La contaminación por metales pesados y metaloides en recursos hídricos, suelos y aire plantea una de las más severas problemáticas que comprometen la seguridad alimentaria y salud pública a nivel global y local. En esta revisión, se aborda el problema específico de contaminación por mercurio (Hg), Arsénico (As), Cadmio (Cd) y Plomo (Pb) en ambiente y alimentos. Se presenta una descripción sobre las fuentes de contaminación y exposición en seres vivos así como la incorporación y retención en alimentos y productos de consumo humano. Se abordan casos de estudio y resultados obtenidos en algunos países del mundo incluido Colombia.

One of the factors that limit the spatial resolution in atomic force microscopy (AFM) is the physical size of the probe. This limitation is particularly severe when the imaged structures are comparable in size to the tip's apex. The resolution in the AFM is usually enhanced by using sharp tips with high aspect ratios. In the present paper we propose an approach to modify AFM tips that consists of depositing nanoclusters on standard silicon tips. We show that the use of those tips leads to atomic force microscopy images of higher aspect ratios and spatial resolution. The present approach has two major properties. It provides higher aspect-ratio images of nanoscale objects and, at the same time, enables to functionalize the AFM tips by depositing nanoparticles with well-controlled chemical composition.

The study of the magnetic properties of Co nanoparticles (with an average diameter of 10.3 nm) grown using a gas-phase aggregation source and embedded in Au and V matrices is presented. We investigate how the matrix, the number of embedded nanoparticles (counted by coverage percentage), the interparticle interactions and the complex nanoparticles/matrix interface structure define the magnetic properties of the studied systems. A threshold coverage of 3.5% of a monolayer was found in both studied systems: below this coverage, nanoparticles behave as an assembly of independent single-domain magnetic entities with uniaxial anisotropy. Above the threshold it is found that the magnetic behavior of the systems is more matrix dependent. While magnetic relaxation and Henkel plots measurements stress the importance of the dipolar interactions and the formation of coherent clusters in the case of the Au matrix, the magnetic behavior of cobalt clusters embedded in the vanadium matrix is explained through the formation of a spin glass-like state at the V–Co interface that screens the magnetic interactions between NPs.