Gold nanoparticles: BSA (Bovine Serum Albumin) coating and X-ray irradiation produce variable-spectrum photoluminescence

• Gold nanoparticles (Au NPs) coated with Bovine Serum Albumin (BSA) are synthesized by x-ray irradiation.
• BSA coated AuNPs with ~1 nm size show strong photoluminescence in red by UV excitation.
• The blue photoluminescence of BSA increase with x-ray irradiation.
• Increase x-ray irradiation time during the synthesis shift the color of the colloid from red to blue.

We show that by using different x-ray irradiation times of BSA-coated Au nanoparticles (NPs) we can change their ultraviolet-stimulated photoluminescence and shift the spectral weight over the visible spectral range. This is due to the interplay of two emission bands, one due to BSA and the other related to gold. The emission properties did not change with time over a period of several months.