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3D plasmonic colloidosomes are superior SERS sensors owing to their high sensitivity and excellent tolerance to laser misalignment. Herein, we incorporate plasmonic colloidosomes in a microfluidic channel for online SERS detection. Our method resolves the poor signal reproducibility and inter-sample contamination in the existing online SERS platforms. Our flow system offers rapid and continuous online detection of 20 samples in less than 5 min with excellent signal reproducibility. The isolated colloidosomes prevent cross-sample and channel contamination, allowing accurate quantification of samples over a concentration range of five orders of magnitude. Our system demonstrates high-resolution multiplex detection with fully preserved signal and Raman features of individual analytes in a mixture. High-throughput multi-assay analysis is performed, which highlights that our system is capable of rapid identification and quantification of a sequence of samples containing various analytes and concentrations.

Point mutations in Ras oncogenes are routinely screened for diagnostics and treatment of tumors (especially in colorectal cancer). Here, we develop an optical approach based on direct SERS coupled with chemometrics for the study of the specific conformations that single-point mutations impose on a relatively large fragment of the K-Ras gene (141 nucleobases). Results obtained offer the unambiguous classification of different mutations providing a potentially useful insight for diagnostics and treatment of cancer in a sensitive, fast, direct and inexpensive manner.

Recognition of chemical modifications in canonical nucleobases of nucleic acids is of key importance since such modified variants act as different genetic encoders, introducing variability in the biological information contained in DNA. Herein, we demonstrate the feasibility of direct SERS in combination with chemometrics and microfluidics for the identification and relative quantification of 4 different cytosine modifications in both single- and double-stranded DNA. The minute amount of DNA required per measurement, in the sub-nanogram regime, removes the necessity of pre-amplification or enrichment steps (which are also potential sources of artificial DNA damages). These findings show great potentials for the development of fast, low-cost and high-throughput screening analytical devices capable of detecting known and unknown modifications in nucleic acids (DNA and RNA) opening new windows of activity in several fields such as biology, medicine and forensic sciences.

Effi cient and homogeneous surface-enhanced Raman scattering (SERS) substrates are usually prepared using lithographic approaches, physical evaporation, or in situ chemical reduction. However, these approaches are time-consuming, expensive, and very diffi cult to upscale. Alternatively, template-assisted approaches using colloidal suspensions of preformed nanoparticles have become more popular because of their low cost, fast production, and ability to be scaled up easily. One of the limitations of these methods is the dimensions of the structured surfaces. In this context, a new method for designing low-cost, up-scalable surface patterns that match building block dimensionality based on anodization of aluminum, enabling a hierarchical organization of anisotropic nanoparticles, is presented. The proposed new technology starts with anodized aluminum oxide with regular parallel linear periodicities. To produce a highly effi cient plasmonic surface, gold nanorods are assembled into parallel lines where the long axes of the Au rods are also oriented along the substrate lines, thus inducing reproducible tip-to-tip plasmonic coupling with the corresponding generation of highly active hotspots. Additionally, this advanced material presents an inherent hydrophobicity that can be exploited as a method for concentration of analytes on the surface. SERS detection is demonstrated with benzenethiol and 2-naphtoic acid.

An optical sensor was developed for the quantitative determination of intracellular nitric oxide. The sensor consists of plasmonic nanoprobes that have a coating of mesoporous silica and an inner gold island film functionalized with a chemoreceptor for NO.

11] and encouraged by the need of optimization of the self-assembly process that may allow the design of large-scale supercrystals with high optical activity for SERS detection, we report on a straightforward approach to obtain long-range plas-monic supercrystals made of standing core-shell gold-silver nanorods (Au@AgNRs), stabilized with gemini surfactants, by controlling the drop casting conditions. Au@AgNRs (length = 71

10 pags., 7 figs., Current understanding of the mechanisms underlying noncovalent interactions between native DNA and nanoparticles, as well as their impact on the double-helix structure, is far from providing a comprehensive view. It is known that these interactions are largely defined by the physicochemical properties of the metal/liquid interface, in particular by the nanoparticle surface charge. Remarkably, while DNA unzipping upon binding with cationic nanoparticles is reported, the exact determinants of this structural perturbation remain unclear. Herein, plasmon-based spectroscopies (surface-enhanced Raman scattering (SERS) and surface-plasmon resonance (SPR) and theoretical simulations are combined to directly investigate the role of the cooperative binding of cationic nanoparticles with different surface charges on the structural integrity of a large variety of DNAs. The intrinsic nature of the SERS effect unlocks the possibility of selectively examining the impact of nanoparticle clustering on the duplex structure over a wide degree of colloidal aggregation and without the need of external intercalating dyes or strand labeling. This extensive work provides new fundamental insights into the interaction between nucleic acids and nanoparticles, addressing key questions regarding the role played by multiple variables such as the nanoparticle surface charge, the DNA-mediated cluster size and geometry, and nucleic acids' length, composition, and conformational properties., Ministerio de Economia y Competitividad. Grant Number: CTQ2014‐59808R European Research Council. Grant Number: 2014 623527 Generalitat de Catalunya. Grant Number: 2014‐SGR‐480

Die oberflachenverstarkte Raman-Streuung (SERS) ist ein leistungsfahiges und relativ direktes molekulspektroskopisches Verfahren aus dem Bereich der Nanoplasmonik. Das Prinzip von SERS ist die Verstarkung der unelastischen Streuung von Molekulen, die sich nahe einer nanostrukturierten Metalloberflache mit durch Bestrahlung angeregten Oberflachenplasmonen befinden. Die SERS-Analytik ist dann weniger geeignet, wenn die Molekule (wie oft bei anorganischen Molekulen der Fall) zu kleine Raman-Querschnitte haben. Noch schwieriger ist die Identifizierung von atomaren Spezies, da diese noch nicht einmal ein Schwingungssignal aufweisen. Hier erortern wir die jungsten Fortschritte beim SERS-Nachweis kleiner anorganischer Spezies, darunter Molekule und Atome.

We introduce a new family of spiked particles resulting from the growth of high aspect ratio gold nanorods. Upon spike growth, elongated beads are obtained with sizes above 300 nm. Interestingly, and in contrast to smooth particles of the same size, these spiked-particles are not only able to sustain localized surface plasmon resonances and consequently enhance Raman signals, but are also big enough to be recognized by standard confocal optical microscopy. These spiked beads have been engineered into thin films to test their surface-enhanced Raman scattering (SERS) enhancing efficiency as a function of the particle density. Such films provide a high level of portability and easiness of use for "in-field" optical ultrasensitive analysis. One to enhance them all: Spiked gold beads are efficient optical enhancers for single-particle SERS ultradetection (see picture), due to the localization of high electric fields at the apex of the tips and the antenna effect displayed by the core. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

This article provides an overview of recent research on the synthesis and surface-plasmon-related properties of noble metal nanoplates. The first part is dedicated to summarizing the most relevant wet-chemical and physical synthetic protocols that have been used to obtain Au and Ag nanotriangles/ nanoplates in high yield, with a discussion of the formation mechanisms proposed by the different authors. Finally, we present a description of the characteristic optical properties of nanoparticles with this particular morphology, in relation with the possibility of exciting different surface plasmon modes and concentrating high electromagnetic fields at certain areas, which is important for applications in surface-enhanced Raman scattering (SERS).

Surface-enhanced Raman scattering (SERS) is a powerful analytical technique for ultrasensitive chemical and biochemical analysis. Among common substrates for SERS, the most important are colloidal nanocrystal suspensions of gold, silver, and their alloys, which are produced by a variety of physical and chemical reduction methods. In a colloidal suspension, the closer interaction between the adsorbent and adsorbate allows the analyte to be naturally retained on the colloid’s surface. These mixed systems may later be studied directly by bulk SERS or cast and air-dried onto an appropriate substrate (glass or silicon wafers) and analyzed by microspectroscopic SERS. The main disadvantage of this method is the low stability of colloidal suspensions; physical (i.e., shape and size) and chemical (i.e., surface charge) properties often vary within days of preparation. Thus, in order to extend the shelf life of the colloidal suspensions, the addition of stabilizers to prevent aggregation and flocculation by increasing the electrostatic potential around the nanoparticles was reported. However, while this process stabilizes the particles, it hinders the interaction between the adsorbent and adsorbate, thus decreasing the SERS output. In recent years, many attempts have been made to deposit optically active nanoparticles on polymer microbeads in order to produce composite materials suitable for SERS. Unfortunately, such materials tend to have low nanoparticle loading and weak SERS because of limited nanoparticle accessibility in the polymer matrix. Recently, Kinoshita et al. established the extraordinary capability of poly(ethylene glycol) (PEG) to selectively retain Au. In the present paper, this property was exploited to produce a gold nanoparticle

This paper describes morphological and optical changes induced by seed-mediated growth of gold nanorods in the presence of iodide ions. Addition of small amounts of iodide to the growth solution results in the growth of nanoparticles with dumbbell-like structure, meaning that gold salt reduction takes place preferentially at the rod tips. However, when excess iodide is added, homogeneous rod growth is observed, and therefore the original shape is retained. By controlling the experimental conditions, the position of the longitudinal plasmon band of grown nanorods can be shifted up to as much as 250 nm. These optical effects were also simulated by means of the boundary element method (BEM), achieving an excellent agreement with the experimental spectra. X-ray photoelectron spectroscopy (XPS) and surface enhanced Raman spectroscopy (SERS) analysis of the gold nanorods before and after iodide addition revealed the presence of AuI and AgI at the particles surface. A growth mechanism is proposed on the basis of preferential iodide adsorption at the tips {111} facets, leading to the formation of AgI, followed by reduction of gold salt precursor due to a decrease in the surface redox potential.

although full characterization and determination of the yield of octahedra with respect to other shapes in the mixture are lacking. [2b] Under the reaction conditions described in this paper, at least 70% of the products are crystalline gold octahedra, permitting detailed analysis by electron microscopy and surface spectroscopy of these nanomaterials. The plasmon-assisted enhancing optical properties were demonstrated by SERS of 2-naphthalenethiol (2-NAT), an analyte with a well-defined SERS spectrum. The gold octahedral nanoparticles were synthesized in high yields by thermal treatment of HAuCl4-loaded polystyreneblock-poly(2-vinylpyridine) (PS-b-P2VP; 91500 gmol –1 105000 gmol –1 ) with a 1:2 ratio of Au III /pyridyl-groups, at a temperature of 250°C in air for 5 min. The block copolymer solution (0.5 wt% in toluene) was loaded with a predefined amount of HAuCl4(s), and spin-coated onto a native oxide capped silicon surface to form a monolayer of block copolymer micelles, followed by brief heating. Scanning electron

Portable multilayer films containing gold nanoparticles embedded in a dendrimer matrix have been fabricated using the layer-by-layer (LbL) technique, characterized and tested for applications in surface-enhanced Raman scattering (SERS). Film formation was monitored by microgravimetry measurements using a quartz crystal microbalance (QCM) and UV-visible spectroscopy. The surface morphology was investigated with atomic force microscopy (AFM) measurements. SERS was recorded for 2-Naphtalenethiol(NFT) cast onto the LbL film and the results show that the optical enhancing ability is a function of the number of bilayers. The analytes show an increase of SERS effect that follows the surface roughness, being stabilized after a certain number of bilayers are deposited.

Surface-enhanced Raman scattering (SERS) is one of the most straightforward applications of the so-called nanoplasmonics. This powerful molecular spectroscopy technique is based on the enhancement of the inelastic scattering from molecules located near nanostructured metallic surfaces when these are illuminated and surface plasmons are excited. The analytical applications of SERS are hindered when the Raman cross-section of the analyte is too low, which is often the case in inorganic molecular species. This problem is even more serious when atomic species are to be identified, since these cannot display a vibrational signal. Herein we discuss the recent advancements toward the SERS detection of small inorganic compounds, including both molecular and atomic species.

Staphylococcus aureus is a common cause of serious infections. One of the main drawbacks in its treatment is the time required for a positive diagnosis, over 24 h, as most methods are still based in bacterial culture. Herein, a microfluidic optical device for the rapid and ultrasensitive quantification of S. aureus in real human fluids is designed. In this approach, the surface-enhanced Raman scattering (SERS)-encoded particles, functionalized with either an antibody or an aptamer, form a dense collection of electromagnetic hot spots on the surface of S. aureus. This allows for an exponentially increase of the SERS signal when particles accumulate on the microorganism as compared to their free condition in bulk solution. Quantification is achieved by passing the sample through a microfluidic device with a collection window where a laser interrogates and classifies each of the induced bacteria–nanoparticle aggregates in real time. Further, the advantages of using aptamers versus antibodies as biorecognition elements are extensively investigated.

Colloidal nanoparticles, in particular gold nanoparticles and quantum dots, can be used in a variety of different assays for optical sensing of small ions in solution. In this review, different detection principles are introduced and their potential use for detection in biological samples (such as intracellular sensing) is discussed.

This article provides an overview of recent research on the synthesis and surface-plasmon-related properties of noble metal nanoplates. The first part is dedicated to summarizing the most relevant wet-chemical and physical synthetic protocols that have been used to obtain Au and Ag nanotriangles/ nanoplates in high yield, with a discussion of the formation mechanisms proposed by the different authors. Finally, we present a description of the characteristic optical properties of nanoparticles with this particular morphology, in relation with the possibility of exciting different surface plasmon modes and concentrating high electromagnetic fields at certain areas, which is important for applications in surface-enhanced Raman scattering (SERS).

The preparation of sulfur-containing aryl and heteroaryl vinyl co-monomers via Suzuki-Miyaura cross-coupling between the corresponding mercaptomethyl arylboronates and in situ-generated vinyl bromides is described. Surface enhanced Raman scattering (SERS) studies of the target compounds on gold nanoparticles confirmed their potential as spectroscopic tags in the fabrication of SERS-encoded polymers for combinatorial screening and biomedical diagnostics.