Crystallization path of aluminum oxides from gels with various shares of chelate

Aluminijevi oksidi široko se koriste kako u znanosti, tako i u industriji. Imaju mnogobrojne primjene u katalizi i keramici, te kao membrane i adsorbensi zbog svojih dobrih kemijskih, mehaničkih i fizikalnih svojstva. Provedbom infracrvene spektroskopije s Fourierovom transformacijom (FTIR), rendgenske difrakcijske analize (XRD) te diferencijalne toplinske i termogravimetrijske analize (DTATGA) istražen je tijek kristalizacije aluminijevih oksida. Aluminijevi oksidi su pripremljeni iz gela koji je dobiven sol-gel metodom iz aluminijevog sec-butoksida keliranog s etil acetoacetatom u različitim omjerima. Uzorci su termički obrađeni u visokotemperaturnoj peći pri temperaturama od 200 do 1200 °C. Iz podataka dobivenih eksperimentalnom analizom uočljivo je da se temperatura kristalizacije γ-Al2O3 pomiče sa 800 na 1000 °C s povećanjem molarnog omjera Eaa/Asb. Također, za uzorke s omjerom etil acetoacetate i aluminijeva sec butoksida od 2.0, 2.5, 3.0 opažen je nastanak kelata tris (etil acetoacetata) aluminija (III), koji je otporan na hidrolizu.Aluminium oxides are used in science and industry with numerous applications such as catalysis, membranes, adsorbents and ceramics, because of their good chemical, mechanical and physical properties. Using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Differential thermal and thermogravimetric analysis (DTA-TGA), the crystallization process of aluminium oxide has been investigated. Aluminium oxide was prepared from gels obtained by the sol-gel method using aluminium sec-butoxide chelated with ethyl acetoacetate in various ratios. Gels were dryed and then thermally treated in a high temperature furnace within the temperature range from 200 to 1200 °C. From the data obtained by experimental analyses, it was shown that the crystallization temperature of γ-Al2O3 shifts from 800 °C to 1000 °C with increment of the molar ratio of Eaa/Asb. In addition, formation of the chelate tris (ethyl acetoacetate) aluminium (III), which is resistant to hydrolysis, for samples with ethyl acetoacetate to to aluminium sec-butoxide ratio of 2.0, 2.5 and 3.0 was observed

Inorganic acid influence on precipitation of nanosilver particles stabilized by poly(acrylic acid)

Cilj ovog rada bila je sinteza nanočestica srebra metodom kemijske redukcije vodene otopine srebrovog (I) nitrata. Kao redukcijsko sredstvo korišten je hidrazin hidrat, dok je za stabilizaciju dobivenih nanočestica korištena poli(akrilna kiselina). Promatran je utjecaj perklorne, fosforne, sumporne i oksalne kiseline koncentracija 0,01 i 0,1 M na taloženje čestica i količinu adsorbiranog stabilizatora. Ispitivana je stabilnost dobivenih formulacija vodljivih tinti u Britton – Robinsonovim puferima u rasponu pH vrijednosti od 10,00 do 3,50. Nadalje, provedena je i elektrokemijska karakterizacija metodom cikličke voltametrije, i spektrofotometrijska karakterizacija UV-Vis spektroskopijom kako bi se odredile pKa vrijednosti poli(akrilne kiseline) adsorbirane na dobivene nanočestice.The aim of this study was to synthesize silver nanoparticles by chemical reduction method of silver (I) nitrate. Hydrazine hydrate was used as a reducing agent and obtained nanoparticles were stabilized with poly(acrylic acid). The effect of 0,01 and 0,1 M perchloric, phosphorous, sulfuric and oxalic acid on particle deposition and amount of adsorbed stabilizer was studied. Furthermore, the stability of the resulting conductive ink formulations in Britton – Robinson buffers, ranged from pH 10,00 to 3,50, was tested. Electrochemical characterization by cyclic voltammetry and spectrophotometric characterization by UV-Vis spectroscopy was performed to determine the pKa values of poly(acrylic acid) adsorbed on the silver nanoparticles

Inorganic acid influence on precipitation of nanosilver particles stabilized by poly(acrylic acid)

Cilj ovog rada bila je sinteza nanočestica srebra metodom kemijske redukcije vodene otopine srebrovog (I) nitrata. Kao redukcijsko sredstvo korišten je hidrazin hidrat, dok je za stabilizaciju dobivenih nanočestica korištena poli(akrilna kiselina). Promatran je utjecaj perklorne, fosforne, sumporne i oksalne kiseline koncentracija 0,01 i 0,1 M na taloženje čestica i količinu adsorbiranog stabilizatora. Ispitivana je stabilnost dobivenih formulacija vodljivih tinti u Britton – Robinsonovim puferima u rasponu pH vrijednosti od 10,00 do 3,50. Nadalje, provedena je i elektrokemijska karakterizacija metodom cikličke voltametrije, i spektrofotometrijska karakterizacija UV-Vis spektroskopijom kako bi se odredile pKa vrijednosti poli(akrilne kiseline) adsorbirane na dobivene nanočestice.The aim of this study was to synthesize silver nanoparticles by chemical reduction method of silver (I) nitrate. Hydrazine hydrate was used as a reducing agent and obtained nanoparticles were stabilized with poly(acrylic acid). The effect of 0,01 and 0,1 M perchloric, phosphorous, sulfuric and oxalic acid on particle deposition and amount of adsorbed stabilizer was studied. Furthermore, the stability of the resulting conductive ink formulations in Britton – Robinson buffers, ranged from pH 10,00 to 3,50, was tested. Electrochemical characterization by cyclic voltammetry and spectrophotometric characterization by UV-Vis spectroscopy was performed to determine the pKa values of poly(acrylic acid) adsorbed on the silver nanoparticles

Inorganic acid influence on precipitation of nanosilver particles stabilized by poly(acrylic acid)

Cilj ovog rada bila je sinteza nanočestica srebra metodom kemijske redukcije vodene otopine srebrovog (I) nitrata. Kao redukcijsko sredstvo korišten je hidrazin hidrat, dok je za stabilizaciju dobivenih nanočestica korištena poli(akrilna kiselina). Promatran je utjecaj perklorne, fosforne, sumporne i oksalne kiseline koncentracija 0,01 i 0,1 M na taloženje čestica i količinu adsorbiranog stabilizatora. Ispitivana je stabilnost dobivenih formulacija vodljivih tinti u Britton – Robinsonovim puferima u rasponu pH vrijednosti od 10,00 do 3,50. Nadalje, provedena je i elektrokemijska karakterizacija metodom cikličke voltametrije, i spektrofotometrijska karakterizacija UV-Vis spektroskopijom kako bi se odredile pKa vrijednosti poli(akrilne kiseline) adsorbirane na dobivene nanočestice.The aim of this study was to synthesize silver nanoparticles by chemical reduction method of silver (I) nitrate. Hydrazine hydrate was used as a reducing agent and obtained nanoparticles were stabilized with poly(acrylic acid). The effect of 0,01 and 0,1 M perchloric, phosphorous, sulfuric and oxalic acid on particle deposition and amount of adsorbed stabilizer was studied. Furthermore, the stability of the resulting conductive ink formulations in Britton – Robinson buffers, ranged from pH 10,00 to 3,50, was tested. Electrochemical characterization by cyclic voltammetry and spectrophotometric characterization by UV-Vis spectroscopy was performed to determine the pKa values of poly(acrylic acid) adsorbed on the silver nanoparticles

Sodelovanje javnosti v postsocialističnih mestih med stagnacijo in napredkom: primer Zagreba in Ljubljane

IN SLOVENIAN: Sodelovanje javnosti pri urbanistični preobrazbi glavnega mesta je pomemben dejavnik, ki ga je treba upoštevati pri presoji kakovosti demokracije v postsocialističnih državah. V članku avtorji obravnavajo procese sodelovanja javnosti pri taki preobrazbi v dveh postsocialističnih glavnih mestih: v Zagrebu in Ljubljani. Predstavljeni so izsledki izbranih študij primerov v obeh mestih (park Tabor in soseska BS 7 v Ljubljani ter Meštrovićev paviljon in park Savica v Zagrebu), poleg tega so izpostavljene podobnosti in razlike, ugotovljene na podlagi njihove primerjave. Izsledki raziskave iz let 2018 in 2019 kažejo dokaj nizko stopnjo sodelovanja javnosti v Zagrebu. V Ljubljani je bila navedena stopnja višja in tudi pravna podlaga zanjo je bila močnejša, opazna pa je bila delna odvisnost od političnih in gospodarskih dejavnikov. V obeh mestih je bilo sodelovanje javnosti v najbolj neposredni obliki pri aktivnostih nevladnih organizacij in civilnih pobud. Komunikacija med prebivalci in mestno upravo je bila slaba, kar ni spodbudno vplivalo na sodelovanje. --------------- IN ENGLISH: Public participation in the urban transformation of capital cities is an important factor to consider when assessing the quality of democracy in post-communist countries. This study examines participatory processes in two capital cities, Zagreb (Croatia) and Ljubljana (Slovenia). The cases studied are summarized, and similarities and differences are pointed out using the comparative method (Tabor Park and the BS 7 neighbourhood in Ljubljana, and the Meštrović Pavilion and Savica Park in Zagreb). Findings from 2018 and 2019 showed a rather low level of public participation in Zagreb. In Ljubljana, the level of public participation was higher and the legal basis for it stronger, although there was a certain amount of dependence on political and economic factors. In both cities, public participation in its most direct form was present at the level of NGO and civil initiative activities. Residents’ communication with the city administration was poor and did not facilitate the participation process. --------------- IN CROATIAN: Participacija javnosti u urbanoj transformaciji glavnih gradova važan je faktor koji treba uzeti u obzir pri procjenjivanju kvalitete demokracije u postsocijalističkim zemljama. Ovo istraživanje ispituje participativne procese u dva glavna grada, Zagrebu (Hrvatska) i Ljubljani (Slovenija). Proučavani slučajevi su sažeto prikazani, te su istaknute sličnosti i razlike korištenjem komparativne metode (park Tabor i naselje BS 7 u Ljubljani, te Meštrovićev paviljon i park Savica u Zagrebu). Nalazi iz 2018. i 2019. godine ukazali su na prilično nisku razinu participacije javnosti u Zagrebu. U Ljubljani je razina participacije javnosti bila viša te je njezina pravna osnova bila snažnija, iako je u određenoj mjeri bila prisutna ovisnost o političkim i ekonomskim faktorima. U oba grada participacija javnosti je u svojem najneposrednijem obliku bila prisutna na razini aktivnosti nevladinih udruga i građanskih inicijativa. Komunikacija stanovništva s gradskom upravom bila je slaba i nije olakšavala proces participacije

Public participation in post-communist cities between stagnation and progress: the examples of Zagreb and Ljubljana

IN ENGLISH: Public participation in the urban transformation of capital cities is an important factor to consider when assessing the quality of democracy in post-communist countries. This study examines participatory processes in two capital cities, Zagreb (Croatia) and Ljubljana (Slovenia). The cases studied are summarized, and similarities and differences are pointed out using the comparative method (Tabor Park and the BS 7 neighbourhood in Ljubljana, and the Meštrović Pavilion and Savica Park in Zagreb). Findings from 2018 and 2019 showed a rather low level of public participation in Zagreb. In Ljubljana, the level of public participation was higher and the legal basis for it stronger, although there was a certain amount of dependence on political and economic factors. In both cities, public participation in its most direct form was present at the level of NGO and civil initiative activities. Residents’ communication with the city administration was poor and did not facilitate the participation process. --------------- IN CROATIAN: Participacija javnosti u urbanoj transformaciji glavnih gradova važan je faktor koji treba uzeti u obzir pri procjenjivanju kvalitete demokracije u postsocijalističkim zemljama. Ovo istraživanje ispituje participativne procese u dva glavna grada, Zagrebu (Hrvatska) i Ljubljani (Slovenija). Proučavani slučajevi su sažeto prikazani, te su istaknute sličnosti i razlike korištenjem komparativne metode (park Tabor i naselje BS 7 u Ljubljani, te Meštrovićev paviljon i park Savica u Zagrebu). Nalazi iz 2018. i 2019. godine ukazali su na prilično nisku razinu participacije javnosti u Zagrebu. U Ljubljani je razina participacije javnosti bila viša te je njezina pravna osnova bila snažnija, iako je u određenoj mjeri bila prisutna ovisnost o političkim i ekonomskim faktorima. U oba grada participacija javnosti je u svojem najneposrednijem obliku bila prisutna na razini aktivnosti nevladinih udruga i građanskih inicijativa. Komunikacija stanovništva s gradskom upravom bila je slaba i nije olakšavala proces participacije

Electrolyte Engineering Stabilizes Photoanodes Decorated with Molecular Catalysts

Molecular catalysts are promising oxygen evolution promoters in conjunction with photoanodes for solar water splitting. Maintaining the stability of both photoabsorber and co-catalyst is still a prime challenge, with many efforts tackling this issue through sophisticated material designs. Such approaches often mask the importance of the electrode-electrolyte interface and overlook easily tunable system parameters, such as the electrolyte environment, to improve efficiency. We provide a systematic study on the activity-stability relationship of a prominent Fe2O3 photoanode modified with Ir molecular catalysts using in-situ mass spectroscopy. After gaining detailed insights into the dissolution behavior of the Ir co-catalyst, a comprehensive pH study is conducted to probe the impact of the electrolyte on the performance. An inverse trend in Fe and Ir stability is found, with the best activity-stability synergy obtained at pH 9.7. The results bring awareness to the overall photostability and electrolyte engineering when advancing catalysts for solar water splitting

Coordination preferences of NNO and NNS Schiff base ligands with Co(III) complexes: Synthesis, characterization and DFT calculation

Two Co(III) complexes with condensation product of thiosemicarbazide and 2-acetylthiazole (HL1 ligand, (E)-2-(1-(thiazol-2-yl)ethylidene)hydrazine-1-carbothioamide) and the condensation product of 2-acetylpyridine and Girard's P reagent (HL2Cl ligand, (E)-1-(2-oxo-2-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)ethyl)pyridin-1-ium chloride) have been synthesized and characterized based on the results of single-crystal X-ray diffraction, NMR and IR spectroscopy and elemental analysis. Cobalt(III) complex with HL1 ligand, [Co(L1)2]BF4⋅H2O (1), is bis octahedral complex in which two deprotonated ligand molecules coordinate in a mer arrangement through two NNS sets of donor atoms. In cobalt(III) complex with HL2Cl, [Co(L2)(N3)3] (2), the ligand is coordinated in deprotonated, formally neutral, form to Co(III) ion in tridentate fashion through NNO set of donor atoms, and the other three coordination sites of a monokis octahedron are occupied by meridionally coordinated azide anions. DFT calculations were performed to elucidate coordination preferences of these ligands toward Co(III) ion