Mid-infrared Biosensor Research Articles

Mid-infrared Biosensor Based on Bloch Surface Mode Excitation in Truncated One-Dimensional Ternary Photonic Crystal Under Kretschmann Configuration

We have theoretically investigated the performance of mid-infrared (mid-IR) sensitive biosensor constructed by truncated one-dimensional (1D) ternary photonic crystal (TPC) on the prism base under Kretschmann configuration coupling technique. The control over resonance wavelength (RW) of the excited Bloch surface modes (EBSMs) for the case of incident transverse magnetic polarized electromagnetic waves (EMWs) has been shown. The band structures and the reflection spectra of the considered model are computed using transfer matrix method (TMM). The variation in different design parameters of the theoretically constructed biosensor, such as thickness of the truncation layer, refractive index of the sensing medium, and number of unit cells in photonic crystal (PC), allows us to have good control over the resonance wavelengths in fixed frequency regime of the PBGs. The excitation of BSMs is characterized by a dip in the reflectance spectra. The measured sensitivity of the sensor is $${10}^{-3}$$ orders of magnitude sensitive to the change in $${d}_{{c}}$$ and $${d}_{{t}}$$ values.

Hybrid Metasurface-Based Mid-Infrared Biosensor for Simultaneous Quantification and Identification of Monolayer Protein

Metasurfaces emerge as a promising photonic platform for biosensing because they offer strong optical confinement and tunable optical resonances. Here, we show that metasurface-based biosensors con...

Scalable and Tunable Periodic Graphene Nanohole Arrays for Mid-Infrared Plasmonics.

Despite its great potential for a wide variety of devices, especially mid-infrared biosensors and photodetectors, graphene plasmonics is still confined to academic research. A major reason is the fact that, so far, expensive and low-throughput lithography techniques are needed to fabricate graphene nanostructures. Here, we report for the first time a detailed experimental study on electrostatically tunable graphene nanohole array surfaces with periods down to 100 nm, showing clear plasmonic response in the range ∼1300-1600 cm-1, which can be fabricated by a scalable nanoimprint technique. Such large area plasmonic nanostructures are suitable for industrial applications, for example, surface-enhanced infrared absorption (SEIRA) sensing, as they combine easy design, extreme field confinement, and the possibility to excite multiple plasmon modes enabling multiband sensing, a feature not readily available in nanoribbons or other localized resonant structures.

Resolving molecule-specific information in dynamic lipid membrane processes with multi-resonant infrared metasurfaces

A multitude of biological processes are enabled by complex interactions between lipid membranes and proteins. To understand such dynamic processes, it is crucial to differentiate the constituent biomolecular species and track their individual time evolution without invasive labels. Here, we present a label-free mid-infrared biosensor capable of distinguishing multiple analytes in heterogeneous biological samples with high sensitivity. Our technology leverages a multi-resonant metasurface to simultaneously enhance the different vibrational fingerprints of multiple biomolecules. By providing up to 1000-fold near-field intensity enhancement over both amide and methylene bands, our sensor resolves the interactions of lipid membranes with different polypeptides in real time. Significantly, we demonstrate that our label-free chemically specific sensor can analyze peptide-induced neurotransmitter cargo release from synaptic vesicle mimics. Our sensor opens up exciting possibilities for gaining new insights into biological processes such as signaling or transport in basic research as well as provides a valuable toolkit for bioanalytical and pharmaceutical applications.

Graphene-based mid-infrared biosensor

We propose a new graphene-based metamaterial biosensor to achieve tunable plasmon-induced transparency in the mid-infrared (mid-IR) regime. The structure consists of a graphene sheet with three cut-out strips that has been located on a substrate. It is shown that the plasmonically induced transparency (PIT) can be realized by breaking the symmetry of the structure in the normal incidence and also changing the polarization of the incident light in the symmetric case. By optimizing the physical parameters of the antennas, an extremely strong optical sensing coefficient (about 99%) is observed in the mid-IR frequency range based on the PIT effect, which is much larger than that of related previous studies. More importantly, we observed a blueshift in the transparency window through the increase of the gate voltage of the graphene’s chemical potential. The transparency window strongly depends on the physical parameters of the substrate and filling material. Furthermore, it is found that the biosensing application of the proposed structure is highly dependent on inserting an ultra-thin buffer layer between the graphene and substrate layer, leading to a tunable PIT in the mid-IR regime.

Nanoplasmonic mid-infrared biosensor for in vitro protein secondary structure detection

Plasmonic nanoantennas offer new applications in mid-infrared (mid-IR) absorption spectroscopy with ultrasensitive detection of structural signatures of biomolecules, such as proteins, due to their strong resonant near-fields. The amide I fingerprint of a protein contains conformational information that is greatly important for understanding its function in health and disease. Here, we introduce a non-invasive, label-free mid-IR nanoantenna-array sensor for secondary structure identification of nanometer-thin protein layers in aqueous solution by resolving the content of plasmonically enhanced amide I signatures. We successfully detect random coil to cross β-sheet conformational changes associated with α-synuclein protein aggregation, a detrimental process in many neurodegenerative disorders. Notably, our experimental results demonstrate high conformational sensitivity by differentiating subtle secondary-structural variations in a native β-sheet protein monolayer from those of cross β-sheets, which are characteristic of pathological aggregates. Our nanoplasmonic biosensor is a highly promising and versatile tool for in vitro structural analysis of thin protein layers.

Hafnia (HfO2) nanoparticles as an X-ray contrast agent and mid-infrared biosensor.

The interaction of hafnium oxide (HfO2) nanoparticles (NPs) with X-ray and mid-infrared radiation was investigated to assess the potential as a multifunctional diagnostic probe for X-ray computed tomography (CT) and/or mid-infrared biosensing. HfO2 NPs of controlled size were prepared by a sol-gel process and surface functionalized with polyvinylpyrrolidone, resulting in relatively spherical and monodispersed NPs with a tunable mean diameter in the range of ∼7-31 nm. The X-ray attenuation of HfO2 NPs was measured over 0.5-50 mM concentration and compared with Au NPs and iodine, which are the most prominent X-ray contrast agents currently used in research and clinical diagnostic imaging, respectively. At clinical CT tube potentials >80 kVp, HfO2 NPs exhibited superior or similar X-ray contrast compared to Au NPs, while both exhibited significantly greater X-ray contrast compared to iodine, due to the favorable location of the k-shell absorption edge for hafnium and gold. Moreover, energy-dependent differences in X-ray attenuation enabled simultaneous quantitative molecular imaging of each agent using photon-counting spectral (multi-energy) CT. HfO2 NPs also exhibited a strong mid-infrared absorption in the Reststrahlen band from ∼250-800 cm(-1) and negative permittivity below 695 cm(-1), which can enable development of mid-infrared biosensors and contrast agents, leveraging surface enhanced mid-infrared and/or phonon polariton absorption.