Nanoparticle Networks Research Articles

Synergistic effects of metal hydroxides and fumed nanosilica as fire retardants for polyethylene

AbstractThis work aims to study the synergistic effect of aluminum/magnesium hydroxide microfillers and organomodified fumed silica nanoparticles as flame retardants (FRs) for linear low-density polyethylene (LLDPE), and to select the best composition to produce a fire-resistant polyethylene-based single-polymer composite. The fillers were added to LLDPE at different concentrations, and the prepared composites were characterized to investigate the individual and combined effects of the fillers on the thermo-oxidation resistance and the fire performance, as well as the microstructural, physical, thermal and mechanical properties. Both filler types were homogeneously distributed in the matrix, with the formation of a network of silica nanoparticles at elevated loadings. Melt flow index (MFI) tests revealed that the fluidity of the material was not considerably impaired upon metal hydroxide introduction, while a heavy reduction of the MFI was detected for silica contents higher than 5 wt%. FRs introduction promoted a noticeable enhancement of the thermo-oxidative stability of the materials, as shown by thermogravimetric analysis (TGA) and onset oxidation temperature (OOT) tests, and superior thermal properties were measured on the samples combining micro- and nanofillers, thus evidencing synergistic effects. Tensile tests showed that the stiffening effect due to a high content of metal hydroxide microparticles was accompanied by a decrease in the strain at break, but nanosilica at low concentration contributed to preserve the ultimate mechanical properties of the neat polymer. The fire performance of the samples with optimized compositions, evaluated through limiting oxygen index (LOI) and cone calorimetry tests, was strongly enhanced with respect to that of the neat LLDPE, and also these tests highlighted the synergistic effect between micro- and nanofillers, as well as an interesting correlation between fire parameters and viscosity.

A hierarchical carbon nanotube/SiO2 nanoparticle network induced superhydrophobic and conductive coating for wearable strain sensors with superior sensitivity and ultra-low detection limit

It is desirable to develop strain sensors with large stretchability, high sensitivity, and good anti-corrosive properties, due to their promising applications in wearable electronics.

Nanopalladium on Magnetic Ionic Nanoparticle Network (MINN) as an Efficient and Recyclable Catalyst with High Ionic Density and Dispersibility

A novel magnetic ionic nanoparticle network (MINN) comprising ultrasmall iron oxide nanoparticles as seeds and an immobilized ionic liquid as the interfacing ionic linker was prepared using a simple coupled ligand exchange–sol–gel strategy. The material demonstrated a combination of interesting features such as network structure, high ionic density, pronounced ionic liquid content, excellent redispersibility, magnetic response, and high surface area, never observed simultaneously in the previous ionic nanoparticle networks. It was found that MINN is an effective support for the immobilization of Pd nanoparticles. The catalyst exhibits outstanding catalytic activity, stability, reproducible dispersibility, and durability in the Suzuki cross-coupling of highly challenging substrates such as heteroaryl halides, ortho-substituted aryl halides, as well as aryl chlorides. Also, the catalyst was efficiently recovered using a new magnetic separation/redispersion strategy and exhibited no noticeable loss of perfor...

Synthesis and characterization of novel Pr6O11/Mn3O4 nanocomposites for electrochemical supercapacitors

This study presents the successful synthesis of praseodymium oxide, Pr6O11 and hausmannite manganese oxide, Mn3O4 nanoparticles, along with a novel synthesis of (Pr6O11/Mn3O4) nanocomposites by employing the hydrothermal route followed by post thermal annealing. X-ray Diffraction, Field Emission Scanning Electron Microscopy and Energy Dispersive X-ray characterization techniques are being adapted to analyze the physical characteristics of all the synthesized materials. XRD results reveal the crystalline nature of the synthesized materials. FE-SEM results display the irregular nanograins of Mn3O4 and a regular network of interconnected Pr6O11 nanoparticles. Nitrogen adsorption/desorption tests confirm the mesoporous nature of all the synthesized electrode materials. The Pr6O11/Mn3O4 − 2 electrode material exhibits an outstanding specific capacitance of 794.58 F/g at a current density of 0.5 A/g, as compared to the 521.24 F/g for the Pr6O11 electrode material. These investigations provide an easy and efficient method to develop nanocomposites (Pr6O11/Mn3O4) with better electrochemical characteristics, as electrode materials for supercapacitor applications.

Second-Generation Nanosponges: Nanonetworks in Controlled Dimensions via Backbone Ketoxime and Alkoxyamine Cross-Links for Controlled Release

We report the synthesis of nanoparticle (NP) networks in a variety of sizes through the controlled cross-linking reaction of ketone groups integrated into linear polyester backbones and a difunctionalized aminooxy ethylene cross-linker. In contrast to previous work forming nanonetworks from linear components with pendant reactive groups, the ketone functional group is part of the polymer backbone accomplished by copolymerization of 2-oxepane-1,5-dione (OPD) monomers together with δ-valerolactone. This process precludes postpolymerization reactions, modifying pendant functional groups in the polyester component, and provides direct access to the cross-linking entity. Reactions with bis(aminooxy)poly(ethylene glycol) form networks in a rapidly proceeding process with linear precursors containing 4%, 8%, and 14% of OPD, in a ratio of two aminooxy groups per keto group. The concentration of the OPD unit in solution is another critical factor contributing to the controlled production of these particles as investigated in two conditions to yield a set of six particles in well-defined dimensions ranging from 39 to 173 nm. Ketoxime linkages are pH-responsive and provide an alternative faster degradation mechanism together with a hydrolysis of the polymer backbone. The reduction of the ketoxime linkages after nanoparticle formation resulted in an additional set of six particles in comparable sizes with stable alkoxyamine groups limiting the degradation to a slower hydrolysis. In this work, we prepared a series of twelve particles in a two- or three-step process starting from the synthesis of three different OPD-containing polymers and controlled cross-linking in two reaction concentrations, with or without reduction of the ketoxime connective group. These particles are promising drug delivery systems as a practical synthesis is combined with a tunable degradation leading to expanded options for drug release and is demonstrated in the release of the natural product Brefeldin A.

Logic Sensing of MicroRNA in Living Cells Using DNA-Programmed Nanoparticle Network with High Signal Gain.

Molecular circuits capable of implementing Boolean logic in cellular environments have emerged as an important tool for in situ sensing, elucidating, and modulating cell functions. The performance of existing molecular computation devices in living cells is limited because of the low level of biomolecular inputs and moderate signal gain. Herein, we devised a new class of DNA-programmed nanoparticle network with integrated molecular computation and signal amplification functions for logic sensing of dual microRNA (miRNA) molecules in living cells. The nanoparticle network, which is composed of DNA-bridged gold nanoparticles and quantum dots (QDs), could simultaneously interface with two miRNA molecules, amplify the molecular inputs, perform a calculation through AND logic gate, and generate QD photoluminescence (PL) as an output signal. Significant improvement in imaging sensitivity is achieved by integrating the signal amplifier into the molecular computation device. It allows discrimination of specific cancer cell types via intelligent sensing of miRNA patterns in living cells.

Tuning Texture and Morphology of Mesoporous TiO₂ by Non-Hydrolytic Sol-Gel Syntheses.

The development of powerful synthetic methodologies is paramount in the design of advanced nanostructured materials. Owing to its remarkable properties and low cost, nanostructured TiO2 is widely investigated for applications such as photocatalysis, energy conversion or energy storage. In this article we report the synthesis of mesoporous TiO2 by three different non-hydrolytic sol-gel routes, and we investigate the influence of the synthetic route and of the presence and nature of the solvent on the structure, texture and morphology of the materials. The first route is the well-known ether route, based on the reaction of TiCl4 with iPr2O. The second and third routes, which have not been previously described for the synthesis of mesoporous TiO2, involve the reaction of Ti(OiPr)4 with stoichiometric amounts of acetophenone and benzoic anhydride, respectively. All materials are characterized by XRD, N2 physisorption and SEM. By playing with the non-hydrolytic route used and the reaction conditions (presence of a solvent, nature of the solvent, calcination), it is possible to tune the morphology and texture of the TiO2. Depending on the reaction conditions, a large variety of mesoporous TiO2 nanostructures could be obtained, resulting from the spontaneous aggregation of TiO2 nanoparticles, either rounded nanoparticles, platelets or nanorods. These nanoparticle networks exhibited a specific surface area up to 250 m2 g−1 before calcination, or up to 110 m2 g−1 after calcination.

Surface-controlled Nb2O5 nanoparticle networks for fast Li transport and storage

Hybrid supercapacitors are successfully introduced to reduce the gap between high-capacity battery electrodes and high-power capacitor electrodes in case of electrochemical energy storage devices. Niobium pentoxide (Nb2O5) has attracted great interest for hybrid supercapacitors because of its moderate capacity and excellent cycle performance. However, its low electronic conductivity is still a major problem. Carbon is usually incorporated to address this limitation. Here, we report the Nb2O5 nanoparticle networks to facilitate electronic transport via continuous connection of materials. Additionally, the high surface area of the nanoparticles is maintained. The Nb2O5 nanoparticle network was synthesized using a simple solvothermal reaction in organic media. The materials characterization was performed using X-ray diffraction analysis, and scanning and transmission electron microscopies. The charge storage mechanism of the synthesized Nb2O5 material was investigated by cyclic voltammetry. In galvanostatic charge–discharge tests, the synthesized Nb2O5 nanoparticle network electrode exhibited stable cycle performance and remarkable rate capability without carbon incorporation.

Particle Cross‐Linking: Thin, Porous, and Conductive Networks of Metal Nanoparticles through Electrochemical Welding on a Liquid Metal Template (Adv. Mater. Interfaces 19/2018)

In article number 1800406, Jianbo Tang, Jing Liu and co-workers propose a liquid-metal-enabled room-temperature particle cross-linking method which is able to “weld” discrete copper nanoparticles into thin, continuous yet porous networks through interfacial electrochemical processes. The authors also demonstrate remarkable mechanical and electrical properties of the materials caused by network formation.

Nanoparticle based gas-sensing array for pesticide detection

The present paper discusses the development of a pesticide gas sensor based on self-assembled nanoparticle networks and four distinctive polymer coatings; the sensor is used as a sensing system for chlorpyrifos detection. For the fabrication of the sensing system the sputtering technique is employed for the simultaneous fabrication and deposition of the nanoparticle film while 4 different polymer coatings are then spin-coated on top. The sensors are ultimately able to distinguish between chlorpyrifos (a commonly used pesticide) and its solvent, detecting chlorpyrifos concentrations as low as 0.7 ppb. Each of the 4 polymer coatings produces a unique sensor response when in the presence of chlorpyrifos vapours; this has served as the basis for the development of a multi-sensor array for chlorpyrifos detection. The capability of the system in distinguishing between pesticide and pesticide solvent has been supported by results obtained by means of Principal Component Analysis (PCA).

NiO–ZnO Nanoheterojunction Networks for Room‐Temperature Volatile Organic Compounds Sensing

AbstractEngineering of highly performing nanomaterials, capable of rapid detection of trace concentrations of gas molecules at room temperature, is key to the development of the next generation of miniaturized chemical sensors. Here, a highly performing nanoheterojunctions layout is presented for the rapid room‐temperature chemical sensing of volatile organic compounds down to ten particles per billion concentrations. The layout consists of a 3D network of nickel oxide–zinc oxide (NiO–ZnO) p–n semiconductors with grain size of ≈20 nm nanometers and a porosity of ≈98%. Notably, it is observed that the formation of the p–n heterojunctions by decoration of a ZnO nanoparticle networks with NiO increases the sensor response by more than four times while improving the lower limit of detection. Under solar light irradiation, the optimal NiO–ZnO nanoheterojunction networks demonstrate a strong and selective room‐temperature response to two important volatile organic compounds utilized for breath analysis, namely acetone and ethanol. Furthermore, these NiO–ZnO nanoheterojunctions show an inverse response to acetone from that observed for all others reducing gas molecules (i.e., ethanol, propane, and ethylbenzene). It is believed that these novel insights of the optoelectrochemical properties of ultraporous nanoheterojunction networks provide guidelines for the future design of low‐power solid‐state chemical sensors.

Bismuth nanoparticles decorated graphenated carbon nanotubes modified screen-printed electrode for mercury detection

Abstract A three-dimensional hierarchical network of bismuth nanoparticles decorated graphene-carbon nanotubes nanocomposite (Bi NPs@Gr-CNTs) was synthesized and employed for electrocatalytic detection of mercury (Hg (II)). The electrocatalyst was characterized via scanning electron microscopy, transmission electron microscopy, Energy-dispersive X-ray spectroscopy, X-ray diffraction, FT-IR, electrochemical impedance spectroscopy, and cyclic voltammetry. The electrocatalytic activity of Bi NPs@Gr-CNTs modified screen-printed carbon electrode (SPCE) toward Hg (II) was studied using cyclic voltammetry, and differential pulse voltammetry. The Bi NPs@Gr-CNTs/SPCE exhibited excellent electrocatalytic ability to Hg (II) in comparison to control electrodes. Under optimized conditions, Bi NPs@Gr-CNTs/SPCE exhibits excellent Hg (II) sensing attributes in the range of 1.0 nM–217.4 µM with 0.2 nM of detection limit. The electrode was specific for Hg (II) in presence of other metal ions ascribe excellent selectivity. Practicality of the method was demonstrated in tap water, fish oil tablet, human serum, and urine samples (spiked method), which presented acceptable recoveries.

Nucleic acid hybridization on an electrically reconfigurable network of gold-coated magnetic nanoparticles enables microRNA detection in blood.

There is intense interest in quantifying the levels of microRNA because of its importance as a blood-borne biomarker. The challenge has been to develop methods that can monitor microRNA expression both over broad concentration ranges and in ultralow amounts directly in a patient's blood. Here, we show that, through electric-field-induced reconfiguration of a network of gold-coated magnetic nanoparticles modified by probe DNA (DNA-Au@MNPs), it is possible to create a highly sensitive sensor for direct analysis of nucleic acids in samples as complex as whole blood. The sensor is the first to be able to detect concentrations of microRNA from 10 aM to 1 nM in unprocessed blood samples. It can distinguish small variations in microRNA concentrations in blood samples of mice with growing tumours. The ultrasensitive and direct detection of microRNA using an electrically reconfigurable DNA-Au@MNPs network makes the reported device a promising tool for cancer diagnostics.

Folic acid–egg white coated IPN network of carboxymethyl cellulose and egg white nanoparticles for treating breast cancer

Recurrent cancer treatments fail to distinguish between the normal cells and cancer cells and lead to severe systemic toxicity and side effects. The current researchers focus to overcome these conventional pharmacological barriers by increasing the selectivity of cancer cell by targeting mechanism. In this study, interpenetrating polymeric network (IPN) of carboxymethyl cellulose (CMC) and egg white (EW), cross-linked with polyethylene glycol (PEG), and polyvinyl alcohol (PVA) loaded with cyclophosphamide (CP) were synthesized by heat coagulation method and coated with folic acid–egg white (FA–EW) conjugate. The prepared IPN–NPs were characterized using FTIR, P-XRD, and FE-SEM. Particle size, polydispersity index and zeta potential were also evaluated. FA–EW/CP [IPN–NPs] shows high entrapment efficiency of 94 ± 1.52%. The release analysis of CP from FA–EW/CP [IPN–NPs] showed a pH-responsive behavior with a rapid release at pH 5.0 and 6.0 rather than pH 7.4. Hemocompatibility of drug delivery systems is proved by hemolysis assay. The confocal microscope studies specify the possible uptake of FA–EW/CP [IPN–NPs] in MCF-7 breast cancer cell lines. The cytotoxicity analysis of MCF-7 cells by fluorescent live/dead cell assay and MTT assay suggest that FA–EW/CP [IPN–NPs] exhibit higher cytotoxicity compared to free CP and IPN–NPs. The obtained FA–EW/CP [IPN–NPs] might serve as a potential candidate for targeted breast cancer drug delivery.

Topological Network Properties of Fractal-Like Metallic Nanoparticle Patterns and Their Effects on Optical Resonances

Fractal-like nanoparticle two-dimensional patterns forming in diffusion-limited aggregation show variant spatial patterns. However, they have invariant statistical properties in their network topologies, even though their formation is completely in self-assembled processes. One of the outputs from these topological properties is optical resonances at invariant frequencies, which is a required feature of a metamaterial alternative. Fractal-like metallic patterns studied here in both experiments and theoretical models exhibit similar resonance frequencies in the infrared-ray range, and they depend on the unit length of nanoparticles composing arbitrary fractal-like structures. The scheme of analysis applied here using complex network theory does not only reveal the topological properties of the nanoparticle network, but points out their optical and possibly other physical potentials arising from their geometrical properties.

Carbon-Free Connected Ru, Ir Based Nanoparticle Catalysts for Polymer-Electrolyte Water Electrolysis

Oxygen evolution reaction (OER) catalysts for polymer-electrolyte water electrolysis (PEWE) suffered from their low surface area because carbon support cannot be used for OER operating at high potential. Connecting metal nanoparticles enable catalysts to conduct electrons through nanoparticle networks without any support materials while keeping their high surface area. Thus, connected nanoparticle catalysts (Fig. 1 (A)) are promising for OER. Previously, we have developed connected Pt-Fe nanoparticle catalysts with hollow capsule structure for oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs).[1] In this study, we proposed Ru and Ir nanoparticle catalysts for OER in water electrolysis because Ru and Ir have high OER activity. Ru and Ir nanoparticle catalysts were synthesized as follows. First, Ru and Ir nanoparticles were synthesized on silica template (PDDA/SiO2) via polyol method using tetraethylene glycol as reducing agent and Ru(III) acetylacetonate or Ir(III) acetylacetonate as the metallic precursors (M/PDDA/SiO2, M is Ru or Ir). Then, these nanoparticles were treated in supercritical ethanol at 330ºC for 90 min (Ru) or 60 min (Ir) (sc-M/SiO2). Dissolution of SiO2 in 3 M NaOH solution at 85ºC for 3 h made porous hollow structure (M capsule). OER performance were evaluated by electrochemical measurement in 0.1 M HClO4 solution. Fig. 1 (B) shows TEM image of Ir capsule. Capsule and networks structure of each catalysts were observed by TEM images. All Ru catalysts inactivated for OER at the first CV cycle. OER activity of Ru/PDDA/SiO2 did not improve by heat oxidation treatment in air at 400ºC. Fig. 1 (C) shows OER curves of Ir catalysts. All Ir catalysts showed stable OER. Among them, Ir/PDDA/SiO2 had the highest OER activity. Mass activity at 1.48 V of Ir/PDDA/SiO2 was higher than RuO2 [2], IrO2 [2] and Ir/C­[3] in previous reports as shown in Fig.1 (D). Heat treatment of Ir/PDDA/SiO2 at 200ºC further improved. In conclusion, we successfully synthesized connected Ru and Ir nanoparticle catalysts. Among them, Ir/PDDA/SiO2 showed the highest OER activity and the activity was further improved by heat oxidation treatment. The results showed that connected Ir nanoparticle catalysts are promising as carbon-free catalysts for water electrolysis. [1] T. Tamaki, H. Kuroki, T. Yamaguchi et al., Energy Environ. Sci., 8, 3545-3549 (2015). [2] Y. Lee et al., J. Phys. Chem. Lett., 3, 399-404 (2012). [3] HN. Nong et al., Chem. Sci., 5, 2955-2963 (2014). Figure 1

Metal Oxide Nanomaterial Network for Lithium-Ion Battery Anodes and Cathodes

Lithium-ion batteries have been investigated for their promising applications in hybrid electric vehicles. A great effort has been made to synthesize a variety of electrode materials to improve the energy density, rate capability, and cycling stability. Nanostructured materials have received much attention as anodes and cathodes due to the short ion transport length, higher electrolyte- electrode contact area and better accommodation of the strain of lithium insertion/extraction. Here we report a facile polymer-assisted chemical solution method to synthesize metal oxides nanoparticle network for lithium-ion battery anodes, such as cobalt oxide, nickel oxide, bismuth oxide, and cathode materials, such as vanadium oxide and lithium manganese oxide. The carbon left from the decomposition of polymers is an effective binder between metal oxides and the current collector. The one step binder-free anodes show much better lithium storage properties with high capacities, stable cyclability, and rate capability, as compared with the electrodes from the conventional slurry-paste way by mixing the active material, polymer binder and carbon black. The good performances of these electrodes could be attributed to intimate contact between the active material and the nickel foam, the porosity of the current collector, and the network structure of the active materials.

Localized Surface Plasmon Resonances with Spherical Metallic Nanoparticles

In this work we review in part of our recent theoretical study on the electrical intensity enhancement in the dielectric medium surrounding metallic nanoparticles due to the effect of their localized surface plasmon resonance (LSPR). The known results in the case of a simple metallic spherical nanoparticle are presented and then extend them to the general case of complex network of the identical spherical metallic nanoparticles. For illustration, several typical lattices of identical spherical metallic nanoparticles will be treated. The findings of electrical intensity enhancements and plasmonic resonance wavelengths of the single and the network of the metallic nanoparticles are obtained based on the analytical expressions. The theoretical results were compared and shown the good agreement with simulation results. The simulation of the LSPRs and the electrical intensity enhancements was performed using the boundary element method.

Environmental Hg vapours adsorption and detection by using functionalized gold nanoparticles network

Adsorption and detection of environmental total gaseous mercury (TGM) was studied by using gold nanoparticles (AuNPs) on purpose functionalized with dithiol ligands, i.e. Biphenyl-4,4′-dithiol (BI) or p-Terphenyl-4,4′′-dithiol (TR), suitable for nanoparticles based network formation. AuNPs-BI and AuNPs-TR with size 6–8 nm were deposited onto quartz fibres and used as adsorbent materials for the detection of TGM, both indoor for adsorption studies, at defined concentrations (∼4.5 ng m−3 Hg), and outdoor, at the vapour mercury concentration of the environmental countryside (∼1.5 ng m−3 Hg). The role of relative humidity (RH) in the absorption process has been observed. A high Hg adsorption capability, also when exposed to sub ppb concentration, has been observed. A cold vapour atomic fluorescence spectroscopy (CVAFS) detector was used to determine gaseous mercury concentrations lower than 2 ng m−3, with a robust and reproducible procedure. Moreover, the use of quartz fibres substrate covered with AuNPs-BI or AuNPs-TR, and used for more than thirty times during the experiments, makes them competitive in the use in large-scale measurement campaigns.

Evaluation and Development of Expanded Equations Based on Takayanagi Model for Tensile Modulus of Polymer Nanocomposites Assuming the Formation of Percolating Networks

In this study, the tensile modulus of polymer nanocomposites is analyzed by the development of expanded Takayanagi models considering the fractions of networked and dispersed nanoparticles above the percolation threshold. The tensile moduli of networked and dispersed phases are calculated by suitable models. This study focuses on “polymer-carbon nanotubes” nanocomposites, but the developed model can be applied for samples reinforcing with long fillers such as clay and graphene. The expanded Takayanagi model suggests two different forms which are evaluated by the experimental results of “polymer-carbon nanotubes” nanocomposites. Only one form shows the best results compared to the experimental data, whereas another form underestimates the modulus. The developed model (correct form) shows that the fraction of filler network meaningfully changes the reinforcement of nanocomposites. The network level and other correlated parameters with the percolation threshold can be calculated by comparing the experimental data with the developed model. The logical outputs confirm the correct development of Takayanagi model assuming the network and dispersion of nanoparticles in polymer nanocomposites.