Studies on electrical switching behavior of As-Te-Tl glasses – effect of local structure on switching type and composition dependence of switching voltages

Bulk As-Te-Tl glasses belonging to the As₃₀Te_70-xTl_x (4≤x≤22) and As₄₀Te_60-xTl_x (5≤x≤20) composition tie lines are studied for their I–V characteristics. Unlike other As-Te-III glasses such as As-Te-Al and As-Te-In, which exhibit threshold behavior, the present samples show memory switching. The composition dependence of switching voltages (V_t) of As-Te-Tl glasses is also different from that of As-Te-Al and As-Te-In glasses, and it is found that V_t decreases with the addition of Tl. Both the type of switching exhibited by As-Te-Tl glasses and the composition dependence of V_t, seems to be intimately connected with the nature of bonding of Tl atoms and the resultant structural network. Furthermore, the temperature and thickness dependence of switching voltages of As-Te-Tl glasses suggest an electro thermal mechanism for switching in these samples. PACS 71.55.Jv; 61.43Fs; 61.43.-j; 72.80.Ey; 73.61.Jc     

A Simple and Efficient Approach for Estimating Recovery of a Preparative Reversed Phase HPLC Purification

The widely applied reversed phase high-performance liquid chromatography (RP-HPLC) is an indispensable purification technique in drug discovery. During drug discovery, recovery was usually calculated based on the weight of the purified product after drying over the weight of the crude material multiplied by the assumed purity from HPLC/UV area percent of the product. Such a purity assumption can be off significantly when the crude material contains water, solvents, other UV-inactive impurities and inorganic salts. In this paper, we report a simple and efficient way to estimate recovery of preparative HPLC purification process. It is based on the ratio of the HPLC/UV peak area measured for the product in the crude solution and that in the final collected fraction with both accounted for their volumes. This approach eliminates not only the need for drying of the collected fraction to calculate recovery but also the inaccuracy associated with the true content in the crude sample using the traditional method. A systematic study was conducted to verify this method using caffeine mixed with various UV-active and -inactive impurities. The calculated recoveries using this approach were found to be consistent within 4% with the true recoveries based on dry weight estimation. The approach has been successfully applied for our in-house purifications. Furthermore, the approach was extended to library purifications, where in many cases heart-cutting the desired peaks is used to meet the purity requirements.

     

Comparative study on low energy ion beam modification of thermoplastic polymers

ABSTRACT

Polycarbonate (PC) and polyethylene terephthalate (PET) thermoplastic polymer films were irradiated by low energy ion beams such as 100 keV Hydrogen (H⁺) ions and 350 keV Nitrogen (N⁺) ions at varied fluence from 1?×?10¹³ ions/cm² to 5?×?10¹⁴ ions/cm². The depth profile concentration of ions was calculated using Stopping and Range of Ions in Matter (SRIM) software code. Fourier Transform Infrared (FTIR) technique shows decrement in the intensity of peaks and disappearance of peaks mainly related to carbonyl stretching at 1770?cm^?1 and C–C stretching at 1500?cm^?1. Scanning electron microscopy (SEM) of irradiated polymers showed the formation of pores. X-ray diffraction (XRD) analysis has showed decrease in the intensity indicating the decrease in crystallinity after irradiation. Mechanical studies revealed that the molecular weight and microhardness decrease with increase in ion fluence due to increase in chain scission. The contact angle increased with increase in ion fluence indicating the hydrophobic nature of polymer after irradiation. Antibiofilm activity test of irradiated films shows resistance to Salmonella typhi (S. typhi) pathogen responsible for typhoid. The study shows that Nitrogen ion induces more damage compared to Hydrogen ions and PC films get more modified than PET films.     

Swift heavy ion-induced effects in Ce-doped nickel ferrite nanoparticles

Swift heavy ions of various energies are being used for material modifications. The induced modifications depend on the kind of defects produced during interaction of ions with the target material. In the present work, irradiation of 200 MeV Ag beam-induced effects in NiFe₂O₄ and NiCe_0.04Fe_1.96O₄ nanoparticles are studied at two different fluences, 2×10¹² and 1×10¹³ ions/cm². Nanoparticles of nickel ferrite and Ce-doped nickel ferrite were prepared by chemical route. X-ray diffraction pattern shows peaks corresponding to pure spinel structure in both the systems, NiFe₂O₄ and NiCe_0.04Fe_1.96O₄. The pristine as well as irradiated nanoparticles were characterized by high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, electron paramagnetic resonance spectroscopy (EPR) and vibrating sample magnetometer (VSM). Raman spectra show bands corresponding to spinel structure. After irradiation, the position of the bands does not change significantly for both samples. The widths corresponding to the same band in both the systems show opposite trend with fluence. VSM results show that after irradiation, the magnetization decreases from 40 to 32 A m²/kg for NiFe₂O₄ and from 39 to 31 A m²/kg for NiCe_0.04Fe_1.96O₄. EPR results show that after doping with Ce as well as irradiation, the EPR line width is reduced, making samples important for applications.     

Swift heavy ion irradiation-induced modifications of tris-(8-hydroxyquinoline)aluminum thin films

Tris-(8-hydroxyquinoline)aluminum (Alq₃), one of the most widely used light emitting and electron transport materials in organic luminescent devices, has been synthesized. Alq₃ thin films have been deposited by a thermal evaporation process on glass substrates. The effect of swift heavy ion (SHI) irradiation using 40 MeV Li³⁺ on the Alq₃ thin films has been studied by UV-visible, infrared, photoluminescence (PL) and time-resolved photoluminescence (TRPL) spectroscopy. From TRPL studies, it is found that the PL of Alq₃ thin films arises from two species corresponding to its two geometrical isomers, namely facial and meridional having two different life times. It is also confirmed that the PL and lifetimes of excitons decrease with the increase of ion fluences of SHI of 40 MeV Li³⁺, indicating a transfer of exciton energy to unstable cationic Alq₃ species generated by SHI irradiation.     

Swift heavy ions-induced degradation on the electrical characteristics of silicon NPN power transistors

ABSTRACT

The pre- and post-irradiation effects on the DC electrical characteristics of 100?MeV Phosphorous (P⁷⁺) and 80?MeV Nitrogen (N⁶⁺) ion-irradiated NPN transistors were studied in the dose range from 600?krad (Si) to 100?Mrad (Si). The different electrical characteristics, such as Gummel characteristics, excess base current (ΔI_B?=?I_B-Post?–?I_B-Pre), current gain (h_FE), damage constant (K) and output characteristics, were measured in situ after ion irradiation. The considerable increase in the base current (I_B) at lower V_BE and slight decrease in the collector current (I_C) at higher V_BE were observed after ion irradiation. The C–V measurements revealed that the doping concentration (N_d) was found decreased, while the built-in potential (V_bi) increased after irradiation. The ion-irradiated results are compared with ⁶⁰Co gamma-irradiated results in the same dose range. The SRIM simulation was performed to understand the range of ions and energy loss in the transistor structure. The SRIM simulation showed that 100?MeV P⁷⁺ and 80?MeV N⁶⁺ ions can easily pass through the active region of transistors by creating ionization and displacement damages in the device structure. The irradiation results showed that ions induce more degradation in the electrical characteristics when compared to ⁶⁰Co gamma radiation at the same dose range.     

Synthesis, growth and characterization of 4-bromo-4'chloro benzylidene aniline--a third order non linear optical material

The organic nonlinear optical material of 4-bromo-4'chloro benzylidene aniline (BCBA) was synthesized and single crystal of BCBA was grown from acetone solution by solvent evaporation method at room temperature. Its three dimensional structure was elucidated from single crystal X-ray diffraction analysis at 173 K. Synthesized compound of BCBA was subjected to FTIR and (1)H and (13)C NMR spectral analyses. The range and percentage of optical transmission of BCBA was determined by UV-vis-NIR spectrum and its fluorescence spectrum was recorded using spectrofluorometer. The mechanical strength of the crystal was estimated using Vickers microhardness test on the (001) plane. Dielectric constant of the grown crystal was measured for various frequencies along (001) plane. The third order nonlinear optical properties of BCBA were investigated by Z-scan technique with He-Ne laser radiation of wavelength at 632.8 nm and the corresponding nonlinear refractive index, absorption coefficient and optical susceptibility were calculated.     

A broad pore size distribution mesoporous SnO2 as anode for lithium-ion batteries

Journal of Solid State Electrochemistry - We demonstrate here that mesoporous tin dioxide (abbreviated M-SnO2) with a broad pore size distribution can be a prospective anode in lithium-ion...     

Synthesis of first ever 4-quinolone-3-carboxylic acid-appended spirooxindole-pyrrolidine derivatives and their biological applications

A series of 4-quinolone-3-carboxylic acid-containing spirooxindole-pyrrolidine derivatives was synthesized via multicomponent 1,3-dipolar cycloaddition reactions of azomethine ylides with new (E)-4-oxo-6-(3-phenyl-acryloyl)-1,4-dihydroquinoline-3-carboxylic acids in good yields with high regioselectivity. The cycloadducts were characterized by analytical and spectral data including \(^{1}\hbox {H}\), \(^{13}\hbox {C}\), 2D NMR and mass spectroscopy. The structure of one of the compounds (8a) was investigated theoretically by computational techniques. DFT studies support the proposed mechanism for this cycloaddition reaction. Furthermore, antibacterial activities of the new compounds were evaluated against Gram-positive and Gram-negative bacterial strains. Compounds 8f, 8m and 8p showed potent inhibition activities against selected bacteria. The in vitro cytotoxicity of spirooxindole derivatives (8a–r) was evaluated against MCF-7 breast cancer cell line. Among the various compounds tested, compound 8f \((\hbox {IC}_{50} = 18.35~\upmu \hbox {M})\) showed significant cytotoxic activity compared to the standard drug doxorubicin \((\hbox {IC}_{50 }= 15.00~\upmu \hbox {M})\).     

Synthesis and Crystal Structure of a New Schiff Base 4-[(2-hydroxy-benzylidene)-amino]-<Emphasis Type="Italic">N</Emphasis>-(5-methyl-isoxazol-3-yl)-benzenesulfonamide

Abstract  The structure of the title compound (C₁₇H₁₅N₃O₄S)₂ the schiff base, bis(N-(5-methyl-3-isoxazolyl)-4-[(2-hydroxy benzylidene)-amino]) benzene sulfonamide was elucidated by H¹, C¹³ NMR, UV–VIS and IR spectroscopic techniques. The X-ray structure was determined in order to establish the conformation of the molecule. The compound crystallizes in the triclinic space group P-1, with a = 11.419(1), b = 11.426(0), c = 13.316(1) ?, α = 71.94(2), β = 89.79(1), γ = 89.14(2)° and Z = 4. Two benzene rings and azomethine group are practically coplanar, as a result of intramolecular hydrogen bonds involving the hydroxy O atom and azomethine N atom. The component species further interact via N–H···N and C–H···O hydrogen bonds and π–π stacking interactions. Index Abstract  The title compound (C₁₇H₁₅N₃O₄S)₂, Schiff base, bis(N-(5-methyl-3-isoxazolyl)-4-[(2-hydroxy benzylidene)-amino]) benzene sulfonamide was synthesized by the condensation of 4-amino-N-(5-methyl-3-isoxazolyl) benzene sulfonamide (SMZ) and 2-hydroxy benzaldehyde (SA). Its structure was confirmed by single crystal X-ray diffraction analysis. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.