There is no easy answer to this question as it depends on a variety of factors including your specific goals and interests. However, both chemical and materials engineering offer unique advantages for those interested in pursuing a career in nanotechnology.
Materials engineering may be a better choice if you are interested in developing new materials or working with existing materials at the nanoscale. This field also offers a more interdisciplinary approach, which can be beneficial for those interested in working in a multidisciplinary field like nanotechnology.
Chemical engineering may be a better choice if you are interested in developing new chemical processes or working with existing chemical processes at the nanoscale. This field offers a more focused approach and may be more suited for those interested in working in a single discipline.