Luminescent Mechanism and Anti-Counterfeiting Application of Hydrophilic, Undoped Room-Temperature Phosphorescent Silicon Nanocrystals

Silicon nanocrystals (SiNCs) have attracted extensive attention in many advanced applications due to silicon's high natural abundance, low toxicity, and impressive optical properties. However, these applications are mainly focused on fluorescent SiNCs, little attention is paid to SiNCs with room-temperature phosphorescence (RTP) and their relative applications, especially water-dispersed ones. Herein, this work presents water-dispersible RTP SiNCs (UA-SiNCs) and their optical applications. The UA-SiNCs with a uniform particle size of 2.8 nm are prepared by thermal hydrosilylation between hydrogen-terminated SiNCs (H-SiNCs) and 10-undecenoic acid (UA). Interestingly, the resultant UA-SiNCs can exhibit tunable long-lived RTP with an average lifetime of 0.85 s. The RTP feature of the UA-SiNCs is confirmed to the n-& pi;* transitions of their surface CO groups. Subsequently, new dual-modal emissive UA-SiNCs-based ink is fabricated by blending with sodium alginate (SA) as the binder. The customized anticounterfeiting labels are also prepared on cellulosic substrates by screen-printing technique. As expected, UA-SiNCs/SA ink exhibits excellent practicability in anticounterfeiting applications. These findings will trigger the rapid development of RTP SiNCs, envisioning enormous potential in future advanced applications such as high-level anti-counterfeiting, information encryption, and so forth. Aqueous-dispersed, undoped silicon nanocrystals (UA-SiNCs) with Room-temperature phosphorescence (RTP) are reported first. Interestingly, the n-& pi;* transitions of the CO on surfaces of UA-SiNCs play a crucial role in generating RTP. Subsequently, new UA-SiNCs-based ink is fabricated by employing sodium alginate (SA), finding the ink has enormous potential in future advanced applications including high-level anticounterfeiting, data storage, and information encryption.image

Automated summary

Water-dispersed silicon nanocrystals with room-temperature phosphorescence have been successfully synthesized and applied in anticounterfeiting ink, showing excellent practicability.