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Indian Institute of Technology (IIT) Roorkee 
Synthesis of highly NIR luminescent gold nanoparticles with high stokes shift 
Kalyan Kumar Sadhu and Meenaxi 
Indian Institute of Technology (IIT) Roorkee 
Application type:
Applied - 2016-06-30 
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Indian Institute of Technology (IIT) Roorkee 
Gold nanoparticles are characterized by their Surface Plasmon Resonance (SPR) peaks, which vary with the size of gold nanoparticles. The particle size within the range 0.3 to 20 nm mainly pre dominates the luminescence properties of gold nanoparticles via surface coating with different types of ligands. Dissociation of polymeric Au(I) thiolates resulted in the formation of luminescent gold nanoparticles. Rigidification of Au(I) thiolate shell also enhanced the emission property. Enhancement of the NIR luminescence was possible due to the oxidation of thio-ligand by hydrogen peroxide at core-ligand interface. Recently, thiolate and sulfide binding units have been used to show very high luminescence up to 3.65% quantum yield. In case of citrate stabilization, CdSe core showed bright luminescence. However, citrate stabilized gold nanoparticles do not show any significant luminescence since its discovery more than fifty years back. In our attempt, we observed characteristic luminescent band from different citrate stabilized gold nanoparticles at 916 nm (Near Infra Red region, NIR) by excitation at 562 nm with Stokes shift greater than 350 nm in presence of controlled amount of aqua regia. Further addition of aqua regia reduced the luminescence intensity significantly. This material has potential in the imaging of cancer cells.  

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