Ge-Bo Pan

2D Assembly of Metallacycles on HOPG by Shape-Persistent Macrocycle Templates

The synthesis and scanning tunneling microscopy (STM) investigations of shape-persistent arylene-ethynylene-butadiynylene macrocycles along with their codeposites with metallacycles are reported. 2D ordered arrays of macrocycles and macrocycle/metallacycle architectures (1:1) have been obtained on HOPG by self-assembly under ambient conditions. It is found that the ordered macrocycle array acts as a template for the deposition of the adlayer molecules. For each underlying macrocycle, one metallacycle has been detected. The unit-cell data of both, the macrocycles and their codeposites, show that the structural information of the macrocycle layer is perfectly transformed to the guest molecules. A rather unexpected observation is that the present compound could not be coadsorbed with C(60), indicating that only a minor change in the structure of the macrocycle has a dramatic effect on the ability of the monolayer to bind additional guest molecules.

Facile microwave-assisted synthesis of uniform Sb2Se3 nanowires for high performance photodetectors

A facile and rapid microwave-assisted method was developed to synthesize uniform single-crystalline Sb2Se3 nanowires in high yields. The as-prepared Sb2Se3 nanowires were directly used for fabricating prototype photodetectors. The device displayed a remarkable response to light intensity with an on/off ratio larger than 150, short response/recovery times (0.2/1.2 s), and long-term durability. The high sensitivity and robust environmental stability of the devices demonstrate the bright prospects for Sb2Se3 nanowires in highly efficient photodetectors for practical use.

Structural selection of graphene supramolecular assembly oriented by molecular conformation and alkyl chain

Graphene molecules, hexafluorotribenzo[a,g,m]coronene with n-carbon alkyl chains (FTBC-Cn, n = 4, 6, 8, 12) and Janus-type “double-concave” conformation, are used to fabricate self-assembly on highly oriented pyrolytic graphite surface. The structural dependence of the self-assemblies with molecular conformation and alkyl chain is investigated by scanning tunneling microscopy and density functional theory calculation. An interesting reverse face “up–down” way is observed in FTBC-C4 assembly due to the existence of hydrogen bonds. With the increase of the alkyl chain length and consequently stronger van der Waals interaction, the molecules no longer take alternating “up–down” orientation in their self-assembly and organize into various adlayers with lamellar, hexagonal honeycomb, and pseudohoneycomb structures based on the balance between intermolecular and molecule-substrate interactions. The results demonstrate that the featured “double-concave” molecules are available block for designing graphene nanopattern. From the results of scanning tunneling spectroscopy measurement, it is found that the electronic property of the featured graphene molecules is preserved when they are adsorbed on solid surface.

Preparation and ambipolar transistor characteristics of co-crystal microrods of dibenzotetrathiafulvalene and tetracyanoquinodimethane

Co-crystal microrods of dibenzotetrathiafulvalene (DBTTF) and tetracyanoquinodimethane (TCNQ) molecules with the mixed-stack structure were prepared via a facile solution process and fully characterized. The as-prepared microrods were directly used for fabricating prototype devices, which exhibited typical ambipolar charge transport characteristics. The result indicated that the co-crystal microrods of DBTTF-TCNQ were potentially useful for miniaturized devices.

Facile microwave-assisted synthesis of Klockmannite CuSe nanosheets and their exceptional electrical properties.

Klockmannite copper selenide nanosheets (CuSe NSs) are synthesized by a facile microwave-assisted method and fully characterized. The nanosheets have smooth surface and hexagonal shape. The lateral size is 200–500 nm × 400–800 nm and the thickness is 55 ± 20 nm. The current-voltage characteristics of CuSe NS films show unique Ohmic and high-conducting behaviors, comparable to the thermally-deposited gold electrode. The high electrical conductivity of CuSe NSs implies their promising applications in printed electronics and nanodevices. Moreover, the local electrical variation is observed, for the first time, within an individual CuSe NS at low bias voltages (0.1 ~ 3 V) by conductive atomic force microscopy (C-AFM). This is ascribed to the quantum size effect of NS and the presence of Schottky barrier. In addition, the influence of the molar ratio of Cu2+/SeO2, reaction temperature, and reaction time on the growth of CuSe NSs is explored. The template effect of oleylamine and the intrinsic crystal nature of CuSe NS are proposed to account for the growth of hexagonal CuSe NSs.

Facile microwave-assisted synthesis of uniform single-crystal copper nanowires with excellent electrical conductivity

A facile and rapid route for the synthesis of uniform single-crystal copper nanowires by a microwave-assisted method is demonstrated. The as-prepared copper nanowires exhibit excellent conductivity, which is comparable with electrospun copper nanofibers.

Oriented Organic Islands and One-Dimensional Chains on a Au(111) Surface Fabricated by Electrodeposition : An STM Study

Organic islands and oriented one-dimensional (1D) chains are fabricated on a Au(111) surface by electrodeposition. The cyclic voltammograms (CVs) of Au(111) in solutions containing nitrobenzene and picric acid show an electrochemical reaction in a negative potential region, which results in irreversible reductive deposition. The deposition process is monitored by in situ electrochemical scanning tunneling microscopy (ECSTM). At the double layer potential region, for example, nitrobenzene molecules form a well-defined adlayer in a (square root(3) x square root(3)) structure. With potential shifting negative to the reductive region, nitrobenzene is reduced to hydroxyaminobenzene. Organic islands were formed first and then aggregated into ordered 1D chains. The formation of these organic islands and 1D chains is completely potential-dependent. Intriguingly, the so-prepared islands and 1D chains are well-oriented along the reconstructed lines of the underlying Au(111) substrate and stable under ambient conditions even if the sample was removed from electrolyte solution. The results reported here provide a simple and effective method to fabricate oriented organic nanodots and nanowires on a solid surface by an electrochemical technique.

One-step fabrication of an ultralong zinc octaethylporphyrin nanowire network with high-performance photoresponse

An interconnected network of ultralong zinc octaethylporphyrin (ZnOEP) nanowires was fabricated via a solution process and directly used for constructing prototype photodetectors. The device exhibited high reproducibility and sensitivity with the largest photoswitching ratio over 104. The facile fabrication process and the superior performance made ZnOEP an ideal candidate for photodetector applications.

Metal Ions Mediated Morphology and Phase Transformation of Chalcogenide Semiconductor: From CuClSe2 Microribbon to CuSe Nanosheet

Foreign ions are of significant importance in controlling and modulating the morphology of semiconductor nanocrystals during the colloidal synthesis process. Herein, we demonstrate the potential of foreign metal ions to simultaneously control the morphology and crystal phase of chalcogenide semiconductors. The results indicate that the introduction of Al(3+) ions can induce the structural transformation from monoclinic CuClSe2 microribbons (MRs) to klockmannite CuSe nanosheets (NSs) and the growth of large-sized CuSe NSs. The as-prepared micrometer-sized CuSe NSs exhibit a high-conducting behavior, long-term durability, and environment stability. The novel properties enable CuSe NSs to open up a bright prospect for printable electrical interconnects and flexible electronic devices.

Linear dislocation tunes chirality: STM study of chiral transition and amplification in a molecular assembly on an HOPG surface

Molecular arrangement and transition in the domain boundary of a chiral two-dimensional assembly is clearly revealed by high-resolution STM images on an HOPG surface and a linear dislocation formed by molecular trimers and located at opposite chiral domains is found to directly reverse the chirality on DTCD self-assembly.