In this work, hydrothermally prepared p−n heterojunction BiOBr/SnO 2 photocatalysts were applied to eliminate NO in visible light. The as-synthesized BiOBr/SnO 2 photocatalysts exhibit superior photocatalytic activity and stability through the establishment of a p−n heterojunction, resulting in a significant improvement in charge separation and transfer properties. The morphological structure and optical property of the BiOBr/ SnO 2 heterojunction were also investigated comprehensively. Extended light absorption into the visible range was achieved by SnO 2 coating on the surface of the BiOBr microsphere through the constructed heterojunction between BiOBr and SnO 2 , thus achieving efficient NO removal. Moreover, the transfer channels and directions of charge at the BiOBr/SnO 2 interface were determined by a combination of theoretical calculations and experimental studies. Within this p− n heterojunction, the charge in SnO 2 migrates into BiOBr through the preformed electron transfer channels, thus generating an internal electric field (IEF) between SnO 2 and BiOBr. Under the influence of IEF, the photogenerated electrons of BiOBr migrate from the conduction band (CB) to the CB of SnO 2 , thus promoting the separation of electrons (e − )−holes (h + ) pairs. The intermediates and final products were monitored by the in situ DRIFTS technology in the process of removal of NO in visible light; hence, the oxidation pathways of NO were reasonably proposed. Meanwhile, the construction of the heterojunction not only achieves more efficient NO photocatalytic oxidation but also inhibits the production of more toxic NO 2 . This work provides mechanistic insights into the interfacial charge transfer for heterojunction photocatalysts and reaction mechanism for efficient air purification.

Poly(amidoamine)(PAMAM) dendrimers with a cinnamoyl shell were prepared by reacting full generation PAMAM dendrimers (Gϭ3.0) with 2-chloroethanol and cinnamoyl chloride, which resulted in densely packed polymerizable unsaturated groups on the periphery. The cinnamoyl shell of the dendrimers dimerized when irradiated under a UV light by using 5-nitroacenaphthylene as an initiator in dilute dimethylformamide (DMF). FTIR, 1 H NMR, UV-Vis, SEC, and a viscosity test certified that the photocycloaddition of the cinnamoyl shell of the dendrimers took place within the molecules with the disappearance of double bond signals in the FTIR. 1 H NMR spectra as well as the intrinsic viscosity and polydispersity value of the products both before and after irradiation showed no difference. It was further found that the cinnamoyl shell-modified dendrimers possessed fluorescence property, and the fluorescence intensity became stronger when the shell was photocyclized under UVirradiation.

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