pág. 12931
BIOSENSING AT THE NANOSCALE: GOLD
FRACTAL NANOANTENNAS FOR NON-
INVASIVE PLASMONIC RESONANCE
FREQUENCY ANALYSIS
BIOSENSADO A NANOESCALA: NANOANTENAS FRACTALES DE ORO
PARA ANÁLISIS DE FRECUENCIA DE RESONANCIA PLASMÓNICA NO
INVASIVE
Alondra Hernandez Cedillo
Department of Applied Physics and Materials Science, Northern Arizona University, Flagstaff,
Arizona
Fernando Sebastián Chiwo González
Universidad Marista de San Luis Potosí
Rosa Angélica Lara-Ojeda
Universidad Marista de San Luis Potosí
María Selene Ordaz Rodriguez
Universidad Marista de San Luis Potosí
Javier Mendez Lozoya
Universidad Marista de San Luis Potosí
pág. 12932
DOI: https://doi.org/10.37811/cl_rcm.v9i1.16906
Biosensing at the Nanoscale: Gold Fractal Nanoantennas for Non-Invasive
Plasmonic Resonance Frequency Analysis
Alondra Hernandez Cedillo1
ah3526@nau.edu
https://orcid.org/0000-0001-7518-2644
Department of Applied Physics and Materials
Science, Northern Arizona University, Flagstaff,
Arizona
Fernando Sebastián Chiwo González
1958@umaslp.maristas.edu.mx
http://orcid.org/0000-0002-1990-163X
Universidad Marista de San Luis Potosí
Rosa Angélica Lara-Ojeda
2004@umaslp.maristas.edu.mx
https://orcid.org/0000-0003-0892-7890
Universidad Marista de San Luis Potosí
María Selene Ordaz Rodriguez
mordaz@umaslp.maristas.edu.mx
http://orcid.org/0009-0004-6166-7148
Universidad Marista de San Luis Potosí
Javier Mendez Lozoya
1974@umaslp.maristas.edu.mx
https://orcid.org/0000-0002-4218-2231
Universidad Marista de San Luis Potosí
ABSTRACT
The biotechnology sector is focusing on developing biosensors that allow us to detect and monitor
substances in vivo using non-invasive methods. For example, in substances detection using the label-
less method, radiation in the mid-infrared (mid-IR) has been used to obtain the vibrational fingerprint.
In this work, we propose to use plasmonic nanoantennas called spaceship to develop a SEIRA substrate
that can be used in disease detection. The spaceship nanoantennas were fabricated using electron beam
lithography. A potential SEIRA device was fabricated with Au spaceship nanoantennas based on gold
fractal nanoantennas with dimensions of 5.5 μm long and 5 μm high, inner structure with 970 nm, 950
nm in length and height respectively. Arm width of 400 nm and 50 nm of thickness. The resonance
frequency (νres) was analyzed using gold nanoantennas absorbance as a function of frequency where one
peak was found at 33THz. Additionally, these results were corroborated with a simulation where the
magnitude of the electric field E=7.79 V/m at 34.98 THz was found. These results allow us to propose
spaceship nanoantennas as good candidates for the design of a SEIRA substrate.
Keywords: electron beam lithography, fractal nanoantenna, SEIRA substrate, resonance frequency,
Fourier transformation infrared spectroscopy
1 Autor principal
Correspondencia: ah3526@nau.edu
DOI: https://doi.org/10.37811/cl_rcm.v9i1.16906
Biosensing at the Nanoscale: Gold Fractal Nanoantennas for Non-Invasive
Plasmonic Resonance Frequency Analysis
Alondra Hernandez Cedillo1
ah3526@nau.edu
https://orcid.org/0000-0001-7518-2644
Department of Applied Physics and Materials
Science, Northern Arizona University, Flagstaff,
Arizona
Fernando Sebastián Chiwo González
1958@umaslp.maristas.edu.mx
http://orcid.org/0000-0002-1990-163X
Universidad Marista de San Luis Potosí
Rosa Angélica Lara-Ojeda
2004@umaslp.maristas.edu.mx
https://orcid.org/0000-0003-0892-7890
Universidad Marista de San Luis Potosí
María Selene Ordaz Rodriguez
mordaz@umaslp.maristas.edu.mx
http://orcid.org/0009-0004-6166-7148
Universidad Marista de San Luis Potosí
Javier Mendez Lozoya
1974@umaslp.maristas.edu.mx
https://orcid.org/0000-0002-4218-2231
Universidad Marista de San Luis Potosí
ABSTRACT
The biotechnology sector is focusing on developing biosensors that allow us to detect and monitor
substances in vivo using non-invasive methods. For example, in substances detection using the label-
less method, radiation in the mid-infrared (mid-IR) has been used to obtain the vibrational fingerprint.
In this work, we propose to use plasmonic nanoantennas called spaceship to develop a SEIRA substrate
that can be used in disease detection. The spaceship nanoantennas were fabricated using electron beam
lithography. A potential SEIRA device was fabricated with Au spaceship nanoantennas based on gold
fractal nanoantennas with dimensions of 5.5 μm long and 5 μm high, inner structure with 970 nm, 950
nm in length and height respectively. Arm width of 400 nm and 50 nm of thickness. The resonance
frequency (νres) was analyzed using gold nanoantennas absorbance as a function of frequency where one
peak was found at 33THz. Additionally, these results were corroborated with a simulation where the
magnitude of the electric field E=7.79 V/m at 34.98 THz was found. These results allow us to propose
spaceship nanoantennas as good candidates for the design of a SEIRA substrate.
Keywords: electron beam lithography, fractal nanoantenna, SEIRA substrate, resonance frequency,
Fourier transformation infrared spectroscopy
1 Autor principal
Correspondencia: ah3526@nau.edu
pág. 12933
Biosensado a nanoescala: Nanoantenas fractales de oro para análisis de
frecuencia de resonancia plasmónica no invasiva
RESUMEN
El sector de la biotecnología se está centrandzo en el desarrollo de biosensores que permitan detectar y
controlar sustancias in vivo mediante métodos no invasivos. Por ejemplo, en la detección de sustancias
mediante el método sin etiquetas se ha utilizado radiación en el infrarrojo medio (medio-IR) para obtener
la huella vibracional. En este trabajo, proponemos utilizar nanoantenas plasmónicas denominadas
spaceship para desarrollar un sustrato SEIRA que pueda utilizarse en la detección de enfermedades. Las
nanoantenas spaceship se fabricaron mediante litografía por haz de electrones. Se fabricó un posible
dispositivo SEIRA con nanoantenas spaceship de Au basadas en nanoantenas fractales de oro con unas
dimensiones de 5.5 μm de longitud y 5 μm de altura, estructura interna con 970 nm, 950 nm de longitud
y altura respectivamente. La anchura del brazo es de 400 nm y el grosor de 50 nm. La frecuencia de
resonancia (𝜈𝑟𝑒𝑠) se analizó utilizando la absorbancia de las nanoantenas de oro en función de la
frecuencia, donde se encontró un pico a 33THz. Además, estos resultados se corroboraron con una
simulación donde se encontró la magnitud del campo eléctrico E=7.79 V/m a 34.98 THz. Estos
resultados nos permiten proponer a las nanoantenas espaciales como buenas candidatas para el diseño
de un sustrato SEIRA.
Palabras clave: litografía por haz de electrones, nanoantena fractal, sustrato SEIRA, frecuencia de
resonancia, espectroscopia infrarroja por transformación de Fourier
Artículo recibido 13 enero 2025
Aceptado para publicación: 19 febrero 2025
Biosensado a nanoescala: Nanoantenas fractales de oro para análisis de
frecuencia de resonancia plasmónica no invasiva
RESUMEN
El sector de la biotecnología se está centrandzo en el desarrollo de biosensores que permitan detectar y
controlar sustancias in vivo mediante métodos no invasivos. Por ejemplo, en la detección de sustancias
mediante el método sin etiquetas se ha utilizado radiación en el infrarrojo medio (medio-IR) para obtener
la huella vibracional. En este trabajo, proponemos utilizar nanoantenas plasmónicas denominadas
spaceship para desarrollar un sustrato SEIRA que pueda utilizarse en la detección de enfermedades. Las
nanoantenas spaceship se fabricaron mediante litografía por haz de electrones. Se fabricó un posible
dispositivo SEIRA con nanoantenas spaceship de Au basadas en nanoantenas fractales de oro con unas
dimensiones de 5.5 μm de longitud y 5 μm de altura, estructura interna con 970 nm, 950 nm de longitud
y altura respectivamente. La anchura del brazo es de 400 nm y el grosor de 50 nm. La frecuencia de
resonancia (𝜈𝑟𝑒𝑠) se analizó utilizando la absorbancia de las nanoantenas de oro en función de la
frecuencia, donde se encontró un pico a 33THz. Además, estos resultados se corroboraron con una
simulación donde se encontró la magnitud del campo eléctrico E=7.79 V/m a 34.98 THz. Estos
resultados nos permiten proponer a las nanoantenas espaciales como buenas candidatas para el diseño
de un sustrato SEIRA.
Palabras clave: litografía por haz de electrones, nanoantena fractal, sustrato SEIRA, frecuencia de
resonancia, espectroscopia infrarroja por transformación de Fourier
Artículo recibido 13 enero 2025
Aceptado para publicación: 19 febrero 2025
pág. 12934
INTRODUCTION
The biotechnology sector is focusing on developing biosensors that allow us to detect and monitor
substances in vivo using non-invasive methods. For example, in substances detection using the label-
less method, radiation in the mid-infrared (mid-IR) [1] has been used to obtain the vibrational
fingerprint. In fact, it has provided an identifying method for molecular capacity using the characteristic
vibrational spectrum, which is directly related to its molecular constituents and chemical bonds. This
allows us to obtain information from biosamples [2], such as lipids or proteins, for detection,
identification, and diagnosis [3]. Therefore, it has been widely proposed that plasmonic nanostructures
(patterned as nanoantennas) seem like candidates to take on a key role in detection using enhanced
surfaces to overcome the problem of limited molecular absorption. Surface Enhanced Infrared
Absorption (SEIRA) spectroscopy [4] [5] of substrates was successfully implemented and shown to
have an advantage in the specific and selective detection of low and ultra-low concentrations of analytes
in the (μM-pM) range [6]. These plasmonic devices based on nanoantenna arrays can be used for gas
sensing, disease detection, and optical imaging [7]. Fractals, on the other hand, are geometric shapes
that exhibit self-similarity at different scales. They are characterized by a repeating pattern that appears
similar at all levels of magnification. Fractals can be found in nature, such as in snowflakes and ferns,
and can also be created artificially using mathematical algorithms. Fractals have many interesting
properties, including infinite complexity, non-integer dimensionality, and the ability to fill space without
repeating. These properties make them useful for a variety of applications, including antenna design,
data compression, and image processing. The combination of nanoantennas and fractals has led to the
development of fractal nanoantennas, which combine the enhanced electromagnetic response of
nanoantennas with the self-similarity and complex geometries of fractals. Fractal nanoantennas can
exhibit a wide range of optical responses, including enhanced absorption, scattering, and fluorescence.
They can also be used for sensing applications, such as detecting small molecules and biomolecules.
Additionally, fractal nanoantennas have been used in the development of metamaterials, which are
engineered materials with properties not found in natural materials.
In the present work, for the fabrication of spaceship nanoantennas, a morphology based on a fractal
nanoantenna that refer to intricate patterns that appear in fields of crops, typically wheat, barley, or other
INTRODUCTION
The biotechnology sector is focusing on developing biosensors that allow us to detect and monitor
substances in vivo using non-invasive methods. For example, in substances detection using the label-
less method, radiation in the mid-infrared (mid-IR) [1] has been used to obtain the vibrational
fingerprint. In fact, it has provided an identifying method for molecular capacity using the characteristic
vibrational spectrum, which is directly related to its molecular constituents and chemical bonds. This
allows us to obtain information from biosamples [2], such as lipids or proteins, for detection,
identification, and diagnosis [3]. Therefore, it has been widely proposed that plasmonic nanostructures
(patterned as nanoantennas) seem like candidates to take on a key role in detection using enhanced
surfaces to overcome the problem of limited molecular absorption. Surface Enhanced Infrared
Absorption (SEIRA) spectroscopy [4] [5] of substrates was successfully implemented and shown to
have an advantage in the specific and selective detection of low and ultra-low concentrations of analytes
in the (μM-pM) range [6]. These plasmonic devices based on nanoantenna arrays can be used for gas
sensing, disease detection, and optical imaging [7]. Fractals, on the other hand, are geometric shapes
that exhibit self-similarity at different scales. They are characterized by a repeating pattern that appears
similar at all levels of magnification. Fractals can be found in nature, such as in snowflakes and ferns,
and can also be created artificially using mathematical algorithms. Fractals have many interesting
properties, including infinite complexity, non-integer dimensionality, and the ability to fill space without
repeating. These properties make them useful for a variety of applications, including antenna design,
data compression, and image processing. The combination of nanoantennas and fractals has led to the
development of fractal nanoantennas, which combine the enhanced electromagnetic response of
nanoantennas with the self-similarity and complex geometries of fractals. Fractal nanoantennas can
exhibit a wide range of optical responses, including enhanced absorption, scattering, and fluorescence.
They can also be used for sensing applications, such as detecting small molecules and biomolecules.
Additionally, fractal nanoantennas have been used in the development of metamaterials, which are
engineered materials with properties not found in natural materials.
In the present work, for the fabrication of spaceship nanoantennas, a morphology based on a fractal
nanoantenna that refer to intricate patterns that appear in fields of crops, typically wheat, barley, or other
pág. 12935
cereal grains. These patterns often involve flattened crops in a circular or geometrically complex
arrangement (see Fig. 1). This morphology was studied by analyzing the electric field generated due to
the interaction between infrared radiation and the nanoantenna as a function of frequency. We analyze
the feasibility of use in a SEIRA substrate based on the obtained results.
Figure 1. Morphology and dimensions used as fractal nanoantenna in numerical simulations.
Materials and Methods
We fabricate plasmonic devices based on Au nanoantenna arrays using electron beam lithography (EBL)
on silicon (Si) substrates with 300nm silicon dioxide (SiO2), and their resonance frequency was
investigated using infrared spectroscopy (FTIR). In addition, the frequency was studied using
simulations by the finite element method to analyze the dependence of the electric field on frequency.
Numerical Simulations
COMSOL Multiphysics is a commercial software package that is widely used for simulating physical
phenomena. It is based on the FEM and can be used to model a variety of engineering systems, including
plasmonic devices [8].
In the simulations described plane waves that are linearly polarized to the z-axis are used to interact with
a plasmonic device based on arrays of gold (Au) nanoantennas [9]. The purpose of the simulations is to
evaluate the absorbance of the plasmonic device as a function of the frequency of the incident wave.
The range of frequencies considered in the simulations is (20 – 90) THz [10], [11], which is in the
terahertz (THz) range. This is an important range for many applications, including imaging, sensing,
and communication.
cereal grains. These patterns often involve flattened crops in a circular or geometrically complex
arrangement (see Fig. 1). This morphology was studied by analyzing the electric field generated due to
the interaction between infrared radiation and the nanoantenna as a function of frequency. We analyze
the feasibility of use in a SEIRA substrate based on the obtained results.
Figure 1. Morphology and dimensions used as fractal nanoantenna in numerical simulations.
Materials and Methods
We fabricate plasmonic devices based on Au nanoantenna arrays using electron beam lithography (EBL)
on silicon (Si) substrates with 300nm silicon dioxide (SiO2), and their resonance frequency was
investigated using infrared spectroscopy (FTIR). In addition, the frequency was studied using
simulations by the finite element method to analyze the dependence of the electric field on frequency.
Numerical Simulations
COMSOL Multiphysics is a commercial software package that is widely used for simulating physical
phenomena. It is based on the FEM and can be used to model a variety of engineering systems, including
plasmonic devices [8].
In the simulations described plane waves that are linearly polarized to the z-axis are used to interact with
a plasmonic device based on arrays of gold (Au) nanoantennas [9]. The purpose of the simulations is to
evaluate the absorbance of the plasmonic device as a function of the frequency of the incident wave.
The range of frequencies considered in the simulations is (20 – 90) THz [10], [11], which is in the
terahertz (THz) range. This is an important range for many applications, including imaging, sensing,
and communication.
pág. 12936
Overall, the simulations using COMSOL Multiphysics, and the FEM are a powerful tool for studying
the behavior of plasmonic devices and can provide valuable insights into their performance and potential
applications.
The software solves equation 1 in the frequency domain
𝛻 𝑥 𝜇𝑟
−1(𝛻 𝑥 𝑬) − 𝑘0
2 (𝜀𝑟 − 𝑗𝜎
𝜔𝜖0
) 𝑬 = 0 (1)
where ω is the frequency, E is the electric field, ε0 is vacuum permittivity, εr is relative permittivity, σ is
material conductivity, μr corresponds to relative permeability, and k0 is the wavelength vector, see Table
1 [12], [13].When using the COMSOL RF module to simulate the absorbance of a material, meshing is
an important factor to consider in order to obtain accurate results. The mesh should be fine enough to
capture the details of the electromagnetic waves at the highest frequency of interest. This means that the
mesh density should be proportional to the wavelength, with smaller mesh elements for shorter
wavelengths.
Table 1. Gold value used to analyze a resonant frequency of fractal nanoantennas at 10.3μm.
Variable Name Value
εr Relative permittivity 1975.6
To explain the resonance phenomenon in the far-field plots using the near-field contours, one can
analyze the spatial distribution of the electric field around the structure at different frequencies. At
frequencies far from the resonance frequency, the near-field contours show weak or spatially uniform
field distributions, indicating weak interactions between the structure and the incident light. This will
lead to far-field plots that show weak or isotropic radiation patterns.
As the frequency approaches the resonance frequency, however, the near-field contours will show strong
and spatially non-uniform field distributions, indicating strong interactions between the structure and
the incident light. This will lead to far-field plots that show enhanced and directional radiation patterns,
with higher intensity in certain directions or polarizations.
By analyzing the near-field contours, one can also gain insight into the physical mechanisms underlying
the resonance phenomenon. Near-field contours may reveal the formation of plasmonic hotspots, where
the electric field is highly concentrated and leads to enhanced absorption. Near-field contours also show
Overall, the simulations using COMSOL Multiphysics, and the FEM are a powerful tool for studying
the behavior of plasmonic devices and can provide valuable insights into their performance and potential
applications.
The software solves equation 1 in the frequency domain
𝛻 𝑥 𝜇𝑟
−1(𝛻 𝑥 𝑬) − 𝑘0
2 (𝜀𝑟 − 𝑗𝜎
𝜔𝜖0
) 𝑬 = 0 (1)
where ω is the frequency, E is the electric field, ε0 is vacuum permittivity, εr is relative permittivity, σ is
material conductivity, μr corresponds to relative permeability, and k0 is the wavelength vector, see Table
1 [12], [13].When using the COMSOL RF module to simulate the absorbance of a material, meshing is
an important factor to consider in order to obtain accurate results. The mesh should be fine enough to
capture the details of the electromagnetic waves at the highest frequency of interest. This means that the
mesh density should be proportional to the wavelength, with smaller mesh elements for shorter
wavelengths.
Table 1. Gold value used to analyze a resonant frequency of fractal nanoantennas at 10.3μm.
Variable Name Value
εr Relative permittivity 1975.6
To explain the resonance phenomenon in the far-field plots using the near-field contours, one can
analyze the spatial distribution of the electric field around the structure at different frequencies. At
frequencies far from the resonance frequency, the near-field contours show weak or spatially uniform
field distributions, indicating weak interactions between the structure and the incident light. This will
lead to far-field plots that show weak or isotropic radiation patterns.
As the frequency approaches the resonance frequency, however, the near-field contours will show strong
and spatially non-uniform field distributions, indicating strong interactions between the structure and
the incident light. This will lead to far-field plots that show enhanced and directional radiation patterns,
with higher intensity in certain directions or polarizations.
By analyzing the near-field contours, one can also gain insight into the physical mechanisms underlying
the resonance phenomenon. Near-field contours may reveal the formation of plasmonic hotspots, where
the electric field is highly concentrated and leads to enhanced absorption. Near-field contours also show
pág. 12937
the formation of standing waves or interference patterns, which can lead to directional scattering of light
[14].
Fabrication
The nanoantennas were fabricated using electron beam lithography on Si wafers with 300 nm SiO2 as a
thermal and electric insulator. The manufacturing procedure used was as follows: 300 nm of
polymethylmethacrylate (PMMA) were deposited on the Si/SiO2 substrates by spin coating, the pattern
was made with a Raith ELPHY Quantum lithography system. Nanoantenna patterns were recorded using
a 30 keV and an area dose of 250 μC/cm2. The development was performed by immersing the Si/SiO2
substrate in a MIBK: IPA solution for 80 seconds. Subsequently, 50 nm gold layer was deposited by RF
sputtering. Finally, the devices were left two hours in acetone to remove excess resin and metal [15].
Results and discussion
FEM is a numerical technique used to solve partial differential equations (PDEs) by discretizing the
problem domain into finite elements. It is commonly used in engineering and physics simulations to
analyze complex physical systems. Here, FEM simulations were employed to study the behavior of an
electromagnetic system. Figure 1 shows a 3D image of electric field enhancement E=7.79V/m at
νres=34.98THz. The resonance frequency of 34.98 THz indicates the specific frequency at which the
system under simulation exhibits resonance behavior. Resonance occurs when the system's response to
the incident electromagnetic wave is maximized, leading to enhanced effects such as increased electric
field strength.
Figure 2. shows the magnitude of the electric field E=7.79 V/m at 34.98 THz.
Figure 2 shows the results obtained from the finite method simulation using COMSOL where
absorbance was analyzed as a function of frequency. One peak corresponding to the resonance
frequencies located at 34.98 THz was found [17].
the formation of standing waves or interference patterns, which can lead to directional scattering of light
[14].
Fabrication
The nanoantennas were fabricated using electron beam lithography on Si wafers with 300 nm SiO2 as a
thermal and electric insulator. The manufacturing procedure used was as follows: 300 nm of
polymethylmethacrylate (PMMA) were deposited on the Si/SiO2 substrates by spin coating, the pattern
was made with a Raith ELPHY Quantum lithography system. Nanoantenna patterns were recorded using
a 30 keV and an area dose of 250 μC/cm2. The development was performed by immersing the Si/SiO2
substrate in a MIBK: IPA solution for 80 seconds. Subsequently, 50 nm gold layer was deposited by RF
sputtering. Finally, the devices were left two hours in acetone to remove excess resin and metal [15].
Results and discussion
FEM is a numerical technique used to solve partial differential equations (PDEs) by discretizing the
problem domain into finite elements. It is commonly used in engineering and physics simulations to
analyze complex physical systems. Here, FEM simulations were employed to study the behavior of an
electromagnetic system. Figure 1 shows a 3D image of electric field enhancement E=7.79V/m at
νres=34.98THz. The resonance frequency of 34.98 THz indicates the specific frequency at which the
system under simulation exhibits resonance behavior. Resonance occurs when the system's response to
the incident electromagnetic wave is maximized, leading to enhanced effects such as increased electric
field strength.
Figure 2. shows the magnitude of the electric field E=7.79 V/m at 34.98 THz.
Figure 2 shows the results obtained from the finite method simulation using COMSOL where
absorbance was analyzed as a function of frequency. One peak corresponding to the resonance
frequencies located at 34.98 THz was found [17].
pág. 12938
Figure 3. Graph of the results of the finite element method simulation where absorbance was analyzed
as a function of frequency; One peak corresponding to the resonance frequency located at 34.98 THz
was found.
Figure 3 shows the results obtained from analyzing the fabricated morphology by electron beam using
the FEI Inspect F50 field emission scanning electron microscope. We can see that each spaceship
nanoantenna measures 5.5 μm in length, 5 μm in height, inner structure with 970 nm, 950 nm in length
and height respectively. Arm width of 400 nm and 50 nm of thickness.
Figure 4. Micrograph of spaceship nanoantennas based on gold fractal nanoantennas which are 5.5
μm long and 5 μm high.
Hence, the optical properties of plasmonic devices based on nanoantenna arrays were studied using
infrared spectroscopy (FTIR) with Bruker Vertex 70 equipment, analyzing the absorbance as a function
of frequency (THz), which allows us to define the resonance frequency of the device. Figure 4 shows
that the resonance frequency (vres) for the nanoantenna named spaceship presents one peak 33 THz [16].
Figure 3. Graph of the results of the finite element method simulation where absorbance was analyzed
as a function of frequency; One peak corresponding to the resonance frequency located at 34.98 THz
was found.
Figure 3 shows the results obtained from analyzing the fabricated morphology by electron beam using
the FEI Inspect F50 field emission scanning electron microscope. We can see that each spaceship
nanoantenna measures 5.5 μm in length, 5 μm in height, inner structure with 970 nm, 950 nm in length
and height respectively. Arm width of 400 nm and 50 nm of thickness.
Figure 4. Micrograph of spaceship nanoantennas based on gold fractal nanoantennas which are 5.5
μm long and 5 μm high.
Hence, the optical properties of plasmonic devices based on nanoantenna arrays were studied using
infrared spectroscopy (FTIR) with Bruker Vertex 70 equipment, analyzing the absorbance as a function
of frequency (THz), which allows us to define the resonance frequency of the device. Figure 4 shows
that the resonance frequency (vres) for the nanoantenna named spaceship presents one peak 33 THz [16].
pág. 12939
Figure 5. Graph of the infrared spectroscopy results where absorbance was analyzed as a function of
frequency; it is seen that the resonance frequency (vres) for the nanoantenna called spaceship based on
the fractal nanoantenna presents one peak at 33 THz.
Comparing resonance frequency obtained from experimental and simulations results of the device, a
shift was observed. This shift can due to different factors, such as material composition or environmental
conditions. The experimental results are based on measurements taken from a physical system, whereas
the simulation results are based on a model created within the finite element method. Discrepancies can
arise due to simplifications or assumptions made in the simulation model that may not perfectly
represent the real-world system.
Nanoantennas themselves are not typically used as biosensors or biodetectors in the same way that
specific biomolecules, enzymes, or antibodies are used. However, nanoantennas can enhance the
performance of biosensors and biodetectors by improving their sensitivity, signal-to-noise ratio, and
detection limits. Nanoantennas can concentrate and enhance the interaction between electromagnetic
waves (e.g., light) and the target molecules in the biosensor. This results in stronger and more detectable
signals, making it easier to identify and quantify biological or chemical analytes. Moreover, plasmonic
nanoantennas made of noble metals like gold or silver, can exhibit surface plasmon resonance (SPR).
SPR is sensitive to changes in the refractive index of the surrounding medium, making it a valuable tool
for label-free biosensing. When target molecules bind to the sensor surface, it causes a shift in the SPR
wavelength, which can be measured and correlated with analyte concentration. Plasmonic nanoantennas,
Figure 5. Graph of the infrared spectroscopy results where absorbance was analyzed as a function of
frequency; it is seen that the resonance frequency (vres) for the nanoantenna called spaceship based on
the fractal nanoantenna presents one peak at 33 THz.
Comparing resonance frequency obtained from experimental and simulations results of the device, a
shift was observed. This shift can due to different factors, such as material composition or environmental
conditions. The experimental results are based on measurements taken from a physical system, whereas
the simulation results are based on a model created within the finite element method. Discrepancies can
arise due to simplifications or assumptions made in the simulation model that may not perfectly
represent the real-world system.
Nanoantennas themselves are not typically used as biosensors or biodetectors in the same way that
specific biomolecules, enzymes, or antibodies are used. However, nanoantennas can enhance the
performance of biosensors and biodetectors by improving their sensitivity, signal-to-noise ratio, and
detection limits. Nanoantennas can concentrate and enhance the interaction between electromagnetic
waves (e.g., light) and the target molecules in the biosensor. This results in stronger and more detectable
signals, making it easier to identify and quantify biological or chemical analytes. Moreover, plasmonic
nanoantennas made of noble metals like gold or silver, can exhibit surface plasmon resonance (SPR).
SPR is sensitive to changes in the refractive index of the surrounding medium, making it a valuable tool
for label-free biosensing. When target molecules bind to the sensor surface, it causes a shift in the SPR
wavelength, which can be measured and correlated with analyte concentration. Plasmonic nanoantennas,
pág. 12940
are often used in immunoassays. Functionalized nanoantennas can serve as labels for antibodies or
antigens, and their plasmonic properties enable sensitive detection through changes in scattering or
absorption when binding events occur. In summary, while nanoantennas themselves do not directly act
as biosensors or biodetectors, they are valuable components in enhancing the performance of these
devices. Their ability to manipulate light at the nanoscale and create localized electromagnetic fields
makes them essential for improving the sensitivity and specificity of detection in various applications,
including biosensing and biodetection.
CONCLUSIONS
A potential SEIRA device was fabricated with Au spaceship nanoantennas based on fractal
nanoantennas with dimensions of 5.5 μm long and 5 μm high, inner structure with 970 nm, 950 nm in
length and height respectively. Arm width of 400 nm and 50 nm of thickness. Using infrared
spectroscopy (FTIR), the gold nanoantennas absorbance was analyzed as a function of frequency, where
one peak was found that correspond to the resonance frequency located at 33 THz. These results were
corroborated with finite method simulations, where it was found that the magnitude of the electric field
was E=7.79 V/m when υres=34.98 THz. These results allow us to propose fractal nanoantennas as good
candidates for the design of a SEIRA substrate. In summary, while nanoantennas themselves do not
directly act as biosensors or biodetectors, they are valuable components in enhancing the performance
of these devices. Their ability to manipulate light at the nanoscale and create localized electromagnetic
fields makes them essential for improving the sensitivity and specificity of detection in various
applications, including biosensing and biodetection.
ACKNOWLEDGMENTS
This work was supported by the Consejo Nacional de Ciencia y Tecnología (CONACyT) – Mexico,
through Grants CEMIE-Sol 105, by the National Laboratory program from CONACYT through the
Terahertz Science and Technology National Lab (LANCYTT) and by the Tecnológico Nacional de
México/I.T. San Luis Potosí.
E. Garduño gratefully acknowledge support from the "Investigadoras e Investigadores por México"
CONACYT program through project No. 674.
are often used in immunoassays. Functionalized nanoantennas can serve as labels for antibodies or
antigens, and their plasmonic properties enable sensitive detection through changes in scattering or
absorption when binding events occur. In summary, while nanoantennas themselves do not directly act
as biosensors or biodetectors, they are valuable components in enhancing the performance of these
devices. Their ability to manipulate light at the nanoscale and create localized electromagnetic fields
makes them essential for improving the sensitivity and specificity of detection in various applications,
including biosensing and biodetection.
CONCLUSIONS
A potential SEIRA device was fabricated with Au spaceship nanoantennas based on fractal
nanoantennas with dimensions of 5.5 μm long and 5 μm high, inner structure with 970 nm, 950 nm in
length and height respectively. Arm width of 400 nm and 50 nm of thickness. Using infrared
spectroscopy (FTIR), the gold nanoantennas absorbance was analyzed as a function of frequency, where
one peak was found that correspond to the resonance frequency located at 33 THz. These results were
corroborated with finite method simulations, where it was found that the magnitude of the electric field
was E=7.79 V/m when υres=34.98 THz. These results allow us to propose fractal nanoantennas as good
candidates for the design of a SEIRA substrate. In summary, while nanoantennas themselves do not
directly act as biosensors or biodetectors, they are valuable components in enhancing the performance
of these devices. Their ability to manipulate light at the nanoscale and create localized electromagnetic
fields makes them essential for improving the sensitivity and specificity of detection in various
applications, including biosensing and biodetection.
ACKNOWLEDGMENTS
This work was supported by the Consejo Nacional de Ciencia y Tecnología (CONACyT) – Mexico,
through Grants CEMIE-Sol 105, by the National Laboratory program from CONACYT through the
Terahertz Science and Technology National Lab (LANCYTT) and by the Tecnológico Nacional de
México/I.T. San Luis Potosí.
E. Garduño gratefully acknowledge support from the "Investigadoras e Investigadores por México"
CONACYT program through project No. 674.
pág. 12941
Funding
The authors declare that no funds, grants, or other support were received during the preparation of this
manuscript.
Competing Interests
The authors have no relevant financial or non-financial interests to disclose.
Data Availability
The datasets generated and/or analyzed during the current study are available from the corresponding
author on reasonable request.
REFERENCES
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Frédérique Deiss, and Rajesh Sardar, Analytical Chemistry 2020 92 (13), 9295-9304, DOI:
10.1021/acs.analchem.0c01639
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Nanotechnol. 17, 5–16 (2022). https://doi.org/10.1038/s41565-021-01045-5
[3] López-Lorente ÁI, Mizaikoff B. Mid-infrared spectroscopy for protein analysis: potential and
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Funding
The authors declare that no funds, grants, or other support were received during the preparation of this
manuscript.
Competing Interests
The authors have no relevant financial or non-financial interests to disclose.
Data Availability
The datasets generated and/or analyzed during the current study are available from the corresponding
author on reasonable request.
REFERENCES
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Frédérique Deiss, and Rajesh Sardar, Analytical Chemistry 2020 92 (13), 9295-9304, DOI:
10.1021/acs.analchem.0c01639
[2] Altug, H., Oh, SH., Maier, S.A. et al. Advances and applications of nanophotonic biosensors. Nat.
Nanotechnol. 17, 5–16 (2022). https://doi.org/10.1038/s41565-021-01045-5
[3] López-Lorente ÁI, Mizaikoff B. Mid-infrared spectroscopy for protein analysis: potential and
challenges. Anal Bioanal Chem. 2016 Apr;408(11):2875-89. doi: 10.1007/s00216-016-9375-5.
Epub 2016 Feb 16. PMID: 26879650.
[4] Odeta Limaj, Dordaneh Etezadi, Nathan J. Wittenberg, Daniel Rodrigo, Daehan Yoo, Sang-Hyun
Oh, and Hatice Altug, Infrared Plasmonic Biosensor for Real-Time and Label-Free Monitoring
of Lipid Membranes, Nano Letters 2016 16 (2), 1502-1508, DOI: 10.1021/acs.nanolett.5b05316
[5] Shabnam Andalibi Miandoab, Robabeh Talebzadeh, Ultra-sensitive and selective 2D hybrid highly
doped semiconductor-graphene biosensor based on SPR and SEIRA effects in the wide range
of infrared spectral, Optical Materials, Volume 129, 2022, 112572,
[6] Brown LV, Yang X, Zhao K, Zheng BY, Nordlander P, Halas NJ. Fan-shaped gold nanoantennas
above reflective substrates for surface-enhanced infrared absorption (SEIRA). Nano Lett. 2015
Feb 11;15(2):1272-80. doi: 10.1021/nl504455s. Epub 2015 Jan 12. PMID: 25565006.
[7] Brolo, Alexandre G., “Plasmonics for future biosensors.” Nature Photonics 6 (2012): 709-713.
pág. 12942
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[10] Johannes Hoffmann, Christian Hafner, Patrick Leidenberger, Jan Hesselbarth, and Sven Burger
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Proc. SPIE 7390, Modeling Aspects in Optical Metrology II, 73900J (17 June 2009);
https://doi.org/10.1117/12.828036
[11] Hao Hu, Wei Tao, Florian Laible, Thomas Maurer, Pierre-Michel Adam, Anke Horneber, Monika
Fleischer, Spectral exploration of asymmetric bowtie nanoantennas, Micro and Nano
Engineering, Volume 17, 2022, 100166, ISSN 2590-0072,
https://doi.org/10.1016/j.mne.2022.100166.
[12] Baokuan Li, Fang Wang, and Fumitaka Tsukihashi, “Current, Magnetic Field and Joule Heating in
Electroslag Remelting Processes”, ISIJ International, Vol. 52 (2012), No. 7, pp. 1289–1295.
[13] Elena E. Antonova and David C. Looman, “Finite Elements for Thermoelectric Device Analysis in
ANSYS”, International Conference on Thermoelectrics, 2005.
[14] Hassani Gangaraj, Seyyed Ali and Monticone, Francesco. "Molding light with metasurfaces: from
far-field to near-field interactions" Nanophotonics, vol. 7, no. 6, 2018, pp. 1025-1040.
https://doi.org/10.1515/nanoph-2017-0126
[15] Javier Mendez-Lozoya, Ramón Díaz de León-Zapata, Edgar Guevara, Gabriel González, and
Francisco J. González "Thermoelectric efficiency optimization of nanoantennas for solar energy
harvesting," Journal of Nanophotonics 13(2), 026005 (2 May 2019).
https://doi.org/10.1117/1.JNP.13.026005
[16] S Kuznetsov et al 2022 J. Phys.: Conf. Ser. 2316 012016
[17] Francisco Javier González, Javier Alda, Jorge Simón, James Ginn, Glenn Boreman, The effect of
metal dispersion on the resonance of antennas at infrared frequencies, Infrared Physics &
[8] A. M. A. Sabaawi, C. C. Tsimenidis, and B. S. Sharif, "Infra-red nano-antennas for solar energy
collection," 2011 Loughborough Antennas & Propagation Conference, 2011, pp. 1-4, doi:
10.1109/LAPC.2011.6114082.
[9] Taflove A, Hagness S C and Piket-May M 2005 Computational Electromagnetics: The Finite-
Difference Time-Domain Method The Electrical Engineering Handbook. (Cambridge:
Academic) 629–70
[10] Johannes Hoffmann, Christian Hafner, Patrick Leidenberger, Jan Hesselbarth, and Sven Burger
"Comparison of electromagnetic field solvers for the 3D analysis of plasmonic nanoantennas",
Proc. SPIE 7390, Modeling Aspects in Optical Metrology II, 73900J (17 June 2009);
https://doi.org/10.1117/12.828036
[11] Hao Hu, Wei Tao, Florian Laible, Thomas Maurer, Pierre-Michel Adam, Anke Horneber, Monika
Fleischer, Spectral exploration of asymmetric bowtie nanoantennas, Micro and Nano
Engineering, Volume 17, 2022, 100166, ISSN 2590-0072,
https://doi.org/10.1016/j.mne.2022.100166.
[12] Baokuan Li, Fang Wang, and Fumitaka Tsukihashi, “Current, Magnetic Field and Joule Heating in
Electroslag Remelting Processes”, ISIJ International, Vol. 52 (2012), No. 7, pp. 1289–1295.
[13] Elena E. Antonova and David C. Looman, “Finite Elements for Thermoelectric Device Analysis in
ANSYS”, International Conference on Thermoelectrics, 2005.
[14] Hassani Gangaraj, Seyyed Ali and Monticone, Francesco. "Molding light with metasurfaces: from
far-field to near-field interactions" Nanophotonics, vol. 7, no. 6, 2018, pp. 1025-1040.
https://doi.org/10.1515/nanoph-2017-0126
[15] Javier Mendez-Lozoya, Ramón Díaz de León-Zapata, Edgar Guevara, Gabriel González, and
Francisco J. González "Thermoelectric efficiency optimization of nanoantennas for solar energy
harvesting," Journal of Nanophotonics 13(2), 026005 (2 May 2019).
https://doi.org/10.1117/1.JNP.13.026005
[16] S Kuznetsov et al 2022 J. Phys.: Conf. Ser. 2316 012016
[17] Francisco Javier González, Javier Alda, Jorge Simón, James Ginn, Glenn Boreman, The effect of
metal dispersion on the resonance of antennas at infrared frequencies, Infrared Physics &
pág. 12943
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https://doi.org/10.1016/j.infrared.2008.12.002.
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https://doi.org/10.1016/j.infrared.2008.12.002.