PARAMETERS OPTIMIZATION OF METAL-DIELECTRIC NANOSTRUCTURES FOR SENSOR APPLICATIONS

We present calculation results of optical properties of silver nanoparticles with dielectric shell in relation to their applications in chemical and biosensors. Absorption cross-section calculation for spherical silver nanoparticles was performed by quasi static dipole approximation. It is shown that dielectric shell thickness equal to 2-3 nm and its refraction index equal to 1,5-1,75 are optimal. Calculation results were compared to experimental data. Experimental investigation of metal-dielectric nanostructures sensitivity to external refraction index was performed. Synthesis of silver nanoparticles with dielectric shell on glass surface was performed by nanosecond laser ablation method in near-surface glass layer at 1,06 μm wavelength (Solar LQ129). Synthesis of silver nanoparticles without a shell on the glass surface with silver ions was performed using thermal treatment in wet atmosphere. Spectrophotometer Cary 500 (Varyan) was used for spectral measurements. In case of laser ablation method application, external refraction index changes from 1 (the air) to 1,33 (water) and plasmon resonance band shift for 6 nm occurs. In case of another method application at the same conditions the registered shift was equal to 13 nm. However, in the latter case the particles can be easily removed from the substrate surface. Obtained results will be useful for developing chemical and biological sensors based on plasmon resonance band shift.