María Comes

A Mesoporous 3D Hybrid Material with Dual Functionality for Hg2+ Detection and Adsorption

Dual-function hybrid material U1 was designed for simultaneous chromofluorogenic detection and removal of Hg(2+) in an aqueous environment. Mesoporous material UVM-7 (MCM41 type) with homogeneously distributed pores of about 2-3 nm in size, a large specific surface area exceeding 1000 m(2) g(-1), and nanoscale particles was used as an inorganic support. The mesoporous solid is decorated with thiol groups that were treated with squaraine dye III to give a 2,4-bis(4-dialkylaminophenyl)-3-hydroxy-4-alkylsulfanylcyclobut-2-enone (APC) derivative that is covalently anchored to the inorganic silica matrix. The solid was characterised by various techniques including X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and nitrogen adsorption. This hybrid solid is the chemodosimeter for Hg(2+) detection. Hg(2+) reacts with the APC fragment in U1 with release of the squaraine dye into the solution, which turns deep blue and fluoresces strongly. Naked-eye Hg(2+) detection is thus accomplished in an easy-to-use procedure. In contrast, U1 remains silent in the presence of other thiophilic transition metal ions, alkali and alkaline earth metal ions, or anions ubiquitously present in water such as chloride, carbonate, sulfate, and phosphate. Material U1 acts not only as chemodosimeter that signals the presence of Hg(2+) down to parts-per-billion concentrations, but at the same time is also an excellent adsorbent for the removal of mercury cations from aqueous solutions. The amount of adsorbed mercury ranges from 0.7 to 1.7 mmol g(-1), depending on the degree of functionalisation. In addition, hybrid material U1 can be regenerated for both sensing and removal purposes. As far as we know, U1 is the first example of a promising new class of polyfunctional hybrid supports that can be used as both remediation and alarm systems by selective signalling and removal of target species of environmental importance. Model compounds based on silica gel (G1), fumed silica (F1), and micrometre-sized MCM-41 scaffolds (M1) were also prepared and studied for comparative purposes.

Hybrid functionalised mesoporous silica–polymer composites for enhanced analyte monitoring using optical sensors

We report herein a new optical sensor for the colorimetric monitoring of aqueous amines designed by anchoring a suitable reactand on a hybrid material that was further incorporated on a polymeric matrix. An azo chromophore containing a trifluoroacetophenone moiety was used as signalling reporter. In this system colour modulation is a consequence of the reversible reaction of the amine with the trifluoroacetyl group that results in the formation of a hemiaminal. Based on this approach but at the same time trying to enhance selectivity the chromoreactand was anchored in a first step onto suitable mesoporous nanoscopic hydrophobic pockets. As a mesoporous system we selected a UVM-7 solid (a MCM41-type material) containing a homogeneous distribution of pores of about 3 nm and a specific surface area of over 1000 m2/g. This material was chemically modified to yield a trifluoroacetylazobenzene indicator dye within the pores, resulting in the hybrid material S3. It was found that whereas the analogous trifluoroacetylazobenzene dye in solution gives an unspecific response, the hybrid material S3 shows enhanced features in terms of selectivity, only reacting with the not-too-large but lipophilic enough aminesn-octylamine and n-decylamine. The material S3 reacts with neither small hydrophilic amines (due to the hydrophobicity of the inner pores in S3) nor very large aliphatic amines (due to the size of the pore). In the second part of this work a composite material (P–S3) was prepared by mixing hydrophilic polyurethane polymer and S3. The X-ray diffraction patterns of P–S3 displays the characteristic intense peak of the MCM-41 type mesoporous material and TEM images show a homogeneous dispersion of the nanometric mesoporous particles into the polymeric matrix. The measurements were carried out in a flow-through module connected to an optical fibre via a Y-probe at pH 9.5 (borax buffer). The P–S3 composite retains the favourable features in terms of selectivity shown by S3 and only displays a clear change in colour for n-octylamine or n-decylamine, but no response to the remaining linear primary amines. The response time of the sensor P–S3 to solutions of these amines was in the range of a few seconds, the regeneration time was between 5 to 10 min and the detection limit was 6 × 10−4 mol L−1. The sensor response was reproducible and reversible.

Hybrid materials with nanoscopic anion-binding pockets for the colorimetric sensing of phosphate in water using displacement assays.

Mesoporous amino-functionalised solids containing certain dyes have been used as suitable anion hosts in displacement assays for the colorimetric signalling of phosphate in water.

N‐Methyl,N‐(propyl‐3‐trimethoxysilyl) Aniline, an Intermediate for Anchoring Dyes on Siliceous Supports

Abstract N‐methyl,N‐(propyl‐3‐trimethoxysilyl) aniline was synthesized and used as an intermediate for anchoring dyes on inorganic siliceous supports through electrophilic aromatic substitution reactions.