Hexavalent Chromium as a Smart Switch for Peroxidase-like Activity Regulation via the Surface Electronic Redistribution of Silver Nanoparticles Anchored on Carbon Spheres.

Although some ions, due to their unique chemical properties, can regulate the enzyme-like activity of nanomaterials, it is still a huge challenge to explore the mechanism of regulation. Herein, we found that Cr6+ (CrO42-) as a smart switch can significantly increase the peroxidase-like (POD-like) activity of silver nanoparticles (Ag NPs), which were anchored efficiently on carbon spheres (Cal-CS/PEG/Ag) using amino-modified poly(ethylene glycol) (PEG) as a bridge. Density functional theory (DFT) calculations demonstrated that the addition of Cr6+ can not only adjust the surface electronic redistribution of Ag atoms but also improve the geometric structure of the adsorbed intermediate, which resulted in the optimization of free energy and change of bond lengths in the catalytic reaction process, increasing the POD-like activity of Cal-CS/PEG/Ag. Based on the Cr6+-increased POD-like activity of Cal-CS/PEG/Ag, we successfully constructed a visual sensor of Cr6+ along with quantitative analysis by the UV spectrum. The sensor has good selectivity for other 29 interfering ions and molecules with a detection limit of 79 nM. In this work, the detailed mechanism of the Cr6+-increased POD-like activity of Ag NPs was studied and a new possibility for the rational design of ion visual sensors using nanomaterials was proposed.

Efficient Visual Chemosensor for Hexavalent Chromium via a Controlled Strategy for Signal Amplification in Water.

Generally, 3,3',5,5'-tetramethylbenzidine (TMB) cannot react with hydrogen peroxide (H2O2) in neutral pH or in water at room temperature and pressure. Herein, we found that hexavalent chromium (Cr6+) can trigger TMB reacting with H2O2 (TMB-H2O2) in ultrapure water along with a weak signal output. Then, to implement signal amplification effectively, we designed a ternary nanohybrid material containing graphene oxide (GO) nanosheets, gold nanoparticles (Au NPs), and hyperbranched polyethylenimine (PEI) to form rGO/PEI/Au nanohybrids via chemical bonding. After addition of a trace amount of Cr6+, rGO/PEI/Au nanohybrids can effectively catalyze TMB-H2O2 in ultrapure water; thus, a visual chemosensor and electronic spectrum quantitative analysis method for Cr6+ based on chromium-stimulated peroxidase mimetic activity of rGO/PEI/Au nanohybrids were established. The visual chemosensor exhibits excellent selectivity and interference immunity against 34 other interfering substances with a detection limit as low as 2.14 nM. The visual chemosensor for Cr6+ with a low detection limit and high selectivity is expected to have a potential application in environmental analysis, monitoring, and human health maintenance.

Embedding Ultrasmall Au Clusters into the Pores of a Covalent Organic Framework for Enhanced Photostability and Photocatalytic Performance.

Gold clusters loaded on various supports have been widely used in the fields of energy and biology. However, the poor photostability of Au clusters on support interfaces under prolonged illumination usually results in loss of catalytic performance. Covalent organic frameworks (COFs) with periodic and ultrasmall pore structures are ideal supports for dispersing and stabilizing Au clusters, although it is difficult to encapsulate Au clusters in the ultrasmall pores. In this study, a two-dimensional (2D) COF modified with thiol chains in its pores was prepared. With -SH groups as nucleation sites, Au nanoclusters (NCs) could grow in situ within the COF. The ultrasmall pores of the COF and the strong S-Au binding energy combine to improve the dispersibility of Au NCs under prolonged light illumination. Interestingly, Au-S-COF bridging as observed in this artificial Z-scheme photocatalytic system is deemed to be an ideal means to increase charge-separation efficiency.

Ultratrace Naked-Eye Colorimetric Ratio Assay of Chromium(III) Ion in Aqueous Solution via Stimuli-Responsive Morphological Transformation of Silver Nanoflakes.

In this work, we discover an effective domino-effect-based detection mechanism for the rapid, high-selectivity, and ultrasensitive naked-eye colorimetric ratio assay of chromium(III) ion (Cr3+) in aqueous solutions. This naked-eye colorimetric ratio assay to Cr3+ relies on changes in absorbance properties that are due to the stimuli response of Cr3+ for the morphological transformation of silver nanoflakes. In the presence of Cr3+, large silver nanoflakes can be stimulated to transform to small nanoparticles (NPs), which promoted a color change in solution from bright yellow to wine red that was detected by the naked eye and spectroscopic absorption methods. The proposed naked-eye sensing strategy was coupled with an ultraviolet (UV)-spectroscopic chemosensor for the detection of trace Cr3+. The detection method showed an ultralow detection limit of 1.4 nM (nanomole) for Cr3+ in ultrapure water and 11.5 nM in human serum sample, respectively. On the basis of colorimetry, the lowest concentration of ∼50 nM for Cr3+ in ultrapure water and human serum can be detected by the naked eye. This naked-eye-based colorimetric ratio assay for accurate and selective identification and high sensitivity of Cr3+ is expected to have large potential and wide applications such as pharmaceutical analysis, clinical diagnosis, and environmental monitoring.

Carbon-Intercalated 0D/2D Hybrid of Hematite Quantum Dots/Graphitic Carbon Nitride Nanosheets as Superior Catalyst for Advanced Oxidation.

Efficient charge separation and sufficiently exposed active sites are important for light-driving Fenton catalysts. 0D/2D hybrids, especially quantum dots (QDs)/nanosheets (NSs), offer a better opportunity for improving photo-Fenton activity due to their high charge mobility and more catalytic sites, which is highly desirable but remains a great challenge. Herein, a 0D hematite quantum dots/2D ultrathin g-C3 N4 nanosheets hybrid (Fe2 O3 QDs/g-C3 N4 NS) is developed via a facile chemical reaction and subsequent low-temperature calcination. As expected, the specially designed 0D/2D structure shows remarkable catalytic performance toward the removal of p-nitrophenol. By virtue of large surface area, adequate active sites, and strong interfacial coupling, the 0D Fe2 O3 QDs/2D g-C3 N4 nanosheets establish efficient charge transport paths by local in-plane carbon species, expediting the separation and transfer of electron/hole pairs. Simultaneously, highly efficient charge mobility can lead to continuous and fast Fe(III)/Fe(II) conversion, promoting a cooperative effect between the photocatalysis and chemical activation of H2 O2 . The developed carbon-intercalated 0D/2D hybrid provides a new insight in developing heterogeneous catalysis for a large variety of photoelectronic applications, not limited in photo-Fenton catalysis.

Self-Assembly of Biocompatible FeSe Hollow Nanostructures and 2D CuFeSe Nanosheets with One- and Two-Photon Luminescence Properties.

Transition metal chalcogenides are investigated for catalyst, intermediary agency, and particular optical properties because of their distinguished electron-vacancy-transfer (EVT) process toward different applications. In this work, one convenient approach for making pure-phased FeSe nanocrystals (NCs) and doped CuFeSe nanosheets (NSs) through a wet chemistry method in mixed solvents is illustrated. The surface modification of each product is realized by using a peptide molecule glutathione (GSH), in which the thiol group (-SH) is ascribed to be the in situ reducer and bonding agency between the crystalline surface and surfactant in whole constructing processes. Due to the functional groups in biological GSH, highly aggregated NCs are rebuilt in the form of an FeSe hollow structure through amino and carboxyl cross-linking functions through a spontaneous assembly procedure. Owing to the coupling procedure of Cu and Fe in the growth process, it generates enhanced EVT. Additionally, it shows the emission spectra of λEM-PL = 436 nm (FeSe) and 452 nm (CuFeSe) while λEX-PL = 356 nm, it also conveys two-photon phenomenon while λEX-PL = 720 nm. Moreover, it also shows strong off-resonant luminescence due to two-photon absorption, which should be valuable for biological applications.

Dual-Emitting Fluorescent Metal-Organic Framework Nanocomposites as a Broad-Range pH Sensor for Fluorescence Imaging.

pH plays an important role in understanding physiological/pathologic processes, and abnormal pH is a symbol of many common diseases such as cancer, stroke, and Alzheimer's disease. In this work, an effective dual-emission fluorescent metal-organic framework nanocomposite probe (denoted as RB-PCN) has been constructed for sensitive and broad-range detection of pH. RB-PCN was prepared by encapsulating the DBI-PEG-NH2-functionalized Fe3O4 into Zr-MOFs and then further reacting it with rhodamine B isothiocyanates (RBITC). In RB-PCN, RBITC is capable of sensing changes in pH in acidic solutions. Zr-MOFs not only enrich the target analyte but also exhibit a fluorescence response to pH changes in alkaline solutions. Based on the above structural and compositional features, RB-PCN could detect a wide range of pH changes. Importantly, such a nanoprobe could "see" the intracellular pH changes by fluorescence confocal imaging as well as "measure" the wider range of pH in actual samples by fluorescence spectroscopy. To the best of our knowledge, this is the first time a MOF-based dual-emitting fluorescent nanoprobe has been used for a wide range of pH detection.

Ultrahigh Selective Colorimetric Quantification of Chromium(VI) Ions Based on Gold Amalgam Catalyst Oxidoreductase-like Activity in Water.

Hexavalent chromium ion (Cr6+) is one of the most toxic substances for plants, for animals, and is a confirmed human respiratory carcinogen. However, so far, there are few independent and efficient colorimetric methods for detection of Cr6+. Here, we introduce a convenient, label-free, catalysis-based, and efficient strategy for quantification of Cr6+ by using a colorimetric sensing probe 3,3',5,5'-tetramethylbenzidine (TMB). In the presence of a trace amount of gold amalgam nanocomposites (Au@Hg) and Cr6+, TMB can be oxidized to oxTMB and the color changed to an intense blue that was observed by naked-eye and absorption spectroscopic method. In addition, the colorimetric method shows the high selectivity against 34 other interfering substances, and it can be performed at room temperature, in water, and requires only ∼5 min. Thus, the catalysis-based colorimetric assay for accurate and ultrahigh selective identification of Cr6+ will find widespread use in the world.

Ultratrace Naked-Eye Colorimetric Detection of Hg2+ in Wastewater and Serum Utilizing Mercury-Stimulated Peroxidase Mimetic Activity of Reduced Graphene Oxide-PEI-Pd Nanohybrids.

Herein, we developed a general strategy for rapid, highly selective, and ultratrace naked-eye colorimetric detection of Hg2+ in aqueous solutions. Two dimensional rGO/PEI/Pd nanohybrids, where rGO, PEI, and Pd were referred to as reduced graphene oxide, polyethylenimine, and Pd nanoparticles, respectively, were synthesized and used as mimetic peroxidase for selective and ultrasensitive detection of Hg2+ in water and human serum samples. In the presence of mercury ions, the peroxidase mimetic activity of rGO/PEI/Pd nanohybrids was found to be stimulated and enhanced significantly, which promoted the effective oxidation and color change of 3,3',5,5'-tetramethylbenzidine (TMB) in solution to dark blue that was detected by the naked-eye and the absorption spectroscopic method. The proposed sensing strategy coupled with spectroscopic detection method showed an ultralow detection limit of 0.39 nM for Hg2+ in ddH2O and ∼1 nM in wastewater as well as serum samples, respectively. On the basis of the colorimetric assay, a minimum concentration of ∼10 nM for Hg2+ in wastewater and human serum can be detected with the naked-eye. The naked-eye-based colorimetric assay for sensitive and selective detection of mercury is expected to hold huge potentials in applications such as environmental monitoring, clinical diagnosis, and pharmaceutical analysis.

Porphyrin aggregates decorated MWCNT film for solar light harvesting: influence of J- and H-aggregation on the charge recombination resistance, photocatalysis, and photoinduced charge transfer kinetics.

J- and H-aggregates of zinc tetraphenylporphyrin (ZnTPP) on carbon nanotube films (CNTFs) were prepared using the mixed solvent method. This resulted in completely different structures, such as the four-leaf clover and flower, on the CNTF, which were observed by recording SEM images. Characteristic changes in the electronic spectra of the ZnTPP monomer appeared when it underwent J- and H-aggregation. The measured photocurrent significantly varied for the same molecule when it was aggregated in two different ways on ITO and ITO/CNTF. The electron recombination resistance of the two aggregates, which was investigated using electrochemical impedance spectroscopy, was also different. The photocatalytic efficiency of the J- and H-aggregates was examined by performing methylene blue dye decoloration studies. In addition, a scanning electrochemical microscope was used to investigate the photoinduced charge transfer kinetics of the J- and H-aggregates at the electrode/electrolyte interface as a fresh attempt. The heterogeneous charge transfer constants for the J- and H-aggregates in the presence of light at varied intensities were calculated. Thereby, striking differences in the photophysical, photocatalytic, and photoelectrochemical properties of the J- and H-aggregates were visualized throughout our studies.

Security issues of the gold industry chain based on smart blockchain in the context of the Internet of Things.

The purpose is to solve the safety production and management problems of the gold Industrial Chain and give early warning of the safety situation of the gold Industrial Chain. According to the theory of industrial chain security governance and the basic situation of the gold Industrial Chain, this work establishes a gold Industrial Chain model based on smart blockchain and system dynamics (SD), and discusses the application of the gold Industrial Chain in the Internet of Things (IoT) environment. The overall goal of the application of IoT technology to the safety management of intelligent gold mines is to take the gold mine production demand as the driving force. The digitalization of production, electromechanical, safety, dispatching, and other information realizes intelligent digital perception, assists decision-making, guides the safety management of gold mining operations, continuously improves the operation efficiency of the gold mining industry, and drives the development of the industry. Finally, it takes the resource reserve of China's gold industry from 2011 to 2021 as the research data introduces the weighting method to assess the security situation of China's gold Industrial Chain from 2011 to 2021. The safety performance of China's environmental industry chain is evaluated through the detailed introduction of the basic information of the gold Industrial Chain. The result shows that the security situation of China's gold Industrial Chain from 2011 to 2021 shows an overall growth trend, 88.42% higher than in 2014. The security situation of China's gold Industrial Chain from 2011 to 2021 positively impacted the opening of the domestic gold market and entering the international gold market, improving the security level of China's gold Industrial Chain. In this work, a gold Industrial Chain security model based on smart blockchain and SD is established to solve the safety problem of the gold Industrial Chain, which can improve the safety level of the gold industry and promote its sustainable development.

Modeling the impact of nickel recycling from batteries on nickel demand during vehicle electrification in China from 2010 to 2050.

China is promoting the production and use of electric vehicles (EVs) to achieve carbon neutrality. However, the shift will drive higher demand and tighter supply of nickel in China. We develop a stock-driven bottom-up dynamic substance flow analysis (SFA) model to simulate the demand trends of various EVs under 3 scenarios, the flow of nickel under 9 scenarios and the amount of recoverable nickel under 27 scenarios in China's EV industry from 2010 to 2050. The results indicate that China's current production capacity and primary reserves of nickel cannot meet the growing nickel demand, especially under the High EVs-LNCT scenarios, and closed-loop nickel recovery from EV batteries can effectively alleviate the demand-supply contradiction. In different scenarios, the annual recycling nickel could cover between 67.7 % and 96.6 % of the demand for EV batteries in 2050, and between 37.9 % and 58.1 % in terms of the cumulative quantity by 2050. When the low nickel battery technology is adopted and the recovery efficiency is rapidly improved, the recovered nickel would meet the demand for EV batteries to the highest degree. Therefore, sufficient attention should be paid to low-nickel battery technology and efficient recycling of spent EV batteries, which is of great significance to ensure the development of EV industry and the availability of nickel in China.

Analysis of the Rare Earth Mineral Resources Reserve System and Model Construction Based on Regional Development.

China is a large rare earth country that has pushed for related rare earth research, development, and application in the global development and progress of rare earths. The rare earth resource reserve strategy must be implemented by China due to the situation of rare earth resources at home and abroad, national security, and the need to strengthen the right to speak in the international market. This article builds the rare earth mineral resources reserve system and model from the perspective of regional development and uses the improved SURF algorithm to solve the problems of inaccurate mine location, mine location deviation, dislocation, overlap, and other issues, resulting in more accurate mineral resources reserve management data. The results show that the maximum relative error between the parallel profile method and the traditional method is 2.6%, which meets the requirement for mineral reserve calculation accuracy and can be used to calculate reserves. China's peak ionic rare earth output will be 46,797.06 tonnes in 2024, and then, it will decline at a 4% annual rate thereafter. This demonstrates how a graded reserve and orderly promotion can improve the workflow and efficiency of the rare earth mineral resources reserve.

Bis{(E)-2-[(2-chloro-3-pyrid-yl)imino-meth-yl]-6-meth-oxy-phenolato-κN,O}copper(II).

In the title mononuclear copper(II) complex, [Cu(C(13)H(10)ClN(2)O(2))(2)], the Cu(II) ion, lying on an inversion center, is four-coordinated in a trans-CuN(2)O(2) square-planar geometry by two phenolate O and two imino N atoms from two symmetry-related N,O-bidentate Schiff base ligands. The shortest Cu⋯Cu distance is 7.5743 (9) Å. However, there are weak intra-molecular electrostatic inter-actions between the Cu atom and the Cl atom of the ligand, with a Cu⋯Cl distance of 3.3845 (9) Å.

Brief cross-linking of Fas/APO-1 (CD95) triggers engulfment of pre-apoptotic target cells.

Macrophage clearance of dying cells is of crucial importance to maintain tissue homeostasis. Here, we show that brief treatment (15min) of Jurkat T cells with agonistic anti-Fas antibodies or recombinant Fas ligand results in efficient phagocytosis by human monocyte-derived macrophages prior to the occurrence of common biomarkers of apoptosis. Similar findings were obtained when using primary human T cells. Macrophage engulfment of pre-apoptotic target cells was suppressed in the absence of serum. Moreover, pre-apoptotic cells secreted annexin I and administration of Boc1, a formyl peptide receptor/lipoxin receptor antagonist markedly attenuated their engulfment. Finally, pre-apoptotic Jurkat cells induced lower macrophage production of tumor necrosis factor-alpha and higher production of interleukin-10 in comparison to apoptotic target cells.

Syntaxin-11 is expressed in primary human monocytes/macrophages and acts as a negative regulator of macrophage engulfment of apoptotic cells and IgG-opsonized target cells.

Syntaxin-11 is a member of a family of membrane-trafficking proteins referred to as soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs). Recent studies have shown that syntaxin-11 is expressed in natural killer cells and cytotoxic T cells and is likely to play a role in the granule exocytosis pathway. However, the biological role of syntaxin-11 in other immune cells has remained elusive. This study found that stimulation with interferon-gamma upregulated syntaxin-11 expression in primary monocytes. Experiments using monocytes from patients with familial haemophagocytic lymphohistiocytosis harbouring mutations in the gene encoding syntaxin-11 (STX11), or monocytes from healthy individuals in which syntaxin-11 was downregulated using specific short-interfering RNA, demonstrated that syntaxin-11 was not required for antibody-dependent cellular cytotoxicity. On the other hand, silencing of syntaxin-11 expression in primary macrophages enhanced the phagocytosis of apoptotic target cells with a concomitant increase in macrophage secretion of tumour necrosis factor-alpha. Moreover, Fcgamma-receptor-mediated uptake of target cells was also enhanced following silencing of syntaxin-11 expression in macrophages. In addition, syntaxin-11 localized to the plasma membrane in macrophages ingesting apoptotic cell corpses. Syntaxin-11 thus appears to act as a negative regulator of human macrophage engulfment of apoptotic cells and IgG-opsonized red blood cells.

Ultratrace and robust visual sensor of Cd2+ ions based on the size-dependent optical properties of Au@g-CNQDs nanoparticles in mice models.

Visual inspection is expected as an ideal technique, which can directly and conveniently detect heavy metal ions by observing the color change. Insensitivity of detecting weakly colored heavy transition metal ions and low adsorptivity of metal ions on nanoparticle surface are two main factors hindering the application of visual detection in heavy metal ions detection. Herein, we demonstrated an operational colorimetric sensor based on the color dependence of nanoparticles aggregation to selective and facile detect weakly colored transition heavy metal Cd2+ ions that have been considered as the origin of the "Itai-itai" disease. Uniform colloidal 15nm graphite-like nitride doped carbon quantum dots-capped gold nanoparticle (Au@g-CNQDs) was successfully prepared, wherein the existence of numerous heptazine, carboxyl and hydroxyl groups on the nanoparticle's surface strengthened adsorption of the Cd2+ ions on the surface of Au@g-CNQDs through the "cooperative effect". As a consequence, without expensive and intricate exogenous indicators or other special additives, the Cd2+ ions could sensitively and quickly captured to detect at ultra-low concentration within 30s by the naked-eye. Under the optimal conditions, the Cd2+ ions sensor possesses good analytical performances with a wide linear range of 0.01-3.0µM and a detection limit of 10nM (S/N = 3). Moreover, the biodistribution and aggregation of Cd2+ ions were detected effectively in mice organ tissues suggesting its great potential use for real-word applications.

Behaviors of the Interfacial Consecutive Multistep Electron Transfer Controlled by Varied Transition Metal Ions in Porphyrin Cores.

Almost all life activities involve the process of multistep electron transfer (ET) which occurs on biomembrane. Metalloporphyrins (MTPPs) are a class of molecules which are closely related to life course. Here, the n-step (n = 1, 2) ET behaviors controlled by different metal ions in porphyrin cores were investigated by thin-layer cyclic voltammetry (TLCV). The bimolecular ET was reacted between the MTPP (M = Fe, Zn, Co, Cu, Ni) and Fe(CN)64- in nitrobenzene and aqueous phase, respectively, and the interface between nitrobenzene and aqueous phase was considered as a bionic membrane. The thin-layer theory, which has been revised, was used to calculate the kinetic constants for each step electron transfer reactions. It was shown that the kinetic data were affected dramatically by the different coordinated ions in porphyrin complexes.

High-throughput and ultratrace naked-eye colorimetric detection of Au3+ based on the gold amalgam-stimulated peroxidase mimetic activity in aqueous solutions.

Herein, we present a catalysis-based, label-free, and efficient strategy for a rapid, high-throughput, highly selective and ultrasensitive naked-eye colorimetric assay of Au3+ in aqueous solutions, based on the gold amalgam-stimulated peroxidase mimetic activity.

A strongly coupled Au/Fe3O4/GO hybrid material with enhanced nanozyme activity for highly sensitive colorimetric detection, and rapid and efficient removal of Hg(2+) in aqueous solutions.

We have developed an efficient strategy for synthesizing a strongly coupled Au/Fe3O4/GO hybrid material to improve the catalytic activity, stability, and separation capability of Au nanoparticles (NPs) and Hg(2+). The hybrid material can be synthesized by the direct anchoring of Au and Fe3O4 NPs on the functional groups of GO. This approach affords strong chemical attachments between the NPs and GO, allowing this hybrid material to ultrasensitively detect Hg(2+) in aqueous solutions with a detection limit as low as 0.15 nM. In addition, the deposition of Hg(0) on the surface of Au/Fe3O4/GO could be quickly (within 30 min) and efficiently (>99% elimination efficiency) removed by the simple application of an external magnetic field and then Au/Fe3O4/GO could be subsequently reused at least 15 times, with the elimination efficiency remaining high (>96%).