Fabrication of highly dispersed Pt NPs in nanoconfined spaces of as-made KIT-6 for nitrophenol and MB catalytic reduction in water

Fabrication of silver nanoparticles decorated on sodium alginate microbeads enriched with keratin and investigation of its catalytic and antioxidant activity

In this study, an environmentally friendly, effective, easily synthesizable and recoverable nano-sized catalyst system (Ag@NaAlg-keratin) was designed by decorating Ag nanoparticles on microbeads containing sodium alginate (NaAlg) and keratin obtained from goose feathers. The structure, morphology and crystallinity of the Ag@NaAlg-keratin nanocatalyst were evaluated by XRD, FT-IR, FE-SEM, EDS/EDS mapping and TEM analyses. Catalytic ability of designed Ag@NaAlg-keratin nanocatalyst was then investigated against 4-nitrophenol (4-NP) and methyl orange (MO) reductions. Ag@NaAlg-keratin nanocatalyst effectively reduced 4-NP in 6 min and MO in 5 min, with rate constants of 0.17 min-1 and 0.16 min-1, respectively. Additionally, activation energies (Ea) were found as 39.8 kJ/mol for 4-NP and 37.9 kJ/mol for MO. Performed recyclability tests showed that the Ag@NaAlg-keratin nanocatalyst was easily recovered due to its microbead form and successfully reused five times, maintaining both its activity and structure. Furthermore, antioxidant activity of Ag@NaAlg-keratin nanocatalyst was the highest (73.16 %).

Charge transfer in TiO2-based photocatalysis: fundamental mechanisms to material strategies

Semiconductor-based photocatalysis has attracted significant interest due to its capacity to directly exploit solar energy and generate solar fuels, including water splitting, CO2 reduction, pollutant degradation, and bacterial inactivation. However, achieving the maximum efficiency in photocatalytic processes remains a challenge owing to the speedy recombination of electron-hole pairs and the limited use of light. Therefore, significant endeavours have been devoted to addressing these issues. Specifically, well-designed heterojunction photocatalysts have been demonstrated to exhibit enhanced photocatalytic activity through the physical distancing of electron-hole pairs generated during the photocatalytic process. In this review, we provide a systematic discussion ranging from fundamental mechanisms to material strategies, focusing on TiO2-based heterojunction photocatalysts. Current efforts are focused on developing heterojunction photocatalysts based on TiO2 for a variety of photocatalytic applications, and these projects are explained and assessed. Finally, we offer a concise summary of the main insights and challenges in the utilization of TiO2-based heterojunction photocatalysts for photocatalysis. We expect that this review will serve as a valuable resource to improve the efficiency of TiO2-based heterojunctions for energy generation and environmental remediation.

Rapid Plasma Electrolytic Oxidation Synthesis of Intermetallic PtBi/MgO/Mg Monolithic Catalyst for Efficient Removal of Organic Pollutants

The intermetallic PtBi/MgO/Mg monolithic catalyst was first prepared using non-equilibrium plasma electrolytic oxidation (PEO) technology. Spherical aberration-corrected transmission electron microscope (ACTEM) observation confirms the successful synthesis of the PtBi intermetallic structure. The efficiency of PtBi/Mg/MgO catalysts in catalyzing the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of NaBH4 was demonstrated. The activity factor for the catalyst is 31.8 s-1 g-1, which is much higher than reported values. In addition, the resultant catalyst also exhibits excellent catalytic activity in the organic pollutant reaction of p-nitrobenzoic acid (p-NBA) and methyl orange (MO). Moreover, benefiting from ordered atomic structures and the half-embedded PtBi nanoparticles (NPs), the catalyst demonstrates excellent stability and reproducibility in the degradation of 4-NP. This study provides an example of a simple method for the preparation of intermetallic structures as catalysts for organic pollutant degradation.

Effect of nanodiamond particles on the structure, mechanical, and thermal properties of polymer embedded ND/PMMA composites

Nanodiamonds (NDs), the allotropic carbon nanomaterials with nanosize, durable inert core, adjustable surface morphology, high thermal constancy, and super mechanical performances, possess the characteristics of promising reinforcement materials for various technological applications. However, ND particles hold a vigorous propensity to aggregate in liquid media, obstructing their implementation in mechanical and thermal sciences. This aggregation is caused by high surface to volume ratio. By reducing the surface energy and lowering cluster formation, the mechanical and thermal properties of NDs can be polished. Herein, we report on the covalent functionalization of NDs with amine moiety through ball milling method. Their dispersion was checked in ethanol and polymethyl methacrylate (PMMA polymer) against nonfunctionalized NDs. The dispersive behavior showed that ball mill functionalized NDs produced preferably stable aqueous dispersions in ethanol media. Furthermore, 0.1, 0.2, and 0.4 wt% ND/PMMA composites were synthesized, and their mechanical and thermal behaviors were studied in terms of hardness, compression, Young`s modulus, flexural strength, tensile strength, and thermogravimetric analysis (TGA). Results revealed that the composites containing 0.2 wt% functionalized ND loaded with PMMA matrix showed outstanding mechanical and thermal performances indicating that 0.2 wt% is the optimum amount for achieving excellent outcomes.

Preparation and comparative evaluation of PVC/PbO and PVC/PbO/graphite based conductive nanocomposites

Two series, A and B, of PVC based nanocomposite polymer membranes (nCPMs) were prepared using PbO only and PbO/graphite mixture as a filler by solution casting method. Seven samples with varying compositions (5–35%) of filler particles were prepared for each series and were compared by thickness measurements, porosity, water uptake, swelling degree, ionic conductivity, ion exchange capacity (IEC), membrane potential and transport number. The maximum values for these characteristics were observed as 0.402 mm, 0.77, 141.3%, 0.11, 0.0033 Scm−1, 8.6 milli-eq.g−1, 0.19 V and 0.01391 for series-A composites whereas that of 0.367 mm, 0.83, 63.4%, 0.019, 0.00981 Scm−1, 5.21 milli-eq.g−1, 0.13 V and 0.0108 for series-B nCPMs respectively. The SEM images of membranes showed greater voids produced in the series-B compared to series-A composites. The maximum Ionic conductivity, IEC, membrane potential and transport number were observed for membrane with 25% PbO/graphite, 20% PbO and 35% PbO particles respectively.

Cu-MOF@Pt 3D nanocomposites prepared by one-step wrapping method with peroxidase-like activity for colorimetric detection of glucose

As an alternative to natural enzymes, artificial enzymes based on nanomaterials have attracted a lot of attention owing to their outstanding catalytic activity and high stability as well as low cost. Cu-MOF loaded with platinum nanoparticles (labeled Cu-MOF@Pt) was prepared by simple one-step wrapping method using platinum nanoparticles, copper nitrate trihydrate and 1,3,5-tricarboxybenzene. It was confirmed that Cu-MOF@Pt exhibits peroxidase-like activity, which can quickly catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) and produce blue oxidized TMB (oxTMB) in the presence of hydrogen peroxide (H₂O₂). Additionally, steady-state kinetics showed that Cu-MOF@Pt exhibits stronger appetency to TMB and H₂O₂ compared with horseradish peroxidase. Thanks to the peroxidase-like activity of Cu-MOF@Pt, a highly selective colorimetric method for glucose detection has been successfully established, the linear range is 2-15 mM (R² =0.9999) and the Limit of Detection (LOD) is 0.42 mM, with a detection range that meets clinical needs. Moreover, its good intra- and inter-assay precision and excellent stability make the results of glucose detection very reproducible. The detection performance of 90.09% was still maintained at 4 ℃ for 2 months. In conclusion, a new nanocomposite was successfully prepared and its selective detection ability for glucose was proved, which established a good basis for the clinical development of new enzymes for biosensors.

TEMPO-oxidized cellulose for in situ synthesis of Pt nanoparticles. Study of catalytic and antimicrobial properties

In this work, platinum nanoparticles (PtNPs) were synthesized by a modified polyol process using TEMPO-oxidized nanocellulose (TOCN) as a stabilizing and co-reducing agent. Different ratios of TOCN nanocellulose to Pt⁴⁺ ions were studied to establish the optimum stabilizing effect of PtNPs. The effect of different pH of aqueous TOCN suspensions on the morphology of PtNPs was also examined. It was proved that PtNPs can be obtained solely in the presence of TOCN without the use of an additional reducing agent or ethylene glycol. The morphology and structural properties of the nanocellulose‑platinum nanoparticles composites were assessed using spectroscopic, microscopic and diffraction techniques, The catalytic performance in 4-nitrophenol reduction was evaluated. Significant differences in reaction rate constants k were found depending on the pH of the TOCN suspension applied during Pt⁴⁺ reduction. The crucial effect of reaction conditions on PtNPs performance was confirmed in tests of antibacterial efficacy against E. coli.

Spectroscopic characterization of biosynthesized lead oxide (PbO) nanoparticles and their applications in PVC/graphite-PbO nanocomposites

Extract of Hibiscus rosa-sinensis plants was used for the green synthesis of PbO nanoparticles. The prepared nanoparticles were conformed with the help of SEM, X-ray diffraction, FTIR and UV-visible spectroscopy. The prepared PbO nanoparticles were dispersed in deionized water and mixed with graphite to get graphite-PbO (G-PbO) filler. Seven different nanocomposite membranes with variable compositions (5, 10, 15, 20, 25, 30 and 35%) of PVC/G-PbO were prepared in tetrahydrofuran (THF) solvent using solution casting method. Different physiochemical parameters of the nanocomposite membranes studied included morphology, porosity, density, water uptake, swelling degree, electrical conductivity and proton adsorption capacity. All these physiochemical parameters were compared with pure PVC membranes available in literature. It was found that the addition of G-PbO filler in PVC polymer improved all the physiochemical properties except density. PVC/G-PbO membranes showed 42.65 times more electrical conductivity and 5.90 times more ion adsorption capacities compare to pure PVC membranes.

Alginate biopolymer as a reactor container for copper oxide-tin oxide: Efficient nanocatalyst for reduction of different pollutants

The need of clean water demands to design an efficient catalytic system with high effective and selective reduction of water pollutants. Here, we successfully prepared copper oxide-tin oxide (CuO-SnO₂) nanomaterial and further wrapped in Na-alginate hydrogel (Alg/CuO-SnO₂). CuO-SnO₂ and Alg/CuO-SnO₂ were characterized by FESEM, EDS, FTIR-ATR, and XRD and tested for the reduction of water pollutants. The catalytic ability of CuO-SnO₂ and Alg/CuO-SnO₂ was examined for numerous pollutants like 4-nitrophenol (4-NP), methyl orange (MO), congo red (CR), methylene blue (MB) and potassium ferricyanide (K₃[Fe(CN)₆]) where the designed CuO-SnO₂ and Alg/CuO-SnO₂ nanocatalysts were most selective toward MB reduction. Further on optimization of catalyst amount, stability, and reducing agent amount, it was found that the increase of nanocatalyst amount and NaBH₄ concentration increase the rate of MB reduction. CuO-SnO₂ and Alg/CuO-SnO₂ nanocatalysts reduced MB in 3.0 min with reaction rate constants (k_app) of 1.2944 min^-1 and 1.2715 min^-1, respectively. Additionally, Alg/CuO-SnO₂ nanocatalyst was easily recovered by simply pulling hydrogel after completion of reaction and reused four times with no loss in efficiency. Besides, Alg/CuO-SnO₂ nanocatalyst was further investigated in real samples like sea water, irrigation water, well water, university wastewater and found effective for MB reduction even in real samples.

MIL-100(Fe) Supported Pt-Co Nanoparticles as Active and Selective Heterogeneous Catalysts for Hydrogenation of 1,3-Butadiene

Superior catalytic performance for selective 1,3-butadiene (1,3-BD) hydrogenation can usually be achieved with supported bimetallic catalysts. In this work, Pt-Co nanoparticles and Pt nanoparticles supported on metal-organic framework MIL-100(Fe) catalysts (MIL=Materials of Institut Lavoisier, PtCo/MIL-100(Fe) and Pt/MIL-100(Fe)) were synthesized via a simple impregnation reduction method, and their catalytic performance was investigated for the hydrogenation of 1,3-BD. Pt1Co1/MIL-100(Fe) presented better catalytic performance than Pt/MIL-100(Fe), with significantly enhanced total butene selectivity. Moreover, the secondary hydrogenation of butenes was effectively inhibited after doping with Co. The Pt1Co1/MIL-100(Fe) catalyst displayed good stability in the 1,3-BD hydrogenation reaction. No significant catalyst deactivation was observed during 9 h of hydrogenation, but its catalytic activity gradually reduces for the next 17 h. Carbon deposition on Pt1Co1/MIL-100(Fe) is the reason for its deactivation in 1,3-BD hydrogenation reaction. The spent Pt1Co1/MIL-100(Fe) catalyst could be regenerated at 200 °C, and regenerated catalysts displayed the similar 1,3-BD conversion and butene selectivity with fresh catalysts. Moreover, the rate-determining step of this reaction was hydrogen dissociation. The outstanding activity and total butene selectivity of the Pt1Co1/MIL-100(Fe) catalyst illustrate that Pt-Co bimetallic catalysts are an ideal alternative for replacing mono-noble-metal-based catalysts in selective 1,3-BD hydrogenation reactions.

One-Pot Facile Synthesis of Noble Metal Nanoparticles Supported on rGO with Enhanced Catalytic Performance for 4-Nitrophenol Reduction

In this study, reduced graphene oxide (rGO)-supported noble metal (gold, silver, and platinum) nanoparticle catalysts were prepared via the one-pot facile co-reduction technique. Various measurement techniques were used to investigate the structures and properties of the catalysts. The relative intensity ratios of I_D/I_G in rGO/Au, rGO/Ag, rGO/Pt, and GO were 1.106, 1.078, 1.047, and 0.863, respectively. The results showed the formation of rGO and that noble metal nanoparticles were decorated on rGO. Furthermore, the catalytic activities of the designed nanocomposites were investigated via 4-nitrophenol. The catalysts were used in 4-nitrophenol reduction. The catalytic performance of the catalysts was evaluated using the apparent rate constant k values. The k value of rGO/Au was 0.618 min^-1, which was higher than those of rGO/Ag (0.55 min^-1) and rGO/Pt (0.038 min^-1). The result proved that the rGO/Au catalyst exhibited a higher catalytic performance than the rGO/Ag catalyst and the rGO/Pt catalyst. The results provide a facile method for the synthesis of rGO-supported nanomaterials in catalysis.

Extended visible light driven photocatalytic hydrogen generation by electron induction from g-C3N4 nanosheets to ZnO through the proper heterojunction

The alarming energy crises has forced the scientific community to work for sustainable energy modules to meet energy requirements. As for this, ZnO/g-C3N4 nanocomposites with proper heterojunction were fabricated by coupling a proper amount of ZnO with 2D graphitic carbon nitride (g-C3N4) nanosheets and the obtained nanocomposites were applied for photocatalytic hydrogen generation from water under visible light illumination (λ > 420 nm). The morphologies and the hydrogen generation performance of fabricated photocatalysts were characterized in detail. Results showed that the optimized 5ZnO/g-C3N4 nanocomposite produced 70 µmol hydrogen gas in 1 h compare to 8 µmol by pure g-C3N4 under identical illumination conditions in the presence of methanol without the addition of cocatalyst. The much improved photoactivities of the nanocomposites were attributed to the enhanced charge separation through the heterojunction as confirmed from photoluminescence study, capacity of the fabricated samples for •OH radical generation and steady state surface photovoltage spectroscopic (SS-SPS) measurements. We believe that this work would help to fabricate low cost and effective visible light driven photocatalyst for energy production.

Synthesis and physiochemical performances of PVC-sodium polyacrylate and PVC-sodium polyacrylate-graphite composite polymer membrane

Three types (type-A, B, and C) of composite polymeric membranes (CPMs) based on poly vinyl chloride (PVC) and different fillers (sodium polyacrylate and sodium polyacrylate-graphite) soaked in water and 0.5 N HCl were prepared using solvent casting method. Different physicochemical parameters such as microscopic surface study, water uptake, perpendicular swelling, density, porosity (ε), ion exchange capacity, and conductivity of the as the prepared CPMs were evaluated. Interestingly, type-A CPM cast with filler-A has greater values of the above parameters except density and ionic conductivity than those of type-B and C CPMs. The water uptake of type-A, B and C composite membranes was respectively in the range of 220.42–534.70, 59.64–41.65, and 15.94–2.62%. Ion exchange capacity of type-A, B and C CPMs was in the range of 3.669 × 107–2.156 × 107, 5.948 × 107–1.258 × 107, and 1.454 × 107–1.201 × 107 m.eq.g−1 respectively while the conductivity order was type-A < B < C. These types of CPMs may be helpful in many applications including proton exchange membranes, fuel cell like devices, as sensors for different metals, gas purification, water treatment, and battery separators.