Sichun Zhang

Growth and photoluminescence properties of PbS nanocubes

This paper reports the synthesis of semiconductor nanocrystals of PbS through a facile and inexpensive synthetic route between lead acetate [Pb(Ac)2·3H2O] and dithioglycol (HSCH2CH2SH) without any surfactant. The products were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Raman spectroscopy, x-ray photelectron spectroscopy (XPS) and infrared (IR) spectroscopy. The size of cube-shaped PbS nanocrystals can be controlled by changing the relative amount of Pb(Ac)2·3H2O and dithioglycol. Smaller cube-shaped PbS nanocrystals were obtained at higher sulfur content in the reaction system. The nanometre-sized single crystals of PbS measure ~83xa0nm × 59xa0nm × 22xa0nm and 39xa0nm × 10xa0nm × 7xa0nm, for lead acetate:dithioglycol ratios of 1:0.375 (denoted as PbS-1) and 1:1.5 (denoted as PbS-2), respectively, when a mixture of NaOH solution of lead acetate and ethyl alcohol solution of dithioglycol is maintained at 220u2009°C for 4xa0h in a Teflon-lined autoclave. XRD patterns and HRTEM images confirm the crystalline structure of the PbS crystals. TEM helped to determine the dimension of the single crystals. Raman, XPS and IR helped to further demonstrate the purity of the as-synthesized samples. The optical absorption spectra of suspensions of the these crystals in glycol show shifts in absorption band edge for as-prepared sample PbS-1 from 246 to 271xa0nm and for PbS-2 from 246 to 275xa0nm, after four days of storage, respectively. The photoluminescence peaks from the two samples are located at 434 and 433xa0nm for photoexcitation radiation of 315–355xa0nm, thus exhibiting a Stokes shift compared with band edge energy. The principal contribution of this work is that the nanometre-size PbS single crystals are prepared without using a surfactant or templating agent. The formation of a five-membered ring via the chelation between the Pb2+ ion and dithioglycol is considered to be crucial in this mechanism.

The synthesis and photocatalytic activity of ZnSe microspheres

This paper reports the synthesis of semiconductor ZnSe microspheres composed of nanoparticles via a solvothermal route between the organic molecule selenophene (C(4)H(4) Se) and ZnCl(2) without adding any surfactant. The ZnSe microspheres were characterized by x-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), specific surface area measurement, and photoluminescence (PL) spectra. A strong and broad blue PL emission at 443 nm in wavelength (∼2.79 eV in photon energy) is attributed to the near-band-edge (NBE) emission of ZnSe, while the 530 nm peak is a defect-related (DL) emission. The photocatalytic activity of the as-prepared ZnSe microspheres was evaluated by photodegradation of methyl orange (MO) dye under ultraviolet (UV) light and visible light irradiation. The degradations of MO reach 94% or 95.1%, close to 100%, in the presence of the as-synthesized ZnSe microspheres or commercial ZnSe powder after 7 or 10 h under UV irradiation, respectively. Meanwhile the degradations of MO reach 94.3% or 60.6% in the presence of the as-synthesized ZnSe microspheres or commercial ZnSe powder after 12 h, respectively. The degradation rate of ZnSe microspheres is twice that of ZnSe commercial powder under UV light irradiation, and three times under visible light irradiation. The degradation process of MO dye on ZnSe microspheres under UV or visible light is also discussed.

Shape controlled synthesis of superhydrophobic zinc coordination polymers particles and their calcination to superhydrophobic ZnO

In this paper, superhydrophobic Zinc-CPPs (coordination polymer particles) with controllable shapes were synthesized by an in situ ligand generating reaction in combination with monofunctional ligands as capping reagents. The as-synthesized samples were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), energy-dispersion X-ray (EDX) spectroscopy, and Brunauer–Emmett–Teller (BET) analysis. The Zn–CPPs exhibit superhydrophobicity. Crystalline ZnO particles were formed from the calcination of Zn–CPPs, exhibiting superhydrophobicity and good photocatalytic activity.

Catalytic chemiluminescence properties of boehmite nanococoons

There have been great interest in constructing advanced nanostructures due to the potential profit of achieving nanodevices with interesting properties; much effort has been devoted to combining biology and nanotechnology to synthesize superstructures, in shapes of higher complexity than those of low-dimensional nanostructures. The advanced nanostructures can function from sensing to emitting light or storing information. Here the authors demonstrate the self-organization of boehmite nanorods into the cocoonlike nanostructures by using glycine as reactant. The growth mechanism is described. The boehmite (γ-AlOOH) nanococoons exhibit excellent sensitivity to ethanol vapor with rapid, stable, and reversible characteristics as catalytic chemiluminescence nanosensors.