High-energy interference-free K-lines synchrotron X-ray fluorescence microscopy of rare earth elements in hyperaccumulator plants

Abstract

Synchrotron-based micro-X-ray fluorescence analysis (µXRF) is a non-destructive and highly sensitive technique. However, element mapping of rare earth elements (REEs) under standard conditions requires care, since energy-dispersive detectors are not able to differentiate accurately between REEs L-shell X-ray emission lines overlapping with K-shell X-ray emission lines of common transition elements of high concentrations. We aim to test REE element mapping with high-energy interference-free excitation of the REE K-lines on hyperaccumulator plant tissues and compare with measurements with REE L-shell excitation at the microprobe experiment of beamline P06 (PETRA III, DESY). A combination of compound refractive lens optics (CRLs) was used to obtain a micrometre sized focussed incident beam with an energy of 44 keV and an extra-thick silicon drift detector (SDD) optimised for high-energy X-ray detection to detect the K-lines of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr) and neodymium (Nd) without any interferences due to line overlaps. High-energy excitation from La to Nd in the hyperaccumulator organs was successful but compared to L-line excitation less efficient and therefore slow (∼10-fold slower than similar maps at lower incident energy) due to lower flux and detection efficiency. However, REE K-lines do not suffer significantly from self-absorption, which makes XRF-tomography of millimetre-sized frozen-hydrated plant samples possible. The K-line excitation of REEs at the P06 CRL setup has scope for application in samples that are particularly prone to REE interfering elements, such as soil samples with high concomitant Ti, Cr, Fe, Mn, Ni concentrations.

Rare Earth Elements (REE): Origins, Dispersion, and Environmental Implications—A Comprehensive Review

“…Ferns strongly accumulate REE and could be used as indicator plants or for phytomining applications [7,243,285,286]. Some species of the Genera Dicranopteris [37,258], Blechnum [287], Pronephrium [288][289][290], Athyrium [223], Stenoloma, Woodwardia [287], Dryopteris [278], and Asplenium [278] accumulate up to 3359 mg/kg of the sum of REE in their shoots.…”

Synchrotron μXRF imaging reveals elemental distribution in the nickel hyperaccumulator Odontarrhena muralis (Brassicaceae) from Serbia

“…The μXRF experiments were performed at DESY (Deutsches Elektronen-Synchrotron) on the hard X-ray microprobe undulator beamline P06 (Boesenberg et al, 2016) at PETRA III. Detailed information on the setup and instrumental parameters has been provided in van der Ent et al (2023). The XRF measurements were performed during two separate experiments with KB mirrors as main focusing optics in both cases: The flower was measured with an incident X-ray energy of 16 keV, beam size of 560 nm  420 nm (h  v) and a photon flux of 3.5  10 10 ph/s, while the leaves and stems were measured at 18 keV with 3.57 μm  920 nm (h  v) beam size and 1.25  10 11 ph/s photon flux using additional pre-focusing CRLs (Compound Refractive Lenses).…”

Design and 3D Electrical Simulations for a Controllable Equal-Gap Large-Area Silicon Drift Detector

“…The silicon drift detector (SDD) has extremely broad application prospects in materials analysis [ 1 , 2 , 3 , 4 , 5 ], X-ray fluorescence spectroscopy [ 6 , 7 ], nuclear physics research [ 8 , 9 , 10 ], medical imaging (such as X-ray CT scanning) [ 11 , 12 , 13 ], and other fields [ 14 , 15 ]. The L-SDD has a larger sensing area, making it suitable for high-resolution, high-counting-rate X-ray spectroscopic analysis, and has been identified as one of the best detectors for pulsar X-ray detection [ 16 , 17 ].…”