questions about process involving new chemicals

Mary Tang mtang at
Thu Jul 15 08:53:05 PDT 2010

Hi Yuxin --

Just a comment about your process...  I suspect the mercaptosuccinic 
acid treatment will be effective only if your polystyrene beads are 
chemically functionalized with carboxylate or other groups which are 
negatively charged at neutral pH.  If the pH isn't right, the sulfhydryl 
groups will fall off the gold and the succinic and carboxylate groups 
won't be negatively charged enough to repel each other.  You should 
check the specifications on your beads:  most of the calibration 
standard beads you can buy are NOT chemically functionalized.  In short, 
you should double-check your references on the details of your surface 
treatment procedure.

As for actually doing your process:

1.  Make up your solution in the wafersaw room.  No powders are allowed 
in the lab.  There are mixing and weighing materials in the wafersaw 
room.  If you do not have storage available in your own lab, it should 
be labeled and stored in the Flammables area outside the cleanroom.  If 
you need a pH meter, let us know.  If you need sodium hydroxide to 
neutralize your solution, you should order a dilute solution from Sigma 
(BioStores may have this).  Mixed chemical solutions should be 
transported in a double-contained carrier to the pass-through area to 
the lab.  Please contact Uli, Mahnaz or me to review the detailed 

2.  The assembly process should be done at wbgeneral.  I see you are 
already qualified on wbgeneral, but you should check with Uli to make 
sure about setting up the heater/stirrer for your process.

3.  Since your solution is dilute, it and the rinse water can be 
aspirated into the AWN (no need for collecting waste.)


Yuxin Zheng wrote:
> Dear staff,
> I would like to use mercaptosuccinic acid(CAS:70-49-5) in my process. Basically I want to self-assemble a layer of thiols on the gold surface. The quality of the layer is not critical as the purpose is only to prevent polystyrene beads sticking to the gold surface. 
> The assembly process is pretty much the last step of my whole process. The sample on which the self-assembly will be done is a 1cm x 1cm silicon wafer piece with thin gold film and nitride layer on it. 
> The details of the assembly process is: dissolve the mercaptosuccinic acid powder into water to form 10ml-20ml solution. Sodium hydroxide may be added to neutralize it to some extent. The concentration is estimated to be 10^15 molecules/mL (or 10^-8 mol/mL). Then the sample is soaked in the solution for couple of minutes up to 8hrs. Besides, the whole reaction needs to be performed under stirring at~ 50°C.
> The 98% mercaptosuccinic acid powder(weight:25g) is purchased from Alfa Aesar. Attached is the MSDS I scanned.
> Can you give me suggestions on where and how I can perform the reactions?
> Thanks,
> Yuxin Zheng

Mary X. Tang, Ph.D.
Stanford Nanofabrication Facility
CIS Room 136, Mail Code 4070
Stanford, CA  94305
mtang at

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