Nonlinear system of PT-symmetric excitations and Toda vibrations integrable by the Darboux–Bäcklund dressing method

The nonlinear dynamics of coupled P T -symmetric excitations and Toda-like vibrations on a one-dimensional lattice are studied analytically and elucidated graphically. The nonlinear exciton-phonon system as the whole is shown to be integrable in the Lax sense inasmuch as it admits the zero-curvature representation supported by the auxiliary linear problem of third order. Inspired by this fact, we have developed in detail the Darboux–Bäcklund integration technique appropriate to generate a higher-rank crop solution by dressing a lower-rank (supposedly known) seed solution. In the framework of this approach, we have found a rather non-trivial four-component analytical solution exhibiting the crossover between the monopole and dipole regimes in the spatial distribution of intra-site excitations. This effect is inseparable from the pronounced mutual influence between the interacting subsystems in the form of specific nonlinear superposition of two essentially distinct types of travelling waves. We have established the criterion of monopole-dipole transition based upon the interplay between the localization parameter of Toda mode and the inter-subsystem coupling parameter.

Darboux Transformation, Exact Solutions and Conservation Laws for the Reverse Space-Time Fokas-Lenells Equation

In this paper, we firstly deduce a reverse space-time Fokas-Lenells equation which can be derived from a rather simple but extremely important symmetry reduction of corresponding local equation. Next, the determinant representations of one-fold Darboux transformation and N-fold Darboux transformation are expressed in detail by special eigenfunctions of spectral problem. Depending on zero seed solution and nonzero seed solution, exact solutions, including bright soliton solutions, kink solutions, periodic solutions, breather solutions, rogue wave solutions and several types of mixed soliton solutions, can be presented. Furthermore, the dynamical behaviors are discussed through some figures. It should be mentioned that the solutions of nonlocal Fokas-Lenells equation possess new characteristics different from the ones of local case. Besides, we also demonstrate the integrability by providing infinitely many conservation laws. The above results provide an alternative possibility to understand physical phenomena in the field of nonlinear optics, and related fields.

Synthesis of prolate gold nanoparticles for use in plasmon-enhanced overtone near-infrared spectroscopy

Gold nanoparticles were obtained by the method of three-stage growth from a seed solution. Scanning electron microscopy images as well as comparison of extinction spectra to the results of numerical simulations prove the formation of prolate nanoparticles. Such particles with localized plasmon resonance in the NIR region are much-needed for the plasmon-enhanced overtone spectroscopy.

Gravitational Decoupling in Higher Order Theories

Gravitational decoupling via the Minimal Geometric Deformation (MGD) approach has been used extensively in General Relativity (GR), mainly as a simple method for generating exact anisotropic solutions from perfect fluid seed solutions. Recently this method has also been used to generate exact spherically symmetric solutions of the Einstein-scalar system from the Schwarzschild vacuum metric. This was then used to investigate the effect of scalar fields on the Schwarzschild black hole solution. We show that this method can be extended to higher order theories. In particular, we consider fourth order Einstein–Weyl gravity, and in this case by using the Schwarzschild metric as a seed solution to the associated vacuum field equations, we apply the MGD method to generate a solution to the Einstein–Weyl scalar theory representing a hairy black hole solution. This solution is expressed in terms of a series using the Homotopy Analysis Method (HAM).

Performance of Dye Sensitized Solar Cells (DSSCs) with ZnO Nanorod Electrode in Different Seed Solution

Studies of comparing the performance of photoelectrode for dye-sensitized solar cells (DSSCs) continue to be carried out and developed. The ZnO nanorods as an electrode for DSSCs have been shown to have high electron collection due to the capability of electron photoexcitation and increased electron transport. Various methods of making ZnO nanorods have been studied and developed. However, the method requires controlled conditions under high temperature and pressure, thus limiting the commercialization of ZnO nanorods. Therefore, the seed solution-based hydrothermal method was chosen in the ZnO nanorod deposition process because it is an effective method, low-cost and easier fabrication process. The method of growing ZnO nanorod was carried out with three times of growing for 6 hours. ZnO nanorod was synthesized using different seed solutions, namely sample 1 and sample 2 by using methoxy and isopropanol, respectively. In this work, the SEM image shows the growth of ZnO nanorods vertically aligned on the FTO substrate and resulted in a smaller diameter for the isopropanol seed solution. The smaller diameter of the ZnO nanorod provides a larger surface area then increasing the total amount of dye attached to the ZnO nanorod and improve the photovoltaic performance.

Seed Mediated Synthesis of Colloidal Halide Perovskite Nanoplatelets

<p><b>Two-dimensional lead halide perovskite nanoplatelets (2D LHP NPLs) have been emerging as one of the most promising semiconductor nanomaterials due to their narrow absorption and emission line widths, tunable bandgaps, high exciton binding energies, high defect tolerance as well as highly localized energy states. Colloidal synthesis of 2D LHP NPLs is generally performed using hot-injection or ligand assisted precipitation techniques (LARP). In the LARP method, perovskites are synthesized in polar solvents, which decrease the stability of the 2D LHP NPLs due to their weakly bonded nature. In fact, the presence of residual polar solvent in the LHP NPL colloid can cause deterioration of thickness uniformity, degradation of NPLs to parent precursors, and undesired phase transformations. Herein, for the first time, we report facile seed-mediated synthesis route of monolayer, 2-monolayers, and thicker lead halide perovskite nanoplatelets without using A site cation halide salt (AX</b><b>;</b><b> A = Cesium, methylammonium, formamidinium and, X = Cl, Br, I) and long chain alkylammonium halide salts (LX; L = oleylammonium, octylammonium, butylammonium and, X = Cl, Br, I). The seed solution has been synthesized by reacting lead (II) halide salt and coordinating ligands (oleylamine or octylamine and oleic acid) in nonpolar high boiling solvent (1-octadecene). The seed mediated synthesis has been carried out in hexane by reacting seed solution with A-site cation precursors (Cs-oleate, FA-oleate, or diluted MA solution in hexane) under ambient conditions. More importantly, the seed mediated growth of NPLs has been tracked for the first time by performing in-situ optical measurements. Furthermore, the optical properties and morphologies of the seeds have been extensively studied. We find that our facile synthesis route provides highly stable, monodisperse NPLs with narrow absorption, and photoluminescence line widths (68-201 meV), and high PLQY (37.6-1.66% for 2ML NPLs). Furthermore, anion exchange reactions have been performed by mixing pre-synthesized LHP NPLs with counter halide seeds. The optical properties of NPLs have been affectively tuned by postsynthetic chemical reactions without changing the thickness of the NPLs. We anticipate that our new synthetic route provides further understanding of growth dynamics of LHP NPLs.</b></p>

Seed Mediated Synthesis of Colloidal Halide Perovskite Nanoplatelets

<p><b>Two-dimensional lead halide perovskite nanoplatelets (2D LHP NPLs) have been emerging as one of the most promising semiconductor nanomaterials due to their narrow absorption and emission line widths, tunable bandgaps, high exciton binding energies, high defect tolerance as well as highly localized energy states. Colloidal synthesis of 2D LHP NPLs is generally performed using hot-injection or ligand assisted precipitation techniques (LARP). In the LARP method, perovskites are synthesized in polar solvents, which decrease the stability of the 2D LHP NPLs due to their weakly bonded nature. In fact, the presence of residual polar solvent in the LHP NPL colloid can cause deterioration of thickness uniformity, degradation of NPLs to parent precursors, and undesired phase transformations. Herein, for the first time, we report facile seed-mediated synthesis route of monolayer, 2-monolayers, and thicker lead halide perovskite nanoplatelets without using A site cation halide salt (AX</b><b>;</b><b> A = Cesium, methylammonium, formamidinium and, X = Cl, Br, I) and long chain alkylammonium halide salts (LX; L = oleylammonium, octylammonium, butylammonium and, X = Cl, Br, I). The seed solution has been synthesized by reacting lead (II) halide salt and coordinating ligands (oleylamine or octylamine and oleic acid) in nonpolar high boiling solvent (1-octadecene). The seed mediated synthesis has been carried out in hexane by reacting seed solution with A-site cation precursors (Cs-oleate, FA-oleate, or diluted MA solution in hexane) under ambient conditions. More importantly, the seed mediated growth of NPLs has been tracked for the first time by performing in-situ optical measurements. Furthermore, the optical properties and morphologies of the seeds have been extensively studied. We find that our facile synthesis route provides highly stable, monodisperse NPLs with narrow absorption, and photoluminescence line widths (68-201 meV), and high PLQY (37.6-1.66% for 2ML NPLs). Furthermore, anion exchange reactions have been performed by mixing pre-synthesized LHP NPLs with counter halide seeds. The optical properties of NPLs have been affectively tuned by postsynthetic chemical reactions without changing the thickness of the NPLs. We anticipate that our new synthetic route provides further understanding of growth dynamics of LHP NPLs.</b></p>

Synthesis, properties and functionalization of gold nanostars for medical diagnostics

Th e aim of the research. To evaluate two approaches to colloidal synthesis using two diff erent non-toxic surfactants (PVP and Triton X-100) and their properties for future use. Material and methods. (PVP) Th e solution of GNSs with short tips was prepared in 200 ml vial. 20 mg of PVP (Polyvinylpyrrolidone, 1-ethenylpyrrolidin-2-one) were dissolved in the 200 mL of DMF (N,N-Dimethylmethanamide) (with the sonication to dissolve well). (Triton X-100) In a typical preparation of GNSs with long tips, the seed solution was prepared in a 20mL vial: 5mL of HAuCl4 5∙10-4M in water are added to 5mL of an aqueous solution of TritonX-100 0.1M. To examinate the shape and properties of prepared gold nanostars Cary 100 Bio Spectrophotometer using quartz cuvettes was used to taken on UV-Vis spectra. Transmission Electron Microscopy (TEM) was used to obtain shape and size of prepared GNSs. Results. Microscopy analysis shows that the obtained GNSs have completely diff erent shapes. Th e GNSs fabricated using synthesis approach with PVP have shorter tips and the cores are larger than the GNSs synthesized with Triton X-100 synthesis approach. TEM-images of the second ones show smaller size nanoparticles with the longer and thinner tips. Optical properties of the synthesized GNSs were analyzed using UV-vis-NIR absorbtion spectra, which shows maximum plasmon existence at 800 nm for GNSs synthesized with PVP and at 850 nm for GNSs synthesized with Triton X-100. Conclusion. In summary, we developed GNSs using two colloidal synthesis approaches with the use of two diff erent non-toxic surfactants (PVP and Triton X-100). In the future, gold nanostars are planned to be used to develop highly sensitive methods of medical diagnostics.

PENGARUH PERLAKUAN HIDROTERMAL TERHADAP MORFOLOGI, SIFAT OPTIK DAN SIFAT LISTRIK LAPISAN TIPIS NANORODS ZNO

Zinc oxide nanorods (ZnO NRs) is a semiconductor material that has been widely applied in various fields. In this research, ZnO NRs were successfully grown on ITO substrates by chemichal bath deposition (CBD) method. The process begins with making a seed solution using an ecimolar mixture of Zn-Nitrate and hexamethylentetramine (HMTA) at 00C for one hour with 0.015 M concentration. Furthermore, making a layer of seeds using spin coating technique. ZnO NRs were grown using the CBD method at 900C for three hours then treated with variations which are hydrothermal method treatment and non-hydrothermal method treatment at 1500C for three hours. Samples were given characterization treatment using SEM, XRD, UV-Vis and four-point probe. SEM results showed that hydrothermal treatment was able to increase the coverage of nanorods on the substrate to be more prevelently and was able to increase the vertical structure of the nanorods. The results of XRD analysis showed that samples given hydrothermal treatment experienced an increase in the crystallite size. The amount of crystallite size in the sample treated with variation of non-hydrothermal treatment and hydrothermal treatment was 71, 198 and 165.696 nm. Hydrothermal treatment of nanorods samples decreased the sample diameter from 288,252 nm to 125,824 nm. The transmittance value of the samples decreased in the presence of hydrothermal treatment which is 56.53% to 38.67%. The hydrothermal treatment was able to reduce the energy bandgap (Eg) of the sample, while the sample of non-hydrothermal treatment showed value of the Eg was 3.22 eV. Meanwhile, the value of Eg after hydrothermal treatment was 3.17 eV. The resistivity value of ZnO NRs with hydrothermal treatment was 0.833 x 10-4 Ωcm, while the resistivity value of non-hydrothermal treatment was 1.126 x 10-4 Ωcm. Key words: zinc-oxide nanorods, chemical bath deposition, hydro-thermal

Symmetry reduction and new interaction solutions for the negative-order potential KdV equation

New soliton–cnoidal interaction solutions for the negative-order potential KdV equation are studied with the help of the consistent tanh expansion method. The non-local symmetry for the negative-order potential KdV equation is derived from the truncated Painlevé expansion method. The non-local symmetry is transformed into the standard Lie point symmetry by introducing new dependent variables and the finite symmetry transformation is also presented to construct new exact solutions with non-zero seed solution. The similarity solutions of the enlarged negative-order potential KdV system are obtained through different constant selections.