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Concerns for the environmental and economic impact of organic solvents and detergents in gold nanoparticle (AuNP) solution synthesis have motivated the search for more environmentally benign alternatives. One approach is to synthesize AuNPs from tetrachloroauric(III) acid (HAuCl4) using triblock copolymers (TBPs). However, a major challenge of using TBPs is the heterogeneous nature of the formed nanocrystals. Establishing control over AuNP size and shape requires a detailed mechanistic understanding of precursor reduction and nanoparticle growth. By using mixtures of TBPs (L31 and F68), we demonstrate a more flexible method for adjusting the hydrophobic/hydrophilic environment to tune the size and shape. We show that AuNP morphology and size can be changed by adjusting the TBP/Au(III) ratio. Kinetic models are used to rationalize why the addition of L31 slows the rate of AuNP formation and growth. Experimental evidence of sigmoidal growth kinetics, early time bimodal gold nanoparticle size distributions, and polycrystallinity suggest that aggregative AuNP growth is an important mechanism.

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In this report, we demonstrate a rapid, simple, and green method for synthesizing silver-gold (Ag-Au) bimetallic nanoparticles (BNPs). We used a novel modification to the galvanic replacement reaction by suspending maltose coated silver nanoparticles (NPs) in ≈ 2% aqueous solution of EO100PO65EO100 (Pluronic F127) prior to HAuCl4 addition. The Pluronic F127 stabilizes the BNPs, imparts biocompatibility, and mitigates the toxicity issues associated with other surfactant stabilizers. BNPs with higher Au:Ag ratios and, subsequently, different morphologies were successfully synthesized by increasing the concentration of gold salt added to the Ag NP seeds. These BNPs have enhanced catalytic activities than typically reported for monometallic Au or Ag NPs (∼ 2–10 fold) of comparable sizes in the sodium borohydride reduction of 4-nitrophenol. The 4-nitrophenol reduction rates were highest for partially hollow BNP morphologies.

Microstructural and biomolecular preservation is reported in fossils as old as the Triassic. Such preservation suggests unusual taphonomic conditions. We collected fragments of fossil whale bone from silty, tuffaceous, and diatomaceous rocks of the middle-upper Miocene portion of the Pisco Formation. The whale fossils within the region are generally well-preserved and mostly articulated, including some specimens with in situ baleen. Due to the depositional setting associated with the preservation of these fossils, they could be expected to be favorable candidates for the preservation of cellular microstructures and/or original biomolecules. To test this hypothesis, fossil whale bone fragments were subjected to microscopic analysis and EDTA-mediated demineralization to release extractable materials. Microscopy of partially demineralized fossil bones revealed quartz-permineralized osteocyte-like and vessel-like structures. Protein assay (micro-Bicinchoninic Acid Assay) of the supernatants obtained from demineralized fossils yielded 12 to 19.5 μg of protein per gram of bone. MALDI-TOF analysis of the extracted protein demonstrated the presence of approximately 5 kD molecules in one fossil sample, consistent with the presence of highly fragmented polypeptides. An LC-MS/MS analysis of the fragmentation pattern of the tryptic digest of extracted protein was performed. However, attempted protein identification was unsuccessful. Nevertheless, this study first documents the microstructural preservation with some silicification of the fossil whale bones of the Pisco Formation, and then quantifies extractable protein from these bones. It adds to the growing body of reports of microstructural and organic preservation in fossils.