共查询到20条相似文献,搜索用时 31 毫秒
1.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(51):16551-16555
Oscillatory flow reactors provide a surface energy‐driven approach for automatically screening reaction conditions and studying reaction mechanisms of biphasic nanocrystal ligand‐exchange reactions. Sulfide and cysteine ligand‐exchange reactions with as‐synthesized CdSe quantum dots (QDs) are chosen as two model reactions. Different reaction variables including the new‐ligand‐to‐QD ratio, the size of the particles, and the original ligand type are examined systematically. Based on the in situ‐obtained UV/Vis absorption spectra during the reaction, we propose two different exchange pathways for the sulfide exchange reaction. 相似文献
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《Angewandte Chemie (International ed. in English)》2017,56(46):14737-14742
Tri(pyrazolyl)phosphanes ( 5 R1,R2) are utilized as an alternative, cheap and low‐toxic phosphorus source for the convenient synthesis of InP/ZnS quantum dots (QDs). From these precursors, remarkably long‐term stable stock solutions (>6 months) of P(OLA)3 (OLAH=oleylamine) are generated from which the respective pyrazoles are conveniently recovered. P(OLA)3 acts simultaneously as phosphorus source and reducing agent in the synthesis of highly emitting InP/ZnS core/shell QDs. These QDs are characterized by a spectral range between 530–620 nm and photoluminescence quantum yields (PL QYs) between 51–62 %. A proof‐of‐concept white light‐emitting diode (LED) applying the InP/ZnS QDs as a color‐conversion layer was built to demonstrate their applicability and processibility. 相似文献
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Mojtaba Mirhosseini Moghaddam Dr. Mostafa Baghbanzadeh Dr. Amin Sadeghpour Prof. Dr. Otto Glatter Prof. Dr. C. Oliver Kappe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(35):11629-11636
In recent years, continuous‐flow/microreactor processing for the preparation of colloidal nanocrystals has received considerable attention. The intrinsic advantages of microfluidic reactors have opened new opportunities for the size‐controlled synthesis of nanocrystals either in the laboratory or on a large scale. Herein, an experimentally simple protocol for the size‐tunable continuous‐flow synthesis of rather monodisperse CdSe quantum dots (QDs) is presented. CdSe QDs are manufactured by using cadmium oleate as cadmium source, selenium dioxide as selenium precursor, and 1‐octadecene as solvent. Exploiting selenium dioxide as selenium source and 1‐octadecene as solvent allows execution of the complete process in open air without any requirement for air‐free manipulations using a glove box or Schlenk line. Continuous‐flow processing is performed with a stainless steel coil of 1.0 mm inner diameter pumping the combined precursor solution through the reactor by applying a standard HPLC pump. The effect of different reaction parameters, such as temperature, residence time, and flow rate, on the properties of the resulting CdSe QDs was investigated. A temperature increase from 240 to 260 °C or an extension of the residence time from 2 to 20 min affords larger nanocrystals (range 3–6 nm) whereas the size distribution does not change significantly. Longer reaction times and higher temperatures result in QDs with lower quantum yields (range 11–28 %). The quality of the synthesized CdSe QDs was confirmed by UV/Vis and photoluminescence spectroscopy, small‐angle X‐ray scattering, and high‐resolution transmission electron microscopy. Finally, the potential of this protocol for large‐scale manufacturing was evaluated and by operating the continuous‐flow process for 87 min it was possible to produce 167 mg of CdSe QDs (with a mean diameter of 4 nm) with a quantum yield of 28 %. 相似文献
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A. S. Chizhov N. E. Mordvinova M. N. Rumyantseva I. V. Krylov K. A. Drozdov Xiaogan Li A. M. Gas’kov 《Russian Journal of Inorganic Chemistry》2018,63(4):512-518
Nanocomposites based on nanocrystalline ZnO and CdSe and InP nanocrystals (quantum dots) have been synthesized by chemical precipitation and high-temperature colloidal synthesis. The microstructure parameters of the oxide matrix and the size of the CdSe and InP nanocrystals have been determined. A correlation was established between the spectral dependence of the photoconductivity of nanocomposites and the optical absorption spectra of quantum dots. The influence of CdSe and InP quantum dots on the interaction of ZnO with NO2 under visible light irradiation has been studied. It has been shown that the synthesized nanocomposites can be used to detect NO2 under illumination with green light without additional thermal heating. 相似文献
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We designed a temperature-controllable droplet microreactor with more precisely temperature control and shorter synthesis time for water-soluble AgInS2 QDs synthesis. When reaction temperature increased from 30 ℃ to 70 ℃, QDs fluorescence peak constantly red-shifted from 590 nm to 720 nm along with enhanced fluorescence QY and intensity, we can get products with the maximum fluorescence intensity and the QY of 8.8% at 70 ℃. 相似文献
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Kim SW Zimmer JP Ohnishi S Tracy JB Frangioni JV Bawendi MG 《Journal of the American Chemical Society》2005,127(30):10526-10532
Quantum dots with a core/shell/shell structure consisting of an alloyed core of InAs(x)P(1-x), an intermediate shell of InP, and an outer shell of ZnSe were developed. The InAs(x)P(1-x) alloyed core has a graded internal composition with increasing arsenic content from the center to the edge of the dots. This compositional gradient results from two apparent effects: (1) the faster reaction kinetics of the phosphorus precursor compared to the arsenic precursor, and (2) a post-growth arsenic-phosphorus exchange reaction that increases the arsenic content. The cores have a zinc blend structure for all compositions and show tunable emission in the near-infrared (NIR) region. A first shell of InP leads to a red-shift and an increase in quantum yield. The final shell of ZnSe serves to stabilize the dots for applications in aqueous environments, including NIR biomedical fluorescence imaging. These NIR-emitting core/shell/shell InAs(x)P(1-x)/InP/ZnSe were successfully used in a sentinel lymph node mapping experiment. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(15):4354-4358
3D‐printed flow reactors were designed, fabricated from different materials (PLA, HIPS, nylon), and used for a catalytic stereoselective Henry reaction. The use of readily prepared and tunable 3D‐printed reactors enabled the rapid screening of devices with different sizes, shapes, and channel dimensions, aimed at the identification of the best‐performing reactor setup. The optimized process afforded the products in high yields, moderate diastereoselectivity, and up to 90 % ee . The method was applied to the continuous‐flow synthesis of biologically active chiral 1,2‐amino alcohols (norephedrine, metaraminol, and methoxamine) through a two‐step sequence combining the nitroaldol reaction with a hydrogenation. To highlight potential industrial applications of this method, a multistep continuous synthesis of norephedrine has been realized. The product was isolated without any intermediate purifications or solvent switches. 相似文献
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This review surveys the synthesis of heterocycles under continuous‐flow conditions, including the use of chip‐based microreactors, coil‐based flow reactors, and capillary or tubular devices. J. Heterocyclic Chem., 2011. 相似文献
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We present a microfluidic artificial photosynthetic platform that incorporates quantum dots and redox enzymes for photoenzymatic synthesis of fine chemicals under visible light. Similar to natural photosynthesis, photochemical cofactor regeneration takes place in the light-dependent reaction zone, which is then coupled with the light-independent, enzymatic synthesis in the downstream of the microchannel. 相似文献
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Sahoo Y Poddar P Srikanth H Lucey DW Prasad PN 《The journal of physical chemistry. B》2005,109(32):15221-15225
Quantum dots of InP:Mn are chemically prepared by following hot colloidal nanochemistry with starting precursors that obviate the need for external surfactant. These quantum dots are uniform spheres with 3-nm diameters; they are crystalline, photoluminescent, and magnetic. The crystallographic and optical properties are similar to those of undoped InP nanocrystallites, while the magnetism is consistent with the ferromagnetic response observed in a class of diluted magnetic semiconductors. Because of the ultrafine sizes, the sample shows superparamagnetic behavior, whereas ferromagnetic hysteresis loops are clearly seen below the blocking temperature. Structural characterization and analysis confirm that the magnetism in these quantum dots is not due to segregated binary MnP or MnO phases and that they truly represent a homogeneous dilute magnetic semiconductor. 相似文献
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《化学:亚洲杂志》2017,12(22):2916-2921
The doping of nitrogen into carbon quantum dots is vitally important for improved fluorescence performance. However, the synthesis of nitrogen‐doped carbon quantum dots (N‐CQDs) is usually conducted under strong acid and high temperature, which results in environmental pollution and energy consumption. Herein, the N‐CQDs were prepared by a mild one‐pot hydrothermal process. The hydrothermal reaction temperature was adjusted to control the particle size, nitrogen/carbon atomic ratio, and quantum yield. The products were water soluble with a narrow particle size distribution and good dispersion stability over a wide pH range. The N‐CQDs could penetrate into the HeLa cell nucleus without any further functionalization. Moreover, the fluorescence of N‐CQDs could be selectively quenched by Cu2+, which suggested applications for the detection of Cu2+ in human plasma. 相似文献
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The synthesis of a novel water‐soluble Mn‐doped CdTe/ZnS core‐shell quantum dots using a proposed ultrasonic assistant method and 3‐mercaptopropionic acid (MPA) as stabilizer is descried. To obtain a high luminescent intensity, post‐preparative treatments, including the pH value, reaction temperature, reflux time and atmosphere, have been investigated. For an excellent fluorescence of Mn‐doped CdTe/ZnS, the optimal conditions were pH 11, reflux temperature 100°C and reflux time 3 h under N2 atmosphere. While for phosphorescent Mn‐doped CdTe/ZnS QDs, the synthesis at pH 11, reflux temperature 100°C and reflux time 3 h under air atmosphere gave the best strong phosphorescence. The characterizations of Mn‐doped CdTe/ZnS QDs were also identified using AFM, IR, powder XRD and thermogravimetric analysis. The data indicated that the photochemical stability and the photoluminescence of CdTe QDs are greatly enhanced by the outer inorganic ZnS shell, and the doping Mn2+ ions in the as‐prepared quantum dots contribute to strong luminescence. The strong luminescence of Mn‐doped CdTe/ZnS QDs reflected that Mn ions act as recombination centers for the excited electron‐hole pairs, attributing to the transition from the triplet state (4T1) to the ground state (6A1) of the Mn2+ ions. All the experiments demonstrated that the surface states played important roles in the optical properties of Mn‐doped CdTe/ZnS core‐shell quantum dots. 相似文献
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Wang F Yu H Li J Hang Q Zemlyanov D Gibbons PC Wang LW Janes DB Buhro WE 《Journal of the American Chemical Society》2007,129(46):14327-14335
Colloidal InP quantum wires are grown by the solution-liquid-solid (SLS) method, and passivated with the traditional quantum dots surfactants 1-hexadecylamine and tri-n-octylphosphine oxide. The size dependence of the band gaps in the wires are determined from the absorption spectra, and compared to other experimental results for InP quantum dots and wires, and to the predictions of theory. The photoluminescence behavior of the wires is also investigated. Efforts to enhance photoluminescence efficiencies through photochemical etching in the presence of HF result only in photochemical thinning or photooxidation, without a significant influence on quantum-wire photoluminescence. However, photooxidation produces residual dot and rod domains within the wires, which are luminescent. The results establish that the quantum-wire band gaps are weakly influenced by the nature of the surface passivation and that colloidal quantum wires have intrinsically low photoluminescence efficiencies. 相似文献
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Mesoporous Silica Particles Integrated with All‐Inorganic CsPbBr3 Perovskite Quantum‐Dot Nanocomposites (MP‐PQDs) with High Stability and Wide Color Gamut Used for Backlight Display
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Hung‐Chia Wang Shin‐Ying Lin An‐Cih Tang Dr. Bheeshma Pratap Singh Hung‐Chun Tong Dr. Ching‐Yi Chen Dr. Yu‐Chun Lee Dr. Tzong‐Liang Tsai Prof. Dr. Ru‐Shi Liu 《Angewandte Chemie (International ed. in English)》2016,55(28):7924-7929
All‐inorganic CsPbX3 (X=I, Br, Cl) perovskite quantum dots (PQDs) have been investigated because of their optical properties, such as tunable wavelength, narrow band, and high quantum efficiency. These features have been used in light emitting diode (LED) devices. LED on‐chip fabrication uses mixed green and red quantum dots with silicone gel. However, the ion‐exchange effect widens the narrow emission spectrum. Quantum dots cannot be mixed because of anion exchange. We address this issue with a mesoporous PQD nanocomposite that can prevent ion exchange and increase stability. We mixed green quantum‐dot‐containing mesoporous silica nanocomposites with red PQDs, which can prevent the anion‐exchange effect and increase thermal and photo stability. We applied the new PQD‐based LEDs for backlight displays. We also used PQDs in an on‐chip LED device. Our white LED device for backlight display passed through a color filter with an NTSC value of 113 % and Rec. 2020 of 85 %. 相似文献
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Kyungnam Kim Dongsuk Yoo Hyekyoung Choi Dr. Sudarsan Tamang Jae‐Hyeon Ko Sungwoo Kim Prof. Yong‐Hyun Kim Prof. Sohee Jeong 《Angewandte Chemie (International ed. in English)》2016,55(11):3714-3718
Wet chemical synthesis of covalent III‐V colloidal quantum dots (CQDs) has been challenging because of uncontrolled surfaces and a poor understanding of surface–ligand interactions. We report a simple acid‐free approach to synthesize highly crystalline indium phosphide CQDs in the unique tetrahedral shape by using tris(dimethylamino) phosphine and indium trichloride as the phosphorus and indium precursors, dissolved in oleylamine. Our chemical analyses indicate that both the oleylamine and chloride ligands participate in the stabilization of tetrahedral‐shaped InP CQDs covered with cation‐rich (111) facets. Based on density functional theory calculations, we propose that fractional dangling electrons of the In‐rich (111) surface could be completely passivated by three halide and one primary amine ligands per the (2×2) surface unit, satisfying the 8‐electron rule. This halide–amine co‐passivation strategy will benefit the synthesis of stable III‐V CQDs with controlled surfaces. 相似文献
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Growth of InP nanostructures via reaction of indium droplets with phosphide ions: synthesis of InP quantum rods and InP-TiO2 composites 总被引:1,自引:0,他引:1
Nedeljković JM Mićić OI Ahrenkiel SP Miedaner A Nozik AJ 《Journal of the American Chemical Society》2004,126(8):2632-2639
InP quantum rods were synthesized via the reaction of monodispersed colloidal indium droplets with phosphide ions. In(0) droplets, which do not act as a catalyst but rather a reactant, are completely consumed. The excess electrons that are produced in this reaction are most likely transferred to an oxide layer at the indium surface. For the synthesis of InP quantum rods with a narrow size distribution, a narrow size distribution of In(0) particles is also required because each indium droplet serves as a template to strictly limit the lateral growth of individual InP nanocrystals. Free-standing quantum rods, 60, 120, or 150 A in diameter, with aspect ratios of 1.6-3.5, and without the residual metallic catalyst at the rod tip, were synthesized from the diluted transparent solution of metallic indium particles. The same approach was used to synthesize InAs quantum rods. A photoactive InP-TiO(2) composite was also prepared by the same chemical procedure; InP nanocrystals grow as well-defined spherical or slightly elongated shapes on the TiO(2) surface. 相似文献
20.
On‐chip generation of monodisperse giant unilamellar lipid vesicles containing quantum dots
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Monodispersed lipid vesicles have been used as a drug delivery vehicle and a biochemical reactor. To generate monodispersed lipid vesicles in the nano‐ to micrometer size range, an extrusion step should be included in conventional hand‐shaking method of lipid vesicle synthesis. In addition, lipid vesicles as a drug carrier still need to be improved to effectively encapsulate concentrated biomolecules such as cells, proteins, and target drugs. To overcome these limitations, this paper reports a new microfluidic platform for continuous synthesis of small‐sized (~10 μm) giant unilamellar vesicles (GUVs) containing quantum dots (QDs) as a nanosized model drug. To generate GUVs, we introduced an additional cross‐flow to break vesicles into small size. 1,2 ‐ dimyristoyl‐sn‐glycero ‐ 3 ‐ phosphocholine (DMPC) in an octanol–chloroform mixture was used in the construction of self‐assembled membrane. Consequently, we have successfully demonstrated the fabrication of monodispersed GUVs with 7?12 μm diameter containing QDs. The proposed synthesis method of cell‐sized GUVs would be highly desirable for applications such as multipurpose drug encapsulation and delivery. 相似文献