Formation Mechanism Of Nanospheres Research Articles

Preparation and formation mechanism of size-controlled lignin nanospheres by self-assembly

Lignin has recently attracted much attention due to their renewable nature. Here we focused on a simple self-assembly method for fabricating size and shape uniform enzymatic hydrolysis lignin (EHL) nanospheres, without chemical modification of lignin. EHL was dissolved in tetrahydrofuran at different initial concentrations and subsequently self-assembly with adding water under magnetic stirring for fabricating the nanospheres. The self-assembled structure, process parameters and formation mechanism of the nanospheres were investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), dynamic light scattering (DLS), fourier transform infrared spectroscopy (FTIR), and UV–vis absorption spectra. Results showed that the nanospheres were formed through a layer-by-layer self-assembly approach from inside to outside based on π–π interactions, which enabled the formation of nanospheres in the size range of 190–590nm. Increasing the pre-dropping EHL concentration resulted in an increase of the average diameter and yield of the nanospheres. The nanospheres have good stability, and their average diameters had no significant change after 30days. The chemical structural features of the nanospheres had not produced a significant change in the preparation process. High preparation temperature brought about the formation of the gaps at the surface of the nanospheres due to the effect of volatile speed of solvent. Moreover, the average diameter of the nanospheres decreased with an increase of stirring rate or the dropping speed of water. The proposed EHL nanospheres are eco-friendly, cost-effective and therefore a promising candidate for biomass based carrier.

The Complete Control for the Nanosize of Spherical MCM-41

In this work, we present a systematic study on the complete control over the sphere diameters of MCM-41 nanospheres with different pore sizes. The mesoporous silica nanospheres with diameter range from 40 nm to 160 nm are synthesized by using cationic quaternary ammonium surfactants as template and TEOS as silicon source in sodium hydroxide aqueous solution via sol-gel supermolecular method. Nanospheres with fixed diameter can be obtained through the precise control over the molar ratio of NaOH/TEOS and other synthetic conditions. The range of sphere diameter for each sample prepared under adjustable reaction conditions is in a sharp distribution. Moreover, the formation mechanism for nanospheres with controlled morphological and structural features is proposed, and we suggest the optimal synthesis conditions of the MCM-41 nanospheres for the minimization of the Gibbs free energy deltaG. Besides, after depositing vanadium species on the MCM-41 support, the catalytic performance of V-MCM-41 for the selective oxidation of styrene by hydroperoxide increases with the diameter of the supports decreasing.

Surfactant-free Synthesis and Formation Mechanism of Fe3O4 Nanospheres in Mixed Solvent Ethylene Glycol–Water System

Abstract Uniform Fe3O4 nanospheres have been synthesized by a simple ethylene glycol–H2O system without adding any additives. The average diameter of the Fe3O4 nanospheres was 120–190 nm, and the nanospheres are formed by nanoparticles of several tens of nanometers. The presence of a certain amount of deionized water and the controlled reaction temperature plays an important role in the formation of the Fe3O4 nanospheres. The formation mechanism of the nanospheres is discussed on the basis of the experimental results.

Preparation of Silicon Nan Spheres by Using Electrical Discharge Machining Method

As one of the key technologies, preparation of silicon nanospheres is very important for developing the new types of silicon based solar cells. In this paper, with the establishment of a novel electrical discharge machining (EDM) system and the raw material of heavy doped mono-crystalline silicon (0.01Ω•cm), silicon nanospheres of which diameter are ranging from 25nm to 280nm have been successfully prepared by using EDM method. The micro surface topography and the elements composition are analyzed by the SEM and the EDS methods respectively. The formation mechanism of nanospheres has also been studied.

Effect of synthesis conditions on luminescence properties of PbWO4 nanospheres and nanoflakes

Lead tungstate (PbWO4) nanospheres and nanoflakes have been prepared by template directed synthesis using a biotemplate based on a new egg shell. The product was characterised by X-ray diffraction, scanning electron microscopy and luminescence spectrophotometer. The product morphology could be transformed from nanospheres to nanoflakes via a simple change of solvent. A green emission peak at 480 nm was observed for the flake PbWO4, whereas the emission peak was blue for the PbWO4 nanospheres. The effect of solvent type on the morphology and properties of the synthesised PbWO4 was investigated and a possible formation mechanism for nanospheres or sheets is proposed. The PbWO4 nanocrystals have potential optical applications.

Synthesis of Colloidal ZnSe Nanospheres by Ultrasonic-Assisted Aerosol Spray Pyrolysis

Colloidal monodisperse ZnSe nanospheres consisting of primary nanocrystals were prepared by aerosol spray pyrolysis with ultrasonic nebulization. The formation mechanism of nanospheres seems to be generation of primary ZnSe nanocrystals and subsequent aggregation of primary nanocrystals in a tube reactor. Monodispersed ZnSe nanospheres were found to be synthesized only from a specific mixture of precursors at a reaction temperature of 525 °C. Typical ratios were ZnO (5 mmol)/OA (10 mL)/TOPO (2 g)/ODE (10 mL) as a Zn precursor and Se (10 mmol)/TOP (5 mL)/ODE (5 mL) as a Se precursor. Those ZnSe nanoparticles were characterized by TEM, EDX, FT-IR, UV−vis, and PL techniques. The TEM image shows that the average diameter of ZnSe nanospheres is 41 nm, and primary ZnSe nanocrystals have a size of 2−3 nm. The XRD pattern of ZnSe nanoparticles shows that the crystal structure is zinc blende. The ZnSe nanospheres were confirmed to have a quantum size effect in their optical spectra and exhibit near band-edge lumin...