Browsing by Subject "Physical chemistry"

Now showing 1 - 5 of 5

Open Access
A comparative study of O2 adsorbed carbon nanotubes
(2003) Dag, S.; Gülseren, O.; Çıracı, Salim
First-principles, density functional calculations show that O2 adsorbed single-wall carbon nanotubes (SWNT) show dramatic differences depending on the type of the tube. Upon O2 physisorption, the zig-zag SWNT remains semiconducting, while the metallicity of the armchair is lifted for the spin-down bands. The spin-up bands continue to cross at the Fermi level, and make the system metallic only for one type of spin. The singlet bound state of O2 occurs at the bridge site of the (6,6) SWNT at small distance from the surface of the tube. However, for the hollow site, the molecule dissociates when it comes close to the surface. © 2003 Elsevier B.V. All rights reserved.
Open Access
Drug delivery system based on cyclodextrin-naproxen inclusion complex incorporated in electrospun polycaprolactone nanofibers
(Elsevier, 2014) Canbolat, M. F.; Celebioglu A.; Uyar, Tamer
In this study, we select naproxen (NAP) as a reference drug and electrospun poly (e-caprolactone) (PCL) nanofibers as a fibrous matrix for our drug-delivery system. NAP was complexed with beta-cyclodextrin (βCD) to form inclusion complex (NAP-βCD-IC) and then NAP-βCD-IC was incorporated into PCL nanofibers via electrospinning. The incorporation of NAP without CD-IC into electrospun PCL was also carried out for a comparative study. Our aim is to analyze the release profiles of NAP from PCL/NAP and PCL/NAP-βCD-IC nanofibers and we investigate the effect of CD-IC on the release behavior of NAP from the nanofibrous PCL matrix. The characterization of NAP-βCD-IC and the presence of CD-IC in PCL/NAP-βCD-IC nanofibers were studied by FTIR, XRD, TGA, NMR and SEM. The SEM imaging of the electrospun PCL/NAP and PCL/NAP-βCD-IC nanofibers reveal that the average fiber diameter of these nanofibers is around 300. nm, in addition, the aggregates of CD-IC in PCL/NAP-βCD-IC nanofibers is observed. The release study of NAP in buffer solution elucidate that the PCL/NAP-βCD-IC nanofibers have higher release amount of NAP than the PCL/NAP nanofibers due to the solubility enhancement of NAP by CD-IC.
Open Access
Local delivery of doxorubicin through supramolecular peptide amphiphile nanofiber gels
(Royal Society of Chemistry, 2017) Cinar, G.; Ozdemir, A.; Hamsici, S.; Gunay, G.; Dana, A.; Tekinay, A. B.; Güler, Mustafa O.
Peptide amphiphiles (PAs) self-assemble into supramolecular nanofiber gels that provide a suitable environment for encapsulation of both hydrophobic and hydrophilic molecules. The PA gels have significant advantages for controlled delivery applications due to their high capacity to retain water, biocompatibility, and biodegradability. In this study, we demonstrate injectable supramolecular PA nanofiber gels for drug delivery applications. Doxorubicin (Dox), as a widely used chemotherapeutic drug for breast cancer treatment, was encapsulated within the PA gels prepared at different concentrations. Physical and chemical properties of the gels were characterized, and slow release of the Dox molecules through the supramolecular PA nanofiber gels was studied. In addition, the diffusion constants of the drug molecules within the PA nanofiber gels were estimated using fluorescence recovery after the photobleaching (FRAP) method. The PA nanofiber gels did not show any cytotoxicity and the encapsulation strategy enhanced the activity of drug molecules on cellular viability through prolonged release compared to direct administration under in vitro conditions. Moreover, the local in vivo injection of the Dox encapsulated PA nanofiber gels (Dox/PA) to the tumor site demonstrated the lowest tumor growth rate compared to the direct Dox injection and increased the apoptotic cells within the tumor tissue for local drug release through the PA nanofiber gels under in vivo conditions.
Open Access
Spectroscopic characterization of vanadium(v) oxo species deposited on zirconia
(Royal Society of Chemistry, 2000) Kantcheva, M.
A method for deposition of vanadium(v) oxo species from acidic solutions of ammonium metavanadate on zirconia is described. The samples are synthesized by suspension of the support (powder) in solutions containing three different vanadium(V) precursor ions: the dioxovanadium(V) ion, VO2+, the yellow diperoxo anion [VO(O-O)2]- and the red monoperoxo cation [VO(O- O)]+. Application of vanadium(V) peroxo complexes increases significantly the uptake of vanadium by zirconia. The state and localization of the VO(x) species on the surface of zirconia were studied by FTIR, UV/VIS and XP spectroscopies. The materials prepared from VO2+ ions contain isolated VO4 groups and domains of orthovanadate species, (VO4)(n). The FTIR spectra of adsorbed CO revealed that the number of exposed Zr4+ ions decreased markedly when vanadium(v) peroxo ions were used as precursors. The predominant surface structure in this case was identified as pyrovanadates, V2O7. On all of the samples studied no separate phase of V2O5 was detected.
Open Access
Weakly hydrated anions bind to polymers but not monomers in aqueous solutions
(Nature Publishing Group, 2021-11-01) Rogers, B. A.; Okur, Halil İbrahim; Yan, C.; Yang, T.; Heyda, J.; Cremer, P. S.
Weakly hydrated anions help to solubilize hydrophobic macromolecules in aqueous solutions, but small molecules comprising the same chemical constituents precipitate out when exposed to these ions. Here, this apparent contradiction is resolved by systematically investigating the interactions of NaSCN with polyethylene oxide oligomers and polymers of varying molecular weight. A combination of spectroscopic and computational results reveals that SCN− accumulates near the surface of polymers, but is excluded from monomers. This occurs because SCN− preferentially binds to the centre of macromolecular chains, where the local water hydrogen-bonding network is disrupted. These findings suggest a link between ion-specific effects and theories addressing how hydrophobic hydration is modulated by the size and shape of a hydrophobic entity.