Hard And Soft Acids And Bases Research Articles

A Functional Air-Stable Li9.8GeP1.7Sb0.3S11.8I0.2 Superionic Conductor for High-Performance All-Solid-State Lithium Batteries.

Solid-state electrolytes (SSEs) based on sulfides have become a subject of great interest due to their superior Li-ion conductivity, low grain boundary resistance, and adequate mechanical strength. However, they grapple with chemical instability toward moisture hypersensitivity, which decreases their ionic conductivity, leading to more processing requirements. Herein, a Li9.8GeP1.7Sb0.3S11.8I0.2 (LGPSSI) superionic conductor is designed with a Li+ conductivity of 6.6 mS cm-1 and superior air stability based on hard and soft acids and bases (HSAB) theory. The introduction of optimal antimony (Sb) and iodine (I) into the Li10GeP2S12 (LGPS) structure facilitates fast Li-ion migration with low activation energy (Ea) of 20.33 kJ mol-1. The higher air stability of LGPSSI is credited to the strategic substitution of soft acid Sb into (Ge/P)S4 tetrahedral sites, examined by Raman and X-ray photoelectron spectroscopy techniques. Relatively lower acidity of Sb compared to phosphorus (P) realizes a stronger Sb-S bond, minimizing the evolution of toxic H2S (0.1728 cm3 g-1), which is ∼3 times lower than pristine LGPS when LGPSSI is exposed to moist air for 120 min. The NCA//Li-In full cell with a LGPSSI superionic conductor delivered the first discharge capacity of 209.1 mAh g-1 with 86.94% Coulombic efficiency at 0.1 mA cm-2. Furthermore, operating at a current density of 0.3 mA cm-2, LiNbO3@NCA/LGPSSI/Li-In cell demonstrated an exceptional reversible capacity of 117.70 mAh g-1, retaining 92.64% of its original capacity over 100 cycles.

Visible light photocatalytic performance of Co/Ag bimetallic coordination polymer catalysts designed from hard and soft acid-base theory

Heterometallic coordination polymers have promising applications in photocatalysis, and the design and selection of suitable organic ligands and coordination metals is the key to improve the catalytic activity of polymer photocatalysts. Herein, a novel Co/Ag bimetallic coordination photocatalyst, designed based on the hard and soft acid-base (HSAB) theory, has been successfully prepared by a stepwise method with Ag-S coordination as the main component and Co-N/Co-S as the complementary component. The obtained Co/Ag photocatalyst demonstrates excellent performance in the photocatalytic degradation (visible light) of halogenated phenolic pollutants. Degradation of 10 ppm of 4-chlorophenol could reach 100 % in 4 h, and 70 % degradation of 4-fluorophenol, which is even more difficult to degrade, could also be achieved. In addition, hydrogen production experiments conducted under visible light irradiation showed that the hydrogen production could reach 36.95 μmol h−1 g−1 for 6 h, which strongly demonstrated the excellent reduction ability of Co/Ag photocatalysts. The photocatalyst exhibits enhanced photocatalytic activity which is ascribed to the formation of Ag-S and Co-N/Co-S coordination, which greatly increases the charge density and facilitates charge transfer. Thus, the photogenerated electrons can induce both the conversion of O2 to •O2- for oxidation reactions, as well as the direct attack of the C-Cl bond for reduction reactions. This study demonstrates the successful design of the synergistic Co/Ag bimetallic coordination photocatalysts based on the HSAB theory, thereby offering a promising research avenue for the fabrication of heterometallic coordination photocatalysts.

Ag-Fe2O3 nanocomposites for synergistically enhanced antibacterial activity

Doping of metal or metal ions in the host lattice with good dopant distribution or forming a local contact boosts materials properties for specific applications. This work used the solution combustion approach (SCA) to synthesize Ag-Fe2O3 nanocomposites (SICs) following the single-source precursor doping strategy with good final material stoichiometry. The elemental distribution and composition, crystallinity, and morphology of SCA-based synthesized materials were analyzed using common techniques such as TEM, FESEM-EDS, and XRD. Even though the Lewis hard and soft acids and bases (HSAB) idea was precise for inclusion of Ag dopant in the Fe2O3 lattice, the formation of Schottky junctions between Ag and Fe2O3 is dominance as a result of dopant-host radii size differences. The independent peak for both Ag and Fe2O3 crystals on the XRD pattern analysis without peak shift confirms the dominance of Schottky junction formation. The presence of local contact between Ag and Fe2O3 was also confirmed by the HRTEM analysis, with d-spacing values of 0.22 and 0.36 nm, respectively. Compared to the bare Fe2O3, the antibacterial potential of the SIC is much greater, with a 23-mm zone of inhibition on Pseudomonas aeruginosa gram-negative bacteria, which confirms the presence of a synergistic effect.

Interaction mechanism of phytic acid functionalized graphene oxide with ionic dyes

Phytic acid functionalized graphene oxide (PA-GO) has fascinating application in environmental remediation. Herein, PA-GO was facilely prepared via hydrothermal method and utilized as adsorbent to remove aqueous Congo red (CR) and malachite green (MG). The adsorbent-adsorbate interaction mechanism was elaborately scrutinized based on the hard and soft acid base (HSAB) principle, spectroscopic analysis and adsorption fitting. Result shows, after five consecutive cycles, PA-GO maintains adsorption quantity 242.82 mg·g−1 and 117.53 mg·g−1 for CR and MG, respectively. The HSAB principle illuminates, primary interaction of PA-GO with both CR and MG is provided by phytic acid moiety (PA). For CR adsorption, electron of N atom in –NH2 group flows towards O atom in OH and O(-O-) of PA. While for MG adsorption, electron of N atom in (CH3)2N– group flows towards O atom in OH and O(-O-) of PA. FTIR, UV–Vis analyses supports the HSAB principle prediction. In brief, the hydroxyls and phosphoric groups introduced by PA functionalization enhance the adsorption affinity of GO. Adsorption of CR, MG by PA-GO under favorable pH is thermodynamically chemical but kinetically impelled by electrostatic interaction. This work may promote the development of efficient adsorbent based on PA-GO architecture for environmental remediation.

Synthesis of hollow Fe3O4 microboxes guided by the hard and soft acid-base principle for enhanced electromagnetic wave absorption

A novel strategy based on the hard and soft acid-base (HSAB) principle to synthesize high-quality Fe3O4 microboxes was investigated. Initially, an Fe3O4 thin shell was generated on the surface of Cu2O cubic templates by meticulously regulating the hydrolysis kinetics of Fe3+. The Cu2O templates were then selectively dissolved using NH4Cl as an etchant, in conjunction with the reduction of Fe3+, yielding the hollow architectures of Fe3O4 microboxes. Capitalizing on the inherent merits of the hollow microstructures, the Fe3O4 microboxes exhibited superior electromagnetic wave (EMW) absorption efficiency. The Fe3O4 microboxes/paraffin composites demonstrated remarkable EMW absorption performance. A sample with 60 wt% loading and 1.16 mm thickness achieved the minimum reflection loss (RLmin) of − 35.9 dB at 16.2 GHz, with an effective absorption bandwidth (EAB) of 3.5 GHz.

Using a Metaverse to Teach Students to Predict the Interaction of Acids and Bases Using Hard and Soft Acids and Bases (HSAB) Theory

Using a Metaverse to Teach Students to Predict the Interaction of Acids and Bases Using Hard and Soft Acids and Bases (HSAB) Theory

Elucidating the Role of Chalcogenide‐Based Interface Passivators in Enhancing the Stability of Perovskite Solar Cells

AbstractChalcogenide‐based Lewis bases are widely used in perovskite solar cells (PSCs) due to their effectiveness in passivating Pb2+ and Pb0‐related defects. However, the underlying principles governing their defect passivation and the relative efficacy of different chalcogen elements remain poorly understood. This study evaluates the effectiveness of oxygen, sulfur, and selenium‐based interface passivator molecules in enhancing the stability and power conversion efficiency (PCE) of perovskite solar cell devices. The hard and soft acid and base (HSAB) principle has been utilized here to gain insights into the defect passivation behavior of chalcogenide‐based molecules. The photoluminescence, ideality factor, and trap density measurements reveal that the sulfide and selenide‐passivated devices exhibit superior defect passivation compared to the oxide‐passivated control device. In terms of stability, the average T75 lifetime (time at which 75% of the initial PCE is retained) of the oxide, sulfide, and selenide passivated samples is 6%, 30%, and 50% higher compared to their un‐passivated counterparts. This enhanced stability with the sulfide and selenide‐based passivators can be attributed to their soft Lewis base nature, which resulted in stronger interaction with the Pb‐related defects, as evidenced by the density‐functional theory calculations and X‐Ray photoelectron spectroscopy study.

Adsorption of Pd(II) ions by electrospun fibers with effective adsorption sites constructed by N, O atoms with a particular spatial configuration: Mechanism and practical applications

The separation and recovery of palladium from electronic waste (e-waste) are of great significance as they can alleviate environmental pollution and avoid resource loss. Herein, a novel nanofiber modified by 8-hydroxyquinoline (8-HQ-Nanofiber) with adsorption sites co-constructed by N and O atoms of hard bases was fabricated, which has good affinity properties for the Pd(II) ions belonging to soft acid in the leachate of e-waste. The adsorption mechanism of 8-HQ-Nanofiber for Pd(II) ions was revealed from the perspective of molecular level relied on a series of characterizations, such as FT-IR, ss-NMR, Zeta potential, XPS, BET, SEM and DFT. The adsorption of Pd(II) ions on 8-HQ-Nanofiber reached equilibrium within 30 min and the maximum uptake capacity was 281 mg/g at 318.15 K. The adsorption behavior of Pd(II) ions by 8-HQ-Nanofiber was described by the pseudo-second-order and Langmuir isotherm models. The 8-HQ-Nanofiber exhibited relatively good adsorption performance after 15 times of column adsorption. Finally, based on hard and soft acids and bases (HSAB) theory, a strategy to regulate the Lewis alkalinity of adsorption sites by specific spatial structures is proposed, which provides a new direction for the design of adsorption sites.

Adsorption mechanism and removal efficiency of magnetic graphene oxide-chitosan hybrid on aqueous Zn(II)

Magnetic architecture incorporating graphene-chitosan has demonstrated encouraging application in wastewater purification. Herein, a ternary hybrid based on Fe3O4-graphene oxide-chitosan (MGOCS) was fabricated and employed as adsorbent to remove aqueous Zn(II). The adsorption mechanism was intensively inspected based on the hard and soft acid base (HSAB) theory. Results present, MGOCS removes 96.73 % of Zn(II) in 38 min, with adsorption quantity 386.92 mg·g−1. Electron transfer and energy lowering determined by the HSAB theory illuminate the plausible adsorption sites in each component of MGOCS: O2− in Fe3O4, -C(=O)NH-, -NH2 in chitosan and -OH in graphene oxide. The exploration was upheld by spectroscopic analyses. Thereby, following adsorption mechanism was proposed. (1) ZnO bond was formed featured by electron donation. (2) The -C(=O)NH- group formed via amidation between graphene oxide and chitosan contributes to Zn(Π) uptake. This work may inspire the development of efficient adsorbent based on magnetic graphene-chitosan for wastewater remediation.

Unraveling Bonding Mechanisms and Electronic Structure of Pyridine Oximes on Fe(110) Surface: Deeper Insights from DFT, Molecular Dynamics and SCC-DFT Tight Binding Simulations.

The development of corrosion inhibitors with outstanding performance is a never-ending and complex process engaged in by researchers, engineers and practitioners. The computational assessment of organic corrosion inhibitors' performance is a crucial step towards the design of new task-specific materials. Herein, the electronic features, adsorption characteristics and bonding mechanisms of two pyridine oximes, namely 2-pyridylaldoxime (2POH) and 3-pyridylaldoxime (3POH), with the iron surface were investigated using molecular dynamics (MD), and self-consistent-charge density-functional tight-binding (SCC-DFTB) simulations. SCC-DFTB simulations revealed that the 3POH molecule can form covalent bonds with iron atoms in its neutral and protonated states, while the 2POH molecule can only bond with iron through its protonated form, resulting in interaction energies of -2.534, -2.007, -1.897, and -0.007 eV for 3POH, 3POH+, 2POH+, and 2POH, respectively. Projected density of states (PDOSs) analysis of pyridines-Fe(110) interactions indicated that pyridine molecules were chemically adsorbed on the iron surface. Quantum chemical calculations (QCCs) revealed that the energy gap and Hard and Soft Acids and Bases (HSAB) principles were efficient in predicting the bonding trend of the molecules investigated with an iron surface. 3POH had the lowest energy gap of 1.706 eV, followed by 3POH+ (2.806 eV), 2POH+ (3.121 eV), and 2POH (3.431 eV). In the presence of a simulated solution, MD simulation showed that the neutral and protonated forms of molecules exhibited a parallel adsorption mode on an iron surface. The excellent adsorption properties and corrosion inhibition performance of 3POH may be attributed to its low stability compared to 2POH molecules.

Titanium Sulfonate-Based Metal–Organic Frameworks

Titanium-based metal–organic frameworks (Ti-MOFs) are one of the most active fields of MOFs due to their intriguing catalytic properties; however, the fast reaction between the widely used carboxylate-based ligand (hard base) and Ti4+ ion (hard acid) makes the syntheses of Ti-MOFs extremely challenging. In this work, we propose a new strategy by adopting sulfonic acid (soft base) as organic ligands to synthesize Ti-MOFs based on hard and soft acid and base (HSAB) theory. As an example of this strategy, seven titanium sulfonate metal–organic frameworks have been synthesized from 1,5-naphthalenedisulfonic acid (H2nds) and titanium isopropoxide and their structures are determined by single-crystal X-ray diffraction. These compounds exhibit permanent porosity, solvent stability, and light adsorption ability with a narrow band gap (2.67 eV). This work demonstrates a powerful method for the single-crystal syntheses of new Ti-MOFs, which will greatly promote the development of Ti-MOFs.

Enhancing the Moisture Stability and Electrochemical Performances of Li6PS5Cl Solid Electrolytes through Ga Substitution

Sulfide solid electrolytes are attracting much attention as a next-generation electrolyte material due to their high ionic conductivity and appropriate mechanical properties. Among them, Li-argyrodite exhibits ultrahigh Li-ion conductivity and has the possibility of process expansion, so it is a material that has been extensively studied in academia and industry. However, due to the high reactivity of S and the weak P-S bond, there are electrochemical and air stability issues, such as undesirable reactions at the interface with the active material in the composite electrode during charge/discharge cycling and reacting readily with moisture in the atmosphere. Herein, we report solid-electrolyte with the composition Li6+2xGaxP1-xS5Cl (x = 0, 0.013, 0.025, 0.038, 0.05, 0.075) in which P is substituted with softer acid Ga, based on Hard and Soft Acids and Bases (HSAB) theory. In the half-cell charge/discharge experiment using synthesized electrolytes for cathode composite, the cell using Li6.1Ga0.05P0.95S5Cl shows a higher capacity retention rate after 50 cycles, and XPS analysis confirmed that lower electrolyte decomposition compared to the cell using Li6PS5Cl. This demonstrates that the electrochemical stability of the solid electrolyte is improved with Ga substitution. Further, the dry air exposure test confirms that the air stability of Li6PS5Cl is increased by Ga substitution. Finally, the Cyclic Voltammetry (CV) tests show that Ga-substitution enhanced the stability against Li-metal.

A density functional based tight binding (DFTB+) study on the sulfidization-xanthate flotation mechanism of cerussite

Cerussite (PbCO3) has now attracted increasing attention due to the increasing demand of Pb metal and rapid depletion of Pb−S minerals. Sulfidization-xanthate method is effective to recover PbCO3. In this paper, density functional based tight binding (DFTB+) method was employed to discuss microscopic mechanism of cerussite sulfidization. Sulfidization model of a PbS film forming on PbCO3 surface was established based on coordination chemistry of mineral flotation, changing ligand type of Pb from O ligand to S ligand. The results showed that after sulfidization surface Pb exhibited significant surface relaxation, leading to enhanced activity of Pb4f and Pb5f 6p orbitals. Density of state (DOS) analysis indicated that S ligand strengths nephelauxetic effect of Pb atoms, resulting in stronger covalent effect of Pb−S bonding compared with Pb−O bonding. Sulfidization turned Pb2+ from hard acid in PbCO3 to soft acid in PbS, making it easier to interact with butyl xanthate (soft base) but harder to interact with water (hard base). Calculation results showed that adsorption energy of water becomes less negative after sulfidization, whereas formation energy of water and xanthate co-adsorbed on sulfidized surface becomes more negative, suggesting calculation results agree with the prediction of hard and soft acids and bases (HSAB) theory.

Hard and Soft Acid and Base (HSAB) Engineering for Efficient and Stable Sn‐Pb Perovskite Solar Cells

AbstractRegulation of Lewis acid‐base adduct intermediate is more critical for the dual metal ions of Sn2+ and Pb2+ than for the single metal ion such as Pb2+ in preparing high quality perovskite films. It has been reported here that the photovoltaic performance of Sn‐Pb alloyed perovskite solar cells is dependent on the interaction between metal ions and Lewis base additives. Urea and thiourea are selected as an O‐ and a S‐donor, respectively, which is used as an additive in the precursor solution including equimolar SnI2 and PbI2 together with organic iodides of formamidinium iodide and methylammonium iodide, forming a nominal composition of FA0.5MA0.5Pb0.5Sn0.5I3. Open‐circuit voltage (Voc) is increased while maintaining short‐circuit photocurrent density (Jsc) after the addition of urea. On the other hand, both Jsc and Voc are simultaneously increased by adding thiourea, leading to a considerable increase in power conversion efficiency from 14.58% (control) to 18.59%. A strong interaction between the relatively soft Sn2+, compared to Sn4+, and the soft sulfur in thiourea, associated with hard and soft acid and base theory, suppresses effectively a disproportionation reaction of 2Sn2+→ Sn4+ + Sn0, which results in a substantial enhancement of carrier lifetime and consequently photovoltaic performance.

Mechanistic study of Hg(II) interaction with three different α-aminophosphonate adsorbents: Insights from batch experiments and theoretical calculations.

Herein, efficient and potential chelating α-aminophosphonate based sorbents (AP-) derived from three different amine origins (aniline/anthranilic acid/O-phenylenediamine) to form AP-H, carboxylated and aminated enhanced aminophosphonate as AP-H, AP-COOH, and AP-NH2 were synthesized via a facile method. The structure of the synthesized sorbents was elucidated using different techniques; elemental analysis (CHNP/O), FT-IR, NMR (1H-, 13C and 31P NMR), TGA and BET. The fabricated sorbents were exploited for Hg(II) removal from aqueous solution via sorption properties. Isotherm fitted by Langmuir equation: the maximum sorption capacities at optimum pH 5.5, and T:25±1°C, were found to be 1.33, 1.23, and 1.15mmol Hg g-1 for AP-COOH, AP-NH2, AP-H, respectively, which is roughly correlated with the active sites density and the hard/soft characteristics of adsorbents' reactive groups. Metal-ligand binding affinities are qualitatively rationalized in terms of hard and soft acids and bases (HSAB) theory. The interaction of Hg(II) (soft) has a stronger affinity to AP-COOH can be considered a softer base compared with reference material (AP-H) over than AP-NH2 (hard). This sequence result showed opposite trends consistent with their reciprocal properties according to the steric effect modulates and the specific surface area. Thermodynamics analysis for absolute values of ΔH°, ΔS° and ΔG° afford the selectivity towards Hg(II) sorption with the following order: AP-COOH>AP-NH2 >AP-H. Elution and regeneration was carried out by HCl solution and recycled for a minimum of five cycles, the sorption and desorption efficiencies are greater than 91%. Such sorbents exhibit good durability, stability and promising potential for Hg(II) removal. Finally, a new modelling technique for quantitative non-linear description and comparison of equivalent geographical positions in 3D space of extended relationships. Exothermic and spontaneous behavior were observed using a proposed Floatotherm that included the Van't Hoff parameters model.

New mixed‐ligand iron(III) complexes containing thiocarbohydrazones: Preparation, characterization, and chemical reactivity analysis through theoretical calculations

Five new mixed ligand Fe(III) complexes, namely, [FeL1(acac)] (L1Fe), [FeL2(acac)] (L2Fe), [FeL3(acac)] (L3Fe), [FeL4(acac)] (L4Fe), and [FeL5(acac)] (L5Fe), were synthesized from the reaction of iron(III) acetylacetonate with [ONS] donor dibasic tridentate symmetrical bisthiocarbohydrazone ligands. Synthesized mixed ligand Fe(III) complexes were characterized with infrared spectra, UV‐Vis spectra, mass spectra, elemental analysis, magnetic susceptibility measurements, and thermogravimetric analysis. The molar conductance measurement in DMF solution confirmed that the complexes are nonelectrolytic. TGA analysis results showed that the thermal stability of the ligands and complexes was high. Antioxidant capacity and free radical scavenging activity of the mixed ligand Fe(III) complexes were investigated using CUPRAC and the DPPH radical scavenging method. Mixed ligand Fe(III) complexes showed higher antioxidant activity than ligands and reference compound. Popular conceptual density functional parameters like hardness, electrophilicity, dipole moment, and chemical potential for new ligands and their Fe(III) complexes were calculated and discussed. Chemical reactivity and stabilities of the studied chemical systems were analyzed with the help of well‐known electronic structure principles like maximum hardness principle (MHP), hard and soft acid–base (HSAB) principle, minimum polarizability principle, and minimum electrophilicity principle. L1Fe, which has the highest chemical hardness value, is the most stable complex according to MHP.

Biosorption of Rubber Seed Shell as a Waste Material in the Removal of Cadmium Ion from Contaminated Water

Heavy metal ion contamination in industrial wastewater is a major source of concern. Among the numerous approaches, biosorption has attracted the greatest attention in the removal of heavy metal ions from water. In particular, cadmium is bio-accumulative that poses a threat to our health when it exists in excess in our bloodstream. Here, the elimination of Cd (II) ions from wastewater using adsorbent derived from rubber seed shell (RSS). Further, thermogravimetric analysis was performed to determine the stability of materials. According to the hard and soft acids and bases (HSAB) principle, the rubber seed shell as novel bioadsorbent creates hard surface sites for cadmium ion adsorption. Batch experiments were carried out to determine the effects of pH, contact time, initial metal ions concentration, and biosorbent dosage on the removal efficiencies of Cd2+ ion using rubber seed shell. Adsorption isotherms and kinetics models were also performed for the elimination of Cd2+ ion. The optimum conditions was conducted and achieved 96% removal efficiencies of Cd2+ ion from water (pH 5.6, temperature 60°C, and initial metal concentration of 150 mg/L, the adsorption dosage 180 mg/g). The outcome of the present investigations indicated that the increasing use of bioadsorbent materials due to their low cost, regeneration ability, high adsorption efficiency, and higher removal percentage of metal ions from water sources.

Adsorptive desulfurization using period 4 transition metals oxide: A study of Lewis acid strength derived from the adsorbent ionic-covalent parameter

Pearson’s Hard and Soft Acids and Bases (HSAB) principle has been widely utilized in describing the adsorption trend of sulfur compounds when using transition metal/metal oxides as adsorbents. This study is the first to report on the use of the ionic covalent parameter (ICP) for explaining the adsorption trend of sulfur compounds. Period 4 transition metal oxides (Zn-oxide, Cr-oxide, Mn-oxide, Co-oxide, Fe-oxide, Cu-oxide, Ni-oxide), which act as intermediate Lewis acids, were incorporated into activated carbon (AC), and used in the adsorptive desulfurization (ADS) of model and commercial diesel samples. The study findings show that desulfurization activity in model diesel increased in proportion to the concentration of adsorbent Lewis acid sites. With commercial diesel, the loading of metal oxides significantly enhanced the sulfur adsorption capacity of AC and increased its selectivity for steric sulfur compounds. The results showed a poor correlation between sulfur removal and the Pearson hardness ηth of the intermediate metal oxide cations. However, a strong inverse linear relationship was observed: sulfur removal decreased as the ICPth of the adsorbent metal oxide increased. The study findings suggest a novel concept, i.e. that the ICP is a more accurate measure of the Lewis acidic strength of transition metal oxides with varying crystal structures and metal geometries, and their subsequent desulfurization performance. Kinetic modelling showed that chemisorption was the controlling mechanism. The fixed-bed ADS of commercial diesel when using unmodified AC is best described by the Yoon-Nelson and Thomas models. Adsorption when using the Ni-oxide/AC adsorbent was correlated to the filtration advection–dispersion equation.

Pearson's principle-inspired hollow metal sulfide for amplified photoelectrochemical immunoassay for disease-related protein

Designing a universal route for rational synthesis of a family of hollow multinary chalcogenide semiconductors for photoelectrochemical biosensors is still facing to the enormous challenges ahead. Herein a template-assisted Cu2O surface vulcanization and etching through a Pearson's hard and soft acid-base (HSAB) principle was utilized to synthesize hollow Cu2-xS photoactive materials for photocurrent detection of prostate-specific antigen (PSA). We initially synthesized cubic Cu2O and further surface sulfidation and HCl etching to obtain cubic Cu2-xS. Inspiringly, stirring of CuS, phosphine (TBP: tributylphosphine) and other metal salts could replace Cu+ ions to obtain new metal sulfides without changing the framework, size and thickness of the original material. This interesting phenomenon could be explained by HSAB theory, which soft base was favorable for combining soft acid (Cu+) to drive Cu+ out of the framework. Based on the results, HSAB-based reaction system was applied to develop novel photoelectrochemical PSA immunoassay. Polymetallic-doped sulfides (ZnxCd1-xS) had better photocurrent response than pure binary sulfides. A copper oxide (CuO)-labeled detection antibody is captured in a microplate along with a sandwich immunoassay in the presence of target PSA. Subsequently, the CuO nanoparticles were dissociated by hydrochloric acid, releasing a large amount of copper ions to participate in the cation exchange reaction with ZnxCd1-xS. Such excellent photoelectric conversion materials could sensitively detect target PSA with a wide linear range from 1.0 pg/mL to 10 ng/mL at a limit of detection down to 0.32 pg/mL. Additionally, favorable stability, great anti-interference ability, easy-fabrication, low-cost, and satisfactory accuracy for the analysis of actual samples were acquired. Importantly, the concept of cation exchange reaction can be widely used to synthesize advanced nanomaterials for fabrication of high-efficiency biosensing systems.

In vivo neurophysiological assessment of in silico predictions of neurotoxicity: Citronellal, 3,4-dichloro-1-butene, and benzyl bromoacetate

Neurotoxicants may be widespread in the environment and can produce serious health impacts in the human population. Screening programs that use in vitro methods have generated data for thousands of chemicals. However, these methods often do not evaluate repeated or prolonged exposures, which are required for many neurotoxic outcomes. Additionally, the data produced by such screening methods may not include mechanisms which play critical biological roles necessary for in vivo neurotoxicity. The Hard and Soft Acids and Bases (HSAB) in silico model focuses on chemical structure and electrophilic properties which are important to the formation of protein adducts. A group of structurally diverse chemicals have been evaluated with an in silico screening approach incorporating HSAB parameters. However, the predictions from the expanded chemical space have not been evaluated using in vivo methods. Three chemicals predicted to be cumulative toxicants were selected for in vivo neurotoxicological testing. Adult male Long-Evans rats were treated orally with citronellal (CIT), 3,4-dichloro-1-butene (DCB), or benzyl bromoacetate (BBA) for 8 weeks. Behavioral observations were recorded weekly to assess motor function. Peripheral neurophysiological measurements were derived from nerve excitability (NE) tests which involved compound muscle action potentials (CMAPs) in the tail and foot, and mixed nerve action potentials (MNAPs) in the tail. Compound nerve action potentials (CNAPs) and nerve conduction velocity (NCV) in the tail were also quantified. Peripheral inputs into the central nervous system were examined using somatosensory evoked potentials recorded from the cortex (SEPCTX) and cerebellum (SEPCEREB). CIT or BBA did not result in significant alterations to peripheral nerve or somatosensory function. DCB reduced grip-strength and altered peripheral nerve function. The MNAPs required less current to reach 50% amplitude and had a lower calculated rheobase, suggesting increased excitability. Increased CNAP amplitudes and greater NCV were also observed. Novel changes were found in the SEPCTX with an abnormal peak forming in the early portion of the waveforms of treated rats, and decreased latencies and increased amplitudes were observed in SEPCEREB recordings. These data contribute to testing an expanded chemical space from an in silico HSAB model for predicting cumulative neurotoxicity and may assist with prioritizing chemicals to protect human health.