I think you can replace "针对" with "对" in this sentence. But why do you replace this word ? "很多科学家都针对人体发光的现象进行了研究。" is ok . it can express what you want to say . And you replace "针对" with "向" is not ok in Chinese .

Both “针对” and "对" can be used in this sentence. "针对" is more formal, while "对" is more common. But “向” is incorrect. I hope this will help.

针对比向要强烈很多，针对，有特指意味。在例句中，不可替换。

向 sounds weird to me. ‘对’ is better.even better than 针对. I just searched “进行了研究” and most results use '对'. You can try it yourself.

Normally ‘针对’ is used when you want to pinpoint a specific matter for discussion, and usually not directed to any person. In this example, '针对‘ is a more appropriate term, as it's aimed at a specific research the scientists are doing. '科学家都针对人体发光的现象' Example: (1) 我们应该针对这次的失误做检讨 - We should look into the reason we failed this time (2) 针对刚才的方案，你有什么想法 - What do you think about the proposal '向‘ is usually used if the subject is a person, For example, (1) 我向他借钱 - I borrowed money from him (2) 学生应该向老师行礼 - Students should greet their teachers (3) 我向你道歉 - I apologized to you