Tuning the Properties of CZTS Films by Controlling the Process Parameters in Cost-Effective Non-vacuum Technique

Highly dispersive Cu₂ZnSnS₄ (CZTS) nanoparticles were successfully synthesized by a simple solvothermal route. A low cost, non-vacuum method was used to deposit CZTS nanoparticle ink on glass substrates by a doctor blade process followed by selenization in a tube furnace to form Cu₂ZnSn (S,Se)₄ (CZTSSe) layers. Different selenization conditions and particle concentrations were considered in order to improve the crystallinity and surface morphology; the annealing temperature was varied between 400°C and 550°C and the annealing time was varied between 5 min and 20 min in a selenium-nitrogen atmosphere. The influence of annealing conditions on structural, compositional, optical and electrical properties of CZTSSe thin films was studied. An improvement in the structural and surface morphology was observed with increasing of annealing temperature (up to 500°C). An enhancement in the crystallinity and surface morphology were observed for thin films annealed for 10–15 min. Absorption study revealed that the band gap energy of as-deposited CZTS thin film was approximately 1.43 eV, while for CZTSSe thin films it ranged from 1.15 eV to 1.34 eV at different annealing temperatures, and from 1.33 eV to 1.38 eV for different annealing times.     

Effective, fast, and low temperature encapsulation of fullerene derivatives in single wall carbon nanotubes

High filling of single wall nanotubes (SWCNTs) with the typical exohedrally functionalized fullerene derivative of C₆₀N-methyl-3,4-fulleropyrrolidine C₆₀-C₃NH₇ is reported at the temperature of refluxing hexane. The new peapod material is characterized by STM (scanning tunneling microscopy), TEM (transmission electron microscopy) and Raman spectroscopy. Atomically resolved STM scans on SWCNT show no excessive defects or sidewall functionalization as a result of this treatment. The radial breathing mode (RBM) mode of SWCNT at 165 cm⁻¹ becomes weaker and shifted to 169 cm⁻¹ indicating filled nanotubes. TEM studies show bundles of SWCNT are highly filled with derivative C₆₀-C₃NH₇ and form the (C₆₀-C₃NH₇)_n peapods. Individual pyrrolidine-type functional groups attached to the fullerene cages are unambiguously visualized by a lower-dose observation.     

The Klein correspondence of line congruences immersed in an elliptic spaceS 3 onto the hyperquadricP 4

This article is devoted to the investigation and the construction of the Klein correspondence of line congruences referred to a specialized moving frame in a 3-dimensional elliptic spaceS ₃ to the hyperquadricP ⁴ of the Klein 5-dimensional elliptic spaceS ₅. The Klein correspondence is given and characterized by Theorems 1, 2. The methods adapted here are based on Cartan's differential calculus [1], [6].     

Smart antenna design for high‐speed moving vehicles with minimum return loss

The Internet of Things (IoT) is a connection amongst people and applications to another dimension of machine‐to‐machine communication. IoT scenario is unequivocally related with the development of the advancement of wireless sensor systems (WSNs) and radio‐frequency identification (RFID) frameworks. Owing to the technological advances around the world, energy demand is increasing exponentially. Energy proficiency has turned out to be one of the real worries in the present life that essentially influence every single human action. In communication system, return loss is a major issue for transmission process. Owing to return loss, a huge amount of power consumption occurs. This phenomenon is contemporary with transmission process, and it will initiate a serious problem for high‐speed moving substance like aircraft, rockets, and spaceship. To overcome this problem, a four‐element cylindrical antenna (conformal) array with better axial radiation is proposed. The four U‐shaped slots are uniformly wrapped around on a cylindrical surface, which produces tilted radiation. To enhance the axial radiation, four conformal elements are reefed by a one‐ to four‐microstrip feed network. The proposed conformal design has a bandwidth of 200 MHz (narrow bandwidth) at the center frequency of 3.9 GHz, covering the range of 3 to 3.9 GHz, with the gain of 4.9 dBic, and can be suitable for unmanned aerial vehicles (UAV), wireless avionics intra‐communication (WAIC), and so forth. The proposed design is low profile and can be used for high‐speed avionic applications. Finally, machine learning technique is explored to design a model for a smart antenna with optimistic parameters to reduce return loss and enhance the transmission rate.     

Synthesis and structural investigation of mono- and polynuclear copper complexes of 4-ethyl-1-(pyridin-2-yl) thiosemicarbazide

The reaction between 2-hydrazinopyridine and ethylisothiocyanate produced 4-ethyl-1-(pyridin-2-yl) thiosemicarbazide (HEPTS). Its reaction with copper fluoride, chloride, bromide, acetate, nitrate, perchlorate, sulfate, carbonate, hydroxide and copper metal produced 15 Cu(II) complexes. The copper metal is easily oxidized in aqueous-ethanol solution of HEPTS giving [Cu(2)(EPTS)(H(2)O)(3)(OH)(3)]EtOH. Different complexes for the same anion were synthesized by controlling the heating time. Characterization by elemental, thermal, magnetic and spectral (electronic, IR, mass and ESR) studies showed the formation of mono-, di-, tri- and tetra nuclear complexes. The room temperature solid state ESR spectra of the complexes show an axial spectrum with d(x)(2)-y(2) ground state, suggesting distorted tetragonal geometry around Cu(II) center. The kinetic and thermodynamic parameters for the different decomposition steps in the complexes were calculated. HEPTS and its Cu(II) complexes showed high activity against gram negative bacteria; [Cu(3)(EPTS)(2)(EtOH)(2)Br(4)] has more activity.     

Cloud point extraction and spectrophotometric determination of Cu(II) in saturated saline solutions using 4-ethyl-1-(pyridin-2-yl)thiosemicarbazide

4-Ethyl-1-(pyridin-2-yl)thiosemicarbazide (HEPTS) has been used as a new complexing agent in cloud point extraction (CPE) for preconcentration and determination of trace amounts of copper in saturated saline medium. The chemical variables affecting the separation and determination processes were optimized. Copper(II) is preconcentrated using 0.05% (w/v) Triton X-114 and 10⁻⁴ M HEPTS at pH 6. The surfactant rich phase containing the complex was dissolved in 2 mL MeOH and determined spectrophotometrically. The calibration curve is linear in the 0.1–25 ng/mL copper range. The proposed method was applied successfully in the determination of copper in water and saturated saline samples. The reaction between CuSO₄ and HEPTS yields a deep-blue solid complex which is characterized by analytical and spectroscopic analyses.     

Templating Ag on DNA/polymer hybrid nanowires: Control of the metal growth morphology using functional monomers

Ag nanowires and nanoparticles have been formed on hybrid λ-DNA/conducting polymer templates. The strong, but non-covalent, interaction of the conducting polymer with the double helix allowed us to incorporate chemical functionalities (alkynyl) into the DNA/conducting polymer strands by synthesis of functional monomers. Oxidative polymerisation of alkynyl-thienylpyrrole in the presence of λ-DNA produced conductive nanowires bearing alkyne groups; we show, using a combination of AFM, cAFM and EFM phase measurements that the alkyne functionality strong influences the subsequent templating reaction of Tollens’ reagent to produce uniform conductive nanowires comprised of many connected Ag clusters.