Characteristics Of Nanostructures Research Articles

Cellulose/polyaniline hybrid nanocomposites: Design, fabrication, and emerging multidimensional applications

Polyaniline, a special class of intrinsic conducting polymers, has a wide range of potential applications in multiple fields, such as in biosensors, electronics devices and biomedical applications. Polyaniline possesses high electrical conductivity, low toxic contents, hydrophilic character, better environmental stability and nanostructured surface characteristics. Polyaniline has however a current limited set of applications because of its low degradation rate and poor processibility; for this reason, polyaniline has been blended with different nano/micro cellulosic biomaterials (i.e. cellulose nano crystals and nano fibers, bacterial cellulose and macro cellulose). Furthermore, cellulose-reinforced polyaniline matrices have shown significant potential for antibacterial agents, antioxidants, sensors, electromagnetic shielding device, adsorbent in water treatment, fuel cells, electrochromic and in biomedical applications. These biodegradable and environmentally benign conducting polymers have also been used in tissue engineering, biosensors, and drug delivery. In the present review article we have surveyed recent advancements in the synthesis process and progress of polyaniline/cellulose based bio-composites for water treatment, electrical devices, biosensors, biomedical application and other areas. The article aims at providing a comprehensive background on the topic, as well as at proposing innovative strategies among investigators for the use of these biobased polymers in future work. The various factors and conditions that impact the adsorption/deterioration behavior of cellulose/PANI composites during the removal of heavy metals, dyes, and other effluents from waste water have also been discussed. Additionally, a comparative view of various fuel cells, electrochromic devices and the electrical and magnetic properties of different cellulose/polyaniline composites has also been provided. • Synthesis and structure of physico-chemical properties of Polyaniline (PANI). • Benefits of blending polyaniline with cellulose. • PANI nanocomposites role in water purification and gas sensing. • Development of electrochromic, fuel cells and electromagnetic shielding devices. • Remarkable potential of PANI-based nanocomposites for bio-medical applications.

Strong influence of morphology on the hemostatic performance of nanofibers irrespective of surface charge

• Chitin nanofibers reduced the blood-clotting time and increased clot firmness. • The morphology of chitin nanofibers impacts their hemostatic properties. • The positively-charged surface of chitin stimulates contact activation pathways. Recently, negatively-charged nanofibers made of macro-scale carbohydrate polymers, such as cellulose, have been investigated for hemostatic applications. It was demonstrated that nanostructural features including specific surface area and aspect ratio can be optimized to increase the interaction of blood components with nanofibers. However, the influence of nanofiber’s surface charge is unknown. In this paper, positively-charged nanofibers were produced from shrimp chitin using a ball-milling technique. In-vitro thromboelastometry studies revealed that nanofibers morphology has much stronger influence than the surface charge on their hemostatic efficacy. Consequently, with optimizing the morphology, clotting time was reduced by 70 ± 2%, and clot firmness was increased by 12 ± 1% comparable to commercial hemostats.

Electrical and Heat Distributions and Their Influence on the Mass Transfer during the Flash Spark Plasma Sintering of a Cu/Cr Nanocomposite: Experiments and Numerical Simulation.

The nanocomposite Cu–Cr powder was consolidated by flash spark plasma sintering (FSPS), which involves applying an extremely rapid change in the electrical power passing through the bulk of the sample. It was demonstrated that an essentially fully dense material could be obtained in 15 s. Such short-term treatment typically preserves the nanostructured features of the material. However, investigation revealed a nonuniformity in the microstructure of the alloys obtained under such extreme conditions. To better understand the observed effects, the FSPS process was simulated. It was observed that a rapid change in the applied electrical power resulted in nonuniform distributions of current density and temperature along the body of the consolidated material. Specifically, the current density was higher on the periphery of the sample, and the temperature was higher in the middle. These findings explain the observed structural transformation during FSPS and suggest an optimization strategy to avoid microstructural nonuniformity.

Promising electrode material of Fe3O4 nanoparticles decorated on V2O5 nanobelts for high-performance symmetric supercapacitors

Bundled V2O5 nanobelts decorated with Fe3O4 nanoparticles (F3V nanostructures) were successfully synthesized to develop a low-cost electrode material for energy storage applications. The synthesized samples were subjected to structural, morphological and electrochemical studies. The Fe3O4 nanoparticles decorated over bundled V2O5 nanobelts exhibited better electrochemical properties than the pristine Fe3O4 nanoparticles and V2O5 nanobelts. The electrochemical behavior of the fabricated electrodes was investigated in an electrolyte of 3 M KOH, demonstrated an exceptional specific capacity values of 750.1, 660.3, and 1519 F g–1 for V2O5, Fe3O4, and F3V respectively at a current density of 15 A g–1. The assembled F3V symmetric supercapacitor (SSC) device exhibited an excellent specific capacitance of 93 F g–1 at a current density of 0.5 A g–1, delivering energy and power densities of 13 Wh.kg–1 and 1530 W kg–1, respectively, and superior long-term cycling stability of ∼84% capacity retention over 5000 galvanostatic charge–discharge cycles. These findings demonstrate the extraordinary electrochemical characteristics of the F3V nanostructures, indicating their potential use in energy storage applications.

On the Evolution of Nano-Structures at the Al-Cu Interface and the Influence of Annealing Temperature on the Interfacial Strength.

Molecular dynamics (MD) simulations are invoked to simulate the diffusion process and microstructural evolution at the solid–liquid, cast-rolled Al–Cu interfaces. K-Means clustering algorithm is used to identify the formation and composition of two types of nanostructural features in the Al-rich and Cu-rich regions of the interface (i.e., the intermetallic Al2Cu near the Al-rich interface and the intermetallic Al4Cu9 near the Cu-rich interface). MD simulations are also used to assess the effects of annealing temperature on the evolution of the compositionally graded microstructural features at the Al–Cu interfaces and to characterize the mechanical strength of the Al–Cu interfaces. It is found that the failure of the Al–Cu interface takes place at the Al-rich side of the interface (Al2Cu–Al) which is mechanically weaker than the Cu-rich side of the interface (Cu–Al4Cu9), which is also verified by the nanoindentation studies of the interfaces. Centrosymmetry parameter analyses and dislocation analyses are used to understand the microstructural features that influence deformation behavior leading to the failure of the Al–Cu interfaces. Increasing the annealing temperature reduces the stacking fault density at the Al–Cu interface, suppresses the generation of nanovoids which are precursors for the initiation of fracture at the Al-rich interface, and increases the strength of the interface.

Non‐Stoichiometric NiFeMo Solid Solutions; Tuning the Hydrogen Adsorption Energy via Molybdenum Incorporation

AbstractSolution precursor plasma spraying is used to produce catalytic trimetallic coatings containing Ni, Fe and Mo directly onto stainless‐steel mesh, Ni foam and carbon paper. The resulting material is mostly comprised of face centered cubic FeNi3 alloy forming a highly porous coating with nanostructured features. The addition of Mo (up to ≈14 at%) generates no new crystal phases but only an increase in the lattice parameter, indicating the formation of FeNi3Mox solid solutions. The FeNi3Mox solid solutions are used as electrocatalyst for the hydrogen evolution reaction (HER) in alkaline media. The addition of Mo increases the HER activity significantly reaching an optimum performance at ≈9 at% Mo (FeNi3Mo0.40) with an overpotential at −10 mA cm−2 of 112 mV and a Tafel slope of 109 mV dec−1. The enhanced HER activity is attributed to the formation of a FeNi3Mox solid solution with an increased work function that is correlated to smaller hydrogen adsorption energies. Theoretical activity maps reveal that sites near superficial Mo atoms forms catalytic hot spots and are responsible for the observed activity.

Comparison of electrochemical characteristics of NiCo2O4 and NiCo2S4 nanostructures for supercapacitors

This paper presents the results on the synthesis and study of the properties of NiCo2O4 and NiCo2S4 nanostructures obtained by hydrothermal synthesis for their use as supercapacitor electrodes. A method is developed for growing a nanostructure from a ternary metal oxide NiCo2O4 on a nickel substrate. The structural features of the synthesized NiCo2O4and NiCo2S4 nanostructures are studied using X-ray phase analysis. The obtained samples have a cubic modification NiCo2O4 and NiCo2S4. The data on the morphology of the synthesized samples obtained by scanning electron microscopy are presented. The samples are in the form of nanoneedles and nanowires grown on a nickel substrate. Methods for the synthesis of NiCo2O4 nanostructures have been studied, optimal conditions for the growth of nanostructures from NiCo2O4 have been determined, and a NiCo2O4 sulfurization method has been developed to obtain a NiCo2O4 nanostructure. Comparative studies have been carried out on the effects of sulfurization on the electrochemical characteristics of the obtained electrodes. It is found that, despite the fact that NiCo2O4 oxide nanostructures have a high theoretical capacitance, the replacement of oxygen atoms by sulfur atoms increases the conductivity of the materials and leads to a further increase in the specific capacitance of the end electrodes. The maximum Cs obtained specific capacitance for NiCo2S4 is 1976 F g-1 and while for NiCo2O4 it is 413 F g-1 at a scan rate of 5 mV/s. The results of the dependence of the specific capacitance on the scanning speed during measurements are also presented.

Turning/Shot peening of Nickel-based powder metallurgy superalloy: Effect on surface integrity and high-temperature low-cycle fatigue properties

In this study, a nickel-based powder metallurgy alloy was processed via turning, ceramic bead peening, and shot peening by high-intensity cast-iron shots and low-intensity ceramic beads (denoted as compound shot peening). We investigated the surface morphology (surface stress concentration factor, Kst), the surface residual stress profile, microstructure, and the hardness gradient of three surface states and compared the high-temperature low-cycle fatigue lives. The results showed that the surface stress concentration coefficients after turning, ceramic bead peening, and compound shot peening were 2.39, 1.98, and 2.12, respectively. The average surface roughness, Sa, after turning was low, but the bottom of the tool mark was sharp, so the Kst value was higher than that after shot peening, which formed a round bottom by bead blasting. Compared with ceramic bead peening, a surface structure with a deeper compressive residual stress profile and a higher hardness gradient was formed after compound shot peening, and nanostructured features appeared on the outermost surface. The estimated low-cycle fatigue lives after the ceramic bead peening and compound shot peening were 0.99 and 3.13 times longer than after the turning process respectively with strain amplitude 0.5% at 538℃. Moreover the gain of compound shot peening on low cycle fatigue performance gradually decreases with the increase of the strain amplitude.

Multiscale modeling of thermal conductivity of hierarchical CNT-polymer nanocomposite system with progressive agglomeration

Agglomeration of carbon nanotubes (CNTs) is a key phenomenon that affects the effective thermal conductivity of CNT-polymer nanocomposites. This issue needs to be adequately studied especially in the practice of prediction of the effective thermal properties of CNT nanocomposites. In this study, we developed a multiscale model within the framework of effective medium theory to predict the effect of CNT agglomeration on the overall thermal conductivity of the hierarchical CNT-polymer nanocomposite system over a wide range of CNT loading. With an introduced Cauchy cumulative probability function, we developed a new model of CNT agglomeration wherein the CNT volume fraction progressively evolves with the total loading of the CNT fillers in the composite. This model is self-consistent and it leads to a very good agreement with experimental observations. The entire multiscale approach consists of the newly developed model of the progressive agglomeration as well as models that altogether take into account the effect of two types of CNT interfacial thermal resistance and the unique feature of the CNT nanostructure. We highlighted this multiscale approach with its implementation in the prediction of the overall thermal conductivity. Good agreement was confirmed between the prediction and the experimental data. The study shows that the existence of CNT agglomerates downgrades the thermal percolation networks and it can cause a decrease up to 50% in the overall thermal conductivity of the nanocomposite. Two important parameters for the progressive agglomeration model were identified and their influences to the predicted results were examined.

Performance of different traditional and machine learning-based atomistic potential functions in the simulation of mechanical behavior of Fe nanowires

Characterization of nanoscale material properties using experimental methods is difficult due to their high costs and complexities. Hence, many researchers apply alternative techniques, such as atomic/molecular simulations, to overcome the limitations of experimental methods. A well-established method to study material behavior at nanoscales is molecular dynamics simulation. However, the accuracy of its results is highly dependent on the selection of appropriate potential functions/force fields modeling atomic interactions. This work investigates the effects of considering different potential functions on the mechanical characteristics of BCC Fe nanostructures using molecular dynamics simulations. Laboratory data are used to verify the calculated elastic properties of bulk structures. Furthermore, systematic simulations are performed to determine the elastic properties of nanowires under tensile loading, various potential functions, and different temperatures. According to the results, Ackland's potential function and experimental data are in excellent agreement. On the contrary, Asadi's potential function shows an opposite trend comparing other functions and experimental mechanical data. In addition, the potential function formulated based on artificial neural networks is capable to capture tension-induced necking phenomena in Fe nanowires.

Designing plasmonically integrated nanoreactors for efficient catalysis

AbstractPlasmonically coupled nanoreactors capable of harnessing light energy and efficiently transforming it to perform chemical reactions are in significant demand in the field of catalysis. The development of unique solution‐phase synthesis techniques for engineering intricate nanoarchitectures by introducing multiple functionalities can dramatically improve the efficacy of these nanostructures. In this context, the precise modulation of the nanostructural features and the integration of other components with the plasmonic nanoparticles within an isolated nanoconfined reaction environment is the current state of the art for their synthesis. This account highlights our achievements in designing different synthesis strategies and elucidating the mechanistic pathways involved in the development of plasmonically integrated nanoreactors. The range of applications of these plasmonic nanoreactors, which employ plasmon‐induced energy for catalytic transformations, is also discussed.

Phonon thermal transport in graphene/h-BN superlattice monolayers

The superlattice monolayers composed of periodically assembled graphene and hexagonal boron nitride (h-BN) superlattices by strong covalent bonds have aroused great interest in academia and industry due to their adjustable physical properties, which are expected to play an important role in the modulation of material properties, especially in thermal transport properties. In general, thermal transport properties highly rely on the characteristic of nanostructures. Thus, understanding the impact of structural characteristics on physical properties is essential for the design of high-performance materials. In this study, we report our results from three different methods including non-equilibrium molecular dynamics, homogeneous non-equilibrium molecular dynamics, and spectral heat current decomposition to explore the phonon thermal transport properties in different graphene/h-BN superlattice monolayers, which are constructed by periodically stitched and equal-sized graphene and h-BN superlattices. We find that the thermal conductivities decrease first and then increase with the increase of periodic length, corresponding to a transition from coherent transport to incoherent transport, and a minimum thermal conductivity at a certain period is identified. These results provide a theoretical validation of a possible control on thermal properties at the nanoscale, which may have potential applications in thermoelectric devices once upon experimental validation.

Influence of sequential pyrolisis methods on the properties of the carbon nanostructure (CNS) from sugarcane leaf biomass

Plant biomass is a potential lignocellulose material for synthesis of carbon nano structure. Its characteristics as adsorbent and its size particle make it good additive for liquid fertilizer. In this research, we study influence of sequential different pressure pyrolysis methods (hydrothermal–microwave method and reflux–microwave method) toward characteristics of carbon nanostructure from sugarcane leaf biomass. Each reflux and hydrothermal method was adjusted at 200oC, then followed by microwave at 800W. Characterization showed that the hydrothermal - microwave method using X-ray diffraction indicates diffractogram patterns of both carbon nanostructure and cellulose. SEM micrographs show sphere and block shapes. FTIR spectra indicates different concentration of oxy surface functional groups. UV spectra of the dispersed product in water indicates existence of aromatics C=C groups. The hydrothermal - microwave method resulted the product inwhich lower crystalinity index of cellulose, smaller particles, lower concentration of oxy surface groups than the reflux - microwave one. Correlation of chemical properties (aromaticity and fraction of polar groups) was more linier than of physical - chemical properties (indexe of cellulose crystalinity and fraction of polar groups). The stability of colloid was indicated by dispersing technique in order of sonication < blending < blending - sonication.

Tailoring nanohole sizes through the deacetylation process in chitosan powders obtained from squid pens

An experimental study on the evolution of the physicochemical, thermal and nanostructural properties of chitosan samples obtained from squid pens as the deacetylation treatment proceeds is presented. To this aim, potentiometric titration, capillary viscosimetry, infrared spectroscopy, differential scanning calorimetry and positron annihilation lifetime spectroscopy were used. The results obtained are discussed in terms of the influence of the deacetylation time on the deacetylation degree, average molecular weight, thermal parameters and average free nanohole size of the different samples. A way of preparing chitosan matrices with tailored nanostructural characteristics for specific applications through the deacetylation process is explored.

Nanoscale Pore-Pore Coupling Effect on Ion Transport through Ordered Porous Monolayers.

Distinct from the conventional view that nanopores are considered independent channels for mass transport, recent study on the covalent organic framework (COF)-based monolayers characteristic of an ordered nanopore array exhibits a series of interesting properties originating from the strong interactions between adjacent pores. These interactions are determined to be highly dependent on interpore distance and pose a significant influence on the ion transport, accounting for the exceptional membrane performance including both selectivity and conductance. In this Perspective, we discuss the recently discovered nanoscale pore-pore coupling as well as the exciting features of porous nanostructures. We also look at the challenges and future opportunities of ion transport in ordered porous monolayers in the aspects of both fundamental research and practical use.

The effect of sodium citrate on NaOH-activated BFS cement: Hydration, mechanical property, and micro/nanostructure

This paper presents a study on the effect of sodium citrate solution (0.25M, 0.5M, 0.75M) on the hydration process and microstructure evolution of NaOH-activated blast furnace slag (BFS) paste. The setting behavior, flowability, mechanical strength, hydration kinetics, and micro/nanostructure characteristics were investigated through multiple tests—such as Vicat test, mini-slump test, x-ray diffraction, spectroscopy analysis, nuclear magnetic resonance, and mercury intrusion porosimetry—to reveal the hydration mechanism of NaOH-activated BFS paste in presence of sodium citrate. The results indicate that the citrate ions retarded the hydration process and contributed significantly to slag dissolution and precipitation of hydration products during the alkali-activated reaction process. The microstructure build-up from the early stage (3 days) to the mature stage (28 days) underwent a different process, resulting in a more densified and less porous matrix with higher compressive strength. However, no significant changes were observed in the type of hydration products and their nanostructural characteristics.

Polyol-assisted hydrothermal synthesis of Mn-doped α – Fe2O3(MFO) nanostructures: Spin disorder-induced magnetism and photocatalytic properties.

Hierarchical nanostructures play an important role in environmental clean-up and sustainability applications. The magnetic and photocatalytic characteristics of flower-like Mn-doped α-Fe2O3 nanostructures were prepared by using a polyol-assisted hydrothermal method. Crystallite sizes are in the range of 35–42 nm, and the existence of 3D hierarchical nanostructures was observed in FESEM pictures. The optical band gap energy varies between 2.08 and 2.16 eV, while XPS examination exposes the ions' charge states and validates Mn3+ inclusion in the Fe3+ lattice. At room temperature, the addition of Mn to α-Fe2O3 results in a spin disorder ferromagnetism and coercivity of about 600 Oe was achieved. Methylene blue (MB) dye solution degraded by 92% when 2.5% Mn doped with α-Fe2O3 under visible conditions for 120 min irradiation time.

Injection moulding of micropillar arrays: a comparison of poly(methyl methacrylate) and cyclic olefin copolymer

Injection moulding of micropillar arrays offers a fast and inexpensive method for manufacturing sensors, optics, lab-on-a-chip devices, and medical devices. Material choice is important for both the function of the device and manufacturing optimisation. Here, a comparative study of poly(methyl methacrylate) (PMMA) and cyclic olefin copolymer (COC) injection moulding of micropillar arrays is presented. These two polymers are chosen for their convenient physical, chemical, and optical properties, which are favoured for microfluidic devices. COC is shown to replicate the mould’s nano/microstructures more precisely than PMMA. COC successfully forms a micropillar array (250 mm diameter; 496 mm high) and closely replicates surfaces with nano-scale roughness (30–120 nm). In the same moulds, PMMA forms lens arrays (not true pillars) and smoother surfaces due to the incomplete filling for all parameters studied. Thus, COC offers finer structural detail for devices that require micro and nano-structured features, and may be more suited to injection moulding microfluidic devices.

BODIPY-Based Nanomaterials—Sensing and Biomedical Applications

Cancerous diseases are rightfully considered among the most lethal, which have a consistently negative effect when considering official statistics in regular health reports around the globe. Nowadays, metallic nanoparticles can be potentially applied in medicine as active pharmaceuticals, adjustable carriers, or distinctive enhancers of physicochemical properties if combined with other drugs. Boron dipyrromethene (BODIPY) molecules have been considered for future applications in theranostics in the oncology field, thus expanding the potential of conceivable applicability. Hence, taking into account positive practical features of both metal-based nanostructures and BODIPY derivatives, the present study aims to gather recent results connected to BODIPY-conjugated metallic nanoparticles. This is with respect to their expediency in the diagnosis and treatment of tumor ailments as well as in sensing of heavy metals. To fulfill the designated objectives, multiple research documents were analyzed concerning the latest discoveries within the scope of BODIPY-based nanomaterials with particular emphasis on their utilization for diagnostical sensing as well as cancer diagnostics and therapy. In addition, collected examples of mentioned conjugates were presented in order to draw the attention of the scientific community to their practical applications, elucidate the topic in a consistent manner, and inspire fellow researchers for new findings.

Reactivity of soot emitted from different hydrocarbon fuels: Effect of nanostructure on oxidation kinetics

Soot oxidation kinetics is relevant for the exhaust pollutant reduction through processing in abatement systems based on filtering and oxidation as diesel particulate filters. Soot nanostructure impact on oxidation reactivity was studied by thermogravimetric analysis of soot produced in premixed laminar flames burning different hydrocarbon fuels, namely methane, ethylene and benzene, and characterized by spectroscopic and microscopic analysis. Soot oxidation kinetics was multistep and two activation energies, 180 and 240 kJ/mol, could be evaluated. Preexponential factors obtained upon data fitting of the Arrhenius plots with the two activation energies, showed an increasing trend going from aliphatic (methane, ethylene) toward benzene soot, consistently with the rise of the maximum oxidation temperature. The higher and lower activation energies were correlated, respectively, to amorphous carbon, coalesced on soot particles and present in form of tortuous and not-stacked lamellae inside the particle, and to the rest of the particle, characterized by a better nanoscale organization. Through a detailed chemico-physical characterization, the different propensity to be oxidized of soot samples was correlated to the nanostructural features of the most ordered part burning at 240 kJ/mol.