Diameter Of Nanospheres Research Articles

Preparation of Multi-colored Binary Silica Supraballs and Color Fine-tuning Based on Color Mixing

Structural colors are highly valued for their eco-friendliness and long-term color stability, deriving from the interaction of structural units with incident light. However, traditional methods for adjusting structural colors typically involve altering the size of structural units, a labor-intensive process necessitating specific diameters for each desired color. Moreover, colors exhibited by photonic crystal materials are monochromatic colors with a narrow wavelength range, failing to exhibit polychromatic colors. This restricts their practical applications, as they do not accurately represent the actual color of objects themselves. Hence, this study focuses on fabricating binary supraballs can display polychromatic colors. These supraballs consist of two types of structural units with distinct diameter differences. By adjusting the mass ratio between these units within the supraballs, fine color tuning is achievable. Utilizing three different diameters of silica nanospheres, this method enables the fabrication of supraballs with a diverse range of colors spanning nearly the entire visible spectrum. The adjustable colors of these binary supraballs not only enhance their ability to replicate the colors of objects, but also reduce the significant workload involved in preparing the original structural units. The synthesized supraballs are in powder form, directly applicable as coatings, inks, and other materials.

One‐Step Fabrication of Nanofiber/Nanosphere Composite Membranes by Airflow/Electrostatic Method

A fabrication technology and equipment for nanofiber/nanosphere composite membranes (NNCMs) is proposed and named as the airflow/electrostatic method (AEM). AEM uses both air flow and induced electric field to stretch the jets. The AEM working mechanisms are proposed and verified. The electric field laws of AEM are obtained by finite‐element simulation and theoretical deduction. Compared with the airflow method (AM), the average fiber diameter, standard deviation of fiber diameter, and NNCMs, porosity of AEM can be reduced by 38.8%, 71.1%, and 87.3%, respectively. AEM can also overcome the shortcoming of the AM that cannot receive nanospheres. Compared with the electrostatic method (EM), AEM can not only fabricate NNCMs with randomly distributed nanofibers and nanospheres in one step, but also greatly improve the yield. The injection speeds of solution X and solution Y of AEM can be increased by 24 000% and 1920%, respectively, compared with that of EM. The diameters of AEM nanospheres and nanofibers increase with the increase of injection speed of solution X and solution Y, respectively. The distance between needle and receiver has little effect on the diameters of nanofibers and nanospheres. AEM NNCMs with excellent quality and high yield will be widely used in many fields.

Broad-band-enhanced plasmonic random laser in silver nanostar arrays

As a novel optical device, the plasmonic random laser has unique working principle and emission characteristics. However, the simultaneous enhancement of absorption and emission by plasmons is still a problem. In this paper, we propose a broad-band-enhanced plasmonic random laser. Two-dimensional silver (Ag) nanostar arrays were prepared using a bottom-up method with the assistance of self-assembled nanosphere templates. The plasmon resonance of Ag nanostars contributes to the pump light absorption and photoluminescence (PL) of RhB. Coherent random lasing was achieved in RhB@PVA film based on localized surface plasmon resonance (SPR) dual enhancement and scattering feedback of Ag nanostars. Ag nanostars prepared with different nanosphere diameters affect the laser emission wavelength. In addition, the random laser device achieves wavelength tunability on a flexible substrate under mechanical external force.

Physiochemical Coupled Dynamic Nanosphere Lithography Enabling Multiple Metastructures from Single Mask.

Metastructures are widely used in photonic devices, energy conversion, and biomedical applications. However, to fabricate multiple patterns continuously in single etching protocol with highly tunable photonic properties is challenging. Here, a simple and robust dynamic nanosphere lithography is proposed by inserting a spacer between the nanosphere assembly and the wafer. The nanosphere diameter decrease and uneven penetration of the spacer during etching lead to a dynamic masking process. Coupled anisotropic physical ion sputtering and ricocheting with isotropic chemical radical etching achieve highly tunable structures with various 3D patterns continuously forming through a single etching process. Specifically, the nanosphere diameters define the periodicity, the etched spacer forms the upper parts, and the wafer forms the lower parts. Each part of the structure is highly tunable through changing nanosphere diameter, spacer thickness, and etch conditions. Using this protocol, numerous structures of varying sizes including nanomushrooms, nanocones, nanopencils, and nanoneedles with diverse shapes are realized as proof of concepts. The broadband antireflection ability of the nanostructures and their use in surface-enhanced Raman spectroscopy are also demonstrated for practical application. This method substantially simplifies the fabrication procedure of various metastructures, paving the way for its application in multiple disciplines especially in photonic devices.

Manipulation of random laser by the bandgap in three-dimensional SiO2 photonic crystals

Photonic crystals (PCs) are artificial structures with different dielectric constants that are arranged periodically in space and can control the propagation of electromagnetic waves of specific frequencies. The photonic bandgap can tune the photon state density, which is beneficial for the generation of random lasers (RLs). In this paper, a thin film of PMMA-doped DCJTB is spun-coated on a silicon dioxide (SiO2)PC to produce an RL. The PC is fabricated by a convenient dip-coating method with variable PBGs by changing the diameter of SiO2 nanospheres. By changing the position of the PBG gap, the RL emission peak can be effectively manipulated with an emission wavelength of up to 16 nm. By adding Au nanoparticles, the lasing performance is improved due to the surface plasmon resonance effect and strong photon scattering, where the emission intensity is increased by 191.9 %, and the threshold is decreased by 37.8 %. The imaging results show that the RL has low spatial coherence, which has a good application in speckle-free imaging. This study provides an effective method to produce a low threshold, high-quality RL with convenient manipulation of lasing properties, which opens the door for expanding its application in optoelectronic devices and speckle-free imaging.

Shock-Induced Microstructural Evolution, Phase Transformation, Sintering of Al-Ni Dissimilar Nanoparticles: A Molecular Dynamics Study.

Molecular dynamic simulations have been performed to explore contact behavior, microstructure evolution and sintering mechanism of Al-Ni dissimilar nanoparticles under high-velocity impact. We confirmed that the simulated contact stress, contact radius, and contact force under low-velocity impact are in good agreement with the predicted results of the Hertz model. However, with increasing the impact velocity, the simulated results gradually deviate from the predicted results of the Hertz model due to the elastic-plastic transition and atomic discrete structure. The normalized contact radius versus strain exhibits a weak dependence on nanosphere diameter. Below a critical velocity, there are very few HCP atoms in the nanospheres after thermal equilibrium. There are two different sintering mechanisms: under low-velocity impact, the sintering process relies mainly on the dislocation slip of Al nanospheres, while the dislocation slip of Ni nanospheres and the atomic diffusion of Al nanospheres predominate under high-velocity impact.

Circularly Polarized Scattering Radiation From a Silicon Nanosphere

AbstractA dielectric nanosphere with orthogonal electric dipole (ED) and magnetic dipole (MD) Mie resonances can be a nanoantenna radiating circularly polarized light in specific directions if the amplitudes and the phase relations are properly designed. First, theoretical calculations show that a silicon nanosphere illuminated with a linearly polarized plane wave radiates circularly polarized light at the wavelength in between the ED and MD resonances if the refractive index of a surrounding medium (nm) is ≈1.3; the ellipticity of the scattered light can be >0.99 when nm is in a 1.19–1.35 range. Size‐purified silicon nanospheres suspended in water (nm = 1.33) are then prepared, and the angle‐ and circular‐polarization‐resolved scattering spectra are studied. It is experimentally demonstrated that circularly polarized light is radiated in specific directions under linearly polarized plane wave illumination. The results also show that the wavelength of the radiation of circularly polarized light can be controlled in the whole visible range by controlling the silicon nanosphere diameter in 100–200 nm range.

Nanoscale goldbeating: Solid-state transformation of 0D and 1D gold nanoparticles to anisotropic 2D morphologies.

Goldbeating is the ancient craft of thinning bulk gold (Au) into gossamer leaves. Pioneered by ancient Egyptian craftsmen, modern mechanized iterations of this technique can fabricate sheets as thin as ∼100 nm. We take inspiration from this millennia-old craft and adapt it to the nanoscale regime, using colloidally synthesized 0D/1D Au nanoparticles (AuNPs) as highly ductile and malleable nanoscopic Au ingots and subjecting them to solid-state, uniaxial compression. The applied stress induces anisotropic morphological transformation of AuNPs into 2D leaf form and elucidates insights into metal nanocrystal deformation at the extreme length scales. The induced 2D morphology is found to be dependent on the precursor 0D/1D NP morphology, size (0D nanosphere diameter and 1D nanorod diameter and length), and their on-substrate arrangement (e.g., interparticle separation and packing order) prior to compression. Overall, this versatile and generalizable solid-state compression technique enables new pathways to synthesize and investigate the anisotropic morphological transformation of arbitrary NPs and their resultant emergent phenomena.

Construction of Three-Dimensional Dendritic Hierarchically Porous Metal-Organic Framework Nanoarchitectures via Noncentrosymmetric Pore-Induced Anisotropic Assembly.

As a unique class of modular nanomaterials, metal-organic framework (MOF) nanoparticles have attracted widespread interest for use in various fields because of their diverse chemical functionalities, intrinsic microporosity, and three-dimensional (3D) nanoarchitectures. However, endowing MOF nanomaterials with precisely controlled structural symmetries and hierarchical macro/mesoporosities remains a formidable challenge for the researchers. Herein, we report a facile noncentrosymmetric pore-induced anisotropic assembly strategy to prepare a series of 3D dendritic MOF (UiO-66) nanomaterials with highly controllable structural symmetries and hierarchical macro/meso/microporosities. The synthetic route of these nanomaterials depends on the anisotropic nucleation of MOF spherical nanocones with noncentrosymmetric center-radial channels and their oriented growth to isotropic nanospheres through a continuous increase in radius and solid angle. This strategy enables the controllable fabrication of asymmetric MOF nanostructures with abundant geometries and porous structures by regulating the concentration of amphiphilic triblock copolymer templates. Furthermore, the average pore diameter of the resultant MOF nanospheres can be systematically manipulated in a wide range from 35 to 130 nm by finely tuning the reaction temperature. Meanwhile, the strategy can also be extended to synthesize other MOF nanoparticles with similar architectures. Compared with microporous UiO-66 nanocrystals, the MOF nanoparticles with controllable structural symmetries and macro/meso/microporosities show enhanced catalytic activity in the CO2 cycloaddition reaction. The methodology provides new insights into the rational construction of sophisticated asymmetric open nanostructures of hierarchically porous MOFs for many potential applications.

Hollow silica nanospheres synthesized by one-step etching method to construct optical coatings with controllable ultra-low refractive index

HypothesisIt is generally believed that silica nanospheres deposited on substrates by sol-gel method to form coatings with low refractive index, if hollow structures are introduced into silica nanospheres, the obtained coatings can easily have an ultra-low refractive index (<1.15). However, with the currently reported techniques, facile and large-scale preparation of hollow silica nanospheres (HSNs) with diameters suitable for transparent optical coatings in a one-step method is hard to realize. Therefore, it is crucial to propose a one-step strategy to prepare HSNs colloids, and also to achieve controllable morphologies. ExperimentalStöber silica nanospheres were used as initial nanospheres, and diameters of nanospheres were controlled by the concentration of ammonia. Nanospheres of different diameters were etched using different concentrations of HF, and the structural transformation of nanospheres before and after etching was recorded. Etched nanospheres were deposited into coatings, refractive index was measured and appropriate coatings were selected to design and prepare a double-layer coating with broadband antireflection performance. FindingsExperiments indicated that nanospheres of different sizes exhibited different structural transformations after being etched by HF, and smaller nanospheres were aggregated and larger ones were hollowed out. It was the first time that HSNs have been prepared by one-step etching method. The refractive index of etched nanospheres was 1.387–1.057. The double-layer broadband antireflective coating designed and prepared using coatings with refractive index of 1.057 and 1.339 as upper and bottom layers respectively had an average transmittance of 99.5% in the visible region and exhibited a good antifogging property and weather durability.

Does the chemical contribution have a secondary role in SERS?

It is an established understanding that the electromagnetic contribution (plasmon-mediated enhancement of a laser and scattered local electromagnetic fields) is the main actor in surface enhanced Raman scattering (SERS), with the so-called chemical (molecule-related) contribution assuming only, if any, a supporting role. The conclusion of our comprehensive experimental resonant study of a broad range of nanosphere lithography based metallic substrates, with covalently attached 4-mercaptobenzoic acid monolayers used as a probe (standard molecules that are non-resonant in solution), is that this accepted understanding needs to be revised. We present a detailed resonant SERS study of metal-film-over-nanosphere (MFON) substrates that is done by both scanning the laser wavelength and tuning the plasmon response through the nanosphere diameter, which is varied from 500 to 900 nm. Far and local field properties are characterized through measures of optical reflectivity and SERS efficiency, respectively, and are supported by numerical simulations. We demonstrate that SERS intensity depends indeed on the electromagnetic mechanism, determined by the plasmonic response of the system, but we observe that it is also strongly defined by a chemical resonant contribution related to a metal-to-ligand electronic transition of the covalently bound probe molecule. Optimum amplification occurs when the plasmon modes intersect with the ligand-to-metal chemical resonance, contributing synergically both mechanisms together. Quite notably, however, the largest SERS signal is observed when the laser is tuned with the metal-to-ligand transition, and typically does not follow the wavelength dependence of the plasmon modes when varying the nanosphere size. The same general trend is observed for other nanosphere lithography based substrates, including sphere segment void cavities and hexagonally ordered triangular nanoparticles, using either Ag or Au as the plasmonic metal, and also with a commercial substrate (Klarite). Interestingly, this extensive comparative investigation shows in addition that MFON substrates are significantly better than these other studied plasmonic substrates in terms of Raman intensity and homogeneity. We conclude that a deep understanding of both electromagnetic and chemical mechanisms is necessary to fully exploit these substrates for analytical applications.

Nanosilk Template-Guided/Induced Construction of Brush-/Flower-like 3D Nanostructures.

Biomaterials with natural hierarchical structures typically exhibit extraordinary properties because of their multilevel structural designs. They offer many templates and models as well as inspiration for material design, particularly for fabricating structure-regulated, performance-enhanced, and function-enriched materials. Biopolymer-based nanocomposites with ingenious nanostructures constructed through ecofriendly and sustainable approaches are highly desirable to meet the multifunctional requirements of developing bioinspired materials. Herein, an all-silk fibroin-based nanocomposite with a brush-like nanostructure was constructed for the first time using a nanotemplate-guided assembly approach in which dissolved silk assembled directly on a silk nanowhisker (SNW) backbone to form peculiar nanobrushes based on the classical micelle model. Three-dimensional spider-like or centipede-like silk nanobrushes (SNBs) were fabricated by varying the SNW backbone length from 0.16 to 6 μm. The branches with average lengths of 32-290 nm were also adjustable. SNBs were further designed to regulate and induce biomineralization of hydroxyapatite (HAP) to form interesting flower-like nanostructures, in which the HAP nanosphere (diameters ∼16 nm) "core" was covered by SNBs with branches extending to form a "shell" (∼101 nm in length). Based on such protein nanotemplate-guided formation of nanoscale structures, practical hollow conduits with remarkable mechanical properties, biocompatibility, shape memory behavior, and bone engineering potential were fabricated. This study inspires the design of polymorphous biopolymer-based nanostructures with enhanced performance at multiple length scales where the weaknesses of individual building blocks are offset.

Development of controlled nanosphere lithography technology

This work is devoted to the development of nanosphere lithography (NSL) technology, which is a low-cost and efficient method to form nanostructures for nanoelectronics, as well as optoelectronic, plasmonic and photovoltaic applications. Creating a nanosphere mask by spin-coating is a promising, but not sufficiently studied method, requiring a large experimental base for different sizes of nanospheres. So, in this work, we investigated the influence of the technological parameters of NSL by spin-coating on the substrate coverage area by a monolayer of nanospheres with a diameter of 300 nm. It was found that the coverage area increases with decreasing spin speed and time, isopropyl and propylene glycol content, and with increasing the content of nanospheres in solution. Moreover, the process of controllably reducing the size of nanospheres in inductively coupled oxygen plasma was studied in detail. It was determined that increasing the oxygen flow rate from 9 to 15 sccm does not change the polystyrene etching rate, whereas changing the high-frequency power from 250 to 500 W increases the etching rate and allows us to control the decreasing diameter with high accuracy. Based on the experimental data, the optimal technological parameters of NSL were selected and the nanosphere mask on Si substrate was created with coverage area of 97.8% and process reproducibility of 98.6%. Subsequently reducing the nanosphere diameter lets us obtain nanoneedles of various sizes, which can be used in field emission cathodes. In this work, the reduction of nanosphere size, silicon etching, and removal of polystyrene residues occurred in unified continuous process of plasma etching without sample unloading to atmosphere.

Deviation from the fcc structure in the vertically deposited opal layers

The discrepancy between the experimental and theoretical results of Bragg diffraction in vertically deposited opal layers occurred in the literature. They refer to diffraction extrema associated with planes other than parallel to the top surface. Analyzing the results of spectrogoniometric studies of the transmission coefficient the new “face-centered tetragonal” (“fct”) structure was proposed. Assuming that structure a satisfactory agreement of the theoretical and experimental dependencies was obtained. Based on the new structure, the diameter of nanospheres, filling factor, deformation coefficient, and thus the length of the opal unit cell edge were obtained for several samples.

Tailorable and Angle-Independent Colors from Synthetic Brochosomes

Although various artificial dyes and pigments have been invented, certain application fields need structural colors because they can last for centuries even under harsh conditions. Here, we report that the antireflective Ag brochosomes (soccer-ball-like microscale granules covered by nanobowls) become colorful when the nanobowls on the Ag brochosomes are filled by polystyrene (PS) nanospheres. The color originates from the enhanced electromagnetic resonances of the PS nanospheres by the surrounding metallic nanobowls, suggested by both the experimental and the simulation results. The color is determined by the size of the PS nanospheres. We can tailor the color simply by reducing the diameter of the PS nanospheres via the plasma etching treatment. The color intensity of the Ag brochosomes filled with PS nanospheres shows weak dependence on the observing angles, benefiting from their spherical shape. Plasma etching treatment of the Ag brochosomes filled with PS nanospheres through different masks can design various structural color patterns. The simple fabrication process and the easy processability make the Ag brochosomes filled with PS nanospheres have promising applications in the structural color fields.

Mass producible, robust SERS substrates based on metal film on nanosphere (MFON) on an adhesive substrate for detection of surface-adsorbed molecules and their evaluation by helium ion microscopy.

We have developed a SERS stamp that can be pressed directly onto a solid surface for characterization of surface-adsorbed target molecules. The stamp was fabricated by transfer of a dense monolayer of SiO2 nanospheres from a glass surface onto a piece of adhesive tape and subsequent evaporation of silver. The performance of the resulting SERS stamps was evaluated by their exposure to methyl mercaptan vapor, and immersion in rhodamine 6G and ferbam solutions. It was found that beside the nanosphere diameter and metal deposition thickness, the extent of burial of the nanospheres into the adhesive tape, dictated by the pressure during the nanosphere transfer process, had a significant effect. We carried out FDTD calculations of the near field. Models are based on morphological information obtained from helium ion microscopy, which can provide high-resolution images of poor electrical conductors such as our SERS stamp. While one of our main eventual goals is detection of pesticides on agricultural produce, we have begun to take a careful step by testing our SERS stamp on better characterized surfaces such as a porous gel surface, having been immersed in fungicides such as ferbam. We also present our preliminary results with ferbam on oranges. It is expected that our well-characterized SERS stamp will play a role in shedding light on the poorly studied transfer process of target molecules onto a SERS surface as well as serving as a new SERS platform.

Bulk synthesis of conductive non-metallic carbon nanospheres and a 3D printed carrier device for scanning electron microscope calibration.

Herein, a facile method is proposed for the bulk synthesis of conductive non-metallic carbon nanospheres with controllable morphology to replace conventional metal calibration reference materials (CRMs), such as gold nanoparticles and copper grids. The prepared nanospheres had an average diameter of ∼222 ± 23 nm, where silicon dioxide formed the core and the shell was comprised of the carbon layer. The structure of the conductive carbon nanospheres was characterized using FTIR, SEM, EDS and TEM. Additionally, an innovative design was demonstrated by 3D printing the calibration carrier device. Furthermore, the stability and image linear distortion of the conductive carbon nanospheres were verified using analysis of variance (ANOVA). The results demonstrated that the accelerating voltage, magnification, and various positions in the X/Y axes had no significant effect on measured diameter of nanospheres, which was evident from all the p values being greater than 0.05. The comprehensive set of results reveal that conductive carbon nanospheres have great potential to replace traditional CRMs.

A hybrid and scalable nanofabrication approach for bio-inspired bactericidal silicon nanospike surfaces

Insects and plants exhibit bactericidal properties through surface nanostructures, such as nanospikes, which physically kill bacteria without antibiotics or chemicals. This is a promising new avenue for achieving antibacterial surfaces. However, the existing methods for fabricating nanospikes are incapable of producing uniform nanostructures on a large scale and in a cost-effective manner. In this paper, a scalable nanofabrication method involving the application of nanosphere lithography and reactive ion etching for constructing nanospike surfaces is demonstrated. Low-cost silicon nanospikes with uniform spacing that were sized similarly to biological nanospikes on cicada wings with a 4-inch wafer scale were fabricated. The spacing, tip radius, and base diameter of the silicon nanospikes were controlled precisely by adjusting the nanosphere diameters, etching conditions, and diameter reduction. The bactericidal properties of the silicon nanospikes with 300 nm spacing were measured quantitatively using the standard viability plate count method; they killed E. coli cells with 59 % efficiency within 30 h. The antibacterial ability of the nanospike surface was further indicated by the morphological differences between bacteria observed in the scanning electron microscopic images as well as the live/dead stains of fluorescence signals. The fabrication process combined the advantages of both top-down and bottom-up methods and was a significant step toward affordable bio-inspired antibacterial surfaces.

Interface Co‐Assembly Synthesis of Magnetic Fe3O4@mesoporous Carbon for Efficient Electrochemical Detection of Hg(II) and Pb(II)

AbstractIn recent years, efficient and porous carbon‐layer‐modified magnetic metal oxides demonstrate potentials for the significant improvement of catalytic and adsorption performance. In this study, a novel magnetic coreshell Fe3O4@mesoporous carbon (Fe3O4@MPC) nanochain electrochemical sensor is constructed by using resorcinol‐formaldehyde resin and magnetic Fe3O4 nanospheres as the carbon shell precursor and core, respectively, with a simple emulsion self‐assembly strategy. Microstructural characterizations revealed that the carbon shell exhibited a mesopore distribution of ≈40 nm and the diameter of Fe3O4 nanospheres embedded into carbon is ≈280 nm. The introduction of mesoporous carbon layer increased the electrical conductivity of the active material and maintained the adsorption properties of magnetic Fe3O4. The synergistic effect of the mesoporous carbon layer and Fe3O4 nanochain is beneficial to electrochemically detect heavy metal ions (HMIs). Under optimal conditions, the typical Fe3O4@MPC‐2/GCE exhibited excellent electrochemical sensing for detecting Hg(II) and Pb(II), with limits of detection (LOD) of 7.8 nm and 12.1 nm (S/N = 3), respectively. These good results are attributed to the Fe3O4@MPC nanochain structure and a relatively high specific surface area. This study provides a novel method to prepare magnetic mesoporous carbon nanochain composites for constructing sensitive electrochemical sensors to monitor water quality.

Fabrication and Surface Modification of Macroporous Silica Fibers by Electrospinning for Super Adsorbent of Oil

Silica fibers were fabricated by sol-gel reaction and an electrospinning process. A high voltage source of electricity was applied to the prepared spinning solution to form the fibers. Macroporous silica fibers were prepared using polystyrene (PS) nanospheres as templates after calcination. The pore size could be controlled by adjusting the diameter of the PS nanospheres in the spinning solution. PS nanospheres with different diameters (250, 430, 600, 870, and 1000 nm) were synthesized for this purpose using the dispersion polymerization method. Silica fibers have a hydrophilic surface. A coating film applied to the fibers showed superhydrophilicity, which is not suitable for adsorbing oil contaminant. Thus, silane coupling agents containing methyl groups were used to modify the surface of the porous fibers to obtain hydrophobic and water-repellent properties. The amount of oil adsorbed by the porous silica fibers modified with various kinds of coupling agent or PS nanospheres with different sizes was investigated, to determine their effects on oil adsorption. When the size of the macropores in the fibers increased, the amount of oil adsorption increased, because oil infiltration through the pores became easier. Small hydrophobic groups of the silane coupling agent, like methyl groups, were able to adsorb more oil compared to bulky functional groups. The measured oil adsorption capacity of the porous fibers was found to be larger than that of mesomacroporous silica particles, since the voids between the fibers might provide additional space for oil adsorption.