Miniaturization of Anthracene-Containing Nonapeptides for Selective Precipitation/Recovery of Metallic Gold from Aqueous Solutions Containing Gold and Platinum Ions

The separation and recovery of noble metals is increasingly of interest, in particular the recovery of gold nanocrystals, which have applications in medicine and industry. Typically, metal recovery is performed using liquid–liquid extraction or electrowinning. However, it is necessary to develop noble metal recovery systems providing high selectivity in conjunction with a one-pot setup, ready product recovery, and the use of dilute aqueous solutions. In prior work, our group developed a selective gold recovery process using peptides. This previous research showed that RU065, a nonapeptide containing an anthracene moiety (at a concentration of 2.0 × 10−4 M), is capable of selective reduction of HAuCl4 to recover gold from a solution of HAuCl4 and H2PtCl6, each at 5.0 × 10−5 M. However, peptide molecules are generally costly to synthesize, and therefore it is important to determine the minimum required structural features to design non-peptide anthracene derivatives that could reduce operational costs. In this study, we used RU065 together with 23 of its fragment peptides and investigated the selective precipitation/recovery of metallic gold. RU0654–8, a fragment peptide comprising five amino acid residues (having two lysine, one L-isoleusine, and one L-alanine residue (representing six amide groups) along with an L-2-anthrylalanine residue) provided an Au/Pt atomic ratio of approximately 8, which was comparable to that for the full-length original RU065. The structural features identified in this study are expected to contribute to the design of non-peptide anthracene derivatives for low-cost, one-pot selective gold recovery.

Determination of the electronic transport in type separated carbon nanotubes thin films doped with gold nanocrystals

We report a systematic theoretical and experimental investigation on the electronic transport evolution in metallic and semiconducting carbon nanotubes thin films enriched by gold nanocrystals. We used an ultra-clean production method of both types of single-walled carbon nanotube thin films with/without gold nanocrystals, which were uniformly dispersed in the whole volume of the thin films, causing a modification of the doping level of the films (verified by Raman spectroscopy). We propose a modification of the electronic transport model with the additional high-temperature features that allow us to interpret the transport within a broader temperature range and that are related to the conductivity type of carbon nanotubes. Moreover, we demonstrate, that the proposed model is also working for thin films with the addition of gold nanocrystals, and only a change of the conductivity level of our samples is observed caused by modification of potential barriers between carbon nanotubes. We also find unusual behavior of doped metallic carbon nanotube thin film, which lowers its conductivity due to doping.