Chemistry Reference
In-Depth Information
within the modern algebraic chemistry (Whitney
2007
). Yet, since the bondonic
masses of chemical bonding ground states seem untouched by the Dirac relativistic
considerations over the Schrödinger picture, it is expected that their analytical values
may make a difference among the various types of compounds, while their experi-
mental detection is hoped to be some day completed (Putz
2010a
,
b
;
2012a
,
b
,
c
,
d
;
Putz and Ori
2012
,
2014
,
2015
/Chapter 10 of this topic), see also the next Chapter
of this topic (Putz et al.
2015b
).
12.3
From Sols, Gels, and Sol-Gel Processes to Silanes and
Bio-Medicine
Sols
are generally referred to stable suspensions comprising colloidal solid parti-
cles, denser than the surrounding liquid (Pierre
1998
), their diameter being ranged
between 2 nm and 0.2
m, corresponding to 10
3
-10
9
μ
atoms/particle. (Livage and
Lemerle
1982
).
Gels
are three-dimensional interconnected solid networks with the ability to have a
space-limited expansion in a liquid environment (Pierre
1998
). When drying methods
at low temperatures (25-100
◦
C) are applied to gels, it is possible to obtain porous
solid matrices (
xerogels)
(Brinker and Scherer
1990
).
Sol-Gel processes
have the capacity to obtain inorganic oxides, starting from
colloidal dispersions, or from metal alkoxydes (Segal
1984
). Nowadays, nitrides
and sulfides are included in these processes, being used in the synthesis of hybrid
organic-inorganic materials (Pierre
1998
). Perhaps one of the most important issue
concerning sol-gel processes is that it is possible to obtain solid (e.g., ceramic) ma-
terials at low temperatures (room temperature). In this way, soft materials (dopants)
can be incorporated in solid materials (such as glasses) (Brinker and Scherer
1990
).
The hydrolysis-condensation reactions of metal alkoxide precursors determine the
integration of organic or biological active molecules within an inorganic network
obtaining new hybrid organic-inorganic materials (Sanchez et al.
2000
).
Sol-gel processes are able to cover a demanding aspect of contemporary techno-
logical requirements: development and practical applicability of new and performing
organic/inorganic hybrid materials. Furthermore, composite and nanocomposite
materials can be obtained by combining the sol-gel method with organic poly-
mers synthesis. These new "clever" materials may improve physical and chemical
properties of classical used materials (e.g., coatings that increase the resistance to
scratching) (Pandey and Mishra
2011
).
Silica shows several advantages, like strength, thermal stability and high mod-
ulus. By incorporating silica and organic polymers (polymers show less thermal
stability), a new material with improved properties can be obtained (mechanical
properties). This may be an important condition for achieving biocompatibility with
direct implications in development of biomedical compounds or devices (Jeon et al.
2009
).
The combination of organic and inorganic parts into a hybrid material provides
the possibility to model especially physical properties of this new hybrid material
