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 γ-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 Vinča 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 (∼34 m2/g) were ∼7 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 Union’s 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

Heterociklične azo boje sa piridonovim jezgrom predstavljaju značajnu 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 potvrđena elementalnom analizom, FT-IR i NMR spektroskopijom. Termička stabilnost boja je ispitana TG/DTA i DSC metodama, i upoređena sa bojama slične hemijske strukture. Amidna grupa u strukturi sintetisanih boja dovodi do drugačije uređenosti molekula u odnosu na jedinjenja ranije poznate strukture, što je predstavljalo veliki izazov za detaljnu analizu njihove stabilnosti i ponašanja. U ovoj disertaciji je prvi put urađeno detaljno ispitivanje termičke stabilnosti i određivanje kinetičkih i termodinamičkih parametara termički aktiviranih procesa degradacije arilazo piridonskih boja. Tehnološki procesi u kojima se azo boje koriste zahtjevaju povišenu temperaturu pa je termička stabilnost od velikog značaja za implementaciju sintetisanih boja. Nova saznanja o odnosu elektronske strukture i svojstava sintetisanih boja dobijena su ispitivanjem uticaja rastvarača različitih svojstava na apsorpcione i fluorescentne spektre boja. Korelacijom apsorpcionih i fluorescentnih frekvenci izvršena je kvantitativna procjena uticaja dipolarnosti, polarizabilnosti, proton-donorskih i proton-akceptorskih karakteristika rastvarača na položaje apsorpcionih i fluorescentnih maksimuma ispitivanih azo boja. Kvantno-hemijski proračuni su primjenjeni za analizu strukture novosintetisanih boja. DFT metodom je analiziran uticaj supstituenata i rastvarača, promjene u osnovnom i pobuđenom stanju kao i oblik i energije graničnih molekulskih orbitala (HOMO, LUMO i Egap). Poređenje eksperimentalnih i izračunatih vrijednosti strukture i svojstava ispitivanih jedinjenja govori o uspješnosti primjenjenih metoda. Za arilazo piridonske boje je karakteristična i komercijalno značajna azo-hidrazon tautomerija. Snimanjem apsorpcionih i fluorescentnih spektara pri različitim pH vrijednostima i primjenom DFT metode analiziran je uticaj prirode i položaja supstituenata u arilazo komponenti, kao i uticaj rastvarača 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 zračenja. Dobijeni filmovi su ozračeni različitim dozama gama zračenja Co60 u INNV, a promjene do kojih je došlo nakon izlaganja γ-zracima praćene su spektrofotometrijski snimanjem refleksionih spektara ozračenih i neozračenih filmova, kao i FTIR analizom. Prednost polimernih obojenih filmova u odnosu na komercijalno poznate dozimetre je vizuelno uočavanje promjene boje nakon izlaganja γ-zracima što ih čini 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 γ-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 γ-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 ∼210 kJ/mol for plum pomace and ∼162 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 FT–IR, 1H and 13C NMR, UV–Vis, 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 Lippert–Mataga, Reichardt–Dimroth and Kamlet-Taft equations. Moreover, UV–Vis 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. © 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, UV–Vis and XRD analysis techniques. The results obtained with thermogravimetric analysis (TGA) – 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. © 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 g−1 for BTEX, 0.625 mg g−1 for malathion, 0.495 mg g−1 for chlorpyrifos and 255 mg g−1 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

Hydrolytic, thermal, and UV stability of urea‐formaldehyde 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