Hao-Li Zhang

Lanzhou University, College of Chemistry and Chemical Engineering, Faculty Member

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Address: 甘肃省兰州市天水南路222号，兰州大学

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Papers by Hao-Li Zhang

The Enhancement of Performance and Mechanism Studies of All-solution Processed Small-Molecule based Solar Cells with an Inverted Structure

ACS applied materials & interfaces, Jan 9, 2015

Both solution-processed polymer and small molecule based solar cells have achieved PCEs over 9% w... more Both solution-processed polymer and small molecule based solar cells have achieved PCEs over 9% with the conventional device structure. However, for the practical applications of photovoltaic technology, further enhancement of both device performance and stability are urgently required, particularly for the inverted structure devices, since this architecture will probably be most promising for the possible coming commercialization. In this work, we have fabricated both conventional and inverted structure devices using the same small molecular donor/acceptor materials and compared the performance of both device structures, and found that the inverted structure based device gave significantly improved performance, the highest PCE so far for inverted structure based device using small molecules as the donor. Furthermore, the inverted device shows a remarkable stability with almost no obvious degradation after three months. Systematic device physics and exciton dynamics studies, includi...

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Understanding the Halogenation Effects in Diketopyrrolopyrrole-Based Small Molecule Photovoltaics

ACS Applied Materials & Interfaces, 2015

Two molecules containing a central diketopyrrolopyrrole and two oligothiophene units have been de... more Two molecules containing a central diketopyrrolopyrrole and two oligothiophene units have been designed and synthesized. Comparisons between the molecules containing terminal F (FDPP) and Cl (CDPP) atoms allowed us to evaluate the effects of halogenation on the photovoltaic properties of the small molecule organic solar cells (OSCs). The OSCs devices employing FDPP:PC71BM films showed power conversion efficiencies up to 4.32%, suggesting that fluorination is an efficient method for constructing small molecules for OSCs.

Redox Behavior and Ion-Pairing Thermodynamics of Ferrocene and Its Derivatives in the Organic Phase

The Journal of Physical Chemistry C, 2010

The redox behavior and ion-pairing thermodynamics of ferrocene and its derivatives (dimethylferro... more The redox behavior and ion-pairing thermodynamics of ferrocene and its derivatives (dimethylferrocene and decamethylferrocene) in a nitrobenzene (NB) thin film imposed between a graphite electrode and an aqueous electrolyte solution have been studied. We have shown that the presence of supporting electrolytes in the organic phase complicates their redox behavior, i.e., both the oxidation potential and peak area change significantly with time. In the absence of supporting electrolytes in the NB phase, the redox potential of the ferrocene molecules also shifts when the concentration of the supporting electrolytes (NaClO4 or HClO4) in the aqueous phase varies. It has been confirmed upon considering the influence of liquid−liquid junction potential that such a potential shift is dictated by the formation of ion pairs between the electrochemically generated ferricenium cations and the counteranions in the organic phase. On the basis of the determination of anion (ClO4−) concentrations in the NB film, we were a...

Surface Plasmon Raman Scattering Studies of Liquid Crystal Anchoring on Liquid-Crystal-Based Self-Assembled Monolayers

by Edward Cheadle, Richard Bushby, and Hao-Li Zhang

The Journal of Physical Chemistry B, 2009

We studied the anchoring of 6CB on a series of self-assembled monolayers (SAMs) with a functional... more We studied the anchoring of 6CB on a series of self-assembled monolayers (SAMs) with a functional group that mimics that of the nematic liquid crystal (LC). The SAMs were first characterized by wetting, Fouriertransform infrared spectroscopy, and surface potential measurements. We found that, in two of these SAMs, the end group dipoles were oriented close to the normal of the surface and that these promoted homeotropic anchoring. In the case of the other SAM, the dipole was oriented parallel to the surface, and planar anchoring was obtained. Raman scattering by adsorbates on thin metal films is enhanced by the electromagnetic fields of surface plasmon polaritons (SPPs). Despite the inherent polarization of SPPs, there have been few reports in which SPP Raman scattering has been used to study molecular orientation. We have developed optical instrumentation to provide efficient excitation and collection of SPP Raman scattered light using attenuated total reflection geometry. The Kretschmann prism coupling configuration was used to excite SPPs on thin (500 Å) gold films with adsorbed SAMs of alkanethiols in contact with thin films (50 µm) of the nematic liquid crystal 4′-hexylbiphenyl-4-carbonitrile (6CB, Merck). The anchoring and orientational wetting of the LC 6CB at the interface with ω-functionalized SAMs was studied using this arrangement. In agreement with the results of previous studies, a high-energy surface (-COOH) was found to promote planar anchoring, whereas a low-energy surface (-CF 3 ) was found to induce homeotropic anchoring.

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Highly efficient heterogeneous synthesis of benzofurans under aqueous condition

Tetrahedron, 2014

The reactions can be performed without microwave irradiation providing the corresponding products... more

Synthesis of novel biotin anchors

by Richard Bushby and Hao-Li Zhang

Tetrahedron, 2001

AbstractÐDetails are reported of the synthesis of biotinylated thiol and cholesteryl derivatives.... more

format_quoteA new synthesis route for biotinylated thiols is introduced, fully characterizing the compounds involved and improving accessibility to the field.format_quote

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Synthesis and characterization of new planar butterfly-shaped fused oligothiophenes

Tetrahedron, 2012

ABSTRACT

New Oligothiophene-Pentacene Hybrids as Highly Stable and Soluble Organic Semiconductors

Organic Letters, 2009

Two series of new oligothiophene-pentacene hybrid compounds were successfully synthesized and cha... more Two series of new oligothiophene-pentacene hybrid compounds were successfully synthesized and characterized, which consist of pentacene and anthradithiophene skeletons modified by different oligothienyl groups at 6,13 sites or 5,11 sites, respectively. Their optical, thermal, and electrochemical properties show regular variations with the length change of the side groups. These materials exhibit much higher solubility and significantly improved thermal and photooxidation stabilities compared with unmodified pentacene and anthradithiophene.

Synthesis of Oligo(phenylene ethynylene)s with Dendrimer “Shells” for Molecular Electronics

Organic Letters, 2007

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Improving gas sensing properties of graphene by introducing dopants and defects: a first-principles study

Nanotechnology, 2009

The interactions between four different graphenes (including pristine, B or N doped and defective... more The interactions between four different graphenes (including pristine, B or N doped and defective graphenes) and small gas molecules (CO, NO, NO 2 and NH 3 ) were investigated by using density functional computations to exploit their potential applications as gas sensors. The structural and electronic properties of the graphene-molecule adsorption adducts are strongly dependent on the graphene structure and the molecular adsorption configuration. All the four gas molecules show much stronger adsorption on the doped or defective graphenes than that on the pristine graphene. The defective graphene shows the highest adsorption energy with CO, NO and NO 2 molecules, while the B-doped graphene gives the tightest binding with NH 3 . Meanwhile, the strong interactions between the adsorbed molecules and the modified graphenes induce dramatic changes to graphene's electronic properties. The transport behavior of a gas sensor using B-doped graphene shows a sensitivity two orders of magnitude higher than that of pristine graphene. This work reveals that the sensitivity of graphene based chemical gas sensors could be drastically improved by introducing appropriate dopant or defect.

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Tuning the electronic structure and transport properties of graphene by noncovalent functionalization: effects of organic donor, acceptor and metal atoms

Nanotechnology, 2010

Using density functional theory and nonequilibrium Green&amp;amp;amp;amp;amp;amp;amp;amp;amp;... more Using density functional theory and nonequilibrium Green&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s function (NEGF) formalism, we have theoretically investigated the binding of organic donor, acceptor and metal atoms on graphene sheets, and revealed the effects of the different noncovalent functionalizations on the electronic structure and transport properties of graphene. The adsorptions of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and tetrathiafulvalene (TTF) induce hybridization between the molecular levels and the graphene valence bands, and transform the zero-gap semiconducting graphene into a metallic graphene. However, the current versus voltage (I-V) simulation indicates that the noncovalent modifications by organic molecules are not sufficient to significantly alter the transport property of the graphene for sensing applications. We found that the molecule/graphene interaction could be dramatically enhanced by introducing metal atoms to construct molecule/metal/graphene sandwich structures. A chemical sensor based on iron modified graphene shows a sensitivity two orders of magnitude higher than that of pristine graphene. The results of this work could help to design novel graphene-based sensing or switching devices.

Can Graphene be used as a Substrate for Raman Enhancement?

by Hao-Li Zhang and Yuan Fang

Nano Letters, 2010

Graphene is a monolayer of carbon atoms packed into a two-dimensional (2D) honeycomb crystal stru... more Graphene is a monolayer of carbon atoms packed into a two-dimensional (2D) honeycomb crystal structure, which is a special material with many excellent properties. In the present study, we will discuss the possibility that graphene can be used as a substrate for enhancing Raman signals of adsorbed molecules. Here, phthalocyanine (Pc), rhodamine 6G (R6G), protoporphyin IX (PPP), and crystal violet (CV), which are popular molecules widely used as a Raman probe, are deposited equally on graphene and a SiO 2 /Si substrate using vacuum evaporation or solution soaking. By comparing the Raman signals of molecules on monolayer graphene and on a SiO 2 /Si substrate, we observed that the intensities of the Raman signals on monolayer graphene are much stronger than on a SiO 2 /Si substrate, indicating a clear Raman enhancement effect on the surface of monolayer graphene. For solution soaking, the Raman signals of the molecules are visible even though the concentration is low to 10 -8 mol/L or less. What's more interesting, the enhanced efficiencies are quite different on monolayer, few-layer, multilayer graphene, graphite, and highly ordered pyrolytic graphite (HOPG). The Raman signals of molecules on multilayer graphene are even weaker than on a SiO 2 /Si substrate, and the signals are even invisible on graphite and HOPG. Taking the Raman signals on the SiO 2 /Si substrate as a reference, Raman enhancement factors on the surface of monolayer graphene can be obtained using Raman intensity ratios. The Raman enhancement factors are quite different for different peaks, changing from 2 to 17. Furthermore, we found that the Raman enhancement factors can be distinguished through three classes that correspond to the symmetry of vibrations of the molecule. We attribute this enhancement to the charge transfer between graphene and the molecules, which result in a chemical enhancement. This is a new phenomenon for graphene that will expand the application of graphene to microanalysis and is good for studying the basic properties of both graphene and SERS.

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Microporous Aluminum Oxide Membrane-Based Optical Interferometric Sensor

Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, 1999

The aluminum oxide membrane containing uniform micro-pores displays well-resolved interference pa... more The aluminum oxide membrane containing uniform micro-pores displays well-resolved interference pattern in the reflectance spectrum. Adsorption of molecules onto the surface of the porous layer leads to pronounced shifts of the interference pattern. Basing on the changes of pattern, the microporous aluminum oxide membrane could be used for fabricating a new class of sensor. Our experiments demonstrate that the detective

Voltage-dependent morphology, wettability and photocurrent response of anodic porous titanium dioxide films

Microporous and Mesoporous Materials, 2009

ABSTRACT a b s t r a c t The effects of anodic voltages on the morphology, wettability and photoc... more ABSTRACT a b s t r a c t The effects of anodic voltages on the morphology, wettability and photocurrent response of the porous titanium dioxide films prepared by electrochemical oxidation in a hydrofluoric acid (HF)/chromic acid electrolyte have been studied. The porous titanium dioxide films showed an increased surface roughness with the increasing anodizing voltages. By controlling the films morphology and surface chemical com-position, the wettability of the porous titanium dioxide films could be easily adjusted between superhy-drophilicity and superhydrophobicity. X-ray diffraction (XRD), Raman and UV–vis spectroscopy revealed that the obtained titanium dioxide films were in anatase phase. The titanium dioxide films showed clear photocurrent response, which decreased dramatically with the increase of the anodizing voltages. This study demonstrates a straightforward strategy for preparing porous titanium dioxide films with tunable properties, and especially emphasizes the importance of understanding their morphology/properties relationship.

Study on the surface dissociation properties of 6-(10-mercaptodecaoxyl)quinoline self-assembled monolayer on gold by chemical force titration

by Huixin He and Hao-Li Zhang

Materials Science and Engineering: C, 1999

. Ž . Chemical force microscopy CFM was used to measure the adhesion force between quinolyl group... more . Ž . Chemical force microscopy CFM was used to measure the adhesion force between quinolyl group -Q -terminated Au-coated tip Ž . Ž . Ž . and gold substrate abbreviated as -Qr-Q modified with self-assembled monolayers SAMs of 6-10-mercaptodecaoxyl quinoline Ž . MDQ in pH buffer solution. From the plot of adhesion force vs. pH value, which is called force titration curve, the p K of surface -Q 1r2 group of MDQ SAM can be estimated to be 5.3, which corresponds to the pH value at the peak. By using the -OH group as a general probe, the similar p K value, estimated from the force titration curve of -OHr-Q and -Qr-OH, which also corresponds to the pH at 1r2 the peak, is 5.2 and 5.4, respectively. From the conventional contact angle titration, p K s 5.9 was obtained. The difference of the 1r2 obtained p K values arises from two different measurement methods and their measurement accuracies. q 1999 Elsevier Science S.A. 1r2 All rights reserved. Ž . Ž .

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Structural evaluation of 6-(10-mercaptodecoxyl) quinoline self-assembled monolayer on gold by reflectance absorption infrared spectroscopy

Materials Science and Engineering: C, 1999

It incorporates referee's comments but changes resulting from the publishing process, such as cop... more

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