Silver-based SERS substrates fabricated using a 3D printed microfluidic device

• Phommachith Sonexai,
• Minh Van Nguyen,
• Bui The Huy and
• Yong-Ill Lee

Beilstein J. Nanotechnol. 2023, 14, 793–803, doi:10.3762/bjnano.14.65

• tool for detecting ultralow concentrations of chemical compounds and biomolecules. We present a reproducible method for producing Ag nanoparticles that can be used to create highly sensitive SERS substrates. A microfluidic device was employed to confine the precursor reagents within the droplets

• catalytic chemistry, where they have been used to develop localized surface plasmon resonance (LSPR) and SERS substrates [8]. For example, Ag NPs yield a strong SERS effect at relatively low cost. However, an issue often encountered in synthetic approaches is the non-uniformity of the Ag NPs. Homogeneous Ag

• NPs are necessary for Ag-based SERS substrates to function well. The microfluidic approach is a technique for the fine control and manipulation of fluids, in which capillary penetration is limited to the micrometer scale and mass transport dominates [9][10]. Microfluidic devices are used in various

SERS performance of GaN/Ag substrates fabricated by Ag coating of GaN platforms

• Magdalena A. Zając,
• Bogusław Budner,
• Malwina Liszewska,
• Bartosz Bartosewicz,
• Łukasz Gutowski,
• Jan L. Weyher and
• Bartłomiej J. Jankiewicz

Beilstein J. Nanotechnol. 2023, 14, 552–564, doi:10.3762/bjnano.14.46

• : GaN/Ag; magnetron sputtering; nanofabrication; pulsed laser deposition; SERS substrates; surface-enhanced Raman spectroscopy (SERS); Introduction Surface-enhanced Raman spectroscopy (SERS) is a highly sensitive and specific technique with multiplexing capabilities [1][2][3][4]. It is considered for

• reliable SERS substrates, which often must be tailored toward specific applications [15][17][18]. The SERS substrates described in the literature include nanoparticles, core–shell nanoparticles, semicontinuous metal films, and many other nanostructures most commonly made of gold or silver [18][19][20][21

• ][22]. Due to the easiness of fabrication, the most extensively studied SERS substrates are those based on metallic nanoparticles and their assemblies [21][22]. Among SERS substrates fabricated using physical methods of particular interest are those based on nanostructured GaN platforms coated with

Combining physical vapor deposition structuration with dealloying for the creation of a highly efficient SERS platform

• Adrien Chauvin,
• Walter Puglisi,
• Damien Thiry,
• Cristina Satriano,
• Rony Snyders and
• Carla Bittencourt

Beilstein J. Nanotechnol. 2023, 14, 83–94, doi:10.3762/bjnano.14.10

• detection properties are mostly observed in noble metal nanoparticles [2][9][10]. Allowed by their localized surface plasmon resonance (LSPR) in the visible region, silver and gold are the most used materials for the preparation of SERS substrates [11][12]. Although Ag has a higher surface plasmon

• substrates with better reliability and stability compared to conventional NP-based SERS substrates [25]. The race towards more efficient SERS platforms has led to the development of highly complex synthesis processes which limits their use in practical applications [15][26][27][28][29]. Most reports on

Zinc oxide nanostructures for fluorescence and Raman signal enhancement: a review

• Ioana Marica,
• Fran Nekvapil,
• Maria Ștefan,
• Cosmin Farcău and
• Alexandra Falamaș

Beilstein J. Nanotechnol. 2022, 13, 472–490, doi:10.3762/bjnano.13.40

• surface features, and the specific location of analyte molecules. Lately, ZnO-based nanostructures have been exploited especially as SERS substrates showing high enhancement factors and increased charge transfer effect. Additionally, applications focused on enhancing the fluorescence of analyte molecules

• as SEF, SERS [16][17], infrared absorption, and even second harmonic generation [18], which can improve the performance of optical sensors and optoelectronic devices. ZnO alone and in combination with noble metals has been recently used for the development of SERS substrates [15][19] due to several

• ZnO and noble metals. Second, the Raman enhancing capabilities and advantages of ZnO-based nanostructures as SERS substrates are discussed. Last, we focus on methods for enhancement of ZnO photoluminescence by noble metal nanoparticles and the enhancement of molecular fluorescence by ZnO alone and by

Modification of a SERS-active Ag surface to promote adsorption of charged analytes: effect of Cu²⁺ ions

• Bahdan V. Ranishenka,
• Andrei Yu. Panarin,
• Irina A. Chelnokova,
• Sergei N. Terekhov,
• Peter Mojzes and
• Vadim V. Shmanai

Beilstein J. Nanotechnol. 2021, 12, 902–912, doi:10.3762/bjnano.12.67

• substrates has been synthesized [1][13]. The design of SERS substrates commonly aims at maximizing the plasmonic effect of Raman enhancement. There are two generally recognized mechanisms responsible for the SERS enhancement, namely electromagnetic enhancement (EM) and chemical enhancement (CE) [14][15]. The

• spots”. The detection of analytes that are not interacting with (or adsorbing to) plasmonic surfaces remains an important practical task. This problem significantly hampers a wider practical application of SERS because even optimally fabricated SERS substrates lose their effectiveness when the analyte

• molecules cannot access the “hot spots”. To address this problem, various techniques have been developed to capture non-adsorbing molecules on SERS-active surfaces [3][18][19][20]. Among various plasmonic materials, silver SERS substrates provide the strongest Raman enhancement for the same structure [8

On the stability of microwave-fabricated SERS substrates – chemical and morphological considerations

• Limin Wang,
• Aisha Adebola Womiloju,
• Christiane Höppener,
• Ulrich S. Schubert and
• Stephanie Hoeppener

Beilstein J. Nanotechnol. 2021, 12, 541–551, doi:10.3762/bjnano.12.44

• spectroscopy (SERS) substrates in different organic solvents and different buffer solutions was investigated. SERS substrates were fabricated by a microwave-assisted synthesis approach and the morphological as well as chemical changes of the SERS substrates were studied. It was demonstrated that the SERS

• sulfoxide (DMSO) treatment completely preserved or even slightly improved the Raman enhancement capabilities. SERS substrates immersed into phosphate-buffered saline (PBS) solutions were observed to be rather instable in low and neutral pH buffer solutions. Other buffer systems showed less severe influences

• on the SERS activity of the substrates and a carbonate buffer at pH 10 was found to even improve SERS performance. This study represents a guideline on the stability of microwave-fabricated SERS substrates or other SERS substrates consisting of non-stabilized silver nanoparticles for the application

Fabrication of nano/microstructures for SERS substrates using an electrochemical method

• Jingran Zhang,
• Tianqi Jia,
• Xiaoping Li,
• Junjie Yang,
• Zhengkai Li,
• Guangfeng Shi,
• Xinming Zhang and
• Zuobin Wang

Beilstein J. Nanotechnol. 2020, 11, 1568–1576, doi:10.3762/bjnano.11.139

• . Additionally, a 10−6 mol·L−1 solution of lysozyme was successfully detected using the Mg–Au nanopore substrates. Our low-cost method is reproducible, homogeneous, and suitable for the fabrication of SERS substrates. Keywords: electrochemical machining; gold (Au); lysozyme detection; magnesium (Mg); micro

• /nanopore; nano/microstructures; SERS substrate; Introduction Surface-enhanced Raman spectroscopy (SERS) can be used to detect biomolecules [1][2][3], explosives [4][5][6], and pesticide residues [7][8][9]. Plasmonic metal nanostructures are often used as SERS substrates to increase the molecule-specific

• is extremely weak [10][11]. SERS is representative of other technologies that can amplify signal intensities based on strong electromagnetic fields and chemical enhancement [12][13][14]. Recently, all kinds of shapes of nanostructures machined by several researchers as SERS substrates have been

Optically and electrically driven nanoantennas

• Monika Fleischer,
• Dai Zhang and
• Alfred J. Meixner

Beilstein J. Nanotechnol. 2020, 11, 1542–1545, doi:10.3762/bjnano.11.136

• breaks down [39][40]. Here, several approaches to create low-cost, large-area SERS substrates that exhibit homogeneous Raman intensity enhancement are introduced. The substrates are based on quasi-hexagonally ordered gold particles prepared by block-copolymer micellar nanolithography and electroless

Highly sensitive detection of estradiol by a SERS sensor based on TiO₂ covered with gold nanoparticles

• Andrea Brognara,
• Ili F. Mohamad Ali Nasri,
• Beatrice R. Bricchi,
• Andrea Li Bassi,
• Caroline Gauchotte-Lindsay,
• Matteo Ghidelli and
• Nathalie Lidgi-Guigui

Beilstein J. Nanotechnol. 2020, 11, 1026–1035, doi:10.3762/bjnano.11.87

• soaking in HAuCl4 solution, as composite SERS substrates for the detection of methylene blue. They reported a successful SERS enhancement, compared to bare Si substrates, with an enhancement factor of ca. 106 and a lower detection limit of 100 nM. Li et al. [15] studied Au NP-coated TiO2 nanotube arrays

• changed due to the morphology change of the deposited Au, from an almost continuous layer to various shape/aspect ratios, size distributions, and average distances between the Au NPs, during annealing (Figure 3). Selection of the TiO2/Au surfaces for E2 detection To test the TiO2/Au surfaces as SERS

• substrates, MBA was used as it is a well-known Raman reporter, showing two intense characteristic peaks at 1080 and 1590 cm−1 from aromatic ring vibrations [30]. The structure of MBA and the grafting process (thiol–gold interaction) guarantee that the molecule will preferentially attach to gold [37][38]. The

Label-free highly sensitive probe detection with novel hierarchical SERS substrates fabricated by nanoindentation and chemical reaction methods

• Jingran Zhang,
• Tianqi Jia,
• Yongda Yan,
• Li Wang,
• Peng Miao,
• Yimin Han,
• Xinming Zhang,
• Guangfeng Shi,
• Yanquan Geng,
• Zhankun Weng,
• Daniel Laipple and
• Zuobin Wang

Beilstein J. Nanotechnol. 2019, 10, 2483–2496, doi:10.3762/bjnano.10.239

• surface-enhanced Raman scattering (SERS) substrates. Recently, in order to obtain a higher enhancement factor at a lower detection limit, hierarchical structures, including nanostructures and nanoparticles, appear to be viable SERS substrate candidates. Here we describe a novel method integrating the

• nanoparticles or micro/nanostructures can be applied as a SERS sensor to detect adsorbed markers. Generally, nanoparticles can be fabricated as SERS substrates at low cost and high production via chemical synthesis methods [8][9][10][11][12][13], including chemical/electrochemical deposition and electrochemical

• etching. For instance, Chen et al. [8] employed an electrochemical etching method to fabricate nanocube structures on a Cu30Mn70 surface by controlling the voltage. In addition, Zhang et al. [10] showed that gold nanoparticles can be fabricated by a gold etchant on a silicon surface as SERS substrates

Materials nanoarchitectonics at two-dimensional liquid interfaces

• Katsuhiko Ariga,
• Michio Matsumoto,
• Taizo Mori and
• Lok Kumar Shrestha

Beilstein J. Nanotechnol. 2019, 10, 1559–1587, doi:10.3762/bjnano.10.153

• system provides dispersed SERS substrates that can be evaluated by confocal Raman imaging. The nanoarchitectonic materials work as freestanding efficient plasmonic substrates for molecular detection. Nanoporous bitter-melon-shaped C60 crystals with face-centred cubic lattice were fabricated through

A silver-nanoparticle/cellulose-nanofiber composite as a highly effective substrate for surface-enhanced Raman spectroscopy

• Yongxin Lu,
• Yan Luo,
• Zehao Lin and
• Jianguo Huang

Beilstein J. Nanotechnol. 2019, 10, 1270–1279, doi:10.3762/bjnano.10.126

• printing [49], successive ionic layer absorption and reaction (SILAR) [50], and photochemical methods [51]. However, there are still challenges regarding the facile fabrication of the SERS substrates with high spectroscopic performance. Regarding SERS substrates, the choice of the substances employed on

• which the metal nanoparticles are deposited influences both the collection efficiencies and detection sensitivities. Cellulose, such as laboratory filter paper and bacterial nanocellulose, have been considered as superior candidates for the fabrication of SERS substrates with silver nanoparticles, due

• , physically flexible and hydrophilic, which allows for a facile and efficient collection of the analytes from solution media. Hence, a number of works have been reported concerning the fabrication of SERS substrates by deposition of silver particles onto cellulose filter paper by means of the silver mirror

Revisiting semicontinuous silver films as surface-enhanced Raman spectroscopy substrates

• Malwina Liszewska,
• Bogusław Budner,
• Małgorzata Norek,
• Bartłomiej J. Jankiewicz and
• Piotr Nyga

Beilstein J. Nanotechnol. 2019, 10, 1048–1055, doi:10.3762/bjnano.10.105

• considerable amount of research has been devoted to this topic. However, there is still a need for further development of reproducible and inexpensive SERS substrates [9]. SERS substrates can be fabricated by a multitude of techniques. These techniques can be divided into chemical and physical methods

• structures [19][20]. Chemical fabrication methods are powerful in terms of the vast variety of attainable structure types, possible enhancement factors, and low cost of fabrication. However, reproducibility of SERS substrates can be an issue and the chemical compounds used for fabrication or stabilization of

• nanostructures can be a source of additional SERS signals [15], which may complicate SERS analysis with their use. Various physical methods may be used to fabricate SERS substrates. Usually in these techniques silver or gold is deposited by physical vapor deposition (PVD) techniques. Nanostructures are obtained

Fabrication of silver nanoisland films by pulsed laser deposition for surface-enhanced Raman spectroscopy

• Bogusław Budner,
• Mariusz Kuźma,
• Barbara Nasiłowska,
• Bartosz Bartosewicz,
• Malwina Liszewska and
• Bartłomiej J. Jankiewicz

Beilstein J. Nanotechnol. 2019, 10, 882–893, doi:10.3762/bjnano.10.89

• and characterization of silver nanoisland films (SNIFs) using pulsed laser deposition (PLD) and the evaluation of these films as potential surface-enhanced Raman scattering (SERS) substrates are reported. The SNIFs with thicknesses in a range of 4.7 ± 0.2 nm to 143.2 ± 0.2 nm were deposited under

• . Keywords: nanofabrication; pulsed laser deposition; SERS substrates; silver nanoisland films; surface-enhanced Raman spectroscopy; X-ray photoelectron spectroscopy; Introduction In recent years, SERS has been intensively investigated as a sensing tool in many applications [1][2][3]. Of particular interest

• cheap, reliable, reproducible and efficient SERS substrates. The SERS effect is generally assumed to mainly originate in the electromagnetic field enhancement caused by a localized surface plasmon excitation in nanostructures through the incident laser light. With respect to the substrate. It depends on

Features and advantages of flexible silicon nanowires for SERS applications

• Hrvoje Gebavi,
• Vlatko Gašparić,
• Dubravko Risović,
• Nikola Baran,
• Paweł Henryk Albrycht and
• Mile Ivanda

Beilstein J. Nanotechnol. 2019, 10, 725–734, doi:10.3762/bjnano.10.72

• flexible silicon nanowires (SiNWs) substrates for surface-enhanced Raman spectroscopy (SERS) applications. The novel SERS substrates are described in detail considering three main aspects. First, the key synthesis parameters for the flexible nanostructure SERS substrates were optimized. It is shown that

• substrates offer high measurement reproducibility, stability, the possibility of precise spot-determined analyte detection and the measurement of water-insoluble substances [12]. Nowadays, the scientific focus is on a subcategory of solid substrates, i.e., “flexible SERS substrates”, which unlike the

• poly(methyl methacrylate) (PMMA) [14]. However, apart from the flexible substrates, also flexible nanostructures are reported on conventional, solid SERS substrates [19][20][21]. In these reports, vertically oriented silicon nanopillars in contact with a liquid would lean towards each other, trapping

Biomimetic synthesis of Ag-coated glasswing butterfly arrays as ultra-sensitive SERS substrates for efficient trace detection of pesticides

• Guochao Shi,
• Mingli Wang,
• Yanying Zhu,
• Yuhong Wang,
• Xiaoya Yan,
• Xin Sun,
• Haijun Xu and
• Wanli Ma

Beilstein J. Nanotechnol. 2019, 10, 578–588, doi:10.3762/bjnano.10.59

• develop SERS substrates. Metal plasmonic nanostructures with specific shapes such as Au nanorods [9], Au nanostars [10], Ag nanocubes [11], porous Au nanoparticles [12] and pyramidal Ag [13] have been successfully synthesized by wet-chemical approaches. These plasmonic nanostructures can be used as SERS

• substrates with low consumption and high EF. However, these synthesis methods are either difficult to control, have a low yield or require harsh experimental conditions as well as sophisticated instrumentation. Hence, a controllable and convenient way to fabricate high-performance SERS substrates would be

• previous reports [29][30]. We adopt a highly efficient route (as shown in Figure 1) using biomimetic synthesis to fabricate 3D Ag nanofilm/glasswing butterfly wing (Ag-G.b.) hybrids as SERS substrates. The wings of the glasswing butterfly (Haetera piera) have an interesting nanostructure that can serve as

Quantification and coupling of the electromagnetic and chemical contributions in surface-enhanced Raman scattering

• Yarong Su,
• Yuanzhen Shi,
• Ping Wang,
• Jinglei Du,
• Markus B. Raschke and
• Lin Pang

Beilstein J. Nanotechnol. 2019, 10, 549–556, doi:10.3762/bjnano.10.56

• intensity dependence of the chemical enhancement and allows for a more systematic design of SERS substrates with desired properties. Keywords: benzenethiol; chemical enhancement; physical enhancement; quantification; surface-enhanced Raman scattering (SERS); Introduction Surface-enhanced Raman scattering

• independence between chemical and electromagnetic enhancement to allow for a more systematic design of SERS substrates with desired properties to turn SERS into a quantitative analytical technique. Experimental A schematic of the experimental approach is shown in Figure 1. Different Au and Ag metal substrates

• provides for a novel design principle to optimize SERS substrates for sensing and photocatalysis in a new systematic manner for quantitative analysis and photochemistry. New theoretical work to investigate the underlying electronic and vibronic structure of the metal–molecule system under different

Controlling surface morphology and sensitivity of granular and porous silver films for surface-enhanced Raman scattering, SERS

• Sherif Okeil and
• Jörg J. Schneider

Beilstein J. Nanotechnol. 2018, 9, 2813–2831, doi:10.3762/bjnano.9.263

• surfaces act as efficient SERS substrates showing greater enhancement factors compared to as prepared, sputtered, but untreated silver films when using rhodamine B as Raman probe molecule. The obtained roughened silver films were fully characterized by scanning electron microscopy (SEM), atomic force

• . Altogether this work shows for the first time the effectiveness of a plasma treatment for surface roughening of silver thin films and its profound influence on the interface-controlled SERS enhancement effect. The method can be used for low-cost, large-scale production of SERS substrates. Keywords: plasma

• not permit the analysis of low concentrations, the SERS signal dramatically enhances the sensitivity typically by orders of magnitude and allows for the analysis of low analyte concentrations [5][7]. The fabrication of SERS substrates began with electrochemical oxidation/reduction cycles especially of

Dumbbell gold nanoparticle dimer antennas with advanced optical properties

• Janning F. Herrmann and
• Christiane Höppener

Beilstein J. Nanotechnol. 2018, 9, 2188–2197, doi:10.3762/bjnano.9.205

• , to be well-suited as SERS substrates [54][55]. The high reactivity of CB[n]s with Au surfaces may lead to the uncontrolled formation nanoparticle aggregates in solution, and often prevents a controlled self-assembly into dimers or small oligomer structures. However, using guided assembly by taking

Facile chemical routes to mesoporous silver substrates for SERS analysis

• Elina A. Tastekova,
• Alexander Y. Polyakov,
• Anastasia E. Goldt,
• Alexander V. Sidorov,
• Alexandra A. Oshmyanskaya,
• Irina V. Sukhorukova,
• Dmitry V. Shtansky,
• Wolgang Grünert and
• Anastasia V. Grigorieva

Beilstein J. Nanotechnol. 2018, 9, 880–889, doi:10.3762/bjnano.9.82

• tinted compounds in a mixture are more complex and still less efficient. Such analyses require specific SERS substrates with a high surface area, hierarchical surface structure and the presence of multiple plasmon bands (“polycolor” plasmons) in the visible range. For this, some prospective but

• nanostructured silver recrystallization and degradation processes. Conclusion In summary, an efficient and convenient synthesis method was proposed for mesoporous silver micrometer and submicrometer-sized particles. The obtained porous silver cubes were found to be highly sensitive SERS substrates with an

• enhancement factor of 105. It was also evident that the mesoporous silver particles are of great functionality and could likely be promising not only as SERS substrates for liquid analysis, but also for gas phase SERS analysis and as catalysts in combustion and mild selective oxidation processes. This same

Fabrication of gold-coated PDMS surfaces with arrayed triangular micro/nanopyramids for use as SERS substrates

• Jingran Zhang,
• Yongda Yan,
• Peng Miao and
• Jianxiong Cai

Beilstein J. Nanotechnol. 2017, 8, 2271–2282, doi:10.3762/bjnano.8.227

• method proposed in this paper is reliable, replicable, homogeneous and low-cost for the fabrication of SERS substrates. Keywords: micro/nanopyramid; nanoimprinting; PDMS substrate; rhodamine 6G; SERS; Introduction Surface enhanced Raman spectroscopy (SERS) is a prominent, highly analytical tool for the

• can be selectively employed to obtain surface enhancement with well-dispersed micro/nanostructures that provide the SERS sensor with an effective identification capability for adsorbed markers. Typically, SERS substrates have been fabricated using lithography-based technologies [11][12][13][14][15][16

• ], such as electron-beam lithography (EBL) [11][12], soft interference lithography (SIL) [13][14], and nanosphere lithography (NSL) [15][16]. To improve the reproducibility and production quantity of SERS substrates, researchers have focused on replicating molded micro/nanostructures as SERS substrates

Near-field surface plasmon field enhancement induced by rippled surfaces

• Mario D’Acunto,
• Francesco Fuso,
• Ruggero Micheletto,
• Makoto Naruse,
• Francesco Tantussi and
• Maria Allegrini

Beilstein J. Nanotechnol. 2017, 8, 956–967, doi:10.3762/bjnano.8.97

• , we obtain and plot the local enhancement parameter, Γ, for a wide variety of patterned surfaces. In particular, we will focus on a specific class of gold nanostructures featuring a rippled surface (which have already demonstrated their potential as SERS substrates) as well as their nonlinear optical

Microfluidic setup for on-line SERS monitoring using laser induced nanoparticle spots as SERS active substrate

• Oana-M. Buja,
• Ovidiu D. Gordan,
• Nicolae Leopold,
• Andreas Morschhauser,
• Jörg Nestler and
• Dietrich R. T. Zahn

Beilstein J. Nanotechnol. 2017, 8, 237–243, doi:10.3762/bjnano.8.26

• employed SERS substrates. However, the citrate reduced colloids are difficult to be prepared in experiments when in situ synthesis is required. In the past years, miniaturization of the systems became important for the development of bioanalytical sensors, having advantages such as precise control over the

• the simple and rapid preparation methodology for obtaining these SERS substrates in situ. The silver spot showed a higher Raman enhancement compared to the gold spot, when using malachite green as test molecule. The results obtained are promising for the development of lab-on-chip approaches for the

Sandwich-like layer-by-layer assembly of gold nanoparticles with tunable SERS properties

• Zhicheng Liu,
• Lu Bai,
• Guizhe Zhao and
• Yaqing Liu

Beilstein J. Nanotechnol. 2016, 7, 1028–1032, doi:10.3762/bjnano.7.95

• 10.3762/bjnano.7.95 Abstract Sandwich-like layer-by-layer thin films consisting of polyelectrolytes and gold nanoparticles were utilized to construct surface-enhanced Raman scattering (SERS) substrates with tunable SERS properties. It is found that both the size of the nanoparticles in the layers and the

• interlayer distance significantly influence the SERS performance of the multilayered thin film. These simple, low-cost, easily processable and controllable SERS substrates have a promising future in the field of molecular sensing. Keywords: assembly; layer-by-layer; multilayer thin film; nanoparticle

• molecular species [1][2][3]. The fabrication of excellent SERS substrates using simple and low-cost methods is currently an attractive topic in this field [4]. Engineering metal nanoparticle assemblies with tunable plasmonic coupling properties shows high potential for that purpose [5]. Among various top

Controlled graphene oxide assembly on silver nanocube monolayers for SERS detection: dependence on nanocube packing procedure

• Martina Banchelli,
• Bruno Tiribilli,
• Roberto Pini,
• Luigi Dei,
• Paolo Matteini and
• Gabriella Caminati

Beilstein J. Nanotechnol. 2016, 7, 9–21, doi:10.3762/bjnano.7.2

• for the realization of efficient SERS substrates. Here we monitored the adsorption of GO onto AgNCs with a controlled step-by-step strategy by direct QCM monitoring of the adsorption process, a method that revealed both the mechanism and kinetics of the composite formation onto the AgNCs-covered SiO2

• the sample. The SERS substrates were pre-immersed in a 9 × 10−4 M or 9 × 10−7 M adenine solution for two hours to ensure that adsorption equilibrium was reached. The samples were rinsed with deionized water and dried under nitrogen flux before each SERS measurement. Procedure A. Formation of AgNC