A Facile Synthesis of Sn-Doped CeO2 Nanoparticles: High Performance Electrochemical Nitrite Sensing Application

Development of novel electrode materials for sensing water pollutant like nitrite, nitrate, paramedical pollutants and fertilizers is a more promising research area in electrochemical sensor field. Various pure as well as doped metal oxides were used as electrodes for sensing the water pollutants but, deficits in stability, reproducibility and real time analysis. In the present work, a promising Sn-doped CeO2 based sensor was fabricated for sensing nitrite in water. A selective concentration of Sn (5%) doped CeO2 nanoparticles were synthesized by facile chemical precipitation method. The structural, optical and morphological information were studied using various techniques. The morphological of the sample was revealed an agglomerated with spherical nanoparticles with size of 8.5 nm. The synergistic effect of Sn-CeO2/GCE improves the electrochemical behavior of nitrite on the modified surface. Sn-doped CeO2 nanoparticles has a better surface property and provides a more fine-grained media to facilitate electron transfer during the reaction between analyte and electrode. The Sn-CeO2/GCE electrode possesses excellent electrocatalytic oxidation of nitrite (NO2–) which was investigated by cyclic voltammetry (CV) and amperometry techniques. The remarkable sensitivities of nitrite were found that 245.4 µA cm−2 mM−1 and 89.53 µA cm−2 mM−1 with R2 = 0.999 and RSD of ∼ 6%. Similarly, the limit of detection (LOD) towards nitrite ion sensing was found to be 16 nM. The real time application of Sn-CeO2/GCE sensor was demonstrated by the detection of nitrite present in environmental water samples with excellent recoveries. Hence, Sn-doped CeO2 modified electrode also demonstrates good reproducibility, long time stability, and excellent selectivity properties. Thus, a developed electrochemical sensor possesses a novel promise for the construction of simple and sensitive nitrite analytical stage. © 2021 Elsevier B.V.The authors thank Chancellor, President and Vice Chancellor, Sathyabama Institute of Science and Technology, Chennai for the support and encouragement. The author R. Jothi Ramalingam thank for the financial support by the Researchers Supporting Project Number (RSP-2021/354), King Saud University, Riyadh, Saudi Arabia

Synthesis, characterization and catalytic activity of melamine immobilized MCM-41 for condensation reactions

In the present study, melamine immobilized MCM-41 is synthesized by grafting on modified MCM-41. The surface area, pore size and pore volume of MCM-41-Mela were found to be decreased after immobilization of melamine. FTIR and Raman spectroscopy results revealed the successful grafting of melamine on the surface of MCM-41. The 29Si CP/MAS NMR of MCM-41-Mela showed the existence of T2, T3, Q3 and Q4 silicon centres. The catalytic activities were investigated through a liquid phase Knoevenagel condensation reaction between furfural and acetylacetone. A conversion of 93.1% was achieved with 100% selectivity towards 3-(2-furylmethylene)-2,4-pentanedione (FMP) under solvent-free condition. The catalytic activity of MCM-41-Mela was then successfully carried out for Knoevenagel condensation with different substrates, giving excellent yields of the corresponding products. The catalyst was easily regenerated and could be reused for three times without loss of catalytic activity. Simple preparation methods, high efficiency and reusability of the heterogeneous MCM-41-Mela catalyst demonstrate a great potential for future catalysis application

Highly efficient green mesostructured urea functionalized on SBA-15 catalysts for selective synthesis of benzlidenemalononitrile

A series of urea-immobilized SBA-15 catalysts were synthesized via post grafting method using 3-chloropropyltriethoxysilane (CPTES) as the anchoring agent. The solid catalyst was characterized by PXRD, N2 adsorption-desorption, FT-IR, elemental analyzer, TEM, CO2-TPD and 29Si CP/MAS NMR. Detailed analysis of the pore size illustrated the mesoporous nature of the immobilized catalyst. The as-prepared catalyst was further evaluated in the Knoevenagel condensation reaction under different reaction conditions. Benzaldehyde was employed in the Knoevenagel condensation reaction with malononitrile. Catalytic results showed that the Urea(4.8)/SBA-15 exhibits high efficacy (98% of yield) for promoting this reaction at 40 °C and in the absence of a solvent. Under the same reaction conditions, acetylacetone led to a lower benzaldehyde conversion of 10%, whereas ethyl cyanoacetate provides up to 88% conversion. The catalyst could be recycled and reused for at least five reaction cycles with slight loss of catalytic activity