1,172 research outputs found
Antibacterial activity studies of Co(II), Ni(II), Cu(II) and Zn(II) complexes with Mannich base ligand
ABSTRACT. A Mannich base ligand (L) was prepared by reacting 2-mercaptobenzimidazole, diphenylamine and benzaldehyde. This ligand (L) was further used for the preparation of four metal complexes with Co(II), Ni(II), Cu(II) and Zn(II) ions. The reactions were monitored by TLC. The synthesized compounds were structurally characterized using FTIR spectroscopy, UV-Visible spectroscopy, 1H- and 13C-NMR spectroscopy, ICP-OES/atomic absorption spectroscopy. It has been observed that the ligand (L) behaved in a monoanionic bidentate mode and the geometry of resulting complexes was tetrahedral. Conductivity analysis revealed their non-electrolytic nature. Antibacterial activity of the synthesized compounds was assessed through an agar well diffusion method against four strains of Gram-negative bacteria. L-Zn(II) complex showed best activity at all four concentrations against the four strains of Gram-negative bacteria. KEY WORDS: Metal complexes, Mannich bases, 2-Mercaptobenzimidazole, Antibacterial activity Bull. Chem. Soc. Ethiop. 2019, 33(3), 485-492.DOI: https://dx.doi.org/10.4314/bcse.v33i3.
Synthesis, structural and photo-physical studies of transition metal complexes with Mannich bases derived from 2-mercaptobenzimidazole
Two Mannich base ligands, [1-(di-n-butylamine-N-methyl)mercapto-1H-benz-imidazole] (L1) and [1-(diphenylamine-N-methyl)mercapto-1H-benzimidazole] (L2)have been synthesized and further reacted with Co(II), Ni(II), Cu(II) and Zn(II) ionsto afford their respective complexes. The progress of the reaction was monitored by thin layer chromatography. The structural elucidation of Mannich base ligands and their metal complexes was done by Fourier Transform Infrared (FTIR), UV-Visible, Nuclear Magnetic Resonance spectroscopy (1H NMR & 13C NMR) and Atomic absorption spectroscopy (AAS) / Inductively coupled plasma emission spectroscopy (ICPES). FTIR and NMR studies supported the monoanionic bidentate coordination mode of L1 and L2 while tetrahedral geometries of metal complexes were proposed on the basis of AAS/ICP, magnetic moment and electronic spectroscopic data. The synthesized compounds were also investigated for their luminescent behavior which exhibited broad emission bands indicating charge transfer nature of the involved transitions. KEY WORDS: Metal complexes, Mannich bases, 2-Mercaptobenzimidazole, Luminescence Bull. Chem. Soc. Ethiop. 2018, 32(3), 481-490.DOI: https://dx.doi.org/10.4314/bcse.v32i3.
Double Dielectric Barrier (DBD) plasma-assisted deposition of chemical stabilized nanoparticles on polyamide 6,6 and polyester fabrics
The development of new multifunctional textiles containing nanoparticles (NPs) has had a special interest in several applications for pharmaceutical, medical, engineering, agricultural, and food products.[1-2] Cu, Zn and especially Ag NPs exhibit strong antibacterial activities on a broad spectrum of bacteria.[3-5] Most of the antimicrobial textiles coated with NPs are not able to perform a controlled release of the antibiotic species. Thus, the immobilization of NPs in the substrate or its inclusion in polymeric matrix is essential to control the NPs antibiotic effect with time. Dielectric barrier discharge (DBD) plasma technology is one of the most effective non-thermal plasma sources.[6] However, an even dispersion and coating of NPs onto fabrics remain a challenge due to the high degree of aggregation of metal NPs.[7] Some capping agents were described to increase the suspension stability such as citrate and SDS.[8] In this work, Ag, Zn, and Cu NPs deposition on DBD plasma pre-treated polyamide 6,6 (PA66) and polyester (PES) were tested for the production of durable antibacterial textiles. SEM-EDX analysis and the effect of some NPs stabilizers (e.g. sodium citrate, sodium alginate and Polyvinyl alcohol (PVA)) was analysed by dynamic light scattering (DLS) in term of size, polydispersity index and zeta potential. XPS analyses prove the DBD efficacy in providing oxygen species onto the fabric’s surfaces. The SEM analyses prove the deposition of the Ag and Cu NPs onto the PES and PA66 fabrics. No zinc was detected. However, antimicrobial tests in PES shows that all the NPs have an antimicrobial effect but Cu and Zn show activity only in S. aureus and Ag only in E.coli. Cu shows a reasonable dispersion onto the fibres but PVP coated AgNPs display a high level of aggregation even after 1 hour of ultrasonic treatment. To solve instability and aggregation problems, NPs suspensions were prepared in different concentrations (1, 2.5 and 5 wt%) of citrate, alginate and PVA using water and ethanol as control by ultrasonic bath. In table 1 are resumed the best results obtained for each NP compared to water as control. Ethanol and PVA were disregarded due to the highest instability and lowest ζ potential, respectively. XPS, SEM and antimicrobial data shows lack in coating uniformity. It is clear that doesn't exist a univocal dispersant and concentration for all NPs. Despite the improving in ζ potentials and stability of the colloids, the obtained sizes still show a high degree of aggregation.info:eu-repo/semantics/publishedVersio
CONSIDERATIONS REGARDING PLANTS PROTECTION BY MEANS OF BIOFERTILIZERS / BIOINSECTICIDES
The paper presents some aspects regarding the utilization of certain ecological substances as an alternative to environmental-friendly insecticides, in order to obtain some ecological products within the context of the increasesd concern for ecological products
Charge separation relative to the reaction plane in Pb-Pb collisions at TeV
Measurements of charge dependent azimuthal correlations with the ALICE
detector at the LHC are reported for Pb-Pb collisions at TeV. Two- and three-particle charge-dependent azimuthal correlations in
the pseudo-rapidity range are presented as a function of the
collision centrality, particle separation in pseudo-rapidity, and transverse
momentum. A clear signal compatible with a charge-dependent separation relative
to the reaction plane is observed, which shows little or no collision energy
dependence when compared to measurements at RHIC energies. This provides a new
insight for understanding the nature of the charge dependent azimuthal
correlations observed at RHIC and LHC energies.Comment: 12 pages, 3 captioned figures, authors from page 2 to 6, published
version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/286
Multiplicity dependence of jet-like two-particle correlations in p-Pb collisions at = 5.02 TeV
Two-particle angular correlations between unidentified charged trigger and
associated particles are measured by the ALICE detector in p-Pb collisions at a
nucleon-nucleon centre-of-mass energy of 5.02 TeV. The transverse-momentum
range 0.7 5.0 GeV/ is examined,
to include correlations induced by jets originating from low
momen\-tum-transfer scatterings (minijets). The correlations expressed as
associated yield per trigger particle are obtained in the pseudorapidity range
. The near-side long-range pseudorapidity correlations observed in
high-multiplicity p-Pb collisions are subtracted from both near-side
short-range and away-side correlations in order to remove the non-jet-like
components. The yields in the jet-like peaks are found to be invariant with
event multiplicity with the exception of events with low multiplicity. This
invariance is consistent with the particles being produced via the incoherent
fragmentation of multiple parton--parton scatterings, while the yield related
to the previously observed ridge structures is not jet-related. The number of
uncorrelated sources of particle production is found to increase linearly with
multiplicity, suggesting no saturation of the number of multi-parton
interactions even in the highest multiplicity p-Pb collisions. Further, the
number scales in the intermediate multiplicity region with the number of binary
nucleon-nucleon collisions estimated with a Glauber Monte-Carlo simulation.Comment: 23 pages, 6 captioned figures, 1 table, authors from page 17,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/161
Multi-particle azimuthal correlations in p-Pb and Pb-Pb collisions at the CERN Large Hadron Collider
Measurements of multi-particle azimuthal correlations (cumulants) for charged
particles in p-Pb and Pb-Pb collisions are presented. They help address the
question of whether there is evidence for global, flow-like, azimuthal
correlations in the p-Pb system. Comparisons are made to measurements from the
larger Pb-Pb system, where such evidence is established. In particular, the
second harmonic two-particle cumulants are found to decrease with multiplicity,
characteristic of a dominance of few-particle correlations in p-Pb collisions.
However, when a gap is placed to suppress such correlations,
the two-particle cumulants begin to rise at high-multiplicity, indicating the
presence of global azimuthal correlations. The Pb-Pb values are higher than the
p-Pb values at similar multiplicities. In both systems, the second harmonic
four-particle cumulants exhibit a transition from positive to negative values
when the multiplicity increases. The negative values allow for a measurement of
to be made, which is found to be higher in Pb-Pb collisions at
similar multiplicities. The second harmonic six-particle cumulants are also
found to be higher in Pb-Pb collisions. In Pb-Pb collisions, we generally find
which is indicative of a Bessel-Gaussian
function for the distribution. For very high-multiplicity Pb-Pb
collisions, we observe that the four- and six-particle cumulants become
consistent with 0. Finally, third harmonic two-particle cumulants in p-Pb and
Pb-Pb are measured. These are found to be similar for overlapping
multiplicities, when a gap is placed.Comment: 25 pages, 11 captioned figures, 3 tables, authors from page 20,
published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/87
A note on comonotonicity and positivity of the control components of decoupled quadratic FBSDE
In this small note we are concerned with the solution of Forward-Backward
Stochastic Differential Equations (FBSDE) with drivers that grow quadratically
in the control component (quadratic growth FBSDE or qgFBSDE). The main theorem
is a comparison result that allows comparing componentwise the signs of the
control processes of two different qgFBSDE. As a byproduct one obtains
conditions that allow establishing the positivity of the control process.Comment: accepted for publicatio
Transverse sphericity of primary charged particles in minimum bias proton-proton collisions at , 2.76 and 7 TeV
Measurements of the sphericity of primary charged particles in minimum bias
proton--proton collisions at , 2.76 and 7 TeV with the ALICE
detector at the LHC are presented. The observable is linearized to be collinear
safe and is measured in the plane perpendicular to the beam direction using
primary charged tracks with GeV/c in . The
mean sphericity as a function of the charged particle multiplicity at
mid-rapidity () is reported for events with different
scales ("soft" and "hard") defined by the transverse momentum of the leading
particle. In addition, the mean charged particle transverse momentum versus
multiplicity is presented for the different event classes, and the sphericity
distributions in bins of multiplicity are presented. The data are compared with
calculations of standard Monte Carlo event generators. The transverse
sphericity is found to grow with multiplicity at all collision energies, with a
steeper rise at low , whereas the event generators show the
opposite tendency. The combined study of the sphericity and the mean with multiplicity indicates that most of the tested event generators
produce events with higher multiplicity by generating more back-to-back jets
resulting in decreased sphericity (and isotropy). The PYTHIA6 generator with
tune PERUGIA-2011 exhibits a noticeable improvement in describing the data,
compared to the other tested generators.Comment: 21 pages, 9 captioned figures, 3 tables, authors from page 16,
published version, figures from
http://aliceinfo.cern.ch/ArtSubmission/node/308
Centrality dependence of charged particle production at large transverse momentum in Pb-Pb collisions at TeV
The inclusive transverse momentum () distributions of primary
charged particles are measured in the pseudo-rapidity range as a
function of event centrality in Pb-Pb collisions at
TeV with ALICE at the LHC. The data are presented in the range
GeV/ for nine centrality intervals from 70-80% to 0-5%.
The Pb-Pb spectra are presented in terms of the nuclear modification factor
using a pp reference spectrum measured at the same collision
energy. We observe that the suppression of high- particles strongly
depends on event centrality. In central collisions (0-5%) the yield is most
suppressed with at -7 GeV/. Above
GeV/, there is a significant rise in the nuclear modification
factor, which reaches for GeV/. In
peripheral collisions (70-80%), the suppression is weaker with almost independently of . The measured nuclear
modification factors are compared to other measurements and model calculations.Comment: 17 pages, 4 captioned figures, 2 tables, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/284
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