Biomimetic Superoxide Dismutase Stabilized by Photopolymerization for Superoxide Anions Biosensing and Cell Monitoring

Photopolymerization strategy, as one of the immobilization methods, has attracted considerable interest because of some advantages, such as easy operation, harmlessness to the biomolecules, and long storage stability. (<i>E</i>)-4-(4-Formylstyryl) pyridine (formylstyrylpyridine) was prepared through Heck reaction and used as a photopolymer material to immobilize biomimetic superoxide dismutase under ultraviolet irradiation (UV) irradiation in a short time. The styrylpyridinium moiety of Formylstyrylpyridine was photoreactive and formed a dimer under UV irradiation. Mn₂P₂O₇ multilayer sheet, a novel superoxide dismutase mimic, was synthesized. The formed photopolymer can immobilize Mn₂P₂O₇ firmly under UV irradiation. On the basis of high catalytic activity of Mn₂P₂O₇ biomimetic enzyme and long-term stability of Mn₂P₂O₇–formylstyrylpyridine film, after introducing multiwalled carbon nanotubes (MWCNTs), a novel electrochemical biosensing platform called MWCNTs/Mn₂P₂O₇–formylstyrylpyridine for superoxide anion (O₂^•–) detection was constructed. The biosensor displayed good performance for O₂^•– detection and provided a reliable platform to adhere living cells directly on the modified electrode surface. Therefore, the biosensor was successfully applied to vitro determination of O₂^•– released from living cells, which had a promising prospect for living cells monitoring and diagnosis of reactive oxygen species-related diseases

Synthesis of PbS/PbI₂ Nanocomposites in Mixed Solvent and Their Composition-Dependent Electrogenerated Chemiluminescence Performance

PbS/PbI₂ nanocomposites were prepared by choosing K­[PbI₃] as both a lead salt and an iodide precursor and acetone/water as a reaction medium. It was found that the amount of the PbI₂ component could be controlled, to some extent, by varying the amount of water used. Further, this simple bicomponent precursor-based synthetic route can be extended to prepare other lead-containing nanocomposites such as Pb₃O₄/PbI₂ and PbSe/PbI₂. Because of the heavy-atom effect, PbS/PbI₂ nanocomposites exhibited good and composition-dependent electrogenerated chemiluminescence (ECL) performance, demonstrating their potential in the development of novel ECL sensors for analytical and clinical applications. These interesting findings would encourage us to gain deep insight on these phenomena, which could lead to the further development of these new inorganic materials and their applications

Electrochemiluminescence Tuned by Electron–Hole Recombination from Symmetry-Breaking in Wurtzite ZnSe

The research of highly active electrochemiluminescence (ECL) materials with low toxicity and good solubility remains a substantial challenge. In this work, we present a synthesis method to prepare soluble wurtzite (WZ) ZnSe nanocrystals (NCs), which exhibit good ECL properties. Using high-angle annular-dark-field imaging together with electron hologram methods, we observe that the WZ ZnSe NCs exhibit an unusual symmetry-breaking phenomenon, where the translational symmetry of the polarized Zn–Se bond is broken. The formation of a symmetry-breaking region leads to an accumulation of charge. The good ECL response originates from the increased efficiency of electron–hole recombination by the excess charge redistribution in WZ ZnSe NCs. This study of the relationship between ECL behavior and the architecture of NCs suggests that careful control over the NC structures of semiconductors can tailor their charge distribution via symmetry breaking, which opens new avenues for the design of novel classes of agents for optoelectronic applications

Synthesis of Octopus-Tentacle-Like Cu Nanowire-Ag Nanocrystals Heterostructures and Their Enhanced Electrocatalytic Performance for Oxygen Reduction Reaction

In this article, the novel octopus-tentacle-like Cu nanowire-Ag nanocrystals heterostructures have been fabricated in solution phase via heterogeneous nucleation and growth of Ag nanocrystals on presynthesized Cu nanowires. The growth environment and dynamic factors of Ag nanocrystals play an important role for formation of such heterostructures. Combined the physical constants of Cu and Ag with a series of control experiments, the epitaxial growth means of Ag nanocrystals on Cu nanowire is found to abide by “layer-plus-island” (Stranski-Krastanow) mode. Because of the presence of multiple junctions and strong synergistic effect of their constituents, the obtained heterostructures exhibit greatly enhanced electrocatalytic performance toward oxygen reduction reaction compared with that of pure Ag nanocrystals, Cu nanowires, and mechanically mixed dual components as well as recently reported some non-Pt materials, which can be served as an alternative cathodic electrocatalyst to apply in alkaline fuel cells. Moreover, our method can be extended to fabricate octopus-tentacle-like Cu nanowire-Au nanocrystals and Cu nanowire-Pd nanocrystals heterostructures

Well-Coupled Graphene and Pd-Based Bimetallic Nanocrystals Nanocomposites for Electrocatalytic Oxygen Reduction Reaction

In this paper, a series of well-coupled graphene (G) and MPd₃ (M = Fe, Cu, Ag, Au, Cr, Mo, W) nanocrystals nanocomposites (G-MPd₃ NCPs) have been synthesized via a versatile electrostatic assembly and hydrogen reduction strategy, i.e., sequential assembly of coordination anions and cations on excess cationic polymer modified graphene oxide to form composite precursors and then thermal treating under H₂/Ar gases atmosphere. In those NCPs, the MPd₃ components are uniform and smaller than 10 nm, which are well anchored on G with “naked” or “clean” surfaces. By adjusting reaction temperature, the interplay of MPd₃ nanocrystals and G can be well-controlled. Below 700 °C, no sintering phenomena are observed, indicating the unprecedented dispersion and stability effect of G for MPd₃ nanocrystals. All the obtained NCPs can be directly used to catalyze oxygen reduction reaction in alkaline media. Compared with single component, monometallic, and some reported non-Pt catalysts, greatly enhanced electrocatalytic performances are observed in those NCPs due to strong synergistic or coupling of their constituents. Among them, G-FePd₃ NCPs exhibit the highest catalytic activity, but their current density needs to be improved compared with G-CrPd₃, G-MoPd₃, and G-WPd₃ ones. This work not only provides a general strategy for fabricating well-coupled G-MPd₃ NCPs but also paves the way for future designing multicomponent NCPs with multiple interfaces to apply in alkaline fuel cells

Five-Fold Twinned Pd₂NiAg Nanocrystals with Increased Surface Ni Site Availability to Improve Oxygen Reduction Activity

The synthesis of highly active oxygen reduction reaction (ORR) catalysts with good durability and low cost is highly desirable but still remains a significant challenge. In this work, we present the synthesis of five-fold twinned Pd₂NiAg nanocrystals (NCs) with a Ni-terminal surface which exhibit excellent electrocatalytic performance for ORR in alkaline media, even better than the performance of the commercial Pt/C catalyst. Using high-angle annular-dark-field imaging together with density functional theory calculations, it is found that the surfaces of the five-fold twinned Pd₂NiAg NCs exhibit an unusual valence electron density. The maximum catalytic activity originates from the increased availability of surface Ni sites in five-fold twinned Pd₂NiAg NCs and the features of twinned structural defects. This study provides an explanation of the enhanced ORR from the special structure of this novel material, which opens up new avenues for the design of novel classes of electrocatalysts for fuel cells and metal–air batteries

Component-Controlled Synthesis and Assembly of Cu–Pd Nanocrystals on Graphene for Oxygen Reduction Reaction

Exploring low-cost, high-activity, and long-durability hybrid electrocatalysts for cathodic oxygen reduction reaction (ORR) is vital to advance fuel cells technologies. In this paper, a series of graphene (G)–Cu_<i>x</i>Pd_<i>y</i> (Cu₄Pd, Cu₃Pd, CuPd, CuPd₃, CuPd₄) nanocomposites (G–Cu_<i>x</i>Pd_<i>y</i> NCPs) is obtained by assembly of Cu_<i>x</i>Pd_<i>y</i> alloy nanocrystals (NCs) with controlled component ratios on G nanosheets using the “dispersing–mixing–vaporizing solvent” strategy and used as electrocatalysts for ORR. Compared with pure Cu_<i>x</i>Pd_<i>y</i> NCs, greatly enhanced interfacial electron transfer dynamics are observed in G–Cu_<i>x</i>Pd_<i>y</i> NCPs, which show a strong correlation with the alloy compositions of the NCPs. The electrocatalytic experiments in alkaline solution reveal that the ORR activities of those G–Cu_<i>x</i>Pd_<i>y</i> NCPs are also strongly dependent on alloy components and exhibit a double-volcano feature with variations of alloy components. Among them, G–Cu₃Pd NCPs possess the highest electrocatalytic activity, which is much better than some reported electrocatalysts and commercial Pd/C catalyst and close to Pt/C catalyst. By correlating the Pd 3d binding energies and the sizes of Cu_<i>x</i>Pd_<i>y</i> NCs with the mass-specific activities of G–Cu_<i>x</i>Pd_<i>y</i> NCPs and considering the interfacial electron transfer dynamics, the best catalytic activity of G–Cu₃Pd NCPs may result from the unique electronic structure and the smallest size of Cu₃Pd NCs as well as the strong synergistic effect between G and Cu₃Pd NCs. Moreover, the durability of G–Cu₃Pd NCPs is superior to that of Pt/C catalyst, indicating that they are promising cathodic electrocatalysts for using in alkaline fuel cells

Ru Modulation Effects in the Synthesis of Unique Rod-like Ni@Ni₂P–Ru Heterostructures and Their Remarkable Electrocatalytic Hydrogen Evolution Performance

The construction of highly efficient and stable Pt-free catalysts for electrochemical hydrogen generation is highly desirable. Herein, we demonstrate the first metal–phosphides–metal system consisting of Ru, Ni₂P, and Ni, which forms unique multiheterogeneous Ni@Ni₂P–Ru nanorods. Interestingly, a Ru modulation effects that promotes the desorption of H₂ to achieve a moderate hydrogen adsorption energy (Δ<i>G</i>_H), and enables the formation of Ni@Ni₂P nanorods via Ru–Ni coordination to enhance the conductivity was discovered. Due to its optimal Δ<i>G</i>_H, improved conductivity and rod-like morphology, this catalyst shows superior electrocatalytic HER performances in both acidic and alkaline conditions, which are superior to those of some recently reported phosphides and close to that of commercial 20% Pt/C. Such a design strategy is not limited to Ni₂P and Ru but also may be extended to other similar phosphides and noble metals, providing a new promising approach and an alternative to Pt catalysts for electrocatalytic applications

A Chromosome-centric Human Proteome Project (C-HPP) to Characterize the Sets of Proteins Encoded in Chromosome 17

We report progress assembling the parts list for chromosome 17 and illustrate the various processes that we have developed to integrate available data from diverse genomic and proteomic knowledge bases. As primary resources, we have used GPMDB, neXtProt, PeptideAtlas, Human Protein Atlas (HPA), and GeneCards. All sites share the common resource of Ensembl for the genome modeling information. We have defined the chromosome 17 parts list with the following information: 1169 protein-coding genes, the numbers of proteins confidently identified by various experimental approaches as documented in GPMDB, neXtProt, PeptideAtlas, and HPA, examples of typical data sets obtained by RNASeq and proteomic studies of epithelial derived tumor cell lines (disease proteome) and a normal proteome (peripheral mononuclear cells), reported evidence of post-translational modifications, and examples of alternative splice variants (ASVs). We have constructed a list of the 59 “missing” proteins as well as 201 proteins that have inconclusive mass spectrometric (MS) identifications. In this report we have defined a process to establish a baseline for the incorporation of new evidence on protein identification and characterization as well as related information from transcriptome analyses. This initial list of “missing” proteins that will guide the selection of appropriate samples for discovery studies as well as antibody reagents. Also we have illustrated the significant diversity of protein variants (including post-translational modifications, PTMs) using regions on chromosome 17 that contain important oncogenes. We emphasize the need for mandated deposition of proteomics data in public databases, the further development of improved PTM, ASV, and single nucleotide variant (SNV) databases, and the construction of Web sites that can integrate and regularly update such information. In addition, we describe the distribution of both clustered and scattered sets of protein families on the chromosome. Since chromosome 17 is rich in cancer-associated genes, we have focused the clustering of cancer-associated genes in such genomic regions and have used the ERBB2 amplicon as an example of the value of a proteogenomic approach in which one integrates transcriptomic with proteomic information and captures evidence of coexpression through coordinated regulation