The Preparation Of Gold/Silver Nanoparticles And Its Sensor Applications

In 21st century, nano materials are necessary materials and play an important role in biomedicine, electrical components, space flight and aviation, catalysis and accumulation energy etc., for their various shapes and surface effect, small size effect, quantum size effect, quantum tunnel effect, as well as their derived magic characteristics in photics, thermotics, magnetics, chemistry, electricity and so on.The metallic nanomaterials have started far more back and ran a longer course. Before 2000 years ago, gold and silver have been used in glass with most of them being nano particles. Metal nanoparticles are also known for their excellent optical, electrical, magnetic and other aspects of natures which have been popular with researchers. Currently, metal nanomaterials including gold, silver, copper, platinum, iridium, rhodium etc., are mainly used for the catalytic, electrochemistry, sensor detection, and etc. This research was based on gold nanoparticles’special properties in sensor aspect. We prepared gold nanoparticle via sodium citrate reducing chloroauric acid, and then modified them so as to detect other materials. The research contents are as follows:(1) Tripolycyanamide combines with gold nanoparticles and the gold nanoparticles’color changes from red to blue. However, when mercury ion added, it would take over the combination site between tripolycyanamide and gold nanoparticles, and thus, the color of gold nanoparticles would remain red. We detected mercury ion following this principle. Through optimizing the conditions, we found the best concentration of tripolycyanamide to lower the LOD which was 0.03 mg/L calculated by linear fit and testified the selectivity for mercury ion of this method through detecting other metal ions.(2) Glutathione combines to gold nanoparticles’surface via Au-S covalent bond to protect gold nanoparticles against salt aggregation. However, the added Cr(Ⅵ) destroys this combination and the color of gold nanoparticles changes.According to the principles that glutathione and chromium (Ⅵ) forms complexes and following the dispersity discrepancy, this method achieved Cr(Ⅵ) with simpleness, speediness and high sensitivity. We greatly improved the sensitivity and lowered the detection limit via seeking the best suitable concentration of glutathione and salt; and we have calculated the detection limit of 0.1 mg/L by linear fit; as well as we testified that this method was selective for Cr(Ⅵ) compelling to other metal ions; at last, we successfully detected Cr(Ⅵ) in practical liquid waste.(3) We modified the gold nanoparticles and silver nanoparticles with ssDNA by their nonconvalent binding between each other to produce an AuNPs/ssDNA probe and an AgNPs/ssDNA probe for L- homocysteine detection. We greatly improved the sensitivity and lowered the detection limit which was 50 nM and 10 nM respectively by salt amplification.