Synthesis Of Aqueous Fluorescent Nanocrystals And Novel Composites

In recent decades, the application of solid-state lighting, such aslight-emitting diodes (LEDs), shows overwhelming promise in meeting thechallenge of saving energy owing to its lower threshold voltage, lower powerand higher brightness. As an important part, the color-converting layer plays akey role in determining Commission Internationale de l’Eclairage chromaticitycoordinates, color rendering index, correlated color temperature, and luminousefficacy of LEDs. Currently, utilizing fluorescent nanocrystals (NCs) ascolor-converting layer have maken some progress, whereas these achievementsare limited in laboratory. Therefore, it is particularly important to investigate thesynthesis of aqueous NCs and NCs-polymer composites. In this paper, we aim todevelop aqueous synthesis approach of NCs, investigate the growth mechanism,and finally prepare composite material.In the second chapter, the nucleation of aqueous semiconductor NCs isidentified by investigating the evolution of precursor solution and the subsequentN2H4-promoted growth at room temperature. Experimental results indicate thatthe highly crystalline nucleus contribute greatly to the fluorescence of theas-prepared NCs, which is particularly important for synthesizing highlyluminescent NCs with small size and alloyed structure. Then, through a room-temperature N2H4-promoted strategy, water-soluble CdTe NCs are facilelysynthesized by a stepwise addition of raw materials in one pot. Noprepreparation of precursors, pH adjustment, heating, and even N2protection arerequired.In the third chapter, on the basis of the studies about the surface liganddynamics of aqueous NCs, highly luminescent NCs-cellulose composites areprepared and employed to fabricate high color purity LEDs. Next, on the basis ofstudying one-pot synthesis, spontaneous assembly, and in situ polymerization ofaqueous NCs, NC self-assembly materials are produced and applied to designhigh performance white LED (WLED). By mixing self-assembly materials withdifferent emissions, NC-based WLED with high color rendering index (86), highluminous efficacy (41lm/W), and controllable color temperature is fabricated.In the fourth chapter, we investigate the temperature sensitivity of aqueousNCs. Upon a multiple covalent linkage of macrocyclic compounds with NCs, forexample, thiolated cyclodextrin (CD) and CdTe, the conformation-relatedtorsional force of CD is conducted to the inner lattice of CdTe under alteredtemperature. And CdTe NCs with temperature sensitivity of0.28nm/oC arefabricated. Upon this resulte, we successfully synthesize CdSexTe1-xNCs withdifferent temperature sensitivities through adjusting the ratio of Se to Te.Afterwards, CdSexTe1-x-based self-assembly matrials with low temperaturesensitivity is fabricated.