9 research outputs found
Radiation, thermal and optical properties of PVA films containing arylazo pyridone dyes
Films based on polyvinyl alcohol (PVA) containing different concentrations of some arylazo pyridone dyes have been introduced as plastic detectors for dosimetry. PVA was chosen due to its water solubility and the possibility to incorporate a variety of dyes. The significance of arylazo pyridone dyes resides in their simple synthesis and wide application areas. The following dyes were used in optical data storage, laser technology, dye-sensitized solar cells, non-linear optics and biological systems. The advantage of polymeric films based on arylazo pyridone dyes is a visual change of color after exposure to gamma radiation, making them easy to use. In addition, this form of dosimeters is cheap and easily portable. Films containing arylazo pyridone dyes change the color when irradiated with Ī³-radiation at least up to 20 kGy. The color changes were confirmed spectrophotometrically. All synthesized films were characterized by FTIR. Optical properties have been analyzed on the basis of reflection and excitation spectra. Thermal degradation processes of PVA films containing arylazo dyes were investigated with thermogravimetric analysis (TGA), derivative thermogravimetry (DTG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC).VII International Conference on Radiation in Various Fields of Research : RAD 2019 : book of abstracts; June 10-14, 2019; Herceg Novi, Montenegr
A comparative study of photocatalytically active nanocrystalline tetragonal T zyrcon- type and monoclinic scheelite-type bismuth vanadate
The authors from VinÄa Institute of Nuclear Sciences acknowledge the financial support of the Ministry of Education, Science and Technological Development of the Republic of Serbia (Project no: 172056 ). The work of K. Smits was supported by Latvian National Research Program IMIS2 (Grant no. 302/2012 ).Monoclinic scheelite-type BiVO4 is currently considered as one of the most promising non-titania photocatalysts, wheras tetragonal zircon-type BiVO4 is still poorly understood. Herein, a new and simple synthetic approach was applied and nanostructured single-phase zircon-type BiVO4 was successfully prepared by a controllable ethylene-glycol colloidal route. In addition, nanostructured monoclinic scheelite-type BiVO4 powders were also fabricated through annealing of the as-prepared samples. A comparative study of the two BiVO4 polymorphs was conducted and it turned out that the novel synthetic approach had a significant impact on porosity and photocatalytic performance of zircon-structured BiVO4. All the prepared materials, as-prepared and annealed, were mesoporous, while measured values of specific surface area of some zircon-structured samples (ā¼34 m2/g) were ā¼7 times higher than those reported thus far for this phase. Interestingly, for the first time, zircon-type BiVO4, previously considered to be a poor photocatalyst, exhibited a better overall performance in degradation of methyl orange compared to monoclinic scheelite-type BiVO4. Hence, it could be expected that the here-presented synthesis and observations will both arouse interest in scarcely studied tetragonal zircon-type BiVO4 and facilitate as well as speed up further research of its properties.Ministry of Education, Science and Technological Development of the Republic of Serbia (Project no: 172056 ); Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Unionās Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART
Synthesis, structure and properties of novel azo dyes based on 6-hydroxy-4-methyl-2-oxo-1,2-dihydropyridine-3-carboxamide
HeterocikliÄne azo boje sa piridonovim jezgrom predstavljaju znaÄajnu klasu organskih azo boja
jer pokazuju visoki molarni ekstinkcioni koeficijent i dobru postojanost na razne vidove obrade.
Sintezom 2-piridona sa amidnom grupom u položaju 3, i kuplovanjem dobijenog piridona sa
supstituisanim i disupstituisanim diazonijumovim solima dobijene su dvije serije novih azo boja.
Struktura novosintetisanih boja na bazi 6-hidroksi-4-metil-2-okso-1,2-dihidropiridin-3-
karboksamida je potvrÄena elementalnom analizom, FT-IR i NMR spektroskopijom. TermiÄka
stabilnost boja je ispitana TG/DTA i DSC metodama, i uporeÄena sa bojama sliÄne hemijske
strukture. Amidna grupa u strukturi sintetisanih boja dovodi do drugaÄije ureÄenosti molekula u
odnosu na jedinjenja ranije poznate strukture, Ŕto je predstavljalo veliki izazov za detaljnu analizu
njihove stabilnosti i ponaÅ”anja. U ovoj disertaciji je prvi put uraÄeno detaljno ispitivanje termiÄke
stabilnosti i odreÄivanje kinetiÄkih i termodinamiÄkih parametara termiÄki aktiviranih procesa
degradacije arilazo piridonskih boja. TehnoloŔki procesi u kojima se azo boje koriste zahtjevaju
poviÅ”enu temperaturu pa je termiÄka stabilnost od velikog znaÄaja za implementaciju sintetisanih
boja. Nova saznanja o odnosu elektronske strukture i svojstava sintetisanih boja dobijena su
ispitivanjem uticaja rastvaraÄa razliÄitih svojstava na apsorpcione i fluorescentne spektre boja.
Korelacijom apsorpcionih i fluorescentnih frekvenci izvrŔena je kvantitativna procjena uticaja
dipolarnosti, polarizabilnosti, proton-donorskih i proton-akceptorskih karakteristika rastvaraÄa na
položaje apsorpcionih i fluorescentnih maksimuma ispitivanih azo boja. Kvantno-hemijski
proraÄuni su primjenjeni za analizu strukture novosintetisanih boja. DFT metodom je analiziran
uticaj supstituenata i rastvaraÄa, promjene u osnovnom i pobuÄenom stanju kao i oblik i energije
graniÄnih molekulskih orbitala (HOMO, LUMO i Egap). PoreÄenje eksperimentalnih i izraÄunatih
vrijednosti strukture i svojstava ispitivanih jedinjenja govori o uspjeŔnosti primjenjenih metoda.
Za arilazo piridonske boje je karakteristiÄna i komercijalno znaÄajna azo-hidrazon tautomerija.
Snimanjem apsorpcionih i fluorescentnih spektara pri razliÄitim pH vrijednostima i primjenom
DFT metode analiziran je uticaj prirode i položaja supstituenata u arilazo komponenti, kao i uticaj
rastvaraÄa na položaj azo-hidrazon ravnoteže kod ovih boja.
Filmovi na bazi poli(vinil-alkohola) i arilazo piridonskih boja su sintetisani u cilju dobijanja novih
dozimetrijskih sistema za detekciju gama zraÄenja. Dobijeni filmovi su ozraÄeni razliÄitim dozama
gama zraÄenja Co60 u INNV, a promjene do kojih je doÅ”lo nakon izlaganja Ī³-zracima praÄene su
spektrofotometrijski snimanjem refleksionih spektara ozraÄenih i neozraÄenih filmova, kao i FTIR analizom. Prednost polimernih obojenih filmova u odnosu na komercijalno poznate dozimetre
je vizuelno uoÄavanje promjene boje nakon izlaganja Ī³-zracima Å”to ih Äini jednostavnim za
upotrebu. Promjene boje mogu se objasniti raskidanjem glavnog lanca polimera, nastajanjem
slobodnih radikala i njihovim reakcijama sa molekulom boje.Heterocyclic azo dyes with a pyridone moiety represent a significant class of organic azo dyes
because of its high molar extinction coefficient and good resistance to various types of processing.
Synthesis of 2-pyridone with the amide group in position 3, and coupling of the obtained pyridone
with substituted and disubstituted diazonium salts gave two series of new azo dyes.
The structure of newly synthesized dyes based on 6-hydroxy-4-methyl-2-oxo-1,2-
dihydropyridine-3-carboxamide was confirmed by elemental analysis, FT-IR and NMR
spectroscopy. The thermal stability of the dyes was performed by TG/DTA and DSC methods and
compared with dyes of similar chemical structure. The amide group in the structure of the
synthesized dyes leads to a different arrangement of the molecules in relation to the compounds of
the previously known structure, which posed a great challenge for a detailed analysis of their
stability and behavior.
In this dissertation, for the first time, a detailed examination of thermal stability and determination
of kinetic and thermodynamic parameters of thermally activated degradation processes of arylazo
pyridone dyes was performed. Technological processes in which azo dyes are used require
elevated temperature, so thermal stability is of great importance for the implementation of
synthesized dyes. New knowledge about the relationship between the electronic structure and the
properties of synthesized dyes was obtained by examining the influence of solvents of different
properties on the absorption and fluorescent spectra of dyes. By correlating the absorption and
fluorescent frequencies, a quantitative assessment of the influence of dipolarity, polarizability,
proton-donor and proton-acceptor characteristics of the solvent on the positions of absorption and
fluorescent maxima of the investigated azo dyes was performed. Quantum chemical calculations
were applied to analyze the structure of newly synthesized dyes. The influence of substituents and
solvents, changes in the ground and the excited state, as well as the shape and energy of boundary
molecular orbitals (HOMO, LUMO i Egap), were analyzed by the DFT method. A comparison of
experimental and calculated values of the structure and properties of the tested compounds
indicates the success of the applied methods. Arylazo pyridone dye is characterized by
commercially significant azo-hydrazone tautomerism. The influence of the nature and position of
the substituents in the arylazo component, as well as the influence of solvent properties on the
position of the azo-hydrazone equilibrium in these dyes were analyzed by recording the absorption
and fluorescence spectra at different pH values and applying the DFT method.
Films based on poly(vinyl alcohol) and arylazo pyridone dyes were synthesized in order to obtain
new dosimetric systems for gamma radiation detection. The obtained films were irradiated with
different doses of gamma radiation Co60 in INNV, and the changes that occurred after exposure to
Ī³-rays were monitored spectrophotometrically by recording the reflection spectra of irradiated and
non-irradiated films, as well as FT-IR analysis. The advantage of polymer colored films over
commercially known dosimeters is the visual detection of color change after exposure to Ī³-rays
which makes them easy to use. The color changes can be explained by the breaking of the main
polymer chain, the formation of free radicals and their reactions with the dye molecule
Characterization and kinetics of thermal decomposition behavior of plum and fig pomace biomass
Redirecting waste biomass back into the economy can reduce their burden on the environment. The use of waste biomass for the production of fuels, value-added materials or natural fillers has significant economic and environmental benefits. Physico-chemical characterization of waste biomass (plum pomace and fig pomace) was done by proximate, elemental, biochemical analysis, FTIR and SEM analysis. The calorific value of both biomasses can be compared with the calorific value of lignite, which rises their potential use as a solid biofuel. The combustion behavior of biomass was investigated by thermal analysis techniques. Based on thermal degradation experiments performed at four heating rates a kinetic analysis of the biomass decomposition process was accomplished. The kinetic study was done using Kissinger method, Ozawa method, Flynn-Wall-Ozawa (FWO) method, Starink method, and Kissinger-Akahira-Sunose (KAS) method. The value of activation energy obtained by different kinetic methods was ā¼210 kJ/mol for plum pomace and ā¼162 kJ/mol for fig pomace. Estimated activation energy values were used to calculate thermodynamic parameters. In addition to the fact that the obtained results can serve as a useful reference for the design of pyrolysis reactors, this research has ecological significance because it solves the problem of solid waste disposal
Absorption and fluorescence spectral properties of azo dyes based on 3-amido-6-hydroxy-4-methyl-2-pyridone: Solvent and substituent effects
A series of nine 5-(4-substituted phenylazo)-3-amido-6-hydroxy-4-methyl-2-pyridones were synthesized and characterized by FTāIR, 1H and 13C NMR, UVāVis, and PL spectroscopy. Photophysical properties of the dyes were examined in solvents of various polarities and at different pH values. The solvent effects on the absorbance and emission spectral shift were analyzed using LippertāMataga, ReichardtāDimroth and Kamlet-Taft equations. Moreover, UVāVis absorption and emission frequencies were correlated with Hammett substituent constants applying the linear free energy relationships. DFT calculations of the investigated dyes were accomplished to determine their structural and electronic properties. Ā© 201
Synthesis and thermal properties of arylazo pyridone dyes
Thermal degradation properties of 5-(4-substitutedphenylazo)-3-amido-6-hydroxy-4-methyl-2-pyridones and 5-(4-substitutedphenylazo)-3-cyano-6-hydroxy-4-methyl-2-pyridones dyes, differing in electron withdrawing and electron donating substituents in para-position of diazo components were examined. The structure of the synthesized compounds has been confirmed by 1H NMR,13C NMR, FTIR, UVāVis and XRD analysis techniques. The results obtained with thermogravimetric analysis (TGA) ā derivative thermogravimetry (DTG) and differential thermal analysis (DTA) were combined with GC-mass spectral fragmentation to obtain thermal decomposition mechanism. Non-isothermal kinetics were monitored by application of TGA-DTG-DTA. For Kinetic behavior of the investigated dyes during their degradation in an inert atmosphere, Kissinger, Ozawa, Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) isoconversional (model-free) methods were applied. It was found that different thermal stabilities of investigated dyes are the consequence of their different chemical structures, including diverse substituents. Ā© 201
Irradiated fig pomace pyrochar as a promising and sustainable sterilized sorbent for water pollutant removal
Irradiated fig pomace pyrochar (IrrPyrFP) is noteworthy as a novel sterilized low-cost sorbent of BTEX, pesticides, and Pb2+ ions. It was produced by applying pyrolysis treatment followed by gamma irradiation modification in order to obtain a highly efficient and sterile sorbent. The characterization of fig pomace before and after pyrolysis, as well as before and after irradiation of the obtained pyrochar, was done using SEM, FTIR, and elemental analysis, while its sorption ability was tested through the removal of examined pollutants by batch sorption experiments. The obtained results suggest that IrrPyrFP could play a significant role in the control of environmental pollutants, as indicated by the maximum adsorption capacities: 42 mg gā1 for BTEX, 0.625 mg gā1 for malathion, 0.495 mg gā1 for chlorpyrifos and 255 mg gā1 for Pb2+. A kinetic study showed that the removal process by IrrPyrFP mainly follows pseudo 2nd kinetics order, while the sorption equilibriums were estimated using the Langmuir and Freundlich model. Overall, the findings of this work suggest that pyrolysis and activation by irradiation of waste biomass is a promising way to produce sterile efficient sorbents for waste-water treatment based on green chemistry. Additionally, the demonstrated application of fig pomace promotes the potential of using this biomass for continual and economical waste management in the rising fig industry
Sorption of divalent heavy metal ions onto functionalized biogenic hydroxyapatite with caffeic acid and 3,4-dihydroxybenzoic acid
Hydrolytic, thermal, and UV stability of ureaāformaldehyde resin/thermally activated montmorillonite nanocomposites
Urea-formaldehyde resin (F/U ratio of 0.8)/thermally activated montmorillonite (UF/Delta TK10) nanocomposite was synthesized. The hydrolytical, thermal, and UV radiation stability of UF/Delta TK10 nanocomposites are determined. UF hybrid nanocomposites have been irradiated with UV light with a wavelength of 254 nm and 366 nm, and after that, their radiation stability was evaluated. The free formaldehyde (FA) percentage in all prepared samples was determined. The sample was characterized by using X-ray diffraction analysis (XRD), nonisothermal thermogravimetric analysis (TGA), differential thermal analysis (DTA), and differential thermal gravimetry (DTG), with infrared (FTIR) spectroscopy. Crosslinked UF/Delta TK10 nanocomposite shows the highest resistance to acid hydrolysis after UV irradiation at a wavelength of 254 nm. The values for T-5% are identical for the unirradiated and UV irradiated (wavelength of 366 nm) UF/Delta TK10 nanocomposite. It can be concluded that this sample is thermally most stable and shows good resistance to UV irradiation