Organization Of Nanoparticles Research Articles

Plasma Parameters During Nanoparticle-Enhanced Laser-Induced Breakdown Spectroscopy (NELIBS) in the Presence of Nanoparticle-Protein Conjugates.

Nanoparticle-enhanced laser-induced breakdown spectroscopy (NELIBS) is an optical emission technique based on the laser-induced plasma (LIP) on a sample after the deposition of plasmonic nanoparticles (NPs) on its surface. The employment of the NPs allows an enhancement of the signal with respect to the one obtained with the conventional laser-induced breakdown spectroscopy (LIBS) enabling an extremely high sensitivity and very low limits of detection compared with the LIBS performance. Recently, NELIBS was used for monitoring the NP protein corona formation. As a matter of fact, the NPs in the presence of proteins adsorbed on the surface change their surface properties, therefore the sensing of protein corona formation was possible because of the strong dependence of NELIBS effects on the NP organization on the substrate, which in turn is deeply affected by the surface properties of the NPs. A correlation was found between NELIBS enhancement and the structure of the NP-protein conjugate in terms of protein content absorbed on the NP surface. An interesting question that was not yet exploited regards the role of LIP during the NELIBS when the NPs are covered with proteins. Since the presence of organic matter can strongly quench the LIP emission, the study of the LIP properties during protein corona sensing by NELIBS is of interest for two main reasons: (i) to understand whether the plasma parameters can vary in the presence of proteins adsorbed on the NP surface and (ii) to investigate how and if the plasma parameters themselves can influence the NELIBS processes. With this aim, the study of plasma parameters, i.e., electron densities and temperatures, during the sensing of NP protein corona by NELIBS is presented and discussed. The NPs used during these experiments were ultrapure gold NPs (AuNPs) produced by pulsed laser ablation in liquid, which are stable without any stabilizer. The human serum albumin protein is used to form AuNP-protein conjugates further deposited on a titanium target in NELIBS measurements. Dynamic light scattering, surface plasmon resonance spectroscopy, and laser Doppler electrophoresis for ζ-potential determination were employed to monitor the protein coverage of NP surface in the conjugate solutions before the NELIBS measurements.

Electric, magnetic, and shear field-directed assembly of inorganic nanoparticles.

Ordered assemblies of inorganic nanoparticles (NPs) have shown tremendous potential for wide applications due to their unique collective properties, which differ from those of individual NPs. Various assembly methods, such as external field-directed assembly, interfacial assembly, template assembly, biomolecular recognition-mediated assembly, confined assembly, and others, have been employed to generate ordered inorganic NP assemblies with hierarchical structures. Among them, the external field-directed assembly method is particularly fascinating, as it can remotely assemble NPs into well-ordered superstructures. Moreover, external fields (e.g., electric, magnetic, and shear fields) can introduce a local and/or global field intensity gradient, resulting in an additional force on NPs to drive their rotation and/or translation. Therefore, the external field-directed assembly of NPs becomes a robust method to fabricate well-defined functional materials with the desired optical, electronic, and magnetic properties, which have various applications in catalysis, sensing, disease diagnosis, energy conversion/storage, photonics, nano-floating-gate memory, and others. In this review, the effects of an electric field, magnetic field, and shear field on the organization of inorganic NPs are highlighted. The methods for controlling the well-ordered organization of inorganic NPs at different scales and their advantages are reviewed. Finally, future challenges and perspectives in this field are discussed.

Controlling the anisotropic self-assembly of polybutadiene-grafted silica nanoparticles by tuning three-body interaction forces.

Recently, the significant improvements in polymer composites properties have been mainly attributed to the ability of filler nanoparticles (NPs) to self-assemble into highly anisotropic self-assembled structures. In this work, we investigate the self-assembly of core-shell NPs composed of a silica core grafted with polybutadiene (PB) chains, generating the so-called "hairy" NPs (HNPs), immersed in tetrahydrofuran solvent. While uncoated silica beads aggregate forming uniform compact structures, the presence of a PB shell affects the silica NPs organization to the point that by increasing the polymer density at the corona, they tend to self-assemble into linear chain-like structures. To reproduce the experimental observations, we propose a theoretical model for the two-body that considers the van der Waals attractive energy together with the polymer-induced repulsive steric contribution and includes an additional three-body interaction term. This term arises due to the anisotropic distribution of PB, which increases their concentration near the NPs contact region. The resulting steric repulsion experienced by a third NP approaching the dimer prevents its binding close to the dimer bond and favors the growth of chain-like structures. We find good agreement between the simulated and experimental self-assembled superstructures, confirming that this three-body steric repulsion plays a key role in determining the cluster morphology of these core-shell NPs. The model also shows that further increasing the grafting density leads to low-density gel-like open structures.

Exploiting Self-assembly of Block Copolymers to Fabricate Nanocomposite Thin Films with Controlled Morphology at Nanoscale

As the advantageous properties of nanoparticles (NPs) often emerge only when appropriate coupling and exchange phenomena between the NPs can take place, the control of the inter-particle distance, regular ordering, and location of the nanoparticles onto solid supports is a critical issue. A robust method to control the spatial organization of NPs onto solid supports, based on the use of self-assembling di-block copolymers (BCPs) as structure-guiding material, is reported. Two different polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) BCPs, characterized by a different PS volume fraction, were used as matrices for the fabrication of nanocomposite thin films with cylindrical and lamellar morphologies controlled at the nanoscale. Selective inclusion of surface functionalized gold (Au) and zinc oxide (ZnO) NPs of appropriate size in the PS nanodomains was achieved from dispersions of the BCPs and NPs in a common solvent. The orientation of the BCPs cylinder and lamellar nanodomains in spin-coated thin films was controlled by solvent and thermal annealing protocols, coupled with techniques of surface neutralization.

Symmetry-Broken Patches on Gold Nanoparticles through Deficient Ligand Exchange.

Symmetry-broken nanoparticles (NPs) are important building blocks with directional interparticle interaction as a key to access the precise organization of NPs macroscopically. We report a facile, one-pot synthetic approach to prepare high-quality symmetry-broken plasmonic gold NPs (AuNPs). Symmetry-broken patterning is achieved through deficient ligand exchange of isotropic AuNPs with thiol-terminated polystyrene (PS-SH) in the presence of an amphiphilic polymer surfactant. The concentration of PS-SH plays a dominant role in tuning surface patterning and coverage of AuNPs. The formation of asymmetric surface patches arises from the interplay between the conformational entropy of polymer ligands and the interfacial energy between polymer-grafted AuNPs and the solvent. Our method illustrates new paradises to design asymmetric NPs with directional interparticle interactions to access the precise organization of NPs.

Selective stabilization of blue phase liquid crystals using spherical and rod-shaped colloidal nanocrystals

Optimizing strategies used for improving the stability and properties of blue phase (BP) liquid crystals directly impact device performance. Various factors ranging from molecular structure to sample size and substrate conditions can influence selective reflection and electro-optics of BPs. More recently, the technique of incorporating colloidal nanoparticle (NP) assemblies has been used to enhance BP ranges. In cubic BPs, disclination networks can act as trapping centers for NPs, reducing the high elastic energy cost of these regions, favoring BP stability. Organization of NPs in the defect regions can sustain stable 3D colloidal structures, widening the scope and applicability of BPs as photonic materials. Physical and chemical properties, size, and shape of the NPs can also determine the utilization of BPs for advanced applications like lasers and high quality displays. In view of this, a mixture of two calamitic chiral compounds in which all three BPs, viz., BPI, BPII, and BPIII, were induced was combined with rod-shaped CdSe/CdS quantum rods (QRs) and spherical CdSe quantum dots (QDs), which were specifically chosen due to their exceptional optical properties. This also provided an opportunity to investigate the effect of the shape of the NPs on the preferential stabilization of the BPs and on the electro-optic Kerr effect. QRs were found to be more efficient in enhancing the overall BP range, with an almost twofold increase of ∼27 °C with ∼0.5 wt. %. On the other hand, with QDs, the BP range showed an initial increase of 20 °C for ∼0.3 wt. %, which, however, decreased with a further increase in QDs. Another major difference is that the Kerr effect was active only in the BPIII in the case of QDs but is measurable in both cubic BPI and BPII in the case of QRs. The results have been described in terms of the organization of the nanocrystals within the defect lines and the lattice orientations imposed by the substrates.

2D and 3D Ruthenium Nanoparticle Covalent Assemblies for Phenyl Acetylene Hydrogenation

The bottom‐up covalent assembly of metallic nanoparticles (NP) represents one of the innovative tools in nanotechnology to build functional heterostructures, with the resulting assemblies showing superior collective properties over the individual NP for a broad range of applications. The ability to control the dimensionality of the assembly is one of the major challenges in designing and understanding these advanced materials. Here, two new organic linkers were used as building blocks in order to guide the organization of Ru NP into two‐ or three‐dimensional covalent assemblies. The use of a hexa‐adduct functionalized C60 leads to the formation of 3D networks of 2.2 nm Ru NP presenting an interparticle distance of 3.0 nm, and the use of a planar carboxylic acid triphenylene derivative allows the synthesis of 2D networks of 1.9 nm Ru NP with an interparticle distance of 3.1 nm. The Ru NP networks were found to be active catalysts for the selective hydrogenation of phenylacetylene, reaching good selectivity toward styrene. Overall, we demonstrated that catalyst performances are significantly affected by the dimensionality (2D vs. 3D) of the heterostructures, which can be rationalize based on confinement effects.

Mechanical properties of glassy polymers with controlled NP spatial organization

Industrially viable processes enabling effective control of nanoparticle (NP) spatial organization in polymers are vitally important for achieving potential of nano-composites as building blocks of dynamic composites. Here, we report on the small and large strain mechanical properties of glassy polymers with spatial organization of spherical NPs controlled by the balance of the (polymer-NP)/(NP-solvent) interfacial attraction and mixing conditions. While strong polymer-NP attraction yielded good NP dispersion regardless of the mixing rate, weak polymer-NP attraction and low shear rate mixing resulted in chain bound NP clusters. Polymers with individually dispersed NPs exhibited the largest elastic moduli and strength while polymers filled with deformable chain bridged NP clusters possessed the largest ductility, at the same NP content. Hybrid systems, consisting of chain bridged NP clusters embedded in a polymer with individually dispersed NPs, exhibited simultaneous enhancement of stiffness, strength and ductility with its extent tunable by the cluster content. Our results confirm the pivotal role of NP spatial organization in translating the nano- and micro-scale phenomena to macro-scale mechanical response of polymer nano-composites. The obtained knowledge enables the design of additive fabrication technologies capable of employing polymer nano-composites in manufacturing of lightweight, functional engineering structures.

Effect of ZnO nanoparticles doping on structural, dielectric and interfacial behavior of polyoxyethylene (20) sorbitan/ethylene glycol lyotropic phases

ABSTRACT We are reporting on the interaction of zinc oxide (ZnO) nanoparticles (NPs) with the lyotropic phase comprises of Polyoxyethylene (20) sorbitan monolaurate and protic solvent ethylene glycol. The concentration of the NPs has been varying from 0.05 to 0.5 wt%. Multiwall lamellar and inverse phases have been observed at lower and higher concentration of ZnO NPs doping. Interestingly, the organization of ZnO NPs on the periphery and inside the periphery of ring-like structures has been observed at lower and higher concentration of the dopant, respectively. Such organization of the NPs can be explained considering interfacial interaction amid host and dopant and may also attribute to the adsorption mechanisms of surfactant. Effects of NPs doping on the dielectric dynamics has also been examined. About 32.6% decrease in the dielectric permittivity has been noticed at higher NPs doping. Such decrement in permittivity could be a result of the screening of the ZnO NPs dipole moment by the adsorption of surfactant molecules on their surface. Relaxation and optical parameters of the non-doped and doped mixtures have also been discussed.

(Invited) Operando Optical Monitoring of Nanoparticle Electrodeposition

Electrodes, made of nanoparticles (NPs), are key components in electrochemistry to store and convert energy. The nanometer scale allows exalting surface properties and revealing, in addition to the composition, the importance of size, shape and NP organization on the kinetic and thermodynamic performance of devices. Therefore, the use of ultra-small objects and the study of their formation and reactivity appear as one of the best ways to meet the current energy challenges.Herein, electrodeposition, one of the most popular electrochemical methods for producing nanostructured electrodes, is coupled to an ultra-sensitive interferometric microscopy technique to probe operando the heterogeneity of electrochemical processes at the single NP level. The strategy is illustrated through the monitoring of the electrochemical growth of individual silver NPs, whose sizes can be tracked dynamically down to 10 nm in diameter. Optical images are further used to quantify the presence of metal nanoclusters at the early stages of the electrodeposition and to highlight galvanic reactions occurring between NPs with distinct surface free energies.As interferometric microscopy relies on refractive index changes, the technique can be applied to many kinds of nanomaterials and electrochemical experiments. For example, the optical coupling has proved to be useful for studying NP transformation.Figure. Schematic representation of the coupling and same location microscopy experiment with a scanning electron microscope.J.-F. Lemineur, J.-M. Noël, C. Combellas, D. Ausserré, F. Kanoufi. Angew. Chem. Int. Ed., 2018, 57,11998-12002.J.-F. Lemineur, J.-M. Noël, C. Combellas, D. Ausserré, F. Kanoufi. Faraday. Discuss., 2018, 210, 381-395. Figure 1

Effects of chain stiffness and shear flow on nanoparticle dispersion and distribution in ring polymer melts

The dispersion behavior and spatial distribution of nanoparticles (NPs) in ring polymer melts are explored by using molecular dynamics (MD) simulations. As polymer-NP interactions increase, three general categories of polymer-mediated NP organization are observed, namely, contact aggregation, bridging, and steric dispersion, consistent with the results of equivalent linear ones in previous studies. In the case of direct contact aggregation among NPs, the explicit aggregation-dispersion transition of NPs in ring polymer melts can be induced by increasing the chain stiffness or applying a steady shear flow. Results further indicate that NPs can achieve an optimal dispersed state with the appropriate chain stiffness and shear flow. Moreover, shear flow cannot only improve the dispersion of NPs in ring polymer melts but also control the spatial distribution of NPs into a well-ordered structure. This improvement becomes more evident under stronger polymer-NP interactions. The observed induced-dispersion or ordered distribution of NPs may provide efficient access to the design and manufacture of high-performance polymer nanocomposites (PNCs).

DNA-functionalized gold nanoparticle assemblies for Surface Enhanced Raman Scattering

The programmable assembly of DNA strands is a promising tool for building tailored bottom-up nanostructures. Here, we present a plasmonic nanosystem obtained by the base-pairing mediated aggregation of gold nanoparticles (NPs) which are separately functionalized with two different single-stranded DNA chains. Their controlled assembly is mediated by a complementary DNA “bridge” sequence. We monitor the formation of DNA assembled NP aggregates in solution, and we study their Surface Enhanced Raman Scattering (SERS) response by comparison with the single NP constituents. We interpret the revealed SERS signatures in terms of the molecular and NP organization at the nanoscale, demonstrating that the action of the DNA bridge molecule yields regular NP aggregates with controlled interparticle distance and reproducible SERS response. In perspective, this demonstrates the potential of the present system as a stable, biocompatible, and recyclable SERS sensor.

Hierarchical Structure and Dynamics of a Polymer/Nanoparticle Hybrid Displaying Attractive Polymer–Particle Interaction

X-ray photon correlation spectroscopy and small-angle X-ray scattering were used to study the thermally driven motion and hierarchical structure of palladium (Pd) nanoparticles (NPs) in the concentrated solutions composed of polymers with different molecular weights. The Pd NPs were formed by in situ reduction of palladium(II) acetylacetonate (Pd(acac)2) in the solution of poly(2-vinylpyridine) (P2VP) and benzyl alcohol which acted as the reduction agent and solvent. Below the entanglement molecular weight (Me) of P2VP, a diffusion mode was found together with a fractal structure built up by the primary particles spanning over a broad range of length scales. Above Me, a subdiffusive motion was identified along with diffusive motion, and the hybrids formed a fractal structure built by the local clusters assembled by primary particles. The structural differences were attributed to different kinetic pathways of NP organization mediated by attractive interaction between P2VP and Pd NPs as well as the viscosit...

Roadmap of ellipsometric characterization of plasmonic nanoparticles

This paper reports recent advances in ellipsometric characterization of silver and gold nanoparticles (NPs). Three systems are investigated: films composed of Au NPs distributed in shape, films with a gradient of concentration of Ag NPs, and colloidal suspensions composed of Au NP chains. The authors show that ellipsometry is highly sensitive to the plasmon resonance of NPs. This later can be used as an efficient probe of the NP morphology. The ellipsometric results are systematically compared to those that are obtained by transmission electron microscopy. The authors demonstrate that quantitative insights such as the shape distribution, the concentration, and the organization of NPs can be extracted from ellipsometric spectra.

Nanoparticle Organization by Growing Polyethylene Crystal Fronts.

We investigate the crystallization-induced ordering of C18 grafted 14 nm diameter spherical silica nanoparticles (NPs) in a short chain (Mw = 4 kDa, ĐM ≈ 2.3) polyethylene and a commercial high-density polyethylene (Mw = 152 kDa, ĐM ≈ 3.2) matrix. For slow isothermal crystallization of the low molecular weight matrix, the NPs segregate into the interlamellar regions. This result establishes the generality of our earlier work on poly(ethylene oxide) based materials and suggests that crystallization can be used to control NP dispersion across different polymer classes. The incompatibility between the particles and the matrix in the Mw = 152 kDa results in a competition between filler organization and filler agglomeration. The mechanical properties improve due to the addition of NPs and are further enhanced by particle organization, even for the case of the macrophase-separated mixtures in the Mw = 152 kDa matrix. In contrast, dielectric behavior is strongly affected by the scale of NP organization, with the lower molecular weight matrix showing more significant increases in permittivity due to the local scale of NP ordering.

Development of Metal Nanoparticle Catalysis toward Drug Discovery.

Transition-metal nanoparticles (NPs) catalysts supported on solid material represent one of the most important subjects in organic synthesis due to their reliable carbon-carbon or carbon-heteroatom bond-forming cross-coupling reactions. Therefore methodologically and conceptually novel immobilization methods for nonprecious transition-metal NPs are currently required for the development of organic, inorganic, green, materials, and medicinal chemistry. We discovered a self-assembled Au-supported Pd NPs catalyst (SAPd(0)) and applied it as a catalyst to Suzuki-Miyaura coupling, Buchwald-Hartwig reaction, Carbon(sp2 and sp3)-Hydrogen bond functionalization, double carbonylation, removal of the allyl protecting groups of allyl esters, and redox switching. SAPd(0) comprises approximately 10 layers of self-assembled Pd(0) NPs, whose size is less than 5 nm on the surface of a sulfur-modified Au. The Pd NPs are wrapped in a sulfated p-xylene polymer matrix. We thought that the self-assembled Au-supported Pd NPs could be made by in situ metal NP and nanospace simultaneous organization (PSSO). This methodology involves 4 kinds of simultaneous procedures: i) reduction of a higher valence metal salt, ii) growth of metal NPs with appropriate size, iii) growth of a matrix with appropriate pores, and iv) wrapping of the metal NPs by matrix nanopores. This methodology is different from previously reported metal NPs-immobilizing methods, which use solid supports with preformed pores or coordination sites. We also applied the in situ PSSO method to prepare various immobilized transition-metal NPs, including base metals. For example, the in situ PSSO method can be applicable to easily prepare Ni, Ru, and Fe NPs with good recyclability and low metal leaching for use in organic synthesis.

Curcumin- and Fish Oil-Loaded Spongosome and Cubosome Nanoparticles with Neuroprotective Potential against H2O2-Induced Oxidative Stress in Differentiated Human SH-SY5Y Cells

Many phytochemical antioxidant compounds, including curcumin (CU), are water-insoluble and thus require delivery carriers in order to increase their bioavailability for in vivo applications. Oxidative stress-related apoptosis is a common cause for the neuronal loss in the progression of neurodegenerative diseases. Lipid nanoparticles (NPs) with internal self-assembled liquid crystalline structures present strong interest as safe drug delivery systems for neuronal regeneration through combination therapies. Here, we report spongosome and cubosome lipid NPs, which co-encapsulate CU and fish oil (FO), rich in ω-3 polyunsaturated fatty acids. The performed structural investigation by synchrotron small-angle X-ray scattering evidenced the liquid crystalline organization of the self-assembled NPs. The encapsulation efficiency for CU in the lipid nanocarriers was found to be higher as compared to that reported for polymer-based carriers. The cytotoxicity of the blank and antioxidant-loaded nanocarriers was negli...

Helicoidal Patterning of Nanorods with Polymer Ligands.

Chiral packing of ligands on the surface of nanoparticles (NPs) is of fundamental and practical importance, as it determines how NPs interact with each other and with the molecular world. Herein, for gold nanorods (NRs) capped with end-grafted nonchiral polymer ligands, we show a new mechanism of chiral surface patterning. Under poor solvency conditions, a smooth polymer layer segregates into helicoidally organized surface-pinned micelles (patches). The helicoidal morphology is dictated by the polymer grafting density and the ratio of the polymer ligand length to nanorod radius. Outside this specific parameter space, a range of polymer surface structures was observed, including random, shish-kebab, and hybrid patches, as well as a smooth polymer layer. We characterize polymer surface morphology by theoretical and experimental state diagrams. The helicoidally organized polymer patches on the NR surface can be used as a template for the helicoidal organization of other NPs, masked synthesis on the NR surface, as well as the exploration of new NP self-assembly modes.

Helicoidal Patterning of Nanorods with Polymer Ligands

AbstractChiral packing of ligands on the surface of nanoparticles (NPs) is of fundamental and practical importance, as it determines how NPs interact with each other and with the molecular world. Herein, for gold nanorods (NRs) capped with end‐grafted nonchiral polymer ligands, we show a new mechanism of chiral surface patterning. Under poor solvency conditions, a smooth polymer layer segregates into helicoidally organized surface‐pinned micelles (patches). The helicoidal morphology is dictated by the polymer grafting density and the ratio of the polymer ligand length to nanorod radius. Outside this specific parameter space, a range of polymer surface structures was observed, including random, shish‐kebab, and hybrid patches, as well as a smooth polymer layer. We characterize polymer surface morphology by theoretical and experimental state diagrams. The helicoidally organized polymer patches on the NR surface can be used as a template for the helicoidal organization of other NPs, masked synthesis on the NR surface, as well as the exploration of new NP self‐assembly modes.

Single-Step Organization of Plasmonic Gold Metamaterials with Self-Assembled DNA Nanostructures

Self-assembled DNA nanostructures hold great promise as nanoscale templates for organizing nanoparticles (NPs) with near-atomistic resolution. However, large-scale organization of NPs with high yield is highly desirable for nanoelectronics and nanophotonic applications. Here, we design five-strand DNA tiles that can readily self-assemble into well-organized micrometer-scale DNA nanostructures. By organizing gold nanoparticles (AuNPs) on these self-assembled DNA nanostructures, we realize the fabrication of one- and two-dimensional Au nanostructures in single steps. We further demonstrate the one-pot synthesis of Au metamaterials for highly amplified surface-enhanced Raman Scattering (SERS). This single-step and high-yield strategy thus holds great potential for fabricating plasmonic metamaterials.