Green and Near-Infrared Dual-Mode Afterglow of Carbon Dots and Their Applications for Confidential Information Readout

Abstract

Near-infrared (NIR), particularly NIR-containing dual-/multi-mode afterglow, is very attractive in many fields of application, but it is still a great challenge to achieve such property of materials. Herein, we report a facile method to prepare green and NIR dual-mode afterglow of carbon dots (CDs) through in situ embedding o-CDs (being prepared from o-phenylenediamine) into cyanuric acid (CA) matrix (named o-CDs@CA). Further studies reveal that the green and NIR afterglows of o-CDs@CA originate from thermal activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) of o-CDs, respectively. In addition, the formation of covalent bonds between o-CDs and CA, and the presence of multiple fixation and rigid effects to the triplet states of o-CDs are confirmed to be critical for activating the observed dual-mode afterglow. Due to the shorter lifetime and insensitiveness to human vision of the NIR RTP of o-CDs@CA, it is completely covered by the green TADF during directly observing. The NIR RTP signal, however, can be readily captured if an optical filter (cut-off wavelength of 600 nm) being used. By utilizing these unique features, the applications of o-CDs@CA in anti-counterfeiting and information encryption have been demonstrated with great confidentiality. Finally, the as-developed method was confirmed to be applicable to many other kinds of CDs for achieving or enhancing their afterglow performances.

Multi‐Level Anti‐Counterfeiting and Optical Information Storage Based on Luminescence of Mn‐Doped Perovskite Quantum Dots

“…[5,6] Currently, anti-counterfeiting labels based on fluorescent patterns have been widely used in various areas around the world. [3][4][5][6][7][8] However, the traditional fluorescent labels can be readily copied or imitated, which are facing rampant counterfeiting phenomena and already cannot meet anti-counterfeiting demands. Therefore, developing advanced anti-counterfeiting technologies with improved security is imperiously demanded.…”

“…[11] Moreover, the information is encrypted by multidimensional parameters, such as wavelength, [12][13][14] luminescent lifetime duration, [15,16] phase [17] and polarization. [18] Carbon dots (CDs), [7,8] halide perovskites, [19][20][21][22] organic dyes, [4] semiconductor quantum dots [23] and nanoparticles [24][25][26] are promising luminescent materials for anti-counterfeiting owing to their superior photoluminescence (PL) intensity [27] and tunable PL behaviors. [28,29] For example, Zhang et al reported that the PL of perovskite nanocrystals encapsulated in lanthanide-based metal-organic frameworks (Ln-MOFs) can be quenched by water treatment, and recovered by adding CH 3 NH 3 Br solution, which realized the repeated fluorescent anti-counterfeiting.…”

Enabling robust and hour-level organic long persistent luminescence from carbon dots by covalent fixation

“…The syntheses of m-CDs, m-CDs@CA, and experimental cyanuric acid (i.e., eCA) were referenced in our previous reports 28 , 49 . The co-crystallized composite (i.e., m-CDs#CA) was prepared according to a literature method 47 .…”

Electron–phonon coupling-assisted universal red luminescence of o-phenylenediamine-based carbon dots

“…Among them, o-phenylenediamine (oPD) is one of the most important precursors to CDs due to its self-doping (i.e., N doping) behavior and low cost. oPD molecules have a conjugated structure and serve as both carbon and nitrogen sources, which are the key elements for PL centers 9 , 10 . Initially, only a variety of blue, green, and yellow emissive CDs with high PLQYs were prepared using oPD as the precursor 11 – 13 .…”