The paper presents the results of the experimental and theoretical study of 3,3′-disulfopropyl-5,5′dichlorothiacyanine sodium salt (TC) adsorption and Jaggregation on the surface of citrate-capped silver nanoparticles (AgNPs) with an average particle size 10 nm. Various nanospectroscopy techniques such as UV−vis, TEM, AFM, DLS, ζ potential, and fluorescence measurements were carried out in order to characterize the hybrid system. Besides this, a set of simple density functional theory calculations (DFT) was performed and this suggested that TC dye, from the thermodynamical point of view, most likely interacted with AgNPs via oxygen atom from SO 3 − groups. The methods, which considered AgNPs as the macromolecule with several binding sites and TC dye as the ligand, were applied for the analysis of saturation curves constructed from the fluorescence data to obtain the binding constant (K a = 1.5 × 10 6 M −1 ) and the average number of TC dye molecules bonded per AgNP (∼330). Moreover, TC fluorescence was quenched in the presence of AgNPs on the concentration dependent manner, yielding the linear Stern−Volmer relation accounting for both static and dynamic quenching with the quenching constant K sv = 2.5 × 10 8 M −1 . Kinetic measurements of J-aggregation as the dependence of AgNPs/TC concentration ratio confirmed that the J-aggregation occurred via a two-step process, the first of them being the initial adsorption of dye on AgNPs surface, followed by dye molecules rearrangement and the consecutive growth of TC aggregate layers.

The wide use of pesticides in modern agriculture and other areas results in an urgent need for their efficient removal from the environment.

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A systematic ab initio (DFT-GGA) study of adsorption of various oxygen species on graphene has been performed in order to find out general trends and provide a good starting point to analyze the oxidation of more complex carbon materials. Particular attention was paid to finding an appropriate supercell model. According to our findings, atomic O is characterized by stable adsorption on graphene and very strong adsorption on defective graphene. On the other hand, O2 does not adsorb on graphene and is allowed to diffuse freely to the defect, where it is expected to dissociate into two strongly adsorbed O atoms. The obtained results were compared with available theoretical data in the literature and good agreement was achieved.Keywords: grapheme; adsorption; density functional theory; oxidation ИСТРАЖУВАЊЕ AB INITIO НА ИНТЕРАКЦИЈАТА НА ГРАФЕН СО O2, O, И O -Извршено е систематско истражување ab initio (DFT-GGA) на атсорпцијата на различни кислородни видови врз графен со цел да се откријат општите трендови што можат да послужат како појдовна основа за анализа на оксидацијата на покомплексни јаглеродни материјали. Посебно внимание е посветено на откривање соодветен модел на суперќелија. Нашите сознанија укажуваат дека атомскиот О се карактеризира со стабилна атсорпција врз графен и многу силна атсорпција на графен со дефекти. Од друга страна, О2 не се атсорбира на графен, но е овозможено слободно да дифундира во дефектите каде што се очекува да дисоцира во два силно атсорбирани атоми на О. Добиените резултати беа споредени со теоретските податоци што се на располагање во литературата при што е добиено задоволувачко совпаѓање.Клучни зборови: графен; атсорпција; теорија на функционалот на густина; оксидација

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