Dendritic Fibrous Colloidal Silica Internally Cross-linked by Bivalent Organic Cations: An Efficient Support for Dye Removal and the Reduction of Nitrobenzene Derivatives

Dendritic mesoporous nanoparticles for the detection, adsorption, and degradation of hazardous substances in the environment: State-of-the-art and future prospects

Equipped with hierarchical pores and three-dimensional (3D) center-radial channels, dendritic mesoporous nanoparticles (DMNs) make their pore volumes extremely large, specific surface areas super-high, internal spaces especially accessible, and so on. Other entities (like organic moieties or nanoparticles) can be modified onto the interfaces or skeletons of DMNs, accomplishing their functionalization for desirable applications. This comprehensive review emphasizes on the design and construction of DMNs-based systems which serve as sensors, adsorbents and catalysts for the detection, adsorption, and degradation of hazardous substances, mainly including the construction procedures of brand-new DMNs-based materials and the involved hazardous substances (like industrial chemicals, chemical dyes, heavy metal ions, medicines, pesticides, and harmful gases). The sensitive, adsorptive, or catalytic performances of various DMNs have been compared; correspondingly, the reaction mechanisms have been revealed strictly. It is honestly anticipated that the profound discussion could offer scientists certain enlightenment to design novel DMNs-based systems towards the detection, adsorption, and degradation of hazardous substances, respectively or comprehensively.

Internally bridged nanosilica for loadings and release of sparsely soluble compounds

The engineering of a new monodisperse colloid with a sea urchin-like structure with a large complex internal structure is reported, in which silica surfaces are bridged by an aromatic organic cross-linker to serve as a nanocarrier host for drugs such as doxorubicin (DOX) against breast cancer cells. While dendritic fibrous nanosilica (DFNS) was employed and we do not observe a dendritic structure, these particles are referred to as sea urchin-like nanostructured silica (SNS). Since the structure of SNS consists of many silica fibrils protruding from the core, similar to the hairs of a sea urchin. For the aromatic structured cross-linker, bis(propyliminomethyl)benzene (b(PIM)B-S or silanated terephtaldehyde) were employed, which are prepared with terephtaldehyde and 3-aminopropyltriethoxy-silane (APTES) through a simple Schiff base reaction. b(PIM)B-S bridges were introduced into SNS under open vessel reflux conditions. SPS refers to the product obtained by incorporating the cross-linker b(PIM)B-S in ultra-small colloidal SNS particles. In-situ incorporation of DOX molecules resulted in SPS-DOX. The pH-responsive SPS nanocomposites were tested as biocompatible nanocarriers for controllable doxorubicin (DOX) delivery. We conclude that SPS is a unique colloid which has promising potential for technological applications such as advanced drug delivery systems, wastewater remediation and as a catalyst for green organic reactions in water.

Cu-Based Catalysts Supported on H3PO4-Activated Coffee Biochar for Selective Reduction of Nitroaromatics

Selective reduction of nitroaromatics to the corresponding aromatic amines is extremely an attractive chemical process for both fundamental research and potential commercial applications. Herewith, we report that a highly dispersed Cu catalyst supported on H₃PO₄-activated coffee biochar and the resulting Cu/PBCR-600 catalyst show complete conversion of the nitroaromatics and >97.0% selectivity for the corresponding aromatic amines. The TOF of catalyzing the reduction of nitroaromatics (1.55-460.74 min^-1) is approximately 2 to 15 times higher than those of previously reported non-noble and even noble metal catalysts. Additionally, Cu/PBCR-600 also shows high stability in catalytic recycles. Furthermore, it exhibits long-term catalytic stability (660 min) for practical application in a continuous-flow reactor. The characterizations and activity tests reveal that Cu⁰ existing in Cu/PBCR-600 acts as an active site in nitroaromatics reduction. Also, the further characterization by FTIR and UV-vis demonstrates that N, P co-doped coffee biochar could selectively adsorb and activate the nitro group of nitroaromatics.

Hybrid Nanostructure Catalyst with Low Loading of Pt for the High-Efficiency Catalytic Hydrogenation of Chloronitrobenzene

Fabrication of low-loading, noble-metal, stable, and high-performance metal catalysts remains a thorny issue. Herein, we demonstrate the successful formation of a hybrid nanostructure Pt/TiO₂/SBA-15 catalyst (denoted as HNSC-P/T/S; Pt, 0.09%; TiO₂, 10%) with satisfactory activity in the hydrogenation of para-chloronitrobenzene (p-CNB). The HNSC-P/T/S showed >99% conversion and a high selectivity of >98%, and the turnover frequency number (TOF) reached 66 766 h^-1, which was impossible to achieve with Pt/TiO₂ (denoted as P/T) or Pt/SBA-15 (denoted as P/S). The success of the catalytic activity of the HNSC-P/T/S mainly relies on its synergistic effect and special structure, which can fully develop the catalytic ability of Pt, thereby reducing the Pt loading in the noble-based catalyst. Furthermore, the HNSC-P/T/S could also achieve an excellent catalytic activity in the hydrogenation of other nitroarenes. Hence, this work proposes a direction to prepare a noble-based catalyst with a low loading of noble metals for diverse applications.

Highly Efficient and Rapid Removal of Methylene Blue from Aqueous Solution Using Folic Acid-Conjugated Dendritic Mesoporous Silica Nanoparticles

Dendritic Mesoporous Silica Nanoparticles (DMSNs) are considered superior in the adsorption of unfavorable chemical compounds and biological pollutants. Herein, we have synthesized folic acid-terminated dendritic mesoporous silica nanoparticles (FA-DMSN) for the removal of cationic dyes, methylene blue (MB), from aqueous solutions. The structural, morphological, functional, specific surface area, pore size distribution, and thermal properties of the synthesized DMSNs were identified using a scanning electron microscope (SEM), a transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), Brunauer−Emmett−Teller (BET), and Thermogravimetric Analyzer (TGA). The synthesized DMSNs exhibited a high surface area (521 m2 −1) and pore volume (1.2 cm3 g−1). In addition, it features both wide pore size and narrow distributions, which strongly affect the adsorption performance in terms of the equilibrium uptake time. Moreover, the impact of pH, contacting time, and dye’s initial concentration on the removal efficiency of MB was studied. The extraction efficiency of FA-DMSN was found to be three times more effective than the bare DMSN materials. Langmuir isotherm fitted the experimental data very well with a correlation coefficient value of 0.99. According to the Langmuir model, the maximum adsorption capacity was 90.7 mg/g. Furthermore, the intra−particle diffusion model revealed a significantly fast intra-particle diffusion which can be attributed to the presence of the large pore’s channels. Finally, the fast adsorption of MB molecules, reaching their equilibrium capacity within tens of seconds, as well as the low cost and ease of FA-DMSN fabrication, makes the developed material an effective adsorbent for water remediations.