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Surface-enhanced Fourier transform Raman scattering (FT-SERS) spectroscopy was used to characterize the adsorption structure of a poly[dA]·2poly[dT] DNA triplex at an ex-situ roughened silver electrode. We found that the triplex molecules have a favorable tendency to be adsorbed without any obvious destabilization at higher positive-charged surfaces via a phosphate-moiety-directed mechanism. However, the observed enhancement of intense Raman signals exhibits long-range rather than short-range character, as evidenced by the appearance of several strong SERS bands involving relevant vibrations of the ribose−phosphate backbone and the dT residues. Therefore, this phenomenon cannot be satisfactorily interpreted by the short-range enhancement mechanism that is usually believed to be the main contribution of the Raman enhancement of double-helical nucleic acids at a charged silver surface.

In this research, we studied the adsorption structure of an RNA triplex, poly[rU]poly[rA]poly[rU], at a silver electrode by surface-enhanced Fourier transform Raman scattering (FT-SERS) spectroscopy and compared it to those of the corresponding single-stranded poly[rA] and duplex poly[rA] · poly[rU]. Some interesting phenomena have been observed. At the ex situ electrochemically roughened silver electrode, the SERS behavior of the duplex RNA is close to that of the single-stranded poly[rA], thereby indicating that the duplex RNA adsorbed at the electrode might be partly destabilized. However, on the highly positively charged surfaces, the SERS spectra revealed that the triplex was predominantly adsorbed at the electrode via the phosphate-moiety-directed mechanism, and thus the helical structure of the triplex molecules was well preserved; furthermore, since the electrode potential was set to approach the potential of zero charge (pzc) of the silver metal, in the spectral region between 1800 and 600 cm−1 the triplex gives rise to SERS spectra similar to those of the corresponding duplex, and also yields only two enhanced signals at 734 and 1382 cm−1, due to the ring-breathing and ring-vibration modes of the adsorbed adenine residues, respectively, along with the disappearance of some bands originating from the corresponding rU residues and phosphate groups. In fact, a dramatic transition of the SERS spectra of the triplex at the electrode was found to occur between −0.2 and −0.4 V. On the basis of the structural characteristics of triple-helical nucleic acids, we concluded that in this case there are two types of competitive adsorbed species—the triplex itself and the unpaired adenine residues in the incomplete region of the triplex RNA—which might be responsible for the unique potential-dependent transition.

The isolation of multiple-isomers of Sc2@C80 (I, II, III) endohedral metallofullerenes is reported for the first time. The new C80-based Sc-metallofullerenes are characterized by UV-Vis-NIR absorption spectroscopy and detailed chromatographic retention time data. A close relationship between the isomer structure and the corresponding HPLC retention time of the metallofullerenes is presented.

The composite material of poly-(L-lactide) (PLLA) and carbon nanotubes (CNTs) were prepared. Its surface morphologies and property were worked out by using atomic force microscopy (AFM) and contact angle measurement. Moreover, the prime cytocompatibility was used to investigate the biocompatibility of the composite material containing CNTs and the effects of CNTs on one aspect of cell function, cell affinity. The results obtained indicate that the composite material of PLLA and CNTs possesses good bio-compatibility for both the 3T3 fibroblasts and Oct-1 osteoblast-like cells. The addition of CNTs will greatly affect cell affinity of the material, which may be disadvantage for the cell adhesion.

Luminescence photobleaching is a long-standing problem encountered in luminescence analysis. There has been a great deal of interest in elucidating the photobleaching of diVerent Xuorescent probes and in deriving methods to delay the photobleaching. In the single-molecule Xuorescence study of organic-dye-labeled molecules, -mercaptoethanol is often used alone or together with scavenging reagents to reduce photobleaching [1]. However, -mercaptoethanol is not always eVective in photobleaching suppression [2]. Despite the studies on photobleaching of diVerent Xuorescent probes, little about the luminescence recovery of the photobleached Xuorophores is known. Fluorescence recovery after photobleaching [3], which has been used extensively to measure translational mobility of Xuorophores, is based on the Xuorescence recovery resulting from passive diVusion and translational processes; thus it is not a direct measurement of the Xuorescence recovery of the bleached Xuorophores. Recently, enzyme-dependent Xuorescence recovery of nicotine adenine dinucleotide by dehydrogenase was reported [4]. Up to now, there has been no report on the luminescence recovery of Xuorophores that intercalate within DNA. Ru(phen)2(dppx) 2+ (dppx, 7,8-dimethyl-dipyridophenazine; phen, 1,10-phenanthroline) is one of the Ru (II)–ligand complexes that have exhibited unique photophysical properties such as the “DNA light switching” eVect [5]. These “light switching” complexes have no lumi

The three-dimensional molecular models of DNA triple helices and triple-stranded brain-like structure were built up by molecular architecture, and their structural features and energy decomposition were examined. The results showed: (i) The base triplet is the element forming braid-like and triple helix DNA; (ii) Under specified conditions, DNA could form the triplet-stranded braid like structure; (iii) DNA stability of the braid-like structure is less than that of the triple-helix structure.

Oligonucleotides with a basic sequence of 5′-d-(TC) 3 T m (CT) 3 C n (AG) 3 -3′ have been designed and chemically synthesized. The pH-stability curves and fluorescence spectra reveal that these oligomers undergo a similar self-folding process on a reduction in pH, and form intramolecular DNA triple-helical structures containing loops of different lengths at acidic pH. FT-IR spectra recorded in D 2 O solution also provide independent evidence of base triad formation, and indicate that the loop length does not significantly influence the conformation of the Py-motif intramolecular DNA triplexes in acidic solution, wherein all four triplexes predominantly take on S-type sugar conformations, but with a different relative proportion of S-type sugar pucker to N-type depending on the loop length.

Fourier transform surface enhanced Raman scattering (SERS) spectroscopy has been used to characterize triplex RNA poly[rU] · poly[rA] · poly[rU] adsorbed on silver colloid using an Nd:YAG laser as an excitation source. In this case, SERS spectra of high quality are recordable in a relatively short time. Compared to the FT-Raman spectrum of the triplex in solid, two distinct SERS bands centered at 835 and 819 cm −1 indicate that the helical structure of the triplex RNA in the proximity of the colloidal silver surfaces is well preserved. From UV-vis spectroscopy, the aggregation state of original silver colloids might not be distinctly altered after the triplex RNA was added up to 1 × 10 −5 M. Moreover, scanning tunneling microscopy (STM) observations of the triplex-silver colloid complex also clearly reveal that the aggregation state of the silver colloids is changed from original dispersed particles to predominantly ordered adsorption along the phosphate backbone of the triplex with some aggregation, indicating that the microstructural changes of the silver surfaces play an important role in the SERS effect.

The surface morphology and growth mechanism ofc-oriented YBa2Cu3O7 thin films deposited on Y-stabilized zirconia substrate by laser deposition has been investigated with scanning tunneling microscopy. Both screw dislocation and layered island growth processes took place. Surface features such as screw dislocation, steps, subgrain boundaries, holes, and troughs were present, suggesting that they may act as pinning sites for flux lines. A thin layer of nonsuperconducting material with a thickness of a few angstroms is seen on the surface of the film.

Three large‐area YBa2Cu3O7(YBCO) superconducting thin films have been laser‐deposited under almost identical conditions. However, the microwave surface resistance Rs of the films deviated greatly, they are 280 μΩ, 3.78 mΩ, and 97 mΩ, respectively. It was found that the structure and morphology of the films greatly influence the resistive losses at 10 GHz and 77 K of the YBCO thin films. Different loss mechanisms were discussed. For high Rs, the large angle grain boundaries were the dominate defect in the thin films and increased the Rs of the film markedly. For low Rs, it was mainly due to the misaligned ‘‘123’’ grains in the thin films and the intrinsic loss. For Rs up to the mΩ range, besides the misaligned 123 grains, domain boundaries and nonsuperconducting outgrowths of different sizes appeared and this caused the rise of Rs value. All these results were given experimentally and discussed theoretically.

Observations of significant template effects of the organic molecular support of tridedycelamine (TDA) lamellae structure with scanning tunneling microscopy (STM) is presented. The site selective adsorption and directional diffusion of single molecules and molecular clusters of copper phthalocyanine (CuPc) are identified. In addition, bimolecular CuPc band structure is achieved as the result of the selective adsorption and diffusion. These results could be beneficial to the construction of molecular nanostructures using organically functionalized substrates as templates.

The interaction of atomic hydrogen with the Si(100)2×1 surface has been investigated in detail by a field ion-scanning tunneling microscope (FI-STM). At low exposure, hydrogen atoms reside singly on top of the dimerised Si atoms, and are imaged brightly. The hydrogen chemisorption induces the buckling of dimers, indicating the strong bonding between Si and hydrogen atoms. The adsorption geometry changed from the (2×1) monohydride phase to the (1×1) dihydride phase with increasing exposure of hydrogen. The former is imaged dark compared with the unreacted Si dimers due to the reduction of the density of electronic states near the Fermi level. Surface etching was also observed during the formation of the dihydride phase. The behavior of hydrogen desorption from the H-saturated Si(100) surface was investigated as a function of annealing temperatures. Our STM results suggest that the desorbing H2 molecules are formed by two hydrogen atoms on the same dihydride species.

The investigations of nonlinear optical crystal surface structures have been reported in this paper for the first time. The AFM observations for cleavage (101) surface and (001) surface of NPP crystal indicate that the molecular arrangements on both of them are the same with its bulk structure, without any superstructure. And the phenyl and pyrrolidine rings in (001) surface can be distinguished. The angle between the molecular charge transfer axis and the binary axis obtained by AFM is 56°, closed to the optimal angle, which leads to the large nonlinear optical efficiency of NPP crystal.

A new compound, 1,3,5-tris(carboxymethoxy)benzene, which forms infinite two-dimensional hexagonal networks, has been synthesized. Its self-assembly behavior at gas–solid interfaces has been studied by scanning tunneling microscopy.

Finely dispersed sandwich composite nanoparticles of Cu–Ni–Cu were prepared by a novel method combining template synthesis and an ultrasonic treatment method. The composite nanoparticles have uniform cylinder shape with tunable diameter and length. Transmission electron microscopy (TEM) and electron diffraction (ED) were employed to characterize the nanoparticles. This method can be used to fabricate shape- and size-controlled composite nanoparticles in a wide range of metals and other materials. The so-prepared particles may be suitable candidates as nanoscale blocks for assembling nanodevices.

The self-assembly of monodendrons with peripherally attached alkyl substituents has been studied by scanning tunneling microscopy. The disklike assembly, a characteristic structure of low generation dendrimers, has been directly observed. The subunits of disk structure can be well resolved as well as the ordered alkyl parts.

A series of 1,3,5-triazines incorporating benzeneazonaphthalene moieties have been synthesized and STM observations have clarified the geometrical configuration of the self-assembled molecules on a graphite surface.

A technique applying voltage across the tunnel junction for writing permanent features on graphite with lines about 10 nm width using our home-build scanning tunneling microscope has been presented. Multiple-tip effects while modifying the surface are often met. The phenomena are explained in terms of the strong electric field existing at the junction between the tip and the surface. In addition, the shape of the structure indented by the tip is in agreement with that of the tip.

This article reports structural and electronic properties of sodium adsorbed on room‐temperature GaAs(110) surface as observed with scanning tunneling microscopy in an ultrahigh vacuum. In the low‐coverage regime, Na adatoms reside on the bridge site encompassing one Ga and two As surface atoms to form linear chains along the [110] direction. The Na–Na nearest‐neighbor distance in this low‐density chain structure is 8 A. When the Na coverage was increased to ∼0.09 ML (1 ML≡2 Na per substrate unit cell), the chains became slightly disordered. Some of them were packed closer to form domains with local 2×2 structure. None of high‐density two‐dimensional ordered structures or low‐density zigzag chains was observed, in contrast to the Cs/GaAs(110) system. Additional Na adsorption resulted in the formation of three‐dimensional disordered clusters. The saturation coverage of Na adsorption on the GaAs(110) surface was determined to be ∼0.1 ML. No evidence of metallic characteristics was found in the I–V curves recorded over the various Na‐covered surfaces.This article reports structural and electronic properties of sodium adsorbed on room‐temperature GaAs(110) surface as observed with scanning tunneling microscopy in an ultrahigh vacuum. In the low‐coverage regime, Na adatoms reside on the bridge site encompassing one Ga and two As surface atoms to form linear chains along the [110] direction. The Na–Na nearest‐neighbor distance in this low‐density chain structure is 8 A. When the Na coverage was increased to ∼0.09 ML (1 ML≡2 Na per substrate unit cell), the chains became slightly disordered. Some of them were packed closer to form domains with local 2×2 structure. None of high‐density two‐dimensional ordered structures or low‐density zigzag chains was observed, in contrast to the Cs/GaAs(110) system. Additional Na adsorption resulted in the formation of three‐dimensional disordered clusters. The saturation coverage of Na adsorption on the GaAs(110) surface was determined to be ∼0.1 ML. No evidence of metallic characteristics was found in the I–V curves r...

A field ion-scanning tunneling microscope has been employed to study the geometry and the coverage-dependent growth structures formed by Na deposition on the GaAs(110) surface at room temperature. Our data showed that at the early absorption stage Na adatoms reside on bridge sites encompassing one Ga and two surface atoms to form linear chains along the [1 1 0] direction. The Na-Na nearest-neighbor distance in this low density chain structure is 8 A. At slightly increased coverage, a local 2 X 2 structure was observed. In contrast to the Cs/GaAs(110) surface, neither a two-dimensional ordered structure nor low-density zigzag chains were observed. Additional Na adsorption resulted in the formation of three-dimensional disordered clusters.

The effect of chemically modified tips on STM imaging was investigated. An electrochemical technique was used to prepare a monolayer of sulfur and iodine on the apex of STM tips. The chemically modified STM tips were first employed to image a 1-octadecanethiol (1-C18H37SH) adlayer on a highly oriented pyrolytic graphite (HOPG) surface. The images acquired with S-modified tips could ascertain the structural detail of thiol groups of the adsorbed molecules, while that acquired with I-modified tips appeared in a low resolution. The contrast variations of STM images are attributed to the changes of electronic states of the tips.

Effect of relative humidity on the surface adhesion force of several inorganic crystals of mica, CaF2 and KCl was studied by atomic force microscopy (AFM). The results showed that the magnitude of surface adhesion force is mainly dependent on the surface free energy of the adsorbed liquid film, but almost independent of the thickness of the film. Furthermore, the deliquescence on the crystal surface was investigated, which demonstrated the capability of the force spectrum method to monitor changes in ionic concentrations of adsorbed liquid film in real-time.

The imaging process with atomic force microscopy (AFM) in air is influenced by many factors, such as tip size and geometry, scan speed, ambient humidity, etc. In an ambient environment the imaging can be affected greatly by the humidity of the atmosphere because of the formation of the meniscus along the tip-sample interface. The capillary force between the tip and the sample is generally large enough to make it difficult to obtain a high-resolution image, therefore it is necessary to eliminate this capillary in order to obtain improved images. To this end, we modified tips with CH 3 -terminated organosilane to make them hydrophobic. With such tips we obtained (in AFM/LFM mode) improved images of soft materials such as the water layer and the self-assembled monolayer (SAM). For octadecantrichlorosilane (OTS) SAM chemisorbed on mica, high-resolution lattice-resolved images also were collected. The results demonstrated that these hydrophobic tips were suitable for obtaining improved images.

Using a monolayer of stearic acid molecules as a buffer layer, nitrobenzene has been immobilized on highly oriented pyrolytic graphite (HOPG) and imaged by scanning tunnelling microscopy (STM) with submolecular resolution. The results indicate that the image contrast is determined by the lowest unoccupied molecular orbital (LUMO) whether a positive or negative bias is applied. This strategy can be used as a general method to characterize small organic molecules by STM under ambient conditions.

With submolecular resolution, scanning tunneling microscopy (STM) has been used extensively to study adsorption phenomena of organic molecules on surfaces. In this paper, we report a STM study of the isomeric compound of 4,4'-bipyridyl (4Bpy) and 2,2'-bipyridyl (2Bpy) co-adsorbed with stearic acid on a highly oriented pyrolytic graphite (HOPG) surface. The 4Bpy and 2Bpy are isomeric compounds, and their only difference is the positions of the nitrogen atoms in each molecule. When Bpy molecules are mixed with stearic acid, the nitrogen atoms of Bpy can hydrogen bond with the COOH group of stearic acid, and hence the positions of the nitrogen atoms determine the hydrogen bond structure. It is observed that in the 4Bpy-stearic acid system the angle of the 4Bpy to the stearic acid molecular axis is ∼165°, whereas in the 2Bpy-stearic acid system the angle of the 2Bpy to the stearic acid molecular axis is ∼125°. The distances between two neighbouring 'bright' rows in an STM image are different in these two systems. Thus, by using this hydrogen bond method we can distinguish the 4Bpy molecule from its isomeric 2Bpy molecule. Furthermore, as reported previously, we observe the enantiomeric molecular patterns in both 4Bpy and 2Bpy systems.

Nanoscience and nanotechnology is the creation and utilization of materials, devices, and systems through the control of matter on the nanometer-scale. Its essence is the ability to work at these levels to generate larger structures exhibiting novel physical, chemical, and biological properties and phenomena. The aim of nanoscience and nanotechnology is to learn to exploit these properties and efficiently manufacture and employ the structures. The control of matter on nanoscale has already played an important role in scientific disciplines as diverse as physics, chemistry, materials science, biology, medicine, engineering, and computer simulation.

Scanning tunneling microscopic images of doped polyaniline (PANI) with HCl are presented. Parallel chains with average separation of 0.4 nm are clearly visible, and the measured distance between the nearest two maxima in the polymer chain is about 1.04 nm. Molecular-mechanic calculations were used to optimize the conformation of a model polyaniline chain, and have yielded numerical values which agree well with measurements taken from the STM images.

A new in-situ electrochemical scanning tunneling microscope (ECSTM) has been designed in our laboratory with the following main features: (1) The normal electrochemical current at the tip during scanning can be automatically corrected by a newly designed special feedback loop and computer program. (2) The tip-sample bias potential and the individual electrode potential of tip or sample can be adjusted, scanned or cycled by computer according to the requirement. (3) Driving and adjusting the tip to a nanometer distance from the sample surface can be carried out by a computer-controlled motor. A preliminary example of application to electrochemical systems is presented.

Participants bring expertise and ideas from diverse scientific backgrounds to the CAKFoS symposia, which are designed to promote cross-disciplinary discussion and generate new ideas. Each symposium is organized around eight topics, jointly selected by a committee of CAS and NAS delegates, and based largely on feedback from the previous year's meeting. Session chairs and speakers highlight the major challenges, methodologies, and limitations in their fields without using technical jargon to ensure that nonspecialists are able to understand and contribute to the meeting. Speakers and participants pose and field challenging questions that probe into and across traditional boundaries of research disciplines.

HgCl2 can disperse onto the surface of activated carbon as a monolayer to form a catalyst for making vinyl chloride from C2H2 and HCl. A monolayer dispersion capacity of 0.020 g. HgCl2/100 m2 activated carbon was determined by x‐ray diffraction. In order to understand further the catalytic mechanism of this kind of catalyst, the dispersed structure of HgCl2 supported on highly oriented pyrolitic graphite (HOPG) has been studied by scanning tunneling microscopy (STM). The HgCl2–HOPG sample is obtained by putting a drop of dilute HgCl2 solution on the surface of HOPG and drying in air. The HgCl2–HOPG surface is imaged by computer controlled STM under ambient conditions and at room temperature. In constant‐current mode, bright spots with regular structure over the periodic structure of HOPG has been observed in the image. The size of bright spot is about (4×9) A which corresponds to a single HgCl2 molecule. It suggests that HgCl2 molecules form a monolayer on the surface of HOPG with a (3.6×3.6) R14.3° surfa...

The surface of silver containing salt of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) was studied with the computer-controlled scanning tunneling microscope developed in our laboratory. The crystal surface of the charge-transfer complex is well ordered and a regular array of corrugations is clearly visible. The prominent feature of the experimental scanning tunneling microscopy images is in agreement with the bulk crystal structure obtained by x-ray diffraction method.

Trudged through my scientific career, I have published key research works in Chinese Science Bulletin. As one of the loyal readers and authors of this prestigious academic journal, I was thrilled when I first published in Chinese Science Bulletin and I believe that numerous scientists share the excitement for the same and benefit from publishing in the journal over years. Chinese Science Bulletin is entering a new era with its invigorated globalization task, fortified effort to increase its academic impact, strengthened engagement of scientists from different but integrated disciplines. Together with all these exciting developments, the journal has adopted a new name—Science Bulletin. Congratulations for the publishing of the inaugural issue of Science Bulletin, in which I see the continuation of a great tradition and the beginning of a rejuvenated excellence. Publishing in top tier academic journals offers great opportunities for communicating scientific discoveries, for inviting widespread academic debates and validation, and for gaining more recognition and exposure for scientists and their research works. This is a critical element of scientific exploration and an essential part of career development of scientists at all stages, more so for those in their early-stage career. The extravagantly increased investment in scientific research from Chinese government in recent years has significantly enhanced the impact of research productivity of Chinese scientists to the scientific publishing world. As a result, China has become the second leading producer in the world in terms of the number of published scientific papers. Chinese Academy of Sciences is committed to further improve the overall quality of the Chinese research publications, continues to encourage Chinese scientists to explore the uncharted scientific frontiers, and will offer substantial support for risky but innovative, long-term but fundamental research projects. Academic journals are usually the voice and image which showcase the scientific excellence and the advances in research and development of a country. From the inauguration of the first academic journal of China, Kexue (Science), in January of 1915 to the arrival of Science Bulletin today, the past century has witnessed the unwavering determination of Chinese scientific community for pursuing the dream of establishing world-leading international academic journals. Currently, Chinese Academy of Sciences sponsors hundreds of academic journals, representing the highest level of scientific publishing activity in China and covering every and all scientific disciplines. Success bestows success. We will enhance the international competitiveness and academic impact of the existing and new journals. In this regard, the launch of Science Bulletin is both timely and opportunistic as we are marching in building prestigious and China-based flagship academic journals. I sincerely wish Science Bulletin will grow into an internationally renowned academic journal and serve as a preferred medium for publishing cutting-edge research discoveries made in China and in the world at large. President of Chinese Academy of Sciences

Scanning tunneling microscope (STM) was used to study the core-shell structures of polymer protected metal nanoparticles. The section analysis permits the determination of the polymer-metal interfaces within individual particles with high reliability. A simple model based on particle geometry is presented to interpreted the fact qualitatively.

Based on the push–pull mechanism, we have developed a piezoelectric micropositioner, with a new mechanical construction. The positioner is basically composed of two piezoelectric actuators as the source of the motion and three permanent magnet feet to produce enough friction force for clamping. The movement of more than 5 mm with the steps of 150–700 nm at the speed of 50–200 steps per second can be accomplished by applying very low driving voltage to the positioner. The absence of clamping voltage in this positioner makes it well suited for use in ballistic electron emission microscope (BEEM). A BEEM operated in a gas-controlled environment based on it has been built and its performances have been tested.

Highly ordered Ni-Pt multilayered nanowire arrays have been fabricated using a porous anodic aluminum oxide (AAO) template by pulse electrodeposition. The cylindrical Ni nanoparticles with different lengths and diameters in these arrays were characterized by transmission electron microscope (TEM) and alternating-gradient magnetometer (AGM) measurements. Magnetization measurements revealed that an array of such nanowires with 20-nm diameters has an enhanced coercivity (ca. 1169 Oe) and a high remanence ratio (ca. 0.96).

The characteristics of the nanostructure on the surface of highly oriented pyrolytic graphite (HOPG) involving field emitted electrons is examined with scanning tunneling microscopy (STM). A simple model based on the continuum electron diffusion is proposed and is compared with the experimental results. It suggests that the process could be associated with the diffusion of electrons at the vicinity of the injection position. It also implies that the characteristics of the as‐produced nanometer sized craters could be correlated to the anisotropy degree of the transport properties of HOPG.

Self-assembled monolayer of a double-stranded DNA, which was formed by a 20-nt 5'-thiol-modified oligonucleotide at the interface of Au(111)/solution, has been imaged and studied with electrochemical scanning tunneling microscopy (ECSTM). The results showed that the preferred directions of the adsorbed DNA were110and112. The measured width of the DNA stripes was 0.95 +/- 0.02 nm, which was consistent with the width of dsDNA base pairs. The contour of DNA in the STM image consisted of a series of blobs, which were due to the anchoring of the bases to the substrate along the dsDNA chain. The imaging of a large-scale array of DNA lying flat on the substrate offers a convenient method for the further application of high-resolution STM to the study of the interaction between DNA and a variety of molecules.