Open Access
Add to BibSonomy
Abstract
As an interesting phenomenon in the field of surface enhanced Raman spectroscopy (SERS), the plasmon-driven catalytic reaction (PDSC) induced by plasmonic hot electrons has great value in the research of novel properties of surface plasmons and accuracy of SERS applications. In this work, an optoplasmonic sandwich hybrid structure is proposed for studying PDSC of $p$-aminothiophenol (PATP) molecules, which is composed of Au film, metal organic frameworks (MOFs) nanoparticles, zeolithic imidazolate (ZIF-8), and single ${{\rm SiO}_2}$ microsphere (Au ${\rm film}@{\rm MOFs}@{{\rm SiO}_{2}}$). In order to analyze the novel, to the best of our knowledge, phenomenon of the PDSC in this micro-nano structure, the hot electron generation in the MOF without the plasmonic core is carried out by combining the plasmonic enhancement of gold film with the light concentration of microspheres. Experimental data show that the PDSC reactions is dependent on the size of the MOFs nanoparticle and the size of the ${{\rm SiO}_2}$ microsphere, which is confirmed by the electromagnetic field simulation of the finite-difference time-domain method (FDTD). Our work not only strengthens the understanding of surface plasmon in optoplasmonic hybrid structures but also has broad application prospects in the SERS and plasmon-driven catalytic fields.
© 2023 Optica Publishing Group
1. INTRODUCTION
In recent years, with the development of nanoscience, surface plasmons in metal nanostructures have attracted a wide range of interests from researchers [1]. Surface plasmons refer to the charge-density wave formed by the collective oscillation of free electrons in the metal surface excited by light [2,3]. Surface-enhanced Raman spectroscopy (SERS) technology achieves high sensitivity through the enhancement of huge electro-magnetic fields induced by surface plasmons, which has been widely used in many fields such as biochemical analysis, food security, environmental pollution, and surface enhanced fluorescence [4–9]. In recent years, a new phenomenon in which the SERS spectrum of certain molecules changes, which is the so-called surface plasmon catalytic reaction. It has been reported that the dimercaptoazobenzen (DMAB) molecule can be produced by $p$-aminothiophenol (PATP) or 4-nitrobenzenethiol (4-NBT) at the metal surface driven by the surface plasmon [10–13]. In the same year, it was theoretically proven that Raman peaks at 1143, 1390, and $1432\;{\rm cm}^{- 1}$ come from the newly generated DMAB molecule [14,15]. Therefore, the emergence of this new field of PDSC is very helpful for the study of surface plasmon properties and SERS applications.
The mechanism of the plasmonic-driven catalytic (PDSC) reaction is closely related to the material, shape, size, configuration, and environment of metal nanostructures. Numerous works have reported PDSC in metal nanostructures with different configurations, such as metal (Ag, Au, and Cu) nanoparticles, Ag nanowires, metal (Ag, Au, and Cu) thin films, and bimetallic nanocrystals [16–20]. Among them, particle systems on thin films have been widely used to study surface plasmons. In this system, the nanoscale gap between the particle and the film can provide a large field enhancement [21]. Specifically, certain designs used the nanoscale coupled gap resonators to design the plasmonic refractive index sensors based on the gap plasmon resonance (GPR) effect, which can significantly enhance the resonator’s surface plasmon polaritons (SPPs) mode [22,23]. In recent years, optoplasmonic systems with synergistic effects of dielectric microstructures and metal plasmonic nanostructures have been widely developed [24–26]. The optoplasmonic structure is composed of plasmonic nanostructures embedded in a dielectric photonic microenvironment, which is able to overcome the limitations of a single structure due to the complementary optical properties of plasmonic and dielectric photonic elements [27]. This photoplasmonic hybrid structure combines photons in micro-structures and plasmons in nanostructures, which has excellent optical performance beyond traditional photonic and plasmonic systems. In the dielectric microstructure, ${{\rm SiO}_2}$ microspheres with efficient light-focusing effects are used as microlenses. It has been found that ${{\rm SiO}_2}$ microspheres contributed to the hot electron excitation [28,29]. Therefore, it is critical to study PDSC in photoplasmonic structures.
In previous reports, it was found that PDSC reactions can occur at metal-graphene [30], metal-${{\rm TiO}_2}$ [31], metal-${{\rm MoS}_2}$ [32], and other metal interfaces. Recently, metal organic frameworks (MOFs) are an interesting class of supramolecular materials with infinite lattices and highly ordered periodic networks using metal cations or clusters as nodes and organic ligands as bridging agents. MOFs, especially the zeolitic imidazolate frameworks (ZIF-8), have the advantages of high porosity, large specific surface area, and mature synthesis methods [33]. MOFs nanoparticles have been widely reported in the field of SERS, for example, in drug delivery, selective gas adsorption, and separation and sensitive SERS detection [34–37]. At present, there are few reports on the study of PDSC in MOF materials [38]. Since MOF materials have the effect of enriching molecules, it is focused on the PDSC effect of the MOF materials in photoplasmonic structures. Therefore, it is important to study the PDSC when a novel micro-nano structure composed of pure MOF materials and ${{\rm SiO}_2}$ microspheres is used as a SERS substrate.
Here, a photoplasmonic sandwich structure is fabricated as a SERS substrate, which consists of an Au thin film on the bottom, a single ${{\rm SiO}_2}$ microsphere on the top, and MOFs nanoparticles as an intermediate layer. The experimental results demonstrate the PDSC of the PATP molecules in this micro-nano structure. The structure combines the plasmonic enhancement of the gold film and the light-converging effect of the microspheres, which exhibits good catalytic performance for the PATP molecules. In addition, the diameters of the MOFs nanoparticles and the ${{\rm SiO}_2}$ microspheres can affect the PDSC of the PATP molecules. At the same time, it has confirmed experimental results by using the simulated electric field distribution of the FDTD method.
2. METHODS AND MATERIALS
A. Synthesis of MOFs (ZIF-8) Nanoparticles
The silver nanoparticles were prepared by hydrothermal synthesis [39]. The steps involved in coating ZIF-8 on the surface of silver nanoparticles are as follows [40]. In the beginning, add 1 mL of 2-methylimidazole solution (1.32 M) and 0.144 mL of a cetyltrimethylammonium bromide (CTAB) solution (1 mM) dropwise to a beaker and mix well without stirring. Next, 1 mL of ${\rm Zn}{({\rm NO3})_2}$ solution (15 mM) was added to this mixed solution. This mixed solution was made in triplicate with the same experimental procedure. The three batches of mixtures were left to stand at room temperature (25°C) for 1.5 h, 2.5 h and 3.5 h, respectively. Then, free reactants were removed by centrifugation 3 times, and the pellet was dispersed in alcohol. Finally, square nanoparticles of MOFs (ZIF-8) with diameters of 100 nm, 200 nm, and 400 nm were obtained.
B. Characterization and SERS Measurements
The surface morphologies of the MOFs nanoparticles and the ${{\rm SiO}_2}$ were obtained by scanning electron microscope (SEM) (TESCAN MIRA 3FE). All of the SERS data was obtained in a homebuilt Raman microscope system equipped with a 632.8 nm He–Ne laser and an iHR550 spectrometer (Horiba, equipped with a charge-coupled device camera). The Raman signal was gathered via a $\times {100}$ air objective (Olympus). 20 µL of PATP alcohol solution was dropped on the prepared gold film, Au film@MOFs, Au ${\rm film}@{\rm MOFs}@{{\rm SiO}_{2}}$ structure. After waiting for another 30 min, the glass substrate was taken out, and the SERS spectrum was recorded. All experimental data were excited at a wavelength of 632.8 nm, and the integration time was 20 s. Raman spectral images (${5} \times {5}\;{{\unicode{x00B5}{\rm m}}^2}$) were obtained under 0.7 mW laser power.
C. Calculation Details
The electromagnetic field simulations in this work were obtained by the finite-difference time domain FDTD method (Lumerical FDTD solution). The finite-element method (FEM) environment of COMSOL Multiphysics (ver. 6.0; COMSOL) was used to test the proposed explanation for the liquid molecule flow, the adsorption, and the reaction of the MOF structure. The FDTD calculation details and COSMOL calculation details shows in Supporting Information.
Fig. 1. (a) Schematic diagram of the optoplasmonic sandwich hybrid structure in SERS. (b) SEM images of the MOFs nanoparticles of different sizes (left) and single ${{\rm SiO}_2}$ microsphere of different sizes (right). (c) SERS spectra of the PATP molecules obtained with Au film, the Au film@MOFs and the Au ${\rm film}@{\rm MOFs}@\;{{\rm SiO}_{2}}$ as SERS substrates, respectively.
3. RESULTS AND DISCUSSION
Figure 1(a) shows the schematic diagram of the photoplasmonic sandwich hybrid structure, which can be used to analyze the PDSC reaction of the PATP. This SERS substrate is composed of Au thin films, MOFs nanoparticles (ZIF-8), and individual SiO2 microspheres. The SEM images of the MOFs nanoparticles of different sizes on the gold film are shown in Fig. 1(b). The MOFs nanoparticles with diameters of 100 nm, 200 nm, and 400 nm are represented from top to bottom on the left side of Fig. 1(b), and the single ${{\rm SiO}_2}$ microspheres with diameters of 5 µm, 10 µm, and 50 µm are represented from top to bottom on the right side of Fig. 1(b). The SERS spectra collected after dropping PATP molecules on the three SERS substrates are shown in Fig. 1(c). As shown in Fig. 1(c), 1) the Raman signal of the molecule is not detected by dropping PATP molecules at a concentration of ${{10}^{- 3}}{\rm M}$ on Au film. Subsequently, the same concentration of PATP molecules is added dropwise to the Au film@MOFs nanoparticle substrate, and the Raman signal was enhanced, as shown in Fig. 1(c). 2) The SERS spectrum showed that the two bands at 1087 and ${1595}\;{{\rm cm}^{- 1}}$ can be assigned to ${\upsilon _{\text{CS}}}$ and ${\upsilon _{\text{CC}}}$ of the PATP, respectively. This result showed that no plasmon-catalyzed reaction of the PATP molecules took place. Finally, the PATP molecules were added to the Au ${\rm film}@{\rm MOFs}@{{\rm SiO}_{2}}$ structure, and the Raman signal of the PATP molecules was further enhanced and catalyzed to the DMAB molecules, as shown in Fig. 1(c). 3) The four characteristic vibrational bands at 1071,1143, 1392, and ${1436}\;{{\rm cm}^{- 1}}$ can be assigned to ${\upsilon _{\text{CS}}}$, ${\beta _{\text{CH}}}\; + {\upsilon _{\text{CN}}}$, ${\upsilon _{\text{NN}}} + {\upsilon _{\text{CN}}}$, ${\upsilon _{\text{NN}}} + {\beta _{\text{CH}}}$ of the trans-DMAB, respectively. The SERS spectrum clearly showed that the PATP molecules were converted into trans-DMAB. The experimental data show that the optoplasmonic sandwich hybrid structure has excellent SERS activity and catalytic activity.
To further prove the above results, i.e., the feasibility of the Au ${\rm film}@{\rm MOFs}@{{\rm SiO}_{2}}$ structure as the SERS substrate for the PDSC reaction of the PATP molecules, we first combined the Au film with the MOFs nanoparticles as SERS substrates for Raman detection. As shown in Fig. 2(a), MOFs nanoparticles with diameters of 100 nm (MOF 1), 200 nm (MOF 2), and 400 nm (MOF 3), respectively, were used to detect the PATP molecules (${{10}^{- 3}}{\rm M}$). After comparing the three SERS spectra, it was found that the Raman characteristic peaks of the PATP molecules can be significantly enhanced, and new bands emerged when the MOFs nanoparticles with 200 nm diameter were used. This result indicates that the PATP molecule is not fully catalyzed to the DMAB when the MOFs nanoparticles with 200 nm diameter were used. This is a result of the closely spaced MOFs nanoparticles and gaps that can be enriched with analytes.
Fig. 2. (a) SERS spectra obtained by depositing the MOFs nanoparticles with diameters of 100 nm, 200 nm, and 400 nm on the Au film as SERS substrates. (b) The ${{\rm SiO}_{2}}$ microsphere with diameters of 5 µm, 10 µm, and 50 µm were used to detect the PATP molecules (${{10}^{- 3}}\;{\rm M}$). (c) The SERS spectra obtained by depositing ${{\rm SiO}_{2}}$ microspheres with diameters of 5 µm, 10 µm, and 50 µm on the Au film@MOFs nanoparticles with 200 nm diameter used as the SERS substrates.
To demonstrate that the ${{\rm SiO}_2}$ microsphere with a concentrating effect exhibit good SERS effects, the ${{\rm SiO}_2}$ microspheres are dropped onto a gold film of functionalized PATP molecules. As shown in Fig. 2(b), a ${{\rm SiO}_2}$ microsphere with diameters of 5 µm, 10 µm, and 50 µm, respectively, were used to detect the PATP molecules (${{10}^{- 3}}{\rm M}$). It was found that the SERS spectral intensity of the PATP molecules was the strongest when the 50 µm ${{\rm SiO}_2}$ microsphere was deposited on the Au film. At the same time, we also found that the PATP molecule was not catalyzed into the DMAB molecule. Next, the MOFs nanoparticles with enriched molecular action and the ${{\rm SiO}_2}$ microsphere with concentrating action are combined and dropped on the gold film. Then, we dropped ${{\rm SiO}_2}$ microspheres with the diameter of 5 µm, 10 µm, and 50 µm, respectively, on the Au film@MOFs nanoparticles with the MOFs diameter of 200 nm. As shown in Fig. 2(b), the SERS spectral intensity of the PATP molecules is significantly enhanced when 50 µm ${{\rm SiO}_2}$ microsphere is deposited on the Au film@MOFs nanoparticles. The result indicates that the PATP molecules are converted to DMAB.
Proving that the MOF structure significantly improves the ability to concentrate liquids can be explained by liquid flow dynamics. When the liquid passes through the porous lactate dehydrogenase (LDH) medium, the liquid molecules are concentrated in the MOF structure. To test the effect of the liquid analyte concentration at any given time point in a diffusion kinetics MOF structure, the local accumulation rule is given by the one-dimensional Fick’s second law, $\partial {\rm c}/\partial {\rm t} = Da(({\partial ^2}c)/\def\LDeqbreak{}(\partial {x^2}))$ [41], where $c$ is the liquid concentration, $t$ is time, $Da$ is the diffusion coefficient of the binary molecules in the liquid, and $x$ is the distance along the flow axis. The $Da$ is influenced by the structure of the fluid medium, such as porosity and pore size distribution. Due to the specific surface area and pore size distribution characteristics of the MOF structure, the MOF structure has better liquid concentration capacity. This equation allows us to calculate the change in the concentration of liquid molecules through the MOF structure. The MOF structure is found to have an adsorption effect on the gas analytes. At the same time, it is also observed that the MOF structure at the 400 nm size has a strong ability to concentrate liquid molecules, as shown in Figs. 3(a)–3(c). These analyses were done in COMSOL Multiphysics software.
Fig. 3. (a), (b), and (c) Simulation concentration change of the MOFs nanoparticles with diameters of 100 nm, 200 nm, and 400 nm. (d), (e), and (f) Electric field distribution of the MOFs nanoparticles with diameters of 100 nm, 200 nm, and 400 nm. (g), (h), and (i) Electric field distribution of the SiO2 microspheres with diameters of 5 µm, 10 µm, and 50 µm.
In order to further verify the above experimental results and analyze the enhancement mechanism, numerical simulations are performed for MOFs nanoparticles of different diameters (100 nm, 200 nm, and 400 nm) using the FDTD method, as shown in Figs. 3(b), 3(d), and 3(f). The gap of the MOFs nanoparticles is 2 nm, and the wavelength of the incident laser is 632.8 nm. It can be seen that the electromagnetic field distribution is stronger for the MOFs nanoparticles with a diameter of 100 nm. However, the enrichment level of the molecules is also affected by the size of the MOFs nanoparticles. Therefore, combining the above factors, it is not difficult to understand that the PATP molecule is not fully catalyzed to the DMAB when the MOFs nanoparticles with 200 nm diameter were used in the experiment. For the Au film@MOFs nanoparticles without the ${{\rm SiO}_2}$, the MOFs nanoparticles with different thickness provide E-field enhancement. This FDTD simulation result also corresponds to the experimental result. This enhancement may be due to the fact that the MOFs as nanoparticles well compensate for the momentum difference of the plasmons on the excitation of the smooth Au film. The gap plasmons at the crevice gap regions (gap plasmons) can all be utilized as highly sensitive SERS substrates. In this system, the nanometer scale gap between the particle and the film provides a hot spot with large field enhancements. In addition, the experimental results show that the larger the ${{\rm SiO}_2}$ microspheres size are, the better the SERS enhancement is achieved, as shown in Fig. 2(b). To verify this conclusion, we performed electric field distribution simulations for ${{\rm SiO}_2}$ microspheres with diameters of 5 µm, 10 µm, and 50 µm [Figs. 3(i), 3(g), and 3(h)]. The dielectric sphere above the Au film@MOFs nanoparticles can effectively guide the incident light to converge near the gaps between the MOFs nanoparticles. Therefore, depositing 50 µm ${{\rm SiO}_2}$ microspheres on the Au film@MOFs nanoparticles can indicate that the PATP molecules are converted to DMAB.
Fig. 4. (a) Reproducibility of the SERS spectra of the PATP molecules (${{10}^{- 3}}\;{\rm M}$) collected at 9 randomly selected spots on the Au ${\rm film}@{\rm MOFs}@{{\rm SiO}_{2}}$ substrate. (b) The signal intensity of the ${1003}\;{{\rm cm}^{- 1}}$ from PATP molecules collected at 9 randomly selected spots on the Au ${\rm film}@{\rm MOFs}@{{\rm SiO}_{2}}$ substrate. (c) The SERS intensity at ${1003}\;{{\rm cm}^{- 1}}$ as a function of the PATP concentrations.
The repeatability and uniformity of the Au ${\rm film}@{\rm MOFs}@\def\LDeqbreak{}{{\rm SiO}_{2}}$ structure in the PDSC of the PATP molecules is analyzed. As shown in Fig. 4(a), the hybrid structure of the photoplasma sandwich provided good spatial uniformity of the PATP molecules and the repeatable SERS signal. Figure 4(b) shows that the relative standard deviation (RSD) of the SERS peak intensity of ${1003}\;{{\rm cm}^{- 1}}$ in 9 measurements is 9.9%. Therefore, this photoplasmonic sandwich hybrid structure substrate provides uniform results with good reproducibility. At the same time, we investigated the quantitative analysis of the SERS intensity in relation to the molecular concentration. Figure 4(c) shows the intensity of the main characteristic Raman peak of the PATP at ${1003}\;{{\rm cm}^{- 1}}$. These data can be represented by a linear relationship of ${\rm I}\;({\rm counts}) = {284}\;{\rm *}\;X(M) + {162},$ where $X$ is the concentration of the PATP, and I is the SERS intensity at ${1003}\;{{\rm cm}^{- 1}}$. The linear regression (${{\rm R}^2}$) of this expression is equal to 0.97, which indicates that the curve has a high degree of linear fit. This result indicates that the PDSC reaction of the PATP molecules can be carried out on Au ${\rm film}@{\rm MOFs}@{{\rm SiO}_{2}}$ substrates. We used the following formula to calculate the enhancement factor [42]:
The concentration used for SERS is ${1} \times {{10}^{- 5}}\;{\rm M}$, and for Normal Raman or reference signal we have used ${1} \times {{10}^{- 2}}\;{\rm M}$ on gold film. The SERS intensity has been collected for ${1003}\;{{\rm cm}^{- 1}}$ peak, which is 423 counts, and from the normal Raman signal it is 340 counts. The enhancement factor calculated according to the formula is ${1.24} \times {{10}^3}$ [43].
4. CONCLUSION
In this work, the optoplasmonic sandwich hybrid structure of a SERS substrate was prepared by using Au film, MOFs nanoparticles, and depositing ${{\rm SiO}_2}$ microspheres. The experimental data demonstrated that the MOFs nanoparticles and single ${{\rm SiO}_2}$ microsphere play important roles in enriching molecules and focusing light in the PDSC reaction. The SERS substrate with this sandwich hybrid structure had the characteristics of high sensitivity and good repeatability. Furthermore, the SERS enhancement effect is strongly dependent on the size of MOFs nanoparticles and the ${{\rm SiO}_2}$ microsphere diameter. Meanwhile, the electromagnetic field simulation also proved this point. Thus, our work not only expands the optoplasmonic research field but also strengthens sensitive SERS analysis in the biochemical field.
Funding
National Science Foundation Project of Chongqing, Chongqing Science and Technology Commission (cstc2019jcyj-msxmX0828); National Natural Science Foundation of China (11974067); Chongqing University’s Large-scale Equipment.
Disclosures
The authors declare no conflicts of interest.
Data availability
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
Supplemental document
See Supplement 1 for supporting content.
REFERENCES
1. S. Yang, X. Dai, B. B. Stogin, and T.-S. Wong, “Ultrasensitive surface-enhanced Raman scattering detection in common fluids,” Proc. Natl. Acad. Sci. USA 113, 268–273 (2016). [CrossRef]
2. K. Kneipp, Y. Wang, H. Kneipp, L. T. Perelman, I. Itzkan, R. R. Dasari, and M. S. Feld, “Single molecule detection using surface-enhanced Raman scattering (SERS),” Phys. Rev. Lett. 78, 1667–1670 (1997). [CrossRef]
3. J. Langer, D. Jimenez de Aberasturi, J. Aizpurua, et al., “Present and future of surface-enhanced Raman scattering,” ACS Nano 14, 28–117 (2020). [CrossRef]
4. B.-Q. Chen, C. Zhang, J. Li, Z.-Y. Li, and Y. Xia, “On the critical role of Rayleigh scattering in single-molecule surface-enhanced Raman scattering via a plasmonic nanogap,” Nanoscale 8, 15730–15736 (2016). [CrossRef]
5. Q. Chen, L. Zhao, H. Liu, Q. Ding, C. Jia, S. Liao, N. Cheng, M. Yue, and S. Yang, “Nanoporous silver nanorods as surface-enhanced Raman scattering substrates,” Biosens. Bioelectron. 202, 114004 (2022). [CrossRef]
6. L. Liang, H. Qu, B. Zhang, J. Zhang, R. Deng, Y. Shen, S. Xu, C. Liang, and W. Xu, “Tracing sialoglycans on cell membrane via surface-enhanced Raman scattering spectroscopy with a phenylboronic acid-based nanosensor in molecular recognition,” Biosens. Bioelectron. 94, 148–154 (2017). [CrossRef]
7. B. Liu, X. Yao, S. Chen, H. Lin, Z. Yang, S. Liu, and B. Ren, “Large-area hybrid plasmonic optical cavity (HPOC) substrates for surface-enhanced Raman spectroscopy,” Adv. Funct. Mater. 28, 1802263 (2018). [CrossRef]
8. A. I. Pérez-Jiménez, D. Lyu, Z. Lu, G. Liu, and B. Ren, “Surface-enhanced Raman spectroscopy: benefits, trade-offs and future developments,” Chem. Sci. 11, 4563–4577 (2020). [CrossRef]
9. C. Zong, M. Xu, L.-J. Xu, T. Wei, X. Ma, X.-S. Zheng, R. Hu, and B. Ren, “Surface-enhanced Raman spectroscopy for bioanalysis: Reliability and challenges,” Chem. Rev. 118, 4946–4980 (2018). [CrossRef]
10. Q. Ding, M. Chen, Y. Fang, Z. Zhang, and M. Sun, “Plasmon-driven Diazo coupling reactions of p-Nitroaniline via −NH2 or −NO2 in atmosphere environment,” J. Phys. Chem. C 121, 5225–5231 (2017). [CrossRef]
11. C. Zhan, X.-J. Chen, Y.-F. Huang, D.-Y. Wu, and Z.-Q. Tian, “Plasmon-mediated chemical reactions on nanostructures unveiled by surface-enhanced Raman spectroscopy,” Acc. Chem. Res. 52, 2784–2792 (2019). [CrossRef]
12. Z. Zhang, P. Xu, X. Yang, W. Liang, and M. Sun, “Surface plasmon-driven photocatalysis in ambient, aqueous and high-vacuum monitored by SERS and TERS,” J. Photochem. Photobiol. C 27, 100–112 (2016). [CrossRef]
13. Z. Zhang, C. Zhang, H. Zheng, and H. Xu, “Plasmon-driven catalysis on molecules and nanomaterials,” Acc. Chem. Res. 52, 2506–2515 (2019). [CrossRef]
14. Y.-F. Huang, D.-Y. Wu, H.-P. Zhu, L.-B. Zhao, G.-K. Liu, B. Ren, and Z.-Q. Tian, “Surface-enhanced Raman spectroscopic study of p-aminothiophenol,” Phys. Chem. Chem. Phys. 14, 8485–8497 (2012). [CrossRef]
15. Y. Fang, Y. Li, H. Xu, and M. Sun, “Ascertaining p,p′-Dimercaptoazobenzene produced from p-aminothiophenol by selective catalytic coupling reaction on silver nanoparticles,” Langmuir 26, 7737–7746 (2010). [CrossRef]
16. Z. Zhang, Y. Fang, W. Wang, L. Chen, and M. Sun, “Propagating surface plasmon polaritons: Towards applications for remote-excitation surface catalytic reactions,” Adv. Sci. 3, 1500215 (2016). [CrossRef]
17. Y. Huang, Y. Fang, Z. Yang, and M. Sun, “Can p,p′-dimercaptoazobisbenzene be produced from p-aminothiophenol by surface photochemistry reaction in the junctions of a Ag nanoparticle–Molecule–Ag (or Au) film?” J. Phys. Chem. C 114, 18263–18269 (2010). [CrossRef]
18. Q. Ding, H. Zhou, H. Zhang, Y. Zhang, G. Wang, and H. Zhao, “3D Fe3O4@Au@Ag nanoflowers assembled magnetoplasmonic chains for in situ SERS monitoring of plasmon-assisted catalytic reactions,” J. Mater. Chem. A 4, 8866–8874 (2016). [CrossRef]
19. J. Li, J. Liu, Y. Yang, and D. Qin, “Bifunctional Ag@Pd-Ag nanocubes for highly sensitive monitoring of catalytic reactions by surface-enhanced Raman spectroscopy,” J. Am. Chem. Soc. 137, 7039–7042 (2015). [CrossRef]
20. Z. Li and D. Kurouski, “Probing the redox selectivity on Au@Pd and Au@Pt bimetallic nanoplates by tip-enhanced Raman spectroscopy,” ACS Photon. 8, 2112–2119 (2021). [CrossRef]
21. C. Zhu, G. Meng, P. Zheng, Q. Huang, Z. Li, X. Hu, X. Wang, Z. Huang, F. Li, and N. Wu, “A hierarchically ordered array of silver-nanorod bundles for surface-enhanced Raman scattering detection of phenolic pollutants,” Adv. Mater. 28, 4871–4876 (2016). [CrossRef]
22. Y. Hong, X. Zhou, B. Xu, Y. Huang, W. He, S. Wang, C. Wang, G. Zhou, Y. Chen, and T. Gong, “Optoplasmonic hybrid materials for trace detection of methamphetamine in biological fluids through SERS,” ACS Appl. Mater. Interf. 12, 24192–24200 (2020). [CrossRef]
23. Y.-F. Chou Chau, T. Y. Ming, C.-T. Chou Chao, R. Thotagamuge, M. R. R. Kooh, H. J. Huang, C. M. Lim, and H.-P. Chiang, “Significantly enhanced coupling effect and gap plasmon resonance in a MIM-cavity based sensing structure,” Sci. Rep. 11, 1–17 (2021). [CrossRef]
24. Y. Hong, W. Ahn, S. V. Boriskina, X. Zhao, and B. M. Reinhard, “Directed assembly of optoplasmonic hybrid materials with tunable photonic–plasmonic properties,” J. Phys. Chem. Lett. 6, 2056–2064 (2015). [CrossRef]
25. S. Hou, J. Wang, C. Wang, Y. Yuan, X. Zhang, Y. Huang, and S. Yan, “Sandwich optoplasmonic hybrid structure for surface enhanced Raman spectroscopy,” Spectrochim. Acta A 264, 120252 (2022). [CrossRef]
26. L. Ju, J. Shi, C. Liu, Y. Huang, and X. Sun, “Optoplasmonic film for SERS,” Spectrochim. Acta A 255, 119698 (2021). [CrossRef]
27. Y. Hong, M. Pourmand, S. V. Boriskina, and B. M. Reinhard, “Enhanced light focusing in self-assembled optoplasmonic clusters with subwavelength dimensions,” Adv. Mater. 25, 115–119 (2013). [CrossRef]
28. A. Le Beulze, S. Gomez-Graña, H. Gehan, S. Mornet, S. Ravaine, M. Correa-Duarte, L. Guerrini, R. A. Alvarez-Puebla, E. Duguet, E. Pertreux, A. Crut, P. Maioli, F. Vallée, N. Del Fatti, O. Ersen, and M. Treguer-Delapierre, “Robust raspberry-like metallo-dielectric nanoclusters of critical sizes as SERS substrates,” Nanoscale 9, 5725–5736 (2017). [CrossRef]
29. P. Wang, W. Liu, W. Lin, and M. Sun, “Plasmon-exciton co-driven surface catalytic reaction in electrochemical G-SERS,” J. Raman Spectrosc. 48, 1144–1147 (2017). [CrossRef]
30. Z.-G. Dai, X.-H. Xiao, W. Wu, Y.-P. Zhang, L. Liao, S.-S. Guo, J.-J. Ying, C.-X. Shan, M.-T. Sun, and C.-Z. Jiang, “Plasmon-driven reaction controlled by the number of graphene layers and localized surface plasmon distribution during optical excitation,” Light Sci. Appl. 4, e342 (2015). [CrossRef]
31. M. Wang, X. Pang, D. Zheng, Y. He, L. Sun, C. Lin, and Z. Lin, “Nonepitaxial growth of uniform and precisely size-tunable core/shell nanoparticles and their enhanced plasmon-driven photocatalysis,” J. Mater. Chem. A 4, 7190–7199 (2016). [CrossRef]
32. C. Zhang, Z. Li, S. Qiu, W. Lu, M. Shao, C. Ji, G. Wang, X. Zhao, J. Yu, and Z. Li, “Highly ordered arrays of hat-shaped hierarchical nanostructures with different curvatures for sensitive SERS and plasmon-driven catalysis,” Nanophotonics 11, 33–44 (2022). [CrossRef]
33. L.-W. Chen, Y.-C. Hao, Y. Guo, Q. Zhang, J. Li, W.-Y. Gao, L. Ren, X. Su, L. Hu, N. Zhang, S. Li, X. Feng, L. Gu, Y.-W. Zhang, A.-X. Yin, and B. Wang, “Metal–organic framework membranes encapsulating gold nanoparticles for direct plasmonic photocatalytic nitrogen fixation,” J. Am. Chem. Soc. 143, 5727–5736 (2021). [CrossRef]
34. H. Lai, G. Li, F. Xu, and Z. Zhang, “Metal–organic frameworks: opportunities and challenges for surface-enhanced Raman scattering–a review,” J. Mater. Chem. C 8, 2952–2963 (2020). [CrossRef]
35. J. W. M. Osterrieth, D. Wright, H. Noh, C.-W. Kung, D. Vulpe, A. Li, J. E. Park, R. P. Van Duyne, P. Z. Moghadam, J. J. Baumberg, O. K. Farha, and D. Fairen-Jimenez, “Core–shell gold Nanorod@Zirconium-based metal–organic framework composites as in situ size-selective Raman probes,” J. Am. Chem. Soc. 141, 3893–3900 (2019). [CrossRef]
36. H. Y. F. Sim, H. K. Lee, X. Han, C. S. L. Koh, G. C. Phan-Quang, C. L. Lay, Y. C. Kao, I. Y. Phang, E. K. L. Yeow, and X. Y. Ling, “Concentrating immiscible molecules at Solid@MOF interfacial nanocavities to drive an inert gas–liquid reaction at ambient conditions,” Angew. Chem., Int. Ed. Engl. 57, 17058–17062 (2018). [CrossRef]
37. H. Sun, S. Cong, Z. Zheng, Z. Wang, Z. Chen, and Z. Zhao, “Metal–organic frameworks as surface enhanced Raman scattering substrates with high tailorability,” J. Am. Chem. Soc. 141, 870–878 (2018). [CrossRef]
38. X. Xie, Y. Zhang, L. Zhang, J. Zheng, Y. Huang, and H. Fa, “Plasmon-driven interfacial catalytic reactions in plasmonic MOF nanoparticles,” Anal. Chem. 93, 13219–13225 (2021). [CrossRef]
39. F. Chu, S. Yan, J. Zheng, L. Zhang, H. Zhang, K. Yu, X. Sun, A. Liu, and Y. Huang, “A simple laser ablation-assisted method for fabrication of superhydrophobic SERS substrate on Teflon film,” Nano. Res. Lett. 13, 244 (2018). [CrossRef]
40. K. Yang, S. Zong, Y. Zhang, Z. Qian, Y. Liu, K. Zhu, L. Li, N. Li, Z. Wang, and Y. Cui, “Array-assisted SERS microfluidic chips for highly sensitive and multiplex gas sensing,” ACS Appl. Mater. Interf. 12, 1395–1403 (2019). [CrossRef]
41. H. T. Ali, A. Mateen, F. Ashraf, M. R. Javed, A. Ali, K. Mahmood, A. Zohaib, N. Amin, S. Ikram, and M. Yusuf, “A new SERS substrate based on Zn2GeO4 nanostructures for the rapid identification of E. Coli and methylene blue,” Ceram. Int. 47, 27998–28003 (2021). [CrossRef]
42. E. C. Le Ru and P. G. Etchegoin, “Quantifying SERS enhancements,” MRS Bull. 38(8), 631–640 (2013). [CrossRef]
43. X. Qiao, X. Chen, C. Huang, A. Li, X. Li, Z. Lu, and T. Wang, “Detection of exhaled volatile organic compounds improved by hollow nanocages of layered double hydroxide on Ag nanowires,” Angew. Chem. Int. Ed. 58, 16523–16527 (2019). [CrossRef]
