Anchoring Carbon Nanodots onto Nanosilica for Phosphorescence Enhancement and Delayed Fluorescence Nascence in Solid and Liquid States

Abstract

photophysical properties that are potentially useful for different applications. [1-5] One of the many fascinating properties of CDs is its fluorescence. Many reports have shown that the fluorescence of CDs originates from the surface fluorophore and graphitizing core. [6-9] However, the transition between singlet and triplet states occurs with extremely low probability due to the spin-forbidden, hence the room temperature phosphorescence (RTP, T 1 →S 0) and thermally activated delayed fluorescence (TADF, transitions T 1 →S 1 →S 0) are difficult to be achieved under ambient conditions. [10-12] Other than that, afterglow from pure CDs is seldom observed and studied. [13-17] A selfquenching resistance CDs with RTP lifetime of 13.4 ms were induced by polyvinyl alcohol (PVA) chains from Liu's group. [13] Through seeded growth method, Andrey et al. prepared several phosphorescent CDs powders with average decay lifetime ranging from 52 to 419 ms. [14] Yang's group focused on suppressing the nonradiative transitions having achieved the adjustable decays between 188 and 658 ms. [15] Feng and co-workers found that fluorine and nitrogen codoped CDs with RTP could realize the decay lifetime of 141 to 1210 ms by adjusting pH values. [16] It is noteworthy that long-lived emission (LLE) about 1.46 s of CDs powder was successfully achieved via microwave irradiation but with very poor ability to resist moisture that RTP totally disappeared in solution and also quite faint emission intensity only with quantum yield (QY) of 3.53% by Lin et al. [17] As for these pure CDs, phosphorescence that is responsible for the total afterglow without TADF component only lasts for a few seconds accompanied by a relatively low phosphorescent efficiency. Furthermore, these pure CDs have extremely poor stability, thus afterglow of them was completely quenched by oxygen or moisture, causing the RTP to be only captured in powdery CDs rather than solution. [13-17] Nevertheless, a great deal of effort was devoted to improving the afterglow behavior. In some cases, the RTP can be ameliorated by introducing heavy atoms, such as halogens and metals which enhanced the intersystem crossing (ISC) process attributed to the strong spin-orbit coupling. [18,19] Alternatively, embedding CDs in solid matrices that serve Carbon nanodots (CDs) anchored onto inorganic supporter (amorphous nanosilica, SiO 2) like a core-satellite structure have enhanced the room-temperature phosphorescence (RTP) intensity along with ultralong lifetime of 1.76 s. Special and quite stable structure should account for these superiorities, including hydrogen network, covalent bond, and trap-stabilized triplet-state excitons that are responsible for the generation of phosphorescence. These multiple effects have efficaciously protected CDs from being restrained by the external environment, providing such long-lived emission (LLE) that can subsist not only in powdery CDs-SiO 2 but also coexist in aqueous solution, pushing a big step forward in the application prospects of liquid-state phosp...

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

“…450 to 620 nm), and PL excitation spectrum at 550 nm and afterglow excitation spectrum at 690 nm (Fig. 3a), the two afterglow emission bands could be tentatively attributed to TADF (λ max = 550 nm) and RTP (λ max = 690 nm) of o-CDs@CA [35,43]. To further confirm such an assumption, their temperature-dependent afterglow emission properties were investigated.…”

“…In comparison with hydrogen bonds, the stronger covalent bonding fixation is beneficial for extending occurrence of afterglow from solid state to dispersion state, and meanwhile for achieving RTP and TADF dualmode afterglows by appropriately decreasing the energy gap between the singlet state (S 1 ) and triplet state (T 1 ) (ΔE ST ) of CDs [32]. Besides, multiple fixation of triplet states by covalent bonds, hydrogen bonds and physical confinements (e.g., rigid network and nanoscale spaces of matrices) had been confirmed enabling more effectively activating afterglow emissions of CDs [33][34][35]. Inspired by these results, we suppose that NIR-containing dual-mode afterglow emission from CDs could be obtained by taking proper CDs (with potential NIR afterglow property) and a high-efficient manner to fix them.…”

Energy Transfer Mediated Enhancement of Room‐Temperature Phosphorescence of Carbon Dots Embedded in Matrixes

“…[3] Considering the excellent water solubility and easy handle, nonmatrix CDs express good potential in ink printing for anticounterfeiting and information encryption/decryption, [3b,4] which is of great significance to the development of CDs. Unfortunately, it has been noticed that pure CDs have very poor stability under ambient conditions, [5] whose afterglow emission totally quenched by oxygen or moisture unless stored in a dryer, which is very unfavorable for practical application.…”

“…[11] In addition, enhanced phosphorescence can be obtained through defects-assist stabilizing triplet state excitons of CDs. [5,12] However, the fabrication of CD-based afterglow materials with ultralong phosphorescence lifetime or long-wavelength afterglow emission originates from CDs remains a challenge.…”

Preparation and characterization of F-, O-, and N-containing carbon nanoparticles for pH sensing

“…Within the phenomenon, pH sensors were already proposed (Benilov et al 2007). Besides, when diferent luminescent NPs are storage in the porous Si and nanosilicas, they can be used as speciic probe units in multicomponent sensors (Serdiuk et al 2011;He et al 2020).…”