Assembly Of Nanorods Research Articles

Multicolor Photonic Pigments for Rotation-Asymmetric Mechanochromic Devices.

Photonic crystals are extensively explored to replace inorganic pigments and organic dyes as coloring elements in printing, painting, sensing, and anti-counterfeiting due to their brilliant structural colors, chemical stability, and environmental friendliness. However, most existing photonic-crystal-based pigments can only display monochromatic colors once made, and generating multicolors has to start with designing different building blocks. Here, a novel photonic pigment featuring highly tunable structural colors in the entire visible spectrum, made by the magnetic assembly of monodisperse nanorods into body-centered-tetragonal photonic crystals, is reported. Their prominent magnetic and crystal anisotropy makes it efficient to generate multicolors using one photonic pigment by magnetically controlling the crystal orientation. Further, the combination of angle-dependent diffraction and magnetic orientation control enables the design of rotation-asymmetric photonic films that display distinct patterns and encrypted information in response to rotation. The efficient multicolor generation through precise orientational control makes this novel photonic pigment promising in developing high-performance structural-colored materials and optical devices.

Spindle-like-aggregating behavior of hydroxyapatite nanorods in polyacrylic acid aqueous system

The aggregating behavior of hydroxyapatite (HAP) nanorods plays a central role in the mechanism of biomimetic mineralization. In this study, the spindle-like aggregating behavior of hydroxyapatite (HAP) nanorods was studied by ultrasonically dispersing HAP in a polyacrylic acid (PAA) aqueous system. Unlike the quick aggregation and precipitation of HAP nanorods without PAA, the spindle-like primary aggregations formed herein could be suspended in water with good stability. The preferential adsorption of PAA on the side surface of HAP nanorods generated steric repulsion opposite to the van der Waals interaction in the radial direction. Accordingly, with an increase in the molar ratio of PAA[-COOH-]/HAP, the HAP nanorods showed a tendency to form spindle-like primary aggregations with decreased diameter and increased aspect ratio. The resulting aggregates possessed sufficient repulsion (steric repulsion and electric double layer repulsion) to overcome van der Waals interactions to remain suspended and dispersed. This study revealed the mechanism of aggregating HAP nanorods into spindle-like aggregates by extended Derjaguin–Landau–Verwey–Overbeek theory, including the steric stabilization mode. We believe that this study will facilitate the ordered structuring of minerals in hard-tissue mineralization processes.

Coordination confinement pyrolysis to hollow sea urchin shaped composite with embedded ultrasmall Co/Ni alloy for overall water splitting

Electrocatalytic water splitting has been extensively studied for producing clean fuels in energy conversion and utilization. However, the huge challenge is remaining existence for developing efficient and low-cost non-noble metal electrocatalysts. Herein, an efficient hollow sea urchin-shaped water-splitting catalyst was prepared by coordination confinement pyrolysis strategy, in which the superminiature Co/Ni alloy (ca. 5 nm) was embedded into the nanorods assembly unit successfully. This as-synthesized catalyst not only reveals satisfactory catalytic efficiencies with 70 and 296 mV overpotentials for HER and OER at the current density of 10 mA cm−2, but also demonstrates the total stabilities for HER, OER, and over water splitting after long-term electrolytic process with the negligible potentials increase by 2.8%, 2.9%, and 1.8%. Therefore, the catalyst integrates the advantages of superminiature Co/Ni alloy particles, hollow structure, and slender nanorods, which could provide a new route to design and prepare other efficient electrocatalysts.

Self-Assembly Mechanism of Complex Corrugated Particles.

A variety of inorganic nanoscale materials produce microscale particles with highly corrugated geometries, but the mechanism of their formation remains unknown. Here we found that uniformly sized CdS-based hedgehog particles (HPs) self-assemble from polydisperse nanoparticles (NPs) with diameters of 1.0-4.0 nm. The typical diameters of HPs and spikes are 1770 ± 180 and 28 ± 3 nm, respectively. Depending on the temperature, solvent, and reaction times, the NPs self-assemble into nanorods, nanorod aggregates, low-corrugation particles, and other HP-related particles with complexity indexes ranging from 0 to 23.7. We show that "hedgehog", other geometries, and topologies of highly corrugated particles originate from the thermodynamic preference of polydisperse NPs to attach to the growing nanoscale cluster when electrostatic repulsion competes with van der Waals attraction. Theoretical models and simulations of the self-assembly accounting for the competition of attractive and repulsive interactions in electrolytes accurately describe particle morphology, growth stages, and the spectrum of observed products. When kinetic parameters are included in the models, the formation of corrugated particles with surfaces decorated by nanosheets, known as flower-like particles, were theoretically predicted and experimentally observed. The generality of the proposed mechanism was demonstrated for the formation of mixed HPs via a combination of CdS and Co3O4 NPs. With unusually high dispersion stability of HPs in unfavorable solvents including liquid CO2, mechanistic insights into HP formation are essential for their structural adaptation for applications from energy storage, catalysis, water treatment, and others.

Dimensional constraints favour high temperature anatase phase stability in TiO2 nanorods

High temperature stable anatase phase TiO2 nanostructures have the potential to advance the fields such as photocatalysis, solar cells and batteries. However, it is challenging to grow TiO2 nanostructures that can retain the anatase phase at high temperatures. Here, we report slanted TiO2 nanorods grown on Si substrates by glancing angle deposition technique employing electron beam evaporation to showcase the anatase phase stability up to 800 °C. FESEM surface morphology shows that the nanorods started deforming above 600 °C and collapsed at 800 °C. We carried out image processing of the nanorods assembly and quantified the deformation with annealing temperature. The x-ray diffraction and Raman spectroscopy utilized for the phase information showed that the anatase phase is stable even at 800 °C. Further, we have studied the effect of deformation on wettability of the nanorods system and found that annealed samples are superhydrophilic. Remarkably, the annealed TiO2 nanorods have transformed to hydrophobic when kept in the dark storage due to the structural contribution to contact angle rather than surface energy. Notably, the hydrophobicity increases with time, which was studied for 25 months. The stable high temperature anatase phase could find application in the solar cells, photocatalysis, smart windows, self-cleaning coatings, etc.

Interfacial Assembly of Nanowire Arrays toward Carbonaceous Mesoporous Nanorods and Superstructures

AbstractSynthesis of anisotropic carbonaceous nano‐ and micro‐materials with well‐ordered mesoporous structures has attracted increasing attention for a broad scope of applications. Although hard‐templating method has been widely employed, overcoming the viscous forces to prepare anisotropic mesoporous materials is particularly challenging via the universal soft‐templating method, especially from sustainable biomass as a carbon resource. Herein, the synthesis of biomass‐derived nanowire‐arrays based mesoporous nanorods and teeth‐like superstructures is reported, through a simple and straightforward polyelectrolyte assisted soft‐templating hydrothermal carbonization (HTC) approach. A surface energy induced interfacial assembly mechanism with the synergetic interactions between micelles, nanowire, nanorods, and polyelectrolyte is proposed. The polyelectrolyte acts not only as a stabilizer to decrease the surface energy of cylindrical micelles, nanowires and nanorods, but also as a structure‐directing agent to regulate the oriented attachment and anisotropic assembly of micelles, nanowires, and nanorods. After a calcination treatment, the carbon nanorod and teeth‐like superstructure are successfully coupled with Ru to directly produce supported catalysts for the hydrogen evolution reaction, exhibiting much better performance than the isotropic nanospheres based catalyst. This HTC approach will open up new avenues for the synthesis of anisotropic materials with various morphologies and dimensions, expanding the palette of materials selection for many applications.

Ultrasonication pretreatment assisted rapid co-assembly of cellulose nanocrystal and metal ion for multifunctional application

Co-assembly of metal ion and cellulose nanocrystals (CNC) is a promising strategy to fabricate novel iridescent CNC materials with advanced applications. By combining ultrasonication pretreatment and vacuum-assisted self-assembly (VASA) technique, a facile and rapid strategy is proposed to prepare the Mn2+-doped carboxylated CNC (C-CNC) iridescent films with multifunctional application. The ultrasonication pretreatment temporarily disassembles the aggregates of C-CNC nanorods caused by the electrostatic interaction between negative charged C-CNC and Mn2+. The subsequent VASA process accelerates the self-assembly of chiral liquid crystals prior to the re-agglomeration of C-CNC by the bridge effect of Mn2+. Furthermore, the as-prepared Mn2+/CNC film exhibits a rapid and visible color change in ammonia atmosphere along with the formation of MnO2. The reversible change can be realized by the stimulation of reducing agent. The derived MnO2/C-CNC composite film displays efficient removal of methylene blue dye in aqueous solution by both of adsorption and degradation procedure.

Effect of Nanorod Physical Roughness on the Aggregation and Percolation of Nanorods in Polymer Nanocomposites.

Using molecular dynamics simulations, we elucidate the effect of nanorod roughness on nanorod aggregation, dispersion, and percolation in polymer nanocomposites (PNCs). By choosing coarse-grained models that enable systematic variation of the nanorod roughness and by selecting purely repulsive pairwise interactions for nanorods and polymer chains, we show how nanorod roughness affects the entropic driving forces for various PNC morphologies. At this entropically driven limit, we find that increasing nanorod roughness hinders nanorod aggregation and promotes nanorod percolation in the polymer melt. As nanorod roughness increases, the nanorod volume fraction needed to induce nanorod aggregation also increases. Increasing nanorod roughness increases the configurational entropy of the polymer chains and lowers the entropically induced depletion attraction between nanorods.

C-amidation of substituted β 3 oligoamides yields novel supramolecular assembly motif

N-acylated substituted β 3 oligoamides are known to form unique supramolecular nanorods based on a 3-point hydrogen bond self-assembly motif. This motif is an intermolecular extension of the hydrogen bonding network that stabilizes the 14-helix secondary structure unique to β 3 oligoamides. Acetylation of the N-terminus of the molecule provides the necessary third hydrogen bond pair of the motif. Here, the possibility of introducing the third hydrogen bond pair via amidation of the C terminus is investigated. While similar in purpose, this modification introduces a chemically distinct new self-assembly motif, also removing the bulky carboxyl group that does not fold into the 14 helix positioning instead as a side chain. Three substituted β 3 oligoamide variants with the base sequence LIA (where the letters denote β 3 residues with side chains analogous to α amino acids) were compared: N-acylated Ac-β 3[LIA] as a reference, C-amidated β 3[LIA]-CONH2, and β 3[LIA] with free unmodified N and C termini as a negative control. The three variants were dissolved in water to promote self-assembly. The self-assembly was characterised using mid- and far-infrared spectroscopy, small angle x-ray scattering (SAXS) and atomic force microscopy (AFM). IR measurements confirmed that all three samples were in a similar conformation, consistent with pseudo 14-helical secondary structures. Far-infrared spectroscopy measurements of β 3[LIA]-CONH2 showed distinct peaks consistent with highly organised skeletal modes, i.e. regular supramolecular assembly, that was largely absent from the other two oligoamides. Modelling of SAXS data is consistent with elliptical cylinder structures resulting from nanorod bundling for both β 3[LIA]-CONH2 and Ac-β 3[LIA], but not in the unmodified sample. Consistently, AFM imaging showed large nanorod bundling structures in β 3[LIA]-CONH2, varied bundling structures in Ac-β 3[LIA], and only aggregation in β 3[LIA]. Amidation showed much more organised and robust assembly compared to acetylation, providing a new, easy to synthesize self-assembly motif for helical nanorod assembly that is similar but distinct to N-acylation

Optimizing SERS performance through aggregation of gold nanorods in Langmuir-Blodgett films

Nanoparticles with a high degree of anisotropy are characterized by large electromagnetic field enhancements at the single-particle level; however, their arrangement into aggregated structures does not lead to significantly better performance. Surprisingly, for nanorods a superior accumulation of hot spots is present at surface coverages above 60%, which ensures a higher efficiency for surface-enhanced Raman spectroscopy (SERS). In this study, we produced pegylated gold nanorods in Langmuir-Blodgett layers in order to optimize SERS performance for the ultrasensitive detection of molecules, by tuning plasmonic coupling and nanoparticle surface coverage. To understand the arrangement of the nanorods in Langmuir and Langmuir-Blodgett layers, we performed spectroscopic and microscopic analysis of the obtained films. Based on the compression isotherms of the nanorods, we proposed the best conditions for nanoplatform design. The Raman enhancement factor was around 2·105 with a deposition surface pressure equal to 12 mN·m−1. Due to the polymer’s presence at the surface of the nanorods and the dewetting process, specific dendritic-like aggregates were observed on the solid substrate. The results obtained indicate the significance of further studies on the arrangement of metallic nanoparticles in monolayers, taking into account the size and shape of the nanoparticles, as well as the type of stabilizing ligands at their surface.

Spontaneous symmetry breaking of semiconductor nanorods and assemblies

In this issue of <i>Chem</i>, Che and co-workers assessed the formation of the helical structure of CdS@CdSe nanorods without the use of chiral reagents. Spontaneous chiral symmetry breaking occurred in the chiral CdSe@CdS nanorod assemblies, which was probably caused by the majority rule.

Assembly of gold nanorods with L-cysteine reduced graphene oxide for highly efficient NIR-triggered photothermal therapy

Near-infrared (NIR) photothermal therapy is an effective partner to the chemotherapy of tumors with the merits of high therapeutic ability and slight side effect on normal tissues. Herein, we synthesized gold nanorods and assembled them with L-cysteine reduced graphene oxide (AuNR@Lcyst-rGO) for efficient photothermal therapy. The high therapeutic efficacy of AuNR@Lcyst-rGO can be due to the high photothermal effect of gold nanorods and reduced graphene oxide, and the synergistic effect of them. The nontoxicity of L-cysteine also guarantees the comfortable biocompatibility of reduced graphene oxide, which is essential for the photothermal absorber used in human tissue. The results demonstrate that assembly of gold nanorods with reduced graphene oxide (AuNR@Lcyst-rGO) is a promising photothermal agent with high efficient NIR-triggered photothermal therapy efficiency, excellent stability, superior biocompatibility.

Gold Nanorods: The Most Versatile Plasmonic Nanoparticles.

Gold nanorods (NRs), pseudo-one-dimensional rod-shaped nanoparticles (NPs), have become one of the burgeoning materials in the recent years due to their anisotropic shape and adjustable plasmonic properties. With the continuous improvement in synthetic methods, a variety of materials have been attached around Au NRs to achieve unexpected or improved plasmonic properties and explore state-of-the-art technologies. In this review, we comprehensively summarize the latest progress on Au NRs, the most versatile anisotropic plasmonic NPs. We present a representative overview of the advances in the synthetic strategies and outline an extensive catalogue of Au-NR-based heterostructures with tailored architectures and special functionalities. The bottom-up assembly of Au NRs into preprogrammed metastructures is then discussed, as well as the design principles. We also provide a systematic elucidation of the different plasmonic properties associated with the Au-NR-based structures, followed by a discussion of the promising applications of Au NRs in various fields. We finally discuss the future research directions and challenges of Au NRs.

Bi nanorods anchored in N-doped carbon shell as anode for high-performance magnesium ion batteries

The rechargeable magnesium batteries are potentially applicable in large-scale energy storage systems because of the low costs and rich sources. But the alternative anodes for magnesium ion batteries have not been fully developed. In this work, a novel bismuth-carbon composite with bismuth nanorods anchored in nitrogen-doped mesoporous carbon matrix (Bi@NC), was prepared as anode for magnesium ion batteries by carbonizing the dopamine-coated bismuth metal precursors. The matrix facilitated the magnesiation/de-magnesiation of bismuth due to its highly electronic conductive network. Moreover, it restrained the aggregation of bismuth nanorods and serves as a buffer layer to alleviate the mechanical strain of bismuth nanorods upon magnesium insertion/extraction. As the anode for magnesium ion batteries, the Bi@NC core-shell nanorods delivered a reversible capacity of 360 mAh g−1 at the current density of 100 mA g−1, and 87 % of the initial capacity was achieved after 100 cycles. The standout rate performance is 275 mAh g−1 at the current density of 1 A g−1. Such a good electrochemical property demonstrated the great application potential of Bi@NC as anode in magnesium ion batteries.

Active Plasmonics with Responsive, Binary Assemblies of Gold Nanorods and Nanospheres.

Self-assembly of metal nanoparticles has applications in the fabrication of optically active materials. Here, we introduce a facile strategy for the fabrication of films of binary nanoparticle assemblies. Dynamic control over the configuration of gold nanorods and nanospheres is achieved via the melting of bound and unbound fractions of liquid-crystal-like nanoparticle ligands. This approach provides a route for the preparation of hierarchical nanoparticle superstructures with applications in reversibly switchable, visible-range plasmonic technologies.

LaF3 Doped Co3O4 Mesoporous Nanomaterials with Hierarchical Structure for Enhanced Triethylamine Gas Sensing Performances

In this study, sea-urchin-like LaF3 doped mesoporous Co3O4 (La-Co3O4) nanomaterials were obtained by the heat treatment of citric acid-assisted hydrothermally-synthesized products at 300 °C. The composition, microstructure, and morphology were investigated by different characterization methods. Structural analyses reveal that La-Co3O4 has a hierarchical structure formed by the assembly of numerous nanorods that are aggregated by countless nanosheets. We probed the sensing ability of the La-Co3O4 based sensors toward a series of volatile organic gases, such as triethylamine, xylene, and ethanol. The results indicate that the sensors exhibited excellent selectivity and responsiveness toward triethylamine, with a lower detection limit of 1.0 ppm and long-term stability at an operating temperature of 195 °C. The prominent gas sensing performance first originates from the high content of adsorbed oxygen for doping LaF3 in which the high mobility of F anions resulted in the presence of F vacancies on the surface of the composites. Additionally, the abundant porosity offered by the hierarchical structure is favorable to the adsorption of oxygen species, surface reactions, and gas diffusion during the sensing process. Doping LaF3 to the semiconductor materials may provide a potential approach for the development of novel gas sensing materials.

Assembly of CuO nanorods onto poly(glycidylmethacrylate)@polyaniline core–shell microspheres: Photocatalytic degradation of paracetamol

AbstractIn recent years, the continuous and uncontrollable presence of drug contaminants and their destructive effects on the environment has been raised as an environmental problem. A large proportion of drug contaminants are related to sedatives. Paracetamol is one of the most widely used sedatives in the world. In this study, the photocatalytic degradation of paracetamol under visible light in the presence of poly(glycidylmethacrylate)@polyaniline/CuO nanocomposite as a photocatalyst was investigated. This prepared nanocomposite was characterized by different techniques such as Fourier transform infrared (FT‐IR), scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDX), thermogravimetric analysis (TGA), X‐ray diffraction (XRD), and transmission electron microscopy (TEM). The effect of various parameters such as the amount of photocatalyst, irradiation time, temperature, and pH of the solution was studied on drug degradation. The degradation of paracetamol (PA) was assessed by adding a number of radical scavengers to the solution. More than 99% of paracetamol (10 mg L−1) was degraded under operating conditions in 90 min.

Direct Preparation of *MRE Zeolites with Ultralarge Mesoporosity: Strategy and Working Mechanism.

Introduction of mesopore is critical for applications where mass-transport limitations within microporous networks, especially for zeolite with one-dimensional microporous network, hinder their performance. Generally, the creation of mesopore in zeolite through a direct synthesis route is strongly dependent on complex and expensive organic molecules, which limits their commercial application. Here, we successfully developed a facile synthesis route for preparing ZSM-48 zeolite (*MRE topology) with ultralarge mesoporosity in which typical 1,6-hexylenediamine worked as an organic structure-directing agent, innovatively assisted by a simple crystal growth modifier (tetraethylammonium bromide, TEABr). The working mechanism of TEABr during crystallization was revealed and proposed on the basis of TEM, thermal gravimetric mass spectrum, and 13C cross-polarization magic angle spinning NMR characterization results. In the process, TEA+ ions preferentially interacted with the solid during the induction period, which effectively suppressed the aggregation of ZSM-48 primary nanorods. As a result, ultralarge mesoporosity of 0.97 cm3·g-1 was constructed through the stacking of the nanorods. Interestingly, TEA+ ions only took part in the crystallization process and did not occlude in the pores of the final zeolites indicating its potential in recyclability. Moreover, similar synthesis strategy could be applied for the preparation of hierarchical ferrierite zeolites, implying the universality of this strategy. Compared with a conventional sample, ZSM-48 zeolite with ultralarge mesoporosity showed superior catalytic stability in the m-xylene isomerization reaction due to its significantly enhanced diffusion and mass transfer capability, which will greatly promote the practical application of ZSM-48 zeolite.

Crystal nucleation in colloidal rod suspensions: The effect of depletant size.

In order to better control the assembly of nanorods, knowledge of the pathways by which they form ordered structures is desirable. In this paper, we characterize crystal nucleation in suspensions of spherocylindrical rods with aspect ratio L/D = 2.3 in the presence of both small and large polymer depletants. Using a combination of Langevin dynamics and Monte Carlo simulations, together with biased sampling techniques, we show that the preferred pathway always involves the formation of monolayer assemblies irrespective of the volume fraction of the initial isotropic phase and the diameter of the depletants. This includes the previously neglected case of nucleation from the colloidal liquid phase and shows that the presence of depletion attraction can alter nucleation pathways even when the initial phase is dense.

Bi2S3 nanorods decorated on bentonite nanocomposite for enhanced visible-light-driven photocatalytic performance towards degradation of organic dyes

In this study, we prepared bentonite-Bi2S3 nanocomposite via decoration of Bi2S3 nanorods on bentonite for the first time to enhance the photocatalytic performance of Bi2S3 nanorods under visible light irradiation. XRD, TEM, SEM-EDX, XPS, UV-DRS, PL, electrochemical impedance spectroscopy, chronoamperometry, zeta potential, and BET techniques were used to compare analysis of structural, morphological, optical, electrochemical and textural properties of raw bentonite, bare Bi2S3 nanorods and bentonite-Bi2S3 nanocomposite. The photocatalytic performances of bentonite-Bi2S3 nanocomposite and bare samples were also investigated and comparatively evaluated by photodegradations of crystal violet and rhodamine B dyes under visible light irradiation. The photocatalytic degradation efficiencies of fabricated bentonite-Bi2S3 nanocomposite for crystal violet and rhodamine B were determined as 100% and 85% after the periods of 30 min and 90 min, respectively, which were more superior compared with those of bare Bi2S3 nanorods. The enhanced photodegradation activity of bentonite-Bi2S3 nanocomposite was assigned to the good visible light absorption ability, enlarged surface area, increased adsorption capability and decreased aggregation of Bi2S3 nanorods with the inclusion of bentonite platform as well as suppressed hole-electron recombination process due to electrostatic interaction between negatively charged bentonite surface and positively charged holes. The reactive species trapping revealed that hydroxyl radicals played a major role on the photodegradation and a plausible mechanism for photodegradation of dye molecules on bentonite-Bi2S3 nanocomposite was suggested. The photodegradation of dyes was found to follow the pseudo-first-order kinetic model. The prepared photocatalyst exhibited good reusability and stability after 4 cycles.