Q2. What have the authors stated for future works in "Practical review on the use of synchrotron based micro- and nano- x-ray fluorescence mapping and x-ray absorption spectroscopy to investigate the interactions between plants and engineered nanomaterials" ?
Multi-scale analyses are of high relevance and for this reason developments at present and future beamlines offering the possibility to perform micro and nano analysis at the same analytical platform on the same sample are envisioned. SR sources providing extremely brilliant beams will make possible to analyze higher num ber of samples in less time with enhanced detection limits and improved lateral resolution. However, it will require a continuous development of highly sensitive and fast detectors. In the near future, 2D speciation in XRF mode ( XANES mapping ) will likely become a standard acquisition strategy, providing more statistically meaningful data sets to entangle the delicate aspects of plant/ENMs interactions.
Q3. What is the way to determine the speciation of a chemical element?
Spatially resolved XAS is a very useful complement to SR-XFM since it allows determining the speciation of a chemical element at micro and nano-scale in a plant sample.
Q4. How does SR-XFM detect a metal in a plant?
Considering the analysis is performed in very small sample volumes (e.g. 1 μm2 beam illuminates 25–40 μm thick plant sample) SR-XFM can detect down to femtograms of the element of interest, depending on flux, detector efficiency, and matrix of the sample.
Q5. How much femtograms of the element of interest would be detected in plant?
Assuming density of plant tissue close to water, femtogram content of the element of interest would translate to ∼10–100 mg/kg local concentration in the tissue.
Q6. What is the impact of accumulating ENMs in edible parts of crops?
Accumulation of ENMs in edible parts of crops, both from soil and foliar applications, could negatively impact human and livestock health (Hong et al., 2013; Rico et al., 2011).
Q7. What is the way to assess the cryo-sections?
Quality assessment of the cryo-sections is important to avoid losing time removing and transferring another sample (particularly for in vacuum experiments this is time consuming).
Q8. Why do nanomaterials have different characteristics than macro or micro sized materials?
Due to their high surface area to volume ratios (>1% atoms at surface), they show different characteristics than the macro or micro sized materials such as high reactivity and conductivity.
Q9. What is the cryo-microtome set-up for frozen-hydrated samples?
For frozen-hydrated samples, the cryo-microtome set-up needs to be optimized for each tissue type: chamber temperature (usually around −20 °C), sample cold finger and knife temperatures, type of knife (e.g. diamond, stainless steel, or tungsten), cutting velocity, and section thickness (Vogel-Mikuš et al., 2009).
Q10. What is the way to transport samples?
Dry ice shipping is a possible option for sample transportation, but a safer and optimal alternative is shipping samples in specialized liquid nitrogen vapor dewars that can preserve samples for several days and are authorized by air transport regulation.
Q11. What is the preferred method for stabilizing biological material near to the in vivo state?
It is now significantly demonstrated that ultra-rapid cryofixation over chemical fixation is the preferred strategy for stabilizing biological material close to the in vivo state (Perrin et al., 2015).
Q12. What is the way to analyze NPs in plants?
This option is of special interest in the study of NPs in plant samples, as they often contribute in a very low proportion to the sum XRF spectrum of the sample.