Kinetika i mehanizam adsorpcije natrijum (Z)-3-(5-hlor-2-((5-hlor-3(3-sulfonatopropil)benzotiazol-2(3H)-iliden)metil )ben zotiazol-3-ium-3-il)propan-1-sulfonata na koloidne čestice zlata različitih svojstava i veličine

Abstract

Primenom više eksperimentalnih metoda (TEM, UV-Vis spektrofotometrija,fluorescentna spektroskopija, FTIR, DLS, merenja zeta potencijala) ispitane sunanočestice zlata različitih svojstava i veličina sa adsorbovanim boratnim (C6 i C9,5) icitratnim (C17 i C30) jonima na površini, u odsustvu i prisustvu TC boje (natrijum-(Z)-3-(5-hlor-2-((5-hlor-3-(3-sulfonatopropil)benzotiazol-2(3H)-iliden)metil)benzotiazol-3-ium-3-il)propan-1-sulfonata) u vodenoj sredini, i potvrđena je adsorpcija TC na površiniovih nanočestica. Merenje fluorescencije agregata čestica-boja, korigovane za efekatunutrašnjeg filtera, je ukazalo da nanočestice zlata, u zavisnosti od koncentracije, gasefluorescenciju TC boje. Nađeno je da je ovaj proces kvantitativno povezan sa stepenompokrivenosti površine nanočestica zlata molekulima TC boje. Pritom je efikasnostgašenja rasla sa povećanjem veličine čestica, pri čemu je koncentracija nanočestica zlatau rastvoru održavana konstantnom. Uz pretpostavku da je maksimalno gašenjefluorescencije TC boje ograničeno na potpunu monoslojnu pokrivenost površinenanočestica TC bojom (zavisno od orijentacije boje), eksperimentalno dobijene vrednostikoncentracije nanočestica C17 i C30 potrebne za potpuno gašenje fluorescencije TC bojesu bile niže od teorijski izračunatih, dok su za gašenje fluorecencije TC boje prikonstantnoj koncentraciji nanočestica dobijene više eksperimentalne vrednosti upoređenju sa teorijski izračunatim, iz čega je zaključeno da je najverovatnija orijentacijamolekula TC boje na površini ovih nanočestica kosa. S druge strane, u slučajunanočestica C6 i C9,5 teorijski dobijene vrednosti za koncentraciju TC boje potrebnu dapokrije površinu nanočestice i da fluorescencija boje bude potpuno ugašena, u slučaju svetri orijentacije, su niže u poređenju sa dobijenim eksperimentalnim vrednostima.Koncentracija nanočestica C9,5, potrebna da bi došlo do potpunog gašenja fluorescencijeTC boje, po vrednosti najpribližnije odgovara vertikalnoj orijentaciji boje duž kraćestrane, dok je u slučaju C6 eksperimentalno dobijen rezultat dosta niži od teorijskiizračunatih vrednosti za sve tri moguće orijentacije boje, iz čega je zaključeno da je napovršini ovih nanočestica boja smeštena u više od jednog sloja. Iz eksperimenata ukojima je ispitivano gašenja fluorescencije, izračunate su i konstante ravnoteže za procesadsorpcije TC na površini svih ispitivanih nanočestica...

The borate (C6 and C9,5) and citrate (C17 and C30) capped gold nanoparticles ofdifferent average core sizes and properties, were characterized by transmission electronmicroscopy (TEM), ultraviolet-visible spectroscopy (UV-Vis), fluorescencespectroscopy, Fourier transform infrared spectroscopy (FTIR), dynamic light scattering(DLS) and zeta potential measurements, in the absence and presence of cyanine dye,sodium (Z)-3-(5-chloro-2-((5-chloro-3-(3-sulfonatopropyl) benzothiazol-2(3H)-ylidene)methyl)benzothiazol-3-ium-3-yl)propane-1-sulfonate (TC) in water conditions,and the obtained results confirmed that TC was adsorbed on the surface of thesenanoparticles. The measurements of fluorescence of the particle–dye assembly, correctedfor inner filter effects, clearly indicated that the fluorescence of TC was quenched bygold nanoparticles on the concentration dependent manner. This process was found to bequantitatively related to the surface coverage of the Au nanoparticle by TC dyemolecules. Significant increase of quenching efficiency was noticed when nanoparticlesize increased, keeping the concentration of nanoparticles of different size constant. Theexperimental results of fluorescence quenching were compared with those obtained bytheoretical calculations, in which we assumed that the maximum quenching of TC dyefluorescence was restricted to full monolayer coverage of TC on the nanoparticlesurface. In case of C17 and C30 nanoparticles, the experimentally obtained values fornanoparticle concentration needed to completely quench TC dye fluorescence werelower than the calculated ones, while higher experimental values in comparision withcalculated ones of quenched TC dye at constant nanoparticle concentration wereobtained. These findings leaded to the conclusion that the most probable orientation ofTC dye molecules on the surface of these nanoparticle was slanted. On the other hand, incase of C6 and C9,5 nanoparticles, the obtained calculated values for TC concentrationneeded to cover the nanoparticle surface and be completely quenched, for all threepossible orientations of TC dye, were lower in comparision with the experimental values.The experimentally obtained value of C9,5 concentration needed to completely quenchTC dye fluorescence most closely corresponds to vertical TC dye orientation along theshort side, while the experimentally obtained results in case of C6 nanoparticles weremuch lower than theoretically calculated values for all three possible TC dye orientations.These findings indicated that on the surface of C6 nanoparticles the dye wasaccommodated in more than one layer. In addition, from the fluorescence quenchingexperiments, the equilibrium constants for the sorption of TC on the surface of allmentioned nanoparticles were calculated...