Browsing by Subject "Oxidation reduction reaction"

Now showing 1 - 3 of 3

Open Access
One-step synthesis of size-tunable Ag nanoparticles incorporated in electrospun PVA/cyclodextrin nanofibers
(Pergamon Press, 2014) Celebioglu A.; Aytac Z.; Umu, O. C. O.; Dana, A.; Tekinay, T.; Uyar, Tamer
One-step synthesis of size-tunable silver nanoparticles (Ag-NP) incorporated into electrospun nanofibers was achieved. Initially, in situ reduction of silver salt (AgNO3) to Ag-NP was carried out in aqueous solution of polyvinyl alcohol (PVA). Here, PVA was used as reducing agent and stabilizing polymer as well as electrospinning polymeric matrix for the fabrication of PVA/Ag-NP nanofibers. Afterwards, hydroxypropyl-beta-cyclodextrin (HPβCD) was used as an additional reducing and stabilizing agent in order to control size and uniform dispersion of Ag-NP. The size of Ag-NP was ∼8 nm and some Ag-NP aggregates were observed for PVA/Ag-NP nanofibers, conversely, the size of Ag-NP decreased from ∼8 nm down to ∼2 nm within the fiber matrix without aggregation were attained for PVA/HPβCD nanofibers. The PVA/Ag-NP and PVA/HPβCD/Ag-NP nanofibers exhibited surface enhanced Raman scattering (SERS) effect. Moreover, antibacterial properties of PVA/Ag-NP and PVA/HPβCD/Ag-NP nanofibrous mats were tested against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria.
Open Access
Reductive deposition of Au3+(aq) on oxidized silicon surfaces
(N R C Research Press, 2000) Süzer, Ş.; Dag, Ö.
X-ray photoelectron spectroscopy (XPS) is used to determine the oxidation state of gold deposited from an aqueous solution of AuCl4- on to various oxidized surfaces of silicon. Although the observed Au4f signal decreased with the thickness of the oxide layer, the oxidation state of Au was determined as 0 for all the samples analyzed. From the angular dependence of the Si2p and Au4f signals it was determined that Au is deposited on top of the oxidized surfaces of metallic silicon. It is postulated that from an aqueous solution of AuCl4-, gold would deposit in its zerovalent form on to any surface due to its large and positive electrochemical reduction potential (ε° (red) (Au3+/Au) = +1.50 V) and the substrate plays a role only in providing active deposition sites. To further support the proposal, it is shown that the same process takes place even in inert and hydrophobic polypropylene substrates. Similarly, it is also shown that more gold deposits if the surface of the polypropylene is made less hydrophobic (but probably more active) via the industrially used corona discharge treatment.
Open Access
Theoretical analysis of substituent effects on building blocks of conducting polymers: 3, 4'-substituted bithiophenes
(American Chemical Society, 1999) Salzner, U.; Kızıltepe, T.
Substituents are widely used to modify the properties of conducting polymers. To study substituent effects on energy levels and energy gaps systematically, CH3-, OH-, NH2-, CN-, and CCH-substituted bithiophenes were examined with density functional theory and NBO analysis. Total charges and :r-electron densities were analyzed separately to examine π- and σ-effects. Second-order perturbation theory was used to quantify conjugation in terms of orbital interactions. NBO orbital energies were employed to investigate the effect of alternating donor-acceptor substitution. Substituents in 3- and 4- positions shift HOMO and LUMO levels in parallel and hardly influence HOMO- LUMO gaps. For level shifting the π-donating and π-accepting abilities are most important; electronegativity mainly influences the σ-orbitals and is less crucial in determining energy gaps. Alternating donor-acceptor substitution leads to HOMO and LUMO energies that are average between those of the parent systems and has little effect on energy gaps.