A pH-Sensitive Polymer Sensor Developed
- PDF / 536,132 Bytes
- 2 Pages / 612 x 792 pts (letter) Page_size
- 30 Downloads / 215 Views
RESEARCH/RESEARCHERS
Human Hair Serves as Scaffold for TiO2 Microtubes with Au Nanoparticles A comparison to human hair is widely used to give a sense of scale when describing tiny structures. Now, human hair has been used as a scaffold for the fabrication of TiO2 microtubes, as reported by S. Liu and J. He of the Chinese Academy of Sciences in the December issue of the Journal of the American Ceramic Society (DOI: 10.1111/j.1551-2916.2005.00615.x; p. 3513). Nanopores in the walls of the titania tubes also serve as formation sites for chemically derived gold nanoparticles. Liu and He dipped human hairs into a solution of titanium tetrabutoxide, Ti(OnBu)4, in toluene or ethanol, allowing the Ti-based molecules to react with hydroxyl and amino acid groups on platelike cells on the outside of the hair shaft. After drying and hydrolyzing the samples, the researchers repeated this sol-gel process a number of times to vary the thickness of the titania. Calcining the hair–titania samples at 800°C removed organic components, leaving behind TiO2 tubes ~40 μm in diameter composed of platelets ~15 μm in diameter and ~0.5 μm thick, with planes perpendicular to the tube axis. X-ray diffraction analysis confirmed that the TiO2 was crystalline, composed of roughly 2/3 rutile and 1/3 anatase phases by weight. Close inspection with scanning electron microscopy revealed that the platelets contained nanopores ~20–200 nm in diameter. The researchers used the pores as templates for gold nanoparticles by immersing the tubes in an aqueous AuCl3 solution and then an aqueous NaBH4 solution. Transmission electron microscopy showed the formation of gold particles with average diameters of ~23 nm, which is consistent with the size of the nanopores. The researchers are extending their work with the goal of improving control of the size of the metal nanoparticles and the crystalline phase of the ceramic matrix, as these properties can strongly influence the performance of the structures in proposed applications, which include catalysis, adsorption, and separation. AMANDA GIERMANN
thesis of a poly(sulfadimethoxine) chain terminated with two fluorescent moieties, pyrene on one end and coumarin 343 on the other. Below pH 7, the polymeric spacer undergoes a rapid conformational transition to a collapsed state. This brings the fluorescent groups, which are a donor–accep-
tor pair, into close proximity and leads to fluorescent emission at a new wavelength, signaling the pH change. This type of sensor has numerous applications in biomedical and environmental applications, including pH monitoring of water sources and the identification of tumor cells.
Nanosensor Uses Quantum Dots to Detect DNA Researchers at the Johns Hopkins University have developed a new method for finding specific sequences of DNA by making them light up beneath a microscope. The researchers, who say the technique will have important uses in medical research, demonstrated its potential in their laboratory by detecting a sample of DNA containing a mutation linked to ovarian canc
Data Loading...
