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Neue Untersuchungen zu Wachstum und Struktur von Fluorapatit-Gelatine-NanokompositenTlatlik, Harald 03 April 2009 (has links)
Die vorliegende Dissertation beschäftigt sich mit Wachstum und Aufbau von Fluorapatit-Gelatine-Nanokompositaggregaten. Diese Aggregate werden im sogenannten Doppeldiffusionsversuch biomimetisch erzeugt und ihre äußere Form bzw. Formentwicklung lässt sich anhand eines fraktalen Modells bis ins Detail nachvollziehen. Sie zeigen einen komplexen inneren Aufbau, in dem die Makromoleküle der organischen Komponente einerseits im Zentrum jeder Nanoeinheit und andererseits zu Strängen, den sogenannten Fibrillen, zusammengelagert am Aufbau der Kompositaggregate beteiligt sind. Im Fall des Kompositkeims ist die innere Architektur in hoher Detailstufe verstanden, auch wenn -- insbesondere bezüglich der späteren Wachstumsphasen -- eine Reihe ungeklärter Fragestellungen verbleibt. Ein zentrales Ergebnis der vorliegenden Arbeit bildet die Entdeckung eines weiteren Wachstumstypen, der im Vergleich zu den bekannten, fraktalen Kompositaggregaten grundsätzliche Unterschiede bezüglich des inneren und äußeren Aufbaus zeigt. Der Grund für die andersartige Formentwicklung liegt in der Versteifung der organischen Komponente durch eine vorangegangene Einlagerung von Calciumionen, wie sowohl experimentell als auch mit atomistischen Computersimulationen gezeigt werden konnte. Aufgrund der hohen Komplexität des Systems ist es bislang allerdings nicht möglich, lokale Ionen-Konzentrationen und pH-Werte vor bzw. während Nukleation und Wachstum der Kompositaggregate im Doppeldiffusionsversuch zu bestimmen. Deshalb wurde ein Ersatzversuch -- der sehr ähnlich strukturierte Aggregate erzeugt, sich aber mit rechnerischen Methoden analysieren lässt -- entworfen und untersucht. Anhand dieser Ergebnisse konnte erstmals die "Geschichte" von Fluorapatit-Gelatine-Nanokompositaggregaten detailliert nachvollzogen werden. Da über die Rolle der Gelatine beim Wachstum der Kompositaggregate nur wenig bekannt ist, wurde eine Reihe von Versuchen durchgeführt, in denen Gelatinen mit verschiedenen Molekülmassenverteilungen eingesetzt wurden. Es stellte sich heraus, dass für selbstorganisiertes und insbesondere fraktales Wachstum der Kompositaggregate lange, möglichst wenig gestörte Makromoleküle von zentraler Wichtigkeit sind. Um die Funktion der organischen Komponente für das Kompositwachstum näher zu untersuchen, wurden Oberflächen von Kompositkeimen mit rasterkraftmikroskopischen Methoden studiert. Durch Säuberung der Oberflächen konnten Austrittsstellen der organischen Komponente durch die Oberfläche der Kompositkeime identifiziert werden. Damit konnte gezeigt werden, dass die organische Komponente aus dem Inneren des Festkörpers teilweise durch die Oberfläche dringt und somit während des Wachstums weit in das Gel hineinreichen sollte. Für die mesoskopische Strukturbildung der Kompositaggregate spielen intrinsische elektrische Felder eine essenzielle Rolle. Deshalb wurde bislang eine Wirkung externer elektrischer Felder auf das Wachstum der Kompositaggregate vermutet. Im Rahmen der vorliegenden Arbeit wurde herausgearbeitet, dass es zwar zu keiner direkten Beeinflussung kommen kann, jedoch in den elektrodennahen Bereichen des Gels eine Ordnung der organischen Moleküle durch externe elektrische Felder zu erwarten ist. Dies könnte eine Wirkung auf wachsende Kompositaggregate zeigen. Da diese Effekte auch aufgrund der elektrischen Felder um die dipolaren Kompositaggregate zu erwarten sind, könnte eine ähnliche Strukturierung der Gelatine in der Nähe der wachsenden Kompositaggregate stattfinden. Insgesamt wurden in dieser Arbeit eine Reihe grundlegender Beiträge zur Erforschung der biomimetisch erzeugten Fluorapatit-Gelatine-Nanokompositaggregate geleistet. Es konnten neue Erkenntnisse zur inneren und äußeren Architektur der Kompositaggregate, zu Mechanismen der Morphogenese und deren wichtigsten Einflussgrößen sowie zum Verständnis der chemisch-physikalischen Vorgänge auf atomarer Größenskala gewonnen werden. Als besonders fruchtbar erwies sich die Verbindung von Experimenten mit theoretischen Untersuchungen, so dass dieser Weg auch in Zukunft grundlegende Erkenntnisse bei der Erforschung der Biomineralisation verspricht und weiterhin verfolgt werden sollte.
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Künstliche und selbstorganisierte Nanokomposite basierend auf oxidischen Verbindungen / Artificial and self-organized nano composites based on oxidic compoundsSchnittger, Sven 18 August 2011 (has links)
No description available.
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Élasticité et endommagement sous chargement bi-axial de nano-composites W/Cuen couches minces sur polyimide : apport des techniques synchrotrons / Elasticity and damage under biaxial loading of W/Cu nanocomposite thin films onpolyimide : contribution of synchrotron techniquesDjaziri, Soundès 25 September 2012 (has links)
Ce travail de thèse porte sur la déformation bi-axiale contrôlée de nano-composites W/Cu en couches minces déposées sur des substrats polyimides. La nano-structuration est obtenue par stratification de deux matériaux immiscibles (W et Cu) par pulvérisation ionique avec contrôle de la taille des grains au sein du film mince par contrôle de l'épaisseur selon la direction decroissance du film. Nous avons développé une procédure permettant de caractériser le comportement mécanique des échantillons à deux échelles différentes. L'essai de traction biaxial est couplé à la diffraction des rayons X (déformation microscopique) et à la corrélation d'images numériques (déformation macroscopique). Nous avons utilisé une machine de tractionbi-axiale développée dans le cadre d’un projet ANR sur la ligne de lumière DiffAbs du synchrotron SOLEIL. Elle permet de contrôler les contraintes dans des films minces supportés par des substrats polyimides. La confrontation des résultats obtenus par ces deux techniques dans le domaine d'élasticité a montré que la déformation est intégralement transmise via l’interfacefilm - substrat. La seconde étape de notre travail a consisté à étudier les déformations du nanocomposite W/Cu au-delà du domaine d’élasticité. Nous avons mis en évidence trois domaines de déformation associés à différents mécanismes de déformation. La limite d'élasticité du nanocomposite W/Cu a été déterminée en comparant la déformation élastique du film mince à la déformation macroscopique du substrat. Enfin, l'étude de la limite d'élasticité du nanocomposite W/Cu pour différents ratios de force a révélé un comportement fragile du nanocomposite W/Cu. / This thesis focuses on the biaxial deformation of W/Cu nanocomposite thin films deposited on polyimide substrates. The grain size in the thin film is controlled by stratification of two immiscible materials (W and Cu) employing sputtering techniques. We developed a procedure to characterize the mechanical behavior of samples at two different scales. A biaxial tensile test is coupled to X-ray diffraction (microscopic deformation) and digital image correlation (macroscopic deformation) techniques. We used a biaxial tensile setup developed in the framework of an ANR project on the DiffAbs beamline at synchrotron SOLEIL allowing forthe control of stresses in thin films supported by polyimide substrates. By comparing the strains obtained by these two techniques, the applied strain is determined to be transmitted unchanged in the elastic domain through the film - substrate interface. The second part of our work was to study the deformation of W/Cu nanocomposite beyond the elastic range. We have highlighted three domains of deformation associated with different deformation mechanisms. The elastic limit of the W/Cu nanocomposite was determined by comparing the elastic deformation of the thin film to the macroscopic deformation of the substrate. Finally, the elastic limit of W/Cu nanocomposite was studied for different load ratios. The overall results emphasized the brittle behavior of these nanocomposites.
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Preparation of PVA / Bioactive Glass nanocomposite scaffolds : in vitro studies for applications as biomaterials : association with active molecule / Préparation du PVA / verre bioactif échafaudages nanocomposites : des études in vitro pour des applications en tant que biomatériaux : association avec molécule activeMabrouk Mohamed, Mostafa 11 June 2014 (has links)
Le Poly Vinyl Alcohol (PVA) a été associé aux verres élaborés dans un système quaternaire (BG) 46S6 par les procédés cités (fusion, sol-gel et sacffolds). Différents paramètres intervenant dans les synthèses des verres bioactifs ont été étudiés, nous citons à titre d’exemple : la température, le pH, la taille des particules, le rapport Polymère / verres, la microstructure, la porosité et la biodégradation. Les caractéristiques thermiques des verres élaborés ont été également déterminées après chaque synthèse par analyse thermique différentielle (DSC/TG, DTA/TG). Ainsi, la température de fusion, la température de transition vitreuse et la température de cristallisation ont été élucidées. Ces caractéristiques thermiques changent lorsque la composition chimique du verre est modifiée. A ce titre, les compositions chimiques ont été étudiées par Fluorescence (XRF) et Inductively Coupled Plasma-Opticale Emission Spectroscopy (ICP-OES) après chaque synthèse pour s’assurer de la pureté des verres bioactifs élaborés et destinés à des applications médicales. Plusieurs techniques physico chimiques d’analyses (DRX, MEB, MET, FT-IR, XRF, ICPOES) ont été mises en oeuvre pour déterminer les propriétés physico chimiques de nos verres bioactifs avant et après expérimentations « in vitro ». Le nano composite Polymère-Verres scaffolds que nous avons obtenu présente des particules de tailles comprises entre 40 et 61 nm et une porosité d’environ 85%. La biodégradation des verres scaffolds décroît lorsque la teneur en verre scaffolds dans le nano composite croît. Les expérimentations « in vitro » montrent qu’après immersion de ces nano composites dans un liquide physiologique synthétique (SBF), une couche d’apatite (phosphate de calcium) se forme à leur surface. L’épaisseur de la couche formée dépend clairement de la taille des particules et du rapport polymère / verre scaffolds. / The aim of the present work is the preparation of Bioactive Glass (BG) 46S6 by different techniques. Fabrication of composite scaffolds by using of Poly Vinyl Alcohol (PVA) and quaternary BG (two methods melting and sol-gel) with different ratios to the prepared scaffolds was carried out. Different factor affecting the final properties of the prepared composite scaffolds were investigated in this study, such as; temperature of treatment, BG particle size, polymer/glass ratio, microstructure, porosity, biodegradation, bioactivity, and drug release. The thermal behavior of the prepared bioactive glass by sol-gel and melting techniques were identified using Differential Scanning Calorimetric/Thermo Gravimetric (DSC/TG) or Differential Thermal Analysis/Thermo Gravimetric (DTA /TG). The elemental composition of the prepared bioactive glasses was determined by X-rays Fluorescence (XRF) to confirm that the prepared bioactive glasses have the same elemental compositions and high purity for biomedical applications. The particle size of the prepared bioactive glass was determined by Transmission Electron Microscopic (TEM). Nano-bioactive glass could be obtained by modified sol-gel and the obtained particle size ranged between 40 to 61 nm. The prepared bioactive glass by both applied methods has the same amorphous phase and all identified groups as well as. The porous scaffold has 85% porosity with a slight decrease by increasing the glass contents. The degradation rate decreased by increasing of glass content in the prepared scaffolds. The bioactivity of the prepared composite scaffolds was evaluated by XRD, FTIR, SEM coupled with EDX and Inductively Coupled Plasma-Optical Emission Spectroscopic (ICP-OES). It has been observed that after soaking in Simulated Body Fluid (SBF), there was an apatite layer formed on the surface of the prepared samples with different thickness depending on the glass particle size and polymer/glass ratio.
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FORMING A METAL MATRIX NANOCOMPOSITE (MMNC) WITH FULLY DISPERSED AND DEAGGLOMERATED MULTIWALLED CARBON NANOTUBES (MWCNTs)Pallikonda, Mahesh Kumar, Pallikonda 01 September 2017 (has links)
No description available.
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Etude et développement de points mémoires résistifs polymères pour les architectures Cross-Bar / Development and Study of Organic Polymer Resistive Memories For Crossbar ArchitecturesCharbonneau, Micaël 19 January 2012 (has links)
Ces dix dernières années, les technologies de stockage non-volatile Flash ont joué un rôle majeur dans le développement des appareils électroniques mobiles et multimedia (MP3, Smartphone, clés USB, ordinateurs ultraportables…). Afin d’améliorer davantage les performances, augmenter les capacités et diminuer les coûts de fabrication, de nouvelles solutions technologiques sont aujourd’hui étudiées pour pouvoir compléter ou remplacer la technologie Flash. Citées par l’ITRS, les mémoires résistives polymères présentent des caractéristiques très prometteuses : procédés de fabrication à faible coût et possibilité d’intégration haute densité au dessus des niveaux d’interconnexions CMOS ou sur substrat souple. Ce travail de thèse a été consacré au développement et à l'étude des mémoires résistifs organiques à base de polymère de poly-méthyl-méthacrylate (PMMA) et de molécules de fullerènes (C60). Trois axes de recherche ont été menés en parallèle: le développement et la caractérisation physico-chimique de matériaux composites, l’intégration du matériau organique dans des structures de test spécifiques et la caractérisation détaillée du fonctionnement électrique des dispositifs et des performances mémoires. / Over the past decade, non-volatile Flash storage technologies have played a major role in the development of mobile electronics and multimedia (MP3, Smartphone, USB, ultraportable computers ...). To further enhance performances, increase the capacity and reduce manufacturing costs, new technological solutions are now studied to provide complementary solutions or replace Flash technology. Cited by ITRS, the polymer resistive memories present very promising characteristics: low cost processing and ability for integration at high densities above CMOS interconnections or on flexible substrate. This PhD specifically focused on the development and study of composite material made of Poly-Methyl-Methacrylate (PMMA) polymer resist doped with C60 fullerene molecules. Studies were carried out on three different axes in parallel: Composite materials development & characterization, integration of the organic material in specific test structure and advanced devices and finally detailed electrical characterization of memory cells and performances analysis.
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Voltametrijske metode zasnovane na primeni jednostavnih i savremenih elektroda/senzora na bazi ugljeničnih materijala za određivanje vodonik-peroksida u odabranim uzorcima / Voltammetric methods based on the application of simple and contemporary carbonaceousmaterials-based electrodes/sensors for the determination of hydrogen-peroxide in the selected samplesAnojčić Jasmina 22 November 2018 (has links)
<p>Cilj ove doktorske disertacije je bio razvoj brzih i pouzdanih voltametrijskih metoda zasnovanih na primeni jednostavnih i savremenih elektroda/senzora na bazi ugljeničnih materijala (ugljenične paste napravljene od grafitnog praha i parafinskog ulja i štampanih ugljeničnih elektroda) za određivanje H <sub>2</sub>O<sub>2 </sub>u odabranim složenim model i realnim uzorcima. U tu svrhu, ispitana je primenljivost različitih radnih elektroda. Amperometrijska metoda zasnovana na elektrodi od ugljenične paste (CPE) zapreminski modifikovane sa 5% (m:m) MnO2 je, pri optimizovanim uslovima i pri radnom potencijalu od 0,40 V u odnosu na zasićenu kalomelovu elektrodu (ZKE) u fosfatnom puferu pH 7,50 kao pomoćnom elektrolitu, omogućila kvantifikaciju H <sub>2</sub>O<sub>2</sub> u opsegu koncentracija od 1,4 do 65 µg mL -1 sa relativnom standardnom devijacijom (RSD) manjom od 10%. Ova metoda je primenjena za određivanje sadržaja H <sub>2</sub>O<sub>2 </sub>u uzorcima podzemne vode iz centralnog Banata (Pokrajina Vojvodina, Srbija) tretirane Fentonovim (Fe<sup> 2+</sup> i H <sub>2</sub>O<sub>2</sub> ) i Fentonu-sličnim (Fe <sup>3+</sup> i H <sub>2</sub>O<sub>2</sub> ) reagensima u cilju uklanjanja prirodnih organskih materija (POM) pri čemu su korišćene različite početne koncentracije gvožđa i različiti odnosi molarnih koncentracija gvožđa i H <sub>2</sub>O<sub>2</sub> . Utvrđeno je da oksidaciono stanje gvožđe (Fe<sup> 2+</sup> ili Fe <sup>3+</sup>) i molarni odnos jona Fe i H<sub> 2</sub>O<sub>2</sub> utiču na stepen potrošnje/razgradnje H<sub> 2</sub>O<sub>2</sub><br />u podzemnoj vodi sa visokim sadržajem POM. Takođe, u slučaju Fentonu-sličnog procesa, za sve početne koncentracije Fe <sup>3+</sup> i H <sub>2</sub>O<sub>2 ,</sub> signifikantna količina H <sub>2</sub>O<sub>2 </sub>ostaje neiskorišćena, što ukazuje na nižu efikasnost ovakvog sistema u poređenju sa Fentonovim procesom.Štampana ugljenična elektroda (SPCE) zapreminski modifikovana sa MnO 2 kao medijatorom je primenjena za određivanje sadržaja H<sub> 2</sub>O<sub>2</sub> u toku Fentonovog (Fe <sup>2+</sup> , H<sub>2</sub>O<sub>2</sub> ) i vidljivom svetlošću potpomognutog foto-Fentonovog (Fe<sup> 2+ </sup>, H <sub>2</sub>O<sub>2 </sub>, hν) procesa uklanjanja neonikotinoidnog insekticida acetamiprida (ACT). Pri optimizovanim uslovima (radni potencijal 0,40 V u odnosu na ZKE, fosfatni pufer pH 7,50 kao pomoćni elektrolit) amperometrijskog određivanja H <sub>2</sub>O<sub>2</sub> , postignuta je linearnost u opsegu koncentracija 0,01–1,24 mmol L-1(0,34– 42,2 µg mL -1<br />) i vrednost RSD nije prelazila 4,2%. U ispitivanimuzorcima (nakon odgovarajućeg<br />podešavanja pH vrednosti od 2,8 do 7,5 odmah nakon uzorkovanja radi stopiranja ili maksimalnog usporavanja procesa oksidacije, filtriranja, zamrzavanja i odmrzavanja neposredno pre merenja) sadržaj H <sub>2</sub>O<sub>2</sub> je određen metodom standardnog dodatka analiziranjem odgovarajućih amperometrijskih krivi. Paralelna HPLC-DAD merenja su vršena u cilju praćenja koncentracije/uklanjanja ACT. U slučaju foto-Fentonovog procesa (početne koncentracije 0,31; 2,0 i 3,0 mmol L -1 (70,0; 111,7 i 102,1 µg mL -1 ) za ACT, Fe<br /><sup>2+</sup> i H <sub>2</sub>O<sub>2</sub>, redom) nakon 10 min H <sub>2</sub>O<sub>2 </sub>je izreagovao, a može se smatrati da je ACT uklonjen nakon 5 min. U toku Fentonovog procesa ACT je uklonjen nakon 20 min tretmana i oko 10% početne koncentracije H <sub>2</sub>O<sub>2</sub> je ostalo u sistemu<br />neiskorišćeno.CPE je površinski modifikovane kompozitom na bazi nanočestica Pt (< 5 nm) i grafitizovanog ugljenika (Pt-C, 10% Pt na Vulkanu XC72) etodom nanošenja kapi. Nemodifikovana CPE i modifikovana (Pt-C/CPE) su okarakterisane primenom SEM/EDS i CV merenja. Pt-C/CPE je pokazala izuzetne elektrokatalitičke osobine u pogledu elektrohemijskeredoks reakcije H<br /><sub>2</sub>O<sub>2</sub> u poređenju sa nemodifikovanom CPE u fosfatnom puferu (0,1 mol L -1 ;<br />pH 7,50), a takođe i u acetatnom puferu (0,1 mol L -1 ; pH 4,50) kao pomoćnim elektrolitima. Prilikom amperometrijskog određivanja H <sub>2</sub>O<sub>2</sub> primenom Pt-C/CPE u model sistemima, zadovoljavajuća linearnost je postignuta u koncentracionom opseguH<sub>2</sub>O<sub>2</sub>od 0,15 do 1,45 µg mL -1 ,dok su vrednosti GO iznosile 0,06 µg mL -1 (pH 7,50, radni potencijal 0,20 V) i 0,10 µg mL -1 (pH<br />4,50, radni potencijal 0,50 V). Optimizovane analitičke metode su primenjene za određivanje sadržaja H <sub>2</sub>O<sub>2</sub> u komercijalno dostupnim proizvodima za ličnu negu: rastvoru za dezinfekciju (pH 7,50) i rastvoru za čišćenje kontaktnih sočiva (pH 4,50). Amperometrijski dobijeni rezultati su u dobrom slaganju sa rezultatima dobijenim primenom tradicionalne spektrofotometrijske metode bazirane na titanijum-sulfatu kao reagensu sa određenim koncentracijama 2,91% i 2,94% za<br />dezinfekcioni rastvor i 3,04% i 3,17% za rastvor zakontaktna sočiva, redom. RSD je bila manja od 2%. Postignuti rezultati su u dobrom slaganju sa sadržajem H<br /><sub>2</sub>O<sub>2 </sub>deklarisanim od strane proizvođača (3%) u oba ispitivana uzorka. Pt-C/CPE je takođe testirana za praćenje koncentracije H<sub>2</sub>O<sub>2</sub> u rastvoru za kontaktna sočiva u toku procesa njegove neutralizacije/razgradnje. Nakon 6 h procesa neutralizacije, 24,68 µg mL -1 je bila određena koncentracija H <sub>2</sub>O<sub>2 ,</sub> što je ispod dozvoljene<br />H<sub>2</sub>O<sub>2 </sub>koncentracije u rastvoru za kontaktna sočiva imajući u vidu granicu koja izaziva iritaciju oka. CPE je površinski modifikovana višezidnim ugljeničnim nanocevima (MWCNT) i kompozitima MnO 2 -MWCNT ili Pt-MWCNT metodom nanošenja kapi radi pripreme jednostavnih, osetljivih i pouzdanih voltametrijskih senzora za određivanje H <sub>2</sub>O<sub>2 </sub>u odabranom uzorku. Rezultati SEM/EDS analize kompozitnih materijala su potvrdili da su medijatori, čestice MnO 2 i Pt, nasumično raspoređeni na površini MWCNT i zastupljeni sa blizu 5% (m:m) u kompozitu izraženo<br />preko Mn i Pt. CV merenja su vršena sa pripremljenim radnim elektrodama u acetatnom (pH 4,50), fosfatnom (pH 7,50) i boratnom (pH 9,18) puferu kako bi se okarakterisalo osnovno elektrohemijsko ponašanje H <sub>2</sub>O<sub>2 </sub>i odabrali pogodni radni potencijali za amperometrijsko određivanje ovog ciljnog analita. Pt- WCNT/CPE je primenljiva za rad kako u fosfatnom puferu pH 7,50 tako i u acetatnom puferu pH 4,50 V kako pri negativnim tako i pri pozitivnim radnim<br />potencijalima, pri čemu su vrednosti RSD uglavnom ispod 2,5%. U slučaju MnO 2<br />-MWCNT/CPE, na potencijalu 0,30 V i višim vrednostima, oksidacioni signali H<br /><sub>2</sub>O<sub>2</sub> su signifikantni u blago alkalnoj sredini (pH 7,50), pri pH 4,50 ova elektroda pokazuje nezadovoljavajuće ponašanje, dok pri pH 9,18 ima prihvatljive performanse. Granice određivanja (GO) su bile u oblasti µg mL -1 . H <sub>2</sub>O<sub>2</sub> je određen u spajkovanom uzorku mleka metodom standardnog dodatka nakon odgovarajuće pripreme uzorka (pH podešavanje i centrifugiranje) i primenom optimizovane amperometrijske procedure (acetatni pufer pH 4,50, radni potencijal-0,75 V) koristeći Pt-MWCNT/CPE kao radnu elektrodu. RSD za tri ponovljena merenja je iznosila 2,5%, dok je prinos metode bio nešto veći od 71%.<br />Kompozitni materijali koji se sastoje od MWCNT i čestica na bazi Pd (Pd-MWCNT) ili Pt (Pt-MWCNT) su primenjeni za pripremu zapreminski modifikovanih SPCE (Pd-MWCNT-SPCE i Pt-MWCNT-SPCE) i površinski modifikovane SPCE (Pd-MWCNT/SPCE). Ove elektrode, kao i nemodifikovana SPCE i MWCNT-SPCE, su okarakterisane primenom CV i amperometrije u fosfatnom puferu pH 7,50 radi određivanja H <sub>2</sub>O<sub>2</sub> . Pd-MWCNT-SPCE i Pd-MWCNT/SPCE su se pokazale pogodnim za određivanje H <sub>2</sub>O<sub>2</sub> na radnim potencijalima između -0,50 i 0,50 V, a PtMWCNT-SPCE na ispitivanim radnim potencijalima od -0,80 do 0,70 V. Ove elektrode su zatim modifikovane enzimom glukoza oksidazom (GOx) metodom nanošenja kapi rastvora GOx i Nafion ® -a na njihovu površinu, pri čemu je optimizovana količina nanetog biofilma. GOx/PdMWCNT-SPCE je pokazala bolje analitičke performanse za određivanje glukoze u poređenju sa GOx/Pd- WCNT/SPCE. Kao optimalan radni potencijal GOx/Pd-MWCNT-SPCE je odabrana<br />vrednost potencijala -0,40 V u odnosu na ZKE, sa zadovoljavajućom linearnošću u ispitivanom opsegu koncentracija glukoze od 0,16 do 0,97 mmol L -1 (od 29,1 do 174 µg mL -1), dok je GO iznosila 0,14 mmol L -1 (25 µg mL<br />-1 ). Optimizovana metoda zasnovana na GOx/Pd-MWCNT-SPCE je uspešno primenjena za određivanje glukoze u uzorku livadskog meda. Dobijeni rezultati su u dobroj saglasnosti sa onima dobijenim primenom komercijalno dostupnog aparata za merenje glukoze. Pogodan radni potencijal za GOx/Pt-MWCNT-SPCE je bio -0,50 V u odnosu na ZKE, pri čemu je zadovoljavajuća linearnost postignuta u ispitivanom opsegu koncentracija glukoze od 65,8 do 260,6 µg mL -1 , sa GO 35 µg mL -1 . Optimizovana metoda zasnovana na GOx/Pt-MWCNT-SPCE je uspešno primenjena za određivanje glukoze u u uzorku belog grožđa i uzorku tableta (Traubenzucker-bonbons), pri čemu su dobijeni rezultati u dobroj saglasnosti sa rezultatima dobijenim primenom Accu-Chek aparata.<br />Na osnovu dobijenih rezultata može se zaključiti da su razvijene analitičke metode pre svega jednostavne, pouzdane i pogodne za dobijanje brzih informacija o sadržaju H <sub>2</sub>O<sub>2</sub> u različitim tipovima uzoraka. Svakako odabir pogodne radne elektrode, kao i optimizacija eksperimentalnih uslova su ključni faktori za uspešno određivanje H <sub>2</sub>O<sub>2</sub></p> / null / <p>The aim of this doctoral dissertation was the development of fast and reliable voltammetric methods based on the application of simple and contemporary electrodes/sensors based on carbonaceous materials (carbon paste made of graphite powder and paraffin oil and screen printed carbon electrodes) for the determination of H <span id="cke_bm_571S" style="display: none;"> </span><sub>2</sub><span id="cke_bm_571E" style="display: none;"> </span>O<sub>2</sub> in the selected complex model and real samples.For this purpose, applicability of different working electrodes was investigated.The amperometric method based on carbon paste electrode (CPE) bulk- modified with 5% (m:m) MnO 2 , under optimized conditions, with a working potential of 0.40 V vs. the saturated calomel elect<span id="cke_bm_572E" style="display: none;"> </span>rode (SCE) and a phosphate buffer solution (pH 7.50) as supporting electrolyte, enabled the quantitation of H <span id="cke_bm_577S" style="display: none;"> </span><sub>2</sub><span id="cke_bm_577E" style="display: none;"> </span>O<sub>2</sub>in the concentration interval from 1.4 to 65 µg mL −1 with a relative standard deviation (RSD) of less than 10%. This meth<span id="cke_bm_578E" style="display: none;"> </span>od was applied for the determination of the H<span id="cke_bm_583S" style="display: none;"> </span><sub>2</sub><span id="cke_bm_583E" style="display: none;"> </span>O<sub>2 </sub>consumption in samples of groundwater fro<span id="cke_bm_584E" style="display: none;"> </span>m the Central Banat region (Province of Vojvodina, Serbia) treated by the Fenton (Fe <sup>2+ </sup>and H <sub>2</sub>O<sub>2</sub> ) and Fenton- like (Fe <sup>3+</sup>and H <sub>2</sub>O<sub>2</sub> ) reagents to remove natural organic matter (NOM) at differentinitial concentrations of iron species, and of their molar ratios to the initial concentration of H<sub>2</sub>O<sub>2</sub> . It was found that the form of Fe (Fe <sup>2+</sup> or Fe <sup>3+</sup> )and the molar ratio to H <sub>2</sub>O<sub>2</sub>influenced the degree of the H<sub> 2</sub>O<sub>2</sub> decomposition in the groundwater with high NOM content. Besides, in the case of the Fenton-like process, for all initial doses of Fe <sup>3+</sup> and H<span id="cke_bm_604S" style="display: none;"> </span><sub> 2</sub><span id="cke_bm_604E" style="display: none;"> </span>O<sub>2</sub>, a sign<span id="cke_bm_605E" style="display: none;"> </span>ificant amount of H<span id="cke_bm_610S" style="display: none;"> </span><sub> 2</sub><span id="cke_bm_610E" style="display: none;"> </span>O<sub>2</sub> remained unused, whi<span id="cke_bm_611E" style="display: none;"> </span>ch also indicates a lower efficiency of such system compared to the Fenton process. Screen printed carbon electrode (SPCE) bulk-modified with MnO <sub> 2</sub> as a mediator was applied for amperometric determination of the H <span id="cke_bm_617S" style="display: none;"> </span><sub>2</sub><span id="cke_bm_617E" style="display: none;"> </span>O<sub>2</sub> content during the Fenton (Fe <sup>2+</sup> , H <span id="cke_bm_624S" style="display: none;"> </span><sub>2</sub><span id="cke_bm_624E" style="display: none;"> </span>O<sub>2 </sub>) and <span id="cke_bm_625E" style="display: none;"> </span>visible light-assisted<span id="cke_bm_618E" style="display: none;"> </span>, photo-Fenton (Fe <sup>2+ </sup> , H <span id="cke_bm_631S" style="display: none;"> </span><sub>2</sub><span id="cke_bm_631E" style="display: none;"> </span>O<sub>2</sub> , hν)<span id="cke_bm_632E" style="display: none;"> </span> based removal of neonicotinoid insecticide acetamiprid (ACT). Under optimized conditions (working potential of 0.40 V vs. SCE, phosphate buffer pH 7.50 as supporting electrolyte) amperometric determination of H <span id="cke_bm_637S" style="display: none;"> </span><sub>2</sub><span id="cke_bm_637E" style="display: none;"> </span>O<sub>2 </sub>showed a linear dynamic range from 0.01 to 1.24 mmol L -1 (from 0.34 to 42.2 µg mL -1) and the RSD did not exceed 4.2%. In the investigated samples (after appropriate pH adjustment from 2.8 to 7.5 instantly after the sampling<span id="cke_bm_638E" style="display: none;"> </span> to stop or maximum decelerate the oxidation processes, filtering, and storage of the deep- frozen sample with defrosting immediately before the measurements) the H <span id="cke_bm_643S" style="display: none;"> </span><sub>2</sub><span id="cke_bm_643E" style="display: none;"> </span>O<sub>2</sub> contents were determined by the standard addition method by analyzing the corresponding amperometric curves. Parallel HPLC-DAD measurements were performed to monito<span id="cke_bm_644E" style="display: none;"> </span>r the concentration/removal of ACT. In the case of the photo- Fenton process (initial concentrations: 0.31; 2.0 and 3.0 mmol L -1 (70.0; 111.7 and 102.1 µg mL -1 ) of ACT, Fe<sup> 2+</sup> and H <span id="cke_bm_650S" style="display: none;"> </span><sub>2</sub><span id="cke_bm_650E" style="display: none;"> </span>O<sub>2</sub>, respec<span id="cke_bm_651E" style="display: none;"> </span>tively) after 10 min of irradiation H <span id="cke_bm_656S" style="display: none;"> </span><sub>2</sub><span id="cke_bm_656E" style="display: none;"> </span>O<sub>2</sub> was consumed and it can be consi<span id="cke_bm_657E" style="display: none;"> </span>dered that ACT was removed after 5 min. During the Fenton process ACT was removed after 20 min of treatment and around 10% of the initial concentration of the H 2O2 remained still unused.<br />CPE was surface modified with a composite of Pt nanoparticles (< 5 nm) on graphitized carbon (Pt-C, 10% Pt on Vulcan XC72) by simply dropcoating method. The unmodified CPE and the modified one (Pt-C/CPE) were characterized by EM/EDS and CV measurements. The PtC/CPE showed remarkable electrocatalytic propertiestoward the electrochemical redox reaction of H<span id="cke_bm_662S" style="display: none;"> </span><sub>2</sub><span id="cke_bm_662E" style="display: none;"> </span>O<sub>2</sub> compared to modified CPE in phosphate buffer (0.1 mol L -1 ; pH 7.50), as well in acetatebuffer (0.1 mol L -1 ; pH .50) supporting electrolytes. Amperometry of H2O2 in the concentration range from 0.15 to 1.45 µg mL -1 with the Pt-C/CPE showed acceptable linearity, while the obtained values of LOQs were 0.06 µg mL -1 (pH 7.50, working potential 0.20 V) and 0.10 µg mL -1 (pH 4<span id="cke_bm_663E" style="display: none;"> </span>.50, working potential 0.50 V). The proposed analytical methods were applied to the determination of the H 2O2 content in commercially available personal care products; i.e., disinfection (pH 7.50) and contact lens cleaning solutions (pH 4.50). The obtained amperometric results are in good agreement with those measured by traditional titanium sulfatereagent based spectrophotometric method with determined concentrations as 2.91% and 2.94% for the disinfection product, and 3.04% and 3.17% for the contact lens solution, respectively. RSD was lower than 2%. The obtained results are in a good agreement with the amounts of the H<span id="cke_bm_668S" style="display: none;"> </span><sub> 2</sub><span id="cke_bm_668E" style="display: none;"> </span>O<sub>2 </sub>declared by producers (3%) in the both investigated samples. The Pt-C/CPE was also tested for monitoring of the H<span id="cke_bm_674S" style="display: none;"> </span><sub> 2</sub><span id="cke_bm_674E" style="display: none;"> </span>O<sub>2</sub> residual concentration in contact lens solution during its neutralization/decomposition rocess. At 6 h of<span id="cke_bm_675E" style="display: none;"> </span> neutralization treatment 24.68 µg mL -1 of the H <span id="cke_bm_680S" style="display: none;"> </span><sub>2</sub><span id="cke_bm_680E" style="display: none;"> </span>O<sub>2 </sub>was determined which is almost half of the allowedH2<span id="cke_bm_681E" style="display: none;"> </span>O2 concentration in the case of the contact lens solution concerningthe limit of eye irritation. CPE was surface modified with multiwalled carbon nanotubes (MWCNT) and with composites of MnO<sub> 2 </sub>-MWCNT or Pt-MWCNT by drop coating method to prepare simply, sensitive and reliable volta<span id="cke_bm_669E" style="display: none;"> </span>mmetric sensors for the determination of H <span id="cke_bm_687S" style="display: none;"> </span><sub>2</sub><span id="cke_bm_687E" style="display: none;"> </span>O<sub>2 </sub>in selected sample. The results of the SEM/<span id="cke_bm_688E" style="display: none;"> </span>EDS analysis of composite materials have confirmed that the mediators, MnO <sub>2</sub> and Pt articles, are randomly distributed on the surface of MWCNT and represent nearly 5% (m:m) of the composite expressed as Mn and Pt. CV measurements were performed with prepared electrodes in acetate (pH 4.50), phosphate (pH 7.50) and borate (pH 9.18) buffers to characterize the basic electrochemical behavior of H <span id="cke_bm_694S" style="display: none;"> </span><sub>2</sub><span id="cke_bm_694E" style="display: none;"> </span>O<sub>2</sub> and to select the working potentials suitable for amperometric determination of this target analyte. The Pt-MWCNT/CPE performs well in phosphate buffer pH .50 and acetate buffer solution pH 4.50 in the negative as well as in the positive polarization range with RSD mainly lower than 2.5%. In case of MnO<sub> 2 </sub>-MWCNT/CPE at <span id="cke_bm_695E" style="display: none;"> </span>0.30 V and above the H<span id="cke_bm_701S" style="display: none;"> </span><sub>2</sub><span id="cke_bm_701E" style="display: none;"> </span>O<sub>2 </sub>oxidation signal is rem<span id="cke_bm_702E" style="display: none;"> </span>arkable in slightly alkaline media (pH 7.50), at pH 4.50 this electrode showed poor behavior and at pH 9.18 offered acceptable performance. LOQs were in the µg mL -1 concentration range. H<span id="cke_bm_707S" style="display: none;"> </span><sub>2</sub><span id="cke_bm_707E" style="display: none;"> </span>O<sub>2 </sub>was determined in a spiked milk sample by standard addition method after appropriate sample preparation (pH adjustment and centrifugation) and using optimized amperometric p<span id="cke_bm_708E" style="display: none;"> </span>rocedure (acetate buffer pH 4.50, working potential -0.75 V) by Pt-MWCNT/CPE as a working electrode. RSD for three repeated measurements was 2.5%, while the recovery of the method was a bit higher than 71%. The composite materials consisting of MWCNT and Pd (Pd-MWCNT) or Pt containing particles (Pt-WCNT) were applied to the preparation of bulk- modified SPCEs (Pd-MWCNTSPCE and Pt-MWCNT-SPCE) and surface modifiedSPCE (Pd- MWCNT/SPCE). These electrodes, as well as unmodified SPCE and MWCNT-SPCE, were characterized by CV and amperometry in phosphate buffer solution of pH 7.50 for the H<span id="cke_bm_713S" style="display: none;"> </span><sub> 2</sub><span id="cke_bm_713E" style="display: none;"> </span>O<sub>2 </sub>determination. Pd-MWCNT-SPCE and PdMWCNT/SPCEare convenient for the etermination of H 2O2 at working potentials from -0.50 to 0.50 V, and Pt-MWCNT-SPCE at investigated working potentials in the range from -0.80 to 0.70 V. These electrodes were then modified with glucose oxidase (GOx) by drop coating a solution of GOxand Nafion ® on their surface, whereby the applied amount of biococktail was optimized. GOx/PdMWCNT-SPCE showed better analytical performance for glucose determination in comparison with GOx/Pd-MWCNT/SPCE. The optimal working potential for GOx/Pd-MWCNT- SPCE was -0.40 V vs. SCE and <span id="cke_bm_714E" style="display: none;"> </span>satisfactory linearity was obtained in the investigated glucose concentration range from 0.16 to 0.97 mmol L -1 (from 29.1 to 174 µg mL -1 ), hile the LOQ was 0.14 mmol L -1 (25 µg mL -1 ). The optimized method based on GOx/Pd-MWCNT-SPCE was successfully applied to the determination of glucose in multifloral honey sample. The results are in a good agreement with those obtained by commercially available equipment for determination of glucose. Optimal working potential for GOx/Pt-MWCNT-SPCE was -0.50 V vs. SCE, and the satisfactory linearity was obtained in the investigated concentration range ofglucose from 65.8 to 260.6 µg mL -1 , with LOQ of 35 µg mL -1 . The optimized method based on GOx/Pt- MWCNT-SPCE was successfully applied for determination of glucose in white grape and glucose tablets (Traubenzucker-bonbons) samples, whereby the obtained results were in a good agreement with the results obtained by Accu-Chek device. Based on the results, the developed analytical methods are first of all simple, reliable and suitable for obtaining fast information about the content of H <sub>2</sub>O<sub>2</sub> in different types of samples. Certainly the selection of a suitable working electrode, as well as the optimization of experimental conditions are key factors for the successful determination of H<sub>2</sub>O<sub>2 </sub>.</p>
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