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Overview of mechanisms of degradation of lithium-ion battery efficiency
No full textLitij-ionska baterija (LIB) pripada skupini baterija koja se može puniti. Tijekom pražnjenja litijevi ioni kreću se od negativne elektrode ka pozitivnoj, a pri punjenu se događa suprotan proces. Litij interkalacijom prolazi u elektrode, za razliku od metalnog litija koji se primjenjuje u jednokratnim litijevim baterijama. Sastoje se od elektrolita, ugljične anode i katode na bazi kobalta. Procese degradacije uzrokuje: - Visoka i niska temperatura. - Visoko i nisko stanje napunjenosti. - Jaka struja. - Broj ciklusa punjenja i pražnjenja. - Općenito prolazak vremena. Neki od načina degradacije su: raspad elektrolita, raspad veziva, ljuštenje grafitne anode, pucanje čestica. Mehanizmi degradacije su: gubitak ciklirajućeg Li+, gubitak anodnog i katodnog materijala, smanjenje brzine interkalacije litija. Degradacije uzrokuju gubitak kapaciteta baterije, te povećanje električnog otpora u bateriji.The lithium-ion battery (LIB) belongs to the group of rechargeable batteries. During discharge, lithium ions move from the negative electrode to the positive one, and the opposite process occurs during charging. Lithium passes into the electrodes by intercalation, in contrast to metallic lithium, which is used in disposable lithium batteries. They consist of an electrolyte, a carbon anode, and a cobalt-based cathode. Degradation processes are caused by: - High and low temperature. - High and low state of charge. - High current. - Number of charge and discharge cycles. - Generally, the passage of time. Some ways of degradation are the breakdown of the electrolyte, breakdown of the binder, exfoliation of the graphite anode, and cracking of the particles. Degradation mechanisms are loss of cycling Li+, loss of anodic and cathodic material, and reduced lithium intercalation rate. Degradations cause a loss of battery capacity and an increase in electrical resistance in the battery
Synthesis of novel benzimidazole quaternary ammonium salts
No full textU ovom diplomskom radu provedene su reakcije kvaternizacije benzimidazola i 2-metilbenzimidazola s odgovarajućim alkil-bromidima (alkilni ogranci s 12 i 18 ugljikovih atoma). Reakcije su provedene u bazičnim uvjetima, uz acetonitril kao otapalo te u inertnoj atmosferi dušika, pri 90 °C. Produkti kvaternizacije korišteni su kao polazni spojevi u reakcijama metateza, u svrhu sinteza ionskih tekućina. Metateze su provođene pri sobnoj temperaturi, u zatvorenom sustavu uz odgovarajuća otapala. Uspješno je sintetizirano dvanaest spojeva, od kojih su tri benzimidazolne kvaterne amonijeve soli te devet ionskih tekućina. Dobiveni su spojevi izolirani, karakterizirani masenom spektrometrijom (MS) i infracrvenom spektroskopijom ((FTIR) te su određena tališta.In this Thesis, reactions of quaternization of benzimidazole and 2-methylbenzimidazole with alkyl-bromide were carried out (the alkyl branches vary with 12 and 18 carbon atoms). Reactions were performed under basic conditions, with acetonitrile as a solvent and in an inert nitrogen atmosphere, at 90 °C. The products of quaternization were then used as starting compounds in metathesis reactions, for the purpose of synthesis of ionic liquids. Metathesis reactions are carried out at room temperature, in a closed system with appropriate solvents. Twelve compounds have been successfully synthesized, three of which are benzimidazole quaternary ammonium salts and nine ionic liquids. The resulting compounds were isolated and characterized by mass spectrometry (MS) and infrared spectroscopy (FTIR), and their melting points were determined
Toxicity of e-cigarettes
No full textPušenje danas predstavlja glavni uzrok smrti u svijetu. Kao odgovor na ovaj negativan trend, proizvode se alternativni uređaji običnim cigaretama - elektronske cigarete (e-cigarete). Osnovi dijelovi svake e-cigarete su: baterija, raspršivač i punjenje, a rade na principu da zagrijavaju e-tekućinu koja sadrži nikotin i oponašaju konvencionalne cigarete. E-tekućina se sastoji od nikotina, glicerola i propilen glikola te sredstava za poboljšanje okusa. Istraživanja su pokazala da su ovi spojevi štetni za ljudski organizam te negativno utječu na kardiovaskularni sustav, oksidativni stres i upalu te dišni sustav. Osim navedenih spojeva, u aerosolu e-cigarete otkriveni su i neki spojevi prisutni u dimu duhana konvencionalnih cigareta: katran, formaldehid, akrolein, acetaldehid i nitrozamini, među kojima su neki identificirani kao kancerogeni spojevi. U ovom završnom radu opisani su princip rada e-cigareta, njihov razvoj tijekom godina, kemijski sastav e-tekućine i spojeva prisutnih u tekućini, toksični učinci e-cigarete na ljudski organizam te usporedba toksičnosti konvencionalnih cigareta i e-cigareta.Smoking is the main cause of death in the world today. In response to this negative trend, alternative devices to regular cigarettes - electronic cigarettes (e-cigarettes), are being produced. The basic parts of every e-cigarette are: battery, atomizer and filling, and they work on the principle of heating of e-liquid which contains nicotine and imitates the conventional cigarettes. E-liquid consists of nicotine, glycerol, propylene glycol and flavor enhancers. Researches have shown that these compounds are harmful to the human body and negatively affect the cardiovascular system, oxidative stress and inflammation, and the respiratory system. In addition to the mentioned compounds, some compounds present in the tobacco smoke of conventional cigarettes were also detected in the e-cigarette aerosol: tar, formaldehyde, acrolein, acetaldehyde and nitrosamines, some of which have been identified as carcinogenic compounds. This final paper describes the working principle of e-cigarettes, their development over the years, the chemical composition of e-liquid and compounds present in the liquid, the toxic effects of e-cigarettes on the human body, and a comparison of the toxicity of conventional cigarettes and e-cigarettes
Sensors for pesticides determination
No full textPesticidi su tvari čija su glavne uloge sprečavanje bolesti biljaka i uklanjanje neželjenih vrsta u poljoprivredi. U današnje vrijeme postoji mnogo vrsta takvih molekula. Mogu biti sintetizirane kemijskim i prirodnim putem, a na tržištu su puno češći kemijski sintetizirani pesticidi. Pošto se radi o kemijskim spojevima, često pitanje je utjecaj njihovih ostataka na okoliš. Za analizu ostataka pesticida koriste se brojne metode od kojih su najčešće tekućinska kromatografija visoke razlučivosti, masena spektrometrija i plinska kromatografija. U novije vrijeme većina tih metoda zamijenjene su senzorima. Razvijanje senzora može biti složen i skup proces. Senzori se najčešće koriste pri analizi za detekciju organofosfata. Od mnogih vrsta senzora u ovom radu naglasak je stavljen na fluorescentne i kolorimetrijske senzore koji kao signal daju vizualnu promjenu boje. Fluorescentni senzori mogu biti posredovani enzimom ili potpomognuti antitijelom ili "plastičnim antitijelom" (molekularno utisnuti polimer, eng. molecular imprinted polymer, MIP). Fluorescentni senzori najčešće prate fluorescentni rezonantni prijenos energije (eng. Fluorescence Resonance Energy Transfer, FRET) gdje postoje akceptorska i donorska boja, a prijelaz energije se događa pri pobuđenom stanju s donorske na akceptorsku boju. Kolorimetrijski senzori na bazi zlatnih nanočestica predstavljaju budućnost detekcije pesticida. Mogu se podijeliti na senzore na bazi aptamera, senzore na bazi antitijela i na enzimske senzore. Osim ove dvije već spomenute vrste senzora, razvijaju se i senzori na bazi Ramanovog raspršenja koji djeluju potpomognuti zlatnim ili srebrnim nanočesticama.Pesticides are substances whose main roles are to prevent plant diseases and eliminate unwanted species in agriculture. There are many types of such molecules nowadays. They can be synthesized chemically and naturally. Chemically synthesized pesticides are much more common on the market. Since these are chemical compounds, the impact of their residues on the environment is a question that is commonly asked. Numerous methods are used to analyze pesticide residues, the most common of which are high-performance liquid chromatography, mass spectrometry, and gas chromatography. More recently, most of these methods have been replaced by sensors. Developing sensors can be complex and expensive process. Sensors are most commonly used for organophosphates detection. Out of the many types of sensors, in this paper emphasis is placed on fluorescent and colorimetric sensors that cause a visual change of color as a signal. Fluorescent sensors can be mediated by an enzyme, assisted by an antibody or polymer-assisted (molecular imprinted polymer, MIP). They ususally follow fluorescence resonance energy transfer (FRET) principles where there are acceptor and donor dyes present, and the energy transition occurs in the excited state from the donor to the acceptor dye. Colorimetric sensors based on gold nanoparticles represent the future of pesticides detection. They can be divided into aptamer-based sensors, antibody-based sensors, and enzyme-based sensors. In addition to these two already mentioned types of sensors, Raman-based sensors supported by gold or silver nanoparticles are also in high demand by scientists
Disorders of amino acid metabolism
No full textAminokiseline su osnovne građevne jedinice proteina. Građene su od središnjeg ugljikovog atoma na kojeg su vezane četiri skupine, amino-skupina, vodikov atom, karboksilna-skupina i bočni ogranak koji čini svaku aminokiselinu jedinstvenom po svojoj strukturi. Svakodnevno organizam razgrađuje i sintetizira aminokiseline stoga u njihovom metabolizmu može doći do pogrešaka koje dovode do raznih poremećaja. Najčešća pogreška koja dovodi do razvitka poremećaja je nedostatak bitnih enzima koji prevode aminokiseline iz jedne u drugu. Zbog toga u organizmu dolazi do nakupljanja štetnih međuprodukata u krvi ili urinu i zbog kojih dolazi do razvitka raznih bolesti. Najčešći poremećaj u metabolizmu aminokiselina je fenilketonurija do koje dolazi zbog nedostatka enzima koji katalizira pretvorbu fenilalanina u tirozin, a karakteriziraju ju ponajviše poteškoće u mentalnom razvoju. Uz fenilketonuriju u poremećaje metabolizma aminokiselina ubrajaju se i bolest urina mirisa javorovog sirupa, homocistinurija, tirozinemija, neketotička hiperglicinemija, te poremećaji u ciklusu uree koji su jednako učestali ali i opasni.Amino acids are the basic building blocks of proteins. They are built of a central carbon atom to which four groups are attached, an amino group, a hydrogen atom, a carboxyl group and a side branch that makes each amino acid unique in its structure. Every day, the body breaks down and synthesizes amino acids, therefore mistakes can occur in their metabolism that lead to various disorders. The most common mistake that leads to the development of disorders is the lack of essential enzymes that convert amino acids from one to another. Because of this, the body accumulates harmful intermediate products in the blood or urine, which leads to the development of various diseases. The most common disorder in the metabolism of amino acids is phenylketonuria, which occurs due to the lack of an enzyme that catalyzes the conversion of phenylalanine to tyrosine, and is characterized mainly by difficulties in mental development. In addition to phenylketonuria, disorders of amino acid metabolism include maple syrup urine disease, homocystinuria, tyrosinemia, non-ketotic hyperglycinemia, and disorders in the urea cycle, which are equally frequent but also dangerous
Prediction of pKa values of morin
No full textMorin (3,5,7,2',4'-pentahidroksiflavon, C15H10O7) je bioflavonoid koji se može naći u brojim biljkama i biljnim prerađevinama. Smatra se fitokemikalijom te se ubraja u skupinu flavonola. Utvrđeno je da ima širok raspon farmakoloških djelovanja, uključujući protuupalno i antidijabetičko djelovanje, a njegova antikancerogena i antioksidacijska svojstva su predmet daljnjih istraživanja. Konstanta kisele disocijacije, pKa (također poznata kao konstanta kiselosti ili konstanta kisele ionizacije) je kvantitativna mjera jačine kiseline u otopini. Vrijednost pKa ovisi o strukturi spoja, a može se odrediti eksperimentalno i predvidjeti računalno. Međutim, pKa za brojne spojeve nije eksperimentalno određena zbog kompleksnosti njihove strukture, pa računalni programi mogu imati veliki značaj u predviđanju vrijednosti ovog parametra. U ovom radu primjenom ACD/pKa predviđene su pKa vrijednosti za morin. Korištena su dva algoritma inkorporirana u Perceptu. Dobiveni rezultati ukazuju na redoslijed disocijacije funkcijskih skupina morina te samu pH pri kojoj se disocijacija odvija.Morin (3,5,7,2',4'-pentahydroxyflavone, C15H10O7) is a bioflavonoid and can be found in many plants and plant products. It is a phytochemical and belongs to the group of flavonols. It shows a wide range of pharmacological effects, including anti-inflammatory and antidiabetic effect, and its anticancer and antioxidant properties are still being researched. The acid dissociation constant, pKa (also known as the acidity constant or acid ionization constant) is a quantitative measure of the strength of an acid in a solution. The pKa value depends on the structure of the compound and can be determined experimentally and computationally. For many compounds, pKa has not been determined experimentally due to the complexity of their structure, so computer programs can be of great importance in predicting the value of this parameter. In this thesis, ACD/pKa was used to predict pKa values of morin. Two algorithms implemented in Percepta were used. Obtained results indicate order of dissociation of functional groups of morin and pH at which the dissociation occurs
Chemical robots
No full textKemijski roboti su podvrsta mekih robota, koji su, u odnosu na klasične mehaničke robote, izrađeni od mekših materijala poput polimernog gela, polupropusne ljuske sa odjeljkom za pohranjivanje, i sl. Stoga kemijski roboti mogu "oponašati" kretnje živih organizama. U današnjem svijetu kemijski roboti mogu imati različite primjene. Mogli bi se koristiti u dostavljanju lijekova unutar samih organizama, za povrat vrijednih kemikalija iz razrijeđenih resursa i kao pomoć pri sanaciji kod ekoloških karastrofa (npr. prilikom izljeva nafte u ocean). Primjer kemijskih robota sa takvom primjenom su choboti (chemical swarm robots), koji su veličinom i strukturom slični jednostaničnim organizmima. Kemijski roboti se također mogu primijeniti u samom kemijskom laboratoriju, gdje mogu ubrzati nastanak novih kemijskih spojeva i smanjiti mogućnost ponavljanja izvođenja reakcija. Uz kemijske robote, važno je spomenuti i biološke robote tzv. bio-bote napravljene od hidrogelova koji čine kostur, u kojima su i dva postolja koja učvršćuju trake mišića kao tetive, a ujedno su i stopala robota. Bio-boti se kreću mišićnim trakama, čije stezanje i opuštanje se kontrolira električnim impulsima, pri čemu prilikom povećanja frekvencije impulsa dolazi do bržih kontrakcija i bržeg kretanja bio-bota.Chemical robots are a subset of soft robotics which, compared to classic mechanical robots, are made of softer materials, such as polymer gel, semi-permeable shell with a storage compartment, etc. Therefore, chemical robots can "mimic" the movements of a living organism. In today`s world, chemical robots could have many different applications. Some of those could be the delivery of medicine within the organism itself, the recovery of valuable chemicals from diluted resources, or as an aid in the recovery of environmental disasters (eg, oil spill in the ocean). An example of chemical robots with such applications are chobots (chemical swarm robots), whose structure and size resemble a single-celled organism. Chemical robots can also be applied in the chemistry laboratory, where they can help in a faster and more efficient production of target molecules. In addition to chemical robots, it is important to mention the biological robots, so-called bio-bots, which are made of hydrogels that form the skeleton, in which we see two stands that strengthen the muscle strips as tendons and also form the feet of the robots. Bio-bots are moved by muscle strips, the contraction, and relaxation of which are controlled via electrical impulses, whereby as the pulse frequency increases so do the contractions, resulting in faster movement of bio-bots
Determination of tangens delta and specific resistance of the oil
No full textElektrični transformatori trebaju odgovarajuću izolaciju. Upravo je, transformatorsko izolacijsko ulje jedna od najvažnijih sastavnica izolacijskog sustava. Transformatorsko ulje je tekućina koja je uobičajena za transformatorski sustav, te je poznata kao najpopularniji izolacijski materijal u cijelom svijetu. Ulje može biti dio izolacijskog kompleksa ili njegova glavna komponenta. Neke od vrsta izolacijskih ulja su mineralna, parafinska, te silikonska ulja. Ono što je posebno važno je da transformatorsko ulje treba biti kvalitetno, tj. imati određena svojstva. Stoga je obavezno napraviti analizu ulja prije upotrebe, jer nije poželjno raditi s uljima sumnjive kvalitete. U ovom radu sam koristila transformatorska ulja različite kvalitete. Ispitivala sam vrijednosti specifičnog otpora i koeficijenta dielektričnih gubitaka, te prema tim svojstvima odredila je li ulje ispravno za korištenje.Electrical transformers need adequate insulation. Precisely, transformer insulation oil is one of the most important components of an insulation system. Transformer oil is a liquid common to the transformer system, and known as the most popular insulating material in the entire world. The oil can be part of the insulation complex or its main component. Some of the types of insulating oils are mineral, paraffin, and silicone oils. First of all, transformer oil should be of good quality, i.e have certain properties. Therefore an oil analysis must be performed before use, because it is not desirable to work with oils of dubious quality. In this work I have used transformer oils of different qualities. I have examined the values of specific resistance and dielectric loss coefficient, and according to these properties have determined whether the oil was suitable to be used
Optimization of lutein extraction method from real samples
No full textLutein je pigment svijetložute boje koji pripada skupini ksantofila. Karakteriziraju ga hepatoprotektivna, neuroprotektivna aktivnost te protuupalno i antioksidacijsko djelovanje. U radu je optimirana ekstrakcija luteina ispitivanjem utjecaja različitih ekstrakcijskih smjesa, utjecaj ultrazvuka, omjera suhe tvari (uzorka) i ekstrakcijske smjese, veličine čestica uzorka te vremena ekstrakcije na uspješnost ekstrakcije luteina iz uzorka. Veći sadržaj luteina određen je u usitnjenim uzorcima, boljom se pokazala direktna ultrazvučna ekstrakcija a od ispitivanih ekstrakcijskih smjesa, smjesa metanol:aceton=1:1. Najbolji omjer suhe tvari i uzorka bio je 1:20 kod metode 1 u kojoj je kao ekstrakcijska smjesa upotrebljena metanol: aceton = 1:1, dok je kod metode 4 u kojoj je heksan dodan kao krajnje otapalo bio 1:40 uz 1 sat stajanja uzorka na tamnom. Za analizu realnih uzoraka korištena je metoda 4 koja se pokazala kao najuspješnija. Ovom metodom određivan je sadržaj luteina u osam vrsta hrane za koke nesilice. Najveći sadržaj luteina određen je u hrani obogaćenoj luteinom, selenom, omega-3 masnim kiselinama i vitaminom E (75,314 mg/kg hrane). Dok je najniži sadržaj luteina određen u hrani dostupnoj na tržištu koja nije pomiješana sa žitaricama, 8,482 mg/ kg hrane.Lutein is a light yellow pigment belonging to the xanthophyll group. It is characterized by hepatoprotective, neuroprotective, anti-inflammatory and antioxidant activity. This paper present the optimisation of lutein extraction by examining the influence of different extraction mixtures, the influence of ultrasound, ratio of dry matter (sample) and extraction mixture, sample particle size and extraction time on the success of lutein extraction from the complex sample. The highest lutein content was determined in grinded samples, the direct ultrasonic extraction proved to be better, and the extraction mixture of methanol:acetone= 1:1 showed best results. The best dry matter to sample ratio was 1:20 in Method 1 in which methanol: acetone= 1:1 was used as the extraction mixture, while in Method 4 it was 1:40 in which hexane was added as the final solvent with 1 hour of sample resting in the dark place. Method 4, which proved to be the most successful, was used to analyze the real samples. This method was used to determine the content of lutein in eight types of food for laying hens. The highest lutein content was determined in food samples enriched with lutein, selenium, omega-3 fatty acids and vitamin E (75.314 mg / kg of sample), while the lowest lutein content was determined in food available on the market that was not mixed with cereals, 8.482 mg / kg of sample
Methods for ibuprofen determination
No full textIbuprofen je nesteroidni protuupalni lijek koji pripada skupini derivata propionske kiseline. Ima antipiretičko i analgetsko djelovanje koje ima široku primjenu u liječenju akutne i kronične boli. Vrlo je bitno moći odrediti ibuprofen u biološkim uzorcima zbog dijagnosticiranja mogućeg predoziranja lijekom ili zbog određivanja odgovarajuće terapije zbog mogućih interferencija u dodiru s drugim aktivnim farmaceutskim tvarima. Također je vrlo važno određivati ibuprofen u lijekovima koji su u obliku tableta, sirupa, krema i sl. Na taj način osigurava se kvaliteta i ispravnost lijeka te se određuje može li izaći na tržište. Koncentracija ibuprofena redovito se kontrolira u otpadnim vodama zbog mogućeg ispuštanja neobrađenog otpada iz farmaceutske industrije, bolnica i kućnih otpadnih voda u okolinu te se zbog toga ibuprofen smatra ozbiljnim zagađivačem okoliša. Najčešće metode određivanja ibuprofena su: tekućinska kromatografija visoke djelotvornosti (engl. high-performance liquid chromatography, HPLC), molekulska fluorescencijska spektroskopija, tj. spektrofluorimetrija te voltametrija. Pri razvoju novih metoda, njihova točnost najčešće se provjerava usporedbom rezultata s rezultatima dobivenim nekom drugom metodom, a najčešće je to HPLC.Ibuprofen is a non-steroidal anti-inflammatory drug which belongs to a group of derivatives of propionic acid. It has antipyretic and analgesic effects which have wide application in treating acute and chronic pain. It is extremely important to be able to determine ibuprofen in biological samples, because of diagnosing a possible overdose with a drug, or because of determining a suitable therapy because of possible interferences in contact with other active pharmaceutical substances. It is also really important to determine ibuprofen in drugs which are in the shape of tablets, syrups and creams. In that way, quality and validity of a drug are being ensured, and it is also determined whether it can be released on the market. The concentration of ibuprofen is being controlled regularly in waste water because of a possible discharge of untreated waste in the environment, usually coming from the pharmaceutical industry, hospitals and domestic waste waters, which is why the ibuprofen is considered to be a serious pollutant. The most common methods of determining ibuprofen are: high-performance liquid chromatography (HPLC), fluorescence spectroscopy or spectofluorimetry and voltammetry. When developing new methods, their accuracy is usually checked by comparing the results with the results obtained using another method, mostly HPLC