luminescence spectroscopy of minerals and materials pdf

Luminescence spectroscopy of minerals and materials pdf

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Spectroscopic Methods in Mineralogy and Material Sciences

Organic luminescent materials

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Of all the elements in the Periodic Table, perhaps none is more complex than uranium. Structurally documented uranium compounds offer many opportunities for study, since they exhibit exact bond angles, distances and crystal lattice details, allowing for theoretical studies involving electron density, electronic transitions and other calculations; some uranium compounds shown as minerals can be seen in Figure 1. These details also provide substantive bonding data for the development of more advanced studies of applied spectroscopy for analytical applications.

We discuss the potential of luminescence spectroscopy, complementary to Raman spectroscopy, for the quantitative estimation of chemical and potentially also radiation-induced disorder. The luminescence emission of rare-earth elements REEs in general is well-studied, stimulated by their importance in various modern technological applications such as lighting, colour-television screens, solid-state lasers, phosphors, and chromophores in different host materials e. In the Earth sciences, one challenging task is the detection of REEs in different host minerals using luminescence methods; a large variety of mineral systems have been studied already Tarashchan ; Ohnenstetter et al. Synthetic minerals individually- or multi-doped with REEs have also been studied routinely, aiming at a better understanding of the luminescence in their natural analogues. For the example of zircon and synthetic ZrSiO 4 , such investigations have been done by Cesbron et al.

Spectroscopic Methods in Mineralogy and Material Sciences

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We present here a quantification of the sorption process and molecular conformation involved in the attachment of bacterial cell wall lipopolysaccharides LPSs , extracted from Escherichia coli , to silica SiO 2 and alumina Al 2 O 3 particles. We propose that interfacial forces govern the physicochemical interactions of the bacterial cell wall with minerals in the natural environment, and the molecular conformation of LPS cell wall components depends on both the local charge at the point of binding and hydrogen bonding potential.

This has an effect on bacterial adaptation to the host environment through adhesion, growth, function, and ability to form biofilms.

Photophysical techniques were used to investigate adsorption of fluorescently labeled LPS onto mineral surfaces as model systems for bacterial attachment. Adsorption of macromolecules in dilute solutions was studied as a function of pH and ionic strength in the presence of alumina and silica via fluorescence, potentiometric, and mass spectrometry techniques. The effect of silica and alumina particles on bacterial growth as a function of pH was also investigated using spectrophotometry.

The alumina and silica particles were used to mimic active sites on the surface of clay and soil particles, which serve as a point of attachment of bacteria in natural systems. Strong adsorption was observed at low pH for both minerals and varied with both pH and mineral concentration, likely in part due to conformational rearrangement of the LPS macromolecules. Bacterial growth was also enhanced in the presence of the particles at low pH values.

This demonstrates that at a molecular level, bacterial cell wall components are able to adapt their conformation, depending on the solution pH, in order to maximize attachment to substrates and guarantee community survival. Figure 1. B Fluorescence anisotropy decays at pH 2 and 12, respectively. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Such files may be downloaded by article for research use if there is a public use license linked to the relevant article, that license may permit other uses.

The authors thank the Libyan Ministry of Education for financial support during the experimental study. More by Fateh El-Taboni. More by Emily Caseley. More by Maria Katsikogianni. More by Linda Swanson. More by Thomas Swift. More by Maria E. Cite this: Langmuir , 36 , 7 , — Article Views Altmetric -.

Citations 2. Abstract High Resolution Image. A lipopolysaccharide LPS is an amphiphilic macromolecule with a hydrophobic lipid unit embedded in the outer membrane of Gram-negative bacteria.

Bacteria found in a biofilm matrix are less susceptible to drugs than they are in vitro 15 and this is a known cause of persistence in infections. LPS coats the outermost layer of many bacteria cell walls and is believed to be a major source of metal binding in Gram-negative bacteria. The chances of bacteria attaching to surfaces for the formation of biofilms depend on the success of creating a matrix of suitable composition to match the host environment.

This is a dynamic process that, in turn, relies on the availability of nutrients, the secretion of outer cell polymers, shear stress, and social collaboration.

Our hypothesis is that at a molecular level, this process also depends on the aqueous pH and ionic strength because the chemical composition in the solution controls the conformation of cell wall polymeric components and hence sorption to the surface. With the aim of providing a molecular level understanding of bacterial cell adhesion to mineral surfaces, we examine here the influence of aqueous chemical composition on the molecular conformation of LPS and its sorption to alumina and silica using fluorescence spectroscopy.

A novel approach was developed involving the synthesis of fluorescently labeled LPS from Escherichia coli , and the use of fluorescence time-resolved anisotropy measurements TRAMS to monitor the conformational behavior of this biopolymer. This was achieved using the fluorescent-labeled 4-amino naphthalenesulfonic acid AmNS , which was covalently bound to the LPS backbone. AmNS has previously shown to be a reliable reporter of polymer conformation in the solution and has been used to study the adsorption of poly acrylic acid onto the surface of calcite.

This approach provides a mechanistic understanding of binding at the interface of the outer cell wall of bacteria and minerals, a process vital to bacterial attachment, growth, and the stability of biofilms.

Experimental Details. Deionized double-distilled water resistivity Molecular weight: Characterization parameters were found as follows: particle diameter: LPS from E. After that, the aqueous layer was removed, and ethanol was added to precipitate LPS.

M V viscosimetry , g mol —1. See the Supporting Information for full characterization details. UV analysis was characterized by a Hitachi U spectrometer, using 1 cm quartz cuvettes, scanning the range — nm with a bandpass of 1 nm.

AmNS 25 mg was added and the resulting mixture was stirred overnight. The product was washed with dichloromethane Sigma-Aldrich , and the aqueous layer evaporated to dryness at a reduced pressure to yield the fluorescently labeled LPS.

M V viscometry , g mol —1. Dev 0. Aqueous LPS solutions were prepared at pH values ranging from 2 to The solution pH was adjusted as required using 0. The suspensions were then stirred or shaken for 18 h. For alumina measurements equilibrated samples were centrifuged at rpm for 40 min, the supernatant was removed and centrifuged for another 40 min. Aliquots of the supernatant were removed for further analysis. For adsorption measurements on silica, equilibrated solutions were centrifuged for 2 h to fully sediment the solid phase from the aqueous phase.

The supernatant was withdrawn and examined as detailed below. Fluorescence steady-state analysis was carried out using a Horiba Fluoromax-4 spectrophotometer. Sample excitation was performed on fluorescently labeled LPS—mineral samples both before and after separation by centrifugation to determine polymer isolation from the supernatant.

The amount of adsorbed LPS was calculated from the difference in the maximum fluorescence intensity of emission in counts per second; all measurements were taken on the same day to ensure an equivalent detector response. Time-correlated single-photon counting fluorescence measurements were carried out on fluorescently labeled LPS—mineral samples using an Edinburgh Instruments fluorescence spectrometer.

A silica prompt designed to scatter light at the incident wavelength was run after each sample to consider scattered light from the source during fluorescence analysis and the fluorescence decay reconvoluted to minimize interference in the decay profile.

The instrumentation and methodology used is the same described in our previous polymeric research. Potentiometric titrations were conducted according to a previously published protocol. The polymer solution was prepared by dissolving a known amount of the polymer in degassed ultrahigh quality UHQ water.

Solutions of 0. The samples were dissolved in 25 mL of the NaCl electrolyte 0. Following the equilibration procedure, a positive pressure of N 2 was maintained by allowing a gentle flow of N 2 into the headspace during the titration.

A control sample without LPS was also titrated. To assess reversibility and protonation behavior, a reverse acidimetric titration was applied following the base titration. Each experiment was carried out in triplicate. Successive addition of an acid or base was carried out using an auto titrator every 20 s. For the inductively coupled plasma mass spectrometry analysis ICP—MS , a PerkinElmer ELAN DRC II was used to determine the amount of unreacted minerals according to the following method: the equilibrated mineral LPS solution was transferred into an ultrafiltration cylinder pore size 1 kDa , and free mineral passed through a filter and collected in a flask.

The adsorbed mineral amount was calculated by the difference between the initial concentration and the amount of free mineral in the solution at the end of the experiment. Colony forming units cfu mL —1 at a 10 4 concentration were transferred into each 96 well plate and prepared to either 0. The absorbance was recorded 24 h later at nm, using a Thermo Scientific Multiscan FC microplate photometer, and correlated to bacterial growth via a calibration curve.

Bacterial suspensions were also plated on TSA toward the production of the calibration curve. Bacterial growth in the presence of silica or alumina particles was also confirmed through growth on TSA. Bacterial growth at pH 2 and pH 10, in the presence or absence of particles, was confirmed through plating on TSA. Results and Discussion. Scheme 1. High Resolution Image. The photophysical behavior observed during TRAMS is a result of the mobility of the AmNS label attached to the polymer backbone, rotating with the speed of the macromolecule in solution.

This causes variation on r 0 values and Chi square goodness of fit. In this study, r 0 was limited to a maximum value of 0. There were no differences between the quality of fit using single or dual exponential equations Figures S20—S22 even considering the scattering interferences and therefore single exponential fittings are reported here.

TRAMS are a powerful tool used to disclose macromolecular conformation, and have previously been used to disclose polymer solution rearrangement 25,28 and binding. Similar behavior has been observed in other pH responsive polymers, 23,30 where the adoption of a small globular polymer chain conformation or micelles is preferred over aggregation because of repulsion between polymer chains because of excess protonation.

Organic luminescent materials

UoM administered thesis : Phd. Uranium VI uptake by geological materials, characterisation by luminescence spectroscopy UoM administered thesis : Phd. Authors: Mark Williams. Abstract Many of the wastes associated with the nuclear fuel cycle are toxic to the biosphere; advancing the use of high resolution spectroscopy applied to these materials will provide the chemical speciation of the interaction between nuclear waste and geological material, improving confidence in a permanent disposal method and informing clean-up operations. Luminescence spectroscopy of uranyl VI is a well-established technique for the molecular speciation of uranium-mineral interactions.

These metrics are regularly updated to reflect usage leading up to the last few days. Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts. The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric. Find more information on the Altmetric Attention Score and how the score is calculated.

The first phosphor synthesized was probably an impure barium sulfide preparation with very low luminance efficiency and with the serious shortcoming that it was rather quickly decomposed in moist air, yielding hydrogen sulfide. A more stable sulfide-type phosphor was produced in by heating zinc oxide in a stream of hydrogen sulfide. In it became known that these sulfides do not luminesce in a chemically pure state but only when they contain small quantities of a so-called activator metal. Later, other materials, such as certain metal oxides, silicates, and phosphates, were found to luminesce if they were prepared by special procedures. The sulfides of zinc and of cadmium are the most important basic materials of sulfide-type phosphors. An important condition of getting highly efficient phosphors is that these sulfides must first be prepared to the highest possible chemical purity before the necessary amount of activator can be added precisely. The emission of zinc sulfide can be shifted to longer wavelengths by increasing substitution of the zinc ions by cadmium ions.

Luminescence Spectroscopy of Minerals and Materials presents an overview of the general concepts in luminescence spectroscopy as well as experimental.

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Modern Luminescence Spectroscopy of Minerals and Materials

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