Lidija V. Trandafilović

ZnO-modified cellulose fiber sheets for antibody immobilization.

Cellulose fiber sheets impregnated with saccharide capped-ZnO nanoparticles were used as bioactive materials for antibody immobilization. First, ZnO nanoparticles were synthesized in the presence of glucose (monosaccharide), sucrose (disaccharide) as well as alginic acid and starch (polysaccharides). The pine cellulose fibers were then modified by the obtained saccharide capped nanoparticles and further incorporated into the sheets. The presence of ZnO significantly improved the immobilization of the antibodies on the surface of the sheets. After rewetting the alginic acid-ZnO modified sheets with saline solution, the retention of antibodies was about 95%. A high degree of the immobilization of biomolecules is an important feature for possible fabrications of bioactive- or biosensing-papers and we successfully tested the sheets on the detection of blood types using (A, B, and D blood antibodies). The ZnO nanoparticles affected also the other properties of the sheets. The ZnO-modified fiber sheets showed higher values of tensile index (strength), smoothness and opacity, while the value of porosity was substantially lower than that of the unmodified sheet. The presence of ZnO nanoparticles provided also the antimicrobial activity to the sheets. They showed a strong activity against bacteria (Escherichia coli and Staphylococcus aureus) and strong resistance to the attack of cellulase producing fungus Gloeophyllum trabeum.

Glycogen and gold nanoparticle bioconjugates: controlled plasmon resonance via glycogen-induced nanoparticle aggregation

Hybrid nanosystems composed of glycogen biopolymers and gold nanoparticles were prepared by an in situ non-toxic synthetic procedure. Transmission electron microscopy (TEM) and various spectroscopic methods (optical absorption, X-ray photoelectron and photoluminescence spectroscopy) were used for the characterization of the obtained bioconjugates. The gold nanoparticles formed in the presence of glycogen were spherical in shape and approximately 15 nm in diameter. The TEM micrographs show that the nanoparticles aggregated on the surface of the glycogen biomolecules. This effect induced a shift of the surface plasmon resonance band towards higher wavelengths on an increase in gold ion concentration. Effective medium theory calculations were carried out in order to explain the observed redshift of the plasmon band in the absorption spectra of the Au–glycogen colloids. The interactions of the gold nanoparticles with glycogen strongly affected the photoluminescence of the glycogenin protein incorporated into its structure. The Au–glycogen hydrocolloids exhibited good chemical stability in the presence of saline, phosphate buffered saline, alanine, histidine and D-glucose.

Enhanced photoredox chemistry in surface-modified Mg2TiO4 nano-powders with bidentate benzene derivatives

Magnesium-orthotitanate (Mg2TiO4) nano-powder was synthesized using a Pechini-type polymerized complex route. Microstructural characterization involving transmission electron microscopy, X-ray diffraction analysis and nitrogen adsorption–desorption isotherms indicated that well-crystallized Mg2TiO4 nanoparticles are small in size (about 10 nm) with large specific surface area (72 m2 g−1). The surface modification of Mg2TiO4 nano-powders with 5-amino salicylic acid and catechol induced a significant shift of absorption to the visible spectral region due to charge transfer complex formation. It should be emphasized that tunable optical properties of Mg2TiO4 nano-powders have never been reported in the literature. Degradation reactions of an organic dye (crystal violet) were used to test the photocatalytic ability of pristine and surface-modified Mg2TiO4 nano-powders under illumination in different spectral regions. Excitation with UV light indicated, for the first time, photocatalytic ability of Mg2TiO4. Also, improved photocatalytic performance of surface-modified Mg2TiO4 nano-powders was found in comparison to unmodified ones.

Semiconductor nanoparticles in poly((2-dimethylamino)ethyl methacrylate-co-acrylic acid) co-polymers

Nanostructured cadmium selenide (CdSe) and lead sulfide (PbS) semiconductors were prepared in a poly(2-(dimethylamino)ethyl methacrylate-co-acrylic acid) matrix. The obtained nanoparticles were characterized by using optical and structural methods. Co-polymers were synthesized in two different molar ratios of pDMAEMA:acrylic acid monomer units (1:2, 1:1). Transmission electron microscopy analysis confirmed the presence of nano-sized CdSe and PbS particles. In the case of CdSe, a shift of the onset of the optical absorption toward lower wavelengths was observed. X-ray diffraction analysis revealed that both CdSe and PbS nanoparticles have cubic crystal structure.