Carbon Dot-Silica Nanoparticle Composites for Ultralong Lifetime Phosphorescence Imaging in Tissue and Cells at Room Temperature

Abstract

Compared to fluorescence imaging with short-lived emissive probes, the use of phosphorescent probes conveys the advantage of long signal persistance in time and this permits one to discriminate against interference from autofluorescence. However, the realization of room temperature phosphorescence (RTP) probes that feature ultralong emission lifetimes in aqueous solution is still a challenge. Here, we present a rational strategy for realizing ultralong RTP in air-saturated aqueous media from carbon dot-based silica composites (CDs@SiO2) which feature emission lifetimes as long as 1.64 s. The excellent phosphorescence properties, their small size, and their water solubility make CDs@SiO2 a promising material for biological imaging application. We demonstrate their use as efficient reporters both in plant tissue and in animal cells where strong autofluorescence poses a severe challenge for conventional, short-lifetime probes.

Ultralong lifetime and efficient room temperature phosphorescent carbon dots through multi-confinement structure design

“…In the past decade, photoluminescence (PL) carbon dots (CDs) have triggered tremendous attention because of their facile preparation, high photo-stability, and low-toxicity 16 . Generally, CDs do not exhibit phosphorescence due to their unstable triplet excited states 17 , 18 . Great effort has been devoted to stabilizing triplet excited states of CDs through constructing hybrid systems of CDs in organic or inorganic matrices in order to achieve RTP 17 – 21 .…”

“…Generally, CDs do not exhibit phosphorescence due to their unstable triplet excited states 17,18 . Great effort has been devoted to stabilizing triplet excited states of CDs through constructing hybrid systems of CDs in organic or inorganic matrices in order to achieve RTP [17][18][19][20][21] . Auxiliary matrices, including inorganic complexes (e.g., KAl(SO 4 ) 2 •xH 2 O, SiO 2 , zeolites, layered double hydroxides (LDHs), etc.)…”

“…Auxiliary matrices, including inorganic complexes (e.g., KAl(SO 4 ) 2 •xH 2 O, SiO 2 , zeolites, layered double hydroxides (LDHs), etc.) [17][18][19][21][22][23][24][25] and polymers/organic compounds (e.g., poly(vinyl alcohol), polyurethane, cyanuric acid, urea, etc.) [26][27][28][29] , were exploited to fabricate a matrix-assisted isolation structure.…”

“…Compared to weak hydrogen bonds, covalent bonds can be employed as a much more effective alternative to fix and rigidify triplet emission species. Therefore, researchers tried to incorporate CDs into colloidal silica through covalent bonds, and some significant features such as long afterglow and aqueous-related afterglow were observed 17,22 , since the emissive moieties could be fixed on certain substances by covalent bonds. However, in previous reports, the carbon and silicon used are usually derived from separate sources, and the recombination of the CDs with the silica matrices are generally carried out at low temperatures, which makes it difficult to form very stable C-Si bonds.…”

Visible-Light-Excited Room Temperature Phosphorescent Carbon Dots

“…[13,[16][17][18][19][20][21][22][23][24]. Interestingly, RTP phenomena of CDs have been discovered recently by embedding or immobilizing in a variety of matrices, including poly (vinyl alcohol), polyurethane, layered double hydroxides, urea/biuret, zeolites and so on [25][26][27][28][29][30][31][32][33][34][35][36]. Although the introduction of matrices could realize RTP of CDs, the inherent chemical and physical properties of matrices would hinder applications of the RTP properties of CDs.…”