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This paper reported the tribological behaviours of Cu nanoparticles as lubricant additives. Cu nanoparticles were prepared by an innovative technology called mass‐produced nanoparticles (MPNP). A SRV‐IV friction and wear tester was used to investigate the influence of load on the tribological performance of 0.1 ~ 2 wt% Cu nanoparticles. The results indicated adding 0.1 wt% Cu nanoparticles into PAO6 base oil and 10 W/40 CH‐4 commercial lubricant, reduce the average friction coefficient by 38% and 3%, and decrease the wear rate by 96% and 66% under 300 N, respectively, compared to the lubricants without nanoparticles. The excellent antiwear and antifriction effect could be attributed to the rolling effect caused by the ideal spherical shape and good dispersibility of the prepared Cu nanoparticles and form deposition film on the surface of the friction pair. Therefore, the Cu nanoparticles prepared by MPNP show excellent tribological performance and possess broad prospects in the fields of lubricant additives. [ABSTRACT FROM AUTHOR]

Separation of Xe and Kr is one of the greatest challenges in the gas industries owing to their close molecular structure and similar properties. Energy‐effective adsorption‐based separation using chemically stable carbon adsorbents is a promising technology. We propose a strategy for Xe/Kr separation using MOF‐derived metallic carbon adsorbents. M‐Gallate (M=Ni, Co) were used as precursors to fabricate CoNi alloy nanoparticles embedded carbon adsorbents by one‐step auto‐reduction pyrolysis. The optimal NiCo@C‐700 exhibits record‐high IAST selectivity (24.1) and Henry's selectivity (20.1) of Xe/Kr among reported carbon adsorbents. DFT calculations, local density of states calculation, charge density difference, and Bader charge analysis reveal the great affinity with Xe benefits from the presence of Ni or CoNi nanoparticles as a result of more charge transfer from Xe than Kr to metal, thus providing higher binding energy. Breakthrough experiments further verify NiCo@C‐700 a promising candidate for Xe/Kr separation. [ABSTRACT FROM AUTHOR]

The metal nanoparticles with ultra‐broad localized surface plasmonic resonance (LSPR) absorption have been widely used to enhance the up conversion luminescence (UCL) of rare‐earth doped nanoparticles. However, there have been no reports on the preparation of metal nanoparticles with the ultra‐broad LSPR in the glasses. In this work, the gold nanoparticles with the ultra‐broad LSPR were prepared for the first time in the rare‐earth doped tellurite glasses by the high‐temperature melting method, and the influence of ultra‐broad LSPR on the UCL of Er3+–Yb3+ and Er3+–Yb3+–Nd3+ co‐doped tellurite glasses was investigated upon 980 and 808 nm excitation, respectively. With the precipitation of the Au NPs, about seven and 12‐fold enhancements were obtained for the green and red UCL of Er3+–Yb3+ co‐doped tellurite glasses excited at 980 nm, respectively, and about 5.9 and sevenfold enhancements were observed for the green and red UCL of Er3+–Yb3+–Nd3+ co‐doped tellurite glasses excited at 808 nm, respectively. The UCL mechanism related to UCL enhancement was confirmed. The results demonstrated that the enhanced excitation field and the increasing rate of radiative decay were responsible for the enhancement of UCL. [ABSTRACT FROM AUTHOR]

Currently, NH3 production primarily depends on the Haber–Bosch process, which operates at elevated temperatures and pressures and leads to serious CO2 emissions. Electrocatalytic N2 reduction offers an environmentally benign approach for the sustainable synthesis of NH3 under ambient conditions. This work reports the development of biomass‐derived amorphous oxygen‐doped carbon nanosheet (O−CN) using tannin as the precursor. As a metal‐free electrocatalyst for N2‐to‐NH3 conversion, such O−CN shows high catalytic performances, achieving a large NH3 yield of 20.15 μg h−1 mg−1cat. and a high Faradic efficiency of 4.97 % at −0.6 V vs. reversible hydrogen electrode (RHE) in 0.1 m HCl at ambient conditions. Remarkably, it also exhibits high electrochemical selectivity and durability. An oxygen‐doped carbon nanosheet is an efficient electrocatalyst for N2 reduction reaction, achieving a large NH3 yield of 20.15 μg h−1 mg−1cat. and a high Faradic efficiency of 4.97 % at −0.6 V vs. reversible hydrogen electrode in 0.1 m HCl. [ABSTRACT FROM AUTHOR]

Abstract: Upconversion luminescence of rare‐earth ions doped nanoparticles can be enhanced by the localized surface plasmon resonance (LSPR) of noble metals nanoparticles, which was extensively investigated. The semiconductor nanomaterials such as the WO2.72 exhibited the tunable LSPR, which provide the possibility for the luminescence enhancement of upconversion nanoparticles. In this work, the urchin‐like WO2.72 was successfully prepared by solvothermal method, exhibiting the LSPR in the near infrared region. The influence of LSPR of WO2.72 on the upconversion luminescence of NaYF4:Yb3+,Er3+ nanoparticles was investigated firstly. The 525, 542, and 660 nm upconversion luminescence of NaYF4: Yb3+,Er3+ nanoparticles was increased by the 10, 8, and 12 factors, respectively, which was from the enhanced excitation field induced by the WO2.72 film. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we present a facile preparation approach of Au nanoparticles embedded LaPO4:Eu3+ inverse opal photonic crystals. In the typical preparation process, the transparent LaPO4:Eu3+ sol including HAuCI4 was infiltrated into the opal templates. After the sintering, the 10‐20 nm Au nanoparticles were formed in the interior of nano‐sized wall of LaPO4:Eu3+ inverse opal and the Au nanoparticles embedded LaPO4:Eu3+ inverse opals were obtained. The luminescence of Au nanoparticles embedded LaPO4:Eu3+ inverse opal was investigated. The emission peaks located at the 593 (5D0→7F1), 618 (5D0→7F2) and 698 nm (5D0→7F4) from Eu3+ ions were observed. The 593, 618, and 698 nm emissions of Au nanoparticles embedded LaPO4:Eu3+ inverse opals were enhanced in contrast to these of LaPO4:Eu3+ inverse opal without the Au nanoparticles, which is from the excitation field enhancement caused by the localized surface plasmon resonance of Au nanoparticles. [ABSTRACT FROM AUTHOR]

Photoluminescence (PL) of WS2 monolayer has attracted attention triggered by potential optoelectronic and photoelectric applications due to the largest direct band gap in WS2 monolayer among transition metal dichalcogenides. The PL of WS2 monolayer is dominated by charged excitons (trions) and bound excitons, which suppress the luminescence of free excitons. Herein, we report a one‐step growth of a nanosheet/nanoparticles hybrid structure to reduce the emission of bound excitons and trions in WS2 monolayer by surface passivation with WO3 nanoparticles. Peak positions of the PL spectra in WS2 monolayers depend on the density of WO3 nanoparticles on their surface. With increasing density of WO3 nanoparticles, the PL of WS2 monolayers experiences the transition from bound excitons and charged excitons (trions) to neutral excitons. These results suggest that the engineering of PL of WS2 monolayers may be realized by surface passivation using nanoparticles of wide band gap semiconductors. [ABSTRACT FROM AUTHOR]

Manganese dioxides (MnO2) are considered one of the most attractive materials as an oxygen evolution reaction (OER) electrode due to its low cost, natural abundance, easy synthesis, and environmental friendliness. Here, metal-ion (Fe, V, Co, and Ni)-doped MnO2 ultrathin nanosheets electrodeposited on carbon fiber paper (CFP) are fabricated using a facile anodic co-electrodeposition method. A high density of nanoclusters is observed on the surface of the carbon fibers consisting of doped MnO2 ultrathin nanosheets with an approximate thickness of 5 nm. It is confirmed that the metal ions (Fe, V, Co, and Ni) are doped into MnO2, improving the conductivity of MnO2. The doped MnO2 ultrathin nanosheet/CFP and the IrO2/CFP composite electrodes for OER achieve a low overpotential of 390 and 245 mV to reach 10 mA cm−2 in 1 m KOH, respectively. The potential of the doped composite electrode for long-term OER at a constant current density of 20 mA cm−2 is much lower than that of the pure MnO2 composite electrode. [ABSTRACT FROM AUTHOR]

Water-soluble polymer nanoparticles NP-1 and NP-2 were prepared by using a three-component self-assembly of an iridium complex, poly(4-vinyl pyridine-b-ethylene oxide) (P4VP-b-PEO), and methane sulfonic acid (MSA). Due to the unique metal-ligand charge-transfer transition property and the heavy-atom effect of the iridium atom, NP-1 and NP-2 showed bright phosphorescence and generated the singlet oxygen (1O2) species effectively under visible-light irradiation ( λ>400 nm) with a power density of 300 mW cm−2. NP-2, an example of the polymer nanoparticles, showed minimal cytotoxic activity in the dark. Laser confocal fluorescence and flow-cytometry microscopy experiments demonstrated that NP-2 could be taken up by a model cancer-cell line of 4T1 cells, which could be used as a phosphorescent probe for cell imaging by preferentially staining the cytoplasm. After 6 hours of incubation with NP-2 (100 μg mL−1), the cell viability of 4T1 cells decreased to approximately 10 % upon visible-light irradiation ( λ>400 nm, 300 mW cm−2) only for 10 minutes as a result of the generation of the 1O2 species, thus indicating a proof of concept for effective photodynamic therapy for cancer cells. [ABSTRACT FROM AUTHOR]

Water-soluble phosphorescent polymeric nanoparticles with an average diameter of approximately 100 nm were synthesized by a coordination cross-linking reaction. The pyridine blocks in poly(4-vinyl pyridine- b-ethylene oxide) (P4VP- b-PEO) were cross-linked by the iridium chloride-bridged dimer in DMF solution. Owing to the presence of an iridium complex with different ligands in the core of the polymeric nanoparticles, NP-1, NP-2, and NP-3 showed bright green, yellow, and red phosphorescence, respectively. PEG chains in the shell gave the polymeric nanoparticles solubility and biocompatibility, which was confirmed by an MTT assay using HeLa cells as a model cancer cell line. The flow cytometry and laser confocal fluorescence microscopy results revealed NP-2, as an example, could be effectively uptaken by HeLa cells. Therefore, these polymeric nanoparticles can be used as luminescent probes for living cells. In addition, 1O2 could be effectively generated in the presence of NP-2 upon irradiation with visible light ( λ>400 nm, 300 mW cm−2), which was confirmed by a clear decrease in the fluorescence intensity of 9,10-dimethylanthracene (DMA). After incubation with NP-2 at a concentration of 200 μg mL−1 for 6 h, approximately 90 % of HeLa cells were effectively ablated upon irradiation with visible light for only 10 min, indicating the potential for photodynamic therapy with polymeric nanoparticles. [ABSTRACT FROM AUTHOR]

Perovskite ZnZrO3 nanoparticles were synthesized by hydrothermal method, and their microstructures and optical properties were characterized. The crystallinity, phase formation, morphology and composition of the as-synthesized nanoparticles were characterized by X-ray diffraction ( XRD), selected area electron diffraction ( SAED), high-resolutiontransmission electron microscopy ( HRTEM), and energy-dispersive X-ray ( EDX) spectroscopy analysis, respectively. TEM images demonstrated that the average particle size of the ZnZrO3 powders was increased with increasing the Zn/ Zr molar ratios in the precursors, and more large ZnZrO3 particles with cubic morphology were observed at high Zn/ Zr molar ratios. In addition, the phase structures of the ZnZrO3 particles were also evolved from a cubic to tetragonal perovskite phase, as revealed by XRD and SAED patterns. HRTEM images demonstrate that surface structures of the ZnZrO3 powders synthesized at high Zn/ Zr molar ratios, are composed of corners bound by the {100} mini-facets, and the surface steps lying on the {100} planes are frequently observed, whereas the (101) facet isoccasionally observed. The formation of such a rough surface structure is understood from the periodic bond chain theory. Quantitative EDX analyses demonstrated that the atomic concentrations (at.%) of Zn: Zr: O in the particles were 20.70:21.07:58.23, as close to the composition of ZnZrO3. In the optical spectra, a significant red shift of the absorption edges (for the ZnZrO3 nanopowders) from UV to visible region (from 394 to 417 nm) was observed as increasing the Zn/ Zr molar ratios in the precursors, which corresponds to that the band gap energies of the ZnZrO3 nanopowders can be continuously tuned from 3.15 to 2.97 eV. This opens an easy way to tune the band gap energies of the ZnZrO3 nanopowders. [ABSTRACT FROM AUTHOR]

Perovskite pure BaTiO3 (BT) nanoparticles with spherical morphology and PX-phase PbTiO3 (PT) nanowires with acicular morphology, were synthesized by microwave–hydrothermal process, and their atomic-scale microstructures were characterized by electron microscopy. Both X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns demonstrated that the produced BT nanoparticles remained a cubic perovskite structure at room temperature. The BT nanoparticles exhibited a spherical morphology with a nearly uniform size of 50 nm. The PX-phase PT nanowires exhibited acicular morphology with diameter sizes of 40–60 nm and length up to several micrometers, and the aspect ratio was close to 90. They tended to grow into a regular structure with parallel arrangement along their long axis in the [001] direction. The extinction rule for the diffraction indexes ( h, k, l ) in the XRD pattern is the sum of ( h, k, l ) equal to odd number, similar to body-centered cubic crystal. In the SAED patterns of the PX-phase PT nanowires, both super electron diffraction spots with a threefold modulated periodicity along the [110] direction and the appearance of strong diffraction spot (008) but the forbidden (004) spot, were clearly observed, which indicated that the PX-phase PT has a threefold modulated periodicity along the [110] direction, and fourfold modulated periodicity in the [001] direction, respectively. This result was confirmed by high-resolution transmission electron microscopy images. The Raman bands centered near 146, 193, and 292 cm−1 observed in the nanowires at room temperature, could be assigned to the E(1LO), E(2TO), and E+ B1 phonon modes of the tetragonal PT structure, respectively. However, no phonon modes of the tetragonal PT structure were responsible for the additional three Raman bands centered near 175, 548, and 832 cm−1, which are presumed to be resulted from the additional Raman modes of the PX-phase PT with a large and complex unit cell. [ABSTRACT FROM AUTHOR]

Nanocrystalline barium titanate (BaTiO3, BT) was synthesized hydrothermally at 220°C by reacting barium hydroxide with titanium dioxide. The resulting BT nanopowders were characterized by X-ray diffraction (XRD), selected area electron diffraction (SAED), Raman spectrum, scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM). The BT nanopowders have a cubic phase as revealed by the XRD and SAED results, whereas the Raman spectrum indicates that tetragonal phase BT exists in the produced nanopowders but is not the dominant phase because of the weak characteristic peak of the tetragonal structure at 305 cm−1. In the SEM and TEM images, many coarse-faceted cubic nanoparticles and a small amount of spherical particles are observed, indicating a developed bimodal size distribution of the BT powders. The variations of electron diffraction contrast across these particles in the TEM images indicate the presence of high strain in the BT nanoparticles, which is probably caused by the lattice defects like OH− ions and their compensation by cation vacancies. The HR-TEM image of a BT nanoparticle with a size of 24 nm and a spherical morphology demonstrates a uniform and perfect crystal structure. The surrounding edges of the particle are very smooth and no surface steps are observed. However, a terrace–ledge–kink (TLK) surface structure was frequently observed at the edges of the BT nanoparticles with rough surface morphology, and in most cases the terrace and ledge lie on the {100} planes. The observed TLK surface structure can be well interpreted by the theory of periodic bond chains. Small nucleated and triangular BT islands with three to four atomic layer thickness, and their outside surfaces faceted as (100) and (010) planes, are also observed in these particles. The rarely seen {110} surface in the BT nanoparticles was found to be reconstructed so that the surface was composed of corners bound by {100} minifaces like the triangular small islands. Microstructural defects such as antiphase boundaries were also observed near the edge of a BT nanoparticle, which were formed by the intersection of two crystalline parts with displacement deviation from each other by , as revealed by the HR-TEM images. [ABSTRACT FROM AUTHOR]