Metamaterial-enhanced vibrational absorption spectroscopy for the detection of protein molecules

Abstract

From visible to mid-infrared frequencies, molecular sensing has been a major successful application of plasmonics because of the enormous enhancement of the surface electromagnetic nearfield associated with the induced collective motion of surface free carriers excited by the probe light. However, in the lower-energy terahertz (THz) region, sensing by detecting molecular vibrations is still challenging because of low sensitivity, complicated spectral features, and relatively little accumulated knowledge of molecules. Here, we report the use of a micron-scale thin-slab metamaterial (MM) architecture, which functions as an amplifier for enhancing the absorption signal of the THz vibration of an ultrathin adsorbed layer of large organic molecules. We examined bovine serum albumin (BSA) as a prototype large protein molecule and Rhodamine 6G (Rh6G) and 3,3′-diethylthiatricarbocyanine iodide (DTTCI) as examples of small molecules. Among them, our MM significantly magnified only the signal strength of bulky BSA. On the other hand, DTTCI and Rh6G are inactive, as they lack low-frequency vibrational modes in this frequency region. The results obtained here clearly demonstrate the promise of MM-enhanced absorption spectroscopy in the THz region for detection and structural monitoring of large biomolecules such as proteins or pathogenic enzymes.

Terahertz Sensing Based on Metasurfaces

“…Due to these characteristics, the biological-related THz research activity has spread throughout the world covering a wide variety of fields such as diagnosis of diseases, [70] detection of protein concentrations, [71,72] DNA sequencing, [73,74] detection of cancer cells and tumors, [17,70] or detection of microorganisms, [75,76] among others. This is mainly because THz radiation has proven to be a non-invasive, contactless, and non-ionizing technique innocuous to living organisms exposed to it.…”

Enhancement of terahertz photoconductive antenna operation by optical nanoantennas

“…The terahertz (THz) spectral range of electromagnetic waves (0.1–10 THz), lying between the microwave and optical regions, is of great interest, primarily due to the fact that in this band of the electromagnetic spectrum reside the frequencies of some elementary excitations in semiconductors and dielectrics , as well as rotational and vibrational resonances of complex, including biological, molecules . As a result, THz waves have a tremendous number of applications in areas ranging from the detection of dangerous or illicit substances and biological sensing to diagnosis and treatment of diseases in medicine . Moreover, this frequency band is of special importance for spectroscopy in astrophysics because many astrophysical objects emit in the THz range of the spectrum.…”

Controlled Defect Based Ultra Broadband Full-sized Metamaterial Absorber

“…Such electronic materials are garnering more and more attraction. Especially, broadband MPAs in GHz and THz regions possess many important technological applications in imaging 21 , sensing 22,23 , energy harvesting 24 or in micro antenna communication 25,26 , which need perfect absorbers to efficiently collect electromagnetic energy. Many efforts to optimize broadband MPAs have been made, such as multi metal-insulator layers 27 , multi resonance mode combination 28 , super unit cell structure 29 .…”