Toward structurally defined carbon dots as ultracompact fluorescent probes.
There has been much discussion on the need to develop fluorescent quantum dots (QDs) as ultracompact probes, with overall size profiles comparable to those of the genetically encoded fluorescent tags. In the use of conventional semiconductor QDs for such a purpose, the beautifully displayed dependence of fluorescence color on the particle diameter becomes a limitation. More recently, carbon dots have emerged as a new platform of QD-like fluorescent nanomaterials. The optical absorption and fluorescence emissions in carbon dots are not bandgap in origin, different from those in conventional semiconductor QDs. The absence of any theoretically defined fluorescence color-dot size relationships in carbon dots may actually be exploited as a unique advantage in the size reduction toward having carbon dots serve as ultracompact QD-like fluorescence probes. Here we report on carbon dots of less than 5 nm in the overall dot diameter with the use of 2,2'-(ethylenedioxy)bis(ethylamine) (EDA) molecules for the carbon particle surface passivation. The EDA-carbon dots were found to be brightly fluorescent, especially over the spectral range of green fluorescent protein. These aqueous soluble smaller carbon dots also enabled more quantitative characterizations, including the use of solution-phase NMR techniques, and the results suggested that the dot structures were relatively simple and better-defined. The potential for these smaller carbon dots to serve as fluorescence probes of overall sizes comparable to those of fluorescent proteins is discussed.
Department of Chemistry and Laboratory for Emerging Materials and Technology, Clemson University , Clemson, South Carolina 29634, United States.
Gregory Ethan
GE
LeCroy
Sumit Kumar
SK
Sonkar
Fan
F
Yang
L Monica
LM
Veca
Ping
P
Wang
Kenneth N
KN
Tackett
Jing-Jiang
JJ
Yu
Eugeniu
E
Vasile
Haijun
H
Qian
Yamin
Y
Liu
Pengju George
PG
Luo
Ya-Ping
YP
Sun
D000818:Animals; D002244:Carbon / Q000737:chemistry; D002247:Carbon Isotopes / Q000737:chemistry; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry*; D049452:Green Fluorescent Proteins / Q000737:chemistry; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008422:Materials Testing; D018625:Microscopy, Atomic Force; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry; D036103:Nanotechnology / Q000379:methods*; D037742:Nanotubes, Carbon / Q000737:chemistry*; D010316:Particle Size; D045663:Quantum Dots / Q000737:chemistry*; D012666:Semiconductors; D013053:Spectrophotometry; D013499:Surface Properties
D002247:Carbon Isotopes; D005456:Fluorescent Dyes; D037742:Nanotubes, Carbon; D049452:Green Fluorescent Proteins; D002244:Carbon