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This study investigated a new category of transparent encapsulant materials for light-emitting diodes (LEDs). It comprised a phenyl group that contained siloxane-modified epoxy (SEP-Ph) hybridized with a cyclic tetrafunctional siloxane-modified epoxy (SEP-D4) with methylhexahydrophthalic anhydride (MHHPA) as a curing agent. The SEP-Ph/SEP-D4 = 0.5/0.5 (sample 3) and SEP-D4 (sample 4) could provide notably high optical transmittance (over 90% in the visible region), high-temperature discoloration resistance, low stress, and more crucially, noteworthy sulfurization resistance. The lumen flux retention of the SEP encapsulated surface mounted device LEDs remained between approximately 97% and 99% after a sulfurization test for 240 h. The obtained comprehensive optical, mechanical, and sulfurization resistance proved the validity and uniqueness of the present design concept with complementary physical and chemical characteristics.

This study focused on the effect of crosslinker structure between PMMA on the dispersity of crosslinked particles in seed swelling polymerisation. We used five different crosslinking agents in an assessment of the dispersity of crosslinking monodisperse particles using PMMA seed particles in seed swelling polymerisation. These results show that the structure of the crosslinking agent affects the dispersity during the swelling stage. According to the solubility parameter theory of computation, the departure of similar solubility parameter causes the swollen particles to segregate into more dispersity.

Controlling the polymerization of aniline in the presence of zirconium-based metal-organic frameworks (Zr-MOFs) using polystyrene sulfonic acid as a dopant resulted in the formation of a new type of free-standing thermoelectric composite film. Polyaniline chains interpenetrate into the Zr-MOFs to enhance the crystallinity of polyaniline, resulting in an improved degree of electrical conductivity. In addition, the inherent porosity of the Zr-MOFs functions to suppress the increase in thermal conductivity, thus dramatically promoting a negative Seebeck coefficient. When 20 wt % Zr-MOF was used, a power factor of up to 664 μW/(m K2) was obtained, which was accompanied by a surprisingly large, negative Seebeck coefficient. The new class of MOF-based composites offers a new direction for developing new types of efficient thermoelectric materials.

p-Phenediamino-modified graphene (PDG) has been newly synthesized via a facile green one-step chemical route as a functionalized graphene-based additive to copolymerize with aniline for fabricating innovative PDG/polyaniline conducting polymer composites containing very special semi-interpenetrating networks (S-IPNs). The S-IPNs not only provide additional pathways by creating chemically bonded PDG and PANI for smoothly transporting carriers but greatly reduce the amount of graphene required to less than a few percent could effectively improve the overall electrical conductivity, Seebeck coefficient, and thus the thermoelectric (TE) performance. The found optimized TE figure of merit (ZT) of 0.74 approaches a practical high level which is comparable or much higher than previously reported ones for TE polymers.

Controlled and continuous electrospinning of approximately pure poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) nanofibers has been successfully realized for the first time by alternating the great amount of conventional carrier polymers with only slight doping of magnesium nitrate which acts as a polymer cross-linker for significantly enhancing the entanglement of PEDOT:PSS. In contrast to the less response of the bulky PEDOT:PSS film, the electrospun PEDOT:PSS nanofibers exhibit remarkably high sensitivities and responding speeds in respectively sensing gas molecules of dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and propylene carbonate (PC).

Nanostructured oxides with characteristic morphologies are essential building blocks for high-performance gas-sensing devices. We describe the high-yield fabrication of a series of functionalized V2O5 nanoassemblies through a facile polyol approach with specific varieties of polyvinylpyrrolidone. The synthesized V2O5 nanoassemblies consisting of tiny one-dimensional nanoblocks with the absence of any extrinsic catalysts exhibit distinct hemispherical or spherical hollow morphologies and operate as room-temperature hydrogen sensors with remarkable sensitivities and responses.

In this study, phosphate surface pretreatment (PSPT) and poly[pyromellitic dianhydride-co-4,4ʹ-oxydianiline] polyimide (PMDA-ODA PI) coating were used to provide corrosion protection for Mg-5 wt.% Sn alloy. PSPT enhanced the adhesion of PI coating by mechanical interlocking and chemical anchoring. Surface roughness was increased and provided stronger mechanical interlocking. Phosphates were formed on the alloy surface to act as anchor groups. Energy dispersive X-ray spectrometer and X-ray photoelectron spectroscopy results indicated that bonds formed between anchor groups and PI coating. The bonds provided chemical anchoring and enhanced the adhesion of PI coating. The increase of corrosion resistance of PI coating on Mg-5 wt.% Sn alloy (Ecorr = −0.86 V/SCE, µA cm−2 and corrosion rate far less than showed the bonds were stable enough to stand the attack of electrolyte and inhibit the electrochemical reaction at the interface.

We describe a facile and one-step pulsed laser deposition (PLD) technique that was utilized for the first time to systematically fabricate a series of innovative Bi2Te3 superassembly-on-epitaxy bi-layer nanostructures, by uniquely coupling the upper self-assembled well-ordered Bi2Te3 hierarchical nanostructures with unusually high surface- and interface-to-volume ratios and a highly electrical conductive epitaxial bottom thin layer on insulated SiO2/Si substrates, as an emerging new class of the most advanced thermoelectric nanomaterials. The optimized power factor of the present superassembly-on-epitaxy films is one to three orders of magnitude higher than that of most Bi2Te3 nanoassemblies defined as the assemblies of nanocrystals, evidently proving the significance and potential of the present new concept and the resulting thermoelectric nanomaterials.

This paper describes a facile low-toxicity synthesis of two different types of Au nanonests and one binary Au–Pt core–shell nanonest with high yield and excellent uniformity in size and morphology using block copolymer P123 (EO20PO70EO20) as a soft template and the main reductant in an ice water bath. The introduction of a suitable second metallic source, i.e. Pt ions in the present case, was proven to be a unique strategy for effectively governing the reduction sites of P123 for Au nucleation, which leads to significant changes especially in the crystallite size of the grown Au nanonests. The Au nanonests exhibited a distinct morphology-dependent surface plasmon resonance (SPR) that is red-shifted by ∼140 nm from the spherical particles wavelength, and significant surface-enhanced Raman scattering (SERS), allowing the rapid determination of rare malachite green oxalate (MGO).

Anti-corrosive polyimide/hexagonal boron nitride (PI/h-BN) composite films were prepared with different monomers to offer different polymer configurations: rigid and soft. In PI/h-BN composite films, different configurations of polymers show different crystallinity trends of the polymer matrix. In our study, the degree of crystallinity in rigid polymer decreases with the BN content; in flexible polymers it is independent of the BN content. It is worth noting that BN in different PI matrices can effectively enhance the protection of steel from corrosion. With a flexible PI matrix, the PI/h-BN coating exhibited better resistance to water vapor and better anti-corrosion. Only 5 wt.% of h-BN in the composite is enough to offer high anti-corrosion, a positive corrosion voltage.

In this study we prepared superhydrophobic polyimide (PI) hybrid coatings for anticorrosion application by adjusting their surface roughness and surface composition through spray-coating with silylated perfluoroalkylsilane-modified organosilicasol (silylated fluoro-organosilicasol), which increased the surface hydrophobicity. After silylation with 1,1,1,3,3,3-hexamethyldisilazane (HMDS), the silylated fluoro-organosilicasol further transformed the PI surface into a superhydrophobic state with a static water contact angle of greater than 160° and a low hysteresis of 10°. We examined the mechanism behind the enhancement in superhydrophobicity through analyses of the surface topology and chemical composition of the films, using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and electron spectroscopy for chemical analysis (ESCA). These analyses suggested that both surface roughness and silylation of the fluoro-organosilicasol making more CF 2 groups on the outmost surface rendered the surface hydrophobicity. The anticorrosion properties of these superhydrophobic coatings were also examined through Tafel measurement. These PI hybrid coatings demonstrated lower corrosion current density and nobler corrosion potential and higher polarization resistance. The enhancement in anticorrosion performance was believed to be contributed from the superhydrophobicity and dual barrier protection from the fully-covered fluoro-organosilicasol, insulating the metal from corrosive species in the medium. This superhydrophobic coating technique with good stability guaranteed better corrosion protection and also has great potential for application to other polymeric films.

We describe an innovative concept and facile approach in fabricating laterally assembled Ga2Te3/Te binary nanocomposite films, which comprise two-dimensional quasi-periodic Ga2Te3 nanoassemblies surrounded by interlocking highly-conductive Te single crystals for comprehensively establishing subnano- to micro-scaled multi-style versatile interfaces. The distinct Ga2Te3/Te nanocomposite film exhibits a power factor that is about 60 times higher than the reported conventional Ga2Te3 and Te materials, mainly due to the 2- to 3-order improved electrical conductivity and the comparable Seebeck coefficient.

INTRODUCTION Poly(3,4ethylenedioxythiophene):poly(styre nesulfonate) (PEDOT:PSS) is a widely investigated ionic conducting polymer (ICP) in many research aspects and serves also as a promising thermoelectric polymer along with its potentially high and tunable electrical conductivity. The effectiveness of a thermoelectric material is related to the dimensionless figure-of-merit (ZT) defined as rST/r, where r is the electrical conductivity, S is the Seebeck coefficient, j is the thermal conductivity, and T is the absolute temperature. Ongoing research efforts on PEDOT:PSS are largely targeted at improving the electrical conductivity mainly due to less-effective strategies in modifying Seebeck coefficient and the intrinsically low thermal conductivity.

A facile approach namely controlling the pH level of 5 wt% dimethyl sulfoxide (DMSO) doped poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) solution with sodium hydroxide (NaOH) was utilized for the first time in successfully optimizing the thermoelectric conversion efficiency of PEDOT:PSS films. The largely varied Seebeck coefficients and electrical conductivities of the pH controlled PEDOT:PSS films which could thus construct a beneficial curve for locating the optimized power factor are clearly shown from the significant changes of the carrier concentration via the dedoping of PEDOT. The correlation between pH value and carrier concentration as well as the power factor is experimentally found with numerical description covering a full pH range. The applied technique and the resulting optimized thermoelectric properties and possible bio-compatibility not only provide a fundamental understanding of the thermoelectric conducting polymers but widely disclose a variety of potential applications in the future.

We present a valuable in situ fabrication process for synthesizing high electrical conductive polyimide/multiwalled carbon nanotube (PI/MWCNT) composite films. The success of this process was achieved the addition of 2,6-diaminoanthraquinone (DAAQ). The DAAQ is not only an excellent dispersion agent to stably disperse pristine MWCNTs in solvent but also a monomer to directly synthesize PI. The strong interaction between DAAQ with MWCNT was verified by FTIR, UV–Vis, Raman, and fluorescence spectra. The highest value of electrical conductivity of 55.6 S/cm are achieved by the PI composite containing 40 wt.% of MWCNT. Moreover, the electrical conductivity of this film further enhanced to 106 S/cm after the thermal compression process. The MWCNT content at the percolation threshold of conductivity is 0.50 wt.% (or 0.32 vol.%) and the critical exponent is equal to 2.52. The developed in situ fabrication process through DAAQ-derived molecules can also be applied to synthesize other polymers requiring diamine structure.

In this study, the polysquaraine SQI0.1, a zwitterionic π-conjugated polymer, was adopted as the matrix for the preparation of flexible and freestanding films; the low band gap of this semiconducting polymer made it a natural choice for use as a thermoelectric (TE) polymer. To enhance their TE applications, both single-walled carbon nanotubes (SWNTs) and mesoporous carbon (i.e., CMK-3) were integrated into the SQI0.1-based films and the effects of doping with iodine were also investigated. Using scanning electron microscopy, the variations in morphology of these SQI0.1-based films were examined. Raman spectroscopy was used to study the π–π interactions between iodine and the carbon materials (i.e., SWNT, CMK-3); X-ray diffraction and Raman spectroscopy to investigate the intercalation of the doped iodine in the composite films; and X-ray photoelectron spectroscopy to determine the valence state of the doped iodine. The TE properties of these materials were characterized in terms of the electrical conductivity (σ), thermal conductivity (κ), and Seebeck coefficient (S). The TE properties of the iodine-doped composite film prepared from SWNTs, CMK-3, and SQI0.1 included a notable value of ZT (Figure of Merit) of 4.563 × 10−3, which was 143% of that of the corresponding iodine-doped SQI0.1 film.

In this study we developed an approach to improve the characteristics of photopolymers for holographic data storage. Through codoping different compounds, N,N-dimethyl-4-nitroaniline (DMNA) and zinc methylacrylate (Zn(MA)2), into 9,10-phenanthrenequinone (PQ) doped poly(methyl methacrylate) (PMMA), the diffraction efficiency and the value of dynamic range (M#) have been progressed. We enhanced the diffraction efficiency (from 36.1 to 86.2%) and the dynamic range (M#, from 2.9 to 10.7) of PQ-doped PMMA through codoping with DMNA and Zn(MA)2. Using mass spectrometry and X-ray photoelectron spectroscopy, we investigated the mechanism behind the improvements in optical storage induced by the presence of Zn(MA)2 and DMNA in PMMA/PQ. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

Aniline-pentamer (AP) in Nafion triggered with humidity content displays an interesting chromism from blue to pink, which is much wider of color shift than general polyaniline. Thermogravimetric analysis confirms the reversal color change related to the moisture content in the sample. IR absorption spectra make known AP having high degree of protonation at lower water content. UV-Vis absorption expose the chromism process having something more than just protonation. The change of electronic energy levels and PL spectra reveal that there must be a complex interaction in NaAP. Raman scattering mapping confirms that drying causes the -SO3 − hydrophilic channels transforming to isolated domains dispersed in matrix, which induces heavy protonation and complexation of AP with -SO3 −groups. We can infer that the interesting humidity-switch chromism is due to the reversible protonation/deprotonation as well as complexation of AP with -SO3 − groups through the reversible change of Nafion’s morphology.

Polycondensation of 4-bis[2-(1-methylpyrrol-2-yl)vinyl]-2,5-didodecyloxybenzene and squaric acid yielded the polysquaraine SQ with two isomeric subunits—1,3-addition (zwitterionic) and 1,2-addition (diketonic) moieties—in the main chain structure. The former featured a C–O/C═O infrared (IR) absorption frequency at 1622 cm–1; the latter, a C═O signal at 1716 cm–1. Traditional synthesis yielded SQ as a powder with metallic luster that could not be cast as a polymer film from solution. When the ionic liquid [Oct3NMe][TfO] (IL) was present in the cosolvent of BuOH and benzene (1:3), however, the resulting SQIx polymers (x = 0.01–5 wt %) did not precipitate from solution, making it possible to cast continuous free-standing films with a large area (>1 × 1 cm2). A greater content of IL in the solution favored the formation of the 1,3-addition zwitterionic subunits in the SQIx polymer main chains, thereby changing the physical and optical properties of the polysquaraine, as evidenced in IR and optical absorption ...

In this investigation, we propose and experimentally demonstrate a method for measuring the refractive index (RI) of liquid organic chemicals. The scheme is based on a single-mode fiber (SMF) sensor and an optical time-domain reflectometer (OTDR). Here, due to the different reflectance (R) between the SMF and organic liquid chemicals, the reflected power level of the backscattering light (BSL) measured by the OTDR would be different. Therefore, we can measure the RI of chemical under test via the measured BSL level. The proposed RI sensor is simple and easy to manipulate, with stable detected signals, and has the potential to be a valuable tool for use in biological and chemical applications.

The doping effects of thermal decomposable ammonium formate (AF) from 5 to 50 wt.% on the electrical conductivity, Seebeck coefficient, and microstructures of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films have been investigated for the first time for modern thermoelectric applications. It has been found that the Seebeck coefficient can be effectively tuned in a very wide range by varying the AF doping concentration, where a maximum value of 436.3 μV/K was obtained, i.e., ∼40 times higher in magnitude than the pure PEDOT:PSS films prepared with same processes. The greatly enhanced Seebeck coefficient is considered to be the result of reducing the carrier concentration, as evidenced by the Hall measurement. In addition, AF also plays an important role in the formation of the closed or open pores and channels within the films for phonon scattering, as can be clearly observed in the SEM images. The present work provides a new procedure to effectively control the Seebeck coefficient as well as the microstructures of PEDOT:PSS polymer by a simple blending approach with suitable thermal steps, which has not previously been reported.

In this study, we developed a simple method for the micropatterned growth of iron phthalocyanine (FePc) nanofiber arrays using a thermal evaporation process. By controlling the surface energy and the temperature of the substrate (Tsub), we obtained FePc films featuring a grain-like (in-plane) morphology on Si surfaces (higher surface energy) and a fiber-like (out-of-plane) morphology on Ag surfaces (lower surface energy) within a certain range of values of Tsub. On the Ag surfaces, these temperature-induced FePc nanofibers featured a high aspect ratio (AR) of 30.3 ± 3.6, with a mean length of 699 ± 216 nm and a mean radius of 22.2 ± 4.3 nm, as-prepared at a value of Tsub of 240 °C. The FePc films obtained at values of Tsub of 25, 120, 180, and 240 °C all possessed α-phase crystalline structures. Because the growth structures of the FePc molecules on the Si and Ag substrates were quite different, we could control the growth of micropatterned 1D FePc nanofiber arrays on previously patterned Ag/Si substrates. From the comparison of the field emission (FE) properties in different ARs of patterned devices, higher AR (30.3 ± 3.6) of devices (FE-240-P; Tsub of 240 °C) exhibited better FE performance than lower AR (6.0 ± 2.6) of devices (FE-180-P; Tsub of 180 °C). The FE current density of devices (Tsub of 240 °C) increased from 0.13 mA/cm2 for the unpatterned device (FE-240-N) to 6.77 mA/cm2 for the patterned device (FE-240-P) at an applied electric field of 12 V/μm. The turn-on electric fields required to produce a current density of 10 μA/cm2 were 7.7 and 10.3 V/μm for the patterned and unpatterned FePc emitters, respectively. From the slopes of Fowler–Nordheim plots, we estimated the field enhancement factors (β) of FE-240-P and FE-240-N to be 314 and 329, respectively. Studies of the emission current stability revealed that the FePc nanofibers possessed outstanding anti-degrading capability. During stability tests, the micropatterned FePc emitter (FE-240-P) displayed an efficient emission current with fluctuations of less than 20%. Because this facile platform allows control over the morphologies of films of small organic molecules merely by tuning the surface energy of the substrates, such micropatterned-FePc nanofibers might have great applicability in practical field emitters.

A novel poly(imide siloxane)/titania (PIS/ TiO2) hybrid film was fabricated by sol-gel process via in situ formation of TiO2 within PIS matrix. Poly(amic acid siloxane) (PAAS) was prepared from 4,4 0 -oxydiphthalic anhydride, 2,2-bis (4-(4-aminophenoxy) phenyl) propane, and a,x-bis(3-aminopropyl)polydimethylsiloxane (APPS). Chelating agent, acetylacetone, and catalyst-free polymer- ization were used to reduce the rate of hydrolysis of titanium alkoxide in the PAAS. X-ray photoelectron spec- troscopy data showed that the presence of APPS promotes the Ti surface composition of PIS/TiO2 hybrid film. The effects of TiO2 and APPS contents on the characteristics of surface, thermostability, coefficient of thermal expansion (CTE), and the strength of adhesion were investigated. The presence of TiO2 on the surface of the hybrid films enhanced the adhesive strength at the interface of PIS/TiO2 hybrid film and copper foil. When more TiO2 was incorpo- rated into the PIS matrix, the PIS/TiO2 hybrid film exhib- ited lower CTE while retaining favorable mechanical and thermal properties. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 124: 1929-1937, 2012

In this study, we used thermal evaporation with a low sublimation temperature (42 °C) to deposit 1,5-diaminoanthraquinone (DAAQ) in various morphologies—including nanorods, nanocornerstones, and nanofibers—onto various substrates. Three major factors influenced the growth of vertically aligned DAAQ nanofibers on the electrodes: a low water contact angle (WCA) for the substrate and intermolecular hydrogen bonding and π–π interactions between the DAAQ molecules. On Au and Ti substrates (low-WCA), the DAAQ nanofibers DAAQ-Au and DAAQ-Ti, respectively, possessed great verticality and high aspect ratios; they also exhibited field emission characteristics, with maximum emission current densities of 0.31 and 0.65 mA/cm2, respectively, at an applied electric field of 12 V/μm. The turn-on electric fields for producing a current density of 10 μA/cm2 were 8.5 V/μm for DAAQ-Au and 8.25 V/μm for DAAQ-Ti. From the slopes of Fowler–Nordheim plots, we calculated the field enhancement factors (β) of DAAQ-Au and DAAQ-Ti to be 447 and 831, respectively. Field emission stability studies revealed that the DAAQ nanofibers possessed outstanding anti-degrading capability. The emission current did not decrease, but rather increased slightly, after 3000 s. Given the advantages of this simple low-temperature process and the impressive anti-degrading field emission characteristics, such DAAQ nanofibers have great potential for use in various electronics applications (e.g., as organic field emitters).

The variation of visible and IR absorption spectra and of small-angle X-ray scattering of poly(3-octylpyrrole)squaraine in trichloromethane solution indicates that, for this zwitterionic conducting polymer (CP), a reversible change of conformation is induced by contact of the solution with the surface of an active metal. The structure of the target polymer might switch from being linear to being folded. For a copper surface, the activation energy of isomerization between the two forms, whatever their nature, is 18.9 ± 0.7 kJ mol−1, whereas for the reverse process the activation energy is 38 ± 6 kJ mol−1. In a folding transformation, formation of intramolecular hydrogen bonds might play a key role. This observation of a reversible conformation for a zwitterionic polymer induced by a metallic surface provides an impetus to investigate both such a structural modification of other CP and applications of this phenomenon.

We have used a bias-assisted microwave plasma chemical vapor deposition system to synthesize carbon nanotubes presenting graphitic nanoflakes, named coral-like carbon nanotubes, and well-aligned carbon nanotubes on carbon cloth substrates. Applying an external bias of -100 V led to the growth of well-aligned carbon nanotubes. In the absence of an external bias, the coral-like nanotubes presenting graphite nanoflakes were formed. The specific surface areas of the well-aligned and coral-like carbon nanotubes electrodes were 90.31 and 143.69 m2/g, respectively. In terms of energy storage, we estimated the capacitance of the coral-like carbon nanotube electrode to be ca. 194 F/g in an electrolyte of 1 M H2SO4. This value is almost double that of the well-aligned carbon nanotubes electrode (104 F/g), presumably because the presence of the carbon nanoflakes had a positive influence on the migration and adsorption of ions within the electrode. The fitting results indicated that the coral-like carbon nanotubes electrode behaved as a traditional electrochemical capacitor. Durability tests revealed that the coral-like carbon nanotube electrode was reliable, with a decay of 9% in capacitance over 1000 cycles.

Poly(1-octylpyrrolyl)squaraine and poly(3-octylpyrrolyl)squaraine were synthesized from squaric acid with 1-octylpyrrole and 3-octylpyrrole under identical conditions of condensation. Visible absorption spectra, photoluminescence spectra, TGA curves, and IR spectra were recorded to characterize the structures of these polymers as synthesized; the measured optical and thermal properties are consistent with backbone structures. The polysquaraine from 3-octylpyrrole possesses mostly zwitterionic repeating units (>97%), but the polymer from 1-octylpyrrole consists of zwitterionic and covalent repeating units in a ratio 2:1. Observations from the visible absorption and photoluminescence spectra in varied solvents, TGA curves, and thermal IR measurements for these two polymers reconciled to their structures. This result indicates that the position of the alkyl group in the pyrrole derivative affects the conformation in the condensation of poly(pyrrolyl)squaraine. These polysquaraines are stable below temperature 155 °C and their visible absorption and photoluminescence properties in hydrogen-bonding solvents exhibit negative solvatochromism.

Here we describe an approach to fabricate addressable cell microarrays, which are based on the patterned switchable superhydrophobic surfaces. The switchable superhydrophobic surfaces were prepared by roughening the surfaces of fluoropolymers on the electrodes. Upon the application of 150 V to the underneath electrodes, the water contact angle on the roughened fluoropolymer surfaces could be decreased from 163° to less than 10° allowing the deposition of fibronectin, which could guide the growth of the cells. Our result indicated that it was possible to control the spatial distribution of two different cells on the cell microarrays.

In this study, we demonstrated that microscale surface undulations induced by acid treatment could serve as the surface relief on diffusers coated with a layer of PDMS polymer. Since the orientation of undulations was found to be always disordered, these undulations would scatter light uniformly. The periodicity of the undulations could be adjusted by the control of duration of the dipping of the elastomer into H 2 SO 4 /HNO 3 solutions and by the volume ratio of H 2 SO 4 /HNO 3 the solution, resulting in the modulation of diffusing ability of diffusers. The optical properties, transmittance, and light diffusivity, were characterised. This proposed approach offers potential for mass production of surface-relief diffusers. In addition, the proposed method allows the creation of undulations on arbitrary substrates.

In this study, we prepared all-solution-processed inverted polymer solar cells (PSCs) incorporating two solution-processed electrodes – surface-nickelized polyimide films (NiPI films) as cathodes and high-conductivity poly(3,4-ethylenedioxythiophene)/poly(styrene-sulfonate) (PEDOT:PSS) films as anodes – and an active layer with a bulk heterojunction morphology of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C 61 -buytyric acid methyl ester (PCBM). The granular Ni thin films, which exhibited good adhesion and high-conductivity (ca. 2778 S cm −1 ) on the polyimide (PI) substrates and possessed a work function different from that of pure Ni metal (WF, 5.4 eV). Using ultraviolet photoelectron spectroscopy, we determined that the WF of the NiPI films was ca. 3.9 eV. Prior to the coating of the photoactive layer, the surface of the NiPI films were treated with titanium(diisopropoxide)bis(2,4-pentanedionate) (TIPD) solution to facilitate the deposition of high-quality active layer and further as a hole blocking layer. The solution processed anodes (solvent-modified PEDOT:PSS films) were further coated and subjected to mild oxygen plasma treatment on the active layer. Short exposure (5 s) to the plasma improved the quality of the surface of the active layer for PEDOT:PSS deposition. These inverted PSCs on flexible granular NiPI films provided a power conversion efficiency of 2.4% when illuminated under AM 1.5 conditions (100 mW cm −2 ). The phenomenon of light absorption enhancement in those inverted PSCs was observed as indicated in reflective UV–vis, haze factor and external quantum efficiency (EQE) responses. The resulting fill factor (FF) of 0.43 is still significantly lower than the FF of 0.64 for standard devices. When compared to the planar structure, the improvement of absorbance of light and good haze factors was obtained for granular structure which suggests NiPI as a better back contact electrode through enhancing the light trapping and scattering in inverted PSCs.

We have used bias-assisted microwave plasma chemical vapor deposition to synthesize (i) carbon nanotubes (CNTs) possessing a graphitic carbon nanoflake (CNF) morphology, (ii) CNF spheres, and (iii) a pure carbon nanoflake film (CNFF) on stainless-steel substrates. We employed CH4 and CO2 as the precursors to these carbon nanomaterials (CNMs); the use of CO2 aided the destruction of the CNT surfaces and reduced the growth temperature range to 380–450 °C at 300 W, as a result of the presence of oxygen-based species in the plasma. Applying an external bias of − 150 V led to the growth of CNTs possessing specifically oriented graphitic CNFs. We used scanning electron microscopy and high-resolution transmission electron microscopy to observe the morphologies and graphitic structures of these CNMs. Field emission measurements of a CNT/CNF-coated electrode revealed that the turn-on field was ca. 2.73 V/μm.

We have used a microwave plasma-enhanced chemical vapor deposition system to synthesize two-dimensional (2D) and three-dimensional (3D) structures of carbon nanoflakes (CNFs). This catalyst-free, low-temperature synthesis involved introducing CO 2 and CH 4 as reactants at a specified ratio of 2:3. We obtained uniform 2D arrays of CNFs at lower microwave powers (200 or 300 W) and substrate temperatures (up to 420 °C); their thickness was close to 1 μm. At a microwave power of 400 W, we obtained a 3D architecture comprising the smallest nanoflakes reported to date. The specific surface area of the 3D structure was double that of the corresponding 2D arrays. We suspect that such structured carbon materials might have great potential for energy storage applications.

Here we describe a simple approach to fabricate robust three-dimensional periodic porous nanostructures inside the microchannels. In this approach, the colloidal crystals were first grown inside the microchannel using an evaporation-assisted self-assembly process. Then the void spaces among the colloidal crystals were filled with epoxy-based negative tone photoresist. After subsequent development and nanoparticle removal, the well-ordered nanoporous structures inside the microchannel could be fabricated. Depending on the size of the colloidal nanoparticles, periodic porous nanostructures inside the microchannels with cavity size of 330 and 570 nm have been obtained. The dimensions of interconnecting pores for these cavities were around 40 and 64 nm, respectively. The behavior of single λ-phage DNA molecules in these nanoporous structures was studied using fluorescence microscopy. It was found that the length of DNA molecules oscillated in the nanoporous structures. The measured length for λ-phage DNA was larger in the 330 nm cavity than those measured in the 570 nm cavity.

Back-surface diffusive reflectors have been widely applied in many optical systems to promote the efficiency used in system. In this work, we propose a novel way to fabricate a soft diffusive reflector by using of silicone (polydimethylsiloxane, PDMS). High-reflectance substrates were first fabricated by mixing nanoscaled TiO2 powders with PDMS polymers, and then microscale wave-like undulations were spontaneously developed after the substrates were dipped into H2SO4/HNO3 solutions. After optical examination, a TiO2/PDMS plate comprising microscale undulations, which can surely serve as a reflector, could reflect and diffuse light effectively. Besides, all fabrication processes can be executed in the ambient environment and at low temperature. This proposed method has a potential for mass production in the future.

In chemical vapor deposition (CVD) technology, the mass flow transport behaviors of precursor gases play an important role particularly in thick-film normal triode structures. The depth dimension of dielectric holes in thick-film normal triode structures may range from 10 to 50 µm. The relationship between carbon nanotube (CNT) synthesis and aspect ratio of dielectric holes is investigated in this work. In high-aspect-ratio dielectric holes (such as narrow and deep holes), precursor diffusion driven by concentration gradient must be combined with pumping assistance in order to force reactive gas to flow toward the catalyst at the bottom of dielectric holes for CNT growth.

Volume holographic recording characteristics of a new bulk photopolymer, in which a bimolecular photoinitiator system, Eosin Y spirit soluble (EYss)/Triethanolamine (TEA) was doped in poly (hydroxyethyl methacrylate-co-methyl methacrylate) copolymer matrix have been investigated and reported in this paper. Experimental results show that, by introducing bimolecular photoinitiator into the polymer system, the material sensitivity of holographic recording has been improved.

Flexible polyimide (PI) films for flexible electronics were surface-nickelized using a fully solution-based process and excellent adhesion between the nickel and polyimide phases was observed. Polyimide substrates were modified by alkaline hydrolysis, ion exchange, reduction and nickel electroless deposition without palladium. Atomic force microscopy and field emission scanning electron microscopy were used to follow the growth of nickel nanoparticles (Ni-NPs) and nickel layers on the polyimide surface. The surface resistances of the Ni-NPs/PI films and Ni/PI films, measured using a four-point probe, were 1.6 × 10 7 and 0.83 Ω/cm 2 , respectively. The thicknesses of Ni-NPs and the Ni layer on the polyimide surface were 82 nm and 382 nm, respectively, as determined by transmission electron microscopy, and the Ni layer adhered well to PI, as determined by the adhesive tape testing method.

We present our studies on the photopolymer of poly(methyl methacrylate) (PMMA) doped with 9,10-phenanthrenequinone based derivatives for volume holographic storage. By introducing different functional groups on the side-chain of 9,10-phenanthrenequinone molecule, the holographic characteristics of the material can be modified. The photoreaction involved with the holographic recording in the samples was investigated by measuring UV–Vis absorption spectrum and mass spectrum. The experimental results show that the similar behaviors were exhibited in these photopolymers. It is found that phase hologram recording in our PQ derivatives doped PMMA photopolymer involves a structure change of the quinone based molecule, which induces a strong change of the refractive index. Experimental characterizations on holographic data storage, including material sensitivity, dynamic range ( M #) and bit-error-rate have been performed. We found that, by selecting appropriate functional groups, an improvement in sensitivity and M # for holographic data storage can be achieved.

This paper reports the fabricated method and optical performance of soft, reflective elements with nonspherical surface. Based on excimer laser microdrilling and spin coating processes, a PMMA film suspended on microdrilled holes was used as a concave mold. Then, a high-reflectance material, mixed PDMS rubber polymers with TiO"2 nanoscale powders, was cast on the PMMA mold. Finally, both of concave and convex elements could be fabricated through soft replica molding processes and these elements could directly reflect light without the deposition of metal coatings. Therefore, we proposed a model regarding a flexible cable with its weight suspended on fixed points to explain the formation mechanism of PMMA molds. With the change of diameters of microholes and thicknesses of PMMA films, the suspended height of films was surely controllable. Therefore, the curvature radiuses and shapes of these aspherical elements also depended on the diameters of microholes and the thicknesses of PMMA films. Experimental results demonstrated that soft reflective elements have good surface qualities and high-quality optical properties. Besides, all fabrication steps can be executed in ambient environment and at low temperature, the proposed method has a potential for mass production.

We have developed two simple techniques to impart superhydrophobic properties to the surfaces of microdevices. In the first approach, thin films of a fluoropolymer were spin-coated on the device surfaces followed by an oxygen plasma treatment. By varying the oxygen plasma treatment time, the water contact angles on device surface could be tuned from 120° to 169°. In the second approach, a nanoimprint process was used to create nanostructures on the devices. To fabricate nanoimprint stamps with various feature sizes, nanosphere lithography was employed to produce a monolayer of well-ordered close-packed nanoparticle array on the silicon surfaces. After oxygen plasma trimming, metal deposition and dry etching process, silicon stamps with different nanostructures were obtained. These stamps were used to imprint nanostructures on hydrophobic coatings, such as Teflon, over the device surfaces. The water contact angle as high as 167° was obtained by the second approach.

Seven polyimides (PIs) of low glass transition temperature were synthesized and their films were uniaxially stretched to observe the variation in their in-plane birefringence (Δn). The intrinsic birefringences (Δn°) of their polymer chains were also estimated using the experimental average refractive indices and computationally calculated polarizability tensors. The observed stretch-induced Δn was markedly affected by the PI structure. A model that shows a good fit to experimental data is proposed to predict the orientation degree of PI chains in different PI films. The model, when combined with the analysis of the estimated Δn°s, is useful in explaining the behavior of stretch-induced Δns in PI films.

We have utilized the π–π interactions between 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) molecules and temperature-induced morphology changes to synthesize one-dimensional (1D) nanostructures of PTCDA on a heated (ca. 100 °C) titanium substrate through vacuum sublimation. Because of the pillared Ti structures and the presence of reactive Ti–Cl sites, the titanium substrate played a crucial role in assisting the PTCDA molecules to form 1D nanostructures. The average diameter of the nanofibers deposited on the Ti-CVD substrate, a Ti substrate formed by chemical vapor deposition (CVD), at 100 °C was ca. 84 nm, with lengths ranging from 100 nm to 3 μm. When the PTCDA nanofibers were biased under vacuum, the emission current remained stable. The turn-on electric field for producing a current density of 10 μA/cm 2 was 8 V/μm. The maximum emission current density was 1.3 mA/cm 2 , measured at 1100 V ( E = 11 V/μm). From the slope of the straight line obtained after plotting ln( J / E 2 ) versus 1/ E , we calculated the field enhancement factor β to be ca. 989. These results demonstrate the PTCDA nanofibers have great potential for applicability in organic electron-emitting devices.

The paper describes a wet process for modifying the surface of polydimethylsiloxane (PDMS) using H2SO4/HNO3 solutions. The oxidation on the surface of PDMS was confirmed by the examinations of Fourier transform infrared spectrometry (FTIR), contact angle of water drop and X-ray photoelectron spectroscopy (XPS). The hydrophobic surface of pristine PDMS was not only changed to hydrophilic, but also formed wrinkles on it after chemical modification. Bilayer systems, stiff oxidized PDMS layers were capped on soft PDMS foundations, would generate easily compressive stresses due to the large difference in volumetric contraction rates and led to form wrinkles on the surface. Experimental results demonstrated the periodicity of wrinkles was controllable by controlling the duration of oxidation. Therefore, wrinkles could be arranged orderly by the guidance of external forces before oxidization. The potential technology for generating and ordering wrinkles on the PDMS surface is valuable in the applications of pressure sensors, biology, micro-optics and nano-/micro-fabrication in the future.

Single and double layer polymer light-emitting diodes (LEDs) were fabricated by using 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole (BAO)-based aromatic polyimides (APIs). All the resultant APIs have high glass transition temperatures ( T g > 250 °C) and high thermal decomposition temperatures ( T d > 510 °C). The APIs exhibit broad fluorescent characteristic, and the fluorescent intensity is related to the intermolecular chain's orientation. BAO-3,3′-oxydiphthalic anhydride (ODPA) and BAO-4,4′-(hexafluoro- iso -propylidene) diphthalic anhydride show electroluminescent property in single layer LED devices. By inserting BAO-ODPA in the poly( p -phenylene vinylene)–poly(vinylalcohol) LED device to form a double layer device, the EL efficiency can be improved by two orders of magnitude.