Surface plasmon resonance of gold nanoparticles as a colorimetric sensor for indirect detection of Cefixime.

This study reports a colorimetric sensor with excellent sensitivity to detect Cefixime base on gold nanoparticles. Cefixime is an antibiotic which has a wide range of applications in medicine. Cefixime did not change the surface plasmon resonance bond in gold nanoparticles solution; therefore, there was no change in the color solution of gold nanoparticles. The presence of Alizarin Red S in the system was necessary for the degradation of Cefixime, resulting in the aggregation of gold nanoparticles and a color change from red to blue. As a result of aggregation, the localized surface plasmon resonance band of gold nanoparticles decreased to around 525 nm and a new red-shifted band at 640 nm appeared which increases gradually as the function of Cefixime concentration. A unique detection limit (2.5 ng mL-1 ) was achieved for Cefixime in comparison with other colorimetric methods. Relative standard deviations (RSD) for 40.0 and 140.0 ng mL-1 of Cefixime were 2.6 and 1.8% for intra-day respectively. A possible mechanism was discussed for the surface plasmon resonance changes of AuNPs in the presence of Cefixime. The proposed method was applied to detect Cefixime in pharmaceutical samples with satisfactory results. This system is low-cost and is highly sensitive with no need for any preconcentration steps or using any expensive or sophisticated instrumentation.