A facile preparation of ZnO nanobelts by chemical precipitation technique and its utility as catalyst in Knoevenagel condensation of 2,4-thiazolidinedione/rhodanine has been described. X-ray diffraction and transmissi...A facile preparation of ZnO nanobelts by chemical precipitation technique and its utility as catalyst in Knoevenagel condensation of 2,4-thiazolidinedione/rhodanine has been described. X-ray diffraction and transmission electron microscopy techniques revealed the formation ZnO nanobelts. Scanning electron microscopic observations indicate that the lengths of nanobelts are ranging from a few hundreds of micrometers to a few millimeters. Its use for the condensation of aldehydes and active methylene compounds under solvent free reaction condition at 90℃ afforded the corresponding products in excellent yields in minute time.展开更多
The chemical vapor deposition(CVD)growth method is applicable to produce high-yield single-crystalline ZnO nanobelts.The Mg-doped ZnO nanobelts with a smooth surface have been successfully synthesized.The morphology,m...The chemical vapor deposition(CVD)growth method is applicable to produce high-yield single-crystalline ZnO nanobelts.The Mg-doped ZnO nanobelts with a smooth surface have been successfully synthesized.The morphology,microstructure and optical properties of the ZnO nanobelts were analyzed by X-ray diffraction(XRD),scanning electron microscope(SEM),transmission electron microscope(TEM),selective area electron diffraction(SAED),energy dispersive X-ray spectroscopy(EDS)and photoluminescence(PL)spectroscopy.Results reveal that the ZnO nanobelts possess good crystalline quality.The special formation mechanism of crystal growth is discussed,emphasizing the effect of polar orientation on the nucleation and growth of the ZnO nanobelts.展开更多
Characterizing the three-dimensional （3D） shape of a nanostructure by con- ventional imaging techniques in scanning electron microscopy and transmission electron microscopy can be limited or complicated by various f...Characterizing the three-dimensional （3D） shape of a nanostructure by con- ventional imaging techniques in scanning electron microscopy and transmission electron microscopy can be limited or complicated by various factors, such as two-dimensional （2D） projection, diffraction contrast and unsure orientation of the nanostructure with respect to the electron beam direction. In this paper, in conjunction with electron diffraction and imaging, the 3D morphologies of ZnO nanowires and nanobelts synthesized via vapor deposition were reconstructed by electron tomography in a scanning transmission electron microscope （STEM）. The cross-sections of these one-dimensional （1D） nanostructures include triangle, hexagonal, and rectangle shapes. By combining the reconstructed shape with the crystalline information supplied by electron diffraction patterns recorded from the same nanowire/nanobelt, the growth direction and its exposed surfaces were uniquely identified. In total, three different growth directions were confirmed. These directions are 〈 0001 〉, 〈21 10 〉 and 〈21 13 〉, corresponding to 〈001〉, 〈100〉 and 〈101〉 orientations in three-index notation. The 〈0001〉 growth nanowires show triangle or hexagonal cross-sections, with exposed {01]-0} side surfaces. The dominant surfaces of the 〈21 10〉 growth nanobelt are _＋（0001） planes. Both hexagonal and rectangle cross-sections were observed in the 〈 2]-13 〉 growth ZnO nanostructures. Their surfaces include the {01]-0}, {]-101} and {2112} planes. The nanobelts with a large aspect ratio of ~10 normally grow along the 〈 21 10 〉 direction, while nanobelts with small aspect ratio grow along 〈21 13 〉 growth direction. The approach and methodology demonstrated here can be extended to any nanostructures that even amorphous. can be crystalline, polycrystalline or展开更多
Sn-doped ZnO particles were successfully synthesized by chemical co-precipitation method.Their morphology,phase,microstructure and infrared emissivity were characterized.The results show that the Sn-doped ZnO particle...Sn-doped ZnO particles were successfully synthesized by chemical co-precipitation method.Their morphology,phase,microstructure and infrared emissivity were characterized.The results show that the Sn-doped ZnO particles are of ellipsoid shape,their crystalline structure changed with thermal process temperature,the optimal thermal process temperature and Sn-doped proportion are 1000℃ and 15%,respectively,the minimum emissivity values are 0.42,0.28,0.46 and 0.48 corresponding to the infrared wavelengths of 0~∞,3~5,8~14 and 14~20 μm,which indicates that the Sn-doped ZnO particles have the application potential as low infrared emissivity material.展开更多
Diluted magnetic semiconductors(DMSs)have traditionally been employed to implement spin-based quantum computing and quantum information processing.However,their low Curie temperature is a major hurdle in their use in ...Diluted magnetic semiconductors(DMSs)have traditionally been employed to implement spin-based quantum computing and quantum information processing.However,their low Curie temperature is a major hurdle in their use in this field,which creates the necessity for wide bandgap DMSs operating at room temperature.In view of this,a single-electron transistor(SET)with a global back-gate was built using a wide bandgap ZnO nanobelt(NB).Clear Coulomb oscillations were observed at 4.2 K.The periodicity of the Coulomb diamonds indicates that the Coulomb oscillations arise from single quantum dots of uniform size,whereas quasi-periodic Coulomb diamonds correspond to the contribution of multi-dots present in the ZnO NB.By applying an AC signal to the global back-gate across a Coulomb peak with varying frequencies,single-electron pumping was observed;the increase in current was equal to the production of electron charge and frequency.The current accuracy of about 1%for both single-and double-electron pumping was achieved at a high frequency of 25 MHz.This accurate single-electron pumping makes the ZnO NB SET suitable for single-spin injection and detection,which has great potential for applications in quantum information technology.展开更多
文摘A facile preparation of ZnO nanobelts by chemical precipitation technique and its utility as catalyst in Knoevenagel condensation of 2,4-thiazolidinedione/rhodanine has been described. X-ray diffraction and transmission electron microscopy techniques revealed the formation ZnO nanobelts. Scanning electron microscopic observations indicate that the lengths of nanobelts are ranging from a few hundreds of micrometers to a few millimeters. Its use for the condensation of aldehydes and active methylene compounds under solvent free reaction condition at 90℃ afforded the corresponding products in excellent yields in minute time.
基金National Natural Science Foundation of China(90301002,90201025)
文摘The chemical vapor deposition(CVD)growth method is applicable to produce high-yield single-crystalline ZnO nanobelts.The Mg-doped ZnO nanobelts with a smooth surface have been successfully synthesized.The morphology,microstructure and optical properties of the ZnO nanobelts were analyzed by X-ray diffraction(XRD),scanning electron microscope(SEM),transmission electron microscope(TEM),selective area electron diffraction(SAED),energy dispersive X-ray spectroscopy(EDS)and photoluminescence(PL)spectroscopy.Results reveal that the ZnO nanobelts possess good crystalline quality.The special formation mechanism of crystal growth is discussed,emphasizing the effect of polar orientation on the nucleation and growth of the ZnO nanobelts.
文摘Characterizing the three-dimensional （3D） shape of a nanostructure by con- ventional imaging techniques in scanning electron microscopy and transmission electron microscopy can be limited or complicated by various factors, such as two-dimensional （2D） projection, diffraction contrast and unsure orientation of the nanostructure with respect to the electron beam direction. In this paper, in conjunction with electron diffraction and imaging, the 3D morphologies of ZnO nanowires and nanobelts synthesized via vapor deposition were reconstructed by electron tomography in a scanning transmission electron microscope （STEM）. The cross-sections of these one-dimensional （1D） nanostructures include triangle, hexagonal, and rectangle shapes. By combining the reconstructed shape with the crystalline information supplied by electron diffraction patterns recorded from the same nanowire/nanobelt, the growth direction and its exposed surfaces were uniquely identified. In total, three different growth directions were confirmed. These directions are 〈 0001 〉, 〈21 10 〉 and 〈21 13 〉, corresponding to 〈001〉, 〈100〉 and 〈101〉 orientations in three-index notation. The 〈0001〉 growth nanowires show triangle or hexagonal cross-sections, with exposed {01]-0} side surfaces. The dominant surfaces of the 〈21 10〉 growth nanobelt are _＋（0001） planes. Both hexagonal and rectangle cross-sections were observed in the 〈 2]-13 〉 growth ZnO nanostructures. Their surfaces include the {01]-0}, {]-101} and {2112} planes. The nanobelts with a large aspect ratio of ~10 normally grow along the 〈 21 10 〉 direction, while nanobelts with small aspect ratio grow along 〈21 13 〉 growth direction. The approach and methodology demonstrated here can be extended to any nanostructures that even amorphous. can be crystalline, polycrystalline or
文摘Sn-doped ZnO particles were successfully synthesized by chemical co-precipitation method.Their morphology,phase,microstructure and infrared emissivity were characterized.The results show that the Sn-doped ZnO particles are of ellipsoid shape,their crystalline structure changed with thermal process temperature,the optimal thermal process temperature and Sn-doped proportion are 1000℃ and 15%,respectively,the minimum emissivity values are 0.42,0.28,0.46 and 0.48 corresponding to the infrared wavelengths of 0~∞,3~5,8~14 and 14~20 μm,which indicates that the Sn-doped ZnO particles have the application potential as low infrared emissivity material.
基金supported by the National Natural Science Foundation of China(Grant Nos.51761145104,11934019,61675228,11721404,and 11874419)the Strategic Priority Research Program,the Instrument Developing Project and the Interdisciplinary Innovation Team of the Chinese Academy of Sciences(Grant Nos.XDB28000000,and YJKYYQ20180036)the Key R&D Program of Guangdong Province(Grant No.2018B030329001).
文摘Diluted magnetic semiconductors(DMSs)have traditionally been employed to implement spin-based quantum computing and quantum information processing.However,their low Curie temperature is a major hurdle in their use in this field,which creates the necessity for wide bandgap DMSs operating at room temperature.In view of this,a single-electron transistor(SET)with a global back-gate was built using a wide bandgap ZnO nanobelt(NB).Clear Coulomb oscillations were observed at 4.2 K.The periodicity of the Coulomb diamonds indicates that the Coulomb oscillations arise from single quantum dots of uniform size,whereas quasi-periodic Coulomb diamonds correspond to the contribution of multi-dots present in the ZnO NB.By applying an AC signal to the global back-gate across a Coulomb peak with varying frequencies,single-electron pumping was observed;the increase in current was equal to the production of electron charge and frequency.The current accuracy of about 1%for both single-and double-electron pumping was achieved at a high frequency of 25 MHz.This accurate single-electron pumping makes the ZnO NB SET suitable for single-spin injection and detection,which has great potential for applications in quantum information technology.
