Metamaterial-Free Flexible Graphene-Enabled Terahertz Sensors for Pesticide Detection at Bio-Interface

Abstract

There is an increasing recognition that terahertz (THz) spectroscopy can be used for high-sensitivity molecular sensing. Therefore, in recent years, much work has been devoted to developing flexible, compact, and high-sensitivity THz sensors. However, most designs employ metamaterials, which require complicated, and often expensive, fabrication procedures. Also, the metamaterial structures create a gap between the sensor surface and the target surface, which decreases the effective contact area between them, resulting in reduced sensing performance. Here, we fabricated a metamaterial-free graphene-based THz sensor with user-designed patterns for sensing at bio-interfaces. External molecules can strongly interact with π electrons in graphene, which moves the Fermi level and changes the amount of THz absorption. We used this sensor to successfully detect chlorpyrifos methyl with a limit of detection at 0.13 mg/L. We also detected pesticide molecules of a concentration of 0.60 mg/L on the surface of an apple, revealing the flexibility of this sensor. The flexible graphene THz sensor showed high sensing stability and robustness over 1000 cycles of bending. These results show that our graphene-based thin-film sensors are easy to fabricate, flexible, versatile, and suited for a wide range of sensing applications.

Fluorescence-Based Sensing of Pesticides Using Supramolecular Chemistry

“…In one example, europium-doped titanium oxide nano-powder responded to the presence of chlorpyrifos with significant fluorescence quenching (Yao et al, 2011). Computational and experimental work indicated the existence of an electron transfer mechanism, and the limit of detection using this system was determined to be in line with or better than other reported chlorpyrifos sensors (Wang et al, 2020f;Xu et al, 2020).…”

Design and Fabrication of a Triple-Band Terahertz Metamaterial Absorber

“…The change of electric and magnetic resonance intensity leads to the change of the second absorption peak amplitude. When the impedance of the absorber matches the impedance of the free space, the absorption will reach to 100% [ 40 ]. The increased thickness h of PET enhanced the impedance mismatch of the first and the third peak between the absorber and free space, resulting in different peak shift [ 40 ].…”

“…When the impedance of the absorber matches the impedance of the free space, the absorption will reach to 100% [ 40 ]. The increased thickness h of PET enhanced the impedance mismatch of the first and the third peak between the absorber and free space, resulting in different peak shift [ 40 ]. Next, we examined the effect of the width (2, 4, 6, 8, and 10 μm) of the metallic resonator on the absorption.…”

“…First, we adjusted the thickness of the PET layer while keeping other parameters unchanged. Figure 6a shows the simulated absorption spectra for four different between the absorber and free space, resulting in different peak shift [40]. Next, we examined the effect of the width (2, 4, 6, 8, and 10 μm) of the metallic resonator on the absorption.…”

Efficient Generation and Arbitrary Manipulation of Chiral Terahertz Waves Emitted from Bi2Te3–Fe Heterostructures

“…With the rapid progress in these years, the spintronic THz emitters have already manifested their advantages of high efficiency, ultrabroadband, and low cost, and been used in ghost microscope imaging and integrated on‐chip biosensing applications. [ 22–25 ] Though the competitive spintronic THz emitters have many merits, the intrinsic spin‐to‐charge conversion (SCC) mechanism impedes the production of elliptically polarized THz waves. [ 17 ] The reported elliptically or circularly polarized THz waves from spintronic THz emitters were produced either by delicately engineering the magnetization vector directions [ 12 ] or using cascading emission method.…”