| In this paper, the dispersion of quantum dots (QDs) in epoxy matrix was effectively improved by surface functionalization of QDs. The influence of surface modification of QDs on its dispersion and the composite interface interaction were studied. Furthermore, the influence of composite structure on its performance was also discussed. Thus functional nanocomposites with excellent optical performances were prepared and used as light emitting diode (LED) encapsulation materials; Besides, a carbon quantum dots functionalized multi-walled carbon nanotubes (MWNTs@CQDs) nanocomposite had been prepared and used as solar photovoltaic materials. The photovoltaic properties of a quantum dots sensitized solar cell (QDSSC) based on the prepared MWNTs@CQDs active material were investigated.1. Epoxy group functionalized oleic acid (C18-epoxy) was successfully synthesized and utilized as an interface compatibilizer. And then, its aliphatic chain self-assembled with original oleic acid ligand of QDs. In this way, epoxy groups were introduced onto the QDs surface by the C18-epoxy. The modified QDs can homogenously disperse in nanocomposites because of similar polarity with epoxy. Compared with original ones, QDs@epoxy/epoxy nanocomposites exhibit almost 3.5 times transparence and twice luminescence. Furthermore, colorrendering index, correlated color temperature and (x, y) of the white LED, which was fabricated by nanocomposites (yellow light emitting) encapsulated InGaN chip, are 65,5260 K and (x=0.3381, y=0.3459), respectively.2. The original carbon quantum dots (CQDs) bearing -COONa groups were obtained via the dehydration of y-butyrolactone with concentrated sulphuric acid. And the CQDs were modified to bear carboxyl groups on the surface by treated with HC1 (CQDs@COOH). The COOH groups may join the curing of epoxy, making the CQDs covalently bond to the epoxy matrix. With such an approach, CQDs@COOH can be homogeneously dispersed without aggregation, and higher transparency and luminescence encapsulating nanocomposites can be obtained. Besides, the CQDs@COOH/epoxy nanocomposite exhibit excellent ultraviolet and thermal stability. Finally, CQDs@COOH/epoxy nanocomposites were employed to construct white LED devices. The colorrendering index, correlated color temperature and (x, y) are 66,7250 K and (x=0.3046, y=0.3122), respectively.3. Amido group modified CQDs (CQDs@NH2) were obtained through amide reaction based on CQDs@COOH. And double enhanced luminescence of CQDs@NH2 is obtained compared with CQDs@COOH because of the decrease of carboxyl groups as non-radiative recombination centers. Besides, optical properties of CQDs@NH2 in amine cured epoxy matrix were researched. Because functional group can participate in curing reaction, covalent bonding is formed and stably bridged the interface. With such a structure, homogenous dispersion of CQDs@NH2 can be readily obtained. Compared with nanocomposites incorporated with original CQDs or CQDs@COOH, CQDs@NH2/epoxy nanocomposites exhibit the highest transparency and strongest fluorescence. Finally, CQDs@NH2/epoxy nanocomposites were employed to construct white LED devices. The colorrendering index, correlated color temperature and (x, y) are 70,6220 K and (x=0.2924, y=0.3242), respectively.4. A facile approach for synthesizing a carbon quantum dots functionalized multi-walled carbon nanotubes (MWNTs@CQDs) nanocomposite had been carried out through chemical reaction between carboxyl and hydroxyl groups on each surface. The photovoltaic properties of a quantum dots sensitized solar cell (QDSSC) based on the prepared MWNTs@CQDs active material were investigated. Because CQDs can be covalent bonded onto MWNTs by forming an ester group, the excited electrons from the CQDs are effectively transferred to MWNTs with minimal energy loss. It is found that the photovoltaic conversion efficiency of QDSSC based on such MWNTs@CQDs active material reaches 1.23% when the thickness of the MWNTs@CQDs film is 5 ±0.5 μm. |
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