Topics in Current Chemistry (2020) 378:35
1 3
1 Introduction
Nanotechnology encompasses the fabrication, characterization, manipulation
and application of materials that have at least one dimension within the range
1–100 nm. When the size of the material is below this threshold, the material
behaves differently from the same material with macroscopic dimensions due to
the quantum confinement of the electrons when the dimensions are smaller than
the Bohr radius, giving rise to unique and extraordinary physicochemical properties [1].
Nanomaterials can be classified according to different criteria, with the most
frequent criterion based on the dimensions of the nanomaterial. Three-dimensional (3-D) nanomaterials are those with three dimensions larger than the
nanometer scale, but which are composed of individual building blocks that are
within the nanometer scale range, such as nanocomposites. Two-dimensional
(2-D) nanomaterials are those that present one dimension in the nanometer scale
and include, for example, thin films or nanocoatings. One-dimensional (1-D)
nanomaterials possess two dimensions within the range of 1–100 nm and only
one dimension larger than the nanometer scale; these nanomaterials include,
among others, nanotubes, nanorods and nanowires. Finally, zero-dimensional
(0-D) nanomaterials are those with three dimensions within the range 1–100 nm,
including nanoparticles (NPs) such as metal NPs, semiconductor quantum dots
(QDs), and carbon-based QDs (CQDs) [2].
The development of novel nanomaterials has gained increasing interest in
recent decades due to their fascinating physicochemical properties, which have a
a great potential for application in different research areas and industries, such as
(bio)analytical chemistry [3, 4], water treatment systems [5], catalysis, electrocatalysis [6–9], cancer treatment [10], energy storage devices [11], among others.
Although little information is currently available on the production of QDs, it
was possible to estimate worldwide and Europe-wide production and use of ten
different nanomaterials, including QDs, from a 2012 survey sent to companies
producing and using engineered nanomaterials, with the results indicating that
the estimated production of QDs was about 10 t/year or lower [12].
Inorganic semiconductor nanocrystals, or QDs, have demonstrated a range of
unique optoelectronic properties and represent novel, attractive options in many
biomedical applications [13–16]. For example, QDs have been widely employed
for fluorescence sensing and bioimaging due to their exceptional photoluminescent characteristics, including the capability to tune the emission wavelength
just by controlling the size of the NP. Although conventional organic fluorescent
molecules are widely used in bioimaging applications, QDs are superior luminescence tags in terms of their photophysical properties, namely, QDs have broad
excitation spectra and narrow and sharp emission spectra and large Stokes shifts
(> 100 nm). Such optoelectronic properties are of great value in multiplexed
applications [17, 18] as by using a single light source it is possible to simultaneously excite multiple QDs of different sizes (multiple emission peaks). Additionally, QDs have very high molar adsorption coefficients, as well as higher
134
Reprinted from the journal
1 3
1 Introduction
Nanotechnology encompasses the fabrication, characterization, manipulation
and application of materials that have at least one dimension within the range
1–100 nm. When the size of the material is below this threshold, the material
behaves differently from the same material with macroscopic dimensions due to
the quantum confinement of the electrons when the dimensions are smaller than
the Bohr radius, giving rise to unique and extraordinary physicochemical properties [1].
Nanomaterials can be classified according to different criteria, with the most
frequent criterion based on the dimensions of the nanomaterial. Three-dimensional (3-D) nanomaterials are those with three dimensions larger than the
nanometer scale, but which are composed of individual building blocks that are
within the nanometer scale range, such as nanocomposites. Two-dimensional
(2-D) nanomaterials are those that present one dimension in the nanometer scale
and include, for example, thin films or nanocoatings. One-dimensional (1-D)
nanomaterials possess two dimensions within the range of 1–100 nm and only
one dimension larger than the nanometer scale; these nanomaterials include,
among others, nanotubes, nanorods and nanowires. Finally, zero-dimensional
(0-D) nanomaterials are those with three dimensions within the range 1–100 nm,
including nanoparticles (NPs) such as metal NPs, semiconductor quantum dots
(QDs), and carbon-based QDs (CQDs) [2].
The development of novel nanomaterials has gained increasing interest in
recent decades due to their fascinating physicochemical properties, which have a
a great potential for application in different research areas and industries, such as
(bio)analytical chemistry [3, 4], water treatment systems [5], catalysis, electrocatalysis [6–9], cancer treatment [10], energy storage devices [11], among others.
Although little information is currently available on the production of QDs, it
was possible to estimate worldwide and Europe-wide production and use of ten
different nanomaterials, including QDs, from a 2012 survey sent to companies
producing and using engineered nanomaterials, with the results indicating that
the estimated production of QDs was about 10 t/year or lower [12].
Inorganic semiconductor nanocrystals, or QDs, have demonstrated a range of
unique optoelectronic properties and represent novel, attractive options in many
biomedical applications [13–16]. For example, QDs have been widely employed
for fluorescence sensing and bioimaging due to their exceptional photoluminescent characteristics, including the capability to tune the emission wavelength
just by controlling the size of the NP. Although conventional organic fluorescent
molecules are widely used in bioimaging applications, QDs are superior luminescence tags in terms of their photophysical properties, namely, QDs have broad
excitation spectra and narrow and sharp emission spectra and large Stokes shifts
(> 100 nm). Such optoelectronic properties are of great value in multiplexed
applications [17, 18] as by using a single light source it is possible to simultaneously excite multiple QDs of different sizes (multiple emission peaks). Additionally, QDs have very high molar adsorption coefficients, as well as higher
134
Reprinted from the journal