Two-dimensional (2D) covalent organic frameworks (COFs) have received much attention due to their tunable electronic structures and superior surface area in visible-light-driven water splitting. Compared to traditional photocatalysts, 2D COFs...

Carbon dots (CDs) with long-lived room-temperature phosphorescence (RTP) or long afterglow properties draw much attention. However, most room-temperature phosphorescent materials are metal containing, and the exploitation of long-lived color-tunable RTP materials faces great challenges. Here, we report metal-free borondoped CDs (B-CDs) for room-temperature phosphorescence with tunable color and an ultralong lifetime. B-CDs were obtained by simply calcining a mixture of boric acid and 1,3,5-benzenetricarboxylic acid in the atmosphere. The as-prepared B-CDs were characterized through UV−vis spectroscopy, photoluminescence spectroscopy, and so forth. Under the excitation of 310 nm UV light, B-CDs show RTP that appears as blue with a phosphorescence lifetime of 1042 ms, and after switching the excited wavelength to 365 nm, the RTP appears as green with a phosphorescence lifetime of 590 ms. Due to the unique RTP properties, B-CDs display promising applications in anticounterfeiting and information encryption.

To accurately determine ultra-trace Pu isotopes in small environmental samples, we explored ICP-MS/MS in NH 3 -He mode, and investigated mechanism of 238 U interference removal and measurement sensitivity improvement for plutonium isotopes. The interference of uranium and uranium hydrides was effectively eliminated using 0.4 mL/min NH 3 as reaction gas by shifting them to U(NH m ) n + and UH(NH m ) n +. The overall interference of uranium was reduced to <2.4 × 10 − 7 , while remaining excellent 239 Pu sensitivity (13,900 Mcps/ (mg/L)) mainly due to ion focusing effect of Pu by helium gas. On this basis, the purification of plutonium using a single AG1-× 4 column was proved to be sufficient for accurate determination of plutonium isotopes by the developed detection method, and the detection limits for the method were estimated to be 0.16 fg (0.4 μBq) for 239 Pu, 0.046 fg (0.4 μBq) for 240 Pu and 0.039 fg (0.15 mBq) for 241 Pu. The method was validated by analyzing plutonium isotopes in certificated reference materials and reported environmental samples of only 1-2 g. The analytical results of ultra-trace Pu isotopes in small amounts (~1 g) of lake sediments obtained by the developed method were successfully applied to sediment dating.