Consequence of doping mediated strain and the activation energy on the structural and optical properties of ZnO:Cr nanoparticles

We report on the sol-gel synthesis of Zn_1−xCr_xO (x=0.0, 0.05, 0.10, 0.15 and 0.20) nanoparticles. These nanoparticles were characterized by using thermogravimetry/differential scanning calorimetry (TG/DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman and Photoluminescence (PL). Electronegativity of Cr ions (Cr³⁺) reduces the final decomposition temperature by 40 °C and activation energy of the reaction when Cr is doped into ZnO. Doping of higher Cr concentration (x≥0.10) into ZnO shows formation of secondary spinel (ZnCr₂O₄) phase along with the hexagonal (ZnO) and is revealed by XRD. Formation of secondary phase changes the activation energy of the reaction and thus the strain in ZnO lattice. In Raman spectra, additional Raman modes have been observed for Zn_1−xCr_xO nanoparticles, which can be assigned to the modes generated due to Cr doping. The Cr doping into ZnO is also supported by PL, in which vacancies are formed with Cr ion incorporation and emission band shifts towards higher wavelength.     

Interface identification by non-local autoionization transitions

We use an autoionization process that involves ultrafast energy transfer to neighbouring sites to characterize the formation of NeAr van der Waals bonds in clusters formed by a coexpansion of both gases. This autoionization process, the so-called interatomic or intermolecular coulombic decay (ICD), is ubiquitous in weakly bonded systems. The energy of the electron being emitted in the ICD process is shown to be characteristic of the two neighbouring entities and is therefore suggested as a new means for structural investigation, such as interface identification, of weakly bonded complexes.     

Stagnation point transient heat flux measurement analysis from coaxial thermocouples

The transient heat flux measurement at stagnation point is a significant solicitation at highly compressed flow field environment. In aerodynamics surface heating point of view, the estimation of stagnation heat fluxes at the tip of a blunt body is very imperative. When the blunt body is exposed to high-speed flow field environments, at the stagnation point heat transfer would be maximum. The coaxial surface junction thermocouples (CSJTs) are convenient for short duration time scale due to the fast response in the range of millisecond or less (?0.1 ms). These robust CSJTs have the tractability of intensifying them directly on any type of surface and can be used for routine measurement in ground-based impulse amenities as a temperature measuring devices where rapid heat loads are anticipated. In this work, three different types of coaxial thermocouples K-type, E-type, and J-type have been designed and contrived. The microstructural analysis of measuring surface property has been carried out to see the surface morphology using field emission scanning electron microscopy (FESME) and chemical characterization of these CSJTs materials using energy dispersive X-ray analysis (EDXA) technique is used to verify qualitatively appraise the CSJTs materials composition. The thermal coefficient of resistance (TCR) and sensitivity (S) of each coaxial thermocouple have been determined by using oil-bath calibration technique with the linear variation of resistance corresponding to the variation of temperature and found that these coaxial thermocouples are highly sensitive and suitable for highly transient heat transfer measurements. For this purpose, these three types of CSJTs have been tested under highly compressed heated air 310 K temperature for 100 ms at pressure 6.1 bar with Mach number unity (M = 1) using compressor test rig. Numerical simulation has also been carried out with these three RTDs to satisfy the experimental parameters using Ansys Fluent 15.0 and typical transient temperature recorded. Surface heat fluxes recovered from experimental and numerical transient temperatures histories using semi-infinite heat conduction modeling having good agreement with accuracy ±3% or less. This study divulges the expertise of these handmade coaxial thermocouples for transient surface heat flux measurement for short durations at highly compressed air facilities.     

A fast response thermocouple for internal combustion engine surface temperature measurements

A fast response thermocouple was developed for measuring surface temperatures of aluminum components in ICE combustion chambers. The key features of the design are the use of the aluminum substrate as one of the thermocouple metals and the use of a thick copper layer as the hot junction at the surface. The copper equalizes the hot junction temperature with the surrounding aluminum to correct for the differences in thermal properties between the two materials. FEA determined the optimum thickness of the copper layer to be between 100 and 125 μm. Under typical SI engine heat flux conditions, the thermocouple should be able to measure average surface temperatures within 0.19 °C and the magnitude of temperature swings within 6% of true values.Following the FEA, the optimized thermocouple was tested in a SI engine. Experimental results displayed the same trends as the FEA at measuring average temperatures and temperature swings, suggesting the thermocouple was performing as predicted.     

Synthesis,characterization, in vitro antimicrobial and cytotoxic evaluation of Co(II), Ni(II), Cu(II) and Zn(II) complexes derived from bidentate hydrazones

Co(II), Ni(II), Cu(II) and Zn(II) complexes have been synthesized from hydrazone ligands (HL¹–HL⁴) obtained by condensation reaction of 6-chlorothiochroman-4-one with benz hydrazide/nicotinic hydrazide/isonicotinic hydrazide/p-toluic hydrazide. The synthesized compounds (1–20) were characterized by physicochemical procedures, i.e. (FTIR, ¹H NMR, ¹³C NMR, mass, ESR, UV–Vis), TGA/DTA, powder XRD, elemental analysis (CHN), magnetic susceptibility and molar conductance measurements. The various data suggested bidentate nature (NO) of hydrazones, which coordinate with central metal ions via nitrogen of azomethine (–C=N–) group and deprotonated carbonyl oxygen in the enolized form, resulting in octahedral complexes. Low values of molar conductance suggested their non-electrolytic nature. Thermal decomposition pattern of complexes confirms the metal oxides as end product. In vitro antimicrobial activity of hydrazones and their metal complexes were evaluated against two gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus); two gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli); and two fungal strains (Candida albicans and Aspergillus niger) by serial dilution method, and it was found that the metal complexes were highly active as compared to hydrazones. Among all the compounds, complexes 11, 13, 14 and 19 were found most efficient antimicrobial agent. The anticancer activity of (1–20) compounds was performed on human cancer cell lines A549 (lung), DU145 (prostate) and SW620 (colorectal) by MTT assay using paclitaxel as reference drug. The cytotoxicity results suggested compounds [Cu(L²)₂(H₂O)₂] 11 as most potent against A549, DU145 and SW620 cancer cell lines with IC₅₀ values of 3.46, 18.21 and 7.61 µM. Furthermore, compounds (9, 10, 11, 12) were also investigated on A549 cell line for their ROS generation and mitochondrial membrane potential loss and suggested that complex [Cu(L²)₂(H₂O)₂] 11 has highest ROS production and induction of apoptosis by mitochondrial depolarization in cancer cells.

Graphic abstract

The synthesized compounds (1–20) were screened for in vitro cytotoxicity against A549 (lung), DU145 (prostate), SW620 (colorectal) human cancer cell lines. Copper complex (11) was found to be the most active antitumor agent which enhance ROS production and MMP loss on A549 cells.

     

Fabrication and characterization of thin films of single-walled carbon nanotube bundles on flexible plastic substrates

A convenient method to obtain patterns of films of single-walled carbon nanotubes (SWNT) bundles on flexible plastic is described. Using the Line Patterning method SWNT films of thickness ranging from approximately 300-1500 nm can be obtained from aqueous surfactant-supported dispersions of chemically purified SWNT bundles synthesized by the pulsed-laser ablation method. These films are strongly adherent and are competitive in performance with commercially available films of indium-tin-oxide (ITO) on plastics. For example, an approximately 1500 thick film of SWNT on poly(ethylene terephthalate) (PET) shows a surface resisitvity of approximately 80 Omega/sq, optical transparency >80%, and robust flexibility. Unlike ITO/PET, films of SWNT/PET can be folded and bent to a crease without cracking. The simple techniques involoved in obtaining these films (i.e., those without requiring lithography or ink-jet printing) could help facilitate the rapid fabrication of transparent, flexible electronic devices, heralding what promises to be a new approach towards the development of next-generation optoelectronic devices.     

Selinidin: Crystal structure generated by C–H···O, C–H···π and π-π interactions

The title compound, 9,10-dihydro-8,8-dimethyl-2-oxo-2H,8H-benzo[1,2-b:3,4-b']dipyran-9-yl-2-methyl-2-butenoate, C₁₉H₂₀O₅, was isolated from the roots of Selinum vaginatum. The compound crystallizes into monoclinic space group P2 ₁ with unit cell parameters: a = 12.830(2) Å, b = 9.041(1) Å, c = 14.983(1) Å, β = 95.09(1)°, Z = 4. The crystal structure has been determined using direct methods and refined by full-matrix least-squares to a final R value of 0.0529 for 3142 observed reflections. There are two independent molecules, A and B, per asymmetric unit. In both the molecules, the coumarin nucleus is planar. However pronounced differences are observed in the conformation of dihydropyran ring which has a half-chair conformation with an 8β-9α orientation in molecule A and is intermediate between half-chair and sofa in molecule B. Differences also occur in the conformation of the 2-methylbutenoyloxy side chain at C9 due to the different geometry of C–H···π interactions in molecules A and B. Molecules A and B are connected by π–π interactions between their coumarin fragments forming dimers. The dimers interact through C–H···O and C–H···πhydrogen bonds.     

Polyimide-epoxy alloys prepared via micro-modification: Water sorption and diffusion

A novel polyimide-epoxy or PI-EP alloys are prepared by the modification of polyamic acid in the concentration range of 1.54×10⁻⁶ to 1.54×10⁻² mol/L. The methanol sorption for these alloys at 24 hrs and at equilibrium conditions are determined and the residual solvent in fully cyclized polyimides were calculated. The presence of the residual solvent is visualized in fully imidized polymer and a structure containing partly imidized amic acid moiety is proposed and their concentration (in percentage) is calculated. The water sorption for these alloys at 24 hrs and at equilibrium conditions and the values of the water diffusion coefficient are determined from absorption isotherms. The PI-EP alloys have shown comparatively lower water sorption and higher diffusion coefficient than the unmodified polyimide. The mechanistic aspects of water sorption and diffusion are discussed.     

Growth of zinc oxide nanostructures

Zinc oxide (ZnO) nanowhiskers have been prepared using a multilayer ZnO(50 nm)/Zn(20 nm)/ZnO(2μm) structure on a polished stainless steel (SS) substrate by high rate magnetron sputtering. The formation of uniformly distributed ZnO nanowhiskers with about 20 nm dia. and 2 to 5 μm length was observed after a postdeposition annealing of the prepared structure at 300–400° C. An array of highlyc-axis oriented ZnO columns (70–300 nm in dia. and up to 10 μm long) were grown on Si substrates by pulsed laser deposition (PLD) at a high pressure (1 Torr), and Raman studies showed the activation of surface phonon modes. The nanosized powder (15–20 nm) and nanoparticle ZnO films on glass substrate were also prepared by a chemical route. Nanowhiskers showed enhanced UV light detection characteristics, and the chemically prepared ZnO nanoparticle films exhibited good sensing properties for alcohol