Xu-dong Wang*,† and Otto S. Wolfbeis*,‡ †Department of Chemistry, Fudan University, 200433 Shanghai, P. R. China ‡Institute of Analytical Chemistry, Chemoand Biosensors, University of Regensburg, D-93040 Regensburg, Germany ■ CONTENTS Books, Reviews, and Articles of General Interest 204 Sensors for (Dissolved) Gases and Vapors 204 Hydrogen 204 Hydrocarbons 206 Oxygen 206 Carbon Dioxide 208 Nitrogen Oxides 208 Other Gases 208 Ammonia 209 Ethanol 209 Other Volatile Organic Compounds (VOC)s 210 Sensors for Humidity, Water Fractions, Hydrogen Peroxide, and Hydrazine 211 Humidity 211 Water Fractions in Organic Solvents 212 Hydrogen Peroxide 213 Sensors for pH Values, Ions, and Salinity 213 pH Values 213 Ions 214 Salinity and Ionic Strength 215 Sensors for Organic Species 216 Glucose Sensing 216 Sucrose 217 Oils 217 Other Organics 217 Biosensors 218 Nucleic Acid-Based Biosensors (DNAand Aptamer-Based) 218 Immunosensors 218 Enzymatic Biosensors 219 Other Biosensors 220 New Schemes and Materials 220 New Sensing Schemes 220 Molecularly Imprinted Polymer (MIP)-Based Sensors 221 Photonic Crystals 223 Author Information 223 Corresponding Authors 223 Notes 223 Biographies 223 Acknowledgments 223 References 223

Fiber-Optic Chemical Sensors and Biosensors (2013-2015).

This paper reviews fundamentals of optical affinity biosensors based on plasmonic nanostructures and discusses recent advances in the development of this technology, including plasmonic nanostructures and surface plasmon phenomena, advances in sensor instrumentation, and functional coatings. Examples of applications for both the detection of chemical and biological substances as well as the investigation of biomolecular interactions are also given.

Optical Biosensors Based on Plasmonic Nanostructures: A Review

Advances in biosensor development for the screening of antibiotic residues in food products of animal origin - A comprehensive review.

A microfluidic colorimetric biosensor for rapid detection of Escherichia coli O157:H7 using gold nanoparticle aggregation and smart phone imaging.

Surface Plasmon Resonance (SPR) fiber sensor research has grown since the first demonstration over 20 year ago into a rich and diverse field with a wide range of optical fiber architectures, plasmonic coatings, and excitation and interrogation methods. Yet, the large diversity of SPR fiber sensor designs has made it difficult to understand the advantages of each approach. Here, we review SPR fiber sensor architectures, covering the latest developments from optical fiber geometries to plasmonic coatings. By developing a systematic approach to fiber-based SPR designs, we identify and discuss future research opportunities based on a performance comparison of the different approaches for sensing applications.

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Plasmonic Fiber Optic Refractometric Sensors: From Conventional Architectures to Recent Design Trends

The enzyme-linked immunosorbent assay (ELISA) has been an integral part of in vitro diagnostic tests due to its high specificity, standard configuration, and convenient readout. The convergence of the plasmonic property, i.e. localized surface plasmon resonance (LSPR), of noble metal nanoparticles with the ELISA technique has established a novel category of immunoassay, known as “plasmonic ELISA” (pELISA). It has enabled the naked eye detection of various disease biomarkers down to attomolar concentration. The color development relies on the biocatalytic reaction mediated modulation of LSPR properties. Through this review we present various current state-of-art pELISA strategies adopted for naked-eye quantification of disease biomarkers along with their advantages, limitations and applicability. These strategies are broadly classified into following four categories based on the different means of LSPR modulation: (i) aggregation, (ii) controlled growth kinetics, (iii) metallization, and (iv) etching of metal nanoparticles. Furthermore, the paper highlights the different biocatalytic reactions and their role in plasmonic color development as a function of analyte concentration. The review ends with an elucidation of current challenges and future perspectives of pELISA precisely focusing on the need for development of next generation low cost point-of-care diagnostic kits.

Plasmonic-ELISA: expanding horizons

The refractive index (RI) sensitivity of a localized surface plasmon resonance (LSPR)-based fiber-optic probes is dependent on surface coverage of gold nanoparticles (GNP), fiber core diameter, and probe geometry. For U-bent LSPR fiber-optic probes, which demonstrated an order higher absorption sensitivity over straight probes, bend diameter and probe length may also have a significant influence on the sensitivity. This study on U-bent fiber-optic LSPR probes is aimed at optimizing these parameters to obtain highest possible RI sensitivity. RI sensitivity increases linearly as a function of surface coverage of GNP in the range of 2–22 %. U-bent fiber-optic probes made of 200-, 400-, and 600-μm fiber core diameter show optimum bend diameter value as ∼1.4 mm. In addition, RI sensitivity is almost the same irrespective of fiber core diameter demonstrating flexibility in choice of the fiber and ease in optical coupling. The length of the probe preceding and succeeding the bend region has significantly less influence on RI sensitivity allowing miniaturization of these probes. In addition to these experimental studies, we present a theoretical analysis to understand the relative contribution of evanescent wave absorbance of GNP and refractive losses in the fiber due to GNP, towards the RI sensitivity.

Optimal Design for U-bent Fiber-optic LSPR Sensor Probes

Evanescent wave absorption (EWA) based fiber-optic sensors have found widespread applications ranging from environmental sensing to biosensing. In these sensors, optical and geometrical characteristics such as optical fiber type (single-mode or multi-mode), fiber core diameter, fiber probe geometry, fiber probe length, etc., are very important. These parameters affect the penetration depth and fractional power by modulating the ray propagating in the fiber probe that ultimately influences the sensitivity of the EWA sensors. Various geometries of fiber probe designs, like bent, tapered, coiled, etc., have been explored for improving the sensitivity. This chapter describes the design, development and fabrication of a novel bent-tapered fiber-optic sensor. A combination of bending and tapering acts as a mode converter, which results in high penetration depth of the evanescent field. In addition, tapered region of the probe increases the coupling efficiency at the detector end by V-number matching and thus improves the signal-to-noise ratio. EWA sensitivity of the sensor was compared for different taper ratios. Finally, the optimized geometrical design was used to demonstrate biosensing application.

Evanescent Wave Absorption Based Fiber-Optic Sensor - Cascading of Bend and Tapered Geometry for Enhanced Sensitivity

Advances in nanoparticle research, particularly in the domain of surface-engineered, function-oriented nanoparticles, have had a profound effect in many areas of scientific research and aided in bringing unprecedented developments forward, particularly in the biomedical field. Surface modifiers/capping agents have a direct bearing on the major properties of metal nanoparticles (MNPs), ranging from their physico-chemical properties to their stability and functional applications. Among the different classes of capping agents, dendrimers have gained traction as effective multifunctional capping agents for MNPs due to their unique structural qualities, dendritic effect and polydentate nature. Dendrimer-coated metal nanoparticles (DC-MNPs) are typically produced by both (i) a one-pot strategy, where metal ions are reduced in the presence of dendrimer molecules and (ii) a multi-pot strategy, where a sequence of reactions involving the reduction of metal ions, activation, conjugation and purification steps are involved. These DC-MNPs have shown remarkable ability to stabilize MNPs by means of electrostatic interactions, coordination chemistry or covalent attachment, due to them entailing a large number of sites at which further molecular moieties can be conjugated. This review article is an attempt to consolidate the on-going work, particularly over the last five years, in the field of the synthesis of dendrimer-coated MNPs and their potential applications in bioimaging, drug delivery and biochemical sensors.

Dendrimer as a multifunctional capping agent for metal nanoparticles for use in bioimaging, drug delivery and sensor applications

This paper describes a sensor configuration for stable, long term, continuous monitoring of sugar content in the product of fruit juice packaging industry. An improvement in refractive index (RI) sensitivity of a gold nanoparticle (AuNP) coated, U-shaped fiber-optic probe was achieved by a deposition of silicon nitride (SiNx) film on the probe surface. AuNP of two distinct sizes, 18 nm and 39 nm, were bound to fiber core surfaces to generate LSPR, when excited by light passing through the fiber. Following this, a thin film of SiNx was deposited over the AuNP coated sensing region of the fiber-optic probe, using hot filament chemical vapor deposition. We investigated the effect of SiNx film coating on RI sensitivity for five different thicknesses: 11 nm, 16 nm, 20 nm, 23 nm and 40 nm. Several concentrations of sucrose solution were used to vary the bulk RI from 1.333 to 1.387 in the sensing region. We have observed 1.24-times RI sensitivity enhancement in case of 39 nm AuNP covered with 20 nm SiNx film compared to only AuNP coated fiber-optic probe. We also successfully determined the sugar content in three different packaged juices (at various dilution levels). The sensor proved its potential for measurement of sugar in solutions having complex composition with error

Nirmal Punjabi

Papers

Plasmonic-ELISA: expanding horizons

Optimal Design for U-bent Fiber-optic LSPR Sensor Probes

Evanescent Wave Absorption Based Fiber-Optic Sensor - Cascading of Bend and Tapered Geometry for Enhanced Sensitivity

Dendrimer as a multifunctional capping agent for metal nanoparticles for use in bioimaging, drug delivery and sensor applications

A silicon nitride coated LSPR based fiber-optic probe for possible continuous monitoring of sucrose content in fruit juices