Sinteza nanokompozitnih hidrogelova poli(etilen-oksida) s nanočesticama srebra gama-zračenjem

master's thesis

• Title (english): Gamma-irradiation synthesis of poly(ethylene oxide)/Ag nanocomposite gels
• Author: Monika Mihaljević
• Mentor: Danijela Ašperger (mentor)
• Mentor: Tanja Jurkin (komentor)
• Committee member: Danijela Ašperger (predsjednik povjerenstva)
• Committee member: Stanislav Kurajica (član povjerenstva)
• Committee member: Tanja Jurkin (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2021-09-24, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Chemistry

Abstract

Zbog njihovih jedinstvenih svojstava, sinteza nanočestica i ostalih nanomaterijala poput nanokompozitnih hidrogelova izaziva veliki interes, kako u znanosti, tako i u inženjerstvu. Zadnjih godina naglasak je na alternativnim, ekološki prihvatljivim načinima sinteze. Sinteza gama-ozračivanjem je relativno nova i efikasna metoda sinteze nanočestica i hidrogelova. Njene glavne prednosti pred klasičnim metodama sinteze su homogena, čista i temperaturno neovisna inicijacija reakcija, a nastali produkt je i sterilan. U ovom radu istražena je mogućnost sinteze nanokompozitnih hidrogelova poli(etilen-oksida) (PEO) s nanočesticama srebra gama-zračenjem, u jednom koraku. U tu svrhu ispitan je utjecaj različitih eksperimentalnih parametara. PEO/Ag hidrogelovi i koloidne suspenzije sintetizirani su gama-ozračivanjem PEO i Ag+ vodenih otopina, ovisno o molekulskoj masi te masenom udjelu polimera, početnoj koncentraciji soli srebra, apsorbiranoj dozi, pH-vrijednosti i atmosferi u kojoj je ozračivanje provedeno. Sinteza pri povišenoj pH-vrijednosti, koncentriranijoj PEO otopini i u internoj atmosferi omogućila je dobivanje hidrogelova s većom koncentracijom ugrađenog srebra. UV-Vis spektroskopska mjerenja pokazala su karakteristične apsorpcijske maksimume na približno 400 nm, koji ukazuju na formiranje nanočestica srebra. SEM mikroskopijom potvrđen je nastanak nanočestica srebra, malih dimenzija (~11 – 23 nm) s homogenom raspodjelom unutar polimerne matrice. Manje čestice formirane su u uvjetima manje koncentracije srebra, više pH-vrijednosti i pri ozračivanju uzoraka u inertnoj atmosferi dušika. XRD analiza također je potvrdila nastanak nanočestica srebra, a zajedno s rezultatima DSC analize pružila informaciju o kristalnosti, a time i gustoći umreženja nastalih gelova. Stupnjevi kristalnosti pokazali su najniže vrijednosti pri višoj dozi, ozračivanju u inertnoj atmosferi te nižoj koncentraciji PEO i Ag+, što ukazuje na veći stupanj umreženja PEO lanaca. Ozračivanje višom dozom rezultiralo je gotovo potpuno amorfnim gelovima sa značajno sniženim temperaturama taljenja i kristalizacije.

Abstract (english)

Due to their unique properties, the synthesis of nanoparticles and other nanomaterials, such as nanocomposite hydrogels, attracts great interest, both in science and engineering. In recent years, the emphasis has been on alternative, environmentally friendly methods of synthesis. Gamma-irradiation synthesis is a relatively new and efficient method for synthesis of nanoparticles and hydrogels. Its main advantages over classical synthesis methods are homogeneous, clean and temperature-independent initiation of reactions, and a sterile final product. In this work, the possibility of one-step synthesis of poly(ethylene oxide) (PEO)/Ag nanocomposite hydrogels by gamma-irradiation was studied. For this purpose, the influence of different experimental parameters was investigated. PEO/Ag hydrogels and colloidal suspensions were synthesized by gamma irradiation of PEO and Ag+ aqueous solutions, depending on the molecular weight and weight precentage of the polymer, initial Ag+ concentration, absorbed dose, pH value and atmosphere in which irradiation was carried out. Synthesis at elevated pH, more concentrated PEO solution and under inert atmosphere enabled formation of hydrogels with a higher concentration of silver nanoparticles. UV-Vis spectroscopic measurements showed characteristic absorption maxima at approximately 400 nm, indicating the formation of silver nanoparticles. SEM microscopy confirmed the formation of silver nanoparticles, which were small in size (~11 – 23 nm) and homogeneously distributed within the polymer matrix. Smaller particles were formed at lower silver concentration, at higher pH values and upon irradiation in an inert nitrogen atmosphere. XRD analysis also confirmed the formation of silver nanoparticles, and together with the results of DSC analysis provided information on the crystallinity and hence crosslinking density of the obtained gels. The degrees of crystallinity showed the lowest values at higher dose, on irradiation in inert atmosphere and lower concentration of PEO and Ag+, which indicates a greater degree of crosslinking of PEO chains. Irradiation with a higher dose resulted in almost amorphous gels with significantly reduced melting and crystallization temperatures.

• Keywords: nanočestice srebra; PEO/Ag nanokompozitni hidrogel; gama-zračenje; sinteza u jednom koraku
• Keywords (english): silver nanoparticles; PEO/Ag nanocomposite hydrogel; gamma-irradiation; one step synthesis
• Language: croatian
• URN:NBN: urn:nbn:hr:149:982407
• Study programme: Title: Applied Chemistry - Graduate study; specializations in: Environmental chemistry and green technologies, Advanced materials and technologies, Applied organic chemistry; Course: Advanced materials and technologies; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra primijenjene kemije (magistar/magistra primijenjene kemije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Closed access
• Created on: 2023-04-17 11:09:56