Blend of electroactive poly(3-dodecylthiophene) with comb-like alkylated polyacrylate

The conformational mode change of the stiff alkylated polymer, poly(3-dodecyl thiophene) (PDDT), with a flexible comb-like coil poly(octadecyl acrylate) (PODA), and the effect of intermolecular interaction between these two alkylated polymers with different chemical structure of the backbone were investigated using UV-Vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimeter (DSC), and wide-angle x-ray diffraction (WAXD). In addition to the characteristics of thermochromism, a homogeneous one phase was observed above 175°C when the PODA content was 10 wt % or less. Increased conductivity in the PDDT/PODA blend due to the highly conjugated π-system of PDDT backbone was observed in the presence of nonelectroactive PODA. A red-shift of absorption maximum of PDDT/PODA blend observed in solid state at room temperature. From the FTIR spectra, the gauche-trans conformational structure change of methylene units was investigated in two alkylated polymer blends. The increase of combined heat of fusion of the alkyl side chain melting of PDDT and the endothermic peak of PODA, as well as the interlayer d-spacing of PDDT main chain were also observed with the addition of PODA in blends. A more ordered conformational structure of rigid rod backbone of PDDT was induced due to the attractive intermolecular interaction which can cause cocrystallization between the alkylated side chains of two polymers. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 :1025–1041, 1997     

Antiferromagnetism of poly(3-dodecylthiophene) irradiated by γ-beams

The magnetic properties of poly(3-dodecyl-thiophene) (PDDT) irradiated by -beams have been studied by measuring the magnetic susceptibility and EPR spectra. The irradiated PDDT is characterized, similarly as the non-irradiated one, by an antiferromagnetic course of magnetic susceptibility with a Néel temperature of 237 K. It is suggested that the antiferromagnetic properties of PDDT are caused by transformation of polarons to bipolarons, which takes place at lower temperatures.     

The conformation of poly(3-dodecyl thiophene) within methacrylic polymer matrix

Blends of poly(3-dodecyl thiophene) (PDDT) with poly(methyl methacrylate), poly(butyl methacrylate) (PBMA), and poly(methyl methacrylate-co-butyl methacrylate) (PMMA/PBMA) were studied by polarization optical microscopy, atomic-force microscopy, and absorption spectroscopy and were modeled using molecular dynamics (MD) simulations. The observed thermochromic transitions are shown to be host-matrix dependent, with PDDT/PBMA absorption spectra differing substantially from pristine PDDT. The dispersion of PDDT within PBMA matrix is observed to be greater than in the other host polymers. MD calculations of both individual PDDT molecules and molecular aggregates suggest that the distribution of dihedral angles present in the PDDT backbone is the narrowest for aggregates of PDDT embedded within a polymer matrix. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2909–2917, 1999     

Chromatic changes in the blends of electroactive polymers with comb-shaped flexible polymers

The effect of blending of alkylated polymers, which have different backbone structures, was investigated in order to improve the electronic properties of conducting polymers. Comb-shaped flexible polymer, poly(octadecyl acrylate) (PODA), was blended with rigid alkylated conducting polymers, poly(3-dodecyl-thiophene)(PDDT), and polyaniline emeraldine base (PANI)/p-dodecyl-benzenesulfonic acid (DBSA) complex, respectively, to investigate the effect of long alkyl chain of flexible polymer on the conformational mode change of rigid backbones and the effect of intermolecular interaction between these alkylated polymers. Optical microscopy was applied to observe the morphology change and obtain the phase diagrams of these blends. The intermolecular interactions that occurred in these blends were explained for each different characteristic peak obtained with FT-IR spectra. Solvatochromism (red-shift) of PDDT/PODA binary blends in solid state due to the planarity change of rigid backbone in the presence of PODA and electrochromism of PANI(DBSA)₄/PODA ternary blends due to the hydrogen bonding between the nitrogen cation of PANI complex and carbonyl group of PODA are observed in UV-Vis-NIR spectra. Interestingly, the increase of conductivity was observed in the presence of 5 wt% of PODA in PDDT/PODA binary blends and a homogeneous smectic liquid crystalline structure was clearly confirmed by cross polarized optical microscopy in PANI(DBSA)₄/PODA ternary blends.     

Moving beyond molecules: patterning solid-state features via dip-pen nanolithography with sol-based inks

Herein, we described a new dip-pen nanolithography (DPN)-based method for the direct patterning of organic/inorganic composite nanostructures on silicon and oxidized silicon substrates. The approach works by the hydrolysis of metal precursors in the meniscus between an AFM tip and a surface according to the reaction 2MCln + nH2O --> M2On + 2nHCl; M = Al, Si, and Sn. The inks are hybrid composites of inorganic salts with amphiphilic block copolymer surfactants. Three proof-of-concept systems involving Al2O3, SiO2, and SnO2 nanostructures on silicon and silicon oxide surfaces have been studied. Arrays of dots and lines can be written easily with control over feature size and shape on the sub-200 nm level. The structures have been characterized by atomic force microscopy, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray analysis. This work is important because it opens up the opportunity for using DPN to deposit solid-state materials rather than simple organic molecules onto surfaces with the resolution of an AFM without the need for a driving force other than chemisorption (e.g., applied fields).     

Catalytic probe lithography: catalyst-functionalized scanning probes as nanopens for nanofabrication on self-assembled monolayers

This article describes the use of scanning catalytic probe lithography for nanofabrication of patterns on self-assembled monolayers (SAMs) of reactive adsorbates. Catalytic writing was carried out by scanning over bis(omega-tert-butyldimethyl-siloxyundecyl)disulfide SAMs using 2-mercapto-5-benzimidazole sulfonic acid-functionalized gold-coated AFM tips. The acidic tips induced local hydrolysis of the silyl ether moieties in the contacted areas, and thus patterned surfaces were created. Diffusion effects arising from the use of an ink were excluded in these type of experiments, and therefore structures with well-defined shapes and sizes were produced. The smallest lines drawn by this technique were about 25 nm wide, corresponding to the actual contact area of the tip. Lateral force microscopy studies performed on different SAMs helped to clarify the nature and cause of the friction contrasts observed by AFM. Dendritic wedges with thiol functions inserted into the catalytically written areas, thus enhancing the height contrast. The created patterns open possibilities to build 3D nanostructures.     

Silicon surface nano-oxidation using scanning probe microscopy

This paper focuses on the nano-oxidation of a silicon surface using scanning probe microscopes in air ambient and in UHV. Special emphasis is put in air ambient on the preparation of the surfaces and on the oxidation mechanism. The characteristics of the patterned nanostructures are reviewed versus the parameters which govern the process (tip–surface voltage, tip speed, humidity) as well as the kinetics models of the oxidation process. The oxide patterns can act as robust masks for dry or wet etching. Fabrication of nanostructures is presented and allows to realize electronic nanodevices. In UHV, there is no direct nano-oxidation of the surface by the microscope tip. First the surface is hydrogenated, second a local hydrogen desorption is performed with the STM tip and finally the bare desorbed area is exposed to oxygen. The desorption process is analyzed versus tip–surface voltage and tunneling current. The oxidation of a desorbed area using molecular or atomic oxygen is actually difficult to achieve.     

Single molecular stamping of a sub-10-nm colloidal quantum dot array

We introduce a nanoscale stamping technique of sub-10-nm colloidal quantum dot (QD) arrays to highly localized areas of three-dimensional nanostructures using a quartz tuning fork employed as the stamp pad (the "Nano Stamp"). CdSe/ZnS core-shell nanoparticles with diameters of 9.8 nm were deposited on microfabricated silicon probe tips. The number of transferred QDs, which ranged from several thousands down to single molecular order (less than 10), was precisely controlled by adjusting the stamping depths and angles. The stamping areas were varied from 1.2 microm x 1.2 microm down to 30 nm x 30 nm. Using the Nano Stamp, QDs can be transferred to a variety of protruding nanostructures. The amount of particles transferred to the tip was assessed by fluorescence intensity measurements, and the number of particles was estimated by direct transmission electron microscopy (TEM) observation. Correlation between the fluorescence intensity and the observed stamping depth and the approaching angle of the tip was found, demonstrating the efficacy of our Nano Stamp technique.     

Nanolithographic write, read, and erase via reversible nanotemplated nanostructure electrodeposition on alkanethiol-modified Au(111) in an aqueous solution

A write, read, and erase nanolithographic method, combining in situ electrodeposition of metal nanostructures with atomic force microscopy (AFM) nanoshaving of a 1-hexadecanethiol (HDT) self-assembled monolayer (SAM) on Au(111) in an aqueous solution, is reported. The AFM tip defines the local positioning of nanotemplates via the irreversible removal of HDT molecules. Nanotemplates with lateral dimensions as narrow as 25 nm are created. The electroactive nanotemplates determine the size, shape, and position of the metal nanostructures. The potential applied to the substrate controls the amount of metal deposited and the kinetics of the deposition. Metal nanostructures can be reversibly and repeatedly electrodeposited and stripped out of the nanotemplates by applying appropriate potentials.     

Directed electroless growth of metal nanostructures on patterned self-assembled monolayers

The directed placement of Cu nanostructures on surfaces has been studied using a combination of scanning probe lithography and electroless metal deposition onto nanopatterned SAMs of 16-mercaptohexadecanoic acid (16-MHA) on Au. In situ studies using nanoscale molecular gradients reveal how controlling the areal density of the 16-MHA molecules dictates the nucleation and growth of the metal nanostructures. The influence of controlling pattern line spacing and tip path on pattern feature fidelity is also discussed.     

In-situ voltage tunneling spectroscopy at electrochemical interfaces

Nanophysics at electrochemical interfaces, probing the physical properties of nanostructures, requires laterally resolved in-situ spectroscopy, in particular voltage tunneling spectroscopy (VTS), which is at present not yet established. In-situ spectroscopy is required to achieve reliable and reproducible measurements of the intrinsic properties of nanostructures in an electrochemical environment, which are mainly determined in small nanostructures by surface atoms rather than bulk atoms. In contrast to tunneling spectroscopy in ultrahigh vacuum, tip and substrate double-layer capacitances as well as Faradaic currents play an important role in voltage tunneling spectroscopy at electrochemical interfaces. Deoxygenation of the electrolyte, fast measurements using appropriate instrumentation, and minimization of the unisolated tip apex and substrate surface areas exposed to the electrolyte are the key parameters to achieve reliable in-situ voltage tunneling spectroscopy data at electrochemical interfaces. The presented data show that bias voltage intervals of more than 1000 mV can be utilized for spectroscopic investigations in aqueous electrolytes, which allow the in-situ study of discrete electronic levels in nanostructures.     

扫描探针刻蚀技术可控构建牛血清白蛋白纳米结构

利用Dip-pen纳米刻蚀技术(简称DPN技术)在云母基底上构建出形状、尺寸可控的牛血清白蛋白(BSA)纳米结构.考察了针尖接触基底时间及针尖下行距离对构建的牛血清白蛋白纳米结构的影响.较长的针尖-基底接触时间及较深的下行距离可以沉积更多的牛血清白蛋白分子,构建牛血清白蛋白纳米结构的形状除了与墨水分子的本身性能有关,还与墨水-基底的相互作用有关.这些形状及尺寸可控的蛋白质纳米结构可以作为模板,进行金属、半导体等其它材料的组装,有望用于制造光电纳米器件及生物纳米器件.     

Fabrication and investigation of nanostructures on transition metal dichalcogenide surfaces using a scanning tunneling microscope

Nanometer-scale holes have been fabricated on the surfaces of the semiconducting transition metal dichalcogenides (TMDCs) molybdenum ditelluride (MoTe2) and molybdenum disulfide (MoS2) by applying voltage pulses from the tip of a scanning tunneling microscope (STM) operating in ultrahigh vacuum (UHV). It was found that the tip geometry (tip shape and sharpness) influences the formation and structure of the atomic-scale nanostructures. Threshold voltage ranges for the surface modification of MoTe2 (3.0 +/- 0.3 V) and MoS2 (3.4 +/- 0.3 V) were determined. Negative sample voltage pulses applied to a p-type MoTe2 surface produced much larger and deeper nanometer-scale holes when compared with those produced by positive voltage pulses. The existence of threshold voltages and the pulse polarity dependence of nanostructure fabrication suggests that an electric field evaporation mechanism is applicable. Support for this mechanism was obtained by nanostructuring metallic TMDC NbSe2, where both the produced features and the threshold voltages (3.0 +/- 0.3 V) were similar for both positive and negative voltage pulses.     

Mg-catalyzed autoclave synthesis of aligned silicon carbide nanostructures

In this article, a novel magnesium-catalyzed co-reduction route was developed for the large-scale synthesis of aligned beta-SiC one-dimensional (1D) nanostructures at relative lower temperature (600 degrees C). By carefully controlling the reagent concentrations, we could synthesize beta-SiC rodlike and needlelike nanostructures. The possible growth mechanism of the as-synthesized beta-SiC 1D nanostructures has been investigated. The structure and morphology of the as-synthesized beta-SiC nanostructures are characterized using X-ray diffraction, Fourier transform infrared absorption, and scanning and transmission electron microscopes. Raman and photoluminescence properties are also investigated at room temperature. The as-synthesized beta-SiC nanostructures exhibit strong shape-dependent field emission properties. Corresponding to their shapes, the as-synthesized nanorods and nanoneedles display the turn-on fields of 12, 8.4, and 1.8 V/microm, respectively.     

Enhanced properties of photovoltaic devices tailored with novel supramolecular structures based on reduced graphene oxide nanosheets grafted/functionalized with thiophenic materials

For verifying the influence of donor–acceptor supramolecules on photovoltaic properties, different hybrids were designed and used in organic solar cells. In this respect, reduced graphene oxide (rGO) was functionalization with 2‐thiophene acetic acid (rGO‐f‐TAA) and grafted with poly(3‐dodecylthiophene) (rGO‐g‐PDDT) and poly(3‐thiophene ethanol) (rGO‐g‐PTEt) to manipulate orientation of poly(3‐hexylthiophene) (P3HT) assemblies. Face‐on, edge‐on, and flat‐on orientations were detected for assembled P3HTs on rGO and its functionalized and grafted derivatives, respectively. Alteration of P3HT orientation from face‐on to flat‐on enhanced current density (J _sc), fill factor (FF), and power conversion efficiency (PCE) and thus J _sc = 7.11 mA cm^?2, FF = 47%, and PCE = 2.14% were acquired. By adding phenyl‐C71‐butyric acid methyl ester (PC71BM) to active layers composed of pre‐designed P3HT/rGO, P3HT/rGO‐f‐TAA, P3HT/rGO‐g‐PDDT, and P3HT/rGO‐g‐PTEt hybrids, photovoltaic characteristics further improved, demonstrating that supramolecules appropriately mediated in P3HT:PC71BM solar cells. Phase separation was more intensified in best‐performing photovoltaic systems. Larger P3HT crystals assembled onto grafted rGOs (95–143 nm) may have acted as convenient templates for the larger and more intensified phase separation in P3HT:PCBM films. The best performances were reached for P3HT:P3HT/rGO‐g‐PDDT:PCBM (J _sc = 9.45 mA cm^?2, FF = 54%, and PCE = 3.16%) and P3HT:P3HT/rGO‐g‐PTEt:PCBM (J _sc = 9.32 mA cm^?2, FF = 53%, and PCE = 3.11%) photovoltaic systems. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 1877–1889     

Ambient Bistable Single Dipole Switching in a Molecular Monolayer

Reported here is a molecular dipole that self‐assembles into highly ordered patterns at the liquid‐solid interface, and it can be switched at room temperature between a bright and a dark state at the single‐molecule level. Using a scanning tunneling microscope (STM) under suitable bias conditions, binary information can be written at a density of up to 41 Tb cm^?2 (256 Tb/in²). The written information is stable during reading at room temperature, but it can also be erased at will, instantly, by proper choice of tunneling conditions. DFT calculations indicate that the contrast and switching mechanism originate from the stacking sequence of the molecular dipole, which is reoriented by the electric field between the tip and substrate.     

Synthesis and synchrotron light-induced luminescence of ZnO nanostructures: nanowires, nanoneedles, nanoflowers, and tubular whiskers

ZnO nanostructures, including single-crystal nanowires, nanoneedles, nanoflowers, and tubular whiskers, have been fabricated at a modestly low temperature of 550 degrees C via the oxidation of metallic Zn powder without a metal catalyst. Specific ZnO nanostructures can be obtained at a specific temperature zone in the furnace depending on the temperature and the pressure of oxygen. Scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD) studies show that ZnO nanostructures thus prepared are single crystals with a wurtzite structure. X-ray excited optical luminescence (XEOL) from the ZnO nanostructures show noticeable morphology-dependent luminescence. Specifically, ZnO nanowires of around 15 nm in diameter emit the strongest green light. The morphology of these nanostructures, their XEOL, and the implication of the results will be discussed.     

Synthesis of hybrid CdS-Au colloidal nanostructures

We explore the growth mechanism of gold nanocrystals onto preformed cadmium sulfide nanorods to form hybrid metal nanocrystal/semiconductor nanorod colloids. By manipulating the growth conditions, it is possible to obtain nanostructures exhibiting Au nanocrystal growth at only one nanorod tip, at both tips, or at multiple locations along the nanorod surface. Under anaerobic conditions, Au growth occurs only at one tip of the nanorods, producing asymmetric structures. In contrast, the presence of oxygen and trace amounts of water during the reaction promotes etching of the nanorod surface, providing additional sites for metal deposition. Three growth stages are observed when Au growth is performed under air: (1) Au nanocrystal formation at both nanorod tips, (2) growth onto defect sites on the nanorod surface, and finally (3) a ripening process in which one nanocrystal tip grows at the expense of the other particles present on the nanorod. Analysis of the hybrid nanostructures by high-resolution TEM shows that there is no preferred orientation between the Au nanocrystal and the CdS nanorod, indicating that growth is nonepitaxial. The optical signatures of the nanocrystals and the nanorods (i.e., the surface plasmon and first exciton transition peaks, respectively) are spectrally distinct, allowing the different stages of the growth process to be easily monitored. The initial CdS nanorods exhibit band gap and trap state emission, both of which are quenched during Au growth.     

Effects of shape and size of cobalt ferrite nanostructures on their MRI contrast and thermal activation

Cobalt ferrite magnetic nanostructures were synthesized via a high temperature solution phase method. Spherical nanostructures of various sizes were synthesized with the help of seed mediated growth of the nanostructures in organic phase, while faceted irregular (FI) cobalt ferrite nanostructures were synthesized via the same method but in the presence of a magnetic field. Magnetic properties were characterized by SQUID magnetometry, relaxivity measurements and thermal activation under RF field, as a function of size and shape. The results show that the saturation magnetization of the nanostructures increases with an increase in size, and the FI nanostructures exhibit lower saturation magnetization than their spherical counterparts. The relaxivity coefficient of cobalt ferrite nanostructures increases with increase in size; while FI nanostructures show a higher relaxivity coefficient than spherical nanostructures with respect to their saturation magnetization. In the case of RF thermal activation, the specific absorption rate (SAR) of nanostructures increases with increase in the size. The contribution sheds light on the role of size and shape on important magnetic properties of the nanostructures in relation to their biomedical applications.     

Size-controlled synthesis of Au/Pd octopods with high refractive index sensitivity

Au/Pd octopods, nanostructures with eight branches and a primarily Au interior, have been synthesized as size-controlled samples through the manipulation of seed-mediated co-reduction. The position of their localized surface plasmon resonance can be controllably tuned throughout the visible and near-infrared regions, and this response is correlated with the structural features (branch length and tip width) of the octopods. These Au/Pd octopods were also found to be highly sensitive to changes in the local refractive index of the surrounding media and suitable substrates for surface enhanced Raman spectroscopy. These findings, coupled with their unique composition, highlight the multifunctional capabilities of the Au/Pd octopods and provide insight into the optical properties of architecturally controlled bimetallic nanostructures.