Surface functionalization and manipulation of mesoporous silica adsorbents for improved removal of pollutants: a review

Abstract

This review presents a broad overview of recent advances in the surface modification of mesoporous silica substrates for improved adsorption capacity and selectivity for both organic and inorganic wastewater pollutants.

Surface Functionalisation of Upconversion Nanoparticles with Different Moieties for Biomedical Applications

“…Silanisation, a popular method for UCNP surface modification due to well-established surface chemistry, [3] allows for the controlled growth and simultaneous functionalisation of a silica shell on UCNPs. Dense (dSiO2) [18,63,64] and mesoporous (mSiO2) [11,15,25,37,39,65,66] silica shells are common surface modifications to UCNPs due to enhanced bio-compatibility and stability within hydrophilic mediums, such as biological fluids, and present minimal influence on luminescence. [5] Encapsulation of nanoparticles in a silica shell coating allows them to be protected from surrounding aqueous media, thus enhancing both the dissolution and denaturation stability of the nanoparticles and preventing their dissolution into individual ionic species [4,6,7] .…”

“…Peer-reviewed version available at Surfaces 2018, 1, 9; doi:10.3390/surfaces1010009 hydroxyls present on the silica shell surface. Examples of such silanes include (3aminopropyl)trimethoxysilane [4,5,36,37,64] (APTES) which imparts amine (-NH2) functionalisation, carboxyethylsilanetriol [4,5,17,67] (CEST) that provides carboxylic (-COOH) functionalisation (demonstrated in Figures X. and X.) and (3-mercaptopropyl)trimethoxysilane [37,68] (MPTMS) which grants thiol (-SH) functionalisation.…”

“…Examples of such silanes include (3aminopropyl)trimethoxysilane [4,5,36,37,64] (APTES) which imparts amine (-NH2) functionalisation, carboxyethylsilanetriol [4,5,17,67] (CEST) that provides carboxylic (-COOH) functionalisation (demonstrated in Figures X. and X.) and (3-mercaptopropyl)trimethoxysilane [37,68] (MPTMS) which grants thiol (-SH) functionalisation. Amine-terminated functional groups are the most common silica surface functionalisation, followed behind by carboxyl functionalisation [3][4][5]29,36] .…”

“…Moreover, nanoparticles intended for use in biomedical applications require uniformity in morphology and size which presents a greater difficulty in obtaining ideal samples [29] .Various modification strategies exist that have tried to develop universal methods and overcome these limitations but stability in aqueous environments is still a considerable challenge [10] . The four main strategies for surface modification include: (a) ligand engineering [2,3,5,7,9,10,12,31] ; (b) layer-by-layer assembly [2,3,5,7,32] ; (c) ligand attraction [2,3,5,7,33] ; and (d) surface polymerisation [2,3,5,6,11,13,[15][16][17][34][35][36][37][38][39] . Each modification method as well as the specific molecules selected, has its own benefits and hindrances.While there are many ways to modify the surfaces of UCNPs, this review aims at covering the two most popular methods, that being ligand engineering and silanisation.Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 15…”

Adsorption of nitrogen-containing compounds on hydroxylated α-quartz surfaces

“…Previous reports containing these species were devoted to prediction of nitroaromatics reactivity, 9 toxicity, 10-12 environmentally important physical properties [13][14][15] and adsorption abilities on various materials. [16][17][18][19][20][21] Silica is one of the most abundant species on earth's crust and is most commonly found in the form of quartz. There is a plethora of studies of organic pollutants on silica, although in most cases mesoporous one.…”