The development of a suitable catalyst for the oxygen reduction reaction (ORR), the cathode reaction of proton exchange membrane fuel cells (PEMFC), is necessary to push this technology toward widespread adoption. There have been substantial efforts to utilize bimetallic Pt−M alloys that adopt the ordered face-centered tetragonal (L1 0 ) phase in order to reduce the usage of precious metal, enhance the ORR performance, and improve catalyst stability. In this work, monodisperse Pt−Co nanocrystals (NCs) with well-defined size (4−5 nm) and cobalt composition (25−75 at%) were synthesized via colloidal synthesis. The transformation from the chemically disordered A1 (face-centered cubic, fcc) to the L1 0 phase was achieved via thermal annealing using both a conventional oven and a rapid thermal annealing process. The structure of the Pt−Co catalysts was characterized by a variety of techniques, including transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy in high-angle annular dark-field scanning transmission electron microscopy (STEM-EDS), small-angle X-ray scattering (SAXS), X-ray diffraction (XRD), and inductively coupled plasma−optical emission spectrometry (ICP-OES). The effects of annealing temperature on the composition-dependent degree of ordering and subsequent effect on ORR activity is described. This work provides insights regarding the optimal spatial distribution of elements at the atomic level to achieve enhanced ORR activity and stability.

Improving communication between people in science, technology, engineering, and mathematics (STEM) fields and the public is critical to the future of STEM. Partnerships between institutions of higher education with K–12 schools are identified as one effective strategy to support community engagement. We have employed a service-learning model to develop a chemistry course (Chemistry 010) that engages undergraduate students in developing and teaching chemistry experiments for a secondary school audience. This service-learning course design provided us with the consistency and flexibility to sustain substantive learning experiences for both the undergraduates and secondary students. In addition to describing the model of this course in detail, we evaluate this course’s impact on undergraduate scientific communication skills. Analysis of reflections written by the undergraduates reveals that Chemistry 010 is an effective course structure for them to explore and assess their competencies to teach and communicate scientific concepts. The course’s influence on the secondary students, teacher partners, and university instructors will be the focus of future studies to ensure the mutual benefit of all involved parties.

Nanoplatelets offer many possibilities to construct advanced materials due to new properties associated with their (semi)two-dimensional shapes. However, precise control of both positional and orientational order of the nanoplatelets in three dimensions, which is required to achieve emerging and collective properties, is challenging to realize. Here, we combine experiments, advanced electron tomography and computer simulations to explore the structure of supraparticles self-assembled from nanoplatelets in slowly drying emulsion droplets. We demonstrate that the rich phase behaviour of nanoplatelets, and its sensitivity to subtle changes in shape and interaction potential can be used to guide the self-assembly into a wide range of different structures, offering precise control over both orientation and position order of the nanoplatelets. Our research is expected to shed light on the design of hierarchically structured metamaterials with distinct shape- and orientation- dependent properties.

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Rare-earth (RE) compounds have been actively pursued for therapeutic and diagnostic applications due to their ability to upconvert near infrared light into the UV–vis range. Through nanoengineering and bottom-up synthesis, additional functionality can be added to these upconverting systems. Herein, we report the synthesis of 90Y-doped β-NaYF4:Er, Yb upconverting nanophosphors (UCNPs) to enable β-particle emission and upconversion by the same UCNP. To homogenously incorporate the radionuclides, we employ a hydroxide metathesis method to produce the RE precursor required for the solvothermal synthesis of monodisperse UCNPs. Once incorporated, we find that the β-emitting 90Y dopants do not influence the energy pathways required for upconversion, enabling simultaneous radio- and optical-tracing. The resulting large (>100 nm in height and width), anisotropic, 90Y-radiolabeled β-NaYF4 UCNPs are then coated with silica using a modified, micelle-driven Stöber process to enable their dispersion in polar solvents. Doing so highlights the importance of surfactant (Igepal CO-520) and silica source (tetraethyl orthosilicate) interactions to the continuity of the silica shell and makes the vast library of silica surface chemistry and functionality accessible to upconverting radiotracers.