Copper Quantum Dots Research Articles

Copper Quantum Dot/Polyacrylamide Composite Nanospheres: Spreading on Quartz Flake Surfaces and Displacing Crude Oil in Microchannel Chips.

Polyacrylamide, silica, and other nanoparticles have all been realized in the field of enhanced oil recovery. Researchers often explore the mechanisms of spreading behavior and simulated displacement to develop more efficient types of nanoparticles. In this study, copper quantum dots were introduced into a acrylamide copolymerization system to obtain composite nanospheres and its structure, topographic, and application performance were characterized. The results show that the composite nanospheres have a particle size of around 25 nm, are uniformly loaded with copper particles, and have good temperature resistance. The spreading ability on the quartz flake surfaces and displacement effect in microchannels of composite nanospheres, acrylamide copolymer nanospheres, and copper quantum dots were compared by nanofluid spreading experiments and microchannel chip oil displacement experiments. The results indicate that the composite nanospheres can effectively reduce the water contact angle, promote the spreading of aqueous phase, and accelerate the oil droplet removal process; the accelerating effect is stronger than other samples. Its oil displacement effect is also the strongest, and it is minimized by the influence of channel size, temperature, and dispersing medium, with better stratigraphic adaptability. This work supports the practical application of copper quantum dot/polyacrylamide composite nanospheres in the oilfield.

Island-Like Heterogeneous Interface Generating Tandem Toroidal Built-In Electric Field for Efficient Potassium Ions Diffusion.

For large-size potassium accommodation, heterostructure usually suffers severe delamination and exfoliation at the interfaces due to different volume expansion of two-phase during charge/discharge process, resulting in the deconstruction of heterostructures and shortened lifespan of batteries. Here, an innovative strategy is proposed through constructing a microscopic heterostructure system containing copper quantum dots (Cu QDs) highly dispersed in the triphenyl-substituted triazine graphdiyne (TPTG) substrates (TPTG@CuQDs) to solve this problem. The copper quantum dots are uniformly anchored on TPTG substrates, generating a myriad of island-like heterogeneous structures, together with tandem toroidal built-in electric field (BIEF) between every micro heterointerface. The island-like heterostructure endows both benefits of exposed contact interface and robust architecture. Generated tandem toroidal BIEF provides efficient transport pathways with lower energy barriers, reducing the diffusion resistance and facilitating the reaction kinetics of potassium ions. When used as anode, the TPTG@CuQDs exhibit highly reversible capacity and low-capacity degradation (≈0.01% over 5560 cycles at 1 A g-1). Moreover, the TPTG@CuQDs-based full cell delivers an outstanding reversible capacity of ≈110 mAh g-1 over 800 cycles at 1 A g-1. This quantum-scale heterointerface construction strategy offers a new approach toward stable heterostructure design for the application of metal ion batteries.

Green Synthesis, Characterization, and Acoustical Analysis of Copper Quantum Dots (Cu QDs) Using Leaf Extract of Mangifera indica Plant

The copper quantum dots (Cu QDs) are successfully green synthesized from copper sulfate (CuSO[Formula: see text] as precursor material using plant leaf extracts of Mangifera indica. The mangiferin as a natural glucosylxanthone present in leaf extract of M. indica acquires antioxidant, antimicrobial, antidiabetic, antiallergic, anticancer, hypocholesterolemic, and immunomodulatory activity, which acts as an effective stabilizing and reducing agent for conversion of the copper ion (Cu[Formula: see text] into the Cu QDs in aqueous medium. The green synthesized Cu QDs are characterized using ultraviolet–visible (UV–Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, fluorescence spectroscopy, dynamic light scattering instrumental techniques, which confirm the successful synthesis and photoluminescence (PL) behavior of the Cu QDs. The ultrasonic investigation was carried out to find out the variation of ultrasonic velocity and density with concentration of Cu QDs in aqueous leaf extracts of M. indica plant as well as to calculate the dependency of acoustical parameter, namely adiabatic compressibility, acoustic impedance, and intermolecular free length on concentrations. The synthesized Cu QDs are biocompatible that can be a potential candidate for various in vivo and in vitro applications such as antioxidant, antimicrobial, anticancer, biosensor, bioimaging, and biocatalysis fields.

The facile synthesis of copper oxide quantum dots on chitosan with assistance of phyto-angelica for enhancing the human osteoblast activity to the application of osteoporosis

Osteoblasts are an important key factor for the pathogenesis of several bone-related diseases, notably in osteoporosis. Osteoporosis is a disorder categorized based on the bone mineral density (BMD) and an alteration in the bone micro-architecture had been considered as the major determinant for increasing the fracture risk. The available medicine for curing the osteoporosis shows a minimal or no activity against the genesis or function of osteoblasts. The present study was conducted to determine the influence of phyto Angelica species (Ang.) mediated synthesized copper quantum dots decorated chitosan on human osteoblast cells for application of osteoporosis. The phyto compound of Angelica sp. was extracted by ethanol as solvent and it has been characterized through spectral analyses. An Angelica sp. mediated synthesized copper oxide quantum dots (CuO QDs) and the presence of CuO QDs on chitosan have been analyzed and exhibited by important spectral investigations. The morphological observation of CuO QDs on the chitosan (CS) was visualized by the microscopic analyses. The MTT assay results showed that cell growth of CuO QDs/CS-Ang. by the concentration dependent. The highest cell growth (87%) was noted at 5 μg/mL followed by 80 and 77% at 15 and 25 μg/mL respectively. The functional groups and potential compounds of Angelica sp. with CuO QDs/CS has been improved the osteoblast cell activity as prophylactic potentials against osteoporosis.

Hexagon Flower Quantum Dot-like Cu Pattern Formation during Low-Pressure Chemical Vapor Deposited Graphene Growth on a Liquid Cu/W Substrate.

The H2-induced etching of low-dimensional materials is of significant interest for controlled architecture design of crystalline materials at the micro- and nanoscale. This principle is applied to the thinnest crystalline etchant, graphene. In this study, by using a high H2 concentration, the etched hexagonal holes of copper quantum dots (Cu QDs) were formed and embedded into the large-scale graphene region by low-pressure chemical vapor deposition on a liquid Cu/W surface. With this procedure, the hexagon flower-etched Cu patterns were formed in a H2 environment at a higher melting temperature of Cu foil (1090 °C). The etching into the large-scale graphene was confirmed by optical microscopy, atomic force microscopy, scanning electron microscopy, and Raman analysis. This first observation could be an intriguing case for the fundamental study of low-dimensional material etching during chemical vapor deposition growth; moreover, it may supply a simple approach for the controlled etching/growth. In addition, it could be significant in the fabrication of controllable etched structures based on Cu QD patterns for nanoelectronic devices as well as in-plane heterostructures on other low-dimensional materials in the near future.

Fabrication of silica nanoparticle-supported copper quantum dots and the efficient catalytic Ullmann coupling reaction

Copper quantum dots (Cu-QDs@silica), with a bird's nest-like structure, were synthesized using silica nanoparticles (NPs) as the support materials for use in the Ullmann coupling reaction of bromamine acid. The average size of the QDs is 2.5nm, with a very narrow diameter range between 1.5 and 4.5nm. The Cu-QDs are imbeded inside the framework of the silica bird's nest-like structure with excellent dispersion stability. The Cu-QDs@silica catalyst showed high catalytic activity for the bromamine acid Ullmann reaction. Using water as the medium, the conversion of bromamine acid reached 96.37% when heated to 90°C after 2h.

Synthesis of copper quantum dots by chemical reduction method and tailoring of its band gap

Metallic copper nano particles are synthesized with citric acid and CTAB (cetyltrimethylammonium bromide) as surfactant and chlorides as precursors. The particle size and surface morphology are analyzed by High Resolution Transmission Electron Microscopy. The average size of the nano particle is found to be 3 - 10 nm. The optical absorption characteristics are done by UV-Visible spectrophotometer. From the Tauc plots, the energy band gaps are calculated and because of their smaller size the particles have much higher band gap than the bulk material. The energy band gap is changed from 3.67 eV to 4.27 eV in citric acid coated copper quantum dots and 4.17 eV to 4.52 eV in CTAB coated copper quantum dots.

Photoelectrochemical enhancement of ternary nanocomposite electrode polyoxometalate/copper quantum dots/TiO2 with electrocatalytic performance of formic acid oxidation

In this work, we fabricate a ternary nanocomposite photoelectrode consisting of TiO2 nanoparticles, polyoxometalate (P2W18) and copper quantum dots (Cu QDs) so as to create a synergistic effect of the ternary nanocomposite on photovoltaic and photoelectrocatalytic performances. Both the high electron mobility from low cost Cu QDs and the high electro-hole separation efficiency from P2W18 could evidently improve the photoelectrochemical performance of TiO2. Transient photocurrent and current-voltage curves measurements demonstrate that both the photocurrent response and power conversion efficiency of the P2W18/Cu/TiO2 film were markedly enhanced in comparison with that of the only TiO2 film and the P2W18/TiO2 film, respectively. Furthermore, the photoelectrode also exhibited significant photoelectrocatalytic activity for formic acid oxidation. The substitute of copper quantum dots for noble metals in electrode is a favorable innovation for the practical application of photoelectrochemical devices.

Improved Photoelectrical Performance of Single-Crystal TiO2 Nanorod Arrays by Surface Sensitization with Copper Quantum Dots

Through the redox reaction between Cu(NH3)42+ and H2O2, copper quantum dots (QDs) were deposited onto the surface of single-crystal rutile TiO2 nanorod arrays that were grown directly on transparent, conductive fluorine-doped tin oxide substrates by a facile hydrothermal process. Compared with pristine TiO2 nanorods, the top facets of TiO2 nanorods decorated with Cu QDs became flattened and adherent to each other, and the lateral facets were rough and covered with vast amounts of extremely small particles. The QDs were tightly attached on the surface of the nanorods, and the nanoparticle size measured from high resolution transmission electron microscopy images was around 6 nm, which is comparable with the Bohr exciton radius. X-ray photoelectron spectroscopy measurements showed that the QDs existed in the form of Cu(II)O and Cu(I)2O after the deposition process, and the Cu(0) QDs were unstable on the TiO2 surface. Furthermore, under the irradiation of a solar simulator, the photocurrent response of the QD sensitized TiO2 nanorods was improved dramatically with a small amount of QDs, and the optimal photocurrent density (98 μA/cm2) was much greater than that of the undecorated sample (16 μA/cm2). Likewise, external quantum efficiency (EQE) characterization demonstrated the superiority of the surface modification with Cu QDs, by which the highest EQE value of the photoanode was enhanced nearly ten times. In addition, a red shift of the peak in EQE measurement was found from the Cu QD sensitized samples, suggesting a quantum size effect caused by small QD particles.

Copper quantum dots on TiO2: A high-performance, low-cost, and nontoxic photovoltaic material

The surface decoration of TiO2 with Cu quantum dots (QDs) was carried out through a simple chemical redox deposition method. The QDs in the form of Cu(I)/(II)-O-Ti(IV) network were attached tightly and highly dispersed onto the pre-sintered TiO2 surface, and no obvious change could be detected from the lattice and surface morphology of TiO2 after the modification. Quantum size effect was evidenced by diffuse reflectance spectra (DRS), from which the absorption spectrum extended from 380 nm to 440 nm. The concentration of Cu measured by energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) was higher than its theoretical value, a result which suggested that the QDs resided on the TiO2 surface and that the QD sensitization was primarily a surface process. In comparison to pure TiO2, the introduction of 1.0 wt. % Cu QDs increased the photocurrent density from 3.1 to 17.0 μA/cm2. Even a trace amount of Cu (only about 0.25 wt. %) can strongly enhance the photoelectric activity of TiO2. When excessive Cu was coated onto the TiO2 surface, the recombination of the photo-induced charges would be aggravated by the aggregation of QDs, and the growth of Cu grains made the bandgap of the QDs and TiO2 unmatched so that the photovoltaic conversion was restrained. Besides Cu QDs, the photoelectrical properties of TiO2 nanoparticles can be enhanced by the incorporation of other copper-based QDs (e.g., CuO, Cu2O, CuS, and Cu2S); the elementary Cu QDs demonstrated the best characteristics among them.

Synthesis, characterization, and third-order nonlinear optical properties of copper quantum dots embedded in sodium borosilicate glass

Copper quantum dots embedded in sodium borosilicate glass matrix were fabricated and analyzed in terms of their structural, chemical, and optical properties. X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses revealed that copper quantum dots were in face-centered-cubic crystalline phase and in the metallic state. Size and distribution of the quantum dots were measured by transmission electron microscopy (TEM) as well as high-resolution transmission electron microscopy (HRTEM). The results showed spherical shape have formed uniformly in the glass, and the size of these quantum dots were range from 1.5 to 5nm with the average particle size about 2.7nm. The third-order nonlinear optical properties of copper quantum dots doped glass were investigated by using Z-scan technique at the wavelength of 800nm with femtosecond Ti: sapphire laser radiation. The value of third-order optical nonlinear susceptibility χ(3) of the glass was estimated to be 2.41×10−11esu.