Correlating chemistry and mass transport in sustainable iron production.

Steelmaking contributes 8% to the total CO2 emissions globally, primarily due to coal-based iron ore reduction. Clean hydrogen-based ironmaking has variable performance because the dominant gas-solid reduction mechanism is set by the defects and pores inside the mm- to nm-sized oxide particles that change significantly as the reaction progresses. While these governing dynamics are essential to establish continuous flow of iron and its ores through reactors, the direct link between agglomeration and chemistry is still contested due to missing measurements. In this work, we directly measure the connection between chemistry and agglomeration in the smallest iron oxides relevant to magnetite ores. Using synthesized spherical 10-nm magnetite particles reacting in H2, we resolve the formation and consumption of wüstite (Fe1-xO)-the step most commonly attributed to whiskering. Using X-ray diffraction, we resolve crystallographic anisotropy in the rate of the initial reaction. Complementary imaging demonstrated how the particles self-assemble, subsequently react, and grow into elongated "whisker" structures. Our insights into how morphologically uniform iron oxide particles react and agglomerate in H2 reduction enable future size-dependent models to effectively describe the multiscale aspects of iron ore reduction.

Collective Plasmon Coupling in Gold Nanoparticle Clusters for Highly Efficient Photothermal Therapy.

Plasmonic nanomaterials with strong absorption at near-infrared frequencies are promising photothermal therapy agents (PTAs). The pursuit of high photothermal conversion efficiency has been the central focus of this research field. Here, we report the development of plasmonic nanoparticle clusters (PNCs) as highly efficient PTAs and provide a semiquantitative approach for calculating their resonant frequency and absorption efficiency by combining the effective medium approximation (EMA) theory and full-wave electrodynamic simulations. Guided by the theoretical prediction, we further develop a universal strategy of space-confined seeded growth to prepare various PNCs. Under optimized growth conditions, we achieve a record photothermal conversion efficiency of up to ∼84% for gold-based PNCs, which is attributed to the collective plasmon-coupling-induced near-unity absorption efficiency. We further demonstrate the extraordinary photothermal therapy performance of the optimized PNCs in in vivo application. Our work demonstrates the high feasibility and efficacy of PNCs as nanoscale PTAs.

Nanoconjugates of Ag/Au/Carbon Nanotube for Alkyne-Meditated Ratiometric SERS Imaging of Hypoxia in Hepatic Ischemia.

We report a ratiometric surface-enhanced Raman scattering (SERS) nanoprobe for imaging hypoxic living cells or tissues, using azo-alkynes assembled on a single-walled carbon nanotube (SWCNT) surface-functionalized with Ag/Au alloy nanoparticles (SWCNT/Ag/AuNPs). Under a hypoxic condition, azobenzene derivatives preassembled on the surface of the nanostructures are reduced stepwise by various reductases and eventually removed from the surface of the SWCNT/Ag/AuNPs, resulting in the loss of characteristic alkyne Raman bands at 2207 cm-1. Using 2D-band of SWCNTs at 2578 cm-1 as the internal standard, we are able to determine the hypoxia level based on the ratio of two peak intensities ( I2578/ I2207) as demonstrated by the successful detection in different cell lines and rat liver tissue samples derived from hepatic ischemia surgery. By combining the outstanding anti-interference property of alkynes as SERS reporters and the distinct Raman responses of alkynes and SWCNTs in complex systems, this novel ratiometric SERS strategy holds promise in becoming a very useful tool for in vitro and in vivo monitoring of hypoxia in research and clinical settings.