You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Simple colorimetric bacterial detection and high-throughput drug screening based on a graphene-enzyme complex. A simple, colorimetric, sensitive, cost-effective and high-throughput system based on a positively charged graphene oxide-enzyme complex was developed for bacterial detection and drug screening.
{"Chemical": ["graphene", "graphene oxide"]}