How we can enhance size homogeneity during nanoparticles synthesis by precipitation method?
Hi, we used to do this - heat the solution at an elevated temperature and wait untill the solution's temperature is reached its precipitation stage and then very very slowly drop its reactant and precipitating agent into the solution. We've always received homogenous nanparticles which we've aimed to produce. I hope this help. If this is what you have been doing already, so I have no more expeiences to add ):
Dear Asim, yet I have no papers on that to upload. Jjust normal routes and common manner we are using in the lab. Rather follow the articles mentioned above by Daniel.
how scalable (in quantity) are those methods and how controllable/uniform is the shape?for long time I am looking for a "nearly-monodispersed" nanoparticle powder to test some XRD WPPM models for size distribution and shape analysis, but so far I found specimens that are not as great/monodispersed as expected..
Synthesis of monodispersed nanoparticles of hydrated oxides by precipitation method is a difficult task since the introduction of alkali (or acid) dropwise always is the heterogeneous process. Better for this purpose is to use the homogeneous hydrolysis (for example, using urea and subsequent heating solution) or forced hydrolysis method described in detail in: Matijevic E., Sapieszko R.S.. Forced Hydrolysis in Homogeneous Solution / In: «Fine particles: Synthesis, characterization, and mechanisms of growth». Surfactant science series. V. 92 // Ed. by T. Sugimoto. – N.Y.: Marcel Dekker, 2000. - P. 2-34.
Centrifugation with sucrose gradient. Vivaspin with different cutoff.
Not a trivial question. More details on the specific system you are interested in would be useful. To obtain a narrow particle size distribution (PSD) a good control of supersaturation and particle nucleation is needed. Supersaturation (S) should be as constant as possible inside the solution. Spatial variations of S determine different values of nucleation and growth rate producing broadening of the PSD. Therefore mixing efficiency is very important. A good approach is the use of a micromixer (a Y connector is the simplest solution). The premixed suspension can then be aged in a batch reactor or sent in a tubular reactor. In this way the mixing efficiency can be optimized and the supersaturation will be constant over time. With conventional methods, i.e. drop by drop addition of solution 1 to solution 2, S will be maximum at the beginning of mixing and then it progressively decrease.
Heterogeneous nucleation should be generally avoided. However, seeding of the solution with nanocrystals of the final product can give good results.
The nanoparticles have a strong tendency towards aggregation. Stabilization against uncontrolled growth/aggregation using specific organic or polymeric species which preferentially adsorb on the solid surface.
A different approach is often indicated as "homogeneous" precipitation. In this case precipitation is induced by the decomposition/reaction of a compound which provides one of the reactant species or determine a change in pH. If the decomposition/reaction only occurs above a critical temperature, by carefully controlling the heating rate and the temperature homogeneity, a burst of nuclei can be produced. If reaction conditions are well controlled, only growth will occur after the initial nucleation, thus leading to very narrow PSD. Reactants suitable for the homogeneous precipitation process include urea (used for rare-earth oxycarbonates and oxides) and thioacetoamyde (for sulphides).
Actually, I want to prepare Chitosan-based ZnO NPs stabilized with some oragnic compounds by precipitation method as it was not realizable with nano spray drying method due to the formation of highly viscous solution...because of chitosan and citric acid/whey powder..???
dissolve and precipate. Repeat the procedures a few time and collect the particle using centrifiguration. This way, the size is more uniform and size distribution is very narrow.
I do not know if you need low temperature to precipate the NPs. Change tempearture is also help to isolate the different size of nanopaticles.
You can use an appropriated surfactant dissolved together with the solution containing the metal ion to form the nanoparticles. For metal NP, sulfur organic compounds, metal oxides with beta diketones, p-toluene sulfonic acids, fatty acids, under strong stirring around 90C. Havy metals chloridez can be dilluted in a n-butOH and pptated by ethyl, di and triethylamine.
The best way to get uniform sized nanomaterials is reverse microemulsion method.
It is very important to have a high nucleation rate and low growing rate. A key factor is to control pH. Always add the solution containing the ions you want to precipitate into the solution containing the precipitating agent (e.g. NaOH, NH4OH) and no vice versa. Working in closed vessels at high temperatures is also very important because you may obtain nanocrystals directly from the solution without further thermal treatment - calcination.
I agree with Radu. Control of pH is the most important factor to get homogeniety in nano particles. Also, if you want to precipitate a hydroxide, then higher the pH, the more the nucleation rate of precipitates as compared to the growth rate of the nucleus, so it will be in the nano range. But at higher pH it becomes difficult to control the basicity of solution, so stringent monitoring is required. Keep adding the solution of ions while you try to keep the pH constant.
Mr Raj Kumar the microemulsion should look like a transperant single phase solution. This should have oil (major), water (minor), surfactant, co-surfactant and the required chemicals dissolved in it. You can follow the papers of myself or others.
I wrote a book about hydrolytical precipitation of ultradisperse ceramic powders in 2000 in Romanian (Editura Tehnica). I would like to upgrade this book and translate in English. Can you reccomend me an editor?
Control of pH and temperatures are equally important apart from the above explained methods.
Strongly agree that the effect of pH and temperature will play an important role in controlling the size. May be you should try also using the surfactant to control the homogenity of size distribution.
in co-precipitation method, you need to take care of many parameters to obtain a very good monodisperse particles. As we know co-precipitation is not a great method to control monodispersity but still u can control the distributions to a great extent. First, you should make the pH as high as 12 or 13 with a very fast alkali addition which gives no time to growth but forms maximum number of nuclei. This is very important as the more the number of nuclei formed lesser will be your polydispersity. Second, you need to maintain a bit higher temperature. Normally we prepare at around 80-90 which is good enough.Third, A more diluted precursor also gives better monodispersity. Fourth, you need to give less digestion time.
Hope it helps
Pati
Few years ago, Prof. Javier Pérez-Ramírez and co-workers reported the in-line dispersion-precipitation method for uniform nano-sized materials . The intrinsic features of this method, such as the continuous operation in a miniaturized precipitation chamber at constant pH, the controlled residence time, and the excellent stirring, are partially responsible for the high uniformity and surface area of the materials. Please find attached several papers of the authors.
I used to synthesize CdSe nanoparticles and although the procedure was rather drude, the size distribution was tunable and narrow.
http://www.amazon.com/gp/product/images/3639136608/ref=dp_image_z_0?ie=UTF8&n=283155&s=books
you can request the dissertation from CUNY City University of New York, since I am leaving for Africa in a few days and will not be able to send large files.
Our Group (Prof. Dan V Goia, Clarkson University) working on this project from past 10 years. You can go through his paper. I think it will help you in maintaining the homogeneity of the particles.
There are numerous methods to produce uniform small particles. There are to books
dealing extensively with sibject published by SpringerPublisher,
edited by myself;
1. Medical Applications of Colloids
2. Fine Particles in Medicine and Pharmacy
This book has 1200 referencies.
Good luck
Egon Matijevic, did you discussed preparing homogeneous nanoparticles using laser in your books??
Precipitation o uniform particles in solutions is by accelerating
reactioins by different processes. Interestingly, the simplkest method requires
heating (mostly aqueous) solutions of appropriate electrolytes) b at moderate
temperatures, often even less than 90 degrees. Such reactions may take a few
hours and low concentration of reactants to keep the ionic strength sufficiently
low (to prevent aggregation of the products)
We never worked with lases . The processes we we use (either chemical or physical) depend on the nature of the material or suitable chemica reactions
or suitable chemical processes
Thanks a lot Egon Matijević for your grate discussion and thanks for
Dr. GS dHiLLoN for good question !
Hi everyone, Have you worked with polysaccharides in this field? I need to make some particles in 200-400nm!!! with high molecular weight polysaccharides
Hi, sonochemistry seems to be very useful to obtain monodispersed nanoparticles. One of the recent reviews on this topic:
Bang J. H., Suslick K. S. Adv. Mater. 2010, 22, 1039.
@ Elham Bidram..Yo can try starch, whey powder, glycerol or organic acids, like lactic acid or citric acid as capping/stabilizing agents. But I am not regarding obtaining homogeneous size distribution along with these compounds...I think it mostly depends upon preparation methods.!!
To achieve uniform size nanoparticles we have to follow size selective precipitation method. To obtain uniform size alkanethiol capped gold and silver nanoparticles chloroform is used as solvent. If you add dropwise less polar solvent like isopropanol, the bigger size particles will settle in the bottom and the small one stay in chloroform layer
Read attached publication
Article Magnetic Gold Nanoparticles in SERS-Based Sandwich Immunoass...
The general strategy is using an extremely short nucleation time followed by slow growth. However, few examples seem to confirm this, such as the famous TOPO method, where the sudden change in temperature upon mixing ensures that there will be no further nucleation, just slow growth, and all seeding methods, that avoid nucleation altogether. So, for a precipitation reaction, you want to have a brief excursion into over saturation, and then grow slowly, hopefully avoiding the formation of new nuclei. In practice, this is trial and error, and many of the best methods, for example Turkevich's citrate gold reduction, work well and nobody knows why.
As prof. Brust pointed out the capping agent control the nucleation. One of earlier study Weller demonstrated size selective precipitation method to isolate uniform size nanoparticles. Pl refer the following articles any further details
J. Phys. Chem. 1994,98, 7665-7673. We follow this paper to isolate uniform nanoparticles
Very easy grean method is described in attached publication:
Article Polymerization Model for Hydrogen Peroxide Initiated Synthes...
I'm working with Xanthan that is aggregating in the solution and I tried to decrease the size of particles by sonication or applying NaNO3 to dispersing the aggregates, but the result is not stable and they will aggregate by the passage of time!!!! I don't think use some organic solvents can be a good idea for this polymer due to its hard solubility. how can I do that?
Hi Swati, thanks for your answer, yes, but unfortunately they can attach to my materials in the solution as well. I'm using PEG-amine as a linker, and it can easily attach to other bio polymers with cooh groups!!!
I use co-precipitaion method for the synthesis of my magnetic nanoparticles and control the reaction at alkaline ph, high rpm and maintained temperature throughout the reaction followed by adding the surfactant, which results in the particle size from 8-10nm range......i think this can help you out.......
In our lab we prepared NaLnF4 nanoparticles with size distributions of 5% in the size range from 5 to 35 nm and in multigram scale.
http://www.researchgate.net/publication/233908996_Effect_of_the_crystal_structure_of_small_precursor_particles_on_the_growth_of_-NaREF(4)_(RE__Sm_Eu_Gd_Tb)_nanocrystals/file/9fcfd50ccfb47d1259.pdf
It's not nice to promote your own paper, but I hope you forgive me. The synthesis is easy and the particles are nearly monodisperse.
Article Effect of the crystal structure of small precursor particles...
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