Parametric optimization of heat transfer characteristics for helical coils

Journal of Thermal Analysis and Calorimetry - In this study, helically coiled tubes are used in a shell, and the effects of tube diameter, coil diameter, Reynolds number, Dean number and flow rate...     

Electrochemical Biosensor Design with Multi-walled Carbon Nanotube to Display DNA-Schiff Base Interaction

This paper demonstrates a Schiff base i. e. 5-(diethylamino)-2-((2,6-diethylphenylimino)methyl)phenol (5-DDMP) that was sensed by DNA biosensor. dsDNA was immobilized onto GCE modified with functionalized multi-walled carbon nanotubes to prepare a biosensor. The efficiency of dsDNA biosensor was determined and binding of 5-DDMP with dsDNA was searched by UV-vis spectrophotometry and differential pulse voltammetry. Molecular docking simulations between 5-DDMP and dsDNA were explored and as a result, a hydrogen bond and a π-π contact were observed between 5-DDMP and deoxyguanosine base (dG22) of the strand B, deoxyadenosine base (dA5) of the strand A, respectively. These studies could be useful for new anticancer drug design and development.     

Microstructural properties and local atomic structures of cobalt oxide nanoparticles synthesised by mechanical ball-milling process

In this study, facile preparation of pure and nano-sized cobalt oxides particles was achieved using low-cost mechanical ball-milling synthesis route. Microstructural and morphological properties of synthesised products were characterised by X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. XRD results indicated that the fabricated samples composed of cubic pure phase CoO and Co₃O₄ nanocrystalline particles with an average crystallite size of 37.2 and 31.8 nm, respectively. TEM images showed that the resulting samples consisted of agglomerates of particles with average diameter of about 37.6 nm for CoO and 31.9 nm for Co₃O₄. Phase purity of the prepared samples was further investigated due to their promising technological applications. Local atomic structure properties of the prepared nanoparticles were probed using synchrotron radiation-based X-ray absorption spectroscopy (XAS) including X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). EXAFS data analysis further confirmed the formation of single-phase CoO and Co₃O₄ nanoparticles. In addition, structural properties of cobalt oxide nanoparticles were investigated by performing density functional theory calculations at B3LYP/TZVP level and Born–Oppenheimer molecular dynamics. Theoretical calculations for both prepared samples were found to be consistent with the experimental results derived from EXAFS analysis. Obtained results herein reveals that highly crystalline and pure phase CoO and Co₃O₄ nanoparticles can be synthesised using simple, inexpensive and eco-friendly ball-milling method for renewable energy applications involving fuel cells and water splitting devices.     

Microstructure of thermoelectric (Bi0.15Sb0.85)2Te3 film

The film of thermoelectric ternary p-type (Bi_0.15Sb_0.85)₂Te₃ was deposited on polyimide foil substrate at 168 °C using direct-current magnetron sputtering. Microstructural investigations of the film were performed by electron microscopy techniques. SEM observations showed that the film surface consisted of large-sized particulates with small-sized particles and also mound-like crystal agglomerates in some areas. Chemical composition of the film was analyzed using energy-dispersive X-ray spectrometer (EDS). It has been observed that the EDS results were in an agreement with nominal composition for the film. Detailed microstructural investigations were carried out using transmission electron microscopy (TEM). TEM images and selected area electron diffraction patterns showed that the film has randomly oriented polycrystalline grain structure. High-resolution TEM images indicated that the microstructure of film also contained nano-crystal structure, smaller than 10 nm.     

Improved diode properties in zinc telluride thin film-silicon nanowire heterojunctions

In this study, structural and optoelectronic properties and photodedection characteristics of diodes constructed from p-zinc telluride (ZnTe) thin film/n-silicon (Si) nanowire heterojunctions are reported. Dense arrays of vertically aligned Si nanowires were successfully synthesized on (1 1 0)-oriented n-type single crystalline Si wafer using simple and inexpensive metal-assisted etching (MAE) process. Following the nanowire synthesis, p-type ZnTe thin films were deposited onto vertically oriented Si nanowires via radio frequency magnetron sputtering to form three-dimensional heterojunctions. A comparative study of the structural results obtained from X-ray diffraction and Raman spectroscopy measurements showed the improved crystallinity of the ZnTe thin films deposited onto the Si nanowire arrays. The fabricated nanowire-based heterojunction devices exhibited remarkable diode characteristics and enhanced optoelectronic properties and photosensitivity in comparison to the planar reference. The electrical measurements revealed that the diodes with nanowires had a well-defined rectifying behaviour with a rectification ratio of 10⁴ at ±2 V and a relatively small ideality factor of n = 1.8 with lower reverse leakage current and series resistance at room temperature in dark condition. Moreover, an open-circuit voltage of 100 mV was also observed under illumination. Based on spectral photoresponsivity measurements, the nanowire-based device exhibited a distinct responsivity and high detectivity in visible and near-infrared (NIR) wavelength regions. The device characteristics observed here offer that the fabricated ZnTe thin film/Si nanowire-based p–n heterojunction structures will find important applications in future and will be a promising candidate for high-performance and low-cost optoelectronic device applications, NIR photodedectors in particular.     

New Electroactive Hybridization Indicators 2‐Phthalimido‐N‐Substitutedphenylethanesulfonamide Derivatives for Biosensor Applications: Ring Substituent Effect on Interaction between Compound and DNA

In this work, an electrochemical DNA‐based sensor was developed for the detection of the interaction between the anticonvulsant compounds 2‐phthalimido‐N‐substituted phenylethanesulfonamides (PMPES‐derivatives) and 24‐mer short DNA sequences by using differential pulse voltammetry (DPV) based on both compound and guanine oxidation signals at the renewable carbon graphite electrode (CGE) surface. The influence of compounds on DNA showed differences depending on the nature and position of the substituent on the N‐phenyl ring. Compounds bearing 3‐methoxy, 4‐chloro and 2,6‐dimethyl substituents bind to single stranded probe DNA more strongly than the other derivatives of PMPES. Thus, these compounds were evaluated for use as an electrochemical hybridization label (indicator).     

Viscosities, Apparent Molar Volumes, Expansivities and Isentropic Compressibilities of some Fatty Acids and their Triglycerides in Benzene at (20, 30, 40 and 60) °C

Viscosities, apparent molal volumes, compressibilities and expansivities of lauric, palmitic and stearic acids and their triglycerides, trilaurin, tripalmitin and tristearin, were determined in benzene at 20, 30, 40 and 60 °C. Accurate density and sound velocity measurements carried out simultaneously with a high-precision vibrating-tube densimeter and sound velocity measuring device were utilized in deriving volume, compressibility and expansivity data. Viscosities were measured with Ostwald type viscometers. Infinite dilution values of the apparent molal volumes and compressibilities were obtained by an extrapolation procedure. Apparent molal expansivities at infinite dilution were obtained from the temperature dependence of the apparent molar volume at infinite dilution. The properties at infinite dilution were evaluated in terms of solute-solvent interactions. Volumetric results in benzene were compared with the corresponding data estimated from group contributions in aqueous solutions using the additivity rule.     

Synthesis,electrochemical, and antibacterial activity of some novel N<Subscript>4</Subscript>O<Subscript>2</Subscript> ligand derivativies

A novel ligand has been synthesized by the condensation of 1,3-diaminoprophane (HL) wıth isonitroso-p-chloroacetophenone. The complexes of cobalt(II), nicel(II), cupper(II) and zinc(II) with HL were prepared. All compounds were characterized by spectroscopic techniques and its antibacterial activities were determined by the disc diffusion method used against to those gram-positive and-negative bacteria. All compounds were investigated by cyclic voltammetry at 25°C. The voltammograms were recorded with a potential scan of 100 mV s⁻¹. The text was submitted by the authors in English.