A plasmonic silicon carbide nanorings based sensor for petroleum derivatives refractive index

Abstract

The application relates to a petroleum derivative refractive index sensor based on a plasma silicon carbide nanoring, which comprises a tunable laser, a silicon carbide nanoring, an SPR layer, a sensitizing layer, a tapered optical fiber, a substrate and a spectrum analyzer; the tunable laser, the tapered optical fiber and the spectrum analyzer are sequentially connected; the silicon carbide nanoring, the SPR layer, the sensitizing layer and the tapered optical fiber are arranged on the substrate; the silicon carbide nanoring is arranged directly above a tapered region of the tapered optical fiber; the SPR layer is arranged around the outer wall of the silicon carbide nanoring; the sensitizing layer is arranged around the outer wall of the SPR layer; and the silicon carbide nanoring is an echo wall mode nanoring. The refractive index sensor provided by the application has the advantages of simple structure, small volume, easy integration, high stability and the like, and the sensitivity can reach 789.8 nm / RIU; the refractive index sensor can be used not only for petroleum derivative detection, but also can be widely applied to the fields of biomedical detection, environmental monitoring, chemical analysis and the like.

Description

Technical Field

[0001] This invention relates to the field of refractive index sensor technology, specifically providing a petroleum derivative refractive index sensor based on plasma silicon carbide nanorings, for achieving high-sensitivity detection of petroleum derivatives (including n-butanol, ethanol, glycerol, benzene, styrene, and nitrobenzene). Background Technology

[0002] In the field of petrochemical testing, refractive index sensors have irreplaceable value. Petroleum derivatives include various substances such as hydrocarbons, alcohols, and aromatic compounds, each with a unique refractive index. Refractive index sensors can quickly and accurately measure the refractive index of petroleum derivatives, and then, combined with a pre-established refractive index-composition database, the specific petroleum derivative can be inferred.

[0003] However, existing technologies have significant limitations: while surface plasmon resonance (SPR) refractive index sensors offer high sensitivity, the intrinsic ohmic loss of the metal thin film exacerbates resonance attenuation, limiting the localization of the optical field and resulting in insufficient detection resolution; whispering-gallery mode optical microcavity refractive index sensors, although capable of achieving ultra-high quality factors (Q>10), still suffer from limitations. 5 However, the sensitivity of traditional medium-based optical microcavity refractive index sensors is mostly limited to 70-200 nm / RIU. Specifically, for metal-based SPR sensors, although the gold or silver thin film structure used has an advantage in sensitivity, it is difficult to distinguish petroleum derivatives with small refractive index differences, and the exposed metal surface is easily oxidized and sulfided in organic solvents, which seriously affects long-term stability. Summary of the Invention

[0004] To address the aforementioned shortcomings, this invention provides a petroleum derivative refractive index sensor based on plasma silicon carbide nanorings. This sensor boasts advantages such as simple structure, small size, high quality factor, and high sensitivity. It can detect petroleum derivatives such as butanol, ethylene glycol, glycerol, benzene, styrene, and nitrobenzene, and has broad application prospects in fields such as petrochemicals, environmental monitoring, drug detection, and explosive material identification.

[0005] The technical solution adopted in this invention is as follows:

[0006] A petroleum derivative refractive index sensor based on plasma-enhanced silicon carbide nanorings includes a tunable laser, a silicon carbide nanoring, an SPR layer, a sensitizing layer, a tapered optical fiber, a substrate, and a spectrometer. The tunable laser, the tapered optical fiber, and the spectrometer are sequentially connected. The silicon carbide nanoring, the SPR layer, the sensitizing layer, and the tapered optical fiber are all disposed on the substrate. The silicon carbide nanoring is positioned directly above the tapered region of the tapered optical fiber. The SPR layer surrounds the outer wall of the silicon carbide nanoring. The sensitizing layer surrounds the outer wall of the SPR layer. The silicon carbide nanoring is a whispering-gallery mode nanoring.

[0007] The silicon carbide nanorings form a whispering-gallery optical microcavity, allowing the laser beam meeting the resonance condition to oscillate multiple times within the microcavity. Due to the excellent physical and chemical properties of silicon carbide, sensors based on silicon carbide nanorings exhibit good robustness, stability, and repeatability. The SPR layer generates a plasmonic effect on the outer wall of the silicon carbide nanorings, enhancing their sensitivity. The sensitizing layer, made of titanium dioxide, enhances the local electric field intensity through its high refractive index and sharpens the plasmonic resonance peak, thereby improving the sensor's detection sensitivity and resolution. Furthermore, titanium dioxide protects the SPR layer from oxidation and corrosion, extending the sensor's lifespan. The tunable laser acts as a light source, generating resonant light that resonates within the plasma-coated silicon carbide nanorings to form a whispering-gallery mode. The tapered fiber couples the tunable laser beam into the silicon carbide nanorings. The spectrometer records and analyzes the whispering-gallery mode transmission spectrum at the output of the tapered fiber-silicon carbide nanoring coupling device.

[0008] The working principle of this invention is as follows: When the sensor is working, a silicon carbide nanoring integrating an SPR layer and a sensitivity-enhancing layer is immersed in the petroleum derivative to be tested. Laser light emitted from a tunable laser is incident from the input end of a tapered optical fiber. When the light propagates to the coupling point in the tapered region, an evanescent wave coupling effect occurs: some of the light energy is coupled into the silicon carbide nanoring, while the remaining light continues to propagate along the tapered optical fiber and is output from the output end. If the light coupled into the silicon carbide nanoring satisfies the whispering-gallery mode resonance condition... Where R is the outer radius of the nanoring, α is determined by the thickness of the sensitizing layer (α = 0.21-0.23), and n SiC Is and Here, m represents the refractive index of the silicon carbide nanoring and the sensitizing layer, respectively, and λ represents the resonant wavelength of the m-th order. Light is coherently enhanced within the silicon carbide nanoring, and light whose wavelength does not meet the resonance condition is output from the coupling point. The plasmon resonance generated by the SPR layer couples with the whispering gallery mode to form a hybrid mode. The sensitizing layer further localizes the light field through its high refractive index, significantly improving sensitivity. By monitoring the shift in the resonant wavelength in the transmission spectrum and combining it with a pre-calibrated refractive index-wavelength shift correspondence, the spectrometer can qualitatively identify the type of petroleum derivative being tested.

[0009] According to a preferred embodiment of the present invention, the SPR layer comprises a titanium nitride adhesion layer and a gold nanoparticle layer. The advantage of this design is that the pre-deposited titanium nitride adhesion layer solves the problem of insufficient adhesion at the silicon carbide-gold interface, thereby improving the adhesion of the gold layer and preventing sensor delamination failure in fluid environments. The synergistic effect of the SPR layer and the silicon carbide nanorings not only significantly improves the sensor's detection sensitivity through localized surface plasmon resonance, but also maintains the high quality factor of the whispering-gallery mode, achieving synergistic optimization of high sensitivity and high-resolution detection.

[0010] According to a preferred embodiment of the present invention, the sensitizing layer is a titanium dioxide thin film layer. The advantage of this design is that the high refractive index of titanium dioxide effectively enhances the local electric field intensity, resulting in a significant sharpening effect on the plasmon resonance peak, thereby improving the sensor sensitivity by more than 30%. Simultaneously, the excellent chemical stability of titanium dioxide forms a protective barrier, preventing oxidation and corrosion of the SPR layer metal material, allowing the sensor to maintain long-term stability in organic solvent environments. Furthermore, the bandgap matching characteristics between titanium dioxide and silicon carbide nanorings can further optimize the optical field localization effect, achieving a synergistic improvement in sensitivity and stability.

[0011] According to a preferred embodiment of the present invention, the thickness W of the SPR layer Au The wavelength is 16-19nm, with 18nm being preferred.

[0012] According to a preferred embodiment of the present invention, the outer wall diameter D1 of the silicon carbide nanoring is 0.8-1.8 μm and the thickness W1 is 115-125 nm.

[0013] According to a preferred embodiment of the present invention, the thickness W of the sensitizing layer Ti The wavelength is 5-10nm, with 8nm being preferred.

[0014] According to a preferred embodiment of the present invention, the distance G from the outer wall of the sensitizing layer to the straight segment of the tapered region in the tapered optical fiber is 205-220 nm, preferably 210 ± 5 nm.

[0015] According to a preferred embodiment of the present invention, the height H of the silicon carbide nanorings is 50-100 nm, preferably 60-80 nm.

[0016] According to a preferred embodiment of the present invention, the height of the SPR layer is 90% to 110% of the height of the silicon carbide nanorings, preferably 96% to 104%.

[0017] According to a preferred embodiment of the present invention, the height of the sensitizing layer is 90% to 110% of the height of the silicon carbide nanorings, preferably 96% to 104%.

[0018] According to a preferred embodiment of the present invention, the diameter D2 of the straight segment of the tapered region in the tapered optical fiber is 80-90 nm.

[0019] According to a preferred embodiment of the present invention, the substrate is a silicon substrate with a surface roughness Ra ≤ 0.5 nm or a hydroxyl content ≤ 5 per nm. 2 The silicon dioxide substrate.

[0020] The beneficial effects of this invention are:

[0021] 1. High sensitivity: The whispering-gallery mode resonance of silicon carbide nanorings is extremely sensitive to changes in refractive index. Combined with the enhancement effect of the SPR layer and the sensitizing layer, the sensitivity of the sensor is significantly improved.

[0022] 2. High selectivity: By optimizing the materials and structure of the SPR layer and the sensitizing layer, the sensor can effectively distinguish different types of petroleum derivatives.

[0023] 3. Structural advantages: The sensor adopts an integrated design, which is easy to miniaturize and mass-produce, and is suitable for applications with demanding space requirements such as microfluidic chips.

[0024] 4. Stability and repeatability: Silicon carbide materials have excellent physical and chemical stability, and the sensor performs stably during long-term use, with repeatable measurement results.

[0025] 5. Wide range of applications: This sensor can be used not only for the detection of petroleum derivatives, but also for biomedical detection, environmental monitoring, chemical analysis and other fields. Attached Figure Description

[0026] Figure 1 This is a top view schematic diagram of a petroleum derivative refractive index sensor based on plasma silicon carbide nanorings provided by the present invention.

[0027] Figure 2 yes Figure 1 The diagram shown is a cross-sectional view along the AA direction of a petroleum derivative refractive index sensor based on plasma silicon carbide nanorings provided by the present invention.

[0028] Figure 3This is a radial mode field distribution diagram of the whispering-gallery mode of a petroleum derivative refractive index sensor based on plasma silicon carbide nanorings provided by the present invention.

[0029] Figure 4 This is a tangential mode field distribution diagram of the whispering-gallery mode of a petroleum derivative refractive index sensor based on plasma silicon carbide nanorings provided by the present invention.

[0030] Figure 5 This is a schematic diagram showing the relationship between the resonant wavelength of a petroleum derivative refractive index sensor based on plasma silicon carbide nanorings and the refractive index of the surrounding medium being measured, provided by the present invention.

[0031] 1. Substrate; 2. Silicon carbide nanorings; 3. SPR layer; 4. Sensitizing layer; 5. Tapered fiber input end; 6. Tapered fiber; 7. Coupling point; 8. Tapered fiber output end; 9. Tunable laser; 10. Spectrometer. Detailed Implementation

[0032] The present invention will be further described below with reference to the embodiments and accompanying drawings, but is not limited thereto.

[0033] Example 1

[0034] A petroleum derivative refractive index sensor based on plasma-enhanced silicon carbide nanorings, such as Figure 1 As shown, the device includes a tunable laser 9, a silicon carbide nanoring 2, an SPR layer 3, a sensitizing layer 4, a tapered optical fiber 6, a substrate 1, and a spectrometer 10; the tunable laser 9, the tapered optical fiber 6, and the spectrometer 10 are connected in sequence; the silicon carbide nanoring 2, the SPR layer 3, the sensitizing layer 4, and the tapered optical fiber 6 are all disposed on the substrate 1; the silicon carbide nanoring 2 is disposed directly above the tapered region in the tapered optical fiber 6; the SPR layer 3 surrounds the outer wall of the silicon carbide nanoring 2; the silicon carbide nanoring 2 is a whispering-gallery mode nanoring.

[0035] In this embodiment, substrate 1 is a silicon substrate with a surface roughness Ra ≤ 0.5 nm or a hydroxyl content ≤ 5 per nm. 2 The silicon dioxide substrate.

[0036] The silicon carbide nanoring 2 serves to form a whispering-gallery optical microcavity, allowing the laser, meeting the resonance conditions, to oscillate multiple times within the microcavity. Due to the excellent physical and chemical properties of silicon carbide, the sensor based on the silicon carbide nanoring exhibits good robustness, stability, and repeatability. The SPR layer 3 generates a plasma effect on the outer wall of the silicon carbide nanoring 2, improving its sensitivity. The sensitizing layer 4, made of titanium dioxide, enhances the local electric field intensity through its high refractive index characteristics and sharpens the plasma resonance peak, thereby improving the sensor's detection sensitivity and resolution. Furthermore, titanium dioxide protects the SPR layer from oxidation and corrosion, extending the sensor's lifespan. The tunable laser 9 acts as a light source to generate resonant light, resonating within the plasma silicon carbide nanoring to form a whispering-gallery mode. The tapered optical fiber 6 couples the laser light from the tunable laser 9 into the silicon carbide nanoring 2. The spectrometer 10 monitors the shift in the resonant wavelength in the transmission spectrum to identify the refractive index and type of the petroleum derivative being tested.

[0037] The working principle of this invention is as follows: When the sensor is working, a silicon carbide nanoring 2 integrating an SPR layer 3 and a sensitizing layer 4 is immersed in the petroleum derivative to be tested. Laser light emitted from a tunable laser 9 is incident from the input end 5 of a tapered optical fiber. When the light propagates to the coupling point 7 in the tapered region, an evanescent wave coupling effect occurs: some of the light energy is coupled into the silicon carbide nanoring 2, and the remaining light continues to propagate along the tapered optical fiber 6 and is output from the output end 8. If the light coupled into the silicon carbide nanoring 2 satisfies the whispering-gallery mode resonance condition... Where R is the outer radius of the nanoring, α is determined by the thickness of the sensitizing layer (α = 0.21-0.23), and n SiC Is and Here, m represents the refractive index of the silicon carbide nanoring 2 and the sensitizing layer 4, respectively, and λ represents the resonant wavelength of the m-th order. Light is coherently enhanced in the silicon carbide nanoring 2, and light whose wavelength does not meet the resonance condition is output from the coupling point 7. The plasma resonance generated by the SPR layer 3 couples with the whispering gallery mode to form a mixed mode. The sensitizing layer 4 further localizes the light field through its high refractive index, significantly improving the sensitivity. The spectrometer 10 can identify the refractive index and type of the petroleum derivative to be tested by monitoring the shift of the resonant wavelength in the transmission spectrum and combining it with the pre-calibrated refractive index-wavelength shift correspondence.

[0038] SPR layer 3 includes a titanium nitride adhesion layer and a gold nanoparticle layer. The plasma silicon carbide nanoring structure provided in this embodiment is based on a 4H-SiC wafer. A cylindrical microdisk is formed by femtosecond laser two-photon etching. The central region of the microdisk is selectively removed by chloride-based reactive ion etching to form silicon carbide nanoring 2. A gold nanoparticle layer is deposited on the outer wall of the nanoring by magnetron sputtering to obtain the structure in this embodiment. Figure 2 for Figure 1 A cross-sectional view along the AA direction, as shown below. Figure 2 As shown, the thickness W of SPR layer 3 Au The thickness of the silicon carbide nanoring 2 is 16-19 nm, preferably 18 nm; the outer wall diameter D1 of the silicon carbide nanoring 2 is 0.8-1.8 μm, and the thickness W1 is 115-125 nm; the thickness W of the sensitizing layer 4 is... Ti The wavelength is 5-10nm, preferably 8nm. The advantage of this design is that it has a simple and compact structure, is easy to fabricate, has a smaller device size, saves space and reduces the amount of test medium used.

[0039] The height H of the silicon carbide nanoring 2 is 50-100 nm, preferably 60-80 nm.

[0040] The height of the SPR layer 3 is 90% to 110% of the height of the silicon carbide nanorings, preferably 96% to 104%.

[0041] The height of the sensitizing layer 4 is 90% to 110% of the height of the silicon carbide nanorings, preferably 96% to 104%.

[0042] The distance G from the outer wall of SPR layer 3 to the straight segment of the tapered region in tapered optical fiber 6 is 205-220nm, preferably 210±5nm; the diameter D2 of the straight segment of the tapered region in tapered optical fiber 6 is 80-90nm.

[0043] Since the gold layer and the TiN adhesion layer form a metal-semiconductor heterojunction, its dielectric response needs to be described using the Maxwell-Garnett effective dielectric theory:

[0044]

[0045] In formula (I), ε TiN and ε Au ε represents the dielectric constants of titanium nitride and gold, respectively, and f is the volume fraction of gold nanoparticles.

[0046] Figure 3 The radial mode field distribution diagram of the whispering-gallery mode of a petroleum derivative refractive index sensor based on plasma-enhanced silicon carbide nanorings provided by this invention. Figure 4 The tangential mode field distribution diagram of the whispering-gallery mode of a petroleum derivative refractive index sensor based on plasma silicon carbide nanorings provided by this invention, with parameters set as follows: Figure 2 The above is consistent. By Figure 3 and Figure 4 As can be seen, the whispering galvanic mode field distribution of the plasma silicon carbide ring provided by the present invention moves towards the outer wall, thus the plasma silicon carbide ring structure provided by the present invention is more sensitive to changes in the surrounding refractive index.

[0047] Figure 5Six different petroleum derivatives to be tested (butanol C4H) were displayed. 10 Transmission spectral responses of O (n = 1.3888), ethanol C2H6O (n = 1.4238), glycerol C3H8O3 (n = 1.4636), benzene C6H6 (n = 1.4810), styrene C8H8 (n = 1.5073), and nitrobenzene C6H5NO2 (n = 1.5306). Figure 5 The medium intensity is the normalized intensity of the transmission spectrum, and the peak position corresponds to the resonant wavelength. Each medium exhibits a characteristic resonant peak in its transmission spectrum, and the wavelength position systematically shifts towards longer wavelengths as the refractive index of the medium increases. The resonant peak spacing between different petroleum derivatives is ≥12 nm, meeting the distinguishing requirements. When the medium is changed from low-refractive-index butanol to high-refractive-index nitrobenzene, the resonant wavelength redshifts from 704 nm to 816 nm, a net shift of 112 nm. According to the sensor sensitivity definition S = Δλ / Δn, where Δλ is the resonant wavelength shift and Δn is the change in the refractive index of the medium, the calculated sensitivity of this structure is 789.8 nm / RIU. Among the published literature on sensor sensitivity, such as Meng Zhang, et al. Hybrid plasmonic microcavity with an air-filled gap for sensing applications[J]. Optics Communications, 2016, 380:6-9, the sensitivity of the plasma whispering-gallery mode microcavity sensor is 100 nm / RIU, and the quality factor is 3062. Therefore, the plasma silicon carbide nanoring structure provided by this invention can significantly improve the sensitivity of the refractive index sensor while maintaining the high quality factor in the microcavity.

Claims

1. A petroleum derivative refractive index sensor based on plasma-enhanced silicon carbide nanorings, characterized in that, The device includes a tunable laser, a silicon carbide nanoring, a SPR layer, a sensitizing layer, a tapered optical fiber, a substrate, and a spectrometer. The tunable laser, tapered optical fiber, and spectrometer are connected sequentially. The silicon carbide nanoring, SPR layer, sensitizing layer, and tapered optical fiber are all disposed on the substrate. The silicon carbide nanoring is disposed directly above the tapered region of the tapered optical fiber. The SPR layer includes a titanium nitride adhesion layer and a gold nanoparticle layer, which are disposed around the outer wall of the silicon carbide nanoring. The sensitizing layer is a titanium dioxide thin film, which is disposed around the outer wall of the SPR layer. The silicon carbide nanoring is a whispering-gallery mode nanoring. The silicon carbide nanoring, SPR layer, and sensitizing layer form a three-layer coaxial structure. The three-layer coaxial structure is disposed directly above the tapered region of the tapered optical fiber.

2. The petroleum derivative refractive index sensor based on plasma-enhanced silicon carbide nanorings according to claim 1, characterized in that, The thickness W of the SPR layer Au The wavelength is 16-19nm, with 18nm being preferred.

3. The petroleum derivative refractive index sensor based on plasma-enhanced silicon carbide nanorings according to claim 1, characterized in that, The outer wall diameter D1 of the silicon carbide nanoring is 0.8-1.8 μm, and the thickness W1 is 115-125 nm.

4. The petroleum derivative refractive index sensor based on plasma-enhanced silicon carbide nanorings according to claim 1, characterized in that, The thickness W of the sensitizing layer Ti The wavelength is 5-10nm, with 8nm being preferred.

5. The petroleum derivative refractive index sensor based on plasma-enhanced silicon carbide nanorings according to claim 1, characterized in that, The distance G from the outer wall of the sensitizing layer to the straight line segment of the tapered region in the tapered optical fiber is 150-180nm, preferably 165±5nm.

6. The petroleum derivative refractive index sensor based on plasma-enhanced silicon carbide nanorings according to claim 1, characterized in that, The height H of the silicon carbide nanorings is 50-100 nm, preferably 60-80 nm.

7. The petroleum derivative refractive index sensor based on plasma-enhanced silicon carbide nanorings according to claim 1, characterized in that, The height of the SPR layer is 90% to 110% of the height of the silicon carbide nanorings, preferably 96% to 104%.

8. The petroleum derivative refractive index sensor based on plasma-enhanced silicon carbide nanorings according to claim 1, characterized in that, The height of the sensitizing layer is 90% to 110% of the height of the silicon carbide nanorings, preferably 96% to 104%.

9. A petroleum derivative refractive index sensor based on plasma-enhanced silicon carbide nanorings according to claim 1, characterized in that, The diameter D2 of the straight segment in the tapered region of the tapered optical fiber is 80-90 nm.

10. A petroleum derivative refractive index sensor based on plasma-enhanced silicon carbide nanorings according to claim 1, characterized in that, The substrate is a silicon substrate with a surface roughness Ra ≤ 0.5 nm or a hydroxyl content ≤ 5 per nm. 2 The silicon dioxide substrate.

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