title: In situ integration of graphene foam-titanium nitride based bio-scaffolds and microfluidic structures for soil nutrient sensors.
abstract: It is challenging to integrate porous graphene foam (GF) and GF-based nanocomposites into microfluidic channels and even create microfluidic structures within these materials. This is because their irregular interior pore shape and geometry, rough exterior surface, and relatively large material thickness make it difficult to perform conventional photolithography and etching. This challenge has largely hindered the potential of using GF-based materials in microfluidics-based sensors. Here we present a simple approach to create well-defined flow-through channels within or across the GF-based materials, using a liquid-phase photopolymerization method. This method allows embedding of a nanocomposite-based scaffold of GF and titanium nitride nanofibers (GF-TiN NFs) into a channel structure, to realize flow-through microfluidic electrochemical sensors for detecting nitrate ions in agricultural soils. The unique GF-TiN nanocomposite provides high electrochemical reactivity, high electron transfer rate, improved loading capacity of receptor biomolecules, and large surface area, serving as an efficient electrochemical sensing interface with the help of immobilized specific enzyme molecules. The microfluidic sensor provides an ultralow limit of detection of 0.01 mg L-1, a wide dynamic range from 0.01 to 442 mg L-1, and a high sensitivity of 683.3 μA mg-1L cm-2for nitrate ions in real soil solution samples. The advantageous features of the GF-TiN nanocomposite, in conjunction with the in situ integration approach, will enable a promising microfluidic sensor platform to monitor soil ions for nutrient management towards sustainable agriculture.
authors.affiliation: Department of Electrical and Computer Engineering, Iowa State University, Ames, Iowa 50011, USA. ldong@iastate.edu.
authors.forename: Md Azahar
authors.initials: MA
authors.lastname: Ali
authors.affiliation: Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695, USA.
authors.forename: Kunal
authors.identifier: 0000-0003-1665-7755
authors.initials: K
authors.lastname: Mondal
authors.affiliation: Department of Electrical and Computer Engineering, Iowa State University, Ames, Iowa 50011, USA. ldong@iastate.edu.
authors.forename: Yifei
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Electrical and Computer Engineering, Iowa State University, Ames, Iowa 50011, USA. ldong@iastate.edu.
authors.forename: Huawei
authors.initials: H
authors.lastname: Jiang
authors.affiliation: Department of Agronomy, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: Navreet K
authors.initials: NK
authors.lastname: Mahal
authors.affiliation: Department of Agronomy, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Castellano
authors.affiliation: Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India.
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Sharma
authors.affiliation: Department of Electrical and Computer Engineering, Iowa State University, Ames, Iowa 50011, USA. ldong@iastate.edu.
authors.forename: Liang
authors.initials: L
authors.lastname: Dong
mesh_terms: D004579:Electron Transport; D006108:Graphite / Q000737:chemistry*; D056656:Lab-On-A-Chip Devices; D012987:Soil / Q000737:chemistry*; D014025:Titanium / Q000737:chemistry*
chemical_list: D012987:Soil; C041500:titanium nitride; D006108:Graphite; D014025:Titanium