Formation Of Nanoflowers Research Articles

Probing real time gold nanostar formation process using two-photon scattering spectroscopy

We report the growth mechanisms for the formation of 40nm star shape gold nanocrystals using real time TEM and in situ two-photon scattering technique. The overall process consists of several intermediate steps and these are: the nucleation process for the formation and accumulation of nanoseeds, Ostwald ripening process for the formation of nanoflower and intraparticle ripening process for the formation of the star sharp nanoparticles via nanocrowns. We demonstrates that the real time shape evolution of intermediate colloidal nanoparticles and their number density change can be fully accessed during the synthesis of star shaped gold nanoparticles using time dependent in situ TPS experiment.

Pattern formation of nanoflowers during the vapor–liquid–solid growth of silicon nanowires

Pattern formation of nanoflowers during the vapor–liquid–solid growth of Si nanowires is reported. Using transmission electron microscopy, scanning electron microscopy, and energy dispersive spectrometer analysis, we show that the flower consists of an Au/SiO x core–shell structure. Moreover, the growth of flower starts at the interface between the gold catalyst and the silicon nanowire, presumably by enhanced oxidation at this interface. The pattern formation can be classified as dense branching morphology (DBM). It is the first observation of DBM in a spherical geometry and at the nanoscale. The analysis of the average branching distance of this pattern shows that the pattern is most likely formed during the growth process, not the cooling process, and that the curvature of the gold droplet plays a crucial role in the frequency of branching.

Shape Evolution of ZnTe Nanocrystals: Nanoflowers, Nanodots, and Nanorods

We synthesized highly crystalline zinc telluride (ZnTe) nanocrystals with a controlled shape using various growth conditions. The following amines were used as activation agents for the zinc precursor: zinc stearate, octylamine (OA), dodecylamine (DDA), octadecylamine (ODA), and trioctylamine (TOA). Unique 3-D nanoflowers (av size = 20−120 nm) that consisted of a number of nanodots (av size = 4−11 nm) were efficiently produced when no amine or TOA was used. Dispersed nanodots were produced when OA, DDA, or ODA were used. These results indicate that the steric effect of alkyl chains plays an important role in the formation of nanoflowers. Furthermore, the shape evolution from nanoflowers to nanorods occurred at higher growth temperatures, and nanoflowers and nanorods eventually evolved into nanodots after incubation.

Synthesis of bismuth oxide nanostructures by an oxidative metal vapour phase depositiontechnique

The large-area arrays of one-dimensional (1D) nanowires and nanoflowers of bismuth oxide(Bi2O3) were synthesized by the oxidative metal vapour phase deposition technique withcontrolled flow of oxygen and constant working pressures. Surface morphology analysisshowed that the as-synthesized product at 10 Torr consisted of 1D nanowires with diametersabout 13–42 nm and lengths up to several tens of micrometres. The other working pressureof 30 Torr accounted for the formation of nanoflowers with a petal-like structure. Elementalanalysis confirms the presence of only the elements Bi and O. The crystalline nature of the1D nanostructure is revealed by high resolution transmission electron microscopy(HRTEM) and selected-area electron diffraction (SAED) studies. X-ray diffraction(XRD) analysis indicates the formation of a two-phase system with monoclinicα-Bi2O3 andtetragonal β-Bi2O3. Raman signals of the synthesized nanostructures are identifiedand assigned to various phonon vibration modes of Bi andBi2O3. The photoluminescence (PL) spectrum shows a visible broadband emission in thewavelength range, 500–800 nm.

Formation of nanostructures of hexaphenylsilole with enhanced color-tunable emissions

Nanostructures of 1,1,2,3,4,5-hexaphenylsilole (HPS) of various types were obtained on simple reprecipitation with THF as solvent and water as non-solvent. The formation and evolution of these nanostructures were monitored with scanning electron microscopy. Using picosecond time-correlated single-photon counting, we observed enhanced emission and fluorescence lifetimes at volume fractions 70–90% of added water. We report the first enhanced color-tunable emissions of a conjugated organic compound (HPS) due to the formation of nanoflowers, nanoglobules and microglobules, and provide time scales for those nanostructures and the corresponding intermolecular interactions in the aggregates.