Making of Silver Nanoparticles 

After centrifugation for 5 min and then put it in oven at 70 degree

the ionic strength of the solution rose and thus resulted in an aggregation of the nanoparticles

@@valerylegasov278 thank you..

its written on the bottle.. watch again..

Maybe your solutions were not dilute enough?

Also possible is that their NaBH4 decomposed so much that only a tiny bit of Ag was reduced.

As we are changing it to Make it basic..so it can immediately be basic after adding of base

As it is titration process

Preparations of solutions: 1. 1000 cm3 of 0.0020 M NaBH4(aq): Weigh 0.076 g of NaBH4(s) and dissolve it in deionised water to volume in a 1000 cm3 volumetric flask. 2. 1000 cm3 0.0010 M AgNO3(aq): Weigh 0.17 g of AgNO3(s) and dissolve it in deionised water to volume in a 1000 cm3 volumetric flask. 3. 200 cm3 of saturated NaCl(aq): Add excess amounts of NaCl(s) into 200 cm3 of deionised water. Note: the sodium borohydride solution must be freshly prepared before the experiment session starts.

NaBH4

@@amritkumar2381 Does sodium borohydride stabilize as well as reduce?

None, I think.

I would use one drop of 0.3% Polyvinylpyrollidone solution + 1 drop of 0.3% sodium dodecyl sulfate as stabilizers...