The active species in surface-enhanced Raman scattering of flavins on silver colloids

Lee, Nam Soo; Sheng, Rong Sheng.; Morris, Michael D.; Schopfer, Lawrence M.

doi:10.1021/ja00280a012

Cited by 36 publications

(34 citation statements)

References 3 publications

(3 reference statements)

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“…The bands used are associated with the ring III stretching modes coupled with a N–H bending mode and ring II modes of riboflavin, respectively. 48 , 49 …”

Section: Resultsmentioning

confidence: 99%

Sheath-Flow Microfluidic Approach for Combined Surface Enhanced Raman Scattering and Electrochemical Detection

et al. 2015

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The combination of hydrodynamic focusing with embedded capillaries in a microfluidic device is shown to enable both surface enhanced Raman scattering (SERS) and electrochemical characterization of analytes at nanomolar concentrations in flow. The approach utilizes a versatile polystyrene device that contains an encapsulated microelectrode and fluidic tubing, which is shown to enable straightforward hydrodynamic focusing onto the electrode surface to improve detection. A polydimethyslsiloxane (PDMS) microchannel positioned over both the embedded tubing and SERS active electrode (aligned ∼200 μm from each other) generates a sheath flow that confines the analyte molecules eluting from the embedded tubing over the SERS electrode, increasing the interaction between the Riboflavin (vitamin B2) and the SERS active electrode. The microfluidic device was characterized using finite element simulations, amperometry, and Raman experiments. This device shows a SERS and amperometric detection limit near 1 and 100 nM, respectively. This combination of SERS and amperometry in a single device provides an improved method to identify and quantify electroactive analytes over either technique independently.

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“…The bands used are associated with the ring III stretching modes coupled with a N–H bending mode and ring II modes of riboflavin, respectively. 48 , 49 …”

Section: Resultsmentioning

confidence: 99%

Sheath-Flow Microfluidic Approach for Combined Surface Enhanced Raman Scattering and Electrochemical Detection

et al. 2015

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“…Hence, with the laser excitation wavelength of 514.5 nm being used, the compound is nonresonant, but the silver colloid is expected to quench and to remove most of the fluorescence background. It has been reported that riboflavin is bound strongly to the silver surface through the N(3) position, highlighted in the chemical structure …”

Section: Resultsmentioning

confidence: 99%

Preparation and characterisation of a stable silver colloid for SER(R)S spectroscopy

White¹,

Hjortkjaer²

2013

J Raman Spectroscopy

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A method for the reproducible preparation of a silver colloid with strong surface-enhanced Raman scattering (SERS) properties, good stability with a zeta potential of À55 mV and a shelf life exceeding 1 year is reported. The mean particle size is 20 nm with a narrow size distribution of 10-30 nm. The colloid is produced by the reduction of silver nitrate with hydroxylamine phosphate to give a negatively charged phosphate surface on the silver particles. This is an ultrafast room temperature reaction and with controlled rapid addition and dispersion of reagents, very reproducible batches of colloid can be prepared making it suitable for commercial applications of Surface enhanced resonance Raman scattering(SER(R)S) spectroscopy. The stability of the colloid is attributed to the extremely low solubility product (K sp ) of silver phosphate. Characterisation and stability study data for this colloid have been obtained by ultraviolet-visible spectroscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, particle size analysis and SERS analyses using a 514 nm laser on a Raman spectrometer. A SERS method to detect and to identify riboflavin in a vitamin B complex tablet is reported to illustrate a SERS application based upon the use of this silver colloid.

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“…Table S-1 lists the observed Raman bands for each spectrum, along with peak assignments. As shown in spectrum A, oxidized riboflavin is present at the initial potential of 0.0 V. 37, 39 There are no changes in the vibrational bands until -0.5 V, which correlates with the beginning of the cathodic peak in the voltammogram. Spectrum B highlights those changes.…”

Section: Resultsmentioning

confidence: 89%

“…36, 37 The main downside of RR is the intense fluorescence of the isoalloxazine group that can obscure the spectra. Surface enhanced Raman spectroscopy (SERS) can avoid the fluorescence interference and the flavin system has been studied utilizing both silver colloids 38, 39 and roughened silver electrodes. 18, 24, 40 Under potential control, the studies on silver electrodes observed the semi-quinone intermediate, but neither detected fully reduced flavin.…”

Section: Introductionmentioning

confidence: 99%

SERS speciation of the electrochemical oxidation–reduction of riboflavin

Bailey

Schultz

2016

Analyst

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The reduction and oxidation of the flavin system is an important electron transfer reaction in biological systems. Several reaction pathways exist to connect oxidized to fully reduced riboflavin, each with unique intermediates including a semi-quinone radical. By performing surface-enhanced Raman scattering (SERS) with simultaneous electrochemical detection of riboflavin at different pH values, we are able to correlate reversible changes in spectral features to the current changes observed in the cyclic voltammetry. Multivariate curve resolution analysis of the SERS spectra indicates that three distinct components were present at the SERS electrode at each pH during the potential sweep. To verify and better understand the variations in Raman bands across the voltammogram, density functional theory (DFT) calculations were performed to model the effect of pH and oxidation state on the riboflavin Raman spectrum. The calculated spectra show qualitative agreement with the species identified in the chemometric analysis. This combination of results indicates the presence of the oxidized, semi-quinone, and reduced forms of riboflavin and provides insight into the mechanism of the flavin redox system.

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The active species in surface-enhanced Raman scattering of flavins on silver colloids

Cited by 36 publications

References 3 publications

Sheath-Flow Microfluidic Approach for Combined Surface Enhanced Raman Scattering and Electrochemical Detection

Sheath-Flow Microfluidic Approach for Combined Surface Enhanced Raman Scattering and Electrochemical Detection

Preparation and characterisation of a stable silver colloid for SER(R)S spectroscopy

SERS speciation of the electrochemical oxidation–reduction of riboflavin

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