Highly sensitive and selective liquid crystal optical sensor for detection of ammonia

Abstract

Ammonia detection technologies are very important in environment monitoring. However, most existing technologies are complex and expensive, which limit the useful range of real-time application. Here, we propose a highly sensitive and selective optical sensor for detection of ammonia (NH) based on liquid crystals (LCs). This optical sensor is realized through the competitive binding between ammonia and liquid crystals on chitosan-Cu that decorated on glass substrate. We achieve a broad detection range of ammonia from 50 ppm to 1250 ppm, with a low detection limit of 16.6 ppm. This sensor is low-cost, simple, fast, and highly sensitive and selective for detection of ammonia. The proposal LC sensing method can be a sensitive detection platform for other molecule monitors such as proteins, DNAs and other heavy metal ions by modifying sensing molecules.

Seeing the Unseen: The Role of Liquid Crystals in Gas‐Sensing Technologies

“…A typical example of chemically functionalized surfaces for gas sensing is the case of transition metal salts, possessing high electron affinity cations (e.g., copper, [ 107–116 ] aluminum, [ 117–123 ] ) and deposited on solid surfaces (Table 1). Cyanobiphenyl‐based LC systems, such as 5CB, assume a homeotropic orientation on these surfaces due to coordination interactions between the nitrile group of 5CB and the cation of the metal salt (serving as a binding receptor).…”

Thermotropic Liquid Crystal-Assisted Chemical and Biological Sensors

“…The solid substrate is typically coated to achieve homeotropic LC alignment, as provided by air but glass substrates can be alternatively treated to provide planar alignment. In some cases, the solid substrate provides not only the alignment layer but are also functionalized with sensing components designed to bind with target analyte, after it diffuses through the bulk of the amplifying LC film and change the director configuration [ 57 ].…”

“…To date a large variety of approaches of LC assisted biological and chemical sensing have been demonstrated [ 7 , 9 , 17 , 47 , 55 ] but examples of LC-based specific sensing of analytes remain scarce [ 14 , 57 , 112 , 113 ]. While non-specific LC-based sensor studies are interesting and insightful, “real life” applications require highly-specific LC assisted platforms for selective sensing of analytes.…”

“…LC-based sensing of ammonia (NH 3 ) gas was recently proposed by Niu et al [ 57 ]. NH 3 was detected by the disruption of the LC alignment on the glass substrate decorated with chitosan-Cu + , which has a higher affinity to NH 3 than to 5CB.…”

Trace Ammonia Detection Based on Near-Infrared Fiber-Optic Cantilever-Enhanced Photoacoustic Spectroscopy

“…Trace ammonia (NH 3 ) detection is important for environment monitoring and medical diagnosis [1][2][3]. Among the proposed trace gas detection methods, laser photoacoustic (PA) spectroscopy (PAS) shows many technical advantages, such as small sample volume, high detection sensitivity, and continuous measurement ability [4][5][6].…”