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Principles Of Fluorescence Spectroscopy

Precious corals have been commercially exploited for many centuries all over the world Their skeletons have been used as amulets or jewellery since antiquity and are one of the most valuable living marine resources Precious coral fisheries are generally characterized by the 'boom-and-bust' principle, quickly depleting a discovered stock and then moving on to the next one Most known stocks are overexploited today, and populations are in decline The unsustainable nature of most fisheries is clearly revealed by analyzing all available data Precious corals belong to the functional group of deep corals and are important structure-forming organisms, so called ecosystem engineers, that provide shelter for other organisms, increasing biodiversity Yet, their management is usually focused on single species rather than a holistic habitat management approach This review compares the biology of precious corals as well as the historical ecology and the socioeconomy of their fisheries to improve precious coral management and conservation The analysis demonstrates that a paradigm shift is necessary in precious coral exploitation, not only to conserve habitats of high biodiversity but also to achieve sustainable fisheries and stabilize a specialized jewellery industry

The Exploitation and Conservation of Precious Corals

Nitrogen is ubiquitous in both natural and laboratory-grown diamond, but the number and nature of the nitrogen-containing defects can have a profound effect on the diamond material and its properties. An ever-growing fraction of the supply of diamond appearing on the world market is now lab-grown. Here, we survey recent progress in two complementary diamond synthesis methods—high pressure high temperature (HPHT) growth and chemical vapor deposition (CVD), how each is allowing ever more precise control of nitrogen incorporation in the resulting diamond, and how the diamond produced by either method can be further processed (e.g., by implantation or annealing) to achieve a particular outcome or property. The burgeoning availability of diamond samples grown under well-defined conditions has also enabled huge advances in the characterization and understanding of nitrogen-containing defects in diamond—alone and in association with vacancies, hydrogen, and transition metal atoms. Among these, the negatively charged nitrogen-vacancy (NV–) defect in diamond is attracting particular current interest in account of the many new and exciting opportunities it offers for, for example, quantum technologies, nanoscale magnetometry, and biosensing.

Nitrogen in diamond

Being nondestructive and requiring short measurement times, a low amount of material, and no sample preparation, Raman spectroscopy is used for routine investigation in the study of gemstone inclusions and treatments and for the characterization of mounted gems. In this work, a review of the use of laboratory Raman and micro-Raman spectrometers and of portable Raman systems in the gemology field is given, focusing on gem identification and on the evaluation of the composition, provenance, and genesis of gems. Many examples are shown of the use of Raman spectroscopy as a tool for the identification of imitations, synthetic gems, and enhancement treatments in natural gemstones. Some recent developments are described, with particular attention being given to the semiprecious stone jade and to two important organic materials used in jewelry, i.e., pearls and corals.

Applications of Raman spectroscopy to gemology.

Diamond hosts a wide variety of colour centres that have demonstrated outstanding optical and spin properties. Among them, the nitrogen-vacancy (NV) centre is by far the most investigated owing to its superior characteristics, which promise the development of highly sophisticated quantum devices, in particular for sensing applications. Nevertheless, harnessing the potential of these centres mainly relies on the availability of high quality and purity diamond single crystals that need to be specially designed and engineered for this purpose. Plasma assisted chemical vapour deposition (CVD) has become a key enabling technology in this field of research. Nitrogen can indeed be directly doped in situ into a high crystalline quality diamond matrix in a controlled way, allowing the production of single isolated centres or ensembles that can potentially be integrated into a device. In this paper we will provide an overview of the requirements for synthesizing 'quantum-grade' diamond films using CVD. These include the reduction of impurities and surrounding spins that limit coherence times, the control of NV density in a wide range of concentrations as well as their spatial localization within the diamond. Enhancing the charge state and preferential orientation of the colour centres is also discussed. These improvements in material fabrication have contributed to positioning diamond as one of the most promising solid-state quantum systems and the first industrial applications in sensing are just starting to emerge.

https://iopscience.iop.org/article/10.1088/1361-6463/ab81d1/pdf

Chemical vapour deposition diamond single crystals with nitrogen-vacancy centres: a review of material synthesis and technology for quantum sensing applications

sure, high-temperature (HPHT) process have been commercially available since the mid1990s. This article presents statistical information and distinctive identification features based on a review of data gathered by GIA, principally at the New York and Carlsbad laboratories, for several thousand HPHT-grown synthetic diamonds. This study includes all HPHT synthetic diamonds submitted to GIA between 2007 (the year GIA started issuing Synthetic Diamond Grading Reports) and 2016. No summary has been published on such a large number of HPHT synthetic samples. We describe here the diagnostic means of identification, with an emphasis on the goods currently being sold for jewelry use. Box A details some of the most important identification criteria that may be used by gemologists. Of this sample set, 12% were colorless to nearcolorless (D–J), 12% blue, 13% yellow, 4% pink to red, and 54% yellowish orange to orangy yellow (e.g., figure 1). The remaining 5% showed other colors, including green-yellow and brown-orange. This set represents both as-grown and treated colors. While some samples were purchased by GIA on the market or from manufacturers, or were loaned or donated to us by manufacturers for study purposes, most were sub-

Observations on HPHT-Grown Synthetic Diamonds: A Review

have been chronicled in natural diamonds using UVVis absorption, cathodoluminescence, and photoluminescence spectroscopy (see, e.g., Zaitsev, 2001), spectral data for fluorescence and phosphorescence are limited in the gemological literature, since luminescence is typically described by visual observations (again, see Fritsch and Waychunas, 1994). However, visual assessment of fluorescence and phosphorescence tells only part of the story. The color discerned by the unaided eye may represent a combination of two or more wavelength regions. For example, Anderson (1960) asserted that although most fluorescing diamonds appear to luminesce blue, a yellow or green component may be present but masked by the stronger blue emission. He used color filters and a spectroscope to try to identify some of the relevant FLUORESCENCE SPECTRA OF COLORED DIAMONDS USING A RAPID, MOBILE SPECTROMETER

Fluorescence Spectra of Colored Diamonds Using A Rapid, Mobile Spectrometer

The first decade of the 2000s continued the trend of using more powerful analytical instruments
to solve gem identification problems. Advances in gem treatment and synthesis technology, and
the discovery of new gem sources, led to urgent needs in gem identification. These, in turn, led to
the adaptation of newer scientific instruments to gemology. The past decade witnessed the
widespread use of chemical microanalysis techniques such as LA-ICP-MS and LIBS, luminescence
spectroscopy (particularly photoluminescence), real-time fluorescence and X-ray imaging,
and portable spectrometers, as well as the introduction of nanoscale analysis. Innovations in laser
mapping and computer modeling of diamond rough and faceted stone appearance changed the
way gemstones are cut and the manner in which they are graded by gem laboratories.

Developments in Gemstone Analysis Techniques and Instrumentation During the 2000s

modifying the occurrence or arrangements of particular lattice defects, either during growth or with post-growth treatments. In this study, we describe a group of strongly colored pink CVD lab-grown diamonds (e.g., figure 1) provided for examination by Apollo Diamond Inc. Standard gemological properties and spectroscopic data are presented, as well as key identification features that help separate these new products from natural, treated-natural, and HPHT-grown synthetic pink diamonds.

Strongly Colored Pink CVD Lab-Grown Diamonds

Sixty-seven natural blue diamonds, including the two largest such gemstones known (the Hope and the Blue Heart), were probed by ultraviolet radiation, and their luminescence was analyzed using a novel spectrometer system. Prior to this study, the fiery red phosphorescence of the Hope Diamond was regarded as quite rare compared to greenish-blue phosphorescence. However, our results demonstrated that virtually all blue diamonds phosphoresce at 660 nm (orange-red) but that this emission often is obscured by a concomitant luminescence at 500 nm (green-blue). Although both bands were nearly always present, the relative intensities of these emissions and their decay kinetics varied dramatically. Consequently, phosphorescence analysis provides a method to discriminate among individual blue diamonds. Treated and synthetic blue diamonds showed behavior distinct from natural stones. Temperature-dependent phosphorescence revealed that the 660 nm emission has an activation energy of 0.4 eV, close to the 0.37 eV acceptor energy for boron, suggesting that the phosphorescence is caused by donor-acceptor pair recombination.

Sally Eaton-Magaña

Papers

Observations on HPHT-Grown Synthetic Diamonds: A Review

Fluorescence Spectra of Colored Diamonds Using A Rapid, Mobile Spectrometer

Developments in Gemstone Analysis Techniques and Instrumentation During the 2000s

Strongly Colored Pink CVD Lab-Grown Diamonds

Using phosphorescence as a fingerprint for the Hope and other blue diamonds