A highly sensitive and selective spectrofluorimetric method for the determination of cerium at pico-trace levels in some real, environmental, biological, soil, food and bone samples using 2-(α-pyridyl)-thioquinaldinamide

Toxicity of rare earth elements (REEs) to marine organisms: Using species sensitivity distributions to establish water quality guidelines for protecting marine life

A lack of chronic rare earth element (REE) toxicity data for marine organisms has impeded the establishment of numerical REE water quality benchmarks (e.g., guidelines) to protect marine life and assess ecological risk. This study determined the chronic no (significant) effect concentrations (N(S)ECs) and median-effect concentrations (EC50s) of eight key REEs (yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), gadolinium (Gd), dysprosium (Dy) and lutetium (Lu)) for 30 coastal marine organisms (encompassing 22 phyla and five trophic levels from temperate and tropical habitats). Organisms with calcifying life stages were most vulnerable to REEs, which competitively inhibit calcium uptake. The most sensitive organism was a sea urchin, with N(S)ECs ranging from 0.64 μg/L for Y to 1.9 μg/L for La and Pr, and EC50s ranging from 4.3 μg/L for Y to 14.4 μg/L for Pr. Conversely, the least sensitive organism was a cyanobacterium, with N(S)ECs ranging from 121 μg/L for Y to 469 μg/L for Pr, and EC50s ranging from 889 μg/L for Y to 3000 μg/L for Pr. Median sensitivity varied 215-fold across all organisms. The two-fold difference in median toxicity (μmol/L EC50) among REEs (Y ∼ Gd > Lu ∼ Nd ∼ Dy ∼ Ce > La ∼ Pr) was attributed to offset differences in binding affinity (log K) to cell surface receptors and the percentage of free metal ion (REE3+) in the test waters. The toxicity (EC50) of the remaining REEs (samarium, europium, terbium, holmium, thulium and ytterbium) was predicted using a combination of physicochemical data and measured EC50s for the eight tested REEs, with good agreement between predicted and measured EC50s for selected organisms. Numerical REE water quality guidelines to protect marine life were established using species sensitivity distributions (e.g., for 95 % species protection, values ranged from 1.1 μg/L for Y to 3.0 μg/L for La, Pr or Lu).

Innovative assembled optode device for enhanced in-situ ceric ions (Ce4+) evaluation and preconcentration in its real human, foods, water, and alloy samples

Cerium (Ce) are the most widely distributed rare earth element. However, humans exposed to Ce through inhalation have been reported to experience heat sensitivity, itching, and heightened taste and odour perception. The present study aims to develop an optical sensor device with a short response time and high selectivity for Ce amongst other ions in various environments. The potential applicability of a 6-hydroxy-5-((4-hydroxy-2-methylphenyl)diazenyl)pyrimidine-2,4(1H,3H)-dione (HHMDPD) assembled ligand as aceric ion (Ce4+)-selective caption optode was examined. After generating an ion pair with Tetra-n-octylammonium bromide (TOABr) and immobilizing on a tri-acetyl cellulose (TAC) membrane, the solubility of the HHMDPD ligand is improved. The constructed optode membrane reacts with Ce4+ by turning its orange colour to violet in Thiel buffer (pH of 5.5), which can be detected spectrophotometrically at λmax 667 nm. The measurement linearity was in the range of 0.70 - 18.7 × 10-6 mol/L of Ce4+ concentration with detection and quantification limits of 0.23 × 10-6 and 0.70 × 10-6 mol/L, respectively. Whatever the Ce4+ concentration in its real samples, the response time of the constructed device was 5.0 min. Additionally, it recorded repeatability and reproducibility with a %RSD of 1.37 and 2.55, respectively (n = 3). The proposed optode device exhibited complete reversibility, for multiple measurements, which could be easily achieved with the aid of a solution of HCl, 0.01 mol/L. The applicability of the proposed device has been effectively extended to analyze synthetic mixes corresponding to different Ce4+ real human, foods, water, and magnesium-based Ce4+ alloys.

A Highly Sensitive and Selective Fluorescent Probe for the Detection of Cerium(III) Using Tridentate Based-Oxazolidine: Experimental and DFT Investigations

A new fluorescent sensor based on oxazolidine derivative, (2-(pyridin-2-yl)oxazolidine-4,4-diyl)dimethanol; TN), was designed and synthesized successfully in high yield (82%) under Schiff base reaction. The structural elucidation of the sensor has been confirmed by Infrared Spectroscopy, Nuclear Magnetic Resonance Spectroscopy, and High Resolution Mass Spectrometry - Electrospray Ionization - Time of Flight. The designed TN sensor exhibited high sensitivity and selectivity towards an aqueous solution of cerium(III) over various metal ions under biologically relevant conditions (100.0 mM HEPES buffer pH 7.4). The limit of detection (LOD) was reported as 54.0 nM. The geometry of tridentate based-oxazolidine (TN) and its coordination of cerium(III) (TN-Ce³⁺) was proven by using the density functional theory (DFT) calculations. The highest occupied molecular orbital - lowest unoccupied molecular orbital energy gap was decreased when TN-Ce³⁺ is formed. The results indicated that TN can be used as a fluorescent probe for high sensitivity and selectivity detection of cerium(III) ions.

Design and construction of an electrochemical sensor for the determination of cerium(iii) ions in petroleum water samples based on a Schiff base-carbon nanotube as an ionophore

A carbon paste sensor (CPE) and screen-printed sensor (SPE) for Ce(iii)-selective determination were prepared using a 2,6-pyridine dicarbomethine-triethylene tetraamine macrocyclic Schiff base ligand (PDCTETA) and multi-walled carbon nanotubes (MWCNTs) as good sensing materials. With respect to most common cations, such as alkali, alkaline earth, transition, and heavy metal ions, the electrodes display high selectivity for the Ce(iii) ion. The sensors respond to Ce(iii) ions in a linear range of 1 × 10-7 to 1 × 10-1 and 1 × 10-8 to 1 × 10-1 mol L-1 with a slope of 18.96 ± 0.73 and 19.63 ± 0.51 mV per decade change in concentration with a detection limit of 1.10 × 10-8 and 5.24 × 10-9 mol L-1 for CPE (sensor IV) and SPE (sensor VIII), respectively. The sensors were found to have a lifetime of 102 and 200 days. The suggested electrodes performed well throughout the pH ranges of 3.5-8.0 and 3.0-8.5, with response times of 8 and 6 seconds for sensor IV and sensor VIII, respectively. The sensors have been used to measure Ce(iii) ions in water samples from several petroleum wells. They have also been utilized as indicator electrodes in Ce(iii) ion potentiometric titrations with EDTA. The results were quite similar to those obtained by employing atomic absorption spectrometry (AAS).

Size-focusing results in highly photoluminescent sulfur quantum dots with a stable emission wavelength

Sulfur quantum dots (SQDs) are a new kind of functional nanomaterial, but several challenges still exist in relation to their synthesis and application, such as low-yield and time-consuming synthetic methods, low photoluminescence quantum yields (PLQYs), and the non-selectivity of their detection mechanisms. Herein, we report the drastic enhancement of the fluorescence performance of water-soluble SQDs via the one-pot synthesis of size-focusing QDs using ultrasound microwave radiation. The synthetic period has been greatly shortened to 2 h via the present process. Notably, the proposed SQDs exhibit a highly stable emission wavelength with a record high PLQY of 58.6%. The mechanistic study indicates that size-focusing is a key factor relating to the proposed high-performance SQDs. As they also have robust stability, the proposed SQDs show a wide range of potential applications. Inspired by the characteristic properties of the SQDs and specific analytes, a simple SQD-based fluorescence sensing platform, via a redox-reaction-mediated mechanism, has been successfully developed for the rapid and selective detection of Ce(iv). In addition, this system has been effectively applied to some Ce(iv)-related biological assays, such as ascorbic acid (AA) analysis. This work is an important breakthrough in the SQD field, opening up avenues for solving the challenging problems relating to SQD-based probes, enriching the fundamental understanding of them, and greatly extending their applications, especially in biomedicine.