材料綜合實驗：lab IV Nanoemulsion syntn-gold alloy nanocrystals-a

1、South University of Science and Technology of ChinaDepartment of Materials Science and EngineeringComprehensive Experiments of MaterialsLab IV: Nanoemulsion synthesis and characterization of iron-gold alloy nanocrystalsObjectivesMaster the principle of the nanoemulsion method.Understand the general

2、procedure of materials preparation: synthesis, characterization, application.Understand the reaction mechanism of synthesizing iron-gold alloy nanocrystals.Learn about how to analyze the data from XRD, UV-Vis spectrum, VSM, SEM and TEM.Introduction Nanocrystals of multiple constituents bestow multi-

3、functionality to accomplish multiple purposes, most promisingly with enhanced performance in a single nanovehicle, and have gained momentum in the interdisciplinary converging exploit of physical and life sciences with nanotechnology, in prospective of practical relevance and basic studies. Of vast

4、awareness, gold is a precious, versatile element and has valuable, diverse applications in the fields of catalysis, electronics, and optoelectronics. And ascribing to its marvelous magnetic properties and readiness to be converted to bio-friendly oxides, the element iron is an excellent candidate fo

5、r a wide range of applications such as magnetic recording, magnetic seals, printing, magnetic resonance imaging, drug delivery, biodetection, and cell tagging and separation. Appreciably, amalgamation of Au and Fe into one AuFe alloy or intermetallic nanostructure can be more fascinating than the co

6、rresponding monoelements, offering potential functions in both magnetic and optical properties in addition to the biological compatibility and easy linkage to biomolecules endowed by the constituents. At present, many methods have been used to synthesis iron-gold alloy nanocrydtals such as sol-therm

7、al, hydrothermal, HYPERLINK /method_of_precipitation precipitation and emulsion. In this experiment, the iron-gold nanocrystals will be synthesized by nanoemulsion and their optical and magnetic properties will be investigated. Emulsion is a thermodynamically unstable system consisting of at least t

8、wo immissible liquid phases, one of which is dispersed as globules in the other liquid phase which is continuous phase. The dispersed phase in nanoemulsion typically comprises ultrasmall particles or droplets, with a size range of 2 nm-200 nm, and has proper oil/water interfacial tension. The synthe

9、sis in this experiment can be roughly divided into three stages: micelle formation, thermal decomposition and alloying. Firstly, micelles which are composed of many tiny colloidal particles shown in figure 1 are formed after all the reactants are stirred vigorously and heated to 80oC. The reactants

10、(including the source of iron and gold as well as the reductant) are uniformly dispersed and covered by the surfactant, thus the dispersed phase is generated. The continuous phase is the solvent. Secondly, when the temperature raise to 280oC, the Fe and Ag precursors are decomposed and undergo reduc

11、tion to be metallic in the colloidal particles. Thirdly, the reduced Au and Fe atoms alloy to form the alloyed nanocrystals during the decomposition and/or under high temperature. Figure 1. Micelles in the emulsion.ExperimentalMaterialsiron (III) acetylacetonate (Fe(acac)3 , 99.9%), 0.25 mmolgold (I

12、II) acetate (Au(OOCCH3)3 , 99.9%), 0.25 mmol1,2-hexadecanediol (C14H29CH(OH)CH2(OH), 90%), 2.5mmoloctyl ether, 10 mloleylamine, 1.5 mloleic acid, 1.5 mlApparatusesHotplate with magnetic stirringOil bath (or heat mantle will be better)250 mL three-necked glass flaskBall condenser with cooling waterWe

13、ighing paper Magnetic stirring barPipetteUltrasonic machineCentrifugation machineProceduresSynthesisAdd 0.25 mmol Fe(acac)3 , 0.25 mmol of gold (III) acetate, 2.5 mmol of 1,2-hexadecanediol, 1.5 ml of oleylamine, 1.5 ml of oleic acid and 10 ml octyl ether as well as a stirring bar into the flask.Pla

14、ce the flask with the condenser and immerse the flask into the oil bath on the top of the hotplate.Under vigorous stirring, gradually increase the reaction temperature to 80oC in 1 h and keep it at 80 oC for.Then rapidly raise the reaction temperature to 280oC and keep it at 280oC for 1 h.After cool

15、ing down to room temperature, 30 ml ethanol was added into the flask.Separation and purifyTransfer the reaction solution into a HYPERLINK /centrifuge_tube centrifuge tube.Put the tube into a centrifuge machine and tighten the inner cover of the machine.Run the machine after the parameters are set co

16、rrectly (the speed is 9000 rmp and the time is 15 min). Repeat the step above to make sure the nanocrystals have been precipitated completely.Take out the tube and dump the supernatant.Add 30 ml of a mixed solution of ethanol/hexane (1:2) into the tube and shake violently or supersonicate the tube t

17、o disperse the nanocrystals again. Repeat the steps from (g) to (k) for three or more times until the supernatant is clear.Disperse the product in 10 ml hexane and transfer the product into a glass bottle Tests of PropertiesRedisperse the nanocyrstals and put a magnetic disk against the sidewall of

18、the bottle. Observe what will happen after repeat one or more times.Use a UV-Visible spectrometer to characterize the optical properties.Study the crystal structure by a powder X-ray diffraction.When other equipments are available, more experiments, such as VSM, SEM and TEM, shall be performed.Repor

19、tDescribe the goal, introduction, materials, apparatuses, and experimental procedure in your own words.Describe the phenomenon of the experiment and analyze. Answer the following questions:What is a nanoemulsion method? Write down the differences between conventional emulsion and nanoemulsionWhats the role of each reactant used in the experiment?How to confirm that the obtained products are FeAu alloy nanocrystals?Writedownallthepossible