Selective SERS detection of each polycyclic aromatic hydrocarbon (PAH) in a mixture of five kinds of PAHs

This paper reports the qualitative analysis and quantitative detection of polycyclic aromatic hydrocarbon (PAH) molecules with per‐6‐deoxy‐(6‐thio)‐β‐cyclodextrin (CD‐SH) modified gold nanoparticles (AuNPs) by surface‐enhanced Raman scattering (SERS) spectroscopy. For the selective sensing of PAHs, which are environmental pollutants with very low affinity to metallic surfaces, by SERS, a stable substrate with AuNPs and CD‐SH was utilized by supramolecular interaction. Quantitative detection of each PAH was carried out by SERS on inclusion complexes with different concentrations. From the SERS spectra of a mixture of five different PAHs, we could easily distinguish each PAH by its discriminant peaks. In addition, quantitative analysis of one component in a mixture of five PAHs was also investigated. This sensing platform revealed matching relationship between the host and the guest and the host–guest interaction mechanism. The proposed approach for the selective detection of PAHs holds great potential in the detection of environmental organic pollutants. Copyright © 2010 John Wiley & Sons, Ltd.     

The superstructures of the clean Pt(100) and Ir(100) surfaces

The clean and reconstructed surfaces of Pt(100) and Ir(100) were investigated by low energy electron diffraction (LEED). It is shown that two superstructures can be observed in the case of platinum. The structure Pt(100)-hex, which is commonly called Pt(100)-(5 × 20), transforms to Pt(100)-hex-R0.7° above 1100 K. It is shown that this stable phase differs from the first one by a slight rotation of the hexagonal surface layer by 0.7°. For Ir(100) only the well known (1 × 5) superstructure is observed without any rotation of the outer layer. The rotation angle of 0.7° for platinum and the stability of the unrelated structure for iridium can be interpreted by simple calculations of the coordination of surface atoms with those of the second layer. The method assumes that the surface layer is of ideal hexagonal structure in the case of platinum and nearly hexagonal in the case of iridium. The results are in good agreement with the experiment.     

Nanoscale probing of adsorbed species by tip-enhanced Raman spectroscopy

Tip-enhanced Raman spectroscopy (TERS) is based on the optical excitation of localized surface plasmons in the tip-substrate cavity, which provides a large but local field enhancement near the tip apex. We report on TERS with smooth single crystalline surfaces as substrates. The adsorbates were CN- ions at Au(111) and malachite green isothiocyanate (MGITC) molecules at Au(111) and Pt(110) using either Au or Ir tips. The data analysis yields Raman enhancements of about 4 x 10(5) for CN- and up to 10(6) for MGITC at Au(111) with a Au tip, probing an area of less than 100 nm radius.     

Mössbauer analysis of the state of iridium and platinum in supported catalysts

The state of iridium and platinum in supported noble metal catalysts was investigated by Mössbauer spectroscopy. With iridium, conventional absorption experiments with the 73 KeV γ-rays of¹⁹³Ir were preformed; platinum was studied in source experiments using the 77 KeV resonance in¹⁹⁷Au. First results for pure Pt catalysts on silica supports and for a used automotive catalytic converter are presented. In Pt-rich bimetallic Pt?Ir catalysts on amorphous silica, both Pt and Ir were studied after different treatments.     

Organic‐inorganic hybrids based on phenanthrene‐functionalized gold nanoparticles for OLEDs

The electroluminescence intensity of the phenanthrene‐functionalized gold nanoparticles, PMPT‐Au nanoparticles/CPB: Ir(PIA)₂ (acac) film, was increased by 4.9 times compared with control device, CPB: Ir(PIA)₂ (acac) due to coupling between the excitons of emissive layer and localized surface plasmonic resonance of PMPT‐Au NPs. The maximum luminous efficiencies of devices II to IV with PMPT‐Au NPs were 39.2 cd A^?1 (11.8 V), 40.1 cd A^?1 (10.5 V), and 43.1 cd A^?1 (9.0 V), respectively. The increment of current efficiency with PMPT‐Au NP coated devices was strongly related to the energy transfer between the radiated light generated from CBP: Ir(PIA)₂ (acac) emissive layer and localized surface plasmonic resonance excited by PMPT‐Au NP layer.     

采用瞬态电致发光研究磷光掺杂体系发光瞬时过冲的发射机理

掺杂型有机电致发光器件中载流子累积、载流子复合等物理过程的深入了解对提高器件效率和稳定性有重要作用。通过瞬态电致发光测量可以研究掺杂型有机电致发光器件内部载流子累积。对结构为: ITO/NPB(30 nm)/host: Ir(ppy)₃/BCP(10 nm)/Alq₃(20 nm)/LiF(0.7 nm)/Al(100 nm)的器件分别研究主体材料以及客体掺杂浓度变化对有机掺杂型器件瞬态发光行为的影响。实验发现,当单脉冲驱动电压关闭后,只有TAZ: Ir(ppy)₃掺杂器件出现发光瞬时过冲现象,即发光强度衰减到一定时间时突然增强;且随着客体掺杂浓度的增加,瞬时过冲强度逐渐增强。通过分析TAZ: Ir(ppy)₃掺杂器件的瞬时过冲强度对主体材料与掺杂浓度的依赖关系,进一步发现,瞬时过冲效应强度主要受限于发光层内部积累的电子载流子;TAZ: Ir(ppy)₃发光层内电子容易被客体材料分子俘获并积累,电场突变时陷阱电子容易跳跃到主体材料上并与主体材料上积累的空穴形成激子,激子能量传递到客体材料上并复合发光继而出现发光强度的瞬时过冲现象。研究发光瞬时过冲行为可探究器件发光层内的载流子和激子的动态行为,有利于指导器件的设计,从而减少积累电荷的影响,提高器件的性能。     

The surface reconstructions of the (100) crystal faces of iridium,platinum and gold: II. Structural determination by LEED intensity analysis

The investigation, in a companion paper, of the reconstructions of the Ir(100), Pt(100), and Au(100) crystal surfaces is completed here with an extensive analysis of low energy electron diffraction (LEED) intensities, using dynamical (multiple scattering) calculations. It is found that a hexagonal rearrangement of the top monolayer is a likely explanation of the surface reconstruction. At least for Ir and Pt (no calculations were made for Au), this hexagonal layer would have a registry involving bridge sites on the next square unit cell metal layer and it is contracted and buckled. Bond length contractions parallel and perpendicular to the surface occur; the Pt top layer is rotated by a small angle (0.7°) with respect to the substrate. A second model that cannot be ruled out by the LEED analysis, but disagrees with ion-scattering data, involves shifted close-packed rows of top-layer atoms and requires domain structures in the case of Pt and Au. Charge-density-wave and missing-row models are ruled out by our structure analysis. A correlation is found between the occurrence of surface reconstructions on metals and a small ratio of their Debye temperature to their melting point. This correlation singles out mainly the 5d metals as having a propensity to surface reconstruction. The effects of adsorbates on the reconstructions are also discussed.     

The non-destructive threshold of the graphite surface by STM in the ultra-fast pulse mode

In this paper single ultra-fast voltage pulses are introduced to the Pt/Ir tip of a scanning tunnelling microscope (STM), and the non-destructive threshold of the graphite surface is studied systematically in a wide range of pulse durations (from 10$^{4}$ to 8\,ns). Considering the waveform distortion of the pulses at the tunnelling region, this paper gives the corrected threshold curve of pulse amplitude depending on pulse duration. A new explanation of threshold power has been suggested and fits the experimental results well.     

Diffusion of single adatoms of platinum,iridium and gold on platinum surfaces

Diffusion of single adatoms of platinum iridium and gold on platinum surfaces has been studied experimentally using field ion microscopy and theoretically using Morse potentials to describe the adatom bonding. The order of increasing activation energies for the surfaces studied was (111), (113), (011), (133), (001) and calculated activation energies agreed satisfactorily with the experimental values. On (113) and (011) platinum the activation energies for the adsorbates increased in the order Au, Pt, Ir. The calculations show that this variation arises largely from differences in the adsorbate binding energy, with the differences in adatom size having little effect. Diffusion of Au on (011) platinum occurred only along the direction of the surface channels, as is to be expected from the surface structure. In contrast, Pt and Ir adatoms were found to diffuse in two dimensions on (011). Since direct inter-channel jumps by adatoms should require large activation energies, it is proposed that the observed inter-channel adatom transfers proceed by a surface vacancy mechanism.     

2-Mercaptopyrimidine as a suitable matrix to trap arenes on Au(111): STM probing of the modified surface

2-Mercaptopyrimidine (2MPy) forms a two-dimensional planar lattice on Au(1 1 1). This structure is able to intercalate guest molecules such as the oligopyridines. To test the ability of the 2MPy lattice as a host able to intercalate a variety of molecules regardless of their geometry and electronic structures, some arenes and polyenes were analyzed as possible guests. Benzene, naphthalene, azulene, phenanthrene, anthracene, biphenyl, fluorobenzene and durene were selected to coadsorb with 2MPy on the Au(1 1 1) surface. These arenes are not known to form stable layers on Au(1 1 1); their adsorption is often studied on Pt and Rh surfaces. The experimental data show that the arenes and polyenes selected coadsorb with 2MPy on Au(1 1 1) under defined experimental conditions, forming a mixed layer with stoichiometry of 2:1 in thiol:guest. The STM contrast observed for the guest molecules is compared to the experimental and theoretical results already published.     

Negative‐Imaging of Citrate Layers on Gold Nanoparticles by Ligand‐Templated Metal Deposition: Revealing Surface Heterogeneity

Surface heterogeneity of a metal nanoparticle is typically regarded as boundary defects and various crystalline facets. While organic capping ligands of a single type are assumed to be homogeneously distributed on the nanoparticle surface, heterogeneous surface coverage of citrate molecules on individual facets of gold nanoparticles (AuNPs) is revealed. Pt metallic clusters with 2 nm in diameter, epitaxially grown on the surface of AuNPs by chemical reaction and imaged by high‐resolution transmission electron microscopy, are utilized as negative‐imaging probes for densely packed adlayers where the underneath gold surface may not be accessible for Pt deposition. At pH > 5.0, citrate anions form only a loosely packed layer. At pH 4.5, citrates and citric acids form both loosely packed and densely packed layers that appear phase separated, and the densely packed domain as small as 5 nm × 5 nm is likely composed of fully protonated citric acids. IR spectra indicate that citric acid binds to a surface Au adatom through the oxygen atom of the central hydroxyl group, and similarly, citrate anions bind to Au adatoms through the carboxylate oxygen atom. This study also reveals the role of Au adatom in the adsorption of citrate species on the metallic surface of AuNPs.     

Theoretical insights into the host–guest interactions between [6]cycloparaphenyleneacetylene and its anthracene‐containing derivative and fullerene C70

The host–guest complexes formed with [6]cycloparaphenyleneacetylene ([6]CPPA) and its anthracene‐containing derivative ([6]CPPAs) hosts and fullerene C₇₀ guest were explored by density functional calculations. Besides two previously reported configurations in which C₇₀ guest is standing or lying in the cavity of the host, we found a new kind of configuration in which C₇₀ guest is half‐lying in the cavity of the host. More interestingly, the calculated results revealed that the fine‐tuning deformations occur readily during the formations of the complexes, suggesting that both [6]CPPA and [6]CPPAs are highly elastic host molecules. The large host–guest binding energies indicate that both two host molecules, [6]CPPA and [6]CPPAs, have excellent encapsulation ability for C₇₀ guest, and the [6]CPPAs even has much better encapsulation ability for C₇₀ than [6]CPPA. Furthermore, the host–guest interactions regions were detected and visualized in real space based on the electron density and reduced density gradient. Additionally, ¹H NMR spectra of those three different kinds of configurations mentioned earlier have been calculated with gage‐independent atomic orbital method, which may be helpful for further experimental characterizations in future. Copyright © 2014 John Wiley & Sons, Ltd.     

Optomechanically Assisted Assembly of Surface‐Functionalized Zeolite‐L‐Based Hybrid Soft Matter

Nanoporous particles are particularly interesting for the assembly of functional nano‐ and microsystems because they provide hierarchical supramolecular organization of a large variety of guest molecules. In this work, arbitrary nanoarchitectures consisting of nanoporous zeolite‐L crystals are assembled by combining holographic optical tweezers (HOT) with polymer brush functionalized particles to overcome the limitations of 1D and restricted self‐assembly of zeolite‐L crystals. Readily prepared and functionalized polymer shells allow for controlled, instant, and highly efficient particle–particle and particle–surface adhesion without the need for an external trigger. In contrast to earlier studies, these assemblies remain permanently stable after release out of the HOT system. This novel strategy can be used to fabricate either motile units or locally grounded 1D, 2D, and 3D microconstructions, which can be further utilized as microtools in microfluidic and nanophotonic applications.     

STM images of transition metal surfaces: Theoretical study

We present a theoretical study of the influence of d orbitals on the evolution of the current tunnelling between the transition metal STM tip and the transition metal surface. This problem is considered for the system formed by Ni(001) surface and Pt tip. We have found that the tunnelling between d orbitals of the transition metal surface and of the apex atom of the transition metal tip may produce very sharp image of the metal surface, contrary to the tunnelling through weakly localized sp orbitals. The high effectivity of the tunnelling through this d-d channel is limited to very small tip-substrate separation. Presented at the VIII-th Symposium on Surface Physics, Třešt’ Castle, Czech Republic, June 28 – July 2, 1999. This work has been supported by the University of Wrocław within the grant No. 2016/W/IFD/98.     

The DFT study on non‐conjugated polymer host materials based on styrene derivatives for phosphorescent polymer light‐emitting diodes

A series of poly(4,4‐vinyltriphenylamine) based non‐conjugated polymer as host molecules are designed and studied by density functional theory. The results show that the substituent has a great influence on the properties of polymer. The parent molecule directly linked para‐carbazole, β‐pyrrole and triphenylamine are favorable to hole injection, and para‐carbazole could significantly increase E_T of the host molecules. The large changes of structural parameters between the lowest triplet state and ground state can cause the decrease of E_T. Moreover, parent molecule directly linked carbazole and triphenylamine units possess strong intramolecular charge transfer and low singlet and triplet energy difference (?E_ST). The calculated results also show that all designed host molecules are suitable for green emitter by comparing with the E_T. S₁ → S₁ and T₁ → T₁ energy transfer mechanism between host and guest is thermodynamically feasible. In addition, host–guest model is built to study the charge transfer nature, and the results indicate that a good intermolecular charge transfer can be achieved between host and guest materials. In the designed host molecules, the N atom of parent molecule linked para‐carbazole substituent shows a great potential for the green phosphorescent polymer light‐emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd.     

Dependence of the cross sections for Ir isotopes on the values of Qgg in the heavy ion collision

197Au were irradiated with 47 MeV/u 12C ions. Iridium was produced via the multinucleon transfer reactions in bombardments of 197Au with 12C. and was separated radiochemically from Au and the mixture of the reaction products. The γ radioactivities of Ir isotopes were measured by using a HPGe detector. The production cross sections of Ir isotopes were determined from activities of Ir isotopes at the end of bombardment and the other relative data. It has been found that the cross sections for neutron-rich isotopes of iridium show an exponential dependence on the values of Qgg. Our experimental results also demonstrate lack of correlation between the cross sections and Qgg in the case of neutron-deficient isotopes of iridium. The fact can be explained from that neutron-rich isotopes of iridium were produced in the deep inelastic transfer reactions.     

On the electronic density of states of the transition metals

XIS measurements of the elements Ir, Pt and Au are reported. High precision and reproducibility is obtained by the application of a “π/2-method” which approximates a Bragg angle of 90° at the dispersing crystal. Theoretical densities of states exist for Pt and Au. The agreement with the measured isochromats is good. A rigid-band model for Ir, Pt, and Au is ruled out by the measurements. Rather they suggest (combined with results of photoemission experiments) a narrowing of thed-bands from Ir through Pt to Au. Moreover, thed-band of Ir lies relative to thesp-band at a lower energy than thed-bands of Pt and Au. A fitting parameter concerning the experimental resolution is explained and considered as a possible indication of localization for XIS.     

Manipulation and control of a single molecular rotor on Au (111) surface

Three different methods are used to manipulate and control phthalocyanine based single molecular rotors on Au (111) surface: (1) changing the molecular structure to alter the rotation potential; (2) using the tunnelling current of the scanning tunnelling microscope (STM) to change the thermal equilibrium of the molecular rotor; (3) artificial manipulation of the molecular rotor to switch the rotation on or off by an STM tip. Furthermore, a molecular `gear wheel' is successfully achieved with two neighbouring molecules.     

Electric-dipole layer on Au(111) surfaces

We measured the barrier height (BH) a UHV scanning tunneling microscope on Au(111) surfaces with Au, Pt, and carbon nanotube tips. The 222?{^[¯] }3^[¯]\sqrt\Box3\Box]] reconstruction was observed with all the tips, and the current-voltage relation reflected the density of states of the tips. The BH measured on the reconstructed Au(111) surface using a modulation method showed a bias-polarity dependence as 30%, at low currents (<100 pA) irrespective of the tip material, while on unreconstructed Au surfaces, BH values were independent of the bias polarity, suggesting a dipole layer originating from the reconstructed Au(111) surface.