Multifunkcionalne nanočestice magnezijum-ortotitanata dopiranog jonima retkih zemalja i prelaznih medalja
Multifunctional nanoparticles of magnesium-titanate doped with rare earth and transition metals ions.
Author
Medić, Mina M.
Mentor
Janaćković, Đorđe
Committee members
Dramićanin, Miroslav D.
Petrović, Rada

Đorđević, Vesna

Metadata
Show full item recordAbstract
Multifunkcionalni materijali se dizajniraju na taj način da mogu da ispune ciljane funkcije,
prilagode se specifikacijama proizvoda i multifunkcionalnim primenama. Multifunkcionalni
nanomaterijali koriste sprege između više svojih svojstava kako bi obavljali kompleksne
funkcije. U ovoj doktorskoj disertaciji sintetisane su nanočestice magnezijum-ortotitanata, kao i
nanočestice magnezijum-ortotitanata dopiranog jonima retkih zemalja i jonima prelaznih metala
sa multifunkcionalnim svojstvima. Navedeni prahovi predstavljaju odličan izbor za brojne
primene. Korišćena je Pećini metoda sinteze koja se pokazala kao efikasna metoda za dobijanje
nanočestica magnezijum-ortotitanata sa tačno određenom strukturom i morfologijom, svojstvima
koji su od presudnog značaja za unapređenje funkcionalnih karakteristika ovih prahova. U ovoj
doktorskoj disertaciji istražena su strukturna, morfološka, luminescentna i fotokatalitička
svojstva ovih nanomaterijala.
U okviru ove doktorske disertacije korišćena j...e metoda Pećinijevog polimerizovanog
kompleksnog rastvora za pripremu nanočestica Mg2TiO4, nedopiranog i dopiranog jonima retkih
zemalja (Eu3+ i Sm3+). Ispitivan je uticaj procesnih parametara na strukturu i svojstva navedenih
prahova, a u cilju optimizacije sinteze uzorci su žareni u temperaturnom opsegu od 400 – 650°C.
Rendgeno-strukturnom analizom utvrđena je kubna struktura inveznog spinela i veličina
kristalita od svega nekoliko nanometara. Morfološke karakteristike sintetisanih uzoraka
ispitivane su transmisionom elektronskom mikroskopijom (TEM) i skenirajućom elektronskom
mikroskopijom (SEM). Utvrđeno je da su nanočestice aglomerisane i imaju nepravilan zaobljen
oblik. Optička svojstva ispitana su fotoluminescentnom spektroskopijom i snimljeni su emisioni
spektri svih sintetisanih uzoraka. Potvrđeno je da intenzitet emisije kod uzoraka dopiranih
jonima retkih zemalja raste sa povećanjem temperature žarenja. Kod uzoraka magnezijumortotitanata
dopiranog jonima retkih zemalja uočeni su svi karakteristični f↔f prelazi, koji potiču
od aktivnih centara Eu3+ (
5D0 → 7
FJ) i Sm3+ (
4G5/2 →
6HJ). Proračunati su i analizirani JuddOfelt-ovi
parametri za uzorak Mg2TiO4:Eu3+ koji karakterišu lokalnu strukturu i veze u okolini
jona retke zemlje. Takođe je potvrđeno da najbolja luminescentna svojstva pokazuju nanočestice
pripremljene na 600°C/1h.
Takođe, metodom Pećinijevog polimerizovanog kompleksa na temperaturi od 600°C/1h
sintetisan je Mg2TiO4:Mn4+ i dobijene su čestice veličine od oko 10 nm. Izvršene su strukturne,
morfološke, spektroskopske analize, kao i analiza kristalnog polja ovog materijala. Uočeni su
karakteristični d↔d
2
Eg →
4A2g elektronski prelazi kod uzorka dopiranog jonima prelaznog
metala (Mn4+) koji su odgovorni za intenzivnu crvenu emisiju čestica. Primenom modela
razmene naelektrisanja dobijene su vrednosti parametara kristalnog polja Mn4+ u trigonalnom
kristalnom polju Mg2TiO4. Jasno se može uočiti slaganje između proračunatih vrednosti
energetskih nivoa i eksperimentalnih vrednosti eksitacionog i emisionog spektra.
Ispitivana su fotokatalitička svojstva čistog Mg2TiO4 i površinski modifikovanog Mg2TiO4
primenom bidentatnih benzenovih derivata, 5-amino salicilne kiseline i katehola. Na taj način
formiran je kompleks prenosa naelektrisanja usled čega dolazi do pomeranja apsorpcije prema
vidljivom spektralnom regionu. Fenomenom fizičke adsorpcije gasova na spoljnu i unutrašnju
površinu nanopraha magnezijum-ortotitanata pomoću BET metode utvrđena je specifična
površina i mezoporoznost ovog praha. Degradacija organske boje (kristal ljubičasta) korišćena je
u cilju ispitivanja fotokatalitičkih svojstava čistog i površinski modifikovanog Mg2TiO4
nanopraha pod osvetljenjem u različitim spektralnim regionima. Ekscitacijom pomoću UV
svetlosti indukovana su po prvi put fotokatalitička svojstva ovih prahova. Takođe, ekscitacijom
pomoću vidljive svetlosti ukazalo je na to da površinski modifikovani nanoprah magnezijumortotitanata
ima bolje fotokatalitičke performanse zbog sniženja energije zabranjene zone nego
što je to u slučaju kod čistog magnezijum-ortotitanata. Dobijeni eksperimentalni rezultati
upoređeni su sa najviše proučavanim fotokatalitičkim materijalom TiO2 (komercijalno Degussa
P25).
Multifunctional materials are designed in order to fulfill the causes of achieving aimed functions,
adjusting to the specifications of products and being multifunctionally applied. Multifunctional
materials use the relations among various characteristics of their own in order to complete
complex functions. In this thesis nanoparticles of the magnesium-orthotitanate are synthetized, as
well as nanoparticles of magnesium-orthotitanate doped with rare earth and transition metals ions
with multifunctional properties. These materials represent an excellent choice for numerous
applications. The Pechini method of synthesis was used which proved itself as an efficient
method for emanating nanoparticles of the magnesium-orthotitanate with the precisely fixed
structure and morphology, which are characteristics essential for improving of functional
characteristics of these powders. Moreover, in this thesis, structural, morphological, luminescent
and photocatalytic characteristics of synthesized m...aterials were researched.
Within this doctoral thesis, for the preparation of nanoparticles of Mg2TiO4, undoped and doped
with the ions of rare earth (Eu3+ i Sm3+), was used the Pechini’s polymerizable complex solution
method. There was investigated the effect of the processual parameters on structure and
characteristics of the mentioned powders, and, in order to optimize the synthesis, the samples
had been fired at a temperature range of 400 – 650ºC. The application of the X-ray structural
analysis identified the cubic structure of the inverse spinel and the crystallite size of only a few
nanometers. Morphological characteristics of the synthetized samples were investigated via
transmission electronic microscopy (TEM) and scanning electronic microscopy (SEM). As a
result, it was established that nanoparticles are agglomerated and have an irregular orbicular
shape. Optical characteristics were investigated by photoluminescence spectroscopy and there
were recorded emission spectra of all synthesized samples. It was confirmed that the emission
intensity of the samples doped by rare earth ions grows with the increase of the heating
temperature. As far as samples of the magnesium-orthotitatanate doped with the rare earth ions
showed all characteristic peaks arising from f↔f transitions, emanating from the active centers of
Eu3+ (
5D0 → 7
FJ) and Sm3+ (
4G5/2 →
6HJ) ions. Moreover, there have been calculated and
analysed Judd–Ofelt’s parameters for the sample of Mg2TiO4:Eu3+ which mark the local structure
and relations within the environment of rare earth ions. In addition to this, it was confirmed that
nanoparticles prepared at 600ºC per hour show optimal luminescent characteristics.
The Pechini’s polymerizable complex method, there was also synthetized Mg2TiO4:Mn4+ at
600ºC per hour and there were obtained particles of about 10 nm in size. There were performed
structural, morphological and spectroscopic analyses, as well as the analysis of the crystal field.
Moreover, there were observed characteristic d↔d
2
Eg →
4A2g electronic transitions on a sample
doped with the transition metal ions (Mn4+) which are responsible for the intensive red particle
emission. The application of the charge-transfer model yielded the values of the parameters of
the crystal field of Mn4+ ions within the trigonal crystal field of Mg2TiO4. The matching between
calculated values of energy levels and the experimental values of excitation and emission spectra
can be noted.
Photocatalytic properties of pure Mg2TiO4 and surface modified Mg2TiO4 via application of
bidentate benzene derivatives, a 5-amino salicylic acid and catechol, were researched. In this
way there was formed the charge transfer complex, during which occurs the moving of the
absorption towards the visible spectral area. By the application of the phenomenon of the
physical adsorption of gases on the external and internal surface of the nanopowder of
magnesium- orthotitanate via BET method there was established specific surface and
mesoporosity of this powder. The degradation of the organic colour (crystal violet) was used in
order to examine photocatalytic properties of the surface modified Mg2TiO4 nanopowder under
the luminance in different spectral areas. Using the excitation, via UV luminance there were, for
the first time, induced photocatalytic properties of this povder. Moreover, the excitation via the
visible light pointed out that the surface modified nanopowder of magnesium-orthotitanate has
better photocatalytic performances due to the lowering energy within the forbidden area
compared with the pure magnesium-orthotitanate. The obtained experimental results were
compared with the most frequently examined photocatalytic material TiO2 (commercially called
Degussa P25).