Facile, Quick, and Gram‐Scale Synthesis of Ultralong‐Lifetime Room‐Temperature‐Phosphorescent Carbon Dots by Microwave Irradiation

Abstract

Long-lifetime room-temperature phosphorescence (RTP) materials are important for many applications, but they are highly challenging materials owing to the spin-forbidden nature of triplet exciton transitions. Herein, a facile, quick and gram-scale method for the preparation of ultralong RTP (URTP) carbon dots (CDs) was developed via microwave-assisted heating of ethanolamine and phosphoric acid aqueous solution. The CDs exhibit the longest RTP lifetime, 1.46 s (more than 10 s to naked eye) for CDs-based materials to date. The doping of N and P elements is critical for the URTP which is considered to be favored by a n→π* transition facilitating intersystem crossing (ISC) for effectively populating triplet excitons. In addition, possibilities of formation of hydrogen bonds in the interior of the CDs may also play a significant role in producing RTP. Potential applications of the URTP CDs in the fields of anti-counterfeiting and information protection are proposed and demonstrated.

Carbon Dots‐in‐Matrix Boosting Intriguing Luminescence Properties and Applications

“…In summary, for TADF materials, the energy gaps (ΔE st ) between the singlet state (S 1 ) and the triplet state (T 1 ) should be sufficiently small so that the nonradiative triplet excitons can transform into radiative singlet excitons through the RISC process . For RTP materials, the efficient spin‐orbit coupling should be acquired for triplet excitons by enhancing the ISC process, thus leading to larger energy gaps between S 1 and T 1 . The key effect of host matrices is to stabilize and protect the triplet states of embedded CDs and suppress the nonradiative transitions.…”

Non‐Metal‐Heteroatom‐Doped Carbon Dots: Synthesis and Properties

“…The authorsf abricateaw hite-light-emitting device by combining an ultraviolet chip with the N,P-co-doped CDs as a phosphor,a ss hown in Figure 8B.J iang et al disclose a methodf or the preparation of room-temperature phosphorescent N,P-co-dopedC Ds by microwave-assisted heating treatment of ethanolaminea nd phosphoric acid. [54] The N,P-codoped CDs in the solid state display al ong afterglow lifetime of 1.46 sa nd more than 10 st ot he naked eye. The authors also confirm that high doping contents of the Na nd Pa toms are ap rerequisite to facilitate the intersystem crossing process and, consequently,p hosphorescence emission.…”

Carbon Dots with Dual‐Emissive, Robust, and Aggregation‐Induced Room‐Temperature Phosphorescence Characteristics

“…Although CDs‐based RTP with diverse properties had been achieved, matrices (for example, polyvinyl alcohol, polyurethane, urea/biuret, and boric acid) usually have to be used to immobilize CDs and subsequently stabilized their excited triplet state . To further expand the applications, however, it is required to prepare effective and self‐protective RTP CDs (that is, non‐composite with matrices), but this is more challenging and had been rarely reported so far …”

“…[26][27][28][29][30][31][32] To further expand the applications,h owever,i ti sr equired to prepare effective and self-protective RTPC Ds (that is,n on-composite with matrices), but this is more challenging and had been rarely reported so far. [33][34][35] Since its discovery by Tang et al in 2001, [36] aggregationinduced emission (AIE) has attracted more and more research interest in the last two decades. [37,38] Contrary to the traditional fluorophores,m aterials with AIE properties are known to exhibit intense fluorescence (FL) only at solid or aggregated state but are not emissive in ad ilute solution.…”