Surface‐enhanced Raman scattering (SERS) has become a mature vibrational spectroscopic technique during the last decades and the number of applications in the chemical, material, and in particular ...life sciences is rapidly increasing. This Review explains the basic theory of SERS in a brief tutorial and—based on original results from recent research—summarizes fundamental aspects necessary for understanding SERS and provides examples for the preparation of plasmonic nanostructures for SERS. Chemical applications of SERS are the centerpiece of this Review. They cover a broad range of topics such as catalysis and spectroelectrochemistry, single‐molecule detection, and (bio)analytical chemistry.
Expanding vibrational spectroscopy: Since its first observation in 1973, surface‐enhanced Raman scattering (SERS) has developed into a mature vibrational spectroscopic technique. The number of applications in chemistry as well as the material and life sciences is increasing rapidly. This Review summarizes the key concepts behind SERS and provides an overview of current applications in chemistry.
Conventional soil chemical analyses are time-consuming and laboratory-based. Spectroscopic techniques have been introduced to make soil measurements more rapid and cost-effective. While portable ...X-ray fluorescence spectrometry (pXRF) has been increasingly adopted for advanced soil analysis in temperate regions, comparatively few applications have been developed for tropical soils. Using PXRF, soil total elemental composition can be obtained in seconds, with properties inferred from the collected data. In the present study, pXRF was used to screen samples (n = 252) from tropical Cerrado agricultural areas under different land uses in Brazil. The objective was to determine the total elemental composition of soil samples and predict soil fertility properties using simple or multiple linear regression with pXRF data as a proxy. Air-dried and sieved soil samples (<2 mm) under laboratory conditions were screened using a pXRF, then compared to soil chemical characterization by conventional methods. pXRF data properly corroborated the known soil mineralogy and geochemical background of Cerrado soils. Based exclusively on pXRF data, clay content was successfully predicted. Also, soil organic matter and plant-available forms of Ca, Mn and Cu were reasonably predicted from pXRF results.
•Cerrado agricultural soils chemically characterized by proximal sensor.•Clay content can be accurately predicted by pXRF.•pXRF data elucidate soil mineralogy and geochemistry of Cerrado soils.•Several plant-available elements were successfully predicted by pXRF.•252 highly weathered Cerrado soils of Brazil were evaluated.
This review covers the current and emerging analytical methods used in laboratory, field, landscape and regional contexts for measuring soil organic carbon (SOC) sequestration in agricultural soil. ...Soil depth plays an important role in estimating SOC sequestration. Selecting appropriate sampling design, depth of soil, use of proper analytical methods and base line selection are prerequisites for estimating accurately the soil carbon stocks. Traditional methods of wet digestion and dry combustion (DC) are extensively used for routine laboratory analysis; the latter is considered to be the “gold standard” and superior to the former for routine laboratory analysis. Recent spectroscopic techniques can measure SOC stocks in laboratory and in-situ even up to a deeper depth. Aerial spectroscopy using multispectral and/or hyperspectral sensors located on aircraft, unmanned aerial vehicles (UAVs) or satellite platforms can measure surface soil organic carbon. Although these techniques' current precision is low, the next generation hyperspectral sensor with improved signal noise ratio will further improve the accuracy of prediction. At the ecosystem level, carbon balance can be estimated directly using the eddy-covariance approach and indirectly by employing agricultural life cycle analysis (LCA). These methods have tremendous potential for estimating SOC. Irrespective of old or new approaches, depending on the resources and research needed, they occupy a unique place in soil carbon and climate research. This paper highlights the overview, potential limitations of various scale-dependent techniques for measuring SOC sequestration in agricultural soil.
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•Methodologies for the measurement of soil carbon sequestration at point, field, ecosystem and regional level reviewed.•Recent developments in spectroscopic techniques are discussed.•Eddy-covariance and indirectly LCA methodological approaches are reviewed.•Methodological potentials and uncertainties of soil carbon research sequestration are highlighted.
Microplastic in Aquatic Ecosystems Ivleva, Natalia P.; Wiesheu, Alexandra C.; Niessner, Reinhard
Angewandte Chemie International Edition,
February 6, 2017, Letnik:
56, Številka:
7
Journal Article
Recenzirano
The contamination of marine and freshwater ecosystems with plastic, and especially with microplastic (MP), is a global ecological problem of increasing scientific concern. This has stimulated a great ...deal of research on the occurrence of MP, interaction of MP with chemical pollutants, the uptake of MP by aquatic organisms, and the resulting (negative) impact of MP. Herein, we review the major issues of MP in aquatic environments, with the principal aims 1) to characterize the methods applied for MP analysis (including sampling, processing, identification and quantification), indicate the most reliable techniques, and discuss the required further improvements; 2) to estimate the abundance of MP in marine/freshwater ecosystems and clarify the problems that hamper the comparability of such results; and 3) to summarize the existing literature on the uptake of MP by living organisms. Finally, we identify knowledge gaps, suggest possible strategies to assess environmental risks arising from MP, and discuss prospects to minimize MP abundance in aquatic ecosystems.
Something in the water: The contamination of aquatic ecosystems with microplastic (MP) is an ecological problem of increasing concern. Since the MP cannot be effectively removed, the risks it poses must be properly evaluated and strategies developed to minimize environmental damage. This Review summarizes the current state of research in the field and discusses potential strategies for improving the evaluation of MP in aquatic ecosystems and reducing MP pollution.
Many proteins bind transition metal ions as cofactors to carry out their biological functions. Despite binding affinities for divalent transition metal ions being predominantly dictated by the ...Irving-Williams series for wild-type proteins, in vivo metal ion binding specificity is ensured by intracellular mechanisms that regulate free metal ion concentrations. However, a growing area of biotechnology research considers the use of metal-binding proteins in vitro to purify specific metal ions from wastewater, where specificity is dictated by the protein's metal binding affinities. A goal of metalloprotein engineering is to modulate these affinities to improve a protein's specificity towards a particular metal; however, the quantitative relationship between the affinities and the equilibrium metal-bound protein fractions depends on the underlying binding mechanisms. Here we demonstrate a high-throughput intrinsic tryptophan fluorescence quenching method to validate binding models in multi-metal solutions for CcNikZ-II, a nickel-binding protein from Clostridium carboxidivorans. Using our validated models, we quantify the relationship between binding affinity and specificity in different classes of metal-binding models for CcNikZ-II. We further illustrate the potential relevance of data-informed models to predicting engineering targets for improved specificity.
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•We demonstrate a general microplate-based intrinsic tryptophan quenching assay to validate kinetic models of metalloprotein binding competition in multi-metal solutions.•Our analysis reveals distinct binding competition mechanisms between NiII and CoII compared to NiII and ZnII.•Mathematical modelling suggests distinct design principles for improving metalloprotein specificity for different binding competition mechanisms.
Aminophenol dioxygenases (APDO) are mononuclear nonheme iron enzymes that utilize dioxygen (O2) to catalyze the conversion of o-aminophenols to 2-picolinic acid derivatives in metabolic pathways. ...This study describes the synthesis and O2 reactivity of two synthetic models of substrate-bound APDO: FeII(TpMe2)(tBu2APH) (1) and FeII(TpMe2)(tBuAPH) (2), where TpMe2 = hydrotris(3,5-dimethylpyrazole-1-yl)borate, tBu2APH = 4,6-di-tert-butyl-2-aminophenolate, and tBuAPH2 = 4-tert-butyl-2-aminophenolate. Both Fe(II) complexes behave as functional APDO mimics, as exposure to O2 results in oxidative CC bond cleavage of the o-aminophenolate ligand. The ring-cleaved products undergo spontaneous cyclization to give substituted 2-picolinic acids, as verified by 1H NMR spectroscopy, mass spectrometry, and X-ray crystallography. Reaction of the APDO models with O2 at low temperature reveals multiple intermediates, which were probed with UV–vis absorption, electron paramagnetic resonance (EPR), Mössbauer (MB), and resonance Raman (rRaman) spectroscopies. The most stable intermediate at −70 °C in THF exhibits multiple isotopically-sensitive features in rRaman samples prepared with 16O2 and 18O2, confirming incorporation of O2-derived atom(s) into its molecular structure. Insights into the geometric structures, electronic properties, and spectroscopic features of the observed intermediates were obtained from density functional theory (DFT) calculations. Although functional APDO models have been previously reported, this is the first time that an oxygenated ligand-based radical has been detected and spectroscopically characterized in the ring-cleaving mechanism of a relevant synthetic system.
Synopsis: Nonheme iron(II) complexes behave as functional models of aminophenol dioxygenases by reacting with O2 to yield oxygenated ring-cleaved products. The mechanism is explored by monitoring the reaction at reduced temperature to observe and trap reactive intermediates. Characterization with multiple spectroscopic techniques revealed that the most stable intermediate contains O2-derived atoms in its molecular structure. Display omitted
•Functional nonheme iron models of aminophenol dioxygenases are prepared and structually characterized.•The models replicate the enzymatic reaction by yielding oxidized ring-cleaved products in the presence of O2.•Intermediates of relevance to enzymatic catalysis are interrogated with multiple spectroscopic techniques.
Convenient one-pot synthetic route for the fabrication of carbon dots (CDs) from Tagetes erecta flower (TEF), named as “TEF-CDs’, through solvo(hydro)-thermal carbonization of the TEF was developed. ...The TEF-CDs revealed high selectivity towards chlorpyrifos and quinalphos, acting as a fluorescent probe. The CDs synthesized from T. erecta flower showed a strong blue color at 495 nm when excited at 420 nm, along with the exhibition of a strong quantum yield of 63.7%. The synthesized CDs revealed their richness in the surface-active organic group that synthesized CDs from T. erecta flower are mainly comprised of C, O, and N, which were crystalline in structure that was revealed by TEM image and XRD spectra. Furthermore, when the probe was exposed to different pH conditions, no major noticeable changes were recorded. Moreover, when the probe was exposed to chlorpyrifos and quinalphos, we have noticed that fluorescence spectra was turned off when the probe was exposed to chlorpyrifos and “turned on” after the exposure quinalphos. Moreover, fluorescence spectral changes showed a good linearity with chlorpyrifos and quinalphos concentrations in the range of 0.05–100.0 μM for chlorpyrifos and 0.01–50.0 μM for quinalphos. The limit of detection are 2.1 ng mL−1 and 1.7 ng mL−1 for chlorpyrifos and quinalphos, respectively. Finally, the TEF-CDs-based fluorescent nanoprobe was successfully applied to estimate chlorpyrifos and quinalphos with an effective accuracy in rice and fruit samples with rapid detection time.
Carbon dots were synthesized from Tagetes erecta flower content with solvo(hydro)thermal procedure which further emits blue-color emission under UV light at 365 nm. Further quenching was observed upon the addition of chlorpyrifos, and signal enhancement in fluorescence spectra was recorded upon the addition of quinalphos. Display omitted
•Carbon dots (CDs) were synthesized using Tagetes erecta flower named as TEF-CDs.•Quantum yield of TEF-CDs was measured to be 63.7% without any modifications.•Detection of chlorpyrifos and quinalphos forward through fluorescence spectra.•Limits of detection with 2.1 ng mL−1 and 1.7 ng mL−1.•Highly selective and sensitive TEF-CDs towards twain pesticides without interference.
•Synthesis and crystal structure of five new coordination compounds with rare earth metal ions.•Investigation of the spectroscopic properties of the synthesized coordination compounds.•Hirshfeld ...surface analysis and investigation of intermolecular interactions in the structure of the synthesized compounds.
Under reflux condition five new lanthanide coordination compounds, Pr(L)2(NO3)3(CH3OH) (1), Sm(L)2(NO3)3(CH3OH) (2), Gd(L)2(NO3)3(CH3OH) (3), Dy(L)2(NO3)3(CH3OH) (4) and Ho(L)2(NO3)3(CH3OH) (5), were synthesized in methanol where L is the Schiff base ligand prepared from the reaction of 4-aminoantipyrine and 5-bromosalicylaldehyde. Elemental analysis, FT-IR, UV/Vis and photoluminescence spectroscopic methods and single crystal X-ray analysis were used to investigate the crystal structure and properties of the synthesized compounds. Using X-ray analysis, it was found that all crystals are isomorphous and the Ln ion (Ln = Pr, Sm, Gd, Dy and Ho) in all of the synthesized compounds is nine-coordinated and the geometry around them is slightly distorted tricapped trigonal prism. Six oxygen atoms are coordinated to the central lanthanide atom by three nitrate groups, one oxygen atom from the methanol group and two oxygen atoms of the Schiff base ligand (L) which create the LnO9 coordination environment. Intermolecular interactions and the distribution of these interactions in all of these crystals were calculated by Hirshfeld surface analysis using Crystal Explorer 17.5 software. The emission spectrum of these compounds was recorded and the obtained results showed that the intensity of peaks has differences and the emission spectrum of the complexes changes by changing the lanthanide ions.
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•Ellagic acid bound to α-LA in spectral and chromatographic analysis.•Ellagic acid exhibited stronger binding with α-LA in aromatic cluster Ⅱ than Ⅰ.•α-LA could protect ellagic acid ...to improve its antioxidant activity.
Ellagic acid possesses numerous bioactivities such as antioxidant activity and anti-inflammatory effect. In this work, the binding interaction between ellagic acid and α-lactalbumin was investigated by multi-spectroscopy and the results suggested that ellagic acid could change the conformation of α-lactalbumin. Chromatographic analysis proved the interaction of α-lactalbumin with ellagic acid taken place in less than 30 min and this interaction was stable. Computer simulations showed that both aromatic clusters Ⅰ and Ⅱ of α-lactalbumin were active sites for ellagic acid. Interestingly, both the results of molecular docking and molecular dynamics simulations suggested that ellagic acid tended to bind to aromatic cluster Ⅱ rather than aromatic cluster Ⅰ. Moreover, α-lactalbumin could enhance the antioxidant property of ellagic acid, indicating that the solubility of ellagic acid might be improved by combining α-lactalbumin. Overall, this work suggested that α-lactalbumin exhibited binding affinity for ellagic acid and enhanced its antioxidant property.
