Mid-Infrared Chemical Sensors Utilizing Plasma-Deposited Fluorocarbon Membranes

Infrared Spectroscopy–Quo Vadis?

Given the exquisite capability of direct, non-destructive label-free sensing of molecular transitions, IR spectroscopy has become a ubiquitous and versatile analytical tool. IR application scenarios range from industrial manufacturing processes, surveillance tasks and environmental monitoring to elaborate evaluation of (bio)medical samples. Given recent developments in associated fields, IR spectroscopic devices increasingly evolve into reliable and robust tools for quality control purposes, for rapid analysis within at-line, in-line or on-line processes, and even for bed-side monitoring of patient health indicators. With the opportunity to guide light at or within dedicated optical structures, remote sensing as well as high-throughput sensing scenarios are being addressed by appropriate IR methodologies. In the present focused article, selected perspectives on future directions for IR spectroscopic tools and their applications are discussed. These visions are accompanied by a short introduction to the historic development, current trends, and emerging technological opportunities guiding the future path IR spectroscopy may take. Highlighted state-of-the art implementations along with novel concepts enhancing the performance of IR sensors are presented together with cutting-edge developments in related fields that drive IR spectroscopy forward in its role as a versatile analytical technology with a bright past and an even brighter future.

Mid-infrared materials and devices on a Si platform for optical sensing

In this article, we review our recent work on mid-infrared (mid-IR) photonic materials and devices fabricated on silicon for on-chip sensing applications. Pedestal waveguides based on silicon are demonstrated as broadband mid-IR sensors. Our low-loss mid-IR directional couplers demonstrated in SiN x waveguides are useful in differential sensing applications. Photonic crystal cavities and microdisk resonators based on chalcogenide glasses for high sensitivity are also demonstrated as effective mid-IR sensors. Polymer-based functionalization layers, to enhance the sensitivity and selectivity of our sensor devices, are also presented. We discuss the design of mid-IR chalcogenide waveguides integrated with polycrystalline PbTe detectors on a monolithic silicon platform for optical sensing, wherein the use of a low-index spacer layer enables the evanescent coupling of mid-IR light from the waveguides to the detector. Finally, we show the successful fabrication processing of our first prototype mid-IR waveguide-integrated detectors.

InP-based short-wave infrared and midwave infrared photodiodes using a novel type-II strain-compensated quantum well absorption region

We report on InP-based p-type/intrinsic/n-type (PIN) photodiodes with a novel strain-compensated type-II InGaAs/GaAsSb quantum well active region. The device has optical response out to 3.0 μm, specific detectivity (D*) of 7.73×10(9) cm Hz(0.5)/W at 290 K for 2.7 μm. These preliminary results show that this novel strain-compensated approach leads to similar performance when compared to a conventional strain-compensated approach.

Towards universal enrichment nanocoating for IR-ATR waveguides

Polymer multilayered nanocoating capable of concentrating various chemical substances at IR-ATR waveguide surfaces is described. The coating affinity to an analyte played a pivotal role in sensitivity enhancement of the IR-ATR measurements, since the unmodified waveguide did not show any analyte detection.

The ways to the trace level analysis in infrared spectroscopy

The future of infrared (IR) spectroscopy as an analytical technique is assured due to its versatility and its numerous advantages; such as the possibility to obtain molecular specific information for virtually any sample in any state with no treatment or minimal sample preparation. However, spectroscopists are not satisfied with relegating IR spectroscopy just to major and minor component analysis and have been looking at analysis at the trace level too. This review is the recognition of the brilliant research performed during the past two decades and the advances achieved in this area, which have made possible the analysis of contaminants at parts per billion (ppb) levels by IR in different matrices; such as water and soils.

Combining scanning electrochemical microscopy with infrared attenuated total reflection spectroscopy for in situ studies of electrochemically induced processes

The combination of scanning electrochemical microscopy (SECM) with single-bounce attenuated total reflection Fourier-transformed infrared spectroscopy (FT-IR-ATR) has been developed for in situ studies on electrochemically induced processes at IR waveguide surfaces via evanescent field absorption spectroscopy. The feasibility of the combined microelectrochemical FT-IR setup was demonstrated by spectroscopically monitoring microstructured polymer depositions induced via feedback mode SECM using a 25 mum Pt disk ultramicroelectrode (UME). The surface of a ZnSe ATR crystal was initially coated with 2,5-di-(2-thienyl)-pyrrole (SNS) layer, which was then locally polymerized during Ru(bpy)(3)(2+) mediated feedback mode SECM experiments. The polymerization reaction was simultaneously monitored by recording absorption intensity changes of SNS specific IR bands, thereby providing information on the polymerization mechanism and on the percentage of surface modification.