Abstract
In this work, we present the fabrication of highly luminescent carbon dots (CDs) by a double passivation method with the assistance of Ca(OH)2. In the reaction process, Ca2+ protects the active functional groups from overconsumption during dehydration and carbonization, and the electron-withdrawing groups on the CD surface are converted to electron-donating groups by the hydroxyl ions. As a result, the fluorescence quantum yield of the CDs was found to increase with increasing Ca(OH)2 content in the reaction process. A blue-shift optical spectrum of the CDs was also found with increasing Ca(OH)2 content, which could be attributed to the increasing of the energy gaps for the CDs. The highly photoluminescent CDs obtained (quantum yield: 86%) were used to cultivate fluorescent carnations by a water culture method, while the results of fluorescence microscopy analysis indicated that the CDs had entered the plant tissue structure.
Highlights
As an emerging class of photoluminescent nanomaterials, carbon dots (CDs) have attracted considerable attention owing to their outstanding photostability, high biocompatibility, and tunable photoluminescence (PL) [1–5]
Because of the high quantum yield (QY) and low cytotoxicity, an exploratory experiment was performed to assess the potential application of Ca-2-CD for cultivating fluorescent flowers
Ca2+ could protect the active functional groups from overconsumption during dehydration and carbonization, and electron-withdrawing groups could be converted to electron-donating groups (–OH) on the CD surface by hydroxyl ions
Summary
As an emerging class of photoluminescent nanomaterials, carbon dots (CDs) have attracted considerable attention owing to their outstanding photostability, high biocompatibility, and tunable photoluminescence (PL) [1–5]. It is especially important to enhance the PL by adjusting the surface chemistry of CDs [11,12]. A surface passivation agent containing amino groups, has reportedly been used to prepare highly photoluminescent CDs by a hydrothermal method [15]. The active functional groups, such as amino and carboxyl groups, could be overconsumed during the reaction process, which might limit the PL quantum yield (QY) of the product [16]. It would be feasible to enhance the PL QY by choosing an appropriate agent that protects the active functional groups from overconsumption during the reaction process, and reduces the number of electron-withdrawing groups on the CD surface. DNuanroimnagtertihales 2r0e1a7,c7ti,o17n6 process, and reduces the number of electron-withdrawing groups on[2] otfh1e0 CD surface. Finusrethcteramttorarcet,iothneteresstuslhtsowofedanthinatsetchteafltturaocrteisocnentet sflt oswhoewrseadrethmatortheeatftlruaocrteivsceentot finloswecetrssthaarne nmonoflreuoarettsrcaecntitvoenetsoininasnecotustdthoaonr ennovnirfolunmoreensct,ebnetnoefinetisnginfroamn tohuetUdoVoirrreandviaitrioonnmfreonmt, bsoelnaerfsitpinecgtrfuromm. the UV irradiation from solar spectrum
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