Iron Sulfide Nanoparticles Embedded Into a Nitrogen and Sulfur Co-doped Carbon Sphere as a Highly Active Oxygen Reduction Electrocatalyst

Synthesis of rhenium disulfide nanodots exhibiting pH-dependent fluorescence and phosphorescence for anticounterfeiting and hazardous gas detection

The synthesis and characterization of ReS2 nanodots (NDs) are detailed, by highlighting their structure, morphological, and optical properties. ReS2 NDs were synthesized using NH4ReO4 as a rhenium source, thiourea as a sulfur source, and N-acetyl cysteine as a capping agent. The synthesis involved the hydrothermal reaction of these precursors, leading to the nucleation and growth of ReS2 NDs. Characterization techniques including transmission electron microscopy, energy dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy confirmed the formation of ReS2 NDs with a spherical morphology, crystalline structure, and rich sulfur sites. The fluorescence behavior of ReS2 NDs was found to be influenced by the solution pH, with fluorescence intensity increasing with rising pH values. This pH-dependent fluorescence response was attributed to the dissociation of functional groups and the subsequent impact on the excited-state proton transfer process. The fluorescence intensity of ReS2 NDs showed a correlation with solution pH, enabling pH detection from 3.0 to 12.5 with an interval of 0.5 pH unit. Additionally, the incorporation of ReS2 NDs into a polyvinyl alcohol (PVA) matrix resulted in pH-sensitive phosphorescence, offering a new avenue for pH sensing. The strong interaction between PVA and ReS2 NDs was proposed to enhance phosphorescence intensity and trigger a blue shift in the phosphorescent peak at high pH. The ReS2 NDs/PVA-deposited filter paper exhibited pH-sensitive fluorescence and phosphorescence, which could be utilized as unique identifiers or authentication markers. Moreover, the ReS2 NDs/PVA-deposited filter paper showed potential for discriminating between hydrogen chloride and ammonia, based on their distinct fluorescence and phosphorescence responses.

A highly effective peroxidase-mimic nanozyme of S, N-carbon dot-decorated cerium organic framework-based colorimetric detection of Hg2+ ion and thiophanate methyl

In this study, we proposed a colorimetric probe as S, N-carbon dot-decorated Ce-MOF (S, N-CD@Ce-MOF) for the dual detection of mercury and thiophanate methyl (TM), which are simultaneously present pollutants in the environment and foodstuffs. These pollutants cause serious threats to human health, such as carcinogenicity and neurovirulence. Herein, we synthesized S, N-CD@Ce-MOF using the hydrothermal method and applied it to a "turn-off-on" probe to detect mercury and TM using the colorimetric method in water and food samples. S, N-CD@Ce-MOF shows excellent peroxidase activity by catalyzing the chromogenic substrate of 3,3',5,5'-tetramethylbenzidine (TMB), resulting in deep blue-colored oxidized TMB product (ox TMB) in the presence of H2O2 with a UV absorption wavelength at 654 nm. However, the addition of Hg(II) ions prohibits the oxidation of TMB by an electron transfer effect and easily binds with -S, -N-containing sites on the surface of carbon dots, obstructing the catalytic active sites and decreasing catalytic efficiency with weak UV absorption at 654 nm as a "turn-off". Subsequently, the addition of TM to the above sensing solution as a "turn-on" was triggered by the TM-Hg complex formation and permitted TMB oxidation with a strong absorption peak at 654 nm. Furthermore, this proposed sensor demonstrates a superior linear response to mercury ions and TM in the ranges from 0 to 15 μM and 0 to 14 μM, respectively. The developed colorimetric assay exhibits good sensitivity and selectivity against various possible interferences. Furthermore, we found that the limits of detection for Hg2+ and TM were as low as 0.01 μM and 0.03 μM, respectively. The developed sensor provides various benefits, such as cost-effectiveness, simplicity without a complex detection process, and naked-eye detection. Consequently, our proposed colorimetric technique worked well for the detection of Hg2+ in real water samples and TM in real apple and tomato juice.

Synthesis of Iron Sulfide Nanocrystals Encapsulated in Highly Porous Carbon-Coated CNT Microsphere as Anode Materials for Sodium-Ion Batteries

Highly porous carbon materials with a rationally designed pore structure can be utilized as reservoirs for metal or nonmetal components. The use of small-sized metal or metal compound nanoparticles, completely encapsulated by carbon materials, has attracted significant attention as an effective approach to enhancing sodium ion storage properties. These materials have the ability to mitigate structural collapse caused by volume expansion during the charging process, enable short ion transport length, and prevent polysulfide elution. In this study, a concept of highly porous carbon-coated carbon nanotube (CNT) porous microspheres, which serve as excellent reservoir materials is suggested and a porous microsphere is developed by encapsulating iron sulfide nanocrystals within the highly porous carbon-coated CNTs using a sulfidation process. Furthermore, various sulfidation processes to determine the optimal method for achieving complete encapsulation are investigated by comparing the morphologies of diverse iron sulfide-carbon composites. The fully encapsulated structure, combined with the porous carbon, provides ample space to accommodate the significant volume changes during cycling. As a result, the porous iron sulfide-carbon-CNT composite microspheres exhibited outstanding cycling stability (293 mA h g-1 over 600 cycles at 1 A g-1 ) and remarkable rate capability (100 mA h g-1 at 5 A g-1 ).

Simultaneous Passivation of Perovskite Interfaces at Multiple Active Sites Improves Device Performance: Combining Theory and Experiment

A multisite interface passivation material named 2-mercapto-4-methyl-5-thiazoleacetic acid (MMTA) is used to optimize the perovskite film top interface. DFT calculations and experiments show that MMTA can effectively passivate interface defects. Finally, the champion device's photoelectric conversion efficiency reached 23.44%, which possessed long-term stability.

Ratiometric electrochemical detection of kojic acid based on glassy carbon modified MXene nanocomposite

The significance of developing a selective and sensitive sensor for quality control purposes is underscored by the prevalent use of kojic acid (KA) in cosmetics, pharmaceuticals, and food items. KA's utility stems from its ability to inhibit tyrosinase activity. However, the instability of KA and its potential adverse effects have created a pressing need for accurate and sensitive sensors capable of analyzing real samples. This research introduces an electrochemical ratiometric sensor designed to accurately detect KA in actual cosmetic and food samples. The ratiometric sensor offers distinct advantages such as enhanced selectivity, reproducibility, and sensitivity. It achieves this by leveraging the ratio between two output signals, thereby producing reliable and undistorted results. The sensor is constructed by modifying a Glassy Carbon Electrode (GCE) with a nanocomposite consisting of Ti3C2 MXene, Prussian blue, and gold nanoparticles. The incorporation of MXene and gold nanoparticles heightens sensitivity and reduces impedance. Meanwhile, the Prussian blue signal diminishes proportionally with increasing KA concentration, forming the basis for the ratiometric sensing mechanism. The outcomes of the study reveal a broad linear range (1-600 μM), a low detection limit (1 μM), and strong selectivity for KA. These findings suggest the sensor's potential efficacy in quality control across cosmetics, pharmaceuticals, and food products.

The synthesis of copper-modified biochar from Elsholtzia Harchowensis and its electrochemical activity towards the reduction of carbon dioxide

Phytoremediation techniques have been widely used in the treatment of heavy metal contaminated soils in recent years, but there is no effective post-treatment method for plant tissues containing heavy metals after remediation. Elsholtzia Harchowensis is a copper hyperaccumulator, commonly distributed in copper mining areas and often used for soil remediation of mine tailings. Moreover, copper-based catalysts are widely used in electrocatalytic reduction of carbon dioxide, which aims to convert carbon dioxide into useful fuels or chemicals. In this study, copper-modified biochar was prepared from Elsholtzia Harchowensis. Its specific surface area can reach as high as 1202.9 m2/g, with a certain porous structure and even distribution of copper on the amorphous carbon. Various products (such as carbon monoxide, methane, ethanol, and formic acid) could be obtained from the electrolytic reduction of carbon dioxide by using the as-prepared catalyst. Instantaneous current density of up to 15.3 mA/cm2 were achieved in 1.0 M KHCO3 solution at a potential of -0.82 V (vs. RHE). Electrolysis at a potential of -0.32 V (vs. RHE) for 8 h resulted in a stable current of about 0.25 mA/cm2, and the Faraday efficiency (FE) of carbon monoxide can reach as high as 74.6%. In addition, electrolysis at a potential of -0.52 V (vs. RHE) for 8 h led to a stable current of about 2.2 mA/cm2 and a FE of 8.7% for the C2 product. The rich variety of elements in plants leads to catalysts with complex structural and elemental characteristics as well, which facilitates the electrolytic reduction of carbon dioxide with a variety of useful products.

Exploration of the Fire-Retardant Potential of Microencapsulated Ammonium Polyphosphate in Epoxy Vitrimer Containing Dynamic Disulfide Bonds

Epoxy vitrimers appear as a promising alternative to common epoxy thermoset composites. Nevertheless, the possibilities of applying these materials are limited due to their high flammability which may cause high fire risks. To date, the flame-retardant epoxy vitrimer systems reported in the literature almost all rely on intrinsic flame retardancy to achieve high fire safety; however, the complex and expensive synthesis process hinders their large-scale application. In this work, disulfide-based epoxy vitrimer (EPV) was fabricated with 4, 4'-dithiodianiline as the curing agent, and microencapsulated ammonium polyphosphate (MFAPP) was employed as a potential additive flame retardant to improve their fire retardancy. As a comparative study, common epoxy (EP) composites were also prepared using 4,4'-diaminodiphenylmethane as the curing agent. The results showed that the introduction of dynamic disulfide bonds led to a reduction in the initial thermal decomposition temperature of EPV by around 70 °C compared to EP. Moreover, the addition of 7.5 wt.% of MFAPP endowed EP with excellent fire performance: the LOI value was as high as 29.9% and the V-0 rating was achieved in the UL-94 test (3.2 mm). However, under the same loading, although EPV/MFAPP7.5% showed obvious anti-dripping performance, it did not reach any rating in the UL-94 test. The flame-retardant mechanisms in the condensed phase were evaluated using SEM-EDS, XPS, and Raman spectroscopy. The results showed that the residue of EPV/MFAPP7.5% presented numerous holes during burning, which failed to form a continuous and dense char layer as a physical barrier resulting in relatively poor flame retardancy compared to EP/MFAPP7.5%.

Neurotherapeutic efficacy of loaded sulforaphane on iron oxide nanoparticles against cuprizone-induced neurotoxicity: role of MMP-9 and S100β

Cuprizone (CUP) induces neurotoxicity and demyelination in animal models by provoking the activation of glial cells and the generation of reactive oxygen species (ROS). Sulforaphane (SF) is a phytochemical that exhibits a neuroprotective potential. In this study, we investigated the neurotherapeutic and pro-remyelinating activities of SF and SF-loaded within iron oxide nanoparticles (IONP-SF) in CUP-exposed rats. Magnetite iron oxide nanoparticles (IONPs) were prepared using the hydrothermal method that was further loaded with SF (IONP-SF). The loading of SF within the magnetite nanoparticles was assessed using FTIR, TEM, DLS, Zetasizer, and XPS. For the in vivo investigations, adult male Wistar rats (n = 40) were administrated either on a regular diet or a diet with CUP (0.2%) for 5 weeks. The rats were divided into four groups: negative control, CUP-induced, CUP + SF, and CUP + IONP-SF. CUP-exposed brains exhibited a marked elevation in lipid peroxidation, along with a significant decrease in the activities of glutathione peroxidase (GPx), and catalase (CAT). In addition, CUP intoxication downregulated the expression of myelin basic protein (MBP) and myelin proteolipid protein (PLP), upregulated the expression of Matrix metallopeptidase-9 (MMP-9) and S100β, and increased caspase-3 immunoexpression, these results were supported histopathologically in the cerebral cortexes. Treatment of CUP-rats with either SF or IONP-SF demonstrated remyelinating and neurotherapeutic activities. We could conclude that IONP-SF was more effective than free SF in mitigating the CUP-induced downregulation of MBP, upregulation of S100β, and caspase-3 immunoexpression.

Sulfurized Cyclopentadienyl Nanocomposites for Shuttle-Free Room-Temperature Sodium-Sulfur Batteries

A major challenge hindering the practical adoption of room-temperature sodium-sulfur batteries (NaSBs) is polysulfide dissolution and shuttling, which results in irreversible capacity decay and low Coulombic efficiencies. In this work, we demonstrate for the first time NaSBs using a ferrocene-derived amorphous sulfurized cyclopentadienyl composite (SCC) cathode. Polysulfide dissolution is eliminated via covalent bonding between the insoluble short-chain sulfur species and carbon backbone. Control experiments with a metal-free composite analogue determined that the iron species in the SCC does not have a significant role in polysulfide anchoring. Instead, the superior electrochemical performance is attributed to sulfur covalently bonded to carbon and the uniform nanoparticulate morphology of the SCC composite. In the carbonate-based electrolyte, a discharge capacity of 795 mAh g_(S)^-1 was achieved during early cycling at 0.2 C, and high Coulombic efficiencies close to 100% were maintained with capacity retention of 532 and 442 mAh g_(S)^-1 after 100 and 200 cycles, respectively.

Coupling Hierarchical Ultrathin Co Nanosheets With N-Doped Carbon Plate as High-Efficiency Oxygen Evolution Electrocatalysts

The rational design of cost-effective and highly efficient catalysts for the oxygen evolution reaction (OER) is vastly desirable for advanced renewable energy conversion and storage systems. Tailoring the composition and architecture of electrocatalysts is a reliable approach for improving their catalytic performance. Herein, we developed hierarchical ultra-thin Co nanosheets coupled with N-doped carbon plate (Co-NS@NCP) as an efficient OER catalyst through a feasible and easily scalable NaCl template method. The rapid dissolution-recrystallization-carbonization synthesis process allows Co nanosheets to self-assemble into plenty of secondary building units and to distribute uniformly on N-doped carbon plate. Benefitting from the vertically aligned Co nanosheet arrays and hierarchical architecture, the obtained Co-NS@NCP possess an extremely high specific surface area up to 446.49 m2 g−1, which provides sufficient exposed active sites, excellent structure stability, and multidimensional mass transfer channels. Thus, the Co-NS@NCP affords remarkable electrocatalytic performance for OER in an alkaline medium with a low overpotential of only 278 mV at 10 mA cm−2, a small Tafel slope, as well as robust electrocatalytic stability for long-term electrolysis operation. The present findings here emphasize a rational and promising perspective for designing high-efficiency non-precious electrocatalysts for the OER process and sustainable energy storage and conversion system.

One-step green fabrication of hierarchically porous hollow carbon nanospheres (HCNSs) from raw biomass: Formation mechanisms and supercapacitor applications

Hierarchical porous hollow carbon nanospheres (HCNSs) were fabricated directly from raw biomass via a one-step method, in which HCNSs were obtained by thermal treatment of raw biomass in the presence of polytetrafluoroethylene (PTFE). The HCNSs possess coupling merits of uniformly distributed hollow spherical architectures, and high specific surface area, abundant accessible/open micropores and reasonable mesopores, the HCNS-based electrodes deliver high electrochemical capacitance. The formation mechanisms of pores and hollow core-shell structures were explored thoroughly, it is found that the key to the formation of hollow core-shell structure is the onset-pyrolysis temperature difference between raw biomass and PTFE. Moreover, the content of silica had significant effects on the textures of HCNSs, and HCNS with the largest SSA of 1984 m²/g was obtained. Accordingly, a possible mechanism of HCNSs formation was proposed here, where PTFE acted as the pore creation and nucleation agents and raw biomasses were the primary carbon precursors.