Facile Synthesis And Fluorescence Properties Of Color-Tunable CuInS₂-Based Nanocrystals

CuInS2quantum dots, with their high absorption coefficient, stable fluorescence performance, low biotoxicity and large stokes shift, has been intensively investigated and gradually replaced traditional quantum dots to become a new generation of fluorescent nanocomposites. However, due to its band gap, the emission range of CuInS2is limited to near infrared region. As a result, how to improve the performances of CuInS2quantum dots, broaden the region of fluorescence emission and promote the application in all fields demands urgent and immediate attention. This thesis is devoted to developing new and feasible strategies for CuInS2-based nanocrystals with wide fluorescence emission region and excellent properties. Main researches and the results as follows:(1) CuInS2nanocrystals of high-quality were prepared by a simple, effective method, and the fluorescence emission colors could be varied from NIR to orange through controlled reaction conditions. After the surface passivation with ZnS shell, a dramatic improvement on PL intensity and stability could be viewed for all the CuInS2NCs. At the same time, an obvious blue-shift in the PL emission appeared during passivation process, which was a benefit to broaden the fluorescence emission region of CuInS2-based nanocrystals.(2) CuxInS2-based nanocrystals with different Cu:In ratios were designed, and the effects of Cu:In ratio to reaction conditions were intensive studied. Compared with CuInS2quantum dots, the fluorescence emission region of CuxInS2nanocrystals was easily broadened, of which the emission colors covered red, orange and yellow. In addition, except for the varied fluorescence emission wavelength, further study showed that the fluorescence intensity of CuxInS2nanocrystals could varied in linear with the change of Cu:In ratios.(3) Highly luminescent Cu-In-Zn-S alloyed NCs were synthesized through a stepwise approach.By adjusting diffusion temperature, the CIZS NCs exhibited broad PL spectra with tunable emission colors from green to NIR region, which was a further improvement. After the deposition of ZnS shell, the PLQY increased substantially with a maximum value of75.8%. The single exponential PL decay with an increased average lifetime suggested a suppressed nonradiative recombination process related to structural defects. Therefore, the obtained NCs exhibit promising applications in cell imaging, LEDs and solid-state lighting.