"extensive knowledge about" is correct and usable in written English.
You can use it to describe a person's vast amount of knowledge on a particular topic or issue. For example, "He has extensive knowledge about ancient history."
Paul has extensive knowledge about the world and the international economy.
He is one of the warmest people you'll ever meet and a great storyteller, with extensive knowledge about Route 66.
Despite extensive knowledge about genes involved in the pathogenesis of RP, the genetic cause remains elusive in many patients.
Previous research also indicates that boards do not have extensive knowledge about talent and succession-related issues at their companies.
She seemed to have extensive knowledge about Damascus, describing intricate details of museums that Brooks, who had been to Syria, knew to be true.
These knowledge sources with different levels of abstraction are all built independently of the specific application field, and require extensive knowledge about different engineering domains.
These knowledge sources with different levels of abstraction are all built independent of the specific application field, and require extensive knowledge about different engineering domains.
Extensive knowledge about the transferability of GDMs in space is needed before the models can be reliably used in climate change explorations.
The ability to design polymers with good scratch visibility resistance requires extensive knowledge about scratch deformation mechanisms and their propensity for light scattering.
"They had extensive knowledge about the environment, about plants and animals – how to refer to the landscape, the way the landscape is broken up – a kind of taxonomy of the land forms".
To my knowledge, no public figure - and certainly not one with such an extensive knowledge about the way the media operate - has ever insisted on telling a journalist that he has killed someone.
