NBEXP0003

=NBEXP0003 Synthesis of 7.5g graphene oxide for NTU=

Aim
To synthesise & characterise 7.5g of graphene oxide for NTU

Procedure
The procedure is a scaled-up version of the standard Hummers synthesis (JACS 1958 p1339) used in previous experiments. Scaling factor = 10x.


 * 1) Cool a large beaker containing 230ml pure sulfuric acid to 0 deg in an ice bath.
 * 2) Add 10g graphite and 5g sodium nitrate to the acid. Stir vigorously.
 * 3) Add 30g of potassium permanganate to the solution with vigorous stirring. Control the addition rate such that the solution temperature does not exceed 20 deg. (When all the potassium permanganate is added the solution will look black with a strong green tint.)
 * 4) 5min after the last of the potassium permangante is added, remove the beaker from the ice bath and warm to 35±3 deg on a hot plate. Stir vigorously for 30 min. The viscosity of the solution will increase and become more like a slurry, and the colour should turn a greyish-purple-brown by the end of the 30 minutes.
 * 5) Very, very carefully add 400ml distilled water to the slurry. The solution temperature will approach 100deg — do not allow the solution to boil.
 * 6) After the water addition is complete, contiune stirring for ~15 min at ~98 deg.
 * 7) Add 400ml of 10% hydrogen peroxide. The solution will bubble vigiorously and turn a bright browny-yellow colour.
 * 8) Stir the solution for 10 min and then filter with rough filter paper while solution is still warm.
 * 9) Resuspend the solution in warm distilled water by sonicating for 20 minutes at low power.
 * 10) Centrifuge the solution for 20 min at 10,000rpm. Discard the supernatatant.
 * 11) Resuspend the solid in warm 5% sulfuric acid and 5% hydrogen peroxide by sonicating for 20 minutes at low power.
 * 12) Filter the solution with rough filter paper.
 * 13) Repeat steps 9-12 two more times.
 * 14) Dry the resulting solid in vacuum at ambient temperature.

2009-09-14
11:00 Prepared solutions, cleaned glassware. 11:55 Added 230ml pure sulfuric acid to beaker, placed beaker in ice bath with stirring and left to cool. 12:06 Acid temp at 9 deg. Added 10.0058g graphite powder (natural, AJAX) and 5.0030g sodium nitrate (univar). 12:08 Realised I'd added sodium nitrite rather than sodium nitrate. Aborted synthesis and disposed of acid solution.

12:45 2nd synthesis attempt. Cooled 230ml sulfuric acid to 7 deg. Added 10.0048g natural graphite (AJAX) and 5.0021g sodium nitrate. Solution temp remained at 7°C. 12:59 Started adding 29.9941g potassium permanganate (Univar) 13:07 Finished adding potassium permanganate. Solution reached maximum temp of 17°C. 13:13 Removed solution from ice bath, placed on hot plate and began warming to 35°C. Increased stirrer RPM from 400 to 500. Solution is black with dark green tint. 13:28 Solution temp stabilised at 39-40°C. 13:45 Reduced stirrer RPM to 400 as solution was becoming viscous. 13:52 Increased stirrer to 450 RPM 14:00 Began adding 400ml MilliQ water. Solution temp had slowly decreased to 36° at this point, and was still black with green tint 14:03 Reduced stirrer RPM to 400 14:18 Finished adding water. Colour turned grayish-purple-brown & went very very viscous. Solution temp did exceed 100°C and hovered around 98°C throughout the water addition. A very thick layer of bubbles/foam formed above the liquid during the addtionm, which had not been observed in previous experiments. The solution turned a light brownish-yellow instead of dark brown — almost as if the hydrogen peroxide solution had already been added. Temp was 98° at the end of the water addition. 14:29 Made up 10% hydrogen peroxide solution. 136ml hydrogen peroxide was added to a beaker and made up to 400ml with milliQ 14:33 Added 10% hydrogen peroxide solution. No effevessing or colour change was observed. Solution was ~68° before the addition and ~55° after. 14:44 Began filtering solution (filter paper: Watson 41 ashless). Solution temp was 50°, was effervessing slightly and emitting invisible vapours that were very harsh on the nose. Left solution to filter while went to lunch.

17:00 Began another synthesis. Prepared glassware. 17:12 Added 10.0011g natural graphite to 15° 230ml sulfuric acid. Stirrer set at 350RPM. 17:18 Added 5.0026g sodium nitrate to solution. Temp = 12° 17:27 Started adding 30.0050g potassium permanganate to solution 17:36 Finished adding potassium permanganate. Max solution temp reached was 17°. Soln. was black with green tint. 17:41 Removed soln from ice bath & began warming to 35° on hot plate. 17:54 Soln temp reached 35°. Purple vapour had begun to effuse from soln. A layer of black foam had formed at the middle of the liquid surface.

18:14 Removed filter cake of 2nd synthesis attempt. Was mid- to light-brown with slight yellow/orange tinge. Was light and crumbly — v. different to normal (thick, viscous dark brown sludge). Placed in vacuum chamber at ambient temp. Assigned label NBEXP0003-1

18:32 Began adding 400ml milliQ water to solution that had been left at 35°. This time placed beaker in an ice bath to prevent excessive temperatures. Initially very intense purple vapours were emitted when each drop of water was added; became less intense as more water was added. 19:02 finished adding water. Max. temp reached was 55°. Solution was a rich dark chocolate brown with a purple tinge. 19:09 Made up 10% hydrogen peroxide solution. Added 138ml hydrogen peroxide to beaker and made up to 400ml with milliQ. The hydrogen peroxide came from 2 bottles: ~80ml from an apparently relatively new bottle that was stored in the fridge and was cold, and the rest from an older bottle that had been kept in the broken fridge at slightly below ambient (frigde broke last week, I think). 19:13 Added hydrogen peroxide solution to acidic mixture; mixture effervessed furiously and turned yellow with a brown and slightly green tinge. 19:25 Began filtering solution (whatman, 41 ashless). 19:40 topped up filter, left remainder of solution stirring in fume cupboard at ambient temp.

2009-09-16
9:11 Set GO soln prepared 2009-09-14 on stirrer @ 400rpm (had been set aside - solids had settled to bottom). Soln was now a dark brown instead of yellow-brown. 9:12 Scraped solid GO in funnel from Monday into beaker & covered w' foil. Cleaned funnel & added new filter (Whatman 41, ashelss) 9:22 Added more GO soln to filter, returned remainder to stirrer. 10:15 Refilled filter funnel w' GO soln 10:55 topped up funnel again 13:09 Added some GO to funnel & it ran straight through - filter paper had decomposed. Left as it was to dry. 14:22 Scraped filter cake into beaker, replaced filter paper & added more GO soln.

2009-09-17
08:30 scraped remainder of solid GO from funnel into beaker, filled beaker w' ~250ml 5% sulfuric acid & 5% sulfuric acid solution. Sonicated for 10 min. 09:00 topped up funnel 17:15 Filter cake dry and sticking to filter paper; wet filter cake slightly and scraped solid into beaker. Replaced filter paper & added remainder of the solution.