Applied Science and Convergence Technology 2022; 31(2): 35-39
Published online March 30, 2022
Copyright © The Korean Vacuum Society.
aInfectious Disease Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 34141, Republic of Korea
bNanobiotechnology and Bioinformatics (Major), University of Science & Technology (UST), Daejeon 34141, Republic of Korea
†These authors contributed equally to this work.
Correspondence to:E-mail: email@example.com
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License(http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
The localized surface plasmon resonance (LSPR) sensor is applied in various fields and has individual detection strategies depending on the target material. The device composition of the LSPR sensor has its own characteristics depending on the detection strategy. Although many studies have been reported on the sensing principle and targets of LSPR, the components of the sensing device have not been well described. In this review, we introduce various device compositions of LSPR sensors. The LSPR sensor consists of three major parts: probe, light source, and spectrometer. First, we report various research results on chip-based LSPR sensors that are typically used. In addition, we provide studies of fiber-based LSPR sensors. Finally, this review concludes with a discussion of portable and smartphone-based LSPR sensors in place of fixed LSPR devices.
Keywords: Localized surface plasmon resonance, Sensor, Device, Chip, Optical fiber
The localized surface plasmon resonance (LSPR)-based sensors are used in various fields, such as medicine, food, the environment, industrial processes, and the military [1, 2]. LSPR sensors start with the theory of a plasmon. Plasmon refers to state-free electrons that vibrate collectively on metal, and LSPR appears when a plasmon occurs locally (e.g., nanoparticle, nanostructure) [3,4]. The well-known characteristic of LSPR is that metal nanoparticles absorb light of a specific wavelength. Gold has a unique yellow color, but gold nanoparticles 20 nm in size strongly absorb the 520 nm wavelength to show red light [5,6]. In this moment, the change in dielectric constant (i.e., change in refractive index) occurring near the metal nanostructure shifts the absorbed wavelength; then, this shift of wavelength can be measured and applied to the LSPR sensor [7, 8].
Three major parts are required to compose the LSPR sensor (Fig. 1) . The first part is a probe fabricated with metal nanoparticles or nanostructures that cause plasmons [9–12]. LSPR sensor probes can be manufactured by various methods, such as immobilizing metal nanoparticles on substrates [13,14] and generating nanostructures using sputtering, evaporation, and deposition [15–17]. Another part is a light source for measuring the fabricated probe. To observe the wavelength bands of the probe, a light source with a wide wavelength band is commonly used [18,19]. The generally used tungsten halogen lamp excites white light and has a wide wavelength band of 340–850 nm . Light emitting diodes are used when the desired wavelength band is limited [21, 22]. The final part is a spectrometer that observes the spectra of the probe with respect to the light source [23, 24]. The spectrometer consists of a component that splits light (e.g., prism and grating) and a photodetector that counts photons .
The LSPR sensor develops in various ways depending on how the abovementioned three parts are configured. A typical LSPR sensor probe is a form of chip. A chip-based LSPR sensor is manufactured by fixing metal nanoparticles on a substrate (e.g., Si wafer, glass, and film) or creating metal nanostructures [26–28]. Another type of LSPR sensor probe applies fibers. A fiber-based LSPR sensor uses an optical fiber to fabricate a plasmonic probe. In addition, the development of a portable LSPR sensor is being studied in place of the immovable LSPR experimental setup [29–31]. Studies on miniaturization of the device using a light source as an LED and a spectrometer as a photodetector have been reported [22, 32]. Moreover, with the development of smartphones in recent years, studies using smartphone cameras to apply LSPR are in progress [33–35]. The early portable LSPR sensor had a large size and low sensitivity, but recently reported sensors have become much smaller and have significantly improved sensitivity. The advancement of these local surface plasmon resonance-based sensors is thought to open a new horizon for future technologies.
The chip-based LSPR sensor is a commonly used method. The plasmon LSPR probe is generated by immobilizing metal nanoparticles or nanostructures on substrates [36, 37]. The manufactured chip strongly absorbs a specific wavelength by the LSPR effect, and then the material is measured by observing the absorption wavelength that changes depending on the concentration of the sensing target [38–40].
The fiber-based LSPR sensor is one of the LSPR-based detection strategies. The configuration of the light source and spectrometer is the same as that of the chip-based LSPR sensing method, but the plasmonic substrate is manufactured with optical fibers. In particular, the advantage of the fiber-based LSPR device is that the light source is protected through the fiber, so materials in the aqueous sample can be measured effectively through the above advantage.
As LSPR sensors develop, various studies have attempted to produce portable LSPR devices. Neužil
In particular, research on portable LSPR sensors based on smartphones is being actively conducted in accordance with the precise development of smartphones. Dutta
Here, we have reviewed the device composition of LSPR sensors. The first part of this review introduced the overview and basic configuration of the LSPR sensor. This section explained the three major parts of LSPR sensors and the pros and cons of device composition. In the second part, we investigated the chip-based LSPR sensor. With the various reported LSPR sensors, the configuration and measurement results of the sensors can be compared. The third part of our review described the fiber-based LSPR sensor. The fiber-based LSPR sensor, which has the advantage that the light source is protected against water, has shown efficient measurement results in water. The last part introduced the smartphone-based LSPR sensor. The application of LSPR sensors to smartphones is expected to increase in value as the device develops.
This research was supported by the Technology Innovation Program (Project No. 20012362) funded by the Ministry of Trade, Industry & Energy (MOTIE, Korea); Smart Farm Innovation Technology Development Program (421020-03); the Bio & Medical Technology Development Program of the National Research Foundation (NRF) funded by the Ministry of Science & ICT (NRF-2021M3A9I5021439); the Research Program to Solve Urgent Safety Issues of the National Research Foundation of Korea (NRF) funded by the Korean government (Ministry of Science and ICT(MSIT)) (NRF-2020M3E9A1111636); the National R&D Program of National Research Foundation of Korea (NRF) funded by Ministry of Science and ICT (NRF-2021M3H4A4079 276, NRF-2021M3H4A4079381); the Korea Research Institute of Bioscience and Biotechnology (KRIBB) Research Initiative Program (1711 134045).
The authors declare no conflicts of interest.