Visible Light‐Activated Ultralong‐Lived Triplet Excitons of Carbon Dots for White‐Light Manipulated Anti‐Counterfeiting

Abstract

Room temperature phosphorescence (RTP) has emerged as an interesting but rare phenomenon with multiple potential applications in anti‐counterfeiting, optoelectronic devices, and biosensing. Nevertheless, the pursuit of ultralong lifetimes of RTP under visible light excitation presents a significant challenge. Here, new phosphorescent materials that can be excited by visible light with record‐long lifetimes are demonstrated, realized through embedding nitrogen doped carbon dots (N‐CDs) into a poly(vinyl alcohol) (PVA) film. The RTP lifetime of the N‐CDs@PVA film is remarkably extended to 2.1 s excited by 420 nm, representing the highest recorded value for visible light‐excited phosphorescent materials. Theoretical and experimental studies reveal that the robust hydrogen bonding interactions can effectively reduce the non‐radiative decay rate and radiative transition rate of triplet excitons, thus dramatically prolong the phosphorescence lifetime. Notably, the RTP emission of N‐CDs@PVA film can also be activated by easily accessible low‐power white‐light‐emitting diode. More significantly, the practical applications of the N‐CDs@PVA film in state‐of‐the‐art anti‐counterfeiting security and optical information storage domains are further demonstrated. This research offers exciting opportunities for utilizing visible light‐activated ultralong‐lived RTP systems in a wide range of promising applications.

Rapid Realization of Multicolor Room Temperature Phosphorescence of Carbon Dot-Based Composites on Natural Polymer Matrix Platforms

“…However, we found that compared with those of the corresponding CDs (3450 and 3440 cm –1 ) and CMSNa (3440 cm –1 ), the characteristic peaks of HA-CDs-CMSNa and Nap-CDs-CMSNa exhibited slight shifts in the level of O–H at 3460 cm –1 . This phenomenon indicates the formation of hydrogen bonds between the two CDs and the CMSNa matrix . Similarly, as shown in Figure S5c,d, the characteristic peaks of Nap-CDs-CMCS and HA-CDs-CMCS at 3430 cm –1 also show slight changes from those of the corresponding CDs (3440 and 3450 cm –1 ) and CMCS (3440 cm –1 ), indicating that hydrogen bonds are also formed between the two CDs and the CMCS matrix.…”

“…This phenomenon indicates the formation of hydrogen bonds between the two CDs and the CMSNa matrix. 44 Similarly, as shown in Figure S5c,d, the characteristic peaks of Nap-CDs-CMCS and HA-CDs-CMCS at 3430 cm −1 also show slight changes from those of the corresponding CDs (3440 and 3450 cm −1 ) and CMCS (3440 cm −1 ), indicating that hydrogen bonds are also formed between the two CDs and the CMCS matrix. In addition, compared with Nap-CDs and HA-CDs, Nap-CDs-CMCS and HA-CDs-CMCS show weak new peaks at 1030 and 1120 cm −1 , respectively, which are caused by the stretching vibration of the C−N bond, indicating that the partial carboxyl groups on the surface of CDs may react with partial amino groups in CMCS to form amide bonds, thus further connecting the CDs to CMCS chains.…”

Blue Light-Excited Carbon Dot/C3N4 Nanocomposites with Long-Lived Thermally Activated Delay Fluorescence for Anti-Counterfeiting and Illumination

“…UV irradiation not only has the potential risk for human health and may be easily mimicked, but it is also inconvenient in daily life. 29 In contrast, a low-power white light source (such as a flashlight on a mobile phone) is safer for human health and has been widely used in our daily lives and is more convenient to acquire and apply. To our knowledge, only a few reports have realized visible light-excited TADF via dropping some electronegative elements (such as composite matrix to redshift the absorption bands.…”

“…could protect the triplet states via the covalent or hydrogen bonds. − A series of CDs@ zeolite composite systems were proposed by Yu’s groups in recent years, and these composites exhibit various TADF emissions due to the rigid structures via the covalent bonds between matrix materials and CDs. − However, most CDs-based TADF emissions have reported a need for the excitation illumination of UV light (<400 nm) due to the limitation of absorption bands. UV irradiation not only has the potential risk for human health and may be easily mimicked, but it is also inconvenient in daily life . In contrast, a low-power white light source (such as a flashlight on a mobile phone) is safer for human health and has been widely used in our daily lives and is more convenient to acquire and apply.…”

Carrier Injection Tailoring and Electroluminescence Properties of Carbon Dots in Electroluminescent Light‐Emitting Diodes

“…For assembling CD-based LEDs, one uses CDs as emitters by constructing multilayer electroluminescent devices, while the other uses photoluminescence (PL) characteristics of CDs pumped by conventional GaN-based UV or blue LED chips. [7][8][9][10][11][12][13] The former benefits to realizing large-size displays and lighting. The stateof-the-art CDs-based electroluminescent LEDs are assembled using pure CDs emitter [14][15][16][17][18] or CDs-doped guest-host emitting system.…”