Abstract
Here, we demonstrate the synthesis of mesoporous carbon dots (Cdot) from date palm fronds and their excellent excitation wavelength-independent photoluminescence (PL), with high photo- and storage-stability, superior biocompatibility and thermal and electrical conductivity for the first-time by a simple, green, one-step carbonization method. Interestingly, the as-obtained Cdot manifest the spherical shape of about 50 nm average diameter having surface mesopores of size less than 10 nm with sp2 hybridized carbon. The as-synthesised mesoporous Cdot, first of its kind, evince yellow-green PL (preferred over blue PL for biological applications) around 450 nm under excitation wavelength range of 320–420 nm with absolute quantum yield of 33.7% exhibiting high photo- and storage-stability. The thermal and electrical conductivity of Cdot/water nanofluids without any surfactants is illustrated. Application of Cdot as interfacial material in organic photovoltaic cell is manifested. The Cdot exhib visible sunlight driven photocatalytic and antibacterial activity. Mesoporous Cdot further reveal excellent biocompatibility with fibroblast cell (greater than 95% viability). The novelty of this study in the formation of multifunctional mesoporous Cdot from date palm fronds could inspire both research and industrial interests in the synthesis of biomass-derived Cdot and their application in a wide array of fields.
Highlights
As a new member of carbon family and potential alternative to classical metal based lethal semiconductor quantum dots and organic dyes[1], carbon dot has extraordinary benefits like simple and convenient synthesis and functionalization, prominent biocompatibility, colourful and stable photoluminescence, low cost and good resistance to photo and chemical degradation[2,3,4,5,6]
The carbonaceous material in date palm fronds gets oxygenated which is an important prerequisite for carbon dots (Cdot) synthesis
Green, cheap, ingenious, rapid, convenient and eco-friendly synthetic route to convert date palm fronds with inherent cross-linked lignocellulose structure into high value added Cdot by a simple carbonization approach
Summary
Is As ηs ηst 2 where QY is quantum yield, I is the integrated emission intensity, η is the refractive index, and A is the optical density, where s refers to Cdot and st to standard reference quinine sulphate[30]. The electrical resistance characterization of Cdot/water suspension was measured with Tektronix DMM 4050 multimeter. 0.1 mg of MO dye was added into the water (10 ml) containing 0.1 mg of Cdot, followed by the addition of 1 ml H2O2. The well plate was added with bacterial suspension (cell density of 106 CFU/ml) of around 170 μL and 30 μL Cdot at different concentrations (0 to 100 μg/ml). Viable cell numbers of both control and treated plated were determined via optical density measurement method after 16 hrs. The cells were treated with an optimized (from first experiment) concentration of Cdot for various time intervals to analyze their growth procedure in comparison to control. 100 μL of a fresh aqueous solution containing Cdot (10 or 100 mg/L) was added into cells containing plate with 1 mL culture medium. A non-treated cell was used as a control and the percent cell viability was calculated using Atest/Acontrol × 100, where Atest and Acontrol are the absorbance’s of the wells (with the Cdot) and control (without the Cdot), respectively
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