Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Reversible optical responses of a 100 nm Fe3O4 colloid under increasing or decreasing external magnetic field (H): (a) digital photos of the Fe3O4 colloid without H (left) and with H (right); (b) blue shift in the reflection when H is enhanced; and (c) red shift in the reflection when H is weakened (adopted from [100] with permission from Elsevier, 2019).
