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Nowadays, nanoscience is strongly intertwined with the biological and medical fields. The functional effectiveness of nanomaterials depends not only on their chemical composition but also on their structural and surface features. In this respect, shape, size, and atomic surface terminations play a key role. One of the most important and challenging parameters of customization of metal and metal oxide nanoparticles is the shape control that can provide the desired optical, electrical, and magnetic properties. The chemical tuning of the morphology following the known synthetic strategies can be exploited in the biomedical application, specifically imaging techniques such as MRI and SERS to build a nano-amplifier and provide higher contrast and clarity in the resulting images. Further, when speaking of biomaterials, other relevant properties come into the spotlight: besides the relevance of the morphological features, atomic features of the surface structure have an effect on the destiny of the interaction of these materials with a host biological system. Hence, understanding the biomaterial surface characteristics at the fundamental level can improve the control in designing the new materials that could be more effective in the applied field. This aspect is considered, particularly on hydroxyapatite- and silica-based nano-biomaterials. Furthermore, the relevant properties of the luminescent lanthanide-containing hydroxyapatite nano-biomaterials, of high importance in the bioimaging field, are also highlighted. On the whole, this chapter discusses the structural engineering and surface features of inorganic materials including metallic and ceramic ones.

Three luminescent Eu-containing phosphate materials (Ca-doped europium phosphate monohydrate, Eu-doped carbonated-apatite, and europium phosphate monohydrate) were prepared and analyzed on the level of bulk structure and surface properties and compared to the biomimetic non-luminescent counterpart hydroxyapatite. Europium-containing phosphate materials exhibited nanosized dimensions but different luminescence emissions and luminescence lifetimes depending on their crystalline structures (i.e., lanthanide phosphate or apatites) and chemical composition. The introduction of Eu in the crystal lattice leads to a notable decrease in the overall Lewis acidity of the surface cationic sites detected by CO probing. Further, the mixed Eu/Ca-containing materials surfaces were found to be very similar to the reference hydroxyapatite in terms of water adsorption energy, while the pure europium phosphate resulted to have the notably higher energy values of direct interaction of water molecules with the surface cations with no detected propagation of this effect towards water overlayers.

This study evaluates the effectiveness of using different plasma treatments to favor the compatibility between rubber and a cement matrix in composites, thus leading to a different surface reactivity of the rubber component. Plasma-treated rubbers were introduced into two different types of concrete. Mechanical tests highlighted that Portland concrete composites filled with N2/H2 plasma-treated rubber had increased flexural strength, toughness, and compression strength compared to composites containing untreated rubber. A scaling law is also proposed to qualitatively discriminate between related effects due to topological/roughness or intrinsic/chemical adhesion modifications. Plasma treatment can improve both intrinsic adhesion and roughness of the rubber–cement interface and thus the overall concrete strength and toughness.

The formation of oriented enamel-like fluoride doped hydroxyapatite (HA) nanorods on amorphous calcium phosphate (ACP) substrates in their bare form and containing citrate is compared. It is found that the presence of citrate delays the conversion into un-oriented HA that in turn affects the overgrowth of nanorods as well as their shape and surface features. With citrate being an important component of bones and teeth, this study is highly relevant to attain new insights into the biomineralization processes and to widen the range of strategies for the design of advanced biomaterials.

The surface structure and hydrophilicity of synthetic nanocrystalline apatite with strongly bound citrates on their surface are here investigated at the molecular level, by combining advanced IR spectroscopy, microgravimetry and adsorption microcalorimetry. Citrate are found to form unidentate-like and ionic-like complexes with surface Ca ions, with a surface coverage closely resembling that present in bone apatite platelets (i.e., 1 molecule/(n nm), with n ranging between 1.4 and 1.6). These surface complexes are part of a hydrated non-apatitic surface layer with a sub-nanometre thickness. Noticeably, it is found that the hydrophilicity of the nanoparticles, measured in terms of adsorption of water molecules in the form of multilayers, decreases in a significant extent in relation to the presence of citrates, most likely because of the exposure toward the exterior of -CH groups. Our findings provide new insights on the surface properties of bio-inspired nano-apatites, which can be of great relevance for better understanding the role of citrate in determining important interfacial properties, such as hydrophobicity, of bone apatite platelets. The evaluation and comprehension of surface composition and structure is also of paramount interest to strictly control the functions of synthetic biomaterials, since their surface chemistry strongly affects the hosting tissue response.