Surface-enhanced Raman Scattering Active Substrate Research Articles

A nano-imprinted graphene oxide-cellulose composite as a SERS active substrate.

Cellulose is a sustainable material capable of forming optically active nanoarrays on its surface. We created a composite of cellulose acetate (CA) and graphene oxide (GO), by mixing GO (0.1 mg mL-1) into CA. This was then imprinted with nanoscale surface features that form Bragg-like modes in resonance with the excitation laser when a thin layer of silver is vapor deposited onto the surface of the substrate. The addition of GO leads to improved surface-enhanced Raman scattering (SERS) signal strengths, obtaining an average SERS signal increase of 1.4-fold following the inclusion of GO. The combination of photonic and electromagnetic effects with charge transfer-based processes that support the SERS chemical mechanism and the possible presence of electromagnetic hot spots from the roughened surface results in an enhanced SERS signal strength when GO is added. This work shows the potential for nanoimprinted graphene oxide/cellulose acetate composites as flexible sensor platforms to detect target molecules.

Off-resonance high-performance surface-enhanced Raman scattering-active substrate by trapping gold nanoparticles using Bessel beam

The surface-enhanced Raman scattering (SERS) technique provides outstanding molecular fingerprint identification and high sensitivity of analytes. Herein, colloidal sphere-shaped gold nanoparticles (Au-NPs) trapped in concentric rings of the Bessel beam generated from the optical fiber-based negative axicon has been reported as a SERS substrate. With the trapping of Au-NPs, the SERS ability of colloidal Au-NPs improved, and the average enhancement factor (AEF) of the rhodamine-6G (R6G) and 4-aminothiophenol (4-ATP) molecules can reach up to the order of 107. Control experiments were also carried out with the trapping of Au-NPs by Gaussian beam illumination, without any illumination of the light and with the trapping of Au-NPs by the Bessel beam illumination on a silver (Ag)-coated silicon (Si) substrate with a self-assembled monolayer (SAM) of 4-ATP. Theoretical studies were also carried out using the finite element method (FEM) to identify the hotspots generated in the gaps formed between the Au-NPs, leading to an enhancement in the SERS signal of the molecules, and the results were consistent with the experimentally determined AEFs. The obtained results demonstrate that the proposed SERS technique is stable. This study has significant potential applications in clinical diagnosis, food safety, environment safety, chemical sensing, and biosensing.

Interface engineering in 2D materials for SERS sensing

In recent years, the use of 2D materials as surface-enhanced Raman scattering (SERS) active substrates has been extensively investigated. This mini review emphasizes the tunable interface characteristics of 2D materials as SERS substrates. Notably, 2D materials exhibit a wealth of tunable properties, encompassing energy levels, band structures, and interlayer coupling, which confer upon them significant potential as versatile SERS substrates. We summarize the recent advances in tunable 2D materials as SERS active substrates, providing guidance for future research in developing tunable multifunctional molecular sensors based on 2D materials.

SERS combined with the difference in bacterial extracellular electron transfer ability to distinguish Shewanella

Shewanella plays an important role in geochemical cycle, biological corrosion, bioremediation and bioenergy. The development of methods for identifying Shewanella can provide technical support for its rapid screening, in-depth research into its extracellular respiratory mechanism and its application in ecological environment remediation. As a tool for microbial classification, identification and detection, Surface-enhanced Raman scattering (SERS) has high feasibility and application potential. In this work, bio-synthesized silver nanoparticles (AgNPs) were used as SERS substrates to effectively distinguish different types of Shewanella bacteria based on the difference in bacterial extracellular electron transfer (EET) ability. AgNPs were combined with the analyzed bacteria to prepare “Bacteria-AgNPs” SERS samples, which can strongly enhance the Raman signal of the target bacteria and reliably obtain spatial information of different molecular functional groups of each bacteria. Our developed approach can effectively distinguish between non-metal reducing and metal-reducing bacteria, and can further distinguish the three subspecies of Shewanella (Shewanella oneidensis MR-1, Shewanella decolorationis S12, and Shewanella putrefaciens SP200) at the genus and species level. The Raman signal enhancement is presumably caused by the excitation of local surface plasma (LSP) and the enhancement of surrounding electric field. Therefore, our developed method can achieve interspecific and intraspecies discrimination of bacteria. The proposed method can be extended to distinguish other metal-reducing bacteria, and the novel SERS active substrates can be developed for practical applications.

Fiber Optic SERS Sensor with Silver Nanocubes Attached Based on Evanescent Wave for Detecting Pesticide Residues.

Surface-enhanced Raman scattering (SERS) has great potential in the field of rapid detection of pesticide residues in food. In this paper, a fiber optic SERS sensor excited by evanescent waves was proposed for efficient detection of thiram. Silver nanocubes (Ag NCs) were prepared as SERS active substrates, which had much stronger electromagnetic field intensity than nanospheres under laser excitation due to much more "hot spots". By using the method of electrostatic adsorption and laser induction, Ag NCs were uniformly assembled at the fiber taper waist (FTW) for enhancing the Raman signal. Different from the traditional way of stimulation, evanescent wave excitation greatly increased the interaction area between the excitation and analyte, while reducing the damage of the excited light to the metal nanostructures. The methods proposed in this work have been successfully used to detect the pesticide residues of thiram and showed good detection performance. The detection limits for 4-Mercaptobenzoic acid (4-MBA) and thiram were determined to be 10-9 and 10-8 M, the corresponding enhancement factor could be 1.64 × 105 and 6.38 × 104. Low concentration of thiram was detected in the peels of tomatoes and cucumbers, indicating its feasibility in actual sample detection. The combination of evanescent waves and SERS provides a new direction for the application of SERS sensors, which had great application potential in the field of pesticide residue detection.

Multifunctional nanocone array as solid immunoassay plate and SERS substrate for the early diagnosis of prostate cancer on microfluidic chip

We reported a novel multifunctional nanocone array as solid immunoassay plate and surface-enhanced Raman scattering (SERS) substrate for the simultaneous immunoassay of prostate-specific antigen (PSA) and thrombin based on microfluidic chip. In traditional immunoassays, microtiter plates are often used as solid capture plates to form immunocomplexes. However, the two-dimensional surface of the microtiter plate limits the efficiency of target antigen capture due to its steric inhibition. To solve this problem, a nanocone array covered with deposited gold film was successfully fabricated on glass slides that could be directly sealed with PDMS microfluidic chip. As a SERS active substrate, it can also provide a large surface area for capture aptamer conjugation to form a “sandwich” immunocomplex. On the strength of this integrated microfluidic chip, we could detect PSA and thrombin simultaneously with the detection limits of 0.01 ng mL−1 and 0.01 nM. Compared to previous reports, this detection strategy demonstrated the rapid and automatic performance with comparable detection limits. It is believed that the proposed microfluidic sensor has great potential for the early diagnosis of prostate cancer.

Hierarchically rough CuO/Ag composite film with controlled morphology as recyclable SERS-active substrate

Oxide semiconductor combined with noble metal nanocomposites have attracted extensive attention because of its excellent surface-enhanced Raman scattering (SERS) effect and photocatalytic degradation ability which can be applied repeatedly to the detection of pollutants. In this work, hierarchically rough copper oxide (CuO) was first prepared on the surface of copper foil by anodic oxidation, and then loaded silver nanoparticles layer by magnetron sputtering method to obtain CuO/Ag composite film. Such CuO/Ag composite substrate exhibits good SERS performance and recyclability due to its efficient photocatalytic degradation ability. Using Rhodamine 6G (R6G) molecules as probe molecules, the influence of the surface hierarchically rough micro/nanostructures, and the amounts of Ag nanoparticles covered on the CuO film surface were both studied in detail. Using optimized CuO/Ag composite film as SERS active substrate, the detection limit of R6G molecules and crystal violet (CV) molecules were as low as 10−11 M and 10−10 M, respectively. The evolution diagram of Raman spectra shows that such substrate can use its own photocatalytic performance to degrade surface adsorbed molecules under light irradiation, so as to achieve self-cleaning and reusable. After repeated use, the SERS performance was only slightly degraded, showing excellent reusability. For the detection of thiram, we found a limit concentration of 10−8 M. In addition, on the basis of material surface morphology and charge transfer, the SERS enhanced mechanism and photocatalytic mechanism were proposed and discussed. The as-prepared hierarchically rough CuO/Ag composite film is expected to be applied to efficient SERS sensors.

Ultrasensitive detection of amoxicillin using the plasmonic silver nanocube as SERS active substrate

Even though amoxicillin is used as an antibacterial drug in some foods such as fish, chick, etc. However, the use of amoxicillin in the food industry is prohibited. Therefore, rapid detection and sensitive detection at ultra-low concentration of amoxicillin is very important for human. Surface enhanced Raman scattering (SERS) is fast and reliable method to determine the molecules at ultra-low concentration. In this study, silver nanocubes were synthesized and used as SERS active substrate. The synthesized Ag NCs exhibit an excellent sensitivity towards the detection of amoxicillin at the lowest concentration of 10−9 M based on the effect resulting from Ag NCs leading to the high electromagnetic effect and chemical mechanism. The dynamic linear regression between the Raman intensity and amoxicillin concentration over seven orders of magnitude (from 10−4 to 10−9 M) was excellent with high reliability (R2 = 0.99). On the one hand, SERS substrate can be used after storing for 20 days. Because Ag NCs also demonstrated remarkable recyclability, reproducibility, and chemical stability. As a result, Ag NCs can be used as a potential SERS substrate to detect amoxicillin at ultra-low concentration.

Plasmonic Azobenzene Chemoreporter for Surface-Enhanced Raman Scattering Detection of Biothiols.

Low molecular weight thiols (biothiols) are highly active compounds extensively involved in human physiology. Their abnormal levels have been associated with multiple diseases. In recent years, major efforts have been devoted to developing new nanosensing methods for the low cost and fast quantification of this class of analytes in minimally pre-treated samples. Herein, we present a novel strategy for engineering a highly efficient surface-enhanced Raman scattering (SERS) spectroscopy platform for the dynamic sensing of biothiols. Colloidally stable silver nanoparticles clusters equipped with a specifically designed azobenzene derivative (AzoProbe) were generated as highly SERS active substrates. In the presence of small biothiols (e.g., glutathione, GSH), breakage of the AzoProbe diazo bond causes drastic spectral changes that can be quantitatively correlated with the biothiol content with a limit of detection of ca. 5 nM for GSH. An identical response was observed for other low molecular weight thiols, while larger macromolecules with free thiol groups (e.g., bovine serum albumin) do not produce distinguishable spectral alterations. This indicates the suitability of the SERS sensing platform for the selective quantification of small biothiols.

Ag Nanoislands Modified Carbon Fiber Nanostructure: A Versatile and Ultrasensitive Surface-Enhanced Raman Scattering Platform for Antiepileptic Drug Detection

A high-efficiency surface-enhanced Raman scattering (SERS) detection method with ultra-high sensitivity has been widely applied in drug component detection to optimize the product quality verification standards. Herein, a controllable strategy of sputtering Ag nanoislands on carbon fiber (C-fiber) via magnetron sputtering technology was proposed to fabricate a versatile Ag-C-fiber SERS active substrate. A wide range of multi-level electromagnetic enhancement “hot spots” distributed on Ag-C-fiber nanostructures can efficiently amplify Raman signals and the experimental enhancement factor (EEF) value was 3.871 × 106. Furthermore, substantial “hot spots” of large-scale distribution guaranteed the superior reproducibility of Raman signal with relative standard deviation (RSD) values less than 12.97%. Limit of detection (LOD) results indicated that when crystal violet (CV) is employed as probe molecule, the LOD was located at 1 × 10−13 M. By virtue of ultra-sensitivity and good flexibility of the Ag-C-fiber nanotemplate, Raman signals of two kinds of antiepileptic drugs called levetiracetam and sodium valproate were successfully obtained using an SERS-based spectral method. The Ag-C-fiber SERS detection platform demonstrated a good linear response (R2 = 0.97486) in sensing sodium valproate concentrations in the range of 1 × 103 ng/μL−1–1 ng/μL. We believe that this reliable strategy has potential application for trace detection and rapid screening of antiepileptic drugs in the clinic.

Controllable fabrication of polymeric nanowires by NIL technique and self-assembled AAO template for SERS application

A controllable strategy to fabricate the polymeric nanowires with high throughput and low cost is developed by using the thermal nanoimprint lithography (NIL) technique and self-assembled anodic aluminum oxide (AAO) template. The length of polymeric nanowires can be controlled by adjusting the duration of thermal NIL. A fill mechanism of thermoplastic intermediate polymer stamp (IPS) polymer pressed into the AAO nanopores is closely studied. The as-prepared IPS polymeric nanowire-based Surface-Enhanced Raman Scattering (SERS)-active substrate exhibits a remarkable reproducibility. The effective adsorption of the R6G as probe molecule near to hotspots generated at 3D vertically aligned polymeric nanowire SERS active substrates shows extraordinary enhancement of Raman signal with an enhancement factor (EF) of 105–106. The present strategy is of great guiding significance to broaden the use of thermal NIL technique and AAO template for the fabrication of other nanomaterials, especially for the flexible and transparent polymer-based nanomaterials.

Rapid and sensitive detection of Rhodamine B in food using the plasmonic silver nanocube-based sensor as SERS active substrate

The use of dye in food is harmful to human health and is prohibited nowadays. However, it is still used because of the benefits, such as cheap prices and abundant resources. Rhodamine B is usually used as the colorant in food such as chili powder, chili oil, etc. It is colorless at very low concentration 10-7 M. The sensitive detection of RhB at ultra-low concentration help to prevent some risk for human. Surface-enhanced Raman scattering (SERS) is a great technique to detect the analytes at ultra-low concentration and provide the molecule’s information as a fingerprint. In this study, silver nano-cube was facilely synthesized by reducing Ag+ in ethylene glycol and upgraded to thin-film as a SERS active substrate. RhB was detected at 10-10 M by a silver nano-cube sensor. The dynamic linear regression between the Raman intensity and RhB concentration over seven orders of magnitude (from 10-4 to 10-10 M) was excellent with high reliability (R2 = 0.99). Moreover, the substrate can be used after storing in a dark area for 60 days. This proposed nano-cube silver could serve as a potential substrate for detecting RhB in food at very low concentration.

Non-invasive SERS serum detection technology combined with multivariate statistical algorithm for simultaneous screening of cervical cancer and breast cancer.

Surface-enhanced Raman scattering (SERS), as a rapid, reliable and non-destructive spectral detection technology, has made a series of breakthrough achievements in screening and pre-diagnosis of various cancerous tumors. In this paper, high-performance gold nanoparticles/785 porous silicon photonic crystals (Au NPs/785 PSi PhCs) active SERS substrates were specially designed for serum testing, and realized highly sensitive detection of serum from healthy people, patients with cervical cancer and breast cancer. Based on the SERS spectra of the three groups of serum, the significant differences between the healthy group and cancer group at 1030cm-1 and 1051cm-1 were analyzed, and the similar but different serum SERS spectra of cervical cancer and breast cancer patients were compared. In addition, the spectral difference detected by SERS technology combined with a multivariate statistical algorithm was used to distinguish three kinds of serum. The serum SERS spectral sensitive bands were extracted by recursive weighted partial least squares (rPLS), and the three classification diagnosis models were established by combining orthogonal partial least squares discriminant analysis (OPLS-DA), linear discriminant analysis (LDA) and principal component analysis support vector machine (PCA-SVM) for synchronous classification and discrimination of the three groups of serum. The diagnostic results showed that the overall screening accuracy of three models were 93.28%, 97.77% and 94.78%, respectively. These above results confirmed that the Au NPs/785 PSi PhCs can realize super-sensitive detection of serum, and the established diagnostic model has great potential for pre-diagnosis and simultaneous screening of cervical cancer and breast cancer.

Template Stripping Method-Based Au Nanoarray for Surface-Enhanced Raman Scattering Detection of Antiepileptic Drug.

Surface-enhanced Raman scattering (SERS) is a potential candidate for highly sensitive detection of target molecules. A SERS active substrate with a noble metal nanostructure is required for this. However, a SERS active substrate requires complicated fabrication procedures. This in turn makes it difficult to fabricate highly sensitive SERS active substrates with high reproducibility. To overcome this difficulty, a plasmonic crystal (PC) with periodic noble metal nanostructures was fabricated via the template-stripping method using a polymer-based template. Using SERS active substrates, SERS was successfully achieved using the PC by detecting low concentrations of phenobarbital which is an antiepileptic drug using a commercially available portable Raman module. The PC can be fabricated by demolding the deposited gold layer from a polymer-based template. This method is rapid, economic, and has high reproducibility. SERS can be achieved easily using this PC for a wide variety of applications such as medical, pharmaceutical, and environmental protection.

Plasmonic Molybdenum Tungsten Oxide Hybrid with Surface-Enhanced Raman Scattering Comparable to that of Noble Metals.

The surface-enhanced Raman scattering (SERS) research is in full swing owing to its high sensitivity and high selectivity; however, the substrates with superexcellent performance for SERS are largely confined to noble metals (Au, Ag, etc.). Although the SERS active substrates have been extended to semiconductors and transition metals, it is frustrating that their sensitivities are insufficient for widespread practical application. Here, we report the plasmonic molybdenum tungsten oxide (MWO) hybrid nanomaterials (NMs), which can be used as high-performance substrates with SERS comparable to that of noble metals. MWO NMs can achieve the trace detection of rhodamine 6G (R6G), basic fuchsin (BF), and oil red O (ORO). The detection limit concentration for R6G is 10-8 M, with the maximum enhancement factor of up to 6.09 × 107. The superexcellent SERS performance was attributed to the cooperative enhancement effect of electromagnetic (EM) enhancement mechanism and the charge transfer (CT) mechanism. Moreover, in the proposed system, the EM and CT contribution was distinguished by employing poly(vinylpyrrolidone) (PVP), which serves as a barrier layer to prevent the CT process from MWO NMs to R6G. These remarkable MWO NMs can be obtained with a facile method, and this research provides new insight into non-noble metal based SERS substrate.

Newly prepared surface-enhanced Raman scattering-active substrates for sensing pesticides

In electrochemical preparations of surface-enhanced Raman scattering (SERS)-active substrates, reactions are generally performed in aqueous solutions using deionized water (DIW) with 0.1 N electrolytes. The prepared SERS-active substrates are then thoroughly rinsed with DIW and dried for subsequent SERS measurements. In this work, we present comprehensive advantages of utilizing innovative plasmon-activated water (PAW) with reduced hydrogen bonds, compared to conventional DIW, on the subsequent signal intensities and reproducibility of SERS performances. Electrochemically roughened gold (Au) and silver (Ag) substrates were additionally immersed in PAW for 15 min to remove impurities, and the relative standard deviations (RSDs) of the SERS signals of model probe molecules of rhodamine 6G (R6G) were lower compared to those of substrates soaked in DIW. Moreover, for the SERS-active substrates prepared with Au/Ag nanocomposites using galvanic replacement reactions (GRRs), the RSD of the SERS signal of R6G was lower for the roughened Ag substrate immersed in the PAW solution containing positively charged Au ions, compared to that which was immersed in a DIW solution. Also, the corresponding SERS signals were higher for Au/Ag nanocomposites based on PAW systems. Similarly, SERS-active filter paper with Au/Ag nanocomposites prepared in a PAW solution, compared to a DIW solution, also demonstrated a better SERS effect. This strategy based on optimally prepared SERS-active Au substrates is also practically applicable for sensing imidacloprid and acetamiprid, commonly used pesticide that are generally detected in farm crops. These interesting findings indicate that SERS-active substrates prepared using PAW are sufficiently sensitive and reliable to develop SERS sensors.

Application of SERS active substrate prepared by nanotechnology in ophthalmic care

The application of nanomaterials in ocular drug delivery is mainly concentrated in nano-controlled release systems. Due to the unique properties of nanomaterials, the use of nanomaterials to carry drugs for treating eye diseases has great advantages compared with traditional drug delivery methods. The nano-formulation of the drug has higher bioavailability and lower side effects. Therefore, the nano-controlled release system has a good application prospect in ophthalmology. In this paper, Fe2O3 magnetic nanoparticles were first prepared by co-deposition, and then the nanoparticles were clad with silica to prepare Fe2O3 @SiO2 core-shell nanostructures. Secondly, an ordered array surface-enhanced Raman scattering (SERS) active substrate was formed on the surface of the porous layer of porous anode aluminium oxide (PAA) and the barrier layer using vacuum electron beam evaporation technology using PAA films as templates. Then, the shell thickness of Fe2O3@SiO2 and the number of coated magnetic particles were controlled by controlling the dosage of ethyl orthosilicate, and a layer of SERS active gold nanoshells was grown after further adsorption of gold seeds to prepare a composite SERS active substrate. Enhanced performance magnetic nanomaterial Fe2O3@SiO2@PAA @Au. Finally, the SERS spectrum and fluorescence quenching characteristics of ocular cells adsorbed on the substrate were detected and analysed. The results show that the magnetic nanomaterial Fe2O3@SiO2@PAA @Au with enhanced performance of SERS active substrate has a good enhancement effect on the Raman scattering signal of eye cells, and to a certain extent, it can eliminate the interference of the fluorescent background. Moreover, the ordered array of SERS active substrates not only has a high SERS enhancement ability and ability to quench fluorescence, but also does not have interference peaks of oxalate impurities remaining in the PAA film, which can obtain more detailed information of the Raman scattering spectrum of eye cells to achieve eye care.

Fabrication of Ag/ZnO nanostructures for SERS applications

A novel and effective approach is suggested for fabrication of composite Ag/ZnO nanostructures for surface-enhanced Raman scattering (SERS) by combining laser and ion implantation techniques. The study explores the relation between the nanoscopic features of the prepared Ag/ZnO nanocomposites and their effectiveness as SERS active substrates. The ZnO thin films are grown by pulsed laser deposition (PLD). Ag+-ion implantation is used for surface synthesis of Ag nanoparticles (NPs) in the ZnO matrix. The implanted samples are annealed by a Nd:YAG laser at various parameters. The surface morphology, composition and optical properties of the nanocomposites are studied before and after the ion and laser modifications. The possibility to apply these structures to ammonium nitrate detection is investigated by identifying the most suitable conditions for laser annealing of the implanted Ag/ZnO structures in view of producing the strongest SERS signal. A comparative Raman study is performed at two laser excitation wavelengths. New results are obtained for different ammonium nitrate (AN) concentrations. The strongest Raman signal of ammonium nitrate is detected for the Ag/ZnO substrate annealed at 532 nm and characterized by a high surface roughness and a wide nanoparticles’ size distribution, where a low surface electron density of silver was obtained.

Raman and SERS spectra of thiamethoxam and the Ag3–thiamethoxam complex: an experimental and theoretical investigation

The insecticide thiamethoxam (TMX) is one of the most important neonicotinoid pesticides. The chromatographic methods currently employed to detect TMX require multiple operational steps. This study proposes a simple method that detects TMX via surface-enhanced Raman scattering (SERS) spectroscopy with Ag nanoparticles (NPs) as the SERS active substrate. Density functional theory (DFT) was used to calculate the structures and vibrational modes of the Ag– and Ag3–TMX complexes at the B3LYP/6-311++G(d,p)(C,H,N)/LanL2DZ(Ag) level of theory. The results reveal that the atoms in the thiazole ring all lie in the same plane, while the six-membered ring is perpendicular to the thiazole ring. Data from both Ultraviolet-visible and Raman spectroscopy indicated that TMX bonds to Ag through its nitro group, vertically. A weak intramolecular (N22–O23…H26) hydrogen bonding and Ag–O bands shift N–O symmetrical vibration to down to lower wavenumber. This was supported by the appearance of a strong 866 cm−1 band in the SERS spectrum assigned to the N–O symmetrical vibration coupled with the N–N stretching vibrational mode of different excitation wavelength. Notably, a good linear relationship was observed in the TMX concentration range 1.0 × 10−6–1.0 × 10−4 mol·L−1 (R2 = 0.9667). SERS is an extremely simple and rapid technique that requires little sample for analysis.

Tunable Silver Nanoparticle Arrays by Hot Embossing and Sputter Deposition for Surface-Enhanced Raman Scattering

Surface-enhanced Raman scattering (SERS) spectroscopy has attracted a lot of attention over the past 30 years. Due to its extreme sensitivity and label-free detection capability, it has shown great potential in areas such as analytical chemistry, biochemistry, and environmental science. However, the major challenge is to manufacture large-scale highly SERS active substrates with high controllability, good reproducibility, and low cost. In this study, we report a novel method to fabricate uniform silver nanoparticle arrays with tunable particle sizes and interparticle gaps. Using hot embossing and sputtering techniques, we were able to batch produce the silver nanoparticle arrays SERS active substrate with consistent quality and low cost. We showed that the proposed SERS active substrate has good uniformity and high reproducibility. Experimental results show that the SERS enhancement factor is affected by silver nanoparticles size and interparticle gaps. Furthermore, the enhancement factor of the SERS signal obtained from Rhodamine 6G (R6G) probe molecules was as high as 1.12 × 107. Therefore, the developed method is very promising for use in many SERS applications.