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1.
Langmuir ; 35(20): 6571-6577, 2019 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-31002519

RESUMO

Adequate control over the structures of molecular building blocks plays an important role in the fabrication of desired supramolecular nanostructures at interfaces. In this study, the formation of a pure hydrogen-bonding co-assembly supramolecular nanonetwork on a highly oriented pyrolytic graphite surface was demonstrated by means of a scanning tunneling microscope. The thermal annealing process was conducted to monitor the temperature-triggered structural transformation of the self-assembled nanonetwork. On the basis of the single-molecule-level resolution scanning tunneling microscopy images, together with the density functional theory calculations, the formation mechanisms of the formed nanoarrays were proposed. The results have great significance with regard to controlled construction of complex nanostructures on the surface.

2.
Anal Chem ; 90(17): 10144-10151, 2018 09 04.
Artigo em Inglês | MEDLINE | ID: mdl-29974736

RESUMO

Frequency shift surface-enhanced Raman scattering (SERS) achieves multiplex microRNA sensing for early serological diagnosis of, and discrimination between, primary liver cancers in a patient cohort for whom only biopsy is effective clinically. Raman reporters microprinted on plasmonic substrates shift their vibrational frequencies upon biomarker binding with a dynamic range allowing direct, multiplex assay of serum microRNAs and the current best protein biomarker, α-fetoprotein. Benchmarking against current gold-standard polymerase chain reaction and chemiluminescence methods validates the assay. The work further establishes the frequency shift approach, sensing shifts in an intense SERS band, as a viable alternative to conventional SERS sensing which involves the more difficult task of resolving a peak above noise at ultralow analyte concentrations.


Assuntos
Detecção Precoce de Câncer , Neoplasias Hepáticas/sangue , Neoplasias Hepáticas/diagnóstico , MicroRNAs/sangue , Análise Espectral Raman/métodos , Biomarcadores Tumorais/sangue , Estudos de Casos e Controles , Estudos de Coortes , Técnicas Eletroquímicas/métodos , Humanos , Luminescência , Reprodutibilidade dos Testes , Reação em Cadeia da Polimerase Via Transcriptase Reversa , alfa-Fetoproteínas/metabolismo
3.
Phys Chem Chem Phys ; 20(9): 6383-6389, 2018 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-29441376

RESUMO

Tetrathiafulvalenes (TTFs) are a class of important functional materials whose intermolecular interaction, which will contribute to constructing a supramolecular structure, still needs further understanding. In this study, the self-assembly behavior and structure of a series of TTFs bearing different alkyl chains and substituents were investigated by scanning tunneling microscopy (STM) in combination with density functional theory (DFT) calculations. Contrary to previous reports, herein, a series of benzoic acid-functionalized TTFs (CnTTFCOOH) and pyridine-functionalized TTFs (CnTTFN) with different lengths of alkyl chains have been substituted on the sulfur atom, where n is equal to 8, 10, 14, or 16. Due to the weak intra- and intermolecular interactions, CnTTFN (n = 8 and 10) molecules cannot be observed during STM scanning. For other cases, various self-assembled monolayers with different nanostructures were observed depending on different substituents. The results reveal that the alkyl chains and functional groups on the TTF skeleton synergistically affect the molecular self-assembly process, which results from the synergism of van der Waals, hydrogen bonding, and SS interactions. These results not only help to explain the relationship between structures and properties, but also help to design better molecular structures for various fields.

4.
ACS Nano ; 11(11): 11701-11713, 2017 11 28.
Artigo em Inglês | MEDLINE | ID: mdl-29091396

RESUMO

Electron-rich (donor) and electron-deficient (acceptor) units to construct donor-acceptor (D-A) conjugated macrocycles were investigated to elucidate their interactions with electron-deficient fullerene. Triphenylamine and 4,7-bisthienyl-2,1,3-benzothiadiazole were alternately linked through acetylene, as the donor and acceptor units, respectively, for pentagonal 3B2A and hexagonal 4B2A macrocycles. As detected by scanning tunneling microscopy, both D-A macrocycles were found to form an interesting concentration-controlled nanoporous monolayer on highly oriented pyrolytic graphite, which could effectively capture fullerene. Significantly, the fullerene filling was cavity-size-dependent with only one C70 or PC71BM molecule accommodated by 3B2A, while two were accommodated by 4B2A. Density functional theory calculations were also utilized to gain insight into the host-guest systems and indicted that the S···π contact is responsible for stabilizing these host-guest systems. Owing to the ellipsoidal shape of C70, C70 molecules are standing or lying in molecular cavities depending on the energy optimization. For the 3B2A/PC71BM blended film, PC71BM was intercalated into the cavity formed by the macrocycle 3B2A and provided excellent power conversion efficiency despite the broad band gap (2.1 eV) of 3B2A. This study of D-A macrocycles incorporating fullerene provides insights into the interaction mechanism and electronic structure in the host-guest complexes. More importantly, this is a representative example using D-A macrocycles as a donor to match with the spherical fullerene acceptor for photovoltaic applications, which offer a good approach to achieve molecular scale p-n junctions for substantially enhanced efficiencies of organic solar cells through replacing linear polymer donors by cyclic conjugated oligomers.

5.
J Nanosci Nanotechnol ; 17(1): 725-28, 2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29633811

RESUMO

A new compound (2,4,6-tris-(3,5-di-methyl formate-4'-hydroxy azobenzene)-1,3,5-triazine,TDHAT) has been synthesized and the scanning tunneling microscopy (STM) is utilized to clarify the geometrical configuration on the highly oriented pyrolytic graphite (HOPG) surface. The star-shaped molecule self-assembles into uniform and regular triangular petal structure at liquid­solid interface, and high-resolution images has been obtained, which implied a high stability of this two dimensional configuration. The distance between the scattered bright spot and the center of the petal is measured to be about 1.2 nm (L2), which corresponds to the actual size of each arm. Moreover, a comparison has been made between the TDHAT molecule and the TMA 4a molecule which has similar star-shaped structure with a long alkyl chain at the each end of the three arms, drawing a conclusion that both the structure of arms and the substituent groups would impact the nanoarchitecture. The results give us insight into a better comprehension of the self-assembly of the star-shaped molecule, which benefits the construction of functional nanostructures.

6.
Sci Rep ; 6: 25544, 2016 05 06.
Artigo em Inglês | MEDLINE | ID: mdl-27150720

RESUMO

The new π-extended redox-active ligand with both TTF and triazole units, 6-(4,5-bis(propylthio)-1,3-dithiol-2-ylidene)-1H-[1,3]dithiolo[4',5':4,5]benzo [1,2-d] [1-3]triazole, has been successfully prepared. Based on the versatile ligand and Cu(tta)2 precursors (tta(-) = 4,4,4-trifluoro-1-(thiophen-2-yl)butane-1,3-dione), a TTF-based pentanuclear Cu(II) cluster (Cu5(tta)4(TTFN3)6) is synthesized and structurally characterized. Their absorption and electrochemical properties are investigated. Antiferromagnetic couplings are operative between metal ion centers bridged by triazoles in the complex. The self-assembled structure of the cluster complex on a highly oriented pyrolytic graphite (HOPG) surface was observed using scanning tunneling microscopy and density functional theory (DFT) calculations have been performed to provide insight into the formation mechanism. The introduction of the redox-active TTF unit into the cluster complexes with interesting magnetic properties renders them promising candidates for new multifunctional materials.

7.
Chemistry ; 21(29): 10379-90, 2015 Jul 13.
Artigo em Inglês | MEDLINE | ID: mdl-26095600

RESUMO

Four new donor-acceptor triads (D-A-D) based on discotic and arylene mesogens have been synthesized by using Sonogashira coupling and cyclization reactions. This family of triads consists of two side-on pending triphenylene mesogens, acting as the electron-donating groups (D), laterally connected through short lipophilic spacers to a central perylenediimide (PI), benzo[ghi]perylenediimide (BI), or coronenediimide (CI) molecular unit, respectively, playing the role of the electron acceptor (A). All D-A-D triads self-organize to form a lamello-columnar oblique mesophase, with a highly segregated donor-acceptor (D-A) heterojunction organization, consequent to efficient molecular self-sorting. The structure consists in the regular alternation of two disrupted rows of triphenylene columns and a continuous row of diimine species. High-resolution STM images demonstrate that PI-TP2 forms stable 2D self-assembly nanostructures with some various degrees of regularity, whereas the other triads do not self-organize into ordered architectures. The electron-transport mobility of CI-TP2, measured by time-of-flight at 200 °C in the mesophase, is one order of magnitude higher than the hole mobility. By means of this specific molecular designing idea, we realized and demonstrated for the first time the so-called p-n heterojunction at the molecular level in which the electron-rich triphenylene columns act as the hole transient pathways, and the coronenediimide stacks form the electron-transport channels.

8.
Phys Chem Chem Phys ; 16(47): 25765-9, 2014 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-25361431

RESUMO

Efficient photochemical reactions on a surface are of great importance for their potential applications in optoelectronic devices. In this work, a highly efficient photodimerization reaction of an olefin cocrystal built from two trans-1,2-bis(4-pyridyl)ethylenes (4,4'-bpe) and two isophthalic acid molecules via N···H-O hydrogen bonds in between was achieved in a nanotemplate on a highly oriented pyrolytic graphite (HOPG) surface. 4,4'-Bpe molecules first undergo the trans-cis isomerization followed by [2+2] photodimerization in the nanotemplate on HOPG upon UV irradiation. The efficiency of the isomerization as well as the photodimerization in the presence of the nanotemplate is much higher than that in its absence. These results provide a facile way to achieve highly efficient photodimerization of olefins on a large scale on surfaces.

9.
Sci Rep ; 4: 5928, 2014 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-25088605

RESUMO

Self-assembly of functional compounds into a prerequisite nanostructure with desirable dimension and morphology by controlling and optimizing intermolecular interaction attracts an extensive research interest for chemists and material scientist. In this work, a new triple-decker sandwich-type lanthanide complex with phthalocyanine and redox-active Schiff base ligand including tetrathiafulvalene (TTF) units has been synthesized, and characterized by single crystal X-ray diffraction analysis, absorption spectra, electrochemical and magnetic measurements. Interestingly, the non-centrosymmetric target complex displays a bias dependent selective adsorption on a solid surface, as observed by scanning tunneling microscopy (STM) at the single molecule level. Density function theory (DFT) calculations are utilized to reveal the formation mechanism of the molecular assemblies, and show that such electrical field dependent selective adsorption is regulated by the interaction between the external electric field and intrinsic molecular properties. Our results suggest that this type of multi-decker complex involving TTF units shows intriguing multifunctional properties from the viewpoint of structure, electric and magnetic behaviors, and fabrication through self-assembly.

10.
Phys Chem Chem Phys ; 16(19): 8778-82, 2014 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-24691352

RESUMO

In the present work flexible binary networks of 1,3,5-benzenetricarboxylic acid (TMA) with 4,4'-bipyridine (Bpy) or 1,3,5-tris(4-pyridyl)-2,4,6-triazine(TPTZ) molecules at the liquid-solid interface were constructed. When coronene (COR) molecules are introduced into these systems, the binary networks collapse and at the same time, new COR/TMA host-guest structures are formed. Both experiments and calculations unambiguously indicate that the COR/TMA host-guest complex structure has stronger adsorption energy, resulting in the deconstruction-reconstruction phenomenon.

11.
Chem Asian J ; 8(10): 2330-40, 2013 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-23825034

RESUMO

Reversible supramolecular self-assemblies have attracted increasing attention in nanoscience and technology during the past few years due to their potential application in the extreme miniaturization of switches and other devices. The building blocks concerned can respond structurally, electronically, optically, and mechanically to external stimuli. Herein, we focus on the recent progress of the supramolecular self-assembly reversibly triggered by temperature, light, electric current, metal ions and protons at the solid-liquid interface. Following this general roadmap, supramolecular systems based on H-bonds, azobenzene derivatives, triple-decker complexes, and the guanine motif are successively discussed in this review. Notably, these reversible phase transformations can be probed by the scanning tunneling microscopy (STM) technique, which has been proven as an effective tool in surface science.

12.
Phys Chem Chem Phys ; 15(30): 12475-9, 2013 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-23632563

RESUMO

2D porous networks have attracted great attention as they can be used to immobilize functional units as guest molecules in a spatially ordered arrangement. In this work, a novel molecular hybrid network with two kinds of cavities was fabricated. Several kinds of guest molecules, such as coronene, copper(II) phthalocyanine (CuPc), triphenylene, heptanoic acid and fullerene molecules, can be immobilized into this template. Site- and size-selective effects can be observed. Furthermore, we have also fabricated interesting 2D crystal architecture with complex four-component structure at the liquid-solid interface, following investigation by scanning tunnelling microscopy (STM). The current findings provide a convenient approach towards the formation of more complex and functionalized surface nanopatterns, which can benefit the study of host-guest assembly behaviour within a monolayer composed by several components at interfaces.

13.
ACS Appl Mater Interfaces ; 5(5): 1583-7, 2013 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-23373722

RESUMO

Nanoscaled two-dimensional (2D) chiral architectures are increasingly receiving scientific interest, because of their potential applications in many domains. In this paper, we present a new method for constructing 2D chiral architectures on surface. Based on in situ Schiff-base reaction of achiral dialdehyde with two types of achiral amines at the solid/liquid interface, two chiral species have been directly formed and confirmed by means of a scanning tunneling microscopy (STM) technique. This work introduces a novel strategy to construct 2D surface chirality, which might be applied in fabricating functional films and nanoelectronic devices.


Assuntos
Nanoestruturas/química , Polímeros/síntese química , Aldeídos/química , Aminas/química , Microscopia de Tunelamento , Modelos Moleculares , Polímeros/química
15.
Nanoscale ; 3(9): 3755-9, 2011 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-21796300

RESUMO

Hexaphenylbenzene (HPB) derivatives, HPB-6a and HPB-6pa, can form a supramolecular network which is stabilized by the intermolecular hydrogen bonding between carboxyl group at an octanoic acid/graphite interface. The observation of the heterogeneous bilayer structure formed exclusively by coronene and HPB-6pa at the octanoic acid/graphite interface is reported. Pronounced selectivity of coronene for the supramolecular networks with different sizes is reflected through the formation of bilayer structure for HPB-6pa network with the introduction of coronene as the guest species, indicating stronger interactions between HPB-6pa and coronene.


Assuntos
Benzeno/química , Benzoatos/química , Grafite/química , Compostos de Terfenil/química , Caprilatos/química , Ligação de Hidrogênio , Conformação Molecular , Nanoestruturas/química , Compostos Policíclicos/química , Propriedades de Superfície
16.
Nano Lett ; 11(8): 3245-50, 2011 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-21732625

RESUMO

Controlled regulation of the switchable behavior of the supramolecular network is central to the potential application in the molecular scale nanodevices. In this work, it is reported that the reversible accommodation of the guest molecules in the nanoporous supramolecular network can be regulated by the UV/visible light. The nanoporous complex template of TCDB/4NN-Macrocycle(trans,trans,trans,trans) with photosensitive units is well-defined. After the UV irradiation, the template can be switched on to encapsulate coronene molecules due to the formation of a new photoisomer(trans,cis,trans,cis) and switched off to expel coronene from the inner cavities under the visible light. The photoregulated switchable multicomponent supramolecular guest-host network provides a novel strategy for fabricating the functional nanodevices at the molecular scale.

17.
Chemistry ; 17(25): 7061-8, 2011 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-21557347

RESUMO

The unfolding process and self-assembly of a foldable oligomer (foldamer 1) at the liquid/graphite interface were investigated by scanning tunnelling microscopy. At the level of molecular conformation, we identified several molecular conformations (A(z), B, C, D, E) that represent intermediate states during unfolding, which may help to elucidate the unfolding process at the liquid/graphite interface. Adsorption at the interface traps the intermediate states of the unfolding process, and STM has proved to be a powerful technique for investigating folding and unfolding of a foldamer at the molecular level, which are not accessible by other methods. The STM observations also revealed that varying the solvent and/or concentration results in different self-assemblies of foldamer 1 as a result of variations in molecular conformations. The solvent and concentration effects were attributed to the changes in existing states (extended or folded) of foldamers in solution, which in turn affect the distribution of adsorbed molecular conformations at the interface. This mechanism is quite different from other systems in which solvent and concentration effects were also observed.

19.
Small ; 6(1): 76-80, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19904764

RESUMO

A new hierarchical self-assembling molecular template, which can size-selectively immobilize fullerene molecules, is reported. The molecular template is fabricated from 1,3,5-tris(10-carboxydecyloxy)benzene (TCDB) and triangle-shaped macrocycles. It is observed that the two-dimensional hydrogen-bonded achiral TCDB network affected by the 3NN-Macrocycle becomes a chiral network. Host and guest molecules both form chiral arrangements with hexagonal empty pores. In addition, fullerenes and other molecules such as coronene can be entrapped in the empty pores or on the 3NN-Macrocycle molecules. The adsorption constant (K) is estimated, from which it is concluded that the different filling behaviors of the fullerenes are associated with the different sizes of the guest species. This method provides a facile approach to molecularly designed surfaces and the study of fullerene molecular arrays on the single-molecule level.


Assuntos
Cristalização/métodos , Fulerenos/química , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Nanotecnologia/métodos , Adsorção , Substâncias Macromoleculares/química , Teste de Materiais , Conformação Molecular , Tamanho da Partícula , Porosidade , Propriedades de Superfície
20.
J Am Chem Soc ; 131(17): 6174-80, 2009 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-19366268

RESUMO

The macrocyclic compounds consisting of photosensitive units as parts of the frame have been extensively studied to mimic photoregulated functions in nature. In this paper, controlled assembly of well-ordered arrays of photosensitive macrocyclic rectangles is demonstrated by using a host-guest molecular template. 4NN-Macrocycle molecules are observed to photoisomerize from trans-trans-trans-trans (t,t,t,t) to a range of isomers including trans-trans-trans-cis (t,t,t,c) and trans-cis-trans-cis (t,c,t,c) isomers after irradiation of UV light. The photoisomers are also observed to affect the guest-host network characteristic appreciably. In the STM observations we can distinguish three (t,t,t,t) conformational isomers, three (t,t,t,c) conformational isomers, and one (t,c,t,c) isomer, which self-assemble into different adlayers with TCDB on a HOPG surface. This study provides a facile approach to study the photoisomerization processes of the azobenzene groups and the conformational photoisomers.

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