Gelatin-Coated TiO2/Pd Hybrid: A Potentially Useful Nanomaterial to Enhance Antibacterial and Anticancer Properties

Hybrid nanomaterials have attracted considerable interest in biomedicine because of their fascinating characteristics and wide range of applications in targeted drug delivery, antibacterial activity, and cancer treatment. This study developed a gelatin-coated Titanium oxide/palladium (TiO2/Pd) hybrid nanomaterial to enhance the antibacterial and anticancer capabilities. Morphological and structural analyses were conducted to characterize the synthesized hybrid nanomaterial. The surface texture of the hybrid nanomaterials was examined by high-resolution transmission electron microscopy (HR-TEM) and field-emission scanning electron microscopy (FE-SEM). The FE-SEM image revealed the bulk of the spherically shaped particles and the aggregated tiny granules. Energy dispersive X-ray spectroscopy (EDS) revealed Ti, Pd, C, and O. X-ray diffraction (XRD) revealed the gelatin-coated TiO2/Pd to be in the anatase form. Fourier transform infrared spectroscopy examined the interactions among the gelatin-coated TiO2/Pd nanoparticles. The gelatin-coated TiO2/Pd nanomaterials exhibited high antibacterial activity against Escherichia coli (22 mm) and Bacillus subtilis (17 mm) compared to individual nanoparticles, confirming the synergistic effect. More importantly, the gelatin-coated TiO2/Pd hybrid nanomaterial exhibited remarkable cytotoxic effects on A549 lung cancer cells which shows a linear increase with the concentration of the nanomaterial. The hybrid nanomaterials displayed higher toxicity to cancer cells than the nanoparticles alone. Furthermore, the cytotoxic activity against human cancer cells was verified by the generation of reactive oxygen species and nuclear damage. Therefore, gelatin-coated TiO2/Pd nanomaterials have potential uses in treating cancer and bacterial infections.

A 3D Covalent Organic Framework with In-situ Formed Pd Nanoparticles for Efficient Electrochemical Oxygen Reduction

Non-platinum noble metals are highly desirable for the development of highly active, stable oxygen reduction reaction (ORR) electrocatalysts for fuel cells and metal-air batteries. However, how to improve the utilization of non-platinum noble metals is an urgent issue. Herein, a highly efficient catalyst for ORR was prepared through homogeneous loading of Pd precursors by a domain-limited method in a three-dimensional covalent organic framework (COF) followed by pyrolysis. The morphology of the Pd nanoparticles (Pd NPs) was well maintained after carbonization, which was attributed to the rigid structure of the 3D COF. Thanks to the uniform distribution of Pd NPs in the carbon, the catalyst exhibited a remarkable half-wave potential of 0.906 V and a Tafel slope of 70 mV dec-1 in 0.1 M KOH, surpassing the commercial Pt/C catalyst (0.863 V and 75 mV dec-1 ). Furthermore, a maximum power density of 144.0 mW cm-2 was achieved at 252 mA cm-2 , which was significantly higher than the control battery (105.1 mW cm-2 ). This work not only provides a simple strategy for in-situ preparation of highly dispersible metal catalysts in COFs, but also offers new insights into the ORR electrocatalysis.

Highly Functionalized SWCNTs with a Dopamine Derivative as a Support for Pd Nanoparticles: A Recyclable Catalyst for the Reduction of Nitro Compounds and the Heck Reaction

Single-walled carbon nanotubes (SWCNTs) were functionalized with a dopamine derivative in which the amine group was converted to azide (dopamine azide). The direct reaction of SWCNTs and dopamine azide in o-dichlorobenzene at high temperature (160 °C) led to very highly functionalized CNTs (≈60 wt.%). Surprisingly, despite this high degree of functionalization, Raman spectroscopy detected a low disruption of the π-network of the carbonaceous support. This finding was justified by the rehybridization from sp3 to sp2 of the sidewall carbon atoms of CNTs involved in the functionalization process. Further characterization by means of different techniques such as X-ray photoelectron spectroscopy (XPS) analysis and transmission electron microscopy (TEM) allowed to shed some light on the chemical composition and morphology of the obtained material. Moreover, the estimation of the total content of phenolic units and their reducing potential after CNTs functionalization was also assessed using Folin and Ciocalteu and 2,2-diphenyl-1-picryl hydrazide (DPPH) assays. The functionalization of CNTs was exploited to immobilize palladium(II) species that were subsequently reduced with NaBH4 leading to the formation of Pd nanoparticles (NPs). The so obtained hybrid material was used as a recyclable heterogeneous catalyst for the reduction of nitro compounds and the Heck reaction.

Lignosulfonate-Assisted In Situ Deposition of Palladium Nanoparticles on Carbon Nanotubes for the Electrocatalytic Sensing of Hydrazine

This paper presents a novel modified electrode for an amperometric hydrazine sensor based on multi-walled carbon nanotubes (MWCNTs) modified with lignosulfonate (LS) and decorated with palladium nanoparticles (NPds). The MWCNT/LS/NPd hybrid was characterized by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The electrochemical properties of the electrode material were evaluated using cyclic voltammetry and chronoamperometry. The results showed that GC/MWCNT/LS/NPd possesses potent electrocatalytic properties towards the electro-oxidation of hydrazine. The electrode demonstrated exceptional electrocatalytic activity coupled with a considerable sensitivity of 0.166 μA μM-1 cm-2. The response was linear from 3.0 to 100 µM L-1 and 100 to 10,000 µM L-1, and the LOD was quantified to 0.80 µM L-1. The efficacy of the modified electrode as an electrochemical sensor was corroborated in a study of hydrazine determination in water samples.

An Unusual Microdomain Factor Controls Interaction of Organic Halides with the Palladium Phase and Influences Catalytic Activity in the Mizoroki-Heck Reaction

In this work, using a combination of scanning and transmission electron microscopy (SEM and TEM), the transformations of palladium-containing species in imidazolium ionic liquids in reaction mixtures of the Mizoroki-Heck reaction and in related organic media are studied to understand a challenging question of the relative reactivity of organic halides as key substrates in modern catalytic technologies. The microscopy technique detects the formation of a stable nanosized palladium phase under the action of an aryl (Ar) halide capable of forming microcompartments in an ionic liquid. For the first time, the correlation between the reactivity of the aryl halide and the microdomain structure is observed: Ar-I (well-developed microdomains) > Ar-Br (microphase present) > Ar-Cl (minor amount of microphase). Previously, it is assumed that molecular level factors, namely, carbon-halogen bond strength and the ease of bond breakage, are the sole factors determining the reactivity of aryl halides in catalytic transformations. The present work reports a new factor connected with the nature of the organic substrates used and their ability to form a microdomain structure and concentrate metallic species, highlighting the importance of considering both the molecular and microscale properties of the reaction mixtures.

The development of folate-functionalised palladium nanoparticles for folate receptor targeting in breast cancer cells

Folate receptor-targeted therapy has excellent prospects for the treatment of breast cancer. A non-toxic concentration of folate-conjugated palladium-based nanoparticles was used to target the overexpressed folate receptor on breast cancer cells. The folate-conjugated nanoparticles were tailored to accumulate selectively in cancer cells relative to normal cells via the folate receptor. The MDA-MB-231, MDA-MB-468, MCF-7 breast cancer cell lines, and MCF-10A normal cell lines were used in the study. Qualitative and quantitative analysis of nanoparticle cellular uptake and accumulation was conducted using transmission electron microscopy and inductively coupled plasma-optical emission spectroscopy. The findings proved that folate-conjugated palladium nanoparticles successfully and preferentially accumulated in breast cancer cells. We conclude that folate-conjugated palladium nanoparticles can be potentially used to target breast cancer cells for radiopharmaceutical applications.

Efficient Reduction in Methylene Blue Using Palladium Nanoparticles Supported by Melamine-Based Polymer

In this work, palladium nanoparticles, supported by polyaminals (Pd@PAN-NA), were synthesized via a reverse double solvent approach and used as a nano catalyst. The thermogravimetric and the elemental analysis revealed that the catalyst had good dispersity and improved thermal stability. The catalytic activity of the prepared Pd@PAN-NA catalyst was studied for a methylene blue chemical reaction in the presence of NaBH4 as a reducing agent. The effect of the catalyst dose, pH, and dye initial concentration were examined to optimize the chemical reduction conditions. The prepared catalyst Pd@PAN-NA removed 99.8% of methylene blue organic dye, indicating its potential effect for treating waste and contaminated water.

Engineering the Metal/Dielectric Interface to Unlock the Potential of Scattered Light for Boosted Photoredox Catalysis

The recycling of scattered light by metals has been emerging as a promising light-manipulation-capture strategy, but how to bring its potential into better play remains to be explored. Herein, we present that constructing dual metal/high-refractive-index dielectric interfaces within the SiO2 core@TiO2 shell-Pd satellite@TiO2 shell effectively strengthens both the scattering efficiency of the dielectric SiO2 support and electric field confinement. Consequently, the absorption of Pd toward near-field scattered light and the interfacial charge carrier separation are both enhanced. The synergy of these effects leads to boosted photoactivity toward the aerobic oxidation of cyclohexanol to cyclohexanone and the anaerobic reduction of proton for hydrogen evolution under visible-light irradiation as compared to the counterparts with a single metal/dielectric interface and dual metal/dielectric interfaces consisting of low-refractive-index dielectric component. Notably, the similar enhancements in both optical absorption and photoactivity can be achieved through the present dual metal/high-refractive-index dielectric interfaces engineering strategy for other metals, such as Pt nanoparticles. This work presents an instructive avenue to upgrade the optical response of metals and thus the photocatalytic performance by engineering metal/dielectric interfaces.

Green Nanoformulations of Polyvinylpyrrolidone-Capped Metal Nanoparticles: A Study at the Hybrid Interface with Biomimetic Cell Membranes and In Vitro Cell Models

Noble metal nanoparticles (NP) with intrinsic antiangiogenic, antibacterial, and anti-inflammatory properties have great potential as potent chemotherapeutics, due to their unique features, including plasmonic properties for application in photothermal therapy, and their capability to slow down the migration/invasion speed of cancer cells and then suppress metastasis. In this work, gold (Au), silver (Ag), and palladium (Pd) NP were synthesized by a green redox chemistry method with the reduction of the metal salt precursor with glucose in the presence of polyvinylpyrrolidone (PVP) as stabilizing and capping agent. The physicochemical properties of the PVP-capped NP were investigated by UV-visible (UV-vis) and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopies, dynamic light scattering (DLS), and atomic force microscopy (AFM), to scrutinize the optical features and the interface between the metal surface and the capping polymer, the hydrodynamic size, and the morphology, respectively. Biophysical studies with model cell membranes were carried out by using laser scanning confocal microscopy (LSM) with fluorescence recovery after photobleaching (FRAP) and fluorescence resonance energy transfer (FRET) techniques. To this purpose, artificial cell membranes of supported lipid bilayers (SLBs) made with 1-palmitoyl-2-oleoyl-sn-glycerol-3-phosphocholine (POPC) dye-labeled with 7-nitro-2-1,3-benzoxadiazol-4-yl (NBD, FRET donor) and/or lissamine rhodamine B sulfonyl (Rh, FRET acceptor) were prepared. Proof-of-work in vitro cellular experiments were carried out with prostate cancer cells (PC-3 line) in terms of cytotoxicity, cell migration (wound scratch assay), NP cellular uptake, and cytoskeleton actin perturbation.

Studies on High-Temperature Evolution of Low-Loaded Pd Three-Way Catalysts Prepared by Laser Electrodispersion

Pd/Al₂O₃ catalyst of the "crust" type with Pd loading of 0.03 wt.% was prepared by the deposition of 2 nm Pd particles on the outer surface of the alumina support using laser electrodispersion (LED). This technique differs from a standard laser ablation into a liquid in that the formation of monodisperse nanoparticles occurs in the laser torch plasma in a vacuum. As is found, the LED-prepared catalyst surpasses Pd-containing three-way catalysts, obtained by conventional chemical synthesis, in activity and stability in CO oxidation under prompt thermal aging conditions. Thus, the LED-prepared Pd/Al₂O₃ catalyst showed the best thermal stability up to 1000 °C. The present research is focused on the study of the high-temperature evolution of the Pd/Al₂O₃ catalyst in two reaction mixtures by a set of physicochemical methods (transmission electron microscopy, X-ray photoelectron spectroscopy, and diffuse reflectance UV-vis spectroscopy). In order to follow the dispersion of the Pd nanoparticles during the thermal aging procedure, the testing reaction of ethane hydrogenolysis was also applied. The possible reasons for the high stability of LED-prepared catalysts are suggested.

Chemiresistive Hydrogen Sensing with Size-Limited Palladium Nanoparticles in Iptycene-Containing Poly(arylene ether)s

Metal nanoparticles have been widely employed in chemical sensing due to their high reactivity toward various gases. The size of the metal nanoparticles often dictates their reactivity and hence their performance as chemiresistive sensors. Herein, we report that iptycene-containing poly(arylene ether)s (PAEs) have been shown to limit the growth of palladium nanoparticles (Pd NPs) and stabilize the Pd NPs dispersion. These porous PAEs also facilitate the efficient transport of analytes. Single-walled carbon nanotube (SWCNT)-based chemiresistors and graphene field-effect transistors (GFETs) using these PAE-supported small Pd NPs are sensitive, selective, and robust sensory materials for hydrogen gas under ambient conditions. Generalizable strategies including presorting SWCNTs with pentiptycene-containing poly(p-phenylene ethynylene)s (PPEs) and thermal annealing demonstrated significant improvements in the chemiresistive performance. The polymer:NP colloids produced in this study are readily synthesized and solution processable, and these methods are of general utility.

The Electrochemical Behavior of Unmodified and Pd-NPs Modified AB5 Hydrogen Storage Alloy in Selected Protic and Aprotic Ionic Liquids (ILs): Towards ILs-Based Electrolytes for Ni-MH Batteries

The objective of this work was to study the electrochemical behavior of AB₅ alloy and its composite with Pd nanoparticles in selected ionic liquids. The protic ionic liquid (diethylmethylammonium triflate) and the mixture of aprotic ionic liquid (1-ethyl-3-methylimidazolium methanesulfonate) with parent superacid were used as electrolytes in the process of hydrogen electrosorption in AB₅ alloy electrodes. The impact of the surface modification of AB₅ electrode with Pd nanoparticles has been checked. The studies revealed that the highest hydrogen absorption capacity can be obtained in Pd-NPs-AB₅ electrode in DEMA-TFO. It was found that the surface modification with Pd-NPs facilitates the activation of the electrode and results in stabilization of the plateau potential of discharging. The studies show that more effort should be put into the synthesis of less corrosive tailored ionic liquids suitable to be used as electrolytes in hydride batteries.

Ultrasensitive and selective colorimetric detection of uric acid using peroxidase mimetic activity of biogenic palladium nanoparticles

Uric acid (2,6,8-trihydroxypurine) is a metabolic product of purine, which is one of the important markers of human health. The development of a rapid, facile, highly sensitive, and selective method for uric acid detection is critical for the diagnosis of related diseases and is still a strategic challenge. In this study, we developed a highly sensitive and selective colorimetric assay for the detection of uric acid using biogenic palladium nanoparticles (Pd NPs). The synthesized nanoparticles were shown to acquire peroxidase mimetic activity that oxidized 3,3',5,5'-tetramethylbenzidine and produced a blue colour in an assay. The developed colorimetric assay is instrument-free detection of uric acid with a limit of detection of 0.05 μM and a 1.11 μM limit of quantification (LOQ). This is the first report determining the LOQ for a colorimetric assay that gives the lowest quantity of analyte that can be evaluated with more precision under the specified conditions of the analysis. The developed assay had a linear response at low uric acid concentrations of 0.05 to 1 μM and a 0.99841 linear regression correlation coefficient. This colorimetric detection provides a rapid, cost-effective, and easy-to-use platform for the clinical diagnosis of uric acid biomarkers.

Improving the Effect of Cancer Cells Irradiation with X-rays and High-Energy Protons Using Bimetallic Palladium-Platinum Nanoparticles with Various Nanostructures

Nano-sized radiosensitizers can be used to increase the effectiveness of radiation-based anticancer therapies. In this study, bimetallic, ~30 nm palladium-platinum nanoparticles (PdPt NPs) with different nanostructures (random nano-alloy NPs and ordered core-shell NPs) were prepared. Scanning transmission electron microscopy (STEM), selected area electron diffraction (SAED), energy-dispersive X-ray spectroscopy (EDS), zeta potential measurements, and nanoparticle tracking analysis (NTA) were used to provide the physicochemical characteristics of PdPt NPs. Then, PdPt NPs were added to the cultures of colon cancer cells and normal colon epithelium cells in individually established non-toxic concentrations and irradiated with the non-harmful dose of X-rays/protons. Cell viability before and after PdPt NPs-(non) assisted X-ray/proton irradiation was evaluated by MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay. Flow cytometry was used to assess cell apoptosis. The results showed that PdPt NPs significantly enhanced the effect of irradiation on cancer cells. It was noticed that nano-alloy PdPt NPs possess better radiosensitizing properties compared to PtPd core-shell NPs, and the combined effect against cancer cells was c.a. 10% stronger for X-ray than for proton irradiation. Thus, the radio-enhancing features of differently structured PdPt NPs indicate their potential application for the improvement of the effectiveness of radiation-based anticancer therapies.

Ethanol Electrooxidation at 1-2 nm AuPd Nanoparticles

We report a systematic study of the electrocatalytic properties and stability of a series of 1-2 nm Au, Pd, and AuPd alloy nanoparticles (NPs) for the ethanol oxidation reaction (EOR). Following EOR electrocatalysis, NP sizes and compositions were characterized using aberration-corrected scanning transmission electron microscopy (ac-STEM) and energy dispersive spectroscopy (EDS). Two main findings emerge from this study. First, alloyed AuPd NPs exhibit enhanced electrocatalytic EOR activity compared to either monometallic Au or Pd NPs. Specifically, NPs having a 3:1 ratio of Au:Pd exhibit an ~8-fold increase in peak current density compared to Pd NPs, with an onset potential shifted ~200 mV more to the negative compared to Au NPs. Second, the size and composition of AuPd alloy NPs do not (within experimental error) change following 1.0 or 2.0 h chronoamperometry experiments, while monometallic Au NPs increase in size from 2 to 5 nm under the same conditions. Notably, this report demonstrates the importance of post-catalytic ac-STEM/EDS characterization for fully evaluating NP activity and stability, especially for 1-2 nm NPs that may change in size or structure during electrocatalysis.

Metal-Micelle Interaction Leading to Spontaneous Formation of Ligand-Free Palladium(0) Nanoparticles: Highly Efficient Catalysis Enabling Biaryl Ketone Formation from Carboxylic Acid Derivatives

A novel strategy has been developed to spontaneously form ligand-free Pd(0) nanoparticles (NPs) from water- and air-sensitive Pd₂dba₃ in water. These NPs are thoroughly characterized by IR, NMR, and mass spectrometry, revealing that the metal-micelle binding plays a critical role in their stability and activity. High-resolution transmission electron microscopy supported the ultrasmall nature of NPs, whereas X-ray photoelectron spectroscopy analysis confirmed the zero-oxidation state of Pd. The shielding effect of micelles and enhanced stability of NPs enabled fast cross-couplings of water-sensitive triazine adducts of carboxylic acid to form nonsymmetrical biaryl ketones. These naturally formed NPs are more efficient than new synthetic NPs formed under a hydrogen atmosphere and traditional NPs formed using the air-sensitive Grignard reagent as a reductant. The activity of naturally formed NPs is compared with that of synthetic NPs over 34 substrates, revealing that naturally formed NPs are much more efficient than synthetic NPs.

Automated Recognition of Nanoparticles in Electron Microscopy Images of Nanoscale Palladium Catalysts

Automated computational analysis of nanoparticles is the key approach urgently required to achieve further progress in catalysis, the development of new nanoscale materials, and applications. Analysis of nanoscale objects on the surface relies heavily on scanning electron microscopy (SEM) as the experimental analytic method, allowing direct observation of nanoscale structures and morphology. One of the important examples of such objects is palladium on carbon catalysts, allowing access to various chemical reactions in laboratories and industry. SEM images of Pd/C catalysts show a large number of nanoparticles that are usually analyzed manually. Manual analysis of a statistically significant number of nanoparticles is a tedious and highly time-consuming task that is impossible to perform in a reasonable amount of time for practically needed large amounts of samples. This work provides a comprehensive comparison of various computer vision methods for the detection of metal nanoparticles. In addition, multiple new types of data representations were developed, and their applicability in practice was assessed.

Transition Metal Catalyzed Hiyama Cross-Coupling: Recent Methodology Developments and Synthetic Applications

Hiyama cross-coupling is a versatile reaction in synthetic organic chemistry for the construction of carbon-carbon bonds. It involves the coupling of organosilicons with organic halides using transition metal catalysts in good yields and high enantioselectivities. In recent years, hectic progress has been made by researchers toward the synthesis of diversified natural products and pharmaceutical drugs using the Hiyama coupling reaction. This review emphasizes the recent synthetic developments and applications of Hiyama cross-coupling.

Organo-Nanocups Assist the Formation of Ultra-Small Palladium Nanoparticle Catalysts for Hydrogen Evolution Reaction

Ultra-small palladium nanoparticles were synthesized and applied as catalysts for a hydrogen evolution reaction. The palladium metal precursor was produced via beta-cyclodextrin as organo-nanocup (ONC) capping agent to produce ultra-small nanoparticles used in this study. The produced ~3 nm nanoparticle catalyst was then characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-Vis), and Fourier transform infrared spectroscopy (FTIR) to confirm the successful synthesis of ~3 nm palladium nanoparticles. The nanoparticles' catalytic ability was explored via the hydrolysis reaction of sodium borohydride. The palladium nanoparticle catalyst performed best at 303 K at a pH of 7 with 925 μmol of sodium borohydride having an H₂ generation rate of 1.431 mL min^-1 mL_cat^-1. The activation energy of the palladium catalyst was calculated to be 58.9 kJ/mol.

Adsorption Sites on Pd Nanoparticles Unraveled by Machine-Learning Potential with Adaptive Sampling

Catalytic properties of noble-metal nanoparticles (NPs) are largely determined by their surface morphology. The latter is probed by surface-sensitive spectroscopic techniques in different spectra regions. A fast and precise computational approach enabling the prediction of surface-adsorbate interaction would help the reliable description and interpretation of experimental data. In this work, we applied Machine Learning (ML) algorithms for the task of adsorption-energy approximation for CO on Pd nanoclusters. Due to a high dependency of binding energy from the nature of the adsorbing site and its local coordination, we tested several structural descriptors for the ML algorithm, including mean Pd-C distances, coordination numbers (CN) and generalized coordination numbers (GCN), radial distribution functions (RDF), and angular distribution functions (ADF). To avoid overtraining and to probe the most relevant positions above the metal surface, we utilized the adaptive sampling methodology for guiding the ab initio Density Functional Theory (DFT) calculations. The support vector machines (SVM) and Extra Trees algorithms provided the best approximation quality and mean absolute error in energy prediction up to 0.12 eV. Based on the developed potential, we constructed an energy-surface 3D map for the whole Pd₅₅ nanocluster and extended it to new geometries, Pd₇₉, and Pd₈₅, not implemented in the training sample. The methodology can be easily extended to adsorption energies onto mono- and bimetallic NPs at an affordable computational cost and accuracy.

Palladium Nanoparticles Supported on Cellulosic Paper as Multifunctional Catalyst for Coupling and Hydrogenation Reactions

Hallmark of a successful catalyst is its high efficiency, economic aspects, operational simplicity, extensive reusability, higher environment friendliness, and potential use in multiple industrial applications. Herein, a facile protocol involving a catalyst with Pd nanoparticles supported on cellulose paper (also known as a "dip-catalyst") for the hydrogenation of a series of quinolines, nitroarene, and C-C bond formation reactions in most benign solvents such as water is described. The mere insertion/removal of the "dip-catalyst" strip enables instantaneous start/stop of the reaction, which enhances its reusability and ease of separation of products. Cellulose paper (CP) strips decorated with Pd nanoparticles (Pd/CP) are prepared by the reduction of K₂ PdCl₄ soaked strips using formic acid as reductant. The resulting spherical shaped Pd particles, confirmed by scanning electron microscopy, form stable catalysis centers on the support. XRD signature confirms the crystallinity of the Pd nanoparticles and the TEM images display 15-20 nm size particles uniformly decorating CP. X-ray photoelectron spectroscopy indicates the formation of metallic Pd. The catalyst is tested for the C-C bond formation reactions. Pd/CP catalyzed Suzuki-Miyaura coupling reaction demonstrate >99% conversion with optimum selectivity. On the other hand, Mizoroki-Heck reaction produced 87% conversion with the reaction of 4-methoxycarbonyl phenylboronic acid and iodobenzene in ethanol:water (1 : 1 v/v) using KOH as base. The developed Pd/CP construct produces >99% of the pyridine-ring hydrogenated product on quinoline hydrogenation using tetrahydroxydiboron (THDB) as the hydrogen source. Diverse and highly reducible functional groups were also evaluated for transfer hydrogenation, which demonstrates a high efficiency in terms of both reactivity and selectivity. The used catalysts are recyclable for the multiple cycles.

Self-Assembled 1-Octadecanethiol Membrane on Pd/ZnO for a Selective Room Temperature Flexible Hydrogen Sensor

A layer of self-assembled 1-octadecanethiol was used to fabricate a palladium (Pd)/zinc oxide (ZnO) nanoparticle-based flexible hydrogen sensor with enhanced response and high selectivity at room temperature. A palladium film was first deposited using DC sputtering technique and later annealed to form palladium nanoparticles. The formation of uniform, surfactant-free palladium nanoparticles contributed to improved sensor response towards hydrogen gas at room temperature. The obtained sensor response was higher than for previously reported room temperature Pd/ZnO sensors. Furthermore, the use of the polymer membrane suppressed the sensor’s response to methane, moisture, ethanol, and acetone, resulting in the selective detection of hydrogen in the presence of the common interfering species. This study shows a viable low-cost fabrication pathway for highly selective room temperature flexible hydrogen sensors for hydrogen-powered vehicles and other clean energy applications.

Palladium Nanoparticles Hardwired in Carbon Nanoreactors Enable Continually Increasing Electrocatalytic Activity During the Hydrogen Evolution Reaction

Catalysts typically lose effectiveness during operation, with much effort invested in stabilising active metal centres to prolong their functional lifetime for as long as possible. In this study palladium nanoparticles (PdNP) supported inside hollow graphitised carbon nanofibers (GNF), designated as PdNP@GNF, opposed this trend. PdNP@GNF exhibited continuously increasing activity over 30000 reaction cycles when used as an electrocatalyst in the hydrogen evolution reaction (HER). The activity of PdNP@GNF, expressed as the exchange current density, was always higher than activated carbon (Pd/C), and after 10000 cycles PdNP@GNF surpassed the activity of platinum on carbon (Pt/C). The extraordinary durability and self-improving behaviour of PdNP@GNF was solely related the unique nature of the location of the palladium nanoparticles, that is, at the graphitic step-edges within the GNF. Transmission electron microscopy imaging combined with spectroscopic analysis revealed an orchestrated series of reactions occurring at the graphitic step-edges during electrocatalytic cycling, in which some of the curved graphitic surfaces opened up to form a stack of graphene layers bonding directly with Pd atoms through Pd-C bonds. This resulted in the active metal centres becoming effectively hardwired into the electrically conducting nanoreactors (GNF), enabling facile charge transport to/from the catalytic centres resulting in the dramatic self-improving characteristics of the electrocatalyst.

Photothermochemical Nanoassembly of 3D Porous Graphene and Palladium Nanoparticles for High-Performance Hydrogen Detection

Hybrid materials comprising graphene and palladium nanoparticles (PdNPs) are desirable for high-performance hydrogen detection because of the high specific surface area, electron mobility, and flexibility of graphene and the high electrochemical responsivity and reversibility of PdNPs. However, obtaining hybrid materials is energy-intensive and time-consuming. Here, a facile and rapid laser photothermochemical single-step processing method to synchronously produce a nanoassembly of three-dimensional porous graphene and PdNPs from polymer films is reported. Polymers with intrinsic microporosity show high solubility in volatile solvents and miscibility with inorganic materials, allowing the fabrication of homogeneous polymer films containing Pd ligands. The films are photothermally processed using a laser to generate a nanohybrid via photoinduced thermal and chemical processes. The nanohybrid exhibits four-times-enhanced electrical conductivity compared to plain porous graphene, high crystallinity, and coherent covalent metal bonds with a homogeneous size and distribution of PdNPs in hierarchical micro/meso/macroporous graphene structures, allowing high-performance hydrogen sensing (1 ppm) with outstanding mechanical reliability, flexibility, and durability upon bending and twisting. The nanoassembly is integrated with a wireless sensing platform, and hydrogen leakage (1 ppm) is detected using a smart phone. This laser-based nanomanufacturing of the nanoassembly can potentially be applied to wearable detector production platforms in the military and industry.

Interfacing with Fe-N-C Sites Boosts the Formic Acid Dehydrogenation of Palladium Nanoparticles

Hierarchical micro-/mesoporous carbons with abundant Fe-N-C sites were prepared through one-step carbonization of a metal-organic framework (MOF) with sodium iron ethylenediaminetetraacetic acid [NaFe(III)EDTA], which can facilitate the nucleation and growth of ultrafine (∼1.4 nm) and highly dispersed palladium nanoparticles (Pd NPs). Interfacing Pd NPs with Fe-N-C sites has been demonstrated for the first time to boost the heterogeneous catalysis of hydrogen production from formic acid, affording an ultrahigh turnover frequency (TOF) value of 7361 h^-1 at 323 K. The robust synergistic interactions between Pd NPs and Fe-N-C sites together with the small size effects of Pd NPs are responsible for the enhanced catalytic activity.

Efficient and Recyclable Heterogeneous Catalyst Based on PdNPs Stabilized on a Green-Synthesized Graphene-like Nanomaterial: Effect of Surface Functionalization

This work reports for the first time a straightforward and efficient approach to covalent surface functionalization of a sustainable graphene-like nanomaterial with abundant carboxylic acid groups. This approach results in an efficient and robust chelatant platform for anchoring highly dispersed ultrasmall palladium particles with excellent catalytic activity in the reduction of both cationic (methylene blue, MB) and anionic (eosin-Y, Eo-Y) toxic organic dyes. The large-specific-surface-area (S_BET = 266.94 m²/g) graphene-like nanomaterial (GHN) was prepared through a green and cost-effective pyrolysis process from saccharose using layered bentonite clay as a template. To introduce a high density of carboxylic acid functions, GHN was first doubly functionalized by successive grafting reaction using two different strategies: (i) in the first case, GHN was first grafted by (3-glycidyloxypropyl) trimethoxysilane (GPTMS) and then bifunctionalized by chemical grafting of tris(4-hydroxyphenyl)methane triglycidyl ether (TGE). In the second case, the grafting order of the two molecules has been reversed. GHN-GPTMS-TGE provided the highest number of grafted reactive epoxy groups, and it was selected for further functionalization with carboxylic acid functions via a ring-opening reaction through a two-step hydrolysis (H₂SO₄)/oxidation (KMnO₄) approach. The GHN nanomaterial bearing carboxylic acid groups was then treated with sodium hydroxide to produce a deprotonated carboxylic acid-rich platform. Finally, due to a high density of accessible chelatant carboxylic acid groups, GHN-COO^- binds strongly a great amount of Pd²⁺ ions to form stable complexes which after reduction by NaBH₄ leads to highly dispersed, densely anchored, and uniformly distributed nanoscale Pd particles (d ∼ 4.5 nm) on the surface of the functionalized GHN. The GHN-COO^-@PdNPs nanohybrid proved to be highly efficient for dye reduction by NaBH₄ in aqueous solution at room temperature. Moreover, because of the high stability of the as-prepared graphene-like supported PdNPs, it exhibited very good reusability and could be recycled up to eight times without any significant loss in activity.

Tracking the Electrocatalytic Activity of a Single Palladium Nanoparticle for the Hydrogen Evolution Reaction

The nanoparticle-based electrocatalysts' performance is directly related to their working conditions. In general, a number of nanoparticles are uncontrollably fixed on a millimetre-sized electrode for electrochemical measurements. However, it is hard to reveal the maximum electrocatalytic activity owing to the aggregation and detachment of nanoparticles on the electrode surface. To solve this problem, here, we take the hydrogen evolution reaction (HER) catalyzed by palladium nanoparticles (Pd NPs) as a model system to track the electrocatalytic activity of single Pd NPs by stochastic collision electrochemistry and ensemble electrochemistry, respectively. Compared with the nanoparticle fixed working condition, Pd NPs in the nanoparticle diffused working condition results in a 2-5 orders magnitude enhancement of electrocatalytic activity for HER at various bias potential. Stochastic collision electrochemistry with high temporal resolution gives further insights into the accurate study of NPs' electrocatalytic performance, enabling to dramatically enhance electrocatalytic efficiency.

Antimicrobial Properties of Palladium and Platinum Nanoparticles: A New Tool for Combating Food-Borne Pathogens

Although some metallic nanoparticles (NPs) are commonly used in the food processing plants as nanomaterials for food packaging, or as coatings on the food handling equipment, little is known about antimicrobial properties of palladium (PdNPs) and platinum (PtNPs) nanoparticles and their potential use in the food industry. In this study, common food-borne pathogens Salmonella enterica Infantis, Escherichia coli, Listeria monocytogenes and Staphylococcus aureus were tested. Both NPs reduced viable cells with the log₁₀ CFU reduction of 0.3–2.4 (PdNPs) and 0.8–2.0 (PtNPs), average inhibitory rates of 55.2–99% for PdNPs and of 83.8–99% for PtNPs. However, both NPs seemed to be less effective for biofilm formation and its reduction. The most effective concentrations were evaluated to be 22.25–44.5 mg/L for PdNPs and 50.5–101 mg/L for PtNPs. Furthermore, the interactions of tested NPs with bacterial cell were visualized by transmission electron microscopy (TEM). TEM visualization confirmed that NPs entered bacteria and caused direct damage of the cell walls, which resulted in bacterial disruption. The in vitro cytotoxicity of individual NPs was determined in primary human renal tubular epithelial cells (HRTECs), human keratinocytes (HaCat), human dermal fibroblasts (HDFs), human epithelial kidney cells (HEK 293), and primary human coronary artery endothelial cells (HCAECs). Due to their antimicrobial properties on bacterial cells and no acute cytotoxicity, both types of NPs could potentially fight food-borne pathogens.

Multifunctional Pd-Based Nanocomposites with Designed Structure from In Situ Growth of Pd Nanoparticles and Polyether Block Amide Copolymer

Nanocomposites containing palladium nanoparticles were synthesized by in situ generation route from palladium acetate and a polyether block amide matrix with the aim to obtain materials with specific nanoparticle location and function properties. The chosen Pebax matrix was composed of a continuous soft phase containing dispersed semi-crystalline rigid domains. Nanocomposite films with Pd amount up to 30 wt% (corresponding to 3.5 vol%) were directly prepared from the palladium precursor and the copolymer matrix through a solvent cast process. The microstructure of the films was investigated by microcalorimetry, X-ray diffraction analyses and transmission electron microscopy. The nanocomposites' function properties in terms of electrical conductivity and interaction towards hydrogen were studied as a function of the palladium content. It was shown that the spherical crystalline Pd nanoparticles that were in situ formed were located in the continuous soft phase of the copolymer matrix. They did not induce modification of Pebax microstructure and chain mobility. The specific location of the metal nanoparticles within the copolymer matrix associated with their low size allowed obtaining conductive materials for Pd amount equal to 3.5 vol%. Moreover, the affinity towards hydrogen evidenced from hydrogen permeation experiments made this nanocomposite series promising for further development in sensing applications.

Palladium Nanoparticle-Induced Oxidative Stress, Endoplasmic Reticulum Stress, Apoptosis, and Immunomodulation Enhance the Biogenesis and Release of Exosome in Human Leukemia Monocytic Cells (THP-1)

Background

Exosomes are endosome-derived nano-sized vesicles that have emerged as important mediators of intercellular communication and play significant roles in various diseases. However, their applications are rigorously restricted by the limited secretion competence of cells. Therefore, strategies to enhance the production and functions of exosomes are warranted. Studies have shown that nanomaterials can significantly enhance the effects of cells and exosomes in intercellular communication; however, how palladium nanoparticles (PdNPs) enhance exosome release in human leukemia monocytic cells (THP-1) remains unclear. Therefore, this study aimed to address the effect of PdNPs on exosome biogenesis and release in THP-1 cells.

Methods

Exosomes were isolated by ultracentrifugation and ExoQuick^TM and characterized by dynamic light scattering, nanoparticle tracking analysis system, scanning electron microscopy, transmission electron microscopy, EXOCET^TM assay, and fluorescence polarization. The expression levels of exosome markers were analyzed via quantitative reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay.

Results

PdNP treatment enhanced the biogenesis and release of exosomes by inducing oxidative stress, endoplasmic reticulum stress, apoptosis, and immunomodulation. The exosomes were spherical in shape and had an average diameter of 50–80 nm. Exosome production was confirmed via total protein concentration, exosome counts, acetylcholinesterase activity, and neutral sphingomyelinase activity. The expression levels of TSG101, CD9, CD63, and CD81 were significantly higher in PdNP-treated cells than in control cells. Further, cytokine and chemokine levels were significantly higher in exosomes isolated from PdNP-treated THP-1 cells than in those isolated from control cells. THP-1 cells pre-treated with N-acetylcysteine or GW4869 showed significant decreases in PdNP-induced exosome biogenesis and release.

Conclusion

To our knowledge, this is the first study showing that PdNPs stimulate exosome biogenesis and release and simultaneously increase the levels of cytokines and chemokines by modulating various physiological processes. Our findings suggest a reasonable approach to improve the production of exosomes for various therapeutic applications.

Green Synthesis of Platinum and Palladium Nanoparticles Using Peganum harmala L. Seed Alkaloids: Biological and Computational Studies

This study reports a facile and eco-friendly method for the green synthesis of platinum and palladium nanoparticles (Pt NPs and Pd NPs) using Peganum harmala seed alkaloid fraction. The ζ-potential of the synthesized Pt NPs, Pd NPs and Pt–Pd NPs were −11.2 ± 0.5, −9.7 ±1.2, and −12.7 ± 2.1 mV; respectively. Transmission electron microscopy (TEM) revealed the formation of spherical-shaped nanoparticles with smooth margins. The mean diameters of the synthesized Pt NPs, Pd NPs, and Pt–Pd NPs were determined using TEM analysis and were found to be 20.3 ± 1.9, 22.5 ± 5.7, and 33.5 ± 5.4 nm, respectively. The nanoparticles’ bioreduction was confirmed by ultraviolet–visible (UV–vis) spectroscopy, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy, and their organic contents were determined by thermal gravimetric analysis (TGA). The Pt–Pd NPs mixture showed more pronounced antioxidant activity of 843.0 ± 60 μM Trolox equivalent (TE)/mg NPs compared to the individual Pt NPs (277.3 ± 13.5 μM TE/mg NPs) and Pd NPs (167.6 ± 4.8 μM TE/mg NPs). Furthermore, the Pt–Pd NPs exhibited significant cytotoxic activities against lung cancer (A549) and breast adenocarcinoma (MCF-7) cells, IC₅₀ of 8.8 and 3.6 µg/mL, respectively; as compared to Pt NPs (IC₅₀ of 10.9 and 6.7 µg/mL, respectively) and Pd NPs (IC₅₀ of 31 and 10.8 µg/mL, respectively and compared to carboplatin (IC₅₀ of 23 and 9.5 µg/mL, respectively). Moreover, molecular docking studies were conducted to explore the possible anticancer and antioxidant mechanisms of the biogenic nanoparticles. Pt NPs, Pd NPs, and their mixture showed inhibitory activity against cysteine proteinase, which supports their high antitumor activity, but moderate antioxidant activity. In conclusion, Pd-Pt NPs mixture prepared using harmala seed alkaloid fraction showed potential as effective antineoplastic agents.

Enhancing the Catalytic Activity of Palladium Nanoparticles via Sandwich-Like Confinement by Thin Titanate Nanosheets

As atomically thin oxide layers deposited on flat (noble) metal surfaces have been proven to have a significant influence on the electronic structure and thus the catalytic activity of the metal, we sought to mimic this architecture at the bulk scale. This could be achieved by intercalating small positively charged Pd nanoparticles of size 3.8 nm into a nematic liquid crystalline phase of lepidocrocite-type layered titanate. Upon intercalation the galleries collapsed and Pd nanoparticles were captured in a sandwichlike mesoporous architecture showing good accessibility to Pd nanoparticles. On the basis of X-ray photoelectron spectroscopy (XPS) and CO diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) Pd was found to be in a partially oxidized state, while a reduced Ti species indicated an electronic interaction between nanoparticles and nanosheets. The close contact of titanate sandwiching Pd nanoparticles, moreover, allows for the donation of a lattice oxygen to the noble metal (inverse spillover). Due to the metal-support interactions of this peculiar support, the catalyst exhibited the oxidation of CO with a turnover frequency as high as 0.17 s-1 at a temperature of 100 °C.

A Sustainable Palladium-Intercalated Montmorillonite Clay Catalytic System for Imine Hydrogenation under Mild Conditions

A series of palladium nanoparticles (Pd NPs) intercalated montmorillonite clay catalysts is reported for hydrogenation of 3-diphenyl prop-2-en-1-imine under mild reaction conditions. Pd/clay catalyst was prepared by a simple wet-impregnation method, and the physicochemical properties were characterized extensively by various techniques including N₂ adsorption, XRD, TEM, XPS and TPR etc., which showed the intercalation of active Pd NPs between the clay layers. The effect of reaction conditions such as catalyst loading, reaction time, temperature and H₂ pressure is explored, and thereby a plausible mechanism is proposed. The optimum amount of 6 wt % Pd/clay catalyst showed significant catalytic activity to yield 3-phenyl propyl aniline with 100 % conversion and selectivity under 5 bar pressure and a shorter reaction period of 3.5 h at 100 °C. The developed catalytic system unveiled excellent reusability over five cycles and hence paved the way for industrial applications.

Phosphine-Built-in Porous Organic Cage for Stabilization and Boosting the Catalytic Performance of Palladium Nanoparticles in Cross-Coupling of Aryl Halides

Herein, we report first a novel phosphine-containing porous organic cage (PPOC) from a [2 + 3] self-assembly of triphenyl phosphine-based trialdehyde and (S,S)-1,2-diaminocyclohexane via dynamic imine chemistry, which was employed as a porous material for the controlled growth of palladium nanoparticles (NPs) due to the strong affinity of Pd to the phosphine ligand based on the principle of hard and soft acids and bases. Comprehensive characterizations including X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, NMR, and X-ray absorption spectroscopy reveal that ultrafine Pd NPs with narrow size distribution (1.7 ± 0.3 nm) and enhanced surface electronic density via a strong interaction between NPs and phosphine were homogeneously dispersed in the PPOC. The resultant catalyst Pd@PPOC exhibits remarkably superior catalytic activities for various cross-coupling reactions of aryl halides, for example, Sonogashira, Suzuki, Heck, and carbonylation. The catalytic activity of Pd@PPOC outperforms the state-of-the-art Pd complexes and other Pd NPs supported on N-containing porous cages under identical conditions, owing to the enhanced surface electronic density of Pd NPs and their high stability and dispersibility in solution. More importantly, Pd@PPOC is highly stable and easily recycled and reused without loss of their catalytic activity. This work provides a new functional POC with extended potentials in catalysis and material science.

Dehydrogenation of Ethylene on Supported Palladium Nanoparticles: A Double View from Metal and Hydrocarbon Sides

Adsorption of ethylene on palladium, a key step in various catalytic reactions, may result in a variety of surface-adsorbed species and formation of palladium carbides, especially under industrially relevant pressures and temperatures. Therefore, the application of both surface and bulk sensitive techniques under reaction conditions is important for a comprehensive understanding of ethylene interaction with Pd-catalyst. In this work, we apply in situ X-ray absorption spectroscopy, X-ray diffraction and infrared spectroscopy to follow the evolution of the bulk and surface structure of an industrial catalysts consisting of 2.6 nm supported palladium nanoparticles upon exposure to ethylene under atmospheric pressure at 50 °C. Experimental results were complemented by ab initio simulations of atomic structure, X-ray absorption spectra and vibrational spectra. The adsorbed ethylene was shown to dehydrogenate to C2H3, C2H2 and C2H species, and to finally decompose to palladium carbide. Thus, this study reveals the evolution pathway of ethylene on industrial Pd-catalyst under atmospheric pressure at moderate temperatures, and provides a conceptual framework for the experimental and theoretical investigation of palladium-based systems, in which both surface and bulk structures exhibit a dynamic nature under reaction conditions.

Palladium Nanoparticles Fabricated by Green Chemistry: Promising Chemotherapeutic, Antioxidant and Antimicrobial Agents

Palladium nanoparticles (Pd NPs) showed great potential in biomedical applications because of their unique physicochemical properties. Various conventional physical and chemical methods have been used for the synthesis of Pd NPs. However, these methods include the use of hazardous reagents and reaction conditions, which may be toxic to health and to the environment. Thus, eco-friendly, rapid, and economic approaches for the synthesis of Pd NPs have been developed. Bacteria, fungi, yeast, seaweeds, plants, and plant extracts were used to prepare Pd NPs. This review highlights the most recent studies for the biosynthesis of Pd NPs, factors controlling their synthesis, and their potential biomedical applications.

Buffered Oxide Etchant Post-Treatment of a Silicon Nanofilm for Low-Cost and Performance-Enhanced Chemical Sensors

The high surface-to-volume ratio of nanostructured materials is the key factor for excellent performance when applied to chemical sensors. In order to achieve this by a facile and low-cost fabrication strategy, buffered oxide etchant (BOE) treatment of a silicon (Si)-based sensor was proposed. An n⁺-n^--n⁺ Si nanofilm structure was treated with a BOE, and palladium nanoparticles (PdNPs) were coated on the n-type Si channel surface via short-time electron beam evaporation to enable a highly sensitive and selective sensing of hydrogen (H₂) gas. The BOE treatment effect on lightly doped n-type Si was investigated, and the surface morphology of the etched Si was analyzed. Furthermore, the H₂ sensing characterization of PdNP-decorated Si devices with various BOE treatment times was systematically evaluated at room temperature. The results revealed that the surface of n-type Si is roughened by BOE treatment, which can further enhance the H₂-sensing performance of Pd-decorated Si. The elaborate study on the BOE-post-treated Si H₂ sensor showed that the performance enhancement was stable. The BOE treatment strategy was also applied to the nanopatterned Si sensors, which induced a clear performance enhancement for the H₂ sensing.

Ultrafine Pd Nanoparticles Supported on Soft Nitriding Porous Carbon for Hydrogen Production from Hydrolytic Dehydrogenation of Dimethyl Amine-Borane

Simple and efficient synthesis of a nano-catalyst with an excellent catalytic property for hydrogen generation from hydrolysis of dimethyl amine-borane (DMAB) is a missing piece. Herein, effective and recycled palladium (Pd) nanoparticles (NPs) supported on soft nitriding porous carbon (NPC) are fabricated and applied for DMAB hydrolysis. It is discovered that the soft nitriding via a low-temperature urea-pretreatment induces abundant nitrogen-containing species on the NPC support, thus promoting the affinity of the Pd precursor and hindering the agglomeration of formed Pd NPs onto the NPC surface during the preparation process. Surface-clean Pd NPs with a diameter of sub-2.0 nm deposited on the NPC support (Pd/NPC) exhibit an outstanding catalytic performance with a turnover frequency (TOF) of 2758 h^-1 toward DMAB hydrolysis, better than many previous reported Pd-based catalysts. It should be emphasized that the Pd/NPC also possesses a good stability without an obvious decrease in catalytic activity for DMAB hydrolysis in five successive recycling runs. This study provides a facile but efficient way for preparing high-performance Pd catalysts for catalytic hydrogen productions.

MWCNT-Supported PVP-Capped Pd Nanoparticles as Efficient Catalysts for the Dehydrogenation of Formic Acid

Various carbon materials were used as support of polyvinylpyrrolidone (PVP)-capped Pd nanoparticles for the synthesis of catalysts for the production of hydrogen from formic acid dehydrogenation reaction. Among investigated, MWCNT-supported catalysts were the most promising, with a TOF of 1430 h⁻¹ at 80°C. The presence of PVP was shown to play a positive role by increasing the hydrophilicity of the materials and enhancing the interface contact between the reactant molecules and the catalytic active sites.

Coulomb Blockade Effect in Well-Arranged 2D Arrays of Palladium Nano-Islands for Hydrogen Detection at Room Temperature: A Modeling Study

The fast growth of hydrogen usage as a clean fuel in civil applications such as transportation, space technology, etc. highlights the importance of the reliable detection of its leakage and accumulation under explosion limit by sensors with a low power consumption at times when there is no accumulation of hydrogen in the environment. In this research, a new and efficient mechanism is presented for hydrogen detection-using the Coulomb blockade effect in a well-arranged 2D array of palladium nano-islands-which can operate at room temperature. We demonstrated that under certain conditions of size distribution and the regularity of palladium nano-islands, with selected sizes of 1.7, 3 and 6.1 nm, the blockade threshold will appear in current-voltage (IV) characteristics. In reality, it will be achieved by the inherent uncertainty in the size of the islands in nano-scale fabrication or by controlling the size of nanoparticles from 1.7 to 6.1 nm, considering a regular arrangement of nanoparticles that satisfies single-electron tunneling requirements. Based on the simulation results, the threshold voltage is shifted towards lower ones due to the expansion of Pd nanoparticles exposed to the environment with hydrogen concentrations lower than 2.6%. Also, exploring the features of the presented structure as a gas sensor, provides robustness against the Gaussian variation in nano-islands sizes and temperature variations. Remarkably, the existence of the threshold voltage in the IV curve and adjusting the bias voltage below this threshold leads to a drastic reduction in power consumption. There is also an improvement in the minimum detectable hydrogen concentration as well as the sensor response.

Melatonin Enhances Palladium-Nanoparticle-Induced Cytotoxicity and Apoptosis in Human Lung Epithelial Adenocarcinoma Cells A549 and H1229

Palladium nanoparticles (PdNPs) are increasingly being used in medical and biological applications due to their unique physical and chemical properties. Recent evidence suggests that these nanoparticles can act as both a pro-oxidant and as an antioxidant. Melatonin (MLT), which also shows pro- and antioxidant properties, can enhance the efficacy of chemotherapeutic agents when combined with anticancer drugs. Nevertheless, studies regarding the molecular mechanisms underlying the anticancer effects of PdNPs and MLT in cancer cells are still lacking. Therefore, we aimed to investigate the potential toxicological and molecular mechanisms of PdNPs, MLT, and the combination of PdNPs with MLT in A549 lung epithelial adenocarcinoma cells. We evaluated cell viability, cell proliferation, cytotoxicity, oxidative stress, mitochondrial dysfunction, and apoptosis in cells treated with different concentrations of PdNPs and MLT. PdNPs and MLT induced cytotoxicity, which was confirmed by leakage of lactate dehydrogenase, increased intracellular protease, and reduced membrane integrity. Oxidative stress increased the levels of reactive oxygen species (ROS), malondialdehyde (MDA), nitric oxide (NO), protein carbonyl content (PCC), lipid hydroperoxide (LHP), and 8-isoprostane. Combining PdNPs with MLT elevated the levels of mitochondrial dysfunction by decreasing mitochondrial membrane potential (MMP), ATP content, mitochondrial number, and expression levels of the main regulators of mitochondrial biogenesis. Additionally, PdNPs and MLT induced apoptosis and oxidative DNA damage due to accumulation of 4-hydroxynonenal (HNE), 8-oxo-2'-deoxyguanosine (8-OhdG), and 8-hydroxyguanosine (8-OHG). Finally, PdNPs and MLT increased mitochondrially mediated stress and apoptosis, which was confirmed by the increased expression levels of apoptotic genes. To our knowledge, this is the first study demonstrating the effects of combining PdNPs and MLT in human lung cancer cells. These findings provide valuable insights into the molecular mechanisms involved in PdNP- and MLT-induced toxicity, and it may be that this combination therapy could be a potential effective therapeutic approach. This combination effect provides information to support the clinical evaluation of PdNPs and MLT as a suitable agents for lung cancer treatment, and the combined effect provides therapeutic value, as non-toxic concentrations of PdNPs and MLT are more effective, better tolerated, and show less adverse effects. Finally, this study suggests that MLT could be used as a supplement in nano-mediated combination therapies used to treat lung cancer.

Palladium/Carbon Nanofibers by Combining Atomic Layer Deposition and Electrospinning for Organic Pollutant Degradation

As organic dyes are a major source of pollution, it is important to develop novel and efficient heterogeneous catalysts with high activity for their degradation. In this work, two innovative techniques, atomic layer deposition and electrospinning, were used to prepare palladium nanoparticles (Pd NPs) supported on carbon nanofibers (CNFs). The sample morphology was investigated using scanning and transmission electron microscopy. This showed the presence of nanofibers of several micrometers in length and with a mean diameter of 200 nm. Moreover, the size of the highly dispersed Pd NPs was about 7 nm. X-ray photoelectron spectroscopy visually validated the inclusion of metallic Pd. The prepared nano-catalysts were then used to reduce methyl orange (MO) in the presence of sodium borohydride (NaBH₄). The Freundlich isotherm model was the most suitable model to explain the adsorption equilibrium for MO onto the Pd/CNF catalysts. Using 5 mL MO dye-solution (0.0305 mM) and 1 mL NaBH₄ (0.026 mM), a 98.9% of catalytic activity was achieved in 240 min by 0.01 g of the prepared nano-catalysts Pd/C (0.016 M). Finally, no loss of catalytic activity was observed when such catalysts were used again. These results represent a promising avenue for the degradation of organic pollutants and for heterogeneous catalysis.

Vanadyl Phthalocyanine Films and Their Hybrid Structures with Pd Nanoparticles: Structure and Sensing Properties

In this work, thin films of vanadyl phthalocyanines (VOPc and VOPcF₄) are studied as active layers for the detection of gaseous ammonia and hydrogen. The effect of F-substituents on the structural features of vanadyl phthalocyanine films and their sensor response toward ammonia (10–50 ppm) and hydrogen (100–500 ppm) is investigated by X-ray diffraction (XRD) and chemiresistive methods, respectively. It is shown that the sensor response of VOPcF₄ films to ammonia is 2–3 times higher than that of VOPc films. By contrast, the sensor response to hydrogen is higher in the case of VOPc films. Apart from this, the hybrid structures of vanadyl phthalocyanine films with Pd nanoparticles deposited on their surface by a chemical vapor deposition method are also tested to reveal the effect of Pd nanoparticles on the sensitivity of VOPc films to hydrogen. Deposition of Pd nanoparticles on the surface of VOPc films leads to the noticeable increase of their sensitivity to hydrogen.

Intracellular Antioxidant Activity of Biocompatible Citrate-Capped Palladium Nanozymes

A method for the aqueous synthesis of stable and biocompatible citrate-coated palladium nanoparticles (PdNPs) in the size range comparable to natural enzymes (4–8 nm) has been developed. The toxicological profile of PdNPs was assessed by different assays on several cell lines demonstrating their safety in vitro also at high particle concentrations. To elucidate their cellular fate upon uptake, the localization of PdNPs was analyzed by Transmission Electron Microscopy (TEM). Moreover, crucial information about their intracellular stability and oxidation state was obtained by Sputtering-Enabled Intracellular X-ray Photoelectron Spectroscopy (SEI-XPS). TEM/XPS results showed significant stability of PdNPs in the cellular environment, an important feature for their biocompatibility and potential for biomedical applications. On the catalytic side, these PdNPs exhibited strong and broad antioxidant activities, being able to mimic the three main antioxidant cellular enzymes, i.e., peroxidase, catalase, and superoxide dismutase. Remarkably, using an experimental model of a human oxidative stress-related disease, we demonstrated the effectiveness of PdNPs as antioxidant nanozymes within the cellular environment, showing that they are able to completely re-establish the physiological Reactive Oxygen Species (ROS) levels in highly compromised intracellular redox conditions.

Recombinant peptide fusion construction for protein-templated catalytic palladium nanoparticles

Although peptide-enabled synthesis of nanostructures has garnered considerable interest for use in catalytic applications, it has so far been achieved mostly via Fmoc based solid phase peptide synthesis. Consequently, the potential of longer peptides in nanoparticle synthesis have not been explored largely due to the complexities and economic constraints of this chemical synthesis route. This study examines the potential of a 45-amino acid long peptide expressed as fusion to green fluorescence protein (GFPuv) in Escherichia coli for use in palladium nanoparticle synthesis. Fed-batch fermentation with E. coli harboring an arabinose-inducible plasmid produced a product containing three copies of Pd4 peptide fused to N-terminus of GFPuv ((Pd4)₃ -GFPuv). Using the intrinsic fluorescence of GFPuv, expression and enrichment of the fusion product was easily monitored. Crude lysate, desalted lysate, and an ion-exchange enriched fraction containing (Pd4)₃ -GFPuv were used to test the hypothesis that high purity of the biologic material used as the nanoparticle synthesis template may not be necessary. Nanoparticles were characterized using a variety of material science techniques and used to catalyze a model Suzuki-Miyaura coupling reaction. Results demonstrated that palladium nanoparticles can be synthesized using the soluble cell extract containing (Pd4)₃ -GFPuv without extensive purification or cleavage steps, and as a catalyst the crude mixture is functional.

An Up-To-Date Review on Biomedical Applications of Palladium Nanoparticles

Palladium nanoparticles (PdNPs) have intrinsic features, such as brilliant catalytic, electronic, physical, mechanical, and optical properties, as well as diversity in shape and size. The initial researches proved that PdNPs have impressive potential for the development of novel photothermal agents, photoacoustic agents, antimicrobial/antitumor agents, gene/drug carriers, prodrug activators, and biosensors. However, very few studies have taken the benefit of the unique characteristics of PdNPs for applications in the biomedical field in comparison with other metals like gold, silver, or iron. Thus, this review aims to highlight the potential applications in the biomedical field of PdNPs. From that, the review provides the perceptual vision for the future development of PdNPs in this field.

Primary Amine-Functionalized Mesoporous Phenolic Resin-Supported Palladium Nanoparticles as an Effective and Stable Catalyst for Water-Medium Suzuki-Miyaura Coupling Reactions

Metal nanoparticles have been recognized and widely explored as unique catalysts for carbon-carbon coupling reactions. However, due to their extreme tendency to agglomeration, the generation and stabilization of metal nanoparticles in a porous matrix is an important research field. Herein, novel mesoporous phenolic resin-supported palladium nanoparticles (Pd@NH₂-MPRNs) were prepared via direct anionic exchange followed by gentle reduction by using primary amine-functionalized ordered mesoporous phenolic resin as the support. The obtained Pd@NH₂-MPRN material still possessed large surface area and ordered two-dimensional hexagonal mesoporous structure. Meanwhile, uniform and well-dispersed palladium nanoparticles were formed in the mesoporous channels, which could be attributed to an efficient complexation and stabilization effect derived from the primary amine groups. As a result, it can promote Suzuki coupling of less activated aromatic bromides to various biaryls in water with high conversion and selectivity. This excellent performance was attributed to small particle sizes, ordered mesopores, and a hydrophobic pore surface, which resulted in the decreased diffusion limitation and the increased active site accessibility. It is noted that it is competitive with the best palladium catalysts known for water-medium Suzuki coupling reaction, and it can be reused at least seven times without significant reduction in the catalytic efficiency, showing a good recyclability. Therefore, this work provides a new potential platform for designing and fabricating robust ordered mesoporous-polymer-supported metal nanoparticles for various catalytic applications.

Photothermal Responsive Porous Membrane for Treatment of Infected Wound

Wound infection is a big issue of modern medicine because of multi-drug resistance bacteria; thus, developing an advanced therapy is curial. Photothermal therapy (PTT) is a newly noninvasive strategy that employs PTT agents to transfer near-infrared (NIR) light energy into heat to kill bacterial pathogens. In this work, the PTT agent-containing dressing was developed for the first time to treat the wound infection. Palladium nanoparticles (PdNPs) were chosen as PTT agents because of their high stability, good biocompatibility, excellent photothermal property, and simple-green preparation. With the flexibility and wettability, highly porous membrane chitosan/polyvinyl alcohol (CS/PVA) membrane was chosen as the dressing. The prepared wound dressings exhibited excellent biocompatibility, high porosity, a high degree of swelling, high moisture retention, and high photothermal performance. The treatment of PdNPs loading CS/PVA dressing (CS/PVA/Pd) and laser irradiation killed most of the bacteria in vitro. The proposed PTT agent containing wound dressing introduces a novel strategy for the treatment of wound infection.

Block-Co-polymer-Assisted Synthesis of All Inorganic Highly Porous Heterostructures with Highly Accessible Thermally Stable Functional Centers

Here, we propose a simple approach for the design of highly porous multicomponent heterostructures by infiltration of block-co-polymer templates with inorganic precursors in swelling solvents followed by gas-phase sequential infiltration synthesis and thermal annealing. This approach can prepare conformal coatings, free-standing membranes, and powders consisting of uniformly sized metal or metal oxide nanoparticles (NPs) well dispersed in a porous oxide matrix. We employed this new, versatile synthetic concept to synthesize catalytically active heterostructures of uniformly dispersed ∼4.3 nm PdO nanoparticles accessible through three-dimensional pore networks of the alumina support. Importantly, such materials reveal high resistance against sintering at 800 °C, even at relatively high loadings of NPs (∼10 wt %). At the same time, such heterostructures enable high mass transport due to highly interconnected nature of the pores. The surface of synthesized nanoparticles in the porous matrix is highly accessible, which enables their good catalytic performance in methane and carbon monoxide oxidation. In addition, we demonstrate that this approach can be utilized to synthesize heterostructures consisting of different types of NPs on a highly porous support. Our results show that swelling-based infiltration provides a promising route toward the robust and scalable synthesis of multicomponent structures.

Highly Efficient Catalytic Performances of Nitro Compounds and Morin via Self-Assembled MXene-Pd Nanocomposites Synthesized through Self-Reduction Strategy

With development of the society, the problem of environmental pollution is becoming more and more serious. There is the urgent need to develop a new type of sustainable green material for degradable pollutants. However, the conventional preparation method is limited by conditions such as cumbersome operation, high energy consumption, and high pollution. Here, a simple method named self-reduction has been proposed, to synthesize highly efficient catalytic nitro compounds and morin self-assembled MXene-Pd nanocomposites. Palladium nanoparticles were grown in situ on MXene nanosheets to form MXene@PdNPs. MXene@PdNPs composites with different reaction times were prepared by adjusting the reduction reaction time. In particular, MXene@PdNPs20 exhibited a high catalytic effect on 4-NP and 2-NA, and the first-order rate constants of the catalysis were 0.180 s-1 and 0.089 s-1, respectively. It should be noted that after eight consecutive catalytic cycles, the conversion to catalyze 4-NP was still greater than 94%, and the conversion to catalyze 2-NA was still greater than 91.8%. Therefore, the research of self-assembled MXene@PdNPs nanocomposites has important potential value for environmental management and sustainable development of human health, and provides new clues for the future research of MXene-based new catalyst materials.