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From colloidal CdSe quantum dots to microscale optically anisotropic supercrystals through bottom-up self-assembly
摘要： The development of fabrication techniques for novel nanostructured materials is one of the key tasks of modern materials science. One pathway to successfully complete this task is the bottom-up assembly of colloidal nanoparticles into ordered superstructures, possessing both the properties of individual nanoparticles and further novel properties resulting from their interactions. However, nanoparticle self-assembly depends on a variety of parameters, which makes the precise control of this process a complicated problem. Here, the time course of quantum dot (QD) self-assembly into ordered superstructures has been analyzed, along with the evolution of their morphological and optical properties. QD self-assembly occurs through two distinct stages (homo- and hetero-geneous), leading to the formation of supercrystals with a layered morphology. Analysis of the optical properties throughout the superstructures’ growth has shown that the absorption and photoluminescence (PL) bands are blue shifted, retaining almost the same PL lifetimes as in the initial QD solution. The supercrystals formed possess a further unique optical property caused by their layered morphology; namely, a four-fold symmetry characterized by strong birefringence. Such supercrystals may be used for the fabrication of microscale optical paths with high extinction coefficients and specific polarization properties for novel optoelectronic devices.
关键词： optical anisotropy,nanostructured materials,birefringence,self-assembly,quantum dots,supercrystals
更新于2025-11-21 11:08:12
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Electrochromic Properties of Nanostructured WO <sub/>3</sub> Thin Films Deposited by Glancing‐Angle Magnetron Sputtering
摘要： Tungsten oxide thin films are prepared by glancing-angle reactive magnetron sputtering at room temperature. The surface and cross-section morphologies are characterized by FE-SEM and TEM. The electrochromic properties of the thin films are studied using a three-electrode system in 1 m LiClO4/PC solution. When the glancing angle is kept at 80°, a nanocolumnar structured film is obtained. This nanocolumnar structured film shows a lower driving potential and better stability compared to the dense film. The charge capacity per unit area of the nanocolumnar structured film is determined to be 30.85 mc cm?2. The diffusion rates of injection and detachment of ions are determined to be Din = 6.57 × 10?10 cm2 s?1 and Dde = 6.55 × 10?10 cm2 s?1 under an applied potential of ±1.2 V, respectively. The optical modulation amplitude of the nanocolumnar structured film reaches 65% at a wavelength of 600 nm and the optical density is superior to that of the dense film.
关键词： nanostructured,electrochromic,WO3 thin films,glancing angle,magnetron sputtering
更新于2025-11-14 17:03:37
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Obtainment of Stabilized Zirconium Dioxide via the High-Frequency Magnetron Sputtering of a Metallic Target
摘要： The influence of the yttrium concentration on the structure of coatings prepared via the high-frequency magnetron sputtering of a metal target is investigated. The results of coating deposition in pure argon and a mixed (Ar + O2), reactive medium are discussed. It is demonstrated that a nonequilibrium body-centered-cubic solid solution based on zirconium with an extended homogeneous region (up to 16 at % Y) is formed under the condition that a target is sputtered in pure argon. During reactive-coating deposition, the formation of cubic or tetragonal zirconium dioxide is generated depending on the yttrium concentration. The tetragonal structure is created if the yttrium concentration is 8 at %. It is found that the obtained tetragonal zirconium dioxide is thermally stable both in terms of structure and in morphology upon heat treatment in air at 1100°C for 11 h.
关键词： zirconium dioxide,magnetron sputtering,nanostructured film,composite,coating
更新于2025-11-14 15:13:28
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Benthic microbial fuel cell equipped with a photocatalytic Cu2O-coated cathode
摘要： In this study, a photocatalytic benthic microbial fuel cell was developed and the cell performance was tested. A photocathode was fabricated by electrodeposition of Cu2O photocatalysts on carbon felt; with a proper deposition time of 15 min, a photocathode with optimal Cu2O compactness and an average Cu2O particle size of 0.97 μm was fabricated and was then covered with an amorphous carbon thin layer. Photoelectrochemical test results prove the pronounced visible light response of the fabricated photocathode. Results show that the coating of carbon thin layer could protect the Cu2O from self-reduction and also improve the photoelectrochemical performance of Cu2O crystalline grains. The photo-benthic microbial fuel cell (BMFC) produces a maximum power density of 249.0 mW m ? 2 and 186.7 mW m?2 under light irradiation and in the dark, which is 17.8 and 13.3 times higher than the common BMFC using carbon felt cathode in parallel, demonstrating the catalytic and photocatalytic effect of the fabricated photocathode. Polarization and EIS results prove the decrease of internal resistance by using the photocathode. The fabricated photocathode could improve the oxygen reduction rate on the cathode side, thus reduce the internal resistance and enhance the BMFC performance.
关键词： Benthic microbial fuel cells,Photocathode,Nanostructured catalyst,Visible light,Cu2O
更新于2025-09-23 15:23:52
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Surfactant templated oriented 1-D nanoscale platinum and palladium systems on a modified silicon surface
摘要： A templating method has been improved to form oriented one-dimensional metal nanostructures on a silicon surface. To achieve this, the silicon surface is modified with 3-aminopropyl trimethoxysilane. The cationic surfactant cetyltrimethylammonium bromide is used as a micellar template. The average width of the obtained Pt strips is 35 nm, the average width of the obtained Pd strips is 60 nm.
关键词： Platinum group,Atomic force microscopy,Surface modification,Nanostructured materials,Micelle templates
更新于2025-09-23 15:23:52
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Fullerene-to-MWCNT Structural Evolution Synthesized by Arc Discharge Plasma
摘要： The growth of multi-walled carbon nanotubes (MWCNTs) has been extensively studied using electron microscopy. The ex situ structural behavior was examined to investigate the growth of the MWCNTs under different environments and pressures using electron microscopy. The arc discharge plasma technique was applied to synthesize the MWCNTs by evaporating carbon through the arc plasma between two cylindrical graphite rods, with a background pressure of 10?2 to 102 mbar, inside a vacuum chamber under different ambient environments. The results showed that long MWCNT structures were successfully grown. We suggest that the mechanism involves: (i) fullerene formation; (ii) the elongation of fullerenes; and (iii) the growth of MWCNTs. Agglomeration with other structures then forms MWCNT bundles. We note that the pressure and environment in the vacuum chamber can affect the structure of the MWCNTs.
关键词： arc discharge,electron microscopy,carbon nanotube,nanostructured
更新于2025-09-23 15:23:52
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Atomically Precise Bimetallic Nanoclusters as Photosensitizers in Photoelectrochemical Cells
摘要： The atomically precise bimetallic nanocluster, Au24Ag20(PhCC)20(SPy)4Cl2 (1), is for the first time employed as a stable photosensitizer for photoelectrochemical applications. The sensitization of TiO2 nanotube arrays (TNA) with 1 greatly enhances the light harvest ability of the composite, as 1 shows high molar-extinction-coefficient in the UV-Vis region. Compared to a more standard Au25(SG)18 -TNA (2-TNA, SG: Glutathione), 1-TNA shows a much better stability under illumination both in neutral and basic conditions. The precise composition of the photosensitizers enables a direct comparison of the sensitization ability between 1 and 2. With the same cluster loading, the photocurrent produced by 1-TNA is 15 times larger than 2-TNA. The superior performance of 1-TNA over 2-TNA is attributed not only to the higher light absorption ability of 1, but also to the higher charge-separation efficiency. Besides, a ligand effect on the stability of the photoelectrode and charge-transfer between the NCs and the semiconductor is revealed. Our work paves the way to study the role of metal nanoclusters as photosensitizers at the atomic level, which is essential for the design of better material for light energy conversion.
关键词： Energy Conversion,Bimetallic Nanoclusters,Photosensitizers,Nanostructured Materials,Photoelectrochemical Cells
更新于2025-09-23 15:23:52
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Sol-gel assisted nano-structured SnO<sub>2</sub> sensor for low concentration ammonia detection at room temperature
摘要： Sol-gel assisted nano-structured SnO2 sensor for low concentration ammonia detection at room temperature. Upon exposure to 500 ppb and 1 ppm of NH3, sensor manifests appreciable response ~ 28 % and ~ 31.5 %, respectively. High response of the sensor at RT is attributed due to porous nanograins (with average particle size ~ 50 nm) based SnO2 thin film layer. Nanograins structure is obtained due to addition of glycerine in the sol solution, which also leads to porosity enhancement of the sensing layer. Good reproducibility and appreciable immunity to drift behavior are other attributes of the fabricated device. High response and good selectivity towards ammonia are observed with very fast response and recovery time at RT, for extreme low concentrations level ~ 55 % RH for concentration range 500 ppb-500 ppm. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and scanning electron microscopy (SEM) results are used to study the structural, chemical composition, topography and morphological characteristics of the prepared SnO2 thin film, respectively.
关键词： Sol-gel,Room temperature,Ammonia sensor,Metal oxides,% Response,Nanostructured
更新于2025-09-23 15:23:52
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Ultra-broadband second harmonic generation in ZnO nano-tetrapod with over-one-octave bandwidth
摘要： Broadband nonlinear optical frequency conversion has attracted considerable interest in many applications such as optical communication, frequency comb generation and so on. Here, we report on the ultra-broadband second harmonic generation (SHG) from the Zinc oxide nano-tetrapod with less stringent phase-matching requirement. Using a super-continuum source together with an optical parametric oscillator as the excitation light, a broadband SHG with over-one-octave bandwidth spanning from the ultraviolet to near-infrared (375-1100 nm) is readily obtained. The SHG dependence of pump polarization and pump power is also characterized systematically. This nanoscale ultra-broadband optical converter may open a new way for various applications ranging from imaging to on-chip all-optical signal processing operations.
关键词： Nonlinear optics,Nanostructured materials
更新于2025-09-23 15:22:29
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Single-Step Synthesis and Optical Properties of Bimetallic Fe–Ag Nanoparticles
摘要： Bimetallic nanoparticles containing ferromagnetic iron (Fe) and plasmonic silver (Ag) are synthesized by one-step chemical reduction process. Structural and optical properties of nanoparticles are studied by transmission electron microscopy, X-ray diffraction technique, UV-Visible spectroscopy and photoluminescence measurement. Tunable optical properties with the variation of Ag percentage in the Fe–Ag nanoparticles are observed. Sharp absorption peak due to localized surface plasmon resonance (LSPR) is observed in the visible spectrum range for Fe–Ag nanoparticles which is absent in Fe nanoparticles. LSPR peak shows redshift due to variation in shape and size of the nanoparticles having higher Ag content. Enhanced photoluminescence in the bimetallic nanoparticles is attributed to the observed surface plasmon resonance.
关键词： Optical Properties,Nanostructured Materials,Luminescence,Chemical Synthesis
更新于2025-09-23 15:22:29