Preparation method of silver nano-particles and application of silver nano-particles to detection of melamin
A technology of silver nanoparticles and melamine, applied in the field of nano-optics, can solve the problems of expensive instruments, high cost, time-consuming, etc., and achieve the effects of uniform particles, easy operation and stable process conditions
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[0025] 1. Preparation of aniline-modified silver nanoparticles
[0026] The present invention adopts the reduction method of sodium borohydride, promptly uses silver nitrate as the source of silver, aniline is used as stabilizer, twice distilled water is used as reaction solvent, and one-pot reaction makes the silver nanoparticle of aniline modification, and specific preparation method is: see Figure 6 , at room temperature, in 94mL water, add 1mL 10 -2 mol / LAgNO 3 Aqueous solution, add 4~12mg NaBH under stirring 4 , stirred for 1 to 5 minutes, added 0.5 to 5 mL of 6 mol / L aniline aqueous solution, and continued to stir for 0.5 hours. The maximum absorption peak of the silver nanoparticles is at 396nm (see image 3 ), the particle size is about 8nm, and the properties do not change in the range of pH=3~10 (see figure 1 ).
[0027] 2. Application of aniline-modified silver nanoparticles to the detection of melamine
Embodiment 1
[0028] Example 1, the detection of melamine in aqueous solution by aniline-modified silver nanoparticles:
[0029] 0.25mL 10 -4 The melamine of mol / L, melamine analogue and ionic solution are added in the silver nanoparticle solution of 1.5mL aniline modification respectively, mix evenly, stand ten minutes, carry out ultraviolet-visible absorption spectroscopic analysis, see figure 2 , only melamine can significantly change the ultraviolet absorption peak of the silver nanoparticles, and change the color of the solution from yellow to dark green at the same time. It can be seen that the melamine analogs and common anions and cations will not interfere with the detection of melamine. figure 2 Middle: 0 is the reference, 1 is 4,6-dichloro-5-aminopyrimidine, 2 is 2,5-diamino-4,6-dichloropyrimidine, 3 is p-phenylenediamine, 4 is m-phenylenediamine Amine, 5 is o-phenylenediamine, 6 is melamine, 7 is K + , 8 is Na + , 9 is Ca 2+ , 10 is Mg 2+ , 11 is Fe 3+ , 12 for H 2 PO 4...
Embodiment 2
[0031] Example 2, the detection of melamine in milk powder by aniline-modified silver nanoparticles:
[0032] Take 20mg of solid milk powder, add 2mL of 0.1mg / mL melamine methanol solution, shake fully, if necessary, shake in an ultrasonic cleaner for 5 minutes, mix well, and make the mass ratio of melamine to milk powder is 1:10 2 of the mixture. According to this method, the mass ratio of melamine to milk powder is 1:10. 3 , 1:10 4 , 1:10 5 , 1:10 6 , 1:10 7 of the mixture. Add 20mg of solid milk powder to 2mL of methanol solution as a reference. Add 0.025 mL of 1% trifluoroacetic acid aqueous solution to the above mixture, mix well, filter with a sand funnel (with 1 cm thick silica gel for column chromatography inside), wash the silica gel with 1 mL of methanol, and collect the filtrate. Take 0.25mL of filtrates with different mass ratios and add them to 1.5mL of aniline-modified silver nanoparticles solution, mix well, and after 5 minutes, the mass ratio is not less...
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