NBEXP0015

=NBEXP0015 — High-resolution AFM imaging of graphene/TiO2=

=Objective=


 * 1) To obtain AFM images of TiO2 particles adhered to individual, single-layer graphene flakes.
 * 2) To determine the concentration of TiO2 particles on the graphene surface
 * 3) To determine the average size of the graphene flakes
 * 4) To determine the average height of the graphene flakes (1 layer, 2 layers, 3 layerss etc.)

=Background=

I attempted to acquire AFM images of G/TiO2 in experiment NBEXP0014. Finding individual or few-layer graphene sheets proved difficult; most material had agglomerated into large clusters & both graphene sheets and TiO2 particles could not be distinguished in the mass. I speculated this may have been because the G/TiO2 solution from which the AFM samples had been made had been left standing for 2 weeks (solution was prepared for an earlier experiment), allowing the material to agglomerate to the extent that a 2-min sonication with the horn probe would not separate the agglomerates. In this experiment GO and TiO2 solutions were sonicated and then UV-reduced immediately before dropping on to mica AFM substrates. It was hoped that this would prevent the graphene/TiO2 from agglomerating.

=Procedure=


 * 1) Sonicate 1ml 4mg/ml TiO2 solution and 0.5ml 1mg/ml GO solution, then combine in a sample tube and make up to 6ml with ethanol
 * 2) Irradiate solution under UV for 1 hr with Ar bubbling
 * 3) Take 1mL of irradiated solution and add to small sample tube, make up to 10mL with ethanol
 * 4) Sonicate solution for 10 min
 * 5) Take 1mL of sonicated solution and add to new small sample tube, make up to 10mL with ethanol
 * 6) Sonicate solution with horn probe for 2 min at amplitude 20
 * 7) Prepare fresh mica substrate by peeling off top layer with scotch tape
 * 8) Deposit 1 drop of horn-sonicated solution on mica
 * 9) Immediately transfer mica substrates to vacuum chamber & leave overnight
 * 10) Remove sample from vacuum just prior to AFM imaging

=Results=

Sample 1 (No decent images of samples 2 and 3.)

=Discussion=

Again, no single or few-layer graphene/TiO2 sheets were found — just large agglomerates and small particles. So it seems that either the TiO2/graphene agglomerates during UV irradiation or in the time between switching off the UV lamp and the solvent drying on the mica substrate. Given this, it seems that a method must be found for stabilising the material.

=Conclusion=

No images of graphene/TiO2 flakes were found — the material had agglomerated into large monolithic mountains. A method for stabilising the graphene/TiO2 colloid likely needs to be found.

=Log=

2009-10-22
16:50 Added 1ml 4mg/ml TiO2 solution & 0.5ml 1mg/ml graphene solution to large sample tube & made up to 6ml. Named sample Sample 1 17:15 Sonicated Sample 1 for 2 min with microtip, amplitude 20. 482J delivered. 17:19 Placed Sample 1 under UV with bubbling (Ar) & stirring 18:25 Removed sample from UV 18:33 Made up 3 samples for AFM: AFM1 (2 drops of Sample 1); AFM2 (1 drop of 1ml Sample 1 in 9ml ethanol); AFM3 (1 drop of 1ml AFM2 solution in 9ml ethanol) 18:36 Put samples into vacuum chamber to dry. The ethanol had not yet evaporated.

2009-10-23
15:00 AFM imaging of AFM1, AFM2 and AFM3 using the Digital Instruments multimode (tapping mode) with a new tip.

=Tags=