High-quality optical fibers can be produced now at a low cost and large quantity, and this has further promoted the development of fiber optic (chemical) sensors. After over 30 years of innovation, fiber optic sensing technology has become mature because of acceptable costs, compact instrumentation, high accuracy and the capability of performing measurements at inaccessible sites, over large distances, in strong (electro)magnetic fields and in harsh environment. The technology is still proceeding quickly in terms of innovation, and respective applications have been found in highly diversified fields. This review covers work published in the time period between October 2015 and October 2019. It is written in continuation of previous reviews.

Fiber-Optic Chemical Sensors and Biosensors (2015-2019).

Femtosecond laser ablation-assisted synthesis of silver nanoparticles in organic and inorganic liquids medium and their antibacterial efficiency

Covalent organic frameworks (COFs) have shown extensive applications in energy storage, catalysis, and gas adsorption because of their regular pore structure, flexible topological connectivity, and...

Covalent Organic Framework Nanosheet-Based Ultrasensitive and Selective Colorimetric Sensor for Trace Hg2+ Detection

Biological agents for synthesis of nanoparticles and their applications

Mercury (Hg), as a highly harmful environmental pollutant, poses severe ecological and health risks even at low concentrations. Accurate and sensitive methods for detecting Hg2+ ions in aquatic environments are highly needed. In this work, we developed a highly sensitive fluorescence sensor for Hg2+ detection with an integrated use of biosynthetic CdSe/CdS quantum dots (QDs) and liposome carrier signal amplification. To construct such a sensor, three single-stranded DNA probes were rationally designed based on the thymine-Hg2+-thymine (T-Hg2+-T) coordination chemical principles and by taking advantage of the biocompatibility and facile-modification properties of the biosynthetic QDs. Hg2+ could be determined in a range from 0.25 to 100 nM with a detection limit of 0.01 nM, which met the requirements of environmental sample detection. The sensor also exhibited a high selectivity for Hg2+ detection in the presence of other high-level metal ions. A satisfactory capacity of the sensor for detecting environmental samples including tap water, river water, and landfill leachate was also demonstrated. This work opens up a new application scenario for biosynthetic QDs and holds a great potential for environmental monitoring applications.

Fluorescence Sensor Based on Biosynthetic CdSe/CdS Quantum Dots and Liposome Carrier Signal Amplification for Mercury Detection.

Abstract Silver nanoparticles (AgNPs) have application potential in diverse areas ranging from wound healing to catalysis and sensing. The possibility for optimizing the physical, chemical and optical properties for an application by tailoring the shape and size of silver nanoparticles has motived much research on methods for synthesis of size- and shape-controlled AgNPs. The shape and size of AgNPs are reported to vary depending on choice of the Ag precursor salt, reducing agent, stabilizing agent and on the synthesis technique used. This chapter provides a detailed review on various synthesis approaches that may be used for synthesis of AgNPs of desired size and shape. Silver nanoparticles may be synthesized using diverse routes, including, physical, chemical, photochemical, biological and microwave -based techniques. Synthesis of AgNPs of diverse shapes, such as, nanospheres, nanorods, nanobars, nanoprisms, decahedral nanoparticles and triangular bipyramids is also discussed for chemical-, photochemical- and microwave-based synthesis routes. The choice of chemicals used for reduction and stabilization of nanoparticles is found to influence their shape and size significantly. A discussion on the mechanism of synthesis of AgNPs through nucleation and growth processes is discussed for AgNPs of varying shape and sizes so as to provide an insight on the various synthesis routes. Techniques, such as, electron microscopy, spectroscopy, and crystallography that can be used for characterizing the AgNPs formed in terms of their shape, sizes, crystal structure and chemical composition are also discussed in this chapter. Graphical Abstract:

Synthesis and characterization of size- and shape-controlled silver nanoparticles

Heavy metal contamination of water bodies has an adverse effect on human health and the environment even at very low concentrations. In this paper, we report U-shaped fiber optic probe coated with glucose capped silver nanoparticles (AgNPs) for label-free detection of mercury ions in aqueous solution. The reaction between glucose capped AgNPs and mercury ions resulted in a reduction in the plasmonic absorbance. The developed sensor probe was able to detect mercury ions concentration as low as 2 ppb, which is less than the World Health Organization acceptable limit for mercury ions in drinking water. The sensor probes displayed excellent selectivity towards mercury ions over other metal ions. Furthermore, the developed sensor probe was able to detect mercury ions down to 5 ppb in domestic tap water, i.e., selective detection of mercury even in real matrix having high concentration mixtures of various essential ions. The response of AgNPs coated sensor probe was found to be better than glucose capped gold nanoparticles and hollow gold-silver nanostructures coated fiber-optic probes.

Optimization of Plasmonic U-Shaped Optical Fiber Sensor for Mercury Ions Detection Using Glucose Capped Silver Nanoparticles

Recent advances in nanotechnology and nanofabrication have helped develop a wide variety of nanostructured platforms for use as nanoplasmonic biosensors. These can either be in solution phase or be confined on a substrate in the form of metallic nanofilms or periodic arrays. Plasmonic properties of these nanostructures depend on the size, shape, position, orientation, etc, and can be altered by interaction between probe and target species on the metal surfaces. This property of nanostructures has been exploited in refractometric nanoplasmonic biosen- sors, surface-enhanced Raman spectroscopy-based biosensors, plasmon-enhanced fluorescence biosensors, etc. These nanoplasmonic biosensors are employed in diverse areas such as clinical diagnosis, biosecurity, food, and environmental monitoring. Among these, clinical diagnosis has attracted the most research and commercial interest. Nanoplasmonic biosensors can detect disease biomarkers using highly specific and selective biological recognition elements on the nanostructured surfaces. Many excellent reviews exist in this area that trace the developments over the past 3 decades. This review focuses on some of the more recent studies on the detec- tion of various disease biomarkers through nanoplasmonic biosensors. In the process, we have

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Nanoplasmonic biosensors: current perspectives

U-shaped fiber optic probe coated with decahedral silver nanoparticles was used for detection of mercury . The sensor could detect mercury concentration as low as 5 ppb.

Decahedral Silver Nanoparticles Coated U-Shaped Fiber Optic Sensor for Mercury Detection

The aim of this paper is to study the effect of dendrimeric and non-dendrimeric support in surface plasmon resonance (SPR) sensors for proteineous antigen analysis. 11-mercapto undecanoic acid (MUA) linker was chosen to fabricate the non-dendrimeric sensor surface while fourth generation poly(amidoamine) (PAMAM) dendrimer was used to design the dendrimeric sensor support on gold disks. Both the surfaces were conjugated with human immunoglobulin G (HIgG) antibodies and the binding was monitored in real time on Autolab Twingle SPR system. Antibodies were covalently attached to the MUA surface using EDC-NHS chemistry while glutaraldehyde was used as linker to conjugate antibodies on MUA-PAMAM surface. Further, both the sensor supports were used to study the antigen-antibody interaction using goat anti-human immunoglobulin (GaHIgG) antigen as sample analyte. Through SPR measurements, we found that dendrimeric sensor support exhibited two fold enhanced signal for HIgG binding than that of MUA surface only. During GaHIgG interaction, dendrimer modified sensor surface displayed enhanced signal with respect to the non-dendrimeric surface. This enhanced sensor response of dendrimeric SPR sensor support is attributed to high functional group density, globular shape and greater accessibility of immobilized probe towards analyte interaction.

Gauri M. Shukla

Papers

Synthesis and characterization of size- and shape-controlled silver nanoparticles

Optimization of Plasmonic U-Shaped Optical Fiber Sensor for Mercury Ions Detection Using Glucose Capped Silver Nanoparticles

Nanoplasmonic biosensors: current perspectives

Decahedral Silver Nanoparticles Coated U-Shaped Fiber Optic Sensor for Mercury Detection

Potential of dendrimeric architecture in surface plasmon resonance biosensor