Surface-functionalization of spherical silver nanoparticles with macrocyclic polyammonium cations and their potential for sensing phosphates
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- Misra, T.K. & Liu, CY. J Nanopart Res (2009) 11: 1053. doi:10.1007/s11051-008-9493-x
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The synthesis of aqueous dispersion of spherical, underivatized silver nanoparticles (Ag-NPs) stabilized by macrocyclic polyammonium chlorides (MCPAC), ane-(NH2+)6O2·6Cl− (28-MCPAC) and ane-(NH2+)8·8Cl− (32-MCPAC), which are evidently anion receptors, is reported. As-synthesized Ag-NPs are characterized by UV-vis spectroscopy and transmission electron microscopy (TEM). The 28/32-MCPAC-stabilized Ag-NPs show the surface plasmon band around 400 nm. The TEM-images show that the particles are spherical and well-dispersed. By tuning the 28/32-MCPAC:Ag-OAc (silver acetate) ratio, nanoparticles with different core diameters ranging from 13 to 8 nm for 28-MCPAC and from 10 to 6 nm for 32-MCPAC can be obtained. The advantage of using MCPAC as stabilizers is that they make the particles functionalized for sensing anions. Thus, the potential of the as-synthesized Ag-NPs for sensing phosphates: H2PO4− (monobasic phosphate, MBP), HPO42− (dibasic phosphate, DBP) and PO43− (tribasic phosphate, TBP) is investigated spectroscopically. Interaction of phosphate ions with macrocyclic polyammonium cations makes the Ag-NPs bare, leading agglomeration. The phosphate-assisted agglomeration of 32-MCPAC-Ag-NPs follow the order TBP > DBP ≫ MBP.