The morphologies of the samples were selleckchem obtained using a scanning electron microscope (SEM; Hitachi
Syk inhibitor S-4800, Chiyoda-ku, Japan). Microstructures of the samples were characterized using a transmission electron microscope (TEM; Tecnai TMG2F30, FEI, Hillsboro, OR, USA) and high-resolution TEM (HRTEM) equipped with selected-area electron diffraction (SAED) and energy-dispersive X-ray spectrum (EDS). The measurements of static magnetic properties were made using a Quantum Design MPMS magnetometer based on a superconducting quantum interference device (SQUID; San Diego, CA, USA). Electron spin resonance (ESR; JEOL, JES-FA300, microwave frequency is 8.984 GHz, Akishima-shi, Japan) spectra were recorded to study the dynamic magnetic properties of the samples. The chemical bonding state and the compositions of the samples were determined by X-ray photoelectron spectroscopy (XPS; VG Scientific ESCALAB-210 spectrometer, East Grinstead, UK) with monochromatic Mg Kα X-rays (1,253.6 eV). The thermogravimetric and differential thermal analysis (TG-DTA; DuPont Instruments 1090B,
Parkersburg, VA, USA) was employed to obtain the variation of mass and phase transition details of the samples during argon annealing. Results and discussion Structural analysis of sphalerite CdS NSs synthesized at different times (samples S1 to S4) was carried out by XRD, and the results are shown in Figure 1. All diffraction peaks can be indexed to the cubic sphalerite structure of CdS (JCPDS card no. 10–0454). The absence of any other peaks suggests that there is no secondary phase present. Using the Scherrer formula find more for the full width at half maximum of the main peaks, the average crystalline size has been estimated to be around 4.0, 4.6, 5.1, and 5.5 ± 0.1
nm for samples S1 to S4 (inset of Figure 1), which implies the increase of the crystalline size as the synthesis time increases. Figure 2a,b shows the SEM images of sample S1. Clearly, all products are in the form of a spherical particle with diameters around 200 nm. Under high magnification, it obviously shows that each spherical particle is made up of smaller parts. Figure 2c shows the TEM image of sample S1; it reveals that many many crystalline grains congregate together to form a spherical particle and the average size is about 200 nm, which matches the SEM result. It can be clearly seen from the HRTEM of sample S1 in Figure 2d that a single-crystalline grain is about 4 nm in diameter, which is consistent with the XRD result, and it has a lattice spacing of 0.21 nm equaling to the interplanar spacing of the sphalerite CdS in (220) plane. The EDS result is shown in the inset of Figure 2d. The result shows that only the elements Cd, S, C, and Cu are present; Cd and S have an atomic ratio of 54:46. C and Cu are from the carbon membranes which hold the samples during measurement. Figure 1 XRD patterns of samples S1 to S4 represented by lines of different colors.