Topochemical behavior of ferrocene embedded in V2O5·nH2O with weak hydrogen bonding enhancing ammonium-ion storage.

Aqueous ammonium ion batteries (AAIBs) are garnering increasing attention due to their utilization of abundant resources, cost-effectiveness, safety, and unique energy storage mechanism. The pursuit of high-performance cathode materials has become a pressing issue. In this study, we propose and synthesize ferrocene-embedded hydrated vanadium pentoxide (Fer/VOH) for implementation in AAIBs. The inclusion of ferrocene serves to expand the interlayer spacing, mitigate interlayer forces, and introduce the electron-rich environment characteristic of ferrocene. This augmentation facilitates the creation of additional oxygen vacancies, substantially enhancing the capacity and efficiency of ammonium ion storage. Notably, our investigation reveals that the incorporation of ferrocene attenuates the hydrogen bonding interactions associated with ammonium ions, rendering them more amenable to the interlayer embedding and release processes. Building upon these advantages, Fer/VOH exhibits a specific capacity of 313 mAh/g at a current density of 0.2 A/g, representing the highest reported performance among vanadium oxides utilized in AAIBs to date. Even after 2000 charge/discharge cycles at a current density of 2 A/g, Fer/VOH maintains a reversible specific capacity of 89 mAh/g, with a capacity retention rate of 54.8%. This study confirms the viability of Fer/VOH as a cathode material for AAIBs and offers a novel approach to enhancing the electrical conductivity and diminishing the hydrogen bonding forces in vanadium oxide intercalation through the embedding of electron-rich species and positronic groups.

Supramolecular Copolymers Under Kinetic, Thermodynamic, or Pathway-Switching Control.

Supramolecular copolymers have attracted much attention due to their potential functionalities. However, the co-assembly strategies to construct co-assemblies of small molecules with well-defined sequence structures are still limited, especially for more complex crystalline block co-assemblies. Herein, we target this challenge by designing IrIII complexes 1 and 2, which possess unique self-assembly pathways and are capable of forming crystalline assemblies in aqueous systems. Specifically, block and random co-assemblies of 1 and 2 can be synthesized by kinetic and thermodynamic control, respectively. Meanwhile, by adjusting the water content to orthogonalize the on-pathway and the off-pathway, an unprecedented pathway-switching approach is realized to synthesize block and random co-assemblies. By coupling the kinetic pathways, the present co-assembly strategies are expected to pave the way for the synthesis of crystalline co-assemblies of small molecules and the construction of organic heterostructures.

Unsupported Nanoporous Platinum-Iron Bimetallic Catalyst for the Chemoselective Hydrogenation of Halonitrobenzenes to Haloanilines.

An unsupported nanoporous platinum-iron bimetallic catalyst (PtFeNPore) was prepared with an electrochemical dealloying technique. Its structure and composition were characterized through various measurement methods, such as X-ray absorption fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS). An intermetallic compound and iron oxide species were both found in the PtFeNPore catalyst. The nanoporous structure and Lewis acidity (caused by iron oxide species) of the PtFeNPore catalyst resulted in superior catalytic activity and high selectivity. The PtFeNPore-catalyzed hydrogenation of various halonitrobenzenes proceeded successfully under mild reaction conditions and produced good to excellent yields of the corresponding haloanilines with high selectivity. PtFeNPore can be recycled through magnetic separation easily and reused five times without significant deactivation.

Accelerating effects of humin on sulfide-mediated azo dye reduction.

As an important fraction of humic substances, humin has been found capable of stimulating bioreduction reactions. However, whether humin could promote abiotic reduction and the effects of coexisting soluble humic substance and insoluble mineral remained unsolved. In this study, a humin sample was isolated from a paddy soil. Cyclic voltammetry, electron paramagnetic resonance, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses of the humin indicated the existence of redox-active quinone moieties and other oxygen-containing groups. The humin could be reduced by sulfide and its presence stimulated the abiotic reduction of acid red 27 (AR27) and four other azo dyes by sulfide. In the presence of 100-1000 mg/L intact humin, the sulfide-mediated AR27 reduction efficiency in 7 d was enhanced from 56.3% to 92.5%. The stimulating behavior of intact humin was observed for 100-300 mg/L AR27 and increased with the increase of sulfide concentration (1.2-3.0 mM). Much higher stimulating effects were found with the presence of humin pre-reduced by sulfide. Moreover, for sulfide-mediated AR27 reduction, the coexistence of humin (500 mg/L) and humic acid (10-30 mg/L) or Wyoming sodium-montmorillonite (SWy-2, 1-4 g/L) led to better promotion activities than the presence of single component. And synergistic promotion of sulfide-mediated AR27 reduction was observed with coexisting humin and SWy-2 due to enhanced Fe(II) production. These findings extended our understanding of the influence of humin on reductive transformation of pollutants in the environment.

Inorganic Colloidal Perovskite Quantum Dots for Robust Solar CO2 Reduction.

Inorganic perovskite quantum dots as optoelectronic materials have attracted enormous attention in light-harvesting and emitting devices. However, photocatalytic conversion based on inorganic perovskite halides has not been reported. Here, we have synthesized colloidal quantum dots (QDs, 3-12 nm) of cesium lead halide perovskites (CsPbBr3 ) as a new type of photocatalytic material. The band gap energies and photoluminescence (PL) spectra are tunable over the visible spectral region according to quantum size effects on an atomic scale. The increased carrier lifetime revealed by time-resolved PL spectra, indicates the efficient electron-hole separation and transfer. As expected, the CsPbBr3 QDs with high selectivity of greater than 99 % achieve an efficient yield of 20.9 µmol g-1 towards solar CO2 reduction. This work has opened a new avenue for inorganic colloidal perovskite materials as efficient photocatalysts to convert CO2 into valuable fuels.

Microbial reduction of Fe(III)-bearing clay minerals in the presence of humic acids.

Both Fe(III)-bearing clay minerals and humic acids (HAs) are abundant in the soils and sediments. Previous studies have shown that bioreduction of structural Fe(III) in clay minerals could be accelerated by adding anthraquinone compound as a redox-active surrogate of HAs. However, a quinoid analogue could not reflect the adsorption and complexation properties of HA, and little is known about the effects of real HAs at environmental concentration on bioreduction of clay minerals. Here, it was shown that 10-200 mg l-1 of natural or artificially synthesized HAs could effectively stimulate the bioreduction rate and extent of Fe(III) in both iron-rich nontronite NAu-2 and iron-deficient montmorillonite SWy-2. After adsorption to NAu-2, electron-transfer activities of different HA fractions were compared. Additionally, Fe(II) complexation by HAs also contributed to improvement of clay-Fe(III) bioreduction. Spectrosopic and morphological analyses suggested that HA addition accelerated the transformation of NAu-2 to illite, silica and siderite after reductive dissolution.

Using silver nanocluster/graphene nanocomposite to enhance photoelectrochemical activity of CdS:Mn/TiO2 for highly sensitive signal-on immunoassay.

A highly sensitive signal-on photoelectrochemical (PEC) immunosensor was fabricated here using CdS:Mn/TiO2 as photoelectrochemical sensing platform, and silver nanoclusters and graphene naocomposites (AgNCs-GR) as signal amplification tags. The immunosensor was constructed based on the specific sandwich immunoreaction, and the photo-to-current conversion efficiency of the isolated protein modified CdS:Mn/TiO2 matrix was improved based on the synergistic effect of AgNCs-GR. Under irradiation, the photogenerated electrons from the AgNCs at a higher conduction band edge level could be transport to the CdS:Mn/TiO2 matrix with the assistance of highly conductive graphene nanosheets, as well as recycle the trapped excitons in the defects-rich CdS:Mn/TiO2 interface. The electron transport and exciton recycle reduced the possibility of electron-hole recombination and greatly improved the photo-to-current conversion efficiency of the sensing matrix. Based on the signal enhancement, a signal-on PEC immunosensors was fabricated for the detection of carcinoembryonic antigen (CEA), a model analyte related to many malignant diseases. Under optimal conditions, the as-prepared immunosensor showed excellent analytical performance, with a wide linear range from 1.0 pg/mL to 100 ng/mL and a low limit of detection of 1.0 pg/mL. The signal-on mode provided 2.48 times higher sensitivity compared with signal-off mode. This strategy demonstrated good accuracy and high selectivity for practical sample analysis, thus may have great application prospective in the prediction and early diagnosis of diseases.

Photostable ester-substituted bis-cyclometalated cationic iridium(III) complexes for continuous monitoring of oxygen.

Three bis-cyclometalated cationic Ir(iii) complexes , and with an ester substituent at the 4-position of the phenyl ring on the 2-phenylpyridine (ppy) have been synthesized and fully characterized. The emission maxima of ester-substituted Ir(iii) complexes show a notable blue-shift compared to the parent complex [Ir(ppy)2(phen)](+)PF6(-) (phen = 1,10-phenanthroline). The influence of an ester group on the photoelectric properties of the Ir(iii) complexes has been investigated systematically. The oxygen sensing films prepared from ethyl cellulose immobilized with Ir(iii) complexes exhibit excellent operational stability, high photostability and a quick response to oxygen. show extended luminescence lifetimes relative to , and display better sensitivity to changes in oxygen partial pressure.

Investigation of factors affecting adsorption of transition metals on oxidized carbon nanotubes.

Adsorption of nickel, copper, zinc and cadmium from aqueous solutions on carbon nanotubes oxidized with concentrated nitric acid was carried out in single, binary, ternary and quaternary systems. TEM and adsorption of nitrogen were used to determine texture and structural parameters, respectively. The surface chemistry was evaluated using the pH at the point of zero charge, FTIR spectroscopy and XPS analysis. The experimental results showed that all isotherms for Cu(2+)(aq) fit to Langmuir model in each system. On the other hand, the isotherms for Ni(2+)(aq), Cd(2+)(aq) and Zn(2+)(aq) in multi-component systems reveal the effect of competition for adsorption sites seen as a decrease in the amount adsorbed. The uptakes at the equilibrium concentration of 0-0.04 mmol L(-1) in single system and 0-0.15 mmol L(-1) in binary system are in the order Cu(2+)(aq)>Ni(2+)(aq)>Cd(2+)(aq)>Zn(2+)(aq) while for the ternary and quaternary, the order is Cu(2+)(aq)>Cd(2+)(aq)>Zn(2+)(aq)>Ni(2+)(aq). The results indicate that the mechanism of adsorption is governed by the surface features, ion exchange process and electrochemical potential. The latter plays a significant role in multi-component adsorption where redox reactions, not only on the adsorbent surface but also between the adsorbates, are likely to occur.

Investigation of the role of surface chemistry and accessibility of cadmium adsorption sites on open-surface carbonaceous materials.

Carbon nanotubes fabricated by the dc arc discharge method (ADCNTs) and chemical vapor deposition method (CVDCNTs) were oxidized with concentrated HNO 3 to modify their surface chemistry. The materials were characterized using SEM, TEM, FTIR, XPS, potentiometric titration, and nitrogen adsorption. The initial and oxidized materials were used as adsorbents of cadmium from aqueous solutions with different pH. Langmuir and Freundlich adsorption models were applied to fit the isotherm data, and both models fit the experimental data very well. The acid oxidation resulted in an increase in the number of oxygen-containing groups without drastic changes in the texture of the adsorbents. Although the small volume of micropores is present, the nanotube structure can be considered as nonporous. The lack of developed microporosity in carbonaceous materials eliminates the inner surface diffusion problems and makes the vast majority of surface groups available for adsorption of cadmium. The availability of these centers depends on the pH of the solution, which controls the protonation level. In spite of the fact that the pH of the solution affects the speciation of cadmium to some degree, the surface chemistry is the predominant force for adsorption at the pH range adopted in the present study, while the texture of materials also affects the nanotube's cadmium-adsorbing performance.