Showing papers on "Fluorescence spectrometry published in 2019"

Rare earth elements:A review of applications, occurrence, exploration, analysis, recycling, and environmental impact

Abstract: Rare earth elements (REE) include the lanthanide series elements (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) plus Sc and Y. Currently these metals have become very critical to several modern technologies ranging from cell phones and televisions to LED light bulbs and wind turbines. This article summarizes the occurrence of these metals in the Earth's crust, their mineralogy, different types of deposits both on land and oceans from the standpoint of the new data with more examples from the Indian subcontinent. In addition to their utility to understand the formation of the major Earth reservoirs, multi-faceted updates on the applications of REE in agriculture and medicine including new emerging ones are presented. Environmental hazards including human health issues due to REE mining and large-scale dumping of e-waste containing significant concentrations of REE are summarized. New strategies for the future supply of REE including recent developments in the extraction of REE from coal fired ash and recycling from e-waste are presented. Recent developments in individual REE separation technologies in both metallurgical and recycling operations have been highlighted. An outline of the analytical methods for their precise and accurate determinations required in all these studies, such as, X-ray fluorescence spectrometry (XRF), laser induced breakdown spectroscopy (LIBS), instrumental neutron activation analysis (INAA), inductively coupled plasma optical emission spectrometry (ICP-OES), glow discharge mass spectrometry (GD-MS), inductively coupled plasma mass spectrometry (including ICP-MS, ICP-TOF-MS, HR-ICP-MS with laser ablation as well as solution nebulization) and other instrumental techniques, in different types of materials are presented.

Protein-Capped Metal Nanoparticles Inhibit Tau Aggregation in Alzheimer's Disease.

Abstract: The Alzheimer's disease (AD) therapeutic research is yielding a large number of potent molecules. The nanoparticle-based therapeutics against the protein aggregation in AD is also taking a lead especially with amyloid-β as a primary target. In this work, we have screened for the first time protein-capped (PC) metal nanoparticles for their potency in inhibiting Tau aggregation in vitro. We present a novel function of PC-Fe3O4 and PC-CdS nanoparticles as potent Tau aggregation inhibitors by fluorescence spectrometry, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and electron microscopy. We demonstrate that the biologically synthesized PC-metal nanoparticles, especially iron oxide do not affect the viability of neuroblastoma cells. Moreover, PC-CdS nanoparticles show dual properties of inhibition and disaggregation of Tau. Thus, the nanoparticles can take a lead as potent Tau aggregation inhibitors and can be modified for specific drug delivery due to their very small size. The current work presents unprecedented strategy to design anti-Tau aggregation drugs, which provides interesting insights to understand the role of biological nanostructures in Alzheimer's disease.

Stable Tb(III)-Based Metal-Organic Framework: Structure, Photoluminescence, and Chemical Sensing of 2-Thiazolidinethione-4-carboxylic Acid as a Biomarker of CS2.

Abstract: A novel three-dimensional microporous framework, [Tb(pddb)phen(ox)0.5] n (Tb-MOF), was synthesized hydrothermally with V-shaped 4,4'-(pyridine-2,6-diyl)dibenzoic acid (H2pddb), oxalate (ox), and 1,10-phenanthroline (phen). The framework of Tb-MOF features one-dimensional channels functionalized with pyridine-N Lewis base groups and the absence of coordinated and lattice water molecules in the structure. The Tb-MOF exhibits high thermostability (up to 385 °C) and chemical stability in a wide pH range (4-11) and common organic solvents as well as boiling water. The luminescence investigations of the Tb-MOF in common solvents, water with different pH values, and inorganic ions were performed. Results show that the Tb-MOF has high luminescence stability and the ability to probe Fe3+ ions. Significantly, the Tb-MOF with particularly high water stability can be first developed as a highly selective and sensitive luminescent sensor for the biomarker 2-thiazolidinethione-4-carboxylic acid (TTCA) via fluorescence quenching. The low detection limit (1 ppm), reusability, and high antidisturbance together make the Tb-MOF become a promising sensor for the practical detection of TTCA in urine systems, and for the first time realize the detection of urinary TTCA through fluorescence spectrometry based on an Ln-MOF sensor.

Microfluidic Synthesis of Semiconducting Colloidal Quantum Dots and Their Applications

Abstract: The large-scale synthesis of high-quality quantum dots (QDs) for commercial applications, such as lighting, displays, and biomedical devices, is an urgent necessity. Batch reactor systems present a number of problems, such as improper mixing, heating, and reagent addition. Hence, controlling the growth and size of nanocrystals is difficult in this type of system. A number of microfluidic techniques have been developed to enable semiconductor colloidal QD synthesis. The reaction parameters of these techniques are controlled precisely during synthesis. Over the last 16 years, many advancements have been introduced to achieve products similar to those obtained from batch systems. Multiphase flow reactors reduce reactor fouling by using immiscible carrier liquids, which decrease the contact between reagents and the channel wall. Online monitoring of the nanocrystal growth through absorbance and fluorescence spectrometry provides detailed information on the reaction parameters. Chip-based reactors with subchan...

Analysis of Trace Elements in Human Brain: Its Aim, Methods, and Concentration Levels.

Abstract: Trace elements play a crucial role in many biochemical processes, mainly as components of vitamins and enzymes. Although small amounts of metal ions have protective properties, excess metal levels result in oxidative injury, which is why metal ion homeostasis is crucial for the proper functioning of the brain. The changes of their level in the brain have been proven to be a risk factor for Alzheimer's, Parkinson's, and Huntington's diseases, as well as amyotrophic lateral sclerosis. Therefore, it is currently an important application of various analytical methods. This review covers the most important of them: inductively coupled ground mass spectrometry (ICP-MS), flame-induced atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (GFAAS), optical emission spectrometry with excitation in inductively coupled plasma (ICP-OES), X-ray fluorescence spectrometry (XRF), and neutron activation analysis (NAA). Additionally, we present a summary of concentration values found by different research groups.

Pollution Assessment and Source Apportionment of Trace Metals in Urban Topsoil of Xi’an City in Northwest China

Abstract: Sixty-two topsoil samples were collected within the third ring road of Xi'an City in Northwest China and analyzed by X-ray fluorescence spectrometry for the concentrations of As, Ba, Co, Cr, Cu, Mn, Ni, Pb, V, and Zn. The pollution levels of trace metals were assessed by pollution index (PI) and Nemerow pollution index (NPI). Meanwhile, the sources of trace metals were apportioned by receptor models, including positive matrix factorization (PMF), UNMIX, and principal component analysis-multiple linear regression (PCA-MLR). The average concentrations of the trace metals analyzed in the urban soil exceeded the corresponding soil element background values of Shaanxi Province, especially for Co, which was 2.38 times higher than the corresponding background value. The mean of PI was 2.38 for Co, reflecting a moderate pollution level, and ranged from 1.07 to 1.72 for other trace metals, presenting slight pollution levels. The NPI of trace metals varied between 1.20 and 3.50 with an average of 2.00, indicating that trace metals presented slight pollution in 62.90% of soil samples, moderate pollution in 30.65% of soil samples, and heavy pollution in 6.45% of soil samples, respectively. Three sources of trace metals apportioned by the three receptor models were mixed nature and anthropogenic source, traffic exhaust, and industrial emissions. The contributions of them were 38.58%, 32.72%, and 28.70% from the PMF, 65.36%, 17.76%, and 16.88% through the UNMIX and 49.16%, 38.90%, and 11.94% via the PCA-MLR, respectively. Meanwhile, the study results suggested that the combined usage of multiple receptor models is a good method to apportion the source compositions and contributions of trace metals in urban soil.

Quantification of known and unknown terpenoid organosulfates in PM10 using untargeted LC–HRMS/MS: contrasting summertime rural Germany and the North China Plain

Abstract: Environmental context Secondary organic aerosols account for a major fraction of atmospheric particulate matter, affecting both climate and human health. Organosulfates, abundant compounds in organic aerosols, are difficult to measure because of the lack of authentic standards. Here we quantify terpene-derived organosulfates in atmospheric particulate matter at a rural site in Germany and at the North China Plain using a combined target/non-target high-resolution mass spectrometry approach. Abstract Organosulfates (OSs) are a ubiquitous class of compounds in atmospheric aerosol particles. However, a detailed quantification of OSs is commonly hampered because of missing authentic standards and the abundance of unknown OSs. Using a combined targeted and untargeted approach of high-resolution liquid chromatography–Orbitrap mass spectrometry (LC–Orbitrap MS), we quantified for the first time the total concentrations of known and unknown monoterpene (MT) and sesquiterpene (SQT) OSs in summertime PM10 particulate matter from field studies in rural Germany (MEL) and the North China Plain (NCP). At each site, we observed more than 50 MT-OSs, 13 of which were detectable at both sites. For both locations, median concentrations of MT-OSs were in the range of 10 to 40 ng m−3, to which the 13 common MT-OSs contributed on average >50 %. The main contributor to MT-OSs was C9H16O7S (MT-OS 267) with average mass concentrations of 2.23 and 6.38 ng m−3 for MEL and NCP respectively. The concentrations of MT-OSs correlated with the concentrations of MT oxidation products only for MEL. For NCP, the low concentrations of MT oxidation products (i.e. typically <1 ng m−3) suggested a suppression of carboxylic acid formation under high concentrations of NOx and particulate sulfate. Furthermore, we observed 17 SQT-OSs for the MEL samples, whereas 40 SQT-OSs were detected in the NCP samples. Only five of these SQT-OSs were detectable at both sites. Correspondingly, the total concentrations of SQT-OSs were larger for NCP than for MEL, which suggested large differences in the particle chemistry. In particular, aerosol acidity was found to be a key factor during SQT-OS formation, and was probably not sufficient in the PM10 from MEL.

Heavy Mineral Sands in Brazil: Deposits, Characteristics, and Extraction Potential of Selected Areas

Abstract: In Brazil, heavy mineral sand deposits are still barely exploited, despite some references to Brazilian reserves and ilmenite concentrate production. The goal of this project is to characterize and investigate the potential recovery of heavy minerals from selected Brazilian placer occurrences. Two areas of the coastal region were chosen, in Piaui state and in Bahia Provinces. In all samples, the heavy minerals of interest (ilmenite, monazite, rutile, and zircon) were identified by scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques and also quantified by X-ray fluorescence spectrometry (XRF) and Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The total heavy minerals (THM) in the Piaui samples were 6.45% and 10.14% THM, while the figure for the Bahia sample was 3.4% THM. The recovery test of the Bahia sample, using only physical separation equipment such as a shaking table and magnetic separator, showed valuable metallurgical recoveries at around or greater than 70% for each stage, and the final concentrate of pure ilmenite was composed of up to 60.0% titanium dioxide after the differential magnetic separation. Another aim is to compile accessible information about Brazilian heavy mineral main deposits complemented with a short economic overview.

Synthesis of MgAC-Fe3O4/TiO2 hybrid nanocomposites via sol-gel chemistry for water treatment by photo-Fenton and photocatalytic reactions.

Abstract: MgAC-Fe3O4/TiO2 hybrid nanocomposites were synthesized in different ratios of MgAC-Fe3O4 and TiO2 precursor. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray fluorescence spectrometry (XRF), electron spin resonance spectrometry (ESR), Brunauer-Emmett-Teller (BET), photoluminescence (PL), and UV photoelectron spectroscopy (UPS) were used to characterize the nanocomposites. The increase of MgAC-Fe3O4, in the hybrid nanocomposites’ core-shell structure, led to the decrease of anatase TiO2 peaks, thus reducing the photo-Fenton and photocatalytic activities. According to the obtained data, MgAC-Fe3O4 [0.05 g]/TiO2 showed the best photo-Fenton and photocatalytic activities, having removed ~93% of MB (photo-Fenton reaction) and ~80% of phenol (photocatalytic reaction) after 20 and 80 mins, respectively. On the pilot scale (30 L), MgAC-Fe3O4 [0.05 g]/TiO2 was completely removed after 27 and 30 hours by the photo-Fenton and photocatalytic activities, respectively. The synergistic effect gained from the combined photo-Fenton and photocatalytic activities of Fe3O4 and TiO2, respectively, was credited for the performances of the MgAC-Fe3O4/TiO2 hybrid nanocomposites.

Evaluation of different quantification modes for a simple and reliable determination of Pb, Zn and Cd in soil suspensions by total reflection X-ray fluorescence spectrometry

Abstract: In view of the large number of soil analyses in environmental studies dealing with metal contamination, the use of simple, fast, sustainable and cost-effective methodologies is desired. In this sense, the role of total reflection X-ray fluorescence spectrometry (TXRF) has to be highlighted due to the possibility of direct analysis of solid suspensions without the need for a digestion process. Internal standardization is successfully used as a quantification approach in multielement TXRF analysis of liquid samples, including soil digests. However, its application for the analysis of soil suspensions is not always possible. In the present manuscript we found that although acceptable results were obtained for TXRF quantification by internal standardization when considering soil certified reference materials (recoveries: 80–120%), a systematic underestimation of the concentration values was found when using the same approach for real soil sample analysis (recoveries <70%). In view of these problems, we explored the possibilities of different quantification approaches, including external calibration, which can be used in combination with soil suspension preparation and TXRF analysis to obtain reliable results for metal determination in soils. Data obtained showed that the best strategy was the use of internal standardization with correction of the TXRF results using a calibration curve obtained in the analysis of a set of soil samples with a matrix similar to the unknown ones by using a reference technique (digestion and ICP-OES analysis). With this analytical approach quantitative results were obtained for all the studied metals with recovery values around 95%. As a study case, the proposed TXRF method has been applied for the specific determination of Pb, Zn and Cd concentrations in soils from an abandoned metal mining area but the developed methodology could be extended to other environmental studies dealing with the determination of other metals and soil types. Taking into account the selectivity and sensitivity limitations when determining high Z elements such as Cd using TXRF systems equipped with Mo X-ray tubes, we compare the analytical performance of TXRF systems with different sources (Mo and W) as well.

Non-Destructive Survey of Early Roman Copper-Alloy Brooches using Portable X-ray Fluorescence Spectrometry

Abstract: This paper argues that portable X-ray fluorescence spectrometry (pXRF) is a suitable elemental measurement technique to study the production of copper-alloy artefacts. However, rather than try to imitate the accuracy and precision of laboratory techniques, it is more beneficial to deploy it in a survey role, one that attempts to model chronological and geographical changes within large quantities of artefacts. To achieve this, it was investigated to what extent corrosion and the issues surrounding surface measurements affect the potential of this type of research. Analyses on early Roman period brooches gathered in the Nijmegen region of the Netherlands were subsequently compared with published data.

Heavy Metals in the Glass and Enamels of Consumer Container Bottles

Abstract: The glass and enameled decorations of bottles of alcoholic beverages sourced from retailers in the U.K. were analyzed by X-ray fluorescence spectrometry for various heavy metals. In the glass substrate, lead, cadmium, and chromium were present at concentrations up to about 1100, 1100, and 3000 μg g-1, respectively, but their environmental and health risks are deemed to be low significance. Of more concern from an environmental and, potentially, occupational exposure perspective are the concentrations and mobilities of Pb and Cd in the enamels of many bottles. Thus, Pb concentrations up to about 100000 μg g-1 were found on the decor of various wine bottles and a beer bottle, and Cd concentrations of up to 20000 μg g-1 were measured in the decorated regions on a range of spirits, beer, and wine bottles. Moreover, maximum concentrations that leached from enameled glass fragments according to a standard test that simulates water and other liquids percolating through a landfill were about 1200 and 3200 μg L-1 for Pb and Cd, respectively, with several fragments exceeding the U.S. Model Toxins in Packaging Legislation and, therefore, defined as "hazardous". Given that safer decorative alternatives are available and that a precautionary principle should be adopted for toxic heavy metals, the pervasive use of Pb and Cd in the enamels of consumer bottles is brought into question.

Synthesis of fluorescent di-dansyl substituted ethoxy compound: A selective sensor for antimony and thallium metals detection

Abstract: Fluorescence assays have been widely engaged to assess the affinity of metallic ions. Dansyl chloride or 5-(dimethyl amino)-naphthalene-1-sulfonyl chloride is considered to be the reagent having potential to react with amino groups to yield stable sulfonamide adducts. A fluorescent sensor associated with crown ether moiety could have a potential to be developed as metal ions radar; cations, anions and other biological moieties. This can be further employed to observe relevant biotic processes. The reaction of dansyl sulfonyl chloride with di-ethoxy amine 1 chain in presence of potassium carbonate base resulted in a formation of compound 2. No change was observed on addition of aliquots of anions with compound 2. However, cation binding studies was performed using the series of metallic cations of constant concentration and its influence on a series of cations has been monitored using fluorescence spectrometry. This has been recorded that highest quenching effect was observed for antimony (Sb) and thallium (Tl) while other anions and cations were having no effect. The fluorescent compound 2 was further confirmed with proton-nuclear magnetic resonance (1H NMR) spectroscopy, 13C NMR spectroscopy and ultra violet spectroscopy. It has been concluded that compound 2 is very much selective for the detection of toxic metals like antimony (Sb) and thallium (Tl) even at parts per billion (ppb) levels. This study could be considered as a contemporary development in design and applications of fluorescent investigations containing crown ethers.

AIE Fluorescent Gelators with Thermo-, Mechano-, and Vapochromic Properties

Abstract: A series of aggregation-induced emission (AIE) fluorescent gelators (TPE-Cn -Chol) were synthesized by attaching tetraphenylethylene (TPE) to cholesterol through an alkyl chain. The properties of the gel, nano-/microaggregate, and condensed phases were studied carefully. TPE-Cn -Chol molecules form AIE fluorescent gels in acetone and in DMF. Their fluorescence can be reversibly switched between the "on" and "off" states by a gel-sol phase transition upon thermal treatment. The AIE properties of aggregated nano-/microstructures in acetone/water mixtures with different water fractions were studied by using fluorescence spectrometry and scanning electron microscopy (SEM). In different acetone/water mixtures, the TPE-Cn -Chol molecules formed different nano-/microaggregates, such as rodlike crystallites and spherical nanoparticles that showed different fluorescence colors. Finally, the condensed phase behavior of TPE-Cn -Chol was studied by using polarizing microscopy (POM), differential scanning calorimetry (DSC), fluorescence spectrometry, fluorescence optical microscopy, and wide-angle X ray scattering (WAXS). The clover-shaped TPE unit introduced into the rodlike cholesterol mesogen inhibits not only the formation of a liquid-crystal phase but also recrystallization upon cooling from the isotropic liquid phase. Very interestingly, TPE-Cn -Chol molecules in the condensed state change their fluorescence color under external stimuli, such as melting, grinding, and solvent fuming. The phase transition is the origin of these thermo-, mechano-, and vapochromic properties. These findings offer a simple and interesting platform for the creation of multistimuli-responsive fluorescent sensors.