Gallium arsenide waveguides as a platform for direct mid-infrared vibrational spectroscopy

Abstract

During recent years, mid-infrared (MIR) spectroscopy has matured into a versatile and powerful sensing tool for a wide variety of analytical sensing tasks. Attenuated total reflection (ATR) techniques have gained increased interest due to their potential to perform non-destructive sensing tasks close to real time. In ATR, the essential component is the sampling interface, i.e., the ATR waveguide and its material properties interfacing the sample with the evanescent field ensuring efficient photon-molecule interaction. Gallium arsenide (GaAs) is a versatile alternative material vs. commonly used ATR waveguide materials including but not limited to silicon, zinc selenide, and diamond. GaAs-based internal reflection elements (IREs) are a new generation of semiconductor-based waveguides and are herein used for the first time in direct spectroscopic applications combined with conventional Fourier transform infrared (FT-IR) spectroscopy. Next to the characterization of the ATR waveguide, exemplary surface reactions were monitored, and trace-level analyte detection via signal amplification taking advantage of surface-enhanced infrared absorption (SEIRA) effects was demonstrated. As an example of real-world relevance, the mycotoxin aflatoxin B1 (AFB1) was used as a model analyte in food and feed safety analysis.

Synthesis of Ordered Pt Nanocube Arrays Directed by Block Copolymer Nanotemplate and Their Potential on Ethanol Oxidation Reaction

“…Self-assembly of block copolymers (BCs) to form nanostructured templates has been considered as promising candidates for preparation of inorganic NPs for their potential in functional materials and devices. − BCs containing a metal-binding block of poly­(vinylpyridine) (P2VP or P4VP) can be coordinated or protonated by metal ions or compounds (particularly precious metals such as gold or platinum), and then the incompatible BC blocks can segregate into various nanopatterns with a wide range of several to thousands of nanometers. , This technique allows one to produce a controlled and predetermined spatial arrangement of metal NPs for the bottom-up synthesis of material construction. However, in contrast to the wet chemistry method, the existing challenge here is the design and the shape control of the individual NP building blocks .…”