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

• reducing plasma results in the formation of complex three-dimensional silver morphologies showing a huge enhancement factor due to the formation of SERS hot spots. The SERS enhancement of the as-sputtered 200 nm silver film is greatly enhanced by an appropriate plasma treatment reaching about 30-fold

Low cost tips for tip-enhanced Raman spectroscopy fabricated by two-step electrochemical etching of 125 µm diameter gold wires

• Antonino Foti,
• Francesco Barreca,
• Enza Fazio,
• Cristiano D’Andrea,
• Paolo Matteini,
• Onofrio Maria Maragò and
• Pietro Giuseppe Gucciardi

Beilstein J. Nanotechnol. 2018, 9, 2718–2729, doi:10.3762/bjnano.9.254

• times of approximately 2 min. The tips can be easily manipulated and safely mounted, by gluing or clamping them into STM- or ShF-based TERS setups. The good performance of the tips is highlighted by TERS spectra of dyes, pigments and biomolecules. The enhancement factor in the range of 104–105 was found

• contact with the surface Figure 8 (black line). After each TERS measurement, the tip is retracted from the sample and its emission is mapped in order to be sure the TERS signal does not come from molecules adsorbed on the tip apex. Evaluation of the enhancement factor An estimation of the enhancement

• factor (EF) can be given by comparing the TERS signal increase with respect to the Raman signal measured when the tip is out of contact (far-field excitation conditions), normalizing to the different areas probed in each case [71]: where INF is the near-field TERS signal, IFF is the far-field Raman

Metal–dielectric hybrid nanoantennas for efficient frequency conversion at the anapole mode

• Valerio F. Gili,
• Lavinia Ghirardini,
• Davide Rocco,
• Giuseppe Marino,
• Ivan Favero,
• Iännis Roland,
• Giovanni Pellegrini,
• Lamberto Duò,
• Marco Finazzi,
• Luca Carletti,
• Andrea Locatelli,
• Aristide Lemaître,
• Dragomir Neshev,
• Costantino De Angelis,
• Giuseppe Leo and
• Michele Celebrano

Beilstein J. Nanotechnol. 2018, 9, 2306–2314, doi:10.3762/bjnano.9.215

• enhancement factor up to 30 with respect to the corresponding individual pillar (r = 410 nm), while for the type-2 configuration (g = 200 nm) the signal enhancement is about one order of magnitude. The contribution of the Au ring to the overall SH emission is negligible (Figure 4b), and thus the signal

Two-dimensional photonic crystals increasing vertical light emission from Si nanocrystal-rich thin layers

• Lukáš Ondič,
• Marian Varga,
• Ivan Pelant,
• Alexander Kromka,
• Karel Hruška and
• Robert G. Elliman

Beilstein J. Nanotechnol. 2018, 9, 2287–2296, doi:10.3762/bjnano.9.213

• shows the peak enhancement factors derived from the measurements results shown in Figure 2. We define the peak enhancement factor as a ratio of the peak intensity of the leaky mode to the PL intensity of the reference SiNC-rich layer at the same wavelength both measured with the optical fiber placed

• the hexagonal-lattice PhCs with hPhC2 was unintentional and occurred due to the fact that the sample etching happens also in the lateral direction. For the case of the PhCs with hPhC2, it also holds that for both lattice symmetries, the enhancement factor decreases with increase of the lattice

• enhancement factor implies that the higher the columns of the PhC (obviously up to a reasonable extent) the better the enhancement factor. We are not taking into account the “blue” lattice PhCs with height hPhC2, which has the worse performance, since it most probably originates from their poorer structural

The role of adatoms in chloride-activated colloidal silver nanoparticles for surface-enhanced Raman scattering enhancement

• Nicolae Leopold,
• Andrei Stefancu,
• Krisztian Herman,
• István Sz. Tódor,
• Stefania D. Iancu,
• Vlad Moisoiu and
• Loredana F. Leopold

Beilstein J. Nanotechnol. 2018, 9, 2236–2247, doi:10.3762/bjnano.9.208

• surfaces has also been proposed by Muniz-Miranda and Sbrana [18]. In contrast to the electromagnetic mechanism, the chemical effect requires an electronic contact between adsorbate and metal surface [14]. The enhancement factor for the chemical effect is estimated to be between 10–100 [8]. In this study

• . Further increasing the Cl− concentration leads to the aggregation of the colloid and therefore the SERS spectrum of the analyte is not observable anymore. Therefore, these results suggest that the number of active SERS sites is the key in determining the enhancement factor and that nanoparticle geometry

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

• quantum emitters with LSPR-matched absorption and emission spectra and high intrinsic quantum yields. The latter ensures that the probed fluorescence enhancement factor stems largely from the provided electromagnetic field enhancement [1][3][56]. Since the measurements are not carried out in the regime of

• fluorescence enhancement factor can be also accomplished by measuring the fluorescence emission of single dye molecule as a function of the antenna–sample separation. The corresponding approach curves account for two mechanisms occurring when the antenna is coupled to the dye molecule: 1.) the absorption

• the maximum spontaneous emission rate and the confocal background are evaluated. For the examples shown in Figure 3A the enhancement factor of the monomer antenna is 11 and for the CB[8]-dimer with an expected gap size of 0.9 nm the fluorescence enhancement factor yields a significantly increased

Self-assembled quasi-hexagonal arrays of gold nanoparticles with small gaps for surface-enhanced Raman spectroscopy

• Emre Gürdal,
• Simon Dickreuter,
• Fatima Noureddine,
• Pascal Bieschke,
• Dieter P. Kern and
• Monika Fleischer

Beilstein J. Nanotechnol. 2018, 9, 1977–1985, doi:10.3762/bjnano.9.188

• increased near-field [29]. To estimate a lower boundary for the enhancement factor of the particles we compared the corrected Raman spectra of sample A to a measurement of 4-MBA on a smooth gold film with a thickness of 70 nm, also on a silicon substrate. Both samples were treated in exactly the same way

• gold film we obtain a lower limit of the enhancement factor of ≈300. This is a very conservative lower limit, and compared to values commonly reported in literature it is significantly smaller, but we would like to stress that the estimation of SERS enhancement factors is inherently difficult and is

Toward the use of CVD-grown MoS₂ nanosheets as field-emission source

• Geetanjali Deokar,
• Nitul S. Rajput,
• Junjie Li,
• Francis Leonard Deepak,
• Wei Ou-Yang,
• Nicolas Reckinger,
• Carla Bittencourt,
• Jean-Francois Colomer and
• Mustapha Jouiad

Beilstein J. Nanotechnol. 2018, 9, 1686–1694, doi:10.3762/bjnano.9.160

• factor) is a particular value of the principal Schottky–Nordheim barrier function U. β is the local electrical field enhancement factor. is the work function of the emitter (considered to be 4.04 eV here [29]). In Figure 6a, the current density versus electric field (J–E) curve of the transferred MoS2

• from the local electric field. The ratio of the actual local electric field to the applied average electric field is known as the field-enhancement factor. In the present case, the field-enhancement factor, commonly used for evaluating FE properties, is calculated from the slope m of the F–N plot (a

• hydrothermally produced MoS2 NSs) [12]. The enhancement factor for our NSs is apparently smaller than the one recently reported on vertically aligned MoS2 NSs (β = 6240 for NSs with ultrathin edges) [9]. However, the electric field required to obtain a high current density of 10 µA/cm2 is much lower for our as

An implementation of spin–orbit coupling for band structure calculations with Gaussian basis sets: Two-dimensional topological crystals of Sb and Bi

• Sahar Pakdel,
• Mahdi Pourfath and
• J. J. Palacios

Beilstein J. Nanotechnol. 2018, 9, 1015–1023, doi:10.3762/bjnano.9.94

• antimonene including SOC, as obtained with the small-core pseudopotential basis set and the same enhancement factor as in the previous section. The results compare rather well down to any practical detail with those reported in the literature. In the inset of Figure 5 we show that the spin texture of the

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

• and Raman signal enhancement mediators. The efficiency of silver reduction was characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The developed substrates were applied for SERS detection of rhodamine 6G (enhancement factor of about 1–5 × 105) and an anti-ischemic mildronate drug

• (meldonium; enhancement factor of ≈102) that is known for its ability to increase the endurance performance of athletes. Keywords: meldonium; mesoporous silver substrates; silver oxide; surface-enhanced Raman spectroscopy; Introduction Nowadays one of the largest sectors of the global chemical industry is

•  4b) [33]. The enhancement factor (EF) for the system was calculated as described according to the standard equation, namely, where ISERS and IRS are the corresponding SERS and Raman spectroscopy signal intensities and nSERS and nRS are the molar quantities of R6G in SERS and Raman experiments. As

Direct writing of gold nanostructures with an electron beam: On the way to pure nanostructures by combining optimized deposition with oxygen-plasma treatment

• Domagoj Belić,
• Mostafa M. Shawrav,
• Emmerich Bertagnolli and
• Heinz D. Wanzenboeck

Beilstein J. Nanotechnol. 2017, 8, 2530–2543, doi:10.3762/bjnano.8.253

• the original morphology largely preserved. As a rule, the Au fraction increased in all the samples, as revealed by EDX analyses. The enhancement factor tended to be greater for the structures (or their parts) that initially had a lower Au content. A typical example presented in Figure 5 demonstrates

• , the shape of the deposit was largely preserved, but more importantly, the EDX analysis showed an increase in Au content throughout the nanostructure. The enhancement factor (EF) was considerably larger on the initially Au-poor, “end” side (EF ≈ 4), while the initially Au-rich “beginning” side saw only

• employs an oxygen-plasma treatment to further increase the purity of the deposited material. It was found that such an approach can significantly increase the Au content in the FEBID nanostructures, while preserving their structural stability. The enhancement factor of Au content was found to be dependent

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

• 1362 cm−1 R6G peak on the structured Au-film-coated PDMS substrate is about 8 times higher than the SERS tests on a commercial substrate (Q-SERS). A SERS enhancement factor ranging from 7.5 × 105 to 6 × 106 was achieved using the structured Au-film-coated PDMS surface, and it was demonstrated that the

• in determining the electric field amplitude distribution and the corresponding Raman enhancement factor. The electric field intensity generated by adjacent structures is higher than the electric field intensity generated by dispersed structures [37]. Therefore, compared to the dispersed pyramids, the

• pyramidal structures machined in the present study exhibit a stronger enhancement. The enhancement factor of the structured gold-coated PDMS surface can be calculated as follows [43][44]: where ISERS and INR are the intensities of SERS and normal Raman scattering, respectively; CSERS and CNR are the

Nanoantenna-assisted plasmonic enhancement of IR absorption of vibrational modes of organic molecules

• Alexander G. Milekhin,
• Olga Cherkasova,
• Sergei A. Kuznetsov,
• Ilya A. Milekhin,
• Ekatherina E. Rodyakina,
• Alexander V. Latyshev,
• Sreetama Banerjee,
• Georgeta Salvan and
• Dietrich R. T. Zahn

Beilstein J. Nanotechnol. 2017, 8, 975–981, doi:10.3762/bjnano.8.99

• CoPc. In the case of nanoantennas, the SERS enhancement is much weaker than that determined for CoPc on Au nanocluster arrays (enhancement factor of 2 × 104) observed in our previous experiments [24]. Much stronger SERS enhancement of CoPc on Au nanocluster arrays with respect to that for nanoantennas

• , the mode at 755 cm−1 is observed only in the case of the CoPc film deposited on the nanoantenna array (Figure 4a,b). Weak oscillations seen in Figure 4a,b are the interference fringes at the sample thickness (about 400 µm). The overall enhancement factor (EF) for the 10 nm thick CoPc film amounts to 2

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

• field enhancement factor that represents the hot spots eventually occurring for a specific illumination condition. In Figure 2, we consider two different rippled morphologies, (A) and (C), with corresponding SPP optical maps with enhancement factor Γ, shown in (B) and (D) respectively, for an applied

• Figure 2B and Figure 2D, respectively. In particular, Figure 2A,C shows that rippled surfaces featuring a quasi-regular pattern of stripes, or nanowires, present a strong enhancement factor: the occurrence of two main peaks in Figure 2A makes impossible to detect (in the dynamics chosen for the

• representation) the weaker peaks. On the contrary, the holed rippled surface (Figure 2C) leads to a smaller enhancement factor by six orders of magnitude. Different from spherical geometries or regular nanowires, rippled surfaces, as in Figure 2, give the possibility to study the enhancement factor on surfaces

Influence of hydrofluoric acid treatment on electroless deposition of Au clusters

• Rachela G. Milazzo,
• Antonio M. Mio,
• Giuseppe D’Arrigo,
• Emanuele Smecca,
• Alessandra Alberti,
• Gabriele Fisichella,
• Filippo Giannazzo,
• Corrado Spinella and
• Emanuele Rimini

Beilstein J. Nanotechnol. 2017, 8, 183–189, doi:10.3762/bjnano.8.19

• surface. The process stops after a certain thickness of oxide is formed and on top of it gold atoms agglomerate as solid clusters [18][19][20][21]. The optical properties of these gold clusters depend on their shape and morphology. It is reported in literature that the local field enhancement factor of

Surface-enhanced Raman scattering of self-assembled thiol monolayers and supported lipid membranes on thin anodic porous alumina

• Marco Salerno,
• Amirreza Shayganpour,
• Barbara Salis and
• Silvia Dante

Beilstein J. Nanotechnol. 2017, 8, 74–81, doi:10.3762/bjnano.8.8

• possible future devices. The enhancement factor in APA-based SERS can be as high as 1000, which means that the technique may detect molecules [15]. Additionally, the pores in tAPA can potentially serve as nano-wells for localized drug delivery [16][17]. In fact, while lower in loading capacity with respect

• enhancement factor G achieved by employing tAPA–Au with respect to the flat Au on silicon substrate can be estimated by using a simple formula: where P, t, A and I are laser power, accumulation time, active area for molecule adsorption and Raman intensity of the specific band, respectively [13]. The

• Raman measurements on bare thiols and on their combinations with lipid membranes, namely MbA with DOTAP and AT with POPC/POPS. The enhancement factor was estimated to be 500 to 1000 on tAPA–Au with respect to the flat Au surface and to the silicon substrate. The chemisorption of thiols and lipids was

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

• increase of the enhancement factor of the SSS thin film could be primarily ascribed to electromagnetic enhancement of increased NP numbers, since there might be more hot-spots in the SSS thin film [25][26]. As shown in Figure 2b and Figure 2c, more hot-spots would also be generated for the SBS thin film

Thickness dependence of the triplet spin-valve effect in superconductor–ferromagnet–ferromagnet heterostructures

• Daniel Lenk,
• Vladimir I. Zdravkov,
• Jan-Michael Kehrle,
• Günter Obermeier,
• Aladin Ullrich,
• Roman Morari,
• Hans-Albrecht Krug von Nidda,
• Claus Müller,
• Mikhail Yu. Kupriyanov,
• Anatolie S. Sidorenko,
• Siegfried Horn,
• Rafael G. Deminov,
• Lenar R. Tagirov and
• Reinhard Tidecks

Beilstein J. Nanotechnol. 2016, 7, 957–969, doi:10.3762/bjnano.7.88

• the free standing Nb film is assumed to be TcS = 6.1 K, yielding hF1 = 8.8 and hF2 = 606. If we take into account an enhancement factor of the slope of the temperature dependence of the upper critical field in [9], we obtain the coherence length in the superconductor ξS = 7.3 nm. According to Butler

Understanding interferometry for micro-cantilever displacement detection

• Alexander von Schmidsfeld,
• Tobias Nörenberg,
• Matthias Temmen and
• Michael Reichling

Beilstein J. Nanotechnol. 2016, 7, 841–851, doi:10.3762/bjnano.7.76

• measuring the Fabry–Pérot enhancement factor , which is defined as In case of negligible optical loss at very small distances d, is related to the cavity finesse by Here, we discuss the beams involved in generating the interference pattern in a typical cantilever setup and describe a systematic approach

• measure for the Fabry–Pérot enhancement factor [8]. We define positive and negative fringes so that a positive fringe covers a region of rising light intensity when the fiber is approached towards the cantilever. This is compatible with the more general definition that, for a positive fringe, the force

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

• nanocubes layers fully covered with GO revealed the presence of a homogeneous, flexible and smooth GO sheet folding over the silver nanocubes and extending onto the bare surface. Preliminary SERS experiments on adenine showed a higher SERS enhancement factor for GO on Langmuir–Blodgett films of AgNCs with

• intensity of the R6G probe and enhancement factor are obtained for the large surface densities, i.e., 32.5 AgNC/μm2. Absorbance spectra for the AgNC arrays obtained with procedure B were tentatively acquired for glass and silicon oxide substrates, respectively. Typical results on glass (see Supporting

Chemiresistive/SERS dual sensor based on densely packed gold nanoparticles

• Sanda Boca,
• Cosmin Leordean,
• Simion Astilean and
• Cosmin Farcau

Beilstein J. Nanotechnol. 2015, 6, 2498–2503, doi:10.3762/bjnano.6.259

• solution, drying). The SERS enhancement factor, EF, for this kind of self-assembled Au nanoparticle films is on the order 106 to 107, as we previously demonstrated in similar systems. It was calculated using the equation: where ISERS is the SERS intensity, IRaman is the Raman intensity, NSERS is the

Surface-enhanced Raman scattering by colloidal CdSe nanocrystal submonolayers fabricated by the Langmuir–Blodgett technique

• Alexander G. Milekhin,
• Larisa L. Sveshnikova,
• Tatyana A. Duda,
• Ekaterina E. Rodyakina,
• Volodymyr M. Dzhagan,
• Ovidiu D. Gordan,
• Sergey L. Veber,
• Cameliu Himcinschi,
• Alexander V. Latyshev and
• Dietrich R. T. Zahn

Beilstein J. Nanotechnol. 2015, 6, 2388–2395, doi:10.3762/bjnano.6.245

• ][5][6][7]. The progress in controlled nanostructuring of metal surfaces has led to the development of high-performance SERS substrates with an average SERS enhancement factor (EF) well above 106 (EF > 108) for ultrasensitive analysis of organic substances [10][11][12]. It was also shown that for

• ), the wavelength of the scattered photons is somewhat higher (λS = 641.4 nm) and even closer to the LSPR wavelength (Figure 5b). Consequently, between these two values, λL and λs, the conditions for the ultimate resonant SERS are fulfilled for which the maximal SERS enhancement factor is expected [48

Au nanoparticle-based sensor for apomorphine detection in plasma

• Chiara Zanchi,
• Andrea Lucotti,
• Matteo Tommasini,
• Sebastiano Trusso,
• Ugo de Grazia,
• Emilio Ciusani and
• Paolo M. Ossi

Beilstein J. Nanotechnol. 2015, 6, 2224–2232, doi:10.3762/bjnano.6.228

• a tiny region of nanometer thickness around a given particle, with a marked dependence of the enhancement factor on the details of the local surface nano-roughness. The size of the inter-island channels makes them likely to have a twofold role. They are suitable to provide preferential, direct

• in Figure 1B. Such Au substrates are thus expected to display spatially uniform optical behavior. The typical enhancement factor determined for these substrates is 107 [24]. SERS spectra of APO aqueous solution The SERS spectra of 100 µg/mL APO collected with different exposure times, ranging from 2

Experimental determination of the light-trapping-induced absorption enhancement factor in DSSC photoanodes

• Serena Gagliardi and
• Mauro Falconieri

Beilstein J. Nanotechnol. 2015, 6, 886–892, doi:10.3762/bjnano.6.91

• . In this paper, this task is addressed by introducing a spectral absorption enhancement factor as a parameter to quantify the light trapping effect. The experimental value of this parameter was obtained by comparing the experimentally determined fraction of absorbed light by a dye-sensitized

• extreme cases of the absence of light trapping and maximum light trapping. Accordingly, the photocurrent was calculated under the assumption of solar irradiation, which defined two useful boundaries. Using the experimentally derived values of the spectral absorption enhancement factor in the photoanode

• measuring the dye content by desorption analysis. The relevant parameter obtained from such an experimental characterization is the spectral dependence of the absorption enhancement factor resulting from the LT. Furthermore, the fraction of absorbed light in a PA composed of a mesoscopic structure based on

Combination of surface- and interference-enhanced Raman scattering by CuS nanocrystals on nanopatterned Au structures

• Alexander G. Milekhin,
• Nikolay A. Yeryukov,
• Larisa L. Sveshnikova,
• Tatyana A. Duda,
• Ekaterina E. Rodyakina,
• Victor A. Gridchin,
• Evgeniya S. Sheremet and
• Dietrich R. T. Zahn

Beilstein J. Nanotechnol. 2015, 6, 749–754, doi:10.3762/bjnano.6.77

• place. The periodic variation of the enhancement factor of the phonon mode in CuS NCs as a function of SiO2 layer thickness (Figure 3) was established for different laser excitation lines (632.8, 514.5, and 325 nm). Here, the intensity of the phonon mode of CuS NCs on a bare Si should be taken as a

• reference. However, it is worth mentioning that the intensity of the phonon mode is equal or below the noise level. Therefore, only an estimate of the IERS (as well as SERS) enhancement factor is possible. The maximal estimated IERS enhancement for the excitation wavelength of 632.8 nm reaches a value of at

• evidence of the phonon modes from CuS NCs is detected. However, a strong Raman band centred near 474 cm−1 arises when the Raman spectra are acquired from the area where CuS NCs are deposited on the nanocluster array. The SERS enhancement factor can hardly be determined since no reference signal from CuS