Formation Of Nanoparticle Networks Research Articles

Influence of Thermal Treatment on Preceramic Polymer Grafted Nanoparticle Network Formation: Implications for Thermal Protection Systems and Aerospace Propulsion Components

Influence of Thermal Treatment on Preceramic Polymer Grafted Nanoparticle Network Formation: Implications for Thermal Protection Systems and Aerospace Propulsion Components

Network of gold conjugates for enhanced sensitive immunochromatographic assays of troponins.

Highly sensitive detection of cardiac troponins I and T (cTnI and cTnT) was completed by immunochromatography with double amplification, through the binding of functionalized gold nanoparticles (GNPs). The robust nature of the approach, based on the formation of nanoparticle networks through the biotin–streptavidin interaction, was confirmed; the choice of the best assay parameters for maximal increase in ICA sensitivity was demonstrated. A bifunctional conjugate of GNPs with biotinylated specific IgG and two auxiliary conjugates, GNP–biotin and GNP–streptavidin, form three-component aggregates in the analytical zone of the test strip. The inclusion of abundant gold labels in the resulting immune complex leads to an amplified colorimetric signal. The limits of detection (LoDs) of cTnI and cTnT were 0.9 and 0.4 ng mL−1, respectively, which is 3 times lower than the LoDs of more commonly used systems. Visual LoDs were 10-fold lower in concentration. The enhancement has been realized both in single and double assay formats; analysis of cTnI and cTnT presented the same characteristics.

Impedimetric Detection of MicroRNAs by the Signal Amplification of Streptavidin Induced In Situ Formation of Biotin Phenylalanine Nanoparticle Networks

This work proposed a strategy for impedimetric detection of microRNAs (miRNAs) by the signal amplification of insulating biomaterials. Specifically, biotinylated miRNA (biotin-miRNA) with the same sequence as that of target miRNA was captured by the sensor electrode. The biotin tags on electrode surface allowed for the attachment of tetrameric streptavidin (SA) protein through the biotin-SA interaction. Meanwhile, biotinylated phenylalanine nanoparticles (biotin-FNPs) in solution triggered the assembly of more SA molecules on electrode surface through the same interaction. The circular recruitment of SA and biotin-FNPs from solution led to the in situ formation of SA-biotin-FNPs networks on electrode surface. The networks created an insulating layer to hamper the electron transfer, thus amplifying the impedance response. The competitive hybridization between target miRNA and biotin-miRNA with the capture probe prevented the attachment of biotin-miRNA by the sensor electrode, thus preventing the in situ formation of SA-biotin-FNPs networks and leading to the decrease in impedance signal. The method was applied to determine miRNA-21 in cell lysates with satisfactory results. The signal amplification strategy by in situ formation of nanoparticle networks can potentially be applied to develop novel affinity biosensors for detection of various biomolecules.

Nanoparticles alloying in liquids: Laser-ablation-generated Ag or Pd nanoparticles and laser irradiation-induced AgPd nanoparticle alloying

Laser irradiation of a mixture of single-element micro/nanomaterials may lead to their alloying and fabrication of multi-element structures. In addition to the laser induced alloying of particulates in the form of micro/nanopowders in ambient atmosphere (which forms the basis of the field of additive manufacturing technology), another interesting problem is the laser-induced alloying of a mixture of single-element nanoparticles in liquids since this process may lead to the direct fabrication of alloyed-nanoparticle colloidal solutions. In this work, bare-surface ligand-free Ag and Pd nanoparticles in solution were prepared by laser ablation of the corresponding bulk target materials, separately in water. The two solutions were mixed and the mixed solution was laser irradiated for different time durations in order to investigate the laser-induced nanoparticles alloying in liquid. Nanoparticles alloying and the formation of AgPd alloyed nanoparticles takes place with a decrease of the intensity of the surface-plasmon resonance peak of the Ag nanoparticles (at ∼405 nm) with the irradiation time while the low wavelength interband absorption peaks of either Ag or Pd nanoparticles remain unaffected by the irradiation for a time duration even as long as 30 min. The nanoalloys have lattice constants with values between those of the pure metals, which indicates that they consist of Ag and Pd in an approximately 1:1 ratio similar to the atomic composition of the starting mixed-nanoparticle solution. Formation of nanoparticle networks consisting of bimetallic alloyed nanoparticles and nanoparticles that remain as single elements (even after the end of the irradiation), joining together, are also formed. The binding energies of the 3d core electrons of both Ag and Pd nanoparticles shift to lower energies with the irradiation time, which is also a typical characteristic of AgPd alloyed nanoparticles. The mechanisms of nanoparticles alloying and network formation are also discussed.

Enabling Nanoparticle Networking in Semicrystalline Polymer Matrices

Among the physical and chemical attributes of the nanocomposite components and their interactions that contribute to the ultimate material properties, nanoparticle arrangement in the matrix is a key contributing factor that has been targeted through materials choices and processing strategies in numerous previous studies. Often, the desired nanocomposite morphology contains individually dispersed and distributed nanoparticles. In this research, a phase-segregated morphology containing nanoparticle networks was studied. A model nanocomposite system composed of calcium phosphate nanoparticles and a poly(3-hydroxybutyrate) matrix was produced to understand how polymer crystallization and crystal structure can facilitate the formation of a phase-segregated morphology containing nanoparticle networks. Two chemically similar calcium phosphate nanoparticle systems with different shapes, near-spherical and nanofiber, were synthesized for use in the nanocomposites. The different shapes were used independently in nanocomposites in an attempt to understand the effect of the nanoparticle shapes on crystallization-mediated nanoparticle network formation. The resulting nanocomposites were characterized to establish the effects of component interactions on the polymer structure. Additionally from the viscoelastic properties, structure-property relationships in these materials can be defined as a function of nanoparticle shape and concentration. The results of this research suggest that when the nanocomposite components are not strongly interacting, polymer crystallization may be used as a forced assembly method for nanoparticle networks. Such a methodology has applications to the design of functional polymer nanocomposites such as biomedical implant materials and organic photovoltaic materials where judicious choice of nanoparticle-polymer pairs and control of polymer crystal nucleation and growth processes could be used to control the length scale of phase segregation.

Charge photogeneration in hybrid solar cells: A comparison between quantum dots and in situ grown CdS

We demonstrate that blend films containing poly(3-hexylthiophene-2,5-diyl) and in situ grown CdS display a greater yield of photogenerated charges than a blend containing an equivalent amount of pre-synthesised CdS quantum dots. Moreover, we show that the greater charge yield in the in situ grown films leads to an improvement in device efficiency. The present findings also appear to suggest that charge photogeneration at the CdS/polymer heterojunction is facilitated by the formation of nanoparticle networks as a result of CdS aggregation.

DNA Gold Nanoparticle Conjugates Incorporating Thiooxonucleosides: 7-Deaza-6-thio-2′-deoxyguanosine as Gold Surface Anchor

A new protocol for the covalent attachment of oligonucleotides to gold nanoparticles was developed. Base-modified nucleosides with thiooxo groups were acting as molecular surface anchor. Compared to already existing conjugation protocols, the new linker strategy simplifies the synthesis of DNA gold nanoparticle conjugates. The phosphoramidite of 7-deaza-6-thio-2'-deoxyguanosine (6) was used in solid-phase synthesis. Incorporation of the sulfur-containing nucleosides can be performed at any position of an oligonucleotide; even multiple incorporations are feasible, which will increase the binding stability of the corresponding oligonucleotides to the gold nanoparticles. Oligonucleotide strands immobilized at the end of a chain were easily accessible during hybridization leading to DNA gold nanoparticle network formation. On the contrary, oligonucleotides immobilized via a central position could not form a DNA-AuNP network. Melting studies of the DNA gold nanoparticle assemblies revealed sharp melting profiles with a very narrow melting transition.

Nanoparticle Network Formation in Nanostructured and Disordered Block Copolymer Matrices.

Incorporation of nanoparticles composed of surface-functionalized fumed silica (FS) or native colloidal silica (CS) into a nanostructured block copolymer yields hybrid nanocomposites whose mechanical properties can be tuned by nanoparticle concentration and surface chemistry. In this work, dynamic rheology is used to probe the frequency and thermal responses of nanocomposites composed of a symmetric poly(styrene-b-methyl methacrylate) (SM) diblock copolymer and varying in nanoparticle concentration and surface functionality. At sufficiently high loading levels, FS nanoparticle aggregates establish a load-bearing colloidal network within the copolymer matrix. Transmission electron microscopy images reveal the morphological characteristics of the nanocomposites under these conditions.

Interfacial Assembly of Nanoparticles with Fluorous-Tagged Organic Molecules

Nanoparticles have been the subject of intensive study recently due to their interesting size- and morphology-dependent functional attributes. The assembly of nanoparticles into higher-ordered structures provides an exciting venue for the generation of novel collective properties. Herein, a versatile, fluorous tag-based method for the assembly of nanoparticles has been developed, leading to the formation of nanoparticle networks at either the gas−liquid, liquid−liquid, or solid−liquid interface. This capability would provide us with a key tool to probe the structures, dynamics, functions, and utilities of nanoparticle assemblies in a variety of environmental settings. Characterization with transmission electron microscopy, scanning electron microscopy, dynamic light scattering, and UV−vis extinction spectroscopy allowed us to gain tremendous insight into this significant process. The method can be readily extended to nanoparticle building blocks of other compositions, and novel functions could be harnessed through this superior strategy.

Effect of carbon nanotubes and montmorillonite on the flammability of epoxy nanocomposites

Addition of just 0.0025 mass fraction of highly aligned multiwall carbon nanotubes (MWCNTs) showed a 45% reduction in the peak mass loss rate (PMLR) during gasification of epoxy/MWCNT composites; this 45% decrease in PMLR at such a low loading (0.0025mass fraction) of MWCNTs, is much better than that reported previously with either MWCNTs (0.02 mass fraction) or SWCNTs (0.005 mass fraction). We attribute this effect to the use of highly aligned MWCNTs which easily exfoliate, or debundle, using high shear mixing. In addition, 0.005 mass fraction MWCNTs showed significant reduction in the initial mass loss rate as compared to other epoxy/MWCNT, epoxy montmorillonite (MMT) and pure epoxy samples. Reduced PMLR was also observed for epoxy/MMT nanocomposites, but required much higher MMT content. The epoxy/MWCNTs composites residue/char integrity (no visible cracks on the char surface of MWCNTs/epoxy samples) appeared to be superior to that for epoxy/MMT samples. The rheological characterization of the epoxy composites was carried out in order to study the effect of nanoparticle network formation on the rheological properties and flammability. Significant increase in thermal conductivity (k) was observed for epoxy/MWCNTs composite with high loadings of MWCNTs. This gasification mass loss behavior of the nanocomposites was investigated using a model that combines a continuum description of the transport of thermal energy with Ahrrenius kinetics for the decomposition of the polymer. The enhanced thermal conductivity for the epoxy/MWCNT composites appears to be responsible for the initial mass loss reduction.

Nanoparticle Networks on Silicon: Self-Organized or Disorganized?

A structural motif that appears very frequently not only in a wide range of nanostructured systems but also on mesoscopic to macroscopic length scales is the “cellular network”. We present a quantitative analysis of the morphology of cellular networks formed by thiol-passivated Au nanoparticles, and, for comparison, organometallic molecules, spin cast onto native oxide-terminated silicon substrates. The structural parameters determined from Voronoi tessellation and Minkowski functional analyses of the experimental data are compared to those extracted from Monte Carlo simulations of nanoparticle network formation. The key result of this comparative study is that although the cell positions are spatially correlated, i.e., they deviate strongly from those expected for a Poisson point set, this correlation arises simply from a coalescence of neighboring cells during network formation. Complex nonlinear processes such as spinodal decomposition or Marangoni convection are therefore not always a prerequisite for...

Study of Relationship between Morphology and Mechanical Properties of SiO2-Polyacrylate Hybrid Nanocomposite

ABSTRACTThe atomic force microscopic technique is utilized to study the spatial distribution of silica nanoparticles embedded in poly(tetraethylene glycol diacrylate) matrix. The cast samples of these hybrid materials show distinct mechanical property change as the weight ratio (SiO2/polyacrylate) reaches 40%. The morphological observation from spin-coated films on silicon substrates shows pronounced nanoparticle network formation correlated to the elasticity transition. The percolating particles reduce the local strain field, i.e. inhibit the deformation of the stratum, and cause the dramatic increase in the Young's modulus. Our experimental result is consistent with recent theoretical prediction [1].