A Review: Application and Implementation of Optic Fibre Sensors for Gas Detection

At the present time, there are major concerns regarding global warming and the possible catastrophic influence of greenhouse gases on climate change has spurred the research community to investigate and develop new gas-sensing methods and devices for remote and continuous sensing. Furthermore, there are a myriad of workplaces, such as petrochemical and pharmacological industries, where reliable remote gas tests are needed so that operatives have a safe working environment. The authors have concentrated their efforts on optical fibre sensing of gases, as we became aware of their increasing range of applications. Optical fibre gas sensors are capable of remote sensing, working in various environments, and have the potential to outperform conventional metal oxide semiconductor (MOS) gas sensors. Researchers are studying a number of configurations and mechanisms to detect specific gases and ways to enhance their performances. Evidence is growing that optical fibre gas sensors are superior in a number of ways, and are likely to replace MOS gas sensors in some application areas. All sensors use a transducer to produce chemical selectivity by means of an overlay coating material that yields a binding reaction. A number of different structural designs have been, and are, under investigation. Examples include tilted Bragg gratings and long period gratings embedded in optical fibres, as well as surface plasmon resonance and intra-cavity absorption. The authors believe that a review of optical fibre gas sensing is now timely and appropriate, as it will assist current researchers and encourage research into new photonic methods and techniques.

Asymmetric misfit nanotubes: Chemical affinity outwits the entropy at high-temperature solid-state reactions

Asymmetric two-dimensional (2D) structures (often named Janus), like SeMoS and their nanotubes, have tremendous scope in material chemistry, nanophotonics, and nanoelectronics due to a lack of inversion symmetry and time-reversal symmetry. The synthesis of these structures is fundamentally difficult owing to the entropy-driven randomized distribution of chalcogens. Indeed, no Janus nanotubes were experimentally prepared, so far. Serendipitously, a family of asymmetric misfit layer superstructures (tubes and flakes), including LaX-TaX2 (where X = S/Se), were synthesized by high-temperature chemical vapor transport reaction in which the Se binds exclusively to the Ta atoms and La binds to S atoms rather than the anticipated random distribution. With increasing Se concentration, the LaS-TaX2 misfit structure gradually transformed into a new LaS-TaSe2-TaSe2 superstructure. No misfit structures were found for xSe = 1. These counterintuitive results shed light on the chemical selectivity and stability of misfit compounds and 2D alloys, in general. The lack of inversion symmetry in these asymmetric compounds induces very large local electrical dipoles. The loss of inversion and time-reversal symmetries in the chiral nanotubes offers intriguing physical observations and applications.

A kinetic model of thin-film fluorescent sensors for strategies to enhance chemical selectivity

An analytical model was developed for thin film chemical sensors which provides insight into the sensor dynamics and potential strategies to develop chemical recognition.

A Spectral Resolution study in Femtosecond Stimulated Raman Scattering Microscopy

The simultaneous mapping and the specificity of different chemical species are desirable in several biological and biomedical applications. The stimulated Raman Scattering technique is a proven and well-established label-free method to map the distributions of individual species in a multi-component-based system due to the linear dependence of signals on concentration and its chemical selectivity. In this framework, spectral resolution, i.e., the ability to distinguish closely lying resonances, plays a fundamental role. Here in this work, the cross-correlation of Ti:Sa & OPO femtosecond laser beams in a stimulated Raman scattering microscope is measured. The separation between protein and lipid bands in the C-H region is important for biochemical research and is successfully classified.

Recent applications of N-acyl imidazole chemistry in chemical biology

N-Acyl imidazoles are unique electrophiles that exhibit moderate reactivity, relatively long-half life, and high solubility in water. Thanks to their tunable reactivity and chemical selectivity, the application of N-acyl imidazole derivatives has launched to a number of chemical biology researches, which include chemical synthesis of peptide/protein, chemical labeling of native proteins of interest (POIs), and structural analysis and functional manipulation of RNAs. Since proteins and RNAs play pivotal roles in numerous biological events in all living organisms, the methods that enable the chemical modification of endogenously existing POIs and RNAs in live cells may offer a variety of opportunities not only for fundamental scientific study but also for biotechnology and drug development. In this review, we discuss the recent progress of N-acyl imidazole chemistry that contributes to the chemical labeling and functional control of endogenous proteins and RNAs under multimolecularly crowded biological conditions of live cells.

Sodium iodide-mediated synthesis of vinyl sulfides and vinyl sulfones with solvent-controlled chemical selectivity

Solvent-controlled selectivity of the elimination/coupling reaction was realized for divergent synthesis of vinyl sulfides and vinyl sulfones. The described protocol is more convenient for the preparation of vinyl sulfide and vinyl sulfone related skeletons.

Fully Printed Flexible Chemiresistors with Tunable Selectivity Based on Gold Nanoparticles

This study presents a method for printing flexible chemiresistors comprising thin film transducers based on cross-linked gold nanoparticles (GNPs). First, interdigitated silver paste electrodes are printed onto polyimide (PI) foil via dispenser printing. Second, coatings of GNPs and dithiol/monothiol blends are inkjet-printed onto these electrode structures. 1,9-Nonanedithiol (9DT) is used as cross-linking agent and a variety of monothiols are added to tune the sensors’ chemical selectivity. When dosing these sensors with different analyte vapors (n-octane, toluene, 4-methyl-2-pentanone, 1-butanol, 1-propanol, ethanol, water; concentration range: 25–2000 ppm) they show fully reversible responses with short response and recovery times. The response isotherms follow a first-order Langmuir model, and their initial slopes reveal sensitivities of up to 4.5 × 10−5 ppm−1. Finally, it is demonstrated that arrays of printed sensors can be used to clearly discern analytes of different polarity.