Robust Au-PEG/PS microbeads as optically stable platforms for SERS

A Barcoded Polymer-Based Cross-Reactive Spectroscopic Sensor Array for Organic Volatiles

The development of cross-reactive sensor arrays for volatile organics (electronic noses, e-noses) is an active area of research. In this manuscript, we present a new format for barcoded polymer sensor arrays based on porous polymer beads. An array of nine self-encoded polymers was analyzed by Raman spectroscopy before and after exposure to a series of volatile organic compounds, and the changes in the vibrational fingerprints of their polymers was recorded before and after exposure. Our results show that the spectroscopic changes experienced by the porous spectroscopically encoded beads after exposure to an analyte can be used to identify and classify the target analytes. To expedite this analysis, analyte-specific changes induced in the sensor arrays were transformed into a response pattern using multivariate data analysis. These studies established the barcoded bead array format as a potentially effective sensing element in e-nose devices. Devices such as these have the potential to advance personalized medicine, providing a platform for non-invasive, real-time volatile metabolite detection.

Artificial Nose Technology: Status and Prospects in Diagnostics

Biomimetic crossreactive sensor arrays have been used to detect and analyze a wide variety of vapor and liquid components in applications such as food science, public health and safety, and diagnostics. As technology has advanced over the past three decades, these systems have become selective, sensitive, and affordable. Currently, the need for noninvasive and accurate devices for early disease diagnosis remains a challenge. This Opinion article provides an overview of the various types of biomimetic crossreactive sensor arrays (also referred to as electronic noses or tongues in the literature), their current use and future directions, and an outlook for future technological development.

Biomimetic Cross-Reactive Sensor Arrays: Prospects in Biodiagnostics

Biomimetic cross-reactive sensor arrays have been used to detect and analyze a wide variety of vapour and liquid components in applications such as food science, public health and safety, and diagnostics. As technology has advanced over the past three decades, these systems have become selective, sensitive, and affordable. Currently, the need for non-invasive and accurate devices for early disease diagnosis remains a challenge. This review provides an overview of the various types of Biomimetic cross-reactive sensor arrays (also referred to as electronic noses and tongues in the literature), their current use and future directions, and an outlook for future technological development.

Integrated nanotechnology for synergism and degradation of fungicide SOPP using micro/nano-Ag3PO4

The integrated nanotechnology utilizes micro/nano-Ag₃PO₄ to enhance the antifungal activity of fungicide SOPP and to successively remove the SOPP residue.

Nanomaterial-based barcodes

Two-dimensional (2D) barcodes ubiquitously used to label, track and authenticate objects face increasing challenges of being damaged, altered and falsified. The past effort in nanomaterials has paved the way for controlled synthesis of nanomaterials with desired size, shape and function. Due to their extremely small sizes, these nanomaterials are promising as next generation barcodes that can be added into or mixed with objects of interest without being noticed. These barcodes can be effectively read owing to their physical properties by manufacturers, law enforcement and security agencies. Meanwhile, nanomaterial-based barcodes are hard to reverse-engineer or imitate without advanced knowledge and technical expertise. This review describes how nanomaterials can be used as barcodes, discusses advantages and limitations of each type of nanomaterial-based barcode, and points out ways that could help design and prepare better nanomaterial-based barcodes.

Polymer-mediated formation and assembly of silver nanoparticles on silica nanospheres for sensitive surface-enhanced Raman scattering detection

To impart a desired optical property to metal nanoparticles (NPs) suitable for surface-enhanced Raman scattering (SERS) applications, it is crucial to assemble them in two or three dimensions in addition to controlling their size and shape. Herein, we report a new strategy for the synthesis and direct assembly of Ag NPs on silica nanospheres (AgNPs-SiNS) in the presence of poly(ethylene glycol) (PEG) derivatives such as PEG-OH, bis(amino)-PEGs (DA-PEGs), and O,O'-bis(2-aminopropyl)PEG (DAP-PEG). They exhibited different effects on the formation of Ag NPs with variable sizes (10-40 nm) and density on the silica surface. As the molecular weight (MW) of DA-PEGs increased, the number of Ag NPs on the silica surface increased. In addition, DAP-PEG (MW of 2000), which has a 2-aminopropyl moiety at both ends, promoted the most effective formation and assembly of uniform-sized Ag NPs on a silica surface, as compared to the other PEG derivatives with the same molecular weight. Finally, we demonstrated that AgNPs-SiNS bearing 4-fluorobenzenethiol on its surface induced the strong SERS signal at the single-particle level, indicating that each hybrid particle has internal hot spots. This shows the potential of AgNPs-SiNS for SERS-based sensitive detection of target molecules.

Asymmetric organic/metal(oxide) hybrid nanoparticles: synthesis and applications

Asymmetric particles (APs) with broken centrosymmetry are of great interest, due to the asymmetric surface properties and diverse functionalities. In particular, organic/metal(oxide) APs naturally combine the significantly different and complementary properties of organic and inorganic species, leading to their unique applications in various fields. In this review article, we highlighted recent advances in the synthesis and applications of organic/metal(oxide) APs. This type of APs is grounded on chemical or physical interactions between metal(oxide) NPs and organic small molecular or polymeric ligands. The synthetic methodologies were summarized in three categories, including the selective surface modifications, phase separation of mixed ligands on the surface of metal(oxide) NPs, and direct synthesis of APs. We further discussed the unique applications of organic/metal(oxide) APs in self-assembly, sensors, catalysis, and biomedicine, as a result of the distinctions between asymmetrically distributed organic and inorganic components. Finally, challenges and future directions are discussed in an outlook section.

Ultrahigh-density array of silver nanoclusters for SERS substrate with high sensitivity and excellent reproducibility

We introduce a simple but robust method to fabricate an ultrahigh-density array of silver nanoclusters for a surface-enhanced Raman spectroscopy (SERS) substrate with high sensitivity and excellent reproducibility at a very large area (wafer scale) based on polystyrene-block-poly(4-vinylpyridine) copolymer (PS-b-P4VP) micelles. After silver nitrates were incorporated into the micelle cores (P4VP) followed by the reduction to silver nanoclusters, we systematically controlled the gap distance between two neighboring silver nanoclusters ranging from 8 to 61 nm, while the diameter of each silver nanocluster was kept nearly constant (~25 nm). To make a silver nanocluster array with a gap distance of 8 nm, the use of crew-cut-type micelles is required. Fabricated SERS substrate with a gap distance of 8 nm showed very high signal intensity with a SERS enhancement factor as high as 10(8), which is enough to detect a single molecule, and excellent reproducibility (less than ±5%) of the signal intensity. This is because of the uniform size and gap distance of silver nanoclusters in a large area. The substrate could also be used for label-free immunoassays, biosensing, and nanoscale optical antennas and light sources.

SERS assisted ultra-fast peptidic screening: a new tool for drug discovery

Herein we present a direct label-free ultra-fast method for the identification and classification of the active members of a combinatorial library directly on the solid support used for their synthesis. The method is based on the appropriate functionalization of polyethylene glycol grafted polystyrene (TentaGel®) microbeads with Au@Ag nanoparticles, the use of these materials directly as solid-phase supports for the synthesis of combinatorial libraries of peptides and the subsequent SERS analysis for identification of each peptide on each bead.

Silver coated aluminium microrods as highly colloidal stable SERS platforms

We report on the fabrication of a novel material with the ability to remain in solution even under the very demanding conditions required for structural and dynamic characterization of biomacromolecule assays. This stability is provided by the increase in surface area of a low density material (aluminium) natively coated with a very hydrophilic surface composed of aluminium oxide (Al(2)O(3)) and metallic silver nanoparticles. Additionally, due to the dense collection of active hot spots on their surface, this material offers higher levels of SERS intensity as compared with the same free and aggregated silver nanoparticles.

Surface-enhanced Raman scattering biomedical applications of plasmonic colloidal particles

This review article presents a general view of the recent progress in the fast developing area of surface-enhanced Raman scattering spectroscopy as an analytical tool for the detection and identification of molecular species in very small concentrations, with a particular focus on potential applications in the biomedical area. We start with a brief overview of the relevant concepts related to the choice of plasmonic nanostructures for the design of suitable substrates, their implementation into more complex materials that allow generalization of the method and detection of a wide variety of (bio)molecules and the strategies that can be used for both direct and indirect sensing. In relation to indirect sensing, we devote the final section to a description of SERS-encoded particles, which have found wide application in biomedicine (among other fields), since they are expected to face challenges such as multiplexing and high-throughput screening.

SERS-based diagnosis and biodetection

Surface-enhanced Raman scattering (SERS) spectroscopy is one of the most powerful analytical techniques for identification of molecular species, with the potential to reach single-molecule detection under ambient conditions. This Concept article presents a brief introduction and discussion of both recent advances and limitations of SERS in the context of diagnosis and biodetection, ranging from direct sensing to the use of encoded nanoparticles, in particular focusing on ultradetection of relevant bioanalytes, rapid diagnosis of diseases, marking of organelles within individual cells, and non-invasive tagging of anomalous tissues in living animals.

Synthesis of Sulfur-Containing Aryl and Heteroaryl Vinyls via Suzuki-Miyaura Cross-Coupling for the Preparation of SERS-Active Polymers

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.