Experimental Principle
Due to their low density and large specific surface area, micrometer or nanoscale hollow spheres generally have nanostructured walls and exhibit many physical and chemical properties that are different from solid particles, such as optical, electrical, and magnetic properties. They have potential application value in many fields such as light, electricity, magnetism, sustained-release capsules, drug delivery, lightweight fillers, selective adsorption, catalysis, etc. Therefore, In recent years, research on hollow microspheres with different compositions has aroused great interest.
Many researchers have prepared a variety of hollow microspheres with crystalline or amorphous nanostructured spherical walls by designing different routes. In previous reports, hollow microspheres were mainly prepared by template methods, including hard template methods and soft template methods.
The hard template method refers to adding a spherical template to the liquid phase precipitation reaction. When the precipitation reaction is completed on the surface of the template, the template is removed to obtain hollow spheres. The hard templates used in the early days are mainly colloidal particles successfully prepared by liquid phase method. For example, spherical SiO2 particles prepared by sol-gel method have been widely used as hard templates for the preparation of hollow spheres, and then polystyrene spheres prepared by emulsion polymerization are widely used in the preparation of hollow spheres. In addition, carbon nanoparticles and other spherical particles are also used as templates to prepare hollow microspheres. The advantage of the hard template method is that the size and uniformity of the hollow spheres can be controlled by controlling the size of the hard template, and the thickness and composition of the sphere wall can be controlled by controlling the reaction system and precipitation process.
The soft template method refers to the preparation of hollow spheres by using a series of supramolecular aggregates composed of amphiphilic molecules such as vesicles, micelles and emulsions as templates. Because the size of this kind of template is in the order of nanometer, nano-sized hollow spheres can be prepared by soft template method, but because supramolecular aggregates such as vesicles and micelles are sensitive to the environmental state of the system, when the system environment changes in the process of precipitation or reaction. The maintenance of the morphology of soft template is the key to the successful preparation of hollow spheres, so there are many reports about the preparation of hollow spheres by hard template technology.
Because of the rich functional groups on the surface of carbon spheres, they are often used as templates to prepare hollow spheres. It has been reported that the hollow spheres prepared by carbon sphere templates mainly include oxides, metals and metal salts and other binary metal compounds, such as TiO2, Ga2O3, WO3, Fe2O3, Ni2O3, Co3O4, CeO2, MgO and CuO, while there are few reports on multi-metal compounds such as metal composite oxides, mainly because it is difficult to achieve uniform coating of various components on the template surface during the precipitation process.
In this experiment, we use the mixed solution of metal oxide precursor-glucose as the precursor solution to synthesize micron CoFe2O4 hollow spheres through hydrothermal treatment and subsequent calcination treatment. The hollow sphere wall is constructed from CoFe2O4 nanocrystals with a particle size of about 20nm. The formation mechanism of CoFe2O4 hollow spheres is further discussed and its magnetic properties are studied.
As an important magnetic material, cobalt ferrite has potential applications in high density magnetic recording, magnetic response imaging and drug delivery because of its high saturation magnetization, high coercivity, good mechanical hardness and excellent chemical stability. In this experiment, a simple hydrothermal method was used to synthesize nanostructured CoFe2O4 hollow microspheres. The purpose is to explore a new route for the synthesis of multicomponent compound hollow microspheres. It is expected that this material can show new or improved physical properties.
Product List
Click the product name to view product details.
| CAS NO. | Product Name | Inquiry |
| 12052-28-7 | Cobalt Iron Oxide Nanoparticles / Nanopowder | Inquiry |
| Nickel Cobalt Iron Oxide Nanoparticle Dispersion | Inquiry | |
| Nickel Cobalt Iron Oxide Nanoparticles / Nanopowder | Inquiry | |
| 1317-80-2 | Titanium dioxide | Inquiry |
| 12024-21-4 | Gallium(III) oxide | Inquiry |
| 12165-25-2 | Tungsten oxide | Inquiry |
| 11115-92-7 | Iron oxide | Inquiry |
| 11104-61-3 | Cobalt(II/III) oxide | Inquiry |
| 1309-48-4 | Magnesium oxide | Inquiry |
| 1317-38-0 | Copper(II) oxide | Inquiry |
Instruments and Reagents
Instruments
Teflon, stainless steel reactor, X-ray diffractometer, transmission electron microscope, high resolution transmission electron microscope, infrared spectrometer, specific surface and pore analyzer, thermogravimetric differential thermal analyzer, electron probe, quantum magnetometer, muffle furnace.
Reagents
Glucose, cobalt sulfate, ammonium ferrous sulfate.
Experimental Procedure
1. All reagents used in the preparation experiment of cobalt ferrite hollow spheres are of analytical grade, and no further drying or purification is required before use. The experimental process is as follows: completely dissolve 15g glucose in 80mL deionized water, then dissolve 7.5mmol (NH4)2Fe(SO4)2·6H2O and 3.75mmol CoSO4·7H2O in 10mL deionized water respectively. Mix the above three solutions thoroughly to obtain a clear mixed solution. Then, the mixed solution was transferred to a stainless steel reactor with a volume of 15 mL and lined with polytetrafluoroethylene for hydrothermal treatment. The temperature of the hydrothermal reaction was 160°C and the reaction time was 24h. After the reaction is completed, cool the reaction kettle to room temperature naturally, filter and separate the solid precipitate, wash the precipitate with deionized water 3 to 4 times, and dry it at 100°C in an air atmosphere. Then, the sample is dried in a muffle furnace at 1°C/min. The heating rate was increased from room temperature to 550°C, and kept at 550°C for 2 hours to completely remove the carbon sphere template, and finally obtain the hollow sphere product.
2. The phase structure of cobalt ferrite hollow sphere sample was characterized by X-ray diffractometer in the scanning range of 10 °~ 80 °. Using the strongest diffraction peak in the diffraction spectrum, the primary particle size of the sample is calculated by Scherrer formula. The morphology and lattice structure of the samples were characterized by transmission electron microscope and high resolution transmission electron microscope, respectively. The surface properties of the samples were characterized by infrared spectrometer and potassium bromide tablet pressing technique. The nitrogen adsorption-desorption curve of the sample was measured by specific surface area and pore analyzer (liquid nitrogen temperature T=-196°C), and the specific surface area of the sample was calculated by BET method. The thermogravimetric curve of the sample was given by thermogravimetric differential thermal analyzer (air atmosphere, flow rate 20mL/min, heating rate 10 °C / min). The samples were analyzed by elemental analysis (EDS) with electron probe technique. The magnetic properties of the samples are measured by a quantum magnetometer.
