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Position:Home > News > Technical Data > A series of measurements, including
A series of measurements, including
Source:    Published:2011/6/10 11:35:35

   the reaction mixture would decrease. To keep a basic reaction medium, an excess amount of base had to be added into the reaction system. Liu and co-workers systemically

   investigated the influence of the amount of NaOH on the stability of the unprotected metal nanoclusters [15]. In their experiments, the metal colloids were prepared at different OH-/MI+ molar ratio, with constant metal concentration. The experimental results revealed that stable metal colloids can be obtained only in a definite concentration range of NaOH, the molar ratios of NaOH to

   metal ranging from 12 t0 25 for Pt and 6 t0 12 for Rh, which is the characteristic of electrostatic stabilization for metal colloids by the surface adsorbed anions [39,40].

  

   A series of measurements, including GC-MS, HPLC, MS, UV-vis, FT-IR and element analysis, have been carried out to analyze the species formed in the alkaline EG synthesis process that may have a contribution to the stability of the nanoscopic Pt particles. These experimental results suggested that in the colloidal solutions of the unprotected metal nanoclusters, EG and the simple anions adsorbed on the surface of metal particles played important roles in stabilizing the nanosized metal clusters. It should be noticed that in the prepared metal colloidal solutions, there should be an adsorptive equilibrium on the metal nanoclusters between the existing simple anions such as OH-, Cl-, acetate, glycolate or oxalate ions, which depended not only on pH and solvents but also on

  

   the metal specificity. According to the DLVO theory for the colloid stability, all of the adsorbed anions would have their contribution to the stabilizing effect on the metal nanoclusters. Precipitating the Pt nanoclusters with a dilute aqueous solution of HCl, followed by "dissolving" the precipitated Pt nanoclusters in EG containing NaOH and repeating the precipitation-redispersion process for several times, could give rise to a very stable Pt colloidal

   solution [11]. A further intensive study is necessary for reveafing the details in the stabilization mechanism.

  

   3.2. Ligand Mothjicatron Nanoclusters The species absorbed on the unprotected metal nanoclusters, i.e. EG and the simple anions, can be easily replaced by many kinds of coordination ligands or protective agents. This character makes it possible to prepare various metal nanoclusters with the same metal core and different modifying or protective shells. The metal

  

CAS NO.39244-80-9
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