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Structure-dependent performance of single-walled carbon nanotube films in transparent and conductive applications
摘要： We investigate a complex relationship between structural parameters of single-walled carbon nanotubes (namely, mean length, diameter, and defectiveness) and optoelectrical properties (equivalent sheet resistance) of thin films composed of the nanotubes. We obtained a systematic dataset describing the influence of CO2 concentration and growth temperature. On the basis of the experimental results, we prove the high Raman peak ratio (IG/ID), length, and diameter of the nanotubes to decrease the equivalent sheet resistance of the nanotube-based film. The approach employed highlights the change in the nanotube growth mechanism at the temperature coinciding with the phase transition between α-Fe and γ-Fe catalyst phases. We believe this work to be of high interest for researchers working not only in the field of transparent and conductive films based on nanocarbons, but also for those who reveals the fundamentals of the nanotube growth mechanism.
关键词： aerosol CVD,nanotube growth mechanism,optoelectronic properties,transparent conductive films,single-walled carbon nanotubes
更新于2025-09-19 17:13:59
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Seed‐Initiated Synthesis and Tunable Doping Graphene for High‐Performance Photodetectors
摘要： Due to the promising utilizations in nanoelectronics, doping-tunable graphene is paid extensive attentions. Nevertheless, a harmless approach to dope/co-dope graphene in a controllable and easy way with low cost is still unattainable. Herein, through seeding of 0D N & S dual-doped graphene quantum dots (N & S dual-doped GQDs) on a catalytic substrate and then dynamic chemical vapor deposition (CVD), a monolayered dual-doped graphene film is demonstrated. The concentrations of dopants in graphene are strictly discerned in accordance with preliminary seeding for dual-doped GQDs. Through the monitoring of growing process, the research elucidates the growth mechanism of the graphene, and unveils that dual-doped GQDs can serve as the nucleation centers for creating doped-graphene films by 2D epitaxial growth and thus graphene with designed dopant concentration can be obtained. Finally, the photodetector built on N & S dual-doped graphene film is found to perform satisfactorily, accompanying high detectivity (≈1.42 × 1010 cm Hz1/2 W?1) and responsivity (61 mA W?1), at wavelength of 1550 nm. The research proposes a dexterous approach for synthesizing tunably doped graphene films by the combination of locally controlled nucleation seeds and in situ CVD, which lays the foundation for applying graphene in industries of photonic and electronic devices.
关键词： growth mechanism,doping-tunable graphene,photodetectors,seed-initiated synthesis
更新于2025-09-19 17:13:59
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CVD controlled growth of large-scale WS <sub/>2</sub> monolayers
摘要： Monolayer tungsten disulfide (WS2) with a direct band gap of ca. 2.0 eV and stable properties has been a hotspot in two-dimensional (2D) nanoelectronics and optoelectronics. However, it remains challenging to successfully prepare monolayer WS2. In this paper, we report the chemical vapor deposition (CVD) growth behavior of hexagonal WS2 monolayers by using WS2 powders and sodium triosulfate (Na2S2O3) as precursors. We observed the Na2S2O3 has a significant effect on the WS2 triangular and leaf-like shapes. In addition, based on proposed S-termination and W-termination theory, the growth mechanisms for different shapes of WS2 were discussed.
关键词： monolayer,WS2,CVD,growth mechanism,Na2S2O3
更新于2025-09-16 10:30:52
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Monotectic growth evolution and raman scattering of self-assembled ZnO hierarchical micro-nanostructures
摘要： The self-assembled hierarchical micro-nanostructures with geometric complexity and/or constituent diversity are becoming a promising class of candidates for the next generation nanotechnology. Different from conventional vapor-liquid-solid (VLS) eutectic liquid droplets for one-dimensional (1D) nanowires, the Zn-Bi VLS monotectic liquid droplets are employed to build 1D, 2D and 3D ZnO into 3D hierarchical micro-nanostructures. As-obtained micro-nanostructures are well de?ned self-assembly and have not yet been observed in the conventional eutectic alloys. The synergy of monotectic droplets and nonthermal equilibrium is responsible for the evolution of ZnO hierarchical micro-nanostructures. Raman spectra show that E2H and E1L modes are shifted slightly towards the high-wavenumber side by an amount of 3.7 and 2 cm?1 as compared with undoped ZnO nanowires and an additional peak at 519.5 cm?1 is associated with Bi38OZn60. The results manifest that 3D ZnO micro-nanoarchitectures possess a bulk phonon structure. The monotectic liquid droplet route presented in this paper may offer a new opportunity to the fabrication of hierarchical nanostructures for realistic technology platforms with multifunctional coupling and interplay.
关键词： nanowires,growth mechanism,nanofabrications,nanostructures,Raman scattering
更新于2025-09-16 10:30:52
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Preparation and growth mechanism of CdS quantum dots in octadecene/glycerol two-phase systems
摘要： Two-phase synthesis is an advantageous alternative to the traditional synthetic method, due to its less toxicity, controllable, mild synthetic conditions and easy large-scale synthesis. However, meeting novel synthesis, the conventional trial-and-error approach could not provide a clear understanding. We herein report synthesis and mechanism investigation of CdS quantum dots in octadecene/glycerol two-phase system. The effects of different reaction parameters and conditions including reaction temperature, reaction time, reactant concentrations, and synthesis routes (one-step and two-step approach) on both nucleation and particle growth were investigated. It was found that the synthesis course was a growth dominated process depending on both CdS(monomer) and CdS (nuclei), and controlled by the interface of ODE/glycerol. The present work provided a new and clear understanding about two-phase system synthesis on semiconductor quantum dots, noble metal nanocrystals and some alloy nanomaterials.
关键词： Octadecene/glycerol two-phase systems,Growth mechanism,CdS quantum dots,One-step synthesis
更新于2025-09-16 10:30:52
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Electrically controlled growths of 4-N,N-dimethylamino-4a?2-Na?2-methyl-stilbazolium tosylate (DAST) organic microcrystals
摘要： 4-N,N-dimethylamino-4′-N′-methyl-stilbazolium tosylate (DAST) is one of the most important organic nonlinear optical (NLO) materials, but its controlled growth remains a challenge. Herein, we describe a novel method to control the growth of DAST on the surfaces of indium tin oxides coated with the patterned photoresists by electric field. Results indicate that zero-dimensional (0D) spherical DAST microcrystals tend to grow along the photoresist lines if an electric field with a low frequency of 500 Hz is applied. Rather differently, one-dimensional (1D) DAST microwires preferentially grow along the gaps of the photoresist lines under the control of an electric field with a high frequency of 1000 Hz. Growth of DAST microcrystals controlled by electric field leads to the increase in the crystallinity, but the chemical structures remain unchanged. Moreover, second harmonic generation signal was measured from the as-grown DAST microcrystals. The results presented in this work are helpful for rationally controlling the growth of 0D or 1D DAST microcrystals, and particularly, the strategy can be further expanded to control the growth of DAST derivatives or other organic NLO materials with similar chemical structures.
关键词： Spectral analyses,Growth mechanism,Electric field induction,DAST microcrystals,Nonlinear optical material
更新于2025-09-16 10:30:52
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Dual growth mode of boron nitride nanotubes in high temperature pressure laser ablation
摘要： The morphological analysis of the end of boron nitride nanotubes (BNNTs) using high-resolution transmission electron microscopy (HR-TEM) can provide valuable insight into the growth mechanism in high temperature pressure (HTP) laser ablation where the best quality of BNNT materials can be obtained so far. Two growth modes of BNNT coexisting during the synthesis process have been proposed based on HR-TEM observation and length analysis. One is the root growth mode, in which boron nitride (BN) species formed via the surface interaction between surrounding N2 molecules and boron nanodroplets incorporate into the tubular structure. Another mode called open-end growth mode means the prolongation of tube growth from the exposed BN edge surrounding the surface of boron nanodroplets which is constructed by the heterogeneous nucleation of absorbed BN radicals from the gas plume. The statistical data, the proportions of end structures and the length of BNNTs, could be fitted to two growth modes, and the open-end growth mode is found to be especially effective in producing longer nanotubes with a higher growth rate. The scientific understanding of the growth mechanism is believed to provide the control for optimized production of BNNTs.
关键词： growth mechanism,high temperature pressure laser ablation,open-end growth mode,root growth mode,boron nitride nanotubes,HR-TEM
更新于2025-09-12 10:27:22
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Growth mechanism of gold nanorods: the effect of tip-surface curvature as revealed by molecular dynamics simulations
摘要： To understand the anisotropic growth mechanism of gold nanorods (AuNRs) during colloidal synthesis is critical for controlling the nanocrystal size and shape and thus has implications in tuning the properties for applications in a wide range of research and technology fields. In order to investigate the role of the cetyltrimethylammonium bromide (CTAB) coating in the anisotropic growth mechanism of AuNRs, we used molecular dynamics (MD) simulations and built a computational model that considered explicitly the effect of the curvature of the gold surface on CTAB adsorption and therefore differentiated the CTAB arrangements on flat and curved surfaces, representing the lateral and tip facets of growing AuNRs, respectively. We verified that on a curved surface, a lower CTAB coverage density and larger intermicellar channels are generated compared to those on a flat surface. Using umbrella sampling simulations, we measured the free energy profile and verified that the environment around a curved surface corresponds to an easier migration from the solution to the gold surface for the [AuBr2]? species than does a flat surface. Long unbiased molecular dynamics simulations also corroborated the umbrella sampling results. Therefore, the [AuBr2]? diffusion through the environment of the tips is much more favorable than in the case of lateral facets. This shows that the surface curvature is an essential component of the anisotropic growth mechanism.
关键词： molecular dynamics,growth mechanism,CTAB,umbrella sampling,surface curvature,gold nanorod synthesis
更新于2025-09-12 10:27:22
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w-ZnO nanostructures with distinct morphologies: Properties and integration into dye sensitized solar cells
摘要： Herein, we report the cost-e?ective and single-step reaction strategies for the synthesis of distinct morphology of ZnO namely, nanoparticles, nanotubes and nanowires involving co-precipitation and hydrothermal methods. Powder X-Ray di?raction analysis indexed nine distinct peaks which correspond to the w-ZnO for all the synthesized nanostructures. The formation mechanism of nanostructures are proposed, in which the role of surfactants (polyvinylpyrrolidone and sodium dodecyl sulfate) and the oriented self-assembly are taken into account. The Raman spectral analysis of the nanostructures con?rms the presence of highly intense E2 high phonon vibrational modes corresponding to the movement of O-atoms and Zn sub-lattices of w-ZnO respectively. The prepared yellowish ZnO nanowires reveal intensi?cation in optical absorption and shrinkage in band gap due to increased oxygen vacancies in the sample. The quenching of green luminescence in the photo-luminescence spectrum of the nanowire further con?rms the oxygen vacancies. All the nanostructures were integrated into dye sensitized solar cells as photoanode materials. The photovoltaic parameters and electrochemical charge transfer properties of the fabricated dye sensitized solar cells (DSSCs) were evaluated by using photocurrent density-photovoltage curves and Nyquist plots of electrochemical impedance spectroscopic (EIS) studies. Due to the presence of large pore size in nanowires and nanotubes, the dye in?ltration and electrolyte di?usion rates are high and cause the highest photocurrent densities of 1.714 mA cm?2 and 1.813 mA cm?2 respectively. The speci?c hollow tube like nanostructures is channelizing the photo-injected electrons directly to the collector electrode and results in high photovoltaic conversion e?ciency of 1.109%. High value of charge transfer resistance across the ZnO/dye/electrolyte interfaces in nanocapsule and nanoparticle based DSSCs enforce low conversion e?ciency to the devices.
关键词： Growth mechanism,Band gap narrowing,Dye sensitized solar cells,Zinc oxide
更新于2025-09-12 10:27:22
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Photoluminescence properties as a function of growth mechanism for GaSb/GaAs quantum dots grown on Ge substrates
摘要： In this work, we use photoluminescence (PL) spectroscopy to investigate how self-assembled GaSb/GaAs quantum dots (QDs) depend on their growth mechanism. Carrier transfer (i.e., carrier recombination in QDs and escape through the barrier layer) is investigated as a function of excitation-power- and temperature-dependent PL measurements. A drastic blueshift of the QD peak energy from 1.23 to 1.30 eV and a further shift to 1.33 eV reveal the influence of the GaSb growth rate and the growth temperature on the optical properties of these QDs. The thermal activation energy is extracted from the temperature-dependent PL by fitting the integrated PL intensity of the QD peaks to the Arrhenius relation. The QDs grown at the growth rate of 0.1 monolayers/s at 450 °C have higher thermal activation energy (109 meV) than those grown at a lower growth rate and higher QD growth temperature. The observed PL characteristics are discussed in terms of QD size, uniformity of QDs, and material intermixing occurring during QD growth on the buffer layer and capping layer.
关键词： Ge substrates,quantum dots,photoluminescence,GaSb/GaAs,growth mechanism
更新于2025-09-11 14:15:04