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:

Superhydrophobic and Superoleophilic PVDF Membranes for Effective Separation of Water-in-Oil Emulsions with High Flux. A superhydrophobic-superoleophilic PVDF membrane is fabricated via an inert solvent-induced phase inversion for effective separation of both micrometer and nanometer-sized surfactant-free and surfactant-stabilized water-in-oil emulsions solely driven by gravity, with high separation efficiency (oil purity in filtrate after separation > 99.95 wt%) and high flux, which is several times higher than those of commercial filtration membranes and reported materials with similar permeation properties.
{"Chemical": ["PVDF"]}