It's takes 1 - 2 weeks for chopped veggies to lose 50% of their Vitamin C. Please don't let that stop you from peeling, slicing and cooking carrots. Nutrition loss is negligible when cut and cooked right away. Sheesh. Carrots are lovely cooked this way.
It is better nutritionally not to chop the carrots as above in diagonal slices. Loses nutrition in the water when chopped. I plan to make theses and leave the carrots pretty much in whole strips. When they are cooked they will fall apart or be soft enough it eat.