In this short communication, we propose a surface plasmon resonance (SPR) sensor based on a ZnO
Surface plasmon resonance (SPR) is the resonance for free electrons with collective oscillations in the metal surface when excited by the incident light, and the energy of the incident light would be absorbed by free electrons during the resonance, so that the energy of the output light would be decreased to some extent (Sharma et al., 2012; Homola et al., 1999; Nikitin et al., 1999). The decreasing degree of the output light is related to the incident light, and the SPR angle is the incident light as the output light is decreased to the minimum. The SPR can be excited in a variety of ways, such as prism coupling, grating coupling, and optical fiber coupling, and SPR has been extensively used in sensing of various physical, chemical, and biochemical parameters. The surface plasmon resonance biosensor (SPR biosensor) has a remarkable capability of real-time detection and monitoring of biomolecules (Nikitin et al., 1999; Wilde et al., 1997; Skalska et al., 2010; Dostálek et al., 2006; Kumar et al., 2014). There are various factors that significantly affect the function of the SPR biosensor, which are needed to be considered for designing a stable and highly sensitive SPR biosensor. The two features, the high detection sensitivity and the good SPR peak for better precision, are critical to the function implementation of the SPR biosensor as well as its application. The SPR biosensor has been studied through the past 30 years.
Conductometric gas sensors exploiting semiconductor sensing materials are exclusively used for fabricating gas sensors due to a simple detection principle and easy sensor fabrication (Sharma et al., 2012; Homola et al., 1999; Nikitin et al., 1999; Wilde et al., 1997; Skalska et al., 2010; Dostálek et al., 2006; Kumar et al., 2014; Manikandan et al., 2016; Thanigai Arul et al., 2016; Paulraj et al., 2020; Saasa et al., 2015; Gaur et al., 2021; Paulraj et al., 2021). However, these types of sensors come with a few disadvantages, such as the requirement of a high operating temperature which results in consumption of high power with a poor selectivity. This paves the way for realizing efficient gas sensors which can operate at room temperature which is provided by optical sensors (Homola et al., 1999). SPR-based sensors have several merits, like simple fabrication, room temperature operation, and fast response at lower concentrations of toxic gases. Many researchers have exploited SPR-based sensors in Kretschmann configuration for detecting toxic gases by coating a suitable sensing film on the plasmonic metal (Nikitin et al., 1999; Wilde et al., 1997). The deposition of a gas-sensitive layer on the noble metal surface (excites surface plasmons (SPs) at the metal–dielectric interface) is the major requirement for SPR-based gas sensors whose refractive index changes in contact with the target gas, in turn bringing the variations in resonance parameters which are in correlation with the interacting gas molecule concentration.
NO
The SPR-based NO
In the present work, variation in optical properties of gas-sensitive thin film (ZnO) with interaction of toxic gas (NO
An angular interrogation method has been exploited to record the SPR reflectance in Kretschmann configuration where Au thin film (around 40 nm)
was deposited on a BK-7 glass prism (right angled) to support the
propagation of SPs at the prism
Physical parameter for the growth of the ZnO thin film. Growth using R.F. magnetron sputtering.
R.F. magnetron sputtering to grow the ZnO
All the technical information regarding the growth of the ZnO thin film is given in Table 1, where the films were prepared by using R.F. magnetron sputtering with a constant thickness of 200 nm on an Au-coated glass prism for sensing applications and the experimental schematic figure shown in Fig. 1.
SPR reflectance curve for prism
The primary application of ZnO thin film for the SPR sensor was as a sensing layer for gas detection. Generally, selection of material for sensing a
particular gas is determined by the interaction of its surface-active side
formed by ions O
The observed SPR reflectance curve (symbols) for prism
The as-prepared sensor structure (i.e., prism
Mechanism of the prism
Panel
This is because of the change in the optical properties of the sensing dielectric layer (i.e., ZnO thin film) in terms of refractive index due to
adsorption of oxidizing NO
The gas-sensing measurements made in the dynamic mode shown in Fig. 5a indicate the change in reflectance for the prism
Recently, recent work has been attempted for the same research group, with various metal oxides, dielectric matrix groups, polymerics blended with metals, and SPR-based metals core-shell structures used to detect the different chemical gas vapors (Manikandan et al., 2016; Thanigai Arul et al., 2016; Paulraj et al., 2020; Saasa et al., 2015; Gaur et al., 2021; Paulraj et al., 2021).
The SPR technique has been effectively used for monitoring the change in dielectric properties of semiconducting hybrid thin films (ZnO
This research has used Origin Scientific Software, available at
The data will be made available upon request to the corresponding author.
RG initiated the experiment to form the thin films by the sputtering unit. HMP assisted in the materials collection and ideas for a further stage of the experiment. EM compiled the results analysis and data processing to make a full shape of the manuscript write-up.
The authors declare that they have no conflict of interest.
The authors are thankful to the University of Delhi for providing a facility to carry out the research work.
This paper was edited by Nobutito Imanaka and reviewed by two anonymous referees.