Self-reductive palladium nanoparticles loaded on polydopamine-modified MXene for highly efficient and quickly catalytic reduction of nitroaromatics and dyes

Fabrication of nano-sized Pd catalyst supported on sodium carboxymethyl cellulose/gum Arabic/sodium alginate functionalized microspheres for catalytic reduction of nitro compounds, organic dyes, K3[Fe(CN)6], and chromium(VI) pollutants

The rapid development of industrialization and urbanization, along with the increasing human population, has led to serious water pollution. Among water pollutants, organic and inorganic pollutants cause serious problems for both the environment and human health due to their toxicity and carcinogenic properties. One of the best ways to eliminate these pollutants is to develop eco-friendly, efficient, and long-life catalysts. For this purpose, in this study, environmentally friendly microspheres containing sodium alginate (SA), sodium carboxymethyl cellulose (Na-CMC), and gum Arabic (GA) were fabricated as potential stabilizers (SA/Na-CMC/GA). Subsequently, newly heterogeneous catalyst system was designed by immobilizing Pd nanoparticles on them and characterized (Pd@SA/Na-CMC/GA). The catalytic reduction ability of Pd@SA/Na-CMC/GA was then investigated against the reduction of 4-nitroaniline (4-NA), 4-nitrophenol (4-NP), 2-nitroaniline (2-NA), 4-nitro-o-phenylenediamine (4-NPDA), methylene blue (MB), methyl orange (MO), Rodamin B (RhB), potassium hexacyanoferrate(III) (K3[Fe(CN)6]), and hexavalent chromium (Cr(VI)) using NaBH4. The Pd@SA/Na-CMC/GA effectively catalyzed these contaminants in a short period of time under mild reaction conditions. As a result of the performed kinetics studies, rate constants were found to be 0.009 s-1, 0.016 s-1, 0.027 s-1, 0.018 s-1, 0.043 s-1, 0.058 s-1, 0.038 s-1 and 0.041 s-1 for the reduction of 4-NP, 2-NA, 4-NA, 4-NPDA, MO, RhB, K3[Fe(CN)6], and Cr(VI), respectively. Additionally, MO was immediately reduced by Pd@SA/Na-CMC/GA. The microsphere nature of Pd@SA/Na-CMC/GA allowed for easy recovery through simple filtration and successful reuse for up to six cycles.

A Critical Review of Palladium Nanoparticles Decorated in Smart Microgels

Palladium nanoparticles (Pd) combined with smart polymer microgels have attracted significant interest in the past decade. These hybrid materials have unique properties that make them appealing for various applications in biology, environmental remediation, and catalysis. The responsive nature of the microgels in these hybrids holds great promise for a wide range of applications. The literature contains diverse morphologies and architectures of Pd nanoparticle-based hybrid microgels, and the architecture of these hybrids plays a vital role in determining their potential uses. Therefore, specific Pd nanoparticle-based hybrid microgels are designed for specific applications. This report provides an overview of recent advancements in the classification, synthesis, properties, characterization, and uses of Pd nanostructures loaded into microgels. Additionally, the report discusses the latest progress in biomedical, catalytic, environmental, and sensing applications of Pd-based hybrid microgels in a tutorial manner.

Preparation of magnetically separable and low-cost MC-FePd3NPs with enhanced catalytic activity in the reduction of p-nitrophenol

To obtain a magnetically separable, low-cost and highly efficient reduction catalyst, microbial carbon-loaded bimetallic palladium/iron nanoparticles (MC-FePd3NPs) were synthesized in this study by using waste yeast residue doped with iron during the preparation process of microbial carbon-loaded monometallic palladium nanoparticles (MC-Pd NPs). The morphology, crystal structure, magnetic properties and catalytic performance of MC-FePd3NPs for the reduction ofp-nitrophenol (p-NP) were investigated by various characterization techniques, such as SEM-EDS, TEM, XRD, PPMS-9 and UV-vis spectroscopy. The catalytic experiments showed that the MC-FePd3NPs prepared under pyrolysis conditions at 700 °C had an apparent rate constant of 1.85 × 10-1s-1which is better than the rate constants of MC-Pd NPs and other palladium-based nanocatalytic materials reported so far. The amount of palladium used in the synthesis of MC-FePd3NPs was half that of MC-Pd NPs. The catalyst exhibited soft magnetic ordering behavior and still showed a catalytic efficiency of 97.4% after five consecutive reaction cycles. Furthermore, employing MC-FePd3NPs reduces the costs of catalyst preparation and use in production. MC-FePd3NPs with efficient catalytic properties, facile magnetic separation and recyclability, and low costs of preparation and use have considerable potential for industrial applications.

AgPd nanocages sandwiched between a MXene nanosheet and PDA layer for photothermally improved catalytic activity and antibacterial properties

In this work, a MXene@AgPd/polydopamine (PDA) nanosheet with excellent photothermal conversion efficiency was successfully synthesized by a simple redox-oxidative polymerization method. Interestingly, AgPd bimetallic nanocrystals sandwiched between a MXene nanosheet and PDA layer have cage-like nanostructure, which is favorable for high catalytic efficiency and antibacterial performance. Importantly, the MXene@AgPd/PDA nanosheet exhibits good catalytic activity for the reduction of 4-nitrophenol (1.2 min^-1 mg^-1) and the catalytic dynamics can be improved by about 1.2 times under NIR (near-infrared light, 808 nm, and 2.5 W cm^-2) irradiation. As the PDA shell is well protected, the MXene@AgPd/PDA nanosheet retained more than 90% catalytic activity after 6 cycles. In addition, due to the presence of the Ag component, the MXene@AgPd/PDA nanosheet exhibited good antibacterial activity against both Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria. Under near-infrared light irradiation, its antibacterial activity was further enhanced due to the NIR photothermal effect.

In Silico Prediction of the Toxicity of Nitroaromatic Compounds: Application of Ensemble Learning QSAR Approach

In this work, a dataset of more than 200 nitroaromatic compounds is used to develop Quantitative Structure-Activity Relationship (QSAR) models for the estimation of in vivo toxicity based on 50% lethal dose to rats (LD₅₀). An initial set of 4885 molecular descriptors was generated and applied to build Support Vector Regression (SVR) models. The best two SVR models, SVR_A and SVR_B, were selected to build an Ensemble Model by means of Multiple Linear Regression (MLR). The obtained Ensemble Model showed improved performance over the base SVR models in the training set (R² = 0.88), validation set (R² = 0.95), and true external test set (R² = 0.92). The models were also internally validated by 5-fold cross-validation and Y-scrambling experiments, showing that the models have high levels of goodness-of-fit, robustness and predictivity. The contribution of descriptors to the toxicity in the models was assessed using the Accumulated Local Effect (ALE) technique. The proposed approach provides an important tool to assess toxicity of nitroaromatic compounds, based on the ensemble QSAR model and the structural relationship to toxicity by analyzed contribution of the involved descriptors.

Exploring the catalytic activity of Nb4C3Tx MXene towards the degradation of nitro compounds and organic dyes by in situ decoration of palladium nanoparticles

We report on the catalytic activity of Nb4C3Tx based composites towards the catalytic reduction of nitro compounds and organic dyes for the first time.