Synthesis of functionalized mesoporous silica nanoparticles for colorimetric and fluorescence sensing of selective metal (Fe3+) ions in aqueous solution.

The fabrication of red fluorescent hybrid mesoporous silica-based nanosensor materials has promised the bioimaging and selective detection of toxic pollutants in aqueous solutions. In this study, we present a hybrid mesoporous silica nanosensor in which the propidium iodide (PI) was used to conveniently integrate into the mesopore walls using bis(trimethoxysilylpropyl silane) precursors. Various characterization techniques including X-ray diffraction (XRD), Fourier-transform infrared (FTIR), N2 adsorption-desorption, zeta potential, particle size analysis, thermogravimetric, and UV-visible analysis were used to analyze the prepared materials. The prepared PI integrated mesoporous silica nanoparticles (PI-MSNs) selective metal ion sensing capabilities were tested with a variety of heavy metal ions (100 mM), including Ni2+, Cd2+, Co2+, Zn2+, Cr3+, Cu2+, Al3+, Mg2+, Hg2+ and Fe3+ ions. Among the investigated metal ions, the prepared PI-MSNs demonstrated selective monitoring of Fe3+ ions with a significant visible colorimetric pink color change into orange and quenching of pink fluorescence in an aqueous suspension. The selective sensing behavior of PI-MSNs might be due to the interaction of Fe3+ ions with the integrated PI functional fluorophore present in the mesopore walls. Therefore, we emphasize that the prepared PI-MSNs could be efficient for selective monitoring of Fe3+ ions in an aqueous solution and in the biological cellular microenvironment.

Dual (pH- and ROS-) Responsive Antibacterial MXene-Based Nanocarrier for Drug Delivery.

In this study, a novel MXene (Ti3C2Tx)-based nanocarrier was developed for drug delivery. MXene nanosheets were functionalized with 3, 3'-diselanediyldipropionic acid (DSeDPA), followed by grafting doxorubicin (DOX) as a model drug to the surface of functionalized MXene nanosheets (MXene-Se-DOX). The nanosheets were characterized using scanning electron microscopy, atomic force microscopy (AFM), transmission electron microscopy, energy-dispersive X-ray spectroscopy (EDX), nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and zeta potential techniques. The drug-loading capacity (17.95%) and encapsulation efficiency (41.66%) were determined using ultraviolet-visible spectroscopy. The lateral size and thickness of the MXene nanosheets measured using AFM were 200 nm and 1.5 nm, respectively. The drug release behavior of the MXene-Se-DOX nanosheets was evaluated under different medium conditions, and the nanosheets demonstrated outstanding dual (reactive oxygen species (ROS)- and pH-) responsive properties. Furthermore, the MXene-Se-DOX nanosheets exhibited excellent antibacterial activity against both Gram-negative E. coli and Gram-positive B. subtilis.

pNIPAm-Based pH and Thermoresponsive Copolymer Hydrogel for Hydrophobic and Hydrophilic Drug Delivery.

The regulated and targeted administration of hydrophobic and hydrophilic drugs is both promising and challenging in the field of drug delivery. Developing a hydrogel which is responsive to dual stimuli is considered a promising and exciting research area of study. In this work, melamine functionalized poly-N-isopropyl acrylamide-co-glycidyl methacrylate copolymer has been developed by copolymerizing glycidyl methacrylate (GMA) monomer with N-isopropyl acrylamide (NIPAm) and further functionalized with melamine units (pNIPAm-co-pGMA-Mela). The prepared pNIPAm-co-pGMA-Mela copolymer hydrogel was characterized using various characterization techniques, including 1H NMR, FTIR, SEM, zeta potential, and particle size analysis. A hydrophobic drug (ibuprofen, Ibu) and hydrophilic drug (5-fluorouracil, 5-Fu) were selected as model drugs. Dual pH and temperature stimuli-responsive drug release behavior of the pNIPAm-co-pGMA-Mela hydrogel was evaluated under different pH (pH 7.4 and 4.0) and temperature (25 °C, 37 °C, and 45 °C) conditions. Furthermore, the in vitro biocompatibility of the developed pNIPAm-co-pGMA-Mela copolymer hydrogel was determined on MDA-MB-231 cells. The pH and temperature-responsive drug delivery study results reveal that the pNIPAm-co-pGMA-Mela hydrogel system is responsive to both pH and temperature stimuli and exhibits about ~100% of Ibu and 5-Fu, respectively, released at pH 4.0/45 °C. Moreover, the MTT assay and hemocompatibility analysis results proved that the pNIPAm-co-pGMA-Mela hydrogel system is biocompatible and hemocompatible, suggesting that that it could be used for drug delivery applications. The experimental results suggest that the proposed pNIPAm-co-pGMA-Mela hydrogel system is responsive to dual pH and temperature stimuli, and could be a promising drug carrier system for both hydrophilic and hydrophobic drug delivery applications.

Triazine-based porous organic polymers for reversible capture of iodine and utilization in antibacterial application.

The capture and safe storage of radioactive iodine (129I or 131I) are of a compelling significance in the generation of nuclear energy and waste storage. Because of their physiochemical properties, Porous Organic Polymers (POPs) are considered to be one of the most sought classes of materials for iodine capture and storage. Herein, we report on the preparation and characterization of two triazine-based, nitrogen-rich, porous organic polymers, NRPOP-1 (SABET = 519 m2 g-1) and NRPOP-2 (SABET = 456 m2 g-1), by reacting 1,3,5-triazine-2,4,6-triamine or 1,4-bis-(2,4-diamino-1,3,5-triazine)-benzene with thieno[2,3-b]thiophene-2,5-dicarboxaldehyde, respectively, and their use in the capture of volatile iodine. NRPOP-1 and NRPOP-2 showed a high adsorption capacity of iodine vapor with an uptake of up to 317 wt % at 80 °C and 1 bar and adequate recyclability. The NRPOPs were also capable of removing up to 87% of iodine from 300 mg L-1 iodine-cyclohexane solution. Furthermore, the iodine-loaded polymers, I2@NRPOP-1 and I2@NRPOP-2, displayed good antibacterial activity against Micrococcus luteus (ML), Escherichia coli (EC), and Pseudomonas aeruginosa (PSA). The synergic functionality of these novel polymers makes them promising materials to the environment and public health.

In situ thermosensitive hybrid mesoporous silica: preparation and the catalytic activities for carbonyl compound reduction.

In this study, free-radical polymerisation inside MCM-41 mesopores was examined to expose a construction route for a temperature-responsive switchable polymer-silica nanohybrid material with well-defined porosity. Herein, we introduced a vinyl monomer (N-isopropyl acrylamide), a cross-linker, and an AIBN initiator into the palladium nanoparticle incorporated MCM-41 pore channels using the wet-impregnation method followed by in situ radical polymerisation. The structural properties of the synthesised PNIPAM-PdNP-MCM-41 catalyst were analysed by various sophisticated analytical techniques. The temperature switchable nanohybrid catalyst was used to reduce carbonyl compounds to their corresponding alcohols. The catalyst showed high catalytic efficiency and robustness in an aqueous medium at 25 °C. Moreover, the system's polymer layer remarkably boosted catalytic selectivity and activity for carbonyl compound reduction as compared to other controlled catalysts. The suggested switchable system can be employed as a temperature-controllable heterogeneous catalyst and highlights a substitute technique to counter the methodical insufficiency in switchable supported molecular catalytic system production.

Synthesis of size-controlled and highly monodispersed silica nanoparticles using a short alkyl-chain fluorinated surfactant.

Highly monodispersed silica nanoparticles (SiNPs) were synthesised using a fluorinated surfactant, HOCH2CH(CF3)CO2H, and its efficiency was compared with efficiencies of five other surfactants. The size of the SiNPs (∼50-200 nm) was controlled by controlling the surfactant amount. The short alkyl-chain fluoro surfactant was found to be more efficient at producing monodispersed SiNPs than its long alkyl-chain fluoro or non-fluorinated surfactant counterparts.

Dual Stimuli-Responsive Copper Nanoparticles Decorated SBA-15: A Highly Efficient Catalyst for the Oxidation of Alcohols in Water.

In the present work, a temperature and pH-responsive hybrid catalytic system using copolymer-capped mesoporous silica particles with metal nanoparticles is proposed. The poly(2-(dimethylamino)ethyl methacrylate)(DMAEMA)-co-N-tert-butyl acrylamide) (TBA)) shell on mesoporous silica SBA-15 was obtained through free radical polymerization. Then, copper nanoparticles (CuNPs) decorated SBA-15/copolymer hybrid materials were synthesized using the NaBH4 reduction method. SBA-15 was functionalized with trimethoxylsilylpropyl methacrylate (TMSPM) and named TSBA. It was found that the CuNPs were uniformly dispersed in the mesoporous channels of SBA-15, and the hybrid catalyst exhibited excellent catalytic performance for the selective oxidation of different substituted benzyl alcohols in water using H2O2 as an oxidant at room temperature. The dual (temperature and pH-) responsive behaviors of the CuNPs/p(DMAEMA-co-TBA)/TSBA catalyst were investigated using the dynamic light scattering technique. The conversion of catalytic products and selectivity were calculated using gas chromatographic techniques, whereas the molecular structure of the products was identified using 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The catalyst showed excellent catalytic activity toward the oxidation of alcohol to aldehyde in an aqueous medium below the lower critical solution temperature (LCST) and pKa values (7-7.5) of the copolymer. The main advantages of the hybrid catalyst, as compared to the existing catalysts, are outstanding alcohol conversion (up to 99%) for a short reaction time (1 h), small amount of the catalyst (5 mg), and good recyclability equal to at least five times.

Palladium nanoparticles-anchored dual-responsive SBA-15-PNIPAM/PMAA nanoreactor: a novel heterogeneous catalyst for a green Suzuki-Miyaura cross-coupling reaction.

To develop a sustainable and cost-effective catalyst for cross-coupling reactions, dual (temperature and pH)-responsive poly(N-isopropyl acrylamide-co-methacrylic acid) (PNIPAM/PMAA) functionalised SBA-15 was synthesised via free radical polymerisation using potassium persulfate as an initiator and decorated with palladium nanoparticles (PdNPs-SBA-15-PNIPAM/PMAA). The X-ray photoelectron spectroscopic analysis revealed that the Pd content in the zero oxidation state of the catalyst was 1.21 wt%. The dynamic light scattering studies showed that the catalyst exhibited swelling behaviours at low temperatures (<32 °C) and high pH (>4), but exhibited deswelling behaviours at high temperatures (>32 °C) and low pH (<4). To examine the performance of the catalyst, Suzuki-Miyaura cross-coupling (SMC) reaction was conducted under batch reaction conditions. The reaction conditions were optimised with various parameters using phenylboronic acid and bromobenzene as the model substrates. High conversions (>90%) were realized for the room-temperature SMC reaction in an aqueous medium for various substituted aryl halides, while the conversion was low at relatively high temperatures (>32 °C). The conversion was dependent on the different electronic effects between the electron-releasing and electron-withdrawing groups of the aryl halides. After the experiment, the catalyst was successfully recovered without any loss of heterogeneity and could be reused at least up to the fifth cycle.