Leptothrix sp. sheaths modified with iron oxide particles: Magnetically responsive, high aspect ratio functional material

Magnetically recyclable copper doped core-shell Fe3O4@TiO2@Cu nanocomposites for wastewater remediation

The smart magnetic nanocomposites have been doped to diminish the energy bandgap of the photocatalyst and to permit recovering of the photocatalyst after the wastewater treatment. The core-shell Fe3O4@TiO2 nanocomposite was synthesised by the hydrothermal method using titanium butoxide as a precursor. The nanocomposites were examined by XRD, VSM, UV-Vis, and TEM techniques. The energy band gap of core-shell Fe3O4@TiO2 nanocomposite is 3.5 eV. Doping of copper with a concentration of 1, 2, and 3 wt% into TiO2 shell was done to increase the performance of photocatalyst. The Fe3O4/PVP@TiO2@Cu photocatalyst was used for dye wastewater treatment. The energy bandgap decreased to 2.2 eV after copper doping into the TiO2 shell specified that copper-doped nanocomposite could be an outstanding photocatalyst. The photocatalytic activity was carried out using methylene blue(MB) and methyl orange (MO) under sunlight. About 65% of methylene blue and 85% of methyl orange degradation was done using Cu (3wt %) doped Fe3O4@TiO2 nanocomposite. These photocatalysts can be easily withdrawn with a magnetic field. The Fe3O4/PVP@TiO2@Cu photocatalyst has been demonstrated to be very functional or effective for the degradation of MB and MO dyes using solar illumination.

Hunter-Gatherers Harvested and Heated Microbial Biogenic Iron Oxides to Produce Rock Art Pigment

Red mineral pigment use is recognized as a fundamental component of a series of traits associated with human evolutionary development, social interaction, and behavioral complexity. Iron-enriched mineral deposits have been collected and prepared as pigment for use in rock art, personal adornment, and mortuary practices for millennia, yet little is known about early developments in mineral processing techniques in North America. Microanalysis of rock art pigments from the North American Pacific Northwest reveals a sophisticated use of iron oxide produced by the biomineralizing bacterium Leptothrix ochracea; a keystone species of chemolithotroph recognized in recent advances in the development of thermostable, colorfast biomaterial pigments. Here we show evidence for human engagement with this bacterium, including nanostructural and magnetic properties evident of thermal enhancement, indicating that controlled use of pyrotechnology was a key feature of how biogenic iron oxides were prepared into paint. Our results demonstrate that hunter-gatherers in this area of study prepared pigments by harvesting aquatic microbial iron mats dominated by iron-oxidizing bacteria, which were subsequently heated in large open hearths at a controlled range of 750 °C to 850 °C. This technical gesture was performed to enhance color properties, and increase colorfastness and resistance to degradation. This skilled production of highly thermostable and long-lasting rock art paint represents a specialized technological innovation. Our results contribute to a growing body of knowledge on historical-ecological resource use practices in the Pacific Northwest during the Late Holocene.

Figshare link to figures: https://figshare.com/s/9392a0081632c20e9484.