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:

A nanosised oxygen scavenger: preparation and antioxidant application to roasted sunflower seeds and walnuts. A novel oxygen scavenger using iron nanoparticle was produced and evaluated as a potential oxygen scavenger. Iron nanoparticle was prepared by liquid phase reduction method in microemulsion systems. The absorption capacity of different kinds of oxygen scavengers was measured as a function of time, and the absorption rate constant was evaluated at 25°C. The absorption kinetic analysis showed that the absorption process followed a first-order reaction. The absorption rate constant of nanosised and conventional oxygen scavenger were 0.45±0.044h(-1) and 0.05±0.006h(-1), respectively. Successful application of the nanosised oxygen scavenger on roasted sunflower seed and walnut demonstrated its ability to inhibit lipid oxidation in lipid-containing food. Roasted nut treated with nanosised oxygen scavenger possessed the lowest PV and AnV in all treatments after 120 days of storage. Therefore, it has the potential for broad application as an active packaging in a variety of oxygen-sensitive foods.
{"Chemical": ["oxygen"]}