Upconverting nano-paste in 3D-printed phone camera setup for soil phyto-iron sensing

Area of Science:

• Agricultural Science
• Analytical Chemistry
• Nanotechnology

Background:

• Conventional soil iron analysis methods are time-consuming and require expensive equipment.
• Efficient detection of available iron (Fe²⁺) is crucial for plant health and crop yield.
• Developing accessible and user-friendly iron detection techniques is a significant agricultural challenge.

Purpose of the Study:

• To develop a facile and affordable nanoscopic method for quantifying available Fe²⁺ in soil.
• To create a user-friendly sensing system for on-site soil iron analysis.
• To validate the developed method against conventional soil analysis techniques.

Main Methods:

• Formation of a luminescence quenching complex using Fe²⁺ and bathophenanthroline disulphonic acid disodium salt (BPDS).
• Incorporation of the complex into a polyvinyl alcohol (PVA) based upconverting nano-paste.
• Development of a portable, 3D-printed smartphone accessory for sample analysis.
• Utilizing ratiometric duplex emission processing (I_R/I_G) for Fe²⁺ quantification.

Main Results:

• The nanoscopic method achieved a limit of detection (LOD) of 3.62 μM for Fe²⁺.
• A linear detection range for Fe²⁺ was established between 10 μM and 500 μM.
• On-site soil Fe²⁺ analysis using the novel method showed consistency with Inductively Coupled Plasma-Mass Spectrometry (ICP-MS).

Conclusions:

• The developed system enables precise and convenient measurement of soil phytoavailable iron (Fe²⁺).
• This method can screen Fe²⁺ concentrations, helping to avoid Fe-deficiency and Fe-toxicity in plants.
• This represents the first smartphone-based system utilizing upconversion nanoparticles for soil iron measurement.