Improved charge transfer by size-dependent plasmonic Au on C_3N_4 for efficient photocatalytic oxidation of RhB and CO_2 reduction

A series of Au/g-C3N4(Au/CN)nanocomposites were successfully prepared,where g-C3N4 nanosheets(CN NSs)served as a substrate for the growth of different sized Au nanoparticles(Au NPs)using the constant temperature bath-reduction method.The effect of Au NP size on electron transfer efficiency between the interfaces of the nanocomposite was studied.The three-dimensional finite-difference time-domain results revealed that larger Au NPs showed increased strength of the localized surface plasmon resonance effect.An increased number of high-energy electrons were available for transfer from Au NPs to CN under the visible light irradiation,inhibiting electron transfer from CN to Au NPs.Photoelectrochemical performance analysis showed that smaller Au NPs exhibited higher separation efficiency of the electron-hole pairs photo-generated with reasonable distribution density.These results are favorable for the improvement of photocatalytic performance.Compared to other nanocomposites,the 3-Au/CN sample(prepared using 3 mL HAuCl4 solution)with reasonable distribution density and small Au NPs exhibited the best photodegradation activity(92.66%)of RhB in 30 min under the visible light irradiation and photoreduction performance of CO2 to CO and CH4 with yields of 77.5 and 38.5μmol/g,respectively,in 8 h under UV light irradiation.Considering the experimental results in the context of the literature,a corresponding size-dependent photocatalytic mechanism was proposed.

Nonlinear free vibrations of porous composite microplates incorporating various microstructural-dependent strain gradient tensors

The main objective of the present numerical analysis is to predict the nonlinear frequency ratios associated with the nonlinear free vibration response of porous composite plates at microscale in the presence of different microstructural gradient tensors.To achieve this end,by taking cubic-type elements into account,isogeometric models of porous composite microplates are obtained with and without a central cutout and relevant to various porosity patterns of distribution along the plate thickness.The established unconventional models have the capability to capture the effects of various unconventional gradient tensors continuity on the basis of a refined shear deformable plate formulation.For the simply supported microsized uniform porous functionally graded material(UPFGM)plate having the oscillation amplitude equal to the plate thickness,it is revealed that the rotation gradient tensor causes to reduce the frequency ratio about 0.73%,the dilatation gradient tensor causes to reduce it about 1.93%,and the deviatoric stretch gradient tensor leads to a decrease of it about 5.19%.On the other hand,for the clamped microsized U-PFGM plate having the oscillation amplitude equal to the plate thickness,these percentages are equal to 0.62%,1.64%,and 4.40%,respectively.Accordingly,it is found that by changing the boundary conditions from clamped to simply supported,the effect of microsize on the reduction of frequency ratio decreases a bit.

Size Depending Separation of HAP:Eu Nanoparticles in Dispersed Sol

The panicle size has a strong impact on the interactions between nanoparticles and cells. However, the synthesis process of nanoparticles limits the range of achievable average panicle sizes. When biocompatible hydroxyapatite nanoparticles （HAP） are doped with the luminescent rare earth elemeat Europium （Eu）, the panicle size becomes larger compared to pure HAP. Hence, a panicle size reduction is necessary to achieve similar experimental conditions when stbstituting pure HAP with luminescent HAP ： Eu nanoparticles to investigate particlecell-interactions in cell culture experiments. While the sedimentation process of particles in liquids and gels has been well described in literature, the separation of particles in dispersed colloids has not been studied, yet. In this study, the size depending separation and particle size redaction of a homogeneous dispersed nanoparticle sol by gravity and centrifugation were investigated. As the results showed, shorter time of centrifugation at higher speed can reduce the average particle size compared to the decline of the panicle concentation in the upper sol layer most efficiently. This ceatrifugation method has some similarity to the overspeeding technique which is commonly used to lower the transient time to reach the equilibrium of sedimentation.

Size Dependence of First-order Hyperpolarizability of CdS Nanoparticles Studied by Hyper-Rayleigh Scattering

The second-order optical nonlinearity of CdS nanoparticles with different diameters of 28.0, 30.0, 31.5, 50.0, and 91.0 A was studied by hyper-Rayleigh scattering technique. Results show that the first-order hyperpolarizability P value per CdS partiele decreases as size is reduced to diameter of 31.5 A; however, as CdS size further decreases, this trend is reversed and (J value increases. Substantially, the normalized P value per CdS formula unit, β0, exhibits systematic enhancement with decreasing size. This phenomenon is interpreted in terms of a so-called surfaee contribution mechanism.

Size-Dependent Analysis of Piezoelectric–Elastic Bilayer Microbeams Based on General Strain Gradient Theory

The classical piezoelectric theory fails to capture the size-dependent electromechanical coupling behaviors of piezoelectric microstructures due to the lack of material length-scale parameters.This study presents the constitutive relations of a piezoelectric material in terms of irreducible transversely isotropic tensors that include material length-scale parameters.Using these relations and the general strain gradient theory,a size-dependent bending model is proposed for a bilayer cantilever microbeam consisting of a transversely isotropic piezoelectric layer and an isotropic elastic layer.Analytical solutions are provided for bilayer cantilever microbeams subjected to force load and voltage load.The proposed model can be simplified to the model incorporating only partial strain gradient effects.This study examines the effect of strain gradient by comparing the normalized electric potentials and deflections of different models.Numerical results show that the proposed model effectively captures size effects in piezoelectric microbeams,whereas simplified models underestimate size effects due to ignoring partial strain gradient effects.

GLOBAL DYNAMICS OF AN SEIR EPIDEMIC MODEL WITH IMMIGRATION OF DIFFERENT COMPARTMENTS

The SEIR epidemic model studied here includes constant inflows of new susceptibles, exposeds, infectives, and recovereds. This model also incorporates a population size dependent contact rate and a disease-related death. As the infected fraction cannot be eliminated from the population, this kind of model has only the unique endemic equilibrium that is globally asymptotically stable. Under the special case where the new members of immigration are all susceptible, the model considered here shows a threshold phenomenon and a sharp threshold has been obtained. In order to prove the global asymptotical stability of the endemic equilibrium, the authors introduce the change of variable, which can reduce our four-dimensional system to a three-dimensional asymptotical autonomous system with limit equation.

Static and Dynamic Pull-In Instability of Nano-Beams Resting on Elastic Foundation Based on the Nonlocal Elasticity Theory

This paper provides the static and dynamic pullin behavior of nano-beams resting on the elastic foundation based on the nonlocal theory which is able to capture the size effects for structures in micron and sub-micron scales. For this purpose, the governing equation of motion and the boundary conditions are driven using a variational approach. This formulation includes the influences of fringing field and intermolecular forces such as Casimir and van der Waals forces. The differential quadrature （DQ） method is employed as a high-order approximation to discretize the governing nonlinear differential equation, yielding more accurate results with a Considerably smaller number of grid points. In addition, a powerful analytical method called parameter expansion method （PEM） is utilized to compute the dynamic solution and frequency-amplitude relationship. It is illustrated that the first two terms in series expansions are sufficient to produce an acceptable solution of the mentioned structure. Finally, the effects of basic parameters on static and dynamic pull-in insta- bility and natural frequency are studied.

Surface-effects-dominated thermal and mechanical responses of zinc oxide nanobelts

t Molecular dynamics （MD） simulations are carried out to characterize the mechanical and thermal responses of [011^-1]-oriented ZnO nanobelts with lateral dimensions of 21.22A × 18.95 A, 31.02A× 29.42 A, and40.81A ×39.89A over the temperature range of 300-1000 K. The Young＇s modulus and thermal conductivity of the nanobelts are evaluated. Significant surface effects on properties due to the highsurface-to-volume ratios of the nanobelts are observed. For the mechanical response, surface-stress-induced internal stress plays an important role. For the thermal response, surface scattering of phonons dominates. Calculations show that the Young＇s modulus is higher than the corresponding value for bulk ZnO and decreases by -33% as the lateral dimensions increase from 21.22 A × 18.95A to 40.81 A × 39.89A. The thermal conductivity is one order of magnitude lower than the corresponding value for bulk ZnO single crystal and decreases with wire size. Specifically, the conductivity of the 21.22 A × 18.95 A belt is approximately （31-18）% lower than that of the 40.81 A × 39.89 A belt over the temperature range analyzed. A significant dependence of properties on temperature is also observed, with the Young＇s modulus decreasing on average by 12% and the conductivity decreasing by 50% as temperature increases from 300 K to 1000 K.

Size and time dependent internalization of label-free nano-graphene oxide in human macrophages

Graphene oxide shows great promise as a material for biomedical applications, e.g., as a multi-drug delivery platform. With this in view, reports of studies on the interaction between nanosized graphene oxide flakes and biological cells are beginning to emerge. However, the number of studies remains limited, and most used labeled graphene oxide samples to track the material upon endocytosis. Unfortunately, the labeling process alters the surface functionality of the graphene oxide, and this additional funcfionalization has been shown to alter the cellular response. Hence, in this work we used label-free graphene oxide. We carefully tracked the uptake of three different nanoscale graphene oxide flake size distributions using scanning/transmission electron microscopy. Uptake was investigated in undifferentiated human monocyte cells （THP-1） and differentiated macrophage cells. The data show clear size dependence for uptake, such that larger graphene oxide flakes （and clusters） are more easily taken up by the cells compared to smaller flakes. Moreover, uptake is shown to occur very rapidly, within two min of incubation with THP-1 cells. The data highlights a crucial need for cellular incubation studies with nanoparticles, to be conducted for short incubation periods as certain dependencies （e.g., size and concentration） are lost with longer incubation periods.

Couple stress-based nonlinear primary resonant dynamics of FGM composite truncated conical microshells integrated with magnetostrictive layers

The size-dependent geometrically nonlinear harmonically soft excited oscillation of composite truncated conical microshells(CTCMs)made of functionally graded materials(FGMs)integrated with magnetostrictive layers is analyzed.It is supposed that the FGM CTCMs are subjected to mechanical soft excitations together with external magnetic fields.An analytical framework is created by a microstructuredependent shell model having the 3rd-order distribution of shear deformation based on the modified couple stress(MCS)continuum elasticity.With the aid of the discretized form of differential operators developed via the generalized differential quadrature technique,a numerical solution methodology is introduced for obtaining the couple stress-based amplitude and frequency responses related to the primary resonant dynamics of the FGM CTCMs.Jump phenomena due to the loss of the first stability branch and falling down to the lower stable branch can be seen in the nonlinear primary resonance of the FGM CTCMs.It is demonstrated that the hardening type of nonlinearity results in bending the frequency response to the right side,and the MCS type of size effect weakens this pattern.Moreover,for higher material gradient indexes,the hardening type of nonlinearity is enhanced,and the MCS-based frequency response bends more considerably to the right side.

Compressibility of Nickel Nanoparticle Chain

We perform the high-pressure energy dispersive x-ray diffraction experiments of nickel nanoparticle chain using a synchrotron source under quasi-hydrostatic compression up to 44.7GPa. There is no phase transition over the pressure range. The bulk modulus Ko, the first pressure derivative of bulk modulus K＇0 and the volume Vo are calculated from the pressure-volume data using the Birch-Murnaghan equation of state. A decrease of compressibility is observed, in agreement with the Hall-Perch effect.

Atomic Simulation of Structure and Deformation＇s Influence on the Mechanical Properties of Single-walled Carbon Nanotubes

Tensile deformation behaviors and the Poisson＇s ratio of single-walled carbon nanotubes （SWCNTs） are numerically studied, using the molecular dynamics （MD） inethod. Effects of several structural features of crystal cells of SWCNTs, i.e., the size, chirality and strain, on their mechanical properties are analyzed systematically. The simulations indicate that Armchair SWCNTs （8, 8）-（22, 22） and Zigzag SWCNTs （9,0）- （29,0） can be stretched by 35%-38% and 20%-27% without sign of plasticity, respectively. The Young＇s modulus of SWCNTs under tension ranges from 960 GPa to 750 GPa as their radii increase. The Young＇s modulus of zigzag SWCNTs is higher than that of armchair SWCNTs. Additionally, three SWCNTs （9,9）, （12,6） and （16,0） are investigated to obtain their Poisson＇s ratio under tensile and compressive loading. The results show that the Poisson＇s ratio of nanotubes decreases generally as the strain increases. Under the same tensile strain, the Poisson＇s ratio decreases as the chiral angles of SWCNTs decrease, while their Polsson＇s ratios increase under the same compressive strain.

Structural and Spectroscopic Properties of Linear Carbon Chains NC_(2n)N and HC_(2n+_1)N(n=1～10)

Using density functional theory, geometries and vibrational frequencies of linear chains NC2nN and HC2n＋1N （n = 1 - 10） have been investigated. Time-dependent density functional theory （TD-DFF） has been used to calculate the vertical transition energies and oscillator strengths for the x^1∑g^＋→I^1∑u^＋ transition in NC2,N （n = 1 -10） and X^1∑ → I^1∑^＋ transition in HC2n＋1N （n =1 -7）. On the basis of present calculations, the explicit expressions for the size dependence of the excitation energy and the first adiabatic ionization energy in both carbon chains have been suggested.

Size Controlling Preparation, Adsorption and Catalytic Properties of Silica Microspheres

The size-controlled silica microspheres were prepared by a facile method and the growth mechanism was simply studied. The as-prepared samples were characterized by scanning electron microscopy and transmission elec- tron microscopy. The CO2 adsorption behaviors and methane catalytic oxidation were also measured. The results show that the as-prepared silica is perfect sphere, and the particle size can be controlled by adding tartaric acid. Spherical silica and sphere/tube（rod）-shaped silica were obtained by adjusting reaction time. Silica microspheres with uniform size exhibit high capacity of CO2 adsorption, while others with wide size-distribution exhibit excellent catalytic performance, suggesting it is an effective method by regulating size to utilize its advantages selectively. Therefore, it will be an ideal strategy to develop the efficient multifunctional materials by a facile route.

Crack and size-dependence of shear modulus in a drying particulate film

We utilized controlled vertical drying deposition (CVDD) method,which can fabricate a uniform face-center-cubic (FCC) structure film,to investigate the crack formation and the size dependence of shear modulus in a drying particulate film.We found that both crack spacing and shear modulus depend on colloidal particle size.They drop with increase of particle radius (R) in a single range.Furthermore,compared with the shear modulus variation of a dry particulate film,it was found that both solid part and liquid part in a drying particulate film play equivalent roles in the film mechanical behavior.

Measurement on Spot Size Dependence of Dense WDM Dielectric Multilayer Filters

We present the spot size dependence of dielectric multilayer filters for use in dense WDM systems. We found large dependences of filter performances on the spot size and the incident angle of input light, which should be important for miniaturizing multi-channel add/drop filters.

Size dependence of twin formation energy of metallic nanowires

Twin formation energy is an intrinsic quantity for bulk crystals.At the nanoscale,the twin formation energy of covalent SiC nanowires goes up with decreasing dimension.In contrast,this article reports that the twin formation energy of metallic nanowires goes down with decreasing dimension.This result is based on classical molecular statics simulations of four representative metals.Cu and Al represent face-centered cubic(FCC)metals of low and high twin formation energies.Ta represents a body-centered cubic(BCC)metal,and Mg represents a hexagonal close-packed(HCP)metal.For all the four metals,the dependence of twin formation energy on size correlates with lower twin formation energy near surfaces,according to atomic-level analysis.Based on this atomic-level insight,the authors propose a core–shell model that reveals the twin formation energy as inversely proportional to the diameter of nanowires.This dependence is in agreement with the results of molecular statics simulations.

Density Effects on Plant Height Growth and Inequality in Sunflower Populations

Comparisons between competing and non-competing sunflower （Helianthus annuus L.） populations demonstrate pronounced effects of density on plant height growth, height-to-crown width ratio, and s popuiaUon＇s height inequality. In the present study, non-destructive measurements of height and the prolected crown area of sunflower plants were taken at seven times from emergence to fruit maturation in even-aged monospeclflc stands with initial densities of 1, 4, 16, and 64 plants/m^2. The mean height of populations Increased and then decreased with increasing population density; the height Inequalities of uncrowded populations decreased during stand growth, whereas the height inequaiiUes of crowded popuisUons decreased first and then increased during stand development. The interindlvidual relationships between the relative height growth rate and height within uncrowded populations became significantly negative during population growth, whereas these relationships were negative first and then became positive during the development of crowded populations. In the uncrowded populations, the static Interindlvldual relationship between height-to-crown width ratio and volume was positive, whereas for the crowded population these relationships became negative with increasing competition for light. The data suggest that the plastic responses of plant height and height-to-crown width ratio to light competition will become more Intense with increasing competition Intensity. The results of the present study argue strongly for the Importance of size-dependent Individual-level plastic responses due to size-asymmetric light competition In generating the variations in population height inequality.

Thermoelastic Damping of Functionally Graded Material Micro-Beam Resonators Based on the Modified Couple Stress Theory

Thermoelastic damping(TED)is one of the main internal energy dissipation mechanisms in micro/nano-resonators.Accurate evaluation of TED is important in the design of micro-electromechanical systems and nano-electromechanical systems.In this paper,a theoretical analysis on the TED in functionally graded material(FGM)micro-beam resonators is presented.Equations of motion and the heat conduction equation governing the thermodynamic coupling free vibration of non-homogenous micro-beams are established based on the Euler Bernoulli beam theory associated with the modified couple stress theory.Material properties of the FGM micro-beam are assumed to change in the depth direction as power-law functions.The layer-wise homogenization method is used for solving the heat conduction equation.By using the mathematical similarity of eigenvalue problem between the FGM beam and the reference homogeneous one,the complex natural frequency including TED is expressed in terms of the natural frequency of the isothermal homogenous beam.In the presented numerical results,influences of various characteristic parameters,such as beam thickness,material gradient index,structure size,vibration mode and boundary conditions,on TED are examined in detail.It shows that TED decreases with the increases in the values of length scale parameters because the latter lead to the increase in structural stiffness.

Molecular Dynamics Studies of the Kinetics of Phase Changes in Clusters IV:Crystal Nucleation from Molten (NaCl)_(256) and (NaCl)_(500) Clusters

Molecular dynamics computer simulation based on the Born-Mayer-Huggins potential function has been carried out to study the effects of cluster size and temperature on the nucleation rate of sodium chloride clusters in the temperature range of 580 K to 630 K. Clusters with 256 and 500 NaCl molecules have been studied and the results have been compared with those obtained from 108 molecule clusters. The melting point (MP) of the clusters were observed to increase with the size of the clusters and can be well described by a linear equation MP=1107(37)-1229(23)N -1/3 (N is the number of molecules in the cluster). The nucleation rate was found to decrease with increasing the cluster size or temperature. Various nucleation theories have been used to interpret the nucleation rates obtained from this molecular dynamics simulation. It is possible to use a constant diffuse interface thickness to interpret the nucleation rate from the diffuse interface theory in the temperature range of this study. However,the interfacial free energy estimated from classical nucleation theory and diffuse interface theory increases too fast with increasing the temperature while that from Gran-Gunton theory does not change with changing temperatures. The sizes of critical nuclei estimated from all the theories are smaller than those estimated from our simulations.