Spherical Silica Functionalized by 2-Naphthalene Methanol Luminophores as a Phosphorescence Sensor

Photoluminescence is known to have huge potential for applications in studying biological systems. In that respect, phosphorescent dye molecules open the possibility to study the local slow solvent dynamics close to hard and soft surfaces and interfaces using the triplet state (TSD: triplet state solvation dynamics). However, for that purpose, probe molecules with efficient phosphorescence features are required with a fixed location on the surface. In this article, a potential TSD probe is presented in the form of a nanocomposite: we synthesize spherical silica particles with 2-naphthalene methanol molecules attached to the surface with a predefined surface density. The synthesis procedure is described in detail, and the obtained materials are characterized employing transmission electron microscopy imaging, Raman, and X-ray photoelectron spectroscopy. Finally, TSD experiments are carried out in order to confirm the phosphorescence properties of the obtained materials and the route to develop phosphorescent sensors at silica surfaces based on the presented results is discussed.

Methods to Improve nZVI Adsorbance on Silicates Surface for Nitrate Reduction

<p>Efforts to remove excess nitrate in the groundwater typically involves expensive ion-exchange membranes or slow reacting bio-reactors. Nano-sized zero valent iron (nZVI) has been used successfully to reduce nitrate into ammonia in various sites in USA and Europe. However, nZVI has a number of major setbacks associated with it, namely the tendency to agglomerate due to magnetic properties, and the possible toxicity due to the nano-sized material. To circumvent these two setbacks, nZVI could be adsorbed onto solid support. In this research, geothermal sediment microsilicate 600 (Misi) was utilised as a support. Initial results suggested that Misi has potential as a support for nZVI, however modifications were required to improve the adsorbance of nZVI onto Misi surface. Calcination, activation, acid wash and iron oxyhydroxide coating were used as surface modifications for Misi. It was found that the two most important modifications for nZVI adsorption was calcination at either 400 or 600 °C and acid washing in 5.6 M HCl. Equipped with this knowledge, other silica and silicates were also used to adsorb nZVI. For pure silica surfaces, 3-APTES and 3-TPTMS ligands and pore enlarging methods of calcination of porogen and salt wash were also used. nZVI was not able to be fully adsorbed on pure silica surfaces. Four other silicates were examined: Rice husk ash, Western Australia silica fume, Mt Piper fly ash, and precipitated aluminium silicate. Of these, only Western Australia silica fume and precipitated aluminium silicate showed potential as nZVI support. Based on the SEM-EDS XRD data of all the silica and silicates, it could be tentatively concluded that nZVI requires an aluminium silicate surface for successful adsorption. Aluminium silicate surfaces typically has an exchangeable cation present, and this cation might play a part in nZVI adsorption. The nZVI/Misi surface was then utilised to reduce nitrate. It was discovered that even though activation and FeOOH did not play a part in nZVI adsorption onto Misi surface, these two steps were important in reduction of nitrate, as the presence of activation and FeOOH increase the reduction of nitrate significantly within 60 minutes. The Misi-supported nZVI were also shown to be more stable in dispersion, and less agglomerated as shown in a sand column experiment.</p>

Methods to Improve nZVI Adsorbance on Silicates Surface for Nitrate Reduction

<p>Efforts to remove excess nitrate in the groundwater typically involves expensive ion-exchange membranes or slow reacting bio-reactors. Nano-sized zero valent iron (nZVI) has been used successfully to reduce nitrate into ammonia in various sites in USA and Europe. However, nZVI has a number of major setbacks associated with it, namely the tendency to agglomerate due to magnetic properties, and the possible toxicity due to the nano-sized material. To circumvent these two setbacks, nZVI could be adsorbed onto solid support. In this research, geothermal sediment microsilicate 600 (Misi) was utilised as a support. Initial results suggested that Misi has potential as a support for nZVI, however modifications were required to improve the adsorbance of nZVI onto Misi surface. Calcination, activation, acid wash and iron oxyhydroxide coating were used as surface modifications for Misi. It was found that the two most important modifications for nZVI adsorption was calcination at either 400 or 600 °C and acid washing in 5.6 M HCl. Equipped with this knowledge, other silica and silicates were also used to adsorb nZVI. For pure silica surfaces, 3-APTES and 3-TPTMS ligands and pore enlarging methods of calcination of porogen and salt wash were also used. nZVI was not able to be fully adsorbed on pure silica surfaces. Four other silicates were examined: Rice husk ash, Western Australia silica fume, Mt Piper fly ash, and precipitated aluminium silicate. Of these, only Western Australia silica fume and precipitated aluminium silicate showed potential as nZVI support. Based on the SEM-EDS XRD data of all the silica and silicates, it could be tentatively concluded that nZVI requires an aluminium silicate surface for successful adsorption. Aluminium silicate surfaces typically has an exchangeable cation present, and this cation might play a part in nZVI adsorption. The nZVI/Misi surface was then utilised to reduce nitrate. It was discovered that even though activation and FeOOH did not play a part in nZVI adsorption onto Misi surface, these two steps were important in reduction of nitrate, as the presence of activation and FeOOH increase the reduction of nitrate significantly within 60 minutes. The Misi-supported nZVI were also shown to be more stable in dispersion, and less agglomerated as shown in a sand column experiment.</p>

Coupling between Polymer Conformations and Dynamics Near Amorphous Silica Surfaces: A Direct Insight from Atomistic Simulations

The dynamics of polymer chains in the polymer/solid interphase region have been a point of debate in recent years. Its understanding is the first step towards the description and the prediction of the properties of a wide family of commercially used polymeric-based nanostructured materials. Here, we present a detailed investigation of the conformational and dynamical features of unentangled and mildly entangled cis-1,4-polybutadiene melts in the vicinity of amorphous silica surface via atomistic simulations. Accounting for the roughness of the surface, we analyze the properties of the polymer chains as a function of their distance from the silica slab, their conformations and the chain molecular weight. Unlike the case of perfectly flat and homogeneous surfaces, the monomeric translational motion parallel to the surface was affected by the presence of the silica slab up to distances comparable with the extension of the density fluctuations. In addition, the intramolecular dynamical heterogeneities in adsorbed chains were revealed by linking the conformations and the structure of the adsorbed chains with their dynamical properties. Strong dynamical heterogeneities within the adsorbed layer are found, with the chains possessing longer sequences of adsorbed segments (“trains”) exhibiting slower dynamics than the adsorbed chains with short ones. Our results suggest that, apart from the density-dynamics correlation, the configurational entropy plays an important role in the dynamical response of the polymers confined between the silica slabs.

Assessing the impact of nonspecific binding on oligonucleotide bioanalysis

Aim: Accurate and reliable quantification of oligonucleotides can be difficult, which has led to an increased focus on bioanalytical methods for more robust analyses. Recent advances toward mitigating sample losses on liquid chromatography (LC) systems have produced recovery advantages for oligonucleotide separations. Results & methodology: LC instruments and columns constructed from MP35N metal alloy and stainless steel columns were compared against LC hardware modified with hybrid inorganic-organic silica surfaces. Designed to minimize metal-analyte adsorption, these surfaces demonstrated a 73% increase in 25-mer phosphorothioate oligonucleotide recovery using ion-pairing reversed-phase LC versus standard LC surfaces, most particularly upon initial use. Conclusion: Hybrid silica chromatographic surfaces improve the performance, detection limits and reproducibility of oligonucleotide bioanalytical assays.