Aqueous-solution synthesis of uniform PbS nanocubes and their optical properties

Abstract

PbS nanocubes with uniform size were generated conveniently in aqueous solution at 100 °C. The products were characterized by XRD, FESEM, TEM, UV–Vis–NIR, PL, DLS, Raman, and FT-IR techniques. The mean edge length of the nanocubes is 60 nm and is in high yield. UV–Vis–NIR absorption spectrum indicated that the sample exhibits a blue-shift from 3024 to 288 nm and PL spectrum also indicated that the sample exhibits a blue-shift from 3200 to 328 nm, compared with bulk PbS, respectively. Dark-field light scattering measurements showed that the nanocubes-scattered orange light have a broad absorption band around 610 nm. Such a special property demonstrates that the PbS nanocubes may find potential application in molecular imaging and in vivo cancer diagnosis and therapy. By investigating the intermediates of the reaction process, we observed the important coarse rod-like structures that formed by PbS particles attached to one another at the initial stage of reaction. Then the particle-joint structures decomposed and finally formed PbS nanocubes. Such a morphology evolution of PbS crystals could be summarized as “particle–rod–cube mechanism,” which might be model systems for understanding the growth process of other kinds of nanocubes and directing their synthesis. High-yield PbS nanocubes with an edge length of 60 nm were fabricated successfully in aqueous solution at 100 °C by the assistance of surfactant CTAB. It has been found that the reaction time, temperature, and CTAB play important roles in the formation of uniform PbS nanocubes. A possible growth mechanism called “particle–rod–cube” has been discussed.