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Structure and biological application based analysis has been carried out for Schiff's base ligand containing nitrogen and sulphur donor atoms and also for a series of its coordination compounds. Ligand benzil-bis(5-amino-1,3,4-thiadiazole-2-thiol) (L) has been prepared and structural features of ligand investigated by elemental analyses, IR, 1H-NMR, mass spectra and molecular modeling studies. The chemical reaction of the prepared ligand with metal ions afforded mononuclear coordination compounds of Mn(II) and Co(II) metal ions. The characterization of the coordination compounds is being based on the techniques i.e. elemental analysis, infra-red, UV-visible as well as melting point, molar conductivity and magnetic moment measurement. A computational study has been done to understand the miscellaneous coordination modes of ligand to metal ions. Characterization result shows that coordination compounds exhibit a six coordinated geometrical arrangement i.e. octahedral geometry. The biological inhibition zone (antifungal and antibacterial activities) of synthesized compounds, i.e. ligand and its coordination compounds, has been monitored using well diffusion technique. [ABSTRACT FROM AUTHOR]

Transition metal complexes of Mn(II) and Ni(II) have been synthesized with novel bioactive Schiff's base ligand. Schiff's base ligand i.e. benzoylacetone-bis(2-amino-4-methylbenzothioazole) has been synthesized via condensation reaction between 2-amino-4-methylbenzothioazole and benzoylacetone in 2:1 ratio, respectively. Synthesized ligand has been characterized using elemental analysis, infra-red, 1H-NMR and mass spectroscopy techniques. Characterization of complexes was based on magnetic moment, molar conductance, elemental analysis, electronic spectra, infra-red and EPR spectroscopic techniques. Molar conductance data suggest that metal complexes are non-electrolytic in nature. Therefore, these complexes are formulated as [M(L)X2], where M = Mn(II), Ni(II), L = Schiff's base ligand, X = Cl−, CH3COO−, NO3−. Data of characterization study suggest octahedral geometry for Mn(II) and Ni(II) complexes. Geometry of metal complexes was also optimized with the help of computational study i.e. molecular modelling. Computational study also suggests octahedral geometry for complexes. Free ligand as well as its all metal complexes have been screened against the growth of pathogenic bacteria ( E.coli, S.aureus) and fungi ( C.albicans, C.krusei, C.parapsilosis, C.tropicalis) to assess their inhibition potential. The inhibition data revealed that metal complexes exhibit higher inhibition potential against the growth of bacteria and fungi microorganisms than free ligand. [ABSTRACT FROM AUTHOR]

High surface area of CNTs makes them an extremely sensitive detection element for a wide variety of analytes present in minute quantities of ppb and ppm levels. CNTs does not inherit selectivity for a particular gas/analyte, it can be introduced in CNT based gas sensor by means of functionalization, along with improvement in gas sensor's response. Effects of Carboxylated group and gold nano-particles were studied on the response of CNT sensors towards toxic gases such as NO2and NH3. Gold nanoparticles have found to enhance the response for NO2and NH3, while oxygenated functional have brought selectivity towards NH3. [ABSTRACT FROM AUTHOR]

Novel Schiff’s base ligand, benzil bis(5-amino-1,3,4-thiadiazole-2-thiol) was synthesized by the condensation of benzil and 5-amino-1,3,4-thiadiazole-2-thiol in 1:2 ratio. The structure of ligand was determined on the basis of elemental analyses, IR, 1 H NMR, mass, and molecular modeling studies. Synthesized ligand behaved as tetradentate and coordinated to metal ion through sulfur atoms of thiol ring and nitrogen atoms of imine group. Ni(II), and Cu(II) complexes were synthesized with this nitrogen–sulfur donor (N 2 S 2 ) ligand. Metal complexes were characterized by elemental analyses, molar conductance, magnetic susceptibility measurements, IR, electronic spectra, EPR, thermal, and molecular modeling studies. All the complexes showed molar conductance corresponding to non-electrolytic nature, expect [Ni(L)](NO 3 ) 2 complex, which was 1:2 electrolyte in nature. [Cu(L)(SO 4 )] complex may possessed square pyramidal geometry, [Ni(L)](NO 3 ) 2 complex tetrahedral and rest of the complexes six coordinated octahedral/tetragonal geometry. Newly synthesized ligand and its metal complexes were examined against the opportunistic pathogens. Results suggested that metal complexes were more biological sensitive than free ligand. [ABSTRACT FROM AUTHOR]

Complexes of nickel(II), and copper(II) were synthesized with pantadentate ligand i.e. 3,3′-thiodipropionicacid-bis(5-amino-1,3,4-thiadiazole-2-thiol) (L). The ligand was synthesized by the condensation of thiodipropionic acid and 5-amino-1,3,4-thiadiazole-2-thiol in 1:2 ratio, respectively. Synthesized ligand was characterized by elemental analysis, mass, 1 H NMR, IR, and molecular modeling. All the complexes were characterized by elemental analysis, molar conductance, magnetic moment, IR, electronic spectra, ESR, and molecular modeling. The newly synthesized complexes possessed general composition [M(L)X 2 ] where M = Ni(II), Cu(II), L = pantadentate ligand and X = Cl − , CH 3 COO − . The IR spectral data indicated that the ligand behaved as a pantadentate ligand and coordinated to the metal ion through N 2 S 3 donor atoms. The molar conductance value of Ni(II), and Cu(II) complexes in DMSO corresponded to their electrolytic behavior. On the basis of spectral study, octahedral and tetragonal geometry was assigned for Ni(II) and Cu(II) complexes, respectively. In vitro fungicidal study of ligand and its complexes was investigated against fungi Candida albicans , Candida parapsilosis , Candidia krusei , and Candida tropicalis by means of well diffusion method. [ABSTRACT FROM AUTHOR]

Carbon Nanotubes (CNTs) are promising candidates for cold cathodes because of their high aspect ratio and robustness. However, the major hindrance in cold cathode based applications is the screening effect, which reduces the effective field at the tip and thereby the current density. The emission current can be improved by minimising the screening effect. The adverse effect of screening can be addressed by either controlling the growth density or by optimising the patterns of CNT cathodes. Here, novel patterns have been used to increase edge length per unit area in planar vertically aligned CNT bundles. Our motive was to increase the number of effective emitters, since the CNT at the edges are less screened by the proximal CNTs. By varying geometry and spacing of solid CNT dot patterns and by introducing the square ring structures; we could successfully enhance the effective emitters at the edges. It has been observed that an enhancement of edge length from 0.032 per micron to 0.2 per micron increases the current density from 0.71mA/cm2to 16.2 mA/cm2at a field of 4.5 V/μm. CNTs in dotted structure with high value of edge length per unit area emit very high current density as compared to other dotted structures with low value of edge length per unit area Simulation studies confirms our argument that CNTs at the corners are the least screened and have the maximum local electric field. [ABSTRACT FROM AUTHOR]

Density functional calculations using B3LYP/6-311G method have been carried out for small to medium-sized lithium clusters (Li N, N = 2-30). The optimized geometries of neutral and singly charged clusters, their binding energies, ionization potential, electron affinity, chemical potential, softness, hardness, highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO-LUMO) gap, and static dipole polarizability have been investigated systematically. In addition, we study the distribution of partial charges in detail using natural population analysis (NPA) in small-sized clusters (Li N, N = 2-10), both neutral and cationic, and demonstrate the correlation between symmetry and charge. Uniform distribution of charges in cationic clusters confirms them to be energetically more favorable than the neutral counterparts. Whenever possible, results have been compared with available data. An excellent agreement in every case supports new results as reliable predictions. A careful study of optimized geometries shows that Li9 is derivable from bulk Li structure, i.e., body centered cubic cell, and higher clusters have optimized shapes derived from this. Further, the turnover form two to three dimensional structure occurs at cluster size N = 6. The quantity α1/3 (α = polarizability) per atom is found to be broadly proportional to softness (per atom) as well as inverse ionization potential (per atom). The present work forms a sound basis for further study of large-sized clusters as well as other atomic clusters. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012 [ABSTRACT FROM AUTHOR]

The structure and electronic and optical properties of hydrogenated lithium clusters LinHm (n = 1-30, m ≤ n) have been investigated by density functional theory (DFT). The structural optimizations are performed with the Becke 3 Lee--Yang--Parr (B3LYP) exchange-correlation functional with 6-311G++(d, p) basis set. The reliability of the method employed has been established by excellent agreement with computational and experimental data, wherever available. The turn over from two- to three-dimensional geometry in LinHm clusters is found to occur at size n = 4 and m = 3. Interestingly, a rock-salt-like face-centered cubic structure is seen in Li13H14. The sequential addition of hydrogen to small-sized Li clusters predicted regions of regular lattice in saturated hydrogenated clusters. This led us to focus on large-sized saturated clusters rather than to increase the number of hydrogen atoms monotonically. The lattice constants of Li9H9, Li18H20, Li20H20, and Li30H30 calculated at their optimized geometry are found to gradually approach the corresponding bulk values of 4.083. The sequential addition of hydrogen stabilizes the cluster, irrespective of the cluster size. A significant increase in stability is seen in the case of completely hydrogenated clusters, i.e., when the number of hydrogen atoms equals Li atoms. The enhanced stability has been interpreted in terms of various electronic and optical properties like adiabatic and vertical ionization potential, HOMO--LUMO gap, and polarizability. [ABSTRACT FROM AUTHOR]

The structure, stability, and effect of doping Aun (n = 1-16) clusters with Si is investigated by DFT calculations. [ABSTRACT FROM AUTHOR]

Abstract: The influence of thick aluminium (Al) ~300nm interlayer on the growth and field emission (FE) properties of carbon nanotubes (CNTs) deposited on silicon coated with a 2nm iron (Fe) catalyst was studied. The CNTs were grown over silicon substrate with and without Al-interlayer via CVD. It was observed that the presence of such high thickness of the interlayer on the substrate resulted in higher growth rate, narrower diameters and longer height of CNTs compared to CNTs grown on silicon (Si) substrate coated only with Fe. Al-interlayer hinders the diffusion of Fe into silicon, hence promotes the growth rate. Literature reports that a thick layer of Al causes Fe to diffuse into it, negatively affecting the growth. However, in our experiments, no evidence of depletion of Fe from the substrate was observed. Unique patterns of grown CNTs could be attributed to anisotropic Al-melting over the silicon substrate resulting in Al/Fe rich and deficient regions. The drastic improvement of current density from 0.41mA/cm2 to 20mA/cm2 at a field of 3.5V/μm was found with Al-interlayer CNT grown samples. These mechanisms of improvements in field emission characteristics have been discussed in detail. [Copyright &y& Elsevier]

For improved field emission behavior, we demonstrate the PECVD technique to grow highly ordered, selectively grown, vertically aligned carbon nanotubes (CNTs) with optimum density. We report the optimization of vertically aligned CNTs by optimizing catalyst thickness, dot size of catalyst and the spacing between them. We made an attempt to optimize the catalyst thickness to understand the effect over density, diameter and height of CNTs. SEM images reveal that the catalyst thickness as well as the dot size and the spacing is helpful in optimizing the vertical alignment of CNTs. The vertically aligned CNTs provide a large number of tips as compared to horizontally aligned CNTs over an area. Also, the high value of the enhancement factor required to achieve a better FE behavior is also plausible with vertical CNTs. The field emission results confirm that the vertically aligned CNTs bring a large current density at relatively low threshold field. We were able to achieve a current density of 100 mA/cm2 at a field of 6 V/µm. Density and therefore screening effect also becomes important factors that hinder the performance of CNT-based emitters. However, in our typical samples we observed less discrepancy in the density, and the density so calculated was in the order of 109/cm2. [ABSTRACT FROM AUTHOR]

Comparison of pristine Single Walled Carbon nanotube (SWCNT) and SWCNT-Metal Phthalocyaines (MPcs) composites towards ammonia gas sensing has been conducted. Interaction mechanism has been explained on the basis of charge transfer between lone pairs of ammonia and majority carriers of materials. Availability of vacant orbitals (MgPc (s orbital), AlPcOH (p orbital) and TiOPc (d orbital)) for lone pairs of ammonia and their dependency on orbital state of MPcs has been discussed and analyzed. [Display omitted] • Enhancement in response of Single Walled Carbon Nanotube (SWCNT) towards NH3 with Metal Pthalocyanines (MPcs) is studied. • Effect of orbital states of MPcs on sensing with NH 3 is analyzed. • MgPc, AlPcOH and TiOPc were added in SWCNT to study SWCT-MPcs composites. • TiOPc was found to increase the response percentages and AlPcOH was found to decrease recovery times of SWCNT. • Relative humidity and repeatability studies of SWCNT-MPcs were also conducted. The present study deals with analysing the effect of central metal atom on interaction behaviour of a composite constituted of two materials, Single walled carbon nanotubes (SWCNT) and metal phthalocyanines (MPcs) (SWCNT-MPc) with ammonia gas. For this purpose, three metal phthalocyanines namely; Magnesium phthalocyanine (MgPc), Aluminum phthalocyanine hydroxide (AlPcOH) and Titanyl phthalocyanine (TiOPc) were taken and their variation in resistances with exposure of ammonia gas is taken as detection parameter. The central metal ions of MPcs were chosen so that valence electrons are in s, p and d orbitals respectively. The surface-interface interaction of pristine SWCNT towards ammonia gas was found to increase with better repeatability and stability after addition of MPcs. SWCNT-TiOPc composite exhibited maximum interaction with ammonia vapors (≈ 3 times pristine SWCNT) followed by SWCNT- MgPc (≈ 2 times pristine SWCNT), while AlPcOH had shown faster desorption (≈ 0.5 times faster) as compared to pristine SWCNT during recovery stage. The concept of charge transfer mechanism between SWCNT-MPcs and ammonia gas and varied orbital state accommodating ammonia lone pairs were used to explain interaction studies. Consistencies observed in physics and chemistry analysis highlighted the significance of both these fields to have complete understanding of the interaction phenomena between SWCNT-MPcs and ammonia gas. [ABSTRACT FROM AUTHOR]

Ammonium nitrate, NH 4 NO 3 (AN) decomposition studies are analyzed using Single Walled carbon nanotube (SWCNT) chemresistor. The vaporized AN vapors are passed towards decomposer through carrier gas. Decomposer temperatures are fixed at 70 °C, 170 °C and 230 °C for fixed flow rates of carrier gases 10 sccm, 25 sccm and 50 sccm. For these fixed parameters, bubbler (vaporizer) temperatures are varied (70 °C–120 °C) and passed through decomposer. The decomposed vapors are sensed by SWCNT chemresistor and its varying trends of resistances are utilized for analyzing thermal decomposition phenomena. [Display omitted] • Thermal decomposition studies of ammonium nitrate (AN) using carbon nanotube sensor are carried. • Effect of flow rate of carrier gas, vaporization and decomposition temperature of AN are analyzed. • The various reaction mechanisms undertaking are observed experimentally using chemresistor. • Sensing results are confirmed using raman spectroscopy and Field emission scanning electron microscopy. • Effect of relative humidity and dry air on the sensor in studying AN decomposition mechanism is also discussed. The role of flow rate of carrier gas and decomposition temperature in sensing mechanism of pristine single walled carbon nanotubes (SWCNT) with ammonium nitrate vapor has been studied. For this purpose, sensing studies were carried out at 10 sccm, 25 sccm and 50 sccm flow rates. Three decomposer temperatures (70 °C, 170 °C and 230 °C) were taken while varying the bubbler temperature from 70 °C–120 °C. It was found that both flow rates and decomposition temperature play a vital role in affecting the interaction mechanism between SWCNT and ammonium nitrate vapors. Low decomposition temperature favors the ammonia sensing and higher decomposition temperatures (170 °C and 230 °C) lead to dominance of NO x vapors on account of strong decomposition of ammonium nitrate. These trends were observed irrespective of vapor pressure and concentration of ammonium nitrate vapors. This highlights the significant role of flow rate of carrier gas and decomposition temperature in determining the sensing behavior of ammonium nitrate. [ABSTRACT FROM AUTHOR]

The PVC based-ion selective electrode viz., bis nitrato[4-hydroxyacetophenone semicarbazone] nickel(II) as an ionophore was prepared for the determination of thiocyanate ion. The ionophore was characterized by FT-IR, UV–vis, XRD, magnetic moment and elemental analysis (CHN). On the basis of spectral studies an octahedral geometry has been assigned. The best performance was obtained with a membrane composition of 31% PVC, 63% 2-nitrophenyl octylether, 4.0% ionophore and 2.0% trioctylmethyl ammonium chloride. The electrode exhibited an excellent Nernstian response to SCN − ion ranging from 1.0 × 10 − 7 to 1.0 × 10 − 1 M with a detection limit of 8.6 × 10 − 8 M and a slope of − 59.4 ± 0.2 mV/decade over a wide pH range (1.8–10.7) with a fast response time (6 s) at 25 °C. The proposed electrode showed high selectivity for thiocyanate ion over a number of common inorganic and organic anions. It was successfully applied to direct determination of thiocyanate in biological (urine and saliva) samples in order to distinguish between smokers and non-smokers, environmental samples and as an indicator electrode for titration of thiocyanate ions with AgNO 3 solution. [ABSTRACT FROM AUTHOR]