Multilayer Nanoparticles Research Articles

Highly Conductive Paper/Textile Electrodes Using Ligand Exchange Reaction-Induced in Situ Metallic Fusion.

Here, we report that metal nanoparticle (NP)-based paper/textile electrodes with bulk metallic conductivity can be prepared via organic linker-modulated ligand exchange reaction and in situ room-temperature metallic fusion without additional chemical or thermal treatments. For this study, amine-functionalized molecule linkers instead of bulky polymer linkers were layer-by-layer (LbL)-assembled with tetraoctylammonium bromide (TOABr)-stabilized Au NPs to form Au NP multilayered films. By conversion of the amine groups of the organic molecule linkers from -NH3+ to the -NH2 groups, as well as by a decrease in the size of the organic linkers, the LbL-assembled Au NPs became highly interconnected and fused during LbL deposition, resulting in Au NP multilayers with adjustable conductivity and transport behavior. These phenomena were also predicted by a density functional theory investigation for the model system. Particularly, LbL-assembled films composed of TOABr-Au NPs and diethylenetriamine ( Mw: ∼104) exhibited a remarkable electrical conductivity of 2.2 × 105 S·cm-1, which was higher than the electrical conductivity of the metal NP-based electrodes as well as the carbon material-based electrodes reported to date. Furthermore, based on our approach, a variety of insulating flexible papers and textiles were successfully converted into real metal-like paper and textile electrodes with high flexibility preserving their highly porous structure. This approach can provide a basis for further improving and controlling the electrical properties of flexible electrodes through the control of organic linkers.

Nanoparticle Delivery of miR-708 Mimetic Impairs Breast Cancer Metastasis.

Triple-negative breast cancer (TNBC) patients exhibit the worst clinical outcome due to its aggressive clinical course, higher rate of recurrence, and a conspicuous lack of FDA-approved targeted therapies. Here, we show that multilayered nanoparticles (NPs) carrying the metastasis suppressor microRNA miR-708 (miR708-NP) localize to orthotopic primary TNBC, and efficiently deliver the miR-708 cargo to reduce lung metastasis. Using a SOX2/OCT4 promoter reporter, we identified a population of miR-708low cancer cells with tumor-initiating properties, enhanced metastatic potential, and marked sensitivity to miR-708 treatment. In vivo, miR708-NP directly targeted the SOX2/OCT4-mCherry+ miR-708low tumor cells to impair metastasis. Together, our preclinical findings provide a mechanism-based antimetastatic therapeutic approach for TNBC, with a marked potential to generate miR-708 replacement therapy for high-risk TNBC patients in the clinic. To our knowledge, this gold nanoparticle-based delivery of microRNA mimetic is the first oligonucleotide-based targeted therapy for TNBC.

Anisotropic infrared plasmonic broadband absorber based on graphene-black phosphorus multilayers

Two-dimensional materials (2DMs) such as graphene and black phosphorus (BP) have aroused considerable attentions in the past few years. Engineering and enhancing their light-matter interaction is possible due to their support for localized surface plasmon resonances in the infrared regime. In this paper, we have proposed an infrared broadband absorber consisting of multilayer graphene-BP nanoparticles sandwiched between dielectric layers. Benefiting from the properties of graphene and BP, the absorber exhibits both perfect broadband responses and strong anisotropy beyond individual graphene and BP layers. The absorber is tunable with the variation of geometric parameters as well as the doping levels of graphene and BP. The physical insight is revealed by electric field distributions. Furthermore, the angular robustness for incident wave is investigated. The proposed anisotropic omnidirectional broadband absorber may have promising potential applications in various biosensing, communication and imaging systems.

Modeling interaction between gp120 HIV protein and CCR5 receptor.

The study of the process of HIV entry into the host cell and the creation of biomimetic nanosystems that are able to selectively bind viral particles and proteins is a high priority research area for the development of novel diagnostic tools and treatment of HIV infection. Recently, we described multilayer nanoparticles (nanotraps) with heparin surface and cationic peptides comprising the N-terminal tail (Nt) and the second extracellular loop (ECL2) of CCR5 receptor, which could bind with high affinity some inflammatory chemokines, in particular, Rantes. Because of the similarity of the binding determinants in CCR5 structure, both for chemokines and gp120 HIV protein, here we expand this approach to the study of the interactions of these biomimetic nanosystems and their components with the peptide representing the V3 loop of the activated form of gp120. According to surface plasmon resonance results, a conformational rearrangement is involved in the process of V3 and CCR5 fragments binding. As in the case of Rantes, ECL2 peptide showed much higher affinity to V3 peptide than Nt (KD =3.72×10-8 and 1.10×10-6 M, respectively). Heparin-covered nanoparticles bearing CCR5 peptides effectively bound V3 as well. The presence of both heparin and the peptides in the structure of the nanotraps was shown to be crucial for the interaction with the V3 loop. Thus, short cationic peptides ECL2 and Nt proved to be excellent candidates for the design of CCR5 receptor mimetics.

Gold-Tagged Polymeric Nanoparticles with Spatially Controlled Composition for Enhanced Detectability in Biological Environments

Organic nanoparticles offer the advantage of high biocompatibility for biomedical applications but suffer frequently from poor visibility in biological environments. While fluorescent-labeling is convenient and allows for fast and extensive histological analysis, fluorescence imaging and quantitative analysis are limited by low resolution and significantly hindered by tissue autofluorescence. Labeling of polymeric nanoparticles with an additional gold tag would allow for high resolution imaging via transmission electron microscopy (TEM) and for quantification of particles by inductively coupled plasma optical emission spectrometry (ICP-OES). However, spatially uncontrolled gold-tagging can cause significant fluorescence quenching. To overcome this restraint, 2.2 nm gold nanoparticles were introduced at the interface between the hydrophobic fluorophore-loaded core and the hydrophilic shell of polymeric nanoparticles. Due to the small size of gold labels and the spatially controlled stratified composition of hybrid nanoparticles, fluorescence quenching by gold tags was minimized to 15.1%, allowing for concomitant detection of both labels via optical microscopy after enhancement of the gold tags. Multilayered hybrid nanoparticles exhibited outstanding detectability in TEM, even without additional sample staining. Furthermore, they were capable of producing remarkable image contrast inside cells after gold or silver enhancement. The interfacial gold layer increased the hydrodynamic particle size only marginally from 71.8 to 89.5 nm and had no negative impact on biocompatibility in vitro. The gold content (0.75% m/m) is sufficiently high for future quantification in tissues after systemic administration. With their clean-cut structure and superior detectability, multilayered hybrid nanoparticles constitute an outstanding blueprint and a precious tool for the development of nanomedicines.

A single light spot GC detector employing localized surface plasmon resonance of porous Au@SiO2 nanoparticle multilayer.

This paper describes the synthesis of a nano-porous multilayered film consisting of Au@SiO2 nanoparticles. This film was used to miniaturize the size of a localized surface plasmon resonance (LSPR)-based capillary gas chromatograph (GC) detector. A layer-by-layer (LbL) approach with proper surface reaction sequences was used to create a multilayer structure that consisted of as many as five layers of Au@SiO2 nanoparticles. The center wavelength of LSPR was shifted from 520 to 634 nm due to the approximation of additional layers of nanoparticles. The vapor response time for this Au@SiO2 multilayer LSPR sensor was identical to that of an Au nanoparticle monolayer, which confirmed that this multilayer structure has a high level of gas permeability. The multilayer was synthesized inside a glass capillary for use as a GC detector. Due to the enhancement of absorbance, the gas chromatographic signal was obtained via a single spotlight that penetrated one side of the glass capillary and was then reflected by a silver mirror coated on the opposite side. The detection limits were ≤20 ng for cyclohexanone and m-xylene.

A Monte Carlo model for self-assembly of polytetrafluoroethylene nanoparticle films via repulsive electrostatic interactions.

Self-assembly of polytetrafluoroethylene (PTFE) nanoparticle films on an aluminum alloy substrate under repulsive electrostatic interactions has been achieved experimentally. However, a theoretical framework which is able to accurately predict the self-assembly kinetics based on their underlying mechanisms is not yet available. In this work, we formulate a Monte Carlo model to make predictions on the formation of close-packed monolayer and multilayer PTFE nanoparticle films during repulsive electrostatic self-assembly. In the model, the parameters are obtained from experimental measurements. Our simulation results demonstrate that the layer number of close-packed PTFE nanoparticle films on the aluminum alloy substrate increases with an increase of nanoparticle concentration and an increase of deposition time, which match well with the experimental observations. Beyond this, the underlying mechanism in which the close-packed PTFE nanoparticle film cannot be formed on the Cu substrate was also revealed, which is attributed to the decrease of the substrate repulsive interaction. Hence, the present work not only unveils the self-assembly kinetics of nanoparticle films, but also provides useful guidelines to controllable self-assembly of nanoparticle films with a desired number of layers.

多层Au-Pd核壳纳米颗粒膜增敏的光纤氢气传感器

多层Au-Pd核壳纳米颗粒膜增敏的光纤氢气传感器

Evolution of ligand-capped nanoparticle multilayers toward a near unique thickness.

The structural evolution of thiol-capped Au-nanoparticle (AuNP) multilayers on a H-passivated Si substrate, formed through a Langmuir-Schaefer (LS) deposition process, has been investigated using complementary grazing incidence X-ray scattering techniques. The fractional coverage multilayers of AuNPs, formed through a multi-transfer process, are found to be quite unstable under ambient conditions. The thickness of these decreases with time and tends to saturate toward a near unique thickness (NUT ≈ 6 nm). Although initial low coverage and their instability create hindrance in the control and formation of desired 3D-nanostructures in the bottom-up approach, the formation of a NUT-layer, through time-evolution, is quite distinctive, thus interesting. It is clear from the evolution that the thermodynamically driven monolayer structures (of AuNPs) at the air-water interface become thermodynamically unstable when transferred sequentially onto the solid substrate. The thermal energy (kT) and the partial change in the substrate surface energy (Δγ) create the instability and induce diffusion in the AuNPs, which in the presence of a net attractive force towards the substrate (arising from anisotropic interaction of the top AuNPs with the other AuNPs and/or hydrophobic substrate) tries to create a thermodynamically favourable and relatively stable NUT-layer through reorganization for a different duration. This happens if the number of AuNPs is less than or equal to the maximum number that can be accommodated within the NUT. The value of the NUT mainly depends on the particle size and a kT-energy related fluctuation of particles. Furthermore, the formation of the NUT-layer indicates that the hydrophobic-hydrophobic interaction mediated net attraction towards the substrate is long range, while the hydrophilic-hydrophobic interaction mediated repulsion and/or kT-energy induced fluctuations are short range.

2D Crystals in Three Dimensions: Electronic Decoupling of Single-Layered Platelets in Colloidal Nanoparticles.

2D crystals, single sheets of layered materials, often show distinct properties desired for optoelectronic applications, such as larger and direct band gaps, valley- and spin-orbit effects. Being atomically thin, the low amount of material is a bottleneck in photophysical and photochemical applications. Here, the formation of stacks of 2D crystals intercalated with small surfactant molecules is proposed. It is shown, using first principles calculations, that the very short surfactant methyl amine electronically decouples the layers. The indirect-direct band gap transition characteristic for Group 6 transition metal dichalcogenides is demonstrated experimentally by observing the emergence of a strong photoluminescence signal for ethoxide-intercalated WSe2 and MoSe2 multilayered nanoparticles with lateral size of about 10 nm and beyond. The proposed hybrid materials offer the highest possible density of the 2D crystals with electronic properties typical of monolayers. Variation of the surfactant's chemical potential allows fine-tuning of electronic properties and potentially elimination of trap states caused by defects.

Methods of the Synthesis of Silicon-Containing Nanoparticles Intended for Nucleic Acid Delivery

A promising new approach to the treatment of viral infections and genetic diseases associated with damaged or foreign nucleic acids in the body is gene therapy, i.e., the use of antisense oligonucleotides, ribozymes, deoxyribozymes, siRNA, plasmid DNA, etc. (therapeutic nucleic acids). Selective recognition of target nucleic acids by these compounds based on highly specific complementary interaction can minimize negative side effects, which occur with currently used low molecular weight drugs. To apply a new generation of therapeutic agents in medical practice, it is necessary to solve the problem of their delivery into cells. Silicon-containing nanoparticles are considered as promising carriers for this purpose due to their biocompatibility, low toxicity, ability to biodegradation and excretion from the body, as well as the simplicity of the synthesis and modification. Silicon-containing nanoparticles are divided into two broad categories: solid (nonporous) and mesoporous silicon nanoparticles (MSN). This review gives a brief overview of the creation of mesoporous, multilayer, and other silicon-based nanoparticles. The publications concerning solid silicon-organic nanoparticles capable of binding and delivering nucleic acids into cells are discussed in more detail with emphasis on methods for their synthesis. The review covers publications over the past 15 years, which describe the classical Stöber method, the microemulsion method, modification of commercial silica nanoparticles, and other strategies.

Effect of gain medium and graphene on the resonance energy transfer between two molecules positioned near a plasmonic multilayer nanoparticle

In this study, we investigate the transfer of energy from a donor molecule to an acceptor molecule nearby a spherical multilayer nanoparticle consisting of a core surrounded by two shells (core@shell@shell nanoparticle), with focus on the role of graphene and gain medium in the resonance energy transfer between molecules. We obtain analytical expressions for the interaction energy between the dipoles and the energy enhancement factor in a hybrid plasmonic nanoshell-molecular system consisting of a pair of molecules positioned near a plasmonic three-layer nanoparticle. Owing to the more flexible tunability of multishell nanoparticles, the resonance energy transfer can be enhanced and tuned from IR-visible-UV regions by controlling the size of the nanosphere core or shells. In addition to the effect of the gain medium which enhances the plasmonic resonance in order of magnitude, the impact of a graphene-coated three-layer nanosphere on the energy transfer is studied by taking into account the role of dipolar, quadrupolar, octupolar, hexadecapolar, and triakontadipolar plasmonic modes.

High‐reflection optical thin films based on SiO 2 /TiO 2 nanoparticles multilayers by dip coating

The alternately stacking layers of SiO2 and TiO2 nanoparticles with different refractive indices were fabricated to form the distributed Bragg reflectors on the silicon wafer by dip coating method. By appropriate design of the thickness of the quarter-wave layers, the peak reflectance region can be tuned from the blue-green to the infrared portion of the electromagnetic spectrum. The peak reflectance of 65% at 800 nm and at 1600 nm has been achieved using seven periods, respectively; meanwhile, compared with the simulation, 80% at 800 nm and 70% at 1620 nm for seven periods, respectively. The scanning electron microscopy and the atomic force microscope studies confirm the thickness uniformity achieved along the fabrication direction, and a good quality of surfaces and interfaces.

Catalytic graphitization of kraft lignin to graphene-based structures with four different transitional metals

Catalytic graphitization of kraft lignin to nano-materials was investigated over four transitional metal catalysts (Ni, Cu, Fe, and Mo) through a thermal treatment process under an argon flow at 1000 °C. The catalytic thermal process was examined using thermal gravimetric analysis (TGA) and temperature-programmed decomposition (TPD) experiments. The crystal structure and morphology of the thermal-treated metal-lignin samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. Catalytic graphitization of kraft lignin to nano-materials was investigated over four transitional metal catalysts (Ni, Cu, Fe, and Mo) through a catalytic thermal treatment process. It was observed that multi-layer graphene-encapsulated metal nanoparticles were the main products, beside along with some graphene sheets/flakes. The particle sizes and graphene shell layers were significantly affected by the promoted metals. BET surface areas of samples obtained from different metal precursors were in the range of 88–115 m2/g within the order of Ni- > Fe- > Mo- > Cu-. Thermal gravimetric analysis (TGA) and temperature-programmed decomposition (TPD) experimental results showed that adding transitional metals could promote the decomposition and carbonization of kraft lignin. The catalytic activity increased with an order of Mo≅Cu < Ni≅Fe. XRD results show that face-centered cubic (fcc) Cu crystals is formed in the thermal-treated Cu-lignin sample, fcc nickel phase for the Ni-lignin sample, β-Mo2C hexagonal phase for the Mo-lignin sample and α-Fe, γ-iron, and cementite(Fe3C) for the Fe-lignin sample. Average particle sizes of these crystal phases calculated using the Scherrer formula are 52.4 nm, 56.2 nm, 21.0 nm, 23.3 nm, 11.3 nm, and 32.8 nm for Ni, Cu, β-Mo2C, α-Fe, γ-iron, and Fe3C, respectively. Raman results prove that the graphitization activity of these four metals is in the order of Cu < Mo < Ni < Fe. Metal properties such as catalytic activity, carbon solubility, and tendency of metal carbide formation were related to the graphene-based structure formation during catalytic graphitization of kraft lignin process.

Adsorption Dynamics and Structure of Polycations on Citrate-Coated Gold Nanoparticles

Despite the widespread application of engineered multilayered polyelectrolyte-coated gold nanoparticles (AuNPs), their interparticle interaction is not fully understood in part because of a lack of molecular scale observation of the layer-by-layer assembly of the polyelectrolyte coating. While top-down coarse-grained models of polyelectrolyte-coated AuNPs have focused on polyelectrolytes of short length, from 10 to a 100 monomers represented as one charged bead per monomer, here we use molecular dynamics and bottom-up coarse-grained approaches to access more typical polymer lengths on the order of 200 monomers. Specifically, we simulate the adsorption dynamics and structure of one or two such long polycations on negatively charged 4 nm citrate-coated AuNPs within implicit or explicit solvents. The first polycation coats approximately half of the AuNP surface regardless of solvent model and leaves a significant part of the anionic citrate layer exposed to absorption by a second polycation. We find that the...

Self-Assembled Antimicrobial Nanomaterials.

Nanotechnology came to stay improving the quality of human life by reducing environmental contamination of earth and water with pathogens. This review discusses how self-assembled antimicrobial nanomaterials can contribute to maintain humans, their water and their environment inside safe boundaries to human life even though some of these nanomaterials display an overt toxicity. At the core of their strategic use, the self-assembled antimicrobial nanomaterials exhibit optimal and biomimetic organization leading to activity at low doses of their toxic components. Antimicrobial bilayer fragments, bilayer-covered or multilayered nanoparticles, functionalized inorganic or organic polymeric materials, coatings and hydrogels disclose their potential for environmental and public health applications in this review.

Nanophotonic particle simulation and inverse design using artificial neural networks.

We propose a method to use artificial neural networks to approximate light scattering by multilayer nanoparticles. We find that the network needs to be trained on only a small sampling of the data to approximate the simulation to high precision. Once the neural network is trained, it can simulate such optical processes orders of magnitude faster than conventional simulations. Furthermore, the trained neural network can be used to solve nanophotonic inverse design problems by using back propagation, where the gradient is analytical, not numerical.

Multilayer biopolymer/poly(ε-caprolactone)/polycation nanoparticles

Combining two or more materials for carrier construction is one of the topical approaches to avoid/diminish deficiencies and to increase functionality in delivery systems for bioactive compounds. In this context, here, multilayered nanoparticles comprising both natural (atelocollagen—AteCol; hyaluronic acid derivative—HA) and synthetic [poly(e-caprolactone)—PCL; polyethylenimine—PEI; poly(l-lysine)—PLL] polymers were prepared and characterized. The combination of a modified double-emulsion method with polymer modification reactions allowed improvement of the polymer particle’s functionality. Fourier transform infrared spectroscopy (FTIR), UV–Vis spectroscopy, fluorescence spectroscopy, dynamic light scattering, transmission/scanning electron microscopy and fluorescence microscopy investigations confirmed the obtention of the envisaged nanomaterials with the expected composition and structure. The double-layered biopolymer/PCL-based nanoparticles formed in a first synthesis step could be successfully coated with PEI and PLL. The gel electrophoresis assay attested the DNA packing ability of the formed nano-vehicles involving surface grafting of the former biopolymer/PCL-based nanoparticles in the case of both cationic polymers, for N/P ratios of 10 (PEI coating) and 3.5 (PLL coating), respectively. According to the FTIR registration, the protein’s native form was preserved. Considering the advantage of biocompatibility and high versatility (controlled size, tuned chemistry and biodegradation rate) some of the resulted nanomaterials may appear as potential candidates for biomedical uses (i.e., drug/gene delivery and tissue engineering).

Efficient upconversion fluorescence in NaYF4:Yb3+, Er3+/mNaYF4 multilayer core-shell nanoparticles

Here, we show a core-shell nanostructure which effectively improves NIR-to-visible upconversion quantum efficiency and luminescence intensity. The NaYF4:Yb3+, Er3+/mNaYF4 (m = 0, 1, 2, 3, 4, 5) core-shell nanoparticles are synthesized using a thermal decomposition method. The structure, morphology and fluorescence spectrum of the nanoparticles are confirmed by XRD, TEM and fluorometer. The average size of the as-prepared NaYF4:Yb3+, Er3+/mNaYF4 cores is about 8 nm while the thickness of the shells varies from 0.5 nm to 8 nm for different m values. With 980 nm excitation, the nanoparticles exhibit distinct emission peaks at 522 nm, 544 nm and 650 nm. It is noticed that an increasing shell thickness enhances their fluorescence intensity. The fluorescence lifetime and quantum yield of obtained multilayer NaYF4:Yb3+, Er3+/mNaYF4 nanoparticles are also discussed.

Co-encapsulation of dual drug loaded in MLNPs: Implication on sustained drug release and effectively inducing apoptosis in oral carcinoma cells

Combinations of natural bee wax flavones chrysin with a chemo drug have been exhibiting high potential with reduced adverse effect. To extend the synergistic effect of chrysin and improve the MLNPs (Multi Layer Nanoparticles) performance in drug release, layer-by-layer of poly [di(sodium carboxyphenoxy)phosphazene] (PDCPP) and poly (diallyldimethyl ammonium chloride) (PDADMAC) deposited on the CaCO3 nanoparticles (CCNPs) surface. The results suggest spherical MLNPs of 237 nm are formed with high drug loading content with enhanced cellular uptake. Under acidic conditions, multi layer structure effectively controls burst release, providing sustained drug release for long period. The combined effect of chrysin and cisplatin improved the cytotoxic potential of MLNPs at 25 μg.mL−1 concentration. Angiogenesis inhibitor chrysin activates reactive oxygen species (ROS) production and eventually leads to mitochondrial dysfunction. Furthermore, significant decreases of buccal pouch carcinoma in hamster model. Dual drug loaded MLNPs achieves 92% regressions of tumor volume as compared to cisplatin alone loaded MLNPs. In addition, Histopathology studies demonstrated the biocompatible effect of MLNPs on vital organs. This work provides a simple method to formulate multiple drugs in single nanosystem with high therapeutic efficacy on oral cancer.