Bimetallic Shells Research Articles

Galvanic engineering of interior hotspots in 3D Au/Ag bimetallic SERS nanocavities for ultrasensitive and rapid recognition of phthalate esters

The ecological and health risks of plasticizer accumulation have reached the global public agenda. For early screening of phthalate esters (PAEs), in the present study, we developed ultrasensitive and reliable bimetallic surface-enhanced Raman spectroscopy (SERS) platforms with Ag nanocavities galvanically replaced by Au (Au/AgNCs) at room temperature. A galvanic reaction (GR) coupled with the Kirkendall effect led to a large population of nanoscale hollow regions within 60 s. The interstitials at the bimetallic shells were activated as both interior hotspots for field confinement and diffusion pathways for small target molecules. The GR based on the intrinsic material properties resulted in an Au/AgNC platform with reliable sensing operation, including a relative standard deviation of <10 % at the individual analytic Raman peaks. The qualified and densified interior hotspots of the Au/AgNC platform led to sub-ppm sensitivity (i.e., the average limit of detection of ∼2.1 × 10−2 ppm) for four different PAEs. As a demonstration of the Au/AgNC platform's performance in actual sample environments, the detection and identification of various PAE combinations were also investigated. Subtle differences in the PAEs' spectral characteristics (i.e., peak positions and intensity ratios) were successfully classified using a machine learning algorithm based on a principal component analysis–linear discriminant analysis model. Furthermore, the amount of PAE released from the real sample and evaluated by SERS was consistent with that evaluated by gas chromatography–mass spectrometry. These results indicate that the SERS platforms with Au/AgNC substrates and portable Raman instruments are suitable for on-site safety monitoring of toxic substances in food and the environment.

Virus-Inspired Hollow Mesoporous Manganese-Bismuth Nanoparticles Loaded with SOCS6 Plasmid for Synergistically Enhanced Radiosensitivity of ESCC

<h3>Purpose/Objective(s)</h3> Radioresistance remains the major obstacle to the failure of radiotherapy for ESCC. SOCS6 was first reported in our previous study to enhance the radiosensitivity of ESCC. Recent studies have shown that various materials were applied as radiosensitizer. Nevertheless, these radiosensitizer still suffer from inadequate tumor uptake of radiosensitizers and radiation sickness. The aim of our study was to generate a tumor targeted virus-inspired hollow mesoporous manganese-bismuth (vHMMn-Bi-PEG) loaded with SOCS6 plasmid and to explore the effect for radiosensitization and safety in vitro and in vivo. We hypothesize that SOCS6@vHMMn-Bi-PEG could enhance ESCC radiosensitivity <h3>Materials/Methods</h3> The vHMMn-Bi-PEG were obtained by the traditional hard template synthesis. SEM and TEM were analyzed for the characterization of vHMMn-Bi-PEG. The expression of SOCS6 were detected by RT-PCR and western blot. MTT was detected cell cytotoxicity. Flow cytometry was used to detect the cellular uptake of SOCS6@vHMMn-Bi-PEG. Colony formation and γ-H2AX foci were assessed the radiosensitization effect of the SOCS6@vHMMn-Bi-PEG. The effect of SOCS6@vHMMn-Bi-PEG on radiosensitization and biosafety were analyzed by subcutaneous xenograft models in vivo. <h3>Results</h3> By using SEM observation, the vHMMn-Bi-PEG exhibited the rough surface morphology, which was similar to the spike on the surface of natural virus. Subsequently, TEM results exhibited that the building blocks of the interpenetrated ultrasmall MnO₂/Bi₂O₃ nanoparticles were constructed to form the bimetallic oxide shells. RT-PCR and western blot results revealed that pCDNA3.1-SOCS6 were successfully loaded into the vHMMn-Bi-PEG. After incubation with vHMMn-Bi-PEG or SOCS6@vHMMn-Bi-PEG, the cell survival rates of TE-10 were greater than 90%, indicating their excellent biocompatibility. Besides, flow cytometry results confirmed that SOCS6@ vHMMn-Bi-PEG could be easily taken up by TE-10 cells. Colony formation results revealed that SOCS6@vHMMn-Bi-PEG (8.90%) was significantly lower than that in the control group (21.90%) and pCDNA3.1-SOCS6 group (18.32%). Moreover, a significantly stronger fluorescence density of γ-H₂AX foci was found in the SOCS6@vHMMn-Bi-PEG + X-ray than that in the control and pCDNA3.1-SOCS6 + X-ray, indicating the effective DNA breakage induced by the vHMMn -Bi-PEG nano-system. Finally, in vivo results found that SOCS6@vHMMn-Bi-PEG with X-ray exhibited a stronger inhibitory effect on tumor growth compared with the pCDNA3.1-SOCS6 + X-ray and vHMMn-Bi-PEG + X-ray group, indicating that SOCS6@ vHMMn-Bi-PEG has the potential to significantly enhance radiosensitivity. <h3>Conclusion</h3> We successfully constructed a novel biomimetic-gene-loaded nano-system SOCS6@vHMMn-Bi-PEG as a radio-sensitizer. Moreover, SOCS6@vHMMn-Bi-PEG exhibited superior antitumor performance of ESCC without systemic toxicity.

In Situ Formed “Sn1–XInX@In1–YSnYOZ” Core@Shell Nanoparticles as Electrocatalysts for CO2 Reduction to Formate

AbstractElectrochemical reduction of CO2 (CO2RR) driven by renewable energy has gained increasing attention for sustainable production of chemicals and fuels. Catalyst design to overcome large overpotentials and poor product selectivity remains however challenging. Sn/SnOx and In/InOx composites have been reported active for CO2RR with high selectivity toward formate formation. In this work, the CO2RR activity and selectivity of metal/metal oxide composite nanoparticles formed by in situ reduction of bimetallic amorphous SnInOx thin films are investigated. It is shown that during CO2RR the amorphous SnInOx pre‐catalyst thin films are reduced in situ into Sn1–XInX@In1–YSnYOz core@shell nanoparticles composed of Sn‐rich SnIn alloy nanocores (with x &lt; 0.2) surrounded by InOx‐rich bimetallic InSnOx shells (with 0.3 &lt; y &lt; 0.4 and z ≈ 1). The in situ formed particles catalyze the CO2RR to formate with high faradaic efficiency (80%) and outstanding formate mass activity (437 A gIn+Sn−1 @ −1.0 V vs RHE in 0.1 m KHCO3). While extensive structural investigation during CO2RR reveals pronounced dynamics in terms of particle size, the core@shell structure is observed for the different electrolysis conditions essayed, with high surface oxide contents favoring formate over hydrogen selectivity.

Real-Time Tracking the Electrochemical Synthesis of Au@Metal Core-Shell Nanoparticles toward Photo Enhanced Methanol Oxidation.

Single particle plasmon scattering can provide real-time imaging information on the synthesis of nanomaterials. Here, an electrochemical deposition strategy is reported to synthesize plasmonic Au@Metal core-shell nanoparticles (Au@M NPs), which exhibit localized surface plasmon resonance (LSPR) properties. Because of the excellent catalytic activity of the methanol oxidation reaction (MOR), Pt, Pd, and Rh were reduced on the surface of Au NPs to form monometallic and bimetallic shells. Under dark field microscopy (DFM), the scattering changes could be utilized to track the surface nucleation and bulk deposition process. The synthesized Au@M NPs, which combined the plasmonic and electrocatalytic features, showed greatly enhanced activity for MOR. Under LSPR excitation, the electroxidation process toward MOR was accelerated and increased approximately linearly with increased illumination intensity, which could be mostly attributed to the generation of energetic charge carriers. This strategy of real-time plasmonic tracking electrochemical deposition at the single particle level is facile and universal, which could be extended to the precise synthesis of other plasmonic core-shell nanomaterials and the investigation of the pathway of plasmon accelerated chemical conversion.

In Situ Pt Staining Method for Simple, Stable, and Sensitive Pressure-Based Bioassays.

Pressure-based bioassays (PASS) integrate a molecular recognition process with a catalyzed gas generation reaction, enabling sensitive and portable quantitation of biomarkers in clinical samples. Using platinum nanoparticles (PtNPs) as a catalyst has significantly improved the sensitivity of PASS compared with protein enzyme-based detection. However, PtNPs are easily deactivated during storage or after being decorated with antibodies. Moreover, nonspecific adsorption of PtNPs on substrates has been a problem, resulting in significant backgrounds. To solve these problems of PtNP-based detection, we report a robust, simple, stable, and sensitive Pt staining method for PASS. Detection antibody-decorated gold nanoparticles (AuNPs) are used to perform enzyme-linked immunosorbent assay, followed by Pt staining to stain AuNPs with Ag and Pt bimetallic shells (Au@AgPtNPs), which endow AuNPs with catalytic activity. The concentration of targets can be quantitatively determined by measuring the pressure due to O2 gas (g) formed by the decomposition of H2O2 catalyzed by Au@AgPtNPs. C-reactive protein and avian influenza hemagglutinin 5 neuraminidase 1 can be quantitatively detected with detection limits of 0.015 and 0.065 ng/mL, respectively. The simple, stable, and sensitive properties of the Pt staining-based method will largely broaden the applications of PASS in clinical diagnosis and biomedicine.

An Approximate Analysis of the Inner Wall Loading of a Bimetallic Camera Shell of Reusable Rocket Engine

В различных технических устройствах в качестве конструктивных элементов достаточно широко используют биметаллические оболочки. Характерным примером применения биметаллических оболочек является конструкция камеры сгорания жидкостного ракетного двигателя (ЖРД). В процессе работы ЖРД оболочка камеры сгорания подвержена интенсивным тепловым и механическим воздействиям, что приводит к необходимости ее охлаждения. Охлаждающий тракт оболочки образован зазором между ее внутренней и наружной стенками, скрепленными между собой гофрированными проставками или фрезерованными ребрами. Наружная стенка выполняет роль силового элемента оболочки, а внутренняя стенка непосредственно контактирует с высокотемпературными продуктами сгорания и подвержена интенсивному нагреву. Различие функций стенок оболочки вызывает необходимость их изготовления из разных материалов с различающимися теплофизическими и механическими характеристиками.

Bimetallic Nanoshells for Metal-Enhanced Fluorescence with Broad Band Fluorophores

In this article, we reported the near-field interactions between the Ru(bpy)(3) (2+) complexes and plasmon resonances from the bimetallic nanoshells. The metallic nanoshells were fabricated on 20 nm silica spheres as cores by depositing 10 nm monometallic or bimetallic shells. There were approx. 15 Ru(bpy)(3) (2+) complexes in the silica core. The metal shells were constituted of silver or/and gold. The bimetallic shells could be generated in homogeneous or heterogeneous geometries. The homogeneous bimetallic shells contained 10 nm silver-gold alloys. The heterogeneous bimetallic shells contained successive 5 nm gold and 5 nm silver shells, or alternatively, 5 nm silver and 5 nm gold shells. Optical properties of metal nanoshells were studied on both the ensemble spectra and single nanoparticle imaging measurements. The heterogeneous bimetallic shells were found to have a large scale of metal-enhanced emission relative to the monometallic or homogeneous bimetallic shells. It is because the heterogeneous bimetallic shells may display split dual plasmon resonances which can interact with the excitation and emission bands of the Ru(bpy)(3) (2+) complexes in the silica cores leading to more efficient near-field interactions. The prediction can be demonstrated by the lifetimes. Therefore, it is suggested that both the compositions and geometries of the metal shells can influence the interactions with the fluorophores in the cores. This observation also offers us an opportunity for developing plasmon-based fluorescence metal nanoparticles as novel nanoparticle imaging agents which have high performances in fluorescence cell or tissue imaging.

Tunable fabrication on iron oxide/Au/Ag nanostructures for surface enhanced Raman spectroscopy and magnetic enrichment

A facile approach was developed to prepare novel multifunctional Fe2O3/Au/Ag nanostructures integrated with isolated functions involving magnetic and optical properties. The Fe2O3/Au/Ag hybrid nanoparticles with different thicknesses of Ag shell were prepared by adjusting the amount of the AgNO3. Surface structures were varied from the rough with pinhole to smooth and pinhole free surfaces with increasing amounts of AgNO3. The surface plasmon resonance was tuned in a very wide region from that of Au to Ag. Surface enhanced Raman scattering (SERS) effects were also investigated, employing thiophenol (TP) and aminothiophenol (PATP) as probe molecules. It was revealed that the SERS intensity was strongly depended on the molar ratio of Ag and Au. With an increase in the Ag molar fractions, SERS signals were enhanced to the maximum due to the surface plasmon resonance of the pinhole structure. The magnetic enrichment for on line SERS monitoring the molecules with low concentration was performed based on the magnetic core and the SERS activity of the bimetallic shells. This enrichment procedure improved efficiently the limits of the SERS detection. It was shown that the multicomponent nanoparticles have potential applications in the fields of optical devices and magnetic separation.

Shallow Axi-symmetric Bimetallic Shell as a Switching Element in a Non-Homogenous Temperature Field

In this contribution we discuss the stability of thin, axi-symmetric, shallow bimetallic shells in a non-homo- geneous temperature field. The presented model with a mathematical description of the geometry of the system, displacements, stresses and thermoelastic deformations on the shell, is based on the theory of the third order, which takes into account not only the equilibrium of forces on a deformed body but also the non-linear terms of the strain tensor. The equations are based on the large displacements theory. As an example, we pre- sent the results for a bimetallic shell of parabolic shape, which has a temperature point load at the apex. We translated the boundary-value problem with the shooting method into saving the initial-value problem. We calculate the snap-through of the system numerically by the Runge-Kutta fourth order method.

Stability of the Shallow Axisymmetric Parabolic‐Conic Bimetallic Shell by Nonlinear Theory

In this contribution, we discuss the stress, deformation, and snap‐through conditions of thin, axi‐symmetric, shallow bimetallic shells of so‐called parabolic‐conic and plate‐parabolic type shells loaded by thermal loading. According to the theory of the third order that takes into account the balance of forces on a deformed body, we present a model with a mathematical description of the system geometry, displacements, stress, and thermoelastic deformations. The equations are based on the large displacements theory. We numerically calculate the deformation curve and the snap‐through temperature using the fourth‐order Runge‐Kutta method and a nonlinear shooting method. We show how the temperature of both snap‐through depends on the point where one type of the rotational curve transforms into another.

Thin double curved shallow bimetallic shell of translation in a homogenous temperature field by non-linear theory

In this contribution, we discuss stress, deformation and stability conditions for thin double curved shallow bimetallic translation shells. According to the theory of the third order by the Czech researcher E. Chawalla, which takes into account the equilibrium of forces and moments acting on a deformed body and the supposition of large displacements, we present a system of three differential equations with boundary conditions for the description of displacements on the shell due to the temperature loading of the shell. The equations are based on the Kirchhoff hypothesis, on the supposition of moderate rotations and small strains of the shell element.

On the nonlinear vibration of heated bimetallic shallow shells of revolution

The axisymmetrically nonlinear free vibration of a bimetallic shallow shell of revolution under uniformly distributed static temperature changes is investigated. Based on the nonlinear bending theory of thin shallow shells, the governing equations are established in forms similar to those of classical single-layered shells theory by redetermination of reference surface of coordinate. These partial differential equations are reduced to corresponding ordinary ones by elimination of the time variable with Kantorovich averaging method following an assumed harmonic time mode. The resulting equations, which form a nonlinear two-point boundary value problem, are then solved numerically by shooting method, and the temperature-dependent characteristic relations of frequency vs. amplitude are obtained successfully. A detailed parametric study is conducted involving shell geometry and temperature parameters. The effects of these variables on the frequency–amplitude characteristics are plotted and discussed.

Thermoelastic stability of bimetallic shallow shells of revolution

This article considers the thermoelastic stability of bimetallic shallow shells of revolution. Basic equations are derived from Reissner’s non-linear theory of shells by assuming that deformations and rotations are small and that materials are linear elastic. The equations are further specialized for the case of a closed spherical cup. For this case the perturbated initial state is considered and it is shown that only in the cases when the cup edge is free or simply supported buckling under heating is possible. Further the perturbated flat state is considered and the critical temperature for buckling is calculated for the case of free and simply supported edges. The temperature–deflection diagrams are calculated by the use of the collocation method for shallow spherical, conical and cubic shells.

Snap-through of the system of open shallow axi-symmetric bimetallic shell by non-linear theory

The paper deals with stresses, strains and buckling conditions in the thin axi-symmetric shallow bimetallic shells with circular opening at the top of the shell. According to the third order theory by the Czech researcher E. Chawalla, which takes into account the equilibrium state of forces and moments acting on the deformed system, the paper presents a model for mathematical description of the system's geometry, stresses, thermo-elastic strains and displacements. The mathematical formulation is based on the theory of large displacements. As an example, the results for spherical shallow shells are shown, approximated by a parabolic function. The shells are loaded with temperature and/or with load acting at the top of the shell or at the shell's inner edge. The displacement state and the snap-through temperature are calculated numerically by the Runge Kutta algorithm of the fourth order, by non-linear shooting method.

Axisymmetric deformation of bimetallic shells of revolution in the supercritical region

Geometrically nonlinear relationships of the theory of thin layered shells are applied to analyze axisymmetric strain of bimetallic shells of revolution in a temperature field. One-dimensional nonlinear boundary-value problems are solved by a combination of the linearization method and the discrete orthogonalization method. A numerical approach is proposed to solve the boundary-value problems in the supercritical strain region.

Non-linear thermal stability of bimetallic shallow shells of revolution

In this paper, a theory for non-linear thermal stability of open bimetallic shallow shells of revolution under a uniform temperature field is developed. To apply the theory to the particular case of some elastic elements in precision instruments, this paper discusses two important kinds of shells, the bimetallic shallow spherical shell with a circular hole at the center and the bimetallic truncated shallow conical shell. The more accurate solutions are obtained by the modified iteration method. All results are expressed in curves which may be applied directly to the design of the elastic elements.

Theory of limit equilibrium of bimetallic shells of revolution and circular plates

Bimetallic shells and plates are widely used in technology (see [1, 2]). An investigation into the flexure and stability of thin shells and various types of loading within the limits of elasticity has been carried out in [3]. An investigation into the load-carrying capacity of cylindrical bimetallic shells made of materials which equally resist tension and compression was carried out in [4]. In many cases the materials of the base and plating layers of bimetallic constructions possess substantially different plastic resistance under tension and compression [5]. The given paper is devoted to the investigation of the load-carrying capacity of bimetallic axisymmetric shells which are made of materials that have different resistances to tension and compression; it is also devoted to the assessment of their economy in comparison with homogeneous shells.

Limit analysis of stiffened axisymmetric shells

Accurate limit ratios have been obtained for stiffened axisymmetric shells. Depending on whether the interaction at the points of intersection is taken into account or disregarded, shells are classified into those of rib-type and waffle-type. In particular cases the ratios obtained may be reduced to limit ratios for shells with ribs running in one direction, for bimetallic shells and uniform isotropic ones. Approximate limit ratios are suggested and a brief survey is given of results obtained in the analysis of other types of rib-type shells. Linearization of limit ratios by replacing the discussed shells by layer models is considered. Application of the limit ratios obtained is illustrated by a problem of the carrying capacity of console stiffened cylindrical shells loaded with internal hydrostatic pressure. Formulas are obtained which allow one to estimate the efficiency of using one or another type of strengthening.