Insight into Surface Electronic Effects on Pd Nanostructures as Efficient Electrocatalysts

Lectin-Mediated Labeling of Alkaline Phosphatase for Enzymatic Silver Deposition-Based Electrochemical Detection of Glycoprotein Tumor Markers

The screening of glycoprotein markers has become an integral part of the in vitro diagnosis of malignant tumors. Herein, an electrochemical method based on alkaline phosphatase (ALP)-mediated enzymatic silver deposition is reported for the highly sensitive detection of glycoprotein tumor markers, in which ALP enzymes are decorated to the glycan moieties of targets via the lectin-carbohydrate interactions. As glycoproteins are conjugated with multiple glycan chains, lectin-mediated labeling can result in the decoration of each target with multiple ALP enzymes. Moreover, the enzymatic hydrolysis of ascorbic acid 2-phosphate into ascorbic acid can result in the deposition of a high density of silver particles, which can then be sensitively assayed via the robust Ag/AgCl solid-state voltammetric process. As a result, the enzymatic silver deposition-based electrochemical method exhibits high sensitivity. Using the aptamer-based electrochemical detection of the breast cancer-associated glycoprotein CA15-3 as a proof of concept, a detection limit of 0.32 mU/mL has been demonstrated. Results show that the synergism of the aptamer-based capture and the glycoform-specific discrimination capability of the lectin-carbohydrate interactions can endow this method with high selectivity, and its practical use in the assay of CA15-3 levels in serum samples has been illustrated. With benefits from the high efficiency, mild reaction conditions, and user-friendly operation, the lectin-mediated labeling of ALP enzymes for enzymatic silver deposition is highly applicable to the electrochemical detection of low-abundance glycoprotein tumor markers.

Etched CoFe Prussian blue analog nanozymes with superior peroxidase activity for colorimetric biosensing of hydrogen peroxide and dopamine

Nanozymes represent a compelling alternative to natural enzymes due to their exceptional stability and cost-efficiency in diagnostic and therapeutic applications. In this work, a nanozyme etched CoFe Prussian blue analog (etched PBA) was designed and fabricated by a simple approach involving first synthesizing CoFe PBA and then chemical etching. The fabricated etched PBA acts as a peroxidase mimic catalyst. Compared to the naturally occurring enzyme (horseradish peroxidase), the etched PBA exhibited improved peroxidase-like catalytic efficiency for oxidizing 3,3',5,5'-tetramethylbnmenzidine (TMB). Particularly, the exceptional peroxidase-like activity of the etched PBA is attributed to modifications in its electronic and structural properties, which improved affinity for hydrogen peroxide (H2O2) and TMB. Hence, these findings highlight etched PBA as a promising peroxidase mimic, enabling a colorimetric assay for real-time H2O2 and dopamine (DA) detection. H2O2 was detected via PBA-catalyzed TMB oxidation (bluish-green color), while DA monitoring occurred through ox-TMB reduction. The detection thresholds for H2O2 and DA were determined to be 0.083 μM and 0.05 μM, respectively, with broad linear ranges of 0.1 μM - 4.0 mM for H2O2 and 0.1-240 μM for DA. In addition, the etched PBA was validated for real sample analysis, showing potential for enzyme catalysis, biosensing, and colorimetric analysis of pharmaceuticals and biomolecules.

Octahedral vs Tiara-like Pd6(SR)12 Clusters

Atomically precise Pd-thiolate clusters are well-known for their well-defined structures and diverse applications involving catalysis, sensors, and biomedicine. While many of these clusters have been studied, their molecular structures typically feature a tiara-like arrangement. In this study, we present the first example of a non-tiara-like Pd-thiolate cluster: the octahedral Pd6(SC6H11)12 (denoted as Pd6-Oct). The composition and geometric structure of the cluster were characterized using electrospray ionization mass spectrometry (ESI-MS) together with single-crystal X-ray diffraction (SXRD). Despite having a similar chemical composition to tiara-like Pd6(SC2H4Ph)12 (denoted as Pd6-Tia), Pd6-Oct exhibits a distinctly different geometric structure. Additionally, UV-vis-NIR absorption spectroscopy combined with quantum chemical calculations provided valuable insights into the electronic structures of these clusters. The excited-state dynamics, host-guest chemistry, and the catalytic properties of Pd6-Oct and Pd6-Tia were examined to compare their structure-property relationships. This research represents significant advances in the synthesis and understanding of structure-property correlations in Pd-thiolate clusters.

Interfacial Push-Pull Dynamics Enable Rapid Had Desorption for Enhanced Formate Electrooxidation

The electrocatalytic conversion of formate in alkaline solutions is of paramount significance in the realm of fuel cell applications. Nonetheless, the adsorptive affinity of adsorbed hydrogen (Had) on the catalyst surface has traditionally impeded the catalytic efficiency of formate in such alkaline environments. To circumvent this challenge, our approach introduces an interfacial push-pull effect on the catalyst surface. This mechanism involves two primary actions: First, the anchoring of palladium (Pd) nanoparticles on a phosphorus-doped TiO2 substrate (Pd/TiO2-P) promotes the formation of electron-rich Pd with a downshifted d band center, thereby "pushing" the desorption of Had from the Pd active sites. Second, the TiO2-P support diminishes the energy barrier for Had transfer from the Pd sites to the support itself, "pulling" Had to effectively relocate from the Pd active sites to the support. The resultant Pd/TiO2-P catalyst showcases a remarkable mass activity of 4.38 A mgPd-1 and outperforms the Pd/TiO2 catalyst (2.39 A mgPd-1) by a factor of 1.83. This advancement not only surmounts a critical barrier in catalysis but also delineates a scalable pathway to bolster the efficacy of Pd-based catalysts in alkaline media.

Cu-Modified Palladium Catalysts: Boosting Formate Electrooxidation via Interfacially OHad-Driven Had Removal

Direct formate fuel cells have gained traction due to their eco-friendly credentials and inherent safety. However, their potential is hampered by the kinetic challenges of the formate oxidation reaction (FOR) on Pd-based catalysts, chiefly due to the unfavorable adsorption of hydrogen species (Had). These species clog the active sites, hindering efficient catalysis. Here, we introduce a straightforward strategy to remedy this bottleneck by incorporating Pd with Cu to expedite the removal of Pd-Had in alkaline media. Notably, Cu plays a pivotal role in bolstering the concentration of hydroxyl adsorbates (OHad) on the surface of catalyst. These OHad species can react with Had, effectively unblocking the active sites for FOR. The as-synthesized catalyst of PdCu/C exhibits a superior FOR performance, boasting a remarkable mass activity of 3.62 A mg-1. Through CO-stripping voltammetry, we discern that the presence of Cu in Pd markedly speeds up the formation of adsorbed hydroxyl species (OHad) at diminished potentials. This, in turn, aids the oxidative removal of Pd-Had, leveraging a synergistic mechanism during FOR. Density functional theory computations further reveal intensified interactions between adsorbed oxygen species and intermediates, underscoring that the Cu-Pd interface exhibits greater oxyphilicity compared to pristine Pd. In this study, we present both experimental and theoretical corroborations, unequivocally highlighting that the integrated copper species markedly amplify the generation of OHad, ensuring efficient removal of Had. This work paves the way, shedding light on the strategic design of high-performing FOR catalysts.

Engineering Phase to Reinforce Dielectric Polarization in Nickel Sulfide Heterostructure for Electromagnetic Wave Absorption

Engineering phase transition in micro-nanomaterials to optimize the dielectric properties and further enhance the electromagnetic microwave absorption (EMA) performance is highly desirable. However, the severe synthesis conditions restrict the design of EMA materials featuring controllable phases, which hinders the tunability of effective absorption bandwidth (EAB) and leads to an unclear loss mechanism. Herein, a seed phase decomposition-controlled strategy is proposed to induct nickel sulfide (NiSx ) absorbers with controllable phases and hollow sphere nature. Transmission electron microscopy holography and theoretical calculations evidence that the reconstruction of atoms in phase transition induces numerous heterogeneous interfaces and lattice defects/sulfur vacancies to cause varied work functions and local electronic redistribution, which contributes to reinforced dielectric polarization. As a result, the optimized NiS2 /NiS heterostructure enables enhanced EM attenuation capability with a wide EAB of 5.04 GHz at only 1.6 mm, compared to that of NiS2 and NiS. Moreover, the correlation between EAB and NiS phase content is demonstrated as the "volcano" feature. This study on the concept of phase transition of micro-nanomaterials can offer a novel approach to constructing highly efficient absorbers for EMA and other functionalities.