Functional Silver Nanoparticles Application In Food Analysis

Materical of nanopartical gets more attention because of its special performance and widely using. More than others, the study of synthesis of metal nanopartical is always the emphases of their work. Silver nanoparticles have the nature as surface effect, quantum size effect and macroscopic quantum tunneling. It owns strong stability and could been decorated easily. Advantage can be applied to the analysis and detection. Comparing with the traditional methods, the work had low limit of detection, high sensitivity, less time consuming, easy operation and low equipment requirements. As a result, deep study of the silver nanoparticles made for the new technology and new method.Based on the above consideration, this paper established colorimetric detection combining optical spectrum analyser method by the help of surface plasmon resonance of silver nanoparticles. And then, it scuccessfully solved the determination of ascorbic acid, tocopherol, p-phenylenediamine, tartrazine and sorbic acid. The main work are as parts:1. Preparation of silver nanoparticles via oxidoreduction and their detection of ascorbic acid and tocopherol. Using the reducibility of ascorbic acid and tocopherol,worked to prepare the silver nanoparticles. The result was the nanoparticles had lower size and steady property when PVP was acted as protection. Detection was based on the production of the silver nanopartical. Instruments such as SEM, fourier infrared spectrometer and ultraviolet-visible spectrophotometer represented the character,optimized the facter. Then applied the software of Expert to analyse the result to make accuracy. The standard curve of ascorbic acid and tocopherol were A=0.2164C-0.0333 and A = 0.0526 C + 0.0109. Their detection range were 0.4-5.0mg L-1 and 0.9-9.5 mg L-1, as their LOD were 0.17 mg L-1 and 0.63 mg L-1.2. Colorimetric detection of p-phenylenediamine using silver nanoparticles functionalized with sulfanilic acid. Making it possible that colorimetric detection of p-phenylenediamine. The theory was the analyte could make the martical ofnanoparticals agminated accompanying the color changed. The sulfanilic acids were deracted on the surface of the silver nanopartical, combining with the p-phenylenediamine, then the particles aggregated seen from the SEM. It was clear the characteristic peak of silver nanopartical was on 395 nm, the new peak of 580 nm was born when contacted with p-phenylenediamine in the ultraviolet spectrum. The value of A580nm/A395 nm was in direct proportion to the purity of p-phenylenediamine.The standard curve had two parts as the concentration of p-phenylenediamine changed. When the concentration of p-phenylenediamine were 0.025- 0.1 × 10-3mol L-1, the curve was y = 0.6756[C] + 0.0284. The other curve was y=2.11591[C] –0.1140, when the concentration was 0.1–0.225 × 10-3 mol L-1. The LOD was 6.2 ×10–6 mol L–1.3. Colorimetric detection of sorbic acid using silver nanoparticles functionalized with cysteine. Cysteine played as deraction on the surface of the silver nanopartical.We studied the mechanism using virous of instrument. The method had the advantage of sensitivity and selectivity played as the new way to apply to the detection of sorbic acid. Sorbic acid could induce the aggregation. The peak of silver nanopartical cutted down and the new born peak grew higher, taking the ratio to detedte the analyte. The value of A540nm/A395 nm was in direct proportion as the concentration of sorbic acid changed. Along with the curve was y = 0.00507 C + 0.0557, the concentration of sorbic acid was 0-3.75 × 10-4 mol L-1. When the concentration was 3.75-6.25 × 10-4mol L-1, the curve was y = 0.01341C- 0.24999.4. Energy transfer of fluorescence resonance detected tartrazine. Bovine serum albumin had its own fluorescence emission peaks, when it combined with the silver nanopartical, it became sensitive. The result indicated that tartrazine would quench the fluorescence of the siiver derected by bovine serum albumin,and the quenching efficiency synchronize wuth the content of tartrazine. The nanopartical material could keep steady in a long time, so it would do well in the actural detection. The standard curve was F0/F = 0.0991 C + 0.8703 when the concentration of tartrazine was 0-3 × 10-5mol L-1.