Raman spectroscopy in Zinc Ferrites Nanoparticles

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

Role of non-magnetic dopants (Ca, Mg) in GdFeO 3 perovskite nanoparticles obtained by different synthetic methods: structural, morphological and magnetic properties

AbstractGdFeO3 perovskite attracted large interest in different fields thanks to peculiar magnetic and optical properties that are further tunable by means of doping processes and achievable on both Gd and Fe sites or by properly choosing the synthesis routes. In this paper, nanometric GdFeO3 compounds, undoped and doped with diamagnetic Ca2+ and Mg2+ ions, were synthesized by microwave assisted, sol–gel, and polyol syntheses and characterized by X-ray diffraction, showing solid solutions formation. Raman spectroscopy allowed us to confirm, from peak enlargements, the Ca and Mg substitution on Gd and Fe sites, respectively. The magnetic data showed the presence of magnetic domains as consequence of doping with diamagnetic ions, which seem to play a crucial role in the magnetic activity of the compounds. A superparamagnetic behaviour is evidenced; nevertheless, its intrinsic character is not definitely demonstrated. Indeed, the possible presence of traces of magnetic impurities, which are easily obtainable in these samples, such as iron oxides, must be taken into account

Micro-Raman Spectroscopy of Dental Implants Subjected to Different Surface Treatments

The aim of the study was to qualitatively investigate the structure of the surface layer of TiO2 on dental implants made of Ti-6Al-4V subjected to different manufacturing treatments. M (machined), B (Al2O3-blasted), E (HNO3HF-etched), B + E and A (B + E + anodized) implants and a further group receiving the same treatments as the first group with the addition of a final decontamination with cold plasma were included in the study. Examination was performed using micro-Raman spectroscopy. The surface treatments evaluated did not achieve the formation of crystalline TiO2. The increase in the complexity of surface treatment produced a proportional increase in the thickness of amorphous TiO2 oxide. In the B + E group, the plasma treatment enhanced the amorphous oxide thickness of TiO2. The other surfaces treated by plasma decontamination did not show a difference to the respective untreated ones. The investigated surface treatments did not change the crystalline cage of TiO2 in Ti-6Al-4V implants but affected the thickness of the oxide layer. The biological response could be influenced by different oxide thicknesses. Additional information on superficial TiO2 structural organization can be obtained by micro-Raman evaluation of dental implants. Dental implants with B + E + plasma and A superficial treatments allowed the maximum formation of the amorphous oxide thickness

Food Safety Issues in the Oltrepò Pavese Area: A SERS Sensing Perspective

Handly and easy-to-use optical instrumentation is very important for food safety monitoring, as it provides the possibility to assess law and health compliances at every stage of the food chain. In particular, the Surface-enhanced Raman Scattering (SERS) method appears highly promising because the intrinsic drawback of Raman spectroscopy, i.e., the natural weakness of the effect and, in turn, of the signal, is overcome thanks to the peculiar interaction between laser light and plasmonic excitations at the SERS substrate. This fact paved the way for the widespread use of SERS sensing not only for food safety but also for biomedicine, pharmaceutical process analysis, forensic science, cultural heritage and more. However, the current technological maturity of the SERS technique does not find a counterpart in the recognition of SERS as a routine method in compliance protocols. This is mainly due to the very scattered landscape of SERS substrates designed and tailored specifically for the targeted analyte. In fact, a very large variety of SERS substrates were proposed for molecular sensing in different environments and matrices. This review presents the advantages and perspectives of SERS sensing in food safety. The focus of the survey is limited to specific analytes of interest for producers, consumers and stakeholders in Oltrepò Pavese, a definite regional area that is located within the district of Pavia in the northern part of Italy. Our attention has been addressed to (i) glyphosate in rice fields, (ii) histamine in a world-famous local product (wine), (iii) tetracycline, an antibiotic often detected in waste sludges that can be dangerous, for instance in maize crops and (iv) Sudan dyes—used as adulterants—in the production of saffron and other spices, which represent niche crops for Oltrepò. The review aims to highlight the SERS performance for each analyte, with a discussion of the different methods used to prepare SERS substrates and the different reported limits of detection

Silver Doped Magnesium Ferrite Nanoparticles: Physico-Chemical Characterization and Antibacterial Activity

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 MgFe2-xAgxO4 (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

Plasmonic Nanomaterials for Micro- and Nanoplastics Detection

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

Superparamagnetic ZnFe 2 O 4 nanoparticles: The effect of Ca and Gd doping

ZnFe2O4 ferrite nanoparticles are arousing a great interest in the biomedical field, in particular for magnetic hyperthermia application, thanks to their superparamagnetic behaviour at room temperature. In order to better tuning the magnetic properties, different doping substitution and synthesis methods have been tried to reduce particle sizes and to vary the cation distribution on the spinel sites. In this paper, we focused on the microwave combustion synthesis method of Ca (on Zn site) and Gd (on Fe site) substituted ferrites. Undoped ZnFe2O4 and Sr and Al doped samples were also synthesized for comparison. The use of X-ray powder diffraction, microscopic and spectroscopic techniques allowed us to ensure the good quality of the spinel structure for all the investigated samples, to determine a homogeneous distribution of the dopants and an average particle size lower than 11 nm. In addition, we estimated the inversion degree of the spinels by using the Rietveld structural refinement and Raman spectroscopy. By means of SQUID magnetometry we found, for all the samples, a superparamagnetic behaviour with saturation magnetization between 6 and 10 emu/g at the maximum applied magnetic field of 3T, with a more effective role played by Ca ions with respect to Gd ions substitutio