Nano-sized Structures Research Articles

Transport mechanism under temperature and concentration gradient for nano-sized species in Maxwell viscoelastic fluid over cylindrical object moving with non-uniform velocity

Non-Newtonian fluids have a wide range of engineering applications, which has drawn researchers to study their puzzling rheology as well as the transport of thermal and somatic energy behaviors. The researchers provide a variety of empirical models to describe the behavior of the non-Newtonian fluids because non-Newtonian fluids alter their flow behavior in response to the applied stress. This study considered a two-dimensional transport mechanism in viscoelastic fluid over convectively heated surface moving with non-uniform velocity is modelled via simplified conservation laws by considering temperature and concentration gradients. Axisymmetric PDEs are further transformed into their dimensionless forms under similarity principle. The associated set of models are solved numerically using finite element numerical technique. Convergent mesh free solutions are further utilized in exploring the underlying physics. The significant role of temperature gradient in transporting species observed whereas impact of compositional gradient in transferring the heat energy is investigated. Brownian motion of solid nano-sized structures in viscoelastic non-Newtonian fluid is rheological observed to strongly impact the simultaneous transport of heat and mass. Convectively heated surface is also responsible for thermal enhancement. Convective transport is being accelerated by convectively varying amount of species at the convectively heat surface of cylindrical body.

Spectroscopic analyses of particle and energy aggregations at the interface of silver nanoparticles and fluorescent carbon nanodots.

We study the change in the surface electromagnetic field provided by photoexcited silver nanoparticles as the field is disturbed by fluorescent carbon nanodots. Fluorescent carbon nanodots with an appropriate quantity and quality of surface functional groups are used to mediate the aggregation of silver nanoparticles of matching size and shape to form available nano-size conical structures. Carbon nanodots in the composite absorb and transfer additional photoenergy to the silver surface, resulting in energy aggregation within the cone structure and enhancement of the electromagnetic field in proximity to the silver surface. This elevated energy state is manifested in the strengthening of the SERS signal of the analytical probe 4-aminophenyl disulfide and the mechanism involved is elucidated by additional molecular spectroscopy studies.

Emerging trends of nanotechnology in beauty solutions: A review

Nanotechnology is the science of manipulating the structural entities at nanoscale and beauty based solution industry is one of the most passionate explorer of nanostructures which contemplated as a huge boon in the cosmeceuticals for various beauty solutions. Exploration of nanostructures is escalating in the cosmeceuticals due to limitations coupled with the conventional products. Although, cosmeceutical is not FDA approved terminology but designate the personal care products at the borderline between cosmetics and pharmaceuticals. Emerging trends in cosmetics frequently include nano-sized structure novel carriers (like nano-emulsions, nanocapsules, nanosomes, niosomes or liposomes) consisting of traditional cosmetic materials. Nanocosmeceuticals contains naturally derived ingredients and synthetics too, but all contains functional ingredients with their therapeutic, disesase-flighting and healing properties. Nanocosmeceuticals has been developing with significant pace over recent years, extensively used to address beauty solutions. Nanocarriers are novel nanostructure having the advantages of effective penetration in skin, controlled site specific targeting, higherstability and entrapment efficiency. The current review put light on various aspects of nanostructure candidates in cosmetics including its synthesis, nanocarriers, regulations potentialconcerns and future trends.

Scanning ion-conductance microscopy technique for studying the topography and mechanical properties of Candida parapsilosis yeast microorganisms.

Super-resolution microscopy is widely used in the development of novel antimicrobial testing in vitro. In the presented work, a scanning protocol was developed by the method of scanning ion-conducting microscopy (SICM), which makes it possible to study microorganisms without rigid fixation and in saline, obtaining an index map of nanosized structures. The effect of azole and echinocandins drugs on the morphology and mechanical properties of Candida parapsilosis yeast was studied. The findings are consistent with previously proposed drug mechanisms and reports that have examined antifungal agents using AFM, SEM, and TEM. We have shown that the SICM method is capable of scanning and detecting the nanomechanical properties of yeast non-invasively.

Polymerization-Induced Self-Assembly for Efficient Fabrication of Biomedical Nanoplatforms.

Amphiphilic copolymers can self-assemble into nano-objects in aqueous solution. However, the self-assembly process is usually performed in a diluted solution (<1 wt%), which greatly limits scale-up production and further biomedical applications. With recent development of controlled polymerization techniques, polymerization-induced self-assembly (PISA) has emerged as an efficient approach for facile fabrication of nano-sized structures with a high concentration as high as 50 wt%. In this review, after the introduction, various polymerization method-mediated PISAs that include nitroxide-mediated polymerization-mediated PISA (NMP-PISA), reversible addition-fragmentation chain transfer polymerization-mediated PISA (RAFT-PISA), atom transfer radical polymerization-mediated PISA (ATRP-PISA), and ring-opening polymerization-mediated PISA (ROP-PISA) are discussed carefully. Afterward, recent biomedical applications of PISA are illustrated from the following aspects, i.e., bioimaging, disease treatment, biocatalysis, and antimicrobial. In the end, current achievements and future perspectives of PISA are given. It is envisioned that PISA strategy can bring great chance for future design and construction of functional nano-vehicles.

Nanotubes from bacteriophage tail sheath proteins: internalisation by cancer cells and macrophages.

Bionanoparticles comprised of naturally occurring monomers are gaining interest in the development of novel drug transportation systems. Here we report on the stabilisation, cellular uptake, and macrophage clearance of nanotubes formed from the self-assembling gp053 tail sheath protein of the vB_EcoM_FV3 bacteriophage. To evaluate the potential of the bacteriophage protein-based nanotubes as therapeutic nanocarriers, we investigated their internalisation into colorectal cancer cell lines and professional macrophages that may hinder therapeutic applications by clearing nanotube carriers. We fused the bacteriophage protein with a SNAP-tag self-labelling enzyme and demonstrated that its activity is retained in assembled nanotubes, indicating that such carriers can be applied to deliver therapeutic biomolecules. Under physiological conditions, the stabilisation of the nanotubes by PEGylation was required to prevent aggregation and yield a stable solution with uniform nano-sized structures. Colorectal carcinoma cells from primary and metastatic tumours internalized SNAP-tag-carrying nanotubes with different efficiencies. The nanotubes entered HCT116 cells via dynamin-dependent and SW480 cells - via dynamin- and clathrin-dependent pathways and were accumulated in lysosomes. Meanwhile, peritoneal macrophages phagocytosed the nanotubes in a highly efficient manner through actin-dependent mechanisms. Macrophage clearance of nanotubes was enhanced by inflammatory activation but was dampened in macrophages isolated from aged animals. Altogether, our results demonstrate that gp053 nanotubes retained the cargo's enzymatic activity post-assembly and had the capacity to enter cancer cells. Furthermore, we emphasise the importance of evaluating the nanocarrier clearance by immune cells under conditions mimicking a cancerous environment.

In English

A review of the works of the authors published in the period 2009–2022 and devoted to the study of the properties of nanosized structures containing contacting layers of Fe, Co, Ni, Fe2O3 / REM (Rare Earth Metal) oxide is carried out. The technology for the creation and structural features of these nanostructures are also considered. Physicochemical phenomena in the interface of contacting layers are very multidisciplinary. This is a consequence of their dependence on various conditions, primarily on the modes of technologies for their production and the properties of the initial components. The problem becomes much more complicated when studying magnetic nanostructures. To study effectively the properties of layered nanostructures containing ferromagnetic films, we used magnetic research methods. Using the EPR method, it has been found that between atoms with unfilled f- and d-electron sub-shells, which are part of the contacting layers, an f-d exchange interaction occurs, which orders the magnetic structure of the ferromagnetic layers. Using the method of the anomalous Hall effect, it is shown that the ordering of the magnetic structure leads to an increase in their magnetization. The enhancement of the galvanomagnetic properties in the Fe3O4/REМ оxide/Fe3O4 structures shows that the exchange interaction can have both f-d and d-d character. And this, in turn, leads to an increase in magnetization-dependent properties, such as galvanomagnetic, magneto-optical, and current-voltage properties. This can be used in nanotechnologies to enhance the above properties without energy consumption and the use of amplifying equipment.

Gradient theory of thermoelasticity for interface crack problems with a quasicrystal layer

The interface crack problem between two dissimilar materials under a thermal load is analyzed by the gradient elasticity theory since the size effect is expected in the very thin quasicrystal layer. The uncoupled thermoelasticity is considered here, where the thermal fields are independent on mechanical ones. The thermal transport can’t be well described by classical Fourier’s law in nano-sized structures. Therefore, a novel gradient theory is developed in such structures, where the second derivatives of temperature in the constitutive equation for the high-order heat flux are considered. Moreover, the phonon strain gradients are incorporated into the higher-grade continuum model. Decagonal quasicrystal material properties are considered here. Governing equations and corresponding boundary conditions are derived from the principle of virtual work. The mixed finite element method (MFEM) is developed for a general 2D boundary value problem. Numerical examples are presented to illustrate the phonon, phason and thermal response to external thermal loading within the considered model.

Epitaxial growth of ultrathin two-dimensional pentacene film with standing-up molecular geometry on nano-size-curved graphene surface

Molecule packing behavior at organic and graphene interface is essential for graphene-based organic electronics since charge carriers are transported within the very few organic layers nearest to graphene substrate. Although organic molecules especially the ones with planar aromatic rings usually adopt recumbent geometry on graphene substrate owning to the maximized π-π interaction, the alignment of organic molecules may be influenced by modifying the interfacial nature between organic molecules and graphene. Here, epitaxy growth of two-dimensional ultra-thin pentacene film with standing-up molecular geometry was observed for the first time on graphene with periodic nano-sized buckling structure. The curvature and strain of graphene was found collectively responsible for the standing-up geometry of pentacene and its oriented growth on graphene surface. This study provides a feasible way for controlling molecular epitaxy on 2D materials interfaces toward functional heterostructures.

N-doped Ni-Co bimetallic derived hollow nano-framework cubes anchored on 3D reduced graphene aerogel with enhanced sodium ion batteries performance

Developing advanced electrode materials for sodium ion batteries (SIBs) to meet the urgent need of high performance is still challenging. In this study, a novel SIBs negative electrode composite material (N/(Ni, Co)Se2 NFCs@RGOA) was prepared by loading N-doped bimetal derived nano-framework cubes (N/(Ni, Co)Se2 NFCs) on reduced graphene oxide aerogel (RGOA). The nano-size and hollow cage structure of N/(Ni, Co)Se2 NFCs cooperate with the layered branched carbon skeleton and porous structure of RGOA to accelerate the reaction kinetics, therefore alleviate the structure collapse caused by volume expansion, and boost the conductivity of the material. The characterization and electrochemical testing results show that the electrode material has remarkable electrochemical performance (reversible capacity of 497 mA h g−1 at 0.1 A g−1), capacity stability (395 mA h g−1 after 200 cycles) and excellent rate performance (389 mA h g−1 at the current density of 2 A g−1). The as designed electrode material will play a significant role to benefit the development of SIBs and advanced electrical storage applications.

A 3D-Simulation and Experimental Study of the Fluid Flow Around a Nano-Step Structure Formed by UV-NIL

In this work, total internal reflection fluorescence microscopy (TIRFM) was combined with the refractive index matching method to measure the three-dimensional motion of a nanoparticle on a nanosized step structure in water. A step (height = 64 nm) based on an ultraviolet (UV)-curable resin was fabricated using UV nanoimprint lithography. The step has a refractive index similar to that of water to eliminate the optical distortion due to light refraction and reflection at the interface between the nano structure and water. TIRFM could clearly capture the motion of a fluorescent nanoparticle in the vicinity of the nanostep in water. Diffusion coefficients of the particle in the vicinity of the nanostep edge were obtained from its time-lapse images, indicating that the diffusion coefficient measured along the edge of the step was 1.2 times larger than that measured across the step. Molecular dynamics simulations were also conducted to calculate the diffusion coefficients of a rigid particle close to the top of the step. The simulation results were qualitatively consistent with the experimental observations. The experimental and simulation methods presented here would help understand the nanoparticle motions and solvent flow dynamics around more complicated nanostructures.

Calcined nanosized tubular halloysite for the preparation of limestone calcined clay cement (LC3)

Halloysite is a kind of 1:1 clay mineral having a special nanosized tubular morphology and pore structure. In this work, nanosized tubular halloysite calcined at 750 °C (Hal750) and limestone (LS) were used to partially replace the ordinary Portland cement (OPC) for the preparation of limestone calcined clay cement (LC3). The mechanical properties and microstructure of LC3 were studied. The results revealed that the obtained LC3 had higher early compressive strengths on 3 and 7 days than did plain OPC. LC3 with a replacement ratio of 22.5% (containing 15.0% Hal750 and 7.5% LS) resulted in maximum compressive strength of 46.38 MPa, being 9.4% higher than OPC's after 28 days of curing. Further, LC3 featured a compact microstructure and smaller critical pore size than OPC, which is mainly because more additional C-(A)-S-H, hemicarboaluminate (Hc), and monocarboaluminate (Mc) were formed in LC3 system, thus contributing to the matrix densification and strength development. However, when the replacement ratio exceeded 37.5%, the insufficient portlandite (CH) limited the pozzolanic reaction with Hal750, leaving excess Hal750 in the LC3 that led to their inhomogeneous microstructure, and thus weakened the mechanical properties. These results show that halloysite is a promising material for the preparation of LC3 whose properties are sensitive to the replacement ratio used.

SHS of highly dispersed powder compositions of nitrides with silicon carbide Review

The application of the process of self-propagating high-temperature synthesis (SHS) to prepare highly dispersed powder nitride-carbide compositions from the most common refractory nitride (Si3N4, AlN, TiN) and carbide (SiC) compounds with a particle size of less than 1 μm is considered. The advantages of composite ceramics over single-phase ceramic materials and such trends of its development as the transition to nanostructured ceramics and the application of in situ processes of direct chemical synthesis of nanoparticles of components in the composite body are described. The attractiveness of the SHS process as one of the promising in situ processes characterized by simplicity and cost-effectiveness, the possibility of obtaining highly dispersed ceramic powders by burning mixtures of inexpensive reagents is shown. Considerable attention is paid to the consideration of the results of the application of azide SHS, based on the use of sodium azide and gasified halide salts as part of mixtures of initial powders of nitrided and carbidized elements during their combustion in nitrogen gas. The review of publications devoted to the application of SHS to obtain highly dispersed composite powders Si3N4–SiC, AlN–SiC and TiN–SiC, promising for use in sintering of the corresponding composite ceramic materials of submicron and nano-sized structure with improved properties, lower brittleness, good machinability, lower sintering temperatures compared with single-phase ceramic materials made of nitrides or carbides as well as for other applications, is presented. The results of the application of azide SHS are presented in detail both in the form of the results of thermodynamic calculations and the results of experimental research of combustion parameters, combustion product structure and composition. The advantages and disadvantages of using the combustion process for the synthesis of nitride compositions with silicon carbide, the causes of the disadvantages and the directions of further research to eliminate them are discussed.

On a comprehensive analysis for mechanical problems of spherical structures

This paper applies a semi-analytical polynomial method (SAPM) to solve the mechanical governing equations of nonlinear static and dynamic deformations, free and forced vibrations, and buckling analyses of nano-sized spherical functionally graded structures. Due to the nano-sized structure, the constitutive equations of motion are obtained based on the nonlocal elasticity theory. The governing equations are solved to obtain the deformations, critical buckling loads, and natural frequencies of the analyzed structure. The SAPM is based on polynomial functions (with no boundary conditions), including unknown finite coefficients. The spherical coordinate system is assumed to obtain several geometrical structures: cylindrical, conical, circular, sectorial, and rectangular. The nonlinear strains and the first-order shear deformation theory (FSDT) are employed to model the structure. The research considers the von Kármán assumptions to formulate the nonlinear strain components in the spherical coordinate system. The obtained results are compared with those in other articles to examine the accuracy of the applied solution method. The formulation's generality and simplicity and the appropriate accuracy of the SAPM's results distinguish this solution method for analyzing all mechanical aspects.

Grain growth kinetics of the gamma phase metallic uranium

Metallic uranium is a leading fuel form for sodium cooled fast reactors as an enabling technology of future nuclear energy systems. Mechanistic understanding of fuel behaviors and kinetics under thermodynamic equilibrium and highly non-equilibrium conditions are essential for evaluating fuel performance. It is important to understand and predict the grain and pore evolutions of metallic fuels under thermal and irradiation conditions. However, very limited data are available on the grain growth kinetics and mechanisms of pure gamma phase uranium. In this paper, the pure gamma uranium pellets with different grain structures were fabricated by combining high-energy ball milling and spark plasma sintering. Isothermal annealing tests were performed to investigate the grain growth behavior of the pure gamma phase uranium with different initial grain sizes. A parabolic relationship in grain growth with time was identified for the submicron-sized (374 nm) sample. In contrast, for the nano-sized (137 nm) sample, the grain growth shows a linear relationship with time. The activation energies of grain growth were determined as 199.5 KJ/mol and 80.6 KJ/mol for nano-sized and submicron-sized grain structures, respectively. For the nano-sized sample, the rate-control step of grain growth is dominated by the triple-junction migration, in which the grain boundary triple junction drags the grain growth, leading to a higher activation energy than the bulk diffusion. The dominating mechanism for the submicron-sized sample is grain boundary diffusion. The mechanistic understanding and critical data obtained on the kinetics of pure uranium phases will be useful to evaluate fuel behavior under thermodynamic equilibrium conditions and develop a high fidelity model to predict fuel performance.

Extracellular vesicles: A potential future strategy for dental and maxillofacial tissue repair and regeneration.

Extracellular vesicles (EVs), nano-sized bilayer membrane structures containing lipids, proteins and nucleic acids, play key roles in intercellular communication. Compared to stem cells, EVs have lower tumorigenicity and immunogenicity, are easier to manage and cause fewer ethic problems. In recent years, EVs have emerged as a potential solution for tissue regeneration in stomatology through cell-free therapies. The present review focuses on the role of EVs in dental and maxillofacial tissue repair and regeneration, including in dental and periodontal tissue, maxilla and mandible bone, temporomandibular joint cartilage, peripheral nerve and soft tissue. We also make a brief overview on the mechanism of EVs performing functions. However, limitations and challenges in clinical application of EVs still exist and should be addressed in future researches.

Integration strategy for facile fabrication of porous carbon coated Fe3O4 nanospindles with enhanced lithium storage

Despite high capacities, the practical use of the Fe3O4-based anodes is still impeded because of poor cyclic performance caused by their large volumetric variation and pulverization during cycle. Aimed at the aforementioned problems, a composite of conformal porous carbon coated Fe3O4 nanospindles (Fe3O4 @PC) has been prepared by a well-designed integration strategy which not only simplifies the experimental steps but also restrains the severe aggregation of nano-sized Fe3O4 during carbon coating process. In particular, the superficially conformal porous carbon is demonstrated to not only accommodate the volumetric variation of the Fe3O4 nanospindles better with its flexible spongy structure but also provide fast and stable diffusion pathways for ions through its defect-enriched pores. With a combination of superficially conformal porous carbon coating, nano-sized one-dimensional structure and Fe–O–C chemical bonding, therefore, the as-prepared Fe3O4 @PC shows outstanding electrochemical behaviors in terms of high capacity, long lifespan and good rate performance, demonstrating 896.3 and 592.9 mA h g−1 after 400 cycles at 200 and 1000 mA g−1, respectively. Moreover, this work is expected to open up new avenues for designing and preparing other conformal porous carbon coated metal oxides for advanced LIB anodes or other applications.

Tensile and stress relaxation characteristics of hybrid PLA-PVA/CS yarns loaded with antibiotic tetracycline hydrochloride used as suture

Antibacterial suture yarns with antibiotic drugs can be applied to protect wounds; so, they can play an important role in preventing and treating the infection. Engineered sutures are expected to have biomechanical properties, i.e. tensile and viscoelastic behavior, for final applications. This research is aimed to consider the tensile and stress-relaxation behavior of drug loaded and raw hybrid suture yarns with the nano-size structure from a mixture of PolyVinyl Alcohol/ChitoSan (PVA/CS) and Poly Lactic Acid (PLA); this was assessed using the electrospinning method. After optimizing the condition for the fabrication of structure, the selection of the finest diameter was done Then, the drug loaded PLA-PVA/CS nanofiber (PLA/TCH-PVA/CS) with the optimum condition was produced and tetracycline hydrochloride (5% wt) was loaded in the PLA solution; after that, both samples were twisted for manufacturing the suture yarns. FTIR and contact angle analysis were then conducted to characterize the samples. Following that, the tensile and stress relaxation of both samples were tested and simulated by the linear standard solid model, considering the mechanical characteristics of the requested suture. As a general conclusion, the experimental tensile results showed that with loading the drug, stress at 0.3 min and initial curve slopes in the tensile tests were reduced; however, the absolute initial discharge curve slopes values in stress relaxation results were also raised by loading the drug.

One-Pot Synthesis of Pt Nanobowls Assembled from Ultrafine Nanoparticles for Methanol Oxidation Reaction.

Simultaneously engineering a bowl-like and ultrafine nano-size structure offers an attractive route to not only increase the utilization efficiency of noble metals, the specific surface areas and the availability of active sites, but also boost the structural robustness and long-term stability. However, a great challenge remains in terms of the methods of synthesis. Herein, we report a facile one-pot hydrothermal method for the preparation of hollow porous Pt nanobowls (NBs) assembled from ultrafine particles. N,N′-methylenebisacrylamide (MBAA) acts as a structure-directing agent that forms a self-template with Pt ions and drives the nucleation and assembly of Pt metals, resulting in the fabrication of Pt NBs from ultrafine particles. By virtue of their unique structure and morphology, the optimized Pt NBs exhibited enhanced electrocatalytic methanol oxidation reaction (MOR) activity with 3.1-fold greater mass activity and 2.6-fold greater specific activities compared with those of commercial Pt black catalysts, as well as excellent stability and anti-poisoning ability.

Rapid production method with increased yield of high-purity extracellular vesicles obtained using extended mitochondrial targeting domain peptide.

Extracellular vesicles (EVs) are nano‐sized membranous structures involved in intercellular communication and various physiological and pathological processes. Here, we present a novel method for rapid (within 15 min), large‐scale production of high‐purity EVs using eMTDΔ4, a peptide derived from Noxa. The treatment of mesenchymal stem cells derived from human Wharton's jelly after trypsinization and subsequent eMTDΔ4 stimulation in a chemically defined sucrose buffer with orbital shaking led to a substantial increase (approximately 30‐fold) in EV production with markedly high purity (approximately 45‐fold). These EVs (TS‐eEVs) showed higher regenerative and immunomodulatory potential than natural EVs obtained from the culture media after 48 h. The calcium chelator BAPTA‐AM and calpain inhibitor ALLM, but not the natural EV biogenesis inhibitor GW4869, blocked the TS‐eEV production induced by eMTDΔ4, indicating that the eMTDΔ4‐mediated regulation of intracellular calcium levels and calpain activity are closely associated with the rapid, mass production of TS‐eEVs. The present study may lead to considerable advances in EV‐based drug development and production of stem cell‐derived EVs for cell therapy.