Study of self- assembly structures of carbon quantum dots

Self-assembly (SA) structures are formed by self-organizing processes in which discrete elements interact spontaneously with one another to produce larger and more complex structures. Compared to disorganized systems, self-assembled nanoparticles with specific functionalities can exhibit enhanced or even novel properties. Among the various nanoparticles capable of forming SAs, we can highlight carbon quantum dots (Cdots). Cdots are photoluminescent core/shell semiconductor nanoparticles with excellent optical properties, such as photo-stability, size-dependent emission energy, and intensity sensitivity to particle aggregation. Thus, the organization of individual Cdots in ordered structures on solid substrates has the potential for possible nanodevices in the area of sensors, catalysis, optoelectronics, and data storage. This study aimed to produce Cdots-based SAs and subsequently study their morphological and optical properties. Cdots were obtained by electrochemical exfoliation of the graphite electrode, and SA structures were obtained by the induced evaporation method under controlled temperature. The effects of the temperature and volume of the deposited Cdots solution in the substrate on the formation of SA were investigated. Optical and fluorescence microscopy images showed the formation of photoluminescent SA structures up to 1 mm in size with different aggregation patterns, such as aggregation by limited diffusion, river-type fractal, fern-leaf-type fractal, films, and bifurcated patterns. The variation of the parameters caused significant changes in some characteristics of the SAs structures, such as an increase in the intensity of the photoluminescence (PL) or its annihilation and change in the self-organization pattern. The results obtained in this work provide a preliminary overview of the different patterns of SA structures that can be obtained using photoluminescent Cdots as building blocks.