Effective construction of a CuCo MOF@graphene functional electrocatalyst for hydrogen evolution reaction.

Electrochemical water splitting is considered a green and sustainable method of producing hydrogen energy. Herein, to pursue a highly efficient hydrogen evolution reaction, we fabricated high-performance electrocatalysts, by utilizing a bimetallic (Cu and Co) metal-organic framework to modify rGO through a one-step in situ approach. The synthesized CuCoOC@rGO presents a highly ordered structure with a defect-rich porous surface for the hydrogen evolution reaction (HER). Specifically, the appropriate adjustment of metal (Cu and Co), 1,3,5-benzenetricarboxylic acid (H3BTC), and rGO ratios leads to a well-defined morphology, which creates a defect-rich porous surface. Characterized by XRD, SEM, EDS, FT-IR spectroscopy, Raman spectroscopy, XPS, and BET, the morphology exposes more active sites, strong evidence for the promotion of electrocatalytic efficiency. Upon the analysis of the experimental data, the obtained CuCoOC@rGO catalyst exhibits excellent activity in alkaline media with a low overpotential of 120 mV at a current density of 10 mA cm-2, and a Tafel slope of 124 mV dec-1 for the hydrogen evolution reaction (HER). Guided by the structure-activity relationship, the superior HER activity of CuCoOC@rGO in alkaline electrolyte could originate from many sources, including: (1) as a self-supported substrate, CuCoOC@rGO not only leads to profitable electrical contact and mechanical stability but also firmly roots into the rGO without extra binders. (2) The highly ordered structure provides smooth ion and electron transport channels, which are conducive to electrolyte infiltration and gas release. (3) The abundance of defective pores on the surface of the nanoarrays, which offers more active sites for the catalytic process. This study provides new prospects for the rational design and fabrication of advanced hierarchical functional electrocatalysts for application in electrochemical energy devices.

Esterification modified starch by phosphates and urea via alcohol solvothermal route for its potential utilization for urea slow-releasing.

The natural starch (NS) is modified by an esterification process which is accomplished by reacting the NS and phosphate together with urea via a facile alcohol solvothermal method. After modification, a series of obvious variations can be easily confirmed for the resulted starch phosphate carbamides (denoted as SPC) compared with that of NS, such as the introduction of new groups of CO, PO, P-O-C and P-O-H together with new elements of N and P in starch molecular structure unit confirmed in FT-IR and XPS analyses and the decreased crystallinity along with formed surface defect demonstrated in XRD and SEM measurements. Furthermore, the formed SPC has a higher viscosity of 480 mPa.s-1 and lower gelatinization temperature of under 10 °C than that of the NS. More importantly, when the SPC is utilized as outer coating material together with ethylcellulose (EC) as inner coating material for preparing double-layer slow-release urea (denoted as EC/SPC based SRU), the EC/SPC based SRU has a desirable slow-release behavior with release percentages of 40.9% for 12 h in water and merely 59.6% for 20 day together with even exceeding 30 days in soil. Conclusively, this work provides a facile preparation approach for the SPC and its creative application for the preparation of SRU.

Facile Synthesis of CoNi Bimetallic Nanoparticle Decorated Reduced Graphene Oxide as Efficient and Low-Cost Counter Electrode for Dye-Sensitized Solar Cells.

In this paper, CoNi bimetallic nanoparticle decorated reduced graphene oxide (CoNi-RGO) was synthesized by a facile hydrothermal method. When applied this CoNi-RGO into counter electrode for dye-sensitized solar cells (DSSCs), it shows smaller charge-transfer resistance and better electrocatalytic activity than that of pure reduced graphene oxide (RGO). At the optimized conditions, the energy conversion efficiency of DSSCs based on CoNi-RGO counter electrode was 3.79%, indicating a higher photovoltaic performance of DSSCs based on CoNi-RGO counter electrode than that of DSSCs based on RGO counter electrode (1.37%), and comparable to the value of DSSCs based on Pt counter electrode as a reference (4.95%). Additionally, the photovoltaic performance of DSSCs based on CoNi-RGO counter electrode strongly depends on its composition. The molar ratio of Co/Ni and the weight ratio of CoNi/GO that used to prepare CoNi-RGO counter electrode are key factors to affect the performance of their cell devices. When both the molar ratio of Co/Ni and the weight ratio of CoNi/GO are 1:1, the CoNi-RGO counter electrode shows the best performance, indicating the potential of such bimetallic nanoparticle decorated RGO as low-cost and efficient counter electrode to replace noble metal Pt counter electrode for the practical application of DSSCs devices.

Synthesis of an Efficient Counter Electrode Material for Dye-Sensitized Solar Cells by Pyrolysis of Melamine and Graphene Oxide.

An efficient counter electrode material for dye sensitized solar cells (DSSCs) was synthesized by pyrolysis of melamine and graphene oxide. The synthesized samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and scanning electrode microscopy, which show that nitrogen doped reduced graphene oxide (NRGO) was obtained by this synthesis method. In the synthesized NRGO, graphitic structure was kept and the nitrogen was existence as pyrrolic, pyridinic, graphitic, and oxidized nitrogen species in the samples. After deposited as counter electrode films for DSSCs, it shows lower charge-transfer resistance at the electrode/electrolyte interface and higher electrocatalytic activity towards reduction of triiodide (I-3) than that of reduced graphene oxide (RGO) prepared also by this method without adding melamine. Consequently, the DSSCs based on NRGO counter electrodes achieve an energy conversion efficiency of 4.60%, which is higher than that of RGO counter electrode (2.35%). Although the photovoltaic performance of NRGO counter electrode was lower than that of Pt counter electrode (5.70%), it is still a promising counter electrode to replace noble metal Pt due to its low cost and simple synthesis process.

Effect of Graphene/TiO2 Composite Layer on the Performance of Dye-Sensitized Solar Cells.

Graphene has attracted a lot of attention because of its unique mechanical, thermal, electrical and optical properties. In this study, a double layered structured photoanode consisting of a graphene/TiO2 composite layer and a TiO2 nanoparticles (P25) underlayer was developed. The photoelectric properties of as-prepared double layer structured photoanode were studied with comparison of the anatase TiO2 photoanode. Graphene was prepared by reduction of graphene oxide (GO) under a hydrothermal conditions and graphenen/TiO2 composite semiconductor materials were prepared by mixing graphene into TiO2 paste. The effect of graphene contents in graphene/TiO2 composite layer was also investigated. After constructing double layer photoanode with proper amount of graphene, the photoanode displayed enhanced light and dye adsorption properties with higher light harvesting efficiency, lower internal resistances, faster electron transport and lower charge recombination rate, which resulted in high current density. At the optimum conditions, the DSSC exhibited a Jsc of 15.01 mA cm-2, a Voc of 0.72 V, and a FF of 0.66 with the energy conversion efficiency (η) of 7.08%, indicating a increase in Jsc and η respectively than that of DSSC based on pure TiO2 photoanode, which gives a Jsc of 13.25 mA cm-2, a Voc of 0.73 V, and a FF of 0.62 with a η of 5.94%. However, the addition of excess graphene in the composite layer led to the enhancement of charge recombination, the reduction of dye adsorption and the decrease of photoelectric conversion efficiency of DSSCs. The graphene/TiO2 composite layer in DSSCs could really enhance its efficiency after the amount of graphene was successfully optimized.

Different conjugated system Zn(ii) Schiff base complexes: supramolecular structure, luminescent properties, and applications in the PMMA-doped hybrid materials.

A series of Zn(ii) complexes with different conjugated systems, [ZnL1Cl2]2 (Zn1), [ZnL2Cl2] (Zn2), [Zn(L3)2]·(ClO4)2 (Zn3), [Zn2L4Cl4] (Zn4), and [ZnL5Cl2] (Zn5), were synthesized and subsequently characterized via single crystal X-ray diffraction, 1H and 13C NMR, FT-IR, elemental analyses, melting point, and PXRD. The X-ray diffraction analyses revealed that the supramolecular frameworks of complexes Zn1-Zn5 are constructed by C-HO/Cl hydrogen bonds and ππ interactions. Complexes Zn1-Zn3 feature 3D 6-connected {412·63} topological structures, whereas complex Zn4 exhibits a 3D 7-connected supramolecular framework with a {417·64} topological structure. However, complex Zn5 shows one-dimensional "wave-like" chains. Based on these varied structures, the emission maximum wavelengths of complexes Zn1-Zn5 can be tuned in a wide range of 461-592 nm due to the red shift direction of λem caused by different conjugated systems and their electron donating abilities. Complex Zn3 shows a strong luminescence in the solid state and in the acetonitrile solution. Therefore, a series of Zn3-poly(methylmethacrylate) (Zn3-PMMA) hybrid materials were obtained by controlling the concentration of complex Zn3 in poly(methylmethacrylate) (PMMA). At an optimal concentration of 4%, the doped polymer film of Zn3-PMMA displays strong green luminescence emissions that are 19-fold in the luminescence intensities and 98 °C higher in the thermal stability temperature compared to the Zn3 film.

HONH3Cl optimized CH3NH3PbI3 films for improving performance of planar heterojunction perovskite solar cells via a one-step route.

Planar heterojunction perovskite solar cells (PHJ-PSCs) constructed with one-step precursor solution spin-coating deposition (OPSSD) usually give an extremely low performance mainly due to the poor morphology and low crystallinity of the perovskite films. In this work, by incorporating a suitable HONH3Cl additive in the perovskite precursor solution, a high quality perovskite film with improved morphology and crystallinity was obtained. The UV-vis measurement of the CH3NH3I solutions without and with HONH3Cl demonstrates that the improved quality of the perovskite film can be easily attributed to a combined effect of N2, I2, H2O and CH3NH3Cl originating from the oxidation of CH3NH3I triggered by the HONH3Cl additive, which can manipulate the crystallization process of the perovskite. Accordingly, the improved performance for the HONH3Cl-induced PHJ-PSCs can also be demonstrated. At the optimized molar ratio of 1 : 1 : 0.1 for PbI2 : CH3NH3I : HONH3Cl, the PHJ-PSCs exhibit an average power conversion efficiency (PCE) of 10.61 ± 0.51%, which is much higher than that of pristine 1 : 1 : 0 based cells without additive (7.21 ± 0.61%), and the best performing HONH3Cl-induced device can yield a PCE as high as 11.12% with a Jsc of 18.42 mA cm-2, Voc of 0.95 V and FF of 0.63. Introducing suitable HONH3Cl as an additive into the perovskite precursor solution is really an effective route to enhance the performance of the PHJ-PSCs via OPSSD.

Tunable Luminescence and Application in Dye-Sensitized Solar Cells of Zn(II)/Hg(II) Complexes: Methyl Substitution-Induced Supramolecular Structures Based on (E)-N-(6-Methoxypyridin-2-ylmethylene)arylamine Derivatives.

Using Schiff-base ligands (E)-N-(6-methoxypyridin-2-yl)(CH═NAr) (where Ar = C6H5, L1; 2-MeC6H4, L2; 2,4,6-Me3C6H2, L3), six Zn(II)/Hg(II) complexes, namely, [ZnL1Cl2] (Zn1), [HgL1Cl2] (Hg1), [ZnL2Cl2] (Zn2), [HgL2Cl2] (Hg2), [ZnL3Cl2] (Zn3), and [HgL3Cl2] (Hg3) have been synthesized under solvothermal conditions. The structures of six complexes have been established by X-ray single-crystal analysis and further physically characterized by EA, FT-IR, (1)H NMR, and ESI-MS. The crystal structures of these complexes indicate that noncovalent interactions, such as hydrogen bonds, C-H···Cl, and π···π stacking, play essential roles in constructing the resulting supramolecular structures (1D for Hg3; 2D for Zn2, Hg2; 3D for Zn1, Hg1, and Zn3). Upon irradiation with UV light, the emission of complexes Zn1-Zn3 and Hg1-Hg3 could be finely tuned from green (480-540 nm) in the solid state to blue (402-425 nm) in acetonitrile solution. It showed that the ligand and metal cation can influence the structures and luminescence properties of complexes such as emission intensities and maximum wavelengths. Since these ligands and complexes could compensate for the absorption of N719 in the low-wavelength region of the visible spectrum and reduce charge recombination of the injected electron, the ligands L1-L3 and complexes Zn3/Hg3 were employed to prepare cosensitized dye-sensitized solar cells devices for investigating the influences of the electron-donating group and coordination on the DSSCs performance. Compared to DSSCs only being sensitized by N719, these prepared ligands and complexes chosen to cosensitize N719 in solar cell do enhanced its performance by 11-41%. In particular, a DSSC using L3 as cosensitizer displays better photovoltaic performance with a short circuit current density of 18.18 mA cm(-2), corresponding to a conversion efficiency of 7.25%. It is much higher than that for DSSCs only sensitized by N719 (5.14%).

Solvatochromic and application in dye-sensitized solar cells of sandwich-like Cd(II) complexes: supramolecular architectures based on N(1),N(3)-bis[(6-methoxypyridin-2-yl)methylene]benzene-1,3-diamine.

A novel polydentate Schiff base ligand N(1),N(3)-bis[(6-methoxypyridin-2-yl)methylene]benzene-1,3-diamine (L) and its two dinuclear sandwich-like complexes {[CdL(NO3)(H2O)]·NO3}2 (1) and {[CdL(CH3CN)(H2O)]·(ClO4)2·(CH3CN)2}2 (2) were synthesized. Both C-H∙∙∙O, C-H∙∙∙N and π-π non-covalent interactions had essential roles in constructing the resulting three-dimensional supramolecular networks. L emits a more intense blue-green fluorescence emission around 493 nm than in dilute solution, exhibiting stacking-induced emission properties. Complexes 1 and 2 exhibited the dual properties of exceptional solvatochromism and fluorescence quenching towards CH3OH molecules. As these compounds could overcome the absent absorption of ruthenium complex N719 in the low wavelength region of the visible spectrum, offset the competitive visible light absorption of I3(-) and reduce the charge recombination of injected electrons, the Schiff base ligand l and complexes 1 and 2 were used as co-sensitizers in combination with N719 to investigate their effect on enhancing the performance of dye-sensitized solar cells. A short circuit current density of 14.37 mA cm(-2), an open-circuit voltage of 0.71 V and a fill factor of 0.61 corresponding to an overall conversion efficiency of 6.17% under AM 1.5 G solar irradiation were achieved when 1 was used as a co-sensitizer, which are much higher than the results obtained for dye-sensitized solar cells sensitized by N719 alone (5.06%).

An insight into the role of oxygen vacancy in hydrogenated TiO2 nanocrystals in the performance of dye-sensitized solar cells.

Hydrogenated titanium dioxide (H-TiO2) nanocrystals were successfully prepared via annealing TiO2 in H2/N2 mixed gas flow at elevated temperatures ranging from 300 to 600 °C. Electron paramagnetic resonance (EPR) spectra were used to determine the produced oxygen vacancy in H-TiO2. Variations in temperature were studied to investigate the concentration change of oxygen vacancy in H-TiO2. The H-TiO2 nanocrystals prepared at different temperatures were employed into photoanodes sensitized by N719 dye and found to have exceptional effect on the solar-to-electric energy conversion efficiency (η). Photoanodes with H-TiO2 nanocrystals hydrogenated at 300 °C show the highest short-circuit current density (Jsc) of 18.92 mA cm(-2) and photoelectrical conversion efficiency of 7.76% under standard AM 1.5 global solar irradiation, indicating a 27 and 28% enhancement in Jsc and η, respectively, in comparison to those with TiO2. The enhancement is attributed to high donor density, narrow band gap and positive shift of flat band energy (Vfb) of H-TiO2 that promote the driving force for electron injection. Intensity-modulated photocurrent spectroscopy (IMPS) accompanied by intensity-modulated photovoltage spectroscopy (IMVS) and other analyses were applied to shed more light on the fundamental mechanisms inside the charge transfer and transport in these systems.

Synthesis and characterization of substituted Schiff-base ligands and their d(10) metal complexes: structure-induced luminescence tuning behaviors and applications in co-sensitized solar cells.

Nine IIB group complexes, [ZnL1Cl2] (Zn1), [CdL1Cl2]2 (Cd1), [HgL1Cl2] (Hg1), [ZnL2Cl2] (Zn2), [CdL2Cl2] (Cd2), [HgL2Cl2] (Hg2), [ZnL3Cl2] (Zn3), [CdL3Cl2] (Cd3) and [HgL3Cl2] (Hg3), have been synthesized from the corresponding ortho-(6-methoxy-pyridyl)(CH[double bond, length as m-dash]NAr) (where Ar = 2,6-iPr2C6H3, L1; 4-MeC6H4, L2; 2-OMeC6H4, L3) Schiff base and structurally characterized by elemental analysis, FT-IR, (1)H NMR and X-ray single-crystal analysis. Crystallographic studies reveal that the center metal of the complexes adopts a distorted tetrahedron geometry (except for Cd1 and Cd3, which display square pyramidal geometry) and C-HCl hydrogen bonds and ππ stacking interactions contribute to three-dimensional supramolecular structures. The series of complexes exhibit tunable luminescence from blue, through green, to light yellow by varying the temperature (298 K and 77 K), both in solution and in the solid state. Moreover, the quantum yields range from 0.027 to 0.422, and decrease according to the order of the periodic table (Zn > Cd > Hg). These results indicate that the center atom of the complexes leads to the geometry differences and hence to the tunable luminescence properties. Because Zn1-Zn3 exhibited higher molar extinction coefficients and a distinct absorption region, they were employed as co-sensitizers in ruthenium dye N719-sensitized photoanodes to deliver light-electricity efficiency enhancement, being assembled with counter-electrodes and electrolyte to prepare ZnX/N719 (where ZnX = Zn1, Zn2, and Zn3) co-sensitized dye sensitized solar cell (DSSC) devices. The prepared co-absorbent could overcome the deficiency of N719 absorption in the low-wavelength region of the visible spectrum, and offset competitive visible-light absorption of I3(-). Application of these prepared complexes in N719-sensitized solar cells enhanced their performance by 10-36%, which indicated a potential application of these types of complexes in DSSCs.

Efficiency of ruthenium dye sensitized solar cells enhanced by 2,6-bis[1-(phenylimino)ethyl]pyridine as a co-sensitizer containing methyl substituents on its phenyl rings.

2,6-Bis[1-(phenylimino)ethyl]pyridine (M0) and its derivatives containing methyl groups on their phenyl rings (M1o, M1p and M2) are employed as co-sensitizers in dye-sensitized solar cells (DSSCs). The prepared co-sensitizers could alleviate the aggregation of ruthenium dye N719 on the TiO2 film, enhance the spectral responses of the co-sensitized TiO2 film in the region from 400 to 750 nm, suppress the electron recombination, prolong the electron lifetime and decrease the total resistance of DSSCs. The number and position of the methyl groups are two key factors that play important roles in the performances of DSSCs. The optimized cell device co-sensitized by the M1p/N719 dye gives a short circuit current density of 16.48 mA cm(-2), an open circuit voltage of 0.72 V and a fill factor of 0.62 corresponding to an overall conversion efficiency of 7.32% under standard global AM 1.5 solar irradiation, which is 35% higher than that of a device solely sensitized by N719 under the same conditions.

Enhanced near-infrared to visible upconversion nanoparticles of Ho³âº-Yb³âº-F⁻ tri-doped TiO2 and its application in dye-sensitized solar cells with 37% improvement in power conversion efficiency.

New near-infrared (NIR)-to-green upconversion nanoparticles of Ho(3+)-Yb(3+)-F(-) tridoped TiO2 (UC-F-TiO2) were designed and fabricated via the hydrosol-hydrothermal method. Under 980 nm NIR excitation, UC-F-TiO2 emit strong green upconversion fluorescence with three emission bands at 543, 644, and 751 nm and convert the NIR light in situ to the dye-sensitive visible light that could effectively reduce the distance between upconversion materials and sensitizers; thus, they minimize the loss of the converted light. Our results show that this UC-F-TiO2 offers excellent opportunities for the other types of solar cells applications, such as organic solar cells, c-Si solar cells, multijunction solar cells, and so on. When integrating the UC-F-TiO2 into dye-sensitized solar cells (DSSCs), superior total energy conversion efficiency was achieved. Under AM1.5G light, open-circuit voltage reached 0.77 ± 0.01 V, short-circuit current density reached 21.00 ± 0.69 mA cm(-2), which resulted in an impressive overall energy conversion efficiency of 9.91 ± 0.30%, a 37% enhancement compared to DSSCs with pristine TiO2 photoanode.

N,N'-Bis((6-methoxylpyridin-2-yl)methylene)-p-phenylenediimine based d(10) transition metal complexes and their utilization in co-sensitized solar cells.

N,N'-Bis((6-methoxylpyridin-2-yl)methylene)-p-phenylenediimine based four-coordinated d(10) transition metal complexes (named ML, M = Zn, Cd, Hg) were synthesized and employed as co-sensitizers and co-adsorbents in combination with a ruthenium complex N719 in dye sensitized solar cells. After co-sensitization, not only the incident-photon-to-current conversion efficiency is enhanced but also the dark current is reduced. A short circuit current density of 14.46 mA cm(-2), an open circuit voltage of 0.74 V and a fill factor of 0.62 corresponding to an overall conversion efficiency of 6.65% under AM 1.5 G solar irradiation were achieved when ZnL was used as a co-sensitizer, which are much higher than that for DSSCs only sensitized by N719 (5.22%) under the same conditions. The improvement in efficiency is attributed to the fact that N,N'-bis((6-methoxylpyridin-2-yl)methylene)-p-phenylenediimine coordinated complexes overcome the deficiency of N719 absorption in the low wavelength region of the visible spectrum, prevent its aggregation, offset competitive visible light absorption of I3(-) and reduce charge recombination due to formation of an effective cover layer of the dye molecules on the TiO2 surface. As a result, the synthesized complexes are promising candidates as co-adsorbents and co-sensitizers for highly efficient DSSCs.

Propofol attenuates lipopolysaccharide-induced monocyte chemoattractant protein-1 production through p38 MAPK and SAPK/JNK in alveolar epithelial cells.

PURPOSE: Propofol is widely used in sedation and surgical procedures involving patients with acute lung injury (ALI), a common complication in critically ill patients. Monocyte chemoattractant protein-1 (MCP-1) plays an important role in pathological changes in ALI. The present study investigated the anti-inflammatory effect and mechanism of propofol on MCP-1 production and mitogen-activated protein kinase (MAPK) phosphorylation induced by lipopolysaccharide (LPS) in alveolar epithelial cells (AECs). METHODS: AECs were treated with 1 µg/ml LPS for 30 min, 1 h, 6 h, or 24 h following pretreatment with 12.5-100 µM propofol for 30 min. Cytokines and chemokines secretion were profiled using cytokine array, and mRNA and protein levels of MCP-1 were measured by RT-PCR and ELISA. The phosphorylation of p38 MAPK, p44/42 MAPK, SAPK/JNK, ATF-2, and c-Jun were measured by Western blot analysis. RESULTS: Propofol at 50 and 100 µM dose-dependently inhibited MCP-1 mRNA expression (P < 0.05), and also propofol at 50 µM decreased extracellular MCP-1 protein levels (P < 0.05) compared to the LPS group. Propofol at 12.5-50 µM inhibited LPS-induced phosphorylation of p38 MAPK, p44/42 MAPK, SAPK/JNK, ATF-2, and c-Jun in AECs. CONCLUSIONS: Propofol at clinically relevant concentrations attenuated LPS-induced MCP-1 mRNA expression and secretion by inhibiting the phosphorylation of p38 MAPK, SAPK/JNK, ATF-2, and c-Jun exerting its anti-inflammatory effects in AECs. These results suggest that propofol may modulate inflammatory response at clinically achievable concentrations in ALI.