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Ultrasonication-assisted synthesis of CsPbBr <sub/>3</sub> and Cs <sub/>4</sub> PbBr <sub/>6</sub> perovskite nanocrystals and their reversible transformation
摘要： We demonstrate an ultrasonication-assisted synthesis without polar solvent of CsPbBr3 and Cs4PbBr6 perovskite nanocrystals (PNCs) and their reversible transformation. The as-prepared CsPbBr3 PNCs and Cs4PbBr6 PNCs exhibit different optical properties that depend on their morphology, size, and structure. The photoluminescence (PL) emission and quantum yield (QY) of the CsPbBr3 PNCs can be tuned by changing the ultrasound power, radiation time, and the height of the vibrating spear. The optimized CsPbBr3 PNCs show a good stability and high PL QY of up to 85%. In addition, the phase transformation between CsPbBr3 PNCs and Cs4PbBr6 PNCs can be obtained through varying the amount of oleylamine (OAm) and water. The mechanism of this transformation between the CsPbBr3 PNCs and Cs4PbBr6 PNCs and their morphology change are studied, involving ions equilibrium, anisotropic growth kinetics, and CsBr-stripping process.
关键词： ultrasonication,polar-solvent-free,CsPbBr3 PNCs,Cs4PbBr6 PNCs,reversible transformation
更新于2025-11-19 16:46:39
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Achieving high yield of graphene nanoplatelets in poloxamer-assisted ultrasonication of graphite in water
摘要： The role of surfactant (Pluronic? F 127) concentration on the yield and morphological characteristics of graphene nanoplatelets (GNPs) produced from the sonication of aqueous graphene suspensions is investigated in this work. By employing a wide surfactant concentration range (0.1–15 wt%) and sonication power densities up to 420 W L?1 we identify two graphene exfoliation regimes: the first occurs at low sonication power densities (<340 W L?1) and produces GNPs with sizes 200–300 nm, aspect ratios between 70 and 100, and concentrations up 1 mg mL?1. In that regime, the surfactant concentration has no effect on the exfoliation results. In the second exfoliation regime (>340 W L?1), surfactant concentrations greater than 10 wt% produce dramatic increases in GNP yields, namely up to 3.0 mg mL?1, and overall larger GNPs (350–500 nm) with smaller aspect ratios (5–60). We attribute these changes to the onset of a more energy intensive mechanism, termed cleavage. Cleavage involves the separation of graphite clusters in sub-bulk multi-layered graphene entities, as opposed to exfoliation, which involves the separation of individual or few-layer GNPs. Choosing an exfoliation regime by tuning simple process parameters enables control over the yield, size and morphology of the produced GNPs.
关键词： Poloxamer,Graphite exfoliation,Surfactant-assisted exfoliation,Ultrasonication,Graphene nanoplatelets
更新于2025-09-23 15:22:29
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From Bulk to Nano: A comparative investigation of Structural, Ferroelectric and Magnetic properties of Sm and Ti co-doped BiFeO3 multiferroics
摘要： In this investigation, multiferroic bulk ceramic materials with nominal compositions Bi1-xSmxFe1-yTiyO3 (x, y=0.00, 0.03, 0.06) are synthesized by conventional solid-state reaction technique. Their corresponding nanoparticles are fabricated from these bulk powder materials using cost-effective ultrasonication method. Then, the structural and multiferroic properties of the synthesized nanoparticles and their bulk-counterparts are compared. The X-ray diffraction patterns of 6% Sm-Ti co-substituted BiFeO3 nanoparticles as well as their bulk powder materials confirm rhombohedral to orthorhombic structural phase transition. Dynamic Light Scattering analysis (DLS) demonstrates the formation of particles with a size in the range of 10-100 nm for the 6% Sm-Ti co-substituted BiFeO3 sample. The fabricated nanoparticles of this particular composition also exhibit suppressed leakage current density and enhanced ferroelectric behavior. These nanoparticles also demonstrate improved ferromagnetic behavior compared to their bulk counterparts. Thus, the present investigation illustrates the impact of Sm and Ti as co-doping elements with 6% concentration in BiFeO3 nanoparticles with improved structural and multiferroic properties required for practical applications.
关键词： nanoparticles,DLS analysis,leakage current density,multiferroic properties,ultrasonication
更新于2025-09-23 15:21:01
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An Unexpected Transformation of Organic Solvents into 2D Fluorescent Quantum Dots During Ultrasonication Assisted Liquid Phase Exfoliation
摘要： Ultrasonication within organic solvents is widely used to exfoliate layered materials and produce two-dimensional (2D) nanostructures. Several 2D materials synthesized by such liquid phase exfoliation (LPE) approaches are reported to exhibit photoluminescence. In these approaches, it is presumed that while the 2D nanostructures are derived from the layered parent material undergoing delamination, the organic solvent serves as a dispersing medium. However, in this study, we show that the organic solvent also contributes towards formation of 2D nanostructures that are optically active. We show that that bare organic solvent, when exposed to ultrasonication, transforms into 2D photoluminescent carbon quantum dots (CQDs) that display blue, cyan, green, and yellow emissions depending upon the excitation wavelength. Although this finding is intuitive, it has remained unacknowledged in the design of experiments which require ultrasonication of layered materials in organic solvents. Our results suggest that optical properties of dispersions obtained by LPE embody a contribution not only from the 2D nanostructures derived from the layered material but also from the 2D CQDs that are formed as a natural result of the liquid medium being exposed to ultrasonication. We anticipate that this new physical insight would form an important addition to the guidelines for exfoliation and help in rightly inferring the optical properties of the 2D material dispersions produced by these methods.
关键词： 2D nanostructures,Carbon quantum dots,Organic solvents,Liquid phase exfoliation,Ultrasonication,Photoluminescence
更新于2025-09-11 14:15:04
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Studies on structural, optical and magnetic properties of (Ru, Mn) codoped ZnO nanostructures
摘要： Ruthenium and manganese codoped ZnO (RuxMn0.01Zn0.99-xO; x = 0.01, 0.02 and 0.03) were synthesized by sol-gel method via ultrasonication. The effects of codoping on structural, microstructural, optical and magnetic properties of the as-synthesized materials were characterized through X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS), photoluminescence (PL) and SQUID magnetometer, respectively. From the XRD pattern, it is evident that all the diffraction peaks can be indexed to the hexagonal wurtzite structure and shows the incorporation of dopants ie. Ru and Mn are substituted in the ZnO lattice. Nanosphere like morphology was observed in HRTEM analysis and the average particle sizes are found to be 20-30 nm, which are good agreement with the XRD crystallite size by Scherrer formula. Photoluminescence (PL) studies were carried out to investigate the optical properties of the as-synthesized materials and the defects related strong green emission peaks was observed in the TM codoped ZnO samples. It can be clearly seen from SQUID results, the loop is linear with the field indicating the presence of paramagnetism / anti ferromagnetism in the samples.
关键词： ZnO,sol-gel,optical properties,codoping,ultrasonication,magnetic properties,structural properties
更新于2025-09-10 09:29:36
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Structural Differences of BaTiO3 Ceramics Modified by Ultrasonic and Mechanochemical Methods
摘要： Barium titanate powders were synthesized by the modified solid-state method with ultrasonic (5 min) and mechanochemical (12 h) deagglomeration methods. The structure of the samples was verified using Fourier transform infrared spectroscopy (FT-IR) and X-ray diffractometer (XRD). Scanning electron microscopy (SEM) analysis of the powders showed that using ultrasonic deagglomeration significantly decreased the particle size with perfect homogeneity in the shortest time. The particle size of the powders was calculated as 44.7 nm and 80.4 nm for ultrasonic and mechanochemical deagglomeration, respectively. The sintered pellet by ultrasonic method had no abnormal grain growth, and the grain sizes were between 10 and 30 μm. The pellet by mechanochemical method had an abnormal grain growth, and the grain sizes were between 10 and 100 μm. The results showed that ultrasonication remarkably improved the structure of the samples in the shortest time.
关键词： deagglomeration,grain size,milling,ultrasonication,BaTiO3
更新于2025-09-10 09:29:36