Browsing by Subject "SERS"

Now showing 1 - 17 of 17

Open Access
Antifouling superhydrophobic surfaces with bactericidal and SERS activity
(Elsevier BV, 2022-03-01) Şahin, F.; Çelik, N.; Ceylan, A.; Pekdemir, S.; Ruzi, M.; Önses, Mustafa Serdar
Fouling and contamination of surfaces are prevailing challenges humanities facing today in fields such as healthcare, hospitality, and food manufacturing. These challenges strongly motivate the development of multifunctional surfaces with antifouling and antimicrobial properties that are coupled with sensing capabilities. To address this challenge, we prepared a multifunctional superhydrophobic surface using eco-friendly materials: polydimethylsiloxane (PDMS) and carnauba wax. After deposition of a thin film of Ag, the surface gained surface-enhanced Raman scattering (SERS) activity and bactericidal property. The multifunctional superhydrophobic surface showed extreme liquid repellency towards water and common liquid food. The strong SERS activity enabled the detection of adulterant rhodamine B in a sausage down to a nanomolar level. Notably, the surface showed excellent bactericidal activity towards two common bacteria, E. coli, and S. aureus, significantly reducing their adhesion and killing. Additionally, the surface showed anti-fouling behavior against common liquid food, and even towards sticky foods such as yogurt, honey, and pomegranate sauce, reducing residual food by >97 %. Furthermore, the superhydrophobic surface showed excellent chemical stability in dynamic and static flow conditions and leaching of Ag in neutral and basic solutions was minimal.
Open Access
An array of surface-enhanced Raman scattering substrates based on plasmonic lenses
(Wiley, 2012-10-01) Kahraman, M.; Cakmakyapan, S.; Özbay, Ekmel; Culha, M.
An array of ring-shaped holes is prepared from silver thin films using electron beam lithography. The optimal conditions for high performance as a surface-enhanced Raman scattering (SERS) substrate are investigated. Either the diameter of the hole (0.5, 1.0, 2.0, 3.0 and 4.0 μm) or the slit width (200, 300, 400, 500 and 600 nm) is varied. 4-Aminothiophenol (ATP) adsorbed on the structures as a self-assembled monolayer (SAM) is used as probe to evaluate the SERS performance of the generated structures. It is found that there is an optimal configuration for ring-shaped holes with a 3.0-μm diameter and 200-nm slit width. The SERS activity on this optimal lens configuration is found to be 13 times greater than that of the activity on the silver thin film. An array of these structures at this optimal configuration can easily be constructed and used in a range of SERS-based sensing applications. An array of ring-shaped holes is prepared from silver thin films using electron beam lithography. The optimal conditions for high performance as a surface-enhanced Raman scattering (SERS) substrate are investigated. It is found that there is an optimal configuration for ring-shaped holes with a 3.0-μm diameter and 200-nm slit with. The SERS activity on this optimal lens configuration is found to be 13 times greater than that of the activity on the silver thin film.
Open Access
Chitosan loses innate beneficial properties after being dissolved in acetic acid: Supported by detailed molecular modeling
(American Chemical Society, 2020-12) Bilican, İsmail; Önses, M. S.; Akyüz, L.; Altuner, E. M.; Koc-Bilican, B.; Zang, L.-S.; Mujtaba, M.; Mulerčikas, P.
Chitosan, which is obtained via deacetylation of chitin, has a variety of uses in agriculture, food, medicine, pharmaceuticals, and cosmetics. Industrial chitosan is in a gel form, which is produced by dissolving in acetic acids. These gels can be chitosan-only films or composite films that include other ingredients such as plant extracts or other polymers. Chitosan-based films, however, are not as natural as chitosan dissolved in weak acids, and they lack some of chitosan’s innate properties. In this study, natural chitosan films (NCFs) were obtained from the pupa shells of black soldier flies through a process that maintains the original structure. The semisynthetic film (SCF) was then produced by dissolving the same NCF in acetic acid along with glycerol and glutaraldehyde. The semisynthetic film remarkably lost the beneficial properties of the natural film. The deteriorated characteristics include hydrophobicity, crystallinity, thermal properties, as well as a loss of fibril structure and a reduction in bacterial attachment. Moreover, the Ag-deposited NCFs manifested strikingly higher surface-enhanced Raman scattering activity as compared with the semisynthetic ones. These results, including the molecular modeling data, demonstrate that dissolving chitosan in acetic acid changes its polymeric structure.
Open Access
Cyclodextrin functionalized nanofibers via electrospinning
(2014) Çelebioğlu, Aslı
Electrospinning is a commonly studied and widely applied technique for generating nanofibers, with a diameter ranging from several tens of nanometers to a few micrometers. The low-cost, simple set-up, relatively high production rate and reproducibility increase the interests on this method in both academia and industry. Electrospun nanofibers are produced from a broad range of materials with extremely high surface area, very light-weight, nano-porous features and distinct physical/mechanical properties. The general talk in this technique focuses on the production of nanofibers from polymer base materials. However, very recent studies demonstrated that, it is also possible to obtain nanofibers from non-polymeric systems. For this novel development in electrospinning researches, we have achieved to generate nanofibers from cyclodextrins (CD) without using a polymeric template. CD are cyclic oligosaccharides consisting of α-(1,4)-linked glucopyranose units. The truncated cone shape structure of CD provides a favorable place for various kinds of organic molecules to form non-covalent host-guest inclusion complexes (IC). The enhancements and progressing at the guest molecules property and situation, creating with the inclusion complexation, make CD applicable in variety of areas including filtration, pharmaceuticals, cosmetics, functional foods, textiles, analytic chemistry etc. In this thesis, we report on the electrospinning of CD nanofibers, represent their functionalization and potential applications. Firstly, we produced CD nanofibers from three different chemically modified CD types (hydroxypropyl-β-cyclodextrin (HPβCD), hydroxypropyl-γ-cyclodextrin (HPγCD) and methyl-β-cyclodextrin (MβCD)). Afterwards, the electrospinning of native CD (α-CD, β-CD and γ-CD) nanofibers was achieved. The molecular entrapment capability of CD nanofibers was shown by capturing toxic volatile organic compounds (VOCs) from the surrounding. As the next step, the polymer-free nanofibers were obtained from the cyclodextrin inclusion complexes (CD-IC) with antibacterial agent, vanillin and essential oils. Here, we have also indicated applicability of CD-IC nanofibers as a result of antibacterial test. The functionalization of the CD nanofibers was continued with the green and one-step synthesis of metal nanoparticles (Ag-NP, Au-NP and Pd-NP) incorporated nanofibers, in which CD were used as reducing, stabilizing agent and fiber template. Even, the antibacterial, SERS and catalyst potential of these CD based nanofibers were demonstrated for the related nanoparticles. Our research is expanded to a new stage by the production of insoluble poly-CD nanofibers. We have worked on different crosslinking agents to attain insoluble poly-CD nanofibers with uniform morphology. After the optimization of poly-CD nanofibers, the most durable polyCD nanowebs were selected for further analysis and evaluation of the filtration performance in liquid environment. Within poly-CD nanofibers, we have eliminated the solubility challenge of CD nanofibers that restrict their usage. So, we assume that, poly-CD nanofibers will lead-up to generation of new advances for practices of CD nanofibers. All studies showed that, the self-assembly and self-aggregation property of CD are the prior requirements for the electrospinnability of these small molecules. To conclude, very intriguing materials were obtained by integrating large surface area of nanofibers with specific host-guest inclusion complexation capability and non-toxic, biocompatible nature of the CD. Moreover, CD molecules, which are generally used in the powder form, were rendered into more applicable nanofibers form that will represent ease during their usage.
Open Access
Disintegration and machine-learning-assisted identification of bacteria on antimicrobial and plasmonic Ag–CuxO nanostructures
(American Chemical Society, 2023-03-08) Şahin, F.; Çamdal, A.; Şahin, G. D.; Ceylan, A.; Ruzi, M.; Önses, Mustafa Serdar
Bacteria cause many common infections and are the culprit of many outbreaks throughout history that have led to the loss of millions of lives. Contamination of inanimate surfaces in clinics, the food chain, and the environment poses a significant threat to humanity, with the increase in antimicrobial resistance exacerbating the issue. Two key strategies to address this issue are antibacterial coatings and effective detection of bacterial contamination. In this study, we present the formation of antimicrobial and plasmonic surfaces based on Ag–CuxO nanostructures using green synthesis methods and low-cost paper substrates. The fabricated nanostructured surfaces exhibit excellent bactericidal efficiency and high surface-enhanced Raman scattering (SERS) activity. The CuxO ensures outstanding and rapid antibacterial activity within 30 min, with a rate of >99.99% against typical Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria. The plasmonic Ag nanoparticles facilitate the electromagnetic enhancement of Raman scattering and enables rapid, label-free, and sensitive identification of bacteria at a concentration as low as 103 cfu/mL. The detection of different strains at this low concentration is attributed to the leaching of the intracellular components of the bacteria caused by the nanostructures. Additionally, SERS is coupled with machine learning algorithms for the automated identification of bacteria with an accuracy that exceeds 96%. The proposed strategy achieves effective prevention of bacterial contamination and accurate identification of the bacteria on the same material platform by using sustainable and low-cost materials.
Open Access
Eco-friendly fabrication of plasmonically active substrates based on end-grafted poly(ethylene glycol) layers
(American Chemical Society, 2019) Karabel Öcal, S.; Pekdemir, S.; Serhatlıoğlu, Murat; İpekçi, H. H.; Şahmetlioğlu, E.; Narin, İ.; Duman, F.; Elbüken, Çağlar; Demirel, G.; Önses, Mustafa Serdar
We report completely sustainable processes and materials for inexpensive and scalable fabrication of plasmonically active solid substrates, which are critical for emerging applications in sensing, catalysis, and metasurfaces. Our approach involves grafting of poly(ethylene glycol) (PEG) onto silicon oxide terminated solid substrates using all-water based processing leading to an ultrathin (12 nm) and smooth (roughness of ∼1 nm) functional layer. The resulting surfaces facilitate robust and effective immobilization of gold nanoparticles (NPs) with a density that is superior to the organic solvent based processing. This new process achieves size dependent assembly of the citrate-stabilized gold NPs resulting in high plasmonic activity in surface-enhanced Raman scattering (SERS). The use of leaf extracts derived from Quercus pubescens as a reducing and stabilizing agent allowed for green synthesis of gold NPs with an average diameter of 25.6 ± 11.1 nm. The assembly of the green synthesized gold NPs on all-water processed PEG grafted layers enabled a fully sustainable route for fabrication of plasmonically active solid substrates. The resulting substrates exhibited high SERS response over the entire (∼1 cm2) substrate surface with an analytical enhancement factor of 9.48 × 104 for the probe molecule rhodamine 6G under 532 nm laser excitation. A microfluidic device was also constructed on the fabricated platform for SERS mediated simultaneous detection of two nonsteroidal anti-inflammatory drugs, dexketoprofen and ibuprofen, which are widely used in human medicine and present as contaminants in wastewater. The biocompatibility of PEG together with all-water based processing overcome the need for waste management and ventilation of the working place enabling cost and energy efficient, environmentally benign fabrication of plasmonic devices.
Open Access
Fabrication of flexible, cost-effective, and scalable silver substrates for efficient surface enhanced Raman spectroscopy based trace detection
(Elsevier BV, 2021-06-20) Khan, G. A.; Demirtaş, Ö.; Aytekin, Ö.; Demir, Ahmet Kemal; Bek, A.; Bhatti, A. S.; Ahmed, W.
The fabrication and optimization of cost-effective, eco-friendly, uniform and flexible SERS platforms by facile synthesis routes has recently attracted great attention for trace detection of various analytes. Herein, we report the fabrication of interconnected Ag nanostructures on the unmodified filter paper-based flexible substrates by a facile recipe, which involves evaporation of Ag precursor solution on the filter paper followed by its reduction with a strong reducing agent, NaBH4. The fabrication process is time-efficient, reproducible, and has the potential of being scaled up. The presence of inter-connected nanostructures results in high concentration of uniformly distributed hotspots on the substrate, which in turn provide excellent and reproducible SERS sensitivity. The finite element simulation results showed that fabricated nanostructures are much more effective for field enhancement as compared to the agglomerated spherical nanoparticles. Crystal violet (CV) concentration of 10−8 M was easily detected with these substrates both via solution drying and swabbing. Similarly, AgFPS have proven effective for swab-based detection of urea nitrate (UN), a well-known constituent of homemade explosives. The C-N and NO3- symmetric stretching modes of UN are detectable down to 1 µM and 100 µM concentrations, respectively. Moreover, these substrates showed SERS signal uniformity both from different spots of a single substrate, and substrates from different batches, with spot-to-spot relative standard deviation (RSD) of 15% and sample-to-sample RSD of 15–19%. This makes them excellent for reliable and quick quantitative detection. The simple synthesis strategy, flexibility, cost-effectiveness, and quantitative detection makes these substrates ideal for SERS based trace detection, especially for on-site analysis, and various sensing applications.
Open Access
From bio-waste to biomaterials: The eggshells of Chinese oak silkworm as templates for SERS-active surfaces
(Elsevier BV, 2021-12-15) Zang, Lian-Sheng; Chen, Yong-Ming; Bilican, Behlül Koç; Bilican, İsmail; Sakir, Menekşe; Wait, James; Çolak, Arzu; Karaduman, Tuğçe; Ceylan, Ahmet; Ali, Asad; Elbüken, Çağlar; Onses, M. Serdar; Kaya, Murat
Although over 80% of the world’s existing animal species are insects, with each of these species having unique eggshell morphologies, limited information is available regarding the use of their eggshells in material science applications. The present research discusses using discarded eggshells of the Chinese oak silkworm (Antheraea pernyi) as a technological material. The 3-dimensional aspects of the insect’s eggshell were examined in detail, demonstrating the complexity of their novel surface morphology. The outer surface of the eggshell was comprised of a hexagonal structure, whereas the inner surface consists of a mostly smooth surface. Distinctive layers of the eggshell were observed when cross sections of the surface were analyzed. The elastic modulus of the inner part of the eggshell is substantially greater than that of the outer part. The physicochemical properties of the eggshell were characterized and no toxic properties were found. The hexagonal structures found on the outer surface of the eggshell provide a highly suitable template for silver nanostructure deposition. The resulting silver decorated surfaces can be used to detect molecules via surface-enhanced Raman scattering (SERS) effects. The deposition of silver renders the surface antimicrobial, whereas the original surface was microbial. Collectively, the insights gained in this study will be key in developing advanced engineering applications of the insect eggshells.
Open Access
Novel materials and techniques for energy conversion and sensing
(2015-12) Ekiz, Okan Öner
In the recent years, characterization of nanomaterials and using them in sensing applications gain considerable attention. Increased research on nanotechnology brings new materials and techniques that come with many unsought properties. Additionally, novel materials and concepts have created new demands for new characterization techniques. In this thesis, our main aim is to characterize novel materials and develop new techniques to use nanotechnology in sensing applications. Graphene is one of the most important material in nanotechnology found in the recent years. In this thesis, we have characterized and explain the electrochemical behavior of graphene oxide. During the experiments, novel properties of graphene oxide have been revealed. Foundings paved the way for new applications of graphene. Recent studies in plasmonic materials made SERS (Surface-Enhanced-Raman- Spectroscopy) an important characterization tool used in nanotechnology. SERS is a powerful technique for chemical speci c and label free analysis of low concentration materials. In this thesis, we have used SERS to build an arti cial nose for detection of VOCs. SERS substrates have been fabricated and used for the experiments. Experiments showed that our technique could detect many VOCs and could be used for several applications such as explosive and drug detection. There is a strong need for easy and cost e ective biosensors especially for homecare applications. Recent advances in nanotechnology help us to develop cost e ective techniques. Reducing costs could make biosensors more accessible for end user applications such. In this thesis, we have developed a biosensor platform by using SPR (Surface Plasmon Resonance) for pathogen detection. Experiments showed that our device could detect 102 pathogens without labeling. Our aim is to improve this platform for rapid food analysis and home-care applications.
Open Access
Physically unclonable surfaces via dewetting of polymer thin films
(American Chemical Society, 2021-03-10) Torun, N.; Torun, İ.; Şakir, M.; Kalay, M.; Önses, Mustafa Serdar
From anti-counterfeiting to biotechnology applications, there is a strong demand for encoded surfaces with multiple security layers that are prepared by stochastic processes and are adaptable to deterministic fabrication approaches. Here, we present dewetting instabilities in nanoscopic (thickness <100 nm) polymer films as a form of physically unclonable function (PUF). The inherent randomness involved in the dewetting process presents a highly suitable platform for fabricating unclonable surfaces. The thermal annealing-induced dewetting of poly(2-vinyl pyridine) (P2VP) on polystyrene-grafted substrates enables fabrication of randomly positioned functional features that are separated at a microscopic length scale, a requirement set by optical authentication systems. At a first level, PUFs can be simply and readily verified via reflection of visible light. Area-specific electrostatic interactions between P2VP and citrate-stabilized gold nanoparticles allow for fabrication of plasmonic PUFs. The strong surface-enhanced Raman scattering by plasmonic nanoparticles together with incorporation of taggants facilitates a molecular vibration-based security layer. The patterning of P2VP films presents opportunities for fabricating hybrid security labels, which can be resolved through both stochastic and deterministic pathways. The adaptability to a broad range of nanoscale materials, simplicity, versatility, compatibility with conventional fabrication approaches, and high levels of stability offer key opportunities in encoding applications.
Open Access
Plasmonic absorbers for multispectral and broadband absorption
(SPIE, 2012) Ayaş, Sencer; Güner, Hasan; Türker, Burak; Ekiz, Öner; Dana, Aykutlu
We present polarization dependent multispectral and broadband plasmonic absorbers in the visible spectrum. The spectral characteristics of these structures are tunable over a broad spectrum. Experimental results are verified with the FDTD and RCWA analysis methods. These structures are used as surface enhanced raman spectroscopy(SERS) substrates. Designed structures have resonances that span the Raman Stokes and excitation wavelength. Such structures can be used for energy, LED and other spectroscopy applications. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
Open Access
Plasmonic band gap cavities
(2008) Kocabaş, Aşkın
Surface plasmon polaritons (SPP’s) are trapped electromagnetic waves coupled to free electrons in metals that propagate at the metal-dielectric interfaces. Due to their surface confinement and potential in sub-wavelength optics, SPP’s have been extensively studied for sensing and nanophotonic applications. Dielectric structures and metallic surfaces, both periodically modulated, can form photonic band gaps. Creating a defect cavity region in the periodicity of dielectrics allows specific optical modes to localize inside a cavity region. However, despite the demonstration of numerous plasmonic surfaces and unlike its dielectric counterparts, low index modulation in metallic surfaces limits the formation of plasmonic defect cavity structures. This thesis describes new approaches for plasmonic confinement in a cavity through the use of selective loading of grating structures as well as through the use of Moiré surfaces. In our first approach, we demonstrate that a high dielectric superstructure can perturb the optical properties of propagating SPPs dramatically and enable the formation of a plasmonic band gap cavity. Formation of the cavity is confirmed by the observation of a cavity mode in the band gap both in the infrared and the visible wavelengths. In addition to the confinement of SPP’s in the vertical direction, such a cavity localizes the SPP’s in their propagation direction. Additionally, we have demonstrated that such biharmonic grating structures can be used to enhance Raman scattering and photoluminescence (PL). Using biharmonic grating structure 105 times enhancement in Raman signal and 30 times enhancement in PL were measured. Furthermore, we show that metallic Moiré surfaces can also serve as a basis for plasmonic cavities with relatively high quality factors. We have demonstrated localization and slow propagation of surface plasmons on metallic Moiré surfaces. Phase shift at the node of the Moiré surface localizes the propagating surface plasmons in a cavity and adjacent nodes form weakly coupled plasmonic cavities. We demonstrate group velocities around v = 0.44c at the center of the coupled cavity band and almost zero group velocity at the band edges can be achieved. Furthermore, sinusoidally modified amplitude about the node suppresses the radiation losses and reveals a relatively high quality factor for plasmonic cavities.
Embargo
Practical SERS substrates by spray coating of silver solutions for deep learning-assisted sensitive antigen identification
(Elsevier BV, 2025-02-20) Şahin, F.; Demirel Şahin, G.; Çamdal, A.; Akmayan, İ.; Özbek, T.; Acar, S.; Önses, Mustafa Serdar
Surface-enhanced Raman spectroscopy (SERS) has long been recognized for its rapid and sensitive detection capabilities; however, challenges persist in practical fabrication of the substrates and interpreting complex data. Herein, we propose a deep learning (DL) assisted SERS approach to enable rapid and sensitive detection of analytes on practical yet highly effective substrates prepared by direct spray-coating of a nanoparticle-free true solution of a reactive Ag ink and on-site thermal annealing mediated generation of nanostructures. This design ensured homogeneous distribution of Ag nanostructures throughout the entire substrate, significantly increasing the number of hotspots and enhancing the Raman signals, thereby achieving an impressive analytical enhancement factor of ~1010 in a reproducible and consistent manner. The diagnostic utility of this platform was demonstrated by detecting the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) protein in both buffer and saliva, with detection limits of 74.3 pg/mL and 7.43 ng/mL, respectively. The DL-assisted SERS not only accurately identified the presence or absence of viral antigen, but also automatically quantified the viral load. This automatic identification achieved an outstanding accuracy of ~99.9 %, highlighting the exceptional performance of the proposed platform. This simple, cost-effective, scalable, and ultra-sensitive DLassisted SERS platform offers significant opportunities for early and precise detection in a range of analytical scenarios
Open Access
Production of natural chitin film from pupal shell of moth: Fabrication of plasmonic surfaces for SERS-based sensing applications
(Elsevier Ltd, 2021-06-15) Chen, Y- M.; Bilican, B. K.; Çakmak, B.; Ali, A.; Zang, L- S.; Kaya, M.; Bilican, İsmail; Önses, Mustafa Serdar
Commercially available types of chitin or chitin isolate are usually in powder form and are nanofibrous in microstructure. However, the surface characteristics of natural chitin in the body of insects are currently understudied. Herein, natural chitin film was successfully produced from bio-waste of insect pupae of the Japanese giant silkworm. Two different surface morphologies of the chitin film were observed. We report for the first time a micropapillary surface structure of chitin which was observed on the dorsal side of the film. To further potential of the micropapillary structured natural chitin in sensing applications, we develop a protocol for generating a nanoscopic film of Ag using thermal evaporation. The Ag-deposited natural chitin films exhibited surface-enhanced Raman scattering (SERS) activity to an extent depending on the structure of the film. In conclusion, materials science has been expanded by addition of a natural, three-dimensional chitin film with utilizable properties.
Open Access
SERS-active linear barcodes by microfluidic-assisted patterning
(Elsevier, 2020-09-28) Pekdemir, S.; Ipekci, H. H.; Serhatlıoğlu, Murat; Elbuken, C.; Onses, M. S.
Simple, low-cost, robust, and scalable fabrication of microscopic linear barcodes with high levels of complexity and multiple authentication layers is critical for emerging applications in information security and anti-counterfeiting. This manuscript presents a novel approach for fabrication of microscopic linear barcodes that can be visualized under Raman microscopy. Microfluidic channels are used as molds to generate linear patterns of end-grafted polymers on a substrate. These patterns serve as templates for area-selective binding of colloidal gold nanoparticles resulting in plasmonic arrays. The deposition of multiple taggant molecules on the plasmonic arrays via a second microfluidic mold results in a linear barcode with unique Raman fingerprints that are enhanced by the underlying plasmonic nanoparticles. The width of the bars is as small as 10 μm, with a total barcode length on the order of 100 μm. The simultaneous use of geometric and chemical security layers provides a high level of complexity challenging the counterfeiting of the barcodes. The additive, scalable, and inexpensive nature of the presented approach can be easily adapted to different colloidal nanomaterials and applications.
Open Access
Silver nanoflowers with SERS activity and unclonable morphology
(Elsevier, 2023-02-26) Şakir, Menekşe; Torun, Neslihan; Kayacı, Nilgün; Torun, İlker; Kalay, Mustafa; Onses, M. Serdar
This manuscript presents surface-growth of silver nanoflowers with high surface-enhanced Raman scattering (SERS) activity and unique morphology. The nanoflower morphology is mediated by the seed-mediated growth of silver nanostructures over gold nanoparticles immobilized on hemispherical polymer features. Randomly positioned hemispherical polymer features are self-assembled via surface dewetting of a nanoscopic film of poly (2-vinylpyiridine) (P2VP) film on the polystyrene-grafted substrate. The time-dependent growth study shows that the silver nanoflowers evolve from the circular contact lines separating the P2VP features and underlying substrate. The three-dimensional nature of the underlying feature facilitates growth in a flower like morphology. The silver nanoflowers exhibit high levels of SERS activity allowing for detection of rhodamine 6G at a 100 pM level under 532 nm laser excitation. A feature matching algorithm-based image analysis confirms the unique morphology of every single silver nanoflower. The direct fabrication of silver nanoflowers at random positions with unclonable morphology and high SERS activity is particularly promising for anti-counterfeiting applications.
Open Access
Tunable plasmonic silver nanodomes for surface-enhanced raman scattering
(Springer, 2018) Kahraman, M.; Ozbay, A.; Yuksel, H.; Solmaz, R.; Demir, B.; Caglayan, H.
Surface-enhanced Raman scattering (SERS) is an emerging analytical method used in biological and non-biological structure characterization. Since the nanostructure plasmonic properties is a significant factor for SERS performance, nanostructure fabrication with tunable plasmonic properties are crucial in SERS studies. In this study, a novel method for fabrication of tunable plasmonic silver nanodomes (AgNDs) is presented. The convective-assembly method is preferred for the deposition of latex particles uniformly on a regular glass slide and used as a template for polydimethylsiloxane (PDMS) to prepare nanovoids on a PDMS surface. The obtained nanovoids on the PDMS are used as a mold for AgNDs fabrication. The nanovoids are filled with Ag deposition by the electrochemical method to obtain metallic AgNDs. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) are used for characterization of the structural properties of all fabricated AgNDs. The optical properties of AgNDs are characterized with the evaluation of SERS activity of 4-aminothiphonel and rhodamine 6G. In addition to experimental characterizations, the finite difference time domain (FDTD) method is used for the theoretical plasmonic properties calculation of the AgNDs. The experimental and theoretical results show that the SERS performance of AgNDs is strongly dependent on the heights and diameters of the AgNDs.