With the features of convenience and eco-friendly, the low-temperature solid-state reaction synthesis was successfully developed as a new approach to prepare quantum-sized ZnS nanocrystals. One major achievement is th...With the features of convenience and eco-friendly, the low-temperature solid-state reaction synthesis was successfully developed as a new approach to prepare quantum-sized ZnS nanocrystals. One major achievement is that the size and shape of ZnS nanocrystals can be tuned by adjusting the surfactant and its feed. The UV-Vis absorption spectra of quasispherical and one-dimensional quantum-sized ZnS nanocrystals all showed a blue-shift from the bulk counterpart, indicating large quantum confinement effects of ZnS nanocrystals. These ZnS nanocrystals all showed well-defined excitonic emission features. Contrastive studies on photoluminescence performances indicated that the bandedge emission experienced only the size-dependent quantum confinement effect, while the trap-state emission experienced the size- and shape-dependences. So we can design a purposeful synthesis route to ZnS nanocrystals with target luminescence emission performances.展开更多
Surface-enhanced Raman scattering（SERS） spectra of different silver nanoplate selt-assembled tllmS at different excitation wavelengths were fairly compared. Shape conversion from silver nanoprisms to nanodisks on sl...Surface-enhanced Raman scattering（SERS） spectra of different silver nanoplate selt-assembled tllmS at different excitation wavelengths were fairly compared. Shape conversion from silver nanoprisms to nanodisks on slides was in situ carried out. The SERS spectra of 4-mercaptopyridine（4-MPY） on these anisotropic silver nanopar- ticle self-assembled films present that strong enhancement appeared when the excitation line and the surface plasmon resonance（SPR） band of silver substrate overlapped. In this model, the influence of the crystal planes of silver na- noplates on SERS enhancement could be ignored because the basal planes were nearly unchanged in two kinds of silver nanoplate self-assembled films.展开更多
Single-crystalline hematite （α-Fe2O3） nanorings （short nanotubes） and nanotubes were synthesized by a hydrothermal method. High-resolution transmission electron microscopy and selected-area electron diffraction c...Single-crystalline hematite （α-Fe2O3） nanorings （short nanotubes） and nanotubes were synthesized by a hydrothermal method. High-resolution transmission electron microscopy and selected-area electron diffraction confirm that the axial directions of both the nanorings and nanotubes are parallel to the crystalline c-axis. Intriguingly, the Morin transition occurs at about 210 K in the short nanotubes with a mean tube length of about 115 nm and a mean outer diameter of about 169 nm. However, it does not occur in the nanotubes with a mean tube length of about 317 nm and a mean outer diameter of about 148 nm. Detailed analysis of magnetization data, X-ray diffraction patterns, and room-temperature M6ssbauer spectra demonstrates that this very strong shape-dependence of Morin transition is intrinsic to hematite. We explain this intriguing shape- dependence quantitatively, in terms of the opposite signs of the surface mag- netic anisotropy constants of the surface planes parallel and perpendicular to the c-axis.展开更多
文摘With the features of convenience and eco-friendly, the low-temperature solid-state reaction synthesis was successfully developed as a new approach to prepare quantum-sized ZnS nanocrystals. One major achievement is that the size and shape of ZnS nanocrystals can be tuned by adjusting the surfactant and its feed. The UV-Vis absorption spectra of quasispherical and one-dimensional quantum-sized ZnS nanocrystals all showed a blue-shift from the bulk counterpart, indicating large quantum confinement effects of ZnS nanocrystals. These ZnS nanocrystals all showed well-defined excitonic emission features. Contrastive studies on photoluminescence performances indicated that the bandedge emission experienced only the size-dependent quantum confinement effect, while the trap-state emission experienced the size- and shape-dependences. So we can design a purposeful synthesis route to ZnS nanocrystals with target luminescence emission performances.
基金Supported by the National Natural Science Foundation of China(Nos.91027010,21073073,20903043,20973075,20773045)the Research Fund for the Doctoral Program of Higher Education of China(No.20090061120089)the Open Project of State Key Laboratory for Supramolecular Structure and Materials of China(No.201125)
文摘Surface-enhanced Raman scattering（SERS） spectra of different silver nanoplate selt-assembled tllmS at different excitation wavelengths were fairly compared. Shape conversion from silver nanoprisms to nanodisks on slides was in situ carried out. The SERS spectra of 4-mercaptopyridine（4-MPY） on these anisotropic silver nanopar- ticle self-assembled films present that strong enhancement appeared when the excitation line and the surface plasmon resonance（SPR） band of silver substrate overlapped. In this model, the influence of the crystal planes of silver na- noplates on SERS enhancement could be ignored because the basal planes were nearly unchanged in two kinds of silver nanoplate self-assembled films.
基金This work was supported by the National Natural Science Foundation of China （No. 11174165）, the Natural Science Foundation of Ningbo （No. 2012A610051）, and the K. C. Wong Magna Foundation. VA acknowledges financial support from NIH and NIGMS under MBRS- RISE M.S.-to-Ph.D. Program （No. R25GM061331）.
文摘Single-crystalline hematite （α-Fe2O3） nanorings （short nanotubes） and nanotubes were synthesized by a hydrothermal method. High-resolution transmission electron microscopy and selected-area electron diffraction confirm that the axial directions of both the nanorings and nanotubes are parallel to the crystalline c-axis. Intriguingly, the Morin transition occurs at about 210 K in the short nanotubes with a mean tube length of about 115 nm and a mean outer diameter of about 169 nm. However, it does not occur in the nanotubes with a mean tube length of about 317 nm and a mean outer diameter of about 148 nm. Detailed analysis of magnetization data, X-ray diffraction patterns, and room-temperature M6ssbauer spectra demonstrates that this very strong shape-dependence of Morin transition is intrinsic to hematite. We explain this intriguing shape- dependence quantitatively, in terms of the opposite signs of the surface mag- netic anisotropy constants of the surface planes parallel and perpendicular to the c-axis.
