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Summary The one-step antisolvent approach is a widely employed method for fabricating perovskite devices at a low cost. However, the current antisolvent approach requires a strict set of processing conditions to obtain high-quality perovskite layers. Here, we introduce sulfolane as an additive in the perovskite precursor to convert the perovskite phase via a new reaction route, providing a large degree of flexibility to process crystalline perovskite layers with high uniformity on a large scale. As it is revealed by X-ray diffraction and Fourier-transform infrared spectroscopy findings, we find that the key concept lies in intermolecular hydrogen-bonding forces’ interaction between sulfolane and methylammonium iodide, which slows down the nucleation and subsequently the crystallization process. As a result, we demonstrate a mini module, 36.6 cm2 active area, and achieve a record PCE of 16.06%. More importantly, the encapsulated mini module retained about 90% of the initial performance after operating at the maximum power point under simulated AM1.5G irradiation for 250 h at 50°C.

A polythiophene homopolymer with conjugated side chains (2D-PT) was applied as a hole transport material (HTM) of perovskite solar cells (PSCs). The all-conjugated two-dimensional structure effectively increases the ionization potential, realizing a high open-circuit voltage near 1 V for the 2D-PT-based PSC. Very interestingly, the two-dimensional wide-angle X-ray scattering measurements show that the 2D-PT molecules are self-assembled into ordered structure with a face-on dominant orientation and exhibit a hole mobility, which is ∼1.6 times faster than that of poly(3-hexylthiophene) (P3HT). Consequently, the power conversion efficiency of PSC is noticeably increased by ∼30% as 2D-PT replaces P3HT as HTM. Moreover, the densely packed 2D-PT slows down the moisture induced degradation of perovskite crystals, leading to a better environmental stability. This work demonstrates that two-dimensional non-donor-acceptor structural conjugated polymers can be utilized as promising HTM of PSCs.

The power conversion efficiency of the perovskite solar cell is high enough to be commercially viable. However, long-term stability is the inevitable issue that obstructs its commercialization. Here, we demonstrate that the half-year (∼4680 h) stable unencapsulated inverted solar cell has almost zero loss in performance, measured under controlled environmental condition, when using montmorillonite (MMT)/CH3NH3PbI3 nanocomposite as photoactive layer. It yields up to 17.29% in power conversion efficiency, owing to the formation of an outstandingly dense gas permeation barrier of exfoliated MMT shell that effectively retards the moisture from penetrating into the perovskite. It is believed that this extensively modified device and low-cost architecture will compellingly lead to the timely commercialization of perovskite solar cells.

A risk-based prioritization of chemical hazards in monitoring programs allows regulatory agencies to focus on the most potentially concerned items involving human health risk. In this study, a risk-based matrix, with a scoring method using multiple factors for severity and probability of exposure, was employed to identify the pesticides presented in crops that may pose the greatest risk to human health. Both the probability of exposure and the severity were assessed for 91 pesticides detected in a Taiwanese postmarketing monitoring program. Probability of exposure was evaluated based on the probability of consumption and evidence of pesticide residues in crops. Severity was assessed based on the nature of the hazard (i.e., the description of toxic effects), and the acceptable daily intake (ADI) reported by available toxicological reports. This study showed that the nature of the hazard and probability of consumption had the strongest contribution to risk score. Dithiocarbamates, endosulfan, and carbofuran were identified as the pesticides with the highest concern for human health risks in Taiwan. These pesticides should be monitored more frequently than others in crops during the postmarketing monitoring program. However, some uncertainties shall be noted or improved when this methodology is applied for risk prioritization in the future. Keywords: Risk-based ranking, Postmarketing monitoring, Pesticides, Crops

In this study a cross-linkable ruthenium complex dye, Ru(2,2′-bipyridine-4,4′-bicarboxylic acid)(4,4′-bis((4-vinyl-benzyloxy)methyl)-2,2′-bipyridine)(NCS) 2 denoted as RuS, was applied to the solid-state dye-sensitized solar cell, by which the photovoltaic performance was superior to the traditional N3 dye. However, the power conversion efficiency (PCE) was only 1.48%, resulting from poor pole filling of the hole conductor, 2,2′,7,7′-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9′-spirobifluorene (spiro-OMeTAD). To modify the interface between RuS and spiro-OMeTAD, additional 4,4′-bis((4-vinylbenzyloxy)methyl)-2,2′- bipyridine (BVP) ligand was employed to crosslink with RuS. The cross-linked dye (denoted as RuS-BVP) on TiO 2 was more sustainable and the PCE rose to 2.12%. Besides, the outward bipyridine groups of RuS-BVP are capable of chelating cations. As lithium bis(trifluoromethane)sulfonimide was applied to modify the interface between RuS-BVP and spiro-OMeTAD, the PCE increased to 2.55% and the interfacial resistance for charge transfer under sunlight dramatically decreased. As divalent cation compounds such as magnesium, calcium and barium acetylacetonate were individually adsorbed onto the RuS-BVP, the cell with magnesium acetylacetonate has the highest PCE of 2.82%, highest open circuit voltage and lowest interfacial resistance. The results suggest that the cations with higher charge density have stronger Coulomb's force to couple between RuS-BVP and spiro-OMeTAD.

The electron transport layer of planar-heterojunction perovskite solar cells was produced by the ultrasonic spray pyrolysis (USP) of organotitanium precursors and the spin-coating of TiO2 sol-gel. Although the TiO2 products prepared from both methods have the same anatase crystal structure, the former route yields an ultra-compact, bulk-like film with reduced defects. Results from the electrochemical impedance spectroscopy measurements reveal the electron transfer resistance through the TiO2/CH3NH3PbIxCl3−x interface for the titanium oxide prepared by ultrasonic spray pyrolysis (TiO2-USP) method is lower than that for the titanium oxide prepared by sol-gel (TiO2-SG) method. Interesting, the TiO2-USP device exhibits relative low interfacial resistance of charge carrier through the CH3NH3PbIxCl3−x/spiro-OMeTAD interface as well. As a result, replacing TiO2-SG with TiO2-USP substantially improves the power conversion efficiency from 12.98% to 16.13%, demonstrating the USP is a facile approach to fabricate high-quality TiO2 for developing high-performance perovskite solar cells.

In this study, we propose a new analysis method using optical coherence tomography to further use the diffusive reflectance measurement to quantify the contribution of the size-dependent multiple-scattering effects of mesoporous TiO2 beads. The diffusive reflectance results from the complex interactions between light and the scattering particles, and influences the slopes of the associated depth-dependent A-scan profiles, which can be fitted based on the extended Huygens–Fresnel model to quantify the contribution ratio of the multiple-scattering effects to the single scattering effects. The mesoporous TiO2 beads with average diameter of 300 nm show higher contribution percentage of multiple-scattering effects inducing reflectivity enhancement in the longer wavelength region. The contribution ratio of multiple-scattering effects can be distinguished numerically, and is enhanced from 5% to 40% and then decreased to 20% for the bead diameters ranging from 20 to 300 nm and then to 500 nm, respectively. The calculated scattering coefficients are 13.5 ± 0.6 mm–1, 16.5 ± 0.6 mm–1, 20.2 ± 0.6 mm–1, and 18.5 ± 0.6 mm–1, respectively.

Incidents of edible oil adulteration have increased all over the world, and improving analytical methods that are capable of identifying adulterated oils has become more important. In this study, we developed an analytical method that uses 4 target compounds belong to phytosterol family to identify lard that has been adulterated with cooked oils. For this, we used five kinds of animal fat, including lard, tallow, duck fat, goose fat, and chicken fat, to estimate the matrix effect, and lard samples were used to verify this analytical method. Specifically, samples inspected by sanitation authorities in a 2014 lard adulteration incident in Taiwan were saponified, and phytosterols were extracted and analyzed by a liquid chromatography-tandem mass spectrometer (LC/MS/MS) equipped with an atmospheric pressure chemical ionization (APCI) source. Parameters for sample extraction, including temperature, concentration of alkaline solution, and duration of saponification, were optimized. Our proposed method was then validated for linearity, matrix effect, precision, accuracy, limit of detection (LOD), and limit of quantitation (LOQ). After using our proposed method to analyze 28 lard samples, we determined that the phytosterol contents of inspected lard obtained from companies that had been found guilty in the 2014 lard adulteration incident were ranged from 19.5 to 205.3 μg/g in campesterol and 17.3–408.8 μg/g in β-sitosterol, and were at most 270-fold higher than that of homemade lard, commercial lard, and inspected lard (ranged from 4.5 to 29.6 μg/g in campesterol and 1.5–44.2 μg/g in β-sitosterol) obtained from companies that had not been found guilty in the 2014 adulteration incident. Therefore, our proposed method should be useful to discriminate between adulterated and unadulterated animal fats.

When applying the voltage pulses (6 V) to the organic light-emitting diode based on tris(8-hydroxyquinolinato) aluminium (Alq 3 ) as the electron transporting layer, current density and luminance increased by 16% and 20%, respectively, by providing the reverse bias (−16 V) during the off-period. By using displacement current measurement, we can deduce that such an enhancement resulted from the interfacial positive charges trapped at the Alq 3 /cathode interface, with the relaxation time ∼0.4 ms. By doping the organic material as the carrier trapping sites at Alq 3 /cathode interface, such current density and luminance increase can be further enhanced. 25% and 36% increase in current density and luminance was demonstrated with such driving technique, respectively.

Polyaniline (PANI)/graphene nanoplatelet (GNP)/multi-walled carbon nanotube (MWCNT) composite films deposited on fluorine-doped tin oxide (FTO) substrates were successfully fabricated through electrochemical method without pre-treatment of GNP and MWCNT to provide a lower cost counter electrode (CE) for dye-sensitized solar cells (DSSCs). By varying the contents of GNP and MWCNT in the PANI composite CE, the short-circuit current density of DSSC was found to linearly relate to the reduction current density of I − /I3 − redox couples measured by cyclic voltammetry. The open-circuit voltage ( V OC ) is also highly dependent on the reduction potential of redox couples. Besides, the charge transfer resistance at the electrolyte/CE interface measured by electrochemical impedance spectroscopy has an approximately linear relationship with the sheet resistance of PANI composite CE. Notably, the DSSC with the CE fabricated by the weight ratio of PANI/GNP/MWCNT at 1:0.003:0.0045 yielded the highest power conversion efficiency of 7.67 ± 0.05%, which is comparable with the conventional Pt cell (7.62 ± 0.07%).

Summary The irreversible phase transition by water incorporation, along with thermal decomposition, has long been thought to be the dominant degradation pathway to deteriorate electronic and optoelectronic properties of perovskite devices. However, comprehensive characterization and insightful understanding of beneficial effect of water incorporation remains scarce. Here, we capture the phase transformation of perovskite in situ from its precursor stage to the final film upon thermal annealing as a function of relative humidity (RH) by grazing-incident wide-angle X-ray scattering. Quantitative structural analyses show that a moderate water content (RH 40%) enhances the texture orientation of the perovskite. A consequence of the guided water-incorporated treatment is that the unencapsulated device, without any sophisticated instability-mitigation approaches, exhibits excellent tolerance to long-term, light soaking and high-temperature aging, retaining more than 80% of the peak power-conversion efficiency under constant 1-sun illumination or heating at 65°C for more than 1,000 h, respectively.

The multi-walled carbon nanotubes (MWCNTs) physisorbed by aromatic ionic salts such as 10-methyl-acridinium iodide (MAcI) were found to well disperse in diglycidyl ether of bisphenol-A epoxy resin. As they were subjected to the rheological study at 30 °C, the gelation of epoxy/MWCNT-MAcI suspension occurred at 0.75 wt% MWCNT-MAcI, which was less than that using pristine MWCNT. As to the viscosity measurements, the dilation effect that the viscosity of epoxy/MWCNT suspension increases with shear rate was found and more pronounced by incorporating MWCNT-MAcI. According to the Thomas-modified Einstein viscosity equation, the dilation effect was attributed to the excess amount of epoxy resin trapping in the aggregated domain of MWCNT. By increasing the shear rate to a certain point, the shear thinning effect that the viscosity decreases with shear rate was also observed. Interestingly, the transition point that the dilation effect changes to shear thinning effect shifted to lower shear rate as the content of MWCNT increased and/or MWCNT-MAcI was incorporated. Notably, better dispersion and less aggregated domains for the suspensions with MWCNT-MAcI compared to pristine MWCNT were further supported by small angle x-ray scattering and transmission electron microscopy.

Diffusionless martensitic transformation (MT) exerts one of the most significant influences on the mechanical properties of alloys. However, the application of martensitic transformation to improve mechanical performance was seldom involved in the manufacture of high-entropy alloys (HEAs) and medium-entropy (MEAs) alloys. In this work, an innovative non-equiatomic MEA, Fe42Co42Cr16, was proposed with incorporation of martensitic transformation during water quenching and plastic deformation. Water quenching for the alloy in the high-temperature single-phase region produced a partial MT; i.e., transformation of γ –FCC austenite phase into an e -HCP martensite phase, responsible for the coexistence of γ and e phases in the dual-phase (DP) alloy. Another triple-phase (TP) alloy, including γ –FCC austenite, e -HCP martensite and B2-BCC precipitates, was obtained by quenching the alloy in γ + B 2 phase region. Owing to the low intrinsic stacking fault energy ( γ I ), both DP ( γ I = 10.9 mJ/m2) and TP ( γ I = 12.2 mJ/m2) alloys involved the complete polymorphic MT process during plastic deformation; i.e., the transformation of the γ –FCC austenite phase into the α -BCT martensite phase with an intermediate e -HCP martensite phase. Due to the transformation-induced plasticity effect and precipitation strengthening, the produced TP alloy exhibited a yield strength above 1 GPa with a total elongation of as high as 25%.

A series of layered-structure perovskite solar cells with three different HTM layers consisting of P3HT, PBTTTV-h, and spiro-OMeTAD were fabricated to investigate intermolecular and interfacial def...

Ion accumulation of organometal halide perovskites (OHPs) induced by electrode polarization of perovskite solar cells (PSCs) under illumination has been intensely studied and associated with a widely observed current–voltage hysteresis behavior. This work is dedicated to the investigation of the behavior of charged species at the compact TiO2/OHP interface with respect to electrode polarization in PSC devices. By providing a comprehensive discussion of open-circuit voltage (VOC) buildup and VOC decay under illumination and in the dark for the PSCs modified with [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) at the TiO2/OHP interface and their corresponding electrochemical impedance spectroscopies (EISs), a justified mechanism is proposed attempting to elucidate the dynamics of interfacial species with respect to the time and frequency domains. Our results demonstrate that the retarded VOC buildup and decay observed in PSC devices are related to the formation of bound charges in TiO2, which is essential...

The thermoresponsive conductive composite (TCC) thin films and fiber mats, whose electrical property changed with temperature, were fabricated successfully. The thermocrosslinkable and thermoresponsive copolymer, poly(N-isopropyl acrylamide-co-N-methylolacrylamide) (PNN), was synthesized. The TCC thin film and fiber mat were fabricated by spin coating and electrospinning process of PEDOT:PSS/PNN solutions, respectively. After thermocrosslinking and doping by DMSO, the composite thin films and fiber mats were obtained. Fibrous structures of TCC fiber mats were observed by SEM. The surface resistance and conductivity of composites were measured. The thermoresponsivity and swelling ratio of TCCs were also studied. The thermoresponsive conductive property was analyzed by measuring the surface resistance of TCCs in water bath under various temperatures from 20 to 50 °C. With the increase of temperature, the TCCs shrank to be dense structure and showed lower surface resistance. The TCC fibers mat exhibited greater sensitivity to temperature than thin film owing to its fibrous structure. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015

Crosslinking magnetic thermoresponsive composite (MTC) fiber mats were fabricated by electrospinning process and followed by UV curing. Thermoresponsive poly-(N-isopropylacrylamide) (PNIPAAm) and magnetic Fe3O4 were firstly synthesized by redox-initiated polymerization and co-precipitation, respectively. A crosslinking agent (dipentaerythritol hexylacrylate) and photoinitiator for providing crosslinking ability were then mixed with PNIPAAm and Fe3O4 in ethanol as the electrospinning solution. After electrospinning and subsequent UV irradiation, the MTC fiber mats were thus obtained. Thermoresponsivity of the MTC fibers was measured by both DSC and swelling test. MTC fiber mat exhibited better water-absorption capability and thermoresponsivity than corresponding film. Morphological analysis was observed by SEM and TEM, and the magnetic property was measured by SQUID. The thermoresponsive magnetic behavior of MTC fiber mat in water was observed under various temperatures and magnetic fields. Vitamin B12 used as a model drug was loaded in the MTC fiber mats and the drug-release behavior was then studied. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2152–2162

Co49Pt51 alloy films with strong perpendicular magnetic anisotropy (PMA) have been most often grown on either single crystal or glass substrates with deposition temperature of about 350 °C using Pt/Ru as an underlayer. In contrast, in this study, 5-nm thick Co49Pt51 alloy films with significant PMA were fabricated on glass substrates at room temperature (RT) using a combination of Ta and Pt underlayers. The structural and magnetic properties of the Co49Pt51 films obtained at RT (RT-CoPt) were compared with that of those produced by the conventional high-temperature route (HT-CoPt). The x-ray diffraction studies showed the evolution of highly textured Pt (111) peak accompanied by a CoPt (222) shoulder for the RT-CoPt films, similar to that of the HT-CoPt films. The microstructural studies revealed extremely smooth surface with root mean square roughness (Rrms) of 0.5 nm for the RT-CoPt films, while the HT-CoPt films showed wavy surface with Rrms of 2.4 nm. The out-of-plane and in-plane hysteresis loops demonstrated the existence of strong PMA for both the RT-CoPt and HT-CoPt films. The estimated magnetic parameters for the RT-CoPt films such as squarness ratio, SQR (0.96), perpendicular coercivity, Hc⊥ (822 Oe) and magneto-crystalline anisotropy constant, Ku (6.4×106 erg/cm3) was found to be comparable to that of those obtained with the HT-CoPt films (SQR=0.96, Hc⊥=1810 Oe and Ku=7.1×106 erg/cm3).

Cation–π effect on physisorption of aromatic ionic salts to multi-walled carbon nanotube (MWCNT) was demonstrated by the excess adsorption over their pre-ionized aromatic compounds through thermogravimetric analysis. Their adsorption layer on the surface of MWCNT was confirmed by high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. Ionic salt-adsorbing MWCNT showed better dispersion in acetone than pristine and pre-ionized compound-adsorbing MWCNT. Incorporation of 1 wt% ionic salt-adsorbing MWCNT is able to gel the epoxy resin at room temperature according to the rheological study. Based on our proposed model, 1 wt% fully-dispersed MWCNTs are enough to form an interconnected network in epoxy resin resulting in gelation. After crosslinking with amine curing agent, the epoxy nanocomposites incorporating 1 wt% ionic salt-adsorbing MWCNT displayed substantially higher glass and s transition temperatures than that incorporating pristine MWCNT.

A series of ruthenium complex dyes with different number and position of carboxyl groups on bipyridine ligands, such as Ru(4-carboxyl-4′-methyl-2,2′-bipyridine)(4,4′-dimethyl-2,2′- bipyridine)(NCS)2 (denoted as Ru1A), Ru(4-carboxyl-4′-methyl-2,2′-bipyridine)2(NCS)2 (Ru11A), Ru(4,4′-dicarboxyl-2,2′-bipyridine)(4,4′-dimethyl-2,2′-bipyridine)(NCS)2 (Ru2A), and Ru(4-carboxyl-4′-methyl-2,2′-bipyridine)(4,4′-dicarboxyl-2,2′-bipyridine)(NCS)2 (Ru3A) were synthesized and compared with Ru(4,4′-dicarboxyl-2,2′-bipyridine)2 (NCS)2, commonly known as N3 dye for the adsorption behavior on the TiO2 surface and photovoltaic properties of dye-sensitized solar cells. The experimental results show that the tilt angle of ruthenium dyes on the TiO2 surface which is dependent on the number and position of their carboxyl groups strongly affected the photovoltaic performance.

The adsorption of sodium dodecylsulfate (SDS) and cetyltrimethylammonium bromide (CTAB) by montmorillonite (MMT), respectively, in aqueous solution and their resulting intercalating structures after removal of water were investigated. The former adsorption results from the Donnan equilibrium for ions leading to hydrophilic nature of SDS/MMT hybrid, whereas the latter results from the Coulomb attraction or so-called cation exchange leading to hydrophobic nature of CTAB/MMT. X-ray scattering and transmission electron microscopy investigations on the dried SDS/MMT hybrids reveal that the adsorbed SDS neither substantially increases the interlayer distance nor changes the rough spherical texture of pristine MMT, whereas the adsorbed cetyltrimethyl ammonium cations significantly increase the interlayer distance of MMT resulting a well-integrated CTAB/MMT lamellar structure.

The exfoliated montmorillonite (exMMT) nanoplatelets that carry negative charges are capable of adsorbing 1-methyl-3-propyl-imidazolium cations to form a gel-type ionic liquid-based electrolyte system for dye-sensitized solar cell (DSSC). Interestingly, it also increases the power conversion efficiency of DSSC from 6.58% to 7.77% at full sun. The increased efficiency is attributed to the decreased resistance of gel electrolyte system and enhanced reduction reaction rate at the counter electrode, both of which are related to the two-dimensional electrolyte nature of exMMTs that repel the I(-)/I(3)(-) redox couples toward their major conduction pathway.

Shear fracture of exfoliated montmorillonite/poly(methyl acrylate-co-methyl methacrylate) (MMT/P(MA-co-MMA)) nanocomposite films fabricated via soap-free emulsion polymerization was studied using a unique test fixture that is capable of controlling the inclined angle between the loading axis and the shear fracture plane. It was found that fracture of the films depended on both shear and normal stresses and could be described by the Mohr–Coulomb criterion. The effects of MMT content on the intrinsic shear strength (i.e. the shear strength at zero normal stress) τs were also examined. The obtained τs increased from 1.66 to 2.78 MPa as 1 wt% MMT was incorporated into P(MA-co-MMA) and then increased almost linearly to 5.32 MPa when the content of MMT increased to 15 wt%. Also, the fracture-surface morphology of the composite film depended on both the MMT content and the inclined angle (and hence the normal-to-shear stress ratio). For low MMT contents and low normal-to-shear stress ratios, striations normal to the shear direction appeared on the fracture surface. As the MMT content or the stress ratio increased, the fracture surface became rough accompanied by the presence of interfacial micro-cracking between MMT nanoplatelets and the matrix. With further increase in MMT content and high stress ratio, the MMT nanoplatelets were compressed into large flakes on the fracture surface. Copyright © 2011 Society of Chemical Industry

Shear strength of the adhesives and polymer films was usually measured by lap shear test method. However, their fracture often associates with the combination of interfacial, interfacial–cohesive and cohesive failures. To confine the shear failure exclusively in cohesion so that the reported shear strength can be regarded as an intrinsic property of the polymer films, in this study we designed a unique test fixture that is capable of controlling the normal to shear plane angle in a confined testing space. Two poly(methyl acrylate-co-methyl methacrylate) film specimens were loaded in series in the test fixture such that as one fractured the other was in a state just prior to fracture and could be used for the investigation of shear bands by scanning electron microscopy (SEM). As the normal to shear plane angle was increased from 30 to 60°, the shear bands were more concentrated on the center region owing to the higher normal compressive stress. For the fractured specimen, the fracture surface investigated by SEM showed the striations which can be related to the shear bands. As the normal to shear plane angle was increased from 30 to 45°, the concentrated shear bands caused less striations perpendicular to the fracture direction. Interestingly, it also leaded to the appearance of the striations parallel to the fracture direction. As the angle was further increased to 60°, small islands formed by the cross-over of parallel and perpendicular striations appeared in the fracture surface. A possible mechanism for the formation of this unique fracture surface was proposed.

Crosslinkable ruthenium complex dye, Ru(2,2′-bipyridine-4,4′-bicarboxylic acid)(4,4′-bis((4-vinyl benzyloxy)methyl)-2,2′-bipyridine)(NCS) 2 (denoted as Ru-S dye), was synthesized and characterized using 1 H-NMR, 13 C-NMR, Fourier transform infrared (FTIR) and UV/vis spectroscopies.The power conversion efficiency of dye-sentitized solar cell (DSSC) using Ru-S and liquid electrolyte containing lithium iodide (LiI) reached 7.53% under standard global AM 1.5 full sunlight, which is partly attributed to Li + being coordinated by Ru-S as verified by ATR-FTIR spectroscopy. As Ru-S was further crosslinked with glycerol propoxylate triacrylate (GPTA), not only 89% of dye retained on TiO 2 mesoporous surface after rinsed by 0.1 N NaOH aqueous solution, the power efficiency was also increased to 7.88%. As poly(methyl acrylate) was used to gel the electrolyte system, the power efficiency of DSSC with Ru-S dye was 6.96% but increased to 7.57% after crosslinking with GPTA. Notably, both DSSCs showed a good long-term stability after one month storage.

This study reports the characteristics of gel-type dye-sensitized solar cells (DSSCs), fabricated with gel-type electrolyte containing poly-1,1′-(methylenedi-4,1-phenylene)bismaleimide (PBMI), or poly-1,1′-(3,3′-dimethyl-1,1′-biphenyl-4,4′-diyl)bismaleimide (PDBBMI), or poly-N,N′-(4-methyl-1,3-phenylene)bismaleimide (PMPBMI), prepared by in situ polymerization of the corresponding monomer without an initiator at 30 °C. Incorporating 0.3 wt % content of exfoliated alkyl-modified nanomica (EAMNM) into PBMI-gelled electrolyte leads to higher short-circuit current density (Jsc = 17.14 mA cm−2) and efficiency (η = 7.02%) than that of neat PBMI-gel electrolyte (Jsc = 15.32 mA cm−2, η = 6.41%). Incorporating 0.3 wt % EAMNM into PBMI-gelled electrolyte results in remarkably stable device performance under continuous light soaking under one sun (100 mW cm−2) at 55 °C. The efficiency of DSSCs based on PBMI/0.3 wt % EAMNM-gelled electrolyte drops by only 1.7% (η = 6.93%) after 500 h of continuous light soaking. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

The exfoliated montmorillonite (MMT) nanoplatelets tended to re-stack with each other after casting the MMT/ polymethylacrylate-co-methylmethacrylate) P(MA-co-MMA) latex solutions fabricated by soap-free emulsion polymerization into films as revealed by X-ray diffraction and transmission electron microscopy. As the content of MMT was increased from 0 to 20 wt %, the T g measured by differential scanning calorimetry was slightly decreased from 19.2 to 17.2 °C, whereas that measured by dynamic mechanical analysis was increased from 22 to 32 °C, indicating that the local motion of polymer segments has been retarded by MMT nanoplatelets. Besides, the elongated elliptical voids appeared during stretching of 1 wt % MMT/P(MA-co-MMA) film to cracking also illustrated the pinning effect provided by the exfoliated MMT. As the content of MMT was increased more than 10 wt %, the mechanical behavior of MMT/P(MA-co-MMA) nanocomposite films was changed from ductile to brittle nature with significant increase of Young's modulus and tensile strength owing to the restacking of exfoliated MMT nanoplatelets.

A flexible surface plasmon resonance (SPR)-based scattering waveguide sensor is prepared by directly imprinting hollow gold nanoparticles (NPs) and solid gold NPs onto flexible polycarbonate (PC) plates—without any surface modification—using a modified reversal nanoimprint lithography technology. Controlling the imprinting conditions, including temperature and pressure, allows for the fine adjustment of the depths of the embedded metal NPs and their SPR properties. This patterning approach exhibits a resolution down to the submicrometer level. A 3D finite-difference time domain simulation is used to examine the optical behavior of light propagating parallel to the air/substrate interface within the near-field regime. Consistent with the simulations, almost an order of magnitude enhancement in the scattering signal after transferring the metal NPs from the glass mold to the PC substrate is obtained experimentally. The enhanced signal is attributed to the particles' strong scattering of the guiding-mode waves (within the waveguide) and the evanescent wave (above the waveguide) simultaneously. Finally, the imprinting conditions are optimized to obtain a strongly scattering bio/chemical waveguide sensor.

Gel-type dye-sensitized solar cells (DSSCs) were fabricated with 5.0 wt% polyvinyidene fluoride-co-hexafluoro propylene (PVDF-HFP) in methoxy propionitrile (MPN) as gel polymer electrolyte (GPE), 1-butyl-3-methylimidazolium iodide (BMII)/iodine (I 2 ) as redox couple, 4-tertiary butyl pyridine (TBP) and guanidine thiocyanate as additives. The incorporation of alkyl-modified nanomica (AMNM) in the PVDF-HFP gel electrolytes caused the reduction of crystallization of PVDF-HFP, which was confirmed by X-ray diffraction (XRD) analysis. The short-circuit current density ( J SC ) of the cell increased due to the decrease of diffusion resistance, as judged by the electrochemical impedance spectra (EIS) analysis, while the open-circuit voltage ( V OC ) remained almost the same. As the loading of AMNM in the PVDF-HFP gel electrolyte was increased to 3.0 wt%, the J SC and power conversion efficiency ( η ) of the cells increased from 8.3 to 13.6 mA/cm 2 and 3.5% to 5.7%, respectively. However, the J SC decreased as the loading of AMNM exceeded 3.0 wt%. At higher AMNM loadings, nanomica acted as a barrier interface between the electrolyte and the dye molecules to hinder electron transfer, and thus reducing the cell’s photocurrent density. Furthermore, the DSSCs fabricated by dispersing polymethyl methacrylate (PMMA) microspheres in the TiO 2 electrode with the GPE containing 3.0 wt% AMNM improved the η to 6.70%. The TiO 2 films would exhibit larger porosity by blending with PMMA, leading the penetration of GPEs into the porous TiO 2 easier, thus improving the contact between the dye-adsorbed TiO 2 surfaces and the GPEs, as characterized by EIS. Moreover, the η of gel-type DSSCs with a 25 μm thickness of surlyn reached 7.96% as compared with 6.70% for the DSSCs with a 60 μm surlyn.

A new crosslinkable light sensitizer, Ru(2,2′-bipyridine-4,4′-bicarboxylic acid)(4,4′-bis(11-dodecenyl)-2,2′-bipyridine)(NCS)2, denoted as Ru-C for titanium oxide nanocrystalline-based solar cells was synthesized with its crosslinking properties invesitigated by Fourier-transform infrared and UV-vis absorption spectroscopies. After crosslinking by itself or copolymerizing with methyacrylic acid, their sensitized solar cells with poly(methylacrylate)-gelled electrolyte system not only attained more than 5% of power conversion efficiency at AM 1.5 illumination (100 mW/cm2), but also gave rise to long storage life. To the best our knowledge, this is the first crosslinkable dye ever applied to the DSSC in the literature. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 366–372, 2010

Two kinds of gel-type dye-sensitized solar cells (DSSCs), composed of two types of electrolytes, were constructed and the respective cell performance was evaluated in this study. One electrolyte, TEOS-Triton X-100 gel, was based on a hybrid organic/inorganic gel electrolyte made by the sol–gel method and the other was based on poly(vinyidene fluoride-co-hexafluoro propylene) (PVDF-HFP) copolymer. TEOS-Triton X-100 gel was based on the reticulate structure of silica, formed by hydrolysis, and condensation of tetraethoxysilane (TEOS), while its organic subphase was a mixture of surfactant (Triton X-100) and ionic liquid electrolytes. Both DSSC gel-type electrolytes were composed of iodine, 1-propy-3-methyl-imidazolium iodide, and 3-methoxypropionitrile to create the redox couple of I 3 − /I − . Based on the results obtained from the I – V characteristics, it was found that the optimal iodine concentrations for the TEOS-Triton X-100 gel electrolyte and PVDF-HFP gel electrolyte are 0.05 M and 0.1 M, respectively. Although the increase in the iodine concentration could enhance the short-circuit current density ( J SC ), a further increase in the iodine concentration would reduce the J SC due to increased dark current. Therefore, the concentration of I 2 is a significant factor in determining the performance of DSSCs. In order to enhance cell performance, the addition of nanosilicate platelets (NSPs) in the above-mentioned gel electrolytes was investigated. By incorporating NSP-Triton X-100 into the electrolytes, the J SC of the cells increased due to the decrease of diffusion resistance, while the open circuit voltage ( V OC ) remained almost the same. As the loading of the NSP-Triton X-100 in the TEOS-Triton X-100 gel electrolyte increased to 0.5 wt%, the J SC and the conversion efficiency increased from 8.5 to 12 mA/cm 2 and from 3.6% to 4.7%, respectively. However, the J SC decreased as the loading of NSP-Triton X-100 exceeded 0.5 wt%. At higher NSP-Triton X-100 loading, NSPs acted as a barrier interface between the electrolyte and the dye molecules, hindering electron transfer, hence, reducing the cell's photocurrent density. The same behavior was also observed in the PVDF-HFP gel electrolyte DSSC system.

Poly(methyl acrylate-co-methyl methacrylate) [P(MA-co-MMA)] nanocomposite film containing 1 wt % of montmorillonite (MMT) exhibited unusual higher ductility, higher strain recovery ratio after creep, and higher modulus and strength compared to neat P(MA-co-MMA) as they were cast from their individual latices fabricated by soap-free emulsion polymerization. The fortified mechanical properties were attributed to the MgO components of exfoliated MMT nanoplatelets being grafted by P(MA-co-MMA) chains as verified by FTIR and XPS spectroscopies, which to the best of our knowledge is the first time in the literature providing the direct evidence for the polymer chains grafting onto the exfoliated MMT. TEM investigation of the stretched nanocomposite film revealed that the microcracks in the nanocomposite film appeared mainly in the bulk region of polymer matrix, implying that the interfacial strength between P(MA-co-MMA) and its grafted MMT nanoplatelets was higher than the cohesion strength of P(MA-co-MMA).

Exfoliated montmorillonite (MMT)/poly(N-isopropylacrylamide) (PNIPAAm) and MMT/poly(N-isopropylacrylamide-co-acrylamide) [P(NIPAAm-co-AAm)] nanocomposites were fabricated by soap-free emulsion polymerization. Interestingly, as the content of MMT was increased from 0 to 10 wt %, the glass transition temperature of MMT/PNIPAAm was decreased from 145 to 122 °C, whereas that of the MMT/P(NIPAAm-co-AAm) increased from 95 to 153 °C. Although the lower critical solution temperature (LCST) of 32 °C for the MMT/PNIPAAm nanocomposites in aqueous solutions was slightly increased with the content of MMT, that of the MMT/P(NIPAAm-co-AAm) was decreased from 70 to 65 °C. A mechanism that the hydrogen bonds between the amide groups of PNIPAAm were interfered by the exfoliated MMT nano-platelets for the MMT/PNIPAAm nanocomposites and the preferred absorption of acrylamide units to the MMT nanoplatelets rather than N-isopropylacrylamide in the MMT/P(NIPAAm-co-AAm) nanocomposites was suggested to interpret these unusual transition behavior. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 524–530, 2009

Soap-free emulsion polymerization of methyl methacrylate (MMA) in the aqueous suspension of montmorillonite (MMT) was able to fabricate the exfoliated MMT/PMMA nanocomposite latex. Because neither MMA nor substantial quantity of potassium persulfide (KPS) initiator could be individually absorbed into the interlayer region of MMT, the polymerizing ionic radicals in water phase were considered as a major component to diffuse into the gallery of MMT. They have been observed to organize into disk-like micelles in the interlayer regions to exfoliate MMT. The diffusion of the polymerizing ionic radicals was further supported by using sodium dodecyl sulfate (SDS) surfactant as a model compound to diffuse into the gallery of MMT. The exfoliation of MMT was almost completed before micellization stage was over. After exfoliation, the disk-like micelles became a polymerization loci for monomers. Because the disk-like micelles in numbers were substantially over the commonly formed spherical micelles in the typical soap-free emulsion polymerization, the conversion rate of MMA to MMT/PMMA nanocomposite latex was faster. Based on the above experimental observation, a justified exfoliation mechanism of MMT was proposed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 459–466, 2009

This first-attempt study tended to inspect the cytotoxic effects of montmorillonite (MMT) or 0.01 N phosphoric acid treated MMT supplemented with L-ascorbic acid (LAA) upon human dermal fibroblasts for possible applications. Light micrographs of human dermal fibroblast cell cultures revealed that more dense black spots in larger sizes were observed when higher levels of MMT were supplemented into the fibroblast culture, indicating that more dermal fibroblasts were covered by MMT particles. Compared with the supplementation of LAA alone, this study selected mitochondrial dehydrogenase activity (MTT) assay as an indicator bioreaction to show possible cytotoxic (or allergic) responses upon human dermal fibroblasts in vitro when LAA/acid-treated MMT composites were added. Statistical analysis showed that LAA augmented with either MMT or 0.01 N phosphoric-acid-treated MMT provoked insignificant cytotoxic responses to human dermal fibroblasts. Thus, an augmentation of MMT or 0.01 N phosphoric-acid-treated MMT to LAA should be biologically feasible for possible skin applications according to this human dermal fibroblasts model.

This study tended to construct new l -ascorbic acid (LAA) composites in low toxicity and high stability for feasible application. LAA is chemically very unstable, since it is easily oxidized into biologically inactive compounds naturally. Our finding showed that introduction of montmorillonite (MMT) could significantly attenuate its toxicity and to sustain the stability of LAA with economic feasibility for practical uses. In addition, as phosphoric acid was biologically compatible, it was used for the pretreatment of MMT to obtain a promising stabilization of LAA. Toxicity assessment also showed that MMT treated with low-concentration acids should be considered as biologically safe according to our assessment. Thus, using acid treated MMT to stabilize LAA in a long-term might be technically feasible for further uses.

Poly(methyl acrylate) (PMA), poly(vinyl acetate) (PVAc) and poly(n-isopropylacrylamide) (PNIPAAm) with their respective Tg of 6, 32, and 145 °C were employed to gel the LiI/I2/tertiary butylpyridine electrolyte system for preparation of the gelled-type dye-sensitized solar cells (DSSC). The light-to-electricity conversion efficiencies of DSSCs gelled by PMA, PVAc, and PNIPAAm were 7.17%, 5.62%, and 3.17%, respectively under simulated AM 1.5 sunlight irradiation, implying that utilizing the polymer of lower Tg to gel the electrolytes leaded to better performance of the DSSCs. Their short-circuit current density and IPCE also showed the similar trend. Electrochemical impedance spectroscopy of the gelled DSSCs revealed that utilizing the polymer of lower Tg resulted in lower impedance associated with the Nernstian diffusion within the electrolytes. The results were consistent with the observation that the molar conductivity of gelled electrolytes was higher as the polymer of lower Tg was applied, which can be justified by Vogel–Tammann–Fulcher (VTF) equation.

The exfoliated poly(methyl acrylate-co-methyl methacrylate)/montmorillonite (MMT) nanocomposite latex solutions fabricated by soap-free emulsion polymerization were able to cast into a film. The films were transparent and ductile unless more than 5 wt% of MMT was incorporated. With the MMT content higher than 5 wt%, the inflammable residuals of nanocomposites after combustion could preserve their original film profile acting like an inflammable scaffold. Moreover, as 20 wt% MMT was incorporated, the yield strength of the films was increased up to 20 times and Young’s modulus up to 2,000 times. However, the water vapor permeability coefficient of the films was only decreased down to its half value. This unexpected behavior of permeability was associated with the decrease of T g as the content of MMT was increased, owing to the large difference of the reactivity ratios between methyl acrylate and methyl methacrylate monomers and their differential absorption to the MMT during copolymerization.

Exfoliated poly(vinyl acetate) (PVAc)/montmorillonite (MMT) and poly(vinyl acetate-co-glycidyl methacrylate) [P(VAc-co-GMA)]/MMT nanocomposite latices, prepared by soap-free emulsion polymerization, were able to be cast into films, and the latter was crosslinked with diethylene triamine as a curing agent. The glass-transition temperature of the crosslinked P(VAc-co-GMA)/MMT nanocomposite films was higher than that of the PVAc/MMT counterparts. Although both the Young's modulus and yield stress for the PVAc/MMT nanocomposite films increased with the content of MMT, the extent of the increase was greater for the crosslinked P(VAc-co-GMA)/MMT nanocomposites. The exfoliated MMT nanoplatelets retarded the cold drawing of the PVAc matrix during tensile testing, resulting in a decrease of the elongation. However, crosslinked P(VAc-co-GMA)/MMT nanocomposite films still had more elongation than the PVAc/MMT counterparts. The drastic decrease of the water vapor permeability with the content of MMT for both types of nanocomposite films suggested that the exfoliated MMT nanoplatelets were dispersed evenly and flattened completely along the film surface. After all the nanocomposite film samples were burned, the inflammable residues for the samples with an MMT content higher than 5 wt % could preserve the original film profile with stiffness, and this indicated that the exfoliated MMT nanoplatelets acted as inflammable scaffolds. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Poly(n-isopropylacrylamide) (PNIPAAm) and its nanocomposite with exfoliated montmorillonite (MMT) were prepared by soap-free emulsion polymerization and individually applied to gel the electrolyte systems for the dye-sensitized solar cells (DSSCs). Each exfoliated MMT nanoplatelet had a thickness of ∼ 1 nm, carried ∼ 1.8 cation/nm2, and acted like a two-dimensional electrolyte. The DSSC with the LiI/I2/tertiary butylpyridine electrolyte system gelled by this polymer nanocomposite had higher short-circuit current density (Jsc) compared to that gelled by the neat PNIPAAm. The former has a Jsc of 12.6 mA/cm2, an open circuit voltage (Voc) of 0.73 V, and a fill factor (FF) of 0.59, which harvested 5.4% electricity conversion efficiency (η) under AM 1.5 irradiation at 100 mW/cm2, whereas the latter has Jsc = 7.28 mA/cm2, Voc = 0.72 V, FF = 0.60, and η = 3.17%. IPCE of the nanocomposite-gelled DSSC were also improved. Electrochemical impedance spectroscopy of the DSSCs revealed that the nanocomposite-gelled electrolytes significantly decreased the impedances in three major electric current paths of DSSCs, that is, the resistance of electrolytes and electric contacts, impedance across the electrolytes/dye-coated TiO2 interface, and Nernstian diffusion within the electrolytes. The results were also consistent with the increased molar conductivity of nanocomposite-gelled electrolytes. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 47–53, 2008