Surface Modification of PP and PBT Nonwoven Membranes for Enhanced Efficiency in Photocatalytic MB Dye Removal and Antibacterial Activity

In this study, we developed highly efficient nonwoven membranes by modifying the surface of polypropylene (PP) and poly(butylene terephthalate) (PBT) through photo-grafting polymerization. The nonwoven membrane surfaces of PP and PBT were grafted with poly(ethylene glycol) diacrylate (PEGDA) in the presence of benzophenone (BP) and metal salt. We immobilized tertiary amine groups as BP synergists on commercial nonwoven membranes to improve PP and PBT surfaces. In situ Ag, Au, and Au/Ag nanoparticle formation enhances the nonwoven membrane surface. SEM, FTIR, and EDX were used to analyze the surface. We evaluated modified nonwoven membranes for photocatalytic activity by degrading methylene blue (MB) under LED and sunlight. Additionally, we also tested modified membranes for antibacterial activity against E. coli. The results indicated that the modified membranes exhibited superior efficiency in removing MB from water. The PBT showed the highest efficiency in dye removal, and bimetallic nanoparticles were more effective than monometallic. Modified membranes exposed to sunlight had higher efficiency than those exposed to LED light, with the PBT/Au/Ag membrane showing the highest dye removal at 97% within 90 min. The modified membranes showed reuse potential, with dye removal efficiency decreasing from 97% in the first cycle to 85% in the fifth cycle.

Cellulose Acetate Incorporating Organically Functionalized CeO2 NPs: Efficient Materials for UV Filtering Applications

One of the major issues faced when constructing various materials incorporating inorganic nanoparticles (NPs) is aggregation leading to loss of their final activity. In our work, cellulose acetate (CA) has been used to serve as matrix for the synthesis of UV-shielding and transparent films containing various amounts (1-5 wt.%) of cerium oxide (CeO2) NPs. In order to attain an improved dispersion and a better connectivity between NPs and the cellulose matrix, the surface of CeO2 NPs have been previously functionalized by the reaction with 3-aminopropyl(diethoxy)methylsilane (APDMS). The uniform dispersion of the NPs in the homogeneous thin films has been evidenced by using Transmission Electron Microscopy (TEM) and Fourier Transformation Infrared Spectroscopy (FTIR) characterization. The investigation of the optical properties for the hybrid films through UV-Vis spectroscopy revealed that the presence of CeO2 NPs in the CA matrix determined the appearance of strong UV absorption bands in the region 312-317 nm, which supports their use as efficient UV absorbers. This study has shown that UV shielding ability of the nanocomposites can be easily tuned by adjusting the numberof inorganic NPs in the CA template.

Plasmon-induced photocatalytic degradation of methylene blue dye using biosynthesized silver nanoparticles as photocatalyst

Bio-fabrication of silver nanoparticles, using stem extracts of Nepeta leucophylla and their photocatalytic degradation activity, has been undertaken. The synthesized silver nanoparticles are characterized using ultraviolet-visible spectroscopy, Fourier transformed infrared spectroscopy, X-ray diffractometry, Transmission Electron Microscopy, Field Emission Scanning Electron Microscopy, Energy-dispersive X-ray spectroscopy and thermal gravimetric and differential scanning calorimetry analysis. The Surface Plasmon Resonance band detected at 430 nm in the ultraviolet-visible spectrum confirms the formation of silver nanoparticles in the aqueous solution. Transmission Electron and Field Emission Scanning Electron micrographs reveal that the synthesized silver nanoparticles are spherical with an average size in the range of 15-25 nm. But, the X-ray diffraction confirms the face-centred cubic structure of silver nanoparticles with an average crystal size of the nanoparticles is about 10 nm. Furthermore, the infrared spectrogram confirms that the stem extract of Nepeta leucophylla contains phenol which causes reduction of silver salt to silver nanoparticles and protein might act as an overlaying agent which prevents the agglomeration of these nanoparticles. Moreover, the photocatalytic degradation of methylene blue dye, by using biosynthesized silver nanoparticles of optimized dose (1.8 ml) for 180 min in the presence and absence of light are 82.8% and 61.25%, respectively, specifies that the resultant photocatalyst is proved to have good photocatalytic activity for the degradation of methylene blue dye from the liquid phase.

Polymer Nanocomposites for Photocatalytic Applications

In the present comprehensive review we have specifically focused on polymer nanocomposites used as photocatalytic materials in fine organic reactions or in organic pollutants degradation. The selection of the polymer substrates for the immobilization of the active catalyst particles is motivated by several advantages displayed by them, such as: Environmental stability, chemical inertness and resistance to ultraviolet radiations, mechanical stability, low prices and ease availability. Additionally, the use of polymer nanocomposites as photocatalysts offers the possibility of a facile separation and reuse of the materials, eliminating thus the post-treatment separation processes and implicitly reducing the costs of the procedure. This review covers the polymer-based photocatalytic materials containing the most popular inorganic nanoparticles with good catalytic performance under UV or visible light, namely TiO2, ZnO, CeO2, or plasmonic (Ag, Au, Pt, Pd) NPs. The study is mainly targeted on the preparation, photocatalytic activity, strategies directed toward the increase of photocatalytic efficiency under visible light and reuse of the hybrid polymer catalysts.

Mussel-inspired immobilization of Au on bare and graphene-wrapped Ni nanoparticles toward highly efficient and easily recyclable catalysts

Bimetallic nanocatalysts have been gaining huge research attention in the heterogeneous catalysis community recently owing to their tunable properties and multifunctional characteristics. In this work, we fabricated a bimetallic core-shell nanocomposite catalyst by employing a mussel-inspired strategy for immobilizing gold nanoparticles (AuNP) on the surface of nickel nanoparticles (NiNP). NiNPs obtained from the reduction of Ni(ii) were first coated with polydopamine to provide the anchoring sites towards the robust immobilization of AuNPs. The as-synthesized nanocomposite (Ni-PD-Au) exhibited outstanding catalytic activity while reducing methylene blue (MB) and 4-nitrophenol (4-NP) yielding rate constants 13.11 min-1 and 4.21 min-1, respectively, outperforming the catalytic efficiency of its monometallic counterparts and other similar reported catalysts by large margins. The superior catalytic efficiency of the Ni-PD-Au was attributed to the well-known synergistic effect, which was experimentally investigated and compared with prior reports. Similar bio-inspired immobilization of AuNPs was also applied on graphene-wrapped NiNPs (Ni-G) instead of bare NiNPs to synthesize another composite catalyst (Ni-G-PD-Au), which yet again exhibited synergistic catalytic activity. A comparative study between the two nanocomposites suggested that Ni-PD-Au excelled in catalytic activity but Ni-G-PD-Au provided noteworthy stability showing ∼100% efficiency over 17 repeated cycles. However, along with excellent synergistic performance, both nanocomposites demonstrated high magnetization and thermal stability up to 350 °C ascertaining their easy separation and sustainability for high-temperature applications, respectively.

Photocatalysis applications of some hybrid polymeric composites incorporating TiO2 nanoparticles and their combinations with SiO2/Fe2O3

Polymer nanocomposites containing titanium oxide nanoparticles (TiO₂ NPs) combined with other inorganic components (Si-O-Si or/and γ-Fe₂O₃) were prepared by the dispersion of premade NPs (nanocrystalline TiO₂, TiO₂/SiO₂, TiO₂/Fe₂O₃, TiO₂/SiO₂/Fe₂O₃) within a photopolymerizable urethane dimethacrylate (polytetrahydrofuran-urethane dimethacrylate, PTHF-UDMA). The physicochemical characterization of nanoparticles and hybrid polymeric composites with 10 wt % NPs (S1-S4) was realized through XRD, TEM and FTIR analyses. The mean size (10-30 nm) and the crystallinity of the NPs varied as a function of the inorganic constituent. The catalytic activity of these hybrid films was tested for the photodegradation of phenol, hydroquinone and dopamine in aqueous solution under UV or visible-light irradiation. The best results were obtained for the films with TiO₂/Fe₂O₃ or TiO₂/SiO₂/Fe₂O₃ NPs. The degradation of the mentioned model pollutants varied between 71% and 100% (after 250 min of irradiation) depending on the composition of the hybrid film tested and the light applied (UV-visible light). Also, it was established that such hybrid films can be reused at least for five cycles, without losing too much of the photocatalytic efficiency (ca. 7%). These findings could have implications in the development of new nanocatalysts.