Usually online courses improves Your knowledge and makes you expert in utilizing your skills to impliment the things at work.there are several ofree online courses which is offered by website and organization they are free so its only for beginners if you are looking for advanced course you need to buy paid courses.

You can do courses like Neuroscience and Neuroimaging,Biochemistry: The Molecules of Life,Principles of Biochemistry etc after MSc chemistry from the website like FutureLearn,coursers,udemy etc.