Bio-hybrid palladium nanoparticle catalysts based on microorganisms for selective hydrogenation reactions

Pd nanoparticles are used in a variety of applications, and thus techniques that enable their high-throughput, label-free detection, as well as in situ reaction monitoring at catalytically relevant sizes, are needed to establish robust structure-function relationships. Here, we introduce wavelength-resolved interferometric scattering (iSCAT) as a strategy for performing these studies, over a range of Pd nanoparticle sizes. From a sample of ∼90 nm Pd octahedra we spectroscopically discriminate structural outliers based on their scattering resonances and spectral lineshapes, using simulations to validate the structure-spectral relationships. We then demonstrate direct detection of single Pd nanocubes with <20 nm edge length and track changes occurring to them in different reactive conditions, uncovering both interparticle heterogeneity and wavelength-dependent photochemistry. The results highlight the power of wavelength-resolved iSCAT for studying Pd nanoparticle transformations in situ and offer new insights into Pd reactivity at the nanoscale.

High-performance nanocatalysts are pivotal for advancing clean energy technologies such as fuel cells; however, conventional fabrication methods are often limited by complex procedures and the difficulty of precisely controlling active sites. Laser solid-phase synthesis (LSPS), characterized by its rapid, clean, and controllable nature, presents a promising avenue for catalyst preparation. Here, we report a strategy combining laser-induced graphene with LSPS to construct semi-encapsulated palladium nanoparticles (Pd NPs) on three-dimensional porous laser-induced graphene supports. The resulting catalysts exhibit enhanced catalytic activity and superior stability toward the ethanol oxidation reaction (EOR), retaining over 90% of their initial activity after 2500 accelerated durability test (ADT) cycles. Mechanistic insights from coupled FEM-MD simulations reveal that the laser-induced non-equilibrium thermal field is pivotal in forming a semi-encapsulated architecture. This work provides a new paradigm for the rational design of stable Pd-based EOR catalysts and demonstrates their potential for use in direct ethanol fuel cells (DEFCs).

Multicomponent reactions (MCRs) offer a sustainable and efficient pathway to complex molecular architectures. Here, we show the design and synthesis of a α-amino(2-hydroxybenzyl)-linked covalent organic framework (Betti-COF) via a one-pot, three-component solvothermal Betti reaction. This approach expands the scope of the MCR-based COF synthesis strategies by introducing a multicomponent pathway to highly ordered crystalline frameworks without the need for step-by-step linkage construction. The resulting s-Betti-COF exhibits a distinct hollow spherical morphology, high thermal stability, and robust porosity. This framework provides ideal support for the immobilization of small palladium nanoparticles (1-2 nm) within its pores to form the s-Betti-COF nanocomposite. The prepared samples were characterized by FT-IR, DNP-enhanced 13C CP-MAS NMR, DNP-enhanced 15N CP-MAS NMR, XRD, HR-TEM, FE-SEM, EDS, XPS, and nitrogen physisorption analysis. Kinetic investigations, including Hammett analysis, support a reaction mechanism involving an anionic intermediate. This study introduces the Betti reaction as a synthetic tool for constructing functional COFs and establishes these materials as highly effective nanoreactors for heterogeneous catalysis.

Hydrogen sulfide sensors are censoriously important for environmental monitoring, industrial safety, and biomedical applications due to the highly toxic and corrosive nature of H2S gas. We report indium sulfide (In2S3) flakes were grown via chemical vapor deposition (CVD) and functionalized with palladium (Pd) nanoparticles(NPs) to develop a high-performance chemiresistive H2S gas sensor. The pristine In2S3 flakes have a porous microstructure with abundance of active sites, however the addition of Pd NPs improves the gas sensing response through enhancing charge transfer interactions along with providing catalytic spillover sites. The Pd-functionalized In2S3 sensor demonstrated a increase in respone (1.4-fold) and selectivity towards H2S, attaining a sensing response of approximately 67.60% at 50 ppm concentration at 75 oC. The sensor demonstrated rapid kinetics with response and recovery times of 48 s and 260 s, respectively, and a remarkably low limit of detection (LOD) of 59 ppb. Furthermore, the sensor confirmed high humidity tolerance up to 80% RH and excellent repeatability. Density functional theory (DFT) calculations discovered an 8-fold increase in adsorption energy (-1.51 eV) and significant charge transfer (-0.086 e-) upon Pd decoration, correlating the electronic sensitization of the Schottky barrier to the observed ppb-level sensitivity. With the use of first-principles calculations that explain the underlying sensing process, this work presents a practical strategy to develop efficient H2S gas sensors through the use of CVD-grown sulfide semiconductors with decoration of noble metal nanoparticles.

Rechargeable Li-CO2 batteries are attractive for next-generation energy storage owing to their high theoretical energy density and capability for CO2 utilization. However, their practical application is hindered by sluggish reaction kinetics, large polarization, and poor cycling stability associated with the reversible formation and decomposition of Li2CO3. Herein, we report a free-standing cathode consisting of palladium nanoparticles uniformly anchored on copper (Pd NPs@Cu) foam, fabricated via a facile one-step galvanic displacement-assisted deposition strategy. The three-dimensional porous architecture combined with highly dispersed Pd nanocatalysts enables enhanced catalytic activity and mass transport, thereby effectively accelerating both CO2 reduction and evolution reactions. The Pd NPs@Cu foam composite delivers a high discharge capacity exceeding 15,000 mAh g-1, excellent rate capability (up to 2000 mA g-1), and outstanding cycling stability with an ultralow overpotential of ∼0.36 V over 160 cycles (1600 h) at 25 °C and 200 mA g-1. Even at the high current density of 1000 mA g-1, stable cycling over 141 cycles is achieved with a low overpotential of ∼0.6 V. Notably, the system demonstrates robust low-temperature performance, sustaining 64 cycles at 0 °C (250 mA g-1) with charge potentials below 4.0 V in the conventional ether-based electrolyte without any additives. Mechanistic investigations combining in situ electrochemical impedance spectroscopy coupled with distribution of relaxation times (in situ EIS-DRT) analysis and ex situ structural characterizations (SEM, XRD, FTIR, and XPS) confirm the highly reversible formation and decomposition of Li2CO3 and reveal that charge-transfer processes dominate the reaction kinetics. Density functional theory (DFT) calculations further demonstrate that Pd incorporation significantly strengthens the adsorption of key intermediate *LiCO3, thereby lowering the reaction energy barriers and overall polarization along the four-electron pathway. These findings highlight the synergistic effect of Pd nanocatalysts and conductive porous Cu foam framework in promoting efficient and reversible CO2/Li2CO3 conversion.

Palladium nanoparticles in lung cancer: Emerging strategies for diagnosis and therapeutic intervention.

Peroxydisulfate (PDS) is widely used as a coreactant in nanomaterial-based electrochemiluminescence (ECL) systems because its activation produces highly oxidative sulfate radical intermediates (SO4•-). However, the symmetrical structure of PDS results in a high activation energy for the cleavage of its O-O bond. This necessitates highly negative cathodic potentials, triggering competing hydrogen evolution reactions (HER) and reducing ECL efficiency. In this study, we exploit the dual functionality of carbon nitride-supported palladium single atoms (PdSA) and nanoparticles (PdNP) for hydrogen-mediated PDS activation. PdNP supply reactive hydrogen species (H*) through electrocatalytic water reduction, while neighboring PdSA sites simultaneously adsorb and activate PDS. The breaking of O-O bonds in PDS is achieved through the interaction of these migrating H* intermediates. The experimental results and theoretical calculations demonstrate that this H*-involved synergistic effect facilitates the activation of PDS, leading to an approximately 2.58-fold enhancement in the ECL intensity of CN-PdSA+NP compared to pristine CN. Furthermore, the constructed ECL sensing platform exhibits remarkable sensitivity for glutathione S-transferase detection. This work provides valuable insights into the H*-mediated coreactant activation mechanism and bridges the gap between HER and ECL.

This review provides a comparative assessment of the synthesis, better network selection, catalytic applications, and stabilization of silver, gold, palladium, nickel, and cobalt nanoparticles. It focuses particularly on nickel and cobalt, which exhibit high surface energies and tend to aggregate due to van der Waals forces and magnetic dipole–dipole interactions. This aggregation presents a significant challenge for stabilization. Magnetic nickel nanoparticles are particularly susceptible to surface oxidation; therefore, most synthesis protocols utilize organic media and hydrophobic capping agents to prevent agglomeration and oxidation. While cobalt nanoparticles hold promise for magnetic and catalytic applications, they exhibit poor stability against oxidation and hydrolysis, which limits their use in catalytic contexts. The electronic properties also contribute to the stability challenges faced by these five nanoparticles. We review various synthesis methods, including chemical, biological, and green approaches, as well as stabilization strategies such as surfactant capping, confinement within metal-organic frameworks or covalent frameworks, and polymeric gels. Additionally, we summarize advanced characterization techniques and propose a data-driven framework that combines density functional theory, materials databases, and machine learning to predict synthesis parameters and surface modifications. This review highlights that when properly stabilized, nickel and cobalt nanoparticles can serve as cost-effective alternatives to noble metals, providing high catalytic efficiencies in reactions such as the reduction of nitro compounds and the degradation of dyes. By comparing noble and base metal nanoparticles and highlighting the underexplored systems of nickel and cobalt, we provide mechanistic insights and design principles that will facilitate the rational development of durable catalysts for environmental remediation and energy conversion.

This study introduces an electrochemical aptasensor for the sensitive determination of the breast cancer biomarker, carbohydrate antigen 15-3 (CA 15-3). The aptasensor was fabricated by modifying a glassy carbon electrode (GCE) with carbon nanofibers (CNFs) and electrodepositing palladium nanoparticles (PdNPs) on it. CNFs provide a large surface area and active sites for the subsequent electrodeposition of PdNPs. Moreover, PdNPs provide binding sites for attachment of aptamers through coordinate bonds between Pd and amino groups. The fabrication process was monitored using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The assay is based on the difference in charge transfer resistance (Rct) before and after CA 15-3 binding. Using the EIS technique, a linear concentration range of 1.0 × 10-2 - 200.0 U mL⁻1 and a detection limit of 7.8 × 10-3 U mL⁻1 were obtained for CA 15-3. Furthermore, its clinical utility was confirmed through successful analysis of human serum samples, with results correlating well with the standard ELISA method.

Metallic nanocatalysts such as palladium nanoparticles (Pd-NPs) possess remarkable catalytic activity owing to their high surface-to-volume ratio; however, aggregation and metal leaching significantly compromise their stability and practical applicability. In this work, we report a facile and sustainable biosynthetic route for the preparation of bio-stabilized Pd-NPs using the fungal strain Aspergillus trinidadensis VM ST01 (OL587588) as a green reducing and capping agent. The strategy enables simultaneous bio-reduction of Pd2+ ions, nucleation and in situ surface functionalization without the use of hazardous chemicals, surfactants, buffer, or external stabilizers. The influence of culture age (24–54 h), biomass loading (0.08–0.24 g mL−1), and incubation time (8–24 h) on NP formation was systematically investigated to achieve controlled synthesis. Comprehensive physicochemical characterization (UV-vis, FT-IR, XRD, SEM, TEM, elemental mapping, EDX, XPS, and TGA) confirmed the formation of uniformly distributed Pd-NPs with an average size of ∼35 nm, embedded and stabilized within the fungal biomass matrix. The bio-organic framework surrounding the nanoparticles effectively suppresses aggregation and minimizes palladium leaching, thereby enhancing catalyst durability. The catalytic performance of the biosynthesized AtPdNPs was evaluated for the hydrogenation of nitro-benzene (NB) to amino-benzene (AB) as a model reaction under mild and aqueous conditions (NaBH4, ambient temperature and ambient pressure). The optimized catalyst (0.16 g mL−1 biomass, 36 h of culture age, and 24 h of incubation) achieved complete conversion within 30 min, delivering a turnover frequency (TOF) of 832 h−1 and a turnover number (TON) of 416. The kinetics for the reduction of NB to AB was investigated, and the catalytic activity of AtPdNPs was evaluated as the pseudo-first-order rate constant (kapp). The in situ bio-coating of AtPdNPs significantly reduces palladium leaching (<1.5% ppm), enhances storage stability and makes it an environmentally compatible material. As a result, the catalyst maintains its structural integrity and catalytic performance under industry relevant conditions.

Converting polyethylene to liquid fuels requires Brønsted acidity, yet conventional acidic zeolites suffer from rapid coking and excessive gas formation. Despite Na-exchanged zeolites are well-known to resist coking in many cracking reactions, they are generally considered catalytically inert for polyethylene cracking due to absent acidity. Here, we show that encapsulated palladium nanoparticles in Na-ZSM-5 catalyze efficient polyethylene hydroconversion to C5-C9 alkanes with minimal gas yield and negligible coke formation. Mechanistic studies reveal that dihydrogen undergoes heterolytic dissociation at the confined Pd-zeolite interface, concurrently generating PdH hydrides and bridging hydroxyl groups that function as Brønsted acid sites. These dynamically created acid centers drive selective C─C bond scission via classical β-scission pathways while circumventing the deleterious side reactions. This study establishes a general paradigm for adaptive catalysis wherein active sites are created in situ within otherwise non-acidic frameworks, offering new strategies for selective bond activation.

A plasmonic nanocomposite composed of gold and palladium nanoparticles, in conjunction with a BODIPY chromophore, was synthesized and explored as an efficient photocatalyst for Suzuki coupling reactions. The unique plasmon-molecule interactions arising from the electronic coupling between gold nanoparticles and the BODIPY chromophore, along with the well-established catalytic activity of palladium, greatly enhance the catalytic efficiency of this nanocomposite. Moreover, their synergistic effect enabled the transformation to proceed under mild, environmentally benign reaction conditions, offering a promising approach for sustainable, energy-efficient catalytic processes.

Although palladium nanoparticles (PdNPs) are widely applied in catalytic, environmental, and biomedical contexts, the ecotoxicological and biosafety implications of biosynthesized PdNPs remain insufficiently characterized. In this study, PdNPs were synthesized using aqueous leaf extract of Dalbergia sissoo (DS-PdNPs). UV-Visible spectroscopy confirmed the reduction of PdCl2 to Pd0, while FTIR analysis indicated biomolecules involved in the bio-reduction and stabilization of DS-PdNPs. TEM revealed an average particle size of 7.5 nm, and P-XRD confirmed the face-centered cubic (FCC) lattice structure. EDX indicated the elemental composition, and zeta potential measurements demonstrated good colloidal stability (-25 mV) of DS-PdNPs. The synthesized DS-PdNPs were evaluated for ecotoxicity and biosafety in Allium cepa (onion bulb) roots, Bacillus subtilis soil bacteria, and human keratinocyte (HaCaT) cells at concentrations of 1, 50, 100, 250, and 500 μg/mL. A dose-dependent response was observed, with A. cepa showing increased root growth inhibition after 3 days (84.37%), a decline in mitotic index (MI) of 66%, and elevated malondialdehyde (MDA) content (5.1 ± 0.14 nmol g-1 FW). Conversely, HaCaT cells exhibited moderate cytotoxicity with an IC50 value of 261 μg/mL and 49.4% cell viability, while the bacterial assay showed a low toxicity profile characterized by a minimal zone of inhibition (7 ± 0.0 mm) at 500 μg/mL. These findings indicate the varied toxicity of DS-PdNPs across different test systems, highlighting their selective biological interactions and the need for careful evaluation of their overall environmental impact.

Nonvolatile glycerol derivatives are employed as effective reaction media for the Pd-catalysed direct CH arylation of 3,4-ethylenedioxythiophene and other thiophenes. The thoughtful design of noninnocent glycerol-derived ionic liquids (ILs) allows them to act simultaneously both as solvent and base, eliminating the need for an additional base and thus improving the sustainability of the process. Moreover, the stabilization of palladium nanoparticles in the task-specific solvent offers an excellent approach by providing the advantages of a homogeneous, selective, and recoverable catalytic system. This multifunctional behaviour highlights the potential of glycerol-derived ILs as sustainable solvents and promoters for transition metal-catalysed CH activation reactions.

Breast cancer bone metastasis is a common and devastating complication among patients with advanced breast cancer, marked by aggressive tumor growth and extensive osteolytic destruction. Effective treatment requires simultaneous elimination of tumor cells and restoration of bone tissue. To address this challenge, we developed a bone-targeting nanomaterial, CPPA NPs, composed of a polydopamine-coated calcium peroxide core embedded with palladium nanoparticles, and functionalized with phytic acid for bone affinity. This design integrates calcification and photothermal activity to achieve synergistic tumor inhibition and bone repair. Within the acidic tumor microenvironment, CPPA NPs release Ca2+ and H2O2, triggering mitochondrial calcium overload and oxidative stress in cancer cells. In the presence of exogenous phosphate, this process drives extensive tumor cell calcification, substantially reducing cell viability. Under 808 nm laser irradiation, the photothermal effect accelerates Ca2+ and H2O2 release, further enhancing calcification and inducing widespread tumor cell death. Laser treatment promotes osteoblast differentiation, supporting bone regeneration. In a murine breast cancer bone metastasis model, the combined calcification-photothermal therapy markedly suppressed tumor burden, mitigated osteolytic lesions, and promoted new bone formation. Together, these findings establish CPPA NPs as a promising therapeutic platform capable of integrating potent antitumor efficacy with osteogenic regeneration, offering a dual-functional strategy for the treatment of breast cancer bone metastasis.

Bone cancer is an uncommon type of malignant tumor that begins in bone tissue and can destroy normal bone structure or develop as metastases from another malignancy. At 30% of all bone cancer cases, osteosarcoma is the most typical primary malignant bone cancer. It frequently appears in the metaphyses of adolescent long bones, which have the most capacity for growth. Therefore, the recent study aims to synthesize safer phytoconstituent mediated- palladium nanoparticles (PdNPs) utilizing aqueous leaves extract of Psidium guajava (PGLE) and for insight into the produced nanoparticles' therapeutic impacts on the pathways that inhibit MG-63 cancer cell lines. The obtained PdNPs displayed amorphous spherical morphology with an average diameter of 4.72±1.616nm and a zeta potential value of -14.8 mV. The extract-suspended palladium nanoparticles (PdNPs-PGLE) exhibited a lower IC50 value of (89.81 ± 0.32 µg/ml) and had a superior cytotoxic effect towards MG-63 cell growth compared to the PGLE (110.65 ± 1.07µg/ml) and PdNPs (198.22 ± 0.24µg/ml) samples. It was shown that (PdNPs-PGLE) increased significantly the % of total apoptotic cells compared to PGLE and PdNPs with higher intensity comet nucleus in treated cells compared to control cells. It is shown that there was an arrest in the S cell cycle phase in MG-63-treated cells. The PdNPs-PGLE had a significant decrease in wound closure % (45.21) compared to control untreated cells (58.78). Furthermore, the PdNPs-PGLE severely suppresses the capacity of MG-63 of colony formation, with a plating efficiency of 0.9% and a surviving fraction of 0.009, compared to control cells. Additionally, the estimation of the expression of protein levels using the ELISA technique revealed that there was an increase in the Bax, cleaved active Caspase-3, and TP53 expression levels with a decrease in the Bcl-2, CDK2, MMP-2, and MMP-9 expression in the PdNPs-PGLE-treated cells compared to control cells (p < 0.05) .These findings point out the potential of Psidium guajava-mediated green synthesis not only as an eco-friendly route for nanoparticle fabrication but also as a means to harness phytochemical-nanomaterial synergy.

In light of increasing population pressures, constrained natural resources and escalating energy requirements, the advancement of energy research and pharmaceutical development has become urgent. In this regard, we employed an ionothermal method to synthesize a covalent triazine framework (CTF) using 2,3,6,7-tetra(4-cyanophenyl)tetrathiafulvalene (TTFCN) and ZnCl2 (1 : 10 molar ratio) at 400 °C. Subsequently, a palladium ion or palladium nanoparticle (Pd-NP) supported CTF material, named CTFTTF@Pd, was prepared through an in situ process in the absence of any reducing agent. The synthesized CTFTTF@Pd was characterized using FTIR, PXRD, X-ray photoelectron spectroscopy (XPS), SEM, TEM, and N2 sorption measurements. The presence of C, N, S and Pd was confirmed by XPS analysis. TEM analysis confirmed the uniform distribution of Pd(II) and Pd(0) sites within CTFTTF@Pd, with an average particle size of approximately 8 nm. The catalyst CTFTTF@Pd exhibited superior efficiency and reusability in Suzuki-Miyaura cross-coupling reactions. The small Pd-NPs in CTFTTF@Pd enhanced the surface-active site density, driving superior catalytic activity. In addition, the electrocatalytic hydrogen evolution performance of the catalyst in alkaline media was investigated, and it was found to exhibit excellent long-term cycling stability. This work highlights the potential of S,N-containing carbon materials to generate catalytically active metal ions without the use of reducing agents, offering a strategy for designing recyclable catalysts for efficient chemical and energy production.

Structure-controlled sulfur poisoning and hydrogen-induced regeneration in single Pd nanoparticles probed by nanospectroscopy.

Corrigendum to ‘Enhancement the electrical conductivity of the synthesized polyvinylidene fluoride/polyvinyl chloride composite doped with palladium nanoparticles via laser ablation’ [J Mater Res Technol 9 (5) (2020) 11178-11188