Near-infrared Surface-enhanced Raman Spectroscopy Research Articles

Differentiating Follicular Thyroid Carcinoma and Thyroid Adenoma by Using Near-Infrared Surface-Enhanced Raman Spectroscopy

Differentiating Follicular Thyroid Carcinoma and Thyroid Adenoma by Using Near-Infrared Surface-Enhanced Raman Spectroscopy

Toward a SERS Diagnostic Tool for Discrimination between Cancerous and Normal Bladder Tissues via Analysis of the Extracellular Fluid.

Vibrational spectroscopy provides the possibility for sensitive and precise detection of chemical changes in biomolecules due to development of cancers. In this work, label-free near-infrared surface enhanced Raman spectroscopy (SERS) was applied for the differentiation between cancerous and normal human bladder tissues via analysis of the extracellular fluid of the tissue. Specific cancer-related SERS marker bands were identified by using a 1064 nm excitation wavelength. The prominent spectral marker band was found to be located near 1052 cm–1 and was assigned to the C–C, C–O, and C–N stretching vibrations of lactic acid and/or cysteine molecules. The correct identification of 80% of samples is achieved with even limited data set and could be further improved. The further development of such a detection method could be implemented in clinical practice for the aid of surgeons in determining of boundaries of malignant tumors during the surgery.

Silk fibroin-decorated with tunable Au/Ag nanodendrites: A plastic near-infrared SERS substrate with periodic microstructures for ultra-sensitive monitoring of lactic acid in human sweat

The flexible and plastic near-infrared surface-enhanced Raman spectroscopy (NIR-SERS) substrate, with efficient tunable surface microstructures for probe molecular detection on irregular targets, has great potential for ultra-sensitive monitoring in real-world scenarios. Herein, we propose an interesting 785 nm laser-excited plastic SERS substrate based on the silk fibroin fibers (SFF) decorated with multiple-branched Au/Ag nanodendrites (NDs). Compared with the original smooth flexible substrate, the further constructed plastic SFF-Au/Ag NDs with concave pyramid surface microstructures provides a relatively higher NIR-SERS activity at bottom of the inward concave region. Moreover, the enhanced NIR-SERS activity is also highly related to the content of Au/Ag NDs in the hybrid flexible substrate. The maximal NIR-SERS signal intensity can be realized at the content of 0.15 wt% Au/Ag NDs in the SFF-Au/Ag NDs, which is about 8-fold enhancement compared to that obtained at the content of 0.01 wt%. Then, the molecular detection limits of crystal violet (CV) and 4-mercaptobenzoic acid (4-MBA) are calculated about 10−15 and 10−13 M, respectively, reaching the ultra-sensitive requirements of NIR-SERS trace detection. Moreover, the substrate can detect lactic acid (LA) molecules with a concentration as low as 10−9 M, and can effectively reflect slight LA fluctuation in human sweat, providing a basis for the realization of ultra-sensitive NIR-SERS health monitoring.

Near-infrared (NIR) surface-enhanced Raman spectroscopy (SERS) study of novel functional phenothiazines for potential use in dye sensitized solar cells (DSSC).

Phenothiazines are of potential use as dye sensitizers in Grätzel-type dye sensitized solar cells (DSSC). Plasmonic nanoparticles like gold nanoparticles can enhance the power conversion efficiency of these solar cells. In this work near-infrared surface-enhanced Raman spectroscopy (NIR-SERS) is used to investigate the interaction between six novel phenothiazine-merocyanine dyes containing the three different functional groups rhodanine, 1,3-indanedione and cyanoacylic acid with plasmonic nanomaterials, to decide if the incorporation of plasmonic nanoparticles could enhance the efficiency of a Grätzel-type solar cell. The studies were carried out in the solution state using spherical and rod-shaped gold nanostructures. With KCl induced agglomerated spherical gold nanoparticles, forming SERS hot spots, the results showed low detection limits between 0.1 μmol L−1 for rhodanine containing phenothiazine dyes, because of the formation of Au–S bonds and 3 μmol L−1 for cyanoacrylic acid containing dyes, which formed H-aggregates in the watery dispersion. Results with gold nanorods showed similar trends in the SERS measurements with lower limits of detection, because of a shielding effect from the strongly-bound surfactant. Additional fluorescence studies were carried out to determine if the incorporation of nanostructures leads to fluorescence quenching. Overall we conclude that the addition of gold nanoparticles to rhodanine and 1,3-indanedione containing phenothiazine merocyanine dyes could enhance their performance in Grätzel-type solar cells, because of their strong interactions with plasmonic nanoparticles.

Direct Chemical Synthesis of Plasmonic Black Colloidal Gold Superparticles with Broadband Absorption Properties.

Self-assembly of plasmonic metal nanoparticles can provide an opportunity of creating colloidal superparticles with fascinating optical properties arising from interparticle plasmonic coupling, but typically requires multiple steps involving solvent and/or ligand exchange. We developed a direct, one-step chemical synthesis of plasmonic black colloidal Au superparticles with broadband absorption in visible and near-infrared regions. During the synthesis, the Au superparticles were formed through self-assembly of in-situ-formed Au nanoparticles driven by solvophobic interactions between nanoparticles and solvent. These superparticles could be solution-processed to fabricate a thin film, which exhibited near-perfect absorption over a broad range from 400 nm to 2.5 μm as well as the excellent antireflective property. Thanks to their broadband absorption property, the Au superparticles showed good performances for near-infrared surface-enhanced Raman spectroscopy and light-to-heat conversion.

Label-Free Detection of Bovine Serum Albumin Protein Based on SiO<SUB>2</SUB>/Au Nanoshells as Near-Infrared Surface-Enhanced Raman Spectroscopy Nanoprobe

Label-Free Detection of Bovine Serum Albumin Protein Based on SiO<SUB>2</SUB>/Au Nanoshells as Near-Infrared Surface-Enhanced Raman Spectroscopy Nanoprobe

基于NIR-SERS技术结合PCA-LDA统计分析肝癌术后恢复状况

基于NIR-SERS技术结合PCA-LDA统计分析肝癌术后恢复状况

Gold nanoparticles as a substrate in bio-analytical near-infrared surface-enhanced Raman spectroscopy.

As biospectroscopy techniques continue to be developed for screening or diagnosis within a point-of-care setting, an important development for this field will be high-throughput optimization. For many of these techniques, it is therefore necessary to adapt and develop parameters to generate a robust yet simple approach delivering high-quality spectra from biological samples. Specifically, this is important for surface-enhanced Raman spectroscopy (SERS) wherein there are multiple variables that can be optimised to achieve an enhancement of the Raman signal from a sample. One hypothesis is that "large" diameter (>100 nm) gold nanoparticles provide a greater enhancement at near-infrared (NIR) and infrared (IR) wavelengths than those <100 nm in diameter. Herein, we examine this notion using examples in which SERS spectra were acquired from MCF-7 breast cancer cells incubated with 150 nm gold nanoparticles. It was found that 150 nm gold nanoparticles are an excellent material for NIR/IR SERS. Larger gold nanoparticles may better satisfy the theoretical restraints for SERS enhancement at NIR/IR wavelengths compared to smaller nanoparticles. Also, larger nanoparticles or their aggregates are more readily observed via optical microscopy (and especially electron microscopy) compared to smaller ones. This allows rapid and straightforward identification of target areas containing a high concentration of nanoparticles and facilitating SERS spectral acquisition. To some extent, these observations appear to extend to biofluids such as blood plasma or (especially) serum; SERS spectra of such biological samples often exhibit a low signal-to-noise ratio in the absence of nanoparticles. With protein-rich biofluids such as serum, a dramatic SERS effect can be observed; although this might facilitate improved spectral biomarker identification in the future, it may not always improve classification between control vs. cancer. Thus, use of "large" gold nanoparticles are a good starting point in order to derive informative NIR/IR SERS analysis of biological samples.

Correction to “Near-Infrared Surface-Enhanced Raman Spectroscopy (NIR-SERS) for the Identification of Eosin Y: Theoretical Calculations and Evaluation of Two Different Nanoplasmonic Substrates”

Correction to “Near-Infrared Surface-Enhanced Raman Spectroscopy (NIR-SERS) for the Identification of Eosin Y: Theoretical Calculations and Evaluation of Two Different Nanoplasmonic Substrates”

Near‐infrared surface‐enhanced Raman spectroscopy (NIR‐SERS) studies on oxyheamoglobin (OxyHb) of liver cancer based on PVA‐Ag nanofilm

A near‐infrared surface‐enhanced Raman spectroscopy (NIR‐SERS) method was employed for oxyheamoglobin (OxyHb) detection to develop a simple blood test for liver cancer detection. Polyvinyl alcohol protected silver nanofilm (PVA‐Ag nanofilm) used as the NIR‐SERS active substrate to enhance the Raman scattering signals of OxyHb. High quality NIR‐SERS spectrum from OxyHb adsorbed on PVA‐Ag nanofilm can be obtained within 16 s using a portable Raman spectrometer. NIR‐SERS measurements were performed on OxyHb samples of healthy volunteers (control subjects, n = 30), patients (n = 40) with confirmed liver cancer (stage I, II and III) and the liver cancer patients after surgery (n = 30). Meanwhile, the tentative assignments of the Raman bands in the measured NIR‐SERS spectra were performed, and the results suggested cancer specific changes on molecule level, including a decrease in the relative concentrations and the percentage of aromatic amino acids of OxyHb, changes of the vibration modes of the CaHm group and pyrrole ring of OxyHb of liver cancer patients. In this paper, principal component analysis (PCA) combined with independent sample T test analysis of the measured NIR‐SERS spectra separated the spectral features of the two groups into two distinct clusters with the sensitivity of 95.0% and the specificity of 85.7%. Meanwhile, the recovery situations of the liver cancer patients after surgery were also assessed using the method of discriminant analysis‐predicting group membership based on PCA. The results show that 26.7% surgeried liver cancer patients were distinguished as the normal subjects and 63.3% were distinguished into the cancer. Our study demonstrated great potentials for developing NIR‐SERS OxyHb analysis into a novel clinical tool for non‐invasive detection of liver cancers. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Near-Infrared Surface-Enhanced Raman Spectroscopy (NIR-SERS) for the Identification of Eosin Y: Theoretical Calculations and Evaluation of Two Different Nanoplasmonic Substrates

This work demonstrates the development of near-infrared surface-enhanced Raman spectroscopy (NIR-SERS) for the identification of eosin Y, an important historical dye. NIR-SERS benefits from the absence of some common sources of SERS signal loss including photobleaching and plasmonic heating, as well as an advantageous reduction in fluorescence, which is beneficial for art applications. This work also represents the first rigorous comparison of the enhancement factors and the relative merits of two plasmonic substrates utilized in art applications; namely, citrate-reduced silver colloids and metal film over nanosphere (FON) substrates. Experimental spectra are correlated in detail with theoretical absorption and Raman spectra calculated using time-dependent density functional theory (TDDFT) in order to elucidate molecular structural information and avoid relying on pigment spectral libraries for dye identification.

Analysis of Intracellular State Based on Controlled 3D Nanostructures Mediated Surface Enhanced Raman Scattering

Near-infrared surface-enhanced Raman spectroscopy (SERS) is a powerful technique for analyzing the chemical composition within a single living cell at unprecedented resolution. However, current SERS methods employing uncontrollable colloidal metal particles or non-uniformly distributed metal particles on a substrate as SERS-active sites show relatively low reliability and reproducibility. Here, we report a highly-ordered SERS-active surface that is provided by a gold nano-dots array based on thermal evaporation of gold onto an ITO surface through a nanoporous alumina mask. This new combined technique showed a broader distribution of hot spots and a higher signal-to-noise ratio than current SERS techniques due to the highly reproducible and uniform geometrical structures over a large area. This SERS-active surface was applied as cell culture system to study living cells in situ within their culture environment without any external preparation processes. We applied this newly developed method to cell-based research to differentiate cell lines, cells at different cell cycle stages, and live/dead cells. The enhanced Raman signals achieved from each cell, which represent the changes in biochemical compositions, enabled differentiation of each state and the conditions of the cells. This SERS technique employing a tightly controlled nanostructure array can potentially be applied to single cell analysis, early cancer diagnosis and cell physiology research.

Reproducible synthesis of silver colloidal particles tailored for application in near-infrared surface-enhanced Raman spectroscopy

Reproducible synthesis of silver colloidal particles, with diameters of hundreds of nanometres, represents an experimentally rather difficult task although they have revealed a great application potential in e.g.SERS. The newly developed method, based on the reduction of the complex anion [Ag(SO3)2]3−, offers an approach enabling to manage the preparation of silver particles with adjustable average diameters in the interval from 200 nm up to 700 nm due to the choice of the reducing agent and the sulfite concentration. These particles proved their efficiency as substrates for surface enhanced Raman spectroscopy with the excitation in the near infrared region (λ = 1064 nm) and therefore this newly developed method confirmed the expected application potential.

Glucose Sensing Using Near-Infrared Surface-Enhanced Raman Spectroscopy: Gold Surfaces, 10-Day Stability, and Improved Accuracy

This research presents the achievement of significant milestones toward the development of a minimally invasive, continuously monitoring, glucose-sensing platform based on the optical quantitation of glucose in interstitial fluid. We expand our initial successes in the measurement of glucose by surface-enhanced Raman scattering (SERS), demonstrating substantial improvements not only in the quality and optical properties of the substrate system itself but also in the robustness of the measurement methodology and the amenability of the technique to compact, diode laser-based instrumentation. Herein, we compare the long-term stability of gold to silver film over nanosphere (AuFON, AgFON) substrates functionalized with a partitioning self-assembled monolayer (SAM) using both electrochemical and SERS measurements. AuFONs were found to be stable for a period of at least 11 days. The switch to AuFONs not only provides a more stable surface for SAM formation but also yields better chemometric results, with improved calibration and validation over a range of 0.5-44 mM (10-800 mg/dL). Measured values for glucose concentrations in phosphate-buffered saline (pH approximately 7.4) based on 160 independent SERS measurements on AuFONs have a root-mean-square error of prediction of 2.7 mM (49.5 mg/dL), with 91% of the values falling within an extended A-B range on an expanded Clarke error grid. Furthermore, AuFONs exhibit surface plasmon resonances at longer wavelengths than similar AgFONs, which make them more efficient for SERS at near-infrared wavelengths, enabling the use of low-power diode lasers in future devices.

Near-infrared surface-enhanced Raman scattering of a kind of self-assemblies film based on coordination bond

Near-infrared surface-enhanced Raman spectroscopy was applied to the investigation of 4,4′-bipyridine, 4,4′-azopyridine, bissalicylaldehydeethylenediimine Co(II) and Ni(II) (abbreviated as Salen-Co and Salen-Ni, respectively) as mono- and alternating multi-layer self-assembly films deposited onto the roughened silver foil substrate. 4,4′-Bipyridine, 4,4′-azopyridine can be adsorbed onto the silver substrate through the interaction of N-atom of the pyridine ring via metal surface. The orientation of molecular long axis for both molecules are normal to the surface of the substrate. The alternating films can be obtained by the coordinate interaction between the pyridine and the metal chelates of Salen-Co and Salen-Ni. The plane of the metal chelates are parallel to the surface of silver substrate.

Time-Resolved Near-Infrared Surface-Enhanced Raman Spectroscopy of a Surface-Confined Electrochemical Reaction of 9,10-Phenanthrenequinone

Abstract A measurement system for time-resolved surface-enhanced Raman spectroscopy with a submillisecond time resolution was developed using a step-scan near-infrared Fourier-transform spectrometer and was applied to analyze a redox reaction of 9,10-phenanthrenequinone (PQ) adsorbed on a polycrystalline gold electrode. In the time-resolved surface-enhanced Raman spectra, both quinone and hydroquinone forms of PQ were recognized, but the intermediate species, semiquinone radicals, were not. It was suggested that the lifetime of the intermedeate species was shorter than 0.5 ms, which was the time resolution of the developed system.

Adsorption and Ordering of Resorcinare Layers on Planar and Colloidal Gold and the Influence of Surface Modification: A SERS and IRRAS Study

Near-infrared surface-enhanced Raman spectroscopy and infrared reflection-absorption spectroscopy have been applied to investigate adsorption and ordering processes of resorcinarene cavitands at interfaces. Colloidal gold was applied in the case of NIR-Raman measurements, and planar gold substrates were used for reflection spectroscopy. Selected cavitands substituted on their upper rim with different functionalities were employed as probe molecules. An assignment of vibrational bands is presented. Interactions between probe molecules and substrates are present in all cases. From Raman measurements, it is difficult to deduce an orientation of the probe molecule adsorbed onto the gold particle, as the selection rules for SERS cannot be applied straightforwardly. Furthermore, an orientation depends on a proper assignment of vibrational bands. Infrared spectroscopy shows that the orientation of the resorcinarene molecules deposited on a planar gold or gold/monolayer interface is influenced by the underlying substrate. The directing effect, however, does not extend into the adjoining bulk of the sample layer.

Near-infrared surface-enhanced Raman spectroscopy of chemisorbed compounds on gold colloids

Near-infrared surface-enhanced Raman scattering (SERS) spectra have been measured for strongly chemisorbed compounds, such as 4-mercaptopyridine and thiophenol, on gold colloids in mixed solvents of ethanol and water using a diode laser as an excitation source. From UV-vis spectroscopy, the aggregated gold colloids show a broad absorbance band through the visible to the near-infrared after adding chemisorbing compounds. The absorption maximum is located in the range 750–850 nm, permitting the use of a near-IR source (826 nm) for the first time in SERS of gold colloid systems. The estimated enhancement is on the order of 10 5. Transmission electron microscopy of aggregated gold particles revealed a cluster morphology. The aggregated mixed-solvent colloids were more stable than those prepared in water, and were useful in dissolving compounds with poor water solubility.

Near-infrared surface-enhanced Raman spectroscopy using a diode laser

Near-infrared surface-enhanced Raman spectroscopy using a diode laser

Near-Infrared Surface-Enhanced Raman Spectroscopy. Part II: Copper and Gold Colloids

Near-infrared (NIR) surface-enhanced Raman spectra (SERS) on copper and gold metal colloids were obtained with a Fourier transform Raman spectrometer using a Nd:YAG laser (1.064 μm) for excitation. Enhanced spectra were observed for pyridine and 3-chloropyridine (CP) on copper colloids and for tris(orthophenanthroline)ruthenium(II), Ru(o-phen)32+, on copper and gold colloids. The copper-colloid surface-enhanced Raman spectra of pyridine and CP were compared with spectra measured for these molecules on copper electrodes. NIR-SERS enhancements on the metal colloids were at least as large as for visible-wavelength excited SERS. Good-quality spectra of Ru(o-phen)32+ were obtained at solution concentrations as low as 0.025 mM.