Hi,
I need to synthesis phytogenic ZVI nanoparticles. So, I want to know that autoclaving iron salt with plant extract is possible or not.
Never tried, but be careful of surface oxidation/hydroxylation/adsorption in aqueous/polar extracts in contact with oxygen. Check nitrogen adsorption as well. And first and foremost, remove hetero-aromatic and hetero-aliphatic unwanted organics from your extract. Control silica and inorganic phosphorus as well. Check Pourbaix diagram for iron, and its applicability on nanoscale reaction kinetics
If you really want to use autoclave (it may sound odd), convert the iron of extract into iron pentacarbonyl (some remaining hydrocarbon would probably do no appreciable harm), convert it into gaseous form and dilute it with inert gas, and carefully decompose inside autoclave. Be sure to check particle size-P relation. You may codeposit B or Si or their oxide-based surface-coating to prevent agglomeration-you may use any suitable CVD technique.
I would prefer moderately high boiling point dilute nonpolar solution of Iron pentacarbonyl in a relatively low-reacting solvent, if you prefer working with liquid. Gaseous phase has risk to form thin film-so choice container materials judiciously.
Anju Rose Puthukkara P
Any 'iron' particles that you make in the presence of air or water will be fully oxidized on the surface. You'll have Fe3+ and not Fe0. XPS will show this.
The redox potential:
Fe3+(aq) + 3e- → Fe(0) is - 0.04 V
means that there is a greater tendency for oxidation to occur. ... Hence you'll need a powerful reducing agent in solution which may not be possessed by plant extracts. See el attacho.
Dear Anju Rose Puthukkara P, unless you are under specifial conditions or targetting specific compound, the answer is yes, and many available documents are dealing with this situation. I attached two papers and please don't hesitate to ask for additional request. My Regards
although i have never tired such experiments, but i think plant phytochemicals are not such strong reducing/stabilizing agent to reduce in to zero- valent Iron.
Anju Rose Puthukkara P
Under pressure in an autoclave, nanoparticles are synthesized by hydrothermal synthesis.
The hydrothermal synthesis method is based on the high solubility of a large amount of inorganic substances in water at elevated temperature and pressure and the possibility of subsequent crystallization of the dissolved material from the liquid phase. High water temperature plays an important role in the transformation of the precursor material, since this creates an increased vapor pressure, and the water structure itself differs from that at room temperature. In addition, at high temperature, the properties of the reactants themselves (solubility, diffusion rates, reactivity) change. Control of vapor pressure, temperature and reaction time provides ample opportunity for the synthesis of high-quality nanoparticles and nanotubes. During the process, these parameters can vary to achieve the highest possible rate of spontaneous nucleation and narrow size distribution of nanoparticles.
Plant extracts are used to reduce precursor ions to zero valence state.
Yuri Mirgorod so the possibility of iron oxide formation was high in the hydrothermal method, right?
Anju Rose Puthukkara P
Yes hydrothermal method can be obtained nanoparticles of maghemite with functionalization for the treatment of diseases.
Anju Rose Puthukkara P
Can anyone comment on the redox potentials?
Seem that there are a few comments relating to iron oxide production but not to iron in the zerovalent state (i.e. metallic iron). Fe3+ to Fe2+ is easier than Fe3+ or Fe2+ to Fe0..
@Alan F Rawle
Can we overcome the problem of iron oxidation using solvothermal method. Is it possible to use ethanol as solvent
Anju Rose Puthukkara P
In air or water, or solvents containing oxygen, I don't believe so, IMHO. The surface will always be fully oxidized and XPS is essential here to demonstrate this. And it's the surface that interacts with the environment. In theory, one could protect any generated Fe0 with a steric barrier (e.g. PEG) but I'm still convinced that the redox potential/thermodynamics doesn't allow this at room temperature. But someone with better knowledge can answer this and I learn more when I'm wrong. Look at how we produce iron - in the blast furnace at high temperatures with C as the reducing agent. Here we can use Ellingham diagrams to look at the reactions as a function of temperature. Graphic from:
Direct Carbothermic Silica Reduction from Purified Silica to Solar-Grade Silicon
Conference Paper Direct Carbothermic Silica Reduction from Purified Silica to...
Dear Anju Rose Puthukkara P you can certainly do the preparation in an autoclave, but according to the attached reference there is no need to do so. This paper describes a "green and eco-friendly" preparation of ZVI nanoparticles at room temperature and normal pressure. Good luck!
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