Hair fiber as a nanoreactor in controlled synthesis of fluorescent gold nanoparticles.

The synthesis and detailed characterization of gold nanoparticles (AuNPs) inside human hair has been achieved by treatment of hair with HAuCl(4) in alkaline medium. The AuNPs, which show a strong red fluorescence under blue light, are generated inside the fiber and are arranged in the cortex in a remarkably regular pattern of whorls based on concentric circles, like a fingerprint. It opens an area of genuine nanocomposites with novel properties due to AuNPs inside the hair shaft.

Convergence study of a Schrödinger-equation algorithm and structure-factor determination from the wavefunction.

The algorithm [Bethanis, Tzamalis, Hountas & Tsoucaris (2002). Acta Cryst. A58, 265-269] which reformulates the quantum-mechanical problem of solving a Schrödinger (S) equation in a crystallographic context has been upgraded and tested for many aspects of convergence. The upgraded algorithm in reciprocal space aims at determining a wavefunction Phi(H) such that (a) Phi(H) fulfils the S equation within certain precision and (b) Phi(H) minimizes by least squares the differences between the calculated structure factors from the wavefunction and the observed ones. Calculations have been made with three molecules (11, 41 and 110 non-H atoms in the asymmetric unit) for different numbers of initially given phases. Three main questions have been addressed: (I) Does the iterative calculation of the wavefunction converge? (II) Do the calculated wavefunctions converge to a unique set of Phi(H) values independent of the initial random set of Phi(H)? (III) Is the calculated Phi(H) set a good approximation of a wavefunction able to produce within certain errors the correct values of the phases of the structure factors? Concerning questions (I) and (II), our results give a strong hint about fast convergence to a unique wavefunction independent of the arbitrary starting wavefunction. This is an essential prerequisite for practical applications. For question (III) in the case closer to the ab initio situation, the final mean phase error, respectively, for the three structures is 3, 26 and 28 degrees. The combination of (a) and (b) in the upgraded algorithm has been proved crucial especially for the results concerning the larger structures.

Early use of PbS nanotechnology for an ancient hair dyeing formula.

Lead-based chemistry was initiated in ancient Egypt for cosmetic preparation more than 4000 years ago. Here, we study a hair-dyeing recipe using lead salts described in text since Greco-Roman times. We report direct evidence about the shape and distribution of PbS nanocrystals that form within the hair during blackening. It is remarkable that the composition and supramolecular organization of keratins can control PbS nanocrystal growth inside a hair.

Synthetic hydrocerussite, 2PbCO(3) x Pb(OH)(2), by X-ray powder diffraction.

Synthetic hydrocerussite [trilead dihydroxide dicarbonate, Pb(3)(CO(3))(2)(OH)(2)] can be easily obtained, as a white powder, by the action of carbon dioxide and water on either lead or litharge at pH 4-5. This compound is also found in lead corrosion technological products as a fine-grained phase. Ab initio crystal structure determination was carried out on X-ray powder diffraction data. The heavy-atom method and the Patterson function helped determine the crystallographic model and the atom locations. The Rietveld fitting procedure was used for the final refinement. The atomic arrangement is closely related to the structures of other lead hydroxide carbonates. The hydrocerussite structure can be viewed as a sequence of two types of layers stacked along [001]. Layer A is composed of Pb and CO(3), and layer B is composed of Pb and OH. The stacking sequence is ...BAABAA...