Search

Iron oxide nanoparticles (NPs) possessing peroxidase-like catalytic activity have been widely explored in recent decades, owing to their high stability against harsh conditions, low cost, flexibility in structure design and composition, adjustable activities and excellent biocompatibility in comparison with natural enzymes. Recently, a lot of great achievements have been made in this field of iron oxide nanozymes, however, this research has now reached a bottleneck in that the maximum activity enhancement is difficult to achieve via a material design. Hence, in this work, visible light was introduced to improve the peroxidase-like activity of Fe 2 O 3 NPs synthesized via a combination of electrospinning technology and hydrothermal reaction. Our results showed that with the assistance of visible light, Fe 2 O 3 NPs exhibited at least 2.2-fold higher peroxidase activity than those tested under darkness, confirming the superiorly visible light promoted peroxidase-like catalytic activity of Fe 2 O 3 NPs. Furthermore, the affinity and maximum reaction velocity of Fe 2 O 3 nanoflowers (bandgap = 1.78 eV) towards 3,3',5,5'-tetramethylbenanozymeidine (TMB) were at least over 3.7 and 4.3 times greater than in Fe 2 O 3 nanocubes (bandgap = 2.08 eV), suggesting that the reaction performance of semiconductors could be controlled by proper adjustment of the bandgap. Moreover, the Fe 2 O 3 NPs were also successfully utilized to detect glucose. Herein, we believe that the present work exhibits a fascinating perspective for peroxidase-like catalytic fields.

This paper reports a facile synthesis of anatase TiO(2) nanocrystals with exposed, chemically active {001} facets. The nanocrystals were prepared by digesting electrospun nanofibers consisting of amorphous TiO(2) and poly(vinyl pyrrolidone) with an aqueous acetic acid solution (pH = 1.6), followed by hydrothermal treatment at 150 degrees C for 20 h. The as-obtained nanocrystals exhibited a truncated tetragonal bipyramidal shape with 9.6% of the surface being enclosed by {001} facets. The use of electrospinning is critical to the success of this synthesis as it allows for the generation of very small particles of amorphous TiO(2) to facilitate hydrothermal crystallization, an Ostwald ripening process. The morphology of the nanocrystals had a strong dependence on the pH value of the solution used for hydrothermal treatment. Low pH values tended to eliminate the {001} facets by forming sharp corners while high pH values favored the formation of a rodlike morphology through an oriented attachment mechanism. When acetic acid was replaced by inorganic acids, the TiO(2) nanocrystals further aggregated into larger structures with various morphologies.

Yunqian Dai and co‐workers report on page 597 how N dopants are tailored in the form of both substitutional and pyrrolic N in graphene quantum dots (N‐GQDs), showing controllable chemical properties. The substitutional N leads to significantly modified photoluminescence properties of the versatile N‐GQDs, which also exhibit highly efficient photocurrent conversion abilities when supported by anatase nanofibers. [ABSTRACT FROM AUTHOR]

• The surface uniformity of substrate was optimized toward sinter-resistant catalyst. • TiO 2 nanofibers were decorated with well-defined rutile nanorods as substrate. • 3 nm-Pt NPs were stabilized under sinter-promoting situations over 600 °C. • Pt NPs on the nanorods-decorated-TiO 2 nanofibers were active for soot oxidation. One of the most urgent concerns for supported catalysts is to enhance their thermal stability against sintering upon high temperatures (above 300 °C). In this work, we decorated the rough surface of TiO 2 nanofibers with a sheath of rutile nanorods to improve their surface uniformity and explored them as new reliable substrates to stabilize Pt nanoparticles without capping shell. During preparation, the surface-initiated grain growth facilitates the decorated TiO 2 crystals to transform into rutile nanorods, exposing rutile {1 1 1} and {1 1 0} facets. With the presence of TiO 2 nanofibers, these rutile nanorods were finely confined against coalescence and reconstruction upon 700 °C, offering reliable supports for stabilizing metal nanoparticles. Therefore, the diminished driving force for sintering enables the whole catalyst system to withstand temperatures up to 500 °C at an oxidative atmosphere. After calcination at 500 °C, the Pt on rutile nanorods-decorated-TiO 2 nanofibers exhibited nearly 3-times higher reaction rate constant (27.8 s−1·g−1·L−1) toward hydrogenation of 4-nitrophenol over those on unmodified TiO 2. Moreover, such a thermally stable catalyst was active for the oxidation of soot particulates, decreasing the conversion temperature and maintaining a small Pt size of 6.99 nm after the sinter-promoting exothermic oxidation. [ABSTRACT FROM AUTHOR]