Charge Transfer Induced Molecular Hole Doping into Thin Film of Metal-Organic-Frameworks

Despite the highly porous nature with significantly large surface area, metal organic frameworks (MOFs) can be hardly used in electronic, and optoelectronic devices due to their extremely poor electrical conductivity. Therefore, the study of MOF thin films that require electron transport or conductivity in combination with the everlasting porosity is highly desirable. In the present work, thin films of Co3(NDC)3DMF4 MOFs with improved electronic conductivity are synthesized using layer-by-layer and doctor blade coating techniques followed by iodine doping. The as-prepared and doped films are characterized using FE-SEM, EDX, UV/Visible spectroscopy, XPS, current-voltage measurement, photoluminescence spectroscopy, cyclic voltammetry, and incident photon to current efficiency measurements. In addition, the electronic and semiconductor property of the MOF films are characterized using Hall Effect measurement, which reveals that in contrast to the insulator behavior of the as-prepared MOFs, the iodine doped MOFs behave as a p-type semiconductor. This is caused by charge transfer induced hole doping into the frameworks. The observed charge transfer induced hole doping phenomenon is also confirmed by calculating the densities of states of the as-prepared and iodine doped MOFs based on density functional theory. Photoluminescence spectroscopy demonstrate an efficient interfacial charge transfer between TiO2 and iodine doped MOFs, which can be applied to harvest solar radiations.Comment: Main paper (19 pages, 6 figures) and supplementary information (15 pages, 10 figures), accepted in ACS Appl. Materials & Interface

Hole-induced polymerized interfacial film of polythiophene as co-sensitizer and back-electron injection barrier layer in dye-sensitized TiO2 nanotube array

In this work, we demonstrate that an ultra-thin film of polythiophene deposited interfacially via hole-induced polymerization on the surface of dye-sensitized TiO2 nanotube array acts as co-sensitizer, and hinders back-electron transfer in a DSSC. Consequently, the dark current, and the recombination reactions can be suppressed, leading to an improved number of electron density at the TiO2 array electrode. Thus, an enhanced photocurrent, and power conversion efficiency of the device is achieved. This logical concept is experimentally justified, and the device, after polythiophene interfacial treatment, demonstrates an enhanced power conversion efficiency by the factor of 39.19%. (C) 2018 Elsevier B.V. All rights reserved.11Nsciescopu

Facile synthesis and optoelectronic exploration of silylthiophene substituted benzodithiophene polymer for organic field effect transistors

This work reports the synthesis, characterization and organic field effect transistors (OFET) application of a novel conjugated polymer (PBDTDPP) based on silylthiophene substituted benzo[1,2-b:4,5-b']dithiophene (BDT) donor and diketopyrrolopyrrole (DPP) acceptor obtained via Stille polymerization reaction. The polymer exhibits a broad absorption in the UV-visible spectrum ranging from 300 nm to 900 nm with the band edge of the polymer at 1.31 eV. Thermogravimetric analysis of the polymer demonstrates the stability up to 303 degrees C, and the cyclic voltammetry shows the HOMO and LUMO levels at -5.42 and -4.11 eV, respectively. Employing the polymer as an active layer in a bottom gate-top contact based OFET, hole mobility of as high as 9.34 x 10(-2) cm(2) V-1 s(-1) with the On/Off ratio of similar to 10(4) was obtained. This work successfully demonstrates that the DPP and the silylthiophene substituted BDT are promising units to build D-A based copolymer for organic electronics. (c) 2018 Elsevier B.V. All rights reserved.11Nsciescopu

Au-Pd bimetallic nanoparticles embedded highly porous Fenugreek polysaccharide based micro networks for catalytic applications

Currently, metallic nanoparticles possessing versatile heterogeneous catalytic functionality such as in hydrogenation, water splitting, hydrogen production and CO2 reduction for global pollution remediation have been paid great attentions due to their high chemical stability, superior activity and unique electrical and optical properties. However, the gradual degradation of their catalytic activity on multiple usage limits the monometallic nanoparticles to industrial applications. Herein, we fabricated the highly porous fenugreek polysaccharide assisted green synthesis of Au-Pd nanostructures for heterogeneous catalytic hydrogenation of the industrial usable highly toxic 4-nitrophenol to the medicinally useful 4-aminophenol. The aqueous method developed in the present work is environmentally friendly, simple and low-cost procedure. The fabricated bimetallic porous Au Pd nano structures characterized using SEM, TEM, UV-Vis, XRD, XPS and FTIR analysis. The catalytic activity of the synthesized nanostructures was studied for the heterogeneous hydrogenation of 4-nitrophenol to 4-aminophenol in presence of NaBH4, and the catalytic kinetic for the hydrogenation was analyzed via an UV-Vis spectrometer. (C) 2018 Elsevier B.V. All rights reserved.11Nsciescopu

Acceptor Unit Effects for Ambipolar Organic Field-Effect Transistors Based on TIPS-Benzodithiophene Copolymers

Two narrow band gap triisopropylsilyl substituted benzo[1,2-b:4,5-b] dithiophene (TIPS-BDT) derivatives, P1 (1.65 eV) and P2 (1.46 eV) are synthesized for ambipolar organic field-effect transistors and complementary inverters. Two electron acceptor units, heptadecanyl substituted thieno[3,4-c]pyrrole-4,6-dione (TPD) and ethylhexyl substituted diketopyrrolo[3,4-c]pyrrole (DPP) are incorporated to tune the structure and resulting properties of the donor-acceptor type copolymers. Structural modification based on the acceptor unit variation, resulted in comparable electrochemical, optical, microstructural, and charge transporting properties, as well as environmental and operational stability. TIPS-BDT copolymers with TPD acceptor units show comparatively superior performance, with field effect mobility approximate to 10(-3) cm(2)V(-1)s(-1) for both holes and electrons and inverter gain approximate to 18 with poly(methyl methacrylate) gate dielectric.11Nsciescopuskc

Highly durable and sustainable copper-iron-tin-sulphide (Cu2FeSnS4) anode for Li-ion battery: Effect of operating temperatures

Operating temperatures considerably influence the energy storage mechanism of the anode of Li-ion batteries (LiBs). This effect must be comprehensively studied to facilitate the effective integration of LiBs in practical applications and battery management. In this study, we fabricated a novel anode material, i.e., copper iron tin sulphide (Cu2FeSnS4, CFTS) and investigated the corresponding LiB performance at operating temperatures from 10 C to 55 C. The CFTS anode exhibited a discharge capacity of 283.1 mAhg1 at room temperature (25 C), which stabilized to 174.0 mAhg1 in repeated cycles tested at a current density of 0.1 Ag−1. The discharge capacity at higher operating temperatures such as 40 C and 55 C, is found to be 209.3 and 230.0 mAhg respectively. In contrast, the discharge capacity decreased to 36.2 mAhg1 when the temperature decreased to 10 C. Electrothermal impedance spectroscopy was performed to determine the rate of chemical reactions, mobility of active species, and change in internal resistance at different operating temperatures. In terms of the cycle life, the CFTS exhibited outstanding cycling stability for more than 500 charge/discharge cycles, with a 146 % capacity retention and more than 80% Coulombic efficiency. The electrochemical investigation revealed that the charge storage in the CFTS anode is attributable to capacitive-type and diffusion-controlled mechanisms