Interpretation of Luminescence Centers

Gaft, M.; Reisfeld, Renata; Panczer, G.

doi:10.1007/978-3-319-24765-6_5

Cited by 7 publications

(4 citation statements)

References 165 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Additional spectral features in sapphires can include two luminescence bands at 693 and 694 nm, due to Cr 3+ ions [ 20 , 21 ], that appear as a single sharp negative band in the FORS spectrum (see Figure 1 ).…”

Section: Resultsmentioning

confidence: 99%

The Use of UV-Visible Diffuse Reflectance Spectrophotometry for a Fast, Preliminary Authentication of Gemstones

et al. 2022

View full text Add to dashboard Cite

The identification of gemstones is an important topic in the field of cultural heritage, given their enormous value. Particularly, the most important precious stones, namely diamond, emerald, ruby and sapphire, are frequently subjected to counterfeit by substitution with objects of lesser value with similar appearance, colour or shape. While a gemmologist is able to recognise a counterfeit in most instances, more generally, it is not easy to do this without resorting to instrumental methods. In this work, the use of UV-visible diffuse reflectance spectrophotometry with optic fibres (FORS) is proposed as a fast and easy method for the preliminary identification of gemstones, alternative to the classical methods used by gemmologists or to Raman spectroscopy, which is by far the instrumental method with the best diagnostic potential, but it cannot be used in situations of problematic geometric hindrance. The possibilities and the limitations given by the FORS technique are critically discussed together with the spectral features of the most important gemstones. Finally, the application of chemometric pattern recognition methods is described for the treatment of large sets of spectral data deriving from gemstones identification.

show abstract

Section: Resultsmentioning

confidence: 99%

The Use of UV-Visible Diffuse Reflectance Spectrophotometry for a Fast, Preliminary Authentication of Gemstones

et al. 2022

View full text Add to dashboard Cite

show abstract

“…The final question pertains to the position of the broad peak associated with the formation of Eu 2+ . It has been suggested that the emission of Eu 2+ in different compounds can vary from UV to blue wavelengths [11,69]. Most silica-based compounds containing Eu 2+ , such as xerogel, SiOC and PMO, exhibit photoluminescence in the blue light range with a maximum located near 450 nm.…”

Section: Discussionmentioning

confidence: 99%

“…Eu 2+ ions demonstrate a remarkably strong emission resulting from dipole-allowed 4f 6 5d → 4f 7 transitions. The intra 4f-shell transition of Eu 3+ ions, being electric dipole-forbidden, results in a less intense luminescence [10,11]. It is wellestablished that the positions of emission bands of Eu 2+ are highly dependent on the host materials.…”

Section: Introductionmentioning

confidence: 99%

Structural and Luminescence Properties of Eu-Doped PMO Films with Ethylene Bridge and Methyl Terminal Groups

Rasadujjaman,

Zhang,

Vishnevskiy

et al. 2023

Coatings

View full text Add to dashboard Cite

Eu-doped periodic mesoporous organosilicate (PMO) films with terminal methyl and ethylene bridging groups have been synthesized using sol-gel technology and spin-coating, employing evaporation-induced self-assembly (EISA), on silicon wafers. Eu doping is achieved by the dissolution of Eu(NO3)3·6H2O in the precursor solution. The deposited films are characterized using Fourier transform infrared (FTIR) spectroscopy, ellipsometric porosimetry (EP), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy. It is observed that Eu doping reduces the concentration of terminal methyl groups, makes the films more hydrophilic and reduces the pore size and open porosity. The reduction reaction Eu3+ → Eu2+ occurs in the pores of organosilicate glass (OSG) films, which was confirmed by the depth profiling XPS. Eu3+ was still present on the top surface of the films. The presence of Eu3+ and Eu2+ gives luminescence emission in the range of 600–630 nm (Eu3+) and 290–400 nm (Eu2+). The Eu2+/Eu3+ concentrations ratio depends on CH3 groups concentration in the films. The concentration of Eu2+ ions in the pores can be reduced by exposure to inductively coupled (ICP) oxygen plasma. The observed shift in the luminescence spectra towards the UV region, in comparison to previously reported Eu-doped organosilicate films, can be attributed to the energy transfer occurring between the host material and Eu2+ ions.

show abstract

“…The rst activation centre de ned by the broad band centred at 592 nm (λ ex = 408; Fig. 3) can be assigned to Mn 2+ that is a well-studied luminescence centre in many minerals (Gaft et al, 2015a). As already mentioned in the crystal chemistry section, the apfu calculations (Table 4) show that all the Mn is assigned to the dodecahedral site (X) as Mn 2+ , leading to the calculation of spessartine end-member as 0.72-0.74 mol % for Tsavo M and Tsavo T, respectively.…”

Section: Discussionmentioning

confidence: 99%

Mineralogical characterization of fluorescent grossular garnet var. tsavorite from Merelani Hills, Tanzania

Idini

Angeli

Frau

et al. 2022

Preprint

View full text Add to dashboard Cite

Tsavorite is the trade name for the green vanadium-chromium variety of grossular. The occurrence of tsavorite plays a key role in the geological research inherent to the formation of Gondwana continent because it is hosted exclusively in the metamorphic unit from the Neoproterozoic Metamorphic Mozambique Belt (NMMB). In fact, the studies on the tsavorite deposit of the NMMB contributed to determine the metamorphic evolution of these Precambrian terrains. The areas of Merelani Hills (Tanzania) and Tsavo Park (Kenya) are by far the most important source of gem grade specimens of tsavorite that are used for high jewellery. Furthermore, the tsavorite crystals from Merelani Hills exhibit a peculiar feature: the fluorescence is easily recognizable lighting up centimetric crystals with a common portable led lamp. Using the long UV a bright pink-orange colour is observed, while exciting with the short UV the effect is a pale yellow. To the best of our knowledge, this phenomenon is unusual among the members of the garnet group and only few research papers have investigated it in natural garnets. With the aim of characterizing the fluorescence, two sets of 20 g of tsavorite crystals were meticulously sampled from the rocky matrix under the UV lamp and then pulverized to perform an accurate XRD acquisition. The results show that no other phases but garnet are recognizable. The Electron Density Map calculated from the XRD data and plotted against a CIF grossular standard shows that an excess of negative charge is clearly pinpointed in the crystallographic site occupied by Al3+ in the grossular standard structure. The bulk elemental analysis of the two sample sets shows that the most represented end-member, besides grossular, is the vanadium garnet goldmanite (3.82–4.08 mol %) and therefore the cause of the excess of electron density could be related mainly to the Al3+ ⇄ V3+ diadochy in the octahedral site. The others calculated end-members above 0.5 mol % are pyrope (1.34–2.14 mol %), schorlomite-Al (0.70–0.86 mol %) and spessartine (0.72–0.74 mol %). Despite the fact that tsavorite is known as vanadium-chromium grossular, the content of chromium expressed as Cr2O3 is only 0.02 wt % in the two sample sets. The fluorometry at room temperature with an excitation beam at 408 nm indicates a complex emission pattern with the most intense emissions at 701 and 716 nm and subordinately at 592 nm. Focusing on the visible part of the spectrum, the colour perception of the emitted light is dominated by the emission yellow band at 592 nm which is close to the peak sensitivity of the human eye at 555 nm, while the contribution of the red band, though more intense, is perceived much weaker due to the lower eye sensitivity and modulates the colour ranging from bright orange to pink-red. The attribution of the emission at 592 nm is related to Mn2+ (in diadochy with Ca in the dodecahedral site) that is the most significative source of the visible fluorescence. The most intense, but less perceptible to the human eye, emissions at 701 and 716 nm could be related to the chromium content and/or to a possibly fraction of vanadium as V2+. Because of the characteristic colour perceived under UV light, the use of a common led lamp can serve as a diagnostic tool to identify tsavorite whenever a rapid test is required, e.g. in the case of field survey or in the gem market.

show abstract

Interpretation of Luminescence Centers

Cited by 7 publications

References 165 publications

The Use of UV-Visible Diffuse Reflectance Spectrophotometry for a Fast, Preliminary Authentication of Gemstones

The Use of UV-Visible Diffuse Reflectance Spectrophotometry for a Fast, Preliminary Authentication of Gemstones

Structural and Luminescence Properties of Eu-Doped PMO Films with Ethylene Bridge and Methyl Terminal Groups

Mineralogical characterization of fluorescent grossular garnet var. tsavorite from Merelani Hills, Tanzania

Contact Info

Product

Resources

About