Showing papers on "Fluorescence spectrometry published in 2020"

Solid sampling: advantages and challenges for chemical element determination—a critical review

Abstract: In recent decades, direct solid sample analysis has been reported in the literature as an alternative to traditional methods of sample preparation, becoming well established in the atomic spectrometry field. Therefore, this review discusses recent advances in different techniques such as flame atomic absorption spectrometry, graphite furnace atomic absorption spectrometry, high-resolution continuum source graphite furnace atomic absorption spectrometry, electrothermal vaporization, laser ablation, laser-induced breakdown spectroscopy, X-ray fluorescence spectrometry, glow discharge optical emission and mass spectrometry and arc/spark optical emission spectrometry, which are the most commonly used techniques for solid sample analysis. New possibilities such as nonmetal detection through molecular emission or absorption signals, speciation analysis, portable instrumentation for in situ analysis, and surface elemental mapping for obtaining chemical imaging will be discussed. Aspects associated with advantages and limitations are presented, relating the main instrumental advances to the expansion of the methods developed in this subject, pointing out the potential ability to overcome spectral interference and matrix effects through the development of calibration strategies to achieve the success of solid sampling in several application areas.

Synthesis of N, Zn-doped carbon dots for the detection of Fe3+ ions and bactericidal activity against Escherichia coli and Staphylococcus aureus.

Abstract: A simple and one-step microwave digestion method was utilized to synthesize the highly photoluminescent glucosamine derived nitrogen and zinc doped carbon dots (N, Zn-CDs) with a bluish-green luminescence property. The synthesized N, Zn-CDs inherited a good photoluminescence property with a quantum yield of 74% and which were characterized by XPS, XRD, TEM, FT-IR, UV–Vis, and fluorescence spectrometry. More importantly, N, Zn-CDs served as a fluorescence sensor for the detection of Fe3+ ions, under optimal conditions, a good linear relationship was established in the concentration range of 0.25–125 μM. Also, the experimental results showed the detection limit of N, Zn-CDs against Fe3+ was 0.15 μM, this could be a promising assay for sensing Fe3+ ions. Also, the role of zinc doping was explored by conducting the detection under similar experimental conditions in the absence of zinc, and reports revealed that the reason for high photoluminescence was due to the zinc doping. Along with the sensing application, our group had investigated the bactericidal property of synthesized N, Zn-CDs against gram-negative (Escherichia coli), and gram-positive pathogens (Staphylococcus aureus). N, Zn-CDs displayed good bactericidal activity against both pathogens under light conditions, but Escherichia coli, even under the dark condition proved its activity. Besides, the morphology of both the strains was displayed before and after the treatment via a scanning electron microscopic images. Also, a plausible mechanism for bactericidal activity was also explained. The reported synthesis method could provide a novel approach for the design of high photoluminescent N, Zn–CDs with good sensing and bactericidal property towards Fe3+ ions, gram-negative and positive bacterial strains.

Flavin Mononucleotide as a Biomarker of Organ Quality-A Pilot Study.

Abstract: Background Flavin mononucleotide (FMN), released from damaged mitochondrial complex I during hypothermic liver perfusion, has been shown to be predictive of 90-day graft loss. Normothermic machine perfusion (NMP) and normothermic regional perfusion (NRP) are used for organ reconditioning and quality assessment before transplantation. This pilot study aimed to investigate the changes of FMN levels during normothermic reperfusion of kidneys, livers, and lungs and examine whether FMN could serve as a biomarker to predict posttransplant allograft quality. Methods FMN concentrations, in perfusates collected during NMP of kidneys, abdominal NRP, and ex vivo lung perfusion, were measured using fluorescence spectrometry and correlated to the available perfusion parameters and clinical outcomes. Results Among 7 transplanted kidneys out of the 11 kidneys that underwent NMP, FMN levels at 60 minutes of NMP were significantly higher in the allografts that developed delayed graft function and primary nonfunction (P = 0.02). Fifteen livers from 23 circulatory death donors that underwent NRP were deemed suitable for transplantation. Their FMN levels at 30 minutes of NRP were significantly lower than those not procured for transplantation (P = 0.004). In contrast, little FMN was released during the 8 lung perfusions. Conclusions This proof of concept study suggested that FMN in the perfusates of kidney NMP has the potential to predict posttransplant renal function, whereas FMN at 30 minutes of NRP predicts whether a liver would be accepted for transplantation. More work is required to validate the role of FMN as a putative biomarker to facilitate safe and reliable decision-making before embarking on transplantation.

Zn(II)/Cd(II)-based metal–organic frameworks: crystal structures, Ln(III)-functionalized luminescence and chemical sensing of dichloroaniline as a pesticide biomarker

Abstract: Mixing transition metal(II) salts with 3,5-di(2,4-dicarboxylphenyl)pyridine (H4pdda), 4,4′-bipyridine (4,4’-bpy) and 1H-tetrazole (HTz) led to the complexes [Zn2(pdda)H2O] (1), [Zn2(pdda)(bpy)0.5] (2), {[NH2(CH3)2]2·[Cd3(pdda)2(H2O)2]}n (3), and {[NH2(CH3)2]4·[Cd6(pdda)4(HTz)1.5(H2O)6]·3/4DMF·7/2H2O}n (4) ([NH2(CH3)2]+ = dimethylammonium cation, DMF = N,N′-dimethylformamide). These complexes were characterized by single-crystal X-ray diffraction. 1 possesses a dense 3D framework consisting of 2Zn dimer-linear chains and Zn2-pdda-Zn1-COO− helices involving {Zn1O3N} and {Zn2O5} polyhedra. 2 exhibits an open 3D framework with paddle-like binuclear Zn2(CO2)4 units, in which bpy as a brace bridges two units to support and segment the rhombus pores. 3 shows a grid-like 3D anionic framework constructed by pdda ligands and Cd3(μ2-OH2)2(CO2)4 units. 4 features a racemic 3D anionic framework with two kinds of chiral nanotube-like channels. The progressive structure variations from dense (1) to open frameworks (2, 3 and 4) are discussed systematically. These complexes exhibit different thermostabilities and chemical stabilities, and 4 shows single-crystal to single-crystal (SC–SC) phase transition in pure water. Moreover, Ln(III)-functionalized MOF hybrids, Ln(III)@4, are first fabricated by straightforward cation-exchange modification to replace [NH2(CH3)2]+ ions in channels of 4 with Ln(III) ions. These hybrids reveal notable and selective luminous sensitization of 4 to Tb(III) ions. Significantly, the Tb(III)@4 hybrid as a promising sensor has been proved for the first time to possess the potential of practical detection of biomarker dichloroanilines via multiple quenching mechanisms, and for the first time the detection of urinary dichloroanilines through fluorescence spectrometry based on a Ln-MOF sensor has been realized.

Cd-Based Metal-Organic Framework Containing Uncoordinated Carbonyl Groups as Lanthanide Postsynthetic Modification Sites and Chemical Sensing of Diphenyl Phosphate as a Flame-Retardant Biomarker.

Abstract: With the judicious selection of an appropriate semirigid polycarboxylate, 2,5-bis(3',5'-dicarboxylphenyl)benzoic acid (H5bdba), and an inorganic metal ion, a novel anionic framework, {[NH2(CH3)2]2·[Cd3.5(bdba)(Hbdba)(H2O)1.5]}n (Cd-MOF), has been synthesized solvothermally. Single-crystal measurement results show that the prepared Cd-MOF features a three-dimensional structure containing two types of one-dimensional channels, and as we expected, there exist accessible uncoordinated -COOH groups on Hbdba pointing toward the rhombus channels. Powder X-ray diffraction and thermogravimetric analysis measurements were performed for the thermal and chemical stability analysis of Cd-MOF. In addition, the lanthanide(III)-functionalized hybrids, Ln(III)@Cd-MOF, were initially prepared by coordinated postsynthetic modification to incorporate luminescent Ln(III) ions into the structure. The luminescence properties of the hybrids are studied, and the results show notable and specialized fluorescent sensitization of Cd-MOF to Tb(III) ions. Moreover, the Tb(III)@Cd-MOF hybrid with outstanding fluorescence properties was developed as a highly sensitive and selective luminescent probe for the biomarker diphenyl phosphate (DPP) based on multiquenching effects. Tb(III)@Cd-MOF is the first case to realize the detection of urinary DPP through lanthanide metal-organic framework fluorescence spectrometry and shows practical detection potential.

Ecological assessment of heavy metals in soil around a coal-fired thermal power plant in Turkey

Abstract: In this study, heavy metal concentrations in agricultural surface soil (0–5 cm) samples collected from the area around the Kangal lignite-fired thermal power plant were determined using energy-dispersive X-ray fluorescence spectrometry. Also, the pH values of agricultural soil samples were measured to assess the level of acidification. Geo-accumulation index (Igeo), enrichment factor (EF), contamination factor (CF), contamination degree (CD), modified contamination degree (mCD), and pollution load index (IPL) were estimated to assess the heavy metals pollution in soil samples. The average concentration of Fe, Ti, Mn, Cr, Ni, Zn, Zr, Co, Cu, Pb, As, Sn and Hg was found as 39,065 ± 5096, 2262 ± 738, 721 ± 119, 713 ± 236, 610 ± 199, 82 ± 37, 65 ± 26, 64 ± 19, 29 ± 3, 17 ± 7, 9 ± 7, 3 ± 1 and 2 ± 1 mg kg−1, respectively. The values of pH varied from 7.5 to 8.2 with an average value of 8.0 (moderately alkaline). The Igeo, EF and CF results reveal that the study area is heavily or very highly contaminated with Cr, Ni, and Hg. On the basis of the IPL value, the soil samples are polluted with heavy metals. However, the mCD indicates moderate heavy-metal contamination of the soil samples.

Thermal behaviour of metakaolin–bauxite blends geopolymer: microstructure and mechanical properties

Abstract: This paper investigates the use of bauxite widely available in northern Cameroon as an additive in the optimization of some properties of metakaolin-based geopolymer. To do this, several geopolymer mixtures were prepared by substituting metakaolin (MK) by bauxite (BA) (from 0 to 50%) and partially kept at room temperature (28 °C), while others were sintered at 200, 800 and 1200 °C. The raw materials and resulting products were characterized using X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), densification parameters, mechanical properties as well as microstructural morphologies. The results revealed that the setting time of the geopolymer pastes increased with the bauxite content due to its low dissolution in alkaline medium at room temperature. The mechanical strength of samples decreased from 35.20 to 11.10 MPa at room temperature. At 1200 °C, the higher strengths (50, 98 and 70 MPa) were achieved in MKBA10, MKBA20 and MKBA30, respectively. These samples also exhibited dense and compact microstructure partially due to packing particles effect and the nature of bauxite known as refractory material. Thermal shrinkage and relatively high mass losses reflected the decomposition of chemical compounds within the system. Thus, the synthesized materials heated at 1200 °C could be used as a potential candidate for refractory applications.

Non-Invasive On-Site Raman Study of Pigments and Glassy Matrix of 17th–18th Century Painted Enamelled Chinese Metal Wares: Comparison with French Enamelling Technology

Abstract: A selection of 10 Chinese enamelled metal wares dating from the 17th–18th centuries (Qing Dynasty) was analysed on-site by mobile Raman microspectroscopy. These wares display cloisonne and/or painted enamels and belong to the collections of Musee du Louvre in Paris and Musee Chinois at the Fontainebleau Castle in France. Pigments (Naples yellow lead pyrochlore, hematite, manganese oxide etc.), opacifiers (fluorite, lead arsenates) and corresponding lead-based glassy matrices were identified. One artefact was also analysed by portable X-ray fluorescence spectrometry (pXRF) in order to confirm the Raman data. In some of these metal wares, it is suggested that cassiterite was unpredictably used as an opacifier in some parts of the decor. The results are compared to previous data obtained on Chinese cloisonne and Limoges enamels as well as recent data recorded on painted enamelled porcelains of the Qing Dynasty. Lead arsenate apatite detected in some of the 17th–18th century blue enamelled decors is related to the use of arsenic-rich European cobalt ores, as also characterized in French soft-paste porcelain and glass decors and high-quality Limoges enamels for the same period. However, lead arsenate could then also have been deliberately used for white opacification. The specific Raman signature displaying the shape of the Raman scattering background indicates the presence of colloidal gold (Au° nanoparticles) in red to violet enamelled and cloisonne areas. At least three types of Naples yellow lead pyrochlore pigments identified with Sb-rich, Sn-rich and mixed Sb–Sn–(Zn, Fe?) compositions prove the use of European pigments/recipes.

Visualising Silicon in Plants: Histochemistry, Silica Sculptures and Elemental Imaging

Abstract: Silicon is a non-essential element for plants and is available in biota as silicic acid. Its presence has been associated with a general improvement of plant vigour and response to exogenous stresses. Plants accumulate silicon in their tissues as amorphous silica and cell walls are preferential sites. While several papers have been published on the mitigatory effects that silicon has on plants under stress, there has been less research on imaging silicon in plant tissues. Imaging offers important complementary results to molecular data, since it provides spatial information. Herein, the focus is on histochemistry coupled to optical microscopy, fluorescence and scanning electron microscopy of microwave acid extracted plant silica, techniques based on particle-induced X-ray emission, X-ray fluorescence spectrometry and mass spectrometry imaging (NanoSIMS). Sample preparation procedures will not be discussed in detail, as several reviews have already treated this subject extensively. We focus instead on the information that each technique provides by offering, for each imaging approach, examples from both silicifiers (giant horsetail and rice) and non-accumulators (Cannabis sativa L.).

Rapid in situ measurements of algal cell concentrations using an artificial neural network and single-excitation fluorescence spectrometry

Abstract: Accurate measurements of the algal cell concentration are very important in microalgae culturing and ecological monitoring. To realize an automatic, in situ measurement of the cell concentration of microalgae and to reduce the measurement cost, a detection method combining single-excitation fluorescence spectroscopy and an artificial neural network (ANN) was developed to monitor the cell concentrations of Chlamydomonas reinhardtii in the range of 2 × 105 to 6.4 × 106 mL−1 cells mL−1. Using a 470 nm wavelength light emitting diode (LED) as a light source, samples with different concentrations of Chlamydomonas reinhardtii were electronically excited. The measured fluorescence emission spectra were used as input, and the algal cell concentration was the output. Because there is a nonlinear relationship between the input and the output, a Back Propagation Neural Network Model Optimized by Genetic Algorithms (GA-BP) was established to predict the cell concentration. Then the model was validated by using samples from different growth batches. In addition, the GA-BP model was compared with the existing algae cell concentration detection methods (Back Propagation Artificial Neural Network), and it was found that the GA-BP model was more accurate. Moreover, the equipment used for this method is simple and easy to carry and install. The combination of single-excitation fluorescence spectrometry and an artificial neural network provides a feasible and cost-effective tool for algal cell concentration monitoring.

Effect of aluminum modification of rice straw–based biochar on arsenate adsorption

Abstract: To evaluate the adsorption capacity of aluminum-modified biochars for arsenate (As(V)) and the effect of the biochars on As(V) adsorption by acidic Ultisols. Rice straw was collected from Yingtan, Jiangxi Province. Rice straw and the biochar derived from rice straw were both treated with aluminum (Al) to prepare two kinds of Al-modified biochars. An Ultisol was collected from Jinxian, Jiangxi Province, and an indoor incubation was used to prepare biochar-ameliorated soil. Zeta potential and Fourier transform infrared spectroscopy (FTIR) were used to characterize the effects of Al modification on surface charge and functional groups of the biochars. The batch method was used to investigate the adsorption and desorption of As(V) by the biochars and the soil. Arsenic in equilibrium solution was determined using hydride generation–atomic fluorescence spectrometry. The yield of biochar derived from Al-treated rice straw was significantly greater than that of the biochar from untreated rice straw. The Al content of Al-treated biochar from rice straw was higher than that of biochar derived from Al-treated rice straw. Modification did not change the morphology of Al oxide on biochar. Zeta potential of the two modified biochars changed to a positive value compared with that of unmodified biochar, and more change in zeta potential was observed for the Al-treated biochar from rice straw than that of biochar derived from Al-treated rice straw. After As(V) was adsorbed by the two modified biochars, new absorption peaks were found in the FTIR spectra from the biochars at 892 cm−1 (biochar from Al-treated rice straw) and 884 cm−1 (Al-treated biochar from rice straw). The peaks suggested that a chemical bond was formed between As(V) and Al on biochars during As(V) adsorption. The two Al-modified biochars adsorbed much more As(V) than the unmodified biochar. The desorption of adsorbed As(V) in the modified biochars was very low, which indicated that specific adsorption was the dominant mechanism for As(V) adsorption. The addition of modified biochar promoted the adsorption of As(V) by the Ultisol. Moreover, Al-treated biochar from rice straw enhanced As(V) adsorption by the soil more than the biochar derived from Al-treated rice straw. Compared with the effect of adding unmodified biochar, adding either of the two Al-modified biochars significantly enhanced the adsorption of As(V) by the Ultisol. Therefore, Al-modified biochar can be used to immobilize As(V) in arsenic-contaminated soils, especially in acidic soils.

Redefinition of the Ligurian Units at the Alps–Apennines junction (NW Italy) and their role in the evolution of the Ligurian accretionary wedge: constraints from mélanges and broken formations

Abstract: We document that the undifferentiated chaotic Ligurian Units of the Monferrato–Torino Hill sector (MO-TH) at the Alps–Apennines junction consist of three different units that are comparable with the Cassio, Caio and Sporno Units of the External Ligurian Units of the Northern Apennines. Their internal stratigraphy reflects the character of units deposited in an ocean–continent transition (OCT) zone between the northwestern termination of the Ligurian–Piedmont oceanic basin and the thinned passive margin of Adria microcontinent. The inherited wedge-shaped architecture of this OCT, which gradually closed toward the north in the present-day Canavese Zone, controlled the Late Cretaceous–early Eocene flysch deposition at the trench of the External Ligurian accretionary wedge during the oblique subduction. This favoured the formation of an accretionary wedge increasing in thickness and elevation toward the SE, from the MO-TH to the Emilia Northern Apennines. Our results therefore provide significant information on both the palaeogeographical reconstruction of the northwestern termination of the Ligurian–Piedmont oceanic basin and the role played by inherited along-strike variations (stratigraphy, structural architecture and morphology) of OCT zones in controlling subduction–accretionary processes. Supplementary material: A spreadsheet with X-ray fluorescence spectrometry and inductively coupled plasma mass spectrometry whole-rock major and trace element composition of mantle peridotites, and photomicrographs of mantle peridotites are available at https://doi.org/10.6084/m9.figshare.c.4519643

Cobalt ion-enhanced photochemical vapor generation in a mixed acid medium for sensitive detection of tellurium(IV) by atomic fluorescence spectrometry

Abstract: A method of cobalt ion assisted enhancement of photochemical vapor generation-atomic fluorescence spectrometry (PVG-AFS) was proposed for sensitive determination of ultratrace tellurium(IV). With a mixture of 5% (v/v) formic acid and 20% (v/v) acetic acid as the reaction medium, more than 13-fold improvement in AFS intensity for Te(IV) was achieved simply by adding 1 mg L−1 Co2+ as a homogeneous catalyst. A possible reaction mechanism was proposed with the characterization results of GC-MS and electron paramagnetic resonance (EPR). Under optimal conditions, the limit of detection (LOD) for Te(IV) was 0.06 μg L−1, with a relative standard deviation (RSD) of 1.3% (10 μg L−1 Te, 7 times). The accuracy and utility of this methodology were validated by analysis of real water samples, with satisfactory recoveries of 91–108%.

Combination of Immunomagnetic Separation with Aptamer-Mediated Double Rolling Circle Amplification for Highly Sensitive Circulating Tumor Cell Detection.

Abstract: Breast cancer is the most frequently diagnosed cancer among women, and the circulating tumor cell (CTC)-meditated distant metastasis is the leading cause of death. Thus, the detection of CTCs is of great importance for the early diagnosis of breast cancer and the prevention of metastasis. In this study, using human breast carcinoma BT474 cells as the model CTCs, a powerful assay platform is demonstrated by fluorescence spectrometry for the highly sensitive CTC detection by combining the dual-recognizing elements receptor-binding antibody and aptamer-mediated separation with double rolling circle amplification reactions (d-RCA, including RCA1 and RCA2). The aptamer-inserted RCA1 product (RCA1-p) exhibits the considerably improved affinity towards target cells originating from the multivalent binding effect. The immunomagnetic separation removes nontarget cells coexisting in complex biological milieu, while the centrifugal separation of cells/DNAs mixture eliminates the excess probes, thereby circumventing the unwanted interferences. The fluorescence spectrometric results show that a 34-fold enhanced fluorescence signal is achieved upon BT474 cells, and the target cells can be quantitatively detected down to 9 cells/200 μL with the linear range of five orders of magnitude, indicating a significantly enhanced detection performance. Even if BT474 cells are spiked in the fresh whole blood, no obvious fluctuation in the fluorescence signal is detected, demonstrating that the newly developed d-RCA assay system is suitable for screening CTCs in complex environments and is expected to be a promising tool for estimating distant metastasis and predicting the recurrence of tumors.