An analytical procedure for dynamic response determination of a viscoelastic beam with moderately large deflection using first-order shear deformation theory

In this article, the dynamic response of a viscoelastic beam with moderately large deflection subjected to transverse and axial loads is studied using the first-order shear deformation theory. The von-Karman strain displacement relations and Hooke's law are used for formulation. The solution of the equations, which are a system of nonlinear partial differential equations, are obtained analytically using the perturbation technique in conjunction with the eigenfunction expansion method. The results are compared with the finite elements method. Also, a sensitivity analysis is performed, and the effects of geometrical and material properties are investigated on the response.     

Dynamic stability of modified strain gradient theory sinusoidal viscoelastic piezoelectric polymeric functionally graded single-walled carbon nanotubes reinforced nanocomposite plate considering surface stress and agglomeration effects under hydro-thermo-electro-magneto-mechanical loadings

In this article, dynamic stability analysis of the viscoelastic piezoelectric polymeric nanocomposite plate reinforced by functionally graded single-walled carbon nanotubes (FG-SWCNTs) based on modified strain gradient theory (MSGT) is explored. The viscoelastic piezoelectric polymeric nanocomposite plate reinforced is subjected to hydrothermal and electro-magneto-mechanical loadings. The viscoelastic piezoelectric polymeric nanocomposite plate is rested on viscoelastic foundation. Uniform distribution (UD), various functionally graded (FG) distribution types such as FG-V, FG-X, and FG-O are considered for single-walled carbon nanotubes (SWCNTs). The extended mixture approach is applied to estimation of the elastic properties. The equations of motion are derived by Hamilton's principle. The resonance frequency or the parametric resonance is obtained then dynamic stability region is specified. There is a good agreement between the present work and the literature result. Various parametric investigations are performed for the influences of the small scale parameters, direct and alternating applied voltage, magnetic field, viscoelastic foundation coefficients, and aspect ratios on the dynamic stability region of the viscoelastic piezoelectric polymeric nanocomposite plate. The results indicated that SWCNT agglomeration and surface stress have significant effects on the dynamic stability region and the parametric resonance. Dynamic stability region increases with increasing of thickness to width ratio, magnetic field, applied voltage, static load factor, viscoelastic foundation parameters, and surface density constant, and decreasing of length to width ratio and residual surface stress constant. Also, the dynamic stability region shifts to lower parameter resonance with increasing of temperature and moisture changes. The results can be employed for design of micro-electro-mechanical systems and nano-electro-mechanical systems.     

Photonic Reactions Leading to Fluorescence in a Polymeric System Induced by the Photothermal Effect of Magnetite Nanoparticles Using a 780 nm Multiphoton Laser

Recently, polymer‐coated magnetite (Fe₃O₄) nanoparticles (NPs) are extensively studied for applications in therapeutics or diagnostics using photothermal effect. Therefore, it is essential to understand the interactions between Fe₃O₄ NPs and polymers when optical stimuli are applied. Herein, the photonic reactions of Fe₃O₄ NPs and polymer composites upon application of a 780 nm multiphoton laser are analyzed. The photonic reactions produce unique results including fluorescence from conformationally changed polymer and low‐temperature phase transformation of Fe₃O₄ NPs. Typically, π‐conjugated chains are formed, inducing fluorescence through a series of main and side‐chain cleavage reactions of polymers with the aliphatic chain. In addition, fluorescence is detected in the cellular system by photonic reactions between Fe₃O₄ NPs and biomolecules. After multiphoton laser irradiation, light emission is detected near the intracellular Fe₃O₄ NPs, and a stronger intensity is observed in large‐sized NPs.     

Tunable SnSe2/WSe2 Heterostructure Tunneling Field Effect Transistor

The burgeoning 2D semiconductors can maintain excellent device electrostatics with an ultranarrow channel length and can realize tunneling by electrostatic gating to avoid deprivation of band‐edge sharpness resulting from chemical doping, which make them perfect candidates for tunneling field effect transistors. Here this study presents SnSe₂/WSe₂ van der Waals heterostructures with SnSe₂ as the p‐layer and WSe₂ as the n‐layer. The energy band alignment changes from a staggered gap band offset (type‐II) to a broken gap (type‐III) when changing the negative back‐gate voltage to positive, resulting in the device operating as a rectifier diode (rectification ratio ~10⁴) or an n‐type tunneling field effect transistor, respectively. A steep average subthreshold swing of 80 mV dec^?1 for exceeding two decades of drain current with a minimum of 37 mV dec^?1 at room temperature is observed, and an evident trend toward negative differential resistance is also accomplished for the tunneling field effect transistor due to the high gate efficiency of 0.36 for single gate devices. The I _ON/I _OFF ratio of the transfer characteristics is >10⁶, accompanying a high ON current >10^?5 A. This work presents original phenomena of multilayer 2D van der Waals heterostructures which can be applied to low‐power consumption devices.     

Broadband photovoltaic effect of n-type topological insulator Bi<Subscript>2</Subscript>Te<Subscript>3</Subscript> films on p-type Si substrates

We report the photovoltaic effects of n-type topological insulator (TI) Bi2Te3 films grown on p-type Si substrates by chemical vapor deposition (CVD).The films containing large nanoplates with a smooth surface formed on p-Si exhibit good p-n diode characteristics under dark and light illumination conditions and display a good photovoltaic effect under the broadband range from ultraviolet (UV) to near infrared (NIR) wavelengths.Under the light illumination with a wavelength of 1,000 nm,a short circuit current (Isc) of 19.2 μA and an open circuit voltage (Voc) of 235 mV are achieved.The maximum fill factor (FF) increases with a decrease in the wavelength or light density,achieving a value of 35.6％ under 600 nm illumination.The photoresponse of the n-Bi2Te3/p-Si device can be effectively switched between the on and off modes in millisecond time scale.These findings are important for both the fundamental understanding and solar cell device applications of TI materials.     

Plasmon enhancement for Vernier coupled single-mode lasing from ZnO/Pt hybrid microcavities

It is essential to develop a single mode operation and improve the performance of lasing in order to ensure practical applicability of microlasers and nanolasers.In this paper,two hexagonal microteeth with varied nanoscaled air-gaps of a ZnO microcomb are used to construct coupled whispering-gallery cavities.This is done to achieve a stable single mode lasing based on Vernier effect without requiring any complicated or sophisticated manipulation to achieve positioning with nanoscale precision.Optical gain and the corresponding ultraviolet lasing performance were improved greatly through coupling with localized surface plasmons of Pt nanoparticles.The ZnO/Pt hybrid microcavities achieved a seven-fold enhancement of intensity of single mode lasing with higher sidemode suppression ratio and lower threshold.The mechanism that led to this enhancement has been described in detail.     

Synthesis of size-controlled CoMn2O4 quantum dots supported on carbon nanotubes for electrocatalytic oxygen reduction/evolution

A combined hot-injection and heat-up method was developed to synthesize monodisperse and uniform CoMn2O4 quantum dots (CMO QDs).CMO QDs with average size of 2.0,3.9,and 5.4 nm were selectively obtained at 80,90,and 105 ℃,respectively.The CMO QDs supported on carbon nanotubes (CNTs) were employed as catalysts for the oxygen reduction/evolution reaction (ORR/OER) in alkaline solution to investigate their size-performance relationship.The results revealed that the amount of surface-adsorbed oxygen and the band gap energy,which affect the charge transfer in the oxygen electrocatalysis processes,strongly depend on the size of the CMO QDs.The CMO-3.9/CNT hybrid,consisting of CNT-supported CMO QDs of 3.9 nm size,possesses a moderate amount of surfaceadsorbed oxygen,a lower band gap energy,and a larger charge carrier concentration,and exhibits the highest electrocatalytic activity among the hybrid materials investigated.Moreover,the CMO-3.9/CNT hybrid displays ORR and OER performances similar to those of the benchmark Pt/C and RuO2 catalysts,respectively,due to the strong carbon-oxide interactions and the high dispersion of CoMn2O4 QDs on the carbon substrate;this reveals the huge potential of the CMO-3.9/CNT hybrid as a bifunctional OER/ORR electrocatalyst.The present results highlight the importance of controlling the size of metal oxide nanodots in the design of active oxygen electrocatalysts based on spinel-type,nonprecious metal oxides.