**1. Introduction**

Green industries imply few research directions: (i) an industry based on recycling the unwanted resources that take care from the beginning of the company construction to conceive a sustainable fabrication process flow; (ii) a traditional industry that becomes sensitive to environment protection, minimizing the waste and pollution; or (iii) a top industry that provides useful tools for the environmental conservation and monitoring.

The nano-biotechnology-based industry which falls into the last category can produce pesticide biosensors, wastewater detectors [1], micro-nano-filters for air-water-soil cleaning [2], and pathogen biosensors using nanomaterials such as metal nanoparticles, quantum

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dots, magnetic nanoparticles, carbon nanotubes, and graphene due to their surface properties, excellent electron transfer, and a large ratio of surface area to volume, making them particularly attractive for use in labels or transducing platforms for optical or electrochemical sensors and biosensors.

straight cavity in Si from 10 to 20 nm depth of only 2 to 3 nm width, without pipes which

Integrated p-NOI Structures on Nanoporous Material Designed for Biodetection

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If the nVn succession is used as the device body, we speak about a NOI (nothing on insulator) transistor [20]. If oxide (O) is used instead of the vacuum (V) cavity and, additionally, a metal is used instead of one semiconductor zone, we speak about a mOn succession as metal/oxide/ n-Si. This structure still conserves the NOI work principle [21]. Also, if oxide is replaced by any insulator (I) placed between two metals placed on a Si wafer surface, we speak about MIM structure [22]. The mOn and MIM structures use the same thin insulator tunneling principle but benefit on materials placed on the front plan of the Si wafer. Both of them are associ-

Therefore, a vertical implementation of the p-NOI variant is more suitable for the integration of the biosensor transducer. The insulator can be oxide or sandwich of insulators of 10 nm up to 50 nm thickness to prevent the substrate tunneling [23]. The oxide is grown by the Si planar technology. Therefore, the presented p-NOI structure is a vertical simplified NOI variant, with the advantage to be inherent integrated on the Si wafer during the biosensor metallic electrode configuration on insulator. On the other hand, the Fowler-Nordheim tunneling through the bottom insulator is poor. Hence, more than 50 nm oxide thickness ensures an excellent dielectric insulation that is suitable for the biosensor transducer purposes. The explanation comes from two Fowler-Nordheim tunneling ways in this transducer: (i) the useful one that acts the p-NOI device at the surface of the device and (ii) the parasitic tunneling toward substrate that must be avoided. The transducer successfully interacts with bio-liquid on the top of the wafer, generating the capacitance variation, while efficiently prevents the leakage current toward substrate, for thick-enough oxide layer. However, a principle that must be checked is to simulate an exponential I–V dependence for a vertical p-NOI, to put in agreement the Fowler-

**Figure 1** presents the proposed vertical p-NOI structure with substrate as back-gate. The usual anodes play the gate role, and the cathodes are the source or drain. Therefore, the notations are kept as in a transistor configuration. Essentially, in **Figure 1** there are three vertical

ated with the planar variant of a NOI device, simply noted by p-NOI device [15].

Nordheim tunneling principle with the p-NOI conduction mechanisms [24].

**Figure 1.** The basic p-NOI device in the planar configuration.

seem to be impossible [20].

The examples of such biosensors are the organophosphorus pesticides using liposome-based nano-biosensors [3]. Gold nanoparticles for pesticide detection using cyclic voltammetry [4], organophosphorous pesticide (OP) biosensor based on quenching of the fluorescence from CdTe QDs [5]. Acetylcholinesterase action is monitored using a localized surface plasmon resonance (LSPR) fiber optic biosensor [6]. AuNP-AChE conjugates for paraoxon electrochemical biosensor [7]. AuNP-AChE onto chemically reduced graphene nanosheets (cr-Gs) [8], graphene oxide/Nafion (RGON) nanohybrids electrochemical biosensor platform to detect organophosphorus hydrolase as an enzyme for the hydrolysis of Ops [9], pathogen detection in soils using nanobiosensors [10, 11].

Unfortunately, the pesticides used in this field not only spoil the soil but also infest the entire food chain. Less toxic new generations of pesticides may reduce the risks transmitted to people and environment, especially by water contamination. The pesticides reduce the nitrogen fixation in plants, consequently decrease the biodiversity, destroy habitats, and threaten jeopardized species [12]. Integrated biosensors usually contain onto the same chip of the semiconductor solid-state support, the transducer as an electronic device, and the biological detector as an enzyme [13] or an antibody [14].

This chapter describes a pesticide biosensors fabricated using nanoporous Si materials to entrap the receptor element, along with the transducer element consisting of an interdigitated capacitive electrodes to detect pesticides, like paraoxon. The novel detection scheme is using interdigitated capacitive electrodes which highlighted a special nanostructure called as the planar nothing on insulator (p-NOI) [15, 16]. The biodetection is based on the hydrolysis under the acetylcholinesterase (AChE) enzyme action, as biosensor-specific receptor [17]. The final product is an integrated biosensor that is constructed by microtechnological processes aided by biotechnological enzyme processing steps, having a nanoporous Si layer coupled to a p-NOI capacitive transducer, which is sensitive to the pesticide concentration.

The p-NOI structure that is integrated inside the biosensor transducer has another facet in this work: the first p-NOI structure still exists between top metal on insulator placed on silicon, and the second p-NOI structure is present between two adjacent lateral metal fingers. The first one must accomplish an isolation through the bottom nanoporous material. The second one has the distance between fingers high enough versus a nanometric p-NOI that allows a tunnel current flow [15]. Hence, the tunneling conduction is missing in this case. But the liquid droplet that connects two adjacent fingers by an ionic conductor offers a novel conduction route.
