ZnFe2O4 ferrite nanoparticles are arousing a great interest in the biomedical field, thanks to their superparamagnetic behavior at room temperature. Functional properties depend on composition, size, nanoparticle architecture and, in turn, on the synthesis methods. Bulk ZnFe2O4 has the normal spinel structure (all Zn2+ ions in tetrahedral and all Fe3+ ions in octahedral positions), but at the nanometric size inversion takes place with a cationic mixing on divalent and trivalent sites. The sensitivity of the Raman probe to cation disorder favored the appearance of several works on a rich variety of nanosized zinc ferrites. An overview on these results is reported and discussed at variance with synthesis methods, grain dimensions, and dopants. We add to this landscape our results from new nanosized powder samples made by microwave-assisted combustion, with different dopants (Ca, Sr on Zn site and Al, Gd on Fe site). A detailed analysis of A1g, Eg, 3F2g Raman modes has been performed and Raman band parameters have been derived from best-fitting procedures and carefully compared to literature data. The vibrational results are discussed taking into account the characterization from X-ray powder diffraction raction, SEM-EDS probe, EPR spectroscopy and, of course, the magnetic responses.

Raman spectroscopy was applied on nanostructured ZnFe₂O₄ system in order to correlate its structural, chemical, and vibrational properties to the functional behaviour, in view of the high sensitivity of the Raman probe to the cationic order in iron oxides. In particular we investigated pure and Ga/Mg doped zinc ferrite nanoparticles synthesised by co-precipitation route by means of Raman spectroscopy with a particular focus on the correlation between their structural and magnetic properties. We firstly studied the homogeneity of the samples at the micrometer scale and their stability under laser irradiation disregarding the presence of spurious iron oxides in favour of a highly defective external shell of the nanoparticles. This hypothesis was corroborated by varying the incident laser wavelength therefore changing the investigated volume. Furthermore, we estimated the inversion degree of the spinel structure finding good agreements with the trend of the magnetic features. All the evidence found through Raman spectroscopy are supported by the results obtained with X-Ray Powder Diffraction, Electron Paramagnetic Resonance and SQUID magnetometry.

The adhesion and proliferation of bacteria on abiotic surfaces pose challenges in both health care and industrial applications. Gold nanostars (GNSs) monolayers grafted on glass have demonstrated to exert antibacterial action due to their photo-thermal features. Here, these GNS layers were further functionalized using thiols monolayers, in order to impart different wettability to the surfaces and thus adding a feature that could help to fight bacterial proliferation. Thiol that has different functional groups was used and the thiol-protected surfaces were characterized by means of UV-vis spectroscopy, contact angles, SEM and surface enhanced Raman spectroscopy (SERS). We verified that (i) coating with the proper thiol allows us to impart high hydrophilicity or hydrophobicity to the surfaces (with contact angle values ranging from 10 to 120°); (ii) GNS monolayers are strongly stabilized by functionalization with thiols, with shelf stability increasing from a few weeks to more than three months and (iii) photo-thermal features and subsequent antibacterial effects caused by hyperthermia are not changed by thiols layers, allowing us to kill at least 99.99% of representative bacterial strains.

Spinel phases, with unique and outstanding physical properties, are attracting a great deal of interest in many fields. In particular, MgFe₂O₄, a partially inverted spinel phase, could find applications in medicine thanks to the remarkable antibacterial properties attributed to the generation of reactive oxygen species. In this paper, undoped and Ag-doped MgFe_2-xAg_xO₄ (x = 0.1 and 0.3) nanoparticles were prepared using microwave-assisted combustion and sol–gel methods. X-ray powder diffraction, with Rietveld structural refinements combined with micro-Raman spectroscopy, allowed to determine sample purity and the inversion degree of the spinel, passing from about 0.4 to 0.7 when Ag was introduced as dopant. The results are discussed in view of the antibacterial activity towards Escherichia coli and Staphylococcus aureus, representative strains of Gram-negative and Gram-positive bacteria. The sol–gel particles were more efficient towards the chosen bacteria, possibly thanks to the nanometric sizes of metallic silver, which were well distributed in the powders and in the spinel phase, with respect to microwave ones, that, however, acquired antibacterial activity after thermal treatment, probably due to the nucleation of hematite, itself displaying well-known antibacterial properties and which could synergistically act with silver and spinel.

Detecting and quantifying micro- and nanoplastics (MNPs) in the environment is a crucial task that needs to be addressed as soon as possible by the scientific community. Many analytical techniques have been proposed, but a common agreement on analytical protocols and regulations still has to be reached. Nanomaterial-based techniques have shown promising results in this field. In this review, we focus on the recent results published on the use of plasmonic noble metal materials for the detection of MNPs. Plasmonic materials can be exploited in different ways due to their peculiar optical end electronic properties. Surface plasmon resonance, plasmon enhanced fluorescence, UV–Vis spectroscopy, and surface enhanced Raman scattering (SERS) will be considered in this review, examining the advantages and drawbacks of each approach.