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The effect of thermodynamic factors on the precipitation od calcium oxalate monohydrate
No full textIstraženo je spontano taloženje kalcijevog oksalata monohidrata (COM) u sustavima bez aditiva s gotovo istom početnom supersaturacijom. Utjecaj termodinamičkih parametara kao što su: temperatura (t = 25, 36,5 i 48 °C), raspon koncentracije kalcija od 5 mmol dm−3 ≤ ci(Ca2+) ≤ 10 mmol dm−3 i pH (5,6, 6,5 i 7,5) proučavane su potencijalne promjene u strukturi, morfologiji i veličini kristala COM. Vrijednosti početnih parametara varirale su u širokom rasponu i uključivale su vrijednosti relevantne za oponašanje fizioloških stanja vezanih uz one u biološkim sustavima i nastajanje bubrežnih kamenaca. Rezultati su pridonijeli saznanjima o utjecaju odabranih pojedinačnih parametara kao i njihovoj međudjelovanje utjecaja na in vitro taloženje COM. Nalazi su pokazali da je COM jedina istaložena faza koja pokazuje dominantnu dendritsku morfologiju. Učinci na veličinu kristala, strukturu i morfologiju izraženiji su pri višoj temperaturi, pH i koncentraciji kalcija. Ovi rezultati daju osnovu za buduća istraživanja cjelokupnog mehanizma stvaranja COM i buduća istraživanja prevencije bubrežnih kamenaca.Spontaneous precipitation of calcium oxalate monohydrate (COM) in additive-free systems with nearly the same initial supersaturation has been investigated. The influence of thermodynamic parameters such as: temperature (t = 25, 36.5 and 48 °C), calcium concentration range of 5 mmol dm−3 ≤ ci(Ca2+) ≤ 10 mmol dm−3 and pH (5.6, 6.5 and 7.5), on the potential changes in structure, morphology and crystal size of COM have been studied. The values of the initial parameters were varied in a wide range and included values relevant for mimicking the physiological conditions related to those in biological systems and kidney stone formation.The results contributed to the knowledge about the influence of the selected individual parameters as well as their interplay influence on in vitro precipitation of COM. The findings have indicated that COM was the only precipitated phase exhibiting predominant dendritic morphology. The effects on crystal size, structure and morphology are more pronounced at higher temperature, pH and calcium concentration. These results provide basis for future studies of overall mechanism of COM formation and the future studies of kidney stone prevention
Selected thermodynamic parameters of antioxidant activity of coumarin based heterocyclic compounds
No full textKumarin (2H-1-benzopiran, 2H-kromen-2-on, 1,2-benzopiron) i derivati kumarina su bioaktivne fitokemikalije koje posjeduju važnu ulogu u razvoju antikoagulacijskih, protuupalnih, anti-HIV, antikancerogenih i antivirusnih lijekova. Dodatno, hidroksilkumarini su veoma snažni antioksidansi koji uspješno "hvataju" reaktivne kisikove vrste i sprječavaju radikalima uzrokovana biološka oštećenja i oksidativni stres. Cilj ovog preliminarnog istraživanja je bio teorijski ispitati antioksidacijski potencijal 51 heterocikličkog spoja na bazi kumarina, odnosno utvrditi vrijednosti reakcijskih entalpija povezanih s dva mehanizma antioksidacijske aktivnosti. Istraženi mehanizmi antioksidacijske aktivnosti su: prijenos atoma vodika (HAT) i prijenos elektrona praćen prijenosom atoma vodika (SET-PT). Za izradu rada je korišten programski paket MOPAC2012 i P7 metoda. Ispitivano je cijepanje O-H, N-H i C-H veza, utjecaj položaja OH- i drugih funkcionalnih skupina. Dobivenim rezultatima je utvrđeno kako Schiffove baze, oksadiazoli, tiosemikarbazidi i 4-tiazolidinoni s više OH- funkcionalnih skupina posjeduju bolje antioksidacijsko djelovanje.Coumarin (2H-1-benzopyran-2-one, 2H-chromen-2-one, 1,2-benzopyrone) and coumarin derivatives are bioactive phytochemicals that have an important role in the development of anticoagulant, anti-inflammatory, anti-HIV, anticancer and antiviral drugs. Additionally, hydroxycoumarins are very powerful antioxidants that successfully scavenge reactive oxygen species and prevent radical induced biological damage and oxidative stress. The antioxidant potential of 51 heterocyclic compounds containing coumarin core was investigated theoretically. Reaction enthalpies related to two mechanisms of free radical scavenging were calculated. Studied mechanism were hydrogen atom transfer mechanism (HAT) and single electron transfer followed by proton transfer mechanism (SET-PT). Calculations were performed using MOPAC2012 PM7. Cleavage of O-H, N-H and C-H bonds was studied. The effect of the position of the hydroxyl group, as well as other functional groups, on the antioxidant activity was examined. Based on obtained results, Schiff bases, thiosemicarbazides, oxadiazoles and 4-thiazolidinones containing one or more OH- groups exhibit higher radical scavenging properties
Electrochemical characterization of zinc complexes with dipicolinic acid hydrazide
No full textGlavni cilj ovog rada bio je provesti elektrokemijsku karakterizaciju dva cinkova kompleksa s hidrazidnim derivatima dipikolinske kiseline ( i ) u tri različita inertna elektrolita (KCl, i LiCl) s cikličkom i diferencijalnom pulsnom voltametrijom. Mjerenja su provedena pomoću potenciostata/galvanostata (PalmSens) pod nadzorom PSTrace 1.2. programskog paketa. Troelektrodni sustav sastojao se od radne elektrode od staklastog ugljika, referentne Ag/AgCl elektrode i protuelektrode od platinske žice. Prije svakog mjerenja, površina radne elektrode polirana je suspenzijom . Elektrokemijski sustav propuhivan je argonom visoke čistoće kako bi se izbjegla kontaminacija kisikom tijekom mjerenja. Ciklički voltamogrami ispitivanog cinkovog kompleksa pokazali su jedan oksidacijski vrh i jedan redukcijski vrh u sva tri ispitivana elektrolita dok su za drugi cinkov kompleks ciklički voltamogrami pokazali samo jedan oksidacijski vrh u sva tri ispitivana elektrolita. Strujni vrh povećavao se kod oba kompleksa s porastom brzine polarizacije. Vrijednost bila je mnogo veća od 57/z mV, što bi moglo ukazivati na ireverzibilni oksidacijski proces. Diferencijalni pulsni voltamogrami također su pokazivali jedan oksidacijski vrh za oba ispitivana cinkova kompleksa u sva tri inertna elektrolita. Oksidacijski vrh smanjivao se uzastopnim skeniranjima što upućuje na adsorpciju oksidacijskog produkta oba ispitivana cinkova kompleksa na površinu elektrode od staklastog ugljika. Ovaj rad također sadrži dio s nastavnim metodama na srednjoškolskoj razini koji uključuje pripremu za nastavnu jedinicu "Elektrodni potencijal i galvanski članci", odgovarajuće radne listiće i njihova rješenja.The main goal of this thesis was to perform electrochemical characterization of two zinc complexes (( and ) with dipicolinic acid hydrazide derivatives in three different inert electrolytes (KCl, and LiCl) with cyclic and differential pulse voltammetry. The measurements were performed using potentiostat/galvanostat (PalmSens) controlled by PSTrace 1.2. software package. The three electrode system consisted of a glassy carbon working electrode, Ag/AgCl reference electrode and a platinum wire counter electrode. Before each measurement, the working electrode surface was polished with suspension. The electrochemical system was purged with purified argon to avoid oxygen contamination during measurements. Cyclic voltammograms of studied zinc complex showed one oxidation and one reduction peak in all three investigated electrolytes while for the second zinc complex cyclic voltammograms showed only one oxidation peak in all three investigated electrolytes. Peak current increased for both complex with the increase of scan rate. value was much higher than 57/z mV, which could indicate an irreversible oxidation process. Differential pulse voltammograms also revealed one oxidation peak for both investigated zinc complexes in all three inert electrolytes. The oxidation peak decreased with succesive scans which confirmed adsorption of the oxidation product of both investigated zinc complexes on the surface of the glassy carbon electrode. This thesis also contains a part with teaching methods on high school level which includes preparation for lesson " Electrode potential and galvanic cells ", corresponding working papers and their solutions
Study of plant material as potential acid-base indicators
No full textU nastavi kemije često prevladava tradicionalni oblik rada kojim se gradivo samo usvoji što rezultira nagomilavanjem informacija. Ovakvim usvajanjem gradiva ostvaruje se niži nivo obrazovanja, ali ne i povezivanje naučenog gradiva sa svakodnevnim životom i njegova praktična primjena. Poznato je da vizualizacija nastave znatno olakšava smisleno i svrsishodno učenje, što se u učionici kemije postiže korištenjem pokusa. Obrada pojmova pH, kiselina, baza i indikator ponekad uključuje pokuse uz upotrebu sintetskih indikatora koji su često nedostupni školama. Međutim, biljni pigmenti mogu poslužiti kao kiselo-bazni indikatori jer ovisno o pH otopine mijenjaju boju od crvene, ljubičaste, plave, zelene do žute. Cilj rada bio je ispitati potencijal primjene odabranog biljnog materijala kao kiselo-baznog indikatora. U tu svrhu ispitano je jagodičasto i bobičasto voće, a korišten je sveži, suhi, smrznuti i prerađeni biljni materijal (džem, sok, vino). Odabrane su prerađevine s najvišim sadržajem voća. Rezultati istraživanja ukazuju na izuzetno veliki potencijal primjene biljnog materijala u nastavi kemije. Niska cijena biljnog materijala, dostupnost cijele godine, jednostavna priprema bez štetnih nusprodukata, mogućnost pripreme u malim količinama, jednostavno skladištenje i mogućnost pohrane na duži period prednosti su ispitanih alternativnih indikatora. Od ispitanog biljnog materijala, među vizualno najdojmljivijima istakli su se kupina, malina, ribiz, aronija i drijenak.In chemistry classroom the dominant teaching methods are traditional ones. Their result is accumulation of information which is a lower level of education with no application of learned lessons in everyday life. Visualization in science class allows meaningful and purposeful learning, with the help of experiments. Teaching of terms like pH, acid, base and indicator occasionally involves experiments, using synthetic indicators, which are often unavailable to many schools. However, plant pigments may be used as acid-base indicators as well, due to their different color depending on the solution pH value - red, purple, blue, green, yellow. The aim of this thesis was to evaluate potential of application of selected plant material as acid-base indicators. Studied plant material was soft fruit (berries) as fresh, dry, frozen fruit and fruit products (jam, juice, wine). Used products had the highest fruit concentration. Results indicate high potential of application of selected plant material in chemistry class. Low price, availability all year, simple preparation with no side products, preparation in small or big quantities, simple storage and possibility of longer storage are the advantages of studied alternative indicators. Of all studied plant material, especially visually impressive were blackberries, raspberries, currants, aronia and European cornel
Application of nanomaterials
No full textNanotehnologija i primjena nanomaterijala nude brojne prednosti u različitim područjima znanosti. Brz napredak nanotehnologije pružio je mogućnost razvoja ambalaža za pakiranje hrane, rješenje dugogodišnjih izazova u prehrambenom sektoru za produženje roka trajanja, smanjenje otpada, procjenu sigurnosti i poboljšanje kvalitete hrane. Nanomaterijali se mogu koristiti za jačanje mehaničke čvrstoće, povećanje plinskih barijera, povećanje otpornosti na vodu i pružiti antimikrobnu i pročišćavajuću aktivnost u ambalaži namirnica. Trenutno je glavni problem cijelog svijeta zagađenje vode, iz nekoliko razloga kao što su neprikladna obrada otpadnih voda, industrijskog otpada, problemi morskog odlaganja i radioaktivni otpadni materijal. Nanofotokatalizatori imaju velik potencijal da vrlo učinkovito tretiraju zagađenu vodu (koja sadrži metalne toksične supstance, različite organske i anorganske nečistoće) zahvaljujući jedinstvenim svojstvima kao što su veća površina, sposobnost djelovanja pri niskim koncentracijama itd. Nanosustavi za dostavu lijekova relativno su nova, ali znanost koja se brzo razvija gdje se nanomaterijali, točnije nanoobjekti koriste kao sredstvo za kontrolirano otpuštanje terapijskih sredstava do određenih ciljanih mjesta.Nanotechnology and application of nanomaterials offer many advantages in various fields of science. The rapid advancement of nanotechnology has provided opportunities for development of food packaging, addressing long-standing challenges in the food sector to extend shelf-life, reduce waste, assess safety and improve the quality of food. Nanomaterials can be used to reinforce mechanical strength, enhance gas properties, increase water repellency, and provide antimicrobial and scavenging activity to food packaging. Currently, major problem of whole world is water contamination, due to several reasons as inadequate sewage treatment, industrial wastes, marine dumping issues and radioactive waste material. Nanophotocatalysts have huge potential to treat polluted water (containing metal toxin substance, different organic and inorganic impurities) very effectively due to unique properties as greater surface area, ability to work at low concentration etc. Nano delivery systems are a relatively new but rapidly developing science where nanomaterials, rather nano objects are employed to serve as means of deliver therapeutic agents to specific targeted sites in a controlled manner
Organic-inorganic hybrids
No full textOrgansko-anorganski hibridi su spojevi dobiveni kombinacijom anorganskih i organskih komponenti. Kako se sastoje od anorganskih i organskih dijelova mogu imati svojstva karakteristična za anorganske i organske spojeve. Sol-gel metoda je najrasprostranjenija metoda dobivanja takvih hibrida, no u ovom završnom radu istražit će se mehanokemijska metoda dobivanja organsko-anorganskih hibrida pomoću planetarnog kugličnog mlina. Cilj je bio sintetizirati 2D hibridni perovskit (MA = ) koji je dopiran s u različitim masenim udjelima: a) 20% , b) 30% , c) 40% i d) 50% . Za dobivanje hibrida korišteni su metil-amonijev bromid, niklov(II) bromid i bakrov(II) bromid. Sinteze su provedene na 900 rpm pri različitim vremenskim intervalima od 10, 20 i 30 minuta kako bi se istražili optimalni uvjeti za nastanak ciljanih spojeva. Dobiveni hibridi su analizirani pomoću infracrvene spektroskopije s Fourierovom transformacijom (FTIR) te termogravimetrijske analize (TGA).Organic-inorganic hybrids are family of compounds made from the combination of inorganic and organic components. Since they are made from organic and inorganic parts, they possess properties from both sides. Sol-gel method is the most widespread method for synthesis of these hybrids, however, in this thesis a different method is used, called the mechanochemical method using a planetary ball mill. The goal was to synthesize 2D hybrid perovskite (MA = ) doped with in different mass fractions: a) 20% , b) 30% , c) 40% and d) 50% . Methylammonium bromide, nickel (II) bromide and copper (II) bromide were used in this synthesis. All the combinations were tried out at 900 rpm in three different time intervals of 10, 20 and 30 minutes to investigate optimal conditions for the formation of targeted compounds. These compounds were analyzed with Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA)
Radionuclides
No full textAtom čine jezgra i elektronski omotač. Radioaktivnost je svojstvo nekih jezgara da se spontano mijenjaju prelazeći u drugu jezgru. Takve jezgre su nestabilne ili radioaktivne dok se one koje nemaju to svojstvo nazivaju stabilnim jezgrama. U prirodi ima oko 300 stabilnih jezgara, sve ostale su nestabilne. Nekoliko tisuća jezgara je nestabilno i podložno je nekoj vrsti spontanog raspada. Pri raspadu radioaktivnih jezgara i radionuklida dolazi do emisije zračenja. Interakcija zračenja i sredine kroz koju ono prolazi dovodi do promjena zračenja i sredine. Ozračena sredina mijenja se fizički i kemijski što je osnova primjene radionuklida.Atoms are composed of nucleus and electron shell. Radioactivity is the property of some atomic nucleus to spontaneously change and transform to another nucleus. Such atomic nucleus are unstable or radioactive while those without this property are called stable atomic nucleus. In nature there are about 300 stable atomic nucleus, all the others are unstable. Several thousand atomic nucleus are unstable and subject to some kind of spontaneous decay. Radiation is emitted by radioactive atomic nucleus and radionuclide discharges. The interaction between radiation and the environment through which it passes leads to changes in radiation and the environment. The irradiated environment is physically and chemically altered, and this is the basis of radionuclide application
Analysis of measured praticulate matter concentrations in urban and rural areas in Eastren Slavonia
No full textLebdeće čestice (eng. Particulate Matter, PM) pripadaju skupini onečišćujućih tvari koje štetno djeluju na zdravlje ljudi, ali i na okoliš. U radu su prikazani i obrađeni rezultati mjerenja koncentracija lebdećih čestica () na području grada Osijeka i Parka prirode Kopački rit za 2018. i 2019. godinu. Rezultati mjerenja su pokazali da čestice u svojim dnevnim vrijednostima koncentracija nisu iznad granične vrijednosti koja je propisana Zakonom o zaštiti zraka. Veće vrijednosti su primijećene samo tijekom zimskih mjeseci. U promatranom vremenskom razdoblju izmjerene srednje vrijednosti koncentracija čestica su veće u gradu Osijeku nego u Parku prirode Kopački rit.Particulate Matter, PM belong to the group of pollutants that affect human health and the environment. This paper shows the results on concentration measurements of particulate matters within the area of nature park Kopački rit and city of Osijek for 2018. and 2019 year. On a daily basis, an average level of particulates concentration did not exceed the limiting value as prescribed by the Law on Protection of Air, however, higher concentration has been recorded during the winter period. Average level of concentration, as well as maximum and minimum levels of these concentrations for observed period are higher in city of Osijek than in nature park Kopački rit
Tropospheric ozone and its precursors in Osijek
No full textTroposferski ozon je sekundarni polutant koji nastaje fotokemijskim reakcijama u nižim dijelovima Zemljine troposfere. Za nastanak ozona bitni su prekursori iz kojih on nastaje; dušikovi oksidi i hlapljivi ugljikovodici, dok ugljikov(II) oksid posredno sudjeluje u produkciji ozona. Prekursori ozona se emitiraju s površine Zemlje u atmosferu, a glavni su im izvor u gradu Osijeku promet i industrijski procesi. U ovom završnom radu prikazani su i analizirani rezultati mjerenja koncentracije ozona, benzena, dušikovih oksida i ugljikovog(II) oksida za 2018. i 2019. godinu. Mjerna postaja se nalazi u gradu Osijeku i pomoću automatskog analizatora mjeri koncentraciju pojedinih zračnih polutanata. Grafičkom analizom prikazan je dnevni hod ozona s karakterističnim podnevnim maksimumom i jutarnjim minimumom. Izradom polarnih dijagrama može se utvrditi povezanost koncentracije ozona, benzena, dušikovih oksida i ugljikovog(II) oksida sa smjerom vjetra. Izračunom koeficijenta korelacije i analizom glavnih komponenata utvrđena je korelacija između prosječnih dnevnih vrijednosti koncentracije polutanta i prosječnih dnevnih vrijednosti meteoroloških parametara.The tropospheric ozone is a secondary pollutant formed by photochemical reactions in the lower parts of the Earth's troposphere. The precursors from which ozone is formed are essential for the formation of ozone; nitrogen oxides and volatile organic compounds, while carbon monoxide indirectly participates in ozone production. Ozone precursors are emitted from the Earth's surface into the atmosphere and the main source of ozone precursors in the city of Osijek are traffic and industrial processes. The measuring results of the concentration of ozone, benzene, nitrogen oxides and carbon monoxide for 2018 and 2019 are presented and analyzed in this paper. The measuring station is located in the city of Osijek and uses an automatic analyzer to measure the concentration of individual air pollutants. The graphic analysis shows the average diurnal distribution ozone with a characteristic noon maximum and morning minimum. The correlation of the concentration of ozone, benzene, nitrogen oxides and carbon monoxide with the wind direction can be determined by making polar diagrams. By calculating the correlation coefficient and principal component analysis, the correlation between the average daily values of the pollutant concentration and the average daily values of meteorological parameters were determined
Sol-gel synthesis of complex metal oxides with double and triple perovskite-type structure
No full textPerovskit je naziv za porodicu spojeva kristalne strukture čija je opća formula ABX3 gdje je A kation većeg ionskog promjera, B kation manjeg ionskog promjera, a X halogenidni anion ili kisik. U ovome diplomskom radu citratnom dvostupanjskom sol - gel metodom sintetizirani su sloţeni metalni oksidi perovskitne strukture , , te . Nakon prvostupanjskog miješanja prekursora i kompleksacije citratnom kiselinom, u drugom koraku su osušeni uzorci kalcinirani pri 600 ˚C i 1000 ˚C u peći u struji zraka s temperaturom zagrijavanja 2 ˚C/min. Uzorci su karakterizirani cikličkom voltametrijom, infracrvenom spektroskopijom (FT - IR), termogravimetrijskom analizom (TGA), rentgenskom difrakcijom na prahu (PXRD) te su im odreĎena magnetska svojstva SQUID mjerenjima. UtvrĎeno je da su sintetizirani spojevi visoke čistoće te da su veličine kristalita male unatoč visokim temperaturama kalciniranja. i pokazuju antiferomagnetska svojstva.Perovskite is the name for a family of compounds with crystal structure of the general formula ABX3 where A is a cation of a larger ionic radius, B is a cation of a smaller ionic radius and X stands for halide or oxide anion. In this diploma thesis, complex metal oxides of perovskite type crystal structure , , and were synthesized by the citrate sol - gel route. Dried samples were calcined at 600 °C and 1000 °C in a furnace with air flow and at a temperature rate of 2 °C per minute. Samples were characterized by the cyclic voltammetry, infrared spectroscopy (FT -IR), thermogravimetric analysis (TGA), Powder X - ray diffraction (PXRD) while magnetic ground state has been determined using SQUID measurement. Obtained results have revealed that synthesized materials are of high purity and their average crystallite size has remained in nanometer range despite the high calcination temperatures. and posses antiferromagnetic properties