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The fundamental mission of materials science is the description of matter over all length scales. In this review, we apply this concept to particle research. Based on metal oxides, we show that every size range offers its specific features, and every size range had its era, when it was in the center of the research activities. In the first part of the review, we discuss on three metal oxides as examples, how and why the research focus changed its targeted size regime from the micrometer to the nanometer scale and back to the macroscopic world. Next, we present the distinct advantages of using nanoparticles over micrometer-sized particles in selected devices and we point out how such a shift in the size regime opens up new research directions. Finally, we exemplify the methods to introduce nanoparticles into macroscopic objects to make functional ceramics.

Host-tissue integration of medical implants is governed by their surface properties. The capacity to rationally design the surface physico-chemical cues of implantable materials is thus a fundamental prerequisite to confer enhanced biocompatibility. Our previous work demonstrated that different cellular processes are elicited by the nanotexture generated on titanium (cpTi) and Ti6Al4V alloy by chemical oxidation with a H2SO4/H2O2 mixture. Here, we illustrate that by varying the etching parameters such as temperature, concentration, and treatment time, we can create a variety of surface features on titanium which are expected to impact its biological response. The modified submicron and nanotextured surfaces were characterized by scanning electron (SEM) and atomic force (AFM) microscopies. Contact angle measurements revealed the higher hydrophilicity of the modified surfaces compared to untreated samples and Fourier transform infrared spectroscopy (FT-IR) established that the etching generated a TiO2 layer with a thickness in the 40–60 nm range.

The energy levels belonging to the three lowest J multiplets of the Er3+ ion in Er2O3 and ErF3 were determined by means of high-resolution optical absorption spectroscopy. A crystal-field analysis of these data by means of Newman's Superposition Model was performed, allowing to determine intrinsic parameters which are quite consistent with other oxides and fluorides and to check the validity of the transferability postulate within these compounds. The possibility to use these data to analyze crystalline nanophases in glasses is briefly discussed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Radiation-induced spectral modifications of the 5 eV excited photoluminescence (PL) of oxygen vacancies have been found in a nanostructured silica-based material. This system, made up of SnO2 nanocrystals embedded in amorphous SiO2, is generated by nano-clustering in oversaturated Sn-doped silica produced by sol-gel method. Treatment in oxygen-poor atmosphere introduces oxygen deficiency in the glassy host and a photo-reactive SnO-like interphase at the SnO2 nanocrystal surface. PL measurements initially show native PL activity at 2.7 eV excited at 5 eV, ascribable to oxygen vacancies in intrinsic two-fold coordinated Si sites. Prolonged UV irradiation at 4.7 eV (fourth harmonic of Nd-YAG pulsed laser) gives rise to extrinsic PL activity at 3.1 eV, ascribable to Sn-variant of oxygen vacancy. The results suggest that the UV irradiation causes a progressive release of Sn from the nanophase surface to the glassy network in oxygen vacancy sites. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim).

In this study we investigate the role of traps on radio- and photo-luminescence properties of terbium doped silica. The investigation is motivated by the promising characteristics of rare-earth doped silica obtained by the sol-gel technique as scintillating material. We focus on those phenomena that can be responsible for problematic properties such as the increase of radio-luminescence sensitivity following repeated irradiations. A set of terbium doped silica with different terbium concentrations (0.03 mol%, 0.1 mol% and 10 mol%) prepared by the sol-gel technique and densified at 1050 °C in oxidizing atmosphere has been considered. The effect of a post-densification rapid thermal treatment on the RL and PL properties has also been investigated. This treatment improved the scintillation characteristics of the samples reducing their RL instability under prolonged irradiation. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The design of nanostructured materials with specific physical properties is generally pursued by tuning nanoparticle size, concentration, or surface passivation. An important step forward is to realize “active” systems where nanoparticles are vehicles for controlling, in situ, some specific, tuneable features of a responsive functional material. In this perspective, this work focuses on the rational design of a nanostructured glass with electrically tuneable dielectric function obtained by injection and accumulation of charge on embedded conductive nanocrystals. This enables electrically controlled switching of semiconducting nanophases to charged polarisable states to be achieved, which could lead to smart, field-enhancement applications in nanophotonics and plasmonics. Here, it is shown that such response switching can be obtained if a percolating charge-transport mechanism is activated through a disordered tree-like network, as is demonstrated to be possible in SiO2 films where suitable dispersions of SnO2 nanocrystals, with conductive interfaces, are obtained as a result of a new synthesis strategy.