Abstract
In recent years, as a new type of carbon dots, carbonized polymer dots (CPDs) have attracted more and more attention in many fields. In this experiment, a new kind of CPDs was synthesized by the hydrothermal treatment of the chemically cross-linked sodium alginate (SA) via glutaraldehyde. The fluorescence of CPDs was greatly enhanced because of the cross-linking enhanced emission effect. The formation process of CPDs at different reaction temperatures was explored. In addition, it was found that CPDs have stable fluorescence properties in mild acidic/basic and metal-ion environments. The in vitro toxicity of CPDs was tested, and based on their nontoxic property, SA films with anti-ultraviolet aging properties were prepared by using CPDs as the additive.
Highlights
As a new type of fluorescent material, carbon dots (CDs), a kind of carbon-based nanomaterial, have attracted people’s attention in recent years.[1−3] Among various types of CDs, carbonized polymer dots (CPDs) are arising as a new kind of CDs, which have a large number of functional groups and polymer chains on the surface and can be seen as a transition material between polymer and fully carbonized CDs.[4−6] A plenty of collectively called CDs prepared by linear polymers or monomers through condensation polymerization, assembly, or slightly carbonization process can be classified as CPDs.[7]
Here we presented the preparation of CPDs with a controlled structure through the hydrothermal reaction of sodium alginate (SA) and glutaraldehyde, which served as the cross-linking agent for SA through the acetalation of hydroxyl and aldehyde groups
SG-CPDs with blue PL were synthesized from chemically cross-linked SA based on the cross-linking enhanced emission (CEE) mechanism
Summary
As a new type of fluorescent material, carbon dots (CDs), a kind of carbon-based nanomaterial, have attracted people’s attention in recent years.[1−3] Among various types of CDs, carbonized polymer dots (CPDs) are arising as a new kind of CDs, which have a large number of functional groups and polymer chains on the surface and can be seen as a transition material between polymer and fully carbonized CDs.[4−6] A plenty of collectively called CDs prepared by linear polymers or monomers through condensation polymerization, assembly, or slightly carbonization process can be classified as CPDs.[7]. Ethylenediamine, chitosan, or other N-containing compounds were incorporated in most of the research studies to ensure an N-doped structure of CPDs to enhance its fluorescent performance.[15] Yu et al prepared cationic CPDs by the hydrothermal reaction of SA and hydrogen peroxide.[16] Choi et al used SA and chitosan as raw materials to obtain CPDs by microwave treatment.[17] Fong et al prepared CPDs from SA nanoparticles preformed in the acid solvent in order to skip the surface passivation process.[18] it still lacks research that makes full use of the intrinsic properties of SA to precisely control the structure and enhance the fluorescent property of CPDs. Recently, Yang et al put forward the cross-linking enhanced emission (CEE) effect as a particular mechanism that attributes to the photoluminescence (PL) of CPDs, which refers to the fact that cross-linked structures (chemical or physical cross-linking) of CPDs can restrain the vibration and rotation of the subfluorophores and as a result decrease the nonradiation vibration, reduce the energy loss in the excited state, and enhance the fluorescence. The in vitro cytotoxicity of CPDs was tested, and CPDs were used as the anti-ultraviolet aging additive for SA films
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