Mg-doped GaN layers prepared by metalorganic chemical vapor deposition were annealed at temperatures between 550 and 950℃. Room temperature （RT） Hall and photoluminescence （PL） spectroscopy measurements were perf...Mg-doped GaN layers prepared by metalorganic chemical vapor deposition were annealed at temperatures between 550 and 950℃. Room temperature （RT） Hall and photoluminescence （PL） spectroscopy measurements were performed on the as-grown and annealed samples. After annealing at 850℃, a high hole concentration of 8 × 10^17 cm^-3 and a resistivity of 0. 8lΩ·cm are obtained. Two dominant defect-related PL emission bands in GaN.. Mg are investigated; the blue band is centered at 2. 8eV （BL） and the ultraviolet emission band is around 3.27eV （UVL）. The relative intensity of BL to UVL increases after annealing at 550℃, but decreases when the annealing temperature is raised from 650 to 850℃, and finally increases sharply when the annealing temperature is raised to 950~C. The hole concentration increases with increased Mg doping, and decreases for higher Mg doping concentrations. These results indicate that the difficulties in achieving high hole concentration of 10^18cm^-3 appear to be related not only to hydrogen passivation, but also to self-compensation.展开更多
Herein, we report a plasmonic metal nanoparti- cle-involved sensor for cyanide ion based on the inner filter effect by using photoluminescent carbon dots as the signal reporter. With commercial bee pollen as the carbo...Herein, we report a plasmonic metal nanoparti- cle-involved sensor for cyanide ion based on the inner filter effect by using photoluminescent carbon dots as the signal reporter. With commercial bee pollen as the carbon resource, we synthesized photoluminescent nitrogen-doped carbon dots by a one-pot hydrothermal process, and their fluores- cence quantum yield reached as high as 10.2 % ± 0.5 %. Fluorescence measurements indicated that the fluorescence of the carbon dots was insusceptible to the presence of many environmentally ordinary ions. Thanks to this “inert” property, we then developed a turn-on fluorescent sensor for cyanide ion in an inner filter effect manner by using carbon dots as the fluorophore and gold or silver nanoparticle as the light absorber. This detection technique is expected to be used for other metal nanoparticles-carbon dots ensemble fluorescent assays.展开更多
Two-dimensional （2D） layered transition metal dichalcogenide （TMD） materials （e.g., MoS2） have attracted considerable interest due to their atomically thin geometry and semiconducting electronic properties. With...Two-dimensional （2D） layered transition metal dichalcogenide （TMD） materials （e.g., MoS2） have attracted considerable interest due to their atomically thin geometry and semiconducting electronic properties. With ultrahigh surface to volume ratio, the electronic properties of these atomically thin semiconductors can be readily modulated by their environment. Here we report an investigation of the effects of mercury（II） （Hg^2＋） ions on the electrical transport properties of few-layer molybdenum disulfide （MoS2）. The interaction between Hg^2＋ ions and few-layer MoS2 was studied by field-effect transistor measurements and photoluminescence. Due to a high binding affinity between Hg2. ions and the sulfur sites on the surface of MoS2 layers, Hg^2＋ ions can strongly bind to MoS2. We show that the binding of Hg^2＋ can produce a p-type doping effect to reduce the electron concentration in n-type few-layer MoS2. It can thus effectively modulate the electron transport and photoluminescence properties in few-layer MoS2. By monitoring the conductance change of few-layer MoS2 in varying concentration Hg2~ solutions, we further show that few-layer MoS2 transistors can function as highly sensitive sensors for rapid electrical detection of Hg^2＋ ion with a detection limit of 30 pM.展开更多
The influence of water permeates almost all areas including biochemistry,chemistry,physics and is particularly evident in phenomena occurring at the interfaces of solid surface such as SiC nanocrystals,which are promi...The influence of water permeates almost all areas including biochemistry,chemistry,physics and is particularly evident in phenomena occurring at the interfaces of solid surface such as SiC nanocrystals,which are promising nanomaterials and exhibit unique surface chemical properties.In this paper,the quantum confinement effect and stability of 3C-SiC nanocrystals in aqueous solution as well as photoluminescence properties in water suspensions with different pH values are reviewed based on design and analysis of surface structures.On this basis,the significant progress of 3C-SiC nanocrystals in efficiently splitting water into usable hydrogen is summarized and the relative mechanisms are described.In addition,the water-soluble 3C-SiC quantum dots as robust and nontoxic biological probes and labels also are introduced as well as future prospects given.展开更多
文摘Mg-doped GaN layers prepared by metalorganic chemical vapor deposition were annealed at temperatures between 550 and 950℃. Room temperature （RT） Hall and photoluminescence （PL） spectroscopy measurements were performed on the as-grown and annealed samples. After annealing at 850℃, a high hole concentration of 8 × 10^17 cm^-3 and a resistivity of 0. 8lΩ·cm are obtained. Two dominant defect-related PL emission bands in GaN.. Mg are investigated; the blue band is centered at 2. 8eV （BL） and the ultraviolet emission band is around 3.27eV （UVL）. The relative intensity of BL to UVL increases after annealing at 550℃, but decreases when the annealing temperature is raised from 650 to 850℃, and finally increases sharply when the annealing temperature is raised to 950~C. The hole concentration increases with increased Mg doping, and decreases for higher Mg doping concentrations. These results indicate that the difficulties in achieving high hole concentration of 10^18cm^-3 appear to be related not only to hydrogen passivation, but also to self-compensation.
基金the funding support from the National Basic Research Program of China(2014CB931800,2013CB933900)the National Natural Science Foundation of China(21407140,21431006,91022032,91227103)+1 种基金J.Zhang is grateful for the China Postdoctoral Science Foundation(2013M531515)the Fundamental Research Funds for the Central Universities(WK2060190036)
文摘Herein, we report a plasmonic metal nanoparti- cle-involved sensor for cyanide ion based on the inner filter effect by using photoluminescent carbon dots as the signal reporter. With commercial bee pollen as the carbon resource, we synthesized photoluminescent nitrogen-doped carbon dots by a one-pot hydrothermal process, and their fluores- cence quantum yield reached as high as 10.2 % ± 0.5 %. Fluorescence measurements indicated that the fluorescence of the carbon dots was insusceptible to the presence of many environmentally ordinary ions. Thanks to this “inert” property, we then developed a turn-on fluorescent sensor for cyanide ion in an inner filter effect manner by using carbon dots as the fluorophore and gold or silver nanoparticle as the light absorber. This detection technique is expected to be used for other metal nanoparticles-carbon dots ensemble fluorescent assays.
文摘Two-dimensional （2D） layered transition metal dichalcogenide （TMD） materials （e.g., MoS2） have attracted considerable interest due to their atomically thin geometry and semiconducting electronic properties. With ultrahigh surface to volume ratio, the electronic properties of these atomically thin semiconductors can be readily modulated by their environment. Here we report an investigation of the effects of mercury（II） （Hg^2＋） ions on the electrical transport properties of few-layer molybdenum disulfide （MoS2）. The interaction between Hg^2＋ ions and few-layer MoS2 was studied by field-effect transistor measurements and photoluminescence. Due to a high binding affinity between Hg2. ions and the sulfur sites on the surface of MoS2 layers, Hg^2＋ ions can strongly bind to MoS2. We show that the binding of Hg^2＋ can produce a p-type doping effect to reduce the electron concentration in n-type few-layer MoS2. It can thus effectively modulate the electron transport and photoluminescence properties in few-layer MoS2. By monitoring the conductance change of few-layer MoS2 in varying concentration Hg2~ solutions, we further show that few-layer MoS2 transistors can function as highly sensitive sensors for rapid electrical detection of Hg^2＋ ion with a detection limit of 30 pM.
基金supported by the National Basic Research Programs of China(Grant Nos.2011CB922102 and 2013CB932901)the National Natural Science Foundation of China(Grant No.11374141)the Natural Science Foundation of Higher Education of Jiangsu(Grant No.12KJB140007)
文摘The influence of water permeates almost all areas including biochemistry,chemistry,physics and is particularly evident in phenomena occurring at the interfaces of solid surface such as SiC nanocrystals,which are promising nanomaterials and exhibit unique surface chemical properties.In this paper,the quantum confinement effect and stability of 3C-SiC nanocrystals in aqueous solution as well as photoluminescence properties in water suspensions with different pH values are reviewed based on design and analysis of surface structures.On this basis,the significant progress of 3C-SiC nanocrystals in efficiently splitting water into usable hydrogen is summarized and the relative mechanisms are described.In addition,the water-soluble 3C-SiC quantum dots as robust and nontoxic biological probes and labels also are introduced as well as future prospects given.
