Amino functionalized mesoporous silica microspheres with perpendicularly aligned mesopore channels for electrochemical detection of trace 2,4,6-trinitrotoluene

Core–shell structured mesoporous silica microspheres with a SiO2 particles core and an ordered perpendicularly aligned mesoporous silica shell to the surface have been prepared. The perpendicular orientation mesoporous silica microspheres (SiO2@mSiO2) then were functionalized with 3-aminopropyltriethoxysilane (APTS) to graft amino functional groups (SiO2@mSiO2@NH2). The SiO2@mSiO2@NH2 was used to modify glassy carbon electrodes (GCE) as sensing material. Square-wave voltammetry was used to detect the reduction peak of 2,4,6-trinitrotoluene (TNT) in a three-electrode system. The results demonstrate that the SiO2@mSiO2@NH2/GCE can greatly improve the response to TNT due to the large active surface area and high preconcentration efficiency via specific interaction between electron-rich amino groups and electron-deficient aromatic rings. The first reduction peak current of TNT at the SiO2@mSiO2@NH2/GCE is ca. 4.6 times larger than that at the un-functionalized SiO2@mSiO2/GCE. A limit of determination of 0.5 nM and a sensitivity of 0.011 μA nM−1 was obtained. Excellent wide linear range (2.0–50.0 nM) and good repeatability (relative standard deviation of 2.4%) were obtained for TNT. Moreover, the SiO2@mSiO2@NH2/GCE shows a higher electrochemical response to TNT than to 1,3,5-trinitrobenzene (TNB) and 2,4-dinitrotoluene (DNT), and the first reduction peak current of TNT at the SiO2@mSiO2@NH2/GCE is 2.9 and 4.8 times larger than that of DNT and TNB, respectively, which shows the as-prepared SiO2@mSiO2@NH2/GCE has a much higher sensitivity to TNT than other kinds of nitroaromatics.