Nano particles are finding their way into the environment through deliberate and accidental actions, ecotoxicological properties and the risks of these nano particles have yet not been fully characterized. In this pre...Nano particles are finding their way into the environment through deliberate and accidental actions, ecotoxicological properties and the risks of these nano particles have yet not been fully characterized. In this present investigation, experiments were carried out to know the effect of Cu oxide-nano particles （〈 50 nm） on germination and growth of seeds of soybean and chickpea. In both the crops, germination was not checked up to 2,000 ppm Cu （applied through Cu oxide-nano particles）, but the root growth was prevented above 500 ppm Cu. With increasing concentration of NPs, the elongation of the roots was severely inhibited as compared to that in control. In many cases root necrosis was occurred. Massive adsorption of Cu oxide-nano particles into the root system was responsible for the toxicity. A parallel experiment was also carried out to know the effect of copper sulphate solution on seed germination, above 200 ppm Cu, it restricted the germination of seeds, because of high salinity.展开更多
We report on a Te-seeded epitaxial growth of ultrathin Bi2Te3 nanoplates （down to three quintuple layers （QL）） with large planar sizes （up to tens of micrometers） through vapor transport. Optical contrast has be...We report on a Te-seeded epitaxial growth of ultrathin Bi2Te3 nanoplates （down to three quintuple layers （QL）） with large planar sizes （up to tens of micrometers） through vapor transport. Optical contrast has been systematically investigated for the as-grown Bi2Te3 nanoplates on the SiO2/Si substrates, experimentally and computationally. The high and distinct optical contrast provides a fast and convenient method for the thickness determination of few-QL Bi2Te3 nanoplates. By aberration-corrected scanning transmission electron microscopy, a hexagonal crystalline structure has been identified for the Te seeds, which form naturally during the growth process and initiate an epitaxial growth of the rhombohedral- structured Bi2Te3 nanoplates. The epitaxial relationship between Te and Bi2T% is identified to be perfect along both in-plane and out-of-plane directions of the layered nanoplate. Similar growth mechanism might be expected for other bismuth chalcogenide layered materials.展开更多
The appropriate choice of chemical composition of a metallic precursor, which produces the basic structure units in the growth process of nanocrystals, is a high priority in the synthesis of metal--especially Au--nano...The appropriate choice of chemical composition of a metallic precursor, which produces the basic structure units in the growth process of nanocrystals, is a high priority in the synthesis of metal--especially Au--nanoparticles. In the present work, Au seeds （prepared by the reduction of Au3＋ solution with NaBI~ in the presence of cetyltrimethylammonium bromide （CTAB）） have been used to initiate the growth of Au nanoparticles from two different Au precursors. When an aqueous Au＋ solution prepared in the presence of CTAB micelles was treated with ascorbic acid in the presence of the gold seeds, a high yield （up to 92%） of gold nanoparticles was obtained. By varying the volume of the seed solution with a fixed amount of Au＋, we can effectively control the morphological transformation of the resulting Au nanoparticles from cubes to octahedra. When an aqueous Au3＋ solution was prepared in the presence of CTAB micelles and treated with ascorbic acid in the presence of the gold seeds, smaller yields of Au nanoparticles were obtained. A preliminary growth mechanism has been proposed based on the changes induced by varying the amount of ascorbic acid and the ratio of the concentration of Au＊ to the number of seeds.展开更多
This review highlights work from the authors' laboratory on the recent development of seed-mediated growth method for noble metal nanocrystals. The seed-mediated growth method has become one of the most efficient ...This review highlights work from the authors' laboratory on the recent development of seed-mediated growth method for noble metal nanocrystals. The seed-mediated growth method has become one of the most efficient and versatile methods for synthe-sizing high-quality noble metal nanocrystals. The seed-mediated growth method can separate the nucleation and growth stages of metal nanocrystals, and thus provide better control over the size, size distribution, and crystallographic evolution of metal nanocrystals. Because of its high controllability, the seed-mediated growth method is especially promising in providing mechanistic insights into the growth mechanisms of noble metal nanocrystals. In this review, the thermodynamic and kinetic parameters for the nucleation and growth of noble metal nanocrystals are systematically summarized. Mechanistic understanding of these parameters is provided. These studies provide useful guidelines for the rational design and synthesis of novel noble metal nanocrystals with high quality.展开更多
Gold nanoparticle （Au NP）@ZnO nanorod （NR） （Au@ZnO） hybrids with various ZnO：Au molar ratios were developed to enhance the generation of reactive oxygen species （ROS） in photodynamic therapy （PDT） applicati...Gold nanoparticle （Au NP）@ZnO nanorod （NR） （Au@ZnO） hybrids with various ZnO：Au molar ratios were developed to enhance the generation of reactive oxygen species （ROS） in photodynamic therapy （PDT） applications. Introducing a metal/semiconductor heterostructure interface between Au NPs and ZnO NRs modulated electron transfer under ultraviolet （UV） irradiation, which dramatically suppressed the electron-hole recombination in ZnO and simultaneously increased the amount of excited electrons with high energy at Au NP surfaces. Hence, the ROS yield of the nanohybrid was considerably improved over those of pristine Au NPs or ZnO NRs alone and demonstrated a ＂1 ＋ 1 〉 2 effect.＂ This enhancement was strengthened with increases in the proportion of Au in the hybrid. The results showed that the Au@ZnO nanohybrids with a ZnO：Au ratio of 20：1 generated the highest ROS yield because they had the largest interface area between Au and ZnO, which in turn led to the lowest cell viability for HeLa and C2C12 cells during PDT. Furthermore, both ROS generation and cell destruction were positively correlated with nanohybrid dosage. The Au@ZnO hybrid （20：1, 100 μg/mL） resulted in HeLa cell viability as low as 28% after UV exposure for 2 min, which indicated its promising potential to improve the therapeutic efficacy of PDT.展开更多
The characteristics of the interactions co-cultures of ultrafine mesoporous silica nanoparticles （MSNs） and the Liriodendron hybrid suspension cells were systematically investigated using laser scanning confocal mic...The characteristics of the interactions co-cultures of ultrafine mesoporous silica nanoparticles （MSNs） and the Liriodendron hybrid suspension cells were systematically investigated using laser scanning confocal microscope （LSCM） and scanning elec- tron microscopy （SEM）. Using fluorescein isothiocyanate （FITC） labeling, the LSCM observations demonstrated that MSNs （size, 5-15 nm） with attached FITC molecules efficiently penetrated walled plant cells through endocytic pathways, but free FITC could not enter the intact plant cells, The SEM measurements indicated that MSNs readily aggregated on the surface of intact plant cells, and also directly confirmed that MSNs could enter intact plant cells; this was achieved by determining the amount of silicon present. After 24 h of incubation with 1.0 mg mL-t of MSNs, the viability of the plant cells was analyzed using fluorescein diacetate staining; the results showed that these cells retained high viability, and no cell death was observed. Interestingly, after the incubation with MSNs, the Liriodendron hybrid suspension cells retained the capability for plant regen- eration via somatic embryogenesis. Our results indicate that ultrafine MSNs hold considerable potential as nano-carriers of ex- tracellular molecules, and can be used to investigate in vitro gene-delivery in plant cells.展开更多
Modulation of the morphology of nanostructures is often a rewarding but challenging task. We have employed the seeded growth method and induced kinetic control to synthesize Bi2Se3 nanoplates with modifiable morpholog...Modulation of the morphology of nanostructures is often a rewarding but challenging task. We have employed the seeded growth method and induced kinetic control to synthesize Bi2Se3 nanoplates with modifiable morphology. By manipulating the rate at which precursor solutions were injected into seeds solution with syringe pumps, two distinctive growth modes could be realized. With a fast injection, the thickness of Bi2Se3 nanoplates slightly increased from N7.5 nm （seeds） to -9.5 nm while the edge length grew up from ~160 nm （seeds） to N12 ~tm, after 6 successive rounds of seeded growth. With a slow injection, the thickness and edge length increased simultaneously to -35 nm and -6 b^m after 6 rounds of growth, respectively. These two modes could be viewed as a competition between atomic deposition and surface migration. The products showed interesting, thickness-dependent Raman properties. In addition, NIR transparent, highly conductive and flexible Bi2Se3 thin films with different thicknesses were constructed by the assembly of the as-synthesized Bi2Se3 nanoplates. This approach based on seeded growth and kinetic control can significantly promote the development of versatile nanostructures with diverse morphology.展开更多
文摘Nano particles are finding their way into the environment through deliberate and accidental actions, ecotoxicological properties and the risks of these nano particles have yet not been fully characterized. In this present investigation, experiments were carried out to know the effect of Cu oxide-nano particles （〈 50 nm） on germination and growth of seeds of soybean and chickpea. In both the crops, germination was not checked up to 2,000 ppm Cu （applied through Cu oxide-nano particles）, but the root growth was prevented above 500 ppm Cu. With increasing concentration of NPs, the elongation of the roots was severely inhibited as compared to that in control. In many cases root necrosis was occurred. Massive adsorption of Cu oxide-nano particles into the root system was responsible for the toxicity. A parallel experiment was also carried out to know the effect of copper sulphate solution on seed germination, above 200 ppm Cu, it restricted the germination of seeds, because of high salinity.
文摘We report on a Te-seeded epitaxial growth of ultrathin Bi2Te3 nanoplates （down to three quintuple layers （QL）） with large planar sizes （up to tens of micrometers） through vapor transport. Optical contrast has been systematically investigated for the as-grown Bi2Te3 nanoplates on the SiO2/Si substrates, experimentally and computationally. The high and distinct optical contrast provides a fast and convenient method for the thickness determination of few-QL Bi2Te3 nanoplates. By aberration-corrected scanning transmission electron microscopy, a hexagonal crystalline structure has been identified for the Te seeds, which form naturally during the growth process and initiate an epitaxial growth of the rhombohedral- structured Bi2Te3 nanoplates. The epitaxial relationship between Te and Bi2T% is identified to be perfect along both in-plane and out-of-plane directions of the layered nanoplate. Similar growth mechanism might be expected for other bismuth chalcogenide layered materials.
基金Acknowledgements This work was supported by National Basic Research Program of China （973 Program No. 2009CB930703） and National Natural Science Foundation of China （No. 21033007）. We thank Dr. Jiawei Yan, Yongli Zheng, and Haixin Lin for helpful discussion. We also thank Zhaobin Chen for ICP-AES measurements.
文摘The appropriate choice of chemical composition of a metallic precursor, which produces the basic structure units in the growth process of nanocrystals, is a high priority in the synthesis of metal--especially Au--nanoparticles. In the present work, Au seeds （prepared by the reduction of Au3＋ solution with NaBI~ in the presence of cetyltrimethylammonium bromide （CTAB）） have been used to initiate the growth of Au nanoparticles from two different Au precursors. When an aqueous Au＋ solution prepared in the presence of CTAB micelles was treated with ascorbic acid in the presence of the gold seeds, a high yield （up to 92%） of gold nanoparticles was obtained. By varying the volume of the seed solution with a fixed amount of Au＋, we can effectively control the morphological transformation of the resulting Au nanoparticles from cubes to octahedra. When an aqueous Au3＋ solution was prepared in the presence of CTAB micelles and treated with ascorbic acid in the presence of the gold seeds, smaller yields of Au nanoparticles were obtained. A preliminary growth mechanism has been proposed based on the changes induced by varying the amount of ascorbic acid and the ratio of the concentration of Au＊ to the number of seeds.
基金supported by the National Natural Science Foundation of China (21175126)
文摘This review highlights work from the authors' laboratory on the recent development of seed-mediated growth method for noble metal nanocrystals. The seed-mediated growth method has become one of the most efficient and versatile methods for synthe-sizing high-quality noble metal nanocrystals. The seed-mediated growth method can separate the nucleation and growth stages of metal nanocrystals, and thus provide better control over the size, size distribution, and crystallographic evolution of metal nanocrystals. Because of its high controllability, the seed-mediated growth method is especially promising in providing mechanistic insights into the growth mechanisms of noble metal nanocrystals. In this review, the thermodynamic and kinetic parameters for the nucleation and growth of noble metal nanocrystals are systematically summarized. Mechanistic understanding of these parameters is provided. These studies provide useful guidelines for the rational design and synthesis of novel noble metal nanocrystals with high quality.
基金This work was supported by the National Basic Research Program of China （No. 2013CB932600）, the Major Project of International Cooperation and Exchanges （No. 2012DFA50990）, the Program of Introducing Talents of Discipline to Universities, the National Natural Science Foundation of China （Nos. 51232001, 51172022, 51372023, and 31371203）, the Research Fund of Co-Construction Program from Beijing Municipal Commission of Education, the Fundamental Research Funds for the Central Univer- sities, and the Program for Changjiang Scholars and Innovative Research Team in University.
文摘Gold nanoparticle （Au NP）@ZnO nanorod （NR） （Au@ZnO） hybrids with various ZnO：Au molar ratios were developed to enhance the generation of reactive oxygen species （ROS） in photodynamic therapy （PDT） applications. Introducing a metal/semiconductor heterostructure interface between Au NPs and ZnO NRs modulated electron transfer under ultraviolet （UV） irradiation, which dramatically suppressed the electron-hole recombination in ZnO and simultaneously increased the amount of excited electrons with high energy at Au NP surfaces. Hence, the ROS yield of the nanohybrid was considerably improved over those of pristine Au NPs or ZnO NRs alone and demonstrated a ＂1 ＋ 1 〉 2 effect.＂ This enhancement was strengthened with increases in the proportion of Au in the hybrid. The results showed that the Au@ZnO nanohybrids with a ZnO：Au ratio of 20：1 generated the highest ROS yield because they had the largest interface area between Au and ZnO, which in turn led to the lowest cell viability for HeLa and C2C12 cells during PDT. Furthermore, both ROS generation and cell destruction were positively correlated with nanohybrid dosage. The Au@ZnO hybrid （20：1, 100 μg/mL） resulted in HeLa cell viability as low as 28% after UV exposure for 2 min, which indicated its promising potential to improve the therapeutic efficacy of PDT.
基金supported by the National Natural Science Foundation of China (30930077,31000164)
文摘The characteristics of the interactions co-cultures of ultrafine mesoporous silica nanoparticles （MSNs） and the Liriodendron hybrid suspension cells were systematically investigated using laser scanning confocal microscope （LSCM） and scanning elec- tron microscopy （SEM）. Using fluorescein isothiocyanate （FITC） labeling, the LSCM observations demonstrated that MSNs （size, 5-15 nm） with attached FITC molecules efficiently penetrated walled plant cells through endocytic pathways, but free FITC could not enter the intact plant cells, The SEM measurements indicated that MSNs readily aggregated on the surface of intact plant cells, and also directly confirmed that MSNs could enter intact plant cells; this was achieved by determining the amount of silicon present. After 24 h of incubation with 1.0 mg mL-t of MSNs, the viability of the plant cells was analyzed using fluorescein diacetate staining; the results showed that these cells retained high viability, and no cell death was observed. Interestingly, after the incubation with MSNs, the Liriodendron hybrid suspension cells retained the capability for plant regen- eration via somatic embryogenesis. Our results indicate that ultrafine MSNs hold considerable potential as nano-carriers of ex- tracellular molecules, and can be used to investigate in vitro gene-delivery in plant cells.
文摘Modulation of the morphology of nanostructures is often a rewarding but challenging task. We have employed the seeded growth method and induced kinetic control to synthesize Bi2Se3 nanoplates with modifiable morphology. By manipulating the rate at which precursor solutions were injected into seeds solution with syringe pumps, two distinctive growth modes could be realized. With a fast injection, the thickness of Bi2Se3 nanoplates slightly increased from N7.5 nm （seeds） to -9.5 nm while the edge length grew up from ~160 nm （seeds） to N12 ~tm, after 6 successive rounds of seeded growth. With a slow injection, the thickness and edge length increased simultaneously to -35 nm and -6 b^m after 6 rounds of growth, respectively. These two modes could be viewed as a competition between atomic deposition and surface migration. The products showed interesting, thickness-dependent Raman properties. In addition, NIR transparent, highly conductive and flexible Bi2Se3 thin films with different thicknesses were constructed by the assembly of the as-synthesized Bi2Se3 nanoplates. This approach based on seeded growth and kinetic control can significantly promote the development of versatile nanostructures with diverse morphology.
