27 research outputs found

    A Novel Photochemical Method for the Synthesis of Au Triangular Nanoplates inside Nanocavity of Mesoporous Silica Shells

    No full text
    We report a new photochemical method for tuning the shapes of gold nanoparticles inside nanocavity of mesoporous silica shells (mHSS) using Ag<sup>+</sup> ions without using any convential organic capping ligands. mHSS acts as a nanocontainer and is used for entrapping the chloroauric acid molecules along with Ag<sup>+</sup> ions. The shape of gold nanoparticles is tuned from spheres to triangular nanoplates inside mHSS by varying the molar ratio of [AuCl<sub>4</sub><sup>–</sup>]/[Ag<sup>+</sup>] in the reaction. The results confirm that the presence of Ag<sup>+</sup> ions promotes the growth of Au triangular nanoplates inside mHSS. The Au triangular nanoplates demonstrate superior catalytic activity than spherical Au nanoparticles

    Controlled Synthesis of Palladium Concave Nanocubes with Sub-10-Nanometer Edges and Corners for Tunable Plasmonic Property

    No full text
    Developing new strategies for tuning the plasmonic properties of palladium nanostructures is of both fundamental and technological interest due to their potential applications in plasmonic hydrogen sensing, in situ surface-enhanced Raman spectroscopy for catalysis, and solar energy harvesting. In this work, a new strategy of tuning the localized surface plasmon resonance (LSPR) property of Pd nanocrystals by selectively sharpening their edges and corners is reported. Through a Cu­(II)-assisted seed-mediated growth approach, sub-10-nm sharp edges and corners were grown on regular Pd nanocubes. The LSPR peaks of the as-formed concave Pd nanocubes could be tuned across the visible spectrum by simply controlling their sizes. Cu­(II) was found to selectively activate the fast growth of Pd atoms along the [110] and [111] directions of the cubic Pd seeds and promote the formation of this new type of Pd concave nanocubes. This strategy of building Pd sharp edges and corners may be applicable for the design of new plasmonic nanostructures by using seeds of different metals, sizes, shapes, and crystal structures

    Tip-Selective Growth of Silver on Gold Nanostars for Surface-Enhanced Raman Scattering

    No full text
    Nanogaps as “hot spots” with highly localized surface plasmon can generate ultrastrong electromagnetic fields. Superior to the exterior nanogaps obtained via aggregation and self-assembly, interior nanogaps within Au and Ag nanostructures give stable and reproducible surface-enhanced Raman scattering (SERS) signals. However, the synthesis of nanostructures with interior hot spots is still challenging because of the lack of high-yield strategies and clear design principles. Herein, gold–silver nanoclusters (Au–Ag NCs) with multiple interior hot spots were fabricated as SERS platforms via selective growth of Ag nanoparticles on the tips of Au nanostars (Au NSs). Furthermore, the interior gap sizes of Au–Ag NCs can be facilely tuned by changing the amount of AgNO<sub>3</sub> used. Upon 785 nm excitation, single Au–Ag NC<sub>350</sub> exhibits 43-fold larger SERS enhancement factor and the optimal signal reproducibility relative to single Au NS. The SERS enhancement factors and signal reproducibility of Au–Ag NCs increase with the decrease of gap sizes. Collectively, the Au–Ag NCs could serve as a flexible, reproducible, and active platform for SERS investigation

    Highly Symmetric Gold Nanostars: Crystallographic Control and Surface-Enhanced Raman Scattering Property

    No full text
    Gold nanostars have attracted widespread interest due to their remarkable properties and broad applications in plasmonics, spectroscopy, biomedicine, and energy conversion. However, current synthetic methods of Au nanostars have limited control over their symmetry; most existing nanostars are characterized by having uncertain number of arms with different lengths and random spatial arrangement. This morphological arbitrariness not only hampers the fundamental understanding of the properties of Au nanostars, but also lead to poor reproducibility in their applications. Here we demonstrate that, by using a robust solution-phase method, Au nanostars with unpreceded degree of symmetry control can be obtained in high yield and with remarkable monodispersity. Icosahedral seeds are used to dictate the growth of 3D evenly distributed arms in an <i>I</i><sub><i>h</i></sub> symmetric manner. Alkylamines serve as shape-control agent to regulate the growth of the hexagonal pyramidal arms enclosed by high-index facets. Benefiting from their high symmetry, the Au nanostars exhibit superior single-particle SERS performance compared to asymmetric Au nanostars, in terms of both intensity and reproducibility

    Ultrathin Ag Nanowires Electrode for Electrochemical Syngas Production from Carbon Dioxide

    No full text
    The mass production of silver nanowires (Ag NWs) with ultrathin diameter (∼35 nm) and a high aspect ratio (>1000) is prepared from an optimized polyol solution. The Ag NWs possess several promising advantages, including good conductivity and excellent film formability, and have already been used to fabricate a large area flexible Ag NWs-based electrode through a simple drop-casting method. The Ag NWs electrode displayed good activity to convert carbon dioxide (CO<sub>2</sub>) to carbon monoxide (CO) in high Faradaic efficiency (FE) of ∼80% under low working potential (−0.9 V vs reversible hydrogen electrode (RHE)), and at the same time, the fraction of CO/H<sub>2</sub> can be tuned from 1/1 to 4/1. A small amount of HCOOH (FE: 2.6–5.6%) was also measured as a byproduct in liquid phase. The constant working current density and CO FE recovered superstability of the Ag NWs electrode. The high-resolution transmission electron microscopy (TEM) recovered the {111} facet exposed to the surface contribuing to the effective performance. Ag NWs with larger diameter (70 nm) and Ag plate electrode were also evaluated under the same condition, where formic acid (HCOOH) was also detected besides CO as another main product. Combined with easy fabrication, low cost, high selectivity, and excellent stability, Ag NWs based electrode is promising for further application in larger scale for syngas production and other electrocatalysis

    Table_2_Characterization of Ferredoxin-Dependent Biliverdin Reductase PCYA1 Reveals the Dual Function in Retrograde Bilin Biosynthesis and Interaction With Light-Dependent Protochlorophyllide Oxidoreductase LPOR in Chlamydomonas reinhardtii.PDF

    No full text
    <p>Bilins are linear tetrapyrroles commonly used as chromophores of phycobiliproteins and phytochromes for light-harvesting or light-sensing in photosynthetic organisms. Many eukaryotic algae lack both phycobiliproteins and phytochromes, but retain the bilin biosynthetic enzymes including heme oxygenase (HO/HMOX) and ferredoxin-dependent biliverdin reductase (FDBR). Previous studies on Chlamydomonas reinhardtii heme oxygenase mutant (hmox1) have shown that bilins are not only essential retrograde signals to mitigate oxidative stress during diurnal dark-to-light transitions, they are also required for chlorophyll accumulation and maintenance of a functional photosynthetic apparatus in the light. However, the underlying mechanism of bilin-mediated regulation of chlorophyll biosynthesis is unclear. In this study, Chlamydomonas phycocyanobilin:ferredoxin oxidoreductase PCYA1 FDBR domain was found to specifically interact with the rate-limiting chlorophyll biosynthetic enzyme LPOR (light-dependent protochlorophyllide oxidoreductase). PCYA1 is partially associated with chloroplast envelope membrane, consistent with the observed export of bilin from chloroplast to cytosol by cytosolic expression of a bilin-binding reporter protein in Chlamydomonas. Both the pcya1-1 mutant with the carboxyl-terminal extension of PCYA1 eliminated and efficient knockdown of PCYA1 expression by artificial microRNA exhibited no significant impact on algal phototrophic growth and photosynthetic proteins accumulation, indicating that the conserved FDBR domain is sufficient and minimally required for bilin biosynthesis and functioning. Taken together, these studies provide novel insights into the regulatory role of PCYA1 in chlorophyll biosynthesis via interaction with key Chl biosynthetic enzyme.</p

    Table_1_Characterization of Ferredoxin-Dependent Biliverdin Reductase PCYA1 Reveals the Dual Function in Retrograde Bilin Biosynthesis and Interaction With Light-Dependent Protochlorophyllide Oxidoreductase LPOR in Chlamydomonas reinhardtii.PDF

    No full text
    <p>Bilins are linear tetrapyrroles commonly used as chromophores of phycobiliproteins and phytochromes for light-harvesting or light-sensing in photosynthetic organisms. Many eukaryotic algae lack both phycobiliproteins and phytochromes, but retain the bilin biosynthetic enzymes including heme oxygenase (HO/HMOX) and ferredoxin-dependent biliverdin reductase (FDBR). Previous studies on Chlamydomonas reinhardtii heme oxygenase mutant (hmox1) have shown that bilins are not only essential retrograde signals to mitigate oxidative stress during diurnal dark-to-light transitions, they are also required for chlorophyll accumulation and maintenance of a functional photosynthetic apparatus in the light. However, the underlying mechanism of bilin-mediated regulation of chlorophyll biosynthesis is unclear. In this study, Chlamydomonas phycocyanobilin:ferredoxin oxidoreductase PCYA1 FDBR domain was found to specifically interact with the rate-limiting chlorophyll biosynthetic enzyme LPOR (light-dependent protochlorophyllide oxidoreductase). PCYA1 is partially associated with chloroplast envelope membrane, consistent with the observed export of bilin from chloroplast to cytosol by cytosolic expression of a bilin-binding reporter protein in Chlamydomonas. Both the pcya1-1 mutant with the carboxyl-terminal extension of PCYA1 eliminated and efficient knockdown of PCYA1 expression by artificial microRNA exhibited no significant impact on algal phototrophic growth and photosynthetic proteins accumulation, indicating that the conserved FDBR domain is sufficient and minimally required for bilin biosynthesis and functioning. Taken together, these studies provide novel insights into the regulatory role of PCYA1 in chlorophyll biosynthesis via interaction with key Chl biosynthetic enzyme.</p
    corecore