Most people are referring to the Stober process (1968), where controlling the conditions can give a good polydispersity. In addition to the controls mentioned already, temp, concentration, pH, it is VERY important to have clean glassware. Any small impurities will act as "seed" surfaces and give you high polydispersion.

Then also a good quality orthosilicate. We have used everything from methyl to glycol, and in all cases it helps to keep it dry since atmospheric moisture slowly hydrolyses the solution.

I agree with Gilbert, the microwave idea is quite good for making all sort of metal oxide particles, but this is not necessary to make narrow distribution silica.

A typical setup for us is 4 mL TEOS in 50 mL Ethanol (again regular bench grade is not good enough since it has a lot of moisture, and absolute has traces of benzene, so dry some carefully). We then add ammonia (or acid) to hydrolyse. 2 mL saturated ammonia solution to the above will give 20 nm particles, 3 mL gives about 50 nm, and 4 gives 100 nm, narrow distribution (

Hi, look into this paper. It may have useful information for you:

http://www.hindawi.com/journals/jnm/2012/132424/

You can adjust the temperature of thepost-treatment and the ratio of capping agent and metal ions.

Hi, You need to control, temperature, PH and surfacant to metal ion ratio

You should carefully control the temperature during the synthesis and during the cure (post-treatment).

Thank you very much! I will start to modify the gelling pH, ageing temperature and adding organic template!

The way that you mix the solutions is also important. (drop-wise or pour ....) It is the experience from my experiment.

Higher temperature combined with shorter reaction time could give you narrower distribution (higher nucleation rate and shorter growth time).

Of what depend the nucleation rate? How homogeneous is the solution? The temperature and his variation? The geometry?

You Can Control PH

pH, temperature of the reaction, molar ratio mainly controls the size distribution and other properties. May I know the type of silica material you would like to prepare. For some type of Si materials, you should add the chemicals drop-wise and for other materials you should add at once. Let me know the type of the Si material you would like to prepare.

In sol-gel method particle size is controlled by decreasing aging time and its depends on the temp also. so u optimize aging time and temp, u will get nanosized particles.

The sol-gel process is strongly dependent of the initial condition of the precipitaion (nanoparticles formation) The main parameters that affect the particles size distribution are, pH, temperature, molar ratios (R) and, the size of the organic chain bonded in the silicon atom in the precursor.

Another approach is to use a microwave system to make your particles. We have observed that microwaves promote nucleation and gives use a lot of control on size. Also changes in viscosity of the solution can also change the shape of the particle.

Gold nanoparticle took ~24 hours in the classical cook in the hood method. Microwave takes about 30 seconds.

You can add different amounts of alcohol to the precursor solution, You should find a range where the distribution is controllable

There is not one parameter to control the nano particles distribution size. But i think that the impact of mechanism of hydrolysis- condensation is very important which, in fact, depend of pH, Temperature, the molar ratio of solvent/precursor

Some time for better size distribution one need to change the solvent bcs it mainly depends on homogeneity of the solution. Sol gel is the best method to get good size distribution but a optimum problem for every system and even some time u can't get same result as published already in literature because of many factors like humidity, temperature will not be the same in your lab as the host.

size of the particles could be controlled by rate of formation, solution concentration, temperature etc. and not the size distribution. Sol-gel is known to produce particles with narrow size distribution. So one need to care after formation. Agglomeration could be avoided by means of surfactant, and reducing the time given for aging.

Hi, Dong Nguyen Thanh. I have tried to drop wise and pour directly, both also can get gel. May I know which method is better to control size?

Most people are referring to the Stober process (1968), where controlling the conditions can give a good polydispersity. In addition to the controls mentioned already, temp, concentration, pH, it is VERY important to have clean glassware. Any small impurities will act as "seed" surfaces and give you high polydispersion.

Then also a good quality orthosilicate. We have used everything from methyl to glycol, and in all cases it helps to keep it dry since atmospheric moisture slowly hydrolyses the solution.

I agree with Gilbert, the microwave idea is quite good for making all sort of metal oxide particles, but this is not necessary to make narrow distribution silica.

A typical setup for us is 4 mL TEOS in 50 mL Ethanol (again regular bench grade is not good enough since it has a lot of moisture, and absolute has traces of benzene, so dry some carefully). We then add ammonia (or acid) to hydrolyse. 2 mL saturated ammonia solution to the above will give 20 nm particles, 3 mL gives about 50 nm, and 4 gives 100 nm, narrow distribution (

It is drop -wise. Aging time is also important. The particle is bigger with the increasing aging time.

In my experiment (synthesis of MnO2), drop wise method makes the more uniform particles, and the more aging time makes bigger particles.

There are many conditions such as temperature, metal fuel ratio, pH, etc are important to control the nano-size of particles by using sol-gel method

Particle size and particle size distribution both are different thing so please be specific ..Tnx

By the use of surfactant and maintaining the synthesis media alkaline u can achieve uniform sized nano particals without agglomeration.

What I focus is particle size (distribution), not the PORE SIZE distribution! Thank for all the reply!

for my previous study, i have tried without using surfactant to synthesize nanosilica in basic medium, however, the particle size distribution is too wide (nano range), hence, I m trying to narrow it! Thanks for the suggestions.

Article A simple template-free sol–gel synthesis of spherical nanosi...

Apart from conventional parameters like pH, temperature, molar ratio surfactant is the leading parameter to control the size by sol-gel synthesis.

In sol-gel without using surfactant, if you want to control the particle size then one has to consider the parameters such as pH, aging temperature, aging time and moisture also plays a role. Have you tried aging in a water bath at constant temperature?

For preparation silica hydrosols with nanoparticles you can use another method - from silicic acid which you can produce fron sodium silicate solutions. This method is good for preparation silica particles 5-25 nm.

Logudurai Radhakrihsnan, so far I have tried aging in room temperature only, however, I will try at different temperature. Perhaps at high and low temperature

I have been used SiO2 nanoparticles for modified electrode. For my opinion, the synthesis of these particles can control the size by the molar ratio of organic sovent / aqueous phase and any parameters.

Chew Thiam-Seng, Please find the articles/books by C Jeffrey Brinker on Sol-Gel and also refer the review article Angew. Chem. Int. Ed. 2006, 45, 3216. which may be useful for ur studies.

Hi Sajjad Ullah, we used ammonia solutions of 29 wt% ammonia or higher - you can supersaturate by bubbling ammonia into a cooled solution of water. Volume depends on the size nanoparticles and temperature, typically 2 to 5 mL.

I dont think that this is a simple method. Try using templating.

Most important to produce a nano size powder on sol gel is, in heat treatment process avoiding hot temperature and agglomeration of powders after drying of gel.

Thank you for all the valuable suggestions!

Rui Krause sir ,can u tell about the yield you observed in that setup? and can you give specific details about feed rate of ammonia and sonicating conditions?