Autocatalytic synthesis of multifunctional precursors for fabricating silica microspheres with well-dispersed Ag and Co3O4 nanoparticles

Synthesis of disordered mesoporous silica loaded with ultrasmall-sized CuO nanoparticles based on an alkali-free strategy and its excellent catalytic performance in the reduction of organic dye

In this paper, disordered mesoporous silica loaded with ultrasmall-sized and highly dispersed CuO nanoparticles was obtained by an alkali-free strategy. Pre-prepared copper bromoacetate (CuBA) and (3-aminopropyl)triethoxysilane (APTES) were selected as reactants, which can be covalently connected with each other for the formation of functional hybrid precursors. Simultaneously, the protonated amino group with the ability to promote the hydrolysis of silane was generated, avoiding any additional catalyst. The covalent introduction of copper salt by chemical bonding promised the molecular-level dispersion of copper ions, favouring the in situ generation of ultrasmall-sized and highly dispersed CuO nanoparticles in the silica matrix. The average diameter of this obtained composited silica material is around 700 nm, and CuO nanoparticles with an average diameter of ∼3 nm were uniformly dispersed in the silica matrix. Typically, disordered mesopores were obtained under the thermolysis of organic chains in the hybrid silica matrix; the BET surface area is 77 m² g⁻¹ and the pore diameter is about 2.5 nm. The catalytic property was investigated and the results show that this obtained CuO@mSiO₂ material has good catalytic performance in the reduction of organic dye with NaBH₄ as the reducing agent.

Mesoporous silica loaded with ultrasmall sized and highly dispersed CuO nanoparticles was synthesized based on an alkali-free strategy. The obtained silica material has excellent catalytic performance on reduction MB dye in the presence of NaBH₄ as reductant.

A simple approach to prepare fluorescent molecularly imprinted nanoparticles

Fluorescent molecularly imprinted polymers (FMIPs) are gaining increasing attention in analytical and medical sciences, particularly silica-based FMIPs due to their low cost, environmentally friendly nature and good biocompatibility. However, at present, silica-based FMIPs are usually prepared through several steps and displayed low selectivity. Here, a simple approach was utilized for preparing silica-based FMIP nanoparticles. The polymerization was initiated by 3-aminopropyltriethoxysilane (APTES), which also acted as the functional monomer in the imprinting system; in addition, to achieve one-pot synthesis, a fluorescent monomer was prepared by a simple reaction between fluorescein isothiocyanate (FITC) and APTES. The as-synthesized FMIP nanoparticles displayed high specificity and fast response time (<1 min) towards the target molecule. Environmental pH and buffer salt could affect the specific recognition behaviors of the FMIP nanoparticles. Such a simple catalyst-free synthetic technique could also be employed for the preparation of FMIP nanoparticles targeting other acidic molecules.

Dual roles of 3-aminopropyltriethoxysilane in preparing molecularly imprinted silica particles for specific recognition of target molecules

3-Aminopropyltriethoxysilane (APTES) is a silane widely used to supply amino groups for further modifications on various materials, but it is less studied as a catalyst to catalyze sol–gel silica polymerization. Here, by using APTES as the catalyst instead of the conventional basic catalysts, a novel strategy was developed to prepare silica-based molecularly imprinted polymers (MIPs). Meanwhile, APTES was employed as the functional monomer to create imprinted nanocavities for specific recognition of target molecules. The as-synthesized MIP exhibited ultra-high recognition capability due to the elimination of the detrimental effect on the imprinting performance caused by the additional catalysts. The preparation process, specificity, pH effect, binding capacity and affinity of the MIP were studied in detail. The MIP microparticles could be packed into a solid phase extraction column for removing the target molecule in water efficiently, and the molecule could easily be enriched by 40 times. The interaction of the functional monomer and template was studied by the calculation method, giving a more clear understanding of the recognition behaviours of the imprinted polymers. The strategy could be extended not only to prepare highly specific MIPs for other small phosphoric molecules, but also for biomolecules e.g. phosphorylated peptides or proteins.

A novel strategy was developed for preparing highly selective molecularly imprinted polymers using 3-aminopropyltriethoxysilane as both a functional monomer and catalyst.

In situ generation of ultrasmall sized and highly dispersed CuO nanoparticles embedded in silica matrix and their catalytic application

CuO nanoparticles (CuO NPs) with ultrasmall size (∼3.6 nm) and a highly-dispersed pattern embedded in a silica matrix were obtained in situ through a calcination process of organic copper salt.

A general autocatalytic route toward silica nanospheres with ultrasmall sized and well-dispersed metal oxide nanoparticles

A facile and efficient approach for the synthesis of metal ions@silica nanospheres is proposed by using an intramolecular autocatalytic route. By the rational selection of reactants, metal ions@silica nanospheres can be obtained via successive spontaneous reactions under near neutral conditions. After thermal treatment, spherical silica equipped with ultrasmall and highly dispersed metal oxides nanoparticles was obtained.

Strategic Synthesis of SiO2-Modified Porous Co3O4 Nano-Octahedra Through the Nanocoordination Polymer Route for Enhanced and Selective Sensing of H2 Gas over NO x

In this work, a strategic synthesis of Co₃O₄ nano-octahedra was developed through the facile nanoscale coordination polymer (NCP) route, which was further modified by SiO₂ to be used as a sensor for enhanced sensing of hydrogen. The Co(II)-NCP-derived Co₃O₄ octahedra and SiO₂-modified Co₃O₄ octahedra were characterized using Fourier transform infrared, powder X-ray diffraction, Brunauer-Emmett-Teller, thermogravimetric analysis, field emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and hydrogen temperature-programmed reduction (H₂TPR) techniques. The SiO₂-modified Co₃O₄ sensor exhibited a stronger and selective electrical response to H₂ gas over NO _x at 225 °C than Co(II)-NCP-derived Co₃O₄ octahedra and the conventional Co₃O₄ powder. The composite sensor shows faster recovery and significant repeatability than the other two. The enhancement in the sensing performance of the SiO₂-modified Co₃O₄ octahedron was explained by the effectiveness of surface modification, controlled morphology, and combination of synergistic effect of Co₃O₄ and SiO₂. Surface engineering of the as-prepared Co₃O₄ nano-octahedra with an exposed (111) surface plane and later SiO₂ modification facilitates effective gas adsorption, resulting in enhancement in sensing and selectivity over NO _x . The details of the synergistic effect and the plausible reasons for the improvement in gas-sensing parameters are discussed here. This study would offer new directions for development on the controlled synthesis of porous materials, in general, and in gas sorption or sensing, in particular.

Passion fruit-like nano-architectures: a general synthesis route

Noble metal nanostructures have demonstrated a number of intriguing features for both medicine and catalysis. However, accumulation issues have prevented their clinical translation, while their use in catalysis has shown serious efficiency and stability hurdles. Here we introduce a simple and robust synthetic protocol for passion fruit-like nano-architectures composed by a silica shell embedding polymeric arrays of ultrasmall noble metal nanoparticles. These nano-architectures show interesting features for both oncology and catalysis. They avoid the issue of persistence in organism thanks to their fast biodegradation in renal clearable building blocks. Furthermore, their calcination results in yolk-shell structures composed by naked metal or alloy nanospheres shielded from aggregation by a silica shell.