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A Simple Synthetic Approach To Prepare Silver Elongated Nanostructures: From Nanorods to Nanowires
摘要： A procedure for one-pot preparation and characterization of silver 1D nanostructures is described. The main advantages of this synthetic approach are the simplicity and reproducibility, where the size of the final product can be controlled just by changing the reaction time. This experiment is designed as a laboratory introduction to colloidal chemistry for undergraduate and graduate students; they can appreciate the role of the different reagents in a relatively complex reaction and understand the relation between the morphology of a metal at the nanoscale and some macroscopic properties, such as its visible absorption spectrum (i.e., color).
关键词： Nanotechnology,Synthesis,Second-Year Undergraduate,UV?Vis Spectroscopy,Physical Chemistry,Laboratory Instruction,Hands-On Learning/Manipulatives,First-Year Undergraduate/General,Metals,Colloids
更新于2025-09-04 15:30:14
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From the Bottom-Up: Toward Area-Selective Atomic Layer Deposition with High Selectivity
摘要： Bottom-up nanofabrication by area-selective atomic layer deposition (ALD) is currently gaining momentum in semiconductor processing, because of the increasing need for eliminating the edge placement errors of top-down processing. Moreover, area-selective ALD offers new opportunities in many other areas such as the synthesis of catalysts with atomic-level control. This Perspective provides an overview of the current developments in the field of area-selective ALD, discusses the challenge of achieving a high selectivity, and provides a vision for how area-selective ALD processes can be improved. A general cause for the loss of selectivity during deposition is that the character of surfaces on which no deposition should take place changes when it is exposed to the ALD chemistry. A solution is to implement correction steps during ALD involving for example surface functionalization or selective etching. This leads to the development of advanced ALD cycles by combining conventional two-step ALD cycles with correction steps in multistep cycle and/or supercycle recipes.
关键词： surface functionalization,semiconductor processing,area-selective atomic layer deposition,catalysts synthesis,selectivity,bottom-up nanofabrication,selective etching,ALD
更新于2025-09-04 15:30:14
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Rare earth phosphors based on spherical infinite coordination polymers
摘要： A novel luminescent infinite coordination polymer (Tb-M), constructed by the interaction between Tb3+ ions and 3,5-pyrazoledicarboxylate and malonate linkers, was prepared by water microwave-assisted synthesis. The material self-assembles into amorphous microspherical particles. Under UV excitation, a very intense green luminescence is observed by the naked eye at room temperature for Tb-M. A Gd3+ analogue compound (Gd-M) was also synthesized. Successful attempts at codoping Tb-M and Gd-M samples with Eu3+ and Dy3+ ions were carried out and different emission colors were obtained, including white-light emission.
关键词： infinite coordination polymers,rare earth phosphors,microwave-assisted synthesis,luminescence,white-light emission
更新于2025-09-04 15:30:14
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Space-Confined Seeded Growth of Black Silver Nanostructures for Solar Steam Generation
摘要： Plasmonic metal nanostructures have attracted considerable attention for solar energy harvesting due to their capability in photothermal conversion. However, the narrow resonant band of the conventional plasmonic nanoparticles greatly limits their application as only a small fraction of the solar energy can be utilized. Herein, a unique confined seeded growth strategy is developed to synthesize black silver nanostructures with broadband absorption in the visible and near-infrared spectrum. Through this novel strategy, assemblages of silver nanoparticles with widely distributed interparticle distances are generated in rod-shaped tubular spaces, leading to strong random plasmonic coupling and accordingly broadband absorption for significantly improved utilization of solar energy. With excellent efficiency in converting solar energy to heat, the resulting black Ag nanostructures can be made into thin films floating at the air/water interface for efficient generation of clean water steam through localized interfacial heating.
关键词： Space-confined synthesis,seeded growth,steam generation,photothermal,broadband absorption,black silver
更新于2025-09-04 15:30:14
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Facile Synthesis and Controllable Emission of Tm <sup>3+</sup> /Er <sup>3+</sup> -Doped and -Co-doped α-NaYbF <sub/>4</sub> Upconversion Nanocrystals
摘要： Tm3+, Er3+-doped and -co-doped α-NaYbF4 nanoparticles were synthesized via a facile hydrothermal route with oleic acid as the capping agent. Experimental results showed that the doped NaYbF4 nanoparticles possessed a cubic phase with the average size of ～13 nm. Upon excitation by a 980 nm laser, the as-synthesized nanoparticles exhibited blue and red upconversion emissions corresponding to the monodoped Tm3+, Er3+ in the cubic-phase NaYbF4, respectively, and intense green and red emissions in the Tm3+/Er3+-co-doped NaYbF4 nanoparticles. Furthermore, the possible energy transfer mechanism among Yb3+/Tm3+/Er3+ in α-NaYbF4 nanoparticles was also proposed. The cell toxicity test revealed that the as-synthesized upconversion nanoparticles possessed remarkably low cytotoxicity. All of the advantageous features including facile synthesis, controllable emission, and low cytotoxicity make the upconversion nanoparticles promising for multicolor bioimaging and anti-counterfeiting applications.
关键词： anti-counterfeiting applications,multicolor bioimaging,upconversion nanocrystals,hydrothermal synthesis,energy transfer mechanism,α-NaYbF4,low cytotoxicity,Tm3+/Er3+-doped
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Synthesis of Multiple Beam Linear Arrays with Uniform Amplitudes
摘要： A convex iterative algorithm for the synthesis of uniform amplitude, space-tapered linear phased arrays with simultaneous multiple beam optimization for 5G applications is presented. The performance of the algorithm is demonstrated by the synthesis of two arrays having 16 and 24 elements with 60 and 90 degree scan range, respectively. The effect of phase shifter quantization is also addressed. The results indicate that the space-tapered arrays with multiple beam optimization have improved radiation performance in terms of the side lobe level when compared to both single, broadside, beam optimized space-tapered arrays and uniformly distributed arrays with half wavelength spacing.
关键词： phased arrays,space taper,antenna synthesis,multibeam optimization,convex optimization,5G communications,density taper,linear antenna arrays
更新于2025-09-04 15:30:14
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Imaging With 3-D Aperture Synthesis Radiometers
摘要： The spatial resolution is still a problem in passive microwave remote sensing, especially in low frequency. In recent years, the satellite formation flying has been proposed. Based on this technique, a large array is able to be synthesized in orbit to achieve higher spatial resolution. However, it is a big challenge for the control system to constrain all the satellites in a coplane in orbit. The 3-D array configuration is a good choice for a synthesized array based on satellite formation flying. In this paper, the complete formulation of visibility functions, including system imperfections, in a 3-D aperture synthesis radiometer (3-D ASR) is derived. The array factor of a 3-D ASR is defined. The reconstructed modified brightness temperature (BT) is a 3-D linear convolution of the modified BT and the array factor. Based on this relationship, the reconstruction method for a practical 3-D ASR is studied. The numerical results demonstrate that the reconstruction method is correct and stable. Finally, a discussion is given to analyze several existing methods that were proposed to reconstruct BT image for 3-D arrays in radio astronomy and earth observation. Compared with these existing methods, our imaging method is more suitable for earth observation based on the technique of satellites formation flying in low earth orbit. In addition, according to the derivations, some mature techniques that were developed for 2-D ASRs may be applied to 3-D ASRs.
关键词： visibility functions,image reconstruction,array factor,3-D aperture synthesis radiometers (3-D ASRs),modified brightness temperature (BT)
更新于2025-09-04 15:30:14
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Application of Al-Doped SiC High Emissivity Powder Material Based on Infrared Radiating Coating
摘要： Combustion synthesis technology was used to prepare an Al-doped SiC infrared radiating ceramic powder material. The material’s microstructure was analyzed by XRD, TEM and an IRE-2 infrared emitting ability survey meter. The relationship between the powder’s architectural feature and the infrared radiating performance was obtained. According to the results, the Al atom enters the intracell by replacing a silicon atom and forms a structure of finite replacement-type solid solution, which results in an expansion of the SiC lattice parameter that consequently forms multiple structural defects, distorts the lattice and improves the emissivity. Furthermore, we found that the powder’s normal emissivity in the scope of 8-12 μm can reach 0.99. Finally, the powder’s application to infrared heating coating is discussed.
关键词： SiC lattice,Emissivity,Infrared radiating coating,Combustion synthesis
更新于2025-09-04 15:30:14
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Synthesis and characterization of alkoxy substituted p-cyano stilbene schiff bases
摘要： Schiff bases consist of aromatic have been used in various application including biological, inorganic and analytical chemistry. It also has been applied in optical and electrochemical sensors to enable detection of enhance selectivity and sensitivity of the sensors. These compounds might give excellent prospect in sensor. Schiff bases derived from 4-(4- aminostyryl)benzonitrile and three 4-alkoxybenzaldehyde derivatives are synthesis using ethanol as solvent. All compounds were characterized by Fourier transform-infrared spectroscopy (FT-IR), UV-Vis spectrophotometer and Nuclear Magnetic Resonance (NMR). FTIR showed formation of C=N (imine) stretching vibrations at range of 1604 cm-1 to 1609 cm- 1. In UV-vis, π-π* electronic transition of the C=N can be observed at peak range 361 nm. While in the δH NMR the peak of CH=N (Imine) group was found at δ 8.32-8.34 ppm and 13C NMR for three Schiff bases were discovered at δ 158.72, 158.73 and 158.71 ppm. In previous study there are several types of linker that have been used in E-DNA, especially alkanethiol. In this study, three new Schiff base derivatives have been synthesized and characterized due to it promising in sensor which prompted us to apply its as future potential linker in electrochemical DNA sensor.
关键词： future potential linker in E-DNA,Characterization,Synthesis,Schiff base
更新于2025-09-04 15:30:14
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Combined mechanochemical/thermal annealing approach for the synthesis of Co9Se8 with potential optical properties
摘要： Synthesis of Co9Se8 phase from metallic cobalt and selenium powders by one-pot mechanochemical synthesis in a planetary ball mill and subsequent thermal treatment in argon atmosphere is reported. Crystal structure and morphology of the products were characterized by X-ray diffraction, specific surface area measurements, and transmission electron microscopy. Our study revealed that only mixture with excess of Co resulted in the formation of higher fraction of the Co9Se8 phase. While milling of Co and Se in 13.5:8 ratio resulted in the synthesis of nanocrystalline hexagonal CoSe (freboldite) and only around 13?wt.% of the targeted Co9Se8 phase, additional isothermal treatment at 450?°C increased yield of the Co9Se8 phase to more than 70%. Optical properties of the product with the highest Co9Se8 fraction showed broad absorption in whole UV–Vis optical region and band-gap energy of 1.93?eV, blue-shifted relative to the bulk Co9Se8. Both UV–Vis and photoluminescence spectra indicated quantum size effect of the finest nanocrystals in Co9Se8 product. The new combined approach represents a simple, fast, and easy up-scalable route for the synthesis of Co9Se8.
关键词： thermal annealing,optical properties,mechanochemical synthesis,Co9Se8,quantum size effect
更新于2025-09-04 15:30:14