Took notice of is a phrase that indicates paying attention or acknowledging someone or something. The opposite of taking notice of can vary depending on the context. One possible antonym could be ignoring, meaning to not pay attention or actively dismiss someone or something. However, in some cases, the opposite of taking notice of could be disregarding, neglecting, or overlooking, all of which suggest a lack of attention or recognition. Another antonym could be overlooking, which means intentionally not noticing something or someone. Ultimately, the best antonym will depend on the specific circumstances in which the phrase is used.