Inner surface potential at (111) fluorite/aqueous electrolyte solution interface

Za svrhu određivanja površinskog potencijala (111) kristalografske plohe fluorita konstruirane su dvije fluoritne monokristalne elektrode novog dizajna. Izrađenim monokristalnim elektrodama ispitana je stabilnost odziva te ponovljivost mjerenja. Potenciometrijskim titracijama istraţio se utjecaj pH sustava, ionske jakosti otopine, koncentracije Ca2+ iona te koncentracije F− iona na površinski potencijal (111) plohe fluorita. Fluorit je slabo topljiv u vodenim otopinama pa se topografskim mjerenjima mikroskopom atomskih sila proučio utjecaj otapanja (111) plohe fluorita na morfologiju njezine površine. Istražena je kinetika otapanja (111) plohe fluorita praćenjem koncentracije Ca2+ i F− iona u otopini tijekom 24 sata otapanja fluorita in situ mjerenjima s fluoridnom i kalcijevom ionski selektivnom elektrodom. Na temelju rezultata navedenih mjerenja predložen je model elektriĉnog međupovršinskog sloja i model površinskih reakcija za međupovršinu (111) fluorit/vodena otopina elektrolita.For the purpose of determining the inner surface potential of (111) fluorite plane two fluorite single-crystal electrodes of the new design were constructed. The reproducibility and sensitivity of the constructed single-crystal electrodes were tested. A series of potentiometric titrations was carried out to examine the surface potential of (111) fluorite plane as a function of pH, ionic strength and concentrations of Ca2+ and F− ions. Due to the fact that fluorite is a semisoluble salt in aqueous solutions the topographic measurements were done by atomic force microscope to examine the influence of dissolving (111) fluorite plane on the morphology of its surface. The kinetics of dissolving (111) fluorite plane was investigated by monitoring the concentrations of Ca2+ and F− ions in solution for 24 hours of dissolution by in situ measurements with fluoride and calcium ion-selective electrode. Based on the results of the above mentioned measurements, a model of the electrical interfacial layer and a surface complexation model for the (111) fluorite/NaCl solution interface was proposed

N-(4-Methyl­benz­yl)-3-nitro­aniline

In the title compound, C14H14N2O2, the angle between the mean plane of the N-methyl-3-nitro­aniline system (r.m.s. deviation = 0.0185 Å) and the p-tolyl unit is 89.79 (4)°. In the crystal, hydrogen-bonded chains running along [10-1] are generated by the linking of neighbouring mol­ecules via N—H⋯O and C—H⋯O hydrogen bonds involving the 3-nitro­aniline systems and forming R 2 2(8) motifs

The Effects on the Response of Metal Oxide and Fluorite Single Crystal Electrodes and the Equilibration Process in the Interfacial Region

Inner surface potential, one of the most important variables affecting the interfacial equilibrium of metal oxide aqueous systems, obtained by means of single crystal electrode gives valuable information about electrical charging of the metal oxide/aqueous electrolyte solu¬tion interfaces. The influence of the potential determining ions and ionic strength on the measured electrode potential as well as time of the equilibration, direction of the titration and the effect of the magnetic stirring enables the critical examination of the processes which take place during the interfacial equilibrium. For that purpose, the selected metal oxides (hematite, ceria, sapphire, and rutile) and fluorite single crystal electrodes were examined. This work is licensed under a Creative Commons Attribution 4.0 International License

Specific effects of ions on the formation and properties of poly(allylamine hydrochloride)/poly(acrylic acid) multilayer

Polielektrolitni kompleksi i višeslojevi poli(alilamin-hidroklorida) i poli(akrilne kiseline) pripravljeni su u vodenim otopinama NaF, NaCl, NaClO4, LiCl i (CH3)4NCl. Nastanak polielektrolitnih kompleksa po prvi puta istražen je visoko-razlučivom ultrazvučnom spektroskopijom. Ovom metodom ustanovljeno je da interpolielektrolitna neutralizacija rezultira ion-specifičnom agregacijom nabijenih koloidnih kompleksa. Analogan utjecaj iona određen je u slučaju odgovarajućih višeslojeva. Elipsometrom i mikroskopom atomskih sila utvrđeno je da debljina i hrapavost filma raste u nizu F − < Cl− < ClO4 − za anione odnosno (CH3)4N + < Na+ < Li+ za katione. Nadalje, ustanovljeno je da hidrofobnost višesloja također slijedi opisani trend za anione kada je polikation završni sloj filma. Zagrijavanjem polielektrolitnih višesloja tijekom njihove priprave potisnut je specifičan utjecaj iona na površinsku hrapavost i močivost zbog reorijentacije i migracije polimernih lanaca na međupovršini višesloj/zrak. Naposlijetku, provedeno istraživanje ukazuje na značajnu korelaciju između procesa interpolielektrolitne neutralizacije u otopini i na površini.Polyelectrolyte complexes and multilayers of poly(allylamine hydrochloride) and poly(acrylic acid) were prepared in aqueous solutions of NaF, NaCl, NaClO4, LiCl, and (CH3)4NCl. The formation of polyelectrolyte complexes was investigated for the first time by high-resolution ultrasonic spectroscopy. Using this method, it was established that interpolyelectrolyte neutralization results in ion-specific aggregation of charged colloidal complexes. Analogous influence of ions was observed in the case of corresponding multilayers. Using ellipsometer and atomic force microscope, it was determined that the thickness and roughness of the film increases in the sequence F− < Cl− < ClO4 − for anions and (CH3)4N + < Na+ < Li+ for cations. Furthermore, it was found that the hydrophobicity of the multilayer also follows the described trend for anions when a polycation is terminating layer of the film. By heating polyelectrolyte multilayers during their preparation, the specific influence of ions on surface roughness and wettability was suppressed due to the reorientation and migration of polymer chains at the multilayer/air interface. Finally, the conducted research indicates a significant correlation between the process of interpolyelectrolyte neutralization in solution and on the surface

Specific effects of ions on the formation and properties of poly(allylamine hydrochloride)/poly(acrylic acid) multilayer

Polielektrolitni kompleksi i višeslojevi poli(alilamin-hidroklorida) i poli(akrilne kiseline) pripravljeni su u vodenim otopinama NaF, NaCl, NaClO4, LiCl i (CH3)4NCl. Nastanak polielektrolitnih kompleksa po prvi puta istražen je visoko-razlučivom ultrazvučnom spektroskopijom. Ovom metodom ustanovljeno je da interpolielektrolitna neutralizacija rezultira ion-specifičnom agregacijom nabijenih koloidnih kompleksa. Analogan utjecaj iona određen je u slučaju odgovarajućih višeslojeva. Elipsometrom i mikroskopom atomskih sila utvrđeno je da debljina i hrapavost filma raste u nizu F − < Cl− < ClO4 − za anione odnosno (CH3)4N + < Na+ < Li+ za katione. Nadalje, ustanovljeno je da hidrofobnost višesloja također slijedi opisani trend za anione kada je polikation završni sloj filma. Zagrijavanjem polielektrolitnih višesloja tijekom njihove priprave potisnut je specifičan utjecaj iona na površinsku hrapavost i močivost zbog reorijentacije i migracije polimernih lanaca na međupovršini višesloj/zrak. Naposlijetku, provedeno istraživanje ukazuje na značajnu korelaciju između procesa interpolielektrolitne neutralizacije u otopini i na površini.Polyelectrolyte complexes and multilayers of poly(allylamine hydrochloride) and poly(acrylic acid) were prepared in aqueous solutions of NaF, NaCl, NaClO4, LiCl, and (CH3)4NCl. The formation of polyelectrolyte complexes was investigated for the first time by high-resolution ultrasonic spectroscopy. Using this method, it was established that interpolyelectrolyte neutralization results in ion-specific aggregation of charged colloidal complexes. Analogous influence of ions was observed in the case of corresponding multilayers. Using ellipsometer and atomic force microscope, it was determined that the thickness and roughness of the film increases in the sequence F− < Cl− < ClO4 − for anions and (CH3)4N + < Na+ < Li+ for cations. Furthermore, it was found that the hydrophobicity of the multilayer also follows the described trend for anions when a polycation is terminating layer of the film. By heating polyelectrolyte multilayers during their preparation, the specific influence of ions on surface roughness and wettability was suppressed due to the reorientation and migration of polymer chains at the multilayer/air interface. Finally, the conducted research indicates a significant correlation between the process of interpolyelectrolyte neutralization in solution and on the surface

Specific effects of ions on the formation and properties of poly(allylamine hydrochloride)/poly(acrylic acid) multilayer

Polielektrolitni kompleksi i višeslojevi poli(alilamin-hidroklorida) i poli(akrilne kiseline) pripravljeni su u vodenim otopinama NaF, NaCl, NaClO4, LiCl i (CH3)4NCl. Nastanak polielektrolitnih kompleksa po prvi puta istražen je visoko-razlučivom ultrazvučnom spektroskopijom. Ovom metodom ustanovljeno je da interpolielektrolitna neutralizacija rezultira ion-specifičnom agregacijom nabijenih koloidnih kompleksa. Analogan utjecaj iona određen je u slučaju odgovarajućih višeslojeva. Elipsometrom i mikroskopom atomskih sila utvrđeno je da debljina i hrapavost filma raste u nizu F − < Cl− < ClO4 − za anione odnosno (CH3)4N + < Na+ < Li+ za katione. Nadalje, ustanovljeno je da hidrofobnost višesloja također slijedi opisani trend za anione kada je polikation završni sloj filma. Zagrijavanjem polielektrolitnih višesloja tijekom njihove priprave potisnut je specifičan utjecaj iona na površinsku hrapavost i močivost zbog reorijentacije i migracije polimernih lanaca na međupovršini višesloj/zrak. Naposlijetku, provedeno istraživanje ukazuje na značajnu korelaciju između procesa interpolielektrolitne neutralizacije u otopini i na površini.Polyelectrolyte complexes and multilayers of poly(allylamine hydrochloride) and poly(acrylic acid) were prepared in aqueous solutions of NaF, NaCl, NaClO4, LiCl, and (CH3)4NCl. The formation of polyelectrolyte complexes was investigated for the first time by high-resolution ultrasonic spectroscopy. Using this method, it was established that interpolyelectrolyte neutralization results in ion-specific aggregation of charged colloidal complexes. Analogous influence of ions was observed in the case of corresponding multilayers. Using ellipsometer and atomic force microscope, it was determined that the thickness and roughness of the film increases in the sequence F− < Cl− < ClO4 − for anions and (CH3)4N + < Na+ < Li+ for cations. Furthermore, it was found that the hydrophobicity of the multilayer also follows the described trend for anions when a polycation is terminating layer of the film. By heating polyelectrolyte multilayers during their preparation, the specific influence of ions on surface roughness and wettability was suppressed due to the reorientation and migration of polymer chains at the multilayer/air interface. Finally, the conducted research indicates a significant correlation between the process of interpolyelectrolyte neutralization in solution and on the surface

Polarimetar kao nastavno pomagalo

U hrvatskim školama postoji problem nedovoljne zastupljenosti pokusâ u nastavi kemije. Uzevši u obzir činjenicu da su pojedine srednje škole opremljene polarimetrom, načinjen je pregled nastavnih aktivnosti koje se mogu ostvariti s polarimetrom. Te su aktivnosti prikazane počevši od najjednostavnijih, koje su prikladne za sve učenike u okviru redovne nastave, preko nešto složenijih, koje se mogu izvoditi u okviru školske kemijske grupe, pa sve do najzahtjevnijih, primjerenih za rad s učenicima koji se pripremaju za natjecanja iz kemije u kategoriji samostalnih učeničkih radova

Suppressing the Hofmeister anion effect by thermal annealing of thin-film multilayers made of weak polyelectrolytes

Thin films made of weak polyelectrolytes poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) have been fabricated on silicon wafers using the layer-by-layer (LbL) method. To study the influence of counteranion type on the growth and properties of PAH/PAA multilayers, the nature of the supporting sodium salt was varied from cosmotropic to chaotropic anions (F–, Cl–, and ClO4–). Results of ellipsometry and AFM measurements indicate that the film thickness and surface roughness systematically increase on the order F– < Cl– < ClO4–. Furthermore, we found that the hydrophobicity of the PAH/PAA multilayer also follows the described trend when a polycation is the terminating layer. However, the heating of PAH/PAA multilayers to 60 °C during the LbL assembly suppressed the influence of background anions on the multilayer formation and properties. On the basis of the obtained results, it could be concluded that thermal annealing induces changes at the polymer–air interface in the sense of reorientation and migration of polymer chains

High-Resolution Ultrasonic Spectroscopy: Looking at the Interpolyelectrolyte Neutralization from a Different Perspective

In this study, the high-resolution ultrasonic spectroscopy (HR-US) technique was applied to examine interpolyelectrolyte neutralization. The mentioned method was tested on the example of complexation between poly(allylammonium) cations and poly(acrylate) anions in aqueous solutions at pH = 7. It was confirmed by HR-US that the type of titration (stepwise or abrupt), the direction of titration, and the type of background salt affect the outcome of interpolyelectrolyte neutralization. The obtained results were explained on the basis of ultrasonic velocity and attenuation changes in the context of suspension compressibility, a parameter that is extremely sensitive to molecular organization and intermolecular interactions. Moreover, the results of HR-US measurements proved to be consistent with previous results obtained by more traditional methods such as dynamic light scattering, microcalorimetry, and electrokinetics. This research demonstrates that HR-US is a convenient and reliable method that can be employed for the investigation of interpolyelectrolyte neutralization and polyelectrolyte-related processes