Dual emission carbon dots from carotenoids: Converting a single emission to dual emission

Abstract

Dual emission carbon dots have a high potential for use as fluorescence-based sensors with higher selectivity and sensitivity. This study demonstrated the possibility of conversion of a biological molecular system with a single emission peak to a double emission carbon dots system. This report is the first to describe the synthesis of dual emission carbon dots by tuning the electronic environment of a conjugated system.Here we prepared carbon dots from a natural extract, from which carotenoids were used as a new source for carbon dots. Formation of the carbon dots was confirmed by images obtained under a transmission electron microscope as well as from a dynamic light scattering study. The prepared carbon dots system was characterized and its optical property was monitored. The study showed that, after irradiation with microwaves, the fluorescence intensity of the whole system changed, without any change in the original peak position of the carotenoid but with the appearance of an additional peak. A Fourier transform infrared study confirmed breaking of the conjugated system. When using ethylene glycol as a surface passivating agent added to these carotenoid carbon dots, the dual emission spectra became more distinct.

Selective Bacterial Growth Inactivation by pH-Sensitive Sulfanilamide Functionalized Carbon Dots

“…Fourier transform infrared spectra (Figures b and S1c) elucidate the retention of surface functional moieties from citric acid and sulfanilamide molecules. The stretching frequencies for both CD2 and CD1 positioned at 3410, 3186, and 2981 cm –1 were ascribed to -OH, -NH 2 , and -CH moieties, respectively. − The FT-IR peaks at 1720, 1650, and 1400 cm –1 correspond to the stretching frequencies of CO and CC and the in-plane bending mode of the carboxylic O–H group. ,− The low-intensity peak at 1335 cm –1 corroborates the presence of SO on the surface of the CDs, and the medium-intensity peaks at 1160 and 1120 cm –1 were assigned as C–O and C–S stretching frequencies. − Additionally, X-ray photoelectron spectroscopy (XPS) data of CD2 and CD1 in Figures and S2 also attest to the presence of molecular fragments of precursors on the CD surface. The deconvoluted spectrum of C 1s (CD2) was associated with five different types of carbon species, designated as sp 2 CC (284.2 eV), C–C/C–H (284.8 eV), C–S/C–N (285.2 eV), C–O and CO (286.5 and 288.7 eV). ,− The deconvoluted high-resolution spectra of N 1s display three peaks at 399.1, 399.9, and 401 eV assigned to C–N, N–H, and S–N groups, respectively. , Deconvoluted O 1s spectral position resembles the SO (531.5 eV), CO/–COOH (532 eV), and C–OH (532.7 eV) functional moieties of CDs. , The peaks at 169 and 170 eV of S 2p high-resolution spectra can be attributed to S–N and SO groups, once again assuring the presence of the sulfanilamide unit on the CD’s surface. ,− …”

Reversible light-controlled fluorescence switch of block polymer-grafted carbon dots and cellular imaging

“…Reversible light-controlled fluorescence switches (RLCFSs), due to their highly sensitive and reversible fluorescence response under light stimulation, 1,2 have attracted much attention for their wide applications in many fields, such as sensors, 3,4 imaging, 5,6 and data storage. 7,8 The traditional strategy for the construction of RLCFSs is to use photodynamic-responsive molecules and fluorophores.…”