Transport and abatement of fluorescent silica nanoparticle (SiO<Subscript>2</Subscript> NP) in granular filtration: effect of porous media and ionic strength

The extensive production and application of engineered silica nanoparticles (SiO₂ NPs) will inevitably lead to their release into the environment. Granular media filtration, a widely used process in water and wastewater treatment plants, has the potential for NP abatement. In this work, laboratory-scale column experiments were performed to study the transport and retention of SiO₂ NPs on three widely used porous materials, i.e., sand, anthracite, and granular activated carbon (GAC). Synthetic fluorescent core-shell SiO₂ NPs (83 nm) were used to facilitate NP detection. Sand showed very low capacity for SiO₂ filtration as this material had a surface with limited surface area and a high concentration of negative charge. Also, we found that the stability and transport of SiO₂ NP were strongly dependent on the ionic strength of the solution. Increasing ionic strength led to NP agglomeration and facilitated SiO₂ NP retention, while low ionic strength resulted in release of captured NPs from the sand bed. Compared to sand, anthracite and GAC showed higher affinity for SiO₂ NP capture. The superior capacity of GAC was primarily due to its porous structure and high surface area. A process model was developed to simulate NP capture in the packed bed columns and determine fundamental filtration parameters. This model provided an excellent fit to the experimental data. Taken together, the results obtained indicate that GAC is an interesting material for SiO₂ NP filtration.     

One-dimensional Bi<Subscript>2</Subscript>Mo<Subscript>x</Subscript>W<Subscript>1-x</Subscript>O<Subscript>6</Subscript> sosoloids: controllable synthesis by electrospinning process and enhanced photocatalytic performance

One-dimensional Bi₂Mo_xW_1-xO₆ (x = 0, 0.2, 0.5, 0.67, and 1) photocatalysts have been successfully synthesized for the first time by a straightforward electrospinning technique with a calcination process. The as-formed Bi₂Mo_xW_1-xO₆ nanofibers are composed of inter-linked nanosheets of 30–50 nm in size and characterized by thermogravimetric and differential scanning calorimetric, Fourier transform infrared, Raman spectra, X-ray powder diffraction, scanning electron microscope, Brunauer-Emmett-Teller, transmission electron microscope, UV-Vis spectroscopy, photoluminescence, HPLC, and EIS. The photodegradation behaviors towards organic dyes, including rhodamine B (RhB) and methylene blue (MB) are investigated, and the results illustrate that Bi₂Mo_0.25W_0.75O₆ nanofibers exhibit the highest photocatalytic performance under visible light irradiation than Bi₂Mo_xW_1-xO₆ (x = 0, 0.2, 0.5, 0.67, and 1) samples. The possible mechanisms of the enhanced photocatalytic properties are discussed in detail.     

In vitro and in vivo comparative study of the phototherapy anticancer activity of hyaluronic acid-modified single-walled carbon nanotubes,graphene oxide,and fullerene

In this work, carbon nanomaterials, single-walled carbon nanotubes (SWNT), graphene oxide (GO), and fullerene (C60) were modified by hyaluronic acid (HA) to obtain water-soluble and biocompatible nanomaterials with high tumor-targeting capacity and then the comparative study of these hyaluronic acid-modified carbon nanomaterials was made in vitro and in vivo. The conjugates of hyaluronic acid and carbon nanomaterials, namely, HA-SWNT, HA-GO, HA-C60, were confirmed by UV/Vis spectrum, Fourier transform infrared spectroscopy (FTIR), and a transmission electron microscope (TEM). After HA modification, the sizes of HA-SWNT, HA-GO, and HA-C60 were in a range of 70 to 300 nm, and all the three HA-modified materials were at negative potential, demonstrating that HA modification was in favor of extravasation of carbon materials into a tumor site due to enhanced permeability and retention effect of tumor. Photothermal conversion in vitro test demonstrated excellent photothermal sensitivity of HA-SWNT and HA-GO. But the reactive oxygen yield of HA-C60 was the highest compared with the others under visible light irradiation, which proved the good photodynamic therapy effect of HA-C60. In addition, cytotoxicity experiments exhibited that the inhibitory efficacy of HA-SWNT was the lowest, the second was HA-C60, and the highest was HA-GO, which was consistent with the uptake degree of them. While under the laser irradiation, the cell inhibition of the HA-SWNT was the highest, the second was HA-GO, and the last was HA-C60. In vivo evaluation of the three targeting carbon nanomaterials was consistent with the cytotoxicity assay results. Taken together, the results demonstrated that HA-SWNT and HA-GO were suited for photothermal therapy (PTT) agents for their good photothermal property, while HA-C60 was used as a kind of photodynamic therapy (PDT) agent for its photodynamic effect.     

Seed-mediated synthesis of acanthosphere-like gold microstructures with tunable LSPR in the NIR region using gemini surfactants as directing agents for SERS applications

Acanthosphere-like gold microstructures (AGMs) were synthesized using a facile, two-step, seed-mediated method and butanediyl-1,4-bis(dimethylhexadecylammonium bromide) (16-4-16) as a structure-directing agent. The morphologies and sizes of the products were controlled during the synthesis process by adjusting the concentrations of 16-4-16, the AgNO₃ feed, HAuCl₄, ascorbic acid, the amount of Ag seeds and the types of gemini surfactants used through systematic inquiry; particle sizes ranging from 130 to 800 nm were well prepared. Correspondingly, the morphology of the products changed between regular and irregular AGMs, and the products presented a number of new morphologies, such as open-mouthed submicrostructures and ribbon nanowires. In particular, with the increase in the 16-4-16 concentration, the structural morphology of the thorns clearly changed from a tip to a lamellar structure. A UV-vis spectroscopic analysis indicated that the localized surface plasmon resonance (LSPR) peak of the AGMs could be adjusted by changing the above factors, which extended from 500 to 1350 nm in the near-infrared (NIR) region, enabling a tremendous potential for using the AGMs as platforms for various biomedical applications. Based on the intermediate products, we propose a two-stage growth mechanism for the AGMs in which their solid cores and tips are generated successively. Surface-enhanced Raman scattering (SERS) measurements indicate that the AGMs can serve as sensitive SERS substrates; a SERS detection limit of 5 × 10^?7 M is presented for rhodamine B molecules.

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Hydrothermal synthesis of graphene oxide/multiwalled carbon nanotube/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> ternary nanocomposite for removal of Cu (II) and methylene blue

In this work, highly activated graphene oxide/multiwalled carbon nanotube/Fe₃O₄ ternary nanocomposite adsorbent was prepared from a simple hydrothermal route by using ferrous sulfate as precursor. For this purpose, the graphene oxide/multiwalled carbon nanotube architectures were formed through the π-π attractions between them, followed by attaching Fe₃O₄ nanoparticles onto their surface. The structure and composition of as-prepared ternary nanocomposite were characterized by XRD, FTIR, XPS, SEM, TEM, Raman, TGA, and BET. It was found that the resultant porous graphene oxide/multiwalled carbon nanotube/Fe₃O₄ ternary nanocomposite with large surface area could effectively prevent the π-π stacking interactions between graphene oxide nanosheets and greatly improve sorption sites on the surfaces. Thus, owing to the unique ternary nanocomposite architecture and synergistic effect among various components, as-prepared ternary nanocomposite exhibited high separation efficiency when they were used to remove the Cu (II) and methylene blue from aqueous solutions. Furthermore, the adsorption isotherms of ternary nanocomposite structures for Cu (II) and methylene blue removal fitted the Langmuir isotherm model. This work demonstrated that the graphene oxide/multiwalled carbon nanotube/Fe₃O₄ ternary nanocomposite was promising as an efficient adsorbent for heavy metal ions and organic dye removal from wastewater in low concentration.     

Symbiotic organism search algorithm for simulation of <Emphasis Type="Italic">J</Emphasis>-<Emphasis Type="Italic">V</Emphasis> characteristics and optimizing internal parameters of DSSC developed using electrospun TiO<Subscript>2</Subscript> nanofibers

In the present investigation, the recently developed, simple, robust, and powerful metaheuristic symbiotic organism search (SOS) algorithm was used for simulation of J-V characteristics and optimizing the internal parameters of the dye-sensitized solar cells (DSSCs) fabricated using electrospun 1-D mesoporous TiO₂ nanofibers as photoanode. The efficiency (η =?5.80%) of the DSSC made up of TiO₂ nanofibers as photoanode is found to be ～ 21.59% higher compared to the efficiency (η =?4.77%) of the DSSC made up of TiO₂ nanoparticles as photoanode. The observed high efficiency can be attributed to high dye loading as well as high electron transport in the mesoporous 1-D TiO₂ nanofibers. Further, the validity and advantage of SOS algorithm are verified by simulating J-V characteristics of DSSC with Lambert-W function.     

Synthesis,structural and dielectric properties of SrBi<Subscript>2 – <Emphasis Type="Italic">x</Emphasis></Subscript>Sm<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Nb<Subscript>2</Subscript>O<Subscript>9</Subscript>

The SrBi_{2 – x} Sm _x Nb₂O₉ (x = 0, 0.4, 0.5) structure were synthesized by a conventional solid-state method. The X-ray diffraction shows an orthorhombic at room temperature. Dielectric constant, loss tangent and Ac conductivity of Sm-doped SrBi₂Nb₂O₉ were carried out, as well. A higher concentration of samarium (x = 0.4 and 0.5) doping leads to a significant reduction in dielectric constant and in Curie temperature. Rather relaxor type of behaviour took place.     

On the ambiguity in the notion of transverse traceless modes of gravitational waves

Somewhat surprisingly, in many of the widely used monographs and review articles the term Transverse-Traceless modes of linearized gravitational waves is used to denote two entirely different notions. These treatments generally begin with a decomposition of the metric perturbation that is local in the momentum space (and hence non-local in physical space), and denote the resulting transverse traceless modes by \(h_{ab}^{\mathrm{TT}}\). However, while discussing gravitational waves emitted by an isolated system—typically in a later section—the relevant modes are extracted using a ‘projection operator’ that is local in physical space. These modes are also called transverse-traceless and again labeled \(h_{ab}^{\mathrm{TT}}\), implying that this is just a reformulation of the previous notion. But the two notions are conceptually distinct and the difference persists even in the asymptotic region. We show that this confusion arises already in Maxwell theory that is often discussed as a prelude to the gravitational case. Finally, we discuss why the distinction has nonetheless remained largely unnoticed, and also point out that there are some important physical effects where only one of the notions gives the correct answer.     

An Novel Protocol for the Quantum Secure Multi-Party Summation Based on Two-Particle Bell States

A protocol for the quantum secure multi-party summation based on two-particle Bell states is proposed. In this protocol, two-particle Bell states are used as private information carriers. Without using the entangled character of Bell states, we also use Pauli matrices operations to encode information and Hadamard matrix to extract information. The proposed protocol can also resist various attacks and overcomes the problem of information leakage with acceptable efficiency. In theory, our protocol can be used to build complex secure protocols for other multiparty computations and also lots of other important applications in distributed networks.     

A highly Selective Fluorescent Sensor for Monitoring Cu<Superscript>2+</Superscript> Ion: Synthesis,Characterization and Photophysical Properties

A new fluorescent sensor, 4-allylamine-N-(N-salicylidene)-1,8-naphthalimide (1), anchoring a naphthalimide moiety as fluorophore and a Schiff base group as receptor, was synthesized and characterized. The photophysical properties of sensor 1 were conducted in organic solvents of different polarities. Our study revealed that, depending on the solvent polarity, the fluorescence quantum yields varied from 0.59 to 0.89. The fluorescent activity of the sensor was monitored and the sensor was consequently applied for the detection of Cu²⁺ with high selectivity over various metal ions by fluorescence quenching in Tris-HCl (pH = 7.2) buffer/DMF (1:1, v/v) solution. From the binding stoichiometry, it was indicated that a 1:1 complex was formed between Cu²⁺ and the sensor 1. The fluorescence intensity was linear with Cu²⁺ in the concentration range 0.5–5 μM. Moreso, the detection limit was calculated to be 0.32 μM, which is sufficiently low for good sensitivity of Cu²⁺ ion. The binding mode was due to the intramolecular charge transfer (ICT) and the coordination of Cu²⁺ with C = N and hydroxyl oxygen groups of the sensor 1. The sensor proved effective for Cu²⁺ monitoring in real water samples with recovery rates of 95–112.6 % obtained.