Quantum active sized silicon nanoparticles with a silicon core covered by a thin 0.5-1.5 nm oxide/nitride shell are described for light exposure in the 300-600 nm range for transforming atmospheric oxygen to singlet oxygen for causing cell apoptosis as a type of photodynamic cancer therapy. A method of use of the nanoparticle in a non-hydrophobic cream is also taught along with a blocking scheme for controlled reaction of the nanoparticle.
