Abstract
Optical sensors are a class of devices that enable the identification and/or quantification of analyte molecules across multiple fields and disciplines such as environmental protection, medical diagnosis, security, food technology, biotechnology, and animal welfare. Nanoporous photonic crystal (PC) structures provide excellent platforms to develop such systems for a plethora of applications since these engineered materials enable precise and versatile control of light–matter interactions at the nanoscale. Nanoporous PCs provide both high sensitivity to monitor in real-time molecular binding events and a nanoporous matrix for selective immobilization of molecules of interest over increased surface areas. Nanoporous anodic alumina (NAA), a nanomaterial long envisaged as a PC, is an outstanding platform material to develop optical sensing systems in combination with multiple photonic technologies. Nanoporous anodic alumina photonic crystals (NAA-PCs) provide a versatile nanoporous structure that can be engineered in a multidimensional fashion to create unique PC sensing platforms such as Fabry–Pérot interferometers, distributed Bragg reflectors, gradient-index filters, optical microcavities, and others. The effective medium of NAA-PCs undergoes changes upon interactions with analyte molecules. These changes modify the NAA-PCs’ spectral fingerprints, which can be readily quantified to develop different sensing systems. This review introduces the fundamental development of NAA-PCs, compiling the most significant advances in the use of these optical materials for chemo- and biosensing applications, with a final prospective outlook about this exciting and dynamic field.
Highlights
Optical sensors are a class of devices that utilize different forms of light–matter interactions to detect, interrogate, and quantify molecules for multiple applications
This review provides a comprehensive and up-to-date collation of fundamental and applied developments of nanoporous anodic alumina photonic crystals as optical platforms for chemo- and biosensing applications
Pioneering studies over the past two decades have demonstrated the potential of this nanoporous material to be integrated with different optical techniques to develop sensing systems with unique properties and capabilities
Summary
Optical sensors are a class of devices that utilize different forms of light–matter (i.e., photon–atom) interactions to detect, interrogate, and quantify molecules for multiple applications. Inverted opal structures produced by a combination of self-organization of silica nanospheres and deposition of oxides or metals are one of the most representative types of nanoporous PCs [20,21] These nanostructures have limited versatility to tune the photonic stopband (PSB) of PCs, are restricted to 3D nanostructures, feature defects that act as light scattering centers, require long synthesis processes (>24 h), and are constrained to small areas (mm2–cm2) [22]. Another prime example of nanoporous PC platform material is porous silicon (pSi), which is typically produced by electrochemical etching of silicon in hydrofluoric acid (HF)-based electrolytes [23,24,25].
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