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Surface engineering of nanozymes has been recognized as a potent strategy to improve their catalytic activity and specificity. We synthesized polydopamine-coated Co[sub.3]O[sub.4] nanoparticles (PDA@Co[sub.3]O[sub.4] NPs) through simple dopamine-induced self-assembly and demonstrated that these NPs exhibit catalase-like activity by decomposing H[sub.2]O[sub.2] into oxygen and water. The activity of PDA@Co[sub.3]O[sub.4] NPs was approximately fourfold higher than that of Co[sub.3]O[sub.4] NPs without PDA, possibly due to the additional radical scavenging activity of the PDA shell. In addition, PDA@Co[sub.3]O[sub.4] NPs were more stable than natural catalase under a wide range of pH, temperature, and storage time conditions. Upon the addition of a sample containing sulfide ion, the activity of PDA@Co[sub.3]O[sub.4] NPs was significantly inhibited, possibly because of increased mass transfer limitations via the absorption of the sulfide ion on the PDA@Co[sub.3]O[sub.4] NP surface, along with NP aggregation which reduced their surface area. The reduced catalase-like activity was used to determine the levels of sulfide ion by measuring the increased fluorescence of the oxidized terephthalic acid, generated from the added H[sub.2]O[sub.2]. Using this strategy, the target sulfide ion was sensitively determined to a lower limit of 4.3 µM and dynamic linear range of up to 200 µM. The fluorescence-based sulfide ion assay based on PDA@Co[sub.3]O[sub.4] NPs was highly precise when applied to real tap water samples, validating its potential for conveniently monitoring toxic elements in the environment.

The article deals with phase relations in the KFeS.sub.2-Fe-S system studied by the dry synthesis method in the range of 300-600 °C and at a pressure of 1 bar. At the temperature below 513 ± 3 °C, pyrite coexists with rasvumite and there are pyrite-rasvumite-KFeS.sub.2 and pyrite-rasvumite-pyrrhotite equilibria established. Above 513 ± 3 °C pyrite and rasvumite react to form KFeS.sub.2 and pyrrhotite, limiting the pyrite-rasvumite association to temperatures below this in nature. The experiments also outline the compositional stability range of the copper-free analog of murunskite (K.sub.xFe.sub.2-yS.sub.2) and suggest that mineral called bartonite is not stable in the Cl-free system, at least at atmospheric pressure and the temperature in the experiments. Chlorbartonite could be easily produced after adding KCl in the experiment. Possible parageneses in the quaternary K-Fe-S-Cl system were described based on the data obtained in this research and found in the previous studies. The factors affecting the formation of potassium-iron sulfides in nature were discussed.

The content of Cu[sup.2+] in lubricants is an essential indicator for determining the quality of the lubricant and predicting mechanical failure. Finding an effective and sensitive method for detecting Cu[sup.2+] in lubricants is of great importance in oil monitoring. In this work, AgInS[sub.2] (AIS) and AgInS[sub.2]-ZnS (ZAIS) nanoparticles (NPs) were synthesized by a simple one-step approach via in-situ surface modification by oleylamine. The as-synthesized AIS and ZAIS NPs exhibit good dispersion stability in various apolar media. The photoluminescence (PL) of AIS and ZAIS NPs as lubricating additives could reflect and monitor the lubrication state of steel-copper pairs due to the quenching effect of Cu[sup.2+] from the friction process. With an optimum concentration of 0.5 wt% in paraffin oil, the friction coefficient of the AIS and ZAIS NPs at 100 N was decreased by 56.8 and 52.1% for steel-steel contacts, respectively. ZAIS was observed to be more effective than AIS in improving anti-wear (AW) and extreme pressure (EP) properties, with a load-bearing capacity of up to 1100 N. Characterization of the wear tracks by SEM and XPS indicates that a tribofilm composed of metal sulfides and oxides was formed during the lubricating process. This work not only reveals AIS and ZAIS NPs as a new class of promising candidates for lubricating additives but also unveils their potential for monitoring lubricant conditions and exploring lubricant service life.

Manganese-based nanomaterials have piqued great interest in cancer nanotheranostics, owing to their excellent physicochemical properties. Here we report a facile wet-chemical synthesis of size-controllable, biodegradable, and metastable γ-phase manganese sulfide nanotheranostics, which is employed for tumor pH-responsive traceable gas therapy primed chemodynamic therapy (CDT), using bovine serum albumin (BSA) as a biological template (The final product was denoted as MnS@BSA). The as-prepared MnS@BSA can be degraded in response to the mildly acidic tumor microenvironment, releasing hydrogen sulfide (H S) for gas therapy and manganese ions for magnetic resonance imaging (MRI) and CDT. experiments validated the pH-responsiveness of MnS@BSA at pH 6.8 and both H S gas and •OH radicals were detected during its degradation. experiments showed efficiently tumor turn-on -weighted MRI, significantly suppressed tumor growth and greatly prolonged survival of tumor-bearing mice following intravenous administration of MnS@BSA. Our findings indicated that MnS@BSA nanotheranostics hold great potential for traceable H S gas therapy primed CDT of cancer.

The extent to which sulfur dissolves in silicate melts saturated in an immiscible sulfide phase is a fundamental question in igneous petrology and plays a primary role in the generation of magmatic ore deposits, volcanic degassing, and planetary differentiation. In igneous systems, sulfide melts can be described as FeS-NiS-CuS0.5 solutions with Fe/(Fe+Ni+Cu) significantly less than 1. Despite the presence of Ni and Cu in the sulfide, however, most experimental studies to date have concentrated on the effects of silicate melt composition on sulfur solubility and have used essentially pure FeS as the sulfide liquid. We have carried out 49 new experiments at pressures of 1.5-24 GPa and temperatures of 1400 to 2160 °C to investigate the effects of sulfide composition on sulfur solubility as well as extending the pressure and temperature ranges of the available data on sulfide saturation. We find that in the compositional range of most igneous sulfide melts [Fe/(Fe+Ni+Cu) > 0.6] sulfur solubility decreases linearly with Fe content such that at Fe/(Fe+Ni+Cu) of 0.6 the sulfur content at saturation is 0.6 times the value at pure FeS saturation. At lower values of Fe/(Fe+Ni+Cu), however, deviations from this ideal solution relationship need to be taken into consideration. We have treated these non-idealities by assuming that FeS-NiS-CuS0.5 liquids approximate ternary regular solutions.We have fitted our data, together with data from the literature (392 in total), to equations incorporating the effects of silicate melt composition, sulfide liquid composition, and pressure on the solubility of sulfur at sulfide saturation ([S]SCSS). The temperature dependence of [S]SCSS was assumed either to be an unknown or was taken from 1 bar thermodynamic data. The most important best-fit silicate melt compositional term reflects the strongly positive dependence of [S]SCSS on the FeO content of the silicate melt. The best-fit value of this parameter is essentially independent of our assumptions about temperature dependence of [S]SCSS or the solution properties of the sulfide. All natural compositions considered here exhibit positive dependences of [S]SCSS on temperature and negative dependences on pressure, in accord with previous studies using smaller data sets.

To develop novel inorganic red pigments without harmful elements, we focused on the band structure of Ca[sub.2](Mg, Co)WO[sub.6] and attempted to narrow its bandgap by replacing the W[sup.6+] sites in the host structure of Mo[sup.6+]. Ca[sub.2]Mg[sub.1−x]CoxW[sub.1−y]MoyO[sub.6] (0.10 ≤ x ≤ 0.30; 0.45 ≤ y ≤ 0.60) samples were synthesized by a sol-gel method using citric acids, and the crystal structure, optical properties, and color of the samples were characterized. The Ca[sub.2]Mg[sub.1−x]CoxW[sub.1−y]MoyO[sub.6] solid solution was successfully formed, which absorbed visible light at wavelengths below 600 nm. In addition, the absorption wavelength shifted to longer wavelengths with increasing Mo[sup.6+] content. This is because a new conduction band composed of a Co[sub.3d]-W[sub.5d]-Mo[sub.4d] hybrid orbital was formed by Mo[sup.6+] doping to reduce the bandgap energy. Thus, the color of the samples gradually changed from pale orange to dark red, with a hue angle (h°) of less than 35°. Based on the above results, the optical absorption wavelength of the Ca[sub.2]Mg[sub.1−x]CoxW[sub.1−y]MoyO[sub.6] system can be controlled to change the color by adjusting the bandgap energy.

With the rapid development of nanotechnology, metal sulfide nanoparticles have been widely detected in the environment including water, soils and sediments. Metal sulfides are considered as stable species in the environment, while transformation and risk of nanoparticles have attracted increasing attention due to their specific physicochemical properties compared to bulk materials. Here we review aggregation, sedimentation, chemical and biological transformations, and potential risk of silver sulfide (Ag 2 S), zinc sulfide (ZnS), copper sulfide (CuS), cadmium sulfide (CdS) and lead sulfide nanoparticles, and quantum dots such as ZnS and CdS. The review shows that both stability and risk of metal sulfide nanoparticles are highly dependent on environmental factors such as pH, inorganic salts and natural organic matter.

Electrocatalytic N₂ reduction reaction (NRR) into ammonia (NH₃), especially if driven by renewable energy, represents a potentially clean and sustainable strategy for replacing traditional Haber–Bosch process and dealing with climate change effect. However, electrocatalytic NRR process under ambient conditions often suffers from low Faradaic efficiency and high overpotential. Developing newly regulative methods for highly efficient NRR electrocatalysts is of great significance for NH₃ synthesis. Here, we propose an interfacial engineering strategy for designing a class of strongly coupled hybrid materials as highly active electrocatalysts for catalytic N₂ fixation. X-ray absorption near-edge spectroscopy (XANES) spectra confirm the successful construction of strong bridging bonds (Co–N/S–C) at the interface between CoSₓ nanoparticles and NS-G (nitrogen- and sulfurdoped reduced graphene). These bridging bonds can accelerate the reaction kinetics by acting as an electron transport channel, enabling electrocatalytic NRR at a low overpotential. As expected, CoS₂/NS-G hybrids show superior NRR activity with a high NH₃ Faradaic efficiency of 25.9%at −0.05 V versus reversible hydrogen electrode (RHE). Moreover, this strategy is general and can be extended to a series of other strongly coupled metal sulfide hybrids. This work provides an approach to design advanced materials for ammonia production.

Through a simple solvothermal method, the bimetallic sulfide nanomaterial (Ni-Mo-S) was successfully grown on the surface of CeO.sub.2 to restrain the severe photogenerated electron-hole recombination of CeO.sub.2. The presence of a close contact interface between the 0D metal sulfide particles and the 2D CeO.sub.2 sheet is conducive to charge transfer. Meanwhile, the introduction of Ni-Mo-S nanoparticles on 2D CeO.sub.2 can accelerate surface electron mobility, which could obviously inhibit the combination of electrons and holes. Also, there are many unsaturation sites of metal sulfide introduced on the surface and low hydrogen evolution overpotential, which can serve as active sites for hydrogen evolution. In addition, the 2D structure of CeO.sub.2 can provide a support framework for the 0D Ni-Mo-S particles, thereby greatly reducing the recombination of useful electrons and holes. All of these advantages of photocatalysts discussed above make for the enhancement of photocatalyst catalytic performance, which equal to about 66 times compared with pure CeO.sub.2. Besides, a series of research tests were carried out from different angles to support the relevant results and proposed possible reaction mechanisms.