No abstract

Tm3+-, Tb3+- and Eu3+-doped ZrO2 nanocrystals were prepared by a facile precipitation method with a hydrothermal process. Structural characterization showed a crystallite size ranging from 30 to 40 nm, and monoclinic and tetragonal zirconia phases were observed depending on the dopant concentration. The monoclinic phase was dominant for 0.5 mol% of Tb3+ and Eu3+, and the tetragonal phase was 100% stabilized for 2 mol% of Tm3+ and Tb3+. The structure of emission bands associated with Eu3+ confirms the substitution of Zr4+ located at C1 and D2h symmetry sites for the monoclinic and tetragonal phases. The emission of three primary colours, red, green and blue, was obtained from Eu3+, Tb3+ and Tm3+, respectively, which makes this nanophosphor an excellent candidate for use in photonics applications. The emitted signal was analysed as a function of ion concentration and the optimum concentration was determined.

Cellulose nanocrystals (CNCs) were isolated from Agave tequilana residues derived from ethanol production. Hemicelluloses and lignin extraction from agave bagasse was carried out via organosolv (ethanol/acetic) digestion followed by conventional sulfuric acid hydrolysis. The ethanol/acetic acid treatment resulted in cellulose yields of approximately 67% after lignin and ash removal. Compared to soda and sodium chlorite treatments with organosolv, the time and chemical load needed for delignification were remarkably reduced. The morphology of the cellulose fiber obtained in the three treatments was between 0.55 and 0.62 mm, with which CNC was obtained in the order of 83 to 195 nm in length. It is noteworthy that the longest cellulose fibers and nanocrystals were obtained from organosolv cellulose. The organosolv treatment led to a high purity cellulose, derived CNCs with a minimum energy consumption and mild chemical usage, and also considered the use of material streams associated with distillation processes. Thus, a viable alternative is suggested for the production of high quality CNC from widely available residual biomass that otherwise poses environmental and health-related risks.

No abstract

The physical, chemical and optical properties of nano-scale colloids depend on their material composition, size and shape. There is a great interest in using nano-colloids for photo-thermal ablation, drug delivery and many other biomedical applications. Gold is particularly used because of its low toxicity. A property of metal nano-colloids is that they can have a strong surface plasmon resonance. The peak of the surface plasmon resonance mode depends on the structure and composition of the metal nano-colloids. Since the surface plasmon resonance mode is stimulated with light there is a need to have the peak absorbance in the near infrared where biological tissue transmissivity is maximal. We present a method to synthesize star shaped colloidal gold, also known as star shaped nanoparticles or nanostars. This method is based on a solution containing silver seeds that are used as the nucleating agent for anisotropic growth of gold colloids. Scanning electron microscopy (SEM) analysis of the resulting gold colloid showed that 70 % of the nanostructures were nanostars. The other 30 % of the particles were amorphous clusters of decahedra and rhomboids. The absorbance peak of the nanostars was detected to be in the near infrared (840 nm). Thus, our method produces gold nanostars suitable for biomedical applications, particularly for photo-thermal ablation.