Surface Electron Density Research Articles

Oxygen defects of MgLa-LDH enhancing electrostatic attraction and inner-sphere complexation during phosphate adsorption from wastewater

The introduction of oxygen defects toward constructing new binding sites is a promising strategy for improving the adsorption performance of layered double hydroxide (LDH). Here, a facile and novel method for adjusting the abundance of oxygen defects by regulating the preparation pH values of MgLa-LDH was used to enhance phosphate efficient adsorption. The MgLa-LDH with high-defect-degree (ML-11) presented a larger adsorption capacity and faster mass-transfer than that of low-defect-degree LDH (ML-10). Particularly, the adsorption capacity (121.56 mg/g) and initial adsorption rate (16.25 mg/g⋅min) of ML-11 were 1.8 times and 2.6 times higher than those in ML-10 in neutral condition, respectively. Characterization results confirmed that oxygen defects played a vital role in phosphate adsorption. The promotion mechanism of oxygen defects on phosphate absorption included the enhancing electrostatic attraction via increasing surface electron density, boosting M-OH groups generated by oxygen defects, and reducing adsorption energy. Compared with ML-10, ML-11 had similar or even better resistance of coexisting anions, and regeneration performance. Furthermore, the performance of ML-11 was verified in fixed-bed column experiment with real wastewater, and the treatment bed volume of it (978.6 BV) was higher than that in ML-10 (509.7 BV). The oxygen defects method can provide a promising choice for improving the material properties of efficient phosphate removal.

Do-It-Yourself 5-Color 3D Printing of Molecular Orbitals and Electron Density Surfaces

This report outlines an approach for preparing 5-color 3D printed plastic models of molecular orbitals and electron density surfaces using a hobby-grade 3D printer. Instructions are provided for preparing 3D orbital and electron density surface (EDS) models using solid or mesh representations in ground state and transition state structures. We show that the information content of 3D orbital and surface models can be enhanced with text annotation, bisection, strut and dashed bond placement, and composite orbital-EDS model constructions. Example prints illustrate orbital concepts in organic and inorganic chemistry, such as the ethyl cation (σ–p hyperconjugation), methane (hybridization and C–H bonding), ethane (σ–σ* hyperconjugation in the staggered and eclipsed conformations), 2-hydroxytetrahydropyran (the anomeric effect/n−σ* hyperconjugation), the water dimer (hydrogen bonding/n−σ* overlap), ethylene, 1,3-butadiene, and benzene (π molecular orbitals), Re2Cl82–, and U2(COT)2 (metal–metal quadruple bonds). Transition state models illustrate orbital interactions in the SN2 reaction of cyanide with methyl, ethyl, and isopropyl chloride and in a hydroboration reaction of BH3 with propene. Composite EDS models of methyl and isopropyl chloride (for exploring their relative reactivities as SN2 electrophiles) and methylcyclohexane (visualizing 1,3-diaxial interactions) are described. Student perceptions of a multicolor 3D orbital print used in an introductory organic chemistry laboratory course are reported.

Computational Evaluation of N-Based Transannular Interactions in Some Model Fused Medium-Sized Heterocyclic Systems and Implications for Drug Design.

As part of a project on fused medium-sized ring systems as potential drugs, we have previously demonstrated the usefulness of Density Functional Theory (DFT) to evaluate amine nitrogen-based transannular interactions across the central 10-membered ring in the bioactive dibenzazecine alkaloid, protopine. A range of related hypothetical systems have been investigated, together with transannular interactions involving ring-embedded imino or azo group nitrogens and atoms or groups (Y) across the ring. Electrostatic potential energies mapped onto electron density surfaces in the different ring conformations were evaluated in order to characterise these conformations. Unexpectedly, the presence of sp2 hybridised nitrogen atoms in the medium-sized rings did not influence the conformations appreciably. The strength and type of the N…Y interactions are determined primarily by the nature of Y. This is also the case when the substituent on the interacting nitrogen is varied from CH3 (protopine) to H or OH. With Y = BOH, very strong interactions were observed in protopine analogues, as well as in rings incorporating imino or azo groups. Strong to moderate interactions were observed with Y = CS, CO and SO in all ring systems. Weaker interactions were observed with Y = S, O and weaker ones again with an sp3 hybridised carbon (Y = CH2). The transannular interactions can influence conformational preferencing and shape and change electron distributions at key sites, which theoretically could modify properties of the molecules while providing new or enhanced sites for biological target interactions, such as the H or OH substituent. The prediction of new strong transannular interaction types such as with Y = BOH and CS should be helpful in informing priorities for synthesis and other experimental studies.

Thyroid hormone transporters binding affinity of methoxypoly chlorinated biphenyls: Insights from molecular simulations and fluorescence competitive binding experiment

Triiodothyronine (T3) and thyroxine (T4) are essential for regulating cell metabolic rate and promoting the development and differentiation of brain tissue, especially in fetuses and newborns. In particular, it has been proved that MeO-PCBs have high binding to thyroid hormone transporters and can competitively bind to thyroid carrier proteins, thus destroying the transport of the thyroid hormone. Fluorescence competition binding experiments and docking results showed that the binding affinity decreased with the increase in number of chlorine atoms of MeO-PCBs. The interaction mechanism of MeO-PCBs with thyroid transporter (TTR) and thyroid binding globulin (TBG) was compared by computational simulation and the binding free energies were calculated by the molecular mechanics/Poisson-Boltzmann surface area (MM/PBSA) method. Electrostatic potential analysis, Hirshfeld surface analysis and electron density difference maps confirmed the existence of electrostatic interactions. Secondly, noncovalent interaction (NCI) analysis further indicated that the main driving force for the combination of MeO-PCBs to TTR and TBG were electrostatic interaction and van der Waals interaction. The conformational changes of the protein after binding were studied by a molecular dynamic simulation.

Computer-Assisted Drug Discovery of a Novel Theobromine Derivative as an EGFR Protein-Targeted Apoptosis Inducer.

The overexpression of the Epidermal Growth Factor Receptor (EGFR) marks it as a pivotal target in cancer treatment, with the aim of reducing its proliferation and inducing apoptosis. This study aimed at the CADD of a new apoptotic EGFR inhibitor. The natural alkaloid, theobromine, was used as a starting point to obtain a new semisynthetic (di-ortho-chloro acetamide) derivative (T-1-DOCA). Firstly, T-1-DOCA's total electron density, energy gap, reactivity indices, and electrostatic surface potential were determined by DFT calculations, Then, molecular docking studies were carried out to predict the potential of T-1-DOCA against wild and mutant EGFR proteins. T-1-DOCA's correct binding was further confirmed by molecular dynamics (MD) over 100 ns, MM-GPSA, and PLIP experiments. In vitro, T-1-DOCA showed noticeable efficacy compared to erlotinib by suppressing EGFRWT and EGFRT790M with IC50 values of 56.94 and 269.01 nM, respectively. T-1-DOCA inhibited also the proliferation of H1975 and HCT-116 malignant cell lines, exhibiting IC50 values of 14.12 and 23.39 µM, with selectivity indices of 6.8 and 4.1, respectively, indicating its anticancer potential and general safety. The apoptotic effects of T-1-DOCA were indicated by flow cytometric analysis and were further confirmed through its potential to increase the levels of BAX, Casp3, and Casp9, and decrease Bcl-2 levels. In conclusion, T-1-DOCA, a new apoptotic EGFR inhibitor, was designed and evaluated both computationally and experimentally. The results suggest that T-1-DOCA is a promising candidate for further development as an anti-cancer drug.

Modulating surface electron density of Ni(OH)2 nanosheets with longitudinal Ti3C2Tx MXenenanosheets by Schottky effect toward enhanced hydrogen evolution reaction.

Due to their low cost and excellent electrocatalytic performance, nickel-based hydroxides are widely used as hydrogen evolution catalysts for large-scale hydrogen production by water electrolysis. In this study, a heterostructured composite with improved electron transport and modulated electron surface density was prepared by combining Ni(OH)2 with two-dimensional layered Ti3C2Tx (Ti3C2Tx-MXene). Ni(OH)2 nanosheets were formed on nickel foam (NF) substrates using acid etching, followed by the longitudinal growth of negatively charged Ti3C2Tx-MXene on positively charged Ni(OH)2/NF via electrophoretic deposition. The resulting structure facilitates spontaneous electron transfer from Ti3C2Tx-MXene to Ni(OH)2/NF by means of the Mott-Schottky heterostructure effect and establishes a continuous electron transport path which effectively increases the concentration of active sites, improving hydrogen evolution during water electrolysis. The obtained electrode is characterized by an HER overpotential of 66 mV (vs. RHE) and a Tafel slope of +105 mV dec-1 at a current density of 10 mA cm-2, combined with good electrochemical stability.

Modulating Surface Electron Density of Heterointerface with Bio‐Inspired Light‐Trapping Nano‐Structure to Boost Kinetics of Overall Water Splitting (Small 3/2023)

Modulating Surface Electron Density of Heterointerface with Bio‐Inspired Light‐Trapping Nano‐Structure to Boost Kinetics of Overall Water Splitting (Small 3/2023)

Surface polarization-induced emission and stability enhancement of CsPbX3 nanocrystals.

Recently, the polarization effect has been receiving tremendous attention, as it can result in improved stability and charge transfer efficiency of metal-halide perovskites (MHPs). However, realizing the polarization effect on CsPbX3 NCs still remains a challenge. Here, metal ions with small radii (such as Mg2+, Li+, Ni2+, etc.) are introduced on the surface of CsPbX3 NCs, which facilitate the arising of electric dipole and surface polarization. The surface polarization effect promotes redistribution of the surface electron density, leading to reinforced surface ligand bonding, reduced surface defects, near unity photoluminescence quantum yields (PLQYs), and enhanced stability. Moreover, further introduction of hydroiodic acid results in the in situ formation of tert-butyl iodide (TBI), which facilitates the successful synthesis of pure iodine-based CsPbI3 NCs with high PLQY (95.3%) and stability under ambient conditions. The results of this work provide sufficient evidence to exhibit the crucial role of the surface polarization effect, which promotes the synthesis of high-quality MHPs and their applications in the fields of optoelectronic devices.

Strategy for reducing the carriers transfer antagonistic effect between heterojunction and plasmonic effect and weakening photocorrosion of Cu2O for excellent photocatalytic bacteriostasis.

Heterogeneous catalysis composed of plasmonic metal and semiconductor has been utilized to tune local surface electron density in MOA (Molecular oxygen activation). However, there is a severe antagonistic effect between Schottky junction carriers and SPR (Surface Plasmon Resonance) induced hot carriers transfer routers when metal and semiconductor are both excited to dramatically reduce carriers separation efficiency. Hence, a highly effective photocatalytic antifoulant obtained by V-CN (carbon nitride with nitrogen vacancies) in-situ loading Cu2O and Ag nanoparticles (Cu2O/Ag/V-CN) was introduced to promote MOA to assist the metal ions sterilization. The DFT calculations (Density Functional Theory) and FEM calculations (Finite Element Method) intuitively proved the photocatalytic antifoulant belonged to a ternary Z-scheme heterojunction and could visibly weaken the antagonistic effect of hot carriers and Schottky carriers transport routes. The delocalized electron structure caused by V-CN and the effective electron mediator of Ag were the key to the formation of Z-scheme interfacial heterojunctions. These conclusions were also supported by experimental data, like more ∙O2- production capacity, efficient carriers separation, and higher carriers lifetime (27% higher than Cu2O and Cu2O/V-CN) as well as the weakened Cu2O photocorrosion tendency (Cu2O turning into CuO). Additionally, except for increasing nearly-three times adsorption energy of O2 for rapid activation, Cu2O/Ag/V-CN with abundant nitrogen vacancies can more significantly slow metal ions release (less about 97% to pure Cu2O and at least 22% higher than reported systems), which can observably save the amount of catalyst and heavy metals content. Therefore, Cu2O/Ag/V-CN has great potential for practical antifouling applications.

Evolving the complexities of glycine magnesium chloride (GMC) crystal through DFT computation for NLO utilizations

A new grown seed's of GMC (Gylcine Magnesium Chloride) are cultivated by slow evaporation technique. Thus grown seeds are developed as a single large crystal within certain temperature conditions into modified dimensions. The lattice boundaries of the crystal were confirmed by SXRD (Single Crystal X-Ray Diffraction) method. FTIR (Fourier Transform Infrared) and UV–VIS-NIR spectrums are used for probing the structural and molecular properties through transmission and absorption of spectrum. The molecular structure of GMC is computed using DFT. Linear and non linear optical properties are calculated with the aid of Gaussian 09 by DFT/B3LYP/CC-PVTZ level of theory software. Through this computation method we had calculated MEP (Molecular Electrostatic Potential) to investigate the mole positions and the charge distributions. HUMO AND LUMO studies also done to know about the electron donor and acceptor characteristics of the GMC further DOS (Density Of States) of the compound was also calculated as spectrum of Gauss sum. The National Bond Orbital Population Analysis (NBO) was carried out for computing the bond strength between the molecules by using the Gaussian B3LYP/6–311++ G (d,p) level of basis set. The Mulliken Charge Analysis (MCA) confirms the atom distributions with different negative and positive potential in reference with the total electron density surface. This studies reveals that GMC as Non-linear characteristics over linear thus it can be applied for optical device fabrications.

Photocatalytic Degradation of VOC Waste Gas in Petrochemical Sewage Fields

The large amount of waste gas containing volatile organic compounds (VOCs) discharged from petrochemical sewage plants will cause air pollution and seriously endanger the safety of human beings and the ecological environment. In this paper, we proposed a photocatalytic oxidation degradation technique of VOCs and designed a photocatalytic reaction device loaded with TiO2/SnO2 catalyst. Under UV light irradiation, there is an energy level difference in the conduction band between TiO2 and SnO2, which makes the photogenerated electrons (e–) migrate to SnO2 and reduces the surface electron density of TiO2. Thus, the recombination of photogenerated electron–hole pairs (e––h+) is inhibited and the catalyst activity is improved. Meanwhile, the synergistic effect of the oxidation of hydroxyl radicals (·OH) and ozone greatly improves the conversion rate. In addition, in the industrial side line, by studying the influence of inlet gas volume, inlet gas concentration, and gas humidity (RH) on the conversion rate of the VOCs, we revealed the operation law of the photocatalytic technique in industrial applications. Under the best working conditions, the purification rate of the VOCs was as high as 92.73%. This technique can not only effectively avoid the damage to the environment caused by polluting VOCs but also promote the low-carbon and green development of enterprises in the industry.

Highly selective epoxidation of styrene at ambient temperature under photo-assisted condition over bimetallic Eu and Ti-doped amino-functionalized mesoporous molecular sieve

Mesoporous molecular sieves silica materials had been functionalized employing 3-aminopropyltriethoxysilane as the surface decoration agent by a post-synthesis method and Eu and Ti with different loading ratio were synchronously anchored on amino-functionalized silica framework by incipient wetness impregnation method, respectively. The structures of the synthesized samples were evaluated by means of X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet-visible spectra, scanning electron microscope, transmission electron microscope, X-ray photoelectron spectroscopy and solid-state 29Si magic angle spinning nuclear magnetic resonance spectra. The results revealed that the highly ordered mesoporous two dimensional hexagonal structure and the mesoporous channel structure were well preserved and isolated tetrahedral surface Eu3+ and isolated [TiO4] or [HOTiO3] species were found to be grafted and highly dispersed in the amino-functionalized mesoporous framework. A significant enhancement in selectivity and conversion for the photocatalytic epoxidation of styrene has been achieved by synergistic effect based on surface ligand effect and electron density effect between Eu3+ and Ti4+ species on amino-functionalized mesoporous silica framework. The factors associated with the conversion of styrene and selectivity to styrene oxide such as the solvent, metal loading, the amount of NaOH, H2O2/Styrene, the amount of catalyst and reaction time were also investigated in details. The desired selectivity (84%) to styrene oxide and excellent conversion (32%) of styrene for the photocatalytic epoxidation of styrene with turnover frequency of 3.1 × 10−4s−1 were obtained using aqueous H2O2 as an oxidant in the presence of acetonitrile solvent under ambient temperature.

Modulating Surface Electron Density of Heterointerface with Bio-Inspired Light-Trapping Nano-Structure to Boost Kinetics of Overall Water Splitting.

Herein, inspired by natural sunflower heads' properties increasing the temperature of dish-shaped flowers by tracking the sun, a novel hybrid heterostructure (MoS2 /Ni3 S2 @CA, CA means carbon nanowire arrays) with the sunflower-like structure to boost the kinetics of water splitting is proposed. Density functional theory (DFT) reveals that it can modulate the active electronic states of NiMo atoms around the Fermi-level through the charge transfer between the metallic atoms of Ni3 S2 and MoMo bonds of MoS2 to boost overall water splitting. Most importantly, the finite difference time domain (FDTD) could find that its unique bio-inspired micro-nano light-trapping structure has high solar photothermal conversion efficiency. With the assistance of the photothermal field, the kinetics of water-splitting is improved, affording low overpotentials of 96 and 229mV at 10mAcm-2 for HER and OER, respectively. Moreover, the Sun-MoS2 /Ni3 S2 @CA enables the overall alkaline water splitting at a low cell voltage of 1.48 and 1.64V to achieve 10 and 100mAcm-2 with outstanding catalytic durability. This study may open up a new route for rationally constructing bionic sunflower micro-nano light-trapping structure to maximize their photothermal conversion and electrochemical performances, and accelerate the development of nonprecious electrocatalysts for overall water splitting.

“On Water” Effect for Green Click Reaction: Spontaneous Polymerization of Activated Alkyne with “Inert” Aromatic Amine in Aqueous Media

“On Water” Effect for Green Click Reaction: Spontaneous Polymerization of Activated Alkyne with “Inert” Aromatic Amine in Aqueous Media

Activated Ni-O-Ir Enhanced Electron Transfer for Boosting Oxygen Evolution Reaction Activity of LaNi1-x Irx O3.

Tuning the structure of the active center of catalysts to atomic level provides the most efficient utilization of the active component, which plays an especially important role for precious metals. In this study, the liquid phase ion exchange method is used to introduce atomic Ir into LaNiO3 perovskite oxide, which shows excellent catalytic performance in the oxygen evolution reaction (OER). The catalyst, LaNi0.96 Ir0.04 O3 , with the optimal concentration of Ir, displays an overpotential of just 280mV at 10mAcm-2 . The introduced Ir enriches the surface electron density significantly, which not only improves site-to-site electron transfer between O and Ni sites but also allows stable adsorption of the intermediates. Theresults of cyclic voltammetry tests reveal the superior overpotential and remarkable efficiency of the OER process because of the strong interactions in Ni-O-Ir. Moreover, the Ir atom inhibits the participation of a lattice oxygen oxidation mechanism (LOM) in LaNiO3 that guarantees the stability of the catalyst in alkaline conditions. It is anticipated that this work will be instrumental for the preparation and study of a broad range of atomic metal-doped perovskite oxides for water splitting.

Investigation of reflection bands of 1D annular photonic crystal containing double negative index material and non-magnetized plasma

In this paper, optical reflectance properties of an annular photonic crystal (APC) composed of alternate layers of double negative (DNG) material and a non-magnetized plasma (NMP) layer, immersed in free space, have been theoretically investigated and studied. The reflectance spectra of the annular PC have been obtained by employing the transfer matrix method (TMM) for the cylindrical waves in the case of TEpolarized wave only. It has been found that the spectral position and width of the reflection bands of APC are greatly influenced by the variation in the thickness of DNG metamaterial and NMP layer, respectively. Interestingly, it is observed that the presence of NMP layer causes the increase in photonic band gap (PBG) whereas the DNG layer reduces the PBG. Further, the effect of azimuthal mode number (m) on the reflectance spectra shows that for m > 0, splitting in the reflection bands occurs at the frequency corresponding to the zero permeability value of DNG metamaterial layer. Moreover, with the increase in azimuthal mode number one PBG is red-shifted and the second one is blue-shifted. Finally, the effect of change in the starting radius parameter of curved surface and plasma electron density on the reflectance spectra of APC has also been studied and very interesting results have been observed.

(Invited) Ligand Effect in Electroreduction of CO2: N-Heterocyclic Carbene-Capped Polymers to Promote Catalytic Efficiency

N-heterocyclic carbenes (NHCs) are excellent ligands that bind to a variety of transition metals with extremely high binding strength via σ donation. In my talk, I will highlight the use of two polymeric N-heretocyclic carbenes (NHC) (polydentate and monodentate) to stabilize metal nanocatalysts (Au and Pd) for efficient CO2 electroreduction in aqueous solution. Compared with other conventional ligands including thiols and amines, metal-NHC bonds are stable under reductive potentials prevent the nanoclustering of nanoparticles, which is of key importance for any practical application. In particular, Au nanocatalysts modified by polymeric NHC ligands show an activity retention of 86% after CO2 reduction at -0.9 V for 11 h, while it is less than 10% for unmodified Au. We demonstrate that the hydrophobicity of polymer ligands and the enriched surface electron density of metal NPs through σ-donation of NHCs substantially improve the selectivity for CO2 reduction over proton reduction. As a passive coating on the surface of metal nanocatalysts, NHC-terminated polymers can control the accessibility of substrates, i.e., CO2 vs. H2O, as a means to improve the Faradic efficiency toward CO2 reduction. Our results provide guideline to improve catalytic efficiency and stability of metal nanocatalysts for CO2 electroreduction and, more generally, as cathodic materials for other electroreduction reactions.

Nanoarchitectonics of n-type organic semiconductors polymerized by Cu(0)-mediated RDRP of acrylates based monomers

Metal silicates, obtained from abundant components in Earth's crust, could offer desirable activity and selectivity in catalytic applications. In this study, density functional theory (DFT), time-dependent DFT (TD-DFT), and Hartree-Fock (HF) calculations were employed to compute specified features of acrylates-based n-type organic semiconductors synthesized by copper(0)-mediated reversible deactivation radical polymerization (Cu0-RDRP). After performing the molecular optimization, particular features of the synthesized semiconductor structure were captured including IR, 1H and 13C NMR, and UV–visible spectra, TDOS spectrum, HOMO and LUMO patterns, and energy gap. Lastly, the contour electron density surface (ESP) and molecular electrostatic potential (MEP) plots were also computed utilizing the gauge independent atomic orbital (GIAO) approach. These analyses reveal existence of an electron cloud around the semiconductor. The role of atomic charge for the transmission of electrons has been well shown in changing cloud charge around the acrylate monomer after polymerization as well as in changing the negative charge from organic to inorganic area in the polymer. According to these analyses, well-agreeable compatibility was attained with by comparing our theoretical simulation data on the acrylate-based n-type organic semiconductors and the reported experimental results in literature.

Increasing electron density by surface plasmon resonance for enhanced photocatalytic CO2 reduction

The photocatalytic CO2 reduction reaction is a multi-electron process, which is greatly affected by the surface electron density. In this work, we synthesize Ag clusters supported on In2O3 plasmonic photocatalysts. The Ag–In2O3 compounds show remarkedly enhanced photocatalytic activity for CO2 conversion to CO compared to pristine In2O3. In the absence of any co-catalyst or sacrificial agent, the CO evolution rate of optimal Ag–In2O3-10 is 1.56 μmol/g/h, achieving 5.38-folds higher than that of In2O3 (0.29 μmol/g/h). Experimental verification and DFT calculation demonstrate that electrons transfer from Ag clusters to In2O3 on Ag–In2O3 compounds. In Ag–In2O3 compounds, Ag clusters serving as electron donators owing to the SPR behaviour are not helpful to decline photo-induced charge recomnation rate, but can provide more electron for photocatalytic reaction. Overall, the Ag clusters promote visible-light absorption and accelerate photocatalytic reaction kinetic for In2O3, resulting in the photocatalytic activity enhancement of Ag–In2O3 compounds. This work puts insight into the function of plasmonic metal on enhancing photocatalysis performance, and provides a feasible strategy to design and fabricate efficient plasmonic photocatalysts.

Interpretable Deep Learning Model for Analyzing the Relationship between the Electronic Structure and Chemisorption Property.

The use of machine learning (ML) is exploding in materials science as a result of its high predictive performance of material properties. Tremendous trainable parameters are required to build an outperforming predictive model, which makes it impossible to retrace how the model predicts well. However, it is necessary to develop a ML model that can extract human-understandable knowledge while maintaining performance for a universal application to materials science. In this study, we developed a deep learning model that can interpret the correlation between surface electronic density of states (DOSs) of materials and their chemisorption property using the attention mechanism that provides which part of DOS is important to predict adsorption energies. The developed model constructs the well-known d-band center theory without any prior knowledge. This work shows that human-interpretable knowledge can be extracted from complex ML models.