Formation Mechanism Of Nanostructures Research Articles

Investigation of the Strain–Stress Field in Nanoscale Multilayer Systems by the Phase Plane Method

This paper presents the results of the study of stress relaxation fields, deformation, and temperature of the system of nanostructured multilayer coatings. In the work, a nonlinear relationship between strain and stress was used to take into account nonlinear effects in the mechanism of nanostructure formation. The paper assumes that a friction surface is provided by the self-organization of shear components: both stress and strain on the one hand, and temperature on the other. The studied objects are described in the adiabatic approximation, taking into account the fact of the evolution of stresses and strains. With the help of phase portraits of the system, the dependence of the deformation processes on the stresses arising in the system without coating and with coating is shown. It is shown that the rate of change of deformation depends on the characteristics of the mechanical impact on the coating and on the amount of stress and deformation. A conclusion is drawn regarding the transition process in the presence of two regions (Hooke and plastic deformation) in the corresponding phase portrait of the strain–stress field of the system. The results of the work can be used to determine the effective parameters of a coating in the analysis of experimental time dependences of stresses.

Revealing a spontaneous two-stage process in femtosecond laser-induced fully-oxidized nanostructures

Femtosecond laser interactions with matter facilitate the creation of diverse structures on material surfaces, including laser induced periodic surface structures (LIPSS), ablation nanoparticles, sub-diffraction nanogrooves, and plasmonic nanostructures. In this study, we reveal a unique nanostructure on silicon induced by femtosecond laser irradiation, distinguished by its pea-shaped morphology. At the center of this nanostructure, a nano-slit is oriented perpendicular to the laser polarization. The nano-slit penetrates the pea-shaped nanostructure and an underlying layer with a depth of approximately 600 nm. Energy dispersive X-ray spectroscopy (EDS) analysis confirms that the nanostructure and the underlying layer consist entirely of silicon oxide. A spontaneous two-stage oxidation process is proposed to explain the formation mechanism of fully-oxidized nanostructures. The presence of nano-slits endows the oxide nanostructures with polarization sensitivity, which shows the potential in applications such as optical encryption and data storage. In addition, the spontaneous two-stage oxidation process allows for the maskless fabrication of oxide nanowires with a precision down to hundreds of nanometers, providing the flexibility to produce arbitrary nanostructures. This capability opens up new possibilities for manipulating light beams and enabling on-chip nano-glass printing.

Controllable Synthesis, Formation Mechanism, and Photocatalytic Activity of Tellurium with Various Nanostructures.

Telluriums (Te) with various nanostructures, including particles, wires, and sheets, are controllably synthesized by adjusting the content of polyvinylpyrrolidone (PVP) in a facile solvothermal reaction. Te nanostructures all have complete grain sizes with excellent crystallinity and mesopore structures. Further, the formation mechanisms of Te nanostructures are proposed to be that the primary nuclei of Te are released from the reduction of TeO32- using N2H4·H2O, and then grow into various nanostructures depending on the different content of PVP. These nanostructures of Te all exhibit the photocatalytic activities for the degradation of MB and H2 production under visible light irradiation, especially Te nanosheets, which have the highest efficiencies of degradation (99.8%) and mineralization (65.5%) at 120 min. In addition, compared with pure Te nanosheets, the rate of H2 production increases from 412 to 795 μmol∙h-1∙g-1 after the introduction of Pt, which increases the output by nearly two times. The above investigations indicate that Te with various nanostructures is a potential photocatalyst in the field of degradation of organic pollutants and H2 fuel cells.

Tungsten nanostructure growth by sputtering and redeposition in BCA-MD-KMC hybrid simulation

The formation mechanism of fibrous tungsten nanostructures, fuzz, induced by helium plasma irradiation on tungsten materials has been investigated. We have developed a BCA-MD-KMC hybrid simulation, which solves the injection process of helium atoms by the Binary Collision Approximation (BCA) method, the diffusion process of helium atoms in tungsten materials by the Kinetic Monte-Carlo (KMC) method, and the deformation of tungsten materials due to helium bubbles by the Molecular Dynamics (MD) method. In addition, the model used to calculate the recoiling of tungsten atoms in BCA was improved to account for the reduced binding energy of tungsten atoms on rough surfaces. Using the hybrid simulation, the height of the nanostructures reached about 50 nm. The main mechanism of nanostructure growth was that sputtering and redeposition caused transport of tungsten atoms perpendicular to the surface. The present simulation was able to represent not only the dependence that the nanostructure height increases in proportion to the square root of the helium fluence, but also the existence of incubation fluence before the growth starts.

Nanostructures in tight oil reservoirs: Multiple perspectives

This study reveals the heterogeneity, anisotropy, and formation mechanism of nanostructures (pores and throats) for the storage and seepage of tight oil by comprehensively unifying the following techniques: FE–SEM, gas adsorption, EDS, HPMI, MICP, and umbrella deconstruction. The results show that for tight oil reservoirs, 82.8% of the nanoscale pore contributes to oil storage, 50.2% of the nanoscale pore contributes to oil seepage, 76.5% of the nanoscale throat contributes to oil storage, and 38.9% of the nanoscale throat contributes to oil seepage. The nanopores were mainly formed in kaolinite, chlorite, K-feldspar, and illite, with 57%, 21%, 14%, and 7% of the contents, respectively. Among them, 85% are clay minerals. The weathering and dissolution of feldspar contributes a great deal to the formation of nanopores, accounting for about 78%, which a follow-up study should target. The relatively large pores can easily form a relatively large throat, and compaction and diagenesis later have little influence on the density of the nanoscale pores. Simultaneously, the pore radius and throat peak radius are the most robust parameters reflecting the reservoir's storage capacity and infiltration difficulty. The conclusion will provide a crucial scientific basis for tight oil storage and underground flow.

KOH-Based Hydrothermal Synthesis of Iron-Rich Titanate Nanosheets Assembled into 3D Hierarchical Architectures from Natural Ilmenite Mineral Sands

The synthesis of titanate nanostructures from low-cost mineral precursors is a topic of continuous interest, considering not only their fundamental aspects but also the benefits of incorporating such nanomaterials in a wide variety of applications. In this work, iron-rich titanate nanosheets were synthesized from Ecuadorian ilmenite sands (ilmenite–hematite solid solution-IHSS) through an alkaline hydrothermal treatment (AHT) using potassium hydroxide (KOH). The effect of the duration of the KOH-AHT was assessed at 180 °C for 24, 48, 72, and 96 h. The morphology evolution over time and the plausible formation mechanisms of titanate nanostructures were discussed. The most significant morphological transformation was observed after 72 h. At this time interval, the titanate nanostructures were assembled into well-defined 3D hierarchical architectures such as book-block-like arrangements with open channels. Based on X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS) analyses, it was determined that these nanostructures correspond to iron-rich layered titanates (Fe/Ti mass ratio of 7.1). Moreover, it was evidenced that the conversion of the precursor into layered nanostructures was not complete, since for all the tested reaction times the presence of remaining IHSS was identified. Our experiments demonstrated that the Ecuadorian ilmenite sands are relatively stable in KOH medium.

Nanostructuring of sapphire by ion-induced plasma

Sapphire single crystals were irradiated with slow highly charged xenon ions from electron beam ion trap (EBIT) facility. Scanning electron microscopic measurements showed the ability of the used ions in creating surface nanohillocks by single ion impacts. A test charge approach is used to provide an explanation for the mechanism of nanostructure formation in the sapphire surface. The model shows an increase of the height of the created nanostructure by increasing of the ionic density and electron temperature. This is in agreement with the dependence of the size of the induced nanostructures as a function of the deposited ion energy. The influence of the test charge speed and the relevance of an attractive wakefield potential are discussed in terms of plasma parameters.

Tracking the Growth of Chiral Plasmonic Nanocrystals at Molybdenum Disulfide Heterostructural Interfaces

The way of accurately regulating the growth of chiral plasmonics is of great importance for exploring the chirality information and improving its potential values. Herein, cysteine enantiomers modulate the anisotropic and epitaxial growth of gold nanoplasmonics on seeds of exfoliated MoS2 nanosheets. The heterostructural Au and MoS2 hybrids induced by enantiomeric cysteine are presented with chiroptical characteristics, dendritic morphologies, and plasmonic performances. Moreover, the synthesis, condition optimization, formation mechanism, and plasmonic properties of Au and MoS2 dendritic nanostructures are studied. The chirality characteristics are identified using the circular dichroism spectra and scanning electron microscopy. Time-resolved transmission electron microscopy and UV-vis spectra of the intermediate products captured are analyzed to confirm the formation mechanism of dendritic plasmonic nanostructures at heterostructural surfaces. The specific dendritic morphologies originate from the synergistic impacts of heterostructural MoS2 interfaces and enantiomeric cysteine-induced anisotropic manipulation. Significantly, the developed synthesis strategy of chiral nanostructures at heterostructural interfaces is highly promising in promoting the understanding of the plasmonic function and crucial chirality bioinformation.

Solvent-nonsolvent regulated nano-functionalization of super-wetting membranes for sustainable oil/water separation

Super-wetting membranes with nano-functionalized surfaces hold great potential for oil/water separation, but it is still a challenge to construct layered nanostructures on hydrophobic PES matrix via the traditional nonsolvent induced phase separation (NIPS) technique. Herein, we propose a method that modulates the phase transition behavior of polyvinylpyrrolidone (PVP) and tannic acid (TA) during the exchange process between solvent and non-solvent, leading to in-situ construction of antifouling membranes with the nano-functionalized surface. By studying the phase transition thermodynamics between polyethersulfone (PES) and PVP-TA systems in different solvents, the formation mechanism of nanostructures was unraveled. Benefiting from the antifouling barrier constructed by the nano-layered structure, the prepared membrane exhibits superhydrophilic/underwater superoleophobic properties and high efficiency in separating oil-in-water emulsions (flux > 2800 L·m−2·h−1·bar−1, rejection rate > 99.5 %) and good recyclability. We believe that this study is expected to provide new insights for the design of nano-functionalized membranes by conventional NIPS technology.

Synthesis and characterization of MgO nanostructures: A comparative study on the effect of preparation route

In this study, MgO nanostructures were synthesized by five facile and diverse chemical synthesis routes, viz. precipitation (PT), sonication-precipitation (SPT), microwave combustion (MWC), conventional combustion (CC), and solvothermal (ST) processes. The influence of aforementioned synthesis routes on crystallinity, crystallite size, morphology, optical, and surface traits of MgO nanostructures was evaluated by XRD, BET, FESEM, FETEM, optical absorption, steady-state and time-resolved photoluminescence analyses. Furthermore, antioxidant and antibacterial properties of MgO nanostructures were examined. XRD analysis revealed that crystallite size and relative crystallinity (%) of MgO varied from 9 to 42 nm and 90.70–99.06%, respectively, depending on the synthesis route followed. The application of microwave irradiation (MWC) and sonication (ST) reduced particle size and increased specific surface area of MgO nanostructures compared to nanostructures obtained via CC and PT methods. This could be due to faster reaction kinetics in MWC and small-scale turbulence generated during sonication that restricts growth and agglomeration of nuclei during nanostructure synthesis. FESEM analysis revealed flake, sphere, natural rose, and marigold flower-like morphologies of MgO due to different methods followed, that can be attributed to the differences in nanostructure formation mechanism involved. The highest photoluminescence intensity observed with MgO synthesized via MWC is likely to produce a maximum number of reactive oxygen species. Consequently, MgO synthesized through MWC process showed highest bactericidal and antioxidant activities compared to MgO synthesized via other routes. Thus, present study demonstrated that properties of nanostructures required for a particular application could be customized by proper choice of the synthesis route.

Microstructure and properties of mono-crystalline germanium enhanced by high-current pulsed electron beam

High current pulsed electron beam (HCPEB) technology was applied to irradiate the surface of mono-crystalline Ge wafers (Ge (100) and Ge (111)) with different orientations, and the microstructure and properties of the irradiated surface were analyzed in detail. The results show that after HCPEB irradiation, numerous molten pits and local microcracks were produced on the surface of mono-crystalline Ge, and the pit density decreased with the increase of irradiation pulses. TEM observations indicated that after irradiation, the defects are mainly vacancy group defects and dislocation rings, and Ge nanocrystals with uniform size distribution are produced. HCPEB irradiation also formed self-assembled nanostructures on the surface of Ge. Cross section TEM indicated that the 250 nm deep defect channels were under the quantum dots, which confirms the formation mechanism of self-assembled nanostructures. The photoluminescence results indicated that the irradiated mono-crystalline Ge still has blue emission properties, and the luminescence mechanism is the quantum confinement effect of Ge nanocrystals embedded in slightly oxidized or nitrided amorphous structures.

Room-Temperature Interconversion Between Ultrathin CdTe Magic-Size Nanowires Induced by Ligand Shell Dynamics.

The formation mechanisms of colloidal magic-size semiconductor nanostructures have remained obscure. Herein, we report the room temperature synthesis of three species of ultrathin CdTe magic-size nanowires (MSNWs) with diameters of 0.7 ± 0.1 nm, 0.9 ± 0.2 nm, and 1.1 ± 0.2 nm, and lowest energy exciton transitions at 373, 418, and 450 nm, respectively. The MSNWs are obtained from Cd(oleate)2 and TOP-Te, provided diphenylphosphine and a primary alkylamine (RNH2) are present at sufficiently high concentrations, and exhibit sequential, discontinuous growth. The population of each MSNW species is entirely determined by the RNH2 concentration [RNH2] so that single species are only obtained at specific concentrations, while mixtures are obtained at concentrations intermediate between the specific ones. Moreover, the MSNWs remain responsive to [RNH2], interconverting from thinner to thicker upon [RNH2] decrease and from thicker to thinner upon [RNH2] increase. Our results allow us to propose a mechanism for the formation and interconversion of CdTe MSNWs and demonstrate that primary alkylamines play crucial roles in all four elementary kinetic steps (viz., monomer formation, nucleation, growth in length, and interconversion between species), thus being the decisive element in the creation of a reaction pathway that leads exclusively to CdTe MSNWs. The insights provided by our work thus contribute toward unravelling the mechanisms behind the formation of shape-controlled and atomically precise magic-size semiconductor nanostructures.

3D CoMoO4 nanoflake arrays decorated disposable pencil graphite electrode for selective and sensitive enzyme-less electrochemical glucose sensors.

Three-dimensional (3D) cobalt molybdate (CoMoO4) hierarchical nanoflake arrays on pencil graphite electrode (PGE) (CoMoO4/PGE) are actualized via one-pot hydrothermal technique. The morphological features comprehend that the CoMoO4 nanoflake arrays expose the 3D, open, porous, and interconnected network architectures on PGE. The formation and growth mechanisms of CoMoO4 nanostructures on PGE are supported with differentstructural and morphological characterizations. The constructed CoMoO4/PGE is operated as an electrocatalytic probe in enzyme-less electrochemical glucose sensor (ELEGS), confronting the impairments of cost- and time-obsessed conventional electrode polishing and catalyst amendment progressions and obliged the employment of a non-conducting binder. The wide-opened interior and exterior architectures of CoMoO4 nanoflake arrays escalate the glucose utilization efficacy, whilst the intertwined nanoflakes and graphitic carbon layers, respectively, of CoMoO4 and PGE articulate the continual electron mobility and catalytically active channels of CoMoO4/PGE. It jointly escalates the ELEGS concerts of CoMoO4/PGE including high sensitivity (1613 μA mM-1cm-2), wide linear glucose range (0.0003-10mM), and low detection limit (0.12µM) at a working potential of 0.65V (vs. Ag/AgCl) together with the good recovery in human serum. Thus, the fabricated CoMoO4/PGE extends exclusive virtues of modest electrode production, virtuous affinity, swift response, and excellent sensitivity and selectivity, exposing innovative prospects to reconnoitring the economically viable ELEGSs with binder-free, affordable cost, and expansible 3D electrocatalytic probes.

Numerical modelling of non-premixed biogas and LPG combustion to study carbon nanostructures formation in flame

This work presents the numerical simulation of biogas and LPG fuelled diffusion flames in an axisymmetric chamber to study in-depth, the formation mechanism of soot and carbon nanostructures in these flames. The simulation is formulated on the set of transport equations that involve the equations for conservation of mass (the continuity equation), momentum (Navier-Stokes equation), energy, and chemical species. The governing equations are solved using ANSYS FLUENT, which is centered on the finite volume method. To predict the soot formation, one step soot model has been incorporated. The solution of these equations permits the estimation of temperature field and species concentrations inside the flame. Simulation is conducted at fixed fuel flow rate and varied oxygen flow rates. The results reveal that the formation of soot and carbon nanostructures is strongly dependent on peak flame temperature and concentration of precursor species formed in the flame. Since two fuels produce an exclusive chemical environment in the flame, the flame temperature and CO concentration that is conducive to the growth of carbon nanostructures is higher for LPG fuel as compared to that for biogas. Hence, the nucleation process of carbon nanostructures is faster for LPG than biogas. Moreover, the reactions taking place inside the flame at different locations can also be predicted from flame temperature and species concentration at that location. Pyrolysis of fuel occur near the burner exit, followed by the nucleation and surface growth of carbon nanostructures in the nearby region and oxidation of formed carbon nanostructures near the flame tip.

Nanostructuring of the tungsten surface under the action of femtosecond laser radiation

In the paper, we show the possibility of nanostructured tungsten surface by femtosecond laser radiation. The features of the LIPPS formation are also shown. The dependence of the formation of the structuring region on the number of femtosecond laser pulses is shown. Based on the analysis of experimental data, the formation mechanisms of nanostructures are discussed.

Toughening of epoxy by nanostructures with ABA triblock copolymers: An influence of organosilicon modification of block copolymer

AbstractIn this work, we investigated the effect of organosilicon modification of an ABA triblock copolymer on the morphologies, thermal properties, and fracture toughness of epoxy thermosets. First, a poly(ε‐caprolactone)‐block‐poly(butadiene) ‐block‐poly(ε‐caprolactone) triblock copolymer was synthesized through the ring‐opening polymerization of ε‐caprolactone by using an α,ω‐dihydroxyl‐terminated polybutadiene as the macromolecular initiator. Thereafter, the triblock was organosilicon‐modified via the hydrosilylation of its midblock (viz. polybutadiene) with pentamethyldisiloxane. It was found that the organosilicon modification resulted in a switch of the nanostructure formation mechanism from reaction‐induced microphase separation to self‐assembly. As a consequence of the organosilicon modification, the morphological structures of the thermoset were significantly changed, and thus, the materials displayed different improvement in fracture toughness. In addition, the organosilicon modification further enhanced the surface hydrophobicity of the materials.

Irradiation-driven molecular dynamics simulation of the FEBID process for Pt(PF3)4.

This paper presents a detailed computational protocol for the atomistic simulation of formation and growth of metal-containing nanostructures during focused electron beam-induced deposition (FEBID). The protocol is based upon irradiation-driven molecular dynamics (IDMD), a novel and general methodology for computer simulations of irradiation-driven transformations of complex molecular systems by means of the advanced software packages MBN Explorer and MBN Studio. Atomistic simulations performed following the formulated protocol provide valuable insights into the fundamental mechanisms of electron-induced precursor fragmentation and the related mechanism of nanostructure formation and growth using FEBID, which are essential for the further advancement of FEBID-based nanofabrication. The developed computational methodology is general and applicable to different precursor molecules, substrate types, and irradiation regimes. The methodology can also be adjusted to simulate the nanostructure formation by other nanofabrication techniques using electron beams, such as direct electron beam lithography. In the present study, the methodology is applied to the IDMD simulation of the FEBID of Pt(PF3)4, a widely studied precursor molecule, on a SiO2 surface. The simulations reveal the processes driving the initial phase of nanostructure formation during FEBID, including the nucleation of Pt atoms and the formation of small metal clusters on the surface, followed by their aggregation and the formation of dendritic platinum nanostructures. The analysis of the simulation results provides spatially resolved relative metal content, height, and growth rate of the deposits, which represents valuable reference data for the experimental characterization of the nanostructures grown by FEBID.

Probing the Formation Kinetics and Thermodynamics with Rationally Designed Analytical Tools Enables One-Pot Synthesis and Purification of a Tetrahedral DNA Nanostructure.

The development of robust analytical tools capable of probing the formation kinetics and thermodynamics of DNA nanostructures is a crucial step toward better understanding and manufacturing of diverse DNA-based materials. Herein, we introduce a real-time fluorescence anisotropy assay and rationally designed DNA reaction termination probes (DRTPs) as a set of new tools for exploring the formation mechanisms of DNA nanostructures. We deployed these tools for probing the formation of a classic tetrahedral DNA nanostructure (TDN) as a model system. Our tools revealed that the formation of TDN was dominated by simultaneous hybridization, whereas its undesired side products were caused mainly through step-wise hybridization. An optimal reaction temperature exists that favors the formation of TDN over side products. With insight into the TDN formation mechanism, we further engineered magnetic DRTPs to achieve single-step purification of TDN, enabling 10-fold improvement in the ratio between the targeted TDN and undesired side products without tedious procedures or bulky instruments. Combining the optimal reaction and purification conditions, we finally demonstrated the one-pot synthesis and purification of TDN. The analytical techniques offered in this work may hold potential to find wide applications and inspire new analytical methods for structural DNA nanotechnology.

Construction of triple-shelled hollow nanostructure by confining amorphous Ni-Co-S/crystalline MnS on/in hollow carbon nanospheres for all-solid-state hybrid supercapacitors

• Amorphous Ni-Co-S/crystalline MnS is confined on/in hollow carbon nanospheres. • The formation mechanism of the triple-shelled hollow nanostructure is studied. • The optimized electrode shows a high capacity of 1093C g −1 at 1 A g −1 . • The capacitance retention of all-solid-state device is 87.7% after 10,000 cycles. Designing novel electrode materials with controlled structure and composition remains a great challenge for high-performance supercapacitors. Here, a triple-shelled hollow nanostructure has been successfully designed and constructed by confining amorphous Ni-Co-S/crystalline MnS on the inner walls and the outer surfaces of hollow carbon nanospheres. The triple-shelled hollow nanostructure can improve the electrochemically active surface areas, accelerate the transport of electrons/ions, and accommodate the volume change during cycling. Additionally, the interlayer (the porous hollow carbon nanospheres) can support each other for enhanced mechanical stability and improve the electrical conductivity of the electrode. More importantly, amorphous Ni-Co-S facilitates diffusion and redox reaction of OH – , while the crystalline MnS offers fast electrons transport and mechanical stability. Meanwhile, the amorphous/crystalline interface can improve charge storage. Benefiting from the structural and compositional advantages, the prepared electrode delivers a high specific capacity (1093C g −1 at 1 A g −1 ) and outstanding cyclic stability (capacity retention ratio of 90.4% at 10 A g −1 after 5000 cycles). The corresponding all-solid-state hybrid supercapacitor achieves long cycle life and high energy density.

Self- and dis-assembly behavior of segmented wormlike nanostructures from an ABC triblock copolymer.

Herein, we described the self-assembly of a triblock copolymer, poly(styrene-b-2-vinylpyridine-b-ethylene oxide) (PS-b-P2VP-b-PEO), in THF/water at room temperature to form segmented wormlike nanostructures. We found two different formation mechanisms of the segmented wormlike nanostructures from PS-b-P2VP-b-PEO with different molecular weights. Moreover, the dimension of such segmented wormlike nanostructures depends on the stirring rate. Interestingly, these wormlike nanostructures disassembled gradually when increasing the temperature, which is reversible. After cooling to room temperature the segmented wormlike micelles reformed gradually with stirring. Furthermore, neither intense stirring nor ultrasonic vibration could damage the structure of these wormlike nanostructures which proves their stability and potential application as drug delivery vehicles.