You will be shown an abstract from a materials science research paper. Your task is to extract all synthesis operations described in the abstract into a structured JSON format. Your output should be a JSON array. Each entry in the array should be a JSON object describing a single synthesis operation. This object should have the following fields:

- "trigger": A verbal predicate indicating a synthesis operation. This should be a string extracted directly from the abstract.
- "arguments": An array of arguments specifying aspects of the synthesis operation. Each entry in the array should be a length-2 array formatted as [<argument_text>, <argument_type>]. The `argument_text` should be a string extracted directly from the abstract. The `argument_type` should be one of the following types: ["Recipe_Precursor", "Atmospheric_Material", "Participant_Material", "Recipe_Target", "Solvent_Material"].

For instance, suppose an excerpt from the abstract reads:

Tetraethoxysilane (TEOS, 98%) and cetyltrimethylammonium bromide (CTAB, 98%) were purchased from Fluka. The MTTZ-siloxy derivative (triethoxysilyl-propyl-5-mercapto-1-methyl-tetrazole) was synthesized as previously described [38].

This excerpt includes two operations, which could be annotated as follows.

[{"arguments": [["Tetraethoxysilane", "Recipe_Precursor"], ["cetyltrimethylammonium bromide", "Recipe_Precursor"]], "trigger": "purchased"}, {"arguments": [["MTTZ-siloxy derivative", "Recipe_Target"]], "trigger": "synthesized"}]

In your response, please include the JSON and no other text.

Abstract:
10.1039/c5tc00196j
A facile fabrication of large-scale reduced graphene oxide-silver nanoparticle hybrid film as a highly active surface-enhanced Raman scattering substrate
Natural graphite flake (99.8% purity), silver nitrate (AgNO3, >99%), and sodium citrate tribasic dehydrate (>=99.0% purity) were purchased from Sigma-Aldrich. R6G and MA were obtained from J&K Scientific Ltd (Beijing, China). H2SO4 (95-98 wt%) and KMnO4 (99.5% purity) were purchased from Beijing Chemical Co., Ltd (Beijing, China). H3PO4 (85% purity) and H2O2 (30% aqueous solution) were obtained from Xilong Chemical Co., Ltd. All chemicals used in this work were of analytical reagent grade and obtained from commercial sources and directly used without additional purification. The water used was purified through a Millipore system (~18.2 MΩ cm-1). Carbon-coated Cu grids for transmission electron microscopy (TEM) characterization were purchased from Plano GmbH (Wetzlar, Germany).
GO was synthesized by the oxidation of natural graphite flakes using a modified Hummers method to produce graphite oxide.31 In detail, 3 g of graphite flakes were mixed with a mixture of concentrated H2SO4/H3PO4 (9:1) under stirring at room temperature; KMnO4 (18 g) was added slowly by stirring, and the mixture was incubated and stirred in the thermostatic water bath for 12 h (50 degC). The mixture was poured slowly onto ice crush (200 mL) and 10% hydrogen peroxide (10 mL) when the temperature was decreased to room temperature. Then the mixture was centrifuged (4000 rpm for 0.5 h), and the remaining solid material was washed in succession with 400 mL of water, 400 mL of 30% hydrochloric acid, and 400 mL of ethanol (2x). The remaining material was filtered and vacuum-dried overnight at room temperature. Finally, 5.8 g of the product was obtained.
AgNPs were synthesized according to the literature previously reported.32 In a typical synthesis, 100 mL of aqueous AgNO3 (0.5 mmol) was added into a 250 mL flask and heated to boil under punchy stirring in an oil bath. After that, 10 mL aqueous sodium citrate (1%) was added, and the color of the solution reached to yellow after 1 h, which indicates the formation of AgNPs.
[{"arguments": [["silver nitrate", "Recipe_Precursor"], ["graphite flake", "Recipe_Precursor"], ["sodium citrate tribasic dehydrate", "Recipe_Precursor"]], "trigger": "purchased"}, {"arguments": [["R6G", "Recipe_Precursor"], ["MA", "Recipe_Precursor"]], "trigger": "obtained"}, {"arguments": [["KMnO4", "Recipe_Precursor"], ["H2SO4", "Recipe_Precursor"]], "trigger": "purchased"}, {"arguments": [["H3PO4", "Recipe_Precursor"], ["H2O2", "Recipe_Precursor"]], "trigger": "obtained"}, {"arguments": [["chemicals", "Participant_Material"]], "trigger": "used"}, {"arguments": [["water", "Solvent_Material"]], "trigger": "used"}, {"arguments": [["Cu", "Participant_Material"]], "trigger": "purchased"}, {"arguments": [["GO", "Participant_Material"]], "trigger": "synthesized"}, {"arguments": [["graphite flakes", "Recipe_Precursor"]], "trigger": "oxidation"}, {"arguments": [["graphite oxide", "Participant_Material"]], "trigger": "produce"}, {"arguments": [["graphite flakes", "Recipe_Precursor"], ["H2SO4/H3PO4", "Recipe_Precursor"]], "trigger": "mixed"}, {"arguments": [["KMnO4", "Recipe_Precursor"]], "trigger": "added"}, {"arguments": [["mixture", "Participant_Material"]], "trigger": "incubated"}, {"arguments": [["ice crush", "Participant_Material"], ["hydrogen peroxide", "Participant_Material"], ["mixture", "Participant_Material"]], "trigger": "poured"}, {"arguments": [["mixture", "Participant_Material"]], "trigger": "centrifuged"}, {"arguments": [["solid", "Participant_Material"], ["water", "Participant_Material"], ["ethanol", "Participant_Material"], ["hydrochloric acid", "Participant_Material"]], "trigger": "washed"}, {"arguments": [["material", "Participant_Material"]], "trigger": "filtered"}, {"arguments": [["product", "Participant_Material"]], "trigger": "obtained"}, {"arguments": [["AgNPs", "Recipe_Target"]], "trigger": "synthesized"}, {"arguments": [["AgNO3", "Recipe_Precursor"]], "trigger": "added"}, {"arguments": [["sodium citrate", "Recipe_Precursor"]], "trigger": "added"}, {"arguments": [["solution", "Participant_Material"]], "trigger": "reached"}, {"arguments": [["AgNPs", "Recipe_Target"]], "trigger": "formation"}]