Surface enhanced raman scattering of biomolecules

Section I Hydrodynamic Instabilities and Critical Phenomena.- To Scale or not to Scale? - The Puzzle at the Lambda Point of Liquid 4He.- Transition to Turbulence in Couette-Taylor Flow.- Hydrodynamic Instabilities and Turbulence.- Light from Gels and a Single Polymer Chain near Phase Transitions.- Interferometric Studies of Thick Film Critical Behavior.- Section II Physics in Two Dimensions and Defects.- Melting and Liquid Crystals in Two Dimensions.- Light Studies of Molecular Orientation Fluctuations in Two Dimensions.- Multiphonon Boundary of the Excitation Spectrum.- Raman Spectra of Proustite and Pyrargyrite Crystals in Low Temperature Phases.- Finite Field Local Field Catastrophe - Application to the Spectra of KCNxCl1?x.- The Effect of Long Range Fluctuations in Impurity Potential on the Electron Light in Heavily Doped Semiconductors.- Resonant and Trapping of 29 cm?1 Acoustic Phonons in Ruby Crystals.- Section III Non-Local and Transient Phenomena.- Some Aspects of the Theory of Surface Polaritons.- Recent Developments in Non-Local Optics.- Resonant Brillouin of Exciton Polaritons.- Ultraslow Optical Dephasing of Pr3+:LaF3.- Picosecond Raman Gain Studies of Molecular Vibrations on a Surface.- Section IV Spins and Excitons.- Brillouin-Mandelstam of Light in Antiferromagnetic CoCO3.- Observation of Pure Spin Diffusion Without Charge Transport by Spin Flip Raman Scattering.- Spin-Flip from Photoexcited Excitons in SiC.- The of Light by Spin Waves on Ferromagnetic Surfaces.- Relaxation of Energy and Polarization in the Resonant Secondary Emission Spectra of Semiconductors.- Resonant Raman from Stress-Split Forbidden Excitons in CU2O.- Low Frequency Exciton and Raman Spectra of CoCO3.- Theoretical and Experimental Determinations of Raman Cross Sections in Simple Solids.- Section V Resonance and Charge Excitations.- Resonant Secondary Emission by Impurities in Crystals.- The Raman and Hot Luminescence of Self-Trapping Excitons.- Phenomenological Description of Light and Thermal Radiation.- Raman from Plasmon-Phonon Coupled Modes in GaP.- Interaction Between Localized Carriers in the Accumulation Layer and Extended Bulk LO Phonons in InSb and GaSb: Raman Interference Lineshapes.- Inelastic Light by the Two Dimensional Electrons in Semiconductor Heterojunction Superlattices.- On the Distinction Between Resonant and Hot Luminescence: Application of Theory to Experiment.- Section VI Phase Transitions.- Light Near Structural Phase Transition Points in Pure Crystals and in Crystals Containing Defects.- Raman From Charge Density Waves and Superconducting Gap Excitations in 2H-TaSe2 and 2H-NbSe2.- Quasielastic Light Near Structural Phase Transitions.- High Resolution X-Ray and Light Spectroscopy of Liquid Crystals.- Optics and Electrooptics of Chiral Smectics.- The Size, Shape and Polydisperity of Micelles of Amphiphillic Molecules.- Resonance Raman Studies of Visual Pigments.- A Nanosecond Probe of Hemoglobin Dynamics Using Time Resolved Resonance Raman Scattering.- Section VII Multi-Photon Spectroscopy.- Recent Results in Four-Photon Spectroscopy of Condensed Media.- Recent Progress in Four-Wave Mixing Spectroscopy in Crystals.- Coherent Raman Ellipsometry of Liquid Water: New Data on the Vibrational Stretching Region.- Time Resolved Coherent Anti-Stokes Raman in Weakly Disordered Molecular Crystals.- Intense Light Resonance Scattering: Spectra and Photon Correlations.- Section VIII Resonance and Surface Enhanced Raman Scattering.- Intensity Effects in Resonance Light Scattering.- The Spontaneous Diffraction of Light by Resonance Atoms.- Raman by Molecules Adsorbed on Metals: an Overview.- Raman Spectroscopy of Molecular Monolayers in Inelastic Electron Tunneling Spectroscopy Junctions.- A Theory of Giant Raman Scattering by Adsorbed Molecules on Metal Surfaces.- Concluding Remarks.- Participants.- Author Index.

The discovery that Raman scattering from molecules adsorbed on metal surfaces (electrodes, colloids and island films) were enhanced by 105–106 has caused extraordinary interest and excitement in recent years1,2. What is the advantage of this Surface Enhanced Raman Scattering (SERS)? 1. The high enhancement factor of the Raman scattering intensity creates a new technique for obtaining high resolution vibrational spectra of molecules (organic, inorganic, biomolecules) from very dilute solutions down to 10-9 M. 2. SERS investigations have shown that this surface spectroscopy is an extemely powerful in-situ vibrational method of studying the interfacial behavior of biomacromolecules in their natural environment: water2. 3. Combining SERS spectroscopy and high-performance thin-layer chromatography (HPTLC) has permitted in situ analysis of HPTLC spots down to nanogram amounts of substances3. 4. It was also demonstrated that ring breathing SERS bands of nucleic acids bases are conformation sensitive for B → Z transitions in DNA4.

Surface-enhanced fluorescence (SEF) and surface-enhanced Raman scattering (SERS) techniques were applied in this work to study the ionization, aggregation, and adsorption onto the metal surface of the antitumoral drug hypericin (Hyp). Hyp is able to interact with Ag nanoparticles under different mechanisms depending on the ionization state of the drug. The monoanionic Hyp− can homoassociate giving rise to H-aggregates which render an intense SEF emission, in contrast to what usually occur in solution, where the fluorescence is quenched. At a pH below 6.0, the neutral Hyp species exist under the 1, 6-dixo tautomer on the metal surface. This structure is able to form J-aggregates by intermolecular H-bonds giving rise to molecular networks that can be adsorbed on the metal surface oriented parallel to this surface. In this case, the SEF enhancement is lower due to this parallel orientation. The SERS spectra were very important to calculate the different ionization pK of Hyp on the surface and to obtain information on key physicochemical processes that Hyp undergoes, such as the tautomerization, intermolecular interaction, and the orientation on the surface.

Surface-enhanced Raman scattering (SERS) has been proposed for the application in the detection of furfural concentration in transformer oil recently. However, the intensity changes of SERS signals, which generate from various vibration modes of furfural molecule, are still unable to be explained well. In this paper, the simulation analysis of the adsorption mode of furfural on the metal surface and its SERS characteristics has been analyzed based on the density functional theory. Firstly, the simulation model of furfural molecule and silver cluster, whose selections of the silver atomic number and the furfural molecule adsorption position had been optimized, was built by GaussView and Gaussian software. Then, SERS signals from different vibration modes of furfural molecule and silver cluster were calculated and identified. By comparing theoretical calculation results with measured furfural spectra, the mode of furfural molecule adsorbed on metal surface was determined. These results can provide theoretical basis for the in-situ SERS detection of furfural dissolved in transformer oil.

Surface-enhanced Raman scattering (SERS) is a powerful analytical technique that enhances the Raman scattering signal from molecules adsorbed on or in close proximity to the metal surface. It is possible owing to localized surface plasmon resonance occurring in nanostructures metal surfaces. There are two commonly considered mechanisms for SERS, electromagnetic and chemical enhancement. The electromagnetic theory emphasizes that the Raman enhancements for adsorbates on particular surfaces occur because of the enhancement in electric field provided by the surface. When the incident light strikes the surfaces, surface plasmons can be excited by radiation, resulting in enhanced electromagnetic fields close to the surface. The chemical theory is thought to involve the creation of new electronic states and the formation of charge transfer complexes in some special cases between the chemisorbed species and the SERS active substrates, resulting in an enhanced Raman cross section of the molecules. This chapter describes the SERS activities of quinone derivatives by plasmonic silver nanoparticles and pollutant detection using gold nanoparticles. SERS studies of 2-bromo-1,4-naphthoquinone and 2,3-dibromo-1,4-naphthoquinone on prepared nanoparticles are described. SERS analysis of polluted soil is also discussed. The orientation of the above molecules on silver nanoparticles was elucidated from the spectral analysis

Η φασματοσκοπία Raman θεωρείται αξιόπιστη μέθοδος χαρακτηρισμού της μοριακής δομής της ύλης. Τελευταία δε καταβάλλεται μεγάλη προσπάθεια να αναδειχθεί και ως μη επεμβατική τεχνική ανίχνευσης ουσιών φαρμακευτικού και βιολογικού ενδιαφέροντος. Επειδή όμως το φαινόμενο Raman είναι ασθενές και τα όρια ανίχνευσης των ουσιών αυτών ιδιαίτερα χαμηλά, η συμβατική φασματοσκοπία Raman ανταποκρίνεται με μεγάλη δυσκολία στις απαιτήσεις μιας μη επεμβατικής τεχνικής. Τα τελευταία χρόνια με την ανακάλυψη της επιφανειακής ενίσχυσης της σκέδασης Raman (Surface Enhanced Raman Scattering) και την ανάπτυξη της ομώνυμης τεχνικής SERS αυξήθηκε η πιθανότητα του φαινομένου κατά τάξεις μεγέθους. Στο πλαίσιο αυτό, έχουν αναφερθεί και μελέτες SERS με ανίχνευση σκέδασης Raman ακόμη και από ένα μόνο μόριο (single molecule detection).Προϋπόθεση όμως ανάπτυξης φαινομένου SERS είναι η γειτνίαση της εξεταζόμενης ουσίας με νανοσωματίδια αργύρου (Ag) ή χρυσού (Au). Τα νανοσωματίδια αυτά χρησιμοποιούνται κυρίως είτε υπό μορφή κολλοειδών διαλυμάτων είτε υπό την μορφή νανοδομημένων επιφανειών. Μια επιπλέον παράμετρος που πρέπει να συνυπολογισθεί ώστε η μέθοδος αυτή να χαρακτηριστεί αναλυτική είναι η δυνατότητα πραγματοποίησης με SERS ποσοτικών μετρήσεων. Στην παρούσα εργασία ως “υπόστρωμα” εμφάνισης του φαινομένου SERS χρησιμοποιήθηκαν κολλοειδή διαλύματα Au και Ag (~2 mL), στα οποία προστίθεντο 25-100 μL διαλύματος της προς ανίχνευσης ουσίας. Η χρησιμοποίηση της γεωμετρίας σκέδασης 90ο, της πλέον ενδεδειγμένης για λήψη φασμάτων Raman από υγρά και κολλοειδή διαλύματα νανομετρικής κλίμακας (10-100 nm), έδωσε τη δυνατότητα ανίχνευσης συγκεντρώσεων ουσιών-στόχων ακόμη και της τάξης των fg/mL. Επιπλέον, η χρησιμοποίηση μιας κυψελίδας με συνεχή ταλάντωση σε κάθετη ως προς το επίπεδο σκέδασης διεύθυνση (oscillating or shaking cell), επέτρεψε την πραγματοποίηση ποσοτικών μετρήσεων SERS σε συγκεντρώσεις της τάξης των (sub)-ng & (sub)-pg/mL. Η διάταξη αυτή φωταψίας δείγματος και συλλογής σκεδαζόμενης ακτινοβολίας εφαρμόστηκε σε αντικαρκινικά φάρμακα (Novantrone® & Doxorubicin), αντιβιοτικό (Ciproxin®) και βάσεις του DNA. Στην περίπτωση του αντιβιοτικού με ενεργή ουσία το Ciprofloxacin ελήφθησαν ποσοτικά αποτελέσματα σε διαλύματα τεχνητών δακρύων της τάξης των ng/mL, κάτω από την συνολική κλίμακα της μέσης ανασταλτικής πυκνότητας (minimum inhibitory concentration range) του φαρμάκου. Στόχος και φιλοδοξία είναι η τεχνική αυτή να αναδειχθεί ως μια ταχεία μη επεμβατική αναλυτική μέθοδος μέτρησης φαρμακευτικών ή/και βιολογικών ουσιών σε σωματικά υγρά (π.χ. σίελος, δάκρυα, …), για την μελέτη της φαρμακοκινητικής, την έγκαιρη διάγνωση ασθενειών καθώς και τη μελέτη ελεγχόμενης αποδέσμευσης ενεργών ουσιών από πολυμερικές μήτρες σε πολύ μικρές συγκεντρώσεις. Επιπλέον, έγινε προσπάθεια μελέτης/ανίχνευσης μορίων Ε18 primary rat cortical cells με την χρήση του SERS σε συνθήκες προσομοίωσης ηλεκτροχημικού εμφυτεύματος. Για τον λόγο αυτό σχεδιάστηκε και αναπτύχθηκε ένας μικρο-επωαστής (micro-incubator) που επιτρέπει αφ’ ενός μεν τη συντήρηση των κυττάρων σε περιβάλλον κατάλληλο για τη μελέτη τους (layer of Neurobasal-culture medium with a 95% air & 5% CO₂ gas flow at 37°C), αφ’ ετέρου δε την προσαρμογή του σε χώρο υποδοχής δείγματος ενός φασματοφωτόμετρου μικρο-Raman για τη λήψη φασματοηλεκτροχημικών μετρήσεων Raman/SERS. Το κύριο σημείο ενδιαφέροντος στο οποίο εστιάσαμε στην παρούσα εργασία αναφέρεται στην διερεύνηση ανίχνευσης βασικών/θεμελιωδών μορίων των κυττάρων στo θρεπτικό υγρό του πειράματος για την ταχεία εκτίμηση ενδεχόμενης αποδέσμευσης DNA που θα αντικατόπτριζε την κατάσταση των κυττάρων.

As considerable attention was recently paid to label-free technology in bioanalysis field,[1–3] analytical techniques employing no label such as surface plasmon resonance,[4] piezoelectrics,[5] cantilevers,[6] and transistors[7] have been increasingly suggested. Surface-enhanced Raman scattering (SERS) is one of the promising candidates for label-free analysis because it can provide molecular fingerprint information in the aqueous phase. It is attractive in that it provides sufficient enhancement, as high as 1010 times that of normal Raman signals, allowing quick detection of low-concentration analytes. Currently, SERS is expected to enable even realtime monitoring of molecular secretions in biological systems[8,9] or intermediate species temporarily present during chemical/electrochemical reactions without labeling.[10,11] SERS, employing visible incident light, is observed at nanoparticles, nanoshells, and the rough surfaces of a few metals like Au, Ag, or Cu, as well as narrow interstices among them (“hot spots”). Since SERS originates from nanostructures per se, its intensity is sensitive to the geometry, size, and shape of the substrates.[12] Sophisticated engineering of nanomaterials became a hot issue in nanoscience and in due course has driven significant recent progress in the development of better SERS substrates.[13] As a consequence, many metallic nanostructures with highly elaborate morphologies have been reported, such as Au nanorods[14] and Ag

Impact of temperature-induced coalescence on SERS properties of Au nanoparticles deposited on GaN nano-columns

In this research, sensing performance of mono and bimetallic nanophotonics SERS sensors of gold-silver nano-columns for the detection of chlorpyrifos was investigated. For optimum substrates for Gold-silver/nano-column surface-enhanced, Raman scattering (SERS) was achieved with the silicon substrate. By combining the Ag SERS activity with the Au chemical stability and nano-columns Si large field enhancement, the Au-Ag/nano-columns Si substrate revealed perfect reproducibility, homogeneity, sensitivity in addition to chemical stability. The sensors were tested by Atomic force microscope (AFM), field emission scanning electron microscope (FESEM), energy-dispersive X-ray analysis (EDS), and X-ray diffraction (XRD). Findings presented in this research indicated modified distributions and sizes of formed alloy nanoparticles, and the hot spots junctions within the nanophotonics layer after changing the nanoparticles types. The SERS sensors performance displayed an excellent recognition of ultra-low concentrations of chlorpyrifos solutions with an exponential relationship with the Raman signal. The highest enhancement factor (Ef=1.56×106) and minimum limit of detection 0.069 mg/Kg were obtained with Au-Ag sensors.

Well defined gold nanostructures of various sizes are fabricated on glass substrates using high-resolution electron-beam lithography/lift-off techniques and detailed surface-enhanced Raman scattering (SERS) properties of crystal violet molecules are studied in order to elucidate electromagnetic (EM) field enhancement effects on the fabricated structures. SERS measurements are performed with high reproducibility using in situ Raman microspectroscopy in aqueous solution. An analysis based on EM theory is performed using field-enhancement factors obtained from finite-difference time-domain (FDTD) simulations and the analysis reproduces experimental results very well. It is noteworthy, furthermore, that the proposed analytic method of EM effects on SERS allows the estimate of the ideal local temperature of gold nanostructures by canceling out the difference in EM field factors at Stokes and anti-Stokes Raman scattering wavelengths. Thus, these experimental results demonstrate that quantitative analysis based on EM theory can be obtained using highly controlled gold nanostructures for SERS measurements with high reproducibility, a result that is promising for the construction of a SERS analysis chip. Although no SERS chip reported so far has been usable for quantitative analysis, this study opens the door for construction of a quantitative SERS chip.

Raman scattering signals can be enhanced by several orders of magnitude on surface‐enhanced Raman scattering (SERS) substrates made from noble metal nanostructures. Some SERS substrates are even able to detect single‐molecule Raman signals. A novel silver nanobud (AgNB) substrate with superior SERS activity was fabricated with a solid‐state ionics method. The AgNB substrate was formed by tightly collocated unidirectional 100 nm size silver buds, presenting a highly rough surface topography. Distinct SERS signals of single λ‐DNA molecules in water were detected on AgNB substrates. AgNB substrates were compared with disordered silver nanowire (AgNW) substrates manufactured by the same method through the SERS detection of λ‐DNA solutions. This original AgNB substrate provides a reliable approach towards trace analysis of biomacromolecules and promotes the utilization of the SERS technique in biomedical research.

Excitation profiles of SERS (surface-enhanced Raman scattering) and/or SERRS (surface-enhanced resonance Raman scattering) spectral bands of two forms of a Ag-bpy (bpy = 2,2'-bipyridine) surface complex and of [Ru(bpy)3]2+ on Ag nanoparticle (hydrosol) surfaces were determined from the spectra excited in the 458-600 nm region and are reported together with the FT-SERS spectra of the Ag-bpy surface complex and FT Raman spectra of [Ru(bpy)3] Cl2. Seven of the observed 11 fundamentals as well as their first overtones and combination bands are selectively enhanced in SERS of the Ag-bpy surface complex formed in the Ag colloid/HCl/bpy system. The profiles of these bands show a common maximum at approximately 540 nm. The selectively enhanced bands of the Ag-bpy surface complex have nearly the same wavenumbers as those enhanced in the SERRS and resonance Raman spectra of [Ru(bpy)3]2+ upon excitation close to the 453 nm maximum of its MLCT absorption band. Moreover, the intensity patterns of the bpy vibrations of the two species match both in resonance (541 nm excitation for Ag-bpy, 458 nm for [Ru(bpy)3]2+) and in off-resonance (458 and 1064 nm for Ag-bpy, 1064 nm for [Ru(bpy)3]2+). The distinct band shapes of the excitation profiles of the selectively enhanced vibrational modes of the Ag-bpy surface complex, as well as the observation of overtones and combination bands in the SERS spectra upon excitation into this "band", are interpreted in terms of a charge-transfer resonance contribution to the overall SERS enhancement. In view of the near-coincidence of the vibrational modes coupled to the resonant electronic transition of Ag-bpy with those coupled to the MLCT transition of [Ru(bpy)3]2+, the resonant electronic transition is tentatively assigned to a Ag metal to bpy (pi*) CT transition.

In this study, we developed a simple surface-enhanced Raman Scattering (SERS) composite substrate, composed of an all-metal metasurface and on-surface random distributing silver nanoparticles (AgNPs), to enhance the performance of SERS sensing. The metasurface is made up of gold (Au) nanopillars array on aluminum (Al), it can localize the electromagnetic field energy with a resonant absorption peak near the 630 nm wavelength, which contributes to the SERS performance of AgNPs deposited into the structure. The composite substrate can significantly improve the sensing performance, and the SERS Enhancement Factor (EF) reaches 2.81 × 106. The substrate also has good stability and reproducibility. The research is based on the combination of Localized Surface Plasmon Resonance (LSPR) and SERS effects, providing a method and idea for improving the sensitivity of SERS detection, and achieving the trace detection of Rhodamine 6G (R6G) and Thiram at 10−10 M, respectively.

Surface-enhanced Raman scattering (SERS) is a unique analytical technique that provides fingerprint spectra, yet facing the obstacle of low collection efficiency. In this study, we demonstrated a simple approach to measure surface plasmon-coupled directional enhanced Raman scattering by means of the reverse Kretschmann configuration (RK-SPCR). Highly directional and p-polarized Raman scattering of 4-aminothiophenol (4-ATP) was observed on a nanoparticle-on-film substrate at 46° through the prism coupler with a sharp angle distribution (full width at half-maximum of ∼3.3°). Because of the improved collection efficiency, the Raman scattering signal was enhanced 30-fold over the conventional SERS mode; this was consistent with finite-difference time-domain simulations. The effect of nanoparticles on the coupling efficiency of propagated surface plasmons was investigated. Possessing straightforward implementation and directional enhancement of Raman scattering, RK-SPCR is anticipated to simplify SERS instruments and to be broadly applicable to biochemical assays.

Surface-enhanced Raman scattering (SERS) has garnered substantial attention due to its ability to achieve single-molecule sensitivity by utilizing metallic nanostructures to amplify the exceedingly weak Raman scattering process. However, the introduction of metal nanostructures can induce a background continuum which can reduce the ultimate sensitivity of SERS in ways that are not yet well understood. Here, we investigate the impact of laser irradiation on both Raman scattering and backgrounds from self-assembled monolayers within nanoparticle-on-mirror plasmonic nanocavities with variable geometry. We find that laser irradiation can reduce the height of the monolayer by inducing an irreversible change in molecular conformation. The resulting increased plasmon confinement in the nanocavities not only enhances the SERS signal, but also provides momentum conservation in the inelastic light scattering of electrons, contributing to the enhancement of the background continuum. The plasmon confinement can be modified by changing the size and the geometry of nanoparticles, resulting in a nanoparticle geometry-dependent background continuum in SERS. Our work provides new routes for further modifying the geometry of plasmonic nanostructures to improve SERS sensitivity.