In order to evaluate potential exposure of ecosystems to engineered as well as natural aquatic colloids and nanoparticles (NPs), methods must be available for measuring spatial and temporal trends in the concentration, size distribution, metal content of these NPs and their interaction in the different environmental compartments. Here an electrochemical and piezo-nanogravimetric study of metal, metal-oxides and chalcogenide nanoparticles in combination with sophisticated methods such as atomic force (AFM) and In-situ Electrochemical Scanning Tunneling Microscopy (EC-STM), Raman Spectroscopy, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and  dynamic light scattering (DLS) was performed. Electrochemistry due to its simplicity and prompt response, low cost and relatively high sensitivity and selectivity, is shown to be very powerfull alternative analytical technique for characterization and quantification of different, here preferably chalcogenide based NPs. Voltammetric measurements in combination with electrochemical nanogravimetric measurements (EQCM), amperometry and EC-STM, AFM on different electrode surfaces (Hg and Au electrode) give more details and information related to attachment, adsorption, deposition and interaction between selected NPs and functionalized electrode surfaces. The particle deposition mechanisms are studied in different environmentally relevant solution chemistries (variation in ionic strength, composition, pH, ion valence), in relation to variations of particle charge and sizes, and applied electrode potentials. The main idea is to improve and develop new analytical method for fast, selective qualitative and quantitative NPs characterization in natural waters.

Results obtained have shown that electrochemical measurements in combination with AFM, EC-STM can be a good methodology for NPs characterization and determination regarding to their sizes and concentration/numbers. Preliminary investigation of chronoamperometric signals of FeS micro- and nano-particles at the Hg electrode shows potential of the chronoamperometry for metal-bearing NPs characterization in natural waters.

The AFM and EC-STM revealed and confirmed existence of FeS NPs on the electrode surface which was previously proposed and analyzed by electrochemical measurements. In relation to other techniques which were also tested for NPs characterization (TEM,SEM,Raman Spectroscopy), combination of in-situ EC-STM, AFM with voltammetric and amperometric measurements as different but complementary techniques appears to be a powerful tool for characterization of complex electrochemical systems such as NPs in the natural waters.

Methods that were used in laboratory are parallely tested and intercalibrated in the field. As study sites four types of samples were tested: 1) oxic seawater samples from North Adriatic as the source of natural aquatic colloids and NPs mainly produced during intensive phytoplankton bloom and occasionally appearance of mucous aggregates; 2) hypoxic/anoxic samples of stratified seawater Lake Rogoznica on the eastern Adriatic coast enriched by FeS; 3) industrial waste waters including sea-marinas of engineered NPs; 4) wet deposition from atmosphere.

One important aim of this project is reinforcement of  LPCAS -RBI with its annex location RBI Marine station Martinska in Šibenik, Adriatic coast, where the main part of electrochemical research activities are carried out during duration of this project. From the project budget around 350 000,00 Kn were invested in technical and analytical instrumentation at marine station Martinska. One new PhD student from Šibenik city was approved by Croatian MSES (as an award of RBI director to this UKF project group) and engaged to work on the UKF project from Novemebr, 2010 as a part of human resources reinforcement at marine station Martinska. PhD student spent 3 months in the laboratory of dr. Nikola Batina in Mexico, where she learned about solid state electrochemistry as well as about use of AFM, and STM in nanoparticle analysis and 1 week at University in Budapest where she studied use of EQCM for NPs dfetermination. Dr. Nikola Batina spent 2 months at RBI in Zagreb and marine station Martinska in Šibenik in 2010. and 2012.

The main feedback of this multidisciplinary project with an international character is reinforcement of human and technical capacities of RBI for advanced research and investigation in the field of applied electrochemistry and nano-science needed for future competitive engagement of RBI group within different specific projects such as EU FP7/8, NATO, UNESCO; what is fully in line with strategic and thematic priorities of RBI and Croatian research strategy.

Published papers:

1. E. Bura-Nakić, D. Krznarić, G.R. Helz, I. Ciglenečki: Characterization of iron sulfide species in model solutions by cyclic voltammetry.  Revisiting an old problem), Electroanalysis,2011, 23(6), 13762.
2. G.R. Helz, E. Bura-Nakić, N. Mikac, I. Ciglenečki: New model for molybdenum behavior in euxinic basins, Chemical Geology, 284 (2011) 323.
3. G. R. Helz, I. Ciglenečki, D. Krznarić, E. Bura-Nakić. Voltammetry of Sulfide Nanoparticles and the FeS(aq) Problem // Aquatic Redox Chemistry / Paul G. Tratnyek, Timothy J. Grundl, Stefan B. Haderlein (ur.). Washington, DC : American Chemical Society, 2011. Str. 265-282.
4. I. Ciglenečki, E. Bura-Nakić, M. Marguš, Zinc sulfide surface formation on Hg electrode during cyclic voltammetric scan: an implication for previous and future research studies on metal sulfide systems, J. Solid State Electrochemistry (2012), DOI: 10.1007/s10008-011-1612-4.

Papers in preparation:

1. E. Bura-Nakić, I.Ciglenečki, E. Viollier: Vertical distribution of FeS species in anoxic water column of Pavin lake, France: electrochemical evidence for nanoparticulate FeS, under Review for Environ.Sci-Technol.
2. M.Marguš, N.Batina, I.Ciglenečki, Electrochemical study of FeS nanoparticles in NaCl solution by voltammetry  and in-situ EC-STM, Langmuir submitted.

Participation at conferences:

1. M. Marguš, I. Ciglenečki, E. Bura-Nakić, I. Milanović, N. Batina, A. Avalos-Perez, D. Krznarić: Nanočestice u vodenom okolišu: elektrokemijska, nanogravimetrijska, STM i AFM istraživanja, proslava obljetnice 30 g. morske postaje IRBa Martinska kod Šibenika, Šibenik 11.05.2011., poster.
2. Ciglenečki I.: Od elektrokemije sumpora do UKFovog projekta o nanočesticama u vodenom okolišu, proslava obljetnice 30 g. morske postaje IRBa Martinska kod Šibenika, Šibenik 11.05.2011.,oral presentation.
3. I. Ciglenečki, E. Bura-Nakić ,M.Marguš, I.Milanović, N.Batina. A.Avalos-Perez, D.Krznarić,  Goldschmidt2011 abstract: Mineralogical Magazine, Vol. 75 (3), 2011, 677.,oral.
4. E. Bura-Nakić, I.Ciglenečki, E. Viollier: Vertical distribution of Fe and S species in anoxic water column of Pavin Lake (France);electrochemical evidence for nanoparticulate FeS Mineralogical Magazine, Vol. 75 (3), 2011, 597.,poster.
5. M.Marguš, I.Milanović: Razvoj metode za detekciju nanočestica u prirodnim vodama: elektrokemija, nanogravimetrija, DLS, STM i AFM istraživanja, poster prezentacija IRB znanstveni susreti III vrste, srpanj 2011., poster.
6. I. Ciglenečki , E. Bura-Nakić ,M.Marguš, I.Milanović, N.Batina. A.Avalos-Perez, D.Krznarić: „Electrochemical, nanogravimetric, STM, AFM and DLS studies of nanoparticles in aqueous environment“, ASC meting San Diego, March 2012, oral presentation.
7. E. Bura-Nakić, M. Marguš, I.Milanović, I. Ciglenečki, Amperometric and voltammetric study of FeS nanoparticles, ISE Regional meeting on Electrochemistry, Buckarest May 2012, oral presentation.
8. Marija Marguš, N. Batina, E. Bura-Nakić ,I. Ciglenečki, Electrochemical and STM studies of FeS nanoparticles in NaCl model solutions, ISE Regional meeting on Electrochemistry, Buckarest May 2012, oral presentation.
9. M.Marguš, E.Bura-Nakić, I.Ciglenečki, I.Morales Reyes, N. Batina, Nove metode u istraživanju nanočestica u modelnim otopinama, 3.Dan Elektrokemije, IRB, 26.travanj 2012.,oral.
10. Ivana Milanović, Damir Krznarić, Maja Dutour Sikirić, Irena Ciglenečki, Karakterizacija nanočestica metalnih sulfida u vodenom sustavu kombinacijom voltametrije i metode dinamičkog raspršenja svjetlosti (DLS), 3.Dan Elektrokemije, IRB, 26. travanj 2012., oral.
11. Elvira Bura-Nakić, Marija Marguš, Irena Ciglenečki, Amperometrijski signali nano- i mikro- FeS čestica na Hg elektrodi, 3.Dan Elektrokemije, IRB, 26.travanj 2012., poster.