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Despite considerable research, the location of an aliovalent dopant into SnO2 nanoparticles is far to be clarified. The aim of the present study on trivalent lanthanide doped SnO2 is to differentiate between substitutional versus interstitial and surface versus bulk doping, delineate the bulk and surface defects induced by doping and establish an intrinsic dopant distribution. We evidence for the first time a complex distribution of intrinsic nature composed of substitutional isolated, substitutional associates with defects as well as surface centers. Such multi-modal distribution is revealed for Eu and Sm, while Pr, Tb and Dy appear to be distributed mostly on the SnO2 surface. Like the previously reported case of Eu, Sm displays a long-lived luminescence decaying in the hundreds of ms scale which is likely related to a selective interaction between the traps and the substitutional isolated center. Analyzing the time-gated luminescence, we conclude that the local lattice environment of the lattice Sn is not affected by the particle size, being remarkably similar in the ~2 and 20 nm particles. The photocatalytic measurements employed as a probe tool confirm the conclusions from the luminescence measurements concerning the nature of defects and the temperature induced migration of lanthanide dopants.

Although homogeneity at the atomic level of CeO2-ZrO2 with a Ce/Zr atomic ratio close to unity is considered to be one of the main causes for the increased total oxygen storage capacity (OSC), the characterization approaches of homogeneity remain a major challenge. We propose a simple, yet effective method, to assess both structural and compositional homogeneity of CeO2-ZrO2 by using Eu(3+) luminescence measured with time and dual spectral resolution (emission and excitation). For Eu(3+)-CeO2-ZrO2 calcined at 750 °C, the X-ray diffraction, Raman and High-Resolution Transmission Electron Microscopy data converge to a single pseudo-cubic phase. However, the evolution of Eu(3+)-delayed luminescence from cubic ceria-like to tetragonal zirconia-like emission reveals the formation of CeO2- and ZrO2-rich nanodomains and provides evidence for early phase separation. For Eu(3+)-CeO2-ZrO2 calcined at 1000 °C, the emission of Eu(3+) reveals both structural and compositional inhomogeneity. Our study identifies the differences between the local structure properties of CeO2 and ZrO2 parent oxides and CeO2-ZrO2 mixed oxide, also confirming the special chemical environment of the oxygen atoms in the mixed oxide as reported earlier by Extended X-ray Absorption Fine Structure investigations.

We propose a physical model for luminescence properties of trivalent lanthanide (Ln) doped into CeO 2 by use of low temperature, site selective, time-gated luminescence spectroscopy seconded by X-ray diffraction, Raman and Fourier transform infrared spectroscopy and transmission electron microscopy. The main findings can be summarized as follows: i) Ln situated to both left and right side to Gd in the Ln series, exhibit a two center distribution. Both Ln centers substitute for the tetravalent Ce fluorite sites being differentiated by the local symmetry: cubic, as a result of zero vacancy in the nearest-neighbor oxygen shell (cubic Ln center) and low symmetry, likely due to one vacancy in the nearest-neighbor oxygen shell (Ln -defect associate center); ii) A first example of Dy emission in an inversion (cubic) symmetry, characterized by strong lines at 679 and 764 nm is reported. This results is expected to challenge the way this lanthanide is currently used as a luminescence probe; iii) the relative contribution of the Ln centers to the overall emission depends on the Ln ionic radius: Sm exists predominantly as a cubic center while Er is found mostly as a vacancy associate; iv) Er, La codoped CeO 2 can be used as an effective model system to separate the effects of Ln concentration and subsequently induced oxygen vacancies on the efficiency of CeO 2 sensitization of Ln emission and v) Zr co -doping of CeO 2 obstructs the formation of Ln -defect associates. The implications of our findings for the interpretation of data already present in the literature are also discussed.

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The ever-changing external environment and the challenges and signals transmitted by the European Single Market have greatly contributed to the dynamism of SMEs in Europe. From the privileged place held by the entrepreneur in SMEs, the present study aims to investigate the role of managerial skills in the sustainable development of small and medium enterprises, focused on self-awareness, emotional intelligence, and interpersonal skills of entrepreneurs. The investigation method consisted of the distribution of anonymous questionnaires to a representative sample of entrepreneurs, in the Mehedinți County, Romania. The collected data were centralized, processed, and assessed. The results of this analysis revealed, besides the emotional intelligence and interpersonal skills which have reached a suitable level, a low level of self-awareness. Therefore, this has been considered as a potential barrier towards sustainable development of SMEs in the analyzed region. However, the high level of emotional intelligence, accompanied by an increasing trend of interpersonal skills as the manager’s experience in working with people increases, is a strong argument for the sustainable development of SMEs. The study comes to support the public policies concerning small and medium-sized entities by using a model of managerial skills testing for applicants. In this way, an increase of the transparency of financing decision and the effectiveness of financial support are ensured.

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Local symmetry distortion by Li addition is acknowledged as an effective strategy for enhancing the luminescence of lanthanide (Ln) doped into a wide range of lattice hosts. Despite extensive literature, direct evidence that supports Li-induced modification of the local crystal-field at the Ln sites is still missing. Herein, we show that the emission enhancement by Li addition in Ln,Li–Y2O3 is due to improved crystallization and not to local structure distortion. Our approach is based on the premise that any distortion/lowering of the local symmetry would reflect into the alteration of the emission shapes and shortening of the emission decays. To this aim, we have extensively investigated the evolution with Li addition and calcination temperature of down (optical and X-ray induced) and up-conversion (UPC) emission of Ln-Y2O3 measured across the visible to near-infrared range. First, a center to center (corresponding to Ln in the C2 and S6/C3i sites of the cubic Y2O3 lattice) as well as global comparison of the emission properties of Li free and Li codoped Y2O3 are presented by use of Eu, Sm, Tb and Dy as local probes in the visible range. Next, the effect of Li on the up-conversion emission of Er- Y2O3 is analyzed in terms of UPC pathways, emission shape and intensity, decays and excitation spectra. It is concluded that Li addition does not change either the local structure around C2 or S6 Ln centers or the relative contribution of these. Moreover, it is found that the effects of Li doping on the emission properties of Ln–Y2O3 are like extending the calcination temperature of Li-free Ln–Y2O3 from 800 °C to ∼1000–1100 °C. Additionally, a relatively intense 1500 to 980 nm UPC emission is evidenced for the first time for Er–Y2O3, while a relatively intense emission around 1500 nm was measured under X-ray excitation. Taken together, our findings highlight the need for revisiting the traditional optimization strategy based on Li modification but also the promise of Er–Y2O3 nanoparticles for optical/X-ray applications in the near-infrared range.