I have synthesized cerium oxide nanoparticles via hydrolysis method using NaOH. I obtained yellow precipitates at the end of reaction indicating synthesis of cerium oxide nanoparticles. But in UV vis spectral scan showing two small humps around 225 and at 350 nm. The FTIR spectra showed absorbance peak at 664 cm-1. In literature, FTIR peaks of cerium oxide nanoparticles are reported at 476 cm-1 (Ce-O stretching), 556 cm-1 (O-Ce-O) and 668 cm-1 (Ce-O) stretching mode. I also have peaks at 1055 and 1318 cm-1 for nitrate.
Does that indicate reduction wasn't complete?
Or Calcination is necessary for Ce oxide nanoparticles synthesis?
I have attached the UV vis spectrum.
Thanks in advance for your assistance and guidance.
It is preferable to re-examine more than one sample because the FTIR spectra appear to be inaccurate.
The discontinuity at ~325 nm in not real, but due to the lamp change in the spectrometer.
the best technique is Nano sizer for characterization of size and charges
by Normal Uv and FT-IR characterization of nano compound is very hard
the other technique is scanning electron spectroscopy.
another technique is BET .
The first time you can characterize cerium oxide by Nano sizer
After you obtained the Data about the Size and charge of your compound, then you can use SEM, TEM, AFM, for understanding the morphology of your compound.
you can not say reduction was complete or not and this is not indicated for complete reduction
it is better to perform calcination but it is not necessary.
Kindly read this article
Supercapacitor Behaviour of Cerium Oxide Nanoparticles in Neutral Aqueous Electrolytes
Nallappan Maheswari, and Gopalan Muralidharan
(Energy Fuels 2015, 29, 12, 8246–8253, Publication Date: December 1, 2015,
https://doi.org/10.1021/acs.energyfuels.5b02144)
The best instrument for the characterization of nano compounds is Nanosizer
Noor Ul Ain
You write that you obtained cerium nanoparticles by hydrolysis. Then you ask the question the restoration was complete. Not restoration, but hydrolysis was complete? As a result of hydrolysis, you get cerium hydroxide. Therefore, calcination is necessary to remove water and obtain oxide from hydroxide. Hydroxide has no chromophores and therefore will not absorb in the visible spectrum. The best analysis is elemental analysis for cerium. It can be done on an energy dispersive attachment to a scanning microscope.
Yes, I wrote that
The first time we do calcinate then Nanosizer or SEM
Noor Ul Ain , Amir Sepehrianazar
Cerium oxide CeO2 and cerium hydroxide Ce(OH)4 cannot be determined using DLS and SEM. With these methods you will see the size of the nanoparticles. Therefore, I propose to determine the content of Ce in nanoparticles. If it matches the theoretical content of cerium in the oxide, then you have synthesized a pure oxide.
Tow time calsination then by SEM and other techniqe cheek the size of your compound
Yuri Mirgorod thank you for your response. I have followed the hydrolysis method for the synthesis as described in the attached paper. In this paper, using hydrolysis method, calcination was not performed. The obtained precipitates were of yellow color and dried at 80 degrees Celsius.
Is calcination must? Although there wasn't clear peak in UV vis spectrum but in FTIR there was peak of 670 cm-1.
Article Experimental and Theoretical Study of Morphological and Char...
Noor Ul Ain
I already wrote that at the beginning hydroxide is formed, and then oxide as a result of heating and splitting off water. For cerium oxide, it is enough to stir it strongly and heat it to 80 °C and the blue hydroxide turns into a yellow oxide. However, the color is not an accurate proof of the receipt of the oxide. You need to do elemental analysis. Spectra should be compared with a standard, for example, from the NIST database, if you have access to it. I don't have such data.
Calcination is necessary and you may identify the annealing temperature by TGA-DTA analysis. Then the desired Nanoparticles can be examined by different techniques such as XRD, SEM, TEM, VSM, etc.
The yellow precipitate which you have got at the end of your reaction is hydroxide of Cerium. Calcination is required to get the cerium oxide. You may also identify the appropriate calcination temperature by thermal analysis (TG-DTA) of the as synthesized material.
Why you dont like to characterize by Raman spectroscopy
Because for identification of your compound may be raman isthe best
Amir Sepehrianazar Thanks for your advice. Actually BET is quite expensive technique for characterization. I just want to confirm whether the cerium nanoparticles are synthesized as its the first time. So I am using UV vis, FTIR and XRD. I have used hydrolysis method and added NaOH 1 M to the cerium nitrate solution. After 20 hr stirring I obtained yellow precipitates, centrifuged them and then dried at 80 degrees. I have shared the spectral scan.
I wanted to confirm whether calcination is must for the cerium oxide nanoparticles as I haven't done calcination yet.
Noor Ul Ain Calcination is a must to produce CeO2 rather than Ce(OH)x. However, this calcination stage will remove all free, discrete, independent particles < 100 nm and essentially your system will not be 'nano' rather consisting of a mass of sub- and post-micron aggregates and agglomerates. Usually a dry powder is used for XRD and the crystallite (rather than particle) size can be measured with line broadening and the Scherrer or Williamson-Hall approaches. Take a look at this webinar (registration required):
Dispersion and nanotechnology
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W190528DispNanoMat
I would add that measurement of specific surface area is a must (BET). The system must be greater than 60 m2/g to be considered 'nano'. Also, as the surface is vital in any nanomaterial I wouldn't even involve myself in a nano project without access to XPS (or perhaps Auger).
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