A novel Nd3+-sensitized upconversion nanoparticle (UCNP) that can be excited by near-infrared 740 nm light-emitting diode (LED) lamps with bright upconversion luminescence is designed. Yb3+ ion distribution is engineered to increase the energy migration efficiency. The benefit of the novel LED-excited UCNPs is demonstrated by imaging of breast cancer cells and enabling an economic handheld semiquantitative visual measurement device.