I am working with silica coated quartz crystal in QCM-D. I want to create amine surface on crystal using silane compounds but my instrument set up is not compatible with toluene. Can anyone suggest me alternate way to modify the crystal or procedure to modify outside the instrument?
Hi Shalini,
You can treat the QCM-D sensor like a Si wafer piece (except that it's much more fragile). Remember to first clean the sensor following the standard protocols for SiO2 QCM-D sensors. Make a solution of your amine compound dissolved in toluene in a small beaker or glass vial. Put the QCM-D sensor at the bottom with the silica surface facing up.
After enough time has passed, you can use tweezers to carefully remove the sensor; only grip the somewhat-transparent outer edge of the sensor. You don't want to scratch the silica surface or the gold electrode pads on the back of the sensor. Briefly rinse the QCM-D sensor by dipping it in another small beaker of toluene. You can do additional rinsing steps as you deem appropriate. Then dry the sensor with dry nitrogen gas. Have the tweezers grip the sensor from below and blow the air from the sides and above so that liquid does not pick up contaminants from the tweezers and allow them to deposit on the sensor -- you want the liquid to instead fall down from the sensor to the tweezers, if that makes sense.
After you dry the sensor, you can take a Q-tip and dip the Q-tip in toluene. While gripping the transparent outer edge of the sensor with tweezers, gently rub the back side of the sensor with the Q-tip to remove any coating on the back side. Dry the back side of the sensor again as above.
You can do before-and-after measurements of the QCM-D sensor in air (and using the Stitch function in QSoft) to get a rough approximation of how thick your silane layer is.
I am trying to functionalize a silica-coated QCM substrate with MPTMS (thiol).
Is it safe to dip and immerse the silica-coated QCM substrates in the mixture of Chromic/Sulfuric Acid or maybe HF 5% for cleaning and removing the oxide layer prior to the functionalization?
In general, how harsh can we treat and clean the QCM substrates compared to regular Si wafer pieces?
To clean QCM-D crystals, mild piranha or ozone cleaning should be used ideally. One should take care of the electrode that it doesn't interact with any chemical, neither chemically nor physically.
Also, the crystal of QCM-D is more sophisticated as compared to QCM crystals. Mahsa Moradipour
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