Biogenic Palladium Improved Perchlorate Reduction during Nitrate Co-Reduction by Diverting Electron Flow in a Hydrogenotrophic Biofilm.

Microbial reduction of perchlorate (ClO4-) is emerging as a cost-effective strategy for groundwater remediation. However, the effectiveness of perchlorate reduction can be suppressed by the common co-contamination of nitrate (NO3-). We propose a means to overcome the limitation of ClO4- reduction: depositing palladium nanoparticles (Pd0NPs) within the matrix of a hydrogenotrophic biofilm. Two H2-based membrane biofilm reactors (MBfRs) were operated in parallel in long-term continuous and batch modes: one system had only a biofilm (bio-MBfR), while the other incorporated biogenic Pd0NPs in the biofilm matrix (bioPd-MBfR). For long-term co-reduction, bioPd-MBfR had a distinct advantage of oxyanion reduction fluxes, and it particularly alleviated the competitive advantage of NO3- reduction over ClO4- reduction. Batch tests also demonstrated that bioPd-MBfR gave more rapid reduction rates for ClO4- and ClO3- compared to those of bio-MBfR. Both biofilm communities were dominated by bacteria known to be perchlorate and nitrate reducers. Functional-gene abundances reflecting the intracellular electron flow from H2 to NADH to the reductases were supplanted by extracellular electron flow with the addition of Pd0NPs.

Bidirectional hybridized hairpin DNA fluorescent aptasensor based on Au-Pd NPs and CDs for ratiometric detection of AFB1.

A novel and simple ratiometric fluorescent aptasensor was developed for the sensitive detection of aflatoxin B1 (AFB1). A hairpin DNA (h-DNA) was independently synthesized as the basic skeleton, and the bidirectional hybridization of h-DNA can increase the load of aptamer and signal probes, thereby realizing signal amplification. The high-efficiency fluorescence resonance energy transfer interaction between gold-palladium nanoparticles (Au-Pd NPs) and the self-synthesized fluorescent probe carbon dots (CDs) was utilized. Moreover, the label-free probe SYBR Green I (SG I) dye was introduced to form a double-signal probe with CDs, and a ratiometric sensor with FCDs/FSG I as a response signal was constructed. The ratio strategy can eliminate the fluctuation of external factors, thus improving the accuracy and reliability of the sensor. The quenching effect of Au-Pd NPs on CDs was 1.4 times that of AuNPs and 3.4 times that of Pd NPs, respectively. In the range 1-100 ng/mL, FCDs/FSG I showed a good linear relationship with the logarithm of the concentration of AFB1, and the limit of detection was as low as 0.07 ng/mL. The sensor was used to detect AFB1 in spiked peanuts and wine samples, and the recovery was between 91 and 115%, indicating that the sensor has high application potential in real sample analysis.

Fluorescence/electrochemical dual-mode strategy for Golgi protein 73 detection based on molybdenum disulfide/ferrocene/palladium nanoparticles and nitrogen-doped graphene quantum dots.

Golgi protein 73 (GP73) is a new serum marker associated with early diagnosis and postoperative assessment of hepatocellular carcinoma (HCC). Herein, an electrochemical/fluorescence dual-signal biosensor was designed for determination of GP73 based on molybdenum disulfide/ferrocene/palladium nanoparticles (MoS2-Fc-PdNPs) and nitrogen-doped graphene quantum dots (NGQDs). GP73 aptamer (Apt) was labeled with NGQDs to form the NGQDs-Apt fluorescence probe. MoS2-Fc-PdNPs served not only as the fluorescence quencher but also as electrochemical enhancer. The sensing platform (NGQDs-Apt/MoS2-Fc-PdNPs) was formed based on the fluorescence resonance energy transfer (FRET) mechanism. In the presence of GP73, the specific binding of NGQDs-Apt to GP73 interrupted FRET, restoring the fluorescence of NGQDs-Apt at λex/em = 348/438 nm and enhancing the oxidation current of Fc in MoS2-Fc-PdNPs at 0.04 V through differential pulse voltammetry (DPV). Under the optimal conditions, the DPV current change and fluorescence recovery have a good linear relationship with GP73 concentration from 1.00 to 10.0 ng/mL. The calibration equation for the fluorescence mode was Y1 = (0.0213 ± 0.00127)X + (0.0641 ± 0.00448) and LOD was 0.812 ng/mL (S/N = 3). The calibration equation of the electrochemical mode was Y2 = (3.41 ± 0.111)X + (1.62 ± 0.731), and LOD of 0.0425 ng/mL (S/N = 3). The RSDs of fluorescence mode and electrochemical mode after serum detection were 1.62 to 5.21% and 0.180 to 6.62%, respectively. By combining the electrochemical and fluorescence assay, more comprehensive and valuable information for GP73 was provided. Such dual-mode detection platform shows excellent reproducibility, stability, and selectivity and has great application potential.

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 Ligand-Free Approach towards Coumarin Analogs via Natural Deep Eutectic Solvent-Mediated Suzuki-Miyaura Coupling.

A ligand-free approach for the Suzuki-Miyaura cross coupling reaction using Natural Deep Eutectic Solvents (NaDES) towards coumarin analogs is described. A model reaction between the synthetically prepared 3-(4-acetyloxy-phenyl)-6-bromo-4-methyl-coumarin (3b) and phenylboronic acid was performed in five different NaDES as well as in pure glycerol, using two inorganic bases and palladium catalysts. The reaction proceeded smoothly in Choline Chloride/Glycerol (ChCl/Gly) and Betaine/Glycerol (Bet/Gly) NaDES at 90 °C in 24 h, affording the desired product in high yields up to 95%. The combination of K2CO3, Pd(OAc)2 and ChCl/Gly NaDES provided optimum yields and high purity of the desired compounds, while the solvent was successfully recycled and reused up to two times. The developed methodology is applicable to boronic acids bearing various substituents. The formation of palladium nanoparticles in the reaction mixture was observed, and the size of the nanoparticles was associated with the reaction yield. In addition, in all the glycerol-based NaDES, an effective removal of the acetyl group of the acetyloxy-coumarin analogs was observed; thus, it is noteworthy that the Suzuki-Miyaura coupling and the deacetylation reaction were achieved in one pot. The ten novel coumarin derivatives synthesized were structurally characterized using 1D and 2D NMR spectroscopy and were tested for their cytotoxicity against the A431 squamous cancer cell line, presenting significant activity.

Fungus mediated synthesis of biogenic palladium catalyst for degradation of azo dye.

Dyes are the coloured substances that are applied on different substrates such as textiles, leather and paper products, etc. Azo dyes release from the industries are toxic and recalcitrant wastewater pollutants, therefore it is necessary to degrade these pollutants from water. In this study, the palladium (0) nanoparticles (PdNPs) were generated through the biological process and exhibited for the catalytic degradation of azo dye. The palladium nanoparticles (PdNPs) were synthesized by using the cell-free approach i.e. extract of fungal strain Rhizopus sp. (SG-01), which significantly degrade the azo dye (methyl orange). The amount of catalyst was optimized by varying the concentration of PdNPs (1 mg/mL to 4 mg/mL) for 10 mL of 50 ppm methyl orange (MO) dye separately. The time dependent study demonstrates the biogenic PdNPs could effectively degrade the methyl orange dye up to 98.7% with minimum concentration (3 mg/mL) of PdNPs within 24 h of reaction. The long-term stability and effective catalytic potential up to five repeated cycles of biogenic PdNPs have good significance for acceleration the degradation of azo dyes. Thus, the use of biogenic palladium nanoparticles for dye degradation as outlined in the present study can provide an alternative and economical method for the synthesis of PdNPs as well as degradation of azo dyes present in wastewater and is helpful to efficiently remediate textile effluent.

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.

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.

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.

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.

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

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

Synthesis and characterization of activated carbon supported bimetallic Pd based nanoparticles and their sensor and antibacterial investigation.

Activated carbon (AC) supported palladium cobalt bimetallic nanoparticles (PdCo@AC NPs) were obtained by green synthesis method using Cinnamomum verum (C. Verum) extract. The obtained NPs were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Crystallography (XRD), Transmission Electron Microscope (TEM) and Ultraviolet Visible (UV-VIS) spectroscopy, and the functional groups and morphology of the nanoparticle were elucidated. The resulting particle size was found to be 2.467 nm. NPs were evaluated using Cyclic Voltammetry (CV), Scan Rate (SR), and Differential Pulse Voltammetry (DPV) techniques for potential dopamine sensors application. According to the obtained DPV results, Limit of Detection (LOD) and Limit of Quantitation (LOQ) values are found to be 5.68 pM and 17.21 pM, respectively. It was also observed that AC supported PdCo nanoparticles obtained from C. verum extract sensed dopamine quite well. Besides, to examine the antibacterial properties of NPs, antibacterial analyzes were performed with Escherichia coli (E. Coli) and Staphylococcus aureus (S. Aureus). It was observed that it showed good antibacterial properties against gram positive (S. aureus) and gram negative (E. coli) bacteria. The study gave important results in terms of the synthesis of bimetallic NPs using the green synthesis method and their usability in different areas. With this study, it was observed that a good antibacterial dopamine sensor were obtained with the successful biogenic synthesis of AC supported PdCo bimetallic NPs.

Characterization, catalytic, and recyclability studies of nano-sized spherical palladium particles synthesized using aqueous poly-extract (turmeric, neem, and tulasi).

Green synthesis of noble metal nanoparticles (NPs) has gained immense significance compared to other metal ions owing to their unique properties. Among them, palladium 'Pd' has been in the spotlight for its stable and superior catalytic activity. This work focuses on the synthesis of Pd NPs using the combined aqueous extract (poly-extract) of turmeric (rhizome), neem (leaves), and tulasi (leaves). The bio-synthesized Pd NPs were characterized to study its physicochemical and morphological features using several analytical techniques. Role of Pd NPs as nano-catalysts in the degradation of dyes (1 mg/2 mL stock solution) was evaluated in the presence of a strong reducing agent (sodium borohydride; SBH). In the presence of Pd NPs and SBH, maximum reduction of methylene blue (MB), methyl orange (MO), and rhodamine-B (Rh-B) dyes was observed under 20nullmin (96.55 ± 2.11%), 36nullmin (96.96 ± 2.24%), and 27nullmin (98.12 ± 1.33%), with degradation rate of 0.1789 ± 0.0273 min-1, 0.0926 ± 0.0102 min-1, and 0.1557 ± 0.0200 min-1, respectively. In combination of dyes (MB + MO + Rh-B), maximum degradation was observed under 50nullmin (95.49 ± 2.56%) with degradation rate of 0.0694 ± 0.0087 min-1. It was observed that degradation was following pseudo-first order reaction kinetics. Furthermore, Pd NPs showed good recyclability up to cycle 5 (72.88 ± 2.32%), cycle 9 (69.11 ± 2.19%) and cycle 6 (66.21 ± 2.72%) for MB, MO and Rh-B dyes, respectively. Whereas, up to cycle 4 (74.67 ± 0.66%) during combination of dyes. As Pd NPs showed good recyclability, they can be used for several cycles thus influencing the overall economics of the process.

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.

Theoretical and experimental study on the photothermal effect of palladium nanoparticles based on a finite element model.

Palladium nanoparticles (Pd NPs) show significant promise as agents for the photothermal treatment of tumors due to their high photothermal conversion efficiency and thermal stability. theoretical calculations were conducted to investigate the electric field and solid heat conduction of Pd NPs with various sizes and particle distances, aiming to achieve the maximum photothermal conversion efficiency during laser irradiation. Subsequently, Pd NPs with optimal size and structure were synthesized. In vitro and in vivo experiments were conducted to evaluate photothermal conversion. The theoretical results indicated that a peak temperature of 90.12 °C is achieved when the side length is 30 nm with a distance of 2 nm. In vitro experiments demonstrated that the photothermal conversion efficiency of Pd NPs can reach up to 61.9%. in vivo experiments revealed that injecting Pd NPs into blood vessels can effectively reduce the number of laser pulses by 22.22%, thereby inducing obvious vasoconstriction.

An electrochemical biosensor for T4 polynucleotide kinase activity identification according to host-guest recognition among phosphate pillar[5]arene@palladium nanoparticles@reduced graphene oxide nanocomposite and toluidine blue.

T4 polynucleotide kinase (T4 PNK) helps with DNA recombination and repair. In this work, a phosphate pillar[5]arene@palladium nanoparticles@reduced graphene oxide nanocomposite (PP5@PdNPs@rGO)-based electrochemical biosensor was created to identify T4 PNK activities. The PP5 used to complex toluidine blue (TB) guest molecules is water-soluble. With T4 PNK and ATP, the substrate DNA, which included a 5'-hydroxyl group, initially self-assembled over the gold electrode surface by chemical adsorption of the thiol units. Strong phosphate-Zr4+-phosphate chemistry allowed Zr4+ to act as a bridge between phosphorylated DNA and PP5@PdNPs@rGO. Through a supramolecular host-guest recognition connection, TB molecules were able to penetrate the PP5 cavity, where they produced a stronger electrochemical response. With a 5 × 10-7 U mL-1 detection limit, the electrochemical signal is linear in the 10-6 to 1 U mL-1 T4 PNK concentration range. It was also effective in measuring HeLa cell lysate-related PNK activities and screening PNK inhibitors. Nucleotide kinase-target drug development, clinical diagnostics, and screening for inhibitors all stand to benefit greatly from the suggested technology, which offers a unique sensing mechanism for kinase activity measurement.

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.

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.

Electrochemically assisted production of biogenic palladium nanoparticles for the catalytic removal of micropollutants in wastewater treatment plants effluent.

Biogenic palladium nanoparticles (bio-Pd NPs) are used for the reductive transformation and/or dehalogenation of persistent micropollutants. In this work, H2 (electron donor) was produced in situ by an electrochemical cell, permitting steered production of differently sized bio-Pd NPs. The catalytic activity was first assessed by the degradation of methyl orange. The NPs showing the highest catalytic activity were selected for the removal of micropollutants from secondary treated municipal wastewater. The synthesis at different H2 flow rates (0.310 L/hr or 0.646 L/hr) influenced the bio-Pd NPs size. The NPs produced over 6 hr at a low H2 flow rate had a larger size (D50 = 39.0 nm) than those produced in 3 hr at a high H2 flow rate (D50 = 23.2 nm). Removal of 92.1% and 44.3% of methyl orange was obtained after 30 min for the NPs with sizes of 39.0 nm and 23.2 nm, respectively. Bio-Pd NPs of 39.0 nm were used to treat micropollutants present in secondary treated municipal wastewater at concentrations ranging from µg/L to ng/L. Effective removal of 8 compounds was observed: ibuprofen (69.5%) < sulfamethoxazole (80.6%) < naproxen (81.4%) < furosemide (89.7%) < citalopram (91.7%) < diclofenac (91.9%) < atorvastatin (> 94.3%) < lorazepam (97.2%). Removal of fluorinated antibiotics occurred at > 90% efficiency. Overall, these data indicate that the size, and thus the catalytic activity of the NPs can be steered and that the removal of challenging micropollutants at environmentally relevant concentrations can be achieved through the use of bio-Pd NPs.

Fabrication of rGO/MXene-Pd/rGO hierarchical framework as high-performance electrochemical sensing platform for luteolin detection.

A  nanocomposite of rGO/MXene-Pd/rGO with hierarchical structure based on Ti3C2Tx MXene, Pd nanoparticles, and reduced graphene oxide (rGO) was synthesized by a green approach. Ti3C2Tx MXene decorated with Pd nanoparticles (MXene-Pd) was prepared first. Then, graphene oxide (GO), MXene-Pd, and GO were coated on the surface of the glassy carbon electrode (GCE) in sequence. After each coating of the GO layer, the GO nanosheets were reduced to rGO electrochemically. The fabricated rGO/MXene-Pd/rGO hierarchical framework performs a pie structure with MXene-Pd as the stuffing and rGO nanosheets as the crust, which will be beneficial to the enhancement of its electrochemical sensing performance. As compared with other electrodes, the rGO/MXene-Pd/rGO/GCE exhibited higher electrocatalytic activity and better sensing performance for luteolin detection, with a wide linear range of 6.0 × 10-10 to 8 × 10-7 M and 1.0 × 10-6 to 1.0 × 10-5 M (oxidation peak potential Epa = 0.34 V vs. SCE), a low detection limit of 2.0 × 10-10 M, and a high sensitivity of 112.72 µA µM-1 cm-2. Moreover, the fabricated sensor also showed high selectivity, reproducibility, and repeatability toward the detection of luteolin. The real sample analysis for luteolin in honeysuckle was successfully carried out by rGO/MXene-Pd/rGO and verified with high-performance liquid chromatography (HPLC) analysis techniques with acceptable results. All the above tests indicate the promising application prospect of the rGO/MXene-Pd/rGO framework for luteolin detection in honeysuckle and other herbs containing luteolin.