Hangjia Shen

Synergistic Effects between Atomically Dispersed Fe−N−C and C−S−C for the Oxygen Reduction Reaction in Acidic Media

Various advanced catalysts based on sulfur-doped Fe/N/C materials have recently been designed for the oxygen reduction reaction (ORR); however, the enhanced activity is still controversial and usually attributed to differences in the surface area, improved conductivity, or uncertain synergistic effects. Herein, a sulfur-doped Fe/N/C catalyst (denoted as Fe/SNC) was obtained by a template-sacrificing method. The incorporated sulfur gives a thiophene-like structure (C-S-C), reduces the electron localization around the Fe centers, improves the interaction with oxygenated species, and therefore facilitates the complete 4 e- ORR in acidic solution. Owing to these synergistic effects, the Fe/SNC catalyst exhibits much better ORR activity than the sulfur-free variant (Fe/NC) in 0.5 m H2 SO4 .

Luminescent properties and sensing performance of a carbon quantum dot encapsulated mesoporous silica/polyacrylonitrile electrospun nanofibrous membrane

A novel turn-off and label-free fluorescent sensor based on a carbon quantum dot encapsulated mesoporous silica/polyacrylonitrile (CDs/mesoSiO2/PAN) electrospun nanofibrous membrane for the determination of Fe(III) was evaluated. Compared with that of the free-state CDs, the fluorescent behavior of the embedded CDs was altered because of the involvement of mesoSiO2/PAN electrospun nanofibers as a supporting matrix. On the basis of previously reported understandings, the photoluminescent (PL) mechanism of the CDs had been further studied. It is evident that the fixed blue emission of CDs occurs from the carbon defect states, whereas the excitation-dependent emission at longer wavelengths is related to confinement effects of the CDs. Moreover, compared with the free-state CDs, the CDs/mesoSiO2/PAN nanofibrous membrane exhibits a more stable PL signal, improved anti-photobleaching performance, and better pH adaptability because of the possible hydrogen bonding between the SiOH groups in nanofibers and the surface oxygen-containing groups of the CDs, which create an adequate chemical environment for the preservation of the carbon defect states in luminescence generation as well as the active sites for Fe(III) binding. Applying the CDs/mesoSiO2/PAN membrane for the determination of Fe(III) in tap water samples indicates that it can work efficiently as a PL sensor.

Atomistic understanding of the origin of high oxygen reduction electrocatalytic activity of cuboctahedral Pt3Co–Pt core–shell nanoparticles

PtM-based core–shell nanoparticles are a new class of active and stable nanocatalysts for promoting oxygen reduction reaction (ORR); however, the understanding of their high electrocatalytic performance for ORR at the atomistic level is still a great challenge. Herein, we report the synthesis of highly ordered and homogeneous truncated cuboctahedral Pt3Co–Pt core–shell nanoparticles (cs-Pt3Co). By combining atomic resolution electron microscopy, X-ray photoelectron spectroscopy, extensive first-principles calculations, and many other characterization techniques, we conclude that the cs-Pt3Co nanoparticles are composed of a complete or nearly complete Pt monolayer skin, followed by a secondary shell containing 5–6 layers with ~78 at% of Pt, in a Pt3Co configuration, and finally a Co-rich core with 64 at% of Pt. Only this particular structure is consistent with the very high electrocatalytic activity of cs-Pt3Co nanoparticles for ORR, which is about 6 times higher than commercial 30%-Pt/Vulcan and 5 times more active than non-faceted (spherical) alloy Pt3Co nanoparticles. Our study gives an important insight into the atomistic design and understanding of advanced bimetallic nanoparticles for ORR catalysis and other important industrial catalytic applications.

Wearable Carbon Nanotube Devices for Sensing

Abstract The application of carbon nanotubes (CNTs) for wearable sensing device fabrication is an interesting area, attracting sustained scientific and technological interest. Acquisition of information from wearable technologies is considered a cornerstone in person-centered health informatics, because of its independence, currency, and timeliness. The unique physical and chemical properties (such as high aspect ratio, ultralight weight, high mechanical strength, high electrical conductivity, and high thermal conductivity) of CNTs make them an attractive nanomaterial for wearable sensor fabrication. Extensive efforts will continuously be made in both academia and industry in the research and development of wearable CNT sensors to enhance their function, flexibility, energy saving, and longevity. We will discuss recent advances in the design and application of wearable devices based on CNT materials for sensing, especially in the fields of medical equipment, motion detection, and environmental sensor.