Cubic versus spherical magnetic nanoparticles: the role of surface anisotropy

The magnetic properties of maghemite (gamma-Fe2O3) cubic and spherical nanoparticles of similar sizes have been experimentally and theoretically studied. The blocking temperature, T(B), of the nanoparticles depends on their shape, with the spherical ones exhibiting larger T(B). Other low temperature properties such as saturation magnetization, coercivity, loop shift or spin canting are rather similar. The experimental effective anisotropy and the Monte Carlo simulations indicate that the different random surface anisotropy of the two morphologies combined with the low magnetocrystalline anisotropy of gamma-Fe2O3 is the origin of these effects.     

Recent advances in capillary electrophoresis for biomarker discovery

The use of non-invasive methods for detecting biomarkers opens a new era in patient care, since clinical investigators have long been searching for accurate and reproducible measurements of putative biomarkers. There are many factors which make this research challenging, beginning with lack of standardization of sample collection and continuing through the entire analytical procedure. Among the variety of methods so far used for biomarker screening, capillary electrophoresis represents a robust, reliable, and widely used analytical tool. This review will focus on recent applications of CE to the analysis of body fluids and tissues for identification of biomarkers.     

Leufolins A and B, potent butyrylcholinesterase-inhibiting flavonoid glucosides from Leucas urticifolia

New flavonoidal glucosides leufolins A (1) and B (2), have been isolated from the ethyl acetate soluble fraction of the whole plants of Leucas urticifolia. Their structures were elucidated on the basis of extensive analysis of nuclear magnetic resonance (1D and 2D NMR) spectral data. Both of these compounds exhibited significant inhibitory potential against the enzyme butyrylcholinesterase.     

Flavonoid dihydromyricetin-mediated silver nanoparticles as potential nanomedicine for biomedical treatment of infections caused by opportunistic fungal pathogens

Dihydromyricetin-mediated silver nanoparticles (DMY-AgNPs) were synthesized and their efficacy against fungal pathogens tested in vitro. The shape of DMY-AgNPs appeared to be spherical with size of ~34 nm. Fourier-transform infrared (FT-IR) analysis indicated that –OH and C=O groups were involved in nanoparticle formation. The XRD pattern of DMY-AgNPs showed strong peaks at 38°, 44°, and 64°, corresponding to reflection from (111), (200), and (220) planes. Five opportunistic fungal pathogens, namely Aspergillus fumigatus, Aspergillus niger, Paecilomyces formosus, Candida albicans, and Candida parapsilosis, were isolated from patients suffering from respiratory tract infections. Growth of each fungal strain was inhibited by DMY-AgNPs. The zone of inhibition of DMY-AgNPs against A. fumigatus, A. niger, P. formosus, C. albicans, and C. parapsilosis was 17.6, 19.2, 22.2, 15.8, and 18.5 mm. The minimal inhibitory concentration was found to be 0.83, 0.73, 0.67, 0.95, and 0.89 µg mL^?1, respectively. This is the first report on DMY-AgNPs as an effective antifungal agent. DMY-AgNPs are a potential alternative to commercially available antifungal fungicidals.     

Voltammetric Characterization of Grafted Polymer Modified with ZnO Nanoparticles on Glassy Carbon Electrode

In this study, a grafted polymer (GP) with ZnO nanoparticles (GP/ZnO NPs) was attached on the surface of glassy carbon electrode (GCE), in order to produce a new modified electrode (GP/ZnO NPs-GCE). The gamma irradiation method was used to grafted polystyrene (polymer) with acrylonitrile (monomer), while slow evaporation process was used to prepare the new modified electrode. The cyclic voltammetry (CV) of K₄[Fe(CN)₆] was used to study the electrochemical properties GP/ZnO NPs-GCE. The peak separation (ΔE_pa-c) was 500 mV between the redox peaks of Fe(II)/Fe(III) in an aqueous solution of 1 M KCl and the current ratio of redox current peaks (I_pa/I_pc) was ≈ 1 for the modified electrode. This indicated that the modified electrode has s good reversibility and conductivity, wherefore; it was applied in the voltammetric filed. It was found that the modified electrode GP/ZnO NPs-GCE have a reasonable solubility and stability at various pH medium. Additionally, the sensitivity of the electrochemical analysis by cyclic voltammetric (CV) method is extensively subjected to the pH medium and the scan rate (SR). A couple of redox current peaks of K₄[Fe(CN)₆] in KCl solution was observed with a reversible process: Fe³⁺/Fe²⁺. Finally a good diffusion coefficient of electroactive species (D) for the new modified electrode was found in this study by chronoamperometry method using Cottrell equation.     

Low temperature synthesis of cubic phase zinc sulfide quantum dots

In this study, we report on a new method for the synthesis of ZnS quantum dots (QDs). The synthesis was carried out at low temperature by a chemical reaction between zinc ions and freshly reduced sulfide ions in ethanol as reaction medium. Zinc chloride and elemental sulfur were used as zinc and sulfur sources, respectively and hydrazine hydrate was used as a strong reducing agent to convert elemental sulfur (S₈) into highly reactive sulfide ions (S²⁻) which react spontaneously with zinc ions. This facile, less toxic, inexpensive route has a high yield for the synthesis of high quality metal sulfide QDs. Transmission electron microscopy (TEM) image analysis and selected area electron diffraction (SAED) reveal that ZnS QDs are less than 3 nm in diameter and are of cubic crystalline phase. The UV-Vis absorption spectrum shows an absorption peak at 253 nm corresponding to a band gap of 4.9 eV, which is high when compared to the bulk value of 3.68 eV revealing strong quantum confinement. PL emission transitions are observed at 314 nm and 439 nm and related to point defects in ZnS QDs.     

Modification of cellulose filter paper with bimetal nanoparticles for catalytic reduction of nitroaromatics in water

Cellulose - In this research work, we present a synthesis of silver and cobalt bimetal nanoparticles stabilized by a carboxymethyl cellulose biopolymer (CMC-AgCo) and its coating on a cellulose...     

Preparation and Characterization of Porous Titania by Modified Sol-Gel Method

Mesoporous titania, especially anatase, is attractive due to its potential applications. A novel method to control pore structure of titania, surfactant- or polymer modification, is proposed. The wet gels and gel films, prepared from Ti(O-nC₄H₉)₄ were dried at 90°C and annealed at 500°C after immersion in surfactant or polymer solutions, and mesoporous anatase was obtained. The pore size, pore volume and specific surface area of the surfactant-modified bulk gels, estimated from N₂ absorption-desorption curves, are more than twice larger than those of the gels without modification. The pore size of the surfactant-modified gel films, observed by SEM, are similar to that of the bulk gels. The pore size obviously depended on the size of micelles. The pore size of the gels modified with hydrophilic polymers hardly increased, but the pore volume and the specific surface area increased.     

Intracellular Modulation of Excited‐State Dynamics in a Chromophore Dyad: Differential Enhancement of Photocytotoxicity Targeting Cancer Cells

The photosensitized generation of reactive oxygen species, and particularly of singlet oxygen [O₂(a¹Δ_g)], is the essence of photodynamic action exploited in photodynamic therapy. The ability to switch singlet oxygen generation on/off would be highly valuable, especially when it is linked to a cancer‐related cellular parameter. Building on recent findings related to intersystem crossing efficiency, we designed a dimeric BODIPY dye with reduced symmetry, which is ineffective as a photosensitizer unless it is activated by a reaction with intracellular glutathione (GSH). The reaction alters the properties of both the ground and excited states, consequently enabling the efficient generation of singlet oxygen. Remarkably, the designed photosensitizer can discriminate between different concentrations of GSH in normal and cancer cells and thus remains inefficient as a photosensitizer inside a normal cell while being transformed into a lethal singlet oxygen source in cancer cells. This is the first demonstration of such a difference in the intracellular activity of a photosensitizer.     

Cyclometallated iridium and platinum complexes with noninnocent ligands

The electronic properties of the cyclometalated (CwedgeN) complexes of iridium and platinum metals with a catechol ligand have been studied experimentally and computationally. The synthesis and characterization of (p-tolylpyridine)Ir(3,5-di-tert-butylcatechol) (abbreviated Ir-sq) and (2,4-diflorophenylpyridine)Pt(3,5-di-tert-butylcatechol) (abbreviated Pt-sq) are reported along with their structural, spectral, and electrochemical properties. Reaction of the 3,5-di-tert-butylcatechol (DTBCat) ligand with the prepared cyclometalated metal complex was carried out in air in the presence of a base. The resulting complexes are air stable and are paramagnetic with the unpaired electron residing mainly on the catechol ligand. The bond lengths obtained from X-ray structure analysis and the theoretical results suggest the semiquinone form of the catechol ligand. Low-energy, intense (approximately 10(3) M-1 cm-1) transitions are observed in the visible to near-infrared region (600-700 nm) of the absorption spectra of the metal complexes. Electrochemically, the complexes exhibit a reversible reduction of the semiquinone form to the catechol form of the ligand and an irreversible oxidation to the unstable quinone form of the ligand. The noninnocent catechol ligand plays a significant role in the electronic properties of the metal complexes. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations on the two open-shell molecules provide the ground-state and excited-state energies of the molecular orbitals involved in the observed low-energy transitions. The spin density in the two complexes resides mainly on the catechol ligand. The intense transition arises from excitation of the beta electron from a HOMO-n (n = 1 or 2 here) to the LUMO, rather than from the excitation of the unpaired alpha electron.