Nickel hexacyanoferrate nanoparticle-decorated 3D rGO composites-based electrochemical sensing platform for detection of di-2-ethylhexyl phthalate.

A label-free and efficient electrochemical (EC) sensing platform for di-2-ethylhexyl phthalate (DEHP) was developed based on in situ probe nickel hexacyanoferrate nanoparticle (NiHCF NP)-decorated three-dimensional reduced graphene oxide (3D rGO) composites. NiHCF NPs in the composites as an in situ probe show a pair of well-defined peaks with good reversibility and stability. Coupling 3D rGO with NiHCF NPs not only improved the electron transfer capability of NiHCF NPs but also provided more sites for aptamer immobilization. The synthesized NiHCF NP-decorated 3D rGO composites were used to act as a substrate for the immobilization of anti-DEHP aptamer by the covalent bonding method. The designed EC sensing platform displays excellent sensing performance for DEHP with a low detection limit of 3.64 pg/L, and a linear working range of 0.01 - 1000 ng/L. The application of the sensing platform to actual environmental samples was studied and satisfactory results were obtained. Thus, the proposed EC sensing platform would provide a potential tool for efficient detection of pollutants in the environment.

NiCo alloy/C nanocomposites derived from a Ni-doped ZIF-67 for lightweight microwave absorbers.

In this work, we prepared NiCo alloy/C with rhombic dodecahedron structure and superior microwave absorption performance by using ZIF-67 as the raw material. The rhombic dodecahedron NiCo alloy/C was with rough particles on the surface was photographed by field emission scanning electron microscopy. By adjusting the doping amount of Ni and the temperature of pyrolysis, improved the impedance matching of NiCo alloy/C. Specifically, NiCo alloy/C exhibits a minimum reflection loss of -65.48 dB at 13.48 GHz, while the thickness is 1.63 mm. Defects introduced in the Ni doping process and the special rhombic dodecahedral structure can cause multiple loss mechanisms. Therefore, this NiCo alloy/C composite has the potential to be a potential microwave absorber material with lightweight and high microwave absorption properties.

The physical nature of the interaction in DMSO extraction separation of C8H10 isomer/n-decane systems.

In this study, the liquid-liquid equilibrium of DMSO-C8H10 aromatic isomer-n-decane systems was measured at 30 °C under atmospheric pressure at first, followed by Othmer-Tobias equation data reliability verification and NRTL/UNIQUAC activity coefficient model correlation. Moreover, intermolecular interaction energies and molecular polarity indexes (MPI) were calculated to interpret the extraction results. Finally, a set of wave function analyses was accomplished to elaborate the physical nature of the interaction in the DMSO extraction process. These investigations show that: (1) intermolecular interaction energy and the MPI results corroborate the aromatic and alkane extraction distribution coefficients well. (2) The interactions between aromatics and DMSO are weak hydrogen bonding and van der Waals (vdW) interactions. The attractive part mainly involves dispersion (49.57-53.30%) and electrostatic (35.49-37.83%) effects. (3) The interactions between aromatics and n-decane are vdW interactions, dominated by attractive dispersion (70.41-70.93%) and repulsive exchange effects.

Insight into molecular characteristics of a Chinese coal via separation, characterization, and data processing.

Dayan lignite was subjected to thermal dissolution sequentially with cyclohexane, acetone, and methanol. Each thermal dissolution extract was subjected to further separation/enrichment using column chromatography, which was sequentially eluted with petroleum ether, a mixture of ethyl acetate and petroleum ether (vol:vol = 1:1), and ethyl acetate. The three thermal dissolution extracts and nine enrichment subfractions were characterized by an Orbitrap mass spectrometry equipped with an atmospheric pressure chemical ionization ion source. The mass spectrometry data were also statistically analyzed by principal component analysis, which can reduce the dimensionality of data and classify multiple samples according to principal components. Identified compounds in the extracts and subfractions are classified into eight classes according to the heteroatom distribution. Hydrocarbon class is mainly presented in the petroleum ether fraction, and oxygen class, nitrogen class, and oxygen-nitrogen class are distributed in both petroleum ether/ethyl acetate and ethyl acetate subfractions. The combination of different analytical methods enhances the understanding of coal at the molecular level and provides important data for downstream refining processes.

Stabilities and electronic properties of nanowires made of single atomic sulfur chains encapsulated in zigzag carbon nanotubes.

Theoretical investigations are carried out on the recently synthesized one-dimensional nanowires made of atomic sulfur chains encapsulated in carbon nanotubes (called S@CNTs). Special attention is paid to stability, electronic property and transport properties of these combined nanowires. It is found that the encapsulation is exothermic when S@CNTs are built from the tubes with diameter larger than 6.4 Å. Thus the experimental results are energetically favorable since the diameters of the CNTs are about 6 Å in the obtained S@CNTs. The combined nanowires can be stabilized by van der Waals interaction between sulfur chain and tube as indicated from radial distribution function and reduced density gradient descriptions. All S@CNTs studied in this work exhibit metallic property with the partially filled bands. However, the conducting component and the pathway of charge carriers are various. For instance, only the sulfur chain is the conducting pathway for S@CNT(8, 0), while both the sulfur chain and tube are the conducting pathways for S@CNT(9, 0). This interesting feature was understood based on the band structures and crystal orbital analysis. The electronic transport properties of the systems are performed by investigating and analyzing the transmission spectra, current-voltage (I-V) curves and transmission eigenstate, which confirm that the sulfur chains can improve the electronic transport of CNTs. Moreover, the electrostatic interaction resulted from the charge transfer between the two components of S@CNTs should be favorable to the stability of the combined nanowires.

Smart D-π-A Type Near-Infrared Aß Probes: Effects of a Marked π Bridge on Optical and Biological Properties.

To expand the scope of D-π-A based near-infrared (NIR) probes for detecting ß-amyloid (Aß) plaques and to systematically explore the relationship among their structural characteristics, optical properties, and biological properties, three series of smart NIR probes with different aromatic rings and up to seven trans double bonds were synthesized and evaluated. Marked correlations between the conjugated π system and properties of these probes, such as optical data, binding ability, and brain uptake, were observed. One probe, PHC-4, displayed improved properties as a NIR probe for the in vivo detection of Aß plaques.

Probing the Properties of Polynuclear Superhalogens without Halogen Ligand via ab Initio Calculations: A Case Study on Double-Bridged [Mg2 (CN)5 ](-1) Anions.

An ab initio study of the superhalogen properties of eighteen binuclear double-bridged [Mg2 (CN)5 ](-1) clusters is reported herein by using various theoretical methods. High-level CCSD(T) results indicate that all the clusters possess strong superhalogen properties owing to their high vertical electron detachment energies (VDEs), which exceed 6.8 eV (highest: 8.15 eV). The outer valence Green's function method provides inaccurate relative VDE values; hence, this method is not suitable for this kind of polynuclear superhalogens. Both the HF and MP2 results are generally consistent with the CCSD(T) level regarding the relative VDE values and-especially interesting-the average values of the HF and MP2 VDEs are extremely close to the CCSD(T) results. The distributions of the extra electrons of the anions are mainly aggregated into the terminal CN units. These distributions are apparently different from those of previously reported triple-bridged isomers and may be the reason for the decreased VDE values of the clusters. In addition, comparisons of the VDEs of binuclear and mononuclear superhalogens as well as studies of the thermodynamic stabilities with respect to the detachment of various CN(-1) ligands are also performed. These results confirm that polynuclear structures with pseudohalogen ligands can be considered as probable new superhalogens with enhanced properties.

Is the regulation of the electronic properties of organic molecules by polynuclear superhalogens more effective than that by mononuclear superhalogens? A high-level ab initio case study.

The regulation of the electronic properties of organic molecules induced by polynuclear superhalogens is theoretically explored here for sixteen composite structures. It is clearly indicated by the higher vertical electron detachment energy (VDE) that polynuclear superhalogens are more effective in regulating the electronic properties than mononuclear structures. However, this enhanced regulation is not only determined by superhalogens themselves but also related to the distribution of the extra electron of the final composites. The composites, in which the extra electron is mainly aggregated into the superhalogen moiety, will possess higher VDE values, as reported in the case of C1', 7.12 eV at the CCSD(T) level. This is probably due to the fact that, compared with organic molecules, superhalogens possess stronger attraction towards the extra electron and thus should lead to lower energies of the extra electrons and to higher VDE values eventually. Compared with CCSD(T), the Outer Valence Green's Function (OVGF) method fails completely for composite structures containing Cl atoms, while MP2 results are generally consistent in terms of the relative order of VDEs. Actually if the extra electron distribution of the systems could be approximated by the HOMO, the results at the OVGF level will be consistent with the CCSD(T) results. Conversely, the difference in VDEs between OVGF and CCSD(T) is significantly large. Besides superhalogen properties, the structures, relative stabilities and thermodynamic stabilities with respect to various fragmentation channels were also investigated for all the composite structures.

Dual mechanisms in hydrogen reduction of copper oxide: surface reaction and subsurface oxygen atom transfer.

The study of the reduction of copper oxide (CuO) by hydrogen (H2) is helpful in elucidating the reduction mechanism of oxygen carriers. In this study, the reduction mechanism of CuO by H2 and the process of oxygen atom transfer were investigated through the density functional theory (DFT) method and thermodynamic calculation. DFT calculation results showed that during the reaction between H2 and the surface of CuO, Cu underwent a Cu2+ → Cu1+ → Cu0 transformation, the Cu-O bond (-IpCOHP = 2.41) of the Cu2O phase was more stable than that (-IpCOHP = 1.94) of the CuO phase, and the reduction of Cu2O by H2 was more difficult than the reduction of CuO. As the surface oxygen vacancy concentration increased, it was more likely that the subsurface O atoms transfer to the surface at zero H2 coverage (no H2 molecule on the surface), allowing the surface to maintain a stable Cu2O phase. However, when the H2 coverage was 0.25 monolayer (ML) (one H2 molecule every four surface Cu atoms), the presence of H atoms on the surface made the upward transfer of O atoms from the subsurface more difficult. The rate of consuming surface O atoms in the reduction reaction was greater than the rate of subsurface O atom transfer induced by the reduction reaction and the surface Cu2O phase could not be maintained stably. Through thermodynamic analysis, at high H2 concentration, the reaction between H2 and CuO was more likely to generate Cu, while at low H2 concentration, it was more likely to generate Cu2O. In summary, the valence state of Cu in the reaction process between CuO and H2 depended on the concentration of H2.

Adsorption Behaviors and Mechanism of Phenol and Catechol in Wastewater by Magnetic Graphene Oxides: A Comprehensive Study Based on Adsorption Experiments, Mathematical Models, and Molecular Simulations.

This study provides a comprehensive analysis of the adsorption behaviors and mechanisms of phenol and catechol on magnetic graphene oxide (MGO) nanocomposites based on adsorption experiments, mathematical models, and molecular simulations. Through systematic experiments, the influence of various parameters, including contact time, pH conditions, and ionic strength, on the adsorption efficacy was comprehensively evaluated. The optimal contact time for adsorption was identified as 60 min, with the observation that an increase in inorganic salt concentration adversely affected the MGOs' adsorption capacity for both phenol and catechol. Specifically, MGOs exhibited a superior adsorption performance under mildly acidic conditions. The adsorption isotherm was well represented by the Langmuir model, suggesting monolayer coverage and finite adsorption sites for both pollutants. In terms of adsorption kinetics, a pseudo-first-order kinetic model was the most suitable for describing phenol adsorption, while catechol adsorption conformed more closely to a pseudo-second-order model, indicating distinct adsorption processes for these two similar compounds. Furthermore, this research utilized quantum chemical calculations to decipher the interaction mechanisms at the molecular level. Such calculations provided both a visual representation and a quantitative analysis of the interactions, elucidating the underlying physical and chemical forces governing the adsorption phenomena. The findings could not only offer crucial insights for the treatment of coal industrial wastewater containing phenolic compounds with bridging macroscopic observations with microscopic theoretical explanations but also advance the understanding of material-pollutant interactions in aqueous environments.

Ti3C2 MXene supporting platinum nanoparticles as rapid electrons transfer channel and active sites for boosted photocatalytic water splitting over g-C3N4.

Two-dimension (2D) MXene materials have increasingly attracted attentions in improving the photocatalytic conversion of solar-to-chemical energy over graphitic carbon nitride (g-C3N4). In this work, Pt nanoparticles modified few-layer Ti3C2 MXene sheet (MXene@Pt) was successfully prepared by chemical reduction, which was used as efficient co-catalysts to enhance the photocatalytic hydrogen evolution over porous g-C3N4 (PCN). The high work function of MXene@Pt and the tight 2D/2D interfacial contact between MXene@Pt and PCN significantly promoted the transfer and separation of photogenerated electron-hole. Besides, the MXene@Pt could enhance the light-harvesting of PCN and provide plentiful active sites for hydrogen evolution reaction. The hydrogen evolution activity of optimum 2D/2D MXene@Pt modified PCN (PCN/MPt-5) composite was dramatically enhanced, even higher than that of equal Pt mass modified PCN. Besides, overall water splitting was realized via a two-electron pathway with H2O2 and H2 generation. This work may provide the fabrication strategy for developing MXene-based co-catalyst in photocatalysis.

Rationally designed rGO@CNTs@CNFs film as self-supporting binder-free Si electrodes for high-performance lithium-ion batteries.

Si has become the most promising anode materials for lithium-ion batteries (LIBs) due to its high theoretical specific capacity and comparable low discharge potential. However, the practical usage of Si is still hindered by its huge volume expansion. To release volume stress and improve conductance, designed self-supporting binder-free Si electrode endowed with three-dimensional structure has been come up in this research. The pore structure is adjusted by rationally designing the proportion of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) to alleviate volume change. Simultaneously, construct stable conductivity network was fabricated via ice crystal self-assemble freezing technique following compress and carbonization process. The electrochemical specific capacity of rGO@CNTs@CNFs@Si-2 electrode has stably remained at 2250 mAh/g after 100 cycles (100 mA/g) with benign rate capabilities. This simple self-assemble method for self-supporting binder-free Si electrode would open a new route to exploit high energy density Si-based electrode for flexible LIBs.

An in situ thermal cross-linking binder for silicon-based lithium ion battery.

Silicon has been regarded as one of the most promising anode materials for lithium-ion batteries (LIBs) due to its highest specific capacity and low (de)lithiation potential, however, the development of practical applications for silicon are still hindered by devastating volume expansion and low conductance. Herein, we have proposed an in situ thermally cross-linked water-soluble PA@PAA binder for silicon-based LIBs to construct dynamic cross-linking network. Specifically, ester bonds between -P-OH in phytic acid (PA) and -COOH in PAA, which are generated by thermal coupling, are designed to synergize with hydrogen bonds between the PA@PAA binder and silicon particles to dissipate the high mechanical stresses, which is verified by theoretical calculation. GO is further adopted to protect silicon particles from immediate contact with electrolyte to improve initial coulombic efficiency (ICE). A range of heat treatment temperatures is explored to optimize the previous process conditions and the optimum electrochemical performance is provided by Si@PA@PAA-220 electrodes with high reversible specific capacity of 1322.1 mAh/g at a current density of 0.5A/g after 510 cycles. Characterization has also revealed that PA@PAA is involved in electrochemical process and tunes the ratio of organic (LixPFy/LixPOyFZ)-inorganic (LiF) to consolidate solid electrolyte interface (SEI) during cycles. In brief, this applicable fascial in situ strategy can effectively improve the stability of silicon anodes for high energy density lithium-ion batteries.

Efficient photoelectrochemical aptasensing of di-2-ethylhexyl phthalate in environmental samples based on N, S co-doped graphene quantum dots/TiO2 nanorods.

An efficient photoelectrochemical (PEC) sensing platform was developed for detection of di-2-ethylhexyl phthalate (DEHP) based on nitrogen and sulfur co-doped graphene quantum dots/TiO2 nanorods (N, S-GQDs/TiO2 NRs) coupling with exonuclease I (Exo I)-assisted target recycling for remarkable signal amplification. N, S-GQDs uniformly grown on TiO2 NRs by simple hydrothermal method showed high electron-hole separation efficiency and superior photoelectric performance, which was explored as the photoactive substrate for anchoring anti-DEHP aptamer and its complementary DNA (cDNA). With the addition of DEHP, aptamer molecules fell from the electrode surface owing to the specific recognition of aptamer to DEHP, resulting in the increment of photocurrent signal. At this moment, Exo I could stimulate aptamer hydrolysis in the aptamer-DEHP complexes, so that DEHP was released from the complexes to take part in the next reaction cycling, which remarkably increasing the photocurrent response and achieving signal amplification. The designed PEC sensing platform exhibited excellent analytical performance for DEHP with a low detection limit of 0.1 pg L-1. Also, its applications in real samples were further investigated in detail. Thus, the established method would provide a simple and efficient tool for DEHP or other pollutants monitoring in the environment.

Robust dual-cross-linked networks enable stable silicon anodes.

The simultaneous attainment of long cycle life and high energy in Si anodes remains challenging. Herein, we introduce the concept of primary building units as organizing units to construct durable and conductive electrode architectures, which helps to facilitate the coalescence of Si nanoparticles with conductive pathways and prevent nanoparticle aggregation.

The magnetic coupling in manganese-based dinuclear superhalogens and their analogues. A theoretical characterization from a combined DFT and BS study.

The structures, relative stabilities, vertical detachment energies and magnetic coupling properties of a series of manganese-based dinuclear superhalogens and their isoelectronic analogues are explored via a combined density functional theory and broken symmetry study. Both the capabilities of various exchange-correlation functionals and basis set effects are investigated. The large magnitudes of the calculated exchange coupling constants indicate clearly the apparent molecular magnetism of these new types of superhalogen. Encouragingly, the high possibility of the coexistence of both high stability and strong magnetic coupling in these new polynuclear superhalogens is also confirmed. Besides these, the larger magnitudes of the calculated coupling constants of iron-based clusters here, compared with the homodinuclear [Mn(2)Cl(5)](-) cluster, demonstrate the possibility of the existence of strong magnetic coupling in potential iron-based homo- and heterodinuclear superhalogens. The analysis of spin density distribution is also performed in order to understand the coupling mechanisms.

Effective Absorption Mechanism of SO2 and NO2 in the Flue Gas by Ammonium-Bromide-Based Deep Eutectic Solvents.

Simultaneous capture of SO2 and NO x from flue gas is critical for coal-fired power generation. In this study, environmentally friendly and high-performance deep eutectic solvents based on ethylene glycol and ammonium bromide were designed to capture SO2 and NO2 simultaneously. The SO2 and NO2 absorption performances and absorption mechanisms were systematically investigated by 1H NMR and Fourier transform infrared (FT-IR) spectroscopy in combination with ab initio calculations using Gaussian software. The results showed that EG-TBAB DESs can absorb low concentrations of SO2 and NO2 from the flue gas simultaneously at low temperatures (≤50 °C). 1H NMR, FT-IR, and simulation results indicate that SO2 and NO2 are absorbed by forming EG-TBAB-SO2-NO2 complexes, Br- is the main active site for NO2 absorption, and NO2 is more active in an EG-TBAB-NO2-SO2 complex than SO2. EG-TBAB DESs exhibit outstanding regeneration capability, and absorption capacities remain unchanged after five absorption-desorption cycles. The fundamental understanding of simultaneous capture of SO2 and NO2 from this study enables DES structures to be rationally designed for efficient and low-cost desulfurization and denitrification reagents.

Bismuth-nickel bimetal nanosheets with a porous structure for efficient hydrogen production in neutral and alkaline media.

Active and durable electrocatalysts are very important for efficient and economically sustainable hydrogen generation via electrocatalytic water splitting. A bismuth-nickel (Bi-Ni) bimetal nanosheet with a mesoporous structure was prepared via a self-template electrochemical in situ process. The Bi-Ni catalyst required overpotentials of 56 mV and 183 mV at 10 mA cm-2 for the hydrogen evolution reaction (HER), which were close to that of commercial Pt/C in 1.0 M KOH and 1.0 M PBS (pH 7.0), respectively. The electrocatalyst maintained a steady current density during 20 h electrolysis in 1.0 M KOH and 1.0 M PBS (pH 7.0). Density functional theory (DFT) indicated that the alloying effect could induce charge transfer from the Bi atom to Ni atom and thus modulate the d-band centre of Bi-Ni nanosheets, which could efficiently accelerate H* conversion and H2 desorption at the Ni active site. This promotes the HER kinetics. By adopting the Bi84.8Ni15.2 alloy as the cathode to establish a full-cell (IrO2∥Bi84.8Ni15.2) for water splitting in 1.0 M KOH, the required cell voltage was 1.53 V to drive 10 mA cm-2, which was lower than that of the IrO2∥Pt/C electrolyzer (1.64 V@10 mA cm-2).

Microstructure regulation of pitch-based soft carbon anodes by iodine treatment towards high-performance potassium-ion batteries.

Soft carbon has been regarded as one of the most promising anode materials for potassium-ion batteries. However, the rearrangement of planar aromatics at high carbonization temperature usually yields a highly graphitized structure, which generally leads to inferior rate and cycle performance. In addition, the role of intrinsic carbon defects on potassium storage has not been well reported yet. In this work, crosslinked pitch-based soft carbon nanosheets have been synthesized through the iodination/dehydroiodination process at low temperature and carbonization with NaCl template. The iodine-treatment efficiently crosslinks the planar aromatics to three-dimensional framework by alkyl-bridged linkages, and reduces the strong π-π interaction during carbonization. This unique microstructure yields an ordered-in-disordered carbon microstructure, enlarged interlayer spacing, and abundant intrinsic defect sites. Benefited from these merits, the optimal sample displays 140% increase of reversible capacity to the pristine pitch-based carbon at 5 A g-1. Particularly, it also presents 87.4% capacity retention after 1000 cycles at 1 A g-1. This facile but simple strategy is expected to expand to other high-performance carbon materials and further understand the effect of intrinsic defects for potassium storage and beyond.

N/O Co-doped Porous Carbons Derived from Coal Tar Pitch for Ultra-high Specific Capacitance Supercapacitors.

In this paper, a series of N/O co-doped porous carbons (PCs) were designed and used to prepare coal tar pitch-based supercapacitors (SCs). The introduction of N/O species under the intervention of urea effectively improves the pseudocapacitance of PCs. The results show that the specific surface area of synthesized N3PC4-700 is 1914 m2 g-1, while the N and O contents are 1.3 and 7.2%, respectively. The unique interconnected pore structure and proper organic N/O co-doping, especially the introduction of pyridine-N and pyrrole-N, are beneficial for improving the electrochemical performance of PCs. In the three-electrode system, the specific capacitance and rate capability of N3PC4-700 are 532.5 F g-1 and 72.5% at the current densities of 0.5 and 20 A g-1, respectively. In addition, the specific capacitance of N3PC4-700 in a coin-type symmetric device is 315.5 F g-1 at 0.5 A g-1. The N3PC4-700 electrode provides an energy density of 43.8 W h kg-1 with a power density of 0.5 kW kg-1 and still maintains a value of 29.7 at 10 kW kg-1. After 10,000 charge/discharge cycles, the retention rate was as high as 96.7%. In order to obtain high-performance carbon-based SCs, the effective identification and regulation of organic N/O species is necessary.