Cactus‐Like Hollow Cu2‐xS@Ru Nanoplates as Excellent and Robust Electrocatalysts for the Alkaline Hydrogen Evolution Reaction

The development of Pt‐free electrocatalysts for the hydrogen evolution reaction (HER) recently is a focus of great interest. While several strategies are developed to control the structural properties of non‐Pt catalysts and boost their electrocatalytic activities for the HER, the generation of highly reactive defects or interfaces by combining a metal with other metals, or with metal oxides/sulfides, can lead to notably enhanced catalytic performance. Herein, the preparation of cactus‐like hollow Cu_2‐x S@Ru nanoplates (NPs) that contain metal/metal sulfide heterojunctions and show excellent catalytic activity and durability for the HER in alkaline media is reported. The initial formation of Ru islands on presynthesized Cu_1.94S NPs, via cation exchange between three Cu⁺ ions and one Ru³⁺, induces the growth of the Ru phase, which is concomitant with the dissolution of the Cu_1.94S nanotemplate, culminating in the formation of a hollow nanostructure with numerous thin Ru pillars. Hollow Cu_2‐x S@Ru NPs exhibit a small overpotential of 82 mV at a current density of ?10 mA cm^?2 and a low Tafel slope of 48 mV dec^?1 under alkaline conditions; this catalyst is among state‐of‐the‐art HER electrocatalysts in alkaline media. The excellent performance of hollow Cu_2‐x S@Ru NPs originates from the facile dissociation of water in the Volmer step.     

DNA‐Driven Two‐Layer Core–Satellite Gold Nanostructures for Ultrasensitive MicroRNA Detection in Living Cells

It is a significant challenge to achieve controllable self‐assembly of superstructures for biological applications in living cells. Here, a two‐layer core–satellite assembly is driven by a Y‐DNA, which is designed with three nucleotide chains that hybridized through complementary sequences. The two‐layer core–satellite nanostructure (C₃₀S₅S₁₀ NS) is constructed using 30 nm gold nanoparticles (Au NPs) as the core, 5 nm Au NPs as the first satellite layer, and 10 nm Au NPs as the second satellite layer, resulting in a very strong circular dichroism (CD) and surface‐enhanced Raman scattering. After optimization, the yield is up to 85%, and produces a g‐factor of 0.16 × 10^?2. The hybridization of the target microRNA (miRNA) with the molecular probe causes a significant drop in the CD and Raman signals, and this phenomenon is used to detect the miRNA in living cells. The CD signal has a good linear range of 0.011–20.94 amol ng_RNA^?1 and a limit of detection (LOD) of 0.0051 amol ng_RNA^?1, while Raman signal with the range of 0.052–34.98 amol ng_RNA^?1 and an LOD of 2.81 × 10^?2 amol ng_RNA^?1. This innovative dual‐signal method can be used to quantify biomolecules in living cells, opening the way for ultrasensitive, highly accurate, and reliable diagnoses of clinical diseases.     

Hybrid Nanoparticle Pyramids for Intracellular Dual MicroRNAs Biosensing and Bioimaging

This study strategically fabricates multifunctional nanopyramids to allow the ultrasensitive quantification of dual microRNAs (miR‐203^b and miR‐21) in living cells and their responsive bioimaging in vivo. The nanopyramids, composed of Au‐Cu₉S₅ nanoparticles (NPs), upconversion NPs (UCNPs), and Ag₂S NPs, emit two luminescent signals simultaneously with excitation at 808 nm, arising from the UCNPs at 541 nm in the visible region and from the Ag₂S NPs at 1227 nm in the second window of near‐infrared (NIR‐II) region. The upconversion luminescence has a linear relationship with miR‐203^b from 0.13 to 54.54 fmol per 10 µg_RNA and a limit of detection (LOD) of 0.09 fmol per 10 µg_RNA, whereas the Ag₂S NP luminescence has a linear relationship with miR‐21 from 0.37 to 43.56 fmol per 10 µg_RNA, with a LOD of 0.23 fmol per 10 µg_RNA. Significantly, this study demonstrates that the nanopyramids can be successfully used for miRs‐responsive bioimaging in a tumor‐bearing animal model. Furthermore, taking advantage of the photothermal capabilities of pyramids, the tumors can also be eliminated completely. These nanopyramids not only overcome the obstacles in the simultaneous detection of multiple miRs at the cellular level but also provide a cancer theranostic platform in vivo.     

Peptide Nanotube‐Templated Biomineralization of Cu2−xS Nanoparticles for Combination Treatment of Metastatic Tumor

1D peptide nanostructures (i.e., peptide nanotubes, PNTs) exhibit tunable chemo‐physical properties and functions such as improved tissue adhesion, increased cellular uptake, and elongated blood circulation. In this study, the application of PNTs as a desirable 1D template for biomineralization of Cu_2?xS nanoparticles (Cu_2?xS NPs, x = 1–2) is reported. Monodisperse Cu_2?xS NPs are uniformly coated on the peptide nanotubes owing to the specific high binding affinity of Cu ions to the imidazole groups exposed on the surface of nanotubes. The Cu_2?xS NP–coated PNTs are further covalently grafted with an oxaliplatin prodrug (Pt–CuS–PNTs) to construct a versatile nanoplatform for combination cancer therapy. Upon 808 nm laser illumination, the nanoplatform induces significant hyperthermia effect and elicits reactive oxygen species generation through electron transfer and Fenton‐like reaction. It is demonstrated that the versatile nanoplatform dramatically inhibits tumor growth and lung metastasis of melanoma in a B16‐F10 melanoma tumor‐bearing mouse model by combined photo‐ and chemotherapy. This study highlights the ability of PNTs for biomineralization of metal ions and the promising potential of such nanoplatforms for cancer treatment.     

Boost antimicrobial effect of CTAB-capped NixCu1−xO (0.0 ≤ x ≤ 0.05) nanoparticles by reformed optical and dielectric characters

Chemical doping and coating have been considered as efficient semiconductor physics strategies to modulate the physical, chemical, and biological properties of materials for the required applications. In this study, cetyltrimethylammonium bromide (CTAB) stabilizer-capped nickel-doped cupric oxide (Ni_xCu_1?xO) nanoparticles (NPs) with different doping concentrations (0.0?≤?x?≤?0.05) were synthesized via a one-step rapid and low-cost solvothermal synthesis route. The as-synthesized CTAB-capped Ni_xCu_1?xO NPs have been sightseen for their structural/morphological, optical/dielectric, and antimicrobial properties using XRD/SEM/TEM, FT-IR/UV–visible/Impedance spectroscopies, and Agar well diffusion method, respectively. Relevant results show enhanced optical, dielectric and antimicrobial properties with Ni doping due to the smaller size effect. Importantly, in vitro examination, the antimicrobial activity of the grown NPs was evaluated against four microbial species, exhibits that the CTAB-capped Ni-doped CuO NPs possess a command antimicrobial toxicity to Staphylococcus aureus (25923-ATCC), Klebsiella pneumoniae (700603-ATCC), and Escherichia coli (25922-ATCC) and an intermediate performance towards Candida albicans (24433-ATCC). The minimum inhibitory concentration (MIC) assay for the obtained CTAB-Ni_0.05Cu_0.95O sample upon S. aureus or K. pneumoniae pathogens reaches extremely as low as 5 μg ml^?1 for all reported CuO NPs. The improved dose-dependent antimicrobial effect has been found to be strongly dependent on the particle size, surface morphology, elemental compositions, and surface bio-functionality of the catalytic nanomaterials. Additionally, Ni-dopant, CTAB-stabilizer, and binding of Cu⁺/Cu²⁺ ions with respiratory enzymes collectively produce an excess amount of reactive oxygen species (ROS) in the bacterial culture medium, which determines a predominant antibacterial mechanism for bacterial cells damage. Overall, these inorganic (Ni_xCu_1?xO) NPs with antimicrobial cationic surfactant (CTAB) have advantages to use as a functionalized disinfection nanoagent to control the microbial infections in the healthcare sector together with various electronic and photonic medical diagnoses.

Graphical abstract

     

Transport Properties and Fluctuations in Underdoped GdBa2Cu3O x Thin Films

We have investigated the transport properties, resistivity and Hall effect, in a series of underdoped GdBa ₂ Cu ₃ O _x thin films grown by off-axis magnetron sputtering. We find a systematic correlation between the critical temperature T _c and the inverse Hall constant R _H ^-1 , related, in simple models, to the carrier concentration n. Our experimental thin film T _c (n) data are in good agreement with the temperature-doping phase diagram obtained for YBa ₂ Cu ₃ O _x single crystals. By measuring the activation energies in the liquid vortex phase, and by using a 2-dimensional model for vortex dynamics, we have extracted the penetration depth of these samples, and studied the relation between the carrier concentration and the superfluid density to probe the role of phase fluctuations on superconductivity.     

Reactive sputtering of thin Cu2S films for application in solar cells

Thin layers of cuprous sulphide were deposited by reactive r.f. sputtering; the target was pure copper and the sputtering gas was an ArH₂S mixture. We describe here how the composition of the films and their stoichiometry can be derived accurately both from X-ray diffraction and the optical reflection and transmission spectra. Measurement of the electrical resistivity can be used as a quick qualitative identification method.The application of these characterization methods to our sputtered films indicates that the crucial parameters to be controlled are the total pressure of the sputtering gas and, in particular, the partial pressure of the H₂S. Too low partial pressures of H₂S result in the presence of copper precipitations in the Cu₂S film, whereas too high H₂S partial pressures result in the presence of copper-deficient Cu_xS phases; there is an intermediate range of H₂S partial pressures in which pure chalcocite films (Cu₂S) are obtained. When these films were sputtered onto evaporated CdS layers, we obtained Cu₂S/CdS solar cells with a total area efficiency of above 4%.     

Preparation of YBa2Cu3O7-x superconducting thick films by the electrophoretic deposition method

YBa₂Cu₃O_7-x thick films have been realised by the Electrophoretic Deposition method (EPD). The influence of several parameters (powder and iodine concentrations in the suspension, applied voltage and deposition time) on the EPD process has been studied by measuring the conductivity of the suspension and the amount of YBa₂Cu₃O_7-x particles deposited on the electrode. Superconducting coatings onto silver substrates have been produced by a multilayer process during different deposition times. The highest critical current density value of these coatings measured by the four-point probe method is about 10³ A/cm² (77 K), in a suitable range for magnetic shielding applications.     

Ultrasmall Cu2‐xS Nanodots for Highly Efficient Photoacoustic Imaging‐Guided Photothermal Therapy

Monodisperse, ultrasmall (<5 nm) Cu_2?xS nanodots (u‐Cu_2?xS NDs) with significantly strong near‐infrared absorption and conversion are successfully demonstrated for effective deep‐tissue photoacoustic imaging‐guided photothermal therapy both in vitro and in vivo. Owing to ultrasmall nanoparticle size and high water dispersibility as well as long stability, such nanodots possess a prolonged circulation in blood and good passive accumulation within tumors through the enhanced permeability and retention effect. These u‐Cu_2?xS NDs have negligible side effects to both blood and normal tissues according to in vivo toxicity evaluations for up to 3 months, showing excellent hemo/histocompatibility. Furthermore, these u‐Cu_2?xS NDs can be thoroughly cleared through feces and urine within 5 days, showing high biosafety for further potential clinical translation. This novel photoacoustic imaging‐guided photothermal therapy based on u‐Cu_2?xS NDs composed of a single component shows great prospects as a multifunctional nanoplatform with integration and multifunction for cancer diagnosis and therapy.     

The effects of oxygen doping on copper Chevrel compounds

The Chevrel compounds Cu_1.8Mo₆S_8–x O _x have been studied, wherex=0.00, 0.05, and 0.10. In order to establish the effects of incorporating a small amount of oxygen into Cu_1.8Mo₆S₈, we have measured lattice parameters, superconducting transition temperatureT _c, and the temperature dependence of both the upper critical fieldH _c2 and the magnetic susceptibility x. We show that the usual method of making this compound incorporates oxygen, and that this impurity may be removed by gettering the material with Y₂S₃. We observe that the substitution of oxygen for sulfur in Cu_1.8Mo₆S₈ increasesT _c and decreases the ratioc/a of the hexagonal lattice constants and x. A breakdown in the rigid-band approximation is indicated by a comparison of the relative signs of the effect onT _c and that on x. In addition to these observations, we report on a correlation between hardness andT _c of Cu_1.8Mo₆S₈ and on the temperature dependence of the magnetic susceptibility of Cu_3.2Mo₆S₈.     

Magnetic-field-modulated microwave-absorption detection in a Bi-Sr-Ca-Cu-O superconductor

Superconducting transitions are observed at 110 K, 100 K, and 72 K in a nominally BiSrCaCu₂O _x ceramic using the novel technique of magnetic-field-modulated microwave-absorption detection. The response of the BiSrCaCu₂O _x ceramic to an external magnetic field differs markedly from that of YBa₂Cu₃O and, in particular, -dT _c /dH is much greater in the bismuth sample.     

Photovoltaic converters based on CdxZn1−x S/Cu2S variband heterostructures

A new design of photovoltaic cells for ground solar energy converters based on Cd_xZn_1−x S/Cu₂S heterostructures is proposed. A technology for fabricating the variband heterostructures is developed, which employs pyrolysis of aerosols of aqueous solutions of metal thiocarbamide complexes.     

Ultrasensitive Surface‐Enhanced Raman Spectroscopy Detection Based on Amorphous Molybdenum Oxide Quantum Dots

Surface‐enhanced Raman spectroscopy (SERS) based on plasmonic semiconductive material has been proved to be an efficient tool to detect trace of substances, while the relatively weak plasmon resonance compared with noble metal materials restricts its practical application. Herein, for the first time a facile method to fabricate amorphous H_xMoO₃ quantum dots with tunable plasmon resonance is developed by a controlled oxidization route. The as‐prepared amorphous H_xMoO₃ quantum dots show tunable plasmon resonance in the region of visible and near‐infrared light. Moreover, the tunability induced by SC CO₂ is analyzed by a molecule kinetic theory combined with a molecular thermodynamic model. More importantly, the ultrahigh enhancement factor of amorphous H_xMoO₃ quantum dots detecting on methyl blue can be up to 9.5 × 10⁵ with expending the limit of detection to 10^?9 m . Such a remarkable porperty can also be found in this H_xMoO₃‐based sensor with Rh6G and RhB as probe molecules, suggesting that the amorphous H_xMoO₃ quantum dot is an efficient candidate for SERS on molecule detection in high precision.     

Hydrothermally fabricated surfactant-free CuxAg1−xS composites with enhanced photocatalytic activity and stability

Here, we report the stable and surfactant-free Cu_xAg_1?xS composites as nanorod clusters was fabricated by a simple hydrothermal method for the degradation of pesticides including malathion (MLT), monocrotophos (MCP), and chlorpyrifos (CPS) under ultraviolet (UV) light. The degradation of MLT, MCP, and CPS using Cu_0.5Ag_0.5S were up to 97% after 1?h of UV irradiation. The Cu_0.5Ag_0.5S nanorods displayed enhanced photocatalytic activity and the rate of degradation was higher than that of pure CuS and Ag₂S due to an efficient electron transfer process. The stability and reusability assays indicated that the Cu_0.5Ag_0.5S retained more than 90% of activity after five cycles of use. The photocatalytic mechanism was explored from the obtained results of enhanced photocatalytic activity of Cu_xAg_1?xS nanorod clusters.     

Colorectal Tumor Microenvironment-Activated Bio-Decomposable and Metabolizable Cu2O@CaCO3 Nanocomposites for Synergistic Oncotherapy

Rational design of tumor microenvironment (TME)-activated nanocomposites provides an innovative strategy to construct responsive oncotherapy. In colorectal cancer (CRC), the specific physiological features are the overexpressed endogenous H₂S and slightly acidic microenvironment. Here, a core–shell Cu₂O@CaCO₃ nanostructure for CRC “turn-on” therapy is reported. With CaCO₃ responsive to pH decomposition and Cu₂O responsive to H₂S sulfuration, Cu₂O@CaCO₃ can be triggered “on” into the therapeutic mode by the colorectal TME. When the CaCO₃ shell decomposes and releases calcium in acidic colorectal TME, the loss of protection from the CaCO₃ shell exposes the Cu₂O core to be sulfuretted by H₂S to form metabolizable Cu₃₁S₁₆ nanocrystals that gain remarkably strong near-infrared absorption. After modifying hyaluronic acid, Cu₂O@CaCO₃ can achieve synergistic CRC-targeted and TME-triggered photothermal/photodynamic/chemodynamic/calcium-overload-mediated therapy. Moreover, it is found that the generation of hyperthermia and oxidative stress from Cu₂O@CaCO₃ nanocomposites can efficiently reprogram the macrophages from the M2 phenotype to the M1 phenotype and initiate a vaccine-like immune effect after primary tumor removal, which further induces an immune-favorable TME and intense immune responses for anti-CD47 antibody to simultaneously inhibit CRC distant metastasis and recurrence by immunotherapy.     

Light-responsive color switching of self-doped TiO2-x/WO3·0.33H2O hetero-nanoparticles for highly efficient rewritable paper

Smart materials that reversibly change color upon light illumination are widely explored for diverse appealing applications.However,light-responsive color switching materials are mainly limited to organic molecules.The synthesis of inorganic counterparts has remained a significant challenge because of their slow light response and poor reversibility.Here,we report a seeded growth strategy for the synthesis of TiO_2-x/WO₃·0.33H₂Ohetero-nanoparticles(HNPs)with networked wire-like structure of?10 nm in diameters that enable the highly reversible light-responsive color switching properties.For the TiO_2-x/WO₃·0.33H₂OHNPs,T P species self-doped in TiO_2-xnanoparticles(NPs)act as efficient sacrificial electron donors(SEDs)and Ti-O-W linkages formed between TiO2-x and WO30.33H2O NPs ensure the nanoscale interfacial contact,endowing the HNPs enhanced photoreductive activity and efficient interfacial charge transfer upon ultraviolet(UV)illumination to achieve highly efficient color switching.The TiO_2-x/WO₃·0.33H₂OHNPs exhibits rapid light response(<15 s)and long reversible color switching cycles(>180 times).We further demonstrate the applications of TiO_2-x/WO₃·0.33H₂O HNPs in ink-free,light-printable rewritable paper that can be written on freehand or printed on through a photomask using UV light.This work opens an avenue for designing inorganic light-responsive color switching nanomaterials and their smart applications.     

Chemical Stability of the Bi(Pb)-Sr-Ca-Cu-O Superconductors

The changes in volume of superconducting high-T _c (2223) phase of the high-temperature superconductors (HTSC) with nominal composition Bi_3.2Pb_0.8Sr₄Ca₅Cu₇O _x are studied by magnetic susceptibility during soaking of material in water and more aggressive aqueous solutions. The apparent volumes of the 2223 superconducting phase after long-term (168 hr) soaking in H₂O, NaCl_(aq), and NaOH_(aq) decreased to 22%, 17%, and 57%, respectively. The atomic absorption analysis of resulting solutions showed high amounts of Sr²⁺ and Ca²⁺ in H₂O and NaCl_(aq) and lower amounts of Sr²⁺ and Ca²⁺ in NaOH_(aq). The highest content of Pb²⁺ and Cu²⁺ was detected in NaOH_(aq).     

Surface Reconstruction of Covellite CuS Nanocrystals for Enhanced OER Catalytic Performance in Alkaline Solution

Oxygen evolution reaction (OER) is one of the important half-reactions in energy conversion equipment such as water-spitting devices, rechargeable metal-air batteries, and so on. It is beneficial to develop efficient and low-cost catalysts that understand the reaction mechanism of OER and analyze the reconstruction phenomenon of transition metal sulfide. Interestingly, copper sulfide and cuprous sulfide with the same components possess different reconstruction behaviors due to their different metal ion valence states and different atomic arrangement modes. Because of a unique atomic arrangement sequence and certain cationic defects, the reconstruction phenomenon of CuS nanomaterials are that S²⁻ is firstly oxidized to SO₄²⁻ and then Cu^x+ is converted into CuO via Cu(OH)₂. In addition, the specific “modified hourglass structure” of CuS with excellent conductivity is easier to produce intermediates. Compared with Cu₂S, CuS exhibits excellent OER activity with a lower overpotential of 192 mV at 10 mA cm⁻² and remarkable electrochemical stability in 1.0 m KOH for 120 h. Herein, this study elucidates the reconstruction modes of CuS and Cu₂S in the OER process and reveals that CuS has a stronger Cu S bond and a faster electronic transmission efficiency due to “modified hourglass structure,” resulting in faster reconstruction of CuS than Cu₂S.     

In Vivo Chemoselective Photoacoustic Imaging of Copper(II) in Plant and Animal Subjects

The detection of Cu²⁺ in living plants and animals is of great importance for environment monitoring and disease diagnosis. Here, a near‐infrared (NIR) turn‐on photoacoustic (PA) probe (denoted as LET‐2) is developed for Cu²⁺ detection in living subjects, such as soybean sprouts and mice. The absorbance band of LET‐2 shifts from 625 to 715 nm after the interaction with Cu²⁺, thus producing strong PA signal output at 715 nm (PA₇₁₅) as an indicator. The PA₇₁₅ value is increased as a function of the concentration of Cu²⁺ (0 × 10^?6–20 × 10^?6m ), with a calculated limit of detection of 10.8 × 10^?9m . More importantly, both in vitro and in vivo studies in soybean sprouts and mice indicate that the as‐prepared LET‐2 PA probe is highly sensitive and selective for Cu²⁺ detection. These findings provide a solution for in vivo detection of metal ions by using chemoselective PA probes.     

The potential of porous silicon gas sensors

Recent developments in porous silicon gas sensors have been reviewed. Monitored species detection levels, and the mechanisms of sensing for different sensor designs are also discussed. Porous silicon surface modification methods have been employed for detecting different gas molecules; H₂O, ethanol, methanol, isopropanol, CO_x, NO_x, NH₃, O₂, H₂, HCl, SO₂, H₂S and PH₃.