Magnetoplasmons for Ultrasensitive Label-Free Biosensing

Abstract

Early detection of immunoglobin G (IgG), a glycoprotein antibody produced in the serum due to various infections, is of paramount importance that will enable effective treatment, immunity assessment, and assist in monitoring outbreaks of contagious diseases. This work demonstrates the transverse magneto-optic Kerr effect (T-MOKE) based magnetoplasmons excited on a composite ferromagnetic/plasmonic grating as a highly sensitive, single wavelength, and target specific biosensing platform. The sharp T-MOKE sensitivity curve corresponding to reduced fwhm results in a two orders of magnitude enhancement in the resolving power compared to conventional propagating surface plasmon polariton (SPP), which is pivotal in identifying minute fluctuations in specific biomolecular concentrations. An order of magnitude improvement in antibody immunoglobin G (IgG) detection limit is observed compared to the SPP based sensing. A detection limit down to 10 ng/mL (66 pM) is achieved using the proposed T-MOKE technique. The results obtained provide compelling evidence of the significantly superior sensitivity and resolving power of the T-MOKE technique for the detection of Human IgG, and it is envisioned that this spectroscopy free, single wavelength measurement approach can be extended to detect biologically/chemically relevant molecules at lower concentrations for early biomedical diagnosis and therapy.

Enhanced transverse magneto-optical Kerr effect using ferromagnetic metal perforated with nanopore arrays

“…6(b), a detection sensitivity of up to S = 650 nm RIU À1 can be achieved. This is comparable to the order of magnitude of reported results; 26,29 however, the advantage is that there is no rapid decay of the T-MOKE as the refractive index of the analyte increases, which is critical in the detection process. Another important parameter for evaluating the sensor performance is the figure of merit (FOM), defined as FOM = S/G, which relates the sensitivity to the line width (G) of the T-MOKE curve with respect to each refractive index.…”

Synthesis and Characterization of Magnetoplasmonic Air-Stable Au@FeCo

“…Various groups have explored this plasmonic property and exploited its uses toward the molecular detection of analytes through the phenomenon termed surface-enhanced Raman scattering (SERS), especially through the use of heterometallic nanoparticles, with many of the nanoparticles proving to be much-needed additions to medical imaging and general molecular detection methods. − However, this plasmonic resonance has only been shown to arise in nonferromagnetic metals as well as more reactive alkali and alkaline-earth metal nanostructures. − This is due to Fe and Co’s real component of permittivity being positive, meaning they have weak interaction with incident light that do not allow the generation of surface plasmons, thereby dampening any possible surface plasmon resonance polaritons (SPP) at their metal/dielectric interface. Specifically, a new method of detection has arisen from the hybridized resonance pattern that occurs because of alloying FeCo with a noble metal to create ferroplasmonic nanostructures. , Lopez-Ortega et al have reported the magneto-optical enhancement in metallic Ag/FeCo core/shell nanoparticles with 50 emu/g magnetization . These ferroplasmonic, or magnetoplasmonic, nanostructures have the capabilities of novel hybridized analytical methods that allow single-molecule detection.…”

“…Specifically, a new method of detection has arisen from the hybridized resonance pattern that occurs because of alloying FeCo with a noble metal to create ferroplasmonic nanostructures. 32,33 Lopez-Ortega et al have reported the magnetooptical enhancement in metallic Ag/FeCo core/shell nanoparticles with 50 emu/g magnetization. 34 These ferroplasmonic, or magnetoplasmonic, nanostructures have the capabilities of novel hybridized analytical methods that allow single-molecule detection.…”

Longitudinal Magneto-Optical Kerr Effect of Nanoporous CoFeB and W/CoFeB/W Thin Films

“…Apart from various heterogeneous structures, including distributed periodic systems, lumped systems, irregular and coupled waveguide systems, and controlled magnetic structures, which are available for data processing and storage in the microwave range [1], the magneto-optical Kerr effect (MOKE) describing the linearly polarized light rotation of the reflection and the relative changes in reflectivity [2][3][4] has been intensively used in optical and magnetic data storage, domain observation [5,6], optical isolators, and fast optical modulation [7,8]. Recently, with the acquisition of high sensing performance in small molecules at low concentrations, MOKE has been widely investigated to enhance the sensing performance on the gas detection [9,10], liquid detection [11][12][13], magnetometry, 2 of 15 magnetic phase probes [14][15][16], and magnetic biosensing [17][18][19][20][21] due to its higher figure of merit (FOM) and sensitivity (they are comprehensive parameters for evaluating sensor performance) than conventional optical-mode or magnetic-mode methods. After summarizing the sensing principle in the MOKE spectrum, it is noteworthy that the MOKE-based sensors always exhibit remarkable sensitivity, flexible light phase, polarization modulation, and a large FOM near the position where the MOKE rotation inversion appears [22,23], which is here called the Kerr null point.…”