Nanoscale Effects Research Articles

Carboxylated Cellulose Nanocrystals Decorated with Varying Molecular Weights of Poly(diallyldimethylammonium chloride) as Sustainable Antibacterial Agents

Cationic nanomaterials are promising candidates for the development of effective antibacterial agents by taking advantage of the nanoscale effects as well as other exceptional physicochemical properties of nanomaterials. In this study, carboxylated cellulose nanocrystals (cCNCs) derived from softwood pulp were coated with cationic poly(diallyldimethylammonium chloride) of varying molecular weights. The resulting cationic carboxylated cellulose nanocrystals coated with poly(diallyldimethylammonium chloride) (cCNCs-PDDA) nanomaterials were characterized for their structural and morphological properties using Fourier transform infrared spectroscopy, dynamic light scattering, zeta potential, elemental analysis, transmission electron microscopy, and thermogravimetric analysis. Cationic cCNCs-PDDA were investigated for their antibacterial properties against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli 23934 and Pseudomonas aeruginosa using a bacterial lawn growth inhibition assay. cCNC-PDDA materials displayed marked antibacterial activity, particularly against Gram-positive Staphylococcus aureus. Overall, our results indicated that cCNCs-PDDA could be a potential candidate for antibacterial applications such as antibacterial surfaces or coatings.

Nano-effect enhanced cooperative luminescence of Yb3+ clusters in bulk materials

In order to improve the multi-ion cooperative transition, we proposed and exploited a novel nanoscale effect, namely the nanoshell effect in bulk materials. Based on the effect, an optimal material structure was designed by coating the surfaces of CaF2:Yb3+ micron size particles with ZrO2. An about 2 times higher intensity of cooperative luminescence is observed upon laser excitation at 980 nm. Dynamical analysis exhibits that the novel effect plays a key role in improving the performance of cooperative transitions. Our results also suggest that the nanoshell effect in bulk materials is likely to be significant in some special cases, which have not been reported yet in the literature.

Coupled dissolution-precipitation and growth processes on calcite, aragonite, and Carrara marble exposed to cadmium-rich aqueous solutions

Calcium carbonate and cadmium-rich fluid interactions have been studied at the nano and microscale with fluid flow and static fluid conditions for three forms of CaCO3: calcite in single crystals of Iceland Spar, calcite in a polycrystalline Carrara marble, and aragonite single crystals. Atomic Force Microscopy (AFM) showed the nanoscale effect of cadmium on CaCO3 dissolution and growth under flow-through conditions at ambient temperature, with the modification of calcite dissolution behaviour and simultaneous precipitation of a Cd-rich phase on all the different samples. Hydrothermal experiments at 200 °C revealed that the reactivity of single calcite crystals is passivated by epitaxial growth of the less soluble Cd-rich endmember of the (Ca,Cd)CO3 solid-solution on the sample surface due to the similar crystallographic structures of calcite and otavite (CdCO3). Conversely, the presence of grain boundaries in Carrara marble or the change of crystallographic structure and reaction-induced fracturing in aragonite allowed, to some extent, the pseudomorphic replacement of Carrara marble and aragonite samples by a porous (Ca,Cd)CO3 solid-solution phase of variable composition. These phenomena have been observed in solutions undersaturated with respect to all solid phases and are the result of an interface-coupled dissolution-precipitation mechanism where the dissolving CaCO3 provides ions to supersaturate the mineral-fluid interfacial layer, leading to the precipitation of a Cd-containing phase on the samples' surfaces. This coupled dissolution-precipitation mechanism could potentially be used as a remediation process to sequester cadmium from contaminated effluents.

Physicochemical properties of nanosized biochar regulated by heat treatment temperature dictates algal responses: From the perspective of fatty acid metabolism.

Nanosized biochar (NBC) is an important fraction of biochar (BC) as it can exert nano-scale effects on aquatic organisms, attracting increasing research attention. However, effects of different physicochemical properties of NBC on biological responses at the metabolic and gene expression level are not comprehensively understood. Here, biological effects of NBCs pyrolyzed at different heat treatment temperatures (HTTs, 350-700°C) were evaluated using freshwater algae Chlorella vulgaris, from the perspectives of growth and fatty acid (FA) profile changes. NBC pyrolyzed at 700°C (N700) induced the greatest algal growth inhibition and oxidative stress than N350 and N500. In addition, NBC exposure to 50mg/L increased saturated and monounsaturated FAs, along with a decrease in polyunsaturated FAs (PUFAs). Exposure to NBC also significantly influenced the expression of key FA metabolism genes (3fad, sad, kasi and accd), demonstrating the potential role of reactive oxygen species-mediated PUFA reduction accompanied by increased membrane permeability in algal toxicity upon NBC exposure. The observed differences in response to N700 were attributed to its smaller particle size and higher abundance of -COOH. These findings reveal the underlying mechanisms in the algal response to NBCs and provide valuable guidance for the safe design and application of BC materials.

Nanoscale effects of TiO2 nanoparticles on the rheological behaviors of ultra-high molecular weight polyethylene (UHMWPE).

Considering the molar mass between entanglements to be an intrinsic property of ultra-high molecular weight polyethylene (UHMWPE), the number of entanglements per chain increases with increasing molar mass, correspondingly making the UHMWPE intractable. Herein, we dispersed TiO2 nanoparticles with different characteristics into UHMWPE solutions to disentangle the molecular chains. Compared with the UHMWPE pure solution, the viscosity of the mixture solution declines by 91.22%, and the critical overlap concentration increases from 1 wt% to 1.4 wt%. A rapid precipitation method was utilized to obtain UHMWPE and UHMWPE/TiO2 composites from the solutions. The melting index of UHMWPE/TiO2 is 68.85 mg, which is in sharp contrast to that of UHMWPE which is 0 mg. We characterized the microstructures of UHMWPE/TiO2 nanocomposites using TEM, SAXS, DMA, and DSC. Accordingly, this significant improvement in processability contributed to the reduction of entanglements and a schematic model was proposed to explain the mechanism by which nanoparticles disentangle molecular chains. Simultaneously, the composite demonstrated better mechanical properties than UHMWPE. In summary, we provide a strategy to promote the processability of UHMWPE without sacrificing its outstanding mechanical properties.

An Analytical Model for Hysteretic Pressure-Sensitive Permeability of Nanoporous Media

Hysteretic pressure-sensitive permeability of nanohybrids composed of substantial nanopores is critical to characterizing fluid flow through nanoporous media. Due to the nanoscale effect (gas slippage), complex and heterogeneous pore structures of nanoporous media, the essential controls on permeability hysteresis of nanohybrids are not determined. In this study, a hysteretic pressure sensitive permeability model for nitrogen flow through dry nanoporous media is proposed. The derived model takes into account the nanoscale effect and pore deformation due to effective stress. The model is validated by comparing it with the experimental data. The results show that the calculated permeability and porosity are consistent with the measured results with the maximum relative error of 6.08% and 0.5%, respectively. Moreover, the hysteretic pressure-sensitive permeability of nanohybrids is related to effective stress, gas slippage, pore microstructure parameters, grain quadrilateral angle, and the loss rate of grain quadrilateral angle. The nanoscale effect is crucial to the permeability of nanoporous media. In addition, as impacted by the comprehensive impact of multiple relevant influential parameters, permeability during the pressure unloading process is not a monotonous function but presents complicated shapes. The proposed model can explain, quantify, and predict the permeability hysteresis effect of nanoporous media reasonably well.

Hot Carrier Injection Reliability in Nanoscale Field Effect Transistors: Modeling and Simulation Methods

Hot carrier injection (HCI) can generate interface traps or oxide traps mainly by dissociating the Si-H or Si-O bond, thus affecting device performances such as threshold voltage and saturation current. It is one of the most significant reliability issues for devices and circuits. Particularly, the increase in heat generation per unit volume due to high integration density of advanced integrated circuits leads to a severe self-heating effect (SHE) of nanoscale field effect transistors (FETs), and low thermal conductivity of materials in nanoscale FETs further aggravates the SHE. High temperature improves the HCI reliability in the conventional MOSFET with long channels in which the energy of carriers can be relaxed. However, high temperature due to severe SHE deteriorates HCI reliability in nanoscale FETs, which is a big concern in device and circuit design. In this paper, the modeling and simulation methods of HCI in FETs are reviewed. Particularly, some recently proposed HCI models with consideration of the SHE are reviewed and discussed in detail.

Dynamics of tangent-hyperbolic nanoliquids configured by stratified extending surface: Effects of transpiration, Robin conditions and dual stratifications

A mathematical study is presented to evaluate double stratification effects on the dual convected flow of a non-Newtonian (tangent-hyperbolic) nanoliquid persuaded by porous stretching surface. Thermal radiation along with transpiration (wall suction/injection) and heat source/sink are included. Buongiorno's model is employed for nanoscale effects and a Rosseland diffusion approximation for nonlinear radiative heat transfer. Appropriate similarity transformations are deployed to alter the dimensional governing nonlinear PDEs (partial differential equations) to a nonlinear differential one with physically viable boundary conditions. The transformed dimensionless BVP (boundary value problem) is computed analytically by a HAM (homotopic analysis method) algorithm and a symbolic software. Validation with earlier studies employing the numerical method (Runge-Kutta-Fehlberg) is included. The evolution in velocity, thermal and solutal (nanoparticle) fields are interpreted through graphical outcomes for the impact of significant sundry parameters. Tabular outcomes are also presented for skin-friction, local Nusselt and Sherwood numbers. A rise in material variable (Weissenberg number), the flow is decelerated while it is accelerated with increasing nonlinear thermal convective parameter, mixed convection parameter and buoyancy ratio values. Temperatures are boosted with increment in radiative, thermophoresis, Brownian motion, thermal Biot number and heat generation parameters whereas they are reduced with increasing thermal stratification parameter. Nanoparticle concentration values are suppressed with higher Schmidt number, Brownian movement and solutal stratification variable however they are boosted with greater values of thermophoresis and concentration Biot number. Local Sherwood number is improved with Schmidt number, concentration stratification parameter and concentration Biot number. Local Nusselt number is strongly increased with greater Prandtl number, thermal stratification number, thermal Biot number and radiative parameter. The study finds applications in thermal nano-polymeric coating flows in materials processing operations.

Molecular dynamics study on melting point of tungsten nanostructures

We used molecular dynamics to study the melting point of tungsten nano-fibers. It is found that the nanoscale effect and helium impurity can significantly reduce the melting point. We use linear model and neural network model to fit the effect of two compound effects on melting point. For fuzz with 1%–4% helium and a diameter of 10–200 nm, its melting point can be reduced by 7.7%–16.4% with linear model and 6.1%–17.0% with neural network model. The actually reduction of melting point may be more than 20% due to the existence of a large number of holes in fuzz and the rough surface of fuzz. The reduction of melting point of tungsten fuzz can accelerate the dynamic phenomenon of fuzz annealing at low temperature, leading to the disappearance of fuzz. Our research is helpful to understand that the temperature limit of fuzz formation is lower than 2000 K to some extent. • Nanoscale effect and He impurity can significantly reduce the melting point of W. • The quantitative relationship of tungsten melting point change was obtained. • Research are helpful to understand the temperature limit of tungsten fuzz formation.

Dewetting acceleration by evaporation

Dewetting of a substrate, i.e. the liquid film retraction under partial wetting conditions, has been studied extensively over the past decades. This theoretical work deals with the dewetting phenomenon in the presence of liquid evaporation into the pure vapour atmosphere driven by substrate superheating with respect to the saturation temperature corresponding to the vapour pressure. The dynamic profile of the vapour–liquid interface is analysed numerically by using the generalised lubrication approximation that can be applied to an interface slope larger than its conventional counterpart. This approximation uses a phenomenological argument to increase the precision of calculations. For small slopes, it reduces to the conventional lubrication approach. Several nanoscale effects are included in the theory to obtain more precise results: the Kelvin effect, the hydrodynamic slip, the Marangoni effect, the vapour recoil and the interfacial thermal resistance. Their relative importance is discussed. The results include the film shape evolution, the apparent contact angle and the contact line speed, all defined by the substrate superheating and its wetting properties. These dependencies agree with existing experimental results. It is found that the dewetting is accelerated by evaporation. The numerical results are compared to those of the multiscale theory that uses two main parameters, the Voinov angle (the apparent angle obtained within the microregion problem) and the Voinov length. The latter is studied for several fluids as a function of superheating, and an approximate expression for it is proposed. A good agreement between the numerics and the multiscale theory shows the validity of the latter. This means that the dewetting speed in the presence of evaporation can be calculated with an analytical expression that requires only the Voinov angle as a numerical input. Such results are important for many applications, for instance, bubble growth in boiling or film dynamics in heat pipes.

Suppression of injected minority carriers in nanoscale field effect diodes to improve the off-current

Suppression of injected minority carriers in nanoscale field effect diodes to improve the off-current

61Ni NMR study of nickel nanoparticles: Nanoscale effect and magnetic state

The 61Ni NMR spectra for Ni-based nanoparticles synthesized by the gas-phase method have been obtained. A nanoscale effect has been found in nickel nanoparticles, consisting in a change of the distribution of induced fields when the size of the nanoparticles decreases below a critical size of a single domain. It has been shown that this effect does not depend on the type of shell and is not associated with surface or interface defects. It is assumed that for particles smaller than the critical size, the shift of the hyperfine field is due to the demagnetizing field of single-domain particles. This shift decreases when an inhomogeneous magnetic structure occurs in larger particles.

Preparation of Three-Dimensional MF/Ti3C2Tx/PmPD by Interfacial Polymerization for Efficient Hexavalent Chromium Removal.

Heavy metal pollution is a serious threat to human health and the ecological environment, but adsorption technology based on nano adsorbents can effectively treat the crisis. However, due to the nanoscale effect, nano adsorbents have some crucial shortcomings, such as recycling difficulty and the loss of nanoparticles, which seriously limit their application. The feasible assembly of nano adsorbents is an accessible technology in urgent need of a breakthrough. In this study, three-dimensional (3D) adsorbent (MF/Ti3C2Tx/PmPD) with excellent performance and favorable recyclability was prepared by interfacial polymerization with melamine foam (MF) as the framework, two-dimensional (2D) titanium carbide (Ti3C2Tx) as the bridge and Poly (m-Phenylenediamine) (PmPD) as the active nano component. The morphology, structure, mechanical property of MF/Ti3C2Tx/PmPD and reference MF/PmPD were investigated through a scanning electron microscope (SEM), Fourier transformed infrared spectra (FT-IR), Raman scattering spectra and a pressure-stress test, respectively. Owning to the regulation of Ti3C2Tx on the morphology and structure of PmPD, MF/Ti3C2Tx/PmPD showed excellent adsorption capacity (352.15 mg/g) and favorable cycling performance. R–P and pseudo-second-order kinetics models could well describe the adsorption phenomenon, indicating that the adsorption process involved a composite process of single-layer and multi-layer adsorption and was dominated by chemical adsorption. In this research, the preparation mechanism of MF/Ti3C2Tx/PmPD and the adsorption process of Cr(VI) were systematically investigated, which provided a feasible approach for the feasible assembly and application of nano adsorbents in the environmental field.

Temporospatial nano-heterogeneity of self-assembly of extracellular polymeric substances on microplastics and water environmental implications

Environmental behavior and ecotoxicity of microplastics (MPs) are significantly influenced by the omnipresent self-assembly of microbial extracellular polymeric substances (EPS) on them. However, mechanisms of EPS self-assembly onto MPs at nanoscale resolution and effects of aging are unclear. For the first time, temporospatial nano-heterogeneity of self-assembly of EPS onto fresh and one-year aged polypropylene (PP) MPs were investigated by atomic-force-microscopy-infrared-spectroscopy (AFM-IR). Natural aging caused high degree nanoscale fragmentation of MPs physically and chemically. Self-assembly of EPS on MPs was aging-dependent. Polysaccharides were assembled on MP surface faster than proteins. Initially, regardless of the fresh or aged MPs, polysaccharides and proteins, with the former being predominant, were successively and separately assembled to different nanospaces because of their competition for binding sites. More and more proteins and polysaccharides were superimposed on each other with assembly time due to intermolecular forces. The nanochemical textural analysis showed that the nano-heterogeneity of EPS assembly to MPs was clearly correlated with the aging-induced nanochemical and nanomechanical heterogeneity of MP surface. The spontaneous self-assembly of EPS with temporospatial nano-heterogeneity on MPs have multiple impacts on behavior, ecotoxicity and fate of MPs and their associated pollutants as well as other key ecological processes in aquatic environment.

Micropolar nanofluid overlying a porous layer: Thermosolutal convection

An investigation of the stability of an micropolar nanofluid overlying a sparsely packed porous medium and implanted in a parallel conduit is reviewed. Linear and also nonlinear terms are incorporated for the study. A Darcy-Brinkman-Forchheimer drag force model is deployed. To evaluate nanoscale effects the Buongiorno model is employed. The equations for mass, momentum, angular momentum, energy and nanoparticle species conservation with correlated wall conditions are non-dimensionalized. Modified diffusivity ratio and Lewis number stable the system, the micropolar parameters concentration Rayleigh number destable system for stationary convection. Concentration Rayleigh number, micropolar parameters stabilize and Lewis number destabilizes the system for oscillatory convection. Applications of the study include micro/nano-fluidic devices, nano-doped energy systems and packed beds in chemical engineering.

Spray-drying construction of nickel/cobalt/molybdenum based nano carbides embedded in porous carbon microspheres for lithium-ion batteries as anodes

In this work, from a practical point of view, a scalable spray-drying strategy is developed to prepare nickel/cobalt/molybdenum-based nano carbides embedded in porous microspherical carbon architectures for LIBs as competitive anodes. The resulted porous Ni1.5Co1.5Mo3C/Mo2[email protected] (NCMC/[email protected]) microspheres exhibit even better lithium storage performance in terms of first Coulombic efficiency, reversible capacities, rate behaviors, and cycling stability than their counterparts including Co3Mo3C/Mo2[email protected] and Ni3Mo3C/Mo2[email protected] MSs, thanks to the involved synergistic contributions from the nanoscale effect, solid-solution feature, porous structure, and abundant hetero-interfaces, which cooperatively guarantee the rapid Li+/electron transport and buffered volume changes over (de)lithiation process. Besides, the NCMC/[email protected] full LIBs demonstrate remarkable electrochemical characteristics with high energy density and cycling stability. More significantly, the methodology here holds great promise for achieving other versatile nano carbides towards advanced LIBs and beyond.

Hygrothermal Buckling of Smart Graphene/Piezoelectric Nanocomposite Circular Plates on an Elastic Substrate via DQM

This paper aims to study the hygrothermal buckling of smart graphene/piezoelectric circular nanoplates lying on an elastic medium and subjected to an external electric field. The circular nanoplates are made of piezoelectric polymer reinforced with graphene platelets that are uniformly distributed through the thickness of the nanoplate. The material properties of the nanocomposite plate are determined based on the modified Halpin-Tsai model. To capture the nanoscale effects, the nonlocal strain gradient theory is applied. Moreover, the principle of virtual work is employed to establish the nonlinear stability equations in the framework of classical theory. The differential quadrature method is utilized to solve the governing equations. Among the important aims of the paper is to study the influences of various parameters such as graphene weight fraction, elastic foundation parameters, external applied electric field, humid conditions, and boundary conditions on the thermal buckling of the smart nanocomposite circular nanoplates. It is found that the increase in graphene components and elastic foundation stiffness enhances the strength of the plates; therefore, the buckling temperature will increase.

Investigation of Non-Newtonian Characteristics of Water Flow in Micro-/Nanochannels and Tight Reservoirs

The characteristic scale of pore flow in tight reservoirs is generally in the range of 0.1 μm to 1 μm, which shows the obvious micro- and nanoscale effect. The traditional oil and gas seepage theory cannot accurately describe the flow law of liquid in the micro- and nanopores. The determination of seepage characteristics is crucial to the development, layout, and prediction of tight oil. Therefore, a non-Newtonian fluid model is established to discuss the flow characteristics of confined liquid in the heterogeneous pores of microtubules and reveal the nonlinear seepage law of water in micro- and nanochannels and tight reservoirs. Based on the characteristics of non-Newtonian fluid of confined fluid in micro- and nanospace, the flow model of non-Newtonian fluid under the action of shear stress was deduced. The flow velocity variation of liquid in micro- and nanochannel and dense core was analyzed, and the flow rate of water was less than that predicted by macro theory. According to the flow experiment of water in micro- and nanochannels, the flow model of power-law non-Newtonian fluid was verified. At the same time, through the flow experiment of water in the dense rock core, the non-Newtonian model was used for nonlinear fitting, and the non-Newtonian power-law parameters and average pore radius were obtained, which verified the effectiveness of the non-Newtonian flow model.

Plasma-affected photo-thermoelastic wave propagation in a semiconductor Love–Bishop nanorod using strain-gradient Moore–Gibson–Thompson theories

In this paper, the photo-thermoelastic wave propagation analysis in a semiconductor nanorod resonator under laser excitation employing the strain-gradient Moore–Gibson–Thompson (MGT) and Love–Bishop theories is presented, which is for the first time to the authors’ knowledge. The governing equations of the photo-thermoelastic wave propagation are derived using the proposed novel size-dependent MGT heat conduction model, strain-gradient and Love–Bishop theories. The size-dependent MGT coupled photo-thermoelasticity theory is developed by taking into account of five nano-scale parameters for the first time, which is employed to derive the governing equations. The governing equations are converted into the Laplace-transformed domain and then analytical solution is obtained for a semiconductor Love–Bishop nanorod resonator subjected to plasma and thermal shock loadings. To obtain the transient field variables in the time-domain, the Talbot Laplace-inversion technique is employed. The size-effects on the propagation of the photo-thermoelastic waves are studied in detail. The transient behaviors of the displacement, temperature and carrier density (plasma density) fields are also investigated with considering the nano-scale effects by performing the parametric studies. The effects of the carrier density, the relaxation time in the size-dependent MGT theory and the nano-scale parameters on the plasma-affected photo-thermoelastic wave propagation are revealed. Numerical examples demonstrate that the derived governing equations and also the proposed analytical solutions can be employed to determine the realistic behaviors of the field variables in a semiconductor Love–Bishop nanorod resonator under laser shock loading with considering the nano-scale effects.

Straightforward fabrication of sub-10 nm nanogap electrode pairs by electron beam lithography

The consistent motivation to observe molecular electronics and quantum effects drives the need for the tunable and robust fabrication of nanogap devices. Electron beam lithography (EBL) offers high fidelity fabrication to construct arrayed nanogaps, and methods have been developed to achieve sub-10 nm channel widths. However, many of these approaches involve multiple lithography steps or specialized techniques that limit throughput and universality. This work describes a simple, single EBL step, continuous dose, and direct feature write method of fabricating electrode pairs with nanogap spacing from 5 to 40 nm. This straightforward technique relies on precise electron beam focusing coupled with cold lithography for developing. Overall, this protocol enables efficient production of electrode nanogaps to facilitate the study of nanoscale materials and effects.