Turn-off Fluorescence Chemosensor for Iron with Bis(2-aminoethyl)-2-(9-fluorenyl)malonamide Functionlized SBA-15

An bis(2-aminoethyl)-2-(9-fluorenyl)malonamide as fluorophore ligand was immobilized onto mesoporous silica type SBA-15 via post synthesis grafting. The obtained material was characterized by small and wide angle X-ray diffraction, N₂ adsorption–desorption, Fourier transform infrared spectroscopy, Raman spectroscopy and thermogravimetric analysis that indicate the successful immobilization of the ligand on the surface of mesoporous silica. The sensing ability of the obtained material was studied by addition of the cations Fe³⁺, Mg²⁺, Cr³⁺, Co²⁺, Ni²⁺, Cu²⁺, Hg²⁺ and Zn²⁺ to water suspensions of the assayed solid. Of all the cations tested addition of Fe³⁺ ion to a suspension of this material resulted in the largest decrease in the fluorescence intensity. Turn-off photoluminescence of this material was remarkably observed for iron ions in comparing of the other cations. A good linearity between the fluorescence intensity of this material and the concentration of Fe³⁺ ion is constructed, which enables it as a fluorescence chemosensor for detecting the Fe³⁺ ion with a suitable detection limit of 1.35?×?10^?5. It can be introduced as a novel fluorescent sensor in aqueous solution for a lot of practical applications in chemical, environmental and biological systems.     

Application of SiO2-Pr-SO3H as an efficient catalyst in the Ritter reaction

Sulfonic-acid-functionalized silica was applied as an efficient heterogeneous acid catalyst in the Ritter reaction to prepare amides by reaction of various benzylic, allylic, and tertiary alcohols with various nitriles in good to excellent yields under solvent-free conditions. The simplicity of the reaction, recovery of catalyst without loss of reactivity, high yield of products, and short reaction time represent improvements over many existing methods.     

Sulfonic acid-functionalized LUS-1: an efficient catalyst for tetrahydropyranylation/depyranylation of alcohols

Efficient acidic functionalization of mesoporous silica LUS-1 (Laval University Silica) and its application as a recyclable heterogeneous catalyst for DHP (3,4-dihydro-2H-pyran) protection of alcohols and the subsequent removal of the corresponding protecting group have been reported. This green method offers a number of advantages such as short reaction time, good yields of protection and deprotection, simple work-up procedure, recyclable catalyst, and environmentally friendly conditions.     

Application of SBA-Pr-SO<Subscript>3</Subscript>H in the synthesis of 2,3-dihydroquinazoline-4(1<Emphasis Type="Italic">H</Emphasis>)-ones: characterization,UV–Vis investigations and DFT studies

An efficient one-pot synthesis of 2,3-dihydroquinazoline-4(1H)-one derivatives 4a–l is described using SBA-Pr-SO₃H as a heterogeneous acid catalyst. The present methodology resulted in various derivatives of 2,3-dihydroquinazoline-4(1H)-one in good yield via a three-component reaction of isatoic anhydride, aldehydes and ammonium acetate. SBA-Pr-SO₃H played a significant role as an efficient mesoporous catalyst due to its pore size of 6 nm. Additionally, UV–Vis spectrum of the products was studied in order to investigate their application as UV absorbers.     

Surface tailoring control in micelle templated silica

Surface tailoring control was studied using new concept surface-protector (SP) group that can covered a part of surface. In micelle templated silica, cationic surfactant had the role of SP group. Various methods of silylation on the surface coverage was done on the hexagonal micelle templated silicas and the samples was characterized using BET surface measurement, pore size distribution, FT-IR and ¹³C and ²⁹Si MAS NMR. Direct silylation of micelle templated silica still containing the templating surfactant can lead to total or partial silylation of the internal (and external) surface depending on the silylation agent. A mixture of chlorotrimethylsilane in hexamethyldisiloxane leads to full coverage by trimethylsilyl groups and to a very hydrophobic surface. Using hexamethyldisilazane, the silylation drops down to 45-65% and displaces only partially the templating CTMA⁺ surfactant. The displacement of the remaining surfactant molecules leaves behind hydrophilic nests of the size of the ammonium heads (∼0.7 nm²). Cation exchange can be performed on these nests at pH to 10 without structure collapse.     

Carbon Paste Electrode Modified with Functionalized Nanoporous Silica Gel as a New Sensor for Determination of Silver Ion

A new dipyridyl‐functionalized silica gel (DPSG) was synthesized. The potentiometric response of silver ion was investigated at a carbon paste electrode chemically modified with functionalized nanoporous silica gel. The electrodes with a DPSG proportions of 10.1% (w/w), showed very stable potential. Calibration plots with Nernstian slopes for Ag⁺ were observed, 58.7 (±0.9) mV decade^?1, over a wide linear range of concentration (5.0×10^?7 to 1.0×10^?1 M). The electrode has a detection limit of 1.0×10^?7 M. The selectivity coefficients measured by the match potential method in acetate buffer, pH 5.5, were investigated. The electrode has fast response time, high performance, high sensitivity in wide cation activity ranges, and good long term stability (more than 6 months). The method was satisfactory and used to determine the concentration of silver ion in waste waters contaminated by this metal.     

Application of SBA-Pr-SO<Subscript>3</Subscript>H as a nanoreactor in the one-pot synthesis of spiroquinazolinones

An efficient method for the synthesis of spiroquinazolinones was developed using isatoic anhydride, hydrazides and cyclic ketones, through a rapid one-pot three-component reaction in the presence of SBA-Pr-SO₃H under solvent-free conditions. SBA-Pr-SO₃H was an efficient heterogeneous nanoreactor with a pore size of 6 nm which can be easily handled and removed from the reaction mixture by simple filtration and can be reused several times without any loss of activity. The main advantages of using this nanoreactor are high product yields, being environmentally benign, short reaction times, and easy handling.     

The role of pyruvic acid as starting material in some organic reactions in the presence of SBA-Pr-SO<Subscript>3</Subscript>H nanocatalyst

Pyruvic acid contains three different reactive positions: –COOH, ketone carbonyl and methyl groups. Correspondingly, pyruvic acid was applied as starting material in the modified Niementowski reaction and Aldol condensation using SBA-Pr-SO₃H as an efficient nanocatalyst. Aldol condensation of pyruvic acid and oxindole provided a new oxindol-based carboxylic acid which was subsequently used in the Ugi four-component reaction. Moreover, through the modified Niementowski reaction of pyruvic acid, new derivatives of quiazoline were produced in the presence of SBA-Pr-SO₃H. The obtained products are important due to their potentially biological active skeletons.     

Microextraction of Rosmarinic Acid Using CMK-3 Nanoporous Carbon in a Packed Syringe

CMK-3 nanoporous carbon was prepared and used as an efficient sorbent for microextraction in packed syringe of rosmarinic acid in Rosmarinus officinalis L. (rosemary). In the proposed method, only 2 mg of the nanoporous material, inserted between a syringe’s barrel and needle, was sufficient for the extraction with minimum consumption of organic solvents. Sample preparation was performed on the packed bed using a laboratory-made programmable apparatus. The apparatus was designed and used for automation of the conditioning, sampling, washing and elution steps of the method, and increasing the reproducibility of the experiments. For optimization of the experimental parameters, a central composite design method was used. Under the optimized conditions (i.e., number of adsorption cycles 14 times, number of elution cycles ten times and volume of elution 100 μL), an extraction recovery of 90 (±4.5) % was obtained for rosmarinic acid. The same packing bed could be used for at least 80 extractions without significant changes in its properties. The efficiency of the nanoporous sorbent was found to be superior to that of activated carbon, by a factor of about 17. The proposed method was successfully applied to the extraction of three rosemary samples before analysis by HPLC.

     

Novel functionalized mesopore of SBA-15 as prospective sorbent for praseodymium and lutetium

In the present work, results of γ-irradiation on normal and functionalized SBA-15 by aurintricarboxylic acid have been reported. Characterization of normal and functionalized SBA-15 particles before and after γ-irradiation was carried out using Fourier-transform infrared technique. Aurintricarboxylic acid ligand connected to SBA-15 was also analyzed using UV/Vis spectrophotometer. The modified sorbent was then used as a new sorbent for separation of trace amounts of praseodymium and lutetium ions from nuclear waste waters in batch techniques. Based on the results of distribution coefficients determination, and investigation of sorption process in various conditions, the parameters were optimized for separation lanthanides. It can be concluded that the functionalized SBA-15 is a promising sorbent for praseodymium and lutetium cations.