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Significantly increased power conversion efficiency (PCE) of polymer solar cells (PSCs) is achieved by applying a plasmonic enhanced light trapping strategy to a low bandgap conjugated polymer, poly(indacenodithiophene- co-phananthrene-quinoxaline) (PIDT-PhanQ) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) based bulk-heterojunction (BHJ) system. By doping both the rear and front charge-selecting interfacial layers of the device with different sizes of Au NPs, the PCE of the devices is improved from 6.65% to 7.50% (13% enhancement). A detailed study of processing, characterization, microscopy, and device fabrication is conducted to understand the underlying mechanism for the enhanced device performance. The success of this work provides a simple and generally applicable approach to enhance light harnessing of low bandgap polymers in PSCs.

For the development of radiation-hard Si detectors for the SiD BeamCal (Si Detector Beam Calorimeter) program for International Linear Collider (ILC), n -type Magnetic Czochralski Si detectors have been irradiated first by fast neutrons to fluences of 1.5×10 14 and 3×10 14 n eq /cm 2 , and then by gamma up to 500 Mrad. The motivation of this mixed radiation project is to test the radiation hardness of MCZ detectors that may utilize the gamma/electron radiation to compensate the negative effects caused by neutron irradiation, all of which exists in the ILC radiation environment. By using the positive space charge created by gamma radiation in MCZ Si detectors, one can cancel the negative space charge created by neutrons, thus reducing the overall net space charge density and therefore the full depletion voltage of the detector. It has been found that gamma radiation has suppressed the room temperature reverse annealing in neutron-irradiated detectors during the 5.5 month of time needed to reach a radiation dose of 500 Mrad. The room temperature annealing (RTA) was verified in control samples (irradiated to the same neutron fluences, but going through this 5.5 month RTA without gamma radiation). This suppression is in agreement with our previous predictions, since negative space charge generated during the reverse annealing was suppressed by positive space charge induced by gamma radiation. The effect is that regardless of the received neutron fluence the reverse annealing is totally suppressed by the same dose of gamma rays (500 Mrad). It has been found that the full depletion voltage for the two detectors irradiated to two different neutron fluences stays the same before and after gamma radiation. Meanwhile, for the control samples also irradiated to two different neutron fluences, full depletion voltages have gone up during this period. The increase in full depletion voltage in the control samples corresponds to the generation of negative space charge, and this increase in concentration of negative space charge goes up with the neutron fluence. If we assume the reverse annealing is also taking place for the two gamma-irradiated samples with similarly different concentrations of negative space charge generated, the observed effect of no changes in space charge (no changes in V fd ) in these two gamma-irradiated samples would imply that concentrations of positive space charge created in these two control samples are different at the same gamma dose, and gamma irradiation effectively “switched off”, the RT (room temperature) reverse annealing of neutron irradiation. It has also been found that as soon as the gamma irradiation stops, the RT reverse annealing of neutron irradiation-induced defects resumes with same rate as that of the control detectors. This behavior in mixed radiation samples (neutron plus gamma) would suggest some nonlinear effect (defects induced by mixed-radiations are not additive of those by individual radiation alone), or interaction of radiation induced acceptor-type and donor-type defects.

Resistive-switching memories based on copolyimides (coPIs), PI-NTCDIX and PI-BTCDIX, with different compositions of 4,4′-diamino-4″-methyltriphenylamine (AMTPA), 4,4′-(hexafluoroisopropylidene)diphthalic anhydride, and N,N′-bis-(4-aminophenyl)-1,8:4,5-naphthalenetetracarboxydiimide (NTCDI) or N,N′-bis-(4-aminophenyl)-1,2:4,5-benzenetetracarboxydiimide (BTCDI) have been developed. By varying the feed ratio of monomers, PI-NTCDIX and PI-BTCDIX showed tunable optical and electronic properties through the charge transfer (CT) between AMTPA and NTCDI or BTCDI. The memory devices based on PI-NTCDIX exhibited the tunable electrical bistability from the volatile dynamic random access memory to nonvolatile write once read many memory characteristics as the NTCDI composition increased. The OFF/ON electrical switching transition was mainly attributed to the CT mechanism for the charge separated high conductance, based on the analysis of model compounds and density functional theory calculation. Also, the volatility of the memory device depended on the stability of CT complex. The long conjugation and high electron affinity of the NTCDI moiety stabilized the radical anion generated in the CT complex and prevented the recombination of segregated radical species even through applying the high positive or negative voltage. On the other hand, the memory devices based on PI-BTCDIX showed a rather unique behavior compared with those based on PI-NTCDIX. At the low BTCDI composition, the device exhibited volatile memory property. However, no switching behavior was observed at the high BTCDI composition due to the low highest occupied molecular orbital energy level of BTCDI. Combining these results and our previous study on perylenebisimide (PBI), we concluded that memory characteristics could be tailored by changing the conjugation length (PBI > NTCDI > BTCDI) and the acceptor composition in random coPIs. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

High Performance organic field-effect transistor (OFET) memory devices were successfully prepared using new dielectric materials, poly(N-(hydroxymethyl)acrylamide-co-5 -(9-(5-(diethylamino)pentyl)-2-(4-vinylphenyl)-9H-fluorene (P(NMA-co-F6NSt)), which contained chemical cross-linkable segment (NMA) and hole trapping building block (F6NSt). The high k characteristics of P(NMA-co-F6NSt)) led to a low voltage operation, a small power consumption, and a good digital information storage capacity. Such P(NMA-co-F6NSt) dielectrics in OFET memories with variant NMA/F6NSt molar ratios (100/0 (P1), 95/5 (P2), 80/20 (P3), and 67/33 (P4)) showed excellent insulating properties and good charge storage performance under a low operating voltage below ±5V, due to the tightly network structures after crosslinking and well-dispersed trapping cites (i.e. fluorene moieties). P3-based memory device, in particular, exhibited largest memory window of 4.13 V among the studied polymers, and possessed stable data retention stability over 104 s with a high on/off current ratio (i.e. 104) and good endurance characteristics of more than 200 write-read-write-erase (WRER) cycles. The above results suggested that a high-performance OFET memory device could be facilely achieved using the novel synthesized high-k copolymers.

A new Maia detector is being currently developed, consisting of an array of 384 silicon drift detectors (SDDs), each having an area of 1 mm2. The detector features a new double metal scheme that supplies biases to the pixel SDD rings. All 384 anodes of SDDs are meant to be connected to individual electronic channels. This effort was motivated by the need of improving the energy resolution and the throughput of the existing Maia detectors whose pixels are based on p-in-n diodes. In order to use the existing circuit boards and back-end electronics that have already developed for the original Maia, the SDD-Maia detector was designed with an identical footprint, after replacing the p-in-n diodes with SDDs. The design, fabrication and performance of a first prototype detector will be presented.

This study demonstrates a facile way to efficiently induce strong memory behavior from common p-type conjugated polymers by adding n-type dopant 2-(2-methoxyphenyl)-1,3-dimethyl-2,3-dihydro-1H-benzoimidazole. The n-type doped p-channel conjugated polymers not only enhance n-type charge transport characteristics of the polymers, but also facilitate to storage charges and cause reversible bistable (ON and OFF states) switching upon application of gate bias. The n-type doped memory shows a large memory window of up to 47 V with an on/off current ratio larger than 10 000. The charge retention time can maintain over 100 000 s. Similar memory behaviors are also observed in other common semiconducting polymers such as poly(3-hexyl thiophene) and poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene], and a high mobility donor–acceptor polymer, poly(isoindigo-bithiophene). In summary, these observations suggest that this approach is a general method to induce memory behavior in conjugated polymers. To the best of the knowledge, this is the first report for p-type polymer memory achieved using n-type charge-transfer doping.

Doped perovskite manganites [1] have attracted renewed attention due to scientific interest and prospective novel device applications [2]. Substitution of ‘Dy3+’ site with isovalent ‘Bi3+’ in DyMnO 3 without changing effective ‘Mn’ valence could generate the A-site cationic mismatch to introduce a “chemical pressure”, leading to an enhanced distortion of perovskite structure [3], which has not been explored widely. Our experiments indicate formation ofBi 2 O 3 impurity when the doping is greater than 2%. In this work, effect of ‘Bi’ doping in Dy l-x Bi x MnO 3 is studied on the variation of structural and magnetic properties. It is observed that the intensity of (210) plane of orthorhombic structure decreases with ‘Bi’ content and vanishes at x = 0.15 (Fig. 1). In the magnetization data, the ZFC-FC curves become irreversible upon doping with ‘Bi’. At 2 K, a spin flop like transition is observed in DyMnO 3 and it gradually decreases with Bi doping with an enhancement of $\mathrm{H}_{\mathrm{C}}$ and $\mathrm{M}_{\mathrm{r}}$ , indicating a change from soft to hard magnet contrary to the case of ‘Bi’ doped LaMnO 3 [4]. Specific heat capacity data implies a ferroelectric transition $\mathrm{T}_{\mathrm{l}\mathrm{o}\mathrm{c}\mathrm{k}}$ to vanish upon doping with ‘Bi’. In addition, the FC magnetization data fitted well with a phenomenological model and the related magneto-caloric effects will be discussed.

Nano-floating gate memory devices (NFGM) using metal nanoparticles (NPs) covered with an insulating polymer have been considered as a promising electronic device for the next-generation nonvolatile organic memory applications NPs. However, the transparency of the device with metal NPs is restricted to 60~70% due to the light absorption in the visible region caused by the surface plasmon resonance effects of metal NPs. To address this issue, we demonstrate a novel NFGM using the blends of hole-trapping poly (9-(4-vinylphenyl) carbazole) (PVPK) and electron-trapping ZnO NPs as the charge storage element. The memory devices exhibited a remarkably programmable memory window up to 60 V during the program/erase operations, which was attributed to the trapping/detrapping of charge carriers in ZnO NPs/PVPK composite. Furthermore, the devices showed the long-term retention time (>105 s) and WRER test (>200 cycles), indicating excellent electrical reliability and stability. Additionally, the fabricated transistor memory devices exhibited a relatively high transparency of 90% at the wavelength of 500 nm based on the spray-coated PEDOT:PSS as electrode, suggesting high potential for transparent organic electronic memory devices.

The NA60 experiment studied low-mass muon pair production in proton–nucleus (p–A) collisions using a 400 GeV proton beam at the CERN SPS. The low-mass dimuon spectrum is well described by the superposition of the two-body and Dalitz decays of the light neutral mesons η, ρ, ω, η ′ and ϕ, and no evidence of in-medium effects is found. A new high-precision measurement of the electromagnetic transition form factors of the η and ω was performed, profiting from a 10 times larger data sample than the peripheral In–In sample previously collected by NA60. Using the pole-parameterisation | F ( M ) | 2 = ( 1 − M 2 / Λ 2 ) − 2 we find Λ η − 2 = 1.934 ± 0.067 (stat.) ±0.050 (syst.) ( GeV / c 2 ) − 2 and Λ ω − 2 = 2.223 ± 0.026 (stat.) ±0.037 (syst.) ( GeV / c 2 ) − 2 . An improved value of the branching ratio of the Dalitz decay ω → μ + μ − π 0 is also obtained, with B R ( ω → μ + μ − π 0 ) = [ 1.41 ± 0.09 (stat.) ± 0.15 (syst.) ] × 10 − 4 . Further results refer to the ρ line shape and a new limit on ρ / ω interference in hadron interactions.

We report the synthesis, properties, and photovoltaic applications of new π-conjugated polymers having thiophene, 3,4-dihexylthiophene, and 1,3,4-oxadiazole (OXD) or 1,3,4-thiadiazole (TD) units in the main chain, denoted as P1 and P2. They were synthesized by the Stille coupling reaction of 2,5-bis(trimethylstannyl)thiophene and the corresponding monomers of 2,5-bis(5′-bromo-3′,4′-dihexylthien-2′-yl)-1,3,4-oxadiazole or 2,5-bis(5′-bromo-3′,4′-dihexylthien-2′-yl)-1,3,4-thiadiazole, respectively. The experimental results indicated that the introduction of an electron-accepting moiety of OXD or TD lowered the highest occupied molecular orbital (HOMO) energy levels, resulting in the higher the open-circuit voltage (Voc) values of polymer solar cells (PSCs). Indeed, the PSCs of P1 and P2 showed high Voc values in the range 0.80–0.90 V. The highest field-effect transistor (FET) mobilities of P1 and P2 with the OXD and TD moieties, respectively, were 1.41 × 10–3 and 8.81 × 10–2 cm2 V–1 s–1. The higher mobility ...

An efficient visible-to-infrared conversion film is made by blending CdTe quantum dots (CdTe QDs) of 12 nm diameter in a polyvinylpyrrolidone 360 (PVP 360) polymer matrix cast by water solution. The solid-state photoluminescence quantum efficiency exceeds 10% with emission peak at 810 nm. Strong 810 emission is obtained by combining the quantum dot film and a green polyfluorene light-emitting diode. Color filter is used to remove residual light below 780 nm to make it entirely invisible. Infrared photo-detector is made by blending poly[5-(5-(2,5-bis(decyloxy)-4-methylphenyl)thiophen-2-yl)-2,3-bis(4-(2-ethylhexyloxy)phenyl)-7-(5-methylthiophen-2-yl)thieno[3,4-b]pyrazine] (PBDOTTP) with band-gap 1.2 eV and (6,6)-phenyl-C61-butyric acid methyl ester (PCBM). The pixel contains one PD

meso -2,6-Dichlorophenyltripyrrinone (TPN-Cl 2 ), a probe molecule for zinc II ions, is dispersed in a polymer host. The red fl uorescence peak at 620 nm appears when the molecule forms a complex with zinc at its center. TPNCl 2 has a high selectivity for zinc II and tolerates many common metal ions present in the human body. The probe molecules are blended with a hydrogel polymer, poly(2-hydroxyethyl methacrylate) (poly HEMA), with 30 wt% dimethylformamide (DMF). The fi ber structure with 1 μ m diameter is made by electrospinning in DMF solution of the probe and poly HEMA mixture. The fi brous fi lm detects zinc ions with concentrations as low as 10 − 6 M in real-time both in water and in the commonly used cell culture liquid media Dulbecco’s modifi ed Eagle medium (DMEM) and fetal bovine serum (FBS), which contain many metal ions and proteins. The time-resolution is 5 min for 10 − 6 M and 1 min for 10 − 5 M. This sensitivity and response speed satisfy the requirements for non-invasive biomedical studies.

A novel ladder-type donor (IDTT) is developed by substituting the two outward thiophenes of the IDT donor with two thieno[3,2-b]thiophenes. The polymer derived from this donor possesses longer effective conjugation and better planarity, which improves electron delocalization along the polymer backbone and charge mobility. The polymer solar cell device using PIDTT-DFBT shows a high power conversion efficiency of 7.03% with a large open-circuit voltage of 0.95 V without using any additives or post-solvent/thermal annealing processes.

The iron nanowires can be fabricated via the process in which sodium borohydride reduces iron salts in external magnetic field. The iron nanowires are found to be covered by passivated layers of iron oxide which prevent the oxidation of iron nanowires. In this process, the boron will include in iron nanowires. The average length and diameter of iron nanowires is around 1.2 micrometers and 60 nanometers, respectively. According to ICP results, the contents of B and Fe are about 1.98 wt% and 87.04 wt%, respectively, in iron nanowires. A wide variety of equipment is used to investigate the morphological, microchemical, and structural characteristics of the newly synthesized iron nanowires ––– e.g., XRD, FE-SEM, HR-TEM, VSM and XANES. XANES analysis indicates the boron in iron nanowires exists in the form of B2O3. The saturation magnetization and the coercive force of iron nanowires are 157.93 emu/g and 9.74 Oe, respectively. In-situ images of synthesized iron nanowires during reduction process in magnetic field are observed by NSRRC transmission X-ray microscope. Thus, this study develop a novel process to produce iron nanowires with large quantitates and can control its length and diameter by various the concentration of precursors for various applications.

We report the nonvolatile memory characteristics of n-type N,N′-bis(2-phenylethyl)perylene-3,4:9,10-tetracarboxylic diimide (BPE-PTCDI) based organic field-effect transistors (OFET) using the polyimide electrets of poly[2,5-bis(4-aminophenylenesulfanyl)selenophene–hexafluoroisopropylidenediphthalimide] (PI(APSP-6FDA)), poly[2,5-bis(4-aminophenylenesulfanyl)thiophene–hexafluoroisopropylidenediphthalimide] (PI(APST-6FDA)), and poly(4,4′-oxidianiline-4,4′-hexafluoroisopropylidenediphthalic anhydride) (PI(ODA-6FDA)). Among those polymer electrets, the OFET memory device based on PI(APSP-6FDA) with a strong electron-rich selenophene moiety exhibited the highest field-effect mobility and Ion/Ioff current ratio of 105 due to the formation of the large grain size of the BPE-PTCDI film. Furthermore, the device with PI(APSP-6FDA) exhibited the largest memory window of 63 V because the highest HOMO energy level and largest electric filed facilitated the charges transferring from BPE-PTCDI and trapping in the PI elec...

We report the synthesis, morphology, and applications of conjugated rod-coil-coil triblock copolymers, polyfluorene-block-poly(N-isopropylacrylamide)-block-poly(N-methylolacrylamide) (PF-b-PNIPAAm-b-PNMA), prepared by atom transfer radical polymerization first and followed by click coupling reaction. The blocks of PF, PNIPAAm, and PNMA were designed for fluorescent probing, hydrophilic thermo-responsive and chemically cross-linking, respectively. In the following, the electrospun (ES) nanofibers of PF-b-PNIPAAm-b-PNMA were prepared in pure water using a single-capillary spinneret. The SAXS and TEM results suggested the lamellar structure of the PF-b-PNIPAAm-b-PNMA along the fiber axis. These obtained nanofibers showed outstanding wettability and dimension stability in the aqueous solution, and resulted in a reversible on/off transition on photoluminescence as the temperatures varied. Furthermore, the high surface/volume ratio of the ES nanofibers efficiently enhanced the temperature-sensitivity and responsive speed compared to those of the drop-cast film. The results indicated that the ES nanofibers of the conjugated rod-coil block copolymers would have potential applications for multifunctional sensory devices.

Organic nonvolatile transistor-type memory (ONVM) devices are developed using self-assembled nanowires of n-type semiconductor, N,N′-bis(2-phenylethyl)-perylene-3,4:9,10-tetracarboxylic diimide (BPE-PTCDI). The effects of nanowire dimension and silane surface treatment on the memory characteristics are explored. The diameter of the nanowires is reduced by increasing the non-solvent methanol composition, which led to the enhanced crystallinity and high field-effect mobility. The BPE-PTCDI nanowires with small diameters induce high electrical fields and result in a large memory window (the shifting of the threshold voltage, ΔVth). The ΔVth value of BPE-PTCDI nanowire based ONVM device on the bare substrate can reach 51 V, which is significantly larger than that of thin film. The memory window is further enhanced to 78 V with the on/off ratio of 2.1 × 104 and the long retention time (104 s), using a hydrophobic surface (such as trichloro(phenyl)silane-treated surface). The above results demonstrate that the n-type semiconducting nanowires have potential applications in high performance non-volatile transistor memory devices.

UV-visible spectroscopy and fluorescence quenching measurements have been employed to study electron transfer from excited Hypocrellin A (HA) into the conduction band of a colloidal ZnO semiconductor. The adsorption of HA on the surface of ZnO colloidal particles and the electron transfer process from its singlet excited state to the conduction band of colloidal ZnO semiconductor were examined under experimental conditions. Exciting HA with visible light could induce electron transfer from its singlet excited state into conduction band of colloidal ZnO semiconductor. Adsorption of HA onto the surface of colloidal ZnO semiconductor extended its absorption spectrum further into the visible region, the quenching behavior were observed as the colloidal ZnO semiconductor was added and determined by fluorescence quenching method.

Random copolyimides, PI–PBIX, with different compositions of 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), N,N′-bis(4-aminophenyl)-3,4,9,10-perylenebis(dicarboximide) (PBI), and 4,4′-diamino-4″-methyltriphenylamine (AMTPA) were designed and synthesized for resistive-switching memory device applications. By varying the feeding ratio of monomers, PI–PBIX (where X = 0, 1, 2.5, 5, and 10 for molar composition of repeating units containing PBI) showed tunable optical and electronic properties through the charge transfer between AMTPA and PBI. Also, the memory devices prepared from PI–PBIX sandwiched between ITO and Al electrodes exhibited the tunable electrical bistability from the volatile to nonvolatile write once read many-times (WORM) memory characteristics as the PBI composition increased. The OFF/ON electrical switching transition was mainly attributed to the charge-transfer mechanism for charge-separated high conductance, based on the analysis of density function theory. Also, the volatili...

We report the synthesis, morphology, and optoelectronic device applications of novel biaxially extended quaterthiophene– (4T−) and octithiophene– (8T−) vinylene conjugated polymers, P4TV and P8TV, synthesized via Stille coupling reactions. P4TV and P8TV exhibited smaller energy band gaps of 1.69 and 1.78 eV than that of parent polythiophenes, respectively, due to the reduced conformation distortion by the vinylene linkage. The HOMO energy levels of P4TV and P8TV were −5.02 and −5.13 eV, respectively, resulting in air stable device performance. The highest field effect hole mobilities of P4TV and P8TV were 0.12 and 0.0018 cm2 V–1 s–1, respectively, with on/off ratios around 104–105. The higher carrier mobility of P4TV was related to its ordered structure as evidenced from the TEM, AFM, and grazing incidence X-ray diffraction results. The power conversion efficiency (PCE) of the P4TV/ PC71BM based photovoltaic cells (PV) under the illumination of AM 1.5G (100 mW/cm2) was 4.04%, which was significantly highe...

The synthesis and characterization of C 60 derivatives with different thiophene units, [6,6]-phenyl-C 61 -butyric acid 2-(2′-thienyl)ethyl ester ( PCBTE ), [6,6]-phenyl-C 61 -butyric acid 2-(2′,2″-bithiophene-5′-yl)ethyl ester ( PCBBTE ), and [6,6]-phenyl-C 61 -butyric acid 2-(2′,2″:5″,2″′-terthiophene-5′-yl)ethyl ester ( PCBTTE ), have been investigated as surfactants for bulk heterojunction (BHJ) organic solar cells comprised of P3HT and PCBM. We found that these surfactants could reduce the interfacial energy to prevent domain coarsening and macrophase separation in an active layer depending on their contents, in which PCBTTE was the most effective surfactant among the derivatives. The device performance was enhanced in presence of 5% PCBTTE with optimized devices showing a power conversion efficiency of 4.37% under AM 1.5 G (100 mW/cm 2 ) illumination. In the P3HT/PCBM/ PCBTTE ternary blends, the highest absorption coefficient was observed at the surfactant ratio of 5%, which led to an improvement in the J SC values. Additionally, the introduction of PCBTTE as a surfactant not only enhanced the power conversion efficiency of the solar cells, but also reduced the PCBM aggregation upon annealing, resulting in a better thermal stability. The compatibilizing effect could also be confirmed by DSC measurement revealing the different selective miscibility of P3HT and those C 60 derivatives with different thiophene units. These results indicated the superior compatibilizing effect of the PCBTTE for organic solar cell applications.

Novel polythiophenes with graphene structures (GPTs) could be synthesized based on intramolecular oxidative coupling of the polythiophene precursors having phenyl groups at the 3-position, poly(3-(4′-(3′′,7′′-dimethyloctoxy)phenyl)thiophene) (P3PhT) and poly(3-hexylthiophene)-b-P3PhT (P3HT-b-P3PhT), using FeCl3 as an oxidative agent. The GPTs were characterized by 1H NMR spectroscopy, UV-vis spectroscopy, FT-IR spectroscopy, cyclic voltammetry and X-ray diffraction. The thin film transistor (TFT) characteristics were also performed for P3HT-b-GPT. The progression of oxidative coupling of P3PhTs was confirmed by 1H NMR and FT-IR spectroscopies. Moreover, GPTs showed significant red-shifts in the UV-vis spectra due to their high coplanarity, extended π-conjugation length, and strong π-stacking formation. P3HT-b-GPT also showed a red-shift in the UV-vis spectra and a reduced band gap as compared to the pristine P3HT. P3HT-b-GPT exhibited hole mobility (∼10−5 cm2 V−1 s−1) which is comparable to that of pristine P3HT having a similar molecular weight.

New donor–acceptor conjugated copolymer, PSeDPP, consisting of selenophene (Se) and 3,6-dithiophen-2-yl-2,5-dialkylpyrrolo[3,4-c]pyrrole-1,4-dione (DPP), was developed for high performance ambipolar field-effect transistors (FETs) and nonvolatile memory applications. The maximum absorption peak and optical band gap of PSeDPP thin film were observed at 849 nm and 1.29 eV, respectively, indicating the strong intramolecular and intermolecular charge transfer. The polymer crystallinity and FET mobility was significantly enhanced as increasing the solvent boiling point and thermal treatment based on the results from four processing solvents of chloroform, chlorobenzene, o-dichlorobenzene and 1,2,4-trichlorobenzene, as evidenced by TEM, XRD, and AFM. The PSeDPP-based FET processed from1,2,4-trichlorobenzene exhibited a dense nanofiber morphology with lamellar chain packing, leading to the relatively high hole and electron mobility up to 1.62 and 0.14 cm2 V−1 s−1, respectively. PSeDPP was also found to exhibit the first transistor memory characteristics for ambipolar conjugated polymers. The retention time of the FET-based nonvolatile memory devices could maintain the high- and low-conductance states longer than 104 s, and the on-off current ratios of 103–104 at the read voltage of 0 V. These results revealed that PSeDPP had potential applications for flexible electronic device applications.

Resistive switchable memory devices were fabricated using self-assembled composite thin films of asymmetric poly(styrene-block-4-vinylpyridine) (PS-b-P4VP) block copolymers (BCP) and fullerene derivatives (PCBM). L1 (with a longer PS block) was comprised of discrete vertical P4VP nanocylinders embedded within the PS matrix whereas L2 (with a longer P4VP block) revealed a reverse morphology with a horizontal orientation. They were used to control the spatial location or distribution of the PCBM and the resultant memory characteristics. The devices with ITO/BCP:PCBM/Al configurations exhibited variable multi-electronic characteristics, changing from insulating to bistable memory switching and highly conducting, as the PCBM content increased. The L1:PCBM memory device showed non-volatile write-once-read-many-times (WORM) memory behavior but the L2:PCBM device exhibited a volatile nature of static random access memory (SRAM). Both L1 and L2:PCBM composite devices revealed the improved switching performance upon solvent annealing procedures of the composite thin film. Our results suggested that the controlled morphology of the BCP/PCBM composite could create nanoscale charge-storage elements for a high density memory device with a reduced bit cell size.

In this study, we report the synthesis, properties, and electrical memory characteristics of new diblock copolymers, polystyrene-block-poly(styrene-pyrene) (PS-b-P(St-Py)), prepared by combining atom transfer radical polymerization and Suzuki coupling reaction. The effects of the St–Py block chain length on the electronic energy level, photophysical properties, and memory characteristics were explored. The PS42-b-P(St-Py)108 and PS66-b-P(St-Py)67 devices exhibited a dynamic random access memory characteristics with different turn-on threshold voltages of −2.7 and −3.1 V, respectively. Moreover, these memory devices showed a high ON/OFF current ratio of 109 and were electrically stable for at least 104 s in both ON and OFF states. However, the PS113-b-P(St-Py)45-based device displayed an insulating state in a low current variation of 10−12 to 10−14 A, which had a short St–Py block length. The mechanism of the switching behavior was explained by the charge hopping conduction between the pyrene units with coexisting charge-trapping environment. The volatility of the memory effect was depended on the ability of charge trapping/back transferring of trapped charge. The present study suggested that the electrical memory characteristics could be efficiently tuned through the block ratio between insulating segment and pendant-conjugated segment of the diblock polymers.

We report the synthesis, properties, and field-effect transistor characteristics of biaxially extended thiophene-fused thiophene conjugated copolymers, P4TDTT and P4TTT, consisting of 2′,5″-5,5‴-di(2-ethylhexyl)-[2,3′;5′,2″;4″,2‴] -quaterthiophene and fused thiophene moieties of dithieno[3,2-b:2′,3′-d]thiophene and thieno[3,2-b]thiophene, respectively. The effect of fused thiophene size on the molecular packing and charge transport characteristics was explored. The high boiling point solvent facilitated the formation of ordered nanofiber morphology and enhanced the optoelectronic properties. P4TDTT exhibited a smaller d-spacing and π–π stacking distance than P4TTT based and a denser nanofiber network. The optical band gaps of P4TDTT and P4TTT films spin-coated from trichlorobenezene (TCB) solvent were 1.84 and 1.86 eV, respectively. The highest hole mobilities of P4TDTT and P4TTT using TCB solvent were 0.610 and 0.396 cm2 V–1 s–1, respectively, with the on/off ratios of 105–106. P4TDTT had better charge-t...

We report the synthesis, morphology, and charge-transporting characteristics of new crystallinecrystalline diblock copolymers, poly(3-hexylthiophene-block-stearyl acrylate) (P3HT-b-PSA). Three different diblock copolymers, P1, P2, and P3, with P3HT/PSA polymerization degree block ratios of 60/26, 60/50, and 60/360, respectively, were prepared for investigating the morphology-property relationship and the dependence of optoelectronic properties on the block copolymer structure. Small- and wide-angle X-ray scattering indicated the presence of both P3HT and PSA crystalline domains and the presence of microphase separation among blocks. The transmission electron microscopy and atomic force microscopy results revealed that the diblock copolymers cast from chlorobenzene, tended to form needle-like morphologies. The field-effect mobilities of the diblock copolymers deposited on untreated SiO(2) substrates, decreased with increasing PSA block length. In a sharp contrast, the mobilities enhanced with increasing PSA content when the P3HT-b-PSA was deposited on phenyltrichlorosilane (PTS)-treated substrates. The copolymers with a 60/360 P3HT/PSA ratio showed a good mobility of 4 x 10(-3) cm(2) V(-1) s(-1) and a high on/off ratio of 7 x 10(6) on PTS-treated substrates. This study highlighted the importance of the block ratio, the substrate and self-assembly structures on the charge transport characteristics of the crystallinecrystalline conjugated diblock copolymers. (c) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 686-695, 2012

A study to investigate matrix properties and their interaction with loaded nanoclay was designed under controlled clay dispersion. Metallocene polyethylene grafted vinyltriethoxy silane (mPE-g-silane) was served as the matrix, with or without silane crosslinking (grafting and post crosslinking with catalyst versus only grafting without catalyst), to assess the strength of commercial organoclay (20A)-filled nanocomposites prepared via a melt mixing. According to X-ray diffraction and transmission electron microscopy analyses, all nanocomposites achieved similar dispersion degrees at specific clay contents mainly due to the silane interaction with the dispersed clay via hydrogen bonding and/or chemical bonding. Chemical bonding of grafted silane with clay was inferred based on the slightly higher crosslinking degree with increasing clay content for crosslinked cases. For uncrosslinked cases, the crosslinking degree was virtually zero regardless of clay content. The dynamic mechanical properties revealed enhanced interaction between mPE-g-silane and clay with increasing clay content based on the increased glass transition temperatures. Young's modulus of nanocomposites with crosslinked cases showed higher values in comparison with uncrosslinked cases at a specific clay content, indicating the significance of matrix crosslinking effect and the effective interfacial interaction between silane and clay especially at higher clay content. To the authors' best knowledge, this is the first study which generally maintains similar clay dispersions through the effect of uncrosslinking (only grafting) and crosslinking (grafting and post crosslinking), and then probes the effect of matrix properties and interfacial interactions at the large deformation state (tensile test) and small deformation state (cutting test). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

We report the fabrication and characterization of polymer resistive switching memory devices fabricated from conjugated rod-coil poly[2,7-(9,9-dihexylfluorene)]-block-poly(2-vinylpyridine) diblock copolymers (PF-b-P2VP) and their hybrids with [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM). PF(10)-b-P2VP(37) and PF(10)-b-P2VP(68)-based devices exhibited the volatile static random access memory (SRAM) characteristic with an ON/OFF current ratio up to 1 × 10(7), which was explained by the trapping/back transferring of charge carrier. PF(10)-b-P2VP(68) had a longer holding time in the ON state than PF(10)-b-P2VP(37) because of the delayed back transfer of trapping carriers originally from the longer P2VP blocks. The PCBM aggregated size in the composite thin films were effectively reduced by PF-b-P2VP compared to the homopolymer of PF or P2VP, because of the supramolecular charge transfer interaction, as evidenced by absorption and photoluminescence spectra. Their PCBM/PF-b-P2VP composite devices changed from the nonvolatile write-once-read-many-times (WORM) memory to the conductor behavior as the PCBM composition was increased. The electric-field induced charge transfer effect enabled the electrical bistable states for the applications in digital WORM memory device. The tunable memory characteristics through the block length ratio of block copolymers or PCBM composition provided the solution-processable charge storage nanomaterials for programmable high density memory device with a reducing bit cell size.

A series of new water-soluble cationic pyrene-dendron derivatives, G1, G2, and G3, was successfully synthesized and characterized. These new dendrons were designed with the quaternized amino moieties at the periphery of the dendrons for DNA detection and functionalized with pyrene as a fluorescent probe. The electrostatic interactions between the plasmid DNA (pDNA) and cationic charged dendrons in an aqueous solution resulted in a change in the photophysical properties of pyrene, which could be shown in the UV-vis and fluorescence spectra. Pyrene dendrons showed a high and rapid fluorescence response upon the addition of pDNA, which was strongly dependent on the size and hydrophobicity of the dendrons. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

High charge carrier mobility solution-processed n-channel organic thin-film transistors (OTFTs) based on core-chlorinated naphthalene tetracarboxylic diimides (NDIs) with fluoroalkyl chains are demonstrated. These OTFTs were prepared through a solution shearing method. Core-chlorination of NDIs not only increases the electron mobilities of OTFTs, but also enhances their air stability, since the chlorination in the NDI core lowers the lowest unoccupied molecular orbital (LUMO) levels. The air-stability of dichlorinated NDI was better than that of the tetrachlorinated NDIs, presumably due to the fact that dichlorinated NDIs have a denser packing of the fluoroalkyl chains and less grain boundaries on the surface, reducing the invasion pathway of ambient oxygen and moisture. The devices of dichlorinated NDIs exhibit good OTFT performance, even after storage in air for one and a half months. Charge transport anisotropy is observed from the dichlorinated NDI. A dichlorinated NDI with −CH2C3F7 side chains reveals high mobilities of up to 0.22 and 0.57 cm2 V−1 s−1 in parallel and perpendicular direction, respectively, with regard to the shearing direction. This mobility anisotropy is related to the grain morphology. In addition, we find that the solution-shearing deposition affects the molecular orientation in the crystalline thin films and lowers the d(001)-spacing (the out-of-plane interlayer spacing), compared to the vapor-deposited thin films. Core-chlorinated NDI derivatives are found to be highly suitable for n-channel active materials in low-cost solution-processed organic electronics.

We report the synthesis, optoelectronic properties, and electrical switching memory characteristics of three new donor–acceptor oligoimides consisting of the electron-donating moieties (triphenylamine or carbazole) and electron-withdrawing phthalimide moieties. The influence of different donor (D)–acceptor (A) arrangements, including D-A-D and A-D-A structures, on the electrical properties was explored. Devices based on D-A-D oligoimides revealed a reversible nonvolatile negative-differential-resistance (NDR) characteristic and excellent stability during operation. Without applying voltage stress, the on and off states of the devices showed no obvious degradation for an operation time of 10 s and 108 read pulses. However, the devices prepared from the A-D-A oligoimide showed only the insulating properties. The different memory characteristic was probably because the terminal donor moieties in the D-A-D structure might facilitate the injection and transporting of the holes. Besides, the D-A-D oligoimide wi...

Polypropylene/metallocene polyethylene (PP/mPE) thermoplastic elastomer nanocomposites were prepared by a melt blending process. Metallocene polyethylenes grafted with vinyltriethoxy silane (mPE-g-silane) and neat mPE, both premixed with commercial organoclay (20A) to serve as the elastomer domains, were compared to investigate the silane curing effect on the prepared nanocomposites. According to X-ray diffraction and transmission electron microscopy analyses, the mPE-g-silane was of help in facilitating the intercalation and partial exfoliation of clay for PP/mPE-g-silane/clay system. A slight melting temperature depression of mPE and its nanocomposites was observed with the introduction of the silane curing due to the induced imperfect crystals. There was no silane curing effect found on the thermal stability, but the incorporation of clay increased the thermal stabilities. The PP/mPE-g-silane/clay system conferred higher tensile strength and tear strength than that of PP/mPE/clay system, mainly attribu...

We report the synthesis, morphology, and properties of new 3-arm AB22 and 5-arm AB44 asymmetric amphiphilic star polymers of poly[4-(9,9-dihexylfloren-2-yl)styrene]-block-poly(2-vinylpyridine) (P(St-Fl)-b-P2VP), with narrow molecular weight distributions (Mw/Mn < 1.11). The asymmetric star polymers were synthesized by living anionic polymerization using 1,1-diphenylethylene (DPE)-functionalized P(St-Fl) with two or four benzyl bromide moieties, followed by linking reaction with a living anionic P2VP. Depending on the arm numbers of P2VP, lamellar and hexagonally perforated lamellae morphologies were observed for the AB22 and AB44P(St-Fl)-b-P2VP from the results of SAXS, WAXS, and TEM. The [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) incorporated in the polymer matrix increased the order degree of the liquid-crystal-like morphology in the P(St-Fl) block. The prepared AB22 and AB44P(St-Fl)-b-P2VP could be blended with PCBM for electrical write-once-read-many times (WORM) memory devices application. The threshold voltage (−2.8 to −3.9 V) and ON/OFF ratio (103 to 106) of the WORM characteristic were obtained by tuning the PCBM content. The ON or OFF state of the WORM memory devices could remain over 104 s without any degradation. The optical absorption and photoluminescence results indicated the formation of charge transfer complexation between PCBM and the 2-vinylpyridine or pendent fluorene chromophores. The switching behavior was further explained by the charge injection dominated thermionic emission in the OFF state and field-induced charge transfer in the ON state. These experimental results provide a new strategy to prepare a conjugated moiety containing asymmetric star polymers and their potential electrical memory device applications.

a b s t r a c t We reported a low band-gap conjugated polymer, poly(2,3-bis(4-(2-ethylhexyloxy)phenyl)-5,7- di(thiophen-2-yl)thieno(3,4-b)pyrazine) (PDTTP), was studied for the near infrared (NIR) photo-detector application. PDTTP shows intense absorption in NIR wavelength (to 1000 nm) and the estimated optical and electrochemical band-gaps of PDTTP are quite small around 1.15 eV and 1.08 eV, respectively. The low band-gap and the extended long wavelength absorption originates from the introduction of alter- nating TP units when its parent polythieno(3,4-b)pyrazine shows excellent narrow band-gap properties. Therefore, the relatively low band-gap and intense absorption in long wavelength of PDTTP make itself a promising candidate for near-infrared photo-detector. The hole mobility of the PDTTP measured from the bottom contact field effect transistor is around 1.40 × 10 −3 cm 2 /V s with a on/off ratio of 2100. The photo-detector based on bulk hetero-junction PDTTP and (6,6)-phenyl-C61-butyric acid methyl ester blend (PCBM) has the incident photon-to-electron conversion efficiency 28.9% at 1000 nm (−5 V) and 6.2% at 1100 nm (−5 V). This photo-detector can be operated at a high-speed of 1 MHz. The experimen- tal result suggests the potential applications of low band-gap conjugated polymers on near-infrared photo-detectors.

Multi-walled carbon nanotubes (MWCNTs) supported Pd–Au nanoparticles for electrooxidation of formic acid (FA) are prepared and compared with Pd/MWCNTs in this study. The nanocatalysts are prepared by a polyol method, and characterized using X-ray diffraction (XRD), thermogravimetry (TGA), SEM, and field emission transmission electron microscope (FE-TEM). Cyclic voltammetry (CV) is used to examine the catalytic activity towards FA electrooxidation. Controlling the contents of the precursors (PdCl2 and HAuCl4·4H2O), the different weight ratios of Pd–Au can be synthesized to form the various solid solution structures of Pd–Au. TEM image results indicate the average diameter of Pd–Au solid solution particles is about 10–30 nm. The results of electrochemical analysis show that the Au (10 wt.%)/[Pd/MWCNTs (1:9)](90 wt.%) hybrid catalysts exhibit the highest catalytic activity and better stability than that of Pd/MWCNTs in FA electrooxidation. The promoting of Pd-based catalyst with Au to form solid solution improves the performance of the catalyst in FA electrooxidation. The newly synthesized electrocatalyst is promising for application in direct formic acid fuel cell (DFAFC).

The functional polyimide (OMe)2TPPA-6FPI (PI) and the polyamide (OMe)2TPPA-6FPA (PA) consisting of elec- tron-donating N,N 0 -bis(4-aminophenyl)-N,N 0 -di(4-methoxylphe- nyl)1,4-phenylenediamine ((OMe)2TPPA-diamine) for memory application were prepared in this study. These polyimide and polyamide memory devices were fabricated with the sandwich configuration of indium tin oxide (ITO)/polymer/Al, and could be switched from the initial low-conductivity (OFF) state to the high-conductivity (ON) state with high ON/OFF current ratios of 10 7 and 10 9 , respectively. PI exhibited dynamic random access memory (DRAM) performance, whereas PA showed static ran- dom access memory (SRAM) behavior. To get more insight into the memory behaviors of these two different types of polymer memory devices, molecular simulation on the basic unit was carried out. Furthermore, the differences of highest occupied molecular orbital (HOMO) energy level, lowest unoccu- pied molecular orbital (LUMO) charge density isosurfaces, dipole moment, and linkage conformation between PI and PA were found to affect the volatile memory behavior. Both polymer memory devices revealed excellent stability with long operation time of 10 4 s at continuous applied voltage of -2 V. The effect of polymer thickness on the volatile memory behavior of PA was also investigated in this study. V C 2011 Wiley Periodicals, Inc. JP olym Sci Part A: Polym Chem 49: 3709-3718, 2011

Hole-transporting triphenylamine (TPA)-based polymers, the linear poly[4-(diphenylamino)benzyl methacrylate] (PTPMA) and the three-armed star-shaped poly[4-(diphenylamino)benzyl methacrylate] (N(PTPMA)3), have been synthesized by group transfer polymerization (GTP). For the synthesis of N(PTPMA)3, the core-first approach coupled with the GTP was adopted using a newly designed silyl ketene acetal initiator with three initiating points. The polymerization results showed that the polymer molecular weights were precisely controlled by the monomer/initiator ratio. The new hole-transporting TPA-based polymers could be blended with electron-accepting [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) for electrical memory device applications. The experimental results showed that pristine PTPMA and N(PTPMA)3 exhibited dynamic-random-access-memory (DRAM) volatile electrical behavior, but their PCBM composite-based devices changed to the write-once-read-many times (WORM) nonvolatile memory characteristic or conducto...

We describe a simple and effective method to obtain colloidal surface-functionalized Au nanoparticles. The method is primarily based on irradiation of a gold solution with high-flux X-rays from a synchrotron source in the presence of 11-mercaptoundecanoic acid (MUA). Extensive tests of the products demonstrated high colloidal density as well as excellent stability, shelf life, and biocompatibility. Specific tests with X-ray diffraction, UV-visible spectrometry, visible microscopy, Fourier transform infrared spectroscopy, dark-field visible-light scattering microscopy, and transmission electron microscopy demonstrated that MUA, being an effective surfactant, not only allows tunable size control of the nanoparticles, but also facilitates functionalization. The nanoparticle sizes were 6.45 ± 1.58, 1.83 ± 1.21, 1.52 ± 0.37 and 1.18 ± 0.26 nm with no MUA and with MUA-to-Au ratios of 1:2, 1:1, and 3:1. The MUA additionally enabled functionalization with l-glycine. We thus demonstrated flexibility in controlling the nanoparticle size over a large range with narrow size distribution. Refereed/Peer-reviewed

Chitosan/modified silica nanocomposites, with a sol–gel process being used to prepare a silanol quaternary ammonium modified silica possessing antimicrobial activity, were investigated, as well as the thermal properties, morphology, optical, mechanical, antimicrobial, and adsorption properties of this type of nanocomposite. Grafting of the modifier onto nanosilica was confirmed through the Fourier transform infrared (FTIR) spectra. X-ray diffraction patterns indicated that the chitosan structure was not disrupted from the incorporation of the modified silica. Fracture surfaces with no clear micro-phase separation were observed by scanning electron microscopy (SEM), which indicated the good interaction of chitosan and the modified silica. The organic modifier tended to cause the aggregation of the modified silica at higher content on a submicron scale based on transmission electron microscopy (TEM) analysis, which might be due to a decrease of the stability factor originating from the negative charges on s...

The NA60 experiment at the CERN SPS has studied ϕ meson production in In–In collisions at 158 A GeV via both the K + K − and the μ + μ − decay channels. The yields and inverse slope parameters of the m T spectra observed in the two channels are compatible within errors, different from the large discrepancies seen in Pb–Pb collisions between the hadronic (NA49) and dimuon (NA50) decay channels. Possible physics implications are discussed.

Conjugated rod–coil block copolymers have been accorded great importance since they provide a powerful route towards supramolecular objects with novel architectures, functions and physical properties. This review summarizes recent progress on the synthesis, morphology, optoelectronic properties and applications of such block copolymers. The combination of the precise condensation and living polymerization through the grafting-from or grafting-onto methodology produce various architectures of conjugated rod–coil block copolymers, including rod–coil, coil–rod–coil, rod–coil–coil, and rod–coil–rod. In the following, the relationships between polymer morphologies and photophysical properties in different phases are reviewed, as classified by solution micelles, thin films or bulk samples, polymer brushes and electrospun nanofibers. The effects of the rod/coil ratio and polymer architecture on the morphology and optoelectronic properties are discussed. The control of nanosize domain and the aligned direction of conjugated rods are the key issues for enhancing the optoelectronic device performance. Moreover, novel multifunctional sensory materials based on combining the tunable photophysical properties of the π-conjugated rod and the stimuli-responsive coil are also highlighted. It is believed that conjugated rod–coil block copolymers could spark the future evolution of nanostructured polymers for multifunctional device applications.

New all-conjugated block copolythiophene, poly(3- hexylthiophene)-block-poly(3-(4 0 -(3 00 ,7 00 -dimethyloctyloxy)-3 0 -pyr- idinyl)thiophene) (P3HT-b-P3PyT) was successfully prepared by Grignard metathesis polymerization. The supramolecular inter- action between (6,6)-phenyl-C61-butyric acid methyl ester (PCBM) and P3PyT was proposed to control the aggregated size of PCBM and long-term thermal stability of the photovol- taic cell, as evidenced by differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and optical mi- croscopy. The effect of different solvents on the electronic and optoelectronic properties was studied, including chloroform (CL), dichlorobenzene (DCB), and mixed solvent of CL/DCB. The optimized bulk heterojunction solar cell devices using the P3HT-b-P3PyT/PCBM blend showed a power conversion effi- ciency of 2.12%, comparable to that of P3HT/PCBM device de- spite the fact that former had a lower crystallinity or absorption coefficient. Furthermore, P3HT-b-P3PyT could be also used as a surfactant to enhance the long-term thermal stability of P3HT/ PCBM-based solar cells by limiting the aggregated size of PCBM. This study represents a new supramolecular approach to design all-conjugated block copolymers for high-performance photovoltaic devices. V C 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 2577-2587, 2011