Določevanje deleža barvila krezola, vezanega na mezoporozen SiO2, z metodami termične analize

Brcar, Nika (author), Cerc Korošec, Romana (mentor)

Namen moje diplomske naloge je bil določiti masni delež barvila krezola v porah mezoporoznega SiO2. Omenjeni material sintetiziramo in preučujemo za namen uporabe pH-indikatorskih barvil. Barva barvila, vezanega v mezoporozni matriki, je odvisna od pH vrednosti površine. Pri nefunkcionaliziranem SiO2 je barvilo na matriko SiO2 vezano v enkrat deprotonirani obliki (HL–) in je oranžne barve. Funkcionalizacija z aminopropil trimetoksisilanom (APTMS), ki se kovalentno veže na površino SiO2, poviša pH vrednost površine in barvilo se nanjo veže v deprotonirani obliki (L2–). Ob določenem zunanjem impulzu se barvilo sprosti iz površine v raztopino, barva barvila v raztopini pa je odvisna od pH medija. Količina vezanega barvila je pomembna za občutljivost senzorskega materiala, zato je pomembno, da jo lahko določimo. Pri nefunkcionaliziranih vzorcih, kjer se barvilo nahaja v matriki mezoporoznega SiO2, lahko količino barvila enostavno določimo s termogravimetrijo. Pri funkcionaliziranih pa naletimo na težavo, saj oba, krezol in APTMS, termično razpadata v istem temperaturnem območju, zato iz celokupne izgube mase ne moremo določiti vsebnosti posamezne komponente. Ker pa se pri termičnem razpadu krezola sprošča karakterističen plin SO2, smo lahko vsebnost krezola določili s sklopljeno metodo termične analize z masno spektroskopijo (TG-MS). Pripravili smo umeritveno krivuljo, iz katere smo lahko določili maso krezola v funkcionaliziranih vzorcih in posledično njegov masni delež. Metodo sem validirala na vzorcih, kjer je bilo v porah le barvilo (nefunkcionaliziranih vzorcih), saj smo lahko njegovo vsebnost določili s termogravimetrijo. Na osnovi dobljenih rezultatov sklepam, da je sklopljena metoda primerna za določitev masnega deleža barvila v funkcionaliziranih vzorcih. Ugotovila sem, da je masni delež krezola v funkcionaliziranih vzorcih manjši, kot v nefunkcionaliziranih, razlika pa se povečuje z naraščajočim masnim deležem barvila krezola.

• Language: Slovenian
• Keywords: funkcionalizacija SiO2, krezol, masna spektrometrija, pH indikatorska barvila, termična analiza
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2023
• PID: 20.500.12556/RUL-149538
• COBISS.SI-ID: 163825667
• Publication date in RUL: 07.09.2023

Secondary language

• Language: English
• Title: Determination of the content of the cresol dye, bound to mesoporous SiO2, using thermoanalytical methods

Abstract

The purpose of this diploma work was to determine the mass fraction of cresol dye in the pores of mesoporous SiO2. The mentioned material is synthesized and studied for the purpose of using pH indicator dyes. The colour of the dye bound in the mesoporous matrix depends on the pH value of the surface. In non-functionalized SiO2, the dye is bound to the SiO2 matrix in a once-deprotonated form (HL–) and is orange in colour. Functionalization with aminopropyltrimethoxysilane (APTMS), which binds covalently to the SiO2 surface, raises the pH value of the surface and the dye binds to it in a deprotonated form (L2–). Upon a certain external impulse, the dye is released from the surface into the solution, and the colour of the dye in the solution depends on the pH of the medium. The amount of bound dye is important for the sensitivity of the sensor material, so it is important to be able to determine it. In non-functionalized samples, where the dye is in the matrix of mesoporous SiO2, the amount of dye can be easily determined by thermogravimetry. However, we encounter a problem with the functionalized ones, since both cresol and APTMS thermally decompose in the same temperature range, and therefore it is not possible to determine the content of an individual component from the overall mass loss. However, since the characteristic SO2 gas is released during the thermal decomposition of cresol, we can determine the cresol content using the coupled method of thermal analysis with mass spectrometry (TG-MS). We prepared a calibration curve from which we could determine the mass of cresol in the functionalized samples and consequently its mass fraction. The method was validated on samples where there was only dye in the pores (non-functionalized samples), as we could determine its content using thermogravimetry. Based on the obtained results, I conclude that the coupled method is suitable for determining the mass fraction of the dye in functionalized samples. It was found out that the mass fraction of cresol in the functionalized samples is smaller than in the non-functionalized ones, and the difference increases with the increasing mass fraction of the cresol dye.

• Keywords: functionalization of SiO2, cresol, mass spectrometry, pH indicator dyes, thermal analysis