ZrS₂ quantum dots: Preparation, structure, and optical properties

In recent years, transition metal chalcogenides (TMDs) have attracted extensive attention of researchers due to their unique electronic structure and excellent photoelectric properties. In this paper, hexagonal structure 1T-ZrS 2 quantum dots (QDs) having a monodisperse grain size of around 3.1 nm is prepared by the ultrasonic exfoliation method. The preparation includes the following steps: ZrS 2 powder is ground, followed by ultrasonic exfoliation in 1-methyl-2-pyrrolidone (NMP), and 1T-ZrS 2 QDs are collected after centrifugation. The structure, morphology and optical properties of the QDs are studied in detail. The structure, morphology, size distribution, and elemental composition of 1T-ZrS 2 QDs are studied by using X-ray diffractometer (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The chemical bonds of 1T-ZrS 2 QDs are characterized by X-ray photoelectron microscopy (XPS) and Fourier transform infrared spectrometer (FTIR). The TEM and AFM results show that the 1T-ZrS 2 QDs are spherical in shape with uniform size distribution. The sizes of the 1T-ZrS 2 QDs follow a Gaussian fitted distribution with an average diameter of W C = 3.1 nm and the FWHM is 1.3 nm. The XRD diffraction pattern of 1T-ZrS 2 QDs show wide dispersed diffraction peaks, which is the characteristic of QDs. The diffraction peak at 2 θ = 32.3° ( d = 0.278 nm) corresponds to the (101) crystal plane, and the weak diffraction peak at 2 θ = 56.8°( d = 0.167 nm) belongs to the (103) crystal plane. The grain size is also calculated by using the Debye-Scherrer formula, and the calculated value (2.9 nm) is consistent with the result of TEM (3.1 nm). Two Raman vibration modes (E 1g and A 1g ) are observed. The E 1g (507.3 cm –1 ) and A 1g (520.1 cm –1 ) modes relate to the in-plane and out-of-plane vibration respectively. The Raman intensity of the A 1g vibration mode is stronger than that of E 1g . The UV-Vis and photoluminescence (PL and PLE) characterizations exhibit that the 1T-ZrS 2 QDs have two UV absorption peaks at 283 nm and 336 nm, respectively. The Stokes shift is ~130 nm, the fluorescence quantum yield reaches up to 53.3%. The results show that the 1T-ZrS 2 QDs have the excellent fluorescence performance and unique optical properties, which make the 1T-ZrS 2 QDs an important material for developing photodetectors, multi-color luminescent devices, and other devices.