Size and Distribution: A Comparison of XRD, SAXS and SANS Study of II–VI Semiconductor Nanocrystals

Abstract

The uniqueness of size dependent functional properties of II-VI semiconductor nanocrystals have led to the development of various techniques for determination of shape, size and distributions, although the accurate measurements of the particle sizes has always been a fundamental task in nanoscience and even become more crucial with the discovery of quantum confinement effect. A comparison of the well established techniques X-ray diffraction (XRD), small angle X-ray scattering (SAXS) and small angle neutron scattering (SANS) with an emphasis on size and distribution of the prepared samples are reported in order to elaborate more precise techniques for the analysis of particles sizes. Modified Scherrer formula for spherical particles has been used to calculate the particle sizes from XRD spectra. Analysis of SAXS data has been reported using Guinier model. Small angle neutron scattering measurements has been performed for ZnO nanocrystals and the scattering data obtained is simulated for polydisperse sphere. The bare ZnO, ZnS and CdS and doped with Mn2+ systems are taken within the framework of our discussion. These materials were synthesized by chemical precipitation route and found to have size distribution from 2 to 6 nm for spherical particles. Sizes determined from various techniques are in good agreement with each other however small angle scattering technique is more reliable than XRD to determine the sizes of the nanoparticles.

Structural characterisation of alkyl amine-capped zinc sulphide nanoparticles

“…Approximating a two step model to the data results in a core radius of 2.1 nm and a total radius of 4.0 nm, which corresponds to a shell thickness of 1.9 nm, which matches well with a previous finding in literature [32]. As also reported by Keshari and Pandey [19], the core radius is again in good agreement with XRD data and the results from SAXS on the solid material, while the organic shell is now found to be considerably thicker. This is consistent with singular dissolved nanoparticles and a ligand shell with almost stretched molecules.…”

“…In this context, small angle X-ray scattering (SAXS) is a valuable complementary method analysing a larger amount of the sample. Although data analysis and interpretation are laborious and sometimes difficult, SAXS is a well suited method for investigating the size, shape and distribution for nanoparticles in the solid state [19] but also in solution [20]. This latter point is of special interest as many applications require stable and well dissolved nanoparticles.…”

Temperature induced size selective synthesis of hybrid Cds/pepsin nanocrystals and their photoluminescence investigation

“…The sizes obtained from SAXS are in well agreement with those computed using the Sherrer's equation from XRD broadening. It is already reported [24] that for very small particles, the sizes obtained from XRD to SAXS are well agreed.…”

“…2(a) shows the initial (raw) SAXS scattering intensity profile of prepared CdS semiconductor nanocrystals in the pepsin solution at different Rx temperatures. It clearly shows that slope of the scattering profile increases with decreasing temperature; it means that sizes get also reduced and distribution becomes narrower [24]. The details about the SAXS can be found elsewhere [25,26].…”

Optical studies of Cd2+ and Mn2+ Co-doped ZnS nanocrystals

“…So, the intense peak at 520 nm in sample A and C corresponds to the transition from Cd ions related defect states (E -D e ) present in between the band gap. Luminescence characteristics of ZnS:Mn 2 + has been extensively studied by several groups [15,[31][32][33]. Bhargava et al [34] reported that in Mn 2 + -doped ZnS nanoparticles, very strong hybridization occurs between the sp levels of Zn and d levels of Mn 2 + ions and it results the crystal field splitting of Mn 2 + levels in between the bands of host material.…”