1 3
Topics in Current Chemistry (2020) 378:2
promote specific reactions even without the use of additive chemicals or another
source of energy. The most important part in heterogeneous photocatalysis is the
development and usage of materials that can function as sufficient photocatalysts,
and nanotechnology has been shown capable of providing solutions. Synthesis of
nanomaterials and tuning specific features of them like nano-morphological and
optical features is an ultimately important and efficient strategy to achieve the above.
Even though the synthesis of nanoscaled photocatalysts has been a hot topic during the last decades with many published articles and end-use applications, the use
of mechanochemical-based synthetic approaches is not so broadly explored. By
gathering the existing knowledge on the effects derived from the mechanochemical forces like ultrasound (US) irradiation and ball milling, it will be realistic to go
a step further. The focus of this work is to collect all the reports in which the two
above-mentioned techniques were applied during the synthesis of two benchmark
semiconductor photocatalysts, titanium dioxide or titanate, in order to obtain various
polymorphs with different structural, morphological, and optical features.
1.2 Mechanochemical Synthesis
The exploration and discovery of new synthetic approaches as well as the incorporation of advantageous techniques for the development of new or improved properties of already known nanomaterials as photocatalysts is an ongoing and interesting
field of research, with fascinating potential [1, 2]. In recent years, mechanochemical processes were found to hold great promise, since they are effective and can
lead to nanomaterials of novel properties. Another important aspect is that various
reported active nanocatalysts can be synthesized in a shorter time compared to traditional wet-chemistry synthesis. In many cases, the design of mechanochemicalbased methods can have a positive effect on the “green” character and environmental
footprint: consumption of less energy, less or even no use of hazardous solvents,
need of recycling, purification, etc. According to the International Union of Pure
and Applied Chemistry (IUPAC), the definition of a mechanochemical process is:
“a chemical reaction that is induced by the direct absorption of mechanical energy”
[3]. The utilization of mechanochemical forces holds great promise and begets novel
approaches in nanocrystalline synthesis (mechanosynthesis), and, more specifically, on how to control the desired features, crucial for different applications [3–7].
Herein, two mechanochemical sources will be introduced: (1) US irradiation (sonochemistry) and (2) ball milling. The rapid growth of the research interest around
the utilization of mechanochemistry methods is due to their unique effects. By the
correct selection of these effects, it is feasible to obtain novel nanomaterials, and to
control desired physical, chemical, and optical properties [5, 8]. Simultaneously, it
is possible to eliminate the environmental footprint of the synthesis, avoiding, for
instance, the usage of high energy, hazardous and non-recyclable chemicals, or by
decreasing the duration and the number of steps of the synthesis [9].
31
Reprinted from the journal
Topics in Current Chemistry (2020) 378:2
promote specific reactions even without the use of additive chemicals or another
source of energy. The most important part in heterogeneous photocatalysis is the
development and usage of materials that can function as sufficient photocatalysts,
and nanotechnology has been shown capable of providing solutions. Synthesis of
nanomaterials and tuning specific features of them like nano-morphological and
optical features is an ultimately important and efficient strategy to achieve the above.
Even though the synthesis of nanoscaled photocatalysts has been a hot topic during the last decades with many published articles and end-use applications, the use
of mechanochemical-based synthetic approaches is not so broadly explored. By
gathering the existing knowledge on the effects derived from the mechanochemical forces like ultrasound (US) irradiation and ball milling, it will be realistic to go
a step further. The focus of this work is to collect all the reports in which the two
above-mentioned techniques were applied during the synthesis of two benchmark
semiconductor photocatalysts, titanium dioxide or titanate, in order to obtain various
polymorphs with different structural, morphological, and optical features.
1.2 Mechanochemical Synthesis
The exploration and discovery of new synthetic approaches as well as the incorporation of advantageous techniques for the development of new or improved properties of already known nanomaterials as photocatalysts is an ongoing and interesting
field of research, with fascinating potential [1, 2]. In recent years, mechanochemical processes were found to hold great promise, since they are effective and can
lead to nanomaterials of novel properties. Another important aspect is that various
reported active nanocatalysts can be synthesized in a shorter time compared to traditional wet-chemistry synthesis. In many cases, the design of mechanochemicalbased methods can have a positive effect on the “green” character and environmental
footprint: consumption of less energy, less or even no use of hazardous solvents,
need of recycling, purification, etc. According to the International Union of Pure
and Applied Chemistry (IUPAC), the definition of a mechanochemical process is:
“a chemical reaction that is induced by the direct absorption of mechanical energy”
[3]. The utilization of mechanochemical forces holds great promise and begets novel
approaches in nanocrystalline synthesis (mechanosynthesis), and, more specifically, on how to control the desired features, crucial for different applications [3–7].
Herein, two mechanochemical sources will be introduced: (1) US irradiation (sonochemistry) and (2) ball milling. The rapid growth of the research interest around
the utilization of mechanochemistry methods is due to their unique effects. By the
correct selection of these effects, it is feasible to obtain novel nanomaterials, and to
control desired physical, chemical, and optical properties [5, 8]. Simultaneously, it
is possible to eliminate the environmental footprint of the synthesis, avoiding, for
instance, the usage of high energy, hazardous and non-recyclable chemicals, or by
decreasing the duration and the number of steps of the synthesis [9].
31
Reprinted from the journal