A method for enhancing recovery of hydrocarbons from a hydrocarbon-bearing subterranean formation includes withdrawing hydrocarbons from a production well and injecting a treatment fluid that includes carbon nanodots dispersed in a brine solution from an injection well that is spaced apart from the production well. The carbon nanodots include carbon, oxygen, nitrogen, and hydrogen and are surface functionalized. A concentration of carbon nanodots in the treatment fluid is less than or equal to 500 parts per million by weight. Injection of the treatment fluid having the carbon nanodots is characterized by an injection duration, an injection pressure, an injection volume, or a combination thereof, that is sufficient to increase cumulative oil recovery of hydrocarbons from the first subterranean formation, the second subterranean formation, or both by at least 10% compared to injecting the brine solution without the carbon nanodots.