Heavy carbon nanodots: a new phosphorescent carbon nanostructure

Abstract

Carbon nanodots are nanometer sized fluorescent particles studied for their distinct photoluminescent properties and biocompatibility. Although extensive literature reports the modification and application of carbon nanodot fluorescence, little has been published pertaining to phosphorescence emission from carbon nanodots. The use of phosphors in biological imaging can lead to clearer detection, as the long lifetimes of phosphorescent emission permit off-gated collection that avoids noise from biological autofluorescence. Carbon nanodots present a desirable scaffold for this application, with advantageous qualities ranging from photostability to multi-color emission. This research reports the generation of a novel phosphorescent "heavy carbon" nanodot via halogenation of the carbon nanodot structure. By employing a collection pathway that effectively incorporates bromine into the nanostructure, T1 triplet character is introduced, and subsequently phosphorescence is observed in liquid media at room temperature for the first time in the nanodot literature. Further experiments are reported characterizing the conditions of observed phosphorescence and its pH-dependence. Our approach for producing "heavy carbon nanodots" is a low-cost and relatively simple method for generating the phosphorescent nanodots, which sets the foundation for its potential future use as a phosphorescent probe in application.

Carbon Nanodots in Photodynamic Antimicrobial Therapy: A Review

“…An example of this is the combustion-based collection of carbon nanodots from methane gas, established by Schmitz et al from our laboratory [ 44 ]. This strategy has been further adapted by us to achieve carbon dot structures of different photophysical characteristics [ 46 , 47 ]; the results of some of these studies will be discussed herein. Although many of the aforementioned synthesis methods can be found in the literature, hydrothermal treatment in either a top-down or bottom-up regime is most commonly employed.…”

“…In a recent report by our lab, the antimicrobial effects of brominated carbon nanodots from photosensitization by UVA light (long wavelength, 365 nm) were studied using Gram-positive Staphylococcus aureus as a model bacterium ( Figure 4 a,b). Previous reports had characterized brominated carbon nanodots (BrCNDs) to be weakly fluorescent, with a phosphorescent signal emerging following bromination that was otherwise unobserved in the non-bromine-containing carbon dots collected by the same combustion-based method [ 46 ]. This phosphorescent signal was found to be pH-dependent, detectable only in acidic environments; at higher pH, fluorescence intensities were restored, and phosphorescence was lost.…”

Influence of humidity on tribo-electric charging and segregation in shaken granular media

“…Such water layers are ubiquitous, however their thickness is limited to the order of a few nm [3,59] as long as the ambient humidity is below 100 %RH [60,61]. Already in 1902, Knoblauch hypothesized that the H + and OH − ions dissolved in the water adsorbed to the surface of polar solids would be reasonable charge carriers [62]. Subsequent experimental observations confirmed the idea of the importance of surface water, however a consistent picture of its role still has to emerge.…”

Visible-Light-Excited Room Temperature Phosphorescent Carbon Dots

“…The AA-CDs-2, however, exhibit similar RTP properties as that of the AA-CDs in the solid state ( Figure S9b, SM), including the visible-light excitable feature ( Figure S10, SM). The quantum yields (QYs) were found to decrease from the AA-CDs (22.45%) to the AA-CDs-2 (18.55%) (Table S1 in SM), implying some of the fluorophores on AA-CDs being consumed when they are subjected to further carbonization [47,63,64].…”

“…More importantly, matrix-free RTP CDs have also been prepared very recently based on the concept of crosslink enhanced emission (CEE), selfimmobilization fluorophores and specific elements (e.g., N, P and halogens) doping [37][38][39][40][41][42][43][44][45][46][47]. The reported matrix-free RTP CDs, however, only showed RTP emission colors from green to yellow and have to be excited by UV light as well [37][38][39][40][41][42][43][44][45][46][47]. To further expand the applications, it is significant to develop matrix-free RTP CDs holding long-wavelength (orange to red, and even to near infrared (NIR)) emissions and capable of being excited by visible-light, but this is still a formidable challenge.…”