(217x) Synthesis of Nano Ag in SBA-15 Using Supercritical Carbon Dioxide and the Influence of Different Co-Solvents On the Morphology of the Nanophase

Synthesis of Nano Ag in SBA-15 Using Supercritical Carbon Dioxide and the Influence of Different Co-solvents on the Morphology of the
Nanophase

Qin-qin Xu
¹, Yu-ling Ma¹ , Ai-qin Wang², Jian-zhong Yin¹*

¹ State Key Laboratory of Fine
Chemicals, School of Chemical Machinery, Dalian University of Technology,
116024, Dalian, China

² Dalian Institute of Chemical
Physics, Chinese Academy of Sciences, 116023, Dalian, China

* Corresponding Author: Jian-zhong Yin,
jzyin@dlut.edu.cn; Tel. and Fax. +86-411-84986274

Supercritical fluid deposition (SCFD) method can provide a simple,
effective and fast approach to synthesize Ag nanopartiles and nanowires in the
nanoscale channels of mesoporous silica. A systematical study was conducted
about depositing inorganic precursor AgNO₃ into mesoporous SBA-15
using supercritical carbon dioxide (scCO₂)as solvent with the addition of a little
co-solvent (ethanol, water, the mixture of
ethanol and water, the mixture of
ethanol and dilute nitric acid) at 50°C and
18MPa within only 1h. Ag/SBA-15 was obtained after deposition followed by
calcinations at 300°C in
air. It was found that the metal loading and the morphology
of the nanophase were quite different when using different
co-solvents. When using ethanol as well as the mixture of ethanol and water as
co-solvent, the morphology of nanophase in the samples was nanoparticle, while
it was nanowire when adding only 0.5ml 8.7wt% nitric acid in the CO₂-ethanol system. It
is obviously that the addition of H⁺ plays an important role in the
formation of Ag nanowire in the channels of SBA-15. However, addition of
nitric acid may influence the dielectric constant, the surface tension and the
viscosity of the systems thus the adsorption of AgNO₃ (solute) on
SBA-15 (adsorbent) from scCO₂/co-solvent (solvent) were different.
And the adsorption of the precursor on the substrate would influence the
dispersion of the precursor in the channels of substrate thus determine the
morphology of the nano-phase. It's quite a complicated question and more
research is underway.

Table 1 Preparation
conditions of Ag/SBA-15 using different co-solvents at 50°C,18MPa (AgNO₃: SBA-15=200mg: 200mg)

Figure 1. TEM image of
Ag/SBA-15 composite using different co-solvent: (1) 5mL ethanol; (2) 5mL ethanol and 0.5 mL deionized water; (3) 5mL ethanol
and 0.5mL 8.7wt% HNO₃ (4) 0.5mL
deionized water ;

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