Which particles bring about the fission of uranium-235?

The low-energy neutrons (or, slow-moving neutrons) bring about the fission of uranium-235.

Explanation

The low-energy neutrons (or, slow-moving neutrons) bring about the fission of uranium-235, because slowing the neutron, the possibilities of the neutron reacting with the nucleus of Uranium-235 increases significantly, allowing the chain reaction to be maintained. 

Nuclear fission - It is defined as the splitting of a heavy nucleus into two lighter or daughter nuclei through a nuclear reaction. The heavy nucleus is bombarded with neutrons, which results in the production of a high amount of energy.