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AbstractA nonlocal layerwise 3D bending solution for multilayered functionally graded shallow nanoshells is presented. Eringen’s nonlocal elasticity theory is used for approaching the small length scale effect. Curvilinear orthogonal coordinate system is employed for writing the constitutive and equilibrium equations. The middle-plane of displacements are assumed as a Navier solution which are only valid for simply supported spherical, cylindrical panels and rectangular plates. The thickness domain is discretized by the well-known Chebyshev–Gauss–Lobatto, and its derivatives are calculated numerically by the Differential Quadrature method (DQM). Lagrange interpolation polynomials are utilized as the basis functions for DQM. The traction conditions at the top and the bottom of the shell panel and continuity conditions of the interlaminar adjacent layers for transverse stresses are considered, so this method presents layerwise capabilities. The results are compared with higher order theories proposed in the literature, and due to the 3D nature of the presented formulation, benchmark solutions are provided. [ABSTRACT FROM AUTHOR]

The ability of Plasmonic nanoparticles (PNPs) to efficiently convert absorbed light energy into localized heat has made them a popular choice for photothermal medical applications. However, during the photothermal process, the diffusion of localized heat can lead to temperature management challenges. To address this issue, researchers have developed a new generation of PNPs incorporating optical phase transition materials, allowing for tunable photothermal responses without altering the geometry. This tunability is achieved through rapid changes in optical and thermal properties during phase transitions. In this study, we conducted a numerical analysis on the photothermal response of a VO2@Au smart nanoshell in both tumor and healthy liver tissue under irradiation with a nanosecond (5 ns) pulsed laser. To obtain the temperature profile, we solved a coupling problem between electromagnetism and thermodynamics.

An unavailable semi-analytical non-local 3D solution for functionally graded nanoshells with constant radii of curvature is presented. The small length scale effect is included in Eringen’s nonlocal elasticity theory. The constitutive and equilibrium equations are written in terms of curvilinear orthogonal coordinates systems which are only valid for spherical and cylindrical shells, and rectangular plates. The stresses and displacements are assumed in terms of the Navier method which is applicable for simply supported structures. The derivatives in terms of thickness are approximated by the differential quadrature method (DQM). The thickness domain is discretized by the Chebyshev–Gauss–Lobatto grid distribution. Lagrange interpolation polynomials are considered as the basis function for DQM. The correct free surface boundary condition for out-of-plane stresses is considered. Several problems of isotropic and functionally graded shells subjected to different types of loads are analyzed. The results are compared with other three-dimensional solutions and higher-order theories. It is important to emphasize that the radii of curvature are crucial at nanoscale, so it should be considered in the design of nanodevices.

Conformal deposition of a Co nanoshell of tailorable thickness (1.5–7.1 nm) on the internal surfaces of nanoporous gold (NPG) was achieved by adapting conventional electroless deposition conditions to circumvent sheath-only deposition on its external surface. Confining electroless deposition onto the ligaments of NPG is challenging as it demands mass transport through the porous network with non-homogeneous deposition likely due to concurrent depletion of the species to be deposited. Spatially-controlled Co electroless deposition into NPG's pores required the sequential addition of dimethylamine borane (DMAB) as reducing agent and an ultra-low concentration of Co ions. DMAB is drawn into the hydrophilic serpentine pores of NPG in a pre-immersion step with temperature elevation prior to addition of Co ions to yield Co@NPG composite. Deposition at planar gold under these conditions was not achieved, emphasising NPG's heightened intrinsic catalytic activity. XPS revealed the presence of cobalt oxide in the nanoshell. Preliminary exploration of oxidized Co@NPG nanocomposite as a potentiometric phosphate sensor revealed a linear dynamic range of 0.10–500 ppm. The facile, exclusively liquid-phase non-conventional electroless deposition approach unveils a new design strategy for a diverse range of core-shell nanoporous catalysts as prospective electrodes in fuel cells, energy conversion devices and sensors.

The highly conserved matrix protein 2 ectodomain (M2e) of influenza viruses presents a compelling vaccine antigen candidate for stemming the pandemic threat of the mutation‐prone pathogen, yet the low immunogenicity of the diminutive M2e peptide renders vaccine development challenging. A highly potent M2e nanoshell vaccine that confers broad and durable influenza protectivity under a single vaccination is shown. Prepared via asymmetric ionic stabilization for nanoscopic curvature formation, polymeric nanoshells co‐encapsulating high densities of M2e peptides and stimulator of interferon genes (STING) agonists are prepared. Robust and long‐lasting protectivity against heterotypic influenza viruses is achieved with a single administration of the M2e nanoshells in mice. Mechanistically, molecular adjuvancy by the STING agonist and nanoshell‐mediated prolongation of M2e antigen exposure in the lymph node follicles synergistically contribute to the heightened anti‐M2e humoral responses. STING agonist‐triggered T cell helper functions and extended residence of M2e peptides in the follicular dendritic cell network provide a favorable microenvironment that induces Th1‐biased antibody production against the diminutive antigen. These findings highlight a versatile nanoparticulate design that leverages innate immune pathways for enhancing the immunogenicity of weak immunogens. The single‐shot nanovaccine further provides a translationally viable platform for pandemic preparedness. [ABSTRACT FROM AUTHOR]

Recent advancements in nanotechnology have made it feasible to excite, control and tune Fano resonance in plasmonic nanosystems, especially through structural and material engineering. Because of various applications in areas such as refractive-index sensing, surface enhanced Raman scattering, and biosensing among others, considerable attention has been devoted to increase the sensitivity of Fano resonance based sensors. In this article, the formation of Fano resonances in graphene-assisted concentric nanoshell and nanomatryoshka is investigated using Mie theory, and the results have been validated using FEM-based COMSOL Multiphysics. It is shown that Fano resonances strongly depend on the chemical potential of graphene and the refractive index of the embedding environment. This makes these nanoparticle systems ultrasensitive sensors for sensing food adulteration. Refractory nitrides (e.g., ZrN and TiN) based plasmonic nanoshell and nanomatryoshka sensor designs optimized for maximum sensitivity are proposed with sensitivity up to 799.02 nm/RIU, representing a 120% increase in the sensitivity from the previous highest reported values. The present work paves way for developing highly sensitive Fano resonance based sensors with applications in diverse fields. [ABSTRACT FROM AUTHOR]

Abstract The highly conserved matrix protein 2 ectodomain (M2e) of influenza viruses presents a compelling vaccine antigen candidate for stemming the pandemic threat of the mutation‐prone pathogen, yet the low immunogenicity of the diminutive M2e peptide renders vaccine development challenging. A highly potent M2e nanoshell vaccine that confers broad and durable influenza protectivity under a single vaccination is shown. Prepared via asymmetric ionic stabilization for nanoscopic curvature formation, polymeric nanoshells co‐encapsulating high densities of M2e peptides and stimulator of interferon genes (STING) agonists are prepared. Robust and long‐lasting protectivity against heterotypic influenza viruses is achieved with a single administration of the M2e nanoshells in mice. Mechanistically, molecular adjuvancy by the STING agonist and nanoshell‐mediated prolongation of M2e antigen exposure in the lymph node follicles synergistically contribute to the heightened anti‐M2e humoral responses. STING agonist‐triggered T cell helper functions and extended residence of M2e peptides in the follicular dendritic cell network provide a favorable microenvironment that induces Th1‐biased antibody production against the diminutive antigen. These findings highlight a versatile nanoparticulate design that leverages innate immune pathways for enhancing the immunogenicity of weak immunogens. The single‐shot nanovaccine further provides a translationally viable platform for pandemic preparedness.

The surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR) can be used to enhance the generation of the hot electrons in plasmon metal nanocavity. In this paper, Pd nanomembrane (NMB) is sputtered on the surface of Si nanosphere (NS) on glass substrate to form the Si@Pd core-Ω shell nanocavity. A plasmon-Mie resonance is induced in the nanocavity by coupling the plasmon resonance with the Mie resonance to control the optical property of Si NS. When this nanocavity is excited by near-infrared-1 (NIR-1, 650 nm–900 nm) femtosecond (fs) laser, the luminescence intensity of Si NS is dramatically enhanced due to the synergistic interaction of plasmon and Mie resonance. The generation of resonance coupling regulates resonant mode of the nanocavity to realize multi-dimensional nonlinear optical response, which can be utilized in the fields of biological imaging and nanoscale light source. [ABSTRACT FROM AUTHOR]

This article presents the finite element method (FEM) used four-unknown shear deformation theory for the static bending and hygro-thermo-mechanical vibration analysis of sandwich functionally graded porous (SFGP) doubly curved nanoshells resting on the elastic foundation (EF). The configurations of SFGP nanoshells include a homogenous core made of full ceramic while the top and bottom layers vary through the thickness with the law of uneven porosity distribution. The governing equations are obtained by using Hamilton's principle and the nonlocal elasticity theory of Eringen (nonlocal theory). For the first time, a four-node quadrilateral element with ten degrees of freedom (DOFs) for each node using Lagrangian and Hermitian interpolation functions to approximate the membrane and bending displacement fields are proposed to analyze the SFGP nanoshells. The numerical results are compared with other exact solutions to evaluate the performance of the proposed method. Furthermore, influences of geometrical parameters and material properties such as the power-law index n , the porosity coefficient ξ , the nonlocal coefficient μ , and EF-stiffness (K w , K s ) on the static bending, free vibration of SFGP nanoshells are comprehensive studied. [ABSTRACT FROM AUTHOR]

This article studies free vibration of a functionally graded porous cylindrical small-scale shell made from porous metal and ceramic based on power law distribution. It is bonded with an adjustable array of strip-like piezoelectric elements. The behavior of integrated structure is modified by change of quantity and location of the elements. Motion equations are achieved through first-order shear deformation theory and principle of virtual work. Stress-strain relations are developed via nonlocal theory. Two comparative studies are presented for validation of formulation. A parametric study is reported to investigate effects of input parameters. [ABSTRACT FROM AUTHOR]

As the main contribution, a nonlocal strain gradient theory (NSGT) is developed in conjugation with the generalized differential quadrature method (GDQM) to analyze the free vibration of a transversely graded nanoshell subjected to magnetic and thermal loads derived by using the first-order shear deformation theory (FSDT) and Hamilton's principle. Comparisons with other common methods have shown the validity of the presented NSGT-GDQM hybrid approach. The effects of power-law exponent, nonlocal parameter, strain gradient parameter, magnetic potential, angular velocity, and temperature for both simply supported and clamped boundary conditions of a nanoshell composed of BaTiO3 and CoFe2O4 materials were investigated. Sensitivity analysis illustrates that more resolution will be available with clamped boundaries. With increasing the temperature gradient, the absolute value of the sensitivity increases and the maximum sensitivity value occurs always on the critical buckling point. Finally, comparing two studied boundary conditions revealed that if there is any temperature rise limit, the clamped boundary condition is suggested because of more sensitivity. Though the temperature gradient could be more than 400 K in the case of simply supported edges, the maximum absolute sensitivity could be obtained is about 0.12 wherein the case of clamped boundary condition it was about 0.17. [ABSTRACT FROM AUTHOR]

Antigen-specific lung-resident memory T cells (TRMs) constitute the first line of defense that mediates rapid protection against respiratory pathogens and inspires novel vaccine designs against infectious pandemic threats, yet effective means of inducing TRMs, particularly via non-viral vectors, remain challenging. Here, we demonstrate safe and potent induction of lung-resident TRMs using a biodegradable polymeric nanoshell that co-encapsulates antigenic peptides and TLR9 agonist CpG-oligodeoxynucleotide (CpG-ODN) in a virus-mimicking structure. Through subcutaneous priming and intranasal boosting, the combinatorial nanoshell vaccine elicits prominent lung-resident CD4+ and CD8+ T cells that surprisingly show better durability than live viral infections. In particular, nanoshells containing CpG-ODN and a pair of conserved class I and II major histocompatibility complex-restricted influenza nucleoprotein-derived antigenic peptides are demonstrated to induce near-sterilizing immunity against lethal infections with influenza A viruses of different strains and subtypes in mice, resulting in rapid elimination of replicating viruses. We further examine the pulmonary transport dynamic and optimal composition of the nanoshell vaccine conducive for robust TRM induction as well as the benefit of subcutaneous priming on TRM replenishment. The study presents a practical vaccination strategy for inducing protective TRM-mediated immunity, offering a compelling platform and critical insights in the ongoing quest toward a broadly protective vaccine against universal influenza as well as other respiratory pathogens.

Flexoelectric and piezoelectric effects have attracted the attention of researchers, owing to their applications in sensing systems and actuators. In this paper, the vibration of functionally graded material (FGM) conical nanoshell is studied, taking into account both piezoelectricity and flexoelectricity. The nanoshell has a sandwich-type structure with a FGM core and two layers of piezoelectric materials on its top and bottom. With the combination of the first order shear deformation and Eringen's nonlocal theories, the vibration equation of the nanoshell is developed. In order to study the governing equations and the frequency of vibrations of nanoshell, the generalized differential quadrature method is implemented. Based on the developed numerical solution procedure, the effect of different parameters, such as flexoelectricity, piezoelectricity, nonlocal term and Pasternak foundation, are shown on the vibrations of conical nanoshell. The presented analysis provides a better insight into the behavior of conical nanoshells, which are highly applicable in bio-sensing and optical devices. [ABSTRACT FROM AUTHOR]

This article aims to investigate buckling characteristics of a functionally graded magneto-electro-thermo-elastic nanoshell based on nonlocal strain gradient theory (NSGT). Accounting for nonlocal and strain gradient size-dependency, NSGT has two scale coefficients. The nanoshell is subjected to external electric, magnetic, mechanical, and thermal fields. The temperature distributions are considered as uniform and linear thorough the nanoshell thickness. All material properties including elastic, piezoelectric, and magnetic properties are defined based on a power-law distribution type. Seven coupled governing equations are derived for the nanoshell based on Hamilton's rule and then solved applying Galerkin's approach. The dependency of the buckling behavior of the nanoshell on applied thermal load, temperature distribution, electric voltage, magnetic potential, material gradient index, scale parameters, and shear deformation will be explored. [ABSTRACT FROM AUTHOR]

Electrocatalytic water splitting, which is an interface‐dominated process, can be significantly accelerated by increasing the number of front‐line surface active sites (NA) of the electrocatalyst. In this study, a unique method is used for increasing the NA by converting the smooth ultrathin atomic‐layer‐deposited nanoshells of the electrocatalysts into nano‐roughened active shell layers using a controlled anion‐exchange reaction (AER). The coarse thin nanoshells present abundant surface active sites, which are generated owing to the inherent unit‐cell volume mismatch induced during the AER. Consequently, the nano‐roughened electrodes accelerate the sluggish water reaction kinetics and lower the overpotentials required for the hydrogen and oxygen evolution reactions. In addition, the electronic modulation induced by the nanoshell layer at the core–nanoshell interface amplifies the local electron density, as confirmed using electrochemical analysis data and density functional theory calculations. Because of the integrity of the composite electrodes during water‐splitting half‐cell reactions, their durability for industrial seawater electrolysis is evaluated. The results indicate that their electrochemical activity does not change significantly after 10 days of continuous overall water splitting. [ABSTRACT FROM AUTHOR]

The surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR) can be used to enhance the generation of the hot electrons in plasmon metal nanocavity. In this paper, Pd nanomembrane (NMB) is sputtered on the surface of Si nanosphere (NS) on glass substrate to form the Si@Pd core-Ω shell nanocavity. A plasmon-Mie resonance is induced in the nanocavity by coupling the plasmon resonance with the Mie resonance to control the optical property of Si NS. When this nanocavity is excited by near-infrared-1 (NIR-1, 650 nm–900 nm) femtosecond (fs) laser, the luminescence intensity of Si NS is dramatically enhanced due to the synergistic interaction of plasmon and Mie resonance. The generation of resonance coupling regulates resonant mode of the nanocavity to realize multi-dimensional nonlinear optical response, which can be utilized in the fields of biological imaging and nanoscale light source.

We investigated the application of gold nanoshell particles as optical sensors and contrast agents to study the blood functional parameters. Gold nanoshell particles with a core size of 1 μ m that exhibit two prominent plasmonic peaks at 750 and 830 nm were developed. The peaks correspond to the wavelengths typically used to study the oxygen saturation of the blood. The plasmonic properties of gold nanoshells in media with various refractive indices were studied. Glucose samples with concentrations 0, 15, and 20%w/v in water were used. The 750 and 830 nm plasmonic peaks exhibit peak wavelength shifts of 63.77 ± 49.40 nm and 31.18 ± 20.94 nm per unit refractive index change. The optical properties of blood samples mixed with gold nanoshells were also measured. The optical absorption of blood samples increased by 7% at these wavelengths in the presence of the nanoshells. The plasmonic peaks at 750 and 830 nm showed a 3.57 ± 0.56 and 1.44 ± 0.55 percentage variation in absorbance for a 1% change in hematocrit. The enhanced optical absorption at these wavelengths suggests that these particles are effective optical sensors/contrast agents for multimodal optical and photoacoustic sensing and imaging.

System of nonlinear partial differential equations with respect to displacements is derived to describe free nonlinear vibrations of multi-walled nanoshell. The geometrically nonlinear vibrations of nanoshell, which is described by Sanders-Koiter nonlinear shell theory, are considered with account of nonlinear van der Waals forces, surface effect and nonlocal elasticity. Using the weighted residual method, the system of the partial differential equations is transformed into the system of nonlinear ordinary differential equations. The nonlinear boundary condition for the longitudinal stresses resultant is accounted in these differential equations. The essentially curvilinear Kauderer-Rosenberg nonlinear normal modes are studied numerically by combination of shooting technique and continuation algorithm. Such NNMs in double-walled nanoshell are undergone the Naimark- Sacker bifurcation. As a result, the curvilinear nonlinear modes are transformed into chaotic motions. • Mathematical model of nanotube with account of surface effect. • Linear vibrations analysis. • Nonlinear ordinary differential equations of free nonlinear vibrations. • Numerical analysis of nonlinear vibrations. [ABSTRACT FROM AUTHOR]

Flexoelectric and piezoelectric effects have attracted the attention of researchers, owing to their applications in sensing systems and actuators. In this paper, the vibration of functionally graded material (FGM) conical nanoshell is studied, taking into account both piezoelectricity and flexoelectricity. The nanoshell has a sandwich-type structure with a FGM core and two layers of piezoelectric materials on its top and bottom. With the combination of the first order shear deformation and Eringen’s nonlocal theories, the vibration equation of the nanoshell is developed. In order to study the governing equations and the frequency of vibrations of nanoshell, the generalized differential quadrature method is implemented. Based on the developed numerical solution procedure, the effect of different parameters, such as flexoelectricity, piezoelectricity, nonlocal term and Pasternak foundation, are shown on the vibrations of conical nanoshell. The presented analysis provides a better insight into the behavior of conical nanoshells, which are highly applicable in bio-sensing and optical devices.

The process of Förster resonance energy transfer (FRET) and molecular fluorescence (MF) plays a vital role in protein–protein interaction, detection of nucleic acids, photochemistry, molecular spectroscopy, forensics, fingerprinting, photovoltaics, etc., to name only a few. The present work focus on developing closed form expressions for FRET enhancement, fluorescence yield (FY), and quantum yield (QY) in the presence of core-shell nanoparticle (CSNP) consisting of dielectric core and metallic shell. It is shown that the plasmonic nanoparticle enhance the FRET significantly only when the donor and acceptor molecules are far apart. When both molecules are closely placed (~ 1 nm), plasmonic nanoparticle does not enhance the FRET significantly. Therefore, when acceptor–donor molecules of chromophore are closely placed, significant FRET enhancement cannot be realized via molecule–surface plasmon interaction. The present work shows that this problem can be resolved by incorporating optical gain in the dielectric core of CSNP, and this is an effective mechanism for enhancing molecular interaction when donor–acceptor molecules are closely placed. In addition to FRET, molecular fluorescence in the presence of CSNP is also studied. The well-established Gersten-Nitzan model is extended to derive closed form expressions for FRET, FY, and QY, albeit near core-shell nanoparticle. Notably, gigantic enhancement in FRET and FY by virtue of loss compensation is accompanied by reduction in resonance linewidth. Refractory nitrides (e.g., ZrN and TiN) based CSNPs are assessed for their feasibility in enhancing FRET, and FY and performance comparison with Au is also presented. [ABSTRACT FROM AUTHOR]

Abstract Gold nanoshell’s high light scattering and absorption at its resonance wavelength have found applications in biomedical imaging and photothermal therapy. However, at nanoscale, metallic material’s dielectric function is affected by nanoparticle’s size, mainly via a mechanism called surface scattering of conduction electrons. In this work, the effect of surface scattering of electrons on the ratios of optical absorption and scattering to extinction (which is the sum of the absorption and scattering) of gold nanoshell is investigated. Simulation results for several shell thicknesses are compared. It is found that the electrons’ surface scattering increases the optical absorption ratio, and the thinner the shell thickness, the larger the increase in the difference of the absorption ratio between the situations with and without the surface scattering considered. The increase of absorption ratio is then verified by comparing simulation results to experimental measurements for three nanoshells. The parameters of the simulations to fit the experimental measurements show that the damping of conduction electrons in metallic shell geometry is larger than that predicted by the billiard scattering model.

Introduction: Hollow gold nanoshells (HAuNS) are one of the most attractive nanostructures for biomedical applications due to their interesting physicochemical properties. This study sought to evaluate the plasmonic photothermal effect of HAuNS irradiated with incoherent light on melanoma cell line. Materials and Methods: After the synthesis of nanostructures, the temperature changes of HAuNS and polyethylene glycol stabilized HAuNS (HAuNS-PEG) were evaluated at different irradiation dose levels. After determining the potential cytotoxicity of the agents, the DFW cells were irradiated by incoherent light with and without the nanostructures at different exposure doses with two spectral bands of 670±25 nm and 730±25 nm. Finally, the rate of the cell survival was determined by 1-Methyltetrazole-5-Thiol assay 24 h after irradiating. Results: The HAuNS, HAuNS-PEG, and light exposure did not have any significant effect on the cell survival, individually. Stabilizing with PEG led to an increase in size and decreased their polydispersity index, zeta potential, and conductivity. The slopes of temperature and cell death caused by 730 nm were greater than 670 nm when the cells were irradiated in the presence of nanostructures. These changes became more significant with increasing the dose of exposure and HAuNS (or HAuNS-PEG) concentration. The lowest cell survival occurred in the concentration of 250 μg/ml of nanostructures and an exposure dose of 9 min (P

An accurate buckling response analysis for functionally graded graphene platelet (GPL) reinforced piezoelectric cylindrical nanoshells subject to thermo-electro-mechanical loadings is presented by a rigorous symplectic expansion approach. Three types of GPL reinforced patterns are considered, and the modified Halpin–Tsai model is employed to determine their effective material properties. By using Eringen's nonlocal stress theory and Reissner's shell theory, new governing equations are established in the Hamiltonian form. Exact solutions are expanded into symplectic series and three possible forms are derived. A comparison with the existing study is presented to validate the solution and very good agreement is observed. The effects of material and geometrical properties of GPLs, electric voltage and temperature rise on critical buckling stresses are investigated and discussed in detail. [ABSTRACT FROM AUTHOR]

Optical properties of core–shell (metal) nanoparticles and composites based on them were investigated in the classical approximation. Frequency dependences of the real and imaginary parts of the dielectric permittivity of bilayer particles and absorption coefficients of composites based on them were calculated. Small-scale oscillations of the real and imaginary parts of the dielectric permittivity and absorption coefficient were found in the low-frequency spectral region. The behavior of the dielectric permittivity of bilayer nanoparticles was analyzed for the limiting cases of thin and thick shells. The influence of the effective mean free pathlength of electrons on the optical characteristics of the bilayer nanoparticles was considered. Two maxima of the composite absorption coefficient were demonstrated to be due to hybridization of polar modes. [ABSTRACT FROM AUTHOR]

In current work, Gurtin–Murdoch surface/interface and nonlocal theories are presented to investigate nonlinear vibration and stability analysis of piezoelectric nanoresonator simultaneously subjected to direct and alternating voltages. Complex averaging method combined with arc-length continuation is used to achieve the nonlinear frequency response and stability analysis of the piezoelectric nanoresonator. It is concluded that ignoring surface and small-scale effects lead to inaccurate results in vibration response of the piezoelectric nanoresonator. Also, with increasing dimensionless nonlocal parameter and decreasing nanoshell stiffness, dimensionless natural frequency, the resonance amplitude, the range of instability with saddle-node bifurcations and nonlinear hardening behavior, and also resonance frequency decrease. In addition, it is found that when the surface/interface effects corresponding to higher surface/interface density are considered, natural frequency is increased. Also, regardless the Lamé's constants lead to decreasing of piezoelectric nanoresonator stiffness, and as a result, the dimensionless natural frequency is lower than all cases. The rest of the surface/interface parameters do not have much effect on the dimensionless natural frequency. Also, with increasing electrostatic and piezoelectric voltages, the oscillation amplitude and range of the piezoelectric nanoresonator system's instability and all nonlinear behavior of piezoelectric nanoresonator are increased. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) constitute a class of universally prevalent carcinogenic environmental contaminants. It is increasingly recognized, however, that PAHs derivatized with oxygen, sulfur, or nitrogen functional groups are frequently more dangerous than their unfunctionalized counterparts. This much larger family of chemicals─polycyclic aromatic compounds─PACs─is far less well characterized than PAHs. Using surface-enhanced Raman and IR Absorption spectroscopies (SERS + SEIRA) combined on a single substrate, along with density functional theoretical (DFT) calculations, we show that direct chemical detection and identification of PACs at sub-parts-per-billion concentration can be achieved. Focusing our studies on 9,10-anthraquinone, 5,12-tetracenequinone, 9-nitroanthracene, and 1-nitropyrene as model PAC contaminants, detection is made possible by incorporating a hydroxy-functionalized self-assembled monolayer that facilitates hydrogen bonding between analytes and the SERS + SEIRA substrate. 5,12-Tetracenequinone was detected at 0.3 ppb, and the limit of detection was determined to be 0.1 ppb using SEIRA alone. This approach is straightforwardly extendable to other families of analytes and will ultimately facilitate fieldable chemical detection of these dangerous yet largely overlooked environmental contaminants.

The thermo-electro-mechanical nonlinear vibration of circular cylindrical nanoshells on the Winkler–Pasternak foundation is investigated. The nanoshell is made of functionally graded piezoelectric material (FGPM), which is simulated by the nonlocal elasticity theory and Donnell's nonlinear shell theory. The Hamilton's principle is employed to derive the nonlinear governing equations and corresponding boundary conditions. Then, the Galerkin's method is used to obtain the nonlinear Duffing equation, to which an approximate analytical solution is obtained by the multiple scales method. The results reveal that the system exhibits hardening-spring behavior. External applied voltage and temperature change have significant effect on the nonlinear vibration of the FGPM nanoshells. Moreover, the effect of power-law index on the nonlinear vibration of the FGPM nanoshells depends on parameters such as the external applied voltage, temperature change and properties of the Winkler–Pasternak foundation. [ABSTRACT FROM AUTHOR]

Abstract Cell delivery in cell therapy is typically challenged by the low cell survival rate and immunological rejection during cells injection and circulation. Encapsulation of cells with semipermeable hydrogels or membranes can improve cell viability by resisting high shear force and inhibit immune response with the physical isolation effect. Herein, the individual HeLa cells and human mesenchymal stem cells (hMSCs) were encapsulated with enzyme responsive polymer nanoshell. The encapsulation shell was prepared via the Layer-by-Layer (LbL) assembly of functionalized gelatin and click chemistry of peptide linker and gelatin. The encapsulated cells showed high cell viability and could resist the physical stress. Moreover, the encapsulation shell had a prolonged encapsulation sustaining period and could effectively prevent the invasion of external entities. In addition, on-site cell release was realized via enzymolysis of the encapsulation shell by human matrix metalloproteinase-7 (MMP-7), an overexpressed enzyme on tumor area. The finding of this study proved a potential approach in cell therapy, especially for cell-based cancer therapy. [ABSTRACT FROM AUTHOR]

It has been revealed that the surface stress effect plays an important role in the mechanical behavior ofstructures (such as bending, buckling and vibration) when their dimensions are on the order ofnanometer. In addition, recent advances in nanotechnology have proposed several applications fornanoscale shells in different fields. Hence, in the present article, within the framework of surfaceelasticity theory, the free vibration behavior of simply-supported cylindrical nanoshells with theconsideration of the aforementioned effect is studied using an exact solution method. To this end, first,the governing equations of motion and boundary conditions are obtained by an energy-basedapproach. The surface stress influence is incorporated into the formulation according to the Gurtin-Murdoch theory. The nanoshell is modeled according to the first-order shear deformation shell theory.After that, the free vibration problem is solved through an exact solution approach. To this end, thedimensionless form of governing equations is derived and then solved under the simply-supportedboundary conditions using a Navier-type solution method. Selected numerical results are presentedabout the effects of surface stress and surface material properties on the natural frequencies ofnanoshells with different radii and lengths. The results show that the surface energies significantlyaffect the vibrational behavior of nanoshells with small magnitudes of thickness. Also, it is indicatedthat the natural frequency of the nanoshell is dependent of the surface material properties.

Optical coherence tomography (OCT) is an established imaging technology for in vivo skin investigation. Topical application of gold nanoshells (GNS) provides contrast enhancement in OCT by generating a strong hyperreflective signal from hair follicles and sweat glands, which are the natural skin openings. This study explores the utility of 150 nm diameter GNS as contrast agent for OCT imaging. GNS was massaged into skin and examined in four skin areas of 11 healthy volunteers. A commercial OCT system and a prototype with 3 μm resolution (UHR‐OCT) were employed to detect potential benefits of increased resolution and variability in intensity generated by the GNS. In both OCT‐systems GNS enhanced contrast from hair follicles and sweat ducts. Highest average penetration depth of GNS was in armpit 0.64 mm ± SD 0.17, maximum penetration depth was 1.20 mm in hair follicles and 15 to 40 μm in sweat ducts. Pixel intensity generated from GNS in hair follicles was significantly higher in UHR‐OCT images (P = .002) and epidermal thickness significantly lower 0.14 vs 0.16 mm (P = .027). This study suggests that GNSs are interesting candidates for increasing sensitivity in OCT diagnosis of hair and sweat gland disorders and demonstrates that choice of OCT systems influences results. [ABSTRACT FROM AUTHOR]