Exploring the potential applications of lead-free organic-inorganic perovskite type [NH3(CH2)nNH3]MCl4 (n = 2, 3, 4, 5, and 6; M = Mn, Co, Cu, Zn, and Cd) crystals

The organic-inorganic hybrid perovskite compounds have been extensively studied since the dawn of a new era in the field of photovoltaic applications. Up to now, perovskites have proven to be the most promising in terms of power conversion efficiency; however, their main disadvantages for use in solar cells are toxicity and chemical instability. Therefore, it is essential to develop a hybrid perovskite that can be replaced with lead-free materials. This review focuses on the possibility of applying lead-free organic-inorganic perovskite types [NH3(CH2)nNH3]MCl4 (n = 2, 3, 4, 5, and 6; M = Mn, Co, Cu, Zn, and Cd) crystals. We are seeking organic-inorganic hybrid perovskite materials with very high temperature stability or without phase transition temperature, and thermal stability. Thus, by considering the characteristics according to the methylene lengths and the various transition metals, we aim to identify improved materials meeting the criteria mentioned above. Consequently, the physicochemical properties of organic-inorganic hybrid perovskite [NH3(CH2)nNH3]MCl4 regarding the effects of various transition metal ions of the anion and the methylene lengths of the cation are expected to promote the development and application of lead-free hybrid perovskite solar cells.

Insights on Stability Constants and Structures of Complexes between Coumarin Derivatives and Pb(II) in Aqueous Media

In the frame of a systematic study on the sequestering ability of natural antioxidants towards metal cations, here the complexation of coumarin-3-carboxilic acid (HCCA) with Pb(II) and the overall stability constants of the resulting complexes, at 37 °C and in 0.16 M NaClO4, are discussed. Reaction of Pb(ClO4)2 with HCCA in an aqueous medium at a pH range from 2 to 6 and various ratios (1:1-1:10) yielded the Pb-CCA complexes, which were characterized spectrometrically by laser desorption ionization mass spectrometry (LD-MS). LD-MS has provided the composition and structure of Pb-CCA species according to the speciation model proposed on the basis of the potentiometric data. The graphic representation of the complex's concentration curves is given by the distribution diagram, which provides a whole depiction of the species present in the solution at the selected pH ranges.

Altitude governs the air pollution tolerance and heavy metal accumulation in plants

Plant response to changing air pollution is a function of various factors including meteorology, type of pollutants, plant species, soil chemistry, and geography. However, the impact of altitude on plant behavior has received little attention to date. A study was therefore conducted to evaluate the impact of altitude on the air pollution tolerance index (APTI), heavy metal accumulation, and deposition in plant species. The results favor the hypothesis of a definite impact of altitude on biochemical and heavy metal accumulation in plants. While a significant decline (p < 0.05) in the relative water content (RWC), APTI, and heavy metal accumulation with increasing altitude was evident in the studied plant species, the behavior of ascorbic acid, leaf extract pH, chlorophyll content, and the particle heavy metal deposition was erratic and did not display any statistically significant differences. The metal accumulation index was in the following order: Ni > Zn > Cu > Pb > Cd > Co. Similarly, the particle heavy metal deposition on the leaf surface (µg/cm2) displayed significant species variability (p < 0.05) and was in the order: Cu (0.303) > Pb (0.301) > Ni (0.269) > Zn (0.241) > Cd (0.044) > Co (0.025). The accumulated heavy metal and RWC showcased a significant positive correlation with the APTI, suggesting the dominant role of RWC in the plant's tolerance against air pollution in an altitudinal gradient. Future studies on the role of micrometeorological conditions in altering APTI may be fruitful in ascertaining these postulations.

Field-scale differences in rhizosphere micro-characteristics of Cichorium intybus, Ixeris polycephala, sunflower, and Sedum alfredii in the phytoremediation of Cd-contaminated soil

Understanding the intricate interplay between Cd accumulation in plants and their rhizosphere micro-characteristics is important for the selection of plant species with profitable Cd phytoextraction and soil remediation efficiencies. This study investigated the differences in rhizosphere micro-ecological characteristics and Cd accumulation in chicory, Ixeris polycephala, sunflower, and Sedum alfredii in low-moderate Cd-contaminated soil. Data reveal that the dominant organic acids in rhizosphere soil that responded to Cd were oxalic and lactic acids in chicory and Ixeris polycephala, tartaric acid in sunflower, and succinic acid in Sedum alfredii. These unique organic acids could also influence the abundance of specific rhizobacterial communities in rhizosphere soil that were Sphingomonadaceae and Bradyrhizobiaceae in both Sedum alfredii (9.75 % and 2.56 %, respectively) and chicory (8.98 % and 2.82 %, respectively) rhizosphere soil, Xanthomonadaceae in both Sedum alfredii and Ixeris polycephala rhizosphere soil, and Gaiellaceae in chicory rhizosphere soil. In this case, the combined effects of the organic acids and unique rhizobacterial communities by plant species increased the bioavailable concentration of Cd in Sedum alfredii, Ixeris polycephala, and sunflower rhizosphere soil, while decreasing the Cd-DOM concentrations in chicory rhizosphere soil and the water-extractable Cd reduced by 88.02 % compared to the control. Though the capacity for Cd accumulation in the shoots of chicory was weaker than of Sedum alfredii but better than either Ixeris polycephala or sunflower, chicory presented better Cd translocation and harbored Cd mainly as the low toxic chemical form of pectates and proteins-bound Cd and Cd oxalate in its shoot. Generally, chicory, as an economic plant, is suitable for phytoremediation of low-moderate Cd-contaminated soil after Sedum alfredii.

A critical review with emphasis on recent pieces of evidence of Moringa oleifera biosorption in water and wastewater treatment

The increasing demand for using competent and inexpensive methods based on biomaterials, like adsorption and biosorption, has given rise to the low-priced alternative biosorbents. In the past few years, Moringa oleifera (MO) has emerged as a green and low-priced biosorbent for the treatment of contaminated waters with heavy metals and dyes, and given its availability, we can create another generation of effective biosorbents based on different parts of this plant. In this review paper, we have briefed on the application of MO as a miraculous biosorbent for water purification. Moreover, the primary and cutting-edge methods for the purification and modification of MO to improve its adsorption are discussed. It was found that MO has abundant availability in the regions where it is grown, and simple chemical treatments increase the effectiveness of this plant in the treatment of some toxic contaminants. The different parts of this miraculous plant's "seeds, leaves, or even husks" in their natural form also possess appreciable sorption capacities, high efficiency for treating low metal concentrations, and rapid adsorption kinetics. Thus, the advantages and disadvantages of different parts of MO as biosorbent, the conditions favorable to this biosorption, also, the proposal of a logical mechanism, which can justify the high efficiency of this plant, are discussed in this review. Finally, several conclusions have been drawn from some important works and which are examined in this review, and future suggestions are proposed.

In situ beam reduction of Pu(IV) and Bk(IV) as a route to trivalent transuranic coordination complexes with hydroxypyridinone chelators

The solution-state interactions of plutonium and berkelium with the octadentate chelator 3,4,3-LI(1,2-HOPO) (343-HOPO) were investigated and characterized by X-ray absorption spectroscopy, which revealed in situ reductive decomposition of the tetravalent species of both actinide metals to yield Pu(III) and Bk(III) coordination complexes. X-ray absorption near-edge structure (XANES) measurements were the first indication of in situ synchrotron redox chemistry as the Pu threshold and white-line position energies for Pu-343-HOPO were in good agreement with known diagnostic Pu(III) species, whereas Bk-343-HOPO results were found to mirror the XANES behavior of Bk(III)-DTPA. Extended X-ray absorption fine structure results revealed An-O_HOPO bond distances of 2.498 (5) and 2.415 (2) Å for Pu and Bk, respectively, which match well with bond distances obtained for trivalent actinides and 343-HOPO via density functional theory calculations. Pu(III)- and Bk(III)-343-HOPO data also provide initial insight into actinide periodicity as they can be compared with previous results with Am(III)-, Cm(III)-, Cf(III)-, and Es(III)-343-HOPO, which indicate there is likely an increase in 5f covalency and heterogeneity across the actinide series.

Combining the Best of Two Chelating Titans: A Hydroxypyridinone-Decorated Macrocyclic Ligand for Efficient and Concomitant Complexation and Sensitized Luminescence of f-Elements

An ideal chelator for f-elements features rapid kinetics of complexation, high thermodynamic stability, and slow kinetics of dissociation. Here we present the facile synthesis of a macrocyclic ligand bearing four 1-hydroxy-2-pyridinone units linked to a cyclen scaffold that rapidly forms thermodynamically stable complexes with lanthanides (Sm³⁺ , Eu³⁺ , Tb³⁺ , Dy³⁺ ) and a representative late actinide (Cm³⁺ ) in aqueous media and concurrently sensitizes them. Extended X-ray absorption fine structure (EXAFS) spectroscopy revealed an increase in the Ln/An-O bond lengths following the trend Cm>Eu>Tb and EXAFS data were compatible with time-resolved luminescence studies, which indicated one to two water molecules in the inner metal coordination sphere of Eu(III) and two water molecules for the Cm(III) complex. Spectrofluorimetric ligand competition titrations against DTPA confirmed the high thermodynamic stability of DOTHOPO complexes, with pM values between 19.9(1) and 21.9(2).

Controlling the Reduction of Chelated Uranyl to Stable Tetravalent Uranium Coordination Complexes in Aqueous Solution

The solution-state interactions between octadentate hydroxypyridinone (HOPO) and catecholamide (CAM) chelating ligands and uranium were investigated and characterized by UV-visible spectrophotometry and X-ray absorption spectroscopy (XAS), as well as electrochemically via spectroelectrochemistry (SEC) and cyclic voltammetry (CV) measurements. Depending on the selected chelator, we demonstrate the controlled ability to bind and stabilize U^IV, generating with 3,4,3-LI(1,2-HOPO), a tetravalent uranium complex that is practically inert toward oxidation or hydrolysis in acidic, aqueous solution. At physiological pH values, we are also able to bind and stabilize U^IV to a lesser extent, as evidenced by the mix of U^IV and U^VI complexes observed via XAS. CV and SEC measurements confirmed that the U^IV complex formed with 3,4,3-LI(1,2-HOPO) is redox inert in acidic media, and U^VI ions can be reduced, likely proceeding via a two-electron reduction process.

Recent advances in environmentally benign hierarchical inorganic nano-adsorbents for the removal of poisonous metal ions in water: a review with mechanistic insight into toxicity and adsorption

Recent developments in nanoscience and technology have addressed many of the problems associated with water quality. Accordingly, using the technological outputs of the recent research on nanomaterials, the best solution for the purification of water is highlighted in this review. Herein, the main objective is to provide mechanistic insight into the synthesis of various inorganic nanoadsorbents and their adsorption chemistry for poisonous metal ions present in polluted water. Initially, the toxicity and carcinogenicity of As3+, Pb2+, Cr6+, Cd2+, and Hg2+ metal ions are highlighted. For the removal of these toxic ions, this review focuses on eco-friendly nanoadsorbents. The various preparation procedures utilized for the preparation of nanoadsorbents are briefly discussed. Generally, this is because of the adsorption capacity of nanoadsorbents depends on their morphology, shape, size, surface area, surface active sites, functional groups, and quantization effect. Also, due to the importance of their mechanism of action, the recent developments and challenges of novel nanoadsorbents such as metal oxides, core shell nanoparticles, magnetic nano ferrates, and functionalized core shell magnetic oxides and the processes for the treatment of water contaminated by toxic metal ions such as As3+, Pb2+, Cr6+, Cd2+, and Hg2+ are exclusively reviewed. Further, the adsorption efficiency of inorganic nanoadsorbents is also compared with that of activated carbon derived from various sources for all the above-mentioned metal ions.

Engineering Mesoporous Silica Nanoparticles for Targeted Alpha Therapy against Breast Cancer

Targeted alpha therapy, where highly cytotoxic doses are delivered to tumor cells while sparing surrounding healthy tissue, has emerged as a promising treatment against cancer. Radionuclide conjugation with targeting vectors and dose confinement, however, are still limiting factors for the widespread application of this therapy. In the current study, we developed multifunctional silica nanoconstructs for targeted alpha therapy that show targeting capabilities against breast cancer cells, cytotoxic responses at therapeutic dosages, and enhanced clearance. The silica nanoparticles were conjugated to transferrin, which promoted particle accumulation in cancerous cells, and 3,4,3-LI(1,2-HOPO), a chelator with high selectivity and binding affinity for f-block elements. High cytotoxic effects were observed when the nanoparticles were loaded with ²²⁵Ac, a clinically relevant radioisotope. Lastly, in vivo studies in mice showed that the administration of radionuclides with nanoparticles enhanced their excretion and minimized their deposition in bones. These results highlight the potential of multifunctional silica nanoparticles as delivery systems for targeted alpha therapy and offer insight into design rules for the development of new nanotherapeutic agents.

Hydroxypyridinone Derivatives: A Low-pH Alternative to Polyaminocarboxylates for TALSPEAK-like Separation of Trivalent Actinides from Lanthanides

Separation of lanthanides (Ln) from actinides (An) is unanimously challenging in reprocessing used nuclear fuel despite of much dedicated efforts over the past several decades. The TALSPEAK process is the current reference method in the United States for Ln³⁺/An³⁺ separation but suffers from several limitations, such as a narrow working pH window (3.5-4.0), costly pH buffers, and slow extraction kinetics. Studies aiming at improving TALSPEAK have so far focused on polyaminocarboxylates hold-back reagents. Here, a new class of water-soluble ligands comprising hydroxypyridinone metal-binding units are evaluated for Ln³⁺/An³⁺ separation. The model octadentate chelator 3,4,3-LI(1,2-HOPO) (abbreviated as HOPO) was used in combination with several industry-relevant organic extractants to separate Gd from four transplutonium elements (Am, Cm, Bk, and Cf). Cyanex 301 GN and HDEHP worked best in combination with HOPO, whereas HEH[EHP], Cyanex 572, and ACORGA M5640 did not yield practical Ln³⁺/An³⁺ separation. Separation factors between Gd³⁺ and Am³⁺ reach about 50 with the HOPO/Cyanex 301 GN system and 30 with the HOPO/HDEHP system. The results using HDEHP (SF_Gd/Am = 30, SF_Gd/Cm = 8.5, and SF_Gd/Cf = 773) are high enough for industrial applications, and the proposed system works at pH values as low as 1.5, which simplifies the process by eliminating the need for pH buffers. In contrast to previously proposed methods, the HOPO-based process is also highly selective at separating Bk from Ln³⁺ (SF_Gd/Bk = 273) owing to in situ, spontaneous oxidation of Bk(III) to Bk(IV) by HOPO. The optimal pH in the case of HOPO/Cyanex 301 GN is 3.6 (SF_Am/Gd = 50, SF_Cm/Gd = 23, SF_Bk/Gd = 1.4, and SF_Cf/Gd = 3.2), but this system has the advantage of extracting An ions into the organic phase while keeping Ln ions in the aqueous phase, which is opposite to the conventional TALSPEAK process. This study represents the first optimization of a TALSPEAK-like Ln/An separation method using a HOPO chelator and paves the avenue for further developments of analytical science and reprocessing of used nuclear fuel.

DFT analysis of the interaction between Hg2+ and monodentate neutral ligands using NBO, EDA, and QTAIM

We report thermodynamic, geometric, and electronic parameters for the interaction between neutral ligands and the [Hg(H₂O)]²⁺ dication, using the B3LYP/6-311 + G(d,p) approach. Gibbs free energies for the interaction were employed to rank the affinity order of the several neutral ligands. To identify the parameters that characterize the affinity between the two fragments, the metal-ligand interaction was analyzed according to the EDA, NBO, and QTAIM decomposition schemes. The phosphine oxide showed the highest affinity for the Hg(H₂O)²⁺ dication, mainly due to the P=O bond polarization. Ligands containing the sulfur atom, characterized by a high covalent component for the metal-ligand interaction, are the following in the interaction order. According to the Gibbs free energy for substitution of one water molecule in the [Hg(H₂O)₂]²⁺ complex, the sequence for the affinity order is: phosphine oxide > thioketone > thioesther > lactam > amide > amine > carboxylic acid > thiophene > ketone > esther > thiol > thiocyanate > ammonia > disulfide > aldehyde > ether > haloydrin > alcohol > enol > azide. Graphical abstract Synopsis The interaction between the Hg²⁺ cation and monodentate ligands containing S, O, or N atoms was evaluated in terms of energetic (bond strength, electrostatic and covalent interactions, donation energy), geometric (metal-ligand distance), electronic (atomic charges, orbital overlap, orbital hybridization) and topologic parameters.

Developing scandium and yttrium coordination chemistry to advance theranostic radiopharmaceuticals

The octadentate siderophore analog 3,4,3-LI(1,2-HOPO), denoted 343-HOPO hereafter, is known to have high affinity for both trivalent and tetravalent lanthanide and actinide cations. Here we extend its coordination chemistry to the rare-earth cations Sc³⁺ and Y³⁺ and characterize fundamental metal-chelator binding interactions in solution via UV-Vis spectrophotometry, nuclear magnetic resonance spectroscopy, and spectrofluorimetric metal-competition titrations, as well as in the solid-state via single crystal X-ray diffraction. Sc³⁺ and Y³⁺ binding with 343-HOPO is found to be robust, with both high thermodynamic stability and fast room temperature radiolabeling, indicating that 343-HOPO is likely a promising chelator for in vivo applications with both metals. As a proof of concept, we prepared a ⁸⁶Y-343-HOPO complex for in vivo PET imaging, and the results presented herein highlight the potential of 343-HOPO chelated trivalent metal cations for therapeutic and theranostic applications.

Selective Lanthanide Sensing with Gold Nanoparticles and Hydroxypyridinone Chelators

The octadentate hydroxypyridinone chelator 3,4,3-LI(1,2-HOPO) is a promising therapeutic agent because of its high affinity for f-block elements and noncytotoxicity at medical dosages. The interaction between 3,4,3-LI(1,2-HOPO) and other biomedically relevant metals such as gold, however, has not been explored. Gold nanoparticles functionalized with chelators have demonstrated great potential in theranostics, yet thus far, no protocol that combines 3,4,3-LI(1,2-HOPO) and colloidal gold has been developed. Here, we characterize the solution thermodynamic properties of the complexes formed between 3,4,3-LI(1,2-HOPO) and Au³⁺ ions and demonstrate how under specific pH conditions the chelator promotes the growth of gold nanoparticles, acting as both reducing and stabilizing agent. 3,4,3-LI(1,2-HOPO) ligands on the nanoparticle surface remain active and selective toward f-block elements, as evidenced by gold nanoparticle selective aggregation. Finally, a new colorimetric assay capable of reaching the detection levels necessary for the quantification of lanthanides in waste from industrial processes is developed based on the inhibition of particle growth by lanthanides.

Ultra-selective ligand-driven separation of strategic actinides

Metal ion separations are critical to numerous fields, including nuclear medicine, waste recycling, space exploration, and fundamental research. Nonetheless, operational conditions and performance are limited, imposing compromises between recovery, purity, and cost. Siderophore-inspired ligands show unprecedented charge-based selectivity and compatibility with harsh industry conditions, affording excellent separation efficiency, robustness and process control. Here, we successfully demonstrate a general separation strategy on three distinct systems, for Ac, Pu, and Bk purification. Separation factors (SF) obtained with model compound 3,4,3-LI(1,2-HOPO) are orders of magnitude higher than with any other ligand currently employed: 10⁶ between Ac and relevant metal impurities, and over 10⁸ for redox-free Pu purification against uranyl ions and trivalent actinides or fission products. Finally, a one-step separation method (SF > 3 × 10⁶ and radiopurity > 99.999%) enables the isolation of Bk from adjacent actinides and fission products. The proposed approach offers a paradigm change for the production of strategic elements.

Radionuclides are of great importance for fields such as nuclear medicine and waste recycling, but their efficient purification remains a challenge. Here the authors show that an octadentate hydroxypyridinone chelator enables efficient and robust separation processes for isotopes of Ac, Pu, and Bk.

Inducing selectivity and chirality in group IV metal coordination with high-denticity hydroxypyridinones

The solution- and solid-state interactions between the octadentate siderophore mimic 3,4,3-LI(1,2-HOPO) (343HOPO) and group IV metal ions were investigated using high-resolution mass spectrometry, liquid chromatography, UV-visible spectrophotometry, metal-competition batch titrations, and single crystal X-ray diffraction. 343HOPO forms a neutral 1 : 1 complex, [HfIV343HOPO], that exhibits extreme stability in aqueous solution, with a log β110 value reaching 42.3. These results affirm the remarkable charge-based selectivity of 343HOPO for octacoordinated tetravalent cations with a Hf(iv) complex 1021 more stable than its Lu(iii) analogue. Moreover, [HfIV343HOPO] and its Zr(iv) counterpart show exceptional robustness, with the ligand remaining bound to the cation over a very broad pH range: from pH ∼ 11 to acidic conditions as strong as 10 M HCl. In stark contrast, Ti(iv)-343HOPO species are far less stable and undergo hydrolysis at pH as low as ∼6, likely due to the mismatch between the preferred hexacoordinated Ti(iv) ion and octadentate 343HOPO ligand. The extreme charge-based and denticity-driven selectivity of 343HOPO, now observed across the periodic table, paves the way for new selective sequestration systems for radionuclides including medical 44Ti, 89Zr or 177Lu/Hf isotopes, toxic polonium (Po) contaminants, as well as rutherfordium (Rf) research isotopes. Furthermore, despite the lack of a chiral center in 343HOPO, its complexes with metal ions are chiral and appear to form a single set of enantiomers.

Is hydroxypyridonate 3,4,3-LI(1,2-HOPO) a good competitor of fetuin for uranyl metabolism?

Identification of stable HOPO–UO₂²⁺–fetuin ternary complexes after a chromatographic separation process.

Solution Thermodynamics and Kinetics of Metal Complexation with a Hydroxypyridinone Chelator Designed for Thorium-227 Targeted Alpha Therapy

The solution chemistry of a chelator developed for ²²⁷Th targeted alpha therapy was probed. The compound of interest is an octadentate ligand comprising four N-methyl-3-hydroxy-pyridine-2-one metal-binding units, two tertiary amine groups, and one carboxylate arm appended for bioconjugation. The seven p K_a values of the ligand and the stability constants of complexes formed with Th(IV), Hf(IV), Zr(IV), Gd(III), Eu(III), Al(III), and Fe(III) were determined. The ligand exhibits extreme thermodynamic selectivity toward tetravalent metal ions with a ca. 20 orders of magnitude difference between the formation constant of the Th(IV) species formed at physiological pH, namely [ThL]^-, and that of its Eu(III) analogue. Likewise, log β₁₁₀ values of 41.7 ± 0.3 and 26.9 ± 0.3 (T = 25 °C) were measured for [ThL]^- and [Fe^IIIL]^2-, respectively, highlighting the high affinity and selectivity of the ligand for Th ions over potentially competing endogenous metals. Single crystal X-ray analysis of the Fe(III) complex revealed a dinuclear 2:2 metal:chelator complex crystallizing in the space group P1̅. The formation of this dimeric species is likely favored by several intramolecular hydrogen bonds and the protonation state of the chelator in acidic media. L_III edge EXAFS data on the Th(IV) complexes of both the ligand and a monoclonal antibody conjugate revealed the expected mononuclear 1:1 metal:chelator coordination environment. This was also confirmed by high resolution mass spectrometry. Finally, kinetic experiments demonstrated that labeling the bioconjugated ligand with Th(IV) could be achieved and completed after 1 h at room temperature, reinforcing the high suitability of this chelator for ²²⁷Th targeted alpha therapy.