Supervisors info:
Μ. Σκούλλος Καθηγητής ΕΚΠΑ, Α. Βαλαβανίδης Καθηγητής ΕΚΠΑ, Α. Χισκιά Ερευνήτρια Α’, ΕΚΕΦΕ Δημοκριτος
Summary:
In this thesis, the production of Silver nanoparticles (Ag-NPs) by
silvernitrate, using photocatalytic method, is studied. The polyoxometalates
(POMs) SiW12O40-4 and H2W12O40-6 were used, as photocatalysts and stabilizers
at the same time. The method is characterised by its simplicity and its
efficiency, as well as its friendliness to the environment (green chemistry).
This is due to the fact that synthesis takes place in aqueous solution, in
ambient conditions (though anoxic conditions are demanded), with minimal
byproducts (oxidation of organic pollutant), in mild and non energy intensive
conditions. Nanotechnology is a modern scientific field that develops rapidly,
as new materials of unprecented properties are created and studied. Silver
nanoparticles are known for years, but scientific interest has been stimulated
again in the framework of nanotechnology, as the new methological approaches of
nanotechnology add a new field of study at nanometer scale. The proposed uses
of Ag-NPs multiply day by day, leading to a production scale of Ag-NPs, with
the consequent pressures to the environment. So, the efficient synthesis of
Ag-NPs in terms of green chemistry, is of particular interest. The production
of Ag-NPs using POMs gives well controlled results, while, at the same time, it
is environmentally friendly and economical. POMs are excellent photocatalysts,
proposed, as anticontaminant technology, for environmental solutions, since
they are capable of complete mineralization of numerous organic pollutants.
According to latest studies, they can be used in metal recovery too. An
extension of the latest, is the production methodology of Ag-NPs. Moreover,
based on latest studies, they can also stabilise the Ag-NPs, making thus
unnecessary the additional use of stabilising agents. This aspect of POMs makes
the production methodology of Ag-NPs even more environmental friendly, through
the reduction of the necessary reagents. A further advantage is, that the
studied methodology can be applied for the synthesis of other nanostructures as
well, for example, the synthesis of gold nanoparticles and other metals or
non-metals, like Selenium. This thesis confirmed the stabilizing property of
POMs for the Ag- NPs, through the study of the stabilization of Ag-NPs by POMs
(chapter 9). A new efficient method for size control of the produced Ag-NPs was
also found (chapter 10), with the use of one or two steps synthesis of Ag-NPs,
photocatalytically, under UV-Vis radiation, using the POM H2W12O40-6, achieving
significant differences in size to simultaneously narrow range of standard
deviation of sizes. The Ag-NPs characterisation was done using
spectrophotometry, electronic microscopy (TEM) and Raman spectroscopy (chapter
11). The photocatalytic behavior of POM was also studied under the presence of
the produced Ag-NPs (chapter 12). The present research study was done at NCSR
Demokritos, using the infrastructure of the center.
Keywords:
Polyoxometalates, Silver nanoparticles, Colloid, Photocatalysis, Nanotechnology
