Nanotechnology is expected to open new avenues to fight and prevent disease using atomic scale tailoring of materials. Among the most promising nanomaterials with antibacterial properties are metallic nanoparticles, which exhibit increased chemical activity due to their large surface to volume ratios and crystallographic surface structure. The study of bactericidal nanomaterials is particularly timely considering the recent increase of new resistant strains of bacteria to the most potent antibiotics. This has promoted research in the well known activity of silver ions and silver-based compounds, including silver nanoparticles. The present work studies the effect of silver nanoparticles in the range of 1-100 nm on Gram-negative bacteria using high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM). Our results indicate that the bactericidal properties of the nanoparticles are size dependent, since the only nanoparticles that present a direct interaction with the bacteria preferentially have a diameter of approximately 1-10 nm.

https://iopscience.iop.org/article/10.1088/0957-4484/16/10/059/pdf

The bactericidal effect of silver nanoparticles

Silver nanoparticles as antimicrobial agent: a case study on E. coli as a model for Gram-negative bacteria

Silver nanoparticles as a new generation of antimicrobials.

/pdf/antimicrobial-effects-of-silver-nanoparticles-57y1xrlo33.pdf

Antimicrobial effects of silver nanoparticles

In this work we investigated the antibacterial properties of differently shaped silver nanoparticles against the gram-negative bacterium Escherichia coli, both in liquid systems and on agar plates. Energy-filtering transmission electron microscopy images revealed considerable changes in the cell membranes upon treatment, resulting in cell death. Truncated triangular silver nanoplates with a {111} lattice plane as the basal plane displayed the strongest biocidal action, compared with spherical and rod-shaped nanoparticles and with Ag+ (in the form of AgNO3). It is proposed that nanoscale size and the presence of a {111} plane combine to promote this biocidal property. To our knowledge, this is the first comparative study on the bactericidal properties of silver nanoparticles of different shapes, and our results demonstrate that silver nanoparticles undergo a shape-dependent interaction with the gram-negative organism E. coli.

http://www.omnis-mg.hr/Radovi/EC-oblik-koreja.pdf

Does the antibacterial activity of silver nanoparticles depend on the shape of the nanoparticle? A study of the Gram-negative bacterium Escherichia coli.

The paper gives the results of electrokinetic measurements on clay minerals, the relation between crystallographic structure and surface charge, and the relationship between the zeta-potential and pH of the solution

Electrokinetic of Clay Mineral Surfaces

Six sediment cores, top 30-40 cm, from two lakes of different sizes, Lake Prosce and Lake Kaluđerovac, situated in the karst region of the Plitvice Lakes system, Croatia, were studied by mineralogical and structural, C/N and total organic carbon (TOC) and isotopic analyses (a14C and δ13C of carbonate and organic fractions). Morphological and structural properties of the calcite particles at micron and submicron-sized level indicate that calcite mineral phase is formed by active authigenic precipitation in investigated lake systems. In the small Lake Kaluđerovac measured distributions of carbonate and OM fractions, C/N, TOC, and a14C and δ13C values of both fractions along the sediment depth showed similar values for all three cores with small variations in each core indicated very homogenous precipitation of autochthonous calcite inside the lake without allochthonous fraction. In the bigger Lake Prosce, the large difference in sediment composition of the three cores indicated different conditions of sediment precipitation inside the lake: in the coastal area the sediment was found to be a mixture of allochthonous and autochthonous fractions, while the deep-water sediment in the same lake indicated in-situ calcite precipitation and aquatic OM produced in the lake. The response of the lake sediment to the environmental conditions does not depend particularly on the size of the lake, but the surrounding environmental conditions could have great influence on the sediment composition. Extreme hydrological events in 1981 and 2010 were identified by disturbances in carbon isotopes distributions. Local anthropogenic influence was not evident, but the response to the global contaminations was observed by the occurrence of the a14C peak in both, carbonate and organic fractions. Increased bioproductivity in the last decades was observed in the Lake Prosce what can be correlated with slight increase of the lake water temperature in last three decades. The detailed work has been described in article accepted for publishing: N. Horvatincic, A. Sironic, J. Baresic, I. Sondi, I. Krajcar Bronic, D. Borkovic, Quarternary International, 2017. doi: 10.1016/j.quaint.2017.01.022

Carbon Based Proxies of Palaeoenvironmental Records in the Sediments of Two Lakes, the Plitvice Lakes, Croatia

Clay Mineral Surfaces: Electrokinetics

s Book • NanoMin Workshop Understanding the (paleo)soils: From palaeoenvironmental reconstruction to the role of iron oxides and soil organic matter on the formation of the surface physicochemical properties and the aggregation processes Goran Durn, Ivan Sondi, Srečo D. Škapin, Marta Mileusnić, Thilo Rennert, Nuša Cukrov, Vedran Rubinić and Stanko Ružičić 1 University of Zagreb, Faculty of Mining, Geology and Petroleum Engineering, Pierottijeva 6, 10 000 Zagreb, Croatia (goran.durn@oblak.rgn.hr) Advanced Materials Department, Jožef Stefan Institute, Ljubljana, Slovenia Department of Soil Chemistry and Pedology, Institute of Soil Science and Land Evaluation, University of Hohenheim, Stuttgart, Germany Ruđer Bošković Institute, Division for Marine and Environmental Research, Zagreb, Croatia University of Zagreb, Faculty of Agriculture, Zagreb, Croatia A multi-proxy analytical approach (MPAA) in the investigation of (palaeo)soils that involves a detailed analysis of soil micromorphology, soil physics and chemistry, geochemistry, and bulk and clay mineralogy is crucial for the determination of the palaeoenvironment in which they were formed. The determination of the soil mineral composition and their surface properties that control the formation of soils by aggregation processes is necessary to understand their response to environmental changes (BRONICK & LAL, 2005). Soil aggregation is a complex process, which involves rearrangement of submicronand micronsized mineral particles into larger clusters by mutual physico-chemical and biological interactions between the mineral surfaces, various organic and inorganic compounds and microorganisms (SIX et al., 2004). Humic compounds are omnipresent in soils and they designate the most important compounds covering the surfaces of the minerals, particularly iron oxides and clay mineral particles (BALDOCK & BROOS, 2012). This lecture aims to demonstrate the significance of MPAA in three different cases, from profile description and palaeoenvironmental reconstruction, to the role of iron oxides and soil organic matter on the formation of the surface physicochemical properties and the aggregation processes. It is based on our previous (DURN et al., 2015; DURN et al., 2017) and current research within the NanoMin project (grant 2504, Croatian Science Foundation). Case 1: A polygenetic soil formed on Late Glacial Loess on the Island of Susak The complete polygenetic profile (A-2C1-2C2-3Btb-4Ck) was formed through both normal pedogenesis and erosion/sedimentation-driven pedogenesis, and is a result of the interaction of the sediments (loess) with environmental conditions from the Late Glacial throughout the Holocene (Fig. 1). This profile bears valuable imprints of climate, vegetation, land surface, and land use changes in this part of the Adriatic area for the time period covering the past 16 ka. A high-resolution approach enabled schematic reconstruction of polygenetic formation of the soil profile while the results of clay fraction analysis and micromorphology in particular helped to understand the genesis of the investigated soil at the Susak Island (e.g. inherited vs. pedogenic clay). Case 2: (Paleo)soils formed in contrasting pedoenvironments (oxidizing vs. reducing) on pure Cretaceous limestones in Istria Terra Rossa soils formed in an oxidizing pedoenvironment, while Cretaceous greenish-grey palaeosols (GGP) formed in a reducingone. While kaolinites and illitic material are dominant clay mineral phases in the clay fraction of Terra Rossa, the main clay mineral phases in GGP are illitic material and ordered and irregularly oriented illite/smectite mixed layer minerals. Terra Rossa soils are slightly enriched in Co and Pb and significantly enriched in REE compared to GGP. The important difference in the total REE content in analysed Terra Rossa soils can be attributed to the REE content of both parent carbonate rocks (their insoluble residues) and different external materials which have contributed in the genesis of Terra Rossa (loess, flysch, bauxite), modified by weathering processes which favour LREE enrichment. Sequential extraction analysis showed that Mn, Co and Pb, mainly bound to the reducible fraction, are potentially the most mobile trace elements in Terra Rossa. , The enrichment of GGP in Cd, Sb, Ni, V and especially in U and Mo is considered typical of reducing environments (Fig. 2). Variation of the total REE content in GGP is much narrower compared to Terra Rossa soils. Total REE content in GGP is dominated by the residual fraction and probably also reflects parent materials (insoluble residue of limestone, aeolian and volcanic dust), modified in an acidic and reductive marshy pedoenvironment which favours HREE enrichment. Cd, Ni and Co, mainly bound to the adsorbed fraction are potentially the most mobile trace elements in GGP. Case 3: The role of iron oxides and soil organic matter (SOM) on the formation of the surface physicochemical properties and the aggregation processes of the Terra Rossa and the Calcocambisol from Istria Terra Rossa is the most common type of soil in Istria, an archetypal example of a non-isolated karst terrain that has been affected by karst processes, (neo)tectonic activity and contributions of external materials since the Late Tertiary. Their clay size fraction contains hematite as a dominant, and goethite as a minor iron oxide. The second most important and insufficiently investigated soil type in Istria is the Calcocambisol, a brown soil on limestone and dolomite. In comparison with Terra Rossa, this soil type contains a higher amount of organic matter while goethite was determined as the only well-crystallized iron oxide. The aim was to determine the character and the role of SOM and iron oxides on the formation of the surface physicochemical properties, electrophoretic mobility (EPM), specific surface area (SSA), and cation exchange capacity (CEC) of mineral particles that are main constituents of submicronand micron-sized aggregates in selected Terra Rossa and Calcocambisol samples from B horizons. Specifically, the ultimate goal is to identify these properties on original soils and on the samples from which the SOM and the iron compounds were selectively removed. This study endeavours to contribute new evidence on the role of SOM and iron oxides in the formation of surface properties of mineral particles and to determine their role in the process of aggregation in these type of soils (Fig. 3). Figure 1. Polygenetic soil profile at the Susak Island (From: DURN et al., 2017). Figure 2. Distribution of trace elements in Terra Rossa and greenish-gray paleosols.

Understanding the (paleo)soils: From paleoenvironmental reconstruction to the role of iron oxides and organic matter on the formation of the surface physicochemical and the aggregation processes

Cette invention a trait a une nanoparticule a semi-conducteur, utilisable pour analyser des prelevements biologiques. Cette nanoparticule se compose d'aminodextrane lie a au moins une nanoparticule correspondant a la formule (X Y)n. Dans cette formule X est selectionne dans le groupe constitue par Cd?2+, Hg2+ et Zn2+? et leurs combinaisons, tandis que Y est selectionne dans le groupe constitue par S?2-, Se2- et Te2-? et leurs combinaisons, la valeur de n s'echelonnant, approximativement, de 50 a 1000. L'invention porte egalement sur des procedes de production de ces particules a semi-conducteur ainsi que sur des procedes de production de conjugats constitues de ces nanoparticules a semi-conducteur liees a des ligands. Elle concerne, de surcroit, l'utilisation qui est faite de ces conjugats dans divers titrages biologiques.

Ivan Sondi

Papers

Electrokinetic of Clay Mineral Surfaces

Carbon Based Proxies of Palaeoenvironmental Records in the Sediments of Two Lakes, the Plitvice Lakes, Croatia

Clay Mineral Surfaces: Electrokinetics

Understanding the (paleo)soils: From paleoenvironmental reconstruction to the role of iron oxides and organic matter on the formation of the surface physicochemical and the aggregation processes

Nouvelles nanoparticules aux fins de l'analyse de populations de globules sanguins