Cation Sites Research Articles

Direct Evidence of Anomalous Peierls Transition-Induced Charge Density Wave Order at Room Temperature in Metallic NaRu2O4.

In the field of quantum materials, understanding anomalous behavior under charge degrees of freedom through bond formation is of fundamental importance, with two key concepts: Dimerization and charge order at different cation sites. The coexistence of both dimerization and charge ordering is unusually found in NaRu2O4, even in its metallic state at room temperature. Our work unveils the origin of the interplay of these effects within metallic single-crystalline NaRu2O4. Employing advanced transmission electron microscopy techniques, we probe the lattice order of NaRu2O4 as a function of temperature and provide direct microscopic evidence of a Peierls-type transition. This transition is accompanied by a pronounced dimerization of the ruthenium chains, resulting in a distinctive twofold superstructure along the b axis below the critical transition temperature of ∼535 K, coinciding with a charge order. In situ heating experiments confirm the reversibility of this first-order phase transition, and periodic lattice displacement maps depict atomic-scale displacements linked to dimerization.

Structural and electric properties of Na super ionic conductor solid electrolyte MIIx/2Li1−xTi2(PO4)3 (MII = Mg, Zn, and Cd)

AbstractAll‐solid‐state lithium‐ion batteries, employing solid electrolytes, offer a promising solution to address safety concerns inherent in conventional lithium‐ion batteries. Among the various types of Li‐ion solid electrolytes, LiTi2(PO4)3 (LTP) with the Na Super Ionic CONductor (NASICON) structure stands out as a particularly attractive material, despite its relatively low ionic conductivity at room temperature. One approach to enhance the performance of LTP solid electrolytes involves modifying the network size or redistributing Li cations and vacancies within the adjacent sites of the NASICON structure. Therefore, this study seeks to replace lithium ions with divalent cations, thereby increasing the concentration of vacancies, and facilitates the migration of Li+ ions between adjacent partially populated M1 sites. Introducing divalent elements not only augments vacancies in the lithium sites but also induces variations in local disorder within NASICON structures. Consequently, NASICON compounds, MIIx/2Li1−xTi2(PO4)3 (MII = Mg, Zn, and Cd), were synthesized via the sol–gel method, and their structural, microstructural, and electrical properties were thoroughly analyzed using a variety of techniques. The presence of divalent cations in the M1 site results in a reduction of symmetry and an enhancement of local disorder. A correlation between ionic conductivity and structure was established, which was linked to the disorder of lithium atoms within the structure. Electric modulus formalism was employed to explore electric relaxation, revealing that the diffusion and relaxation processes are thermally activated.

Effects of Ca-Zr co-substitution on cation site occupancy and electromagnetic properties of YIG garnet ferrite with narrow ferromagnetic resonance linewidth

Effects of Ca-Zr co-substitution on cation site occupancy and electromagnetic properties of YIG garnet ferrite with narrow ferromagnetic resonance linewidth

Visible Light Photolysis at Single Atom Sites in Semiconductor Perovskite Oxides.

Designing catalysts with well-defined active sites with chemical functionality responsive to visible light has significant potential for overcoming scaling relations limiting chemical reactions over heterogeneous catalyst surfaces. Visible light can be leveraged to facilitate the removal of strongly bound species from well-defined single cationic sites (Rh) under mild conditions (323 K) when they are incorporated within a photoactive perovskite oxide (Rh-doped SrTiO3). CO, a key intermediate in many chemistries, forms stable geminal dicarbonyl Rh complexes (Rh+(CO)2), that could act as site blockers or poisons during a catalytic cycle. For the first time, we demonstrate that CO removal can occur at mild temperatures (323 K) under low-energy red light (635 nm) irradiation, which is not possible for supported isolated-site Rh catalysts (0.2 wt % Rh/γ-Al2O3). Photolysis of supported Rh+(CO)2 complexes (e.g., 0.2 wt % Rh/γ-Al2O3) has been demonstrated but is limited to high energy UV photons. Rigorous kinetic experiments elucidate disparate mechanisms for CO photodepletion from Rh-doped SrTiO3 and supported isolated site Rh/γ-Al2O3. CO photodepletion from supported isolated site Rh/γ-Al2O3 involves a direct metal to ligand charge transfer mechanism, whereas Rh-doped SrTiO3 is governed by electron-hole pair formation in the perovskite. We show that under visible, low-energy red light, surface Rh species in Rh-doped SrTiO3 introduce midgap energy states above the valence band that facilitate electronic excitations leading to surface CO removal. Isolated Rh sites in Rh-doped SrTiO3 also exhibit exceptional stability under multiple CO photodepletion cycles. Overall, incorporating single sites into photoactive perovskite oxides is an effective strategy to influence surface chemistries with visible light.

Relationship Between Electronegativity of the Extra-Framework Cations and Adsorption Capacity for CO2 Gas on Mordenite Framework.

Synthetic mordenite is widely used as a molecular sieve, adsorbent, and catalyst. To enhance these functionalities, it is crucial to understand the ion-exchange properties and cation-exchange sites of the zeolite. In this study, we analyzed the structural changes in fully Cs-, Sr-, Cd-, and Pb-exchanged mordenite by using synchrotron X-ray powder diffraction under ambient conditions. Rietveld structure refinement revealed that the Cs+ cation is predominantly located near the 8-membered ring (8MR) due to its low electronegativity and hydration energy. In contrast, divalent cations such as Sr2+ and Cd2+ cations, with higher hydration energies compared to monovalent cations, are present as hydrated ions at the center of the 12-membered ring along the c-axis (12MRc). Pb2+ ions, due to their higher electronegativity than the framework atoms, exhibit a strong affinity for the electron cloud of framework oxygen atoms, which positions them close to the wall of the 12MRc. The observed differences in the locations of the extra-framework cations are attributed to electrostatic and hydration effects. Furthermore, the CO2 adsorption capacity was assessed based on the type and site of exchangeable cations. The findings indicate that an increase in the CO2 adsorption capacity correlates with the number of cations that can effectively interact with CO2.

60Coγ activation of Cladophora rupestris biomass functional groups and its effect on Pb2+ adsorption.

To investigate the modification of Pb2+ adsorption of the functional groups of Cladophora rupestris (C. rupestris) biomass by gamma radiation (60Coγ-ray), the interface structure, chemical properties, adsorption behaviors, and Pb2+ adsorption mechanisms of C. rupestris biomass were investigated after irradiation with varying doses of 60Coγ-ray. The results indicate that 60Coγ-ray significantly changed the surface characteristics and interfacial chemistry of the C. rupestris biomass.This led to fracturing and fragmentation that produced a larger specific surface area and more abundant pore structure, increasing the electronegativity in the C. rupestris biomass. The theoretical Pb2+ adsorption capacity increased significantly (2.6-2.9 times) after 60Coγ-ray irradiation. 60Coγ-ray caused preferential degradation of protein components in the dissolved organic matter of the C. rupestris biomass, and protein deamination increased the absorption sites of cations. In the C. rupestris biomass, 60Coγ-ray altered the elemental composition and functional groups, particularly the carbon- and oxygen-containing functional groups, to improve Pb2+ adsorption. In conclusion, 60Coγ-ray can activate the functional groups of C. rupestris biomass and improve their Pb2+ adsorption sites. This study provides new insight into modification of biomass materials for enhanced removal of heavy metals from waterbodies.

Tunability in Heterobimetallic Complexes Featuring an Acyclic "Tiara" Polyether Motif.

Both cyclic "crown" and acyclic "tiara" polyethers have been recognized as useful for the binding of metal cations and enabling the assembly of multimetallic complexes. However, the properties of heterobimetallic complexes built upon acyclic polyethers have received less attention than they deserve. Here, the synthesis and characterization of a family of eight redox-active heterobimetallic complexes that pair a nickel center with secondary redox-inactive cations (K+, Na+, Li+, Sr2+, Ca2+, Zn2+, La3+, and Lu3+) bound in acyclic polyether "tiara" moieties are reported. Structural studies with X-ray diffraction analysis were carried out on the monometallic nickel precursor complex to the heterobimetallics and the adducts with K+, Li+, Sr2+, Zn2+, and Lu3+; the results confirm the binding of secondary cations in the tiara site and demonstrate that the tiara moiety is more conformationally flexible than the analogous 18-crown-6-like moiety of a closely related macrocyclic "crown" ligand. Spectroscopic and electrochemical studies show, however, that the stability and cation-driven tunability of the tiara-based heterobimetallic species are quite similar to those previously measured for crown-based species. Consequently, the tiara motif appears to be at least as equally useful for constructing tunable multimetallic species as the more commonly encountered crown motif; a comprehensive set of titration data collected in an acetonitrile solution support this conclusion as well. Because the use of acyclic tiaras avoids the need for tedious and/or time-intensive syntheses of macrocyclic structures, these findings suggest that tiara motifs could be broadly advantageous in the design of ligands to support multimetallic chemistry.

Regulated Li+ Solvation via Competitive Coordination Mechanism of Organic Cations for High Voltage and Fast Charging Lithium Metal Batteries.

Li+ solvation exerted a decisive effect on electrolyte physicochemical properties. Suitable tuning for Li+ solvation enabled batteries to achieve unexpected performance. Here, we introduced inert organic cations to compete with Li+ for combining electrolyte molecules to modulate Li+ coordination in the electrolyte. The relevance between the number of cationic sites in organic cations and the competitive solvation ability was explored. The organic cations with multiple cationic sites attracted solvent molecules and anions away from Li+ to form new solvated shell, improving the Li+ transport kinetics and desolvation process in electrolyte while enhancing electrolyte oxidation tolerance. Moreover, electrostatic shielding provided by organic cations and anion-derived robust SEI promoted uniform and rapid Li+ deposition on Li electrodes. With the positive effect of organic cations, Li||LiCoO2 (LCO) batteries showed high specific capacity (136.46 mAh g-1) at high charge/discharge rate (10 C). Furthermore, Li||LCO batteries exhibited good capacity retention (70 % after 500 cycles) at 4.6 V charge cut-off voltage. This work provides fresh insights for the optimization of electrolytes and battery performance.

Regulated Li+ Solvation via Competitive Coordination Mechanism of Organic Cations for High Voltage and Fast Charging Lithium Metal Batteries

AbstractLi+ solvation exerted a decisive effect on electrolyte physicochemical properties. Suitable tuning for Li+ solvation enabled batteries to achieve unexpected performance. Here, we introduced inert organic cations to compete with Li+ for combining electrolyte molecules to modulate Li+ coordination in the electrolyte. The relevance between the number of cationic sites in organic cations and the competitive solvation ability was explored. The organic cations with multiple cationic sites attracted solvent molecules and anions away from Li+ to form new solvated shell, improving the Li+ transport kinetics and desolvation process in electrolyte while enhancing electrolyte oxidation tolerance. Moreover, electrostatic shielding provided by organic cations and anion‐derived robust SEI promoted uniform and rapid Li+ deposition on Li electrodes. With the positive effect of organic cations, Li||LiCoO2 (LCO) batteries showed high specific capacity (136.46 mAh g−1) at high charge/discharge rate (10 C). Furthermore, Li||LCO batteries exhibited good capacity retention (70 % after 500 cycles) at 4.6 V charge cut‐off voltage. This work provides fresh insights for the optimization of electrolytes and battery performance.

Triggering Oxygen Redox Cycles in Nickel Ferrite by Octahedral Geometry Engineering for Enhancing Oxygen Evolution.

Spinel-type nickel ferrite (NixFe3-xO4, x≤1) is a widely used electrocatalyst for the oxygen evolution reaction (OER). Due to the lower hybridization of metal-d and oxygen-p orbitals, the OER process on NixFe3-xO4 follows the sluggish adsorbate evolution mechanism (AEM). Generally, activating the lattice oxygen to trigger the lattice-oxygen-mediated mechanism (LOM) can enhance the OER activity. Herein, to trigger the LOM pathway while maintaining high stability, iron foam (IF)-supported Ni0.75Fe2.25O4 (NiFeO) with geometrical defects of [NiO6] (nickel cation coordinated with six oxygen anions) units and higher ratio of Fe to Ni cations in octahedral sites (d-NiFeHRO/IF) is prepared by ion-exchanging with polar aprotic solvent followed by annealing. As a result, as-synthesized d-NiFeHRO/IF exhibits excellent activity (at 295mV overpotential to achieve 100mA cm-2), fast kinetics (Tafel slope of only 34.6mV dec-1), and high stability (maintaining a current density of 100mA cm-2 over 130h) for the OER. The theoretical calculations reveal that the construction of octahedral defect in NixFe3-xO4 enhances the overlap of Fe-d and O-p orbitals, which can activate the lattice oxygen. Therefore, increasing the ratio of Fe to Ni will further improve the lattice oxygen redox activity, and thus trigger the fast LOM pathway, ultimately facilitating the OER process.

Regulating the surface chemistry of covalent organic frameworks for enhancement cationic dye removal and identification.

Simultaneous removal and identification of trace-level cationic dye pollutants from water is both important and challenging owing to their highly polar and complex sample matrices. In this study, three covalent organic frameworks (COFs) were synthesized using 2, 4, 6-triformylphloroglucinol with ethidium bromide (EB) containing positively charged groups, 3, 5-diaminobenzoic acid (DABA) containing negatively charged groups, and p-phenylenediamine (Pa) lacking charged groups. These were named EB-COFs, TpPa-1, and DP-COFs, respectively, and were employed as adsorbents for the extraction and identification of cationic dyes. The adsorption performance of the three COFs toward methylene blue (MB) and crystal violet (CV) was investigated. By incorporating carboxyl groups into DP-COFs, the surface chemistry of the adsorbent was effectively tailored, enabling complete exploitation of selective cationic sites. This facilitated dynamic interactions with cationic dyes through multiple adsorption mechanisms, including electrostatic, π-π, and H-bonding interactions. DP-COFs exhibited high adsorption capacities for MB and CV, achieving 383 and 326mgg-1, respectively. The adsorption behavior was further analyzed using adsorption isothermals, kinetics, and thermodynamics. Moreover, DP-COFs were employed as a matrix in laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF MS) to adsorb and directly identify both cationic dyes without the need for an elution process. This approach demonstrated high sensitivity, high reproducibility, low background interference, and excellent salt tolerance. The limits of detection for MB and CV were 0.12 and 0.04ngmL-1, respectively, representing improvements of 166-fold and 225-fold compared with using DP-COFs solely as a matrix. Recovery rates of both dyes in spiked industrial wastewater and lake water samples ranged from 81.4 to111.1% with RSDs of 1.9-6.3%. These results highlight the high reliability of the proposed method.

Manipulating Electron-Phonon Coupling for Efficient Tin Halide Perovskite Blue LEDs.

Low-dimensional perovskites have opened up a new frontier in light-emitting diodes (LED) due to their excellent properties. However, concerns regarding the potential toxicity of Pb limited their commercial development. Sn-based perovskites are regarded as a promising candidate to replace Pb-based counterparts, while they generally exhibit strong electron-phonon coupling and consequently blue emission quenching at room temperature (RT), thus the Sn-based perovskite blue LED devices have not yet been reported. Herein, the luminescence properties are regulated by assembling a rigid organic skeleton within perovskite structure, and the protonated 4-bromobenzylamine (BrPMA+ = C7H9BrN+) is employed as A site cation to synthesize a 100-oriented 2D perovskite (BrPMA)2SnBr4, which exhibits a strong lattice rigidity via strong intermolecular interaction and consequently weak electron-phonon coupling, achieving the excellent blue PL emission at RT. The high quality (BrPMA)2SnBr4 perovskite thin films are obtained by further inhibiting oxidation and promoting crystallization. Finally, the Sn-based perovskite blue emission LED is successfully fabricated for the first time at 467nm with a champion EQE of 1.3% and a maximum brightness of 800cdm-2. This work gives insights into the luminescence mechanism of Sn-based perovskites and provides a new theoretical basis for the development of lead-free blue LEDs.

Chrome-free leather processing based on amine pendant metal-organic frameworks and dialdehyde with enhanced dye affinity.

To overcome the stringent regulations in the usage of chromium salts and dye-rich effluent let out by the tanning industry, a sustainable way of leather processing has been demonstrated utilizing amine pendant metal-organic frameworks (MOF) UiO-66-NH2 along with glyoxal. It was found that an offer of 8% (w/w) MOF along with 6% (w/w) glyoxal increased the shrinkage temperature of the leathers to 89 ± 2°C with exhaustion of MOF up to 84.3 ± 1.5%. The presence of cationic amine sites in the MOF aided in the fixation of anionic post-tanning agents and improved the adsorption of dyes from 74.3 ± 2.5% in the case of conventional leather to 91.8 ± 1.7% for experimental leather. In comparison to chrome-tanned leather, the experimental leathers were rated the highest in terms of dye fastness concerning rubbing action and against perspiration, showcasing the washable properties and better affinity and irreversible binding of dyes to the leather matrix. Mechanism studies through XPS spectroscopy revealed the interaction between the acidic amino acids of collagen and free zirconium metal sites and the imine linkage between amine pendants of MOF and basic amino acids of collagen protein. Further, the BOD5/COD ratio of 0.36 confirmed the better treatability of the wastewater emanating from the proposed process making it a sustainable tanning system. Thus, the combination of amine pendant MOFs with dialdehyde can be a promising strategy for the development of robust chrome-free leathers with excellent functional properties.

Raman scattering of omphacite at high pressure: Toward its possible application to elastic geothermobarometry

Abstract Due to their widespread occurrence in several geological settings, omphacite inclusions could be used for elastic Raman geothermobarometry. However, the Raman scattering of complex silicate minerals entrapped in a host depends on both the chemical composition and elastic strain developed during the metamorphic pathway, which makes the task very challenging. Here, as a very first step to probe the potential of omphacite to be used as a mineral inclusion in elastic geothermobarometry, we report the pressure dependence of the Raman spectra of omphacite crystals with the same composition, approximately Jd43Di57, but having different symmetry because of the existence (P2/n) or absence (C2/c) of chemical order at the six- and eight-coordinated cation sites. The experimental results are complemented by ab initio quantum mechanical simulations on fully ordered omphacite (Jd50Di50). We demonstrate that the position of the well-resolved Raman peak near 688 cm–1, arising from Si-O-Si bond bending, is very sensitive to pressure but independent of the state of chemical order, which makes it promising to be utilized in Raman geobarometry. The width of this peak varies with chemical order but not with pressure and therefore can be used to constrain the temperature of inclusion entrapment, because the chemical order is indicative of the closure temperature of the cation-exchange reaction. However, further detailed analyses on the compositional variation of the Raman spectra of omphacite is required before considering omphacite-in-garnet systems to be suitable for Raman elastic geothermobarometry.

Highly efficient iron and cobalt benzimidazole metal organic framework electrocatalysts for hydrogen evolution reaction

Reported herein were two new electrocatalysts based on metal-organic frameworks (MOFs) that were easily crystallized into the pure 3D net. The cobalt (Co-MOF) and iron (Fe-MOF) metal bearing MOFs were prepared with the reaction of cobalt or iron cations with a benzimidazole linker in the mixture of dimethyl formamide (DMF), ethanol, and water using a solvothermal synthesis method. Without any further post-treatments, Co-MOF and Fe-MOF were directly used as promising electrocatalysts for facilitating hydrogen evolution reactions (HER). Remarkably, the high HER catalytic activity was provided through practical measurements with incredible achievement by utilizing Co-MOF and Fe-MOF. The experimental studies showed that both Co-MOF and Fe-MOF coordinated with water molecules and opened access to the metal cation site which facilitated the electrocatalytic activity of them with the lattice water. Both MOFs exhibited superior HER activity including very low overpotentials, low Tafel slopes, high exchange current densities, and long-term stabilities. While the HER overpotential of the GCE/Co-MOF electrode decreased up to 50 mV at a current density of 10 mA/cm2 with a Tafel slope of 38.57 mV.dec−1, Fe-MOF also achieved another incredible overpotential reduction with 46 mV and a Tafel value of 46.71 mV.dec−1, which were very close to the commercial Pt/C electrocatalyst having 42 mV of overpotential with a Tafel slope of about 34.32 mV.dec−1. Additionally, these electrocatalysts showed great current stability with linear sweep voltammetry and good chronoamperometric stability of 86.7% with Fe-MOF and 67.7% with Co-MOF with 12 h tests under stirring for HER. Consequently, this research study represented one of the most successful studies that were done and managed to report one of the best electrocatalytic performances with two simple MOF structures since we managed to break off the limitation for finding available and inexpensive catalysts that were competitive with platinum catalysts that represented the major obstacles (being expensive and rare) that hampered the development of more sophisticated hydrogen production systems.

Nano‐Springe Enriched Hierarchical Porous MOP/COF Hybrid Aerogel: Efficient Recovery of Gold from Electronic Waste

AbstractExtraction of gold from secondary resources such as electronic waste (e‐waste) has become crucial in recent times to compensate for the gradual scarcity of the noble metal in natural mines. However, designing and synthesizing a suitable material for highly efficient gold recovery is still a great challenge. Herein, we have strategically designed rapid fabrication of an ionic crystalline hybrid aerogel by covalent threading of an amino‐functionalized metal‐organic polyhedra with an imine‐linked chemically stable covalent organic framework at ambient condition. The hierarchically porous ultra‐light aerogel featuring imine‐rich backbone, high surface area, and cationic sites have shown fast removal, high uptake capacity (2349 mg/g), and excellent selectivity towards gold sequestration. Besides, the aerogel can extract ultra‐trace gold‐ions from different terrestrial water bodies, aiming towards safe drinking water. This study demonstrates the great potential of the composite materials based on a novel approach to designing a hybrid porous material for efficient gold recovery from complex water matrices.

Nano-Springe Enriched Hierarchical Porous MOP/COF Hybrid Aerogel: Efficient Recovery of Gold from Electronic Waste.

Extraction of gold from secondary resources such as electronic waste (e-waste) has become crucial in recent times to compensate for the gradual scarcity of the noble metal in natural mines. However, designing and synthesizing a suitable material for highly efficient gold recovery is still a great challenge. Herein, we have strategically designed rapid fabrication of an ionic crystalline hybrid aerogel by covalent threading of an amino-functionalized metal-organic polyhedra with an imine-linked chemically stable covalent organic framework at ambient condition. The hierarchically porous ultra-light aerogel featuring imine-rich backbone, high surface area, and cationic sites have shown fast removal, high uptake capacity (2349 mg/g), and excellent selectivity towards gold sequestration. Besides, the aerogel can extract ultra-trace gold-ions from different terrestrial water bodies, aiming towards safe drinking water. This study demonstrates the great potential of the composite materials based on a novel approach to designing a hybrid porous material for efficient gold recovery from complex water matrices.

Discovering Multi-Compositional Li-Argyrodite Solid-State Electrolytes via Experimental Active Learning.

Significant research has focused on doping third-party elements into representative Li-Argyrodites, which typically consist of a metal cation, a sulfide anion, and a halide. These efforts have generally been limited to doping or substituting a single element at each atomic site in the Argyrodite structure, resulting in, at most, binary combinations at each site. Multi-elemental doping or substitution poses a challenge due to the so-called combinatorial explosion issue. Here, the study reports quaternary and ternary combinations at either the cation or anion sites, optimizing the composition for ambient-temperature ionic conductivity. Managing such a complex multi-compositional system requires artificial intelligence that surpasses human intuition. A particle swarm optimization (PSO) algorithm is employed within an active learning framework to tackle this multi-dimensional optimization problem. Unlike typical active learning approaches that rely on theoretical computational data, the process is driven by experimental data from the synthesis and characterization of a few hundred multi-compositional Argyrodite samples This experimental active learning approach ultimately enables identifying a novel multi-compositional Li-Argyrodite, exhibiting ambient-temperature ionic conductivity of 13.02 mS cm⁻¹ and enhanced cell performance, with the composition Li6.425Ge0.25Si0.375Sb0.375S4.8I1.2.

Cation Vacancy-Mediated Ultrafast Hole Transport in CuBi2O4 Photocathodes.

As a promising photocathode candidate, tetragonal CuBi2O4 (CBO) has been studied extensively in recent years. As an intrinsically p-type material, its acceptor sites originate from the cation vacancies, which are also a potential cause of hindered hole utilization in photocathodes. In this study, the ultrafast transport dynamics of the valence band hole states in CBO photocathodes were investigated by varying their atomic compositionand manipulating the p-type character. As a comprehensive ultrafast optical transient absorption spectroscopy (TAS) investigation of compositionally manipulated CBO that combines both ex situ and in situ TAS experiments with photoelectrochemical (PEC) performance tests, the study reveals the polaron formation tendencies of the valence band (VB) holes at cationic vacancy sites. Therefore, it draws a complete picture of the ultrafast hole transport dynamics and provides valuable insights into the hindrance of the photocurrent generated in CBO.

Physicochemical characterization and cytotoxicity assessment of sodium dodecyl sulfate (SDS) modified chitosan (SDSCS) before and after removal of aflatoxins (AFs) as a potential mycotoxin Binder

Aflatoxins in food and feed with prominent toxic effects have jeopardized public health for decades. This investigation intends to explore synthesized SDS-modified chitosan as new generation of binder for removal of aflatoxin using a straightforward ionic cross-linking approach. The primary objective of this technique was to enhance affinity and adsorption capability of SDSCS towards aflatoxins. In this context, physicochemical properties of SDSCS characterized with advanced analytical techniques such as scanning electron microscope (SEM) coupled with energy dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FT-IR) before and after removal of aflatoxin. In this study, effect of the pH on the adsorption of aflatoxins (6ppb) indicated that the increase in SDSCS concentration from low (0.5) to high (2 %) resulted in an increase of about 80 %, 78 % and 81 % in the adsorption percentage of AFB1, AFG1, and AFB2 & AFG2, respectively. FT-IR analysis showed the intramolecular interactions of the amine groups of chitosan and sulfate group of SDS formed a stable complex in the removal of aflatoxin that verified with appearance of three new additional peaks at 1323.50, 984.34 and 603.42 cm−1. Notably, SEM images revealed that the porous SDSCS network was filled with aflatoxin molecules supported with EDS findings. Also, in vitro cytotoxicity assessments demonstrated that SDSCS protected HepG2 cells against cytotoxic effect caused by aflatoxin (5 µM) in a concentration-dependent manner compared to the control (p<0.01). Collectively, the adsorption mechanism may involve attraction of anionic aflatoxin molecule into the interconnected pores of SDSCS complex with numerous cationic active site via hydrogen bond and van der waals force.