Energy Dispersive X-ray Fluorescence Spectra Research Articles

Using laser ablation in liquid (LASIS) method to synthesize silver nanoparticles for SERS applications

In this work, colloid formation with laser ablation in distilled water was used to investigate the influence of ablation time and pulse repetition frequency in generating silver nanofluids. The nature (size and shape) of the nanoparticles were investigated using transmission electron microscopy (TEM) while the elemental composition of the generated nanoparticles was explored using energy-dispersive X-ray fluorescence (EDXRF). The EDXRF spectra confirmed the presence of silver as the dominant element in the nanofluid. TEM showed that the size of the generated nanoparticles varies with the concentration of silver based on the change in Laser ablation time (LAT) and the pulse repetition frequency (PRF). The localized surface plasmon resonance band of silver in the fluid was explored using UV–VIS with the absorption band observed at around 408 nm. The generated nanofluid was then used as a substrate in surface enhanced Raman spectroscopy (SERS). The conclusion drawn from this work is that the laser ablation time and pulse repetition rate can be modified to produce reproducible silver nanofluids for subsequent SERS applications.

Applications of the non-negative least-squares deconvolution method to analyze energy-dispersive x-ray fluorescence spectra.

We used the Monte Carlo simulation method to establish a detector response matrix and the non-negative least-squares method to deconvolute x-ray spectra. The simulation and experimental data verified the effectiveness of this method, and the influence of full-width at the half of the maximum calibration accuracy on the deconvolution results was investigated. The non-negative least-squares method had high accuracy and efficiency compared with others. The results showed that, except for Zn, the relative errors between the inversion and the standard values were less than 0.1% for the simulated spectra. For the experimental data, the relative errors were within 0.2%. The peaks with similar characteristic energies can be better distinguished in the deconvolution spectra, reducing the errors caused by overlapping peaks in subsequent analysis.

Interface engineered nanostructured phase formation at Se/In sites by Ag ion irradiation and its structural, optical and morphological behavior

Thermally evaporated Se/In bilayer films were irradiated by 120 MeV Ag ion at different fluences. Energy-dispersive X-ray fluorescence (EDXRF) spectra of the films showed the 1:2 ratio concentration of In and Se. After six months of preserving the films under ambient condition, four phases: In2Se3, In4Se3, In and Se developed in the films as revealed by Grazing incidence X-ray diffraction (GIXRD) study. The In4Se3 and In were completely insensitive to the irradiation while the other two phases (In2Se3 and Se) were completely amorphized at high ion fluences. The Poission fitting of the fluence dependence area under X-ray diffraction (XRD) peaks showed the radius of amorphized latent tracks along the path of 120 MeV Ag ions in In2Se3 and Se as 8.4 nm and 9.5 nm respectively. The lattice fringe images of High-resolution transmission electron microscopy (HRTEM) showed the presence of the four phases as observed by GIXRD study. The UV-visible study revealed the band gap reduction at the low fluence region from pristine to 3 × 1011ions cm−2 and increased at high fluence from 1 × 1012 ions cm-2 to 1 × 1013 ions cm-2. This variation of band gap may be due to the formation of localized states and annealing effect due to ion irradiation. Field emission scanning electron microscopy (FESEM) images showed the nano needle shaped structure formation at 1 × 1012 ions cm−2 which increased with ion fluences. The appearance of needle shaped structures may be due to the In2Se3 phase. The I-V study showed the excellent current response in mA range which enables the films for various electrical applications. The surface wettability study showed the hydrophobicity nature of the films which enables it for application in different coating materials.

Development and validation of energy dispersive x‐ray fluorescence method for quantification of cubic zirconia in diamond matrix

AbstractQualitative and quantitative tests of gemstones and diamonds are routinely performed nondestructively in the laboratory of Gemmological Institute of India (GII), Mumbai, India. Qualitative tests are based on microscopic examination. Energy Dispersive X‐Ray Fluorescence (EDXRF) spectrometry is used in the laboratory for quantitative analysis of elements. However, in some cases like determination of trace levels of cubic zirconia (CZ) in diamond powder, it is difficult to estimate simultaneously both CZ and diamond powder directly using EDXRF method. In view of this, a method was developed for estimation of ZrO2 present at low levels in diamond powder. In this method, EDXRF spectra of a series of simulated mixtures containing ZrO2 were measured. Peak areas under the characteristic Kα x‐ray of Zr (15.7 keV) in each mixture were computed and, a calibration plot was made between the peak areas and % fractions of ZrO2. From the calibration plot, a dynamic range of 0.1%–10% was obtained. From XRF spectra of the test sample, in duplicate, of diamond powder, Zr was estimated using the peak area and the percentage fraction was found to be 0.181 ± 0.020. Neutron activation analysis (NAA) was used for method validation with the same set of simulated samples used in EDXRF analysis. Results obtained by both the methods are found to be in good agreement and this newly developed method based on EDXRF spectrometry is in regular use in GII.

Energy-dispersive X-ray fluorescence combined with chemometric tools applied to tomato and sweet pepper classification

Consumers' interest in organic foods is increasing, and robust analytical tools are necessary to authenticate them. This study investigated the potential of Energy-Dispersive X-Ray Fluorescence (EDXRF) under two measurement conditions combined with chemometric tools to classify tomato and sweet pepper samples according to the agronomic production mode and geographical area cultivation. Initially, the Common Dimension Analysis (ComDim) was applied to 15 kV (Na–Sc) and 50 kV (Ti–U) EDXRF spectra to extract the common information generated by both spectral measurement conditions. According to the ComDim analysis, it was possible to verify that the data generated by both instrumental conditions are complementary. In contrast, it was impossible to cluster tomato or sweet pepper samples effectively according to the agronomic production mode or geographical origin. On the other hand, the junction between EDXRF data and Partial Least Squares with Discriminant Analysis (PLS-DA) proved to be a perfect match, reaching optimal prediction accuracy values for the classifications between 98.8 and 100.0%. These results suggest that EDXRF associated with chemometrics can be an excellent technique to verify the authenticity of tomato and sweet pepper. Besides, it does not require complex sample preparation steps and is fast and relatively inexpensive compared to some chromatographic or spectrometric analytical techniques.

Machine Learning Strategy for Improved Prediction of Micronutrient Concentrations in Soils of Taif Rose Farms Based on EDXRF Spectra

This study attempts to utilize newly developed machine learning techniques in order to develop a general prediction algorithm for agricultural soils in Saudi Arabia, specifically in the Taif region. Energy dispersive X-ray fluorescence (EDXRF) measurements were used to develop national predictive models that predict the concentrations of 14 micronutrients in soils of Taif rose farms, for providing high-quality data comparable to conventional methods. Machine learning algorithms used in this study included the simple linear model, the multivariate linear regression (MLR); and two nonlinear models, the random forest (RF) and multivariate adaptive regression splines (MARS). Our study proposes a machine learning (ML) strategy for predicting fertility parameters more accurately in agricultural soils using 10 farms of the Taif rose (Rosa damascena) in Taif, Saudi Arabia as a case study. Results demonstrated that MARS provides higher prediction performance when the number of explanatory variables is small, while RF is superior when the number of variables is large. On the other hand, the MLR is recommended as a moderate method for predicting multivariate variables. The study showed that multivariate models can be used to overwhelm the drawbacks of the EDXRF device, such as high detection limits and an element that cannot be directly measured.

Application of ED-XRF spectra for determination of macroelements in edible seaweeds

The application of an increased number of edible seaweeds in gastronomy requires accurate, rapid, and non-destructive mineral evaluation. In this work, energy dispersive X-ray fluorescence (ED-XRF) spectra were used to determine Ca, K, and P in edible green, red, and brown seaweeds from the Portuguese coasts. ED-XRF raw spectra of seaweed samples were correlated against results of conventional inductively coupled plasma-optical emission spectrometry (ICP-OES), by the full cross-validation partial least-square (CVPLS) regression method, with nonlinear iterative partial least squares (NIPALS) algorithm. The standard reference material (Thallus laminariae) was used for the validation of CVPLS. Statistical parameters, correlation coefficients (R2), root mean square errors (RMSE), and bias, were used for the assessment of the CVPLS method. For selected minerals, R2 was high (0.88–0.95), while RMSE values (< 1.02) and bias (0) were low, thus indicating a viable potential for their routine analysis by ED-XRF. These findings highlighted the quality of ED-XRF spectral data, which can be used for an efficient non-destructive determination of macroelements in edible seaweeds on a large food industrial scale.

Screening of uranium contamination on waste surfaces using X-ray fluorescence analysis

X-ray fluorescence (XRF) analysis is useful for detecting radionuclides with long half-lives, such as most isotopes of uranium (234U, 235U, and 238U), as the detection of uranium by radiation measurements can be difficult. Therefore, we propose energy dispersive X-ray fluorescence (EDXRF) analysis as a method for the rapid screening of pollution from substances that are contaminated with uranium-containing water droplets. Sealed uranium-containing filter paper, which was used as the contaminated area model, was layered on top of a rubber plate to simulate a rubber plate whose surface was contaminated with uranium. The measured EDXRF spectra revealed a U Lα peak at the tail of a strong Br Kβ peak, and the contribution of this U Lα peak was extracted by peak fitting. The obtained results suggested a linear relationship between the uranium concentration of the filter paper and the signal intensity of the U Lα peak. The proposed method is more sensitive than the α-particle counting method for long half-life radionuclides, and can be used at uranium handling facilities.

Thin thickness gilding determined by x‐rays ratios from EDXRF‐spectra

AbstractA by‐product of energy‐dispersive X‐ray fluorescence (EDXRF)‐analysis consists of using the ratios of selected X‐ray peaks to determine the thickness of multilayered objects. Three different methods were developed in the past, all because the two main K or L X‐lines from an EDXRF spectrum emitted by a chemical element have a distinct energy and are differently attenuated by an overlying layer. This specific subject has many papers dedicated, but only a few considerations were devoted to the limits of these methods, that is, the range, for example, of gold thickness that can be usefully determined by each method. This paper defines these limits in the specific case of thin gilding (with d &lt; 1 μm). Three typical situations were considered, and the following artefacts were studied: two artefacts on gilded lead, where the gold leaf is superimposed to a white lead pigment, both in the painting “La Fornarina” of Raphael, dated 1520 AD, and in the imperial carriage of Dom Pedro II emperor of Brazil. In this last case, the white lead pigment was painted over the wood structure of the carriage; four artefacts on gilded copper, three crowns and a pendant, from the tomb of the Lady of Cao, from the Moche civilization of the North of Peru, dated around 350 AD; finally, an artefact on gilded silver, a vase from the Chavín civilization of the North of Peru, dated around 1000‐200 BC.

Improved prediction of soil properties with multi-target stacked generalisation on EDXRF spectra

Energy dispersive X-ray fluorescence (EDXRF) is one of the most quick, environmentally friendly and least expensive spectroscopic analytical methodologies for assessing soil quality parameters. However, challenges in EDXRF spectral data analysis still demand more efficient methods. One possible solution is using Machine Learning (ML), particularly Multi-target Regression (MTR) methods, which predict multiple parameters taking advantage of inter-correlated parameters. In this study, we proposed the Multi-target Stacked Generalisation (MTSG), a novel MTR method relying on learning from different regressors in stacking structure for a boosted outcome. We compared MTSG and 5 MTR methods for predicting 10 parameters of soil fertility. Random Forest and Support Vector Regression (SVR) were used as learning algorithms embedded into each MTR method. Results showed the superiority of MTR methods over the Single-target Regression (the traditional ML method), reducing the predictive error for 5 parameters. Particularly, MTSG obtained the lowest error for phosphorus, total organic carbon and cation exchange capacity. When observing the relative performance of SVR with a radial kernel, the prediction of base saturation percentage was improved by 19%. Finally, the proposed method was able to reduce the average error from 0.67 (single-target) to 0.64 analysing all targets, representing a global improvement of 4.48%.

Polyethyleneimine Coated Polyacrylonitrile Cellulose Membrane for Colorimetric Copper(II) Determination

Polyethyleneimine (PEI)-polyacrylonitrile (PAN)-cellulose membrane (PEI-PAN cellulose membrane) was developed by immobilizing PEI onto PAN coated cellulose support via electrostatic force to be used for determination of Cu(II) by colorimetric method. The membrane was prepared in two-step process, in which 4% PAN solution was prepared and coated onto the membrane via filtration method, followed by the immersion of the dried PAN-cellulose membrane in the 2% PEI solution. The morphologies of the PEI-PAN membranes were investigated with field emission scanning electron microscope. The results confirmed the presence of a coated layer on the surface. Infrared spectra of before and after coated samples were obtained by Fourier transform infrared (FTIR) spectroscope. The results showed that there were NH2 functional group of PAN and PEI with their characteristic transmittance peaks. Determination at the parts per million level of Cu(II) (0.5–2.0 mg L–1) was achieved by filtration of a sample solution and simultaneous colorimetric analysis using a UV-Vis spectrophotometer (at 650 nm). Cu(II) ion formed the light blue cupramine complex with PEI immobilized on the membrane by filtration of a 50 mL sample solution buffered with 0.01 M dihydrogen phosphate (pH 7). Energy dispersive X-Ray fluorescence spectrum of the Cu(II) detected membrane confirmed the capability of Cu(II) extraction of the PEI-PAN cellulose membrane from the water samples. The detection limit of the Cu(II) determination by this method was found to be 0.27 mg L–1. The accuracy and precision of the method were estimated by Cu(II) determination at 0.5 and 2 mg L–1 of Cu(II) solutions and the results were accurate with above 89% recovery percentage and below 5.5% relative standard deviation. Interference ions were studied and found that Fe(III) and Zn(II) slightly interfered with the Cu(II) determination. The present method was tested for the detection of treated textile wastewater and tap water spiked with 2 mg L–1 of Cu(II). The test results were acceptable and good to determine wastewater prior to discharge into the environment that could be applied for on-site monitoring of Cu(II) in treated wastewater by filtration detection method.

An improved SNIP denoising algorithm applied in EDXRF

Based on the phenomenon of peak height reduction in existing denoising algorithms, this paper modifies the traditional SNIP algorithm, proposes an improved SNIP algorithm and applies it to EDXRF denoising. Two evaluation parameters RMSE and PCC are used to compare the improved SNIP algorithm with the traditional SNIP algorithm. The experimental results show that the improved SNIP algorithm has great advantages both in similarity and relevance, and the results of the improved SNIP algorithm are more consistent with the characteristics of the original data peak than the original SNIP algorithm, which is beneficial to the qualitative and quantitative analysis of the energy dispersive X-ray fluorescence spectrum.

Characterization of a system that combines energy dispersive X-ray diffraction with X-ray fluorescence and its potential applications in archeometry

We report a proof of concept constructing an experimental setup to explore the imaging capability of a single X-ray detector, simulating a pixelated X-ray detector, to measure EDXRF (Energy Dispersive X-ray Fluorescence) and EDXRD (Energy Dispersive X-ray Diffraction) image spectra simultaneously. Combining a conventional rotating anode Cu X-ray source and assembling a single X-ray detector (Si-PIN Amptek, 139 eV at 5.98 keV) on a computer controlled XY stage, a proxy of an imaging X-ray detector was constructed for the measurement of simultaneous EDXRD and EDXRF of the same spot of a sample. The main advantages of this setup are the virtual need for sample preparation and the simultaneous XRF-XRD measurements of the same spot, enabling a combined and consistent analysis of a sample. The time consumed in an analysis using this setup is largely due to the need for acquiring multiple (several hundred) single spectra, which can be compensated, by using a variable acquisition time, depending on the count rate, exploring the high dynamic range of the X-ray emission during data acquisition. A Python code was written for offline data filtering and analysis. Using a simple geometrical model, d-spacings were calculated, and the model predictions were superimposed to the ED (Energy Dispersive) surface plots with good agreement. The instrument proved to work according to expectations and helped set the main experimental parameters for a more compact and portable setup under development.

Effect of mechanical noise upon X-ray fluorescence analysis

The effect of the external mechanical noise on energy dispersive X-ray fluorescence (EDXRF) spectra has been investigated. A Nd2O3 sample was bombarded by the gamma-rays of 59.54 keV energy. The annular radioactive source (americium-241) with intensity equal to 1 Curie was used. The intensities of characteristic x-rays emitted from the Nd2O3 sample were measured using a high purity germanium detector. The mechanical noise applied to the experimental system had intensity values of 50 dB, 60 dB, 70 dB, 80 dB, 90 dB, and 100 dB. A sound level meter (Model 8928) was used to measure the external mechanical noise levels. The net area (P), background intensity (B), peak-to-background ratio (P/B), and full width at half-maximum (FWHM) of the characteristic peaks were determined in the energy dispersive X-ray fluorescence spectra obtained from Nd2O3 sample. It was observed that the background intensities of and peaks of the sample increased with the increasing mechanical noise level. The peak-to-background ratios (P/B) and the peak resolution decreased with increasing mechanical noise level.

Study on charge transportation and scaling behavior of CsPbI3 microwires

Cesium lead iodide (CsPbI3) has been prepared by a new experimental hazard free precipitation technique. X-ray diffraction spectra have been interpreted with Rietveld refinement which assures the orthorhombic phase of CsPbI3. Energy dispersive X-ray fluorescence spectra confirms the formation of ternary compound. Orthorhombic to cubic phase transition has been studied by observing hysteresis loop in R(T)-T plot for forward-reverse temperature scan. The intra-grain and inter-grain contribution of CsPbI3 to dielectric relaxation has been accounted by fitting the complex impedance plot (Cole-Cole plot). The value of FWHM in Z″(ω)-lnf or M″(ω)-lnf plot is greater than 1.141 decades which reveals the non-Debye type relaxation within material. The broad relaxation peak signifies that there is a distribution of relaxation time over a mean value. Moreover, Z″ & M″ have been plotted in scaled coordinate to check whether the distribution of relaxation time is temperature dependent or not. The frequency dependent relative permittivity represents the decreases of polarizations with frequency which have been successfully analyzed by Koop's theory. Here, activation energies are equal for different formalism, suggests that the same type charge carriers involved in conduction as well as relaxation process. Ac conductivity has been interpreted by using Jonncher's power law and frequency exponent (n) increases with temperature which suggests the presence small polaron hopping mechanism.

In vitro study of the demineralization induced in human enamel by an acidic beverage using X‐ray fluorescence spectroscopy and Raman microscopy

This study was conducted with the purpose of evaluating the demineralization effect of a widely consumed acidic soft drink, Coca‐Cola®, in human enamel. This way, an in vitro model for the daily intake of this beverage was developed taking into account the intraoral environment. The evaluation of the enamel specimens was undertaken considering two approaches, the direct analysis of enamel surface and the study of specimens as cross sections. The depolarization ratio of the phosphate symmetric stretching band in Raman spectra was used to evaluate the loss of mineralization of the hydroxyapatite matrix, and the changes regarding the elemental content was performed using energy‐dispersive X‐ray fluorescence (EDXRF). For comparison, the Rayleigh‐to‐Compton ratio in EDXRF spectra of enamel samples was also determined in order to establish alterations in the average atomic number of the samples before and after erosive challenge.Considering the model applied and the timeframe of study, we determined evidences of demineralization after consumption of this drink. There was a significant increase of depolarization ratio in most of the analyzed specimens as well as a decrease of the concentration of major elements concomitant with apparent increase of the concentration of trace elements. Moreover, depths of demineralization of tens of micrometers were obtained with both spectroscopic techniques, showing consistency between the obtained results.

Partial least squares modelization of energy dispersive X-ray fluorescence

As a proof of concept, a green methodology has been developed for the energy dispersive X-ray fluorescence (ED-XRF) determination of calcium, potassium, iron, magnesium, aluminum, chromium, strontium, phosphorus and nickel in the peel of untreated kaki fruit (Diospyros kaki. L) samples. ED-XRF spectra of fifty-six kakis purchased in the local area of LLombay (Valencia) were obtained directly from samples without any previous treatment and without sample damage just after cleaning the fruit with distilled water. Inductively Couple Plasma Optical Emission Spectrometry (ICP-OES) was used as a reference method to determine the mineral elements after microwave assisted acid digestion. XRF spectra and concentration values obtained by ICP-OES were processed using partial least squares (PLS) data treatment to build the corresponding chemometric models for prediction of mineral profile of samples. PLS-ED-XRF permits a direct and accurate determination of Ca and K in kaki peel. For Al, Fe, Mg, Ni and Sr screening semiquantitative results were obtained. Concentrations obtained directly by the internal calibration of instrument, using GeoChem Trace model, were also compared with data predicted by chemometric models being found that PLS models must replace the calibration of the instrument for thus kind of analysis.

Analytical Energy Dispersive X-Ray Fluorescence Measurements with a Scanty Amounts of Plant and Soil Materials

Elemental evaluations in scanty powdered material have been made using energy dispersive X-ray fluorescence (EDXRF) measurements, for which formulations along with specific procedure for sample target preparation have been developed. Fractional amount evaluation involves an itinerary of steps; (i) collection of elemental characteristic X-ray counts in EDXRF spectra recorded with different weights of material, (ii) search for linearity between X-ray counts and material weights, (iii) calculation of elemental fractions from the linear fit, and (iv) again linear fitting of calculated fractions with sample weights and its extrapolation to zero weight. Thus, elemental fractions at zero weight are free from material self absorption effects for incident and emitted photons. The analytical procedure after its verification with known synthetic samples of macro-nutrients, potassium and calcium, was used for wheat plant/ soil samples obtained from a pot experiment.

A wavelet-based Gaussian method for energy dispersive X-ray fluorescence spectrum.

This paper presents a wavelet-based Gaussian method (WGM) for the peak intensity estimation of energy dispersive X-ray fluorescence (EDXRF). The relationship between the parameters of Gaussian curve and the wavelet coefficients of Gaussian peak point is firstly established based on the Mexican hat wavelet. It is found that the Gaussian parameters can be accurately calculated by any two wavelet coefficients at the peak point which has to be known. This fact leads to a local Gaussian estimation method for spectral peaks, which estimates the Gaussian parameters based on the detail wavelet coefficients of Gaussian peak point. The proposed method is tested via simulated and measured spectra from an energy X-ray spectrometer, and compared with some existing methods. The results prove that the proposed method can directly estimate the peak intensity of EDXRF free from the background information, and also effectively distinguish overlap peaks in EDXRF spectrum.

Validation of the Geant4 Monte Carlo package for X-ray fluorescence spectroscopy in triaxial geometry

In this study, we investigated the potential of the Geant4 Monte Carlo simulation package for retrieving accurate elemental concentrations from energy dispersive X-ray fluorescence spectra. For this purpose, we implemented a Geant4 code that simulates an energy dispersive X-ray fluorescence spectrometer in a triaxial geometry. In parallel, we also performed measurements in a spectrometer with the same geometry, for validation of the present code. This spectrometer allows low limits of detection and permits an effective comparison of elemental concentrations down to tens of part-per-million. Several standard reference materials of both light, medium and heavy matrices were employed in order to attest the validity of simulations for several values of averaged atomic number. We observed good agreement of better than 25% for most fluorescence lines of interest, and for all materials. Discrepancies were observed at the multiple Compton scattering tail. We thus concluded from this experimental and theoretical study that the present Geant4 code can be incorporated in a quantitative method for the determination of trace elements in a triaxial-type spectrometer.