Activating efficient room temperature phosphorescence of carbon dots by synergism of orderly non-noble metals and dual structural confinements

Abstract

Obtaining high efficiency room temperature phosphorescence (RTP) by employing non-noble metals poses two challenges: (1) strengthening spin-orbit coupling of excitons to improve the rate of intersystem crossing (ISC) by using non-noble metals with small-atomic-number; (2) employing structural confinement to enhance radiation relaxation because harsh conditions, including carefully selected matrices, rigid solid-state crystalline structure and low temperature, are commonly needed. Here, layered double hydroxides (LDHs) with orderly non-noble metal arrangements were used as an inorganic matrix to activate RTP of carbon dots (CDs). The Zn orderly arranged on the LDH layer contributes to the enhancement in spin-orbit coupling of excitons and the decrease in the energy gap for the singlet-triplet state. The structural confinements of the LDH layer and nano-interlayer testify that the phosphorescence of CDs-LDHs originates from the suppressed radiationless relaxation processes. Using the high tunability of metal species and ratios on the LDH layer, this method can be widely applied to optimize ISC and phosphorescence properties.

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

“…Recently, a green afterglow with a lifetime of 1.8 s has been reported in a CDs@nSiO 2 phosphorescence composite . The RTP of CDs with a lifetime of 386.8 ms is presented in CDs@LDHs assisted by an orderly arrangement of metals and a rigid and confined LDH layer …”

“…Interestingly, the bridge‐like H‐bonded networks similar to matrices were formed between CDs and CA after putting CDs@CA powder in water. In addition, CDs can be embedded in the silica gel and layered double hydroxides (LDHs) matrices to generate CDs‐based composites …”

Self‐Protective Room‐Temperature Phosphorescence of Fluorine and Nitrogen Codoped Carbon Dots

“…And specific molecular configuration and special intermolecular interactions are requisite for RTP function . As an added benefit, RTP carbon dots (CDs) can be utilized as ideal agents for high‐security materials because they allow the elimination of short‐lived background fluorescence, as well as high photostability, high (aqueous) solubility, low toxicity, excellent biocompatibility, and cost‐effective preparation …”

“…Some CD‐based RTP materials have already been reported. However, the typical methods for obtaining these RTP materials involves embedding CDs into a polymer matrix (e.g., poly(vinyl alcohol), polyurethane, and silica gel), layered double hydroxides, host matrices, two‐component matrices, or similar systems. These matrices are crucial for stabilizing phosphors with regards to the long lifetime triplet state, which can be easily quenched by molecular vibrations, oxygen molecules, and high temperatures .…”

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

“…[15,19,34] According to these considerations,w ehave found ao nepot method for the facile and quick preparation of ultralong RTP( URTP) CDs.A ss hown in Figure 1a,b,g ram-scale URTP CDs can be obtained in afew minutes via microwaveassisted heating of an ethanolamine and phosphoric acid aqueous solution, and subsequent dialysis purification and freeze-drying (more details in Supporting Information). [26][27][28][29][30][31][32] Note that the as-developed method features facile,quick and scalable merits,t he obtained product possesses URTP life-time and could potentially be employed as security ink in anti-counterfeiting and information protection. Importantly,t he CDs present the longest RTPlifetime to be 1.46 s(more than 10 s to naked eye,F igure 1c and Video 1i nS upporting Information) among the reported CDs-based materials to date.…”