I prepared the gold nanoparticles using plant extract and characterized using XRD. Result displays four prominent diffraction peaks indexed as (111), (200), (220) and (311) miller indices which are the characteristics of fcc crystalline structure of metallic gold. Several other extra peaks were also observed. What is the reason behind those extra peaks? How to specify the phase of all the peaks in XRD pattern? I am attaching the pdf file. Thank you in advance.
Hello Pratibha:
Most likely if you are observing additional extra peaks in comparison with the XRD pattern of pure metallic gold is because you are having other intermetallic phases between the gold and other components on your sample.
Gold is the most unreactive element in nature, among all the elements in the periodic table. Therefore it's not easy to guess what intermetallic phases could have being forming on your sample, in combination with gold. It could be due to some contamination during the synthesis process.
What precursors are you using for the synthesis of the Au nps ?
The peaks matching with the peaks that appear in the crystallographic sheet of the corresponding structure belong all to the corresponding structure.
So look at the corresponding crystallographic sheet of the proposed structure, and match all the peaks that appear also in the corresponding XRD patter.
Hope it helps ! regards !
Hi
Withvthe help of JCDPS files you can interpret the results findings
I fully agree with Franklin Uriel Parás Hernández . I will add that we synthesized gold nanoparticles in a green leaf. Otherwise, they forced him to synthesize when a gold precursor was added to the water, where the plant sprig was. After the synthesis, we observed only the main peak that you have.
Thank you all.
Franklin Uriel Parás Hernández I used sodium tetrachloroaurate for preparation of gold nanoparticles.
You can use MATCH xrd software..Also you can use X'perts Highscore Software.
http://www.crystalimpact.com/match/
best wishes
Dear Pratibha:
I see.
XRD is not enough to determine what other phases may be present on your sample. XRD is a technique which gives you general results from a large and statistical number of measurements, from a 'relative' large region of your sample. It is not used to look the details of a given region of your sample. XRD just can help you to determine what the dominant phase on your sample may be.
This is the reason you need a relative big amount of sample to be able to get reliable XRD results.
So, if you have addition phases in minimum amounts XRD cannot give you the whole patter of these 'secondary' components
So what you are gonna have to do is to run chemical analysis techniques.
Maybe XPS will be the best technique for your case. since you have a nanoscale material (XPS is sensitive to the first 10 nanometers from the surface to the interior of the sample) and because what you are interested for is on detecting the presence of a contaminant (it could be in the form of a phase, or a chemical component or element, but you are asking yourself: What other phases could be present on my Au NPs ?), So with XPS you can determine what other chemical elements and compounds you have on your nanoparticles, and in what concentration.
Another technique you could use to support your XPS results is Atomic Emission (or Absorption) Spectroscopy, I don't know if you can have acces to an Optic-ICP (Inductive Coupled Plasma) Atomic Spectrometer. This technique can give you the elemental composition of your sample and the elemental concentration of each element.
Regards !
Although I don't know if you can prepare a powder sample of your nps for the XPS experiment. Because you need your sample to be solid to put it in the XPs Spectrometer...
If you have indexed and you found it is cubic then check out for systematic absences. If your indices are all odd or even as is your result 111, 200,220, 311 then it appears your structure is fcc.
Dear Pratibha Acharya
The X-ray results can be interpreted either for gold or other metals by ASTM Cards. Then the results are discussed based on the ratios of the minerals formed.
Regards
Prof. G.A. Khater
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