Structural and optical properties of ～ 20 nm Ge nanoislands grown on Si（100） by radio frequency （rI） magnetron sputtering under varying annealing conditions are reported. Rapid thermal annealing at a temperature...Structural and optical properties of ～ 20 nm Ge nanoislands grown on Si（100） by radio frequency （rI） magnetron sputtering under varying annealing conditions are reported. Rapid thermal annealing at a temperature of 600 ℃ for 30 s, 90 s, and 120 s are performed to examine the influence of annealing time on the surface morphology and photoluminescence properties. X-ray diffraction spectra reveal prominent Ge and GeO2 peaks highly sensitive to the annealing time. Atomic force microscope micrographs of the as-grown sample show pyramidal nanoislands with relatively high-density （～ 10^11 cm^-2）. The nanoislands become dome-shaped upon annealing through a coarsening process mediated by Oswald ripening. The room temperature photoluminescence peaks for both as-grown （～ 3.29 eV） and annealed （～ 3.19 eV） samples consist of high intensity and broad emission, attributed to the effect of quantum confinement. The red shift （～ 0.10 eV） of the emission peak is attributed to the change in the size of the Ge nanoislands caused by annealing. Our easy fabrication method may contribute to the development of Ge nanostructure-based optoelectronics.展开更多
Controlling the atomic configurations of structural defects in graphene nanostructures is crucial for achieving desired functionalities.Here,we report the controlled fabrication of high-quality single-crystal and bicr...Controlling the atomic configurations of structural defects in graphene nanostructures is crucial for achieving desired functionalities.Here,we report the controlled fabrication of high-quality single-crystal and bicrystal graphene nanoislands(GNI)through a unique top-down etching and post-annealing procedure on a graphite surface.Low-temperature scanning tunneling microscopy(STM)combined with density functional theory calculations reveal that most of grain boundaries(GBs)formed on the bicrystal GNIs are 5-7-5-7 GBs.Two nanodomains separated by a 5-7-5-7 GB are AB stacking and twisted stacking with respect to the underlying graphite substrate and exhibit distinct electronic properties,forming a graphene homojunction.In addition,we construct homojunctions with alternative AB/twisted stacking nanodomains separated by parallel 5-7-5-7 GBs.Remarkably,the stacking orders of homojunctions are manipulated from AB/twist into twist/twist type through a STM tip.The controllable fabrication and manipulation of graphene homojunctions with 5-7-5-7 GBs and distinct stacking orders open an avenue for the construction of GBs-based devices in valleytronics and twistronics.展开更多
By the decomposition of copper nitrate at 400 ℃, oriented islands of copperoxide crystals were successfully fabricated on the amorphous glass surface. X ray diffraction (XRD), atom force microscope (AFM), and X ray p...By the decomposition of copper nitrate at 400 ℃, oriented islands of copperoxide crystals were successfully fabricated on the amorphous glass surface. X ray diffraction (XRD), atom force microscope (AFM), and X ray photoelectron spectroscopy (XPS) confirm the presence of copper oxide islands. The formation of oriented island structures is attributed to the following reasons: 1) the mismatch between the glass substrate and the copper oxide crystals during the relaxation of thermal expansion leads to the formation of islands; 2) the preorganized copper nitrate particles in the voids of colloidal crystals determine their ordered spatial distribution; 3) the strain of the glass substrate developing during calcination provides the driven energy for the orientation of copper oxide crystals along the same direction.展开更多
High-throughput small-molecule assays play essential roles in biomedical diagnosis,drug discovery,environmental analysis,and physiological function research.Nanoplasmonics holds a great potential for the label-free de...High-throughput small-molecule assays play essential roles in biomedical diagnosis,drug discovery,environmental analysis,and physiological function research.Nanoplasmonics holds a great potential for the label-free detection of small molecules at extremely low concentrations.Here,we report the development of nanoplasmonic paper(NP-paper)for the rapid separation and ultrasensitive detection of mixed small molecules.NP-paper employs nanogap-rich silver nanoislands on cellulose fibers,which were simply fabricated at the wafer level by using low-temperature solid-state dewetting of a thin silver film.The nanoplasmonic detection allows for the scalable quantification and identification of small molecules over broad concentration ranges.Moreover,the combination of chromatographic separation and nanoplasmonic detection allows both the highly sensitive fluorescence detection of mixed small molecules at the attogram level and the label-free detection at the sub-nanogram level based on surface-enhanced Raman scattering.This novel material provides a new diagnostic platform for the high-throughput,low-cost,and label-free screening of mixed small molecules as an alternative to conventional paper chromatography.展开更多
Glioblastoma multiforme(GBM)is the most common malignant primary brain tumor in adults.The precise identification and distinction of GBM heterogeneity from surrounding brain parenchyma at the cellular level and even a...Glioblastoma multiforme(GBM)is the most common malignant primary brain tumor in adults.The precise identification and distinction of GBM heterogeneity from surrounding brain parenchyma at the cellular level and even at the tissue level are important for GBM therapy.In this study,GBM cells are distinguished from normal astrocytes and non-central nervous system(CNS)tumor cells by surface-enhanced Raman scattering(SERS)based on gold nanoshell(SiO_(2)@Au)particles and support vector machine(SVM)algorithm.In addition,the gold nanoisland(AuNI)SERS substrates are further developed and explored for accurate detection of GBM at the tissue level.The distinction between glioma and trauma tissues,identification of different tumor grades,and IDH mutation are realized with the assistance of orthogonal partial least squares discriminant analysis(OPLS-DA)in a rapid,non-invasive,and convenient method.The results show that the developed SERS-based analytical method has the potential for practical application for the detection of GBM at the single-cell and tissue levels and even for real-time intraoperative diagnosis.展开更多
Finite-sized graphene sheets, such as graphene nanoislands （GNIs）, are promising candidates for practical applications in graphene-based nanoelectronics. GNIs with well-defined zigzag edges are predicted to have spi...Finite-sized graphene sheets, such as graphene nanoislands （GNIs）, are promising candidates for practical applications in graphene-based nanoelectronics. GNIs with well-defined zigzag edges are predicted to have spin-polarized edge-states similar to those of zigzag-edged graphene nanoribbons, which can achieve graphene spintronics. However, it has been reported that GNIs on metal substrates have no edge states because of interactions with the substrate. We used a combination of scanning tunneling microscopy, spectroscopy, and density functional theory calculations to demonstrate that the edge states of GNIs on an Ir substrate can be recovered by intercalating a layer of Si atoms between the GNIs and the substrate. We also found that the edge states gradually shift to the Fermi level with increasing island size. This work provides a method to investigate spin-polarized edge states in high-quality graphene nanostructures on a metal substrate.展开更多
基金supported by the International Doctoral Fellowship (IDF), Ibnu Sina Institute for Fundamental Science Study and research grants of MoHE GUP. Vot No. 02H94 and 07J80
文摘Structural and optical properties of ～ 20 nm Ge nanoislands grown on Si（100） by radio frequency （rI） magnetron sputtering under varying annealing conditions are reported. Rapid thermal annealing at a temperature of 600 ℃ for 30 s, 90 s, and 120 s are performed to examine the influence of annealing time on the surface morphology and photoluminescence properties. X-ray diffraction spectra reveal prominent Ge and GeO2 peaks highly sensitive to the annealing time. Atomic force microscope micrographs of the as-grown sample show pyramidal nanoislands with relatively high-density （～ 10^11 cm^-2）. The nanoislands become dome-shaped upon annealing through a coarsening process mediated by Oswald ripening. The room temperature photoluminescence peaks for both as-grown （～ 3.29 eV） and annealed （～ 3.19 eV） samples consist of high intensity and broad emission, attributed to the effect of quantum confinement. The red shift （～ 0.10 eV） of the emission peak is attributed to the change in the size of the Ge nanoislands caused by annealing. Our easy fabrication method may contribute to the development of Ge nanostructure-based optoelectronics.
基金We acknowledge financial support from the National Key Research&Development Projects of China(Nos.2016YFA0202300 and 2019YFA0308500)the National Natural Science Foundation of China(Nos.61888102,51872284,51922011,11974045,and 51761135130)+1 种基金the CAS Pioneer Hundred Talents Program,Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB30000000)China Postdoctoral Science Foundation(Nos.2018M641511,2018M630217,and 2019T120148).A portion of the research was performed in CAS Key Laboratory of Vacuum Physics.
文摘Controlling the atomic configurations of structural defects in graphene nanostructures is crucial for achieving desired functionalities.Here,we report the controlled fabrication of high-quality single-crystal and bicrystal graphene nanoislands(GNI)through a unique top-down etching and post-annealing procedure on a graphite surface.Low-temperature scanning tunneling microscopy(STM)combined with density functional theory calculations reveal that most of grain boundaries(GBs)formed on the bicrystal GNIs are 5-7-5-7 GBs.Two nanodomains separated by a 5-7-5-7 GB are AB stacking and twisted stacking with respect to the underlying graphite substrate and exhibit distinct electronic properties,forming a graphene homojunction.In addition,we construct homojunctions with alternative AB/twisted stacking nanodomains separated by parallel 5-7-5-7 GBs.Remarkably,the stacking orders of homojunctions are manipulated from AB/twist into twist/twist type through a STM tip.The controllable fabrication and manipulation of graphene homojunctions with 5-7-5-7 GBs and distinct stacking orders open an avenue for the construction of GBs-based devices in valleytronics and twistronics.
文摘By the decomposition of copper nitrate at 400 ℃, oriented islands of copperoxide crystals were successfully fabricated on the amorphous glass surface. X ray diffraction (XRD), atom force microscope (AFM), and X ray photoelectron spectroscopy (XPS) confirm the presence of copper oxide islands. The formation of oriented island structures is attributed to the following reasons: 1) the mismatch between the glass substrate and the copper oxide crystals during the relaxation of thermal expansion leads to the formation of islands; 2) the preorganized copper nitrate particles in the voids of colloidal crystals determine their ordered spatial distribution; 3) the strain of the glass substrate developing during calcination provides the driven energy for the orientation of copper oxide crystals along the same direction.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MEST)(2014022751,2014039957,2011-0031866)supported by a grant of the Korea Health Technology R&D Project through the Korea Health Industry Development Institute(KHIDI),funded by the Ministry of Health&Welfare,Republic of Korea(grant number:HI13C2181).
文摘High-throughput small-molecule assays play essential roles in biomedical diagnosis,drug discovery,environmental analysis,and physiological function research.Nanoplasmonics holds a great potential for the label-free detection of small molecules at extremely low concentrations.Here,we report the development of nanoplasmonic paper(NP-paper)for the rapid separation and ultrasensitive detection of mixed small molecules.NP-paper employs nanogap-rich silver nanoislands on cellulose fibers,which were simply fabricated at the wafer level by using low-temperature solid-state dewetting of a thin silver film.The nanoplasmonic detection allows for the scalable quantification and identification of small molecules over broad concentration ranges.Moreover,the combination of chromatographic separation and nanoplasmonic detection allows both the highly sensitive fluorescence detection of mixed small molecules at the attogram level and the label-free detection at the sub-nanogram level based on surface-enhanced Raman scattering.This novel material provides a new diagnostic platform for the high-throughput,low-cost,and label-free screening of mixed small molecules as an alternative to conventional paper chromatography.
基金supported by Key Research and Development Program:Social Development Project(No.BE2021653)Natural Science Foundation of Jiangsu Province(No.BK20201172)+1 种基金Key Program of Health Commission of Jiangsu Province(No.ZBD2020016)Zhejiang Provincial Natural Science Foundation of China(No.LR19H180001)。
文摘Glioblastoma multiforme(GBM)is the most common malignant primary brain tumor in adults.The precise identification and distinction of GBM heterogeneity from surrounding brain parenchyma at the cellular level and even at the tissue level are important for GBM therapy.In this study,GBM cells are distinguished from normal astrocytes and non-central nervous system(CNS)tumor cells by surface-enhanced Raman scattering(SERS)based on gold nanoshell(SiO_(2)@Au)particles and support vector machine(SVM)algorithm.In addition,the gold nanoisland(AuNI)SERS substrates are further developed and explored for accurate detection of GBM at the tissue level.The distinction between glioma and trauma tissues,identification of different tumor grades,and IDH mutation are realized with the assistance of orthogonal partial least squares discriminant analysis(OPLS-DA)in a rapid,non-invasive,and convenient method.The results show that the developed SERS-based analytical method has the potential for practical application for the detection of GBM at the single-cell and tissue levels and even for real-time intraoperative diagnosis.
基金This work is supported by the National Key Research and Development Projects of China （No. 2016YFA0202300）, the National Basic Research Program of China （Nos. 2013CBA01600 and 2015CB921103）, the National Natural Science Foundation of China （Nos. 61390501, 51325204, 51210003, and 61622116）, and the CAS Pioneer Hundred Talents Program. Work at Yanderbilt is partially supported by the Department of Energy grant DE- FG02-09ER46554 and by the McMinn Endowment. Y. Y. Z and S. T. P acknowledge the National Energy Research Scientific Computing Center （NERSC）, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231, and the Extreme Science and Engineering Discovery Environment （XSEDE）, which is supported by the National Science Foundation Grant ACI-1053575.
文摘Finite-sized graphene sheets, such as graphene nanoislands （GNIs）, are promising candidates for practical applications in graphene-based nanoelectronics. GNIs with well-defined zigzag edges are predicted to have spin-polarized edge-states similar to those of zigzag-edged graphene nanoribbons, which can achieve graphene spintronics. However, it has been reported that GNIs on metal substrates have no edge states because of interactions with the substrate. We used a combination of scanning tunneling microscopy, spectroscopy, and density functional theory calculations to demonstrate that the edge states of GNIs on an Ir substrate can be recovered by intercalating a layer of Si atoms between the GNIs and the substrate. We also found that the edge states gradually shift to the Fermi level with increasing island size. This work provides a method to investigate spin-polarized edge states in high-quality graphene nanostructures on a metal substrate.
