employed to detect the surface functionality of ENPs (Jiang
et al. 2012). Mostly, FT-IR data was utilized to study humic
substance adsorption onto silica and magnetite ENPs (Ma
et al. 2018). These types of analysis are quite helpful in
quantifying the quality of ENPs and also which type of
functional group are present. It also detect surface charge
present on ENPs and address different types of ENPs and
their suitability to various type of soil for nutrient arability and
deficiency to enhance soil quality. Mostly, XRD techniques
are acquired to determine the crystalline nature, phase, and
grain size of the nanoparticles (Jorge et al. 2013).
Dynamic light scattering (DLS) is the most commonly
used technique to measure the aggregation rate/kinetics of
ENPs through the measurement of zeta potential (Peijnenburg et al. 2015). Zeta potential helps to study particle
aggregation or particle behavior of ENPs in the environment.
Another is the mass spectrometry techniques, which generally consist of inductively coupled plasma-mass spectroscopy (ICP-MS), matrix-assisted laser desorption/
ionization (MALDI), laser-induced fluorescence (LIF), or
iron-trap (IT) mass spectrometry. Total metal concentrations
in metallic nanoparticles can easily analyzed by aqua regia
digestion followed by ICP–OES and ICP-MS measurements. Commonly used separation methods based on filtration, centrifugation, chromatography, and electrophoresis
techniques are the conventional available strategies for the
detection of size, shape, and charge of ENPs. Among that
the most popularly high-performance liquid chromatography
(HPLC), field-flow fractionation (FFF), size-exclusion
chromatography (SEC), and capillary electrophoresis
(CE) are used (Luo et al. 2014). They were well applied to
study the various features of multiwalled carbon nanotubes,
silica nanoparticles, and metal nanoparticles due to faster
separation, high efficiency, low sample volume, and high
sensitivity (Navratilova et al. 2015). Their combination with
appropriate techniques like ICP-MS, UV–visible spectroscopy, nephelometry, and static light scattering (SLS) can
extend their applications due to their broad size separation
ranges and relatively moderate sample disruption (Choi et al.
2007). While the size-exclusion chromatography has higher
partition efficiency, it can undergo as of fixed-phase interactions. FFF and HDC are having high detection limits (as
per detector) but non-ideal samples of ENPs require additional pre-fractionation steps during sample preparation
(Pornwilard and Siripinyanond 2014).
In the advancement of techniques, few methods like
small-angle X-ray scattering (SAXS), small-angle neutron
scattering (SANS), X-ray reflectometry (XR), and neutron
reflectometry (NR) are advantageous due to fast sample
analysis and data extraction. The knowledge about the surface properties, organic coatings, and crystallographic
behavior can excogitate by application of X-ray-based
methods such as X-ray absorption (XAS), fluorescence
(XRF), and photoelectron spectroscopy (XPS) as well as
diffraction (XRD) as they are non-destructive, flexible, and
relatively less expensive (Nurmi et al. 2005). Extensive
applications of these techniques include the measurement of
percentage crystallinity, detection of fine-grained minerals
such as nanoparticles, nano-clays, and mix layer identifications. The XAS technique is often preferred due to its
non-destructive nature, collection of wet samples (soil,
sediments, and tissue) with absorption spectra but high metal
concentration often creates hindrances in measurement
(Tiede et al. 2008).
As emerging techniques currently small-angle neutron
scattering (SANS), small-angle X-ray scattering (SAXS),
and static light scattering (SLS) are utilized to study the
presence of ENPs in the solid and liquid phase (Polte et al.
2010). To study the atomic, molecular, and structural features mostly RAMAN and laser-induced fluorescent spectroscopy were utilized. As an advanced mechanism,
synchrotron radiation-based techniques were being adapted
for localization and speciation of ENPs as they are
non-destructive, higher spatial resolution, and higher detection limits (Castillo-Michel et al. 2017). These are often
combined with XAS, photothermal flow cytometry (PTFC),
and photoacoustic flow cytometry PAFC to study the ENPs
in live plant tissue (Nedosekin et al. 2010). Also, the
radioactive stable isotopes based methods such as autoradiography and positron emission tomography are combined
with SEM and TEM to track and visualize ENPs in the
in vivo soil–plant system. Stable isotopes provide as a tracer
with no harm to radiation and have a long half-life. Although
rapidly evolving sophisticated analytical techniques have
shown its immense potential in testing the localization,
speciation, uptake, availability, biotransformation, and toxicity in the soil–plant system. But in the future, the focus
should be more on isotopic and sensors based methods with
the right synchronization of technologies to understand the
exposure risk of ENPs.
8 Conclusions and Future Directions
The exposure, transfer, accumulation, and transformation of
ENPs in the agro-ecosystem have now become an imperative subject to address their environmental fate and risk.
Engineered nanoparticles (ENPs) have been enacted as
sophisticated technology with conceivable consequences for
sustainable agriculture. A significant contribution of ENPs
for crop management, delivery agents, sensing material,
disease control, and soil conservation is well known. But the
unregulated exposure of ENPs in soil has shown serious
implications on soil health like damage of soil structure, loss
of soil fertility, and toxicity in soil microflora. Therefore, the
key focus should be on the development of biodegradable
Engineered Nanoparticles in Agro-ecosystems: Implications …
113
et al. 2012). Mostly, FT-IR data was utilized to study humic
substance adsorption onto silica and magnetite ENPs (Ma
et al. 2018). These types of analysis are quite helpful in
quantifying the quality of ENPs and also which type of
functional group are present. It also detect surface charge
present on ENPs and address different types of ENPs and
their suitability to various type of soil for nutrient arability and
deficiency to enhance soil quality. Mostly, XRD techniques
are acquired to determine the crystalline nature, phase, and
grain size of the nanoparticles (Jorge et al. 2013).
Dynamic light scattering (DLS) is the most commonly
used technique to measure the aggregation rate/kinetics of
ENPs through the measurement of zeta potential (Peijnenburg et al. 2015). Zeta potential helps to study particle
aggregation or particle behavior of ENPs in the environment.
Another is the mass spectrometry techniques, which generally consist of inductively coupled plasma-mass spectroscopy (ICP-MS), matrix-assisted laser desorption/
ionization (MALDI), laser-induced fluorescence (LIF), or
iron-trap (IT) mass spectrometry. Total metal concentrations
in metallic nanoparticles can easily analyzed by aqua regia
digestion followed by ICP–OES and ICP-MS measurements. Commonly used separation methods based on filtration, centrifugation, chromatography, and electrophoresis
techniques are the conventional available strategies for the
detection of size, shape, and charge of ENPs. Among that
the most popularly high-performance liquid chromatography
(HPLC), field-flow fractionation (FFF), size-exclusion
chromatography (SEC), and capillary electrophoresis
(CE) are used (Luo et al. 2014). They were well applied to
study the various features of multiwalled carbon nanotubes,
silica nanoparticles, and metal nanoparticles due to faster
separation, high efficiency, low sample volume, and high
sensitivity (Navratilova et al. 2015). Their combination with
appropriate techniques like ICP-MS, UV–visible spectroscopy, nephelometry, and static light scattering (SLS) can
extend their applications due to their broad size separation
ranges and relatively moderate sample disruption (Choi et al.
2007). While the size-exclusion chromatography has higher
partition efficiency, it can undergo as of fixed-phase interactions. FFF and HDC are having high detection limits (as
per detector) but non-ideal samples of ENPs require additional pre-fractionation steps during sample preparation
(Pornwilard and Siripinyanond 2014).
In the advancement of techniques, few methods like
small-angle X-ray scattering (SAXS), small-angle neutron
scattering (SANS), X-ray reflectometry (XR), and neutron
reflectometry (NR) are advantageous due to fast sample
analysis and data extraction. The knowledge about the surface properties, organic coatings, and crystallographic
behavior can excogitate by application of X-ray-based
methods such as X-ray absorption (XAS), fluorescence
(XRF), and photoelectron spectroscopy (XPS) as well as
diffraction (XRD) as they are non-destructive, flexible, and
relatively less expensive (Nurmi et al. 2005). Extensive
applications of these techniques include the measurement of
percentage crystallinity, detection of fine-grained minerals
such as nanoparticles, nano-clays, and mix layer identifications. The XAS technique is often preferred due to its
non-destructive nature, collection of wet samples (soil,
sediments, and tissue) with absorption spectra but high metal
concentration often creates hindrances in measurement
(Tiede et al. 2008).
As emerging techniques currently small-angle neutron
scattering (SANS), small-angle X-ray scattering (SAXS),
and static light scattering (SLS) are utilized to study the
presence of ENPs in the solid and liquid phase (Polte et al.
2010). To study the atomic, molecular, and structural features mostly RAMAN and laser-induced fluorescent spectroscopy were utilized. As an advanced mechanism,
synchrotron radiation-based techniques were being adapted
for localization and speciation of ENPs as they are
non-destructive, higher spatial resolution, and higher detection limits (Castillo-Michel et al. 2017). These are often
combined with XAS, photothermal flow cytometry (PTFC),
and photoacoustic flow cytometry PAFC to study the ENPs
in live plant tissue (Nedosekin et al. 2010). Also, the
radioactive stable isotopes based methods such as autoradiography and positron emission tomography are combined
with SEM and TEM to track and visualize ENPs in the
in vivo soil–plant system. Stable isotopes provide as a tracer
with no harm to radiation and have a long half-life. Although
rapidly evolving sophisticated analytical techniques have
shown its immense potential in testing the localization,
speciation, uptake, availability, biotransformation, and toxicity in the soil–plant system. But in the future, the focus
should be more on isotopic and sensors based methods with
the right synchronization of technologies to understand the
exposure risk of ENPs.
8 Conclusions and Future Directions
The exposure, transfer, accumulation, and transformation of
ENPs in the agro-ecosystem have now become an imperative subject to address their environmental fate and risk.
Engineered nanoparticles (ENPs) have been enacted as
sophisticated technology with conceivable consequences for
sustainable agriculture. A significant contribution of ENPs
for crop management, delivery agents, sensing material,
disease control, and soil conservation is well known. But the
unregulated exposure of ENPs in soil has shown serious
implications on soil health like damage of soil structure, loss
of soil fertility, and toxicity in soil microflora. Therefore, the
key focus should be on the development of biodegradable
Engineered Nanoparticles in Agro-ecosystems: Implications …
113