Peiguang Hu

University of California, Santa Cruz, Santa Cruz, California, United States

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Publications (15)66.63 Total impact

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    ABSTRACT: Faceted silver nanostructures including triangular nanoprisms, nanotetrahedra, and nanodecahedra were synthesized via a facile photochemical method at controlled wavelengths using spherical nanoparticles as the seeds. Scanning transmission electron microscopy studies showed that the resulting nanostructures were much larger in size (20–50 nm) than the spherical seed nanoparticles (under 5 nm), and X-ray diffraction as well as high-resolution transmission electron microscopy measurements confirmed that these nanostructures exhibited predominantly {111} faceted surfaces. Importantly, the silver nanostructures demonstrated markedly better antimicrobial activity than the spherical seed nanoparticles as evidenced by a lower minimum inhibitory concentration and more dramatic changes in both growth rate and lag phase at lower concentrations, which were attributed to the greater reactivity of the {111} faceted surfaces toward oxygen-rich bacterial surface moieties that allowed for more rapid localization to bacterial cells and increased interactions with structurally vital outer-membrane proteins. These results highlight the significance of surface morphologies of metal nanostructures in the manipulation of their antimicrobial activity.
    Journal of Materials Science 04/2015; 50(7). DOI:10.1007/s10853-015-8847-x · 2.31 Impact Factor
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    ABSTRACT: Stable platinum nanoparticles were synthesized by the self-assembly of alkene derivatives onto the platinum surface, possibly forming platinum-vinylidene (Pt=C=CH-) and/or -acetylide (Pt-Csp) interfacial bonds as a result of dehydrogenation and transformation of the olefin moieties catalyzed by platinum. Transmission electron microscopic measurements showed that the nanoparticles were well dispersed without apparent agglomeration, indicating effective passivation of the nanoparticles by the ligands, and the average core was estimated to be 1.34 to 0.39 nm. FTIR measurements showed the emergence of a new vibrational band at 2023 cm-1 which was ascribed to the formation of Pt-H and CC from the dehydrogenation of alkene ligands on platinum surfaces. Consistent behaviors were observed in photoluminescence measurements, where the emission profiles were consistent with those of alkyne-functionalized Pt nanoparticles that arose from intraparticle charge delocalization between the particle-bound acetylene moieties. Selective reactivity with imine derivatives further confirmed the formation of Pt=C=CH- and/or Pt-Csp interfacial linkages, as manifested in NMR and electrochemical measurements. Further structural insights were obtained by X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) analysis, where the coordinate numbers and bond lengths of the Pt-Pt and Pt-C linkages suggested that the metal-ligand interfacial bonds were in the intermediate between those of Pt-Csp and Pt-Csp2.
    Langmuir 12/2014; 31(1). DOI:10.1021/la503995c · 4.38 Impact Factor
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    ABSTRACT: Stable ruthenium nanoparticles protected by ferrocenecarboxylates (RuFCA) were synthesized by thermolytic reduction of RuCl3 in 1,2-propanediol. The resulting particles exhibited an average core diameter of 1.22 ± 0.23 nm, as determined by TEM measurements. FTIR and 1H NMR spectroscopic measurements showed that the ligands were bound onto the nanoparticle surface via RuO bonds in a bidentate configuration. XPS measurements exhibited a rather apparent positive shift of the Fe2p binding energy when the ligands were bound on the nanoparticle surface, which was ascribed to the formation of highly polarized RuO interfacial bonds that diminished the electron density of the iron centers. Consistent results were obtained in electrochemical measurements where the formal potential of the nanoparticle-bound ferrocenyl moieties was found to increase by ca. 120 mV. Interestingly, galvanic exchange reactions of the RuFCA nanoparticles with Pd(II) followed by hydrothermal treatment at 200 C led to (partial) decarboxylation of the ligands such that the ferrocenyl moieties were now directly bonded to the metal surface, as manifested in voltammetric measurements that suggested intervalence charge transfer between the nanoparticle-bound ferrocene groups.
    Physical Chemistry Chemical Physics 07/2014; 16(35). DOI:10.1039/C4CP01890G · 4.20 Impact Factor
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    ABSTRACT: Platinum nanoparticles functionalized with 4‒ethynylphenylboronic acid pinacol ester (Pt‒EPBAPE) were successfully synthesized by a simple chemical reduction procedure. Because of the formation of conjugated metal‒ligand interfacial linkages, the resulting nanoparticles exhibited apparent photoluminescence arising from the nanoparticle‒bound acetylene moieties that behaved analogously to diacetylene derivatives. Interestingly, the nanoparticle photoluminescence was markedly quenched upon the addition of fluoride ions (F‒). In contrast, significantly less or virtually no change was observed with a variety of other anions such as Cl‒, Br‒, I-, NO3-, HSO4-, H2PO4-, ClO4- , BF4-, PF6^-, etc. The high selectivity towards fluoride ion is most probably because of the strong specific affinity of the boronic acid moiety to fluoride. The formation of B‒F bonds led to the conversion of Bsp2 to Bsp3, as manifested in 11B NMR measurements, which impacted the intraparticle charge delocalization between the particle‒bound acetylene moieties and hence the nanoparticle photoluminescence.
    Langmuir 04/2014; 30(18). DOI:10.1021/la5001123 · 4.38 Impact Factor
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    ABSTRACT: Silver nanoparticles capped by a variety of organic ligands (i.e., 1-hexanethiol, 1-octyne, and 4-trifluoromethylphenyl fragments) were synthesized by a chemical reduction route, with the resulting nanoparticles denoted as AgSC6, AgHC8, and AgPhCF3, respectively. The nanoparticle structures were characterized by using a variety of techniques including NMR, UV-vis, infrared, thermogravimetric analysis, and X-ray photoelectron spectroscopies, high-resolution transmission electron microscopy, and electrochemical methods; and their electrocatalytic activities in oxygen reduction in alkaline media were evaluated and compared within the context of metal-ligand interfacial bonding interactions by using “bare” Ag nanoparticles supported on carbon black (Ag/C) as the benchmark materials. The results demonstrated that the electrocatalytic activity increased in the order of AgSC6
    Science of Advanced Materials 11/2013; 5(11):1727-1736. DOI:10.1166/sam.2013.1624 · 2.91 Impact Factor
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    ABSTRACT: Ruthenium nanoparticles were stabilized by the self-assembly of 1-decyne forming ruthenium-vinylidene interfacial bonds and further functionalized by metathesis reactions with 4-ethynyl-N,N-diphenylaniline (EDPA) and 9-vinylanthracene (VAN). Photoluminescence studies of the resulting bifunctionalized Ru(EDPA/VAN) nanoparticles showed that as both ligands were bound onto the nanoparticle surface, effective mixing of the π electrons occurred leading to the appearance of excitation and emission profiles that were completely different from those of ruthenium nanoparticles functionalized with only EDPA or VAN. Furthermore, in photoelectrochemical studies, the EDPA moieties exhibited a pair of well-defined voltammetric peaks in the dark, which were ascribed to the redox reaction involving the formation of cationic radicals; however under UV photoirradiation the voltammetric features diminished markedly. These results strongly suggest that the particle-bound EDPA and VAN moieties behaved analogously to those of conventional molecular dyads based on the same electron-donating and -accepting units, where the intraparticle charge transfer was facilitated by the conjugated metal-ligand interfacial bonds.
    Physical Chemistry Chemical Physics 09/2013; 15(40). DOI:10.1039/c3cp52584h · 4.20 Impact Factor
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    Ruoyu Liu, Peiguang Hu, Shaowei Chen
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    ABSTRACT: Heterostructures based on Ag3PO4 nanoparticles and TiO2 nanobelts were prepared by a coprecipitation method. The crystalline structures were characterized by X-ray diffraction measurements. Electron microscopic studies showed that the Ag3PO4 nanoparticles and TiO2 nanobelts were in intimate contact which might be exploited to facilitate charge transfer between the two semiconductor materials. In fact, the heterostructures exhibited markedly enhanced photocatalytic activity as compared with unmodified TiO2 nanobelts or commercial TiO2 colloids in the photodegradation of methyl orange under UV irradiation. This was accounted for by the improved efficiency of interfacial charge separation thanks to the unique alignments of their band structures. Remarkably, whereas the photocatalytic activity of the heterostructure was comparable to that of Ag3PO4 nanoparticles alone, the heterostructures exhibited significantly better stability and reusability in repeated tests than the Ag3PO4 nanoparticles.
    Applied Surface Science 10/2012; 258(24):9805–9809. DOI:10.1016/j.apsusc.2012.06.033 · 2.54 Impact Factor
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    ABSTRACT: TiO(2) nanobelts were prepared by the hydrothermal growth method. The surface of the nanobelts was coarsened by selective acid corrosion and functionalized with Pd catalyst particles. Three nanobelt samples (TiO(2) nanobelts, surface-coarsened TiO(2) nanobelts and Pd nanoparticle/TiO(2) nanobelt surface heterostructures) were configured as gas sensors and their sensing ability was measured. Both the surface-coarsened nanobelts and the Pd nanoparticle-decorated TiO(2) nanobelts exhibited dramatically improved sensitivity to ethanol vapor. Pd nanoparticle-decorated TiO(2) nanobelts with surface heterostructures exhibited the best sensitivity, selectivity, working temperature, response/recovery time, and reproducibility. The excellent ethanol sensing performance is attributed to the large surface area and enhancement by Schottky barrier-type junctions between the Pd nanoparticles and TiO(2) nanobelts.
    Journal of Colloid and Interface Science 08/2012; 388(1):144-50. DOI:10.1016/j.jcis.2012.08.034 · 3.55 Impact Factor
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    ABSTRACT: The Ag/TiO(2) nanobelt heterostructures were prepared by the acid-assisted hydrothermal method followed by an in situ photo-reduction process. The photocatalytic activity of TiO(2) nanobelts was evidently enhanced by the heterostructures between Ag nanoparticles and TiO(2) nanobelts. The nanopapers based on Ag/TiO(2) nanobelt heterostructures were fabricated via a modified paper-making process. A novel continuous photocatalytic reactor was designed, and MO removal rate of Ag/C-TiO(2) nanopaper was achieved to 100% in 40 min for single layer and only in 6 min for three layers. The self-supported TiO(2) nanopapers with porous structures also showed an excellent continuous photocatalytic performance for toluene gas under UV light irradiation, and the corresponding degradation rate was 69.5% in 184 min. Moreover, the Ag/TiO(2) nanobelts nanopaper showed a good antibacterial effect. The multifunctional TiO(2) nanopapers modified by the heterostuctures could have potential applications in the environmental and biomaterial fields.
    Journal of hazardous materials 12/2011; 197:19-25. DOI:10.1016/j.jhazmat.2011.09.051 · 4.33 Impact Factor
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    ABSTRACT: An alkaline hydrothermal and acid etching process was used to prepare surface-coarsened anatase TiO2 nanobelts (CTNs) with enhanced (001) facets. The CTNs were used for electrochemical selective determination of the perfect match and mismatch of single nucleobases at the physiological pH of 7.4. It is supposed that the structure and surface morphology of CTNs play important roles in the nature of the adsorption/bonding and packing density of single base pairs on the nanobelt surfaces. Within the present experimental context, the CTNs are considered to be promising candidates for biosensing of nucleic acids that will be of fundamental significance to diagnostic medicine and molecular biology research.
    Journal of Materials Chemistry 07/2011; 21(29):10633-10636. DOI:10.1039/C1JM11805F · 6.63 Impact Factor
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    ABSTRACT: Nano-p–n junction heterostructure TiO 2 nanobelts have been produced by assembling p-type semiconductor NiO nanoparticles on n-type TiO 2 nanobelts for enhancement of the photocatalytic properties of TiO 2 nanobelts. NiO/TiO 2 nano-p–n junctions were synthesized on the surfaces of TiO 2 nanobelts and surface-coarsened TiO 2 nanobelts. The nanobelts were obtained using alkaline-and acid-assisted hydrothermal processes. The chemical-solution-deposition–decomposition process was used to form NiO nanoparticle/TiO 2 heterostructure composite nanobelts (NiO-NP/TiO 2 NBs), and NiO nanoparticle/surface-coarsened TiO 2 heterostructure composite nanobelts (NiO-NP/TiO 2 coarsened NBs). The uniform assembly of p-type NiO nanoparticles produces a large number of nano-p–n junction heterostructures on the surface of the TiO 2 nanobelts, where NiO and TiO 2 form p-and n-type semiconductors, respectively. Compared with both pure NiO nanoparticles and TiO 2 nanobelts, NiO-NP/TiO 2 NBs exhibit much enhanced photocatalytic activity. Interestingly, the optimized composite NiO-NP/TiO 2 coarsened NBs exhibit an enhanced photocatalytic activity in the decomposition of a model dye compound, methyl orange (MO), under both ultraviolet and visible light irradiation. It is argued that the nano-p–n junctions effectively reduce the recombination of electrons and holes, thus leading to the enhancement of the photocatalytic properties of the heterostructure composites. The larger number of abundant photocatalytic-active surfaces in the surface-coarsened nanobelts increases photo-absorption and the production of charge carriers, which gives the composites an enhanced photocatalytic performance. The established approach allows for controlling the nano-p– n junction heterostructure of the nanobelts, and hence, their photocatalytic effect. The NiO/TiO 2 nanobelt-based nano-p–n junction heterostructure TiO 2 can provide a practical way to design and prepare nano-composites for applications as solar-cell electrodes, in solar photocatalysis, solar photolysis of water and other related fields.
    Journal of Materials Chemistry 06/2011; DOI:10.1039/C0JM04131A · 6.63 Impact Factor
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    ABSTRACT: Two kinds of TiO(2) nanobelts were prepared from commercial P-25 powders via an alkaline hydrothermal method with and without an acid etching process. The uncauterized nanobelts (TNs) exhibited a smooth surface, and mixed phases of anatase and TiO(2) (B), whereas the cauterized ones (CTNs) displayed a rough surface and a pure anatase structure. TNs and CTNs were then deposited onto a glassy carbon electrode (GCE) surface with a conductive adhesive (CA), and the resulting chemically modified electrodes exhibited electrocatalytic activities in the oxidation of nucleobases in a 0.1 M phosphate buffer solution (PBS) at pH 7.4. For guanine and adenine, well-defined oxidation peaks were observed in voltammetric measurements at about +0.62 and +0.89 V, respectively, at a potential sweep rate of 100 mV s(-1), whereas for cytosine, uracil and thymine, the voltammetric features were not obvious. The average surface coverages (Γ) of guanine and adenine on the CTNs/CA/GCE electrode were estimated to be 4.75 × 10(-10) and 7.44 × 10(-10) mol cm(-2), respectively, which were about twice those at the TNs/CA/GCE electrode. The enhanced activity of the CTN-based electrode towards purine nucleobase oxidation was ascribed to the large specific surface area and anatase structures with enhanced (001) facets of the CTN that facilitated adsorption of the analytes onto the electrode surface and charge transport through the electrode surface layer.
    Physical Chemistry Chemical Physics 04/2011; 13(20):9232-7. DOI:10.1039/c1cp20082h · 4.20 Impact Factor
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    ABSTRACT: TiO2 nanobelts are very attractive due to their dimensional confinement and structurally well-defined physical and chemical properties. However, the obscure phase transformation mechanism and the low photocatalytic activity of TiO2 nanobelts limit their wide applications. Here, the phase transformations among H2Ti3O7, TiO2(B), anatase and rutile nanobelts were characterized in detail by X-ray powder diffraction, high resolution transmission electron microscopy, Raman spectroscopy and UV-Vis diffuse reflectance spectra. TiO2(B) is inevitable in the phase transformation of TiO2 nanobelts due to the shape limiting effort and the similar crystal structure between H2Ti3O7 and TiO2(B). TiO2 nanobelts have a good thermal stability for the crystal phase and nanostructures. TiO2(B)/anatase interface heterostructure nanobelts were obtained by calcining H2Ti3O7 nanobelts at 800 degrees C, which had an enhanced photocatalytic ability comparing with pure TiO2(B) and anatase nanobelts. The mechanisms of the phase transformation of TiO2 nanobelts and the enhanced photocatalytic activity of TiO2(B)/anatase interface heterostructure nanobelts were discussed. The self-transformed heterostructure nanobelts have good photocatalytic activity, stability and easy-recovery properties, which will have important practical applications.
    CrystEngComm 01/2011; 13(22). DOI:10.1039/C1CE05638G · 3.86 Impact Factor
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    ABSTRACT: Nanoheterostructures of TiO 2 nanoparticles/TiO 2 nanobelts and Ag/TiO 2 nanoparticles/TiO 2 nanobelts are prepared by the acid-assisted hydrothermal method followed by an in situ photo-reduction process. The experimental parameters, including acid corrosion time and calcination temperature, are investigated in detail. Compared with TiO 2 nanobelts, the single nanoheterostructure TiO 2 nanoparticles/TiO 2 nanobelts have a better photocatalytic activity. The double nanoheterostructure Ag/TiO 2 nanoparticles/TiO 2 nanobelts can further dramatically enhance photocatalytic properties of TiO 2 nanobelts. The mechanisms for formation of the heterostructure and the enhanced photocatalytic effect of the heterostructure are discussed. The liquid continuous-flow photocatalysis based on TiO 2 nanobelt nanopaper with different heterostructures is carried out, which has an efficient photocatalytic ability. At the same time, the obtained TiO 2 nanobelt heterostructures have a good gas sensitive performance for ethanol.
    Journal of Materials Chemistry 01/2011; 21(22). DOI:10.1039/C1JM10588D · 6.63 Impact Factor
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    ABSTRACT: TiO(2) nanobelts were prepared by a hydrothermal process, and the structures were manipulated by surface engineering, including surface coarsening by an acid-corrosion procedure and formation of Ag-TiO(2) heterostuctures on TiO(2) nanobelts surface by photoreduction. Their performance in the detection of ethanol vapor was then examined and compared by electrical conductivity measurements at varied temperatures. Of the sensors based on the four nanobelt samples (TiO(2) nanobelts, Ag-TiO(2) nanobelts, surface-coarsened TiO(2) nanobelts, and surface-coarsened Ag-TiO(2) nanobelts), they all displayed improved sensitivity, selectivity, and short response times for ethanol vapor detection, in comparison with sensors based on other oxide nanostructures. Importantly, the formation of Ag-TiO(2) heterostuctures on TiO(2) nanobelts surface and surface coarsening of TiO(2) nanobelts were found to lead to apparent further enhancement of the sensors sensitivity, as well as a decrease of the optimal working temperature. That is, within the present experimental context, the vapor sensor based on surface-coarsened Ag-TiO(2) composite nanobelts exhibited the best performance. The sensing mechanism was interpreted on the basis of the surface depletion model, and the improvement by oxide surface engineering was accounted for by the chemical sensitization mechanism. This work provided a practical approach to the enhancement of gas sensing performance by one-dimensional oxide nanomaterials.
    ACS Applied Materials & Interfaces 10/2010; 2(11):3263-9. DOI:10.1021/am100707h · 5.90 Impact Factor

Publication Stats

148 Citations
66.63 Total Impact Points

Institutions

  • 2012–2015
    • University of California, Santa Cruz
      • Department of Chemistry & Biochemistry
      Santa Cruz, California, United States
  • 2010–2012
    • Shandong University
      • State Key Laboratory for Crystal Materials
      Chi-nan-shih, Shandong Sheng, China