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:
10.1016/j.nanoen.2014.10.008
Formic acid-reduced ultrasmall Pd nanocrystals on graphene to provide superior electocatalytic activity and stability toward formic acid oxidation

The graphene oxide (GO) was synthesized from graphite by using a modified Hummers method [20] and [21]. The prepared graphene oxide was dried in normal vacuum at 70 degC for 12 h and then put into a glass bottle under high vacuum level at 60 degC overnight, followed by heating to 220 degC quickly. The obtained highly loose black powder was denoted as graphene.

In a typical synthesis of Pd@Graphene electrocatalyst (30% Pd), graphene 10.5 mg, poly(vinyl pyrrolidone) (PVP) 40 mg, and (NH4)2PdCl4 12 mg were dissolved in 2 mL of deionized water. The mixture was treated in an ultrasonic bath to form a uniform aqueous dispersion, then added 3 mL HCOOH and ultrasonically treated for 10 min. which was placed in a 25 mL Teflon-sealed autoclave and maintained at 120 degC for 12 h. The obtained black power was isolated by centrifugation, cleaned by three cycles of centrifugation/washing, and oven-dried at 60 degC for more than 6 h. The obtained sample was denoted as Pd@Graphene materials.
[{"arguments": [["graphite", "Recipe_Precursor"], ["graphene oxide", "Participant_Material"]], "trigger": "synthesized"}, {"arguments": [["graphene oxide", "Participant_Material"]], "trigger": "dried"}, {"arguments": [["poly(vinyl pyrrolidone)", "Participant_Material"], ["water", "Solvent_Material"], ["(NH4)2PdCl4", "Recipe_Precursor"], ["graphene", "Participant_Material"]], "trigger": "dissolved"}, {"arguments": [["mixture", "Participant_Material"]], "trigger": "treated"}, {"arguments": [["HCOOH", "Participant_Material"]], "trigger": "added"}, {"arguments": [["power", "Participant_Material"]], "trigger": "isolated"}]