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Preparation of methacrylate polymer nanocomposites with cellulose
No full textPolimerni kompoziti predstavljaju skupinu materijala vrlo široke primjene koji omogućavaju napredak u brojnim područjima kao što su ambalažni materijali, folije, filmovi, zatim konstrukcijski materijali i slično. Nanoceluloza, jedan od prirodnih i obnovljivih polimera čijom se upotrebom pridonosi zaštiti okoliša, postaje popularna zbog jednostavne mogućnosti primjene i dobrih svojstava. Koristi se kao punilo u sintetskom polimeru s ciljem da ga zamijeni u što većem udjelu i ujedno ne pogorša njegova svojstva. Cilj ovog rada je prirediti polimerne kompozite na osnovi kopolimera metil-matakrilata i funkcionalnih metakrilata s kristalnom nanocelulozom i ispitati im glavna svojstva. Kopolimerizacija je provedena u zelenom otapalu dobivenom iz obnovljive biomase. Dihidrolevoglukozenon, koji je korišten u ovom radu te poznatiji pod nazivom CyreneTM, potpuno je biorazgradivo otapalo dobiveno pirolizom iz celuloze. U polimerizaciji su dobivene visoke konverzije monomera, te visoke molekulske mase i razmjerno niska polidisperznost kopolimera. Temperatura staklastog prijelaza polimernih nanokompozita se povećava s povećanjem udjela celuloznih nanokristala. Modul elastičnosti kompozitnih materijala je nešto veći ili manji u odnosu na čisti kopolimer i nema značajan utjecaj na primjenska svojstva. Utjecaj na prekidnu čvrstoću kopolimera dodatkom celuloznih nanokristala nije velik osim kod kopolimera metil-metakrilata s hidroksietil-metakrilatom. Istraživanjem je potvrđeno da se upotrebom zelenog otapala i celuloze kao punila mogu proizvesti polimerni materijali veće obnovljivosti i sa znatno manjim štetnim utjecajem na okoliš.Polymer composites present a group of materials that have very wide use and provide improvement in many areas such as materials for packaging, foils, films, construction materials and others. Nanocellulose, one of the natural and renewable polymers that contribute to environmental sustainability, is becoming very important because of its easy application possibilities and good properties. It is used as a filler in a synthetic polymer and it aims to replace it in the largest quantity possible and thereby does not worsen its properties. The purpose of this work is to prepare polymer composites based on the methyl methacrylate copolymer and functional methacrylates with crystal nanocellulose and to test their main properties. The copolymerization was conducted in a green solvent obtained from renewable biomass. Dihydrolevoglucosenone, which was used in this work, also known as CyreneTM, is a completely biodegradable solvent obtained through pyrolysis from cellulose. In the polymerization high conversions of the monomers, high molecular weights and low polydispersity are achieved. The glass transition temperature of the polymer nanocomposites increases with an increased addition of cellulose nanocrystals. The modulus of elasticity of composite materials is slightly higher or lower in regard to the pure copolymer and does not have a significant impact on the application properties. The influence on the breaking strength of the copolymer with the addition of cellulose nanocrystals is not big except for the copolymer methyl methacrylate with hydroxyethyl methacrylate. The research confirmed that by using a green solvent and cellulose as a filler, polymer materials can be produced with higher renewability and the harmful impact on the environment is significantly lesser
Effect of thermooxidative ageing on PET and PE microplastics
No full textVelik porast potražnje za plastičnim proizvodima u posljednjim desetljećima doveo je do znatnih razmjera onečišćenja okoliša plastikom. Različitim procesima starenja i mehaničke degradacije plastika se postupno usitnjava na sitnije dijelove (<5 mm) i nastaje mikroplastika koja se smatra jednim od prioritetnih onečišćivala današnjice. Mikroplastika negativno utječe na sve sastavnice okoliša, a može imati i znatne posljedice na ljudsko zdravlje. U ovom radu polimeri poli(etilen-tereftalat) (PET) i polietilen visoke gustoće (HDPE), toplinski su stareni u laboratorijskoj peći iznad temperature taljenja. Uzorci polimera potom su usitnjeni do veličine mikroplastike te karakterizirani pomoću infracrvenog spektrofotometra s Fourierovom transformacijom signala koji koristi metodu atenuirane totalne reflektometrije (ATR-FTIR) i diferencijalnog pretražnog kalorimetra (DSC). Kod HDPE-a nisu vidljive značajne promjene između nestarenih i starenih uzoraka, zbog nedovoljno visoke temperature zagrijavanja koja je potrebna za inicijaciju toplinske degradacije. U starenim uzorcima PET-a vidljive su promjene u boji te dolazi do pogoršanja pojedinih svojstava poput temperature taljenja (Tm), temperature staklastog prijelaza (Tg), postotka kristalnosti (χ), i tako dalje. Iako su u PET uzorcima neke promjene vidljive, svejedno temperatura pri kojoj smo starili materijal nije dovoljna za neke značajnije promjene.The high demand for plastic products in the last several decades resulted in significant environmental contamination with plastics. Through various aging processes, and mechanical degradation, plastics breaks down into ever smaller particles (< 5 mm) and forms microplastics, which are considered one of today's priority pollutants. Microplastics have negative effects on all components of the environment and can also have significant consequences on human health. In this study, polyethylene terephthalate (PET) and high-density polyethylene plastics were thermally aged at the melting temperatures of the polymers. Pristine and aged polymers were grind to microplastic size and then characterized by Fourier transform infrared spectroscopy (ATR-FTIR) and differential scanning calorimetry (DSC). For HDPE, no significant changes were observed between pristine and aged samples, indicating that the polymer was not aged at a sufficiently high temperature to initiate thermal degradation within the material. Aged PET samples showed visible colour changes as well as a decrease in certain values such as melting temperature (Tm), glass transition temperature (Tg), and crystallinity percentage (χ). Although some changes can be seen in the PET samples, the aging temperature of the material was not sufficient to cause major changes
Validation of the HPLC-DAD method for the determination of pollutants in model and real samples
No full textOnečišćivala ljudskim djelovanjem dospijevaju u okoliš gdje se akumuliraju i zbog svoje toksičnosti predstavljaju problem za sve žive organizme. Danas ne postoji zakonska obveza praćenja koncentracija istih u okolišu, no trenutno se radi na tome da se uvedu i takve regulative pored postojanih pravilnika. Kako bi se omogućilo praćenje koncentracija i emisija onečišćivala u okolišu, potrebno je definirati pouzdanu metodu analize koja je primjenjiva za rad na svim uzorcima voda. Tekućinska kromatografija visoke djelotvornosti s detektorom s nizom dioda (HPLC-DAD) je kromatografska metoda analize koja je cjenovno vrlo pristupačna, brza i pouzdana metoda analize zbog svoje robusnosti, selektivnosti i osjetljivosti na niske koncentracije analita u uzorcima. Kromatografija se u biti dešava u koloni gdje dolazi do različitog zadržavanja analita na nepokretnoj odnosno u pokretnoj fazi što opet ovisi i o fizikalno-kemijskim svojstvima ne samo analita koji se određuje već i sorbensa u koloni te pokretnoj fazi. Međutim, jednom kada analiti prođu kroz kolonu sva redom odlaze na detektor s nizom dioda gdje se spektrofotometrijski detektiraju, a kao rezultat se dobivaju kromatogrami i apsorpcijski spektri za dobivanje kvantitativnih i kvalitativnih prametara za određivanje i detekciju ispitivanih analita. Da bi neka metoda mogla biti primjenjiva i pouzdana za određenu analizu ispitivanih analita, mora proći postupak validacije. Validacijom se određuju izvedbene značajke instrumenta i optimirane metode određujući parametre poput linearnosti, ponovljivosti, stabilnosti i iskoristivosti instrumentalne metode koji se zatim uspoređuju s definiranim kriterijima. U biti cilj postupka validacije je da se potvrdi je li izabrana i optimirana metoda prikladna za analizu ispitivanih analita u određenim uzorcima.Contaminants introduced by human activities enter the environment, where they accumulate and pose a problem for all living organisms due to their toxicity. Currently, there is no legal obligation to monitor their concentrations in the environment, but efforts are underway to introduce such regulations alongside existing guidelines. To enable the monitoring of concentrations and emissions of contaminants in the environment, it is necessary to define a reliable analytical method applicable to all water samples. High-performance liquid chromatography with diode array detector (HPLC-DAD) is a chromatographic analysis method that is cost-effective, fast, and reliable due to its robustness, selectivity, and sensitivity to low concentrations of analytes in samples. Chromatography occurs primarily in the column, where analytes experience different retention times depending on their interactions with the stationary and mobile phases. These interactions are influenced by the physical and chemical properties of both the analytes and the stationary phase (sorbent) in the column, as well as the mobile phase. However, once the analytes pass through the column, they proceed to the diode array detector, where they are detected spectrophotometrically, resulting in chromatograms and absorption spectra that provide quantitative and qualitative parameters for the identification and detection of the analytes. For a method to be applicable and reliable for the analysis of specific analytes, it must undergo a validation process. Validation determines the performance characteristics of the instrument and the optimized method by assessing parameters such as linearity, repeatability, stability, and recovery of the instrumental method, which are then compared to defined criteria. Essentially, the goal of the validation process is to confirm whether the selected and optimized method is suitable for analyzing the target analytes in specific samples
Antibacterial porous chitosan-based scaffolds
No full textZbog svojih izvrsnih svojstava poput biokompatibilnosti, biorazgradljivosti, antibakterijskog te antimikrobnog djelovanja, kitozan (CHT) pokazuje široku primjenu u prehrambenoj, poljoprivrednoj i farmaceutskoj industriji te medicini. Cilj ovoga rada bio je istražiti antibakterijska svojstva pripremljenih poroznih nosača na temelju kitozana s bakrovim(II) ionima uz dodatak hidroksiapatita (CHT-Cu/HAp) na gram-pozitivnu (Staphylococcus aureus) i gram-negativnu bakteriju (Klebsiella pneumoniae). CHT-Cu/HAp hidrogelovi različitih masenih udjela hidroksiapatita (0, 5, 10 i 20 mas.%) dobiveni su neutralizacijom s
1,25 mol dm^-3 otopinom natrijeva hidroksida, a suhi porozni nosači (aerogelovi) procesom liofilizacije. Suhi porozni CHT-Cu/HAp uzorci istraženi su infracrvenom spektroskopijom s Fourierovom transformacijom (FTIR), a dobiveni rezultati ukazuju na postojanje interakcije između polimerne matrice i punila. Stupanj bubrenja (SB), istražen u fosfatom puferiranoj otopini soli (PBS) pri fiziološkim uvjetima (pH 7,4; 37 °C) tijekom 24 h, ukazuje na izostanak značajnih statističkih razlika između uzoraka različitog kemijskog sastava, odnosno stupanj bubrenja za sve uzorke iznosi između 17–21. Antibakterijska svojstva pripremljenih poroznih CHT-Cu/HAp nosača istražena su primjenom disk-difuzijske metode na dvije bakterijske kulture: Staphylococcus aureus (gram-pozitivna bakterija) i Klebsiella pneumoniae
(gram-negativna bakterija). Rezultati pokazuju da uzorci s dodatkom hidroksiapatita
(CHT-Cu/HAp5, CHT-Cu/HAp10 i CHT-Cu/HAp20), prethodno nabubreni u PBS-u tijekom 3 i 24 h, posjeduju antibakterijsko djelovanje na gram-pozitivnu bakteriju. Kod svih CHT-Cu/HAp uzoraka je uočen izostanak antibakterijskog djelovanja za gram-negativnu bakteriju. Također, svi suhi uzorci nisu pokazali antibakterijsko djelovanje na obje bakterije. Uspješno pripremljeni porozni nosači na temelju kitozana, bakrovih(II) iona i hidroksiapatita pokazali su dobra antibakterijska svojstva protiv gram-pozitivnih bakterija, uz potencijalnu primjenu u biomedicinskom području.Due to its excellent properties such as biocompatibility, biodegradability, antibacterial, and antimicrobial effects, chitosan (CHT) demonstrates wide application in the food, agricultural, and pharmaceutical industries, as well as in medicine. The aim of this study was to investigate the antibacterial properties of the prepared porous
chitosan-copper (II)/hydroxyapatite-based (CHT-Cu/HAp) scaffolds on Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Klebsiella pneumoniae).
CHT-Cu/HAp hydrogels with varying amount of hydroxyapatite (0, 5, 10, and 20 wt.%) were obtained by neutralisation with 1.25 mol dm^-3 sodium hydroxide solution, while dry porous carriers (aerogels) were obtained through lyophilization. The dry porous CHT-Cu/HAp samples were analysed by Fourier-transform infrared spectroscopy (FTIR), and the results indicate the presence of interactions between the polymer matrix and the filler. The swelling degree (SB) was investigated in phosphate-buffered saline solution (PBS) under physiological conditions (pH 7.4; 37 °C) for 24 hours, and there were no significant statistical differences between samples with different chemical composition, with the swelling degree for all samples ranging between 17–21. The antibacterial properties of the prepared porous CHT-Cu/HAp scaffolds were examined using the disk diffusion method on two bacterial cultures: Staphylococcus aureus (Gram-positive bacteria) and Klebsiella pneumoniae
(Gram-negative bacteria). The results show that the samples with the addition of hydroxyapatite (CHT-Cu/HAp5, CHT-Cu/HAp10 i CHT-Cu/HAp20), pre-swollen in PBS for
3 and 24 h, exhibited antibacterial activity against the Gram-positive bacteria.
All CHT-Cu/HAp samples show no antibacterial activity against the Gram-negative bacteria. Additionally, all dry samples showed a lack of antibacterial activity against both Gram-positive and Gram-negative bacteria. The successfully prepared porous scaffolds based on chitosan, copper (II) ions, and hydroxyapatite demonstrated good antibacterial properties against Gram-positive bacteria, with potential applications in biomedical field
Photoelectrochemical characterisation BiVO4 modified by iron and silver
No full textCilj ovoga završnog rada bio je ispitati fotoelektrokemijske odzive nemodificirane BiVO4 elektrode i elektrode željezom i srebrom modificiranog BiVO4 u otopini 0,5 M natrijeva sulfata, koje su priređene uz vezivo ili iz alkoholne suspenzije. Za karakterizaciju korištena je metoda linearne polarizacije, elektrokemijska impedancijska spektroskopija, praćenje napona otvorenog kruga i Mott-Schottky analiza. Ispitivanja su provedena za osvjetljene i neosvjetljene elektrode, pri čemu je LED lampa bila izvor svjetla. Rezultati dobiveni metodom linearne polarizacije pokazuju da elektrode pripravljene na oba načina pokazuju fotoaktivnost, ali da se zbog različitih učinaka nemodificirana elektroda pokazala boljom. Ispitivanje metodom elektrokemijske impedancijske spektroskopije zabilježeno je da su bez prisustva svjetla zabilježene veće impedancije, što nam govori o dobroj fotoaktivnosti materijala. Također, ovom metodom je utvrđeno kako modificirani BiVO4 pokazuje bolju fotoaktivnost. Praćenjem napona otvorenog kruga potvrđena je fotoaktivnost obje elektrode, a budući da napon prilikom osvijetljenja poprima negativniju vrijednost u odnosu na protuelektrodu od platine može se zaključiti da su ispitani materijali n-tip poluvodiča.
Napon otvorenog kruga ukazuje da je bolja fotoaktivnost dobivena kod modificirane elektrode.The aim of this study was to investigate the photoelectrochemical responses of unmodified BiVO4 electrodes and BiVO4 electrodes modified with iron and silver in a 0.5 M sodium sulfate solution. These electrodes were prepared either with a binder or from an alcoholic suspension. Characterization was performed using linear polarization, electrochemical impedance spectroscopy, open circuit potential monitoring, and Mott-Schottky analysis. Testing was conducted on both illuminated and non-illuminated electrodes, with an LED lamp serving as the light source. Linear polarization results indicate that both types of electrodes exhibit photoactivity; however, due to varying effects, the unmodified electrode demonstrated superior performance. Electrochemical impedance spectroscopy revealed higher impedances in the absence of light, suggesting strong photoactivity of the materials. Furthermore, this method established that the modified BiVO4 exhibits enhanced photoactivity. Open circuit potential monitoring confirmed the photoactivity of both electrodes. Since the potential under illumination is more negative compared to the platinum counter electrode, it can be inferred that the materials under investigation are n-type semiconductors. The open circuit potential indicates that the modified electrode shows better photoactivity
Reduction methods for degradation of perfluorinated compounds in water
No full textPerfluorirani spojevi (engl. Perfluoroalkyl substances, PFAS) koriste se kao aditivi u raznim proizvodima, poput posuđa s neprijanjajućim slojem, vodootpornog materijala, ambalaže za hranu, kao pjena za gašenje požara, zbog njihove stabilnosti i otpornosti na masnoću, vodu i toplinu. Prilikom upotrebe tih proizvoda, a posebno prilikom njihovog neadekvatnog odlaganja u okoliš, može doći do onečišćenja tla, a posljedično i voda. Kada dospiju u okoliš, dolazi do bioakumulacije PFAS-a, pri čemu mogu imati negativno djelovanje na fluoru i faunu, te posljedično, na ljudsko zdravlje; zbog čega često nose naziv "vječne kemikalije". Europska regulativa prepoznala je ovu opasnost i ustanovila maksimalno dozvoljenu koncentracija PFAS spojeva u vodi za piće 0,5 μg/L, stoga ih je važno ukloniti iz otpadnih voda, odnosno razgraditi. Konvencionalni sustavi za obradu otpadnih voda nisu dovoljno učinkoviti za tu svrhu. S druge strane, napredne metode uključuju membrane koje nisu učinkovite za razgradnju već uklanjanje PFAS-a; za razliku od njih napredni oksidacijski procesi djelomično su učinkoviti za razgradnju PFAS spojeva pomoću hidroksilnih radikala; ipak, krajnji je cilj postizanje defluorizacije PFAS spojeva, što je moguće postići reduktivnim procesima.
Cilj je ovog rada dati literaturni pregled postojećih reduktivnih naprednih metoda ARP (engl. Advanced Reduction Process, ARP) za razgradnju PFAS spojeva. Pritom se ARP odvija pomoću fotogeneriranih elektrona, odnosno superoksidnih radikala. U slučaju fotokatalitičke reduktivne razgradnje PFAS spojeva nastaju razgradni produkti jednostavnije strukture, pri čemu su korišteni mehanizmi H/F supstitucije i skraćivanje alifatskog lanca, što podrazumijeva kidanje C-F veze. Elektrokemijska razgradnja podrazumijeva razgradnju PFAS spojeve do odgovarajućeg stupnja mineralizacije, no pri tome nastaje nusprodukt HF čiju je emisiju potrebno kontrolirati. Termička reduktivna metoda podrazumijeva korištenje visokih reduktivnih temperatura prilikom razgradnje PFAS spojeva, gdje je također potrebno obratiti pozornost na emisiju HF.Perfluorinated substances (PFAS) are being used as additives in various products, such as cookware with a non-stick layer, waterproof material, food packaging and as firefighting foam due to their stability and resistance to grease, water and heat. During the use of these products, especially during their inadequate disposal in the environment, both soil and water pollution may occur. When they reach the environment, bioaccumulation of PFAS occurs, whereby they may not only have a negative effect on fluorine and fauna but also on human health. Therefore, they are often called "eternal chemicals". European regulations recognized this danger and established the maximum allowed concentration of PFAS compounds in drinking water of 0.5 μg/L, therefore it is important to remove them from wastewaters, which means to decompose them. Conventional wastewater treatment systems are not efficient enough for this purpose. On the other hand, advanced methods include membranes that are not effective for degradation but removal of PFAS. Unlike the latter, advanced oxidation processes are partially effective for the degradation of PFAS compounds using hydroxyl radicals. Nevertheless, utter gaol is to achieve defluorination of PFAS compounds, which can be achieved by reductive processes. The aim of this paper is to give a literature review of the existing reductive advanced methods (ARP) for the degradation of PFAS compounds. Thereat, ARP takes place with the help of photogenerated electrons, that is superoxide radicals. In the case of photocatalytic reductive decomposition of PFAS compounds, decomposition products of a simpler structure are formed, whereby the mechanisms of H/F substitution and shortening of the aliphatic chain, which implies breaking the C-F bond, are used. Electrochemical decomposition implies the decomposition of PFAS compounds to the appropriate degree of mineralization, but in doing so, the byproduct HF is formed and its emission must be controlled. The thermal reductive method implies the use of high reductive temperatures during the decomposition of PFAS compounds, where it is also necessary to pay attention to the emission of HF
Preparing titanium oxide films using spark plasma deposition technique
No full textOvaj rad bavi se istraživanjem priprave tankih filmova titanijevog dioksida (TiO₂) pomoću tehnike nanošenja ablacije iskrom. Titanijev dioksid odlikuju odlična fotokatalitička, kemijska i optička svojstava, zbog čega se široko koristi u područjima fotokatalize, zaštite okoliša i pretvorbe energije. Tehnika ablacije iskrom nudi prednosti u odnosu na druge metode zbog svoje brzine, efikasnosti i ekološke prihvatljivosti. U ovom radu analizirat će se utjecaj parametara ablacije na strukturu, morfologiju i optička svojstva TiO₂ filmova. Za detaljnu analizu korištene su metode kao što su rendgenska difrakcija pri okrznujućem upadnom kutu (engl. grazing incidence X-ray diffraction, GIXRD) za istraživanje kristalne strukture, mikroskopija atomskih sila (engl. atomic force microscopy, AFM) i pretražna elektronska mikroskopija (engl. scanning electron microscopy, SEM) za ispitivanje površinske morfologije, te difuzna refleksijska spektroskopija (engl. diffuse reflectance spectroscopy, DRS) za analizu optičkih svojstava filmova. Rezultati istraživanja pružit će uvid u kvalitetu filmova dobivenih ovom tehnikom i njihovu primjenjivost u različitim područjima.This thesis focuses on the investigation of the preparation of thin titanium dioxide (TiO₂) films using the spark ablation technique. Titanium dioxide is characterized by excellent photocatalytic, chemical, and optical properties, which is why it is widely used in the fields of photocatalysis, environmental protection, and energy conversion. The spark ablation technique offers advantages over other methods due to its speed, efficiency, and environmental friendliness. In this work, the effect of ablation parameters on the structure, morphology, and optical properties of TiO₂ films will be analysed. Methods such as grazing incidence X-ray diffraction (GIXRD) for studying the crystal structure, atomic force microscopy (AFM) and scanning electron microscopy (SEM) for examining surface morphology, and diffuse reflectance spectroscopy (DRS) for analysing the optical properties of the films were used for detailed analysis. The results of the research will provide insight into the quality of the films produced by this technique and their applicability in various fields
Indirect carbon dioxide emissions from electric vehicles
No full textOvaj rad analizira indirektne emisije ugljičnog dioksida električnih vozila u usporedbi s emisijama automobila s motorima na unutarnje izgaranje. Cilj istraživanja bio je procijeniti stvarne ekološke prednosti električnih vozila, uzimajući u obzir energetski miks i način za punjenje. Rezultati pokazuju kako električni automobili mogu značajno smanjiti emisije stakleničkih plinova, ali samo uz uvjet da je energetski sektor dekarboniziran. Rad također ističe važnost zakonskih regulativa i poticaja za ubrzavanje tranzicije prema održivoj mobilnosti.This paper analyzes the indirect carbon dioxide emissions of electric vehicles in comparison to those of internal combustion engine vehicles. The aim of the study was to assess the true environmental benefits of electric vehicles, considering the energy mix and charging methods. The results demonstrate that electric cars can significantly reduce greenhouse gas emissions, but only if the energy sector is decarbonized. The paper also highlights the importance of legal regulations and incentives to accelerate the transition towards sustainable mobility
Synthesis and biological activity of novel azalide compounds
No full textMakrolidi predstavljaju dobro poznatu skupinu antibiotika, a karakterizira ih visoko supstituirani makrolaktonski prsten, aglikon, na koji su glikozidnom vezom vezani jedan ili više neutralnih ili aminošećera. Uvođenjem dušikovog atoma u aglikonski prsten otkrivena je nova grupa 15-članih makrolidnih antibiotika − azalidi. Azalidi pokazuju povećanu metaboličku stabilnost, izuzetnu farmakokinetiku i širok spektar antibakterijske aktivnosti. Prvi i zasad jedini azalidni makrolidni lijek na tržištu je azitromicin. Nezavisno od antibakterijske aktivnosti, makrolidi također pokazuju i protuupalnu aktivnost. Izoksazol je peteročlani heterociklički spoj koji pokazuje različita farmakološka djelovanja te je zbog toga važan intermedijer za sintezu novih spojeva u medicinskoj kemiji. Izoksazolni prsten može se koristiti za razvoj novih spojeva s različitim biološkim djelovanjem poput antimikrobnog, antivirusnog, antikancerogenog, protuupalnog, imunomodulatornog, antikonvulzivnog ili antidijabetičkog. Cilj ovog diplomskog rada je priprava novih azalidnih spojeva u kojima je makrociklički laktonski prsten povezan s izoksazolom. Novosintetiziranim spojevima ispitat će se antiinfektivno djelovanje određivanjem minimalne inhibicijske koncentracije (MIC) na različitim sojevima Gram-pozitivnih i Gram-negativnih bakterija.Macrolides represent a large group of compounds with antibacterial activity. They are characterized by a highly substituted macrolactone ring, an aglycone, to which are attached one or more neutral or amino sugars via a glycosidic bond. By introducing a nitrogen atom into the aglycone ring, a new group of 15-membered macrolide antibiotics − azalides, was discovered. Azalides show increased metabolic stability, exceptional pharmacokinetics and antibacterial spectrum. The first and so far the only azalide macrolide on the market is azithromycin. Macrolides also possess anti-inflammatory properties, independent of their antibiotic actions. Isoxazole is a five-membered heterocyclic compound having various pharmacological action, and because of that is an important intermediate for the synthesis of new chemicals in medicinal chemistry. Isoxazole scaffold can be used to develop new agents with various biological activities (e.g. antimicrobial, antiviral, anticancer, antiinflammatory, immunomodulatory, anticonvulsant or antidiabetic properties). The aim of this thesis is to prepare new hybrid molecules of azalides and isoxazole. Minimum inhibitory concentration (MIC) of synthesized compounds will be determined against Gram-positive and
Gram-negative bacterial strains
Mechanochemical synthesis of cerium phosphate
No full textOvaj rad bavi se mehanokemijskom sintezom nanočestica, novog potencijalnog UV filtra, cerijeva (III) fosfata. Radi se o obećavajućem materijalu za primjenu u formulacijama za zaštitu od Sunca, zbog dobrih svojstava aspsorpcije UV dijela spektra, niskog indeksa loma, relativne prozirnosti za vidljivo svjetlo te kemijske inertnosti. U tu svrhu, nanočestice CePO4 sintetizirane su u planetarnom mlinu iz različitih prekursora (natrijeva fosfata dodekahidrata, natrijeva dihidrogenfosfat hidrata, natrijeva hidrogenfosfata) uz cerijev klorid kao drugi reaktant i natrijev klorid kao razrjeđivač, uz različito vrijeme miješanja (15, 30 i 60 minuta), kako bi se utvrdili optimalni uvjeti. Kao najpogodnija, ispostavila se sinteza u posudi od cirkonijeva dioksida, iz natrijeva fosfata dodekahidrata u trajanju od 15 minuta, pri čemu se dobivaju nanočestice rabdofana (CePO4 ∙ H2O). Dobiveni prašci karakterizirani su rendgenskom difrakcijskom analizom (XRD), diferencijalnom termalnom i termogravimetrijskom analizom (DTA/TGA), infracrvenom spektroskopijom s Fourierovom transformacijom (FTIR), pretražnom elektronskom mikroskopijom (SEM) i difuznom refleksijskom spektroskopijom (DRS). Uz to određena je raspodjela veličina čestica uzorka u vodi i ulju, adsorpcijsko-desorpcijske izoterme, fotokatalitička aktivnost u procesu fotokatalize ricinusovog ulja te citotoksičnost u usporedbi s trenutno najčešće korištenim anorganskim
UV filtrom, titanijevim dioksidom. Niska fotokatalitička aktivnost, visoka apsorpcija u
UV području kao i niska citotoksičnost ukazali su na moguću primjenu rabdofana kao UV filtra u novim formulacijama fotoprotektivnih sredstava kako bi se zamijenili trenutno korišteni anorganski UV filtri ZnO i TiO2.This thesis provides the insight into mechanochemical synthesis of nanoparticles of a new and potential UV filter, cerium (III) phosphate. It is a promising material for use in sunscreen formulations due to its good absorption properties of the UV part of the spectrum, low refractive index, relative transparency to visible light and chemical inertness.
For this purpose, CePO4 nanoparticles were synthesized in a planetary mill from different precursors (sodium phosphate dodecahydrate, sodium dihydrogenphosphate hydrate, sodium hydrogenphosphate) with cerium chloride as a second reactant and sodium chloride as a diluent, with different mixing times (15, 30 and 60 minutes), in order to determine the optimal conditions. Synthesis in a zirconium dioxide vessel with sodium phosphate dodecahydrate for 15 minutes turned out to be the most suitable, whereby nanoparticles of rhabdophan (CePO4 ∙ H2O) are obtained. The resulting powders were characterized by X-ray diffraction analysis (XRD), differential thermal and thermogravimetric analysis (DTA/TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), diffuse reflection spectroscopy (DRS). In addition, the size distribution of the particle sample in water and oil, the adsorption-desorption isotherm, the photocatalytic activity in the photocatalysis process of castor oil, and the cytotoxicity in relation to the currently most commonly used filter, titanium dioxide, were determined. Low photocatalytic activity, high absorption of the UV range as well as low cytotoxicity indicated the possible use of rhabdophane as a UV filter in new formulations of photoprotective agents to replace the currently used inorganic UV filters ZnO and TiO2