Guoyi Dong

Effects of alkanethiols chain length on the synthesis of Cu2−xS nanocrystals: phase, morphology, plasmonic properties and electrical conductivity

Cu2−xS nanocrystals with different morphologies and crystal phases have been synthesized by using a simple one-pot and phosphine-free colloidal method, in which different alkanethiols (CnH2n+1SH, n = 8, 12, 18) have been selected as sulfur sources and capping ligands. The crystal phase can be transformed from monoclinic Cu1.94S to tetragonal Cu1.81S by varying the alkyl chain length of alkanethiols, and the morphology changes from nanospheres to nanodisks during the phase transformation. Strong localized surface plasmon resonance (LSPR) absorbance in the near-infrared (NIR) region has been observed in these Cu2−xS nanocrystals, which originates from excess holes in the valence band due to copper deficiencies. The alkyl chain length of alkanethiols plays an important role in the crystal phase, morphology and plasmonic properties of the as-obtained Cu2−xS nanocrystals.

Heating-up Synthesis of MoS2 Nanosheets and Their Electrical Bistability Performance.

Molybdenum disulfide (MoS2) nanosheets were synthesized by using a simple heating-up approach, in which 1-dodecanethiol (DDT) was used not only as a sulfur source but also as the surface ligand. The sheet-like morphology was confirmed by the transmission electron microscopy (TEM) and atomic force microscopy (AFM) results, and the X-ray diffraction (XRD) patterns and Raman spectrum were employed to characterize the structure of the as-synthesized MoS2 nanosheets. The as-obtained MoS2 nanosheets blending with a polymer could be used to fabricate an electrically bistable device through a simple spin-coating method, and the device exhibited an obvious electrical bistability in the I-V curve. The charge transport of the device was discussed based on the organic electronic models.

Excitation-dependent carbon dots powders based on dehydration condensation by microwave–hydrothermal method

AbstractA green and economical microwave–hydrothermal method is employed to prepare carbon dots (CDs) that low-cost dl-malic acid serves as the carbon source and the formamide serves simultaneously as the pyrolysis solvent and carbon source. In the reaction process, neither assistant catalytic treatment nor further surface modification is necessary. We obtain better disperse CDs powders whose quantum yield reaches 25% as well as explain the dehydration condensation reaction mechanism based on the analysis by XPS and FTIR data. The luminescent properties are investigated in detail, and the results reveal that the excitation-dependent feature of as-prepared CDs has the potential for anti-counterfeiting mark and luminescence picture field.n

Synthesis and Luminescent Properties of Eu 2+ Doped Sr 5 SiO 4 Cl 6 Phosphor by Sol–Gel Method

The paper discusses preparation and luminescent properties of Sr5SiO4Cl6:Eu2+ blue phosphor, which was synthesized by sol-gel method. The emission and excitation spectra, SEM, XRD and diffuse reflection of the fluorescent powder were measured. It was shown that the samples were single phase of Sr5SiO4Cl6 by the XRD patterns. The photoluminescence and excitation spectra of this phosphor were investigated. The phosphor excited by 278 nm light showed an asymmetric spectrum. The emission spectra can be separated into three distinct peaks located at 450, 480 and 540 nm, respectively. The influences of Eu2+ ions concentration on the emission intensity of Sr5SiO4Cl6:Eu2+ phosphors were studied in detail. The influences of different sintering temperature on the emission intensity were also investigated. The optimal sintering temperature was 750 °C. Effects of the amount of complexing agent were studied and a ratio of 1~1.1 to that of the cation was the best. The particle diameter of the phosphor was studied by SEM. The potential applications were also discussed.

Preparation, structure and luminescent properties of Eu3+ doped MBPO5 (M = Ca, Sr, Ba) red phosphor for white LED

Motivation A suite of MBPO5 (borophosphates-BPO):Eu3+ (M = Ca, Sr, Ba) red emitting phosphors were synthesized and their luminescent properties were studied by excitation and emission spectra. Results The energy gap of CBPO, SBPO and BBPO are 5.481, 5.498 and 5.604 eV, respectively. While, these samples showed similar total and partial densities of states. The x-ray powder diffraction (XRD) patterns indicated that the samples were simple MPBO5 phase. According to the absorption spectra, the band gap energies of CBPO:Eu3+, SBPO: Eu3+ and BBPO:Eu3+ were calculated to be 5.499, 5.516 and 5.659 eV, respectively. The spectra of all three MBPO5:Eu3+ samples were similar with main excitation and emission peaks at 394 nm and 594 nm, respectively. The concentration quenching did not appear with the increase of the concentration of Eu3+. The charge compensator can improve the emission intensity. The average decay time of CBPO:0.05Eu3+, SBPO:0.05Eu3+ and BBPO:0.05Eu3+ was 3.29, 2.54, and 3.15 ms, respectively. The above results suggested that this phosphor was qualified as red phosphor, which could be used as a near UV-based white LED.