition, molecular imprinting, fluorescence spectroscopy, polymeric gels.

Dizajn maske za lice s UVC-LED zračenjem i njezina djelotvornost protiv uobičajenih klica

During the Covid-19 pandemic, one of the best means of personal protection was using face masks. In this context, the World Health Organization has declared the attempts to produce masks inactivating airborne virus species a welcome initiative. This preliminary study aimed to prove that airborne germs passing through a mask filter cartridge can be destroyed by the rays emitted from UVC LEDs placed in such cartridge. We therefore designed such a face mask and tested the efficiency of UVC LEDs placed in its cartridge against common contaminants, gram-positive Staphylococcus aureus, gram-negative Pseudomonas aeruginosa, and the influenza A/Puerto Rico/8/1934 virus because of its similarity with SARS CoV-2. Eight UVC LEDs with a total power of 75 mW provided sufficient germicidal effect for all three germs. In terms of safety, ozone production released during UVC LED emission was negligible. Our findings are promising, as they show that well-designed UVC-based face masks can be effective against airborne germs, but further research on a greater sample may help us learn more and optimise such face masks.Tijekom pandemije Covida-19 jedan od najboljih oblika osobne zaštite bilo je nošenje maski za lice. U tom je smislu Svjetska zdravstvena organizacija pozdravila pokušaje izrade maski koje ubijaju virusne vrste koje se prenose zrakom. Cilj je ovoga preliminarnog istraživanja bio dokazati da se zrakom nošene klice koje prolaze kroz filtarske uloške mogu uništiti zračenjem UVC ledica smještenih u takve uloške. Stoga smo osmislili masku za lice s tom namjenom i iskušali djelotvornost UVC ledica protiv uobičajenih izvora zaraza: gram-pozitivnoga Staphylococcus aureus, gram-negativnoga Pseudomonas aeruginosa i virusa influence A/Puerto Rico/8/1934 zbog njegove sličnosti s virusom SARS CoV-2. Osam UVC ledica ukupne snage 75 mW iskazale su dovoljan germicidni učinak protiv svih triju klica. U smislu sigurnosti primjene, ozon proizveden tijekom UVC-LED zračenja pokazao se zanemarivim. Naši su rezultati obećavajući jer pokazuju da dobro osmišljene maske za lice s UVC zračenjem mogu biti djelotvorne protiv zrakom nošenih klica, ali će tek daljnja istraživanja na većem uzorku pomoći da doznamo više i usavršimo takve maske za lice

Monitoring the film formation process of polystyrene/poly acrylamide (PS/PAAm) composite films annealed by IR heating

In this study, UV-visible (UVV) technique was used to probe the evolution of optical transmission during the film formation from composites of polystyrene (PS) latex particles and poly acrylamide (PAAm) films annealed by the infrared radiative heating (IRH) and convectional heating. Activation energies corresponding to the void closure and the interdiffusion stages were calculated. It was shown that the activation energy for the void closure processes of viscous flow from the composite films decreased considerably in IRH annealing technique. It was observed that IRH heating speeds up the film formation process and the decrease the required energy. POLYM. ENG. SCI., 58:353-360, 2018. (c) 2017 Society of Plastics Engineer

The ONN-complexes of dioxomolybdenum(VI) with dibasic 2-hydroxy-1-naphthaldehyde S-methyl/allyl-4-phenyl-thiosemicarbazones

New dioxomolybdenum(VI) complexes were prepared by reacting S-methyl/allyl-4-phenyl-thiosemicarbazones of 2-hydroxy-1-naphthaldehyde (L H-1(2) and L H-2(2)) and [MoO2(acac)(2)] in methyl, ethyl and propylalcohols. In the complexes the doubly deprotonated ligands are coordinated to molybdenum as tridentate ONN-donors through phenolic-oxygen, azomethine- and thioamide-nitrogen. The solid complexes of general formula [MoO2L(ROH)] which contain an alcohol (ROH) as second ligand were characterized by physico-chemical and spectroscopic methods. The fluorescence emission intensities of the compounds were recorded in chloroform, and the intensity changes were evaluated depending on chelation and time. The structure of the S-allyl-4-phenyl-thiosemicarbazone complex has been determined by the single crystal X-ray diffraction method

Electrodeposition of zinc and reduced graphene oxide on porous nickel electrodes for high performance supercapacitors

Electrochemical properties of porous nickel (Ni) foam, electrodeposited zinc (Zn) on Ni foam (Ni-Zn) and electrodeposited reduced graphene oxide (rGO) on Ni-Zn foam electrodes (Ni-Zn-rGO) in 6 M KOH electrolyte were investigated. Cyclic voltammetry (CV) and galvanostatic charge-discharge cycling (GCD) techniques were used to carry out the redox interactions, and cycling capacitive properties of the electrodes in KOH solution. Platinum (Pt) and gold (Au) foil were used as a counter electrode and the current collector in the electrochemical measurements, respectively. The specific capacitances of the electrodes were found from the GCD measurements as 155, 722 and 1820 F/g for Ni, Ni-Zn and Ni-Zn/rGO electrodes at the current density of 1 A/g, respectively. Scanning electron microscope (SEM) images of the three electrodes were also taken into account to associate all the electrochemical measurements. These results clearly show that specific capacitance values highly increased after the deposition of Zn and rGO to Ni electrode

Effect of IR heating and the annealing time on the optical transmittance of polystyrene/Na-Alginate polymer composite films

Composite films of Na-Alginate (Mg) and Polystyrene (PS), which have different glass transition temperatures (T-g), with different weight ratios were prepared. Characterization of the film formation process was carried out by using the photon transmission (PT) measurements and the scanning electron microscopy (SEM) imaging. The composite films were annealed in the standard oven and under the IR lamp (IRH) for comparison. It was observed that IRH speeds up the film formation and decreases the required energy for film formation. On the other hand, the healing energies calculated for the films annealed in IRH were higher than those of the films annealed in the oven. In addition, it was shown that the optical transmittance of the films annealed in IRH increases as the annealing time increases while it is almost constant for the films annealed in the oven. Finally, it was observed that IRH causes some deformations on the surface of the composite films, especially at high temperatures, which may be due to the decomposition of low-T-g Alg polymers