Ordered mesoporous materials have great potential in the field of gas sensing. Today various template-assisted synthesis methods facilitate the preparation of silica (SiO2) as well as numerous metal oxides with well-defined, uniform and regular pore systems. The unique nanostructural properties of such materials are particularly useful for their application as active layers in gas sensors based on various operating principles, such as capacitive, resistive, or optical sensing. This review summarizes the basic aspects of materials synthesis, discusses some structural properties relevant in gas sensing, and gives an overview of the literature on ordered mesoporous gas sensors.

Mesoporous materials as gas sensors

Periodic Mesoporous Organosilicas (PMOs) were developed in 1999 and are basically ordered templated mesoporous organosilicas, prepared by the combination of a surfactant as template and a silsesquioxane as the organosilica precursor. They were one of the first examples of the so-called "hybrid" organic/inorganic materials. In the years that followed, an amazing variety of functional groups, morphologies and applications has been developed. Some of these high-end applications, like low-k buffer layers in microelectronics, chiral catalysts, chromatographic supports, selective adsorbents and light-harvesting devices, have clearly shown their potential. In this review, we will give a comprehensive overview of all these different functionalities and applications that have been created for Periodic Mesoporous Organosilicas.

Periodic mesoporous organosilicas : from simple to complex bridges : a comprehensive overview of functions, morphologies and applications

The present invention provides an inexpensive and sensitive device and method for detecting and quantifying analytes present in a medium. The device comprises a metalized film upon which is printed a specific, predetermined pattern of a analyte-specific receptors. Upon attachment of a target analyte to select areas of the plastic film upon which the receptor is printed, diffraction of transmitted and/or reflected light occurs via the physical dimensions and defined, precise placement of the analyte. A diffraction image is produced which can be easily seen with the eye or, optionally, with a sensing device.

Biosensing devices which produce diffraction images

The present invention provides an inexpensive and sensitive device and method for detecting and quantifying analytes present in a medium. The device comprises a metalized film (20) upon which is printed a specific, predetermined pattern of analyte-specific receptors (25). Upon attachment of a target analyte to select areas of the plastic film upon which the receptor is printed, diffraction of transmitted and/or reflected light occurs via the physical dimensions and defined, precise placement of the analyte. A diffraction image is produced which can be easily seen with the eye or, optionally, with a sensing device.

Optical diffraction biosensor

The present invention provides solid supports (e.g., glass) and polymer hydrogels (particularly polymer hydrogel arrays present on a solid support) comprising one or more reactive sites for the attachment of biomolecules, as well as biomolecules comprising one or more reactive sites for attachment to solid supports and polymer hydrogels. The invention further provides novel compositions and methods for the preparation of biomolecules, solid supports, and polymer hydrogels comprising reactive sites. The invention also provides for preparation of crosslinked solid supports, polymer hydrogels, and hydrogel arrays, wherein one or more biomolecules is attached by means of the reactive sites in a photocycloaddition reaction. Advantageously, according to the invention, crosslinking of the hydrogel and attachment of biomolecules can be done in a single step.

Methods and compositions for attachment of biomolecules to solid supports, hydrogels, and hydrogel arrays

The presently claimed invention is directed to novel biochips and a method for forming said biochips and novel photoactivatable compounds, 2,6-DOCA, 2-NOCA and LC-ASA Amine.

Photoactivatable polymers for producing patterned biomolecular assemblies

The development of porphyrin-embedded mesoporous organosilicate materials for application to the detection of volatile hydrocarbon solvents is described. Design of the receptor and optical indicator construct begins with parallel selection of the porphyrin indicator and design of the mesoporous sorbent. For the porphyrin indicator, high binding affinity and strong changes in spectrophotometric character upon target interaction are desired. The sorbent should provide high target binding capacity and rapid binding kinetics. A number of porphyrin/metalloporphyrin variants and organosilicate sorbents were evaluated to determine the characteristics of their interaction with the targets, benzene, toluene, and hexane. The selected porphyrin candidates were covalently immobilized within a benzene-bridged sorbent. This construct was applied to the detection of targets using both fluorescence- and reflectance-based protocols. The use of red, green, and blue (RGB) color values from the constructs in a highly simplified detection scheme is described.

https://www.mdpi.com/1424-8220/11/1/886/pdf

Porphyrin-Embedded Silicate Materials for Detection of Hydrocarbon Solvents

A molecularly imprinted material made from polymerizing a monomer having the structural formula (OR) 3 Si—B-A-B—Si(OR) 3 . A is a divalent organic group, B is a saturated or unsaturated divalent hydrocarbon group or a covalent bond, and R is an independently selected saturated or unsaturated monovalent hydrocarbon group. A preconcentrator having: a container comprising in inlet and an outlet and the above material within the container. The inlet is capable of allowing a fluid to enter the container. The outlet is capable of being coupled to a sensor and of allowing the fluid to exit the container.

Nanoporous organosilicas as pre-concentration materials for sensors

Periodic mesoporous organosilicas (PMO) which incorporate an optically active molecule into the material for use as an optical indicator of target binding. This material combines the stability, selectivity, and high density of binding sites characteristic of the PMO with the sensitivity and selectivity of the optically active molecule. The material undergoes a change when exposed to a sample containing a target molecule. The change can be observed by visual inspection or through the use of fluorescence spectra.

Fluorophore embedded/incorporating/bridged periodic mesoporous organosilicas as recognition elements for optical sensors

We have previously described the application of novel porous organosilicate materials to the preconcentration of nitroenergetic targets from aqueous solution prior to HPLC analysis. The performance of the sorbents and the advantages of these types of materials over commercially available solid phase extraction sorbents have been demonstrated. Here, the development of systems for application of those sorbents to in situ monitoring is described. Considerations such as column pressure, particulate filtration, and component durability are discussed. The diameter of selected column housings, the sorbent bed depth, and the frits utilized significantly impact the utility of the sorbent columns in the prototype system. The impact of and necessity for improvements in the morphological characteristics of the sorbents as they relate to reduction in column pressure are detailed. The results of experiments utilizing a prototype system are presented. Data demonstrating feasibility for use of the sorbents in preconcentration prior to ion mobility spectrometry is also presented.

https://www.mdpi.com/1424-8220/12/11/14953/pdf

Paul T. Charles

Papers

Photoactivatable polymers for producing patterned biomolecular assemblies

Porphyrin-Embedded Silicate Materials for Detection of Hydrocarbon Solvents

Nanoporous organosilicas as pre-concentration materials for sensors

Fluorophore embedded/incorporating/bridged periodic mesoporous organosilicas as recognition elements for optical sensors

Toward In Situ Monitoring of Water Contamination by Nitroenergetic Compounds